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R e p o r t N o . F H W A - R D - 7 5 - 4 8

REVIEW OF ENGINEERING EXPERIENCES WITHEXPANSIVE SOILS IN HIGHWAY SUBGRADES

D.R. S n e t h e n and o t h e r s

U.S. Army Engineer Waterways Experiment Station

June 1975I n te r i m R epor t O R E X H I I T O N L Y

lease o Not Remove

This document s available to the public

through the National Technical Information

Service Springfield Virginia 22 6

Prepared for

FEDERAL HIGHWAY ADMINISTRATION

Offices of Res earch Development

Washington0 0

20590



NOTICE

This document i s disseminat ed under t h e spo nsorsh ip of t he Department

of Transpor ta t ion in th e in te re s t o f in format ion exchange. The United

S t a t e s G overnment a ssumes no l i a b i l i t y f o r i t s c o n t e n t s o r u s e t h e r e o f .

The c on t e n t s o f t h i s r e p o r t r e f l e c t t h e v ie ws o f t h e U S. Army Engi-

neer Waterways Experiment Station, which s r e sp o ns i bl e f o r t h e f a c t s

and th e accuracy of th e data presen ted here in . The conte nts do not

n e c e s s a r i l y r e f l e c t t h e o f f i c i a l vi ew s o r p o l i c y o f t h e D epartm ent of

Trans por ta t ion . Th i s r ep o r t does no t co ns t i t u t e a s t a n d a r d , s p e c i f i c a -

t i o n , o r r e g ul a t io n .

The United S ta te s Government does not endorse pro duc ts o r manufacturers .

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D i r ec t d i s t r i b u t i o n i s be in g made t o t h e d i v i s i o n o f f i c e s .



Technical keport Documentation Page

1 . R e p o r t N o . 2 . G o v er n m e nt A c c e s s ~ o n o

4 . Title a n d S u b t l fl e

A 3EVIEW OF ENGINEERING EXPERIENCES KITH EX?AKS17<E

SOILS IN EIGHWAY SUBGRA3ES

7 A u t h o r s ) Donald R. Snethen, Frank 'C. Townsend, Lawrence

C. Johnson, 3avid M. Patrick, Philip J. 'Vedros

P e ~ f o r r n ~ n ~r g a n i z a t i o n N a m e on A d d r e s s

Soil Fecha2ics Divisio~

Scils azd ?avernents Laborazory

U. S. Army Engineer Wzterways Experinent Station

P . 0. Box 631 Vicksburg, PS 3 9 1 8 0

1 2 . S p o n s o r i n g A g e n c y N a m e a n d A d d r e s s

Offices of Research and Gevelopment

Federal Eigh.way Administration

U. S. Department of Transpcrtation

Washington, D. C. 2C5931 5 . S u p p l e m e n t a r y Notrr

FHWA Contract Manager ?reston C. S x t h (H3.S-21)

3 . R e c ~ p ~ e n t sa t a l o g N o

5 R e p o r t D a t e

une 19756 . P e r l o r r n ~ n ~r g o n l z o t ~ o nC o d e

8 P e r i o r m ~ n g r g o n i z a t ~ o nR e p o r t N O

10 ork U n ~ tN O . T R A I S )

FCP 34~1-13211. Contract or rant NO.

Intra-Gxernmenr Fcrchase

Order NO. b 1 0195

13 T y p e of R e p o r t a n d P e r ~ o d o v e r ed

Interm Report

1 4 . S p o n s o r i n g A g e n c y C o d e

{-Csii

1 6 . A b s t r a c t

Volzme change resulting from moistxre variaticns in expansive soil sgbgrades

is estimated to cause damage t o s t r e e t s and highways in excess of 1.1 bil-

lion annually in the United Szates. Expansl ve sc:ls are S a r e a l l y extensive

within parts of the 3nited States that alterati3- of the highway routes to

avoid the material is virtuzlly inpossikle. This report presents the re-

sults of a review of current literature corrkined wlth jetails of ex?erie-ces

of selected scate highway agencies on prcceciures fcr copizg with problemassociated with expansive soil subgraies. The report disccsses the geologic,

mineralogic, physical, and physicochernical ~rcperties which ixfluence the

volume change characteristics of expansive soils. Currer.tly csed Eechniqses

for samplxg, ider.tifying, ani testing expans;ve materials aze reviewed and

Ciscussed. Treatment alzernatives for the creventicn cr redcctron of cetri-

mental volume change cf expansive soil subgrades beneath new an3 exiszing

pavemects are presented and disccssed.

17. K e y W o r d s

Expansive solls

klighways

Soil mclsture

Subgrades

18 D l s t r ~ b u t l o n S t a t e m e n t

Th-s socument is ava~lable to :he p~bllc

tnrougn the Natlonal Technical Informa-t-on Service S ~ r ~ n g feld, VA 22161

19 S e c u r i t y C l o s s i f . ( o f t h i s report

Unclassified

F o r m D O T F 1 7 0 0 . 7 ( 8 - 7 2 ) R e p r o d u c t i o n o f c o m p l e t e d pog a u t h o r i z e d

8 e c u r it y C l o s s i f . ( o f t h i s

Unclassified

2 1 . N o . o f P a g e s

137

2 2 . P r i c e



PREFACE

The study of the nethodology for prediction and minimization of

detrimental volume change of expansive soils in highway subgrades is a

4-yr investigazion f3;nded by the Department of Transportation, Federal

Highway Administration, under Intra-Government Purchase Order No.

4-1-0195, Work Unit No. FCP 3401-132.

The work was initiated during June 1974 by the Soils and Pave-

r,ents Laboratory (s PL) f the U. s rmy Engineer Waterways Experiment

Station (WES) Vicksburg, Mississippi. Dr. Donald R. Snethe?, Research

Group, Soil Mechanics Division (SMD), was the principal investiga~or

during the period of this report. The work reported herein was per-

forned by Dr. Snethen; Dr. Frank C. Townsend, Chief, Laboratory Re-

search Facility, SMD, Dr. Lawrence D. Johnsoc, Research Grcup, SKD;

Dr. David M. Patrick, Engineeri~g Geology Research Facility, E~gineer-

ing Geology and Rock Mechanics Division; and Mr. Philip J. Vedros,

Special Projects Branch, Pavement Investigation Division, S PL. The

investigstion was accomplished under the direct supervision of

Mr. Clifford L. McAnear Chief, SMD, and under the general supervision

of Mr. James P. Sale, Chief,S PL.

Director of W S during the conduct of this portion of t he study

and preparation of the report was COL G. H. Hilt, CE. Technical 3irec-

tor was Mr. F. R. Brown.



3 Distribution o f potentially expansive materials in the

. . . . . . . . . . . . . . . .nited States: FHWARegion 15 16

Distribution of potentially expansive materials in the

United States: FHWA Region 6 . . . . . . . . . . . . . . . . 17 18Distrlbution of potentially expa~sive materials in the

United Scates: FHWA Regions 7 arid 8 . . . . . . . . . . . . . 19 20

Distribution of potentially expansive materials in the

Un i~ ed States: FHWA regions and 10 . . . . . . . . . . . 21 22

Typical structural configurations of clay minerals . . . . . . 28

Deflocculated clay mineral associations showing

surface water illite) and surface and interlayer water

montmoril1on:te) . . . . . . . . . . . . . . . . . . . . . . 34

Moldlng water content versus cry density and particle

orlentation . . . . . . . . . . . . . . . . . . . . . . . . . 37

X-radiograph o f undisturbed clay shale sample . . . . . . . . 4

Correlation of percent swell, liquid limit, and dry uzit

w e i g h t . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Typical construction of moist_re barriers used by the

Colorado Department of Hlghways . . . . . . . . . . . . . . . 74

Membrane section on Kaycee Project showing moisture

buildup under center portion of roadway from

hydrogenesis . . . . . . . . . . . . . . . . . . . . . . . . . 76

Percentage of expansion for various placement conditions

under a 1-psi surcharge . . . . . . . . . . . . . . . . . . . 90

Total uplift press7Jre caused by wetting for various

placement conditions . . . . . . . . . . . . . . . . . . . . . 9

Effects of method of compaction on swell pressure

saturation . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Electrochemical stabilization experiment, Friant-Kern

. . . . . . . . . . . . . . . . . . . . . .anal, California 1

LIST OF TABLES

Tabulation of Potentially Expansive Materials in

the United States 23 24

Typical Values of Free Swell for Co mon Clay

M i n e r a l s . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Cation Exchange Capacities of Cla y Minerals . . . . . . . . . 49

Natural Microscale Mechanisms Causing Volume

Change i n Expansive Soils . . . . . . . . . . . . . . . . . . 5



Indirect Techniques for Identification/Cl~ssification

f Expansive Soils 58

6 D;rect Techniques for Quantitatively Measur:r g Volume

Change f xpan s l v e ells 62

7Metho ds for Volure Change Contrcl Uslng Add lt ~v es 81



CONVERSION FACTCRS, J. S. CUSTOMARY TO METRIC (SI)

UNITS OF MEASUREMENT

U. S. customary mi t s of measurercect used in this report can be con-

verted to metric (SI) units as follows:

Multiply By To Obtain

inches 2.54 centimeters

feet 0 .3048 rneters

rr.iles (U. S. statute) 1.609344 kilometers

sq;are feet 0.092903 square meters

square yards 0 836127k square r,eters

gallons 3. S. liquid) 3.785412 cubic decimeters

pounds (mass) 3.4535924 kilograms

zons (200C lb) 907.185 kilograms

pounds (mass) per square

foot 4.882429 kilograms per square meter

pounds (mass) per cubic f o o ~ 16.0185 kilograms per cubic meter

pounds (force) per square

inch 6894.757 pascals

tons (force) per sqsare foot 95.7606 kllonewtcns per sqcare meter

Fahrenheit degrees 519 Celsius or Kelvin degrees

To obtain Celsius (C) temperature readings from Fahrenheit (F) read-

iggs, use the following formula: 5 / 9 ) ~ 32). To obtain Kelvin

(K) readings, use: 5 / 9 ) ~ 32) 273 .15 .



A REVIEW 0 ENGINEZXKG EXPERIEKCES WITH EXPAKSIVE

SOILS IK HIGHWAY S Y G R X E S

1. Volume change resulting fro- r.3;sture varlazl3r.s expanslve

soil subgrades 1s estxated to cause dmage to streets anc hghways ln

excess of 1.1 bllllon a:nuall;i, parzl~~larly: :he western, central,

2and southeastern United States. A 1972 survey o =he hlghway depart-

nents In the 50 states, 2strlct of Cclurzbla, ano F~erto 3:cc 1nd;cated

that 36 states have expanslve so ls wlth;n tnelr geograph;cal :urlsdlc-

ticn. Zxpansive scils are so area l ly extensive w~zhin parts cf the

Vnited States that alteration of :he highway rcutes zc avcld the mate-

rial is virtually i~possible. In addition, the currently used pro-

cedures for the deslgn and constructlor. of paverents cn expa-slve solls

do cct systematically conslder tke variety of factors and condltlons

which Influence volurre change as evlde-ced by the contlnded occurrence

of warped and cracked pavements i- are-s where expansil~e soils exist.

Thus more accurate methods are needed for identifying, zesting, and

treating expansive clays to improve highway design, ccnstrucr;on, and

xaintenance techniqaes

2 The U. S. Army Engineer Waterways Experiment Stat~on WES)

has recently undertaken a 4-yr study entitled Developrent of Method-

clogy for Prediction and Yininizaticn sf Derrircental Vclume Change of

Expansive Clays in Highway S.~bgracies, ponsored by zhe Federal High-

way Adininistration (FHWA). The stzdy has as its m j 3 r objectives (a)

the eszablishment of physiographic areas of sixilar natural smrces acd

manifestations of swelling behavior, b ) the development of expedient

procedures for identifying expansive clays, c) the developr.ent of

testirg prccedures for qsantitatively [aro.mt aca rate cf vclume

change) describing the behavior of expansive clays, (d) the develop-

ment and evaluation of innovative tecknclogies fcr prevezticn of

detrimental swell under rew and existicg pavements, an- (e) the devel-

opment of recommended desigr. cri~eria , cocstructior. procedcres, anB



speciflcatlons fcr the economical cocstructl on of w ;ave~,ents and

aaintenance or reconstruction of existing pavements oc expansive clays.

All of the majcr objectives involve speclflc probierns w h i ~ h have been

studied by numerous Independent and university researchers and staze

highway agencies. Ir. crder to fully understand th e proble ms an d :he

sol,itions afforded them by t he varlous individua ls acd agen cies ccc-

cerned, a technical literature review acd state highway agency contact

program was undertaker.. 3 e icfcrm;tion for the tezhniczl literature

review was assexbled with tie aid of three ma:or coxpuzer informatio n

retrieval systems; namely, Highway Research Inforxation Service (HRIS)

Kational Techical Icformaticn Service K E S ) , and the Defense Documen-

tation Center DDC) facilities. The state highway ageccy contacts were

limited to those states having a greater distributicn acd f re y en c y of

occurrence of prcblems with expansive soils as specified by the HWA. A

total of fourteen state highway ageccies located in the wstern and cen-

tral United States were coctacted. Suksequect to preliminary discussicns

eleven of these agencies were visited to discuss in detall their prob-

>

lems with expansive s o i ~ s . 9 1 e -1t era ~ur e review and inforsaticn derived

from the aqency contacts provide an updated surncary of engirieericg expe-

rierces with expansive soils in hlghway subgrades The information

.

coilected also provlced qdidance for detailing specific research topics

included in this study. This report represents the results cf the ef-

forts expended on the review cf current literature ccnbined with details

of experiences of various srate highway agencies in c o ~ i n g with the

problem f expansive sol-s.

3 , The prpose of this report is to present a sumrnzry of tech-

nologies used to identify, test, and treat ex pa ~s iv e clays. The report

disccsses the geologic, in era logic physical, and physicochemical

properties of expansive materials. Currently used techriques for iden-

tifying and testing expansive materials are categorized and evaluated

with respect to the applicability to highway engineering. Treatment

techniques usec :n research studies and routine construction practice

are presented acd discussed. State highway agency practices with re-

gard to constrcction guidelines and specifications for highways on



e x p a n s i v e c l a y s a r e p r e s e n t e d . .era: C - c i - L s l o ~ s are drawn w l t h r e -

g a rd t o s c c ce s s o f te hniques c l s c , ~ s s e d .



degrees of expansion due to the presence of actlve clay ~lcerals In

the material.

7 The actlve clay mlr.erals lzclude ncn=rror,llcnlte, mlxez-layer

co ~blratlons of r-ontmorl1lon:te and zther clayaminerals, r ;rider scrxe

cond1t:ons c h l o r i t e s ard verrnlculites. Ka cl ln lt es and i l l i t s are usu-

ally nct considered actlve alzhc,;gh thcy may ccntr;octe tc expansive

properties lf suff;clent arcunzs are presert 1r the rater;al. The

nlneraloglcal aspects of the prsklem are discussed In rcre cetall ~naer

Xireralogy. Expansiveness caused by ~ ln er al s other t h m montmoril-

lonite is discussed under Yineralogy. I? gexra l, h e distrlDuticn of

expansive materials is contrclled Cy thcse ccnditiors w'c;ck facilitate

the fcrma-tion, accunl;lat;on, ana preservatlcn of mcrtmcr;llo~~:e.

Format or.

8 The fol1ow:ng cond:t:cns, e-ther :nclv:dually or In corrbl-

natlon, lead to the fo rma t~ on cr crlgl? of expa7.s17<e xaterlals: a )

weathering, (b) aiagenetic alteration cf preexisting . e l s and

(c) nydrothermal alteration. Of these ccnditicns, weatherlng and

diagenesis are probably the more lmpcrtan:. o r exa~ple:

2 Montcorillonite will fcrr from :he weathering of vol-c a n i c ash or ~ r i m a r y ilicate minerals such as feld-

spars, pyroxenes, cr arrphibcles ur.der those conjitions

which result in che rezexticn cf bases a?.d sllica within

the weathering syste?,. Th es e co nd it io ns are ,promoted

by insufficient leaching of :he scil prcflle by downward

movicg water due tc low permeability, and excessive

evapcration in regicr>s of aridlty.

b The distincticn between diagenesis and wea~hering,

althcugh somewhat vague, 1s between alteraticn which

occurs at depch (dlaqenesis) or within :he top few feet

of the soil profile (wea~heri?g). 20th involve sirrilar

chern;cal and physical crccesses acd bcrh cccur in and

as a result cf gro.2-dwarer. The diage?.etic fornation

cf monxorillonite res:lts fron the de7J:tr;fica:ion of

volcanic ash part:cles or shards which have ac cmulated

as sedirents :n sedimen~ary casir~s. ?he shards are more

cr less amorpho,;~, range in size fror, sand z clay, and

are chemically quize umt ab ie. The instabillzy and rhe

composition, which is 3fte: intermediate between rhyollte

ard basalt and thus rich. ;n silica as xell as bases, usu-

ally lead to tke formarion of n0ntmor:llocite. The shards

may occur intermixed with cther land- o r basin-derived



sediments or as relatively psre discrete layers several

feet tk-ick. Discrete layers of volcanic ash which have

altered to rnontmorillonize are termed ber.tonite.

Accumulation

9, Sedimentary accumulations of montmorillcnite originate in

those areas which receive land-derived nontmcrillonite anclcr volcanic

ash. sediments. The areas must either lie near or be stream connected

to land areas where montmoril1on:te was formed by weathering andor 1:e

sufficiently near volcanic areas suck. :hat.volcanic ash sediments can be

carried either in the air or by streams c the areas of accumulaticn.

;O The energy conditions at the depositiocal areas must be

conducive to the deposition and accumulaticn o essentially silt- and

clay-size particles. These ccn6itions may exist in several types of

sedinentary environments. The principal controlling conditions are

relatively flat gradients and mimu mum wave energies. The following

tabulation shows typical sedinectary environments suitable for the

accunulaticn of volcanic ash and montmorillonite clay:

Sedimentary Snvircnments

Marine Mixed Continental

Neritic Delta ic Lacustrine

Bathyl

Abyssal

Floodplain

Bolson p laya)

11 The pertinent characteristics of the environments listed in

the tabulation relate to the size and shape of the sedimentary deposit.

The marine environments, particularly the bathyl ahd abyssa l , may be

a r e a l l y extensive, while the coctinental enviro~ments are limited

a re a l ly and nay even consist of isolated deposits.

Preservation

12 The preservation of sedimentary deposits of montmor:llonite

involves all those factors which may affect the material from the time

that it was depcsited unt;l it is exposed at the earth s surface;

basically, this falls within the lixits cf diagenesis. The diagenetic

factors that nay affect a sedimentary deposit consist cf the following:

(a) deep burial resulting in high lithostatic overburden) pressure,



( b ) t em p er at ur e x c r e a s e s r e s u l t q frcrr, :he b c r l a l , c ) c n e m c a i e f f e c t s

p r od ~ c ed by po re s3 lu :i ons , ar.d d ) t m e expcsed t o h g c p r e ss u r es .

.- 2 'h ese d l a gen e t i c f& c: cr s tt.a : l ave cc - i r l bu t e c t he f c r -

mat lon of mo ntm crl l lon l te ky tn e de-~ l : r l f :c? t : sn cf vo- canlc ?sh may.

wi h s u f f i c i e n t tim e and B u r i al c l ~ l a a t e l y - ea 2 t c :he d e s t r , ~ c : l c c o f. .

t h e min era l , whether prodnced s r:gl :a --y f r oc ash c r by weatkerlng of

vo lca nic ash . Thus the o ld er rocks (Fa leo zc i c a r,d o l de r) ex21bl t co:-

s i d e r a b l y l e s s r n o n tm o r il lo n i te t h a n I l e ss z c ic - o r C e n o z o i c - a ~ e r o c k s .

. . . .

9 e s e o ld e r rc ck s c cn si s: n z i n l y c f n c r , s ~ e -- 1 n g : - - l t e a z t l c r i t e.

c l ay m i n e r a ls . I t i s b e l ie v e d t k t u i t h t n e and bu r l; - t r: e x o r, tr n or ll -

l o n i t e s t r u c t u r e i s a l t e r e d a n3 ar i l l l t e l i k e s t r ~ c t u r e i s s r c iu c e d .

A l so , t ne Paleozoic rocks ex h l r l t m x ed - l ay e r zxrb:n?; lccs c f n c ~ t r c c r l l -

lo n l t e and ot he r c-ay rv ne ra ls wh::h ar e the r e s c l t 3f 3:aGenesls.

. .4 F h y s i c a l a n d c h e x i c z l w e a t h e r i ~ g of a r g l - : 3 c e c ; s s e d i ~ e r ~ t s

a n d r o c k s r e s u l t s i n changes i t h e properties cf t )ese m t e r l a l s which

may a f f e c t t h e l r expansiveness Tne zore of weathering and proper ty

alteration nay vary i n deptn f ro x a few ;? .ekes to :ens s f fe e t . he

a c t u a l thickness of the weathering z n x 1 s g e c e r a l l y de pe cd en : u p o ~

climate and topo grap hy. The we atn erl cg pr oce sse s wn:ch play a f fe c t vo l -. .

, m e change a re d i s cus sed i n t he fo- -3wicg pa rag rap?.^.

1 5 P h y s i i ~ l w e a ~ h e r l n q . The t x c r , s s t i r c p o r t a r t physical

w e a t h e r i n g p r o c e s s e s a r e s t r e s s r e l e a s e 5 u e t; p a s t c r Z u r r e n t o v e r -

b ur de n rem oval an 8 c y c l i c w er tl ng and ~ r y l ~ q . t r e s s : ? le as e i s s i a p l y. .

p a r t l c l e r eo r : en ta t l on r e su l t: n: from re rr cva l i f ex : srn i- - c a a s .

C y c l l c w e t t l n g a n d d r y l n g 1s a phys icochemica l p r o c e s s n t n a t w a t e r

:s ad so rbed on c l a y r c l ce ra l s ~ r f a c e s d u r l ~ g we: pe r i o ds a rA d 1s rem oved

by evap c ra t l o n du r l c g d ry pe r l c ds . ?he p rec es s ccc t r : ~ u ; e s t o :he

ceveiopm en : of c r acks and nay d l s r ~ p t :he nr9an:zat :on cf dc ub le- lay er

water on and I n t h e excandab-? c -ay m l r er a l s . ? t.e ex-en t t 3 ht. lch

w e t t l n g a nd d r y l n q a f f e c t v o l u r ~ e z h a q e d e c e r d s Jpon t - e n sit?

na t u re o f t he r r . a t e r l a i s and t he t ype c f m l ne ra l s preset: F or s ed i xen t s

t k i s p r o c e s s may a c t u a l l ; ~ d e c r e a s e t h e p t e s t i a l v3lum e c k,ange by 31s-

r cp t i ng cccb l e - l aye r w a re r . F i rg i l l a ceous rocks , how eve r , m?y e x h i b l t



an increase in volune change since zhe process contributes to breaking

dow?. the rock by cracking and the acliissicr of water. Generally,

weathering of this type resulEs in an increase in plasticity for the

argillaceous rock.

