F i e l d S t a b i l i z a t i o n o f Chinle Clay by E l e c t r o Osmosis and Base Exchange o f Ions.

Arizona Department o f T r a n s p o r t a t i o n

Arizona Department o f T r a n s p o r t a t i o n
206 South 1 7 t h Avenue
Phoenix, AZ 85007

I

I

Prepared i n c o o p e r a t i o n with t h e U.S. Department o f T r a n s p o r t a t i o n , Federal
Highway Administration
A l a r g e s c a l e s o i l s t a b i l i z a t i o n p r o j e c t was i n i t i a t e d i n J u l y 1973 by t h e Arizona
Department o f T r a n s p o r t a t i o n . This p r o j e c t was sponsored by t h e Federal Highway
Administration.

A 500-foot s e c t i o n , which i s p a r t o f a 1300 f o o t c u t on 1-40 35 m i l e s e a s t of
Holbrook, Arizona, was s e l e c t e d a s t h e t e s t s i t e . The n a t u r a l s o i l i n t h e a r e a
i s Chinle c l a y , a h i g h l y expansive Montmorillon$te c l a y .

The s t a b i l i z a t i o n t e c h n i q u e used on t h e Chinle c l a y was treatment with a 0,4N
s o l u t i o n o f KCL and electrochemical a c t i o n .
R e s u l t s show t h a t t h i s method o f s o i l s t a b i l i z a t i o n produced a moderate decrease
i n t h e s w e l l i n g c h a r a c t e r i s t i c s o f t h e Chinle c l a y , i . e . , about a 50% decrease i n
expansive p r e s s u r e and a 36% decrease i n p e r c e n t s w e l l .
Moreover, t h e e l e c t r o n miciographic and x-ray d i f f r a c t i o n d a t a have i n d i c a t e d
some probable c a u s a t i v e f a c t o r s f o r t h e decrease i n t h e s w e l l i n g c h a r a c t e r i s t i c s
of t h e e h i n l e c l a y .

diffraction, electron diffraction,

This document i s a v a i l -

irst p r i n t i n g ) .

i n g number.

I

Unclassified
form

DOT F 17Q0,7

(8-72)

UncJassified

Reproduction o f eampleted p a g e authorized

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%he c o n t e n t s of t h i s r e p o r t r e f l e c t t h e views of
t h e a u t h o r s who a r e r e s p o n s i b l e f o r t h e f a c t s and
t h e a c c u r a c y of t h e d a t a p r e s e n t e d h e r e i n .

The

c o n t e n t s do n o t 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
views o r p o l i c i e s of t h e Arizona Department of
T r a n s p o r t a t i o n o r t h e F e d e r a l Highway A d m i n i s t r a t i o n .
T h i s r e p o r t does n o t c o n s 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 , or regulation.

The c o n t e n t s of t h i s r e p o r t r e p r e s e n t over two
y e a r ' s work conducted by t h e Arizona Department
of T r a n s p o r t a t i o n , Research S e c t i o n .

T h i s work

e n t a i l s t h e development and a n a l y s i s of a f i e l d
procedure f o r t h e s t a b i l i z a t i o n of
Clay u s i n g e l e c t r o - c h e m i c a l methods,

Chin l e

The p r i n i c i p a l r e s e a r c h e r s on t h i s s t u d y f e e l a deep s e n s e of a p p r e c i a t i o n
and g r a t i t u d e t o many i n d i v i d u a l s and O r g a n i z a t i o n f o r t h e e x c e l l e n t , and
c o n t i n u i n g s p i r i t of c l o s e c ~ o p e r a t i o nt h a t e x i s t e d d u r i n g t h e 2 y e a r p e r i o d
of t h i s s t u d y .
T h i s p r o j e c t i n v o l v e d elements of d i f f i c u l t f i e l d c o n s t r u c t i o n work,
s o p h i s t i c a t e d l a b o r a t o r y a n a l y s i s and e f f o r t s of many h i g h l y q u a l i f i e d e n g i n e e r s
and t e c h n i c i a n s w i t h o u t whose h e l p l i t t l e could have been accomplished,
We wish t o thank:
1,

The management of t h e Arizona Department of T r a n s p o r t a t i o n ,

2.

Engineers and S p e c i a l i s t of t h e M a t e r i a l s S e r v i c e s D i v i s i o n ,
Arizona Department of T r a n s p o r t a t i o n , i n p a r t i c u l a r

M r . Grant S , A l l e n P,E,
Engineer of M a t e r i a l s
M r , Rowan J. P e t e r s P.E.
A s s i s t a n t Engineer of M a t e r i a l s
M r . Douglas A. F o r s i t e P.E,
S o i l s Engineer

M r , George B. Way P.E.
C i v i l Engineer I
M r . Hubert He Rosenstock
Chemist
M r . G a m i n Skaggs
Drilling operations

3.

Our s p e c i a l thanks t o t h e Engineer of Research Gene R. Morris

who t o o k g r e a t p a i n s t o p r o v i d e i n s p i r a t i o n and e x c e l l e n t res e a r c h ~ o r k i n g c & n d ~ l i ~ ~ ~w~i tah l iomnpgo r t a n t i n s i g h t ,

4.

Engineers of t h e F e d e r a l Highway A d m i n i s t r a t i o n i n
i n t h e D i v i s i o n and Region and Washington o f f i c e s ,

5

.

D r . John M. Cowely, Calvin P r o f e s s o r of physics
Arizona S t a t e U n i v e r s i t y , D r . John Wheatley e l e c t r o n
m i c r o s c o p i s t and D r . David Hestenes f o r time devoted
t o lengthly but f r u i t f u l l discussions.

6.

A l l p e r s o n n e l a t t h e Arizona Department of T r a n s p o r t a t i o n
D i s t r i c t IV o f f i c e i n Holbrook, Arizona i n p a r t i c u l a r
M r , E. P, Gentsch P.E.
D i s t r i c t Engineer
M r . Rex Wolfe P,E,
A s s i s t a n t D i s t r i c t Engineer

M r , Cliff Foster
Laboratory Supervisor
and f o r t h e v e r y a b l e t e c h n i c a l a s s i s t a n c e we r e c e i v e d
from M r . John Trajanovich, w i t h o u t whose h e l p t h e
p r o j e c t may n o t have g o t t e n beyond t h e planning s t a g e .

Charles E. O'Bannon
Prank P. Mancini

TABLE OF CONTENTS

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Preface . . . . . . .
Table of Contents. . .
L i s t o f Figures. . . .
L i s t of Tables . . . .
Abstract

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CHAPTER

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III.

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Sponsorship . . . . . . . . . . . .
Nature of and Approach t o Problem .
Object o f Research . . . . . . . .
Scope o f Report . . . . . . . . . .

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Geology and Preliminary Sampling of t h e Areas . .
Physicochemical Aspects . . . . . . . . . . . . .
Base Exchange . . . . . . . . . . . . . . . . . .
C l a s s i c a l Modes of Swelling Mechanisms. . . . . .
Introduction

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Clay S t a b i l i z a t i o n by Electso-Osmosis

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Introduction . . . . . . . .
Solute Displacement . . . . .
Experimental Procedure. . . .
Breakthrough Curves . . . . .
Miscible Displacement

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Base Exchange of Ions

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CHAPTER
IV.

V.

PAGE

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General . . . . . . . . . . . . . . .
S i t e S e l e c t i o n and Sampling . . . . .
Sample P r e p a r a t i o n . . . . . . . . .

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Soil properties of untreated material
Expansive p r e s s u r e and percent s w e l l t e s t s . . . . . . .
Determination of optimum p KCL/gm c l a y . . . . . . . . .
Fieldwork . . . . . . . . . . . . . . . . . . . . . . .
General . . . . . . . . . . . . . . . . . . . . . . . . .
S i t e s e l e c t i o n and sampling . . . . . . . . . . . . . . .
F i e l d Test . . . . . . . . . . . . . . . . . . . . . . .
Laboratory work

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Discussion of Operational C h a r a c t e r i s t i c s o f
E. 0 Soil Stabilization

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VI.

VTI

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Results and a n a l y s i s of f i e l d t e s t .
Intmduction . . . . . . . . . . . .
X-ray d i f f r a c t i o n a n a l y s i s . . . . .

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41 I
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Conclusions from X-ray d i f f r a c t i o n d a t a . . . . . . . . .
Transmission E l e c t r o n Microscope . . . . . . . . . . . .
Conclusions from Transmission Electron Miscroscope Data .
Elegainsive p r e s s u r e and % s w e l l i n g o f Post-Test samples .
Conclusions fmm S o i l Test Data . . . . . . . . . . . . .

107

Monetory 4 Energy Expenditures fir Electrochemical
Qperation

109

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VIII .
Nuclear Moisture h n i t o r i n g . . . . . . . . . . . . . . .
IX.
S m a r y . Conclwions and Recornendations . . . . . . . .

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96
10%

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120

LIST OF FIGURES
PAGE

FIGURE
1
2

3
4

5
6
7
8-a
8-b

9 &

a1
J. 2
13

14

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L o c a t i o n of T e s t S i t e . . . . . . . . . . . . . . . . . . . .
Soil Profile
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S u r f a c e Symmetries . . . . . . . . . . . . . . . . . . . . . .
b-dimension v s water c o n t e n t . . . . . . . . . . . . . . . . .
...............
E f f e c t of C a t i o n on b-dimension
M i s c i b l e Displacement . . . . . . . . . . . . . . . . . . . .
M i s c i b l e Displacement . . . . . . . . . . . . . . . . . . . .
Break-through Curve . . . . . . . . . . . . . . . . . . . . .
J.0 M i s c i b l e Displacement . . . . . . . . . . . . . . . . . . . .
Displacement of KC% S o l u t i o n i n s o i l . . . . . . . . . . . . .
TestSiteLayout
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Sampling P l a n Layout . . . . . . . . . . . . . . . . . . . . .
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Flowchart
Major C h i n l e Outcrops

S o i l Grain s i z e d i s t r i b u t i o n
Expansive p r e s s u r e v s % KCL
P r e - t e s t Sampling P l a n

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. Electrical Circuit . .
Cathode S e c t i o n Shown . . .
E.O. E l e c t r i c f i e l d . . . .
E.0

Auger h o l e r shown

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27" l o n g s t e e l S l e e v e shown

Auger h o l e d r i l l i n g

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3
6

9
18

19
20

26
28
29
31

33
36
38
39

FIGURIF,

24
25
26

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29

30
31

32
33
34
35
36
37
38
39
40
41

42

43
44

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46

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3 / 4 view of t e s t s i t e . . . . . . . . . . . . . . . . . . . .
Cathode Trenching O p e r a t i o n . . . . . . . . . . . . . . . . .
P r e p a r a t i o n of snode t r e n c h e s . . . . . . . . . . . . . . . .
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60 KW D.C. Generator
314 view of Generator . . . . . . . . . . . . . . . . . . . .
TransverseE.O.Cables . . . . . . . . . . . . . . . . . . . .
Cathode welding o p e r a t i o n . . . . . . . . . . . . . . . . . .
2500 g a l l o n t a n k e r . . . . . . . . . . . . . . . . . . . . . .
MCL S o l u t i o n p r e p a r a t i o n . . . . . . . . . . . . . . . . . . .
S o l u t i o n d e l i v e r y system . . . . . . . . . . . . . . . . . . .
S o l u t i o n d e l i v e r y system . . . . . . . . . . . . . . . . . . .
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On s i t e s o l u t i o n i n p u t
Close up of s o l u t i o n h o s e and n o z z e l . . . . . . . . . . . . .
P o s t test sampling p l a n . . . . . . . . . . . . . . . . . . .
P r e - t e s t , X-ray d i f f r a c t i o n . t e s t s i t e m a t e r i a l . . . . . . .
P o s t - t e s t . X-ray d i f f r a c t i o n . t e s t s i t e m a t e r i a l . . . . . . .
X-ray d i f f r a c t i o n . sample m a t e r i a l n o t from s i t e . . . . . . .
X-ray d i f f r a c t i o n . sample m a t e r i o a n o t from s i t e . . . . . . .
X-ray d i f f r a c t i o n . sample m a t e r i a l n o t from s i t e . . . . . . .
X-ray d i f f r a c t i o n . sample m a t e r i a l n o t from s i t e . . . . . . .
Electron diffraction pattern fromtreatedtes% s i t e . . . . . .
E l e c t r o n d i f f r a c t i o n p a t t e r n from t r e a t e d t e s t s i t e . . . . .

P a r t i a l view of test s i t e

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FIGURE
47

Electron diffraction pattern from untreated test site

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48

Electron diffraction pattern from untreated test site

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Electron micrograph sample preparation

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Wyoming bentonite electron diffraction pattern

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51-c

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Old E.0 . site electrqn diffraction pattern
Electron transmission micrograph
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Electron transmission micrograph
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ASU designed expansometer. full view

51-a
51-b

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98

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101
101

105

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I05

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ASU designed expansometer. partially disassemble
ASU designed expansometer. fully disassemble
ASU designed empansometer. full view

94

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Typical access tube installation
K+ ion concentration vs distance from auger hole . . . . .
CL-ion concentration vs distance from auger hole . . . . .

Nuclear moisture monitor lay-out

Typical diffusion curves under action of constant force
Electrochemical soil stabilization flow chart

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115
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127

L I S T OF TABLES

TABLE //

PAGE

1

Untreated soil index properttes

42

2

Untreated expansive pressures

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and percent swell . . . .

43

3

X-ray diffraction data of treated and untreated soil

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Engineering properties of treated soil

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5

Post test samples

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T h i s r e p o r t i s based on work performed by t h e Arizona Highway Department, under c o n t r a c t w i t h t h e Department of T r a n s p o r t a t i o n t o i n v e s t i g a t e
" E l c t r o - C h e d c a l Hardening of Expansive Clays",

P m d s f o r t h e p r o j e c t were

provided by t h e F e d e r a l Highway A d m i n i s t r a t i o n through t h e Arizona Department of T r a n s p o r t a t i o n ,

F r e q u e n t l y t h e s o i l s a v a i l a b l e f o r c o n s t r u c t i o n cannot meet t h e r e q u i r e ments, such a s s t r e n g t h and i n c o m p r e s s i b i l i t y , imposed by t h e i r use i n embankments o r subgrades.

The p r o c e s s of improving t h e s o i l s o t h a t i t can

meet t h e r e q d r e m e n t s i s known as s t a b l i l i z a t i o n .

3hny d i f f e r e n t methods of s t a b i l i z a t i o n have been proposed.

From t h e

s t a n d p o i n t of t h e i r f u n c t i o n o r e f f e c t on t h e s o i l t h e y can b e c l a s s i f i e d
as follows :

1.

: h t a i n moisture i n s o i l ,

2.

: P r e v e n t moist.ure from e n t e r i n g s o i l o r from

a f f e c t i n g clay m a t e r i a l s .

3.

:

Binding t h e p a r t i c l e s t o g e t h e r w i t h o u t t h e i r a l t e r a t i o n .

4.

:

5.

Mechanical S t a b i l i z a t i o n :

Plugging t h e Voids.

Improving t h e s o i l g r a d a t i o n .

4*

:

Cbanging t h e c l a y d n e r a l

o r c l a y m i n e r a l absorbed-water system.

A s a t i s f a c t o r y s t a b i l i z i n g t e c h n i q u e must p r o v i d e t h e r e q u i r e d s o i l
q u a i i t i e s and i n a d d i t i o n must s a t i s f y t h e f o l l o w i n g c r i t e r i a :
with t h e s o i l material;

(2) Pemanent;

(1) Compatible

(3) E a s i l y handled and Implemented;

( 4 ) Low c o s t .
The problem of s t a b i l i z i n g Chinle Clay h a s been under c o n s i d e r a t i o n by
A,B.O.T,

s i n c e t h e e a r l y 1960's because of t h e v a s t d e p o s i t s of Swelling Clay

i n Northern Arizona, some 6,000 s q , m i l e s of s u r f a c e exposure, a s shown i n
f i g u r e 1.

The s w e l l i n g c h a r a c t e r i s t i c s of t h e s e Chinle Clay d e p o s i t s a r e l a r g e and
have caused e x c e s s i v e h e a v i n g i n highway s u b g r a d e s ,

This v o l m e t r i c s t r a i n

w i t h r e s u l t i n g pavement s t r e s s h a s caused damage o r f a i l u r e t o many m i l e s of
e x i s t i n g highways i n t h i s r e g i o n of Northern Arizona.

R e c o m i z i n g t h i s c o n d i t i o n t h e Arizona aepartment o f T r m s p o r t a t i o n a d
t h e P.H.W.A.

s u p p o r t e d t h e work of D r . C h a r l e s E. OqBannon, of A,S.U.'s

Engineering Department, on d i a g e n i s i s o f C b i n l e Clay by e l e c t r o c h e m i c a l
methods.

Civil

PHOENIX

@

Fig. 1

TUCSON

The o b j e c t of t h i s r e s e a r c h w a s t o u t i l i z e D r . Charles ~ ' ~ a n n o n ' s
eleetrochermical s o i l - t r e a t m e n t technology and, i f n e c e s s a q t o modify port i o n s of i t f o r t h e e x p r e s s puspose o f c r e a t i n g a v i a b l e s o i l s t a b i l i z a t i o n
t e c h n i q u e t h a t is implementable b y Highway D i v i s i o n M a i n t e n a c e p e r s o n n e l .

T h i s r e p o r t on t h e E l e c t r o - C h e ~ c a l h a r d e n i n g of Ghinle Clay i s presented i n e i g h t chapters.

These c h a p t e r s e x p l a i n i n d e t a i l t h e v a r i o u s

a r e a s of l a b o r a t o r y and f i e l d e x p e r i m e n t a t i o n conducted s i n c e J u l y 1, 1973.
Chapter I1 d i s c u s s e s t h e Geology of s i t e and t h e p r e l i m i n a r y sampling l a y out.

Chapter III i s a review of some Electro-Chemical s o i l h a r d e n i n g con-

c e p t s a s i t a p p l i e s t o t h e e x i s t i n g problem.

Chapter I V p r e s e n t s t h e work

conducted i n t h e l a b o r a t o r y i n p r e p a r a t i o n f o r t h e f i e l d test.

Chapter V

d i s c u s s e s t h e work p e r f o m e d i n t h e f i e l d t e s t i n t h e s p r i n g and summer of
1974.

Chapter V I p r e s e n t s t h e r e s u l t s of t h e f i e l d t e s t w i t h an a n a l y s i s of

t h e data.

Chapter V I I i s a p r e l i d n a s y c o s t s t u d y f o r t h e method.

Chapter

V I I I d i s c u s s e s t h e o n - s i t e m o i s t u r e c o n t e n t measurements u s i n g Nuclear Gauges.

Chapter I X i s t h e c o n c l u s i o n and recommendation t h a t have been reached d u r i n g
t h i s study.

CHAPTER %I
GEOLOGY AND PRELIMINARY SAMPLING OF THE AREA AND SITE

The s i t e i s l o c a t e d i n N o r t h e a s t e r n Arizona on t h e Colorado P l a t e a u
geological province, s e e f i g u r e 2.

The n e a r l y h o r i z o n t a l s a n d s t o n e s and

s h a l e s of T r i a s s i c and J u r a s s i c age i n t h i s a r e a a r e i n t e r m i t t a n t l y covered
by thin-bedded T e r t i a r y s a n d s t o n e s and s h a l e s .

This region i s characterized

by low, broad mesas o v e r l o o k i n g wide, f l a t , s t r e a m v a l l e y s c o n t a i n i n g Quat e r n a r y t o Recent sands and s i l t a l l u v i u m w i t h low terraiaces c o n t a i n i n g a
v e r y l i m i t e d q u a n t i t y of g r a v e l .
U.S.

I n t e r s t a t e 40 t r a n s v e r s e s p r i m a r i l y t h e T r i a s s i c C h i n l e f o r m a t i o n

as i t crosses t h i s area.

The C h i n l e f o r m a t i o n i s composed of s h a l e , c l a y

s a n d s t o n e , and minor amounts of l i m e s t o n e .
C h a r a c t e r i s t i c s of t h e C h i n l e f o r m a t i o n v a r y g r e a t l y i n b o t h t h e physic a l and chemical a s p e c t s .

C h i n l e f o r n a t i o n c o l o r s i n c l u d e r e d , p i n k , brown

g r e e n , p u r p l e , and grey t i n t s ,

I t h a s been p r e v i o u s l y mentioned t h a t s h a l e ,

c l a y , s a n d s t o n e , and minor amounts of l i m e s t o n e a r e p r e s e n t .

P h y s i c a l and

chemical c h a r a c t e r i s t i c s of sedimentary d e p o s i t s a r e dependent f o r t h e most
p a r t on t h r e e f a c t o r s :

1) O f course, dependence

on parent

m a t e r i a l , 2)

method of t r a n s p o r t a t i o n of s e d i m e n t s , and 3) changes a f t e r d e p o s i t i o n .
S e v e r a l d e p o s i t i o n a l environments a r e r e s p o n s i b l e f o r t h e c h a r a c t e r i s t i c s
of t h e C h i n l e formation,

It i s h e l d t h a t t h e c o n d i t i o n s under which t h e

0 1 0 2 0 3 0 4 0
Figure 2

MILES

c h i n l e was d e p o s i t e d were wholly c o n t i n e n t a l - - p r o b a b l y

t h o s e of a w e l l -

graded b u t r a t h e r a r i d p l a i n a c r o s s which s t r e a m s meandered and on which
t h e r e were perhaps s c a t t e r e d l a k e s .

Conglomerates of r e s i s t a n t m a t e r i a l s

t r a n s p o r t e d from a g r e a t d i s t a n c e a r e s c a r c e ; hence, i t i s e v i d e n t t h a t
s t r e a m g r a d i e n t s were low.
of fresh-water
forest.

C o n t i n e n t a l o r i g i n i s evidenced by t h e presence

f o s s i l s , l a n d v e r t e b r a t e s and t h e t r e e s of t h e p e t r i f i e d

Evidence i s p r e s e n t f o r t h e e x i s t e n c e of a warm marine environ-

ment i n p o r t i o n s of t h e a r e a i n which t h e C h i n l e o u t c r o p s .

Montmorillo-

n o i d and b e n t o n i t i c c l a y m i n e r a l s a r e s u g g e s t i v e of v o l c a n i c a c t i v i t y a t
t h e time of t h e warm marine c l i m a t e .

The a l t e r a t i o n of v o l c a n i c ash i n

such a n environment i s f a v o r a b l e t o t h e i n f o r m a t i o n of t h e aforementioned
clays.
I n t h e g e n e r a l a r e a of t h e s i t e , t h e C h i n l e v a r i e s i n t h i c k n e s s and
had a macimum depth of 1,500 f e e t a t t h e t e s t s i t e on I n t e r s t a t e 40, t h e
highway i s i n a 15-foot s h a l e c u t .

The weathered m a t e r i a l on t h e s l o p e s

of t h e c u t s e x t e n d s t o a d e p t h of about one f o o t .

This m a t e r i a l has t h e

t y p i c a l r e t i c u l a t e d appearance of an expansive c l a y , weathered i n p l a c e
from t h e p a r e n t m a t e r i a l .

The u n d e r l y i n g m a t e r i a l i s v e r y h a r d and b r i t t l e ,

The out-crop i s f r a c t u r e d , s l i c k e n s i d e d , and shows no v i s i b l e bedding p l a n e s .
During t h e f i r s t weeks of J u l y , 1973 A.D.O.T,

D i s t r i c t I V personnel

s e t down e n g i n e e r i n g r e f e r e n c e s t a t i o n s on t h e west bound l a n e of U.S.
I n t e r s t a t e 40 a t M.P.

323,82 f o r approximately 1200' of t h e c u t .

A f t e r due c o n s i d e r a t i o n w i t h a n a l l - s y s t e m go t a r g e t d a t e of September

4 , 1993 i n mind i t was decided t h a t t h e o p t i m a l pre-sampling procedure,
b o t h from an e n g i n e e r i n g and economic v i e w p o i n t , was t o a c q u i r e a l l s o i l
samples i n a continuous s t r a i g h t l i n e p a t t e r n .

The samples would b e t a k e n

o n l y over a 500 f a a t s e c t i o n of t h e c u t s e l e c t e d a s t h e t e s t s i t e ,
Taken i n t h i s manner t h e s o i l samples would p r o v i d e a d e q u a t e d a t a on
t h e s o i l c h a r a c t e r i s t i c s of t h e s e c t i o n f o r t h e purposes of t h i s s t u d y .

It s h o u l d b e p o i n t e d o u t t h a t t h i s sampling procedure was conceived
under t h e c o n s t r a i n t s of minimal time and money e x p e n d i t u r e s which would
b e e s s e n t i a l c o n s i d e r a t i o n s f o r an implementable maintainence o p e r a t i o n .
However, t h i s type of sampling procedure i s n o t recommended i f t h e s o i l
s t u d y i s t o b e one of a g e n e r a l i n v e s t i g a t o r y n a t u r e .

Samples were o b t a i n e d from s t a 7+00 t o s t a 12+00 on 20' i n t e r v a l s and
t e s t e d f o r expansive c h a r a c t e r i s t i c s and a t t e r b e r g l i m i t s .
Based on t h e a t t e r b e r g l i m i t s t h e s o i l specimens were c l a s s i f i e d v i a
t h e U n i f i e d S o i l C l a s s i f i c a t i o n s Systems,
and a s o i l p r o f i l e a r e shown i n f i g u r e 3,

The r e s u l t of t h e c k a s s i f i c a t i o n

CWTER I11
Phys ieochemical Aspects
C l ay S t r u c t u r e

Because t h i s work w i t h e l e c t r o - o s m o s i s i s p r i m a r i l y concerned w i t h
s t a b i l i z a t i o n o f Chinle Clay f o r m a t i o n s , a b r i e f review o f c e r t a i n f a c t s
and models of c l a y minerology and e l e c t r o - o s m o s i s i s fundamental.
I t i s w e l l known t h a t t h e s o i l p a r t i c l e s i z e s t r o n g l y a f f e c t s t h e

appearance and b e h a v i o r o f s o i l s .

These e f f e c t s on s o i l b e h a v i o r a r e due

t o t h e i n c r e a s i n g magnitude of t h e f o r c e s among t h e molecules of a d j a c e n t
p a r t i c l e surfaces a s the s i z e decreases,

I n s i l t o r sand and l a r g e r s o i l

s i z e s , t h e r a t i o o f t h e a r e a o f t h e s u r f a c e t o t h e volume o f t h e sample i s
r e l a t i v e l y s m a l l , hence t h e i n t e r s u r f a c e s f o r c e s s m a l l .

I n such c a s e s t h e

shape o f t h e g r a i n , s u r f a c e roughness and r e s u l t i n g i n t e r p a r t i c l e a b r a s i v e
f o r c e s determine t h e o v e r a l l b e h a v i o r o f t h e s o i l mass.
I n t h e c a s e o f s m a l l s o i l p a r t i c l e s , t h e molecules forming t h e p a r t i c l e
s u r f a c e c o n s t i t u t e a l a r g e p r o p o r t i o n o f t h e t o t a l number o f molecules, and
t h e i n t e r p a r t i c l e f o r c e s a s s o c i a t e d w i t h t h e s e s u r f a c e molecules have a
s i g n i f i c a n t e f f e c t on t h e b e h a v i o r o f t h e p a r t i c l e and hence, t h e mass o f
the soil.
I t i s found, i n g e n e r a l , t h a t allowance f o r t h e e f f e c t o f s u r f a c e
f o r c e s must b e made when t h e s i z e o f t h e p a r t i c l e becomes l e s s t h a n one
micron

cm) , a s i z e which corresponds t o t h e upper l i m i t of c o l l o i d s ,

I t was formerly b e l i e v e d t h a t c l a y m i n e r a l s were amorphous i n s t r u c t u r e ,
b u t i n v e s t i g a t i o n s c a r r i e d o u t w i t h x - r a y d i f f r a c t i o n and e l e c t r o n microscopy s i n c e t h e 1920's have shown them t o b e predominately c r y s t a l l i n e ;
moreover, i t i s found t h a t c l a y m i n e r a l s a r e c r y s t a l l i n e h y d r a t e d aluminum
silicates.

Although t h e molecular s t r u c t u r e s a r e complicated, i t has been

shown t h a t c l a y m i n e r a l s a r e c o n s t r u c t e d e s s e n t i a l l y from two b a s i c s t r u c t u r a l
u n i t s : The s i l i c a t e t r a h e d r o n (SIOZ) and t h e o c t a h e d r a l aluminum hydroxide
A 1 (OH) 3 .
A s i l i c a t e t r a h e d r o n c o n s i s t s of a c e n t r a l s i l i c o n atom surrounded by

f o u r oxygen atoms a r r a n g e d a t t h e apexes o f e q u i l a t e r a l t r i a n g l e s .

The o t h e r

s t r u c t u r a l element, h y d r a t e d aluminum, t a k e s t h e form o f an o c t a h e d r a l c r y s t a l , i n which t h e aliuninum atom o c c u p i e s t h e c e n t e r o f t h e s t r u c t u r e , above
and below which t h e oxygen and hydroxyl i o n s a r e a r r a n g e d .
The c l a y m i n e r a l s d e s i g n a t e d S m e c t i t e s a r e composed o f b a s i c u n i t s o f
two s i l i c a t e t r a h e d r a l s h e e t s w i t h a c e n t r a l alumina o c t a h e d r a l s h e e t . These
u n i t s a r e continuous i n t h e a and b d i r e c t i o n s and a r e s t a c k e d one above t h e
other i n the c direction.

These b a s i c u n i t s a r e r e f e r r e d t o a s s i l i c a - a l u m i n a -

s i l i c a units.
I n t h e s t a c k i n g o f t h e b a s i c u n i t s , one above t h e o t h e r , t h e 0 - l a y e r s
o f each u n i t a r e adjacent t o 0-layers o f t h e neighboring u n i t s .

Because

o f t h e p m x i m i t i t y of t h e 0 - l a y e r s , t h e r e i s a weak bonding energy which
p e r m i t s e a s y expansion o f t h e l a t t i c e i n t h e c - d i r e c t i o n ,

I t is t h i s high

swelling c h a r a c t e r i s t i c t h a t i s the outstanding f e a t u r e o f Smectites ,

C h i n l e Clay i s a random-mixed l a y e r e d m i n e r a l c o n t a i n i n g minor t o major
amounts of t h e S m e c t i t e m i n e r a l ; i , e . ,

about 10%

-

SO% by w t . of S m e c t i t e .

S i n c e D r , OqBannon's t r e a t m e n t of s w e l l i n g c l a y s r e s t s on b a s e exchange
phenomena, a s h o r t d i s c u s s i o n of t h i s phenomena i s i n o r d e r ,
The absorbed i o n s on a c l a y s u r f a c e a r e p r e s e n t i n a d i f f u s e double l a y e r .
Each of t h e i o n s r e q u i r e d t o n e u t r a l i z e t h e charge on t h e p a r t i c l e s u r f a c e i s
o s c i l l a t i n g due t o Browniw motion, t h u s t h e i o n i s assumed t o b e o s c i l l a t i n g i n a c e l l , c a l l e d an o s c i l l a t i o n c e l l , a d j a c e n t t o a charged a r e a on t h e
particle surface,
tion

Other i o n s from an added e l e c t r o l y t e may e n t e r t h e o s c i l l a -

c e l l s o r may remain i n t h e e x t e r n a l phase,

naked r a d i u s , i.e., K,'

A given ion w i t h a l a r g e

w i l l have a s m a l l e r h y d r a t i o n r a d i u s and t h u s b e a b l e

t o approach t h e charged s u r f a c e c l o s e r t h a n an i o n w i t h a s m a l l e r naked r a d i u s ,
i , e , ,,'N

and a corresponding l a r g e r h y d r a t i o n r a d i u s ,

Thus, t h e potassium

i o n w i l l , on t h e average, bond t o t h e s u r f a c e w i t h a c o r r e s p o n d i n g l y g r e a t e r
energy t h a n a sodium i o n ,
Such concepts have been evolved i n t o mathematical models which d e p i c t t h e
i o n exchange p r o c e s s a s a s t o c h a s t i c p r o c e s s ,
These t h e o r i e s , i n p a r t i c u l a r t h e one by H, Jenny, l e a d t o mass-law o r
mass-action e q u i l i b r i u m e q u a t i o n s .

However, t h e s e models of base-exchange

imply t h e exchange phenomena i s e s s e n t i a l l y a complex r e d i s t r i b u t i o n of i o n s

b o t h between a n e x t e r n a l phase and t h e i o n swarm and a l s o w i t h i n t h e i o n
swarm.

U n f o r t u n a t e l y t h i s p r o c e s s depends on s e v e r a l f a c t o r s ,

The i o n

r e d i s t r i b u t i o n cannot b e r e g a r d e d a s simple m e t a t h e s i s , p r e c i s e l y d e f i n e d
by a s i m p l e e q u a t i o n of t h e mass-law t y p e ,

The mass-law e q u a t i o n s o f t e n

quoted i n t h e l i t e r a t u r e , w i t h r e g a r d t o b a s e exchange phenomena, must b e
c o n s i d e r e d a s only approximations from which t h e r e may b e c o n s i d e r a b l e
v a r i a t i o n i n "unfavorable" c a s e s .

Because o f t h e s t o c h a s t i c n a t u r e of base-ewshmge phenomena , m y s o i l
t r e a t m e n t b a s e d on t h i s phenomena must t h e r e f o r e a l s o b e regarded a s a
s t o c h a s t i c process,

Of c o u r s e one may r a i s e t h e "odds" i n f a v o r of a

s u c c e s s f u l t r e a t m e n t a l o n g t h e s e l i n e s by p r e p a r i n g t h e e x t e r n a l phase t o
be "rich" i n t h e preferred ions, e.g.,

u t i l i z e a h i g h c o n c e n t r a t i o n KC1

solution t o t r e a t the s o i l .

S t must b e borne i n mind t h a t an ion-exchange s o i l t r e a t m e n t c m a l t e r
t h e physicochemical p r o p e r t i e s of t h e s w e l l i n g c l a y and i s one o f t h e most
e f f e c t i v e ways t o combat problem o v e r a r e l a t i v e l y s m a l l l o c a l i z e d r e g i o n
on which an e x p e n s i v e i n p l a c e s t r u c t u r e , s a y a pavement, rests.
The a b i l i t y of a c l a y t o absorb i o n s on i t s s u r f a c e s o r edges i s c a l l e d
i t s b a s e o r c a t i o n (anion) exchange c a p a c i t y , which i s a f m c t i o n of t h e

s u r f a c e chemistry of t h e c l a y and t h e s i z e o f t h e c l a y p a r t i c l e s .

Thus t h e

term b a s e exchange i s w i d e l y employed, a l t h o u g h i n f a c t hydrogen i o n s and
even o r g a n i c i o n s may b e i n v o l v e d i n t h e exchange.

The b a s e exchange c a p a c i t y of a c l a y m i n e r a l i s r e l a t e d b o t h t o t h e
charge d e f i c i e n c y caused by isomorphous s u b s t i t u t i o n s w i t h i n t h e l a t t i c e
of t h e m i n e r a l and a l s o t o t h e number of d a n g l i n g bonds around t h e edges
of p a r t i c l e s .
cations.

The absorbed i o n may b e N

a

+

C

a

++

K

F

i

e

++o r

other

These absorbed i o n s w i l l n o t a l t e r t h e b a s i c c l a y chemical formula,

b u t t h e y s i g n i f i c a n t l y a l t e r t h e e n g i n e e r i n g b e h a v i o r of t h e c l a y m i n e r a l
s i n c e t h e y a f f e c t t h e bonding energy of t h e v a r i o u s b a s i c s t r u c t u r a l s h e e t s
t o one a n o t h e r .

Xoreover, i n occupying s p a c e s on t h e s u r f a c e of t h e c l a y

p a r t i c l e s t h e i o n s i n t e r f e r e w i t h development of w a t e r l a y e r s a t t h e s u r f a c e .
A f t e r a n a l y z i n g t h i s base-exchange phenomena, D r . C h a r l e s O'Bannon of
t h e A,S.U,

C i v i l Engineering Department employed e l e c t r o - c h e m i c a l s t a b i l i z a -

t i o n t o t h e problem of s w e l l i n g s c l a y s .

D r . O'Bannon f f e t t h a t two primary

e f f e c t s c o u l d b e r e l i e d upon t o a l t e r t h e c l a y p r o p e r t i e s .

(a)

The r e l e a s e of i o n s from t h e anodes, an exchange of i o n s i n t h e
s o i l s o l u t i o n and t h e m i g r a t i o n of s o l u t e s i n t h e p o r e w a t e r o r
i n t h e absorbed w a t e r l a y e r s .

The a c t i v a t i o n of such a system

can l e a d t o new p a r t i c l e c o n f i g u r a t i o n s ( e . g . ,

c l o s i n g o r opening

t h e s p a c e between c l a y p l a t e l e t s and l o c k i n g them t o g e t h e r w i t h
d i f f e r e n t c a t i o n s e i t h e r f a c e t o f a c e o r edge t o f a c e ,
(b)

Mass-transfer

phenomena, i . e . ,

i o n i c t r a n s p o r t and w a t e r t r a n s p o r t

t o a s s i s t s t a b i l i z i n g s o l u t i o n s t o p e n e t r a t e i n t o s o i l s which may
b e o t h e m i s e n e a r l y impermeable t o t h e passage of s o l u t i o n ,

I n o r d e r t o f u r t h e r i l l u m i n a t e t h e r a t i o n a l e behind D r . ~ ' ~ a n n o n ' s
usage of e l e c t r o c ~ h e m i c a ls t a b i l i z a t i o n a s h o r t d i s c u s s i o n o f some fundamental
i d e a s r e l a t i n g t o s w e l l i n g c l a y s and e f f e c t s of e a e c t r o l y t e s on c l a y s w e l l i n g

i s presented,

The observed s w e l l i n g p r e s s u r e of m o n t o m o r i l l o n i t e i s , of c o u r s e , t h e
d i f f e r e n c e between t h e a t t r a c t i v e and r e p u l s i v e f o r c e s o p e r a t i n g between t h e
l a y e r s per u n i t area.

A t s m a l l h a t e r l a y e r d i s t a n c e s two a t t r a c t i v e f o r c e s p r e d o ~ n a t e ;namely,

e l e c t r o s t a t i c f o r c e s between t h e n e g a t i v e l y charged s u r f a c e s and t h e i n t e r vening excnangeable c a t i o n s , and van d e s Waals f o r c e s .

The magnitude of

t h e f o m r depends on t h e s u r f a c e charge d e n s i t y r e s u l t i n g from isomorphous
substitution.

Thus, t h e f o r c e s between t h e charge s u r f a c e and t h e c a t i o n s

depend on t h e composition of t h e m i n e r a l .

The van d e r Waals f o r c e s a r e n o t

g r e a t l y dependent of t h e m a t e r i a l composition; however, t h e y a r e i n f l u e n c e d
by t h e e x t e r n a l e n v i r o n m n t .