16 Chemical weathering. The chemical weatheri~g processes are

those wkich produce a change i?. the chemical constituency of the rrate-

rial. The changes may be small, such as the exchange cf i~terlayer

catio~s on clay minerals, or large, involving the destruction of min-

eral constituents and the fcrnat:on of new mineral types. Those

chenical weathering processes believed to be imporcart in this study

are as follows:

a Cazion exchange. Cation exchange will occur in the zone

of weathering when a chemical energy gradient exists

between the groundwater and the clay ~ine rals . The

gradient, if present, tends to affect a replacement of

the cations on clay minerals b y cations in the ground-

water. The existence of the energy gradiect is Be-

pendent upon size of, charge ef, and co-cen~ration C l f

ferences between the ions in the groundwater and those

on c1 ay minerals. The replacing power of the common

cations generally decreases in zhe following order:

magnesi.;m, calcium, potassicm, and sodium. This means

that other parav,eters being eqaal, magnesium will re-

place calciurm easier than calcium will replace mag-

nesiux. The replacement may be partFally a function of

clay mineral type and therefcre the replacement series

may not hold for all cases. A case in point is potas-

sium which on some clays is tightly bonded and is removed

with difficulty. Th e typ e cation in th e grou ndwater an d

on the clay minerals in argillaceous rocks or sediment

may be quite variab:Le The cations present in groundwater

are dependent generally upon present climate. Sodium is

ccmmonly associated with arid climates whereas calcium and

magnesium tend to predominate under wetter conditions;

furthermore, the arid climates usually exhibit higher

cation concentra~ion in groundwater than. the wetter cli-mates. The cations commonly present on nontmorillonite

are calcium, magnesium, and sodiun. These may occur in

variable proportions but generally one cation will pre-

dominate. The type of cation is determined by the chem-

istry of the erLvironnent of fornation, chemistry of parent

material, an d the cher?.ical effects produce d d u r ~ n g ia-

genesis. Often, but ~ o t xcl~~sively, montmorillonite

derived from volcanic ash devitrification in marine envi-

ronments carries sodium, whe reas montmor illonit e of



com bined expe r iences o f geo log i s t sand e n ~ in e e r s w i th in the So i l s and

Fave~.ents Laboratory, WES.

19 The discussior, of expans ive materials has been categorize d

by physiographic province. Figure 1 illustrates the first-order

physlographlc provinces that were selected to form tne basls of the

pre sen tat lo2. The are al cistrlbu::oc and deg ree of expanslveness of

e x p an s iv e m a t e r i a l s w i t h i n t h e U n it ed S ~ a t e s a r e shown i n F i g u re s 2 6

acd described ir Table 1 . The in fo rm a t ion pe r t a in i ng to t h e physio

graphic provinces is preliminary 2 s presented in this report.

cietails acd di sc ~s si on s of the provinces will be presented in

sequent report.

2 3 The distribution ci expansive materials shown in

Further

a sub-

2 6 kas been categorized on two bases: a ) degree of expanslveness and

(b) expected frequency cf ocw rr en ce of expanslve naterlals. The bases

for categorlzatlcn are q~ al lt at lv e. Three majcr sources of 1nformat;on

fcrmed the bases for classlfica tlonal dec;slons. Flrstly, the repor ted

ccccrrences of expanslve razerlais as lnalcated In published literature

or otker sources of data which revealed actual problems or fallures

d to expansive nate rlsls. 7he se sources were not necessarl:y

limited to hlghway subgrades. Secondly, inaterlals maps provlded scm-

nar,es of l ll us tr ~t ed earth materlal properties pertinent zc thls

study. Reference 10 was used to delineate areas of argil-aceous

materials, and the sclls surveys were used t o s u b s t a r . t l a t e s u s p e c t e d

cccurrences of expanslve materials. Ilhlrd, geolcglc naps and crcss

s e c t i o n s w e r e u s e c t o i d e n t i f y a n d d e l i n e a t e a r e a s o f rgill ce ous

rocks and se dl me ~t s whlch were belleves to possess expanslve

1 2 - 2 0properties.

2 1 . These zhree general scurces were combined to produce four

mapping categories tkat reflect the degree of expanslveness and ex-

pected frequency of occurrefice. ?he four categories are as foll ows:

1 imy expansive and or high frequency of

occurrence.

2 . Medium. Moderately expansive and/or moderate frequencyof occurrecce.



Figure 1 Firs t o rder phys iograph ic p rov inces w hin th e cont ir iental United St ates



llap compiled by D Patrack H K Wmds and Freder~ck . Smtth.

Engincelmg Geology and Rock M e c h a n a D w s ~ o n . 5. Army

Enplneer Waterways Ewer~menl tat~on.Vtcksburg Ms.



M a p c o m p li e d b y 0 . M P a t r ~ c k H . K. Woods and Fredet lck L S m ~ t h .E n g ~ n e e r n g e o l o g y and Rock Mechanics O v i s ~ o n . 5. ArmyE n g ~ n e e rWa te r way s E x p e r ~m e n t ta t i o n V ~c k r b u r g Ms



A: X I t , X \ A K

> . ? A . Y ? , s c , Y ; , , Y

A : . CA : I ? SC . A .

7:L i ~ c p n : f s ~ c u k r . 3 . - r -x p c n s ; v ca : c u d rock :~ L - F . -rr .. . ; . i c 1

I - I L I R :

LA w ?;; Y

La v, A? w

L4 WE 7

LA u



i. Volcanic areas c on si s~ in g mainly of extruded basalts

and kindred rocks Ray also contair tuffs and volca~ic

ash depcsits which have devitrified acd altered to

montmorillonite.

A Areas along the glaciated bcucdary may have such a thic

ccver c f drlft that the exp nsive character of the

materials under the drift n y predominate.



i o n s i n sixfold coordination with hydroxyl or oxygen. The silica

tetrahedral layer has siliccn ions in fcurfold coordination with oxyge?.

These three coEfiguratior.s ray be further subdivided on the basis of

ionlc substitutions within both structxral layers, e.g., aluminun for

silic ~n, and iron or magnesium for aluminum. Clay minerals which have

a1umin.m or trivalent ions in the octahedral layers are termed di-

octahedral, wherea s those whic h contain magnesi um or d i v a l e n t ions are

termej trioctahedral.

26 The clay minerals are classified in che following fashion:

a. Two-layer c lays consist of one silica tetrahedral

layer bo?ded to one aluminum octahedral layer. Kaoli-

nite is the common mineral, in which the octahedrallayer contaics mainly alur8izum; serpentine consists of

a r.agnesium-rich octahedral layer.

b Three-layer clays have one octahedral layer bonded

between two tetrahedral layers; examples cf this type

are illite, vermiculite, and montmorillonite. Tine

term moztmorillonite, as used here, bdicates the

dioctahedral nagnesium bearing member of the smectite

group. These ainerals may occur as di- or

trioctahedral.

c . Mixed-layer clays consist of interstratifications

of the two- acd three-layer clay minerals previously

described. The mixing may be regular or random.

Examples of regular mixing include chlorite, a three-

layer plus octahedral l ayer repetition. Another

common reqtilar nixed-layer clay is montmcrillonite-

chlorite. The randomly mixed-layer clays consist of

any of xany possible ccmbinations.

The structural configurations of these three classes of clay minerals

are shown in Figure 7.

27 The small grain size and resulting large surface area are

due to the clay nineral s origin by weathericg or diagenetic alteration

of preexisting minerals. In these processes alteratior, beglns at very

small centers or points on the grain surfaces and eventually spreads

throughout the grain. The resultant alteration product may have

crystallographic continuity throughout the surface but lacks physical

continuity. Thus the size of the clay rineral is inherited from the

size of the lnitial weathering center.



C A T E G O R Y

2 L AY E R CL AY MINE RAL S

3 L AY E R CL AY MINE RAL S

MIX E D L AY E R CL AY

MINERALS:

R E G U L A R

THI CKN ESS CON FIGU RATI ON

O C T A H E D R A L

T E T R A H E D R A L

r - R T E T R A H E D R A L

10 1 A O C T A H E D R A L

/ T E T R A H E D R A L

f a C T A H E D R A L


O C T A H E D R A L


MONT MORIL L ONIT E

C H L O R I T E

MONT MORIL L ONIT E

RANDOM

V A R I A B L E

I C H L O R I T E

MONT MORIL L ONIT E

C H L O R I T E

C H L O R I T E

M O N T M O R I L L O N I T E

MONT MORIL L ONIT E

I L L l T E

V E R M I C U L I T E

M O N T M O R I L L O N I T E

C H L O R I T E

I N T E R L A Y E R E D M O N T M O R I L L O N I T E

AND CHL ORIT E

MIX E D L AY E R MONT MOR IL L ONIT E

AND CHL ORIT E

F i g u r e 7 T y p i c a l s t r uc t u rd 1 c o r l f i y u r a ti o n s o f c l a y m i n e r a l s

... ... ... . . ... 7 . . .. . .



the tetrahedral layer and is thus tightly bonded. These

characteristics effectively preclsde the admissicn cf

significant amouncs of water between the cnit layers.

Clay mineral-water interaction2l-23 27

29. The electrical charges exhibited by cl y mineral ,grains

are caused by the following: (a) charge deficiencies d ~ e o lcnlc

sukstitution within the lattice, (b) broken bonds at grain edges,

c ) imperfeczions withln the lattice, and i d the pclar nature of lcns

exposed at clay surfaces. '21s last cause incicdes :he regazlve elec-,

trical 'charge of oxygen in the silicon tetrahedral layer ard a pos::lve

char.ge due to the hydroxyl porticn ir. the aluminum octahedral layer.

lattice lmperfectlons ard arcken bcnds may produce elther a posltlve

o r neqative charge, whereas ionic substituticn cs,:ally resclts in a

cegative charge

3 0 The magcltude ard location cf these electrical charges are

different for the varlous clay minerals and are fundamental in ex-

plaining the ability of some minerals to imbibe significantly m3re

water than cthers. W a ~ e r asscclated w the clay rrlnerals conslsts

of three types:

2 Eydroxyi cr b o x d water. This water forms a part of

the octahedral layer anc cannot be removed ky heatlng

at temperatures below 400°C for most clay rnir,erals.

b Interlayer water. :h;s 1s double-layer water w -.lch

occurs between clay rnlneral surfaces In some clays.

1 1s gradually removed by heating ~p to 150 200°C.

c Fore water. 3 1 s water occurs In the open spaces

between gralrs and also constltufes the more tlghtly

bocnd dcuble-layer water on grain surfaces. 9.1s. .

water 1s essentla--y removed by drylng at room temper-

atcres and completely renoved by heatlng aapproximately 100°C.

31. The clay rnlnerals which exhlbli a?preclable expanslcn cr

shrinkage are called expansive clay minerals ar.d inclc de montmoril

icnlte, vermiccllte, chlorite, and mixed-layer cornbl~ations of these

minerais with each other or with other zlay riner als. Halloysite, t -.e

tubular, hydrous member of the k a ol i ni ~e group may aiso exhibit expan-

sive properties . Kaolinite and i l l i t e genera l ly do not exhibi t volume



change tc 'the extent of acntxorillanite, vermicclite, : chlarite a?.C

are called nonswel1:ng clay i e r a Table2

lists sone recresenza-

tive free swell data f3r the comm on clay r.inerals.

3 2 The distizc:ior.s betwee:. swellizg x,c nonswelling clays and

between interlayer and pore water ar e illustrated in Flgure 8. The

clay particles are represented in the defl3cculareB state. The lower

diagram shows a three-layer swelling clay s ~ c h s ver~iculi:e or mont

morillcnite with water in interlayer a?.d pcre areas, while the upper

diagram shows a n3nswellir.g clay s ~ c h s illite :iitl-. s~~rrounding cre

water.

33. The docble-layer water adscrbed 'cetweer. clay layers in

expardable clays and the water edscrbed o the surfaces 3f other clays

possess properties which are somewhat different fro? thcse sf the waEer

., pore spaces. The double-layer water exhibics a cert3in degree cf

crystallinity which is n3t a cro?erry cf the core water. The crystal-

linity is greates: adjacent to the clay mineral itself and decreases

0,~tward from the rcineral s.drface. The thickness of =he criented water

and whether the decrease in crystallizity is graoual : abr.~pt acpears

tc be dependent c y n the nature cf the clay mineral c d the type

cation present. Yontrnoril1o:ite e~l-~ikizs larger thickcesses sf

oriented water than che cther clay mir.erals. Those ca tion s whic h en

hance'the orie~tation are thcse whose hydrated cr nochyBrated size can

be accormodatea within the water s:ructure, f r example, sadiurr ar.d

lithium fit, whereas calciun and mgnesium Bo cot.

Physical Fropertles

34 Physical prcpercies 3f expazsive scils which detersice the

behavioral characteristics of the material have Beer. er.un.erated and

defined n a nultitade of pub1icat;sns. Ic rr,any cases, a:te:pts have

beec made to isclate the individzal pr2perties and explain the behavicr

on the basis of a single prcperty or a coxbiratian 3f single property

contribztions. However, in b o ~ h he laborztory and field si~uaticns,

the actual behavior is a function of ccrrbinaticns andinterrelztionships



particles which m y be considered ccllcid. In the corc?etely dispersed,

deflocculated c o n d i t o n sizes on the crder of a few ,..'t.1- cells m y be

present. Cn zhe other hand, kaolizlte xay occar as rather large par-

ticles which rnay be of a fine silt size. Chlcrlze, verx~cullte,

illite, anj nixed-layer clays are generally intermediate size be-

tween montmorillonize ard kaolir.ite. In sumrary, clay mineral size

and specific surface area are inversely proporzioral s ~ c h t h ~ t surface

area increases with decreasing mineral partlcle size fray, kaolinite to

ncntrnorillonite.

- . 28,41,43-49; c Cry density. The dry densizy is Z ixportanc

factor in determining the rnaqnitude of vclaxe change. The swell or

swelling pressure cf an expansive soil i-creases with i-creasing Cry den-

sity for constant moistcre ccntent. The reascn, simcly stated, is that

higher densities result ir clcser carticle spacing, tk.erefcre causing

greater particle, izteraction. This particle :zteracz:or., or mcre

precisely, double-layer water interacticn, resxl~s in higher osmo~ic

reculsive forces and a greater vol.xe chanqe. This holds trce for both

rexolded and unjis~xrbed materials. Anozher irrportant and scmewhat

indirect influence of dry density . volume change is ~ t s nzerrelaticn-

ships with some of the cther ir~trinsic factzrs. Fcr example, the dry

density of a xaterial, particularly compaczed scils, will influence :he

soil fabric (interparticle arrangezent) Details cf the kf lu ence have

been described by Pacey and Seed and Chan5

Flgure 9. Fcr a givec csmpactlon effcrt anc

contents, a less o rl e~t ed fabrlc 1s cctalnes.

increases, the soil fabric is m r e oriented.

i 9Scil fabrlc. 2 7 3 1 3 3 4 1 4 3 5 0 5 1

an2 are depicted

at lsw ifiitial misture

As 'he ~cisture conzent

The soil fabric refers tc

:he crientation or arrangemezt in space zf the cs?.stituen: particles.

In the case of ;rgillaceous seckmerts and racks, ,he fabric consists

of the arrangements of zk.e plaze1ik.e clay ~~inerals itk e6ch other and

with the n o n c l a y cm,ponents. W e type cf clay ~ ~i ne ra l rrangement

presen- will ir fl u e n c e th e amsun: anci t c m e ieqrse the dire tion

(lateral or vertical) cf vslune chanqe exhibited by an excansive mace-

rial. The f a b r i c s e x h i b i ~ e d by a r g i l l a c e o s s e d i m e n t s a n d rocks a r e



MOLDING WATER CONTENT.

a. BOSTON BLUE CLAYFROM REFERENCE 50)

20 22 24 26 28 3 32 34

MOLDING WATER CONTENT,

b. COMPACTED SAMPLES OFK OLINITE (FROM REFERENCE 51)

Figure 9 Molding water content versus dry density and particle orientation



cations i .e. soluble salts, tend to reduce the magnitude of volume

change of an expansive scil. On the other hand, pore fluicis with low

icnic concentraticns may actually leach. out the'charge balancing cations

and cerenting agents and render the soil more susceptible to volume

chanqe

4 3 Confinement. 28 29331-33y445 54-59 The application of a sur-

charge or external load to an expansive material will obviously re uce

the amount of volume change that is likely to occur. In the laboratory

measurement of swelling pressure, less than 1 percer.t deformation cf

the testing device may result in large errors in nagnitude of the

swelling pressure. For In situ conditions, the presence of a layer of

nonexpansive overburden raterial may eliminate the probabil~ty of damage

frorr, the underlying expansive material. t may be noted that confine-

mert has its greatest influence on expansive soils in a stress-relateci

sense (swelling pressure) The greater the conflnernent, the greater

the stress and che smaller the deforrration. Generally, the load applied

by a pavement is far less than that required to maintain minimal de-

formation; therefore, problems with expansive clays in highway subgracies

are more related to deformation.

44. Time, 8,32 ,33 ,44 ,55 ,57-59 The influence of time on v3lcrr.e

change is another interrelated property which has its major impact on

the rate at which expansion occurs. The time to the first occurrence

of volume change and the rate of expansion are functions of the pene-

ability of the scil and tke availability of water. Expansion occurs as

soon as moisture is made available and continues until En equilibrium

condition is reached with regard to the source cf water.or the hydra-

tion of the clay minerals.

4 5 Permeability.54,57360-62

As indicated in the previous

discussion on the influence of time oc volume change, the permeability

plays an important role in the time rate of volcme change. The perme-

ability is a function of the initial moisture content, dry density, and

soil fabric. For compacted soils, the permeability is greater at the

lower noisture concents and dry densities and decreases to s o w rela-

tively constant value at about the optirrum moisture content. Above



maxmurn dry dens l:y 1s tn a t t n e x : i s available f c r r c l s t 3 : r e m ove ren t

a r e a t a m n l r u m be c au s e 3f t h e c l ; s e particle sFac:ng. Above op:lr url,

th e in te r a c t i c n cf the dou ble-la l ler water al s 3 rr,in:rr,:zes :he vc ids

necessary for mcl s t c re r rcvenen: . 3 :n s i c3 exF ars:.de s o i l s , t he

p e r r c e a b i l i ~ y i s normal ly enhanced b y s ~ c h s t r x t c r a l ' 5 i s c o r L t i n , ~ i t i e s

-

a s : l s s u r e s , f r a c t u r e s , and desiccation z rac : i s .

46. Temperature.29 44 63 64

-he 1nf l . i en ce c f t e cpe raI ure :s

p r l na r ; -y l i rn i t e5 t o i:s e f f e c t on t he viscosity an specific 3 r a v i t y

c f t h e a d s o rb e 5 w a t e r . I c c r e z s e s ;r t e ~ y e ~ a t u r eend t. depress :hedoub l e - l aye r w a t e r , w h i le t ernpe racn re dec rea se s r e s u l t I n doub l e - i zye r

e x p a s i o n . Of r ,c re i mp or an ce i s t he influence cf texF eraL IJre o? :he.

rnovenent of moi s csre , bo th vapor aca - lqu : i, as re su l t s f t hermal

g r a d i e n t s w i t h l r t h e sol^ n a s s . K h te r v a c z r a t 3 f , lqkser teniperzture

w i n i g r a t e t o w z r d a c o o l e r a r e a I n an e f f o r t t c e q u z l l z e t h e t h e rm a l

energy i n t he sy s t em . L i qci 'd m 3 i s tl ;r e x svem e?c by t h e r a t l g r a d i e n ~ s

occu r s a s a che r r , c c sm o t i c film a n a l c a s c s t 3 e l e c t r o c s m o t : c f l o h .

men:s and r o ck s i n c l u d e s t h a s e f e h t u r e s r d l s c c c z i n ~ ~ i t l e s : ~ , l z hop-

t r ib u te to the nochonogenei:y c f :he Ka :er l s l . 2f mast ccncern wi th

r e s p e c + t o v o l , ~ r , e c ha ng e a r e f r a c t u r e z o ne s , f i s s u r e s , c r t c k s , and

micro and ~ a c r o f a u l t s . 9 e s t r u c ~ u r a l d i s c ~ n t i ~ c i t l e s exh ib i :

v a r i a b l e c r i e n t a r i c n s i n s pa ce and c r l g i c a t e a s a r i s ' l l t cf s t r e s s c cp -

d i t i o n s which have develcped i? t he n a ~ c r a l s e d i ~ ~ e r .c s r rcck m s s . _ ne

c c n d i t i o n s vh ic k c o n t r i b u t e t: frac:cri:g a d fz ulc :n g ~ r c l c d e d e s i c -

c a t i o n , s t r e s s r e l e as e dc ri ng ~ c l 3 a d i r . g ~ nd p o ss ib ly t e c t s n i c l o a d i ~ g .

? h e s t r u c t u r e s , i f r 3 t cemenzed , pr cv i i e avenues fo r :he Lnt roductlo ;.. .of m o i s t ~ r e i c t o t h e e xp an si ~: e s c l - . -:e ir o c c u rr e n c e i s g e r e r a - - y c 3n -

c e n t r a t e d i n th e zp pe r la y e r s w::h:r. a fe v f e e t cf :he s .;r fa ce . ow-

e v e r, l f t h e up pe r r a t e r l a l l s r e a c x d , r.ew s t r o c t c r e s wlll a p p e a r i n

th e overbur den press: ; re was redu,ce2. Tigure 2 s ~ ~ c ~ sraiiogr ;3.hs8



is available throughout the layer. Variations in thickness of the layer

will result in variaticns of the magnitjides of volum cha~ge, or more

precisely, differential volume change. Ciffereritial expansion, lust

like differential settlerent, is the major problem with regard to dam-

age to structures. The depth of the layer below gro,xd surface may

actually be a positive influence since the deeper the material, the

greater the confinemnt cn the expansive soil. In addition, the deeper

the ateri rial the less likely the expansive soil will be affected by

seasonal rnoistijre varl a t ions. The presence cf lenses or layers of

higher perceability will provide avenues for the ingressicn of water.

In facz, a ass of scil which requires that mcisture aust move fror, its

extrercities will take rcch longer to develop its total volume becsuse as

the mcist.~re is introduce5 and expacsion occurs, the aven:es of rnaiszure

transfer are sonewhat decreased. Lenses or layers of mcre porous mate-

rial withi: the mass tezd to overskdow this advantage since they are a

relctively contin~oas socrce of moisture.

5 5 Depth of desiccaticn.30,3l, 9,48,55-57365 66 The

desiccatron is xportant to the magnitude and rate of volurne change.

The thickness of the desiccated layer represents the material i which

a moisture deficiency exists. I addition, the layer nornally has a

large number of avenues (desiccat:cn cracks) available for movement of

noisture irto the material. The depth of desiccation is generally de-

fined as :he depth to which a differezce exists between the equillbzium

noisture conte-t profile resulti7g from minimal loss of moiszure to the

atmospkre (evapcratior:) and the amhien: soil ~ o i s ~ u r e ontenz profile

in which the soil straturn is in equilibrium with its environmect

(climate and overburden). In simpler terms, the depth of desiccation

is that depth to wkich evaporation influences are reflected in tke soil

x3isture content profile. Generally, the hotter and drier the climate,

the greater the depth of desiccation. Changes i the overbur en condi-

tions and the proximity of :he grcundwater table have an inportant 19

fluence on the depth of 5esiccat:on. T date, no absol.jte method exists

for definina the value.

56. ~ e c z h of seasor,al rnoisture variation.30 ,39 ,43 ,55 ,57 ,62 ,75-78



type of material i n -,he s e c t io r , . The prcblerr . C OL ~ : he e l l x l na t ed by

r ; o~v iq t he c :t ches as f a r away as poss ib le f r m th e h ighway and as s ur in g

c r cpe r g r ad i ec t s s o t ha t t he s u r f ace w a t e r can be r em cved .

59 Modes of moiszure t ransfer . 2 9 9 4 3 In s i t ; s o l l s a r e ge n-.

e r a l l y c o c si d e re d t o be a th r ee -p h as e s ys te m ; t h a t i s , s c l - p a r t i c l e s ,

>

water , a a I c s cch ys tem i c i s pos s i b l e f o r w a t e r t o m cve

e i t h e r n t he l i qu i d phase c r vapc r phas e , o r a ccnb i na t i cc c f bo r h .

For water t 3 nove n e i t h e r p h a se , t h e r e m ust be a d r i v i n g f c r c e w i t h in

t h e system t o p ro v i d e a r,o de o f t r a n s f e r . T he se r o d e s a r e g e n e r a l l y

d e s c r ib e d 2 s g r a v i t y , c a p i ; l a r i t y , an d : h e r m l g r a d i e n t s . G r a v i t a-. . .

t i o na l rr,ovem ent c f w a t e r i s p r i x a r l - y - i m i t ed t o t i e - ; qu id phas e nw h i c h d i f f e r e n t i a l 3 e a d s will c au se th e m ~ i s t u r e t~ s eek an equ i l i b -

,

riurr. c o fi d it io n . Exam ples of g r a ~ i t a t i o ~ a lcvemect are s imple :nr ;_ t r a-. . .

t i o n c f s u r f ac e w a t e r , l a t e r a l s eepage from ava l - ZD - e s o ;r ces, and t he

cpward mcvemen: of the ground water ta b l e . Tr an sf er of wa ter by c a p i l -

larity is a g a i n p r i m a r i l y l i m i t e d t o t h e l i q u i d p h a s e . :he n a t u r e of

c l ay s o i l s , w hich pos s es s ex t r e r e l y f i n e por e open ir .g s , and t he s u r f a ce

t e ~ s i c n e f f e c t s of w a te r c c n b in e t o im bib e m i s t u r e from t h e g rc un d-. .

b ia te r l e ve l . The zone o f cap l - - a r y r i s e i s t he l ay e r of m a t e r i a l d i -

r e c t l y a b o v e t h e s u b m e r g e d m a t e r i a l w i t k i n t h e i n f l a e n c e of t h e ground

wazer table and can extend upward from :he groundwater t a b l e f o r c o n s i d -

e r a b l e d i s t a n c e s d ep en di ng oc t h e e f f e c t i v e p o re s i z e s of t h e s c i l . I f

pave rt ec ts a r e cons t r 1~c t ed wl:hin t h i s zone c f c ap i l l a r y r i s e , t hen a

coc ti nco, ;s s ou r ce of w a t e r i s av a i l ab l e t o t he expans i ve s- bq r ade .

M o is tu re r r a n s f e r a s a r e s u l t o f t he r m a l q r a c i e n t s i s a p p l i c z b l e t o

both the l lq a- d acd vapcr phases , wi th the vapcr phase predominant ..

Tke p l ace r . ec t of a s t r uc ' cu r e eve r an expans i ve s o l - x i l l a l t e r i z s

am bien t t em per a t u re cond i t i ons ge ne r a l l y dec r eas i ng -,he subgrade tern-

pe r a t u r e . W ate r vapor a t a h i ghe r t em per a t 3 re n t he s u r r ound i ng a r e2. .

~ i ; - i g r a t e t o t h e c o o l e r a r e a l n a n e f f c r t t o e q u a l i z e t h e t h e r m a l

ene r g i e s o f t he s ys t em . A s t h e vapor moves i n t o t he coo l e r a r ea , i t

. .wl-l condense and form a sol ;rce of f re e wa ter . is i s t he b a s i s

hydr ogenes i s a s des c r i bed by Brakey.80 81

The movemect 3f l i q c i d wate r

by t he r r ca l g r ad i en t s cccu r s a s a t he r xoos m ot i c f i l m a r . d 1 s s l n i l a r nn a t ~ r e t o e l e c t r c o s n o ti c f lo w.

6



T a b l e 4

N a tu ra l M ic ro sc a l e Me c h an i sm s C a u s in q V olum e Ch a ng e i n Ex p a n s iv e S o i l s

Me c h a n i sm Ex p la n a t - i o n i n f l u e n c e o n V o lu m e C h a nq e

O s m o t ic r e p u l s i o n P r e s s u r e g r d d i e n t s d e v e l o p e d i n t h e d o u b l e - l a y e r T he d o u b l e - l a y e r b o u n d a r y a c t s a s a n o s m o t i c mem-

w a te r d u e t o v a r i a t i o n s i n t .h e i o n i c c o n c e n t r a - b ran e when ex po se d t o an e xt e rn al so u rc e of f r e e

Lion i n t h e d o u b l e l a y e r . T he g r e a t e s t c o nc en - w a t e r; t h a t i s , it t r i es to draw the water in to

t r a t i o n o c c u r s n e a r t h e c ld y p a r t i c l e a n d d e c re a se s t h e d o ub le l a y e r t o r ed uc e t h e i o n i c c o n c en t ra -

outward t.o the boun hry of t.he double layer tio n.. The res ult i s an increase in the double-

layer water volume and the deve lop rlt. of repul-s i v e l o r c e s b e tw e en i n t e r a c t l n q d o u b l e l a y e r s .

The net resu lt i s an ircred se in the volime of

the so11 mass

C l a y p a r t i c l e Clay part ic les possess a net negatlve charqe or, the lr In an effo rt t o sa t i s fy t h e ch arge h a l a n c e , t h e

a t t . r a c t . i o n s u r f a c e s an d ed g e s w h i ch r e s u l t i n a t t r a c t i v e volume of water in the double layer w i l l con-i f

f o r c e s l o r v a r i o u s c a t i o n s and i r : pa rt ic ul ar fo r t inue to i rc rease ~ :nt . i i a volume change of t.he

dipol r molec~iies such as water . This mkes up the s o i l mass occ urs

m a j or " k , o ld i n g " f o r c e f o r t h e d o c b l e - l a y e r w a t e r

C a tl o r; h y d r a t i o ~ T he p h y s l c a i k . y dr a ti o n of c a .l on s s c b s t ~ t c t e t i i n t o o r As t h e c - it .i o cs h y d r a t e , t h e i r i o r . 1 ~ r a d i i i ~ c r e a s e ,

a t t a c h e d t.o t h e c l d y p a r t i c l e r e s ul t in q ir d net vo luw change of the s ol1 mass

L o rd on -v an d e r F ja al S e c o r dd r v v d l e n c e l o r c e s a r i s i n q f ro m t k e i r t e r l o c k The i n t e r l o c k i n q of e l e c t . r i c a 1 f i e l d s c a u s e sf o r c e s

C a p i l l a r yi m b l b i t l o n

E 1 d s t . i ~ r e l a x a t i o n

l n g of e l e c t r i c a l f i e l d s o f m o l ec c le a s s o c ~ a t e d

w i t h m ov em en ts o f e l e c t r o n s i n t h e i r o r b i t s . T h e

p he no me no n f r e q ~ e r t s m o l e c ul e s I n w hi ch t h e e l e c -

t r o n s h e l l s a r e c o t c o m p l e te l y T i l l e d

Movement of water ict.0 a mass of clay p ar tic le s re -

s c l t i n q f ro m s c r f a c e t e n s i o n e f f e c t s o f w at .e r a c d

a ir mixtures i n the por es of the cla y mass. Com-

p r e s s i v e f o r c e s re a p p l i e d t o L he c l a y p a r t i c l e sby the menisci of the water In the pores

readjmtment of clay particles due to sow chanqe

i n t h e d i a q e n e t ~ f d c t o r s

c h a r g e i m b a la r . ce w hl c h c r e a t e s a n a t t r a c t - l v ef o r c e f o r m o l e c u l e s s u c h a s w a t e r

PLS free water becomes available t.o the cldy mass,

the pore water mecisci begin to erlarge and the

c : ) r n p ~ e s s i v e f o rc e :; a r e r e l a x e d . T he c d p i l l a r y

film will enlarqe d i d r e s l j l i i n a v o l ~ m c ha r, geor supply water fo r one of th e othe r mechanisms

V olu me c h an g e r e s u l t s f ro m p d r t l c l e r e o r i e n t a t - i o nand/or chdnges in soil st.nict.ure due to chdnges

i n t h e d i c i q e n e t . i c f a c t o r s



g e r . e r ~ l i n fe r en c e o f t h e l i t e r a t , r e is -hat t he m j c r co rzlc r . c f t he

volume change i s a t t r ik uza ble O fc.;r c f t he s ix ~ .echanisms: zsnc t ic

rep:: ls ion, c lay pa r t ic le a t - r ac t i cn , cc t ior . hyd7-- ;- -* 3 - ~ . . ~C capillary

imbibi:;on. The ren si r lng twc ~ e c h a c i s x a re reccgnised t c be presec t

but a r e of a le ss er conseq_er .ce and sc ~e wha t m r e z ; rSicul t v explazn

phys ica l ly . The in f l c ences of the fcx r mx sr ~echan i s ms a re ge re ra l ly

co+ir.ed and de sc ri bed ES t h e t e z a l s c i : s u c t i cn , z term ta ke n f r m t h e

s o i l ph ys ic is t . Tct al s c i i suc tion 1s :he sun cf th e zsrncz:; suct-or.

and r,a:rlx s ~ c z i o n . 3 l ; m t i t a z ~ v e l y , t h e o s n c t i z s u c t i on i ~ c l a d e s t h e

osmozic re px ls io n mechar,ism anC; natr;x s.:ct:cri, -he re na in ln ? th r e e

r z j o r ~ e c h a n i s m s . The r zg ni zu ae ar.5 r a t e of v c l ~ r ~ ehange : expansive

clay s may be e s c i c ~ t e d frcm :he mgnitu 'Ae and r at e sf char.ge of s c i l

suc t ior . as ind ica t e& by rnc is tc re 5 i fL . - - -~ - ~ 2 nk.eor1es as ing sce c i f ie d

f i e l d condi t i cns an5 s c i l suc t icr . -vol8 raz io-water ccntent re lzz is7 . -

s h i p s . n li g ht of th;s ab:lity t o eszlmaze :he magnizude as 5 r at e f

vclume change , a co ~s id e r ab le e f fc r t k s beec expended t c &e .~e lop

instru mentat ion t o rneascre to za l 5 3 1 1 . ~ l x t i o ~nd 1:s ~ndepe:der.t corn-

pon ent s. This approa ch, r,easure.-ent cf s o i l s.:c:icn . csrrelatio:.

w it h t k e v ar i ou s i r . f l; ~ e n ci n g f a c ~ o r s , eppears zo hcid Frorrlse f cr v er i-

fy in g :he mi cr cs ca le nech.ar.:srns. The te s yi ng cro ced ilr es f o r ir.de-

pendent ly measur5r.g t o ~ a l , cs- .o~i c , and m tric sucz icn a re r e l az ive ly

simple and straighzforw ard. 3nce he s s i l s c c t i o s c c c p ~ n e z t s an5 t h e

physical an2 physicochemical pro pe r t i es (have beer, evaluate&, the pos-

s i b i l l t y ex l s t s f c r deve loping a be tzer . ;c5ers tan5ir .g ~ t h t e r -

relstionships between cl-,e xecb.anisms czuslnq volarne ck.ange ~ t he

ph ys ic al parame ters in f 1uencir.q xi.:rne change.



SWPLIKG, JCEIiTI?ICATI~N, AND TESTING CF 3XPANSITJE SOILS

67. Expazsive soils are distinguishable fror; other soils by their

ability to swell f r c ~ mbibition cf moisture wizh resclting volune

chacge. An acceptable apprsach tc evaluate the behavior cf expansive

scil subgr~des ir.volves a subsurfaze Soil inveszigation of the route,

identification of the potentially expansive s~:ls, a ~ d stir.ation cf

zhe ir, sitc volume change behavior of the expar,sive soils. 8asec on

this infcrxation a s.;itable an6 ecocomical sol1 treatment a-d pavement

design car. be selected. The subsurface soil ir.vestigaticn will deflne

the physical limits of zhe materials and the relative vulnerability cf

the soils for volume change with respect to axCient cccditions, an will

prcvide soil samples for laboratcry testizg. Idenzificatioc of the ex-

pacsive soils will indicate the scil strata that possess the highesz

pctenzial for volume change. Soil samples from tkese straza ray be

selected for laboratory tests f r m which Bata can'be colleczed to de-

scribe the in situ volume change behavior cf the expansive soils and

forrr zhe basis for the best possible desig~s based on currect technolcgy.

68. he natu re of volurr,e change beneath pavemen ts in the verti-

cal ciirecticn often takes the form of a general .;pw~rd novement be-

ginnicg shortly afzer the start of c o n s t r u c t i o n ans coctin.;ing until

an ecuilibriun subgrade yoisture condition is achieved. Cyclic

e x p a r . s i c n c o n c r a c t i o f i s sf the subgrade soils usually occur at the

peri~eter of pavements which are related to the rainfall and evapo

transcirazion. Lccal expansio~. cay also cccur frcm ponaing and pocr

drainage. C.;ts in highway sections may lead zc local keavicg d>;e to

rer,oval of surcharge presslxe a-d subsequent increase in the moisture

deficiency of the slibgrade soils.

69. The amount ar,d rate of v~li;rr,e change that actually accGmu-

lates in an expansive fo.;ndation soil is a co~.plex functioz of nany fac-

tors that have previoasly been disc~ssed. Therefore, t~ make an accurate

estiaate of the ic sit behavior, some corsiderat;oc sho~ld be given zo

as zany of the irif1uenci;g factcrs as poss~ble, both ~echnological and

ecocomical. The economic factors are variable from location ta locazion



are best suized for rredlurc-stiff sr sclrr clays ,~h:ck are,free cf graT--

els or small rocks which could d x a g e =he 1eadir.g edge cf the :;be.

75. Rctary core barrel smplers xa;. be zateqcrlzee as double-

barrel cr single-barrel. The 2cukle-barrel type, s,;ct, as ;er:scn,

Pitcher, cr WEC samplers, zcnsists nf zc c,;ter barrel with a cczter shoe

tc advacce the sanpler anC an inner barrel with a cutter eCqe tz fine

trim an5 contain the sa3cle. single-zarrel rntary ccrt? saxpler is

simply a core barrel w:th a ci~zter tot; .is:ally xizk. a xamon: fieas,

to a5vance and conzain :he sample. The dcuble-barrei sarplers X best

suited for hard oils and soi ls zcr.tai:-.irg qra7:el. Single-barrel sam-

plers are best suized zo samy;llng rzck.

Sample cisturbance

76. The s,b;ecz of sn c l e ciist;rbar.ce is p.rtici:larl;. important

when sampling acd test-ng exeacslve na~er:als. The dir-..,rbance which

cccurs juring sam pl iq :s cr:rari?l~ lixteC : =he exErer1t:es cf the

s a q l e and is the result cf fricti-nal resistance betxeen =he sa:,ple

t..re anc the soil. In most cases this is f rir.cr consequence anC car.

be minimized by conrrolling the angle c f the c.:tt:r.g eCqe a z reeucicg

the frictional resistance betweer :he smcle a d =he sa71y;ler. The re-

d.:cticn of the resistacce wizhin zhe sa3pler car. be achieves by =he

acplicaticn of lubricant such as slliccn cr Teflcn sFra:;s, by pcllshing

the inner surface, or by platicg :he inner s.~rface, i.e., ck.rome platin?.

(7. A s e x n d 2r.d probably m r e ~rob lexa ziz tyce cf dist:rhance,

at least with respect to the naqr2lt,Be cf neasurec celurne change, is zi-.e

stress relief a sanple undergces wher. 1 is ex~ri ded f r m zhe sarpler,

sealed, an6 zhen store6 prior to fes~i7.g. Tkis zype cf Bistzrbacce will

allow some particle recrien~aticn Sue t- szress rellef anc nay eve?

result in volume change if tk.e envircnmr.t is con4,:cive tc xlsture

accumulation. The effect of th:s zLrpe of 2st.irbance zap. ke red.:ced hy

testing che material in rings cuz direcrly frc~. he sa~.eler 3r ,:sing a

sampler co~sisting cf a series of ring:. If ttlis is ;ct feasible, then

the sar,ple skould be stcred iz the saFpler :nzil the testing crcgram is

ready to begin. If this is not possible a d the samcle must be exzruded

and sealed, then the exposure time shccld be an acsolsze ~~icimurn nB the



a . Eulk s ~ x ~ l e . he XFL s n a l y s i s sf :he b,:lk sample icier.-

z i f r e s -he ove ra l l cmpssi t :cn and i s 2 basis fcr esz:-

mazing the re l a t iv e amcxz sf c l ay ~ i c e r a l s p r es en t :n

the sarcp le . Thi s ,~ sca l l : ; b e 3 r.cc l l c w f c r i r e ry p re-

c i s e i d e ~ t i f i c a t : c c sf i:divi&:al cla y Ti cer a1 ty pes .

5 Seciinented-oriente5 clay-s:ze fracti o:. -4 x c r o x e t e r s ) .

Th:s p rov ide s f3 r r c re z eza i l e5 id en - ' z ' - - - ---:-a,-cn cf t h e

c l z y k n e r a l c or pc ne r. ts k t x y n et aececz montmorillo-

n l t e i z t h e p r e se nc e : v r ri c u1 : te o r c k l c r i ~ e .

c . Sclvazec, seci~ented-cr:er.=emd clay-s ize ~ r a c z i c n . The

as c i t i cn 3f a pc l z r , c rqanic a lcohol sxch as e -hylene

g l yc a l 3 r g l y ~ e r c l zo t h e s e d h e n t e c c l ay 111 expan5t h e s t r ~ c t u r a l s t t i c e s c f r cn tr nc ri ll cn :t e a nd expan-

s iv e ch lo ri te s ar,d ver: ic;lites 5 :hl;s perri: th e

idez t if i ca : ic r , c f t he se r l ~ e r a l s ?:her t e -b - '..-aues

scch as hea t i?g T L S ~ he ~ s e 5 o d:s=:nguish bezween

mcnzmcri l lor i te , exca?dzble ver rLc - l i t es , c r expandable

ch lo ri te s i f tklese laz zi r two zypes are r,c: ir . a mixed-

layer co~b:naz lcc .

85. Gene ral ly, a f t e r t he se 1~1 t : i l anclyses have beer racie,

XR c f =he s o l v a ~ e d s a a c l e a l o r e

8 6 . ~ h e o s t w ld el y u s e d L n d ~ c a t c r r ou p f o r ~ de nt :f :e at lo n/

experience has shown tha: th e volu-e -hange behavior c or re la te s reason-

a b l y w e l l w i th l i q u i d l i r , i t , p l a s t i c i t y i n de x , a n d s h r i n ka g e l i n i t . ;n

nost s ta ze h ighway agenc ies , a ccrb inar i cn c f cbser7 ;e3 At te rBerg l k i t s

azd c r i c r experience wick. materi als wizk.:n a g l - ~ e r , a r e a a r e -he p r i m r y

~ d e ~ t l f l c a t l o r .r,ethods csed for expazslve s e l l s . ?c r ex arr ~l e , I

Louisiana i f t h e li q u i d l l x t i s below 5 3 th e res;lz:r.p d is t r es s fro-

expans ive so i l s w i l l be min lx l a -d 2 3 s p e c ~z : t re at re ?: i s r e q ~ i r e d .

I f t h e liquid l i m l t 1s betweer C O and C, z ten sc re t g e zf t re at re r, :,

us ua lly l in e, i s cieerned nec ess ary . If the l i q c i z 1:rriz :s above 7 3

-

:hen the mater ia l i s d iscard e5 fo r 1;se r : l l s . 3 ther s t a te h ighxay

agenc ies re ly o plasticity ir-.dex; f c r example, 5:. Kansas i f zke plas-

tic:ty lnciex i s belox 15 t h e n m ~ n i r n a l problems a r e a n t i c: p a t ed . I f



tke p l s t i c i t y index is between 5 and 35, mc erate problers are ex-

pected a d some minim l treatnenz is considered. If the plasticity

index is greater zhan 35, the mte rial r,ust be treated t3 r.i-imize the

problem or discarded. The South Dakota Department of Transportazion has

ccrxelated ktterberg li~.its (liquid li~.its) wizh the Soil Conservaticn--

Service Pedological Soil S,~rveys and developed a nap showirg the dis-

tribution of soils within specified limits of the liquid linit acd use

this as an indicator cf potential volume change.