The r e p u l s i v e f o r c e s i n v o l v e d have been g e n e r a l l y c o n s i d e r e d t o be osmotic
i n nature.

It is assumed t h a t when m o n t o m o r i l l o n i t e i s p l a c e d i n c o n t a c t w i t h

w a t e r , t h e w a t e r i n i t i a l l y e n t e r s between t h e l a y e r s because t h e molar energy
of t n e w a t e r i s seduced by t h e h y d r a t i o n of t h e c a t i o n s p r e s e n t between t h e
l a y e r s a d h y d r a t i o n of t h e l a y e r s u r f a c e s .

Hence, a h i g h l y c o n c e n t r a t e d s o l u t i o n of c a t i o n s i s formed between t h e
clay layers.

Moreover, b e c a w e of t h e n e g a t i v e l y charged l a y e r s tan e l e c t r o -

s t a t i c f i e l d i s p r e s e n t which c o n s t r a i n s t h e c a t i o n i c t h e r m a l motion.

This t h e r m a l o r Brownian motion of t h e c a t i o n s i s always p r e s e n t and
without t h e c o n s t r a i n t of t h e i n t e r l a y e r e l e c t r o s t a t i c f i e l d t h e c a t i o n s
between t h e l a y e r s would d i f f u s e o u t t o t h e e x t e r i o r s o l u t i o n u n t i l an e q u i l i b -

rium c o n c e n t r a t i o n w a s e s t a b l i s h e d ,
The osmotic model used t o d e s c r i b e s w e l l i n g phenomna i s f o m u l a t e d
around t h e s e f a c t s a s f o l l o w s :

Because t h e i n t e r l a y e r e l e c t r i c f i e l d a c t s a s

a s e d p e r m e a b l e membrae and causes t h e i n t e r l a y e r s o l u t i o n t o have a h i g h
c o n c e n t r a t i o n of c a t i o n s , e x t e r i o r w a t e r e n t e r s due t o an osmotic g r a d i e n t .
The r e s u l t i n g r e p u l s i v e p r e s s u r e s i s , t h u s l y , assumed t o b e an o s m o t i c one.

This osmotic t h e o r y of s w e l l i n g seems t o b e a p l a m i b l e one and indeed
some ewperimental e v i d e n c e a t l e a s t q u a l i t a t i v e l y , s u p p o r t s i t .

However,

D r , P h i l l i p P , Low,among o t h e s , s u g g e s t s t h a t t h i s i s n o t t h e f u l l s t o r y .

It

h a s been shown thermodynamically t h a t t h e r e p u l s i v e p r e s s u r e h a s n o t only t h e
osmotic c o n t r i b u t i o n , but. a l s o a c o n t r i b u t i o n from t h e molar p o t e n t i a l energy
of t h e w a t e r .

The molar p o t e n t i a l energy Is a f a c t o r because t h e i n t e r l a y e r w a t e r
i n t e r a c t s w i t h l a t t i c e s t r u c t u r e of t h e c&ay c r y s t a l .

That i s t h e s t r u c t u r e s

of t h e i n t e r l a y e r w a t e r and m o n t m o r i l l o n i t e c o n f o m t o one a n o t h e r , i . e . ,
e p i t a x y o c c u r s , because of t h e hydrogen bonding between them,

What t h i s metans

i s t h a t as t h e t h i c k n e s s of t h e i n t e r l a y e s w a t e r i n c r e a s e s i t ' s s t r u c t u r e
a s s m e s a p r e f e r r e d c o n f i g u r a t i o n and t h e m o n t m o r i l l o n i t e c r y s t a l a d j w t s

accordingly.

This adjustment continues u n t i l t h e water achieves i t s p r e f e r r e d

configuration.

.An a l t e r n a t i v e i n t e r p r e t a t i o n i s t h a t t h e m o n t m o r i l l o n i t e

s t r u c t u r e r e l a x e s a s s t r e s s e s a c t i n g on i t a r e r e l i e v e d by t h e i n c l u s i o n of
w a t e r , and t h e w a t e r s t r u c t u r e changes conformably.

This r e l a x a t i o n continues

u n t i l the water structure r e s i s t s further s t r a i n .

Now a s t h i s phenomena o c c u r s t h e b-dimension of t h e w i t c e l l * i n c r e a s e s
due t o an a l t e r n a t i v e clockwise and counterclockwise r o t a t i o n o f t h e c l a y ' s
s i l i c a t e t r a h e d r a about t h e i r v e r t i c a l axes.

See f i g u r e s 4 and 5.

t i o n of t h e t e t r a h e d r a a l t e r s t h e b-dimension of t h e u n i t c e l l .

This rota-

Thus, a l l

maximally s w o l l e n m o n t m o r i l l o n i t e s have t h e same b-dimension f o r t h e i r s i l i c a
tetrahedra.

This value i s a l i t t l e over 9 x

cm o r 9%.

It h a s been e s t a b l i s h e d t h a t t h e p r e s e n c e of' g o t a s s i m i o n s i n t h e i n t e r -

l a y e r s of m o n t m o r i l l o n i t e s i g n i f i c m t l y i n f l u e n c e s t h e l a t t i c e s t r u c t u r e
of t h e c l a y .

Work done by D r . P h i l l i p Low a d o t h e r s shows t h a t t h e potassium

i o n i n c r e a s e s t h e b-dimension,
of t h e m o n t m o r i l l o n i t e c l a y .

s e e f i g u r e 6 , hence r e d u c e s t h e s w e l l p o t e n t i a l
D r . O'Bannon h a s found t h a t t h e r e q u i r e d amount

of potassium t o s i g n i f i c a n t l y a f f e c t t h e s w e l l of t h e C h i n l e Clay v a r i e s from
about 0.008 g m K+/garib c l a y t o about 0.02 gsae K+/gm c l a y ,

*The u n i t c e l l i s t h e s m a l l e s t s t r u c t u r a l w i t which, when r e p e a t e d i n s p a c e ,
reproduces t h e g i v e n c r y s t a l l i n e s t r u c t u r e ,

DIFFERENT SURFACE SYMMETRIES
OF
MONVMORILLONiTE

b' = 4/3 h cos e t c
Bitrigonal Symmetry

Fig. 4

b dim

(A0)

0

5

10
15
20
Water Content (gM20/g Clay)

Relation between b-dimension
and
Water content for N, Saturated
Montmorillonites (Ravina & bow)
Figure

fj

25

THE EFFECWOF THE EXCHANGEABLE CATION
ON THE B-BIMENSlOlaB $OF NA-MONTM0WtbbONla"E

CATION TYPE
Fig. 6

It i s g e n e r a l l y b e l i e v e d t h a t D r , 0 ' ~ a n n o nu t i l i z e d an e l e c t r i c f i e l d

t o move a chemical s o l u t i o n through t h e c l a y r e g i o n s o l e l y because of t h e
low h y d r a u l i c p e r m e a b i l i t y c o e f f i c i e n t of Chinle Clay.
not s t r i c t l y correct.

T h i s , however, i s

It i s w e l l known** t h a t e l e c t r o l y t e s have an e f f e c t

on t h e magnitude of t h e s o i l p e r m e a b i l i t y .

For example f i e l d & l a b o r a t o r y

work f o r t h i s p r o j e c t showed t h a t a 0.4 N K C 1 s o l u t i o n moves t h r o u g h C h i n l e
Clay, m d e r a h y d r a u l i c g r a d i e n t , a t a s i g n i f i c a n t l y h i g h e r v e l o c i t y t h a n
d e i o n i z e d w a t e r does ( i . e . ,

w e l l o v e r an o r d e r of magnitude i n c r e a s e i n

velocity).

Because o f t h i s , s e v e r a l a t t e m p t s were made i n p r e v i o u s s t u d i e s , t o i n t r o duce t h e KC1 s o l u t i o n i n t o t h e s o i l u s i n g only h y d r a u l i c g r a d i e n t s .

Thus w i t h

a s i m p l e "pending" t e c h n i q u e one could r e l y on t h e base-exchange o f i o n s t o
e f f e c t a change i n t h e c l a y s t r u c t u r e .

While b a s e exchange produces long-

term e f f e c t s on t h e c l a y s t r u c t u r e i t w a s found t h a t a p p l i c a t i o n of an e l e c t r i c
f i e l d i n d u c e s a d d i t i o n a l e l e c t r o - c h e d c a l phenomena which a l s o g r e a t l y a l t e r e d
the s o i l structure,

With t h e a p p l i c a t i o n of t h e e l e c t r i c f i e l d t o t h e KCI s o l u t i o n
c l a y a v a r i e t y of e l e c t r o - c h e d c a l phenomena o c c u r .

-

saturated

Among t h e v a r i o u s mass-

t r a n s f e r e f f e c t s a r e i o n - t r a n s p o r t and w a t e r - t r a n s p o r t .

**Lutz, J . F . , and W.B. Kemper, " I n t r i n s i c B e m e a b i l i t y of Clay a s A f f e c t e d
by Clay-Water I n t e r a c t i o n " , S o i l S c i e n c e v o l . 88, 1959, pg. 83.

~ ' ~ a n n o n 'sst a b i l i z a t i o n method r e l i e s p r i m a r i l y on i o n i c - t r a n s p o r t t o
e f f e c t i v e l y move t h e p o t a s s i m i o n s t o t h e i n t e r s t i t i a l c l a y sites.
e v e r , i n conjunction w i t h t h e i o n i c - t r a n s p o r t ,

Wow-

water-transport occurs, a d

s o 0 ' ~ a n n o n bs o i l s t a b i l i z a t i o n technique was i n i t i a l l y c a t e g o r i z e d a s
employing electro-osmosis f o r t h e purpose of s o i l s t a b i l i z a t i o n .

Clearly,

t h i s i s n o t t h e most comprehensive t e r m t o use f o r t h i s p r o c e s s ,

I n f a c t as s o i l s t a b i l i z a t i o n r e s e a r c h work proceeded,it b e c m e c l e a r
t h a t 0 ' ~ m n o n %electro-chemical technique c m be c h a r a c t e r i z e d as b a s i c a l l y
t h e e l e c t r o l y s i s of s w e l l i n g c l a y s .

MISCIBLE DISPLACEMENT

Introduction
S i n c e t h e s o i l s t a b i l i z a t i o n p r o c e s s a s developed by D r . O'Bannon cons i s t s of t r a n s p o r t i n g K C 1 s o l u t i o n through t h e s o i l a i t was found t o b e necess a r y t o examine what c o n d i t i o n s a f f e c t e d t h i s mass t r a n s p o r t and how t h e y
affected it.

The s t u d y of t h e movement of w a t e r , c o n t a i n i n g d i s s o l v e d s o l u t e s , i n t o
a d through t h e s o i l i s c a l l e d M i s c i b l e Displacement.
The term KLscible Displacement i s a r e l a t i v e l y new one, however, t h e
t e c h n i q u e i s v e r y o l d and h a s l o n g been used.

For example, r e c l a i m i n g s a l i n e

and a l k a l i s o i l s by l e a c h i n g o u t t h e e x c e s s s a l t s h a s been used f o r many y e a r s
b u t t h e p r o c e s s has been examined m a l y t i c a l l y only r e c e n t l y .

B r i e f l y , t h e f o l l o w i n g t a k e s p l a c e i n a porous medium as one f l u i d , s a y
p u r e w a t e r , d i s p l a c e s a KGL s o l u t i o n .

The

s o l u t e s , i n t h i s c a s e RC1, i n t h e d i s p l a c e d f l u i d a r e t r m s f e r r e d

through t h e s o i l by t h e m a s s t r a n s p o r t of t h e moving f l u i d and by t h e r m a l
agitation.

F l u i d f l o w through s o i l i s , o f c o u r s e , v e r y complex.

The f l u i d

v e l o c i t y f l u c t u a t e s r a p i d l y due t o t h e complex geometary of t h e medim.
complex flow c a u s e s t h e KC1 i n t h e s o l u t i o n t o move i n t o t h e p u r e w a t e r ,

This
The

term f o r t h i s mass-transport i s d i s p e r s i o n , o f t e n c a l l e d hydrodynancbc d i s p e r s i o n , t o d i s t i n g d s h t h i s s p r e a d i n g mechanism from t h a t due t o d i f f u s i o n ,
T h i s d i s t i n c t i o n i s n e c e s s a r y b e c a u s e d i f f u s i o n i s due t o t h e random t h e r m a l
motion of t h e s o l u t e molecules, whereas d i s p e r s i o n i s due t o t h e macroscopic
f l u c t u a t i o n s i n t h e flow of t h e f l u i d s t h r o u g h t h e c o q l e x p o r e systems.

Thus,

t h e movement o f a s o l u t e a c r o s s t h e i n i t i a l l y s h a r p boundary between t h e d i s p l a c i n g and t h e d i s p l a c e d f l u i d can b e due t o d i s p e r s i o n o r d i f f u s i o n o r b o t h .
The s h a p e of a b o m d a q between two d i f f e r e n t f l u i d s and c o n c e n t r a t i o n
g r a d i e n t s a s t h e y emerge from a s o i l column c o u l d y i e l d i n f o r m a t i o n about t h e
magnitude of v i s c o u s d r a g of t h e f l u i d on t h e p o r e w a l l s , t h e v e l o c i t y d i s t r i b u t i o n o f t h e f l u i d i n t h e p o r e s , t h e c o n f i g u r a t i o n of t h e p o r e s , t h e a m o k t
of digfaasion t a k i n g p l a c e i n t h e p o r e s , and even t h e d e g r e e o f i o n e x c h m g e
taking place.

However, s u c h an e x p e r i m e n t a l procedure i s n o t e a s y t o s e t up,

i n f a c t , l i t t l e earperimental work u s i n g such a procedure h a s even been a t t e m p t e d .

b o t h e r approach adopted by D r s , O'Bannon and Mansini f o r t h i s p r o j e c t , i s
t o examine t h e c o n c e n t r a t i o n change of a d i s p l a c e d s o l u t e i n t h e e f f l u e n t a s
t h e boundary of t h e d i s p l a c i n g f l u i d and t h e d i s p l a c e d f l u i d emerges from a
soil colm.

The manner i n which t h e c o n c e n t r a t i o n changes can g i v e w some

i n f o r m a t i o n about t h e porobas media and t h e p h y s i c a l b e h a v i o r of t h e f l u i d s
moving through t h e media,

To a n a l y z e t h e c o n c e n t r a t i o n change o f s o l u t e i n t h e e f f l u e n t from a s o i l
column t h e d a t a i s p r e s e n t e d i n a s t m d a r d form c a l l e d a b r e A t h r o u g h eu-rve.

A b r e a k t h r o u g h curve i s a graph of t h e r a t i o C/Co v e r s u s t h e number of
p o r e volumes of e f f l u e n t c o l l e c t e d .

Here C i s t h e c o n c e n t r a t i o n of t h e

s o l u t e f o m d i n t h e e f f l u e n t , Go i s t h e i n i t i a l c o n c e n t r a t i o n of t h e s o l u t e
i n t h e d i s p l a c i n g f l u i d and t h e p o r e volume Vo i s t h e volume of t h e porous
medium occupied by f l u i d .

The number of p o r e volumes of e f f l u e n t c o l l e c t e d

i s g i v e n by Q t / V o where Q i s t h e q u a n t i t y of flow p e r u n i t t i m e and t t h e
i n t e r v a l of time t h a t has e l a p s e d s i n c e t h e d i s p l a c i n g f l u i d was added t o
t h e medium.

The q u a n t i t y Q t i s a l s o t h e volume of e f f l u e n t c o l l e c t e d .

The

r a t i o C/Co w i l l be z e r o a t f i r s t and t h e n approach 1 a s t h e c o n c e n t r a t i o n
of t h e e f f l u e n t approaches t h a t of t h e d i s p l a c i n g f l u i d , t h a t i s when most
of t h e d i s p l a c e d has been removed from t h e medium and t h e e f f l u e n t i s composed nos t l y of t h e d i s p l a c i n g f l u i d .

There a r e two c l a s s e s of M i s c i b l e Displacement, t h e y a r e " p i s t o n flow"
o r flow w i t h o u t mixing and flow w i t h mixing,

P i s t o n flow i s s c h e m a t i c a l l y shown i n f i g u r e 7 ,

I n t h e upper p a r t of

t h a t f i g u r e t h e r e i s a t u b e w i t h a p i s t o n at t h e l e f t end and a s m a l l o u t l e t
t u b e a t t h e r i g h t end,

I n the tube t h e r e i s a

salt solution, say a satura-

t e d K C 1 s o l u t i o n , i n i t i a l l y s e p a r a t e d from p u r e w a t e r by a membrane.

I f we

p u l l o u t t h e membrane and push t h e p i s t o n f a i r l y r a p i d l y t o t h e r i g h t s o t h a t
t h e r e i s no t i m e f o r d i f f u s i o n t o occur a c r o s s t h e boundary Pine between t h e

s a l t s o l u t i o n and t h e w a t e r , t h e w a t e r w i l l b e moved t o t h e r i g h t w i t h o u t
any mixing a t t h e i n t e r f a c e .

T h i s i s shown i n t h e middle p a r t of f i g u r e 7 .

The e f f l u e n t w i l l b e KC1 s o l u t i o n u n t i l t h e w a t e r f r o n t r e a c h e s t h e end of
t h e tube.

Then, onIy p u r e w a t e r w i l l come o u t of t h e t u b e a s shown i n a t t h e

Miscible Displacemnt

KC%
Solution

KCL
Solution

Water

Schemtic

Figure 7

:

Drawing of P i s t o n Plow i n a
Tube, no mixing involved.

bottom of f i g u r e 7.

Hence, i n t h i s t y p e of flow t h e d i s p l a c e d f l u i d w i l l

move a t t h e r a t e o f t h e moving p i s t o n .

I n p i s t o n flow t h e r e i s no v i s c o u s

d r a g of t h e f l u i d a l o n g t h e w a l l s of t h e t u b e and no t u r b u l e n c e , moreover
p i s t o n flow almost never o c c u r s i n s o i l s .

A more r e a l i s t i c t y p e of flow througla a t u b e i s shown i n f i g u r e 8-a.

The t u b e i s shown t o e x h i b i t a d r a g on t h e f l u i d .

It i s shown i n t h e upper

p a r t of t h i s f i g u r e t h a t a s t h e w a t e r i s pushed i n t o t h e t u b e a t t h e l e f t
i t moves f a s t e r down t h e c e n t e r of t h e t u b e t h a n i t does a l o n g t h e w a l l s .

T h i s i s , of c o u r s e , due t o t h e v i s c o u s d r a g of t h e f l u i d n e a r t h e w a l l which
c a u s e s t h e v e l o c i t y of t h e f l u i d n e x t t o t h e w a l l t o b e l e s s t h a n t h a t n e a r
t h e c e n t e r of t h e t u b e ,

I n t h e lower p a r t of t h e f i g u r e i t i s shown t h a t t h e s a l t f r o n t h a s
advanced much f u r t h e r a l o n g t h e a x i s and i t w i l l n o t be long b e f o r e t h e w a t e r
w i l l move o u t of t h e t u b e and be found i n t h e e f f l u e n t ,

Then a s a d d i t i o n a l

w a t e r i s moved through t h e t u b e t h e c o n c e n t r a t i o n of t h e s a l t i n t h e e f f l u e n t

w i l l decrease.

This i s d i s t i n c t i v e from t h e p u r e p i s t o n t y p e flow s i n c e n o t

j u s t s a l t s o l u t i o n t h e n w a t e r w i l l move o u t of t h e t u b e , b u t an e f f l u e n t w i t h
a measurably d e c r e a s i n g c o n c e n t r a t i o n of s a l t .