87. In sumnary, it is evidert from the literature that only a

few of zhe indirect techniqces are capable of general application for

the recognition of the po~ential volcne change of exp nsive soils. Sev-

eral procedures are available for deficing the clay mineral constit-ents

and thus a reasonable indicazion cf swell potential. The index proper-

ties have shown reasonable correlations with swell sctential; however,

general application is somewhat i-.indereC by the relative degrees cf

vclume change fro? oze area to another. Ir other words, zhe swell

pctential in one srea defined by a given range of izdex prcperties may

cause micimal problems, while the same linit m y inclcate sericl-s prob-

lens in azother area. Th:s ~o in zs to the pcssible zeed for identifica-

=ion techniq.:es for physiographic areas in which the rneck.anisss of

volume chznge are bssically sixlar and zhe variations in arrbient en-

vironmental ccndizions are ~,inimal.

Direct techniy~es

C8 The direct techr:iq.;es include all those methods which quan-

titatively Essess the volcre change characteriszics of expansive scils.

In their basic forms, the neasured volume change characteristics are

swell and swelllng pressure. The applied loads and structural rigidity

generally determine wk.ich of the characteristics (deforxation or stress)

control the design of a specific structure. The 3,easurement cf these

characteristics is acc3mplished by the use of odomezer-type testing

procedures. If the defcrmation (swell) characteristics are req~ ired,

the speciren on which the lEformatioz is desired is loaded to some seat-

ing lcad cr some s.:rck.arge pressxre decernined by experience cr related

tc overburdened conditlo-s, then izundated and allowed zo swell ~o



t h e p er ce nt s ~ i e l l . I f t h e s t r e s s c : ri a ra c te r is t ic s ( swel l ing pressu re)

ar e required, the specimen 1s loaded ro scme sea tl ng h a d cr precieter-

~ i n e d surcharge pressLre , :hen in .;?. rrd 2r.d a loa5 a p ~ l l e d to malnzain

a constar,: volume. T h i s l c a d defines t h e s w e l l l n g p r e s s u r e . An a l t e r -

nace proced ure th a t h i s been _se d fo r defir.:ng swel1:r.g press.:re i s t s

allow :he specime: t o swe ll , the: apply e?.oush 1366 t c retx rr. th e sp eci -

Ten t o i t s c r i g i - a l he iqhc. The 2orh:na~ioz z f th ese Cas;c var i ab le s

(t es t i ng mezhcci) the fz cto rs ; h: h infl ,e? .ce the la bcr ata ry neasuEe-

ment cf vo l ~ m e chanqe have rrLaae h e s:a:carciiza:io: ~f :es:inq c r s c e d ~ r e s

sorewhat c ax pl ic az e& . T a b l e 6 d e f i n e s a n d d e s c r ~ b e s c x e o f t:?e v a r i ~ u s

pub lis hed prcceciures in which th e sw el i ann s\cel:ing ;ress,re of bc th

.~ n d i s t u r b ed a ~ d ezc lde5 so i l s have en Teaswe n.

89 Krazyzski has def:?eci a ae sc ri bed =h.c la bc ra tc ry re la ze d

var i able s which inf lue nce =he meas ure~ ez t ~f volume c'r.any a s :

a . I n i t i z l r c i s z . ~ r e c z rt e nt .-I z i t i a l d r y d e c s i t y .

c S o i l f a b r i c .

d Ssrckarge 1ozd.-e . So luz icn c t a rac te r : s t l c s .-f Time allowe5 for swell.

g Curing zime for remolden samples.

h St ress t l s t ~ r y ( l oa d lc g seq.;ence)

Tertperazare .

I t i s h i s opinio:: t h a t a reliable and reprodcc:ble test,, f3r =he c;irecz

,

xeasLrement of volume change shoulci s t an d ar x ze az l ea s t elghz cf tk e

ter. v ari abl es . Lcading sequence azci texp erat xre ar e nzt necessary be-

cause , as descr ibe& in the 3revious ~a ra gr ap k, the loadi-g seq .Jence can

deternine which basic characteristic s being xea sl i re c, x d the va r i a -

t:or.s In labora tc ry temperazures a r e i sc a l ly ~ l n l m a l . Isea l l; l , a scan-

dard methcd should cons ij er each. of the above fa ct or s as well as s l m -

l a t e t h e ex pe cz ec lo a di z g c o s x t l o n s : ha= h e s t r x c z u r e w l l urcergc

To date, no reliable o rc ce d ~ re has Dee- aeve l-pez t a de gx ze ly s i a ~ l a t e



dong and Yong Ear. a s cre.:::ds z c ?~r? except :?a: z ax.:.xa. 5-r::a:qe e q i.tE ? t e l E ::.::r : . .........-:.- . .s 1 5 22353.- - . . - .

Z d r t a .A. t.:2. ~1: :?3.: 5



9 2 ?ne

a c t s r w:~cF

o r s l c u l a t l n g .

t n e 3 r y a n c a r e

t n r o u g n t h e u s e

t i r e r ac e 1299138-141 2: d~~elsc-er : ;3l17e ~k,z:ge s

.cLr re r . t :es:lnq c rc ced ur e s - r e c ~ c a pa c - e c f d e f l ~ l n g

7 -. .

da Li ma te s a r e gene r - - -y rnade y s i r izcs:l:dati:n

scrnei iha t q u e s t h r ~ b l e . 2e:er.t a ica r .ce s ha-;e beer . rna ie-

1 1 n l t e d i f i z r e n e e 1 3 8 a n d i r i t e elenen: ' : ec h iq ~e s

a nC C l r e c t t e c hn i que s :3 p r x i d e b et ze r zlass:::cat:sr. ?r;:Fs xl:h

r e q a r C t o s e v e r i t y o f ,.-'u -u ne c .ar:ge ar.d de ve lc y: ?.izr.:::st:~e es: im :i zr,

-

t e c h i q u e s f c r c l t i m a t e v o l u r ~ c han qe . z can cf ily e ccrre-j:::fi ~ o r n -

vclurre change; k.cwewr, :fi s zx e c z s z s r e : ? u a t x f i s r e o b t a i r . e i



94. 3~ re a u of Reclamaticn re:hod. 28 This rethe; invclves the

direct correlation of cbserved v olme cha~ge with colloidal csntent,

~lastic 5.-.sex and shrinkage linut. The measured volume change is zaken

fror odometer swell tests sing 1 psl surcharge press.;res fro7 air-dry

to sa:uratlon. The degree of expanslcn ana llmlts of correlatecl proper-

ties are shown In the followi~g tabilat~on:

Date from Index Tests Pr ~b ac le

Zollold Ccn:e?t PI SL Expansl3r. Degree cf

-I Ilm Exoanslor.

<15 (18 15 <lo L

l3-23 15-26 10-16 13-2C Yedlum.

25-4;C I

20-2- 20-30 ~:gh

> 8 >35 11 30 Very h g h

Zxperience has shown :hat this nethod czrrelates reasonably well with

expected behavior and provides a gcod indicator cf pozential vol.~me

change. The major criticisms of tke method are zhat the collcidal

ccnze~t ~ndlcates amcunc kuz not the type of clay c3rszlt:e~ts a?d that

the hydroneter tes: is net a rcuti?e test in maray agency laboratories.

j Altreyer methcd. In a discussion t Holtz's paper pre

sentlng the JSER ~ethod, Altmeyer brought out cke ma;or crlzicls~,s to

the method a d suggested a methcd based on ccrrelatlons between ~er cent

swell and he shrinkage limit and linear shrlnkspe. The cercent swell

is determined :n ac oooneter test on comcacted saxples (95 standard

AkS?TO T-99 de ns ~z y) under 650-psf surcharge. The results of his recon-

mendations are tabulated as fcllcws:

Linear Shrinkage Probable

Shrinkage L k , i ~ Swell Degree of

Expansio;

< 5 >12 <o 5 Ncncritical

5 8 13-12 0.5-1.5 Marginal>8 <lo >1.5 Critical

One ricor criticism t3 this method is izs lack of appllcatioc to in sit2

oehsvior since the aaza were collected on remclded samples.

106 4296 Seed, Woodward, and Lilncgren xethoc. The swell pozey-

tlal cf a? expansive soil is deflned f r m ccrrelattlo3s of percent swell

from odcmezer zests asing labcratory prepared and compacted sanples



equivalent and the shr:ckaqe 1 irsing tt.ese p a r m e z e r s , 3 cmblr.ea

YC rstizg was dezerniwd and tie res,;ltinq deqree of expznsion cste-

gories are 2s fo--cxs:

in e app are nt siort:oming is :hat the sacple mus t be run in the F ,JC

m t e r ; zherefc re, th e sddltisna car ame ter s are ncr a8iva:tagec,;s. nfact, the oethcd 1s scmewhzt m r e c on ~ l ic a ~ ed ec z~ se cf tb-e exTra data

required.

99 Chen nethod. lo in an effort tc simplify the CEBR nethod

( i , linin ate t he nee i for h.ydrometer 2 7alys is) and -3 prcvide scr,e

reiatlve measure of soil density, 2 c o r r e la ~ i o n w ~ s a de b etw een od cne ter

swell data (undisturbed s m p l e under 0.5 tsf scrcharge) and percert pass-

ing

The resulting c1~ss:flcatio: of the degree cf expan slcn is as f3llow s

Laboratory acd Fleld Cata Prcbable

L Std Penezratlcn Ex ca ns lc n Deqree cf

<No . 200 Bl ows per f oot E x ~ a n s l c n

30 30 10 <1 L O W

30-60 30-40 10-20 1 - 5 M e a l u m

60-95 40 60 20-30 3 :C ~ - g h

9 5 >60 30 >lo very k.lg.7I

Although attempts have been made to correlate decsity with stadard

peretration and hav e be en q. ~i te successful in cchesior,;ess materials,

the extrapclation to cchesive materials (especiaily cvercccsolidated

clays) has net been very meanlngfu-.

n1 Sorochank method. 56 7he :3rre.atlon i n v o l ~ e i re.az:ng th e

swelllng lncex (vold razlo, e , afcer free expansi3n alvlced by the

1rlt:al sample vo:d ratlo, eo : the plastlclty lndex. he resultlrg

aegrees cf exparslon hltb. regard io correlated paraneters zre as follows:



Natura l Xater c n t e n t

L l q , ~ l d Llr::

l tion of odometer swell j a z z 1-psi s x c 5 a r g e w i t h l l i q u i d limit ar.5



L IQU ID L IM IT 7

F l w - e 11 corre la t ;on o f percer.t swell iqUidlmLz

d r y unit welg:: f ron Reference 144



PXECONST3LCTICN TECHNIQZES F3R MINIMIZING DETRIYZNTAL

VOLUME CHANGZ 7 EXPANSIVE SCIL 53EGRk3ES

Introdcction

106 3urlng the past decaze the methods reported far controll~ng

or llmltlng detrlmenzal volume changes lr subgrades has cha~ged llttle.

In 1964 a l i t e r a t u r e rev ie w oz sdelllng solls46

by the Colorado State

.L:~gb.way Department ~ de n tl f~ ed he fo l lowing cou r ses of actlan for zeal-

i ~ g izh the prcblex:

a Remcval ~f

sive soil.

b Ap~lication

c Preven~ing

d Prewetting

expansive soil

cf s~rcharge

access of water

the scil.

e Stabilizazion by chemlcal

f Meekmica1 stabilizazion.

and replacemert with nonexpan-

pressure.

to the soil.

107 Since that t h e few if ar.y adciitional rr ethods have been

added to the list an5 every maj3r literature review or cczference on

swelling scils29 43 147-150 has reiterated these remedies. However an

examination of the literature of the past decade reveals that enorr o_s

strides and nany innovative ~echr~iq.des ave been developed for applying

tkese methods with literally hundreds of accuments publisked. While

it is impossible to tabulate and review all tkese puklications the

following paragraphs summarize various crojects and general cocclusions

concerni~.g these r.ethods.

Methods of Controlling Volume Change of Expansive Solls

gemoval of expansive soil and

replacement w no~expansive soil

108. Removal cf natural expans-ve subgrade materlal a nd replace-

ment wltb. a Yonexpanslve materlal IS a rosz ocv:ous method of elxnlnat-

lng shell problems. In some cases this approach may be economical i



zhe e xp an si ve s tr at ur n i s t h i ~ n 5 r e p i a ce m n t x t e r i a l s a r e a r:2i1ak1e

Unfor tuna te ly , tk is i s genera l l y :.at tk.? czse , 5 the excclTraz:cr, a ~ d

replacemen: so lu zi cn :s extende 5 cn ly :a a d e c t t wk.ich ?; i l l r e d ~ c e s we ll -

i n g t o a to le ra bl e minimum. Hence =he re ss ir ed depzk. sf exz avat ior

depends upor. th e expaps:veness cf th e s o i l an5 t h e a~::z:oa:ed weiqht cf

ba ck fi l l and szr uctg re which coxntersz: the . : -z r ~ r c e s : the swel1ir.g

so i l . The se l ec t io n of zhe pa rz kc la r nc r. expans i-~e hack f i l l r a t e r i a l i s

c r i t i c a l . Hol tz1 5 1

s u g ge s ts z h at r e c 1 i c e ~ e r . z s c r l s c e : ~ ~ e r . ; i a - s a s

perv icu s s o i l s may cr ea te co cdi ti ons csnd,:ci:e r c zhe cc ll ec ti cn of

wazer c r the conaen satian of mcis tur e frcr: :he a i r tk.rz,jk kydrcqei-,esis.

2109. Holtz desc r ibe s r epa i r s r a ze :c the Mckaxk x d Well ton

Canals by removing the subgrade so11 2nd re pl ac i? j i t ;i:tk sar,5-gravel

compac:ed so t h a t soxe compr essic n cf th e gr av el wo.:ld occ gr , th er eb y

re l i ev i ng pa r t o f the expansive f c r c e .

11 McDowell125 recorzs constr; ; t loi : l t r g e Du:ldirq en a

50 ft d e p o s i t o f Del R:o c l a y I n wh ich t h e z l a y was e x c a v at e d t o a d e p t h

cf 6 f t ar.d b a c k f i l l e d wizh a r.=r.excar,sive ateri rial. T x c z h e r c a s e

reporzed ky McCcwell152 a 2- t o 3- f t l z y e r cf e x pa n si v e s c i l o v e r l y i ng

rcck was s t r i pp ea c ff 3rd rep laced Cy coxpaczed crcsheci r x k f i l l .

111. Contrary t o the se afore~ e:?t:or ~eci s>Jcce sses us:r.q excava:iar

ana replacerrent nethods, the k l s r e c o 2epzrt ren t cf 9-at-hays has r e -

por ted a l sna l failures uslng zh;s zech-l que. 81 153-15kn t n e s e c a s e s ,

swel1ir .g subgrades were s~b exca vaze d z 5ecth cf f t ard 5ackf;i led

w it h varlo,;s g r ad a ti o ns and :lSpes cf 2 rar .u lar e r a . L nf cr zu na te ly ,

:he pe rv io .~ s gran.:lar mate rial p e r ~ i t t e 5 the enErance cf ? ,oisz.Jre

through surface r l ncf f and ty6roger,es:s1 anci sw el lin g oc ccr re 5. IL was

. r

112. Scuth Dakota s experie nce - ' nd lc az ed th at i :r,i:ed urder-

cut t i ng and reconpac t ion c f the subgrade 6 - 1 8 i ? . ) d i5 r .ct scl ve the::

pavernert warping problem. Howe7~er, c n I- :-,, 2 p e r ce r t l:?e w3s added

t o a c u s h i c n g r a v e l a n d b a s e c o u r s e g r a v e l tc r e d u ce t h e ?I f r o r 10 20

t o l e s s t h a n 10 and place5 ci re cz ly c:: the cncr eate 5 subqra je . The



results showed :hat although several warped paverenLs have Beveloped,-

the overall serv1ceac;l;ty lndex cf the project 1s gcsd. Llkewlse,

on 1-95 east of Cact.:s Flat, it was d e t e r m n e d t h t a 4-in. layer of

lime-treazed gravel c~shion gave as gsod as cr better protecticn to the

subgrade for retentic:: sf the co=str.:czion 2oisture and density at a

lower ccst char. did lime stabilizatxn cf the upper 6 in. of subgrade

with percent KC-1 being mixed in the ,;pper in. zo fcrm a 2oist:re

barrier. 156 These experiences suggest that line treztmezt cf the grav-

els ray elxinate problems encountered by the Colorado Departne-t of

Highways. However, it wocld appear that sufficienz fines for line reac-

tion r . u s ~ e present in the base co7Jrse gravels ard a fairly impervio:~

material should res.:lz for this mezhod to be effeczive.

113. Experzences of the Wym ir q StaLe d~ gh wa y Deparzment ccncern-

icg the use of urtreatec gravel bases placed direc~ly 3 the subgrade

have been sirilar to thcse of the Colcrado Departmenz of Highways.153 153

The experimental project on 1-25 south of Kaycee resulted in moisture

accl~mulations in the granular base course fcllowed by heaving. Origi-

nally, roads built In Wyoming were constructed using gravel (with fines)

bases with soTe surfac~ng, anB i?eavir.g was r,ot a major problem, Eowever,

with the advezt of keavier lcacis and faster speeds cf ~,oder: traffic,

clean gravel bases and gentle side slopes with several feet cf exposed

gravel base became cornmor practice. The result was swelling soil prob-

lems. Initial reactiozs were to thicken the gravel sectior.; however,

the thicker the secEion and b ec~er the gravel, the higher the heaves.

In some cases a gravel with fines was used with scme retardat:on of che

swelling.

A~plication of surcharge pressure

i 1 4 Loading the expansive soil with pressure greater tkaz the

swelling press.Jre is a metho by which swellizg can be prevented. .?ow-

ever, pa ve~ent loads Ere generally insufficle-t to prevent expansicn,

and this method is usually applied i~ =he case cf large buildings 3r

31structures nposing high loads. Sallberg me;tio:s that pavement de-

signs developed by the California Civislcn of Eighways are based partly

2 the requirement chat the pavement weigh e x u g h to prevent expansion



COVER O F 6 LOOSE SOIL ASPHALT BASE COURSE ASPHALT WEARING COURSE

ASPHALT MEMBRANE

FULL-DE PTH ASPHALT PAVEMENT WITH LINED DITCHES

2.5 ASPHALT PAVEMENT\

M l N l M U M C O V k R

O 6 LOOSE kOIL

14 - 77 SUBBASE

4 BASE COURSE

ASPHALT MEMBRANE .;ANCOX SHALE

CONTINUOUS ASPHALT MEMBRANE APPLIED TO SUBGR DE A N D D I T C H E S

Figure 12. Typical construction of moisture barriers used by the

Colorado Department of Highways from Reference 80)



s w e l l i n g .subgrade wizh aspha l t - l i r ,e d a i tc hes and cackslcpes c r as pha l t

r.embrar.es Betweep. the swellin? subgrade and the read s,iBkase, The full

dep th a spha l t sec t l an p rov ide s ac l rp e r ~e zb le s -pp -r t r a t e r i a l which

eli r.i ?.at es no is tu re acc.:r,ulazicn by hy2rogenesis zr s.:rZace r um o f f .

The asphalz merbrane permits mcisture :3 accumu late ir J t h e Lase a7.d

subbase, but prevenzs i t frc: seep:?g 5cwr.warc Lnzc :he su bg ra de ; 1.1-

s t ea d , zhe w ~ t e r ?,erely drains c r r zo zk.e si de di tc he s.

119. The use cf m i s t ~ r e ~ z r r i e r s r. a?. e x ~ e r h e n t a l s ec t i c r . w ~ s

evaluatea by he So_ th Dakoza 3epartxe:.: cf 7 - a . . 2 p ~ - t a r i c n 37 L3 3w-Y 1 2p .

- L

ove r tke P ie r re sha le . TP.2 ,:cper 6 i n . of t h e subgrade was t r e a t e d

with a mixture cf lime and R>l asphal: t c for ? :he wazerprcof ccv er .

. .In add i t ion , a polyezhylene c l a s t i c b l ~ c k e t ;<as p laced - : er t ic z l-y z 3 a

d e p t h o f f t a t a d i s t a n c e of 2 3 f t e l t h e r s i d e of t h e c e r ' te r l i n e , l u s t

:nside th e sk oc ld er l i n e . The res.:l:s inb icaz ed hat there were r,c

s ig n i f i c an t d i f fe rences in rnc:stxre c3 : ;~en t s c f sec t i2 r .s v i ~ h x3:st.ire

ba rr ie r s and those w i th s u ~. Apparec t ly , .-he pclye thy1er .e c la s t i c c , tc f f

was not placed deep enccgh anti th e frazt. ;red cat.:re 3f zhe sh al e per -

mi t t ed no i s tu r e to rove u n d e r n e a t h . t h e wall . Tkere were yore no is ta re

fl uct uat io ns i c zhe area s with the rnclsture ba rr ie r, a:, :b.e ri dl ng

s u r f a ~ e was bezce r in a rea s w iz hc~ z tk.e c o i s ~ _ r e x r r l e r . The mc:szure

seexed zo be h igher an5 f luc tua tec i rc re in the a rea c lcs e t z th e bar r l e r

iz se l f , i ~ d i c a t i n g th a t a the rra l ck.ar.qe m y be ca>slnq ccn5ezsst :on near

t h e c l a s t i c c u z o f f .

1 2 0 . The Mi ss is si pp i 2:ate E:ghCday Cepart-enz cs e5 a ~, oi sr l; re

b a r r i e r f n a s p h a l t m r b r a n e p l a c e d a t t h e r a t e of ? g a l / y d 2 ir. a t e s t

se cz io- cn St a t e Highway 475 cc ns zr x t ec cver Yazoo c lay .163 165

While

the companion ccnzrol sect io xs experiecced severe 5:stsrrie : dzring the

34-month 3bservatior. per iod , t he i t n c me5irar .e ~ r c v i 2 e d a very

e f f e c t i v e w a n s of w a t er pr oo f -r g t h e r ad lw ay a?d pr e ve n ti n g ay d e t r l -

mezta? swell . I had been fea rec t h ~ t ac i l la ry r:se xo.:ld xake the

membrane in ef fe ct iv e, but ap pa rel t l y ~,c:szure rni~ra ziz: l the Yazss

c lay i s nc t due zo cap i l l a r y r i se ; r z: te r, i t c 3 r t r c l l e ~ by s u rf ac e

rznoff and cracks and fi ss ur es In zhe clay.

1 2 1 . The Arizcna Deparzmer~z 3f Tr azs po rt ati cc l i k e t he Colorads



Iepartment of Hlghways h s used merbranes andlor full-depth asphalt

roadways. These -nolst ure b a r ri e rs have prcven t o be a fairly gocd solu-

t i o n , p a r t i c u l a r l y I n a r i d r e g i on s .