It i s shown i n t h e o r e t i c a l

t r e a t m e n t s t h a t t h e s m a l l e r t h e d i a m e t e r of t h e t u b e and t h e l o n g e r i t s l e n g t h ,
t h e g r e a t e r i s t h e mixing,

h example of breakthrough c u r v e s f o r b o t h p i s t o n flow and flow i n a
t u b e a r e provided i n f i g u r e 8-b.

N o t i c e t h a t f o r p i s t o n flow one pore volume

of e f f l u e n t p a s s e s o u t of t h e m e d i m b e f o r e any change i n t h e c o n c e n t r a t i o n

Mscible

Displacement

KCL S o l u t i o n

W x i n g of Water and S o l u t i o n
s e c u r i n g h e r e due t o exchange
d i f f u s i o n of s o l u t e and water
a c r o s s Water-Solbtion Boundary.

Outflow

Schematic drawing o f A c t u a l flow i n t u b e

F i g u r e 8-a

UNITY

i

'
l
i
.

3
PORE VOLUME
BREAKTHROUGH CURVE FOR PISTON FLOW

BREAKTHROUGH CURVE FOR FLOW I N A TUBE

F i g u r e 8-b

r a t i o C/Co t a k e s p l a c e ,

Then, i n a very s h o r t time i n t e r v a l t h e concentra-

t i o n r a t i o goes t o z e r o .

I n t h e c a s e of flow through a tube t h e concentra-

t i o n r a t i o remains c o n s t a n t u n t i l about a p o r e volume o r s o i s c o l l e c t e d t h e n
t h e c o n c e n t r a t i o n r a t i o b e g i n s t o d e c r e a s e i n a r e l a t i v e l y g r a d u a l manner.
I n f i g u r e 9 one s e e s how a d i s p l a c i n g f l u i d w i l l move through a s a t u r a t e d non-swelling s o i l .

The d i s p l a c i n g f l u i d w i l l t e n d t o move mostly through

t h e l a r g e p o r e s and displacement w i l l b e slow i n t h e s m a l l e r p o r e s , moreover
d i f f u s i o n w i l l occur.

I n l a b o r a t o r y e q e r i m e n t a l s e t - u p t h e s o i l sample was n o t s a t u r a t e d , t h e
m o i s t u r e c o n t e n t b e i n g about 5 p e r c e n t .

Indeed i t was found t h a t i f t h e s o i l

was s a t u r a t e d w i t h d e i o n i z e d w a t e r t h e n t h e e l e c t r o l y t e would n o t move i n t o
t h e s o i l even under a p p l i e d p r e s s u r e g r a d i e n t s .

With u n s a t u r a t e d s o i l t h e

s i t u a t i o n i s more complex t h a n f o r s a t u r a t e d s o i l s .

T h i s c a s e i s shown i n

f i g u r e 10 where t h e r e a r e s o i l p a r t i c l e s , w a t e r and a i r s p a c e s ,

It s h o u l d b e

s t r e s s e d t h a t t h i s f i g u r e i s drawn w i t h o u t t & i n g i n t o account m y v o l u m e t r i c
change due t o s w e l l i n g .

I n t h i s s i t u a t i o n t h e l a r g e p o r e s , which, under

s a t u r a t e d c o n d i t i o n s conducted t h e s a l t s o l u t i o n e a s i l y , a r e now p a r t l y f i l l e d
w i t h air and have l o s t t h e i r conducting e f f e c t i v e n e s s .

The s a l t s o l u t i o n w i l l

t e n d t o go where t h e water f i l m s a r e t h e t h i c k e s t .

D i f f u s i o n o f a s o l u t e m y t a k e p l a c e d u r i n g d s c i b l e displacement.

If

t h e f l u i d s of t h e m i s c i b l e displacement p r o c e s s move i n t h e s o i l at p r a c t i c a l l y
z e r o v e l o c i t y , some o f t h e s a l t molecules may move forward and completely o u t
of t h e s o i l j u s t by t h e t h e r m a l motion of d i f f u s i o n .

Miscible Bisg lacement

S o i l Sample

Soil Particles

Solution

S c h e m a t i c drawing of f l e w i n a
Saturated S o i l

S o i l Sample

Soil Particles

Solution

S c h e m a t i c drawing o f f l o w i n a n
unsaturated S o i l

F i g u r e 9 & 10

Under f i e l d c o n d i t i o n s one w i l l almost always have an u n s a t u r a t e d s o i l
mediaam a t hand.

I n t h i s c a s e t h e t h e o r y as developed can only s e r v e a s

g e n e r a l guides f o r q u a l i t a t i v e judgments.

T h i s i s due t o t h e wide range of

p o r e v e l o c i t i e s p r e s e n t , d u r i n g t h e displacement p r o c e s s , i n t h e m s a t u r a t e d
soil.
The m i s c i b l e displacement experiments p e r f o m e d f o r t h i s p r o j e c t were
n e c e s s a r i l y r e s t r i c t e d i n scope because of t h e l i d t e d time a v a i l a b l e .
It i s a p p a r e n t from f i g u r e 11 t h a t a f t e r a C h i n l e Clay s o i l i s s a t u r a t e d

w i t h an e l e c t r o l y t e (0.4 N KC1) and t h e n t h e s o l u t i o n i s d i s p l a c e d w i t h deion i z e d w a t e r t h e removal of t h e c h l o r i d e s t & e s p l a c e v e r y n e a r l y l i k e a
c l a s i c a l "bre&throughn
c l e s =king

curve.

This d a t a suggests t h a t t h e c o l l o i d a l p a r t i -

up t h e s o i l have agglomerated, from t h e a c t i o n of t h e e l e c t r o l y t e

on t h e double l a y e r , and c r e a t e d continuous p o r e s s o t h a t t h e s o l u t i o n and
w a t e r can p a s s through t h e c l a y cslumaa w i t h r e l a t i v e e a s e .
More o v e r even a f t e r s e v e r a l mP o f d e i o n i z e d w a t e r were run through t h e
sample a d t h e e f f l u e n t ' s s a l t c o n c e n t r a t i o n had reached an equilibriraan v a l u e
t h e c l a y ' s p r o p e r t i e s d i d n o t s i g n i f i c a n t l y a l t e r and t h e s a p l e r e t a i l e d i t s
r e l a t i v e l y high p e m e a b i l i t y r e l a t i v e t o t h e deionized water.
I n a t t e m p t i n g t o run t h e e w e r i m e n t i n t h e o t h e r d i r e c t i o n , t h a t i s by
u s i n g a sample s a t u r a t e d w i t h d e i o n i z e d water and t h e n u s i n g t h e e l e c t r o l y t e
a s t h e d i s p l a c i n g f l u i d , o u r e f f o r t s were t h w a r t e d by t h e p r o p e r t i e s of t h e
clay.

That i s , t h e c l a y s o t e n a c i o u s l y h e l d o n t o t h e d e i o n i z e d w a t e r t h a t

t h e O , 4 N K C 1 s o l u t i o n was n o t a b l e t o e n t e r t h e s o i l and d i s p l a c e t h e w a t e r ,
t h i s o c c u r r e d even w i t h a p p l i e d p r e s s u r e g r a d i e n t s ,

These experiments c l e a r l y i n d i c a t e t h a t t h e e l e c t r o l y t e s t r o n g l y i n t e r a c t s with d r y Ghinle Clay and i s a b l e t o e a s i l y a f f e c t t h e p e r m e a b i l i t y of
the c l a y i f c l a y has n o t been p r e - s a t u r a t e d with pure water.

CHAPTER I V
L a b o r a t o r y Work

General
The p u r p o s e o f t h e l a b o r a t o r y work d u r i n g P h a s e V I was t o d e t e r m i n e
t h e e x p a n s i v e and s w e l l c h a r a c t e r i s t i c s of t h e u n t r e a t e d s o i l o b t a i n e d
from t h e t e s t s i t e .

The f i e l d work f o r t h i s s t u d y began i n J u l y , 1973, w i t h t h e s e l e c t i o n
of t h e t e s t s i t e a t m i l e p o s t 328.85 on t h e westbound l a n e of I n t e r s t a t e

40,

For a p l a n view of t h e s i t e s e e f i g u r e 1 2 ,

S i n c e t h i s p r o j e c t was

i n i t i a t e d a s a n implementation s t u d y an e n g i n e e r i n g d e c i s i o n a s

"t

pre-

t e s t s a m p l i n g t e c h n i q u e was made a t t h e o n s e t of t h e p r o j e c t .
T h i s e n g i n e e r i n g d e c i s i o n i s b a s e d on t h e f o l l o w i n g g e n e r a l c o n s i d e r ations:

most problems a r e a s of s w e l l i n g c l a y s t r a v e r s e d b y a roadway are

easily identifiable visually,

A f t e r a n a r e a h a s been i n d e n t i f i e d a s a

p o s s i b l e problem a r e a , a q u i c k economical way of s a m p l i n g must b e ilsed,
i t i s c l e a r t h a t i n a s t u d y o r i e n t e d towards p u r e l y i n v e s t i g a t o r y g o a l s

of s o i l

phenomena a s a m p l i n g t e c h n i q u e u s e d o v e r a s e l e c t e d r e g i o n

s h o u l d b e b a s e d on a random p r o c e d u r e .

However, t h e p r i m a r y g o a l was t o

u t i l i z e knowledge of p a s t electrochemical work and a p p l y t h e same t e c h n i q u e q p r o p e r l y modified, t o e n a b l e a r a p i d e v a l u a t i o n of t h e s w e l l i n g
problems o f a g i v e n a r e a .

LAYOU1 OF TCS1 SITE FOR SOllilllllLIZAIION PUOJfCI
LOCATION 8.40 WEPIMUNO LANE
ICII12" CIlcLXl

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From Sir l r d d to S a 11 175

- E0

Rolwl Stntlons EJI 7-16-79

I t was decided t h a t t h e sampling procedure would b e undertaken
s o t h a t t h e d r i l l r i g would n o t have t o move l a t e r a l l y b u t o n l y longi t u d i n a l l y , t h i s would s a v e a g r e a t d e a l of time, hence money,

Moreover,

t h e r i g was p o s i t i o n e d a s c l o s e t o t h e c e n t e r of t h e i n t e r s t a t e a s p o s s i b l e
w i t h o u t i n t e r f e r i n g w i t h t r a f f i c i n one t r a v e l l a n e of t h e westbound
roadway.

Twenty-six t e s t h o l e s were d r i l l e d and samples were o b t a i n e d

t o a d e p t h from z e r o t o 15 f e e t i n t h e c l a y subgrade.

See f i g u r e 13.

The samples were t r a n s p o r t e d t o t h e Arizona Department of T r a n s p o r t a t i o n
M a t e r i a l s S e r v i c e s where t h e y were p r e p a r e d and used i n l a b o r a t o r y

stradies ,

The samples were p r e p a r e d i n t h e f o l l o w i n g manner, s e e f i g u r e 14.
The s o i l was s i e v e d through a # 4 s i e v e ,
s i e v e was s t o c k p i l e d .
jaw c r u s h e r ,
stockpile,

A l l m a t e r i a l p a s s i n g t h e /,4

The m a t e r i a l r e t a i n e d on t h e # 4 was crushed i n a

The m a t e r i a l was a g a i n s i e v e d and t h e minus #4 added t o t h e
This c r u s h i n g and s i e v i n g p r o c e s s was r e p e a t e d u n t i l a l l t h e

m a t e r i a l had passed t h e 54 s i e v e ,

The minus . # 4 m a t e r i a l sfas t h e n mixed and

s t o r e d u n t i l needed f o r l a b o r a t o r y t e s t i n g .

I n t h i s manner, a homogeneous

sample c o u l d b e obeained f o r a l l f u r t h e r t e s t i n g o p e r a t i o n s .

14 f o r t h e flow diagram of l a b o r a t o r y work.

See f i g u r e

Note Stations o + oo - 1 3 + 40 were set down July,
1973 by Bist. IV for Project HPR-1-11 (145)

1

Pre-samples
Taken Approx.
July 16, 1973

Fig.

13

LAV-OUT FOR PROCUREMENT OF SAMPLES FOR HPR-1-31 (145)

FLOW CHART FOR EXPANS$VE PRESSURE
(% SWELL FOR UNTREATED SAMPLES)

1

PRESSURE & %

CONTENT

PRESSURE, % SWELL
& INITIAL WATER

Figure

-39-

14

I

A s e r i e s of t e s t s w e r e conducted t o d e t e m i n e t h e i n d e x p r o p e r t i e s

and g r a i n s i z e d i s t r i b u t i o n of t h e s o i l .

The average v a l u e s f o r t h e

a t t e r b e r g L i m i t s on t h e samples were l i q u i d l i m i t 39, p l a s t i c l i m i t 1 7 ,
and p l a s t i c i n d e x 22.

The a v e r a g e p e r c e n t p a s s i n g t h e #200 s i e v e was

70% and i t s g r a i n s i z e d i s t r i b u t i o n i s shown i n f i g u r e 15.
g r a v i t y of t h e s o i l was 2,75.

The s p e c i f i c

The s o i l would c l a s s i f y a s a CL m a t e r i a l

based on t h e u n i f i e d s o i l c l a s s i f i c a t i o n system.

See t a b l e No. 1 and

f i g u r e 3 f o r t h e r e s u l t s of t h e a t t e r b e r g l i m i t s t e s t s ,

afhe expansive p r e s s u r e of t h e u n t r e a t e d s o i l was d e t e m i n e f o r
m a t e r i a l p a s s i n g a #40 s i e v e i n a s t a n d a r d R-value t e s t i n g a p p a r a t u s ,
The d e n s i t y of t h e s o i l was approximately 106 # / f t d and t h e m o i s t u r e
c o n t e n t s were 10 and 15 p e r c e n t .
i n t a b l e No. 2.

The r e s u l t s of t h e s e t e s t s a r e shown

The p e r c e n t s w e l l was d e t e m i n e d on t h e u n t r e a t e d s o i l

u s i n g a modified c l o c k house a p p a r a t u s .

The d e n s i t y was m a i n t a i n e d a t

106 # / f t 3 and t h e m o i s t u r e c o n t e n t s were approximately 10 and 15 p e r c e n t .
The r e s u l t s of t h e s e tests a r e a l s o shown i n t a b l e No. 2.
These t e s t s i n d i c a t e t h a t t h e s e l e c t e d a r e a i s r e p r e s e n t a t i v e of a
r e g i o n w i t h moderate s w e l l i n g c h a r a c t e r i s t i c s ,

Table No, 9
lNDEX PROPERT-l ES

Sample

Loca-ti on

No.
40133

7+00

Depth

fee

8-9,s

Lb

BL

P1

X-#ZOO

Unified

Classification
Symbol

43

22

21

9%

GL

T a b i e No.

2

-

EXPAPISI\lE FRESSURES AND PERCEtlT SWELL
Sampi e
Nu.

Location

Depth

Dens i t y

Pt.

#1ft3

%

-

k'atcr

Expansive Pressure

81

ft2

X

-

Swell

The n e s t important determination t o make was t h e amount of KG1 p e r u n i t

w t . of c l a y necessary f o r proper s t a b i l i z a t i o n of t h i s p a r g i c u l a r clayey
mass.
work

Because of t h e l a r g e mass of d a t a from previous s o i l s t a b i l i z a t i o n
using t h i s technique

i t was r e l a t i v e l y s t r a i g h t f o r n a r d t o c l o s e l y

e s t i m a t e t h e amount of KC1 r e q u i r e d t o reduce t h e e q a n s i v e p r e s s u r e by
some reasonable f a c t o r ,
It was decided t o u s e an expansive p r e s s u r e r e d u c t i o n factor of 2 a s

a g u i d e l i n e i n determining t h e o v e r a l l amount of KC1 needed.

To use h i g h e r

f a c t o r s , say 4 o r 5, would r e s u l t , when coupled w i t h t h e e l e c t r o c h e m i c a l
e f f e c t s induced by t h e e l c t r i c a l c u r r e n t i n t h e s o i l . , i n a very earpensive
overkill,
'%faus, based on previous s o i l s t a b i l i z a t i o n work a d e c i s i o n a s t o t h e
gm, w t . of KC1 p e r gm, w t , of c l a y was made during t h e l o g i s t i c a l b u i l d up
period,
It was determined from f i g u r e 16 t h a t a b e s t e s t i m a t e from b o t h an

engineering and economic st;mdpoin"cas

about 0.02 gm K G l / p c l a y ,

This

amount of KC1 added t o t h e c l a y i n a d d i t i o n t o t h e f a b r i c changes i n t h e
c l a y , induced by t h e e l c t r o c h e m i c a l p r o c e s s , was adjudged t o be s u f f i c i e n t
f o r our purposes.

EXPANSIVE PRESSURE VS. % KCL

-#4B SQlb

7000

6000

0yd =

-

MOISTURE CONTENT

5000

La.

V)

!5
Md
i
x

2
V)

ILI

BE

8,

105 pcf

4000

LU

>
V)

;Z

2
x
1M

3000

2000

1000

0

Fig. 16

% KCL

General
The scope of t h e f i e l d work of t h e e l e c t r o c h e m i c a l s t a b i l i z a t i o n of
Chinbe c l a y w a s

(1)

To choose a t e s t s i t e on a paved s e c t i o n of 1-48 n e a r Holbrook,

Arizona and o b t a i n r e p r e s e n t a t i v e samples of t h e expansive c l a y

(2)

To d e s i g n , i n s t a l l and o p e r a t e a f u l l - s c a l e f i e l d t e s t on t h e

t e s t section.
(3)

To sample t h e e l e c t r o c h e m i c a l l y t r e a t e d s e c t i o n .

(4)

E v a l u a t e t h e a b i l i t y of e x i s t i n g m a i h t a i n e n c e r e s o u r c e s t o

c a r r y o u t t h i s work w i t h a minimum of s p e c i a l i z e d p e r s o n n e l i n a t t e n d e n c e ,

The f i e l d work of t h i s projece: began i n J u l y , 1973 w i t h t h e s e l e c t i o n
of a new test s i t e e a s t of Holbrook,

T h i s s i t e i s l o c a t e d approximately

on MP 323,8& i n t h e westbound l a n e of 1-40,

Engineering s t a t i o n s were s e t

up and r e p r e s e n t a t i v e samples of t h e s o i l were t a k e n from t h e t e s t s e c t i o n ,
s e e f i g u r e 14.

The Department of T r a n s p o r t a t i o n M a t e r i a l s S e n i c e s D i v i s i o n

t r a n s p o r t e d t h e m a t e r i a l t o t h e main l a b o r a t o r y where i t was p r e p a r e d and
used i n l a b o r a t o r y s t u d i e s .

-

The highway f i e l d i n s t a l l a t i o n was designed t o reproduce

t h e s i m p l e e l e c t r o d e c o n f i g u r a t i o n s used i n p r e v i o u s s t u d i e s ,

The e l e c t r i c a l design was such t h a t t h r e e s e p a r a t e s e c t i o n s o f t h e
500' t e s t s e c t i o n could b e e l e c t r i f i e d s i m u l t a n e o u s l y w i t h t h e same v o l t a g e
gradient .
The e l e c t r o d e c o n f i g u r a t i o n s f o r t h e whole t e s t s i t e i s shown i n
Figure 18.

I t s h o u l d b e n o t e d t h a t t h e c e n t e r s e c t i o n h a s , a s anodes,

v e r t i c l e #8-l'l (.0254 M) r e b a r about 5 ' ( 1 . 5 3 M) l o n g .