166

122. The Wyoming St at e Xighway Departrent t r i ed plant- nixed as-

phaltic bases over gra nl ~la r subbases and exper ie rcec prcble-s s i x i la r

L O th os e of th e Colorado Departmen: of Elghways. Spec:f:cally, I T I O ~ S ~ U ~ ~

accxrula ted i tk.e g r a ~ u l a r l a y e r which s ub se qu en tl y i n f ~ l t r a t e d t h e

expans:ve subgrade ca;s:y.g k.eaves. Eoh~ever, the use of 11-depzh pl a - t -

r ixed bases and a sch a l t i c membra~es has ~ r odu cea an ecm or ica l , e f f ec t i ve

r e an s of p r e v e rt i n g m c is t ur e ~ i g r a t l c n t t he subgrade by szrface

moiszure.1

123. Cn t he Kaycee-So7:tk. e xper imen ta l se ct ion cf 1-25 :he Nyo-

micg St at e Highway Department placed se ct ic n co nsi sti ng of 2- ic. p la nt-

mixed asp hal t ccnc rete s xr fa ce coc rse, an 6-i n. hot-mixed asphalt

stabilized base, and a va ri ab le secti or. minilrc: 3 f t ) cf s e l e c t s o f t

sandstom base over the expacsive Ccdy shale. A p l a s t i c rrembr ane un-

sea led a t e i th e r edge) was p laced i n e i t he r d izch s e c~ io n pa r t way ,;c ir

t h e se le ct sandszoce base , Figur e 13. In zhe ccmpanicn nonmerrkrane

sec t ion , a conside rab le inc rease i n nc i s tu re occur red a t th e s e lec t s aed-

stone base acd clay subgrade in te rface . Likewise , i -,he merbraa sec-

t i on s under zhe dri vin g lane where co membra~e was placed) s i gn if ic an t

10 ASPHALT P 4 L . M EYT- DRIVING LANES

6 B E L O W S U R F A C E

CHANGE IN MOISTURE FRO,

EPT 6 T MAY 68

* FINAL READINGS IN MAR 68

Flgure 13. Membrane s e c t l o n on Kaycee P r o j e c t s ho wl ng r n o ls t u re

b u l l d ~ p ucaer center por t lon of roaaway from kydrogeres ls .

Memrane kept sh3,lder are a dry (froq Xeference 1 5 9 )



mater ial shcld be ponded and zo what depLk the moistzre should pene-

trate tc be effective are still unk-own.

2 , One of the earliest, xore notable highway ponding projects

was on US Hwy 81 north of Waco, Texas, over Wilscn clay loam which is. - .:i

develcpeC from the Taylor ~n 1948 two areas were ponded; one

site had 4-in.-dim holes drilled to a depch of 8 f cn 5 f t centers;

az the second size, 4 - i n . - d i m holes were drilled tc a depth cf 7.5 ft

oc 6-ft centers. The holes were backfilled with sand or gravel tc mini-

rr,ize sloughing cf the walls and filled with. wazer daily fcr 4 months.

Most of the water entered the .;?per 3.5 ft of soil, and the quan~ity

added was so m al l conzared to the volume of soil being wetted thaz some

parts 3f the soil were still below the shrinkage level 2 monzhs after

-

r11lir.g of the hcles begas. TO expedite the swellicg process, two areas

were ponded fcr approximazely 3 nor.ths. In the 40 cays prior to ponding,

there was no evidence of surface heave resul~ing frcm the daily filling

of the holes with water. However, after 3 days of po-ding the surface

rose 1 in. Several excerimects to accelerate water movement from the

kales were tried. In one experiment, pressures of 25 90 psi were applied

in sealed hales. Two comparison experirental sections, one with b i n .

d i m holes 8 ft deep on 5 f t centers and one without any holes, were b o ~ h

p o n d e d . All these experiments concluded that the holes ere of little

v z l ~ e in wetting the soil and that ponding was nore effeczive. The ap-

parenz reason for this ccnclusion was thaz the blocky-structured nat.;ral

clay afforded easy penetration cf the water. 5ence it was recormended

that ponding Be completed prior to any grading which may alter ;he

natural fissures.

. q

L C . In 1958 a section of 1-35 r.orth of Waco, again crossing the

lower member 3f the Taylor marl, was ponded for 22-41 days. Results of

the project showed that the water did not penetrate more than 4 ft down-

~ a r d uring a pcnding period of 24 days. Nevertheless after several

days of po?ding, the moisture conzents at :he 20-ft depth level in-

creased. Results of this ponding show that after 7 yr cf service, only

2 of the 15 ponded sections have becore ro.;gh, while several unponded

sections in the same area have heaved and been overlaid or replaced. 15



McDowell152 feels chat pcnd;:g :i app:cx::azely 3: 3ij.s is reco~xendec.

After ponding, lime s ta bi li za~ i~ c y se req.:ire'd : crovide a fizz

work~ng platforr, and t3 decrease evaccratlxi a7.9 dry xeacih.er crack1r.g of

tke uncerlyirg subgrace.124

1 3 0 Pending of fourdatlrs fcr building sizes an9 highway sub-

1 2 5 ,:_ , 168grades have been repor:eG cy :cDowell, , , O ~ L a7.d Szeicbsrp,

Blight, 169 Oawsor,,17 6-d Haynes. 17' 2 the tio exiaplec ~:teJ by

McDowell1 2 5 1 5 2 a .

zhe iou?dazicn soils 5,:ere ponded fcr I cays, followes

by lixe stabiliza-ticn tc prmlde a wcrking piazform 2nd decrease a?y

dry weather cracking acd evapcra:lsL. Fes,lzs here successf-1.

success was re p~ rt ed cy Da~5son70 ,, ,h, fln-Lced e fc;r,dat:cr zrenches

for a b:llalng on expansive clay. After 4 ronzns cf p on d~ ng , enetra-

tion cf wzter lnto the sell was fcur.a to be very l1xzec. Nexb7erzheless,

the subseqcent heave cf the str;ct,re crcved to be less the that sc-

serve- for s ixlar strdctures 1r. the are-.

171131. Baynes and Masor. repsrt a prewetti~g :eckxiq,:e 1 . which

6-lr. .-wlde, 3-fz-aeep trenches cr, a 10- b y 30-ft grid were fllled to a

depth of 1 f-, wl-,h lime an5 cackfillen wlth g r a v ~ l . Water w:th a SUr

f a c t a n t Kyro EO was placed ir, che zrer.ches fcr abcuz 1 173r.tl- . L tkis

~ i m e he soil had reached the reqxired prewezzed noisture contecz cor-

re sp cn di ng tc the fu ll y sw el le d cond:t:cn 2n d the floor slab was placed

wlth co subse q~enz heave prn ble ~s.

.132. Po nd ~n g f a 27-f t -deep c ~ t n ,S Ewy 90 wesz of Sac Ar,zcn:c,

Texas, 1 the Taylor for ~at -on was iccmplishea In 197068 172

Ar. area

from 3 ft up the backslcpe acrDss zhe maii-, larjes, zedian, azc sk3,ilders

was ponded for 4 days. It was obser.,ied that little uazer reactec below

3 ft e to the lack cf a fissured slrstern in the cia;. arc the sc:rze

cf swelling was prinarlly in :he :Fper 4 fz. Ir, o cf the ponds a

, .

surfacxznt was usea, buz ?.a percecz:Dle d:fferer,ce ic tLe s-rfaze and

depth elevations r mcisture reaainqs xis ckserved. Tk:s, clus zhe fact

that the surfaczant-water ccmbinacicr .*.as tox:c to gc~lzfish, lead to izs

dlscontlnuance. The areas were 1:re-stablllzea a f ~ e r cralnaqe t3 kcld

the molscure. AC thls z m e , a road c o n d ~ t l o n urvey of tne ponded and



l a r g e - s c a l e r o u t i n e t r e a t me n t o f s w e l l in g s o i l s . 1 7 3 Lime cont inu es t o

b e t h e mos t w i d el y u se d an d most e f f e c t i v e a d d i t i v e f o r s t a b i l i z a t i o n o f

e x p a n s i v e c l a y s . 167 y173 Table 7 e xc e r p te d f r om M i tc he l l 173 summarizest h e u s e o f v a r i o u s c he mi ca l a d d i t i v e s f o r c o n t r o l l i n g volume c h an ge .

135. The Universi ty of Wyoming evaluated approximately 1 7 d i f f e r -

e n t a d d i t i v e s f o r s t a b i l i z i n g a n e x pa n si v e c l a y on 1 -80 w es t o f L ar a-

Ef f e c t iv e ne s s was e va lua te d by volume e xpans ion t e s t s u s in g a

CBR mold and sw e l l p r e s su r e t e s t s u s ing a 4 - in . - d i m P r oc to r m old.

B r i e f l y t h e f o l l o wi n g a d d i t i v e s were e v a l u a t e d :

Alcohols and formaldehyde . I sop rop yl a l coh ol caused t h e

s o i l t o become f r i a b l e a nd r e duc ed t h e s we l l in g a s much

a s l im e f o r a s h o r t p e r i o d o f t i m e . N eg at iv e r e s u l t swer e ob ta ine d wi t h a l i me - is o p ro p y l a l c o h o l s l u r r y i n an

a t te m pt t o m i g r at e d i s s o l v e d l i me i n t o t h e c l a y . E t h y l

a l c o ho l a nd f o rm aldehyde a l so r educe d swe l l ing bu t t h e

t e s t s showed t h a t t h i s r e d u c t i o n was o n l y t em p o ra r y.

B Quat 2 CoCo. Th is ag en t i s a qu at er na ry ammonium

c h l o r i d e a n d was a dd ed t o t h e s o i l i n a n a tt e m p t t o f o rm

a w a t e r - r e p e l l e n t f i l m c o v e r i n g t h e c l a y . G e l a t i o n oc-

cur s when CoCo i s added t o wat e r . Addi t ion of concen-

t r a t e d CoCo-water m i xt u re t o t h e s o i l c a us ed t h e s o i l

t o become f r i a b l e . R e duc tion in sw e l l compar ed fa vor -

a b l y w i t h l i m e b u t a s w i t h l i m e go od m i xi ng i s

r e q u i r e d .

Reten. Reten 210 and Reten A 1 a r e s y n t h e t i c w at er -

so l ub i e po lym er s ; t he f o rm e r i s c a t i on i c w hi le t h e l a t t e r

i s a n io n ic . They a r e use d a s f loc c u l a n t s i n sewage

t r e a tm e n t a nd a s e xpe c te d when th e y were adde d t o th e

s o i l a spongy f r i a b l e m ix tu r e was ob ta ine d . However

when very s l i g h t amounts were added t o wat er unmanage-

a b l e g e l a t i o n o c c u r r e d t h e r e b y p r e c l u d i n g an y m i g r a t i o n

and ease of mixing .

Na lc o ly te . Nalcolyte 605 and 675 are a c a t i o n i c p o l y -

e l e c t r i c a l o r g a n i c c o a g u l an t a n d a w at e r - so l u b l e p ol ym er

f l o c c u l a n t r e s p e c t i v e l y . N a lc o ly t e 6 05 c au s ed t h e s o i l

t o become f r i a b l e b u t f a i l e d t o r ed u ce s w el l . N a lc o ly t e675 behaved s i m i la r t o Reten wi th a c o ns i de r ab l e l o s s i n

d e n s i t y o b s er v ed .

S i l i c o n e . S i l i c o n e 770 a nd 772 a r e s i l i c o n e r e s i n con-

c e n t r a t e s u sed f o r wa te r p r oof ing m asonr y a nd a wa te r -

s o l u b l e s odi um m et hy l s i l i c o n a t e u se d a s a d i s p e r s i n g

a g en t i n c l a y s an d c e ra m ic s r e s p e c t i v e l y . F or t h e

p e r c en t a g e s t e s t e d s i l i c o n e 770 f a i l e d t o p r ov i d e a ny

a p p r e c i a b l e s w e l l r e d u c t i o n s . S i l i c o n e 77 a t 3 percent



d. PDC Formula (4 :2 :1 ; 1ime :Por t la nd cement:soy f l o u r ) ,

p e r c e n t .

R e s u l t s o f t h i s e x p er im e nt a l p r o j e c t show t h a t a l l o f t h e s t a b i l i z i n g

a g e n ts a l t e r e d t h e p h y s i c a l c h a r a c t e r i s t i c s t o some d e g re e , w i t h l i me

having a more pe rma nent e f f e c t i n l o we r in g t h e s e c h a r a c t e r i s t i c s . CBR

r a t i n g s showed t h a t a f t e r y r t h e p h os p ho r ic a c i d s e c t i o n h ad a v a l u e

o n l y s l i g h t l y h i g he r th a n u n t r e a t e d s o i l . C on ve rs el y, l i m e , l i me p l u s

RC-1 , and t h e PDC fo r mu la , i n t h a t o r d e r , cau s ed s ig n i f i ca n t CBR i n -

c r e as e s . S e r v i c e a b i l i t y r a t i n g s o f t h e s t a b i l i z e d s e c t i on s e xc ep t f o r

t h e p ho s ph o ri c a c i d we re b e t t e r t h a n t h o s e o f t h e s t a n d a r d de s i g n s e e -

t i o n . L ime-t r ea ted s e c t i o n s had t h e b es t r a t i n g s , w h i l e PDC and l ime

p l u s RC -1 f o l l o w e d v e r y c l o s e l y . The us e o f s t a b i l i z i n g a g e n t s i n 19 64

c ha ng ed t h e av e ra g e i n i t i a l c o s t p e r m i l e fro m 6 7, 50 0 f o r u n t r e a t e d

s o i l t o 8 5, 20 0 p e r m i l e f o r l i m e , 9 3, 30 0 p e r mi l e f o r l i me p l u s RC-1 ,

95 ,700 fo r PDC f o r mu la , an d 1 20 ,6 00 p e r m i l e f o r p h o s p h o r i c ac id p l u s

f e r r i c s u l f a t e . t w a s co n c lu d ed fr om th e s tu d y t h a t p h o s ph o r ic ac id

w a s n o t e f f e c t i v e a s a s t a b i l i z i n g ag e nt of t h e P i e r r e s h a l e , a nd t h a t

t h e e f f e c t o f t h e PDC formula was due t o th e l ime-cement combinat ion of

t h e f or mu la r a t h e r t h a n t h e s oy f l o u r a a d i t i v e .

Methods o f l ime t r ea tment

137 . Lime con t inu es t o be t h e mos t e f f e c t iv e and mos t widely

us ed a d d i t i v e f o r t r e a t i n g e xp an si ve s o i l s . I n i t i a l l y , l im e t r ea t me n t

was co n f in ed t o t h e u p pe r few in ch es o f s u b g rad e , p e r h ap s p r ima r i l y t o

a c h i e ve s t r e n g t h b e n e f i t s a nd n ot s o much t o t r e a t t h e e x p an s iv e p ro b-

l em . R e c e nt l y , e f f o r t s ha ve be en d i r e c t e d t ow ar d s t a b i l i z i n g o r modi-

f y i n g d e ep e r l a y e r s . I n a d d i t i o n t o c o n v e n t i o n a l m ix i n -p l a c e o r b a t c h

m ix in g, o t h e r methods f o r i n c o rp o r a t i n g l i me i n c lu d e e l e c t r i c a l , d r i l l -

ho l e , p r es su re , and deep-plow.

1 38 . E l e c t r i c a l . The u se of an e l e c t r i c a l p o t e n t i a l t o i n c r e a s e

t h e r a t e o f l im e m i gr a t io n was e v a l u a te d i n t h e l a b o r a t o r y by t h e Uni-

versity of Wyoming. 19 Lime s lu r ry 7 p a r t s w a t e r : l p a r t l i m e ) was p l ac e d

on to p o f a compact ed s pecimen an d an e l e c t r i c a l cu r r e n t o f 1-4 amps

p laced ac r o s s t h e s l u r r y an d s ample f o r 1 5 min . The r e s u l t s s howed

t h a t l i t t l e l im e o r few c al ci um i o n s m ig ra te d i n t o t h e s o i l , and t h i s



method was abandoned. Ele ctro osm oti c methods were re po rt ed by t h e

L ou is ia na Department o f ~ i g h w a y s l ~ ~i t h s i mi l a r r e s u l t s Lime s lur ry

( 1 0 p e r c e n t by v ol um e) was p l a c e d i n a t r e n c h b e tw ee n s t e e l e l e c t r o d e s ,

and an e l e c t r i c a l g r a d i e n t r a ng i ng f rom 0 .7 5 t o 2 . 0 vo l t s / c m was a pp l i e d

f o r d u r a t i o n s r a n g i n g f ro m 75 t o 1584 k r . Water movement was sa t i s -

fa c t or y , bu t no app re c ia bl e amount of l i me migra t ed and t h e method was

abandoned.1 9 9

1 39 . D r i l l -h o l e . T h is t e ch n i qu e c o n s i s t s b a s i c a l l y o f d r i l l i n g

h ol es i n t o t h e , s u b g ra d e m d . b a c k f i l l i n g w i th a l i me s l u r r y o r l i m e

s l u r r y - s a n d m i x t u r e . Once p l a c e d i n t h e h o l e s , t h e l i m e m i g r a t e s o r

d i f f u s e s i n t o t h e s o i l s ys te m, i n i t i a t i n g t h e s o i l - li m e r e a c t i o n s . How-

e v e r , t h i s d i f f u s i o n p r o c e s s c an be q u i t e s l o w , a n d t i m e may b e r e q u i r e d

b ef or e a s u b s t a n t i a l q u a n t i t y o f t h e s o i l s a f f e c t e d 2 0 0 u n l e s s a s y st em

o f c r a c k s a nd f i s s u r e s e xt e n d s t o t h e d e p th o f t h e h o l e . The d r i l l - h o l e

t e c hn i que ha s be en use d f o r r e m e d ia l m e asu r es a nd new c on s t r uc t ion by a

number of highway agencies.

140. The Oklahoma Department o f ~ i ~ h w a y s ~ as rep or ted numerous

s u c c e s s f u l i n s t a n c e s o f d r i l l e d - h o l e l i m e a p p l i c a t i o n s . T y p i c a l l y ,

9 - i n . - d i m , 3 0- in .- de ep h o l e s o n 5 - f t c e n t e r s h av e b ee n b a c k f i l l e d w i t h

l im e s l u r r y .

141 Exper iences of t h e Colorado Depar tment of Highways us in g

d r i l l e d - h o l e l i m e t e c h n i q u e s h av e ( p ro v e n q u i t e s u c c e s s f u l . 02 G e n e r a l l y ,

12 -in .- d ia m ho l e s w i t h de p th s r a ng in g f rom 6 -20 f t , depending upon t h e

e x t e n t o f t r e a t m e n t d e s i r e d , on a 5 by 6 - ft g r i d o r 5 - f t c e n t e r s , a r e

u s ed . E x p er i en c e showed t h a t s l u r r i e s o f more t h a n l b o f l i m e p e r

g a l l o n o f w a t er r e s u l t i n l e s s l i m e an d w a t er m i g r a ti o n . H ol es a t l e a s t

12 in . i n d i a m e te r a r e recommended a s sm a l l e r ho l e s do no t p r ov ide su f -

f i c i e n t wa te r a nd soa k ing a r e a s and a r e more c o s t ly . The m echan ism o f

s t a b i l i z a t i o n o b s er v ed shows t h a t l i m e do es n o t m i g r a t e o v e r 2-3 i n . f r o m

t h e p e r i p h e r y o f t h e h o l e a nd m o st l y a t t h e bo tt om o f t h e s h a f t ( l i m e i s

s l i g h t l y s o l u b le i n wa te r and r a p i d l y s e t t l e s o u t of t h e s l u r r y ) . The

s w el l in g p o t e n t i a l i s r ed uc ed d ue t o t h e mo is t ur e i n c r e a s es i n t h e s o i l

( s i m i l a r t o p on di ng a c t i o n ) and s t r e s s r e l i e f . S t r e s s r e l i e f a l l ow s d ry

m a t e r i a l a way f ro m t h e h o l e t o e xp and l a t e r a l l y i n t o t h e h o l e , t h e r eb y



r ed u c i n g t h e v e r t i c a l s we l l com po nent . From t h e s e co n s i d e ra t i o n s , i t

would appear tha t l ime i s of l i t t l e b e n e f i t t o t h e t e ch n iq u e however,

ex p e r im en t s s u g g es t t h a t wa t e r m i g ra t i o n i s more e f f ec t i v e when wa t e r i sa dd ed a s a l i m e s l u r r y t h a n a s w a t er a l o n e . B h c k f i l l i n g t h e h o l e s w i t h

s an d o r g ra v e l p e rm i t s ex ces s m o i s t u re accu mu l at ed i n t h e b as e an d s ub -

b as e co u r s e s by h y d rog en es is t o be d ra i n ed ev en l y i n t o t h e s u bg rade

i n s t ea d o f co l l ec t i n g u n even ly an d cau s i n g u neven h eavi n g .

>42 Ef fo r t s by t he Lou is ian a Depar tmen t o f Highways t o use

d r i l l - h o l e l im e s t a b i l i z a t i o n t o improve t h e s t r e n g t h and s t a b i l i t y o f a

f i l l were u n s u cc e s s fu l . 203 I n t h i s c as e , a h a l f b ag o f l i m e 2 5 ib w a s

p l ac e d i n 9 - i n . - d i m h o l e s , 18 o r 24 in . deep on ,3 -f t ce n t er s , wh i le one

b ag o f l i me 5 0 l b ) w a s p l a c e d i n 36 o r 48- in . -deep ho l es on 5 - f t

c e n t e r s . R e s u l t s o b t a in e d by t e s t p i t s showed l i t t l e o r no li me m ig ra -

t i o n from t h e h o l e p e ri p he r y a f t e r y r .

1 4 3 . I n a rem edi al measure, t h e South Dakota Department o f Trans-

p o r t a t i o n 1 5 7 p l aced l ime s l u r r y composed of bart l i m e , p a r t w a t e r ,

a nd p a r t s an d i n t o 4 -f t- de ep h o l e s p l a c e d on 5 - f t c e n t e r s n o h o l e s i z e

g i v e n ) i n t o an expans ive subgrade of P i e r r e s h a l e c l a y . R e s u l t s showed

some red uct i on i n t h e f requency and sharpne ss o f th e bumps. With t ime a

d e f i n i t e improvement i n s e r v i c e a b i l i t y i n de x w a s n ot ed f o r t h e s e s e c t i o n s

o v e r com pan ion u n t r e a t ed a r ea s . T hese s t u d i e s -an d f i e l d s ec t i o n s show

t h a t l im e mi g ra t io n f rom t h e d r i l l h o l e was q u i t e l i m i t e d and r e s t r i c t e d

t o t h e p e r i p h e r y o f t h e h o l e . S uc ce ss u s i n g t h i s t ec h ni q ue a r i s e s f rom

a ) an i n c r e a s e i n m o is t u r e c o n t e n t o f t h e s u r r o u n di n g s ub gr ad e due t o

m i g r at i o n o f t h e w a te r a i d e d b y l i m e ) from t h e h o l e a nd b ) s t r e s s

r e l i e f o f l a t e r a l e x pa n si v e p p e s su r e , t h e r e b y r e du c in g upward s w e l l

p r e s s u r e s .

1 4 4 Lime s l u r r y p r e s s u r e i n j e c t i o n . I n n a t te m pt t o o b t a i n

g r e a t e r d i s t r i b u t i o n o f l i m e i n s w e l l i n g s u bg r ad e s, t h e t e c h n i q u e o f

l im e s l u r r y p r e ss u r e i n j e c t i o n L S P I ) was developed. The te ch niq ue

c o n s i s t s o f p umping l i m e s l u r r y u n de r p r e s s u r e s o f u p t o 200 p s i , de-

p e nd i ng upon s o i l c o n d i t i o n s , t h r o ug h h ol lo w i n j e c t i o n r o d s i n t o t h e s ub -

g r a d e . The i n j e c t i o n r o d s p e n e t r a t e t h e s o i l i n a p p r ox i m a t el y 1 2 -i n .

i n t e r v a l s , a nd t h e s l u r r y , 2 .5 -3 .0 l b o f l i m e p e r g a l l o n of wa t e r , i s



i n j e c t e d i n t o r e f u s a l . R ef us al i s d e fi n ed a s 1) s o i l w i l l n o t t a k e

a d d i t i o na l s l u r r y , ( 2 ) s l u r r y i s r un ni ng f r e e l y e i t h e r around t h e p i pe

o r o u t of p r e vi o u s i n j e c t i o n h o l e s , o r 3 ) t h e s l u r r y ha s f r a c t u r e d t h e

s u r f a c e a nd s f l o wi n g . A w e t ti n g a ge n t i s o f t e n added t o t h e s l u r r y

t o a s s i s t i n m ig ra t i on , and s p x i n g s o f 3-5 f t on ce n te r s i s

comrnon 204-206 The l i n e s l i l r r y l e f t o n t h e s u r f a c e i mm e di a te l y f o ll o w-

i ng i n j e c t i o n i s mixed i n t o t h e t o p 4-6 i n . o f s o i l a c d r ec om pa ct ed .

1 4 5 . The Lou is i an a Department of Highways has r ep or te d

r e s u l t s199'203 o f a LSPI experiment used on a h y d r a u l i c f i l l on 1- 55.

Lime s l u r r y , e i t h e r 0 . 5 p e r c e n t l i m e b y w e ig h t o r 1 . 5 p e rc en t l i m e by

w e i g h t , was i n j e c t e d on 5 - ft c e n t e r s t o d e pt h s o f e i t h e r 5 , 10 , o r 20

f t . I n j e c t i o n was made e v er y 8 4 2 n . o f d e pt h. D ur ing t h e p r o ce s s ,

v a r io u s q u a n t i t i e s o f l i m e s l u r r y wouid br ea k o u t o f t h e s o i l a t d i s -

t a n c e s r a n g i n g f ro m 1 - 5 f t from t h e i n j e c t i o n p o i n t , a nd an e s t i m a t e d

2-30 p e r c e n t o f t h e l i m e s l u r r y was l o s t a t t h e s e b r ea k ou t p o i n t s .

D i s t u r b e d a n d u n d i s t u r b e d s am pl es an d t e s t p i t o b s e r v a t i o n s a p p r o x i -

mate ly 2 and 4 y r a f t e r i n j e c t i o n r e ve a le d t h a t t h e l im e d i s t r i b u t i o n

was s t r a t i f i e d i n n a t u r e . T h e l i m e s l u r r y f lo we d th r ou g h f i s s u r e s

c au se d by t h e p r e s s J r e , f r a c t u r i n g t h e s i l t y s o i l s o r p r e e x i s t in g vo i ds .

L i t t l e p e n e t r a t i o n i n t o t h e h e a v ie r c l a y s o c c ur r ed , and b ul g in g o f

t h e h i g hl y p l a s t i c m a t e r i a l a ll ow ed t h e s l u r r y t o go a ro un d t h e i n j e c -

t o r . The a r e a o f t r e a t m e n t , a f t e r y r , ex t en d ed 1 12 -1 -1 /2 i n . a bo ve

a nd b el ow t h e s l u r r y se am , a nd no a c t i v e l i m e was a v a i l a b l e f o r f u r t h e r

r e a c t i o n s w i t h t h e s u r ro un di ng s o i l . Th er e was l i t t l e i n c r e a se i n t h e

u n co nf i n ed co m pres s iv e s t r e n g t h o f s am p le s , an d no l e s s e n i n g o f s u b-

s id enc e due t o LSPI was obse rved .

1 4 6 . Wright 2049205 a l s o o b s er v ed t h a t when l i m e s l u r r y i s i n -

j e c t e d i n t o heavy c l a y s , t h e s l u r r y m i gr a t e s t h ro u gh a v a i l a b l e f r a c -

t u r e s and f i s s u r e s i n t h e s o i l , c r e a t i n g a network o f l ime seams . The

a dd ed m o i s t u r e may c a u s e a n o t i c e a b l e s w e l l o f 2 -8 i n . a t t h e t i m e o f

i n j e c t i o n , d ep en di ng upon t h e o r i g i n a l m o i st u r e c o n te n t o f t h e s o i l .

T h i s p r e s w e l l i s b e n e f i c i a l a s t h e l i m e s eams a nd u pp er 4 t o 6 -i n.

s t a b i l i z e d l a y e r c r e a t e m o i st u r e b a r r i e r s w hich a s s i s t I n ma i nt a in i ng a

c o n s t a n t m o i s t u r e c o n t e n t , nd thus e l i m i n a t e s u b s equ en t c r ac k i n g an d



s w e l l i n g . B ec au se of t h e l i me seam e f f e c t , t h e q u a l i t y o f t h e LSPI can -

n o t be e v a l u a t e d b y c o n v e nt i o n a l t e s t s , i . e . , A t t e r b e r g l i m i t s , pH,

s w e l l , o r s t r e n g t h t e s t s , o n r e co v er e d s am pl es .

1 4 7 . I n g l e s and l ? e i l l H Oeva lua ted l ime and cement grout ing a t

s ev en s i t e s i n A u s t r a l i a. Two l im e- wa te r g r o u t s , 1 : l an d 1 : 2 by we igh t ,

and a comparison cement grout , 1:1 were i n j e c t e d un de r p re s s u r e i n t o

t h e s o i l v i a s e a l e d 4 -i n. a u ge r h o l e s r a n g i ng from t o 8 f t d eep .

V i s u a l i n s p e c t i o n o f r e c o v er e d c o r e s showed t h a t t h e g r o u t p e n e t r a t e d

f i s s u r e s an d n o t p o re s . I n t h i s c o n t e x t , dr y -s ea so n g r o u t i n g , when d es -

i c c a t i o n c r a c k s a r e most p r e v a l e n t , e n h an ce s g r o u t p e n e t r a t i o n . P o s t -

g r o u t in g r e s u l t s i n d i c a t e d t h a t s u r f a c e movements o c c u r re d s h o r t l y a f t e r

g r o u t i n g due t o t h e m o i s t ur e b e i n g ad de d, b u t t h a t s u r f a c e l e v e l f l u c -

t u a t i o n s i n m o n t m or i l l o ni t i c s o i l s a nd t o t a l s w e l l we re r ed u ce d by 50

p e r ce n t o v e r u n t r e a t e d a r e a s . By c om par i son , ce me nt g r o u t i ng was l e s s

s a t i s f a c t o r y w i t h s u r f a c e movements i n t h e m o n t m or i l l o ni t i c s o i l b ei n g

r e duc ed by 1 0 pe r c e n t .

148 . I n a re ce nt pub l i ca t i on 19 75 ) , Thompson and Robne t t2 6

summarized t h a t a l th o u gh t h e r e a r e c o n f l i c t i n g r e p o r t s c o nc e rn i ng t h e

e f f e c t i v e n e s s o f L S P I it see ms l og ic a l t o c onc lude th a t LSPI may be

a n e f f e c t i v e s w e l l c o n t r o l p r o c e du r e u n de r c e r t a i n c i r c um s t a n ce s . The

c ond i t ion most f a vor a b le t o t he a c h ie ve m en t o f suc c e ss f u l LSPI t r e a tm e n t

o f e x pa n si v e s o i l s i s t h e p r es e n c e o f a n e x t e n s i v e f i s s u r e and c r a c k

n et wo rk i n t o w hi ch t h e l i me s l u r r y c an b e s u c c e s s f u l l y i n j e c t e d . The

t r e a t m e n t mechani sms e x p l a i n i n g LSPI e f f e c t i v e n e s s , i . e . , p r e w e t t i n g ,

dev elop ment o f s o i l - l i m e m o i s t u r e b a r r i e r s , e f f e c t i v e s w e l l r e s t r a i n t

w i t h t h e f o r m at i o n o f l i m i t e d q u a n t i t i e s o f s o i l - l i m e r e a c t i o n p r o d u c t s ,

a l l have v a l i d i t y

149 . Deep-plow l im e s t a b i l i z a t io n . C onve nt iona l so i l - l im e

c ons t r u c t i on t e c hn iq ue s a r e no r m a l ly l i m i t e d t o maximum de p ths o f 8-12

i n . W ith t h e s e l i t t h i c k n e s s e s , t y p i c a l s o i l s t a b i l i z a t i o n eq uip ment

i s c a pa b le o f p u l v e r i z a t i o n , b l e n d in g , and mi xi ng r e q u i r e d f o r h i g h

q u a l i t y s o i l - l i m e m i x t u re s . However, i f g r e a t e r d e p t h s o f s t a b i l i z a t i o n

a r e r e q u i r e d i n on e l i f t t h e s e c o n v e n t i o n al t e c h n iq u e s a r e i n a d e qu a t e .

~ h a m p s o n l ~ ~escribes success fu l use of deep plow lime st biliz tion t o



i n c r e a s e i n d e n s i t y c a us e s an i n c r e a s e i n s w e l l ) . Hence low d e n s i t i e s

and h i g h w a t er c o n t e n t s a r e c on d uc i ve t o s m a l l e r e x p a n si o n . Seed and

chan5 obse r ved th a t s o i l s c om pa cted d r y o f optimum e x h i b i t h ig he r

s w e l l i ng c h a r a c t e r i s t i c s a n d s w e l l t o h i g h er w a t er c o n t e n t s t h a n d o

samples a t t h e same de ns it y compacted wet of optimum.

153. The method of compac t ion a ls o in f l ue nc es sw el l i ng charac-

t e r i s t i c s o f c om pact ed s w e l l i n g s o i l s . An ex p an s iv e s o i l w i t h a d i s -

p e rs e d , ( d e f l o c c u l a t e d ) s t r u c t u r e s w e l l s l e s s t h a n one w i t h a f l o c c u l a t e d

s t r u c t u r e f o r t h e same w a t er c o n t e n t a c d d e n s i t y . Seed e t a l . 142 have

shown i n F i g u r e 1 6 t h a t k n ea di n g c om pa ct io n l e a d s t o d i s p e r s e d s t r u c t u r e s

and l e s s s w e l l th a n s t a t i c c om pa ct io n an d f l o c c u l a t e d s t r u c t u r e .

1 5 4 From t h e s e c o n s i d e r a t i o n s , t h e s w e l l o r s w e l l p r e s s u r e c an

b e r ed u ce d b y c o mp a ct i ng t h e s o i l t o medium o r l ow d e n s i t i e s a t w a t e r

co nt en ts above optimum. Compaction equipment produ cing a kneading

a c t i o n an d c o r r es p o n d i n g d i s p e r s e d s t r u c t u r e , s u ch a s a s h e e p s f o o t

r o l l e r , wo ul d b e most a p p r o p r i a t e . O b v io u s ly , i f hi g h s t r e n g t h s we re

i m p o r t a n t , l ow d e n s i t i e s wet o f o ptimum a r e i m p r a c t i c a l a s t h i s c o n di -

t i o n i s c o n du c iv e t o l ow s t r e n g t h s a nd s u b se q u en t d e f o r m a ti o n s .

155. ~ o h n s o n * ~i t e s examples by t h e 0maha211 and Kansas C i t y

212

D i s t r i c t s of t h e U S. Army Corps of Engin eers u si ng moi st ur e and

d e n s i t y c o n t r o l meth ods f o r m in im iz in g s o i l h ea ve . I n t h e s e D i s t r i c t s ,

wat er con te nt s 2-5-1/2 pe rce nt above optimum and compaction t o 88-93

p e r c e n t o f s t a n d a r d d e n s i t y w ere s u c c e s s f u l i n c o n t r o l l i n g he av e.

156. ~ e e r ~ l ~escr ibes North Dakota Highway Department experiences

us ing c om pac tion c o n t r o l t o m inim iz e e xpa ns ive subgr a de p r ob le ms . P r io r

t o 1967 , s t a nda r d c ompac t ion f o r e a r thwor k was t o c om pa ct t h e subgr a de

t o 90 pe rc en t of t h e AASHTO T 180 maximum dry density and use a minimum

wa te r c on te n t o f 75 pe r c e n t o f opt im um. The se c r i t e r i a r e su l t e d i n com-

p a c t i n g t h e s o i l t o f a i r l y low w a t er c o n t e n t s , w hi ch was c o nd uc iv e t o

swe l l . S inc e 1967 , c om pac tion sp e c i f i c a t io ns have bee n c ha nge d t o 85

p e r c e n t of AASHTO T-180 maximum d ry d e ~ s i t y nd a minimum wat er co nt en t

of optimum. These new compac tion s ta nd ard s and t h e use of co nt i nuo usl y

r e in f o r c e d c onc r e te pavem en ts ha ve v i r tu a l ly e l im ina te d pa ve me nt r ough-

n e ss i n e xp an s iv e s o i l a r e a s .



D R Y D E N S I T Y P C F

a PITTSBURGS NDY CL Y

D RY D E N S IT Y P C F

b VICKSBURG S L T Y C L Y

Figure 16. Effects of method of compaction on swell

pressure saturation from Reference 142



56157. The South Dakota Department of Tra nsp or t a t i on used spe c i -

f i c a t i o n s r e q u i r in g t h a t t h e upper 3 f t o f t h e s ub gr ad e i n b o th c u t s a nd

f i l l s b e c o n s t r u c t e d of' w ea th er ed s o i l s e l e c t e d f o r t h a t p u r po s e . The

3- t o 6 - f t zone o f t h e e n t i r e s u bg ra de s t o be c o n s t r u c t e d o f n o rm al

s o i l u s ing h igh e r wa te r c on te n t s a nd lowe r de ns i t y minimum r e qu i r e m e n t s

t h a n t h e u n d e r l y i n g embankment. S u bs e qu e nt f i e l d t e s t s r e v e a l e d t h a t

t w a s n o t al wa ys p r a c t i c a l t o h o ld t h e w a te r c o n te n t t o p er ce n ta g e

po in ts above optimum, and t h e heavy con s t ru c t io n equipment us ua l l y com-

pac te d t h e s o i l above th e ta rg e t low den s i ty of 92 per cen t of AASHTO

T-99. The s p e c i f i c a t i o n s w ere r e v i s e d t o s e t a minimum d e n s i t y o f t h e

upper 6 f t of subgrade t o 92 per ce nt AASHTO T 99 w i t h a t a r g e t d e n s i t y

o f 95 pe r c e n t . The c o r r e spond ing wa te r c on te n t was s e t a t no t lowe r

tha n optimum wi th a t a r g e t c o n te n t o f pe r c e n ta ge po in t s above opt imum.

P r e l i m i n a r y c o n c l u s i o n s b a s ed on r o u gh n e ss i n d e x ch e ck s i n d i c a t e t h a t

t h e s p e c i a l m o i s tu r e -d e n si t y c o n t r o l s h av e r e t a r d e d t h e a d v e r s e e f f e c t s

o f t h e e x pa n si v e s o i l .

1 5 8. The Wyoming S t a t e Highway ~ e p a r t m e n t l ~ ~a s e xpe r im e n te d

w i t h s u b e x c a v a ti o n an d r e p l a c i n g t h e m a t ' e r i a l w i t h m o i s t u r e a nd d e n s i t y

c o n t r o l . I n a r e a s w here t h e i nt e r b e d d ed l a y e r s i n t e r s e c t t h e s u bg ra d e,

a more un i f or m subgr a de i s ob ta i ne d , a nd many o f t h e s ho r t , c hoppy he a ves

o f t e n p ro du ce d b y t h i s f o rm a t i o n a r e e l i m i n a t e d . H owever, t h e y f e e l

t h a t u s e o f m oi s t ur e d e n s i t y c o n t r o l i n h ar d s h a l e s p l a c e s m o is t u re i n

a r e a s whe r e it o r d i n a r i l y would n o t r e a c h an d t h a t a b e t t e r a pp ro ac h s

t o p r e v e n t m o i s t u r e i n t r u s i o n . The p ro bl em s t h a t t h e m a t e r i a l u s ed

i n l a b o r a t o r y d e t e r m i n a t i o n s o f c om pa ct io n c u r v e s s l i m i t e d t o minus

No. 4 s i e v e m a t e r i a l . However, t h e m a t e r i a l i n t h e f i e l d ne ve r i s

b ro ke n u p t h i s f i n e . S p e ci f y in g w a t er c o n t e n t s ab ov e l a b o r a t o r y d e t e r -

mined optimum w a t e r c o n t e n t s p l a c e s a g r a n u l a r a c t i n g f i l l a t w a t e r

c o n t e n t s f a r ab ov e f i e l d c o n d i t i o n optimum. The r e s u l t s s h a l e f r a g -

m en ts o r c l a y c l o d s d r y on t h e i n s i d e w i th f r e e wa te r i n t h e v o i d s.

T h i s r e s u l t s i n a n u n s t a b l e c o n d i t i o n wh ic h c an c a u s e i n t e r n a l b r ea k -

downs o r e x p a ns i o n a f t e r s u r f a c i n g e v en i t h e s u r f a c e m o i s t u r e i s ke p t

o u t .

159. Exper ience o f t h e Colorado Department o f Highways2 4



c o nc e rn i ng c o n s t r u c t i o n i n a r i d r e g i o n s w i t h o r w i t h o ut m o i s t u r e o r d en-

s i t y c o n t r o l h as shown t h a t s a t i s f a c t o r y f i l l s c an be c o n s t r u c t e d w i t h

s w el l in g s o i l si

t h e r e i s good m o i s t ur e - de n s i ty c o n t r o l . O ft en t h e

e xp en se of mo i s t u re - d en s i t y c o n t r o l f o r t h e e n t i r e d e pt h of h i g h f i l l s

i s n o t e c o n o mi c al l y j u s t i f i e d w here w a te r i s a t a premium. However,

a comparison of two s i mi la r roadways, one cons t ru c te d wi th mois tu re den-

s i t y c o n t r o l a nd t h e o t h e r w i t ho u t , shows t h a t 33 p e rc e nt o f t h e d i s t r e s s

o bs er ve d i n t h e l a t t e r o c c ur r ed i n f i l l s , w h il e no d i s t r e s s was o bs er ve d,

i n f i l l s c f t h e f ormer . By i n c o rp o r at i n g s u f f i c i e n t m oi st ur e i n t h e

u pp er l a y e r s a nd a v o i d i n g c o n s t r u c t i o n o f d r y f i l l s s u c ce s s fu l r e s u l t s

can be obta ined . The sugge s te d de p th o f m oi s tu r e - de ns i ty c on t r o l be low

g r ad e f o r c u t s a nd t o p s o f f i l l s f o r i n t e r s t a t e a nd pr i ma r y h ig hw ay s a r e

a s f o l l o w s :

P l a s t i c i t y

Index

10-20

20-30

30-40

40-50

50

Depth of

T re at me nt , f t

s l i g h t l y d i f f e r e n t s e t of g u i d e l i n e s a r e u se d f o r s ec on da ry and s t a t e

highways

P l a s t i c i t y

Index

10-30

30-50

50

Depth of

T re at me nt , f t

2

3

Heat t rea tment

160. Hea t t r e a tm e n t a s a t e c hn ique o f m od i fy ing e xpa ns ive s o i l s

fo r minimiz ing volume change has not been s t ud ied o r appl ied e xt ens iv e ly

i n t h e Un it ed S t a t e s . 73 N e v e r t h e l e s s , i t i s we l l known t h a t he a t ing

c a n c a use c ons ide r a b le a l t e r a t i o n o f t h e mi n er a lo g ic a l and hence physica l

a nd e n g i n e e r i n g p r o p e r t i e s o f c l a y s . Aylmore e t a l . 215 o b s e r v e d t h a t

s w e l l i n g c h a r a c t e r i s t i c s may b e re du ce d s i g n i f i c a n t l y by h e a t i n g t o

+20O0C.



161 l Jppa1216 r e po r t s f i e l d he a t t r e a tm e n t e xpe r im e n t s on I nd ia n

B la ck C o t ton S o i l s u s ing t h e I r v i ne m a ch ine a mob i le f u r na c e ma nufa c-

tu r e d i n c o l l a bo r a t io n wi th th e Aus t r a l i a n gover nm en t. The m ac hine con-

s i s t s o f two u n i t s on p n e u m at i c - ti r e d w h ee l s a t r a c t o r and a t r a i l e r

h av in g a t o t a l w ei gh t o f ab ou t 20 t o n s . H ea ti n g o f t h e s o i l i s from

two b o t t om l e s s c h am be rs l i n e d w i t h f i r e b r i c k a t t h e t o p . The two cham-

be r s a r e se pa r a te d by a gap o f a bou t f t wh ic h house s a mechan ism f o r

t u r n i n g o v er t h e s o i l bu r n t i n t h e f i r s t chamber. F i r i n g i s accomplished

by bu r ni n g f u e l o i l th r ou g h j e t s u nd er a p r e s s u r e o f C p s i .