T h i s is i n c o n t r a s t

t o t h e o t h e r two s e c t i o n s which have h o r i z o n t a l anodes made up of 20'
(6.10 M) s e c t i o n o f 8% r e b a r welded t o g e t h e r end t o end t o form t h e anodes,
A f t e r t h e h o r i z o n t a l anodes were formed i n t h i s manner t h e y were manually
p l a c e d i n t o t h e p r e v i o u s l y p r e p a r e d 4 ' (1.22 M) deep t r e n c h ,
The c a t h o d e s , shown i n F i g u r e 19 a l o n g s i d e 1-40 was formed of 20'
(6.10 M) s e c t i o n s o f #8 r e b a r welded end t o end and t h e n c a r e f u l l y lowered
into the trench.
The e l e c t r o d e c o n f i g u r a t i o n was designed t o b e v e r y e a s y t o assemble
and y e t be a n e f f e c t i v e item.
exist(')

While many s o p h i s t i c a t e d d e s i g n p a t t e r n s

it was obvious t h a t t h e s i m p l e d e s i g n used i n t h i s p r o j e c t would

r e q u i r e t h e minimum amount o f e x p e r t man h o u r s t o p r o p e r l y i n s t a l l on s i t e .
F i g u r e 20 p r o v i d e s an i d e a l i z e d p a t t e r n o f t h e e l e c t r i c f i e l d c r e a t e d
by t h i s e l e c t r o d e p a t t e r n .

I t must b e n o t e d t h a t i n t h i s i l l u s t r a t i o n one

h a s n o t t a k e n i n t o account t h e e f f e c t s o f t h e a u g e r h o l e s t e e l s l e e v e , on
the electric field.

These s l e e v e s would n o t o n l y d i s t o r t t h e f i e l d , b u t

can even a c t a s p a r t i a l s c r e e n t o t h e f i e l d t h u s r e d u c i n g t h e o v e r a l l e f f e c t
of the e l e c t r i c a l f i e l d .
(1)See : "Innovations i n Ground S t a b i l i z a t i o n " by James K. Mitches s ; ASCE
1992, Chicago S o i l Mechanics L e c t u r e S e r i e s , " i n n o v a t i o n s i n Foundation
Construction."

F i g u r e 19

Figure 19 shorvs a s e c t i o n o f t h e cathode b e f o r e b e i n g p l a c e d i n t o t h e
t r e n c h s e e n n e a r t h e l e f t -hand c o r n e r o f t h e p i c t u r e .

Note t h e s l e e v e d

a u g e r h o l e s c l e a r l y showing t h e 10" ( . 2 5 4 M) p l a t e with t h e s o l u t i o n i n p u t
opening i n t h e c e n t e r .

A s a r e s u l t o f p a s t f i e l d t e s t s u s i n g e l e c t r o c h e m i c a l methods f o r

s t a b i l i z a t i o n o f C b i n l e c l a y i t was d e c i d e d t o d e s i g n t h e f i e l d i n s t a l l a t i o n s around t h e d e s i r e t h a t t h e c l a y s h o u l d b e t r e a t e d t o a depth of
o n l y 3 f e e t ( - 9 1 5 M).

T h i s e s t i m a t e was o b t a i n e d based on l a b o r a t o r y

t e s t s which showed t h a t i f t h e c l a y were e f f e c t i v e l y t r e a t e d t o t h i s depth
t h e s i t e c o u l d b e judged a s s t a b i l i z e d .

Moreover, because o f t h e s e p r e -

v i o u s s t u d y r e s u l t s , it was obvious t h a t t o a t t e m p t t o t r e a t t h e c l a y t o
a g r e a t e r depth t h a n 3 ' ( . 9 l S M)

,

s a y 4 ' (. 122 M) would r e s u l t i n an

" o v e r k i l l " o f t h e f i r s t 3 ' ( - 9 1 5 M)

.

I n o r d e r t o p r o p e r l y s u f f u s e t h e s o i l p o r e s with t h e KCL s o l u t i o n it
was d e c i d e d t o d r i l l 6" (, 1524 M) d i a m e t e r a u g e r h o l e s on 8 ' (2.44 M)
c e n t e r s , approximately 5 - 5 (1.68 M) deep throughout t h e t e s t s e c t i o n .
The p o s i t i o n i n g o f t h e a u g e r h o l e s was based on p r e v i o u s s t u d i e s . ( 2 )
There was a t o t a l o f 285 o f t h e s e a u g e r h o l e s p o s i t i o n throughout t h e
s i t e , s e e F i g u r e 21.
To d i s c o u r a g e caving o f t h e blow sand subbase m a t e r i a l each a u g e r
h o l e was s l e e v e d with a 6" ( . 152 M) O . D .

s t e e l p i p e , 29" (.686 M) long,

topped w i t h a 10" ( , 2 5 4 M) diameter, 1" (.0254 M) t h i c k s t e e l p l a t e s ,
The p l a t e had a l - l / 2 "

(,0381 M) h o l e i n t h e c e n t e r t o p e r m i t i n t r o d u c t i o n

of t h e KCL s o l u t i o n i n t o t h e auger h o l e ,

The 10" (.254 M) diameter s t e e l

p l a t e was o b v i o u s l y n e c e s s a r y t o g i v e a s t a b l e p l a t f o r m f o r t h e s t e e l and
t o provide a s u f f i c i e n t l y r i g i d surface f o r vehicular t r a f f i c .
22 f o r

See F i g u r e

an example o f one o f t h e s t e e l s l e e v e s .

The l0" (.254 M) d i a m e t e r , 1" (.0%54 M) "chick s t e e l p l a t e welded t o
t h e t o p o f each s t e e l s l e e v e c e r t a i n l y would g i v e a rough s u r f a c e

"c

the

(2) S e e : " S t a b i l i z a t i o n o f Chinle Clay by E l e c t r o Osmosis and Base Exchange
o f Ions" by Charles OtBannon, Feb. 1973, F i n a l Report f o r Arizona Department o f Trans. Research S e c t i o n ,

Figure 21.

View of auger holes on 8 ' centers with steel sleeves in place.
View i s transverse to roadway looking north.

Figure 2 2 shows 2'7" (.686 M) long s t e e l s l e e v e 6" ( . I 5 2 M) O . B . topped with
a 1" (.0254 M) t h i c k s t e e l p l a t e , The p l a t e i s 10" C.254 M) i n
d i a m e t e r with a 1 - 1 / 2 " (.0381 M) h o l e i n t h e c e n t e r t o permit
t h e i n p u t o f KCL s o l u t i o n i n t o t h e a u g e r h o l e .

roadway throughout t h e length of t h e 500' (152.5 M) t e s t s e c t i o n a f t e r t h e
Obviously, 285 p r o t r u d i n g 10" (-254 M) s t e e l p l a t e s

s l e e v e s were i n p l a c e .

p r e s e n t e d a p o t e n t i a l t r a f f i c problem and made i t n e c e s s a r y t o c o u n t e r s i n k
each auger h o l d with a c o n c e n t r i c c i r c u l a r 10" 1.254 M) diameter, 1" (-0254 M)
deep d e p r e s s i o n .

The c o u n t e r s i n k i n g o p e r a t i o n was accomplished e a s i l y by

welding t o t h e t o p o f t h e auger d r i l l stem one o f t h e l0I1 (.254 M) s t e e l p l a t e s .
A f t e r t h i s was accomplshed, s i x o l d d r i l l i n g t e e t h were s e t f l a t a g a i n s t
t h e bottom o f t h e p l a t e , spaced about 60' a p a r t i n a symmetrical p a t t e r n and
then welded i n t o p l a c e .

The t e e t h then provided an a b r a s i v e s u r f a c e f o r t h e

countersinking operation.
For t h e auger h o l e d r i l l i n g o p e r a t i o n s e e Figure 23.

I t should be

noted i n t h a t f i g u r e t h e countersink a p p a r a t u s i s shown welded onto t h e
t o p o f t h e auger d r i l l stem.
Each o f t h e a85 auger h o l e s were s l e e v e d down t o 29" (,686 M) below
the asphalt surface.

The s l e e v i n g d i d prevent e x t e n s i v e caving of t h e

base course and KCL s o l u t i o n from w e t t i n g t h e base course.
was some caving and wetting.

However, t h e r e

The f i g u r e o f 27'l (, 686 M) of base course

m a t e r i a l was s u p p l i e d by D i s t r i c t S V personnel a s a b e s t e s t i m a t e t o use
throughout t h e s i t e .

In t h e f u t u r e i t i s recommended t h a t t h e s l e e v i n g

be placed about 6" ( . I 5 2 M) below t h e e s t i m a t e d b a s e course m a t e r i a l .
See Figures 24 and 25 f o r a view of t h e s i t e a f t e r i n s t a l l a t i o n s of
the casings.
The s l e e v e s were s o designed t h a t t h e i r r e u s e was p o s s i b l e a f t e r comp l e t i o n of t h e p r o j e c t .

Moreover, only a minor amount o f c o r r o s i v e a c t i o n

due t o t h e s a l t s o l u t i o n was noted on t h e s l e e v e s a t t h e end of t h e f i e l d
work.
-55-

Figure 23.

Auger hole d r i l l i n g . The round plate shown on the asphaltic
surface i s the countersink p l a t e . I t i s welded onto the t o p
of the auger d r i l l stem.

Figure 24.

S i t e view showirlg auger h o l e s wit41 s t e e l s l e e v e s i n p l a t e . Crewnan
is unloading 20' (6.10 kl) s e c t i o n s o f #8 r e b a r , t o b e used f o r
electrodes.

I,igrlrc 25. S i t e view looking s o u t h ~ v e s t a l o n g westbound l a n d o f 1-40.

The t o t a l d r i l l i n g and s l e e v i n g o p e r a t i o n l a s t e d approximately 2
working weeks of t h e d r i l l c r e w ' s time.
Upon completion of t h e d r i l l i n g and s l e e v i n g t h e e l e c t r i c a l i n s t a l l a t i o n
was i n i t i a t e d ,
This o p e r a t i o n c o n s i s t e d of t r e n c h i n g f o r h o r i z o n t a l e l e c t r o d e s and
d r i l l i n g f o r a s e c t i o n of v e r t i c a l anodes,

See f i g u r e s 26 and 2 7 f o r an

i l l u s t r a t i o n of t h i s o p e r a t i o n ,
The e l e c t r i c a l c o n n e c t i o n s a r e shown i n f i g u r e s 28 t h r u 31.
The manner of mixing and placement of s o l u t i o n was accomplished by
D i s t r i c t EV personnel. u s i n g a modified 2500 g a l , (9463 l i t r e ) c a p a c i t y "goose neck,"
water truck.
obtained.

The w a t e r and KC% was mixed s o t h a t a 0 . 4 N s o l u t i o n was

See f i g u r e s 32 and 33 f o r t h i s o p e r a t i o n ,

A 0 , 4 N s o l u t i o n was used i n o r d e r t o i n t r o d u c e t h e s a l t s o l u t i o n
i n t o t h e s i t e a t a maximum r a t e .

The 0 , 4 N s o l u t i o n i s e q u i v a l e n t t o

about 300 gms KCL p e r l i t y e of w a t e r .
Given t h e o u t s i d e ambient w a t e r t e m p e r a t u r e s i n t h e Holbrook a r e a
a t t h a t time of y e a r (May t h r u August about 2 3 ' ~ ) t h i s was t h e maximum
amount of KCL s o l u a b l e i n w a t e r , a t t h a t t e m p e r a t u r e .
more KCL i n t h e w a t e r w0ul.d n o t have been p o s s i b l e .

To attemp t o d i s s o l v e
So w i t h t h e given

ambient w a t e r t e m p e r a t u r e s t h e o p t i m a l KCL c o n c e n t r a t i o n p o s s i b l e , i n
o r d e r t o d e l i v e r t h e r e q u i r e d amount of s a l t t o t h e s i t e i n t h e s h o r t e s t
time, was about a 0.4 N s o l u t i o n .
A f t e r mixing i n t h e t a n k e r t r u c k t h e 0 . 4 N KCL s o l u t i o n was p l a c e d
i n t o t h e a u g e r h o l e s under p r e s s u r e u s i n g o r d i n a r y g a s o l i n e n o z z e l and
h o s e f i x t u r e s l e a d i n g from t h e s o l u t i o n t r u c k .

Figure 26 shows cathode trenching operation on North side of westbound lane
o f 1-40, The cathode trench was formed on both sides of the
westbound Sane and each was 4801(146,4 bi) long, 4' (1 - 2 2 M) deep.

Figure 27 shows preparation of one of the anode trenches.
on 1-40,

-59-

The view i s east

Figure 28 shews 60 KW D . C , generator with #4/0 anode and #2/0 cathode cables
connected.

Figure 29.

3/4 view s f generator w i t h monitoring-control panel shown open,
-60-

Figure 30 shows cable i n transverse c u t across roadway.
wore connecting t h e cathodes.

Figure 31 shows cathode welding operation.

The cable i s #2/0

Each cathode consisted of 24 20' (6.10 M)

S e c t i o n s of 1" ( . 0 2 5 4 PI) r e b a r welded together f o r e l e c t r i c a l continuity.

Figure 32 sk~ows 2500 gallon (9463 l i t r e ) t a n k e r b e i n g f i l l e d w i t h water i n p r e p a r a t i o n f o r t h e KGL s o l u t e .

F i g u r e 33 shows one of t h e s i x t y 100 pound (45.4 KG) KCL bags b e i n g emptied
i n t o t h e water f i l l e d tanker.

I n t h i s manner t h e auger h o l e s were f i l i e d twice a day f o r a p e r i o d
of 0 , 4 N s o l u t i o n was i n t r o d u c e d i n t o t h e s i t e r e g i o n .

See f i g u r e s 3 4

t h r u 37 f o r t h i s o p e r a t i o n .
It was determined e a r l y i n t h e p r o j e c t t h a t p r i o r t o t h e i n t r o d u c t i o n

of t h e e l e c t r i c f i e l d t h e s o l u t i o n would be d e l i v e r e d t o t h e s i t e f o r about

30 t o 35 days.

With t h i s procedure t h e c l a y could b e p r e - s a t u r a t e d w i t h

t h e KCL s o l u t i o n by u t i l i z i n g t h e r e l a t i v e e a s e w i t h which an e l e c t r o l y t e
moves through t h e c l a y e y m a t e r i a l and s i m u l t a n e o u s l y avoid t h e expense of
running an e l e c t r i c a l g e n e r a t o r d u r i n g t h e i n i t i a l s o i l s a t u r a t i o n p e r i o d .
During t h i s p e r i o d about 16,894 g a l l o n s of s o l u t i o n was d e l i v e r e d t o t h e
site.
On J u l y 8 , 1993 t h e 60 KW D.C,

g e n e r a t o r was s t a r t e d and an o v e r a l l

c u r r e n t of about 400 amps was r e c o r d e d w i t h a v o l t a g e g r a d i e n t of about

0.3 volt/cm.

On t h e average about 133 amps flowed through each of t h e

t h r e e s e c t i o n s during t h e f i e l d t e s t .

A f t e r approximately 40 days con-

t i n u o u s o p e r a t i o n an e l e c t r o d e p o l a r i z a t i o n phenomena was n o t e d which
caused a r a p i d power l o s s .

E l e c t r i c a l o p e r a t i o n s were d i s c o n t i n u e d imme-

diately thereafter.
A f t e r t h e e l e c t r i c a l system was s h u t down s u f f i c i e n t s o i l samples
were o b t a i n e d and shipped t o t h e M a t e r i a l s S e r v i c e s L a b o r a t o r i e s f o r t e s t i n g and e v a l u a t i o n ,

See f i g u r e 38 f o r t h e sampling p l a n used.

sampling p l a n was randomized i n c o n t r a s t t o t h e p r e - t e s t

This

sampling p l a n .

This was p o s s i b l e s i n c e t h e s w e l l i n g had been s u f f i c i e n t l y c h a r a c t e r i z e d
by t h e p r e - t e s t sampling, t h e r e f o r e i t was t h e n decided t h a t randomizing
t h e p o s t - t e s t sampling would g i v e a much b e t t e r p i c t u r e of how t h e s i t e
was a f f e c t e d o v e r a l l .

Figure 34

Figure 35.

shows converted gasoline hoses and nozaels For solution
del ivery system,

Close u p of converted gasoline nozzel,

-64-

Figure 36 shows 0.4N KCL solution being introduced into the sleeved auger
holes.

Figure 37,

Close u p of s o l u t i o n hose and n o z z l e . Note t h a t t h e n o z z l e ' s
o r i f ice i s f i t t e d i n t o t h e 1
(. 0x18 M) diameter llolc i n t h e 10"
(-254 M) diameter p l a t e .

+"

DISCUSSION OF OPERATIONAL CHARACTERISTICS OF ELECTROCHEMICAL SOIL STABILIZATION
The s t a b i l ' i z a t i o n o f s o i l u t i l i z i n g a KCL s o l u t i o n i s s t r o n g l y dependent
on t h e ambient w a t e r t e m p e r a t u r e

s i n c e t h e w a t e r t e m p e r a t u r e determines t h e

s o l u b i l i t y o f t h e KCL s o l u t e hence t h e s o l u t i o n s t r e n g t h , hence t h e e f f e c t i v e ness o f the solution a s a s t a b i l i z i n g agent.
Moreover, a s F i g u r e 16" hows, t h e g r e a t e r t h e weigkt o f KCL i n t r o d u c e d
i n t o the s o i l the greater the reduction i n the swell potential.

F i g u r e 16

i s a r e p r e s e n t a t i v e b e h a v i o r a l c u r v e o f s w e l l i n g c h i n l e c l a y when s u b j e c t e d
t o t r e a t m e n t with a KCL s o l u t i o n .
I f a swell reduction f a c t o r o f say 3 f o r a section o f c h i n l e clay is
d e s i r e d , F i g u r e 16 can b e used t o g i v e a n
t h e t a s k a t hand.

for

However, it i s s t r e s s e d t h a t t h e s i g n i f i c a n t v a r i a n c e s

i n t h e physio-chemical makeup o f c h i n l e c l a y make it i m p e r a t i v e t o s u f f i c i e n t l y
sample any chosen s i t e o f c h i n l e c l a y and s u b j e c t t h e samples t o a l a b o r a t o r y
s w e l l t e s t b e f o r e making a f i n a l d e c i s i o n on t h e amount o f KCL r e q u i r e d .
I f t h e t e s t s i n d i c a t e t h a t an amount o f KCL g r e a t e r t h a n t h a n shown
i n F i g u r e 1 6 i s needed t o g i v e a r e d u c t i o n f a c t o r o f 3 then more s o l u t i o n
i s required.

That i s , given t h e u s u a l water t e m p e r a t u r e s encountered i n

n o r t h e a s t e r n Arizona d u r i n g t h e summer (23"C, 73'F)

it i s not p o s s i b l e t o

g r e a t l y i n c r e a s e t h e amount o f KCL i n a 30-35 p e r c e n t by weight s o l u t i o n
without h e a t i n g t h e w a t e r ( s e e p l a t e 1) which could b e an expensive p r o c e s s
u n l e s s s o l a r h e a t were u s e d .

Hence, t h e o n l y way t o e f f i c i e n t l y g e t more

KCL i n t o t h e s o i l i s t o u s e more s o l u t i o n o r t o h e a t t h e water u s i n g s o l a r

energy ( i . e . , p a i n t i n g t h e w a t e r t a n k b l a c k ) .
During t h e c o u r s e o f s o i l t r e a t m e n t about 36,000 g a l l o n s (136,000 l i t e r s )
of 0.4N KCL s o l u t i o n was d e l i v e r e d t o t h e s i t e .

The i n t r o d u c t i o n of t h i s

l a r g e q u a n t i t y o f l i q u i d i n t o t h e s i t e on 1-40 a p p a r e n t l y d i d not have any
a d v e r s e e f f e c t s on t h e c a r r y i n g c a p a c i t y o f t h e pavement over a two-month
-6 7 *See Page 45

period.