162. I n i t i a l e f f o r t s w i th t h e m achine r e s u l t e d i n a baked c r u s t

3 4 i n . t h i c k s t h e f la me s d i d n o t p e n e t r a t e t h e s o i l a nd we re m er el y

r e f l e c t e d . To i n c r e a s e t h e d e pt h o f p e n e t r a t i o n t h e s o i l was b ro ke n

up t o a de p th o f i n . wh ic h p r oduc ed bu r n t c lo ds o f 2 - in. s i z e . The

te c hn ique was f ound t o be qu i t e une c onom ic a l c o s t i ng a bou t th e same

a s h a u l i n g a g g r e g a t e 3 0 m i l e s o r 2 . 5 t i m e s t h e c o s t o f c o n v e n t i o n al

5 p e r c e n t l i m e s t a b i l i z a t i o n . N e v e r t h e l e s s t h e t e c h n i q u e may h av e

some promise i n emergency or ha s t y co ns t r uc t io n .

Summary

1 6 3. B as ed upon t h e s e c a s e h i s t o r i e s i t i s o bv i ou s t h a t e xc av a-

t i o n an d re pl ac em en t t e c h n iq u e s a r e n o t a p a na ce a u n l e s s t h e e n t i r e o r

s u f f i c i e n t d e p t h s o f e x p a n si v e s t r a t u m ca n b e removed s o t h a t s w e l l i n g

i s n e g l i g i b l e o r t o l e r a b l e . U n fo r tu n at e ly t h i s i s seldom t h e c a s e.

R ep la ce me nt s h o u l d b e w i t h r e l a t i v e l y i mp er vi o us m a t e r i a l s t o a v o i d p r o-

v i d i n g m o is t u r e a c c e s s r o u t e s t o t h e s w e l l i n g s u bg ra de .

1 6 4 . The t e c h n i q u e o f a p p l y i n g h ea vy l o a d s t o c o u n t e r a c t s w e l l i n g

pr e s su r e s h a s ge ne r a l l y no t be en a pp l i e d t o pavem en ts a s pa vem en t

w ei gh ts a r e u s u a l l y i n s u f f i c i e n t .

165. M o is t u re b a r r i e r s h av e w i d es p re a d u s ag e a s a n e f f e c t i v e

means f o r c o n t r o l l i n g volume ch a n ge s . I n c a s e s s uc h a s a r i d r e g i o n s

w here s u r f a c e m o i s t u r e e i t h e r r u n o f f o r f rom h y d r o ge n e s i s i s t h e

s o u r c e o f i n f i l t r a t i o n a s p h a l t i c membranes o r f u l l -d e p t h a spha l t pa ve -

ment s a r e e f f e c t i v e . However i n c a s e s where c a p i l l a r y ~ o i s t u r e r h ig h



w a t er t a b l e s p r e c l u d e e f f e c t i v e s e a l i n g o f t h e e x p an s iv e s u bg ra d e from

mois tu re accumula t ions , membranes obv ious ly w l l b e i n e f f e c t i v e . A sp ha l-

t i c p ro du ct s a p p ea r t o b e t h e m ost widely used ma te r i a l fo r membranes.

To b e e f f e c t i v e , c om pl et e s e a l i n g a c r o s s d i t c h e s a nd up t h e b a c k s l o p e s

i s r e q u i r e d .

1 6 6 . Pon ding h as b een s u c ce s s f u l l y u s ed i n T ex as an d M is s i s s ip p i

t o i n c r e as e s u b gr ad e mo i s tu r e c o n t en t s and t h e r e b y min imize s u b s eq u en t

s w e l l i n g . Su cc es s f u l p o n din g r e q u i r e s p r e s en ce o f an ex t en s iv e n e tw or k

o f f i s s u r e s a nd c r a c k s . R e l a t i v e l y im pe rm ea ble n a t u r a l c l a y s o r f i l l s

p robab ly w l l n o t re s po nd w e l l t o t h i s t e c h n i q u e . The u s e o f h o l e s ,

s a n d d r a i n s , o r t r e n c h e s w it h ou t po nd in g g e n e r a l l y i s i n e f f e c t i v e ;

however , where used i n con jun ct i on wi th ponding, th ey may be o f some

b e n e f i t . Lime s t a b i l i z a t i o n a f t e r p on di ng s o f t e n u se d t o p ro v id e a

w or ki ng p l a t f o r m a n d im pe rm ea bl e m o i s t u r e b a r r i e r t o p r e v e n t d e s i c c a t i o n

of th e ponded ar ea s . Some pr ov is io ns shou ld be made t o p re ven t mois tu re

l o s s s ub s eq ue n t t o p on d in g, i . a r e t u r n o f s o i l t o a p re po nde d

c o n d i t i o n .

1 6 7 . Lime co n t in u es t o b e t h e mos t e f f e c t i v e and w id e ly u s ed ad d i -

t i v e f o r r e du c i ng s w e l l in g c h a r a c t e r i s t i c s o f e x pa n si ve c l a y s . I n a d d i-

t i o n t o c o n v e n t i on a l s h a l l o w mix i n - p l a c e o r b a t c h mix s u r f a c e t r e a t m e n t ,

d r i l l - ho le l im e, LSPI, and deep-plow tec hn i que s have been used success -

f u l l y . F i e l d s t u d i e s show t h a t l im e m i g ra t io n from t h e d r i l l h o l e s i s

l i m i t e d t o t h e p er i p h e ry o f t h e h o l e . The p ri m ar y b e n e f i t a r i s e s from

an i n c r e a s e i n m o i s t u re c o n t e n t o f t h e s u r r o un d i n g s u bg ra d e l i m e a i d s

t h e m ig r at i on o f w a te r ) and s t r e s s r e l i e f o f l a t e r a l e xp an si ve p r e s s u r e s .

1 6 8 . A lt ho ug h c o n t r o v e r s i a l , LSPI i s a n e f f e c t i v e s we l l c o n tr o l

p r o ced u re u nd e r ce r t a in c i r cu ms tan ces . Co n d i t i o n s most f av o r in g s u cces s -

f u l t r e a t m e nt a r e t h e p r es e n ce o f e x t e n s i v e f i s s u r e s and c r a ck s i n t o

which t h e s l u r r y can b e i n j e c te d . I t s e f f e c t i v e n e s s i s a t t r i b u t e d t o

p r ew e t t i n g , d ev elop ment o f s o i l - l ime mo i s tu r e b a r r i e r s , an d t h e fo rma-

t i o n of l i m i t e d q u a n t i t i e s o f s o il - l i m e r e a c t i o n p r o d u c ts .

169. Deep-plow t ech n iq u es h av e d emon s t ra t ed t h a t l i f t s up t o

24 and 36 i n . can be s uc ce ss fu l l y mixed wi th l ime and compacted.

1 7 0 . Compact io n o f t h e s o i l t o low o r medium d e n s i t i e s a t w a t e r



contents above optimum can reduce the swell pressures or volume change

of compacted clays. Compaction equipment producing a kneading actionand corresponding dispersed structure such as a sheepsfoot roller are

appropriate. As an alternative to requiring good moisture-density com-

paction control for an entire high fill experience indicates that good

moisture-density control particularly ainimum moisture contents of

optimm in the upper several feet is successful in alleviating swelling

problems.



i n ex ch an g eab le s o dium ca t i o n s an d i n c r eas ed p o t a s s iu m ca t i o n s and pr ob -

ab l e s t ab i l i z in g e f f e c t s o f alumin um. Whi le some s t r en g t h was un do ub t-

e d l y ad de d t o t h e s l o p e by t h i s t r e a t m e n t,i t

was co n s id e r ed i n ad eq u a t e

t o p r ev e n t h ea vi ng o f t h e c o nc r e t e l i n e d s e c t i o n s .

1 7 6 . I n a r ev i ew o f e l ec t r o k in e t i c phenomena , Z as l avs k y and

~ n v i n a ~ ~ep o r t t h a t a lu min un ano d es h ave b een shown t o h av e an i r

r e v e r s i b l e s t a b i l i z i n g e f f e c t on c l a y s o i l s , w h i l e a no de s o f o t h e r m et a ls

a r e l e s s e f f e c t i v e . The i n t r o d u c t i o n o f aluminum s a l t s o l u t i o n s i n t o

t h e s o i l was shown t o be l e s s e f f e c t i v e . G e ne r al l y t h e i r r ev ie w of v a r i -

o u s l a b o r a to r y r e s ea r ch b y o th e r s s howed th a t maximum s t r e n g th en in g

was u s u a l l y o b t a i n ed a f t e r 30 kwhr p e r cu b i c me te r o f s o i l .

1 7 7 , 4 s r i g s219 l a b o r a t o r y e x pe ri me nt s on e l e c t r o k i n e t i c s t a b i -

l i z a t i o n o f a n i l l i t i c c l a y u s i n g c al ci um i o n s wi t h c ar bo n ro d a no de s

a nd s t e e l o r b r a s s mesh f o r c a t h o d e s showed a g e n e r a l l y i n c r e a s i n g

s t r e n g t h w i t h i n c r e a s i n g t i m e s o f t r e a t m e n t . I t was con c lu ded t h a t

t h e s e s t r e n g t h g a i n s we re t h e r e s u l t o f v a r i a t i o n s i n s o i l - m o is t u re con-

t e n t a nd i o n e x ch a ng e w i t h e s s e n t i a l l y no a p p a r e n t c h e m ic a l c e m e n t at i o n

o c c u r r i n g .

1 7 8. The most co mp le te a p p l i c a t i o n o f e l e c t r o k i n e t i c s t a b i l i z a -

t i o n f o r r educ ing swe l l ing under h ighways was conducted by OIBannon f o r

t h e A r i zo n a D e pa rt me nt o f T r a n s p o r t a t i o n22C7221 on t h e r n o n t m o r i l l o n i t i c

C h in l e c l a y . I n l a b o r a t o r y s t u d i e s e v a l u a t i n g alurninun v e r s u s s t e e l

e l e c t r o d e s , a nd c a lc i u m c h l o r i d e , c a l c i w n c h l o r i d e p l u s m ag n es i ur c hl o -

r i d e , aluminum c h l o r i d e , c a l c i um c h l o r i d e p l u s m a g n es i m c h l o r i d e p l l ~ s

a luminum c h l o r i d e , p o ta s si u m c h l o r i d e , a nd s od iu m c h l o r i d e s o l u t i o n s ,

i t was f ou nd t h a t p o ta s si u m c h l o r i d e a nd s t e e l e l e c t r o d e s we re c o n s i s -

t e n t l y t h e most e f f e c t i v e e le c t r od e - c he m i c a l c om bi na ti on f o r t r e a t m e n t

o f t h e C h i n le . F u r t he r t e s t i n g e s t a b l i s h e d t h a t4 5

p er cen t b y w e ig h t

o f co mmerc ia l g r ad e p o t a s s iu m ch lo r i d e was t h e optimum p e r cen t a g e . I n

a n a t t e n p t t o i n c r e a s e t h e r a t e o f p e n e t r a t i o n o f t h e p ot as si um c h l o-

r i d e s o l u t i o n i n t o t h e c l a y , s e v e r a l w e t t i n g a g e n ts were e v a l u a t ed .

These inc lu ded Aeroso l T ( s o J i m J i o c t y l s d f o s u c c i n e t e ) ; Aeroso l A Y

( s o d i m d ia my l s u l f o s u c c i n a t e ) , C-61 ( e t h a n o l a t e 4 a l k y lq u c i ni d i n ea m i n e

c o mp l ex ) , p r o pa n o l a l c o h o l , a nd U l t r a , J e t . he r e s h l t s o f l a b o r a t o r y



and f i e l d t e s t s showed t h a t C 61 and Aerosol Y were p romis ing , w i th C-61

being t h e mos t e f f e c t i v e and recommended f o r usage . From th es e cons id -

e r a t i o n s , a f i e l d t e s t s e c t i o n u s i ng v a r i o u s e l e c t r o d e a rr an ge m en ts an d

me thods o f a d d i ng p o ta s si u m c h l o r i d e t o t h e c l a y we re e v a l u a t e d . S i t e

o ne us e d h o r i z o n t a l e l e c t r o d e s a nd s o l u t i o n w e l l s 6 i n . i n di a me t e r,

18 i n . d eep i n s u b g r ad e , o n 5 - f t c e n t e r s ; s i t e two us ed h o r i z o n t a l

e l e c t r o d e s , a nd t h e b a s e c o u r s e was f l o o de d w i t h t h e c h e mi c a l s o l u t i o n ;

and s i t e t h r e e us ed h o r i z o n t a l e l e c t r o d e s and a c e n t r a l t r e n c h c u t

18 i n . d ee p i n t h e s ub gr ad e an d f i l l e d w i t h p ot as si um c h l o r i d e s o l u t i o n .

E v al u at i on o f t h e s e s i t e s showed th a t t h e So lu t i o n w e l l s p r o v id ed t h e

g r ea t e s t u n i f o r mi t y , d ep th , an d economy o f t r ea t men t . t w a s recom-

mended t h a t No. 8 r e b a r o r e q u i v a l e n t s h ou l d be u s e d a s t h e a no de ,

w h i le t h e c a th o de s s ho ul d b e No. b a r s . I f v e r t i c a l e l e c t r o d e s a r e

u se d, t h e y s ho ul d ex te n d t h e e n t i r e d e p th o f t h e s e c t i o n t o be t r e a t e d ,

w h i le h o r i z o n t a l e l e c t r o d e s s h ou l d b e p l a c e d a p pr o xi m a te l y a t a d ep th

of o ne -h al f t h e t o t a l t h ic k n e ss o f t h e s e c t i o n t o b e t r e a t e d . A v o l t -

a g e g r a d i e n t o f 0 .6 -1 .0 v o l t p e r i n c h i s s u gg e st e d. A p p l i c a t i o n o f

t h e s e c r i t e r i a have p ro ve n e f f e c t i v e i n r e du c in g h ea vi ng i n t h e C h in l e.

179 . OIBannonls 222 l ab o r a to r y ex p e rimen t s u s in g 10 -4 0 p e r cen t

mo n tmo r i l l o n i t e p lu s 90-60 p e r cen t k ao l i n i t e s u b j ec t e d t o p o t a ss iu m

c h l o r i d e e l e c t r o k i n e t i c s t a b i l i z a t i o n s howed t h a t t h e mechanism o f e l e c -

t r o k i n e t i c s t a b i l i z a t i o n was t o pe rm an en tl y a l t e r t h e m i ne r a l og i c a l

c h a r a c t e r i s t i c s o f m o nt m or i ll o ni t e. T h e p o t a s s iu m io n p o s s es s es t h e

c o r r e c t s i z e an d c o o rd i n a ti o n p r o p e r t i e s s o t h a t i t c an e a s i l y e n t e r t h e

b a s a l s h e e t a nd become f i x e d . The r e s u l t o f t h i s a l t e r a t i o n i s a r e -

d u c t i o n i n ex p an s iv e p r es s u r e b y a a f a c t o r r an g in g f ro m 2 t o 8

I o n mig r a t i o n

180 . A p a t en t e d t ech n iq u e h e ld by I o n T ech, I n c . , o f D aly C i ty ,

C a l i f o r n i a , h a s be en s u c c e s s f u l l y us ed f o r t r e a t i n g l a n d s l i d e s a nd e x-

p an s iv e s o i l p ro b lems . 223y224 The te c h n iq u e c o n s i s t s o f t r e a t i n g t h e

c l a y min e r a l w i th a co n cen t r a t ed ch emica l s o lu t i o n . The ch emica l s o lu -

t i o n add ed d epen ds u pon t h e c l ay min e r a l s p r e s en t and t h e g r ou n dw ate r .

A f t e r s e l e c t i o n o f t h e a p p r o p r i a t e ch em ic a l, t h e s o l u t i o n i s a p p l i e d

t o t h e c l a y t hr ou gh c ra c k s a n d/ o r d r i l l ho l es . S u cc es s i s due t o



PAVEIYlENT DESIGN AND CONSTRUCTION METHODS FOE

HIGHWAYS O EXPANSIVE SOIL SUBGRADES

I n t r o d u c t i o n

184 T he re a r e a wi de v a r i e t y o f c u r r e n t d e s i g n an d c o n s t r u c t i o n

p r a c t i c e s b e i n g u s ed by t h e s t a t e s f o r hig hw ay c o n s t r u c t i o n o v e r e xp an -

s i v e c l a y s ub g ra d es . The v a r i e t y o f d e s i g n s r e f l e c t s t h e d i f f e r e n c e s

i n su bg ra de s o i l e nv i ro n me nt al c o n d i t i o n s a v a i l a b i l i t y o f r oa d-

b u i ld i ng m a t e r i a l s and t r a f f i c . The c r i t e r i a f o r u si n g s p e c i a l t r e a t -

m en ts i n de s ign a r e g e n e r a l l y te mpe re d by pa s t e xpe r i e nc e wi th a combi-

na t i on of measures aimed a t minimiz ing mois t ure changes or minimiz ing

t h e e f f e c t s o f s u c h c ha n ge s.

S t at e Highway Agency Pr ac t i ce s

185 . C ur r e nt de s ign t e c hn ique s used by th e s t a t e h ighway

a g en c i es w i t h i n t h e a r e a o f c o nc er n o f t h i s p r o j e c t a r e d e f i n e d an d

d e s c ri b e d i n t h e f o ll o w in g p a ra g ra p h s. T hes e a r e p r a c t i c e s a c t u a l l y

u se d i n t h e d e s i g n an d c o n s t r u c t i o n o f p a v em en ts w h er ea s t h e p r e v i o u s

s e c t i o n i n v ol v ed t h e t r e a t m e nt t e c h n iq u e s p r i m a r i l y from t h e s t a n d p oi n t

o f r e s e a r c h a n d t o a l e s s e r e x t e n t common p r a c t i c e .

150 225 226Kansas

1 8 6 . C u r r en t e n g i n e e r i n g p r a c t i c e s i n c l u d e t r e a t m e n t w i th l im e

and t h e u t i l i z a t i o n o f p o s i t i v e d e s ig n f e a t u r e s a nd c o n s tr u c t io n c o n t r o l .

C u rr e nt l i m e t r e a t m e n t p r a c t i c e f o r c o n c r e t e pa ve me nt s i n v o l v e s x o d i f i -

c a t i o n o f t h e t o p 6 i n . o f t h e s u bg r ad e w i t h h y d r a t ed l i m e when s w e l l

p o t e n t i a l s i n e xc es s o f 2 pe r c e n t a s m e asur ed i n a n odem eter swe l l

t e s t w i t h l - p s i s u r c h ar g e a r e e n co u nt er ed . An i d e n t i c a l p ro ce du re i s

u se d f o r f l e x i b l e p av em en ts i n a r e a s o f e a s t e r n Ka ns as w here p a s t p e r -

f or ma nc e ha s bee n a dve r s e ly a f f e c te d by nonun if o rm subgr a de s wi th d i f -

f e n t i a l s we l l c h a r a c t e r i s t i c s . Any ad ded s o i l su p p or t w hi ch i s r e a l -

i z e d b y t h i s l i m e m o d i f i c a t i o n p r o ce d ur e s r e f l e c t e d i n t h i n n e r d e s ig n

s e c t i o n s . Lime a p p l i c a t i o n r a t e s a r e g e n e r a l l y p e r c e n t by w e i g h t .



U t i l i z a t i o n o f p o s i t i v e d es ig n f e a t u r e s a nd c o n st r u c ti o n c o n t r o l t o

m inim ize t h e d eg re e t o whic h s w e ll p o t e n t i a l i s r e a l i z e d i n cl u de t h e

f o l l o w i n g :

a . S p e c i f i c a t i o n s n or ma ll y r e q u i r e t h a t s o i l m o is t ur e

under con cre te pavements a t t h e t ime of compact ion

be maintained between optimum and 5 percen t above

optimum MR-0) f o r t h e s o i l i n t h e t o p 18 i n . o f t h e

s u bg r ad e . M o i s t ur e c o n t r o l f o r f l e x i b l e p av em en ts

s n o t a s s t r i c t ; t h e l ower bound i s s p e c if i e d a s

5 percent below optimum MR-5 .b . I n b o t h r i g i d an d f l e x i b l e pa vem ents i n c u t s of

w e at he re d s h a l e s t h e s o i l s a r e s ub gr ad ed t o a d e pt h

of 1 2 i n . an d a w idth o f 2 f t be yon d t h e r o a d s u r f a c e .

An ad d i t i on al 6 i n . i s s c a r i f i e d a nd re co mp ac te d t o9 5 pe rc en t o f s ta nd ar d AASHTO T-99 d e n si t y wi th

m o is t ur e c o n t r o l s a s s p e c i f i e d i n t h e s t a n d a r d

s p e c i f i c a t i o n s e i t h e r MR-0 o r NR 5. The subgraded

m a t e r i a l i s r ep l ace d w i th t h e same d e n s i t y and

m o i s t u r e r eq u i r e me n t s p ro v i d i n g a t o t a l o f 18 i n . o f

u ni fo rm m a t e r i a l t h ro u gh t h e c u t . The same dens i ty

an d m o is t ur e c o n t r o l s a r e s p e c i f i e d f o r t h e t o p

18 i n . o f embankment s ec t i on s .

c . F or c o n t r o l o f s u r f a c e a nd s u b s ur f a c e w a t e r a t y p i c a l

d e s i g n roa dwa y s e c t i o n p i a c e s t h e b ot to m o f t h e d i t c h

3 f t be low t h e s h o u ld e r p o i n t . A l so s u b s ur f a c e

i n t e r c e p t o r d r a i n s a r e u se d t o c o n t r o l s u b su r fa c ew a te r i n c u t s e c t i o n s .

187 . Approximate ly 99 percen t o f t h e high ways i n t h e e x p an s iv e

c l a y a r e as h av e been comp let ed so t h e main p ro blem a t t h e p r es en t

t i me i s t o c o n t r o l t h e e x p an s io n a nd volume c ha ng e s p r i o r t o p e r fo r m i n g

m a in t e na n ce . P r e s e n t d e s i g n r e q u i re m e n t s f o r new c o n s t r u c t i o n i f

n ee de d u t i l i z e s a f u l l - d ep th a s p h a l t s e c t i o n o v e r a b i tu min o us mem-

brane p lac ed on t h e subgrade . The membrane ex tend s over t h e wid th o f

t h e r oadw ay sh o u ld e r cu t d i t c h e s an d up th e b ack s lo p e . D esign

s e c t i o n a l s o r e q u i r e s w ide s h o u l d e r s l o p e s a nd good d r a i n a ge i n c u t

d i t c h e s . A s t r u c t u r a l number o f 2 s a s si g ne d e xp an si ve s o i l s i n t h e

SHTO d e s i g n e q u a t i o n .