However, d u r i n g t h e l a s t week o f t h e p r o j e c t some r u t t i n g was n o t e d

a t t h e west end of t h e t e s t s e c t i o n .

Undoubtedly, i f t h e s o l u t i o n d e l i v e r y

had c o n t i n u e d a t t h e avg. r a t e o f about 600 g a l l o n s p e r day f o r a s i g n i f i c a n t l y l o n g e r p e r i o d of time, t h e c a r r y i n g c a p a c i t y o f t h e pavement would
have been i m p a i r e d .

This f a c t o r does add a c o n s t r a i n t t o t h e KCL + w a t e r

t r e a t m e n t of s o i l problems b e n e a t h a roadway s u r f a c e .

However, most roadway

s e c t i o n s of s w e l l i n g c h i n l e c l a y encountered d u r i n g t h e t e n y e a r s t h a t
aqeuous KCL s o l u t i o n p l u s e l e c t r o - o s m o s i s was employed by ADOT d i d n o t r e q u i r e
an amount o f s o l u t i o n , f o r s a t i s f a c t o r y t r e a t m e n t , t o d i s r u p t t h e c a r r y i n g
c a p a c i t y of t h e roadway.

Because o f t h i s past-performance r e c o r d it can

b e s a i d t h a t most s i t e s l o c a t e d b e n e a t h a roadway s u r f a c e can b e t r e a t e d
by t h i s method without s i g n i f i c a n t l y i m p a i r i n g t h e c a r r y i n g c a p a c i t y o f t h e
pavement .
During t h e a c t u a l f i e l d o p e r a t i o n u s i n g e l e c t r o c h e m i c a l methods s e v e r a l
components o f t h e system must have a h i g h r e l i a b i l i t y f o r t h e t r e a t m e n t t o
be s a t i s f a c t o r y .

They a r e :

(1) t h e e l e c t r i c a l c i r c u i t r y , ( 2 ) t h e R O C .

g e n e r a t o r and (3) t h e s o l u t i o n d e l i v e r y system.

I f (1) o r (2) were t o f a i l ,

t h e t r e a t m e n t would n o t c e a s e , however, i t s e f f i c i e n c y would b e s i g n i f i c a n t l y
c u r t a i l e d due t o t h e l a c k o f t h e e l e c t r o c h e m i c a l a c t i o n .

I f (3), the solution

d e l i v e r y system, were t o f a i l some s o i l t r e a t m e n t could s t i l l be c a r r i e d o u t
by m a i n t a i n i n g an e l e c t r i c a l c u r r e n t through t h e s o i l mass, however, a f t e r
a 24-hour t o 48-hour p e r i o d i t would be v e r y i n e f f i c i e n t s i n c e t h e s o i l would
begin t o dry out with a corresponding i n c r e a s e i n s o i l r e s i s t i v i t y .
The p a r t i c u l a r c i r c u i t r y p a t t e r n used on t h i s p r o j e c t i s a v e r y s i m p l e
one which i s almost f o o l - p r o o f t o i n s t a l l and r e l a t i v e l y e f f i c i e n t .

Care

must be t a k e n , however, i n checking t h e r e b a r welds and c a b l e - r e b a r connections f o r electrical integrity.

These a r e t h e o n l y p o s s i b i l e t r o u b l e

trouble points f o r the c i r c u i t set-up.

Since t h e s e p a r t i c u l a r operations a r e

r e l a t i v e l y e a s y f o r one s k i l l e d maintenance man t o perform, t h i s p o r t i o n o f
the operation is not d i f f i c u l t .

Moreover, s i n c e t h e c i r c u i t i s i n use f o r

o n l y a m a t t e r o f a few weeks c o r r o s i o n o f t h e e l e c t r i c a l c o n n e c t i o n s w i l l be
l i t t l e o r no problem,

The o n l y major e l e c t r i c a l problem encountered d u r i n g

t h i s t e s t was caused by inclement weather.

That i s d u r i n g a p e r i o d of heavy

r a i n s , w h i l e t h e e l e c t r i c a l components were i n o p e r a t i o n , t h e r e s i s t i v i t y of
t h e s o i l would n e c e s s a r i l y b e s i g n i f i c a n t l y lowered with a c o r r e s p o n d i n g s u r g e
This, o f course, w i l l destroy t h e

i n c u r r e n t o f 50 p e r c e n t t o 100 p e r c e n t .

s a f e t y f u s e s which were i n s t a l l e d i n t h e c i r c u i t t o p r o t e c t t h e g e n e r a t o r ,
Of c o u r s e , when t h i s o c c u r s t h e e l e c t r i c a l o p e r a t i o n i s brought t o a h a l t
u n t i l new f u s e s a r e i n s t a l l e d , b u t s o l u t i o n d e l i v e r y may c o n t i n u e .
G e n e r a l l y s p e a k i n g , b a r r i n g a sudden c o l d f r o n t , heavy r a i n s a r e t h e
o n l y form o f a d v e r s e weather c o n d i t i o n s which can b r i n g an e l e c t r o c h e m i c a l
operation t o a h a l t .

R i s i s because o f t h e r e s u l t i n g changes i n s o i l con-

d u c t i v i t y which cause o v e r l y l a r g e c u r r e n t s u r g e s t h a t can o v e r l o a d t h e
c i r c u i t r y and even damage t h e g e n e r a t o r u n l e s s it i s p r o t e c t e d by t h e p r o p e r
s a f e t y f u s e s (200-amp f u s e s i n t h i s c a s e ) .
The power s o u r c e used, a 60-KW D . C .

g e n e r a t o r , f u n c t i o n e d without m i s -

hap d u r i n g t h e a p p r o x i m a t e l y 40 days o f c o n t i n u o u s 24-hour o p e r a t i o n , d i s r e g a r d i n g a s e v e r a l hour s h u t down d u r i n g heavy r a i n s because o f blown
e l e c t r i c a l 200-amp s a f e t y f u s e s .

One major s a f e t y d e v i c e used on t h e g e n e r a t o r

was a r.p.m. r e g u l a t o r f o r i t s e n g i n e .
llsu.n-away".

The r.p.m.

r e g u l a t o r prevented a

That i s , it p r e v e n t s t h e g e n e r a t o r ' s rep.m. from i n c r e a s i n g t o o

f a r above t h e s a f e o p e r a t i o n a l r a t e o f 1200 r , g , m .

I f a run-away were t o

o c c u r , t h e g e n e r a t o r ' s engine would l i t e r a l l y shake i t s e l f t o p i e c e s .

Also,

a f u e l c u t - o f f was i n s t a l l e d a s a back-up s a f e t y d e v i c e f o r t h i s purpose.

.

1 I' tllc g e n e r a t o r were t o f a i l f o r any o t h e r r e a s o n , i e . , a broken rod,

p i s t o n o r f u e l e x h a u s t i o n , s o l u t i o n d e l i v e r y c o u l d s t i l l b e c o n t i n u e d with
a l o s s o f t r e a t m e n t e f f i c i e n c y due t o t h e l o s s o f t h e e l e c t r o c h e m i c a l a c t i o n
i n the s o i l .
A f t e r completion o f t h e e l e c t r o c h e m i c a l t r e a t m e n t , assuming t h a t t h e
r e s u l t s were proven t o b e s a t i s f a c t o r y v i a l a b o r a t o r y s o i l t e s t s , t h e o n l y
remaining t a s k i s t o remove t h e a u g e r h o l e c a s i n g s and f i l l i n t h e h o l e s .
I t must be p o i n t e d o u t , however, t h a t t h e procedure a s u t i l i z e d on t h i s
p r o j e c t , i . e . , employment o f a u g e r h o l e s a s s o l u t i o n w e l l s does cause una c c e p t a b l e damage t o t h e roadway s u r f a c e .

Hence, i t must b e s t r e s s e d t h a t

t h i s method o f s o i l t r e a t m e n t s h o u l d o n l y b e u s e d o v e r a s e c t i o n of roadway

Labor r e q u i r e m e n t s , a f t e r such a t r e a t m e n t and a f t e r t h e scheduled o v e r l a y , a r e n o n - e x i s t e n t except f o r a y e a r l y e l e v a t i o n r u n .

Since t h e s i t e

t r e a t e d on 1-40 was s h o r t l y t h e r e a f t e r o v e r l a y e d and, moreover, a t t h e time
of t h i s r e p o r t w r i t i n g o n l y a few months have p a s s e d s i n c e t h e o v e r l a y no
meaningful e l e v a t i o n d a t a can b e i n c l u d e d i n . t h i s r e p o r t .
The long t e r m e f f e c t s o f t h i s k i n d o f t r e a t m e n t have been examined i n
t h e l a b o r a t o r y by u s i n g samples t a k e n from a s m a l l s i t e t r e a t e d i n 1968.
Through t h e u s e o f e l e c t r o n micrographs and e l e c t r o n d i f f r a c t i o n t h e s e samples
were shown t o be s t r u c t u r a l l y i d e n t i c a l t o t h o s e from t h e r e c e n t l y t r e a t e d
s i t e on 1-40 ( s e e f i g u r e s 46 and 5 l a ) .

Moreover, D i s t r i c t I V p e r s o n n e l a r e

watching f o r any s i g n s o f h e a v i n g o f t h e s i t e on 1-40.

To d a t e none have

been r e p o r t e d .
In comparison t o o t h e r k i n d s o f t r e a t m e n t s such a s t h e one used by
Ion-Tech it a p p e a r s t h a t t h e e l e c t r o c h e m i c a l t r e a t m e n t , w h i l e more expensive,
seems t o b e much more e f f e c t i v e i n r e d u c i n g s w e l l ,

C l e a r l y , i f one were t o

s i m p l y o v e r l a y a s w e l l i n g s i t e w i t h o u t any k i n d o f t r e a t m e n t , t h i s would be
-71-

a k i n t o p l a c i n g a bandage on a f e s t e r i n g wound because a s soon a s t h e s o i l
m o i s t u r e e q u i l i b r i u m i s d i s t u r b e d t h e c l a y would s w e l l and a n o t h e r o v e r l a y
would be needed.

However, a s o f l a t e , membrane e n c a p s u l a t i o n o f t h e roadway

subgrade t o s t a b i l i z e t h e subgrade s o i l m o i s t u r e c o n t e n t coupled with an
o v e r l a y could p r o v i d e a v i a b l e s o l u t i o n t o t h e s w e l l i n g c l a y problem.

This

method, i f proven s u c c e s s f u l , would undoubtedly b e t h e p r e f e r r e d s o l u t i o n
s i n c e i t would be much l e s s expensive i f done o v e r a l o n g s t r e t c h of roadway
t h a n t h e e l e c t r o c h e m i c a l t r e a t m e n t would b e .
P r e l i m i n a r y Conclusions:
A t t h i s time i t i s n o t p o s s i b l e t o u s e documented s u r v e y measurements

t o d e t e r m i n e , with a s s u r a n c e , i f s o i l expansion a t t h e s i t e has b e e n a r r e s t e d
because o f t h e s h o r t span o f time s i n c e t h e t r e a t m e n t was concluded.

However,

it i s c e r t a i n l y p o s s i b l e t o s t a t e t h a t t h e e f f e c t s o f t h e e l e c t r o c h e m i c a l

t r e a t m e n t w i l l have a l i f e span a t l e a s t a s long a s t e n y e a r s a s evidence by
t h e e l e c t r o n m i c r o s c o p i c work done with t e n y e a r o l d t r e a t e d c h i n l e c l a y
samples.
In a d d i t i o n , t h e f i n d i n g s o f t h i s p r o j e c t s u g g e s t t h a t e l e c t r o - o s m o t i c
s o i l s t a b i l i z a t i o n , u s i n g a 0.4N KCL s o l u t i o n can b e a p p l i e d e f f i c i e n t l y o n l y
on a h i g h l y l o c a l i z e d mass o f s w e l l i n g c l a y , i . e . ,

electro-osmosis is apparently

i n h e r e n t and hence unavoidable d i f f i c u l t y i n u n i f o r m l y i n d u r a t i n g t h e c l a y
mass with t h e e l e c t r o c h e m i c a l t r e a t m e n t .

The p r o j e c t f i n d i n g s a l s o i n d i c a t e d

t h a t t h e s o l u t i o n - w e l l - n e t used was t o o c o a r s e ,
forced

i . e . , t h e 8 ' (2.4M) c e n t e r s

each w e l l t o i n u n d a t e s o i l up t o 4 ' (l.2M) from t h e w e l l 's k.

A finer

n e t would have been more e f f i c i e n t ; however, t h e c o s t o f i n s t a l l i n g a s o l u t i o n w e l l - n e t based on s a y 5 ' (l.5M) c e n t e r s would have been n e a r l y double t h e one
-72-

based on 8 ' (2.4M) c e n t e r s .

Moreover, because o f t h e wide v a r i a t i o n i n t h e

b e h a v i o r o f t h e s o l u t i o n flow through C h i n l e Clay a r e l a i b l e d e s i g n f i g u r e
f o r t h e s o l u t ion-well - n e t can o n l y b e o b t a i n e d a f t e r a p p r o p r i a t e l a b o r a t o r y
t e s t s ; hence, t h i s p a r a m e t e r w i l l , t h e r e f o r e , b e t a i l o r e d t o each p a r t i c u l a r
r e g i o n one i s working i n and c o u l d c o n c e i v a b l e v a r y from 4 ' (1.2M) t o 8 '
(2.4M)

,

A s t o t h e p h y s i c a l e f f e c t s on t h e c l a y s t r u c t u r e induced by e l e c t r o -

osmosis one f a c t i s a c e r t a i n t y :

no measureable d i a g e n e s i s o f t h e c h i n l e

c l a y o c c u r s , t h a t is, no measurable amount of C h i n l e c l a y goes o v e r i n t o an
I l l i t i c Clay.

The e f f e c t s a p p a r e n t l y a r e c o n f i n e d t o a l t e r i n g t h e s t a c k i n g

c o n f i g u r a t i o n s o f t h e u n i t c e l l s making up t h e c l a y p a r t i c l e s a s shown i n
Figure 44 I I I ( i - e . , r e o r i e n t i n g t h e u n i t c e l l s ) ,
a t by t h e f o l l o w i n g r a t i o n a l e :

T h i s c o n c l u s i o n was a r r i v e d

While OqBannon had shown i n p r e v i o u s work t h a t

t h e M o n t m o r i l l o n i t e ' s x-ray i n t e n s i t y was reduced a f t e r E .O

.

t r e a t m e n t it

was n o t e d by D r . Cowley o f ASU t h a t t h e e l c t r o n micrographs showed t h e s t a c k i n g
number o f t h e c l a y t o b e markedly reduced.
I t i s w e l l documented i n x - r a y d i f f r a c t i o n t h e o r y t h a t t h e i n t e n s i t y

o f any peak i s p r o p o r t i o n a l t o t h e s q u a r e o f t h e number o f p l a n e s c o n t r i b u t i n g
t o t h i s i n t e n s i t y peak.

This f a c t i s i l l u s t r a t e d i n F i g u r e 44 11.

Since

Cowley's e l e c t r o n micrographs i n d i c a t e d t h a t t h e number o f t h e s e p l a n e s was
reduced b e c a u s e o f t h e d i s r u p t i o n o f t h e s t a c k i n g geometry it a p p e a r s t h a t
t h e r e d u c t i o n i n t h e x-ray d i f f r a c t i o n peak f o l l o w s b e c a u s e o f t h i s r e o r i e n t a t i o n o f t h e u n i t c e l l s and n o t because o f any d i a g e n e t i c a c t i o n on t h e c l a y .
The u n d e r l y i n g f a c t # f o r recommending t h a t E.O. o p e r a t i o n s b e confined
s o l e l y t o s m a l l r e g i o n s * i s t h a t t h e t r e a t m e n t i s fundamentally n o t uniform
i n i t s e f f e c t s , which i s t h e c a u s a t i v e f a c t o r f o r r e q u i r i n g v e r y f i n e s o l u t i o n well n e t s ; i . e . , v e r y c l o s e l y spaced s o l u t i o n - w e l l h o l e s .
Moreover, because o f t h i s , t h e c o s t o f E . O . o p e r a t i o n s i s n o t s m a l l .

*

A roadway s e c t i o n 4 0 ' x 200' (12.2M X 6lM)

-73-

Based on o u r o p e r a t i o n s i t was c a l c u l a t e d t h a t t h e c o s t o f s t a b i l i z i n g one
c u b i c yard is approximately $9 o r $11-80 p e r M ~ . Also, i t s h o u l d be n o t e d
t h a t t h e s w e l l p r e s s u r e was reduced by o n l y 50 p e r c e n t and t h e p e r c e n t s w e l l
by 36 p e r c e n t .

To g e t b e t t e r r e d u c t i o n , with s o l u t i o n - w e l l - n e t used, would

have r a i s e d t h e c o s t much h i g h e r because more s o l u t i o n would have been r e q u i r e d ,
Weather c o n d i t i o n s a l s o p l a y a r o l e i n d e t e r m i n i n g when t o use o r n o t
u s e t h i s e l e c t r o c h e m i c a l method o f s o i l s t a b i l i z a t i o n .

P r i m a r i l y , i t should

o n l y be u t i l i z e d i n mild o r warm weather and s h o u l d n e v e r be a t t e m p t e d when
t h e ambient w a t e r t e m p e r a t u r e s f a l l below 10°C (50°F) otllerwise t h e r e s u l t i n g
KCL

-

w a t e r s o l u t i o n s t r e n g t h would b e r e l a t i v e l y weak and, hence, i n e f f i c i e n t

t o use,

Moreover, d u r i n g heavy r a i n s problems may a r i s e from c u r r e n t s u r g e s

due t o r a i n - i n c r e a s e d s o i l conductance.

Because o f t h e very low v o l t a g e

g r a d i e n t s used d u r i n g work of t h i s kindj0.3v/cm,the danger t o p e r s o n n e l i s
minimal u n l e s s , o f c o u r s e , t h e b a r e "hot" l i n e from t h e g e n e r a t o r was touched
while s t a n d i n g i n v e r y wet s o i l .

However, s i n c e t h i s e l e c t r o d e i s w e l l i n s u -

l a t e d t h i s k i n d o f mishap i s n o t going t o o c c u r by chance.

In f a c t , during

t h i s p r o j e c t l a r g e l y u n s k i l l e d maintenance p e r s o n n e l were a b l e t o f u e l t h e
g e n e r a t o r and s t a r t i t , even d u r i n g some v e r y heavy r a i n s , without any problems.
In g e n e r a l , t h e main problem encountered w i t h t h e e l e c t r i c a l system was
overloaded e l e c t r i c a l f u s e s (200 amps) caused by heavy r a i n s .

These problems

amounted t o o n l y an annoyance s i n c e a s soon a s t h e s o l u t i o n d e l i v e r y was made
o r t h e g e n e r a t o r was r e f u e l e d t h e f u s e s would b e r e p l a c e d .

T h i s would g i v e

a maximum p o s s i b l e shutdown p e r i o d o f about 12 h o u r s , more l i k e l y much l e s s .
Also d u r i n g t h e t i m e o f s o l u t i o n i n - p u t t o t h e s i t e (approximately 36,000
g a l l o n s ) e l e v a t i o n checks were made o v e r t h e s i t e which showed t h a t t h e pavement s u r f a c e remained l a r g e l y s t a b l e d u r i n g t h i s p e r i o d with t h e e x c e p t i o n
o f minor r u t t i n g s l e s s t h a n l / 2 " deep, a t t h e west end of t h e s e c t i o n which
extended f o r a b o u t 5 ' i n t h e r i g h t wheel p a t h .

- 74-

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and t h e a n g l e of i n c l i n a t i o n of t h e X-ray p a t h t o t h e sample u s i n g Bragg's
law.

The v a r i o u s c r y s t a l l i n e c l a y and non-clay m i n e r a l s a r e t h e n i d e n t i f i e d

from t h e i r v a r i o u s c h a r a c t e r i s t i c s p a c i n g s .

Two t y p e s of sample mounts a r e used i n o r d e r t o i d e n t i f y t h e non-clay
and c l a y m i n e r a l s .

A powder mount which i s a randomly o r i e n t e d f i n e l y ground

p o r t i o n of t h e sample p r e s s e d i n t 0 . a p l a s t i c mount i s used t o i d e n t i f y t h e
non-clay m i n e r a l s .

A t r e a t m e n t by which an o r i e n t e d mount i s g l y c o l a t e d w i l l cause t h e

s w e l l i n g components, s m e c t i t e and v e r m i c u l i t e , t o i n c r e a s e t h e i r s p a c i n g .

A 24-hour

3 0 0 o
~ r ~5 2 5 ' ~ h e a t t r e a t m e n t of a d r y o r i e n t e d mount i s u s e f u l

t o i d e n t i f y v a r i o u s c l a y m i n e r a l s from t h e c h a r a c t e r i s t i c s p a c i n g s which
r e s u l t from t h e d i f f e r e n t w a t e r l a y e r t h i c k n e s s e s a t d i f f e r e n t t e m p e r a t u r e s
and by t h e c o l l a p s e of t h e s t r u c t u r e of c e r t a i n m i n e r a l s at t h e s e temperatures.

The g l y c o l a t e d and h e a t t r e a t e d specimens a r e n o t run p a s t 15O, 2 e ,

s i n c e a t t h a t p o i n t t h e s p a c i n g i s approxi.mately 6

% which

i s considerably

l e s s t h a n t h e predominant. c h a r a c t e r i s t i c s p a c i n g s of t h e c l a y m i n e r a l s .

The r e l a t i v e amounts of t h e v a r i o u s c l a y and non-clay m i n e r a l s a r e
i d e n t i f i e d by t h e headings

'

minor

9 9-

or t r a c e

A l l p r i n c i p a l peaks a r e

i d e n t i f i e d by l e t t e r a b b r e v i a t i o n s which correspond t o t h e m i n e r a l s given
i n t h e key on t h e f o l l o w i n g page,

The random-dxed-layer

clay minerals a r e

composed predominatly of s m e c t i t e ( m o n t m o r i l l o n i t e ) .

A rough i d e a of t h e r e l a t i v e amounts of t h e v a r i o u s m i n e r a l s i s o b t a i n e d

from a comparison of t h e r e l a t i v e i n t e n s i t i e s of t h e c h a r a c t e r i s t i c peaks.

Usually t h e non-clay m i n e r a l f r a c t i o n i s more abundant i n accordance
w i t h t h e m a j o r i t y of sample h a v i n g a g r a i n s i z e l a r g e r than 2/11, t h e s t a r t
of t h e c l a y m i n e r a l s i z e r a n g e ,

The c l a y m i n e r a l component i s u s u a l l y

more i m p o r t a n t t h a n t h e non-clay m i n e r a l component s i n c e c l a y m i n e r a l s a r e
o r d e r s of magnitude more r e a c t i v e t h e non-clay m i n e r a l s due t o t h e i r l a r g e
specific surface area.
A i n t e r p r e t a t i o n of t h e r e s u l t s s o a s t o p r e d i c t t h e e f f e c t s on t h e

c l a y r e s u l t i n g from t h e e l e c t r o c h e m i c a l t r e a t m e n t can b e had by n o t i n g t h e
i n t e n s i t y of t h e d i f f r a c t e d r a d i a t i o n r e l a t i v e t o t h e i n c i d e n t r a d i a t i o n .
It i s w e l l known t h a t t h e r e l a t i v e i n t e n s i t i e s i s a f u n c t i o n of t h e p h y s i c a l
c o n s t a n t of t h e X-ray a p p a r a t u s , t h e t y p e of atoms comprising t h e d i f f r a c t i o n p l a n e s and t h e r e l a t i v e number of p l a n e s o r i e n t e d s o t h a t t h e d i f f r a c t e d r a d i a t i o n from t h e s e p l a n e s r e i n f o r c e t h e observed i n t e n s i t y p a t t e r n .
It i s t o b e n o t e d t h a t i n a l l of t h e p r e - t e s t

samples, from t h e 1-40

s i t e , checked by X-ray d i f f r a c t i o n t h e p r e s e n c e of S m e c t i t e o r Montmorillon i d e s ranges from one sample w i t h minor amounts t o 3 samples w i t h major
amounts.
However, i n t h e p o s t - t e s t

samples checked, o n l y 2 o u t of 7 r e a d i n g s

show minor amounts of S m e c t i t e , t h e o t h e r 5 showing o n l y a t r a c e .

A

s i g n i f i c a n t example of t h i s g i v e n i n f i g u r e s 39 and 40 where t h e p o s t t e s t
sample shows o n l y a t r a c e of montmorillonoids p r e s e n t ,
T h i s work i s comparable w i t h p r e v i o u s X-ray work p e r f o m e d on e l e c t r o chemically t r e a t e d Montmorillonite-Kao%in samples a s shown i n f i g u r e s 41
khru 44.
Table 3 g i v e s , i n t a b u l a r form, t h e r e s u l t s of t h e X-ray d a t a .

UNTREATED
BLANK NO, 1 - 10% MONTMORILLONIPE - 90% KAOLIN
TREATED
SAMPLE S-9
10% MONTMQRILLONIVE - 90% KAOLIN
80 LBS./FT.~
3 DAY TREATMENT
80% SATURATION

DEGREES 20
X-Ray Diffraction on Treated and Untreated Samples
Figure 41

UNTREATED
BLANK NO. 2 - 20% MONTMORILLONITE - 80% KAOLIN

TREATED
SAMPLE S-31
20% MONTMOWILLONITE - 80% KAOLIN

80 LBS./ F T ~
4 DAY TREATMENT
80% SATURATION

UNTREATED

JKAOLIN

DEGREES 20
X-ilay Diffraction an Treated and Untreated Samples

Figure 42

UNTREATED
BLANK NO. 3 - 30% MONVMORILLQNITE - 70% KAQbiN
TREATED
SAMPLE S-39
30% MONVMORlLbQNITE - 70% KAOLIN
80 LBS./FT~
1 DAY TREATMENT
80% SATURATION

UNTREATED -/

DEGREES 20
X-Ray Diffraction on Treated and Untreated Samples
Figure 4 3

UNTREAKED
BLANK NO. 4

- 40% MQNTMQWILLONIPE - 60% KAOLIN

TREATED
SAMPLE S-54R
40% MONTMORILLONITE - 60% KAOLIN
$OLBS./FT~
2 DAY TREATMENT
80% SATURATION

DEGREES 20
X-Ray Diffraction on Treated and Untreated Samples
Figure 44

CONCLUSION FROM X-RAY DIFFRACTION DATA

C l e a r l y t o a t t e m p t a r i g o r o u s c r y s t a l l o g r a p h i c a n a l y s i s of t h e t r e a t e d
and u n t r e a t e d m a t e r i a l from t h i s t e s t would b e beyond t h e scope, time, and
b u d g e t a r y l i m i n t a t i o n s of t h e p r o j e c t .

However, some d e f i n i t e i n f e r e n c e s

can b e drawn from t h i s d a t a .
The X-ray d a t a c l e a r l y i n d i c a t e s t h a t t h e c l a y h a s been a f f e c t e d by
t h e electro-chemical

t r e a t m e n t , moreover, t h i s d a t a i s supported by e l e c t r o n

micrographs and t e s t s on t h e e n g i n e e r i n g p r o p e r t i e s of t h e o i l .

Based on

b o t h e l e c t r o n micrograph and X-ray d i f f r a c t i o n d a t a , i t appears t h a t t h e
s t a c k i n g geometry of t h e c l a y p a r t i c l e s has been modified by t h e e l e c t r o chemical t r e a t m e n t .
Each c l a y p a r t i c l e c o n s i s t s of from one t o hundreds of s t a c k e d b a s i c
u n i t s a s shown i n f i g u r e 4411.

The number of b a s i c u n i t s comprising t h e

p a r t i c l e w i l l b e c a l l e d t h e s t a c k i n g number.
f i g u r e 4411 how t h e X-rays,

It i s a l s o d e p i c t e d i n

from a s e r i e s of e q u a l l y spaced p a r a l l e l p l a n e s

of atoms, w i l l add t o g e t h e r t o produce d e t e c t a b l e X-ray d i f f r a c t i o n p a t t e r n s .
Moreover, i t s h o u l d b e noted t h a t t h e maxima of i n t e n s i t y of t h e X-ray
p a t t e r n w i l l b e roughly p r o p o r t i o n e d t o t h e s q u a r e of t h e number of p a r a l l e l
p l a n e s c o n t r i b u t i n g t o t h e p a r t i c u l a r d i f f r a c t i o n maxima under o b s e r v a t i o n .
Now t h e e l e c t r o n micrograph d a t a i n d i c a t e d t h a t t h e s t a c k i n g number of b a s i c
u n i t s h a s d e c r e a s e d and t h i s d e c r e a s e would c o n t r i b u t e t o t h e r e d u c t i o n i n
t h e i n t e n s i t y peak.
i n f i g u r e 44111.

A s c h e m a t i c of t h i s s t a c k i n g number d e c r e a s e i s shown

GEOMETRIC CONDITIONS FOR SCATTERING OF X-RAYS

Fig 44-11

S i n c e n o a d d i t i o n a l m i n e r a l s were found i n t h e t r e a t e d m a t e r i a l s a s
opposed t o t h e u n t r e a t e d , i t i s n o t p o s s i b l e t o conclude t h a t t h e
s m e c t i t e s w e r e t r a n s f o m e d i n t o an i l l i t i c - l i k e c l a y ,

Thus, t h e f a c t

of r e d u c t i o n i n t h e d i f f r a c t e d i n t e n s i t y of t h e t r e a t e d c l a y coupled w i t h
t h e r e d u c t i o n i n t h e s t a c k i n g number, a s shown by t h e e l e c t r o n micrograph,
i n d i c a t e s t h a t t h e treatment a f f e c t e d p r i m a r i l y t h e 0

-

0 bonds between t h e

b a s i c u n i t s b u t d i d n o t cause s i g n i f i c a n t d i a g e n i s i s of t h e c l a y .

Moreover,

s i n c e t h e e n g i n e e r i n g p r o p e r t i e s 06 t h e c l a y a r e h i g h l y dependent on t h e
n a t u r e and s t a b i l i t y of t h e i n t e r l a y e r environment between t h e u n i t c e l l s ,
i t i s a p a r a n t , from t h e s o i l t e s t s , t h a t t h e e l e c t r o c h e m i c a l t r e a t m e n t of

c h i n l e c l a y a l s o a l t e r s t h e i n t e r l a y e r complex, which i s composed of
i n o r g a n i c i o n s , w a t e r , and even o r g a n i c complexes i n a d d i t i o n t o i n t e r f e r r i n g with the b a s i c 0

-

0 bounding between t h e u n i t c e l l s .

B e n t o n i t e - t y p e m a t e r i a l s were observed by u s i n g Transmission E l e c t r o n
Microscope t e c h n i q u e s ,

Standard B e n t o n i t e m i n e r a l s (Wyoming B e n t o n i t e and

USP B e n t o n i t e ) were compared t o p r e - t e s t
post-test

c l a y samples (40133 and 40188) and

clay samples (40415A).

A sample which h a s been t r e a t e d w i t h p o t a s s i ~ l r nc h l o r i d e several y e a r s

p r i o r t o the t r e a t m e n t 06 40415A was a l s o o b s e n e d t o s e e what t h e long
r a n g e e f f e c t s 06 t r e a t m e n t were,

A l l specimens w e r e i n i t i a l l y suspended i n a c e t o n e , s o n i c a t e d i n a n
u l t r a s o n i c c l e a n e r t o b r e a k up l a r g e clumps and t h e n d i s p e r s e d o n t o e l e c t r o n m i c r o s c o p e p r i d s which had t h i n c a r b o n f i l m s u p p o r t s t o h o l d t h e sample.
The a c e t o n e e x t r a c t e d a n o r g a n i c s u b s t a n c e from t h e samples which
showed up on t h e m i c r o g r a p h s a s a d a r k amorphous s p o t t y s u b s t a n c e ,
The f i r s t samples w e r e d i s c a r d e d b e c a u s e o f t h e e x t r a c t e d o r g a n i c
m a t e r i a l and new samples w e r e suspended i n d i s t i l l e d w a t e r r a t h e r t h a n
acetone.

The same p r o c e d u r e f o r p r e p a r i n g t h e specimen was c a r r i e d o u t

a s o u t l i n e d above,
The p r e l i m i n a r y r e s u l t s showed t h a t t h e p r e - t e s t m a t e r i a l s ( 4 0 1 3 3 and

40188) w e r e n o t a s w e l l d i s p e r s e d a s was t h e p o s t - t e s t sample ( 4 0 4 1 S A ) The E l e c t r o n Microscope P h o t o g r a p h s f o r t h e p o s t - t e s t m a t e r i a l s
show t h e t h i n c r y s t a l l a y e r s t o b e d i s p e r s e d b e t t e r t h a n f o r t h e p r e -

t e s t s a m p l e s f o r which t h e u n i t c e l l s t e n d e d t o remain s t a c k e d i n t o
thicker crystals.
The d i f f r a c t i o n p a t t e r n s f o r t h e p o s t - t e s t

m a t e r i a l s , f i g u r e 45 and

45, shows d i f f r a c t i o n s p o n t s on t h e c i r c l e s where t h e p r e - t e s t d i f f r a c t i o n
p a t t e r n , f i g u r e s 47 and 4 8 , shows t h a t some o f t h e d i f f r a c t i o n s p o t s a r e
d i s p l a c e d from t h e c i r c l e s .

A g e n e r a l i n t e r p r e t a t i o n of t h i s i s :

When

d i f f r a c t i o n s p o t s a r e d i s p l a c e d from t h e d i f f r a c t i o n r i n g s , t h i s i n d i c a t e s
t h a t t h e u n i t c e l l s a r e s t a c k e d up on t o p of e a c h o t h e r t o form w e l l
ordered three-dimensional

crystals,

Another s a m p l e r u n was made t o see i f t h e p r e l i m i n a r y r e s u l t s c o u l d
be duplicated,

T h i s t i m e e x a c t amounts o f s a m p l e w e r e p l a c e d i n 6 m l of

d i s t i l l e d w a t e r f o r e a c h specimen.

I n e a c h c a s e 0.5 gm of sample w e r e

suspended i n 6 m l o f d i s t i l l e d , w a t e r .

The w a t e r s o l u t i o n was s o n i c a t e d i n

an u l t r a s o n i c c l e a n e r f o r t h r e e minutes.

F i g u r e 45
Electron diffraction from treated test site
Chinle clay

F i g u r e 46
E l e c t r o n d i f f r a c t i o n from t r e a t e d r e s t s i t e
Cl~inLe c l a y

F i g u r e 47
E l e c t r o n d i f f r a c t i o n from u n t r e a t e d t e s t s i t e
Chinle clay

F i g u r e 48
E l e c t r o n d i f f r a c t i o n f r ( x ~u n
~t r e a t e d t e s t s i t e
Chinle clay

Each s a m p l e was a l l o w e d t o s e t t l e f o r t e n m i n u t e s s o t h e l a r g e r

A 0.3 m l aliquot

p a r t i c l e s would go t o t h e b o t t o m of t h e s a m p l e v i a l .

of sample s u s p e n s i o n was t h e n suspended i n a n o t h e r s i x m l of d i s t i l l e d
water,

This technique helped t o d i l u t e t h e suspensions,

T h i s was n e c e s s a r y

t o keep t h e c r y s t a l s from s t a c k i n g on t o p of e a c h o t h e r a f t e r d r y i n g ,
The d i l u t e d s u s p e n s i o n would l e t t h e specimen d r y s o one c o u l d d i s t i n g u i s h
between c r y s t a l s which w e r e d i s p e r s e d from e a c h o t h e r and c r y s t a l s which
n a t u r a l l y p i l e d on e a c h o t h e r d u e t o f o r c e s which k e p t t h e c r y s t a l s
together,
The s u s p e n d e d samples w e r e p l a c e d on t h i n c a r b o n f i l m s which had
a t h i n l a y e r of SiO e v a p o r a t e d on b o t h of i t s s i d e s , s e e f i g u r e 49.

Carbon film
///'

/'

/

Si O

-

-Microscope g r i d

f

The SiO e v a p o r a t e d on t h e c a r b o n f i l m c a u s e s t h e c a r b o n s u r f a c e t o
be hydrophillic.

Carbon t e n d s t o b e h y d r o p h o b i c .

A hydrophobic f i l m

w i l l c a u s e t h e sample t o c o a l e s c e i n t o p o o l e d a r e a s as t h e w a t e r evap o r a t e s from t h e g r i d .

The SiO p r e v e n t s t h e specimen from c o a l e s c i n g

and t h u s a l l o w s t h e e v a p o r a t i o n t o p r o c e e d t h r o u g h o u t t h e a r e a o f t h e whole
grid.

The specimen w i l l r e m a i n d i s p e r s e d on t h e c a r b o n b e c a u s e t h e

c r y s t a l s w i l l n o t b e p o o l e d a s t h e s u r f a c e t e n s i o n of t h e w a t e r p u l l s t h e
c r y s t a l s i n t o themselves,

Samples 40133, 40188, 40415A and t h e Old E.O.

s i t e were observed.

The e v i d e n c e seems t o show t h a t t h e t r e a t e d sample h a s m i n e r a l
f l a k e s which a r e l e s s t h i c k compared t o t h e p r e - t e s t

samples.

This

i s presumably b e c a u s e t h e n a t u r e and s t a b i l i t y of t h e b o n d i n g between t h e

s u c c e s s i v e b a s i c s t r u c t u r a l u n i t s (Lamella) h a s b e e n a l t e r e d c a u s i n g t h e
s t a c k i n g of t h e u n i t s t o changes geometrically,
The USP and Wyoming b e n t o n i t e samples r e s e m b l e d e a c h o t h e r morphologically.

T h e s e samples a l s o more c l o s e l y r e s e m b l e d t h e p r e - t e s t

samples

b e c a u s e t h e y showed t h e t h i n c r y s t a l s t o b e s t a c k e d up on e a c h o t h e r , s e e
f i g u r e 50.
The Old E,O. S i t e C r y s t a l s a p p e a r e d t o l o o k l i k e t h e p o s t - t r e a t e d
samples as shown i n f i g u r e 51-a.

As was p o i n t e d o u t i n t h e d i s c u s s i o n of t h e E l e c t r o n M i c r o s c o p i c
procedure, t h e evidence c l e a r l y i n d i c a t e s t h a t t h e c r y s t a l l i n e f a b r i c
of t h e c l a y h a s b e e n a f f e c t e d b y t h e t r e a t m e n t .

I n p a r t i c u l a r it appears

t h a t t h e S m e c t i t e l a y e r s have been d i s p e r s e d a f t e r t h e t r e a t m e n t .
i s i n d i c a t e d by t h e e l e c t r o n - d i f f r a c t i o n

This

p a t t e r n s which i s p r e - t r e a t e d

material depicts a thick layered structure,

T h i s i s noted by t h e Gider

i n t h e p r e - t r e a t e d m a t e r i a l as opposed t o t h e r e l a t i v e l y
t h i n d i f f r a c t i o n r i n g s o b t a i n e d from t h e t r e a t e d m a t e r i a l ,
a r e c h a r a c t e r i s t i c of a many l a y e r e d c r y s t a l ,

The w i d e r i n g s

I f the layers a r e dispersed,

a p a t t e r n of t h i n d i f f r a c t i o n r i n g s i s o b t a i n e d .