L o u i s i an a228

1 88 . D es ig n p o l i c y i n t h e S t a t e of L o ui s ia n a p r ov i d e s t h a t

s p e c i a l p r o v i s i o n s a r e r e q u i r e d f o r s u bg ra d e m a t e r i a l s h a vi ng a l i q u i d



l m t a bo ve t h e , v a l u e o f 50 . F o r m a t e r i a l w i t h a l i q u i d l i m i t o f 50 and

be low, a normal d es ign would be sp ec i f ie d f o r embankment co ns t r uc t i on .

The s o i l s d e s i g n e n g i n e e r w i l l s p e c i f y e i t h e r mo i st u re - de n s it y c o n t r o l

o r l i me tr e at m en t f o r s o i l s w it h a l i q u i d l i m i t range of from 5 t o 70.

M o i s t u r e c o n t r o l w i l l be a t opt imum or 2 percen t above optimum, and i f

t h i s c r e a t e s a t o o wet s u b gr ad e c o n d i t i o n , t h e n l i me t r e a tm e n t a b o u t 3

p e r c e n t ) w i l l b e r e q u i r e d f o r t h e u p pe r 2 3 f t of t h e embankment, Mate-

r i a l s w i t h l i q u i d l i m i t s a bove 7 0 w i l l no t no r m a l ly be used i n th e r oad -

way bu t may be used i n nonlo ading ar ea s of t h e embankment such as t h e

sho uld ers . Lime t rea tmen t of th e upper 2-3 f t of th e embankment w i l l

b e re q ui r ed i f t h i s hi g he r l i q u i d l m t ma te r ia l must be used .

Colorado

150,225,229

189 . Ge ne r a l de s ign gu id e l i ne s f o r h ighways on expa ns ive c l a y

subgr a des i n C o lo ra do invo lve a ) a vo id i ng c u t s e c t i o n s and u s i ng f i l l

s e c t io n s a t a l l t i me s , i f p o s s ib l e ; b ) keep ing mo is tu re f rom i n f i l t r a t -

in g in t o th e subgra de by us ing a s ph a l t i c membranes o r f u l l - de p th pave-

ment l a y e r s ; a nd c ) w here c u t s e c t i o n s a r e u s e d , t h e d i t c h s h ou l d b e

p l a c e d a t l e a s t 2 5 f t fro m t h e s h o u l d e r a nd u nd e rc u t t h e s ub g ra de a nd

re comp ac t t o ASSHTO T 99 s p e c i f i c a t i o n s w i t h s t r i c t m o is t ur e- de ns i ty

c o n t r o l . The t a b u l a t i o n i n pa ra gr ap h 15 9 d e f i n e s t h e g u i d e l i n e s f o r

d e p t h o f u n d e r cu t f o r i n t e r s t a t e a nd p r im a ry r o a d s a nd f o r s ec on d ar y

an d s t a t e ro a d s .

M i s s i s s i o ~ i50,230

190 The S t a t e o f M i s s i s s i p p i s i n c o r p o r a t i n g v a r i o u s e x p e r i -

m e n ta l i t e m s suc h a s a sp ha l t mem branes , m o i s tu r e - de ns i ty c o n t r o l ,

r e p la ce m e n t o f m a te r i a l , a nd l im e t r e a tm e n t f o r new c ons t r uc t ion now in

p r o gr e s s ; a nd some of t he se t e c hn iqu e s may be in c o r por a te d i n t o de s ign

p r o c e d ur e s i n t h e f u t u r e . Highways a r e p r e s e n t l y d e s i gn e d u s i n g t h e

AASHTO eq ua ti on i n which co e f f i c i e n t s of r e l a t i v e s t r e ng t h p e r i n ch

o f t h i c k n e s s a r e a s s i g ne d t h e m a t e r i a l s u se d i n t h e l a y e r s . Lime s t a -

b i l i z a t i o n , w hich i n c re a s e s t h e c o e f f i c i e n t o f r e l a t i v e s t r e n g t h of

t h i s l a y e r a nd r e du c es t h e e x p a ns i v e p r o p e r t i e s , would b e c o n s id e r e d

t h e o n l y a pp ro ac h a t t h e p r e s e n t t i me t o t h e e xp a ns i ve s o i l pr ob le m.

Lime content w i l l g e n e r a l l y r an g e from about t o 8 p e r c e n t .



South Dakota50,225,231

191 For primary and high type roads, design procedures incor-

porate undercutting, moisture and density control, and lime stabiliza-

tion. These procedures are used under asphalt or concrete roadways;

however, where areas have indicated extremely unstable characteristics

from past performances, an asphalt-surfaced roadway will be specified.

This is primarily for easier maintenance. The asphalt pavements are

full-depth asphalt (12-13 in. thick) placed directly on the treated

subgrade. South Dakota has stopped constructing jointed concrete pave-

ments and is building continuous reinforced pavements. The embankment

under both rigid and flexible pavements is treated the same where

expansive soils are encountered. The specification requires that the

upper ft of the subgrade in both cuts and fills is to be constructed

of weathered soil. This is accomplished by undercutting the subgrade

soil in 3-ft increments to a depth of 6 ft. The top ft of subgrade

material that was removed and stockpiled is placed in the bottom of

the excavation and compacted to about 92 to 95 percent of AASHTO T-99

density at moisture contents just above optimum. The remaining 3 ft of

material is compacted in place with the same density and moisture re-

quirements. Approximately 5-6 percent of lime is added to the top

in. layer of this material. The undercut and backfill in the lower

3 ft is from shoulder line to shouider line whereas the upper 3 ft of

backfill material is from toe to toe of the embankment. For secondary

roads, only 3 ft of material is undercut and replaced, extending from

toe to toe of the embankment.

Wyoming50,225,232,233

2 . here expansive soils are encountered in Wyoming, general

practice in design involves undercutting the subgrade to a maximum

depth of 5 ft and recompacting the material at moisture contents between

minus 4 percent and plus 2 percent of AASHTO 'I1-99ptimum. Swell pres-

sure tests are determined on subgrade soils to determine the required

thickness necessary to prevent volume change. The use of full-depth

asphalt sections placed directly on grade are being used to help pre-

vent infiltration into the subgrade. Asphalt membranes are also being



u se d w i t h t h e f u l l - d e p t h a s p h a l t t o p r o t e c t t h e s ub gr a de s h o u l d e r s a nd

d i t ch es f ro m i n t r u s i o n o f wa t e r . Removal and r ep l acem en t o f t h e ex -

p a ns i ve m a t e r i a l w i t h a no ne xp an si ve s o i l may be s p e c i f i e d i n d e s i g n i f

t h i s s f e a s i b l e . S ta ge s ur f a c i ng i s a l s o u se d, i f p o s s i b l e . C os t o f

e a ch a l t e r n a t e d e s i gn i s co n s i d e red , an d t h e most eco n o mi ca l o ne i s

u s ed .

Oklahoma225,234,235

193. Pavement des ign i n Oklahoma i s based on t h e Oklahoma S o i l

In dex OSI ) whi ch i s d e r i v ed f ro m t h e A t t e rb e rg l i m i t s an d g ra i n - s i ze

d i s t r i b u t i o n o f i ,h e s u bg rad e m a t e r i a l . Lime m o d i f i c a t i o n s r o u t i n e l y

u s ed i n a rea s whe re ex p an s i v e s o i l s a r e p red om i nan t. Lime p e rcen t ag es

u sed a re g en e ra l l y b et ween 4 and 6 p e r c e n t , a nd t h e s t r e n g t h o f t h e

l im e -m od if ie d l a y e r i s a c c o u nt e d f o r i n t h e d e s i gn m eth od. The l i m e

t r e a t m e n t i n c r e a s e s t h e O SI, w hi ch r e d uc e s t h e t h i c k n e s s r e q u i r e d .

T y pi c a l pa vem ent s e c t i o n s u se d i n e x p a n si v e s o i l a r e a s a r e 24 i n o f

s e l e c t b or ro w o r 2 4 i n . o f l ime-modi f ied subgrade under i n . o f b la ck

b as e and 9 i n . o f r e i n f o rc ed co n c re t e p av em en t. F l ex i b l e pavement s

a r e u s u a l l y 4 1/2 i n . o f a s p h a l t i c c o n c r e t e o v er 9 i n . o f b la c k b a s e on

a 6 - in . l ime-modi f ied subgrade la ye r .

Montana150,225,236

194 S p e c i a l p r o v i si o n s a r e i nc lu de d i n t h e s p e c i f i c a t i o n s whic h

r e q u i r e t h a t s ub ex ca va te d c l a y s h a l e and s h a l e m a t e r i a l s b e p l a c ed i n t h e

l ow e r p o r t i o n s o f t h e s u be x ca v at e d a r e a s a nd i n t h e embankment not with-

i n t h e t o p 3 f t . The c l ay s h a l e m a t e r i a l s a r e com pact ed b et ween 9 t o

98 p e r c e n t o f AASHTO T 99 de ns i t y a t abou t 2 per cen t above optimum

m o i s t u re . The t o p 3 f t o f b a c k f i l l m a t e r i a l i s low s w el l m a t e r i a l , and

m o i s tu r e a nd d e n s i t y c o n t r o l s a r e a l s o r e q u i r e d on t h i s m a t e r i a l .

C a l i f o r n i a150,225,237

195 . Design p roced ures f o r por t la nd cement con cre te pavements

i n C a l i f o r n i a i n c o r p o r a t e t h e e x p m s i v e p r e s s u r e a nd l i n e a r e x p an si on

t e s t s t o d e t e rm i ne t h e m o is t u r e a d ju s tm e n t n e c e s s a r y i n t h e s ub gr a de

and re qu i re d overburden t o overcome the expans ive p res su r e . The pave-

ment t h i c k ne s s i s de s ig n ed a c c o r di n g ly . Some d i s t r i c t s i n t h e s t a t e

u se l im e t r e a t n e n t i n t h e u pp er 6-12 i n . o f t h e s u bg ra de m a t e r i a l , a nd



th e s l a bs may be l ev e le d by s l a b j ack ing o r in some cases l ev e le d by

ap p ly i n g w a t er i n h o l e s t h a t have been d r i l l e d i n th e s l ab s . The

Arizona Department of Transportation has been usin a ru b b e r i zed a s p h a l t

membrane sp rayed ove r t h e e x is t i n g roadway and s h o ul d e rs p r i o r t o o v er -

l ay in g t o p re ve nt i n f i l t r a t i o n o s u r f ace w a t e r .



SUMMARY

2 00 . T h i s r e p o r t , w hich s based on a r ev ie w o f l i t e r a t u r e

combin ed w i t h . e x p e r i e n ce s o f t h e s t a t e high way ag en c i e s co n ta c t e d , p r o -

v i de s an updated summary of t h e p ro pe r t ie s which in f l ue nc e vo lume

c ha ng e o f e x pa n s iv e s o i l s , t e c h n i q ue s us ed f o r i d e n t i f i c a t i o n a nd t e s t -

i n g o f e x p a ns i v e s o i l s , a nd p r e - a n d p o s t c o n s t r u c t i o n t r e a t m e n t t e c h -

n iq u es f o r ex p an s iv e s o i l su b g r ad es. Some o f t h e more imp o r t an t p o in t s

c o n ce r ni n g e x p an s iv e s o i l s an d t h e t o p i c s d i s c u s s e d w i t h i n t h e r e p o r t

a r e s um mari ze d i n t h e f o l l o wi n g p a r a g r a p h s .

2 01 . E x pa n si ve s o i l s a r e a r e a l l y e x t e n s i v e i n many r e g i o n s o f

t h e U ni t ed S t a t e s . The o r i g i n an d d i s t r i b u t i o n o f e x pa n si v e s o i l s a r e

f u n c t i o n s o f t h e i r p a s t g e o l o g i c c o n d i t i o n . E xp an si ve s o i l s a r e form ed

a s a r e s u l t o f w e at he ri ng e i t h e r p h y s i c al o r c he m i c a l ) , d l a g e n e t i c

a l t e r a t i o n , a n d/ or h yd ro th er ma l a l t e r a t i o n o f e x i s t i n g m a t e r i a l s . The

d i s t r i b u t i o n o f p o t e n t i a l l y e x p a n si v e s o i l s h a s be en d e f i n e d a nd maps

p r e p a r e d s ho wi ng r e l a t i v e d e g r e e s o f e x p a n s i v i t y b a s ed on g e o l o g i c

c o n d i t i o n s p e r t i n e n t t o t h e f o rm a t io n , a c c um u l at i on , and p r e s e r v a t i o n

o f t h e m a t e r i a l s . T he se f a c t o r s h av e be en c om bi ne d w i t h e x p e r i e n c e s o f

s t a t e h ig hw ay a g e n c i e s t o p r o v i d e a summary o f p o t e n t i a l p ro bl em a r e a s .

2 02 . Th e c l ay min e r a l s w hich ex h i b i t ap p r ec i ab l e vo lu me chan ge

w i t h v a r i a t i o n s i n m o i s t u r e c o n t e n t i n c l u d e m o n t m o r i l l o n i t e , v er mi cu -

l i t e , c h l o r i t e , a nd m ix ed -l ay er c o mb in a ti o ns o f t h e s e m i n e r a l s w i t h one

a n o t h e r o r w i t h o t h e r c l a y m i n e r a l s . T he se c l a y m i n e r a l s e x h i b i t volume

c ha ng e b e ca u se of e l e c t r i c a l c ha r ge c h a r a c t e r i s t i c s , d e g re e o f c r y s t a l -

l i n i t y , a nd p a r t i c l e s i z e . The m i n e r a lo g i c c om p os it i on o f e x p an s iv e

s o i l s d e t er m i ne s wh e th e r t h e s o i l h a s a p o t e n t i a l f o r v olume c h a n ge ,a nd t h e p h y s i c a l a nd e n v ir o nm e n ta l f a c t o r s c o n t r o l t h e amount of volume

change t h a t t h e s o i l w l l undergo.

203. The amount of volume change e x h i b i t e d by an e x pa n si ve s o i l

s i n fl u en c e d by t h e i n t r i n s i c p r o p e r t i e s b o t h p h y s i ca l nd phys ico-

c h e mi c a l) o f t h e m a t e r i a l a n d t h e e n v ir o nm e n ta l c o n d i t i o n s p r e v a i l i n g

a t a s p e c i f i c s i t e . The l a b o r a t o r y an d i n s i t u b e h av i or s o f e x pa n si v e

s o i l s a r e f u n c t io n s o f n umerous i n t e r r e l a t i o n s h i p s among t h e i n t r i n s i c



p r o p e r t i e s a nd e n vi r on m en t al c o n d i t i o n s .

2 0 4 The sampl ing o f expans ive so i l s i s compl ica ted by t h e wide

v a r i a t i o n s o f t h e i n s i t u c on d it io n s a s s o c i a t e d w i th t h e m a t e r i a l s .

Gen era l ly t h e sampling p rograms per formed by t h e s t a t e highway agenc ies

i n c l u d e sh a l l o w a u g e r b o r i n g s a nd a l i m i t e d number o f u n d i s t u r b e d

samples. I n a d d i t i o n t h e c a p a b i l i t i e s f o r u n d i st u r b ed s am pl in g h ave

n o t b e en d ev el op ed t o t h e e x t e n t r e q u i r e d t o p r o v id e a s u f f i c i e n t number

o f go od sa mp l es f o r t e s t i n g . T h i s l a c k o f a d eq u a t e u n d i s t u r b e d sa m p li n g

co mbin ed wi t h p o o r q u a l i t y s am p le s r e d u c e s t h e e f f e c t i v e n e s s o f a ny

d i r e c t t e s t i n g metho d u s ed t o e s t i m a t e p o t e n t i a l volume c ha ng e. The

i n f l u e n c e o f s t o r a g e o f e x p a ns i ve s o i l s am pl es f o r e x t e nd e d p e r i o d s

s n o t f u l l y u n d e r st o o d ; h owe ve r t s g e n e r a l l y c o n s id e r e d t o be

d e t r i m e n t a l t o t h e q u a l i t y of t h e s am pl e. T h e r ef o r e t e s t i n g s ho ul d b e

c om p le te d a s soo n a s p o s s i b l e a f t e r s a m p li n g.

205. I d e n t i f i c a t i o n o f p o t e n t i a l l y e xp an si ve s o i l s can b e

accompl ished by numerous methods a s des cr ibe d i n Table 5 Many o f

t h e s e me th od s p r o v i d e q u a l i t a t i v e a s se s sm e n t s o f t h e t y p e a n d amount o f

c l a y m i n e r a l p r e s e n t . Most o f t h e s t a t e h ig hway a g e n c i e s r e l y on i n d e x

p r o p e r t y t e s t s a n d e x pe r ie n ce t o i d e n t i f y e x p an si ve s o i l s . A l a r g e

v a r i e t y o f c o mb in at io n te c h n i q u e s e x i s t w hich c o r r e l a t e i n d e x p r o p e r t i e s

and pro bab le volume change. No ge ne ra l l y ap pl ic ab le tech niqu e i s c u r -

r e n t l y a v a i l a b l e ; h o we ve r l o c a l e x p e r ie n c e s w i t h many o f t h e s e c o r r e -

l a t i o n s ha ve be en s u c c e s s f u l .

206 The qu an t i t a t i ve measurement o f p o t en t i a l volume change i s

e s s e n t i a l f o r e s t i m a t i n g t h e amount o f i n s i t u sw e l l . Odometer t e s t s

f o r m e a su r in g s w e l l a nd s w e l l i n g p r e s s u r e a r e t h e most w i d e ly u s e d .

However a v a i l a b l e t e s t i n g pr o ce d ur e s a r e q u i t e v a r i e d w it h r es p e c t t o

p la ce me nt c o n d i t i o n s l o a d i n g c o n d i t i o n s s u r c h ar g e p r e s s u r e s t i m e

a ll ow ed f o r s w e l l and i n t e r p r e t a t i o n of r e s u l t s . Many s t a t e h i g h wa y

a g e n ci e s do n ot u s e a t e s t o f t h i s n a t u r e f o r e s t i m a t i n g i n s i t u volume

change. Even i n t h o s e s t a t e s w hi ch u s e some t y p e o f d i r e c t t e s t i n g

t e c hn i q u e t h e r e s u l t s a r e o f t e n n o t c o n s i d e r ed i n t h e pavement d e si g n

p ro ce du re s o r i n t h e s e l e c t i o n o f a t r ea t me n t a l t e r n a t i v e .

207 Based on case histories descr ib ing p r e c o n s t r u c t i o n



t r e a t men t a l t e r n a t i v e s , t h e more s u cce s s f u l t e ch n i q u es i n c l u d e mem-

b ran es , p o n di n g , l i me t r ea t men t , s u b g rad e co mp act i on co n t ro l , and p o s i -

t i v e s u r f a c e d r a i n a g e . No g e n e r a l l y a p p l i c a b l e g u i d e l i n e s e x i s t w hi ch

d e f i n e t h e m a t e r i a l p r o p e r t i e s and e n vi r on m en ta l c o n d i t i o n s f o r w hic h

a s p e c i f i c t r e at m e nt a l t e r n a t i v e p er fo rm s b e s t . G ui de l in e s o f t h i s

t y p e would e nh an ce t h e s e l e c t i o n o f a s u i t a b l e a l t e r n a t i v e by c o n s i d er -

i n g t h e p er fo rm an ce o f t h e a l t e r n a t i v e u nd er v a r yi n g c o n d i t i o n s a s w e l l

a s t h e c o s t o f t h e a l t e r na t i v e .

208 P o s t c o n s t r u c t i o n t r e a t m e n t t e c h n iq u e s a r e g e n e r a l l y

l i m i t e d t o pavement m ai nt en an ce p r o c e d ~ r e s i . e . , m ud ja ck in g, l e v e l i n g

a nd o v e r l a y i n g , a nd l o c a l e x c a v a t io n a nd r e p l a c e m e n t ) . A p p l i c a t i o n o f

l i m e i n d r i l l h o l e s h a s be en s u c ce s s i u i ly u s ed a s a r emed i a l t r e a t men t

o n a l i m i t e d b a s i s . Some p o s s i b l e t e c h n i q u e s f o r r e m e d i a l t r e a t m e n t

i n c l u d e e l e c t r o k i n e t i c s t a b i l i z a t i o n and i o n m i g r a t i on . E xp er ie nc e

w i t h t h e s e t e ch n i q u es i s somewhat l i r x i t ed an d w l l r e q u i r e f u r t h e r i n -

v e s t i g a t i o n w i t h r e g a r d t o pr o b ab l e s u cc e s s and r e l a t i v e c o s t . t i s

g e n er a l ly ac c ep te d t h a t t h e c o s t o f e l e c t r o k i n e t i c s t a b i l i z a t i o n i s

p r o h i b i t i v e ; h owe ver , w i t h t h e r a p i d l y i n c r e a s i n g c o s t o f c o n s t r u c t i o n

m a t e r i a l s i t may be f e a s i b l e i f a s u f f i c i e n t r e d u c t i o n i n volume ch an ge

can b e o b t a i n ed .



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17. American Association of Petroleum Geologists, Geologic Highway Map:

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18. Geologic Highway Map: Pacific Northwest Region 1973,Tulsa, Okla.

19 Geologic Highway Map: Southern Rocky Mountain Region,1967, Tulsa, Okla.

20. U. S. Geological Survey and State Geological Survey Geological Maps

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Elsevier Press, London, 1973.

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28. Holtz, W. G., ~xpansive lays-

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230. Little, W S., ~o ad wa y esign, Paper Presented to Asphalt Pave-

ment Seminar, Mississippi State University, University, Miss. 1974.

3 . outh Dakota Highway Department, Standard Specifications, t 1969,

and special Provisions for Subgrade Construction, 1969.

232. Nolan, P. R., ~hickness esign for Flexible Pavement, 1970,

Wyoming State Highway Department.

233. Wyoming Highway Department, Standard Specifications, 1971.

234. Oklahoma Highway Department, Standard Specifications, 1967.

235. Haliburton, T A. subgrade Moisture Variations, Final Report,

Aug 1970, Oklahoma State University, Stillwater, Okla.



236. Montana Highway Department, Standard Specifications,'' 1970.

237 California Highway Department, Highway Design Manual, Oct 1974.

238 Marchino, J. L., State of the Art Study, Mancos Shale and Swell-

ing Soils, Mar 1971, Utah Department of Highways.

2 3 9 Texas Highway Department, Standard Specifications, 1972.

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