Moreover i n t h e e l e c t r o n

t r a n s m i s s i o n p h o t o g r a p h s f i g u r e s 51-b and 51-c i t i s shown how t h e l a y e r s

of t h e t r e a t e d m a t e r i a l appear much more t r a n s p a r e n t t o t h e e l e c t r o n s
(51-b)

t h a n does t h e u n t r e a t e d m a t e r i a l (51-c),

indicating, respectivily,

v e r y t h i n c r y s t a l l i n e l a y e r s a s opposed t o v e r y t h i c k c r y s t a l l i n e l a y e r s .

F i g u r e 50
Wyoming B e n t o n i t e Diffraction P a t t e r n

F i g u r e 51-a
E l e c t r o n Diffraction f r o m O l d E . O .
C11inI.c. Clay
-99-

Figure 51-b
Electron Transmission of Treated Test Site
Chinle Clay
3300QX

Figure 51-c
Electron Transmission of Untreated Test Site
Chinle Clay
33000X

Upon completion of t h e e l e c t r o c h e m i c a l t r e a t m e n t samples were o b t a i n e d
and r e t u r n e d t o t h e M a t e r i a l s S e r v i c e s L a b o r a t o r y i n Phoenix where expansive
p r e s s u r e and % s w e l l t e s t s were performed i n t h e s t a n d a r d Clock-House Apparatus.

The r e s u l t s of t h e s e t e s t s a r e shown i n Table 4.

EXPANSIVE
DEPTH
- LL

Pb PI
-

44

0'-3'

34

22

12

40420B

44

3'-6926

23

3

40420C

14

6'-9'

38

25

13

404208

14

9'-15' 34

22

12

404218

15

O"3-7

19

18

40421 B

15

3'-6'

22

14

40421 C

15

6'-!9'41

22

19

40421 8

I5

9'-15'41

20

21

SAMPLE #

HOLE #

40420A

39

PERCENT
SWELL 'c
-

v

d'
-

'c
d'
-

F i g u r e 54

A f t e r t h e % s w e l l and expansive p r e s s u r e t e s t s were completed i n
Clock-House Apparatus i t was determined t h a t t h e sample could p o s s i b l y
s w e l l and f l a k e o f f because i t was n o t p r o p e r l y c o n f i n e d .

In addition,

a q u e s t i o n of r e l i a b i l i t y of t h e Revalue method of o b t a i n i n g expansive
p r e s s u r e was r a i s e d .

I t was decided t o u s e t h e A.S.U.

meter and % s w e l l a p p a r a t u s a s a means of c o n t r o l ,

designed expanso-

See f i g u r e s 52 t h r u 55

f o r i l l u s t r a t i o n s of t h i s a p p a r a t u s ,
The r e s u l t s of t h e s e t e s t s a r e shown i n T a b l e 5 ,
T h i s d a t a i n d i c a t e s t h a t t h e expansive p r e s s u r e was d e c r e a s e d
somewhat o v e r 50%. The % s w e l l was d e c r e a s e d by over 36%, T h i s i s a
s i g n i f i c a n t r e d u c t i o n and is a n i n d i c a t i o n of t h e s u c c e s s of t h e e l e c t r o chemical t r e a t m e n t .

CONCLUSIONS FROM S O I L TEST DATA

The e l e c t r o chemical t r e a t m e n t moderately decreased b o t h expansive
p r e s s u r e and % s w e l l , i t d i d n o t have any a p p a r e n t a f f e c t on t h e a t t e r b u r g

l i m i t s of t h e s o i l ,
It is a l s o apparent t h a t

t h e s o i l mass t r e a t e d by t h e method was

i n t e r s p e r s e d w i t h "hot" and "cold" s p o t s .

That i s , some p a r t s of t h e s o i l

mass were s i g n i f i c a n t l y a f f e c t e d by t h e t r e a t m e n t and o t h e r s were l a r g e l y
untouched, moreovel"these "hot" and "cold" s p o t s were randomly d i s t r i b u t e d
throughout t h e s o i l mass.

TABLE 5
POST PEST
-

IniLia1
Moisture
Content

Initial
Dry

SAMPLES

%

Swell

PRE TEST
-

Ini t i a1
Moisture
Content

%nit i a l
Dry
Densi t y

Expansive
Pressure
(PSF )

SAMPLES

16

2-3

40183

13.9

107.9

6.9

--

--

--

18

0-3

40188

13.9

109.8

9.7

15.3

906.3

5888

21

0-3

40197

14.2

187.4

6.0

14.2

109.2

2471
-

ave. 7.53

aye, 3779

CHAPTER V I I
MOI\TETRRY

ENERGY EDENDITmES FOR ELECTROCHEMICAL OPERATIONS

The f o l l o w i n g i t e m i z e d c o s t s a r e p r e s e n t e d t h a t t y p i f y t h e monetary and
energy e x p e n d i t u r e s t o o p t i m a l l y p r e p a r e and t r e a t , e l e c t r o c h e m i c a l l y , a
480' l o n g , 40' wide, i n - p l a c e s e c t i o n of a s p h a l t i c paved i n t e r s t a t e highway
t o a depth o f 3' below t h e s e l e c t m a t e r i a l .
It must b e s t r e s s e d t h a t t h e s e 1973-1975 money f i g u r e s a r e s u b j e c t t o

b o t h monetary and wage i n f l a t i o n a r y f o r c e s and t h e i r usage a t any f u t u r e
d a t e should be adjusted accordingly.

A.

1.

D r i l l 285 6" d i a m e t e r , 6 ' deep a u g e r h o l e s on 8' c e n t e r s and

s l e e v e w i t h 6" O.D.

2.

27" l o n g s t e e l c a s i n g ,

-

$4,000.

Big two t r e n c h e s 4 ' deep, 6" wide and 460' l o n g , a l o n g w i t h
t h r e e t r e n c h e s i n c e n t e r of roadway s u r f a c e 6" wide and 138'
l o n g each

3.

-

$1,000.

I n s t a l l a t i o n of e l e c t r i c a l components:

(Note:

$700.

U t h o u g h t h e s t e e l s l e e v e s were designed t o f a c i l i t a t e t h e i r

r e u s a g e on f u t u r e p r o j e c t s , c i r c u m s t a n c e s may render i t t o o expensive
t o attempt salvaging the sleeves.
a s e v e n d a b l e items)

.

Thus we a r e c o n s i d e r i n g t h e s l e e v e s

1.

Cost f o r 300, 6" O.B.,

27" l o n g c a s i n g s each topped w i t h a 10"

d i a m e t e r 1/2" t h i c k s t e e l p l a t e w i t h a 1-1/2"
c e n t e r of p l a t e
2.

-

diameter h o l e i n

$2,000.

Cost f o r K C 1 s o l u t i o n d e l i v e r y s y s t e m ( e x c l u d i n g t a n k e r t r u c k )

-

$400.

3.

Cost f o r 15001, 1" r e b a r s t e e l (#8 g r a d e 60) t o use f o r e l e c t r o d e s

4.

E l e c t r i c a l w i s i n g components: 6 0 ' of 4 / 0 i n s u l a t e d w i r e ( s t r a n d e d
copper) s u i t a b l e f o r b u r i a l

-

$65.

500' of 2/0 i n s u l a t e d w i r e ( s t r m d e d copper) s u i t a b l e f o r b u r i a l

-

$354.
5.

K C 1 ( p o t a s s i m c h l o r i d e ) , 90,000 l b s . g r a n u l a r a g r i c u l t u r a l g r a d e ,

i n 100# m u l t i - w a l l p a p e r b a g s on wood p a l l e t s

6.

$3,100.

860 l b s o f a e r o s o l C-61 w e t t i n g a g e n t ( S u r f a c t a n t ) i n 430 l b
drums

7.

-

-

$860.

3120 g a l l o n s o f d i e s e l f u e l a t 4 0 ~ / g a l , t o o p e r a r e 60 KW B.C.
g e n e r a t o r f o r 40 days continaaous o p e r a t i o n

-

$1,248.

1.

2,500 g a l l o n c o n v e r t e d w a t e r t r u c k , ADOT equipment.

2.

60 KW D. C, g e n e r a t o r , ABOT equipment.

-

1.

-

200 man hours a t $3.50/hr.

$700.

Hence t h e t o t a l c o s t t o p r e p a r e and o p t i m a l l y t r e a t a 480' l o n g , 40'
wide i n p l a c e , a s p h a l t i c paved, roadway s e c t i o n 3 ' below s e l e c t m a t e r i a l
was $14,997.

Based on t h e assumption t h a t t h e m a t e r i a l i s
a s w e l l r e d u c t i o n f a c t o r of 2 o r more, i t i s . e s t i m a t e d t h a t t h e c o s t p e r
ft

a

i s approximately 2 b c / f t 3 .

C l e a r l y i f t h e m a t e r i a l mass i s n o t uniformly

t r e a t e d by t h e e l e c t r o c h e m i c a l p r o c e s s t h i s c o s t / f t 3 f i g u r e w i l l i n c r e a s e
correspondinglys

The energy in-put

from t h e s t a r t o f t h e e l e c t r o c h e m i c a l t r e a t m e n t t o

t h e f i n i s h w a s o b t a i n e d from t h e energy r a t i n g o f t h e 3120 g a l l o n s of d i e s e l
f u e l sonslamed by t h e 6 Q KW g e n e r a t o r ,

Each g a l l o n of d i e s e l f u e l h a s an

energy r a t i n g of 140,000 B.T.U.

-

4.368 x 108 B.T.U,

A*

Energy in-put

B,

T o t a l generator output

-

19,657,296 w a t t h o u r s ,

J o u l e s t h i s f i g u r e i s 1.9657296 x 10' x 3 , 6 ,
Joules.

So u s i n g a B.T.U.

7.076626560 x
1.05587

lo7

B.T.U.

lo3

I n t e r n s of
= 7.076626560 x 10''

r a t i n g t h e g e n e r a t o r o u t p u t was
= 6.702175988 x

B.T.U.

T h i s gave a u s a b l e energy f a c t o r of about 15,34 p e r c e n t ,

So about 84.66

p e r c e n t of t h e a v a i l a b l e energy was l o s t because of g e n e r a t o r e f f i c i e n c y and
e l e c t r i c a l bosses.

-all-

With a g e n e r a t o r i n top running c o n d i t i o n i t i s e s t i m a t e d t h a t i t would
b e p o s s i b l e t o r a i s e t h e u s a b l e energy f a c t o r t o o v e r 40%.

Although t h e L a s t f i g u r e s given h e r e appear t o r e f l e c t e x c e s s i v e c o s t s ,
i t must be borne i n mind t h a t t h i s f i e l d work h a s a f i r s t time o p e r a t i o n .

Correspondingly t h e man h o u r s i n v o l v e d were much l o n g e r t h a n would b e t h e c a s e
i n any f u t u r e work u t i l i z i n g p e r s o p n e l f a m i i i a r w i t h t h e t e c h n i q u e .

CHAPTER V I I I
NUCLEAR MOISTURE MONITORING

Midway i n t h e p r o j e c t t h e M a t e r i a l s S e r v i c e s of t h e Arizona Department
of T r a n s p o r t a t i o n s e t up two e x p e r i m e n t a l s i t e s l o c a t e d a t S t a t i o n 12+00
11+76 and S t a t i o n 11+76

-

-

114-52 f o r t h e purposes of m o n i t o r i n g s o i l m o i s t u r e

movement d u r i n g t h e a c t u a l f i e l d work,
T r o x l e r n u c l e a r depth m o i s t u r e gauges were employed d u r i n g t h e f i e l d
work t o d e t e r m i n e t h e m o i s t u r e movement d u r i n g t h e s o l u t i o n i n p u t p e r i o d .
Moreover, i o n movement d e t e r m i n a t i o n was a l s o made s i n c e i t was f e l t t h a t
potassium R

-P

o r c h l o r i d e 61- i o n s could have i n t e r f e r r e d w i t h n u c l e a r

r e a d i n g s , t h i s was done c h e m i c a l l y ,
To m o n i t o r t h e m o i s t u r e movement from t h e p o s t h o l e s aluminum a c c e s s
t u b e s were p l a c e d i n a p a t t e r n a s shown i n f i g u r e 56, i n a l l 38 t u b e s were
used,

The AL t u b e s allowed t h e n u c l e a r m o i s t u r e probes t o b e i n s e r t e d i n t o

them t o any d e p t h from 12'' below t h e pavement s u r f a c e t o a depth of n e a r l y
96".

A t y p i c a l a c c e s s t u b e i n s t a l l a t i o n i s shown i n f i g u r e 57.
L a b o r a t o r y t e s t s were made on s o i l samples, a f t e r t h e f i e l d work

was completed, t o determine t h e t o t a l d i s t a n c e of i o n i c movement v s
c o n c e n t r a t i o n l e v e l from t h e c e n t e r l i n e of a p o s t h o l e .

The r e s u l t s of

t h e s e t e s t s a r e shown i n f i g u r e s 58 and 59 f o r b o t h K and CL.

It s o u l d b e noted t h a t t h e K c o n c e n t r a t i o n r a p i d l y diminished w i t h
d i s t a n c e from t h e p o s t h o l e , indeed c o n c e n t r a t i o n g r e a t e r t h a n one perc e n t by weight was n o t found two f e e t from t h e p o s t h o l e .

A t f i r s t glance

i t may a p p e a r t h a t t h e CL c o n c e n t r a t i o n i s much g r e a t e r a t any d i s t a n c e t h a n
t h a t of M, however, n o t e t h a t t h e CL c o n c e n t r a t i o n i s p l o t t e d on a d i f f e r e n t s c a l e t h a n i t i s f o r K, however t h e CL seemed t o move f u r t h e r t h a n t
t h e M+ i o n s .

NUCLEAR MOISTURE MONITOR LAY-OUT
FOR HPR-1-"I ((14%)

same as in Control Section

A1 Moisture Sensors

A Moisture Sensors

Sta: 12t00
F i g u r e 56

END OF E.P. TEST-SITE

K

' Ion C o n c e n tofr a tAuger
ion
Hole

WS D i s t a n c e from

f o r Various T e s t Depths

0

1

2

3

4

D i s t a n c e from P o s t Hole i n P t .
F i g u r e 58

5

CL

-

C o n c e n t r a t i o n ag T;

D i s t a n c e from

$ of p o s t h o l e f o r v a r i o u s t e s t d e p t h s
-

Distance in f e e t from
F i g u r e 59

of post: h o l e

It i s i n t e r e s t i n g t o n o t e t h a t t h e s e c u r v e s a r e s i m i l a r t o s t a n d a r d one
g i v e n f o r d i f f u s i o n of p a r t i c l e s i n f o r c e f i e l d s a s shown i n f i g u r e 60,
Note. t h a t b o t h c u r v e s g i v e n f o r K and CL a t a d e p t h of 60" appear
t o b e s i m i l a r t o t h e " t a i l s " of curves 2 , 3 , o r 4 shown i n f i g u r e 60.

The

c u r v e f o r CL a t a d e p t h of 44" seems l i k e c u r v e 5 o r 6 of f i g u r e 60 w h i l e
t h e curve f o r K a t a d e p t h of 76" seems l i k e 5 o r 6 ,

This s t r o n g l y indi-

c a t e s t h a t t h e i o n s were indeed a c t e d on by an e l e c t r i c f i e l d d u r i n g t h e i r
m i g r a t i o n through t h e s o i l .

Conclusions from Nuclear
The t e s t r e s u l t s i n d i c a t e d an o v e r a l l d r y i n g t r e n d f o r t h e t e s t s i t e
d u r i n g t h e c o u r s e of t h e s o l u t i o n i n p u t ,

That i s t o s a y , t h e n u c l e a r

gauge i n f o r m a t i o n i m p l i e d t h a t t h e s o i l mass, comprising t h e s i t e r e g i o n ,
was d r y i n g o u t d u r i n g t h e c o u r s e of t h e f i e l d work.

Moreover, t h e M a t e r i a l s

S e r v i c e s of Arizona Department. of T r a n s p o r t a t i o n f e e l s t h a t t h e n u c l e a r
gauge h a s proven i t s e l f t o b e a u s e f u l t o o l i n m o n i t o r i n g long-term m o i s t u r e
changes i n s u b g r a d e o r b a s e m a t e r i a l s .

CWTER IX

S

, CONCLUSIONS AND

aECOMMENDATIONS

This s t u d y focused p r i m a r i l y on t h e implementing E l e c t r o c h e m i c a l s o i l
t r e a t m e n t procedures developed i n p r e v i o u s P.N.W.A,

sponsored work.

I n i t i a l l y a s i t e f o r t h e f i e l d work was chosen a l o n g a s e c t i o n o f 1-40
t h a t w a s e x p e r i e n c i n g s w e l l i n g problems.

The s i t e was s e l e c t e d a l o n g a

roadway of h i g h t r a f f i c volume s o t h a t t r a f f i c c o n t r o l problems d u r i n g an
o p e r a t i o n of t h i s s o r t could be f u l l y c o n s i d e r e d s i n c e t h i s method of s o i l
s t a b i l i z a t i o n is i n t e n d e d t o become p a r t of A.D.O.T,

Maintenance procedures.

I n t h i s work t h e primary c o n s i d e r a t i o n s were:

(I)

R e l a t i v e e a s e of f i e l d i q l e m e n t a t i o n of e s t a b l i s h e d e l e c t r o c h e m i c a l
s o i l t r e a t m n t technology,

(2)

The e f f e c t i v e n e s s of s o i l t r e a t m e n t by e l e c t r o c h e d c a l methods when
t h e f i e l d o p e r a t i o n s a r e conducted l a r g e l y by u n s k i l l e d and semis k i l l e d maintenance p e r s o n n e l .

(3)

Cost of f i e l d o p e r a t i o n .

Based on t h i s s t u d y i t can be s t a t e d t h a t t h e u s e of e l e c t r o c h e m i c a l
s o i l treataaent technology can be e f f e c t i v e l y implemented u t i l i z i n g e x i s t i n g
manpower and material r e s o u r c e s o f A.D.O.T.

supplemented by minor purchases

of s p e c i a l i z e d hardware and software, however, it is t o b e s t r e s s e d t h a t t h e
method is an expensive one, c o s t i n g about $9 p e r c u b i c y a r d of s o i l t r e a t e d *

Moreover, t h i s s t u d y has i n d i c a t e d t h a t e l e c t r o c h e m i c a l s t a b i l i z a t i o n i s
a v i a b l e method which w i l l moderately reduce e x c e s s i v e s w e l l i n g p r e s s u r e s i f
t h e y a r e encountered i n a l o c a l i z e d a r e a o v e r which an e x i s t i n g pavement r e s t s ;
however, u s i n g t h e same r e s o u r c e s a s were used on t h i s p r o j e c t , t r e a t m e n t o f
a volume o f m a t e r i a l g r e a t e r than 1800 c u b i c y a r d s (approximately 1380 c u b i c
meters) s h o u l d n o t b e a t t e m p t e d .
Conclusions
(I)

Based on t h i s s t u d y e l e c t r o c h e m i c a l s o i l t r e a t m e n t can b e s u c c e s s f u l l y
completed by A.D.O.T. Maintenance p e r s o n n e l u s i n g t h e p r e v i o u s l y
established f i e l d procedures,

(2)

From t h e x - r a y d i f f r a c t i o n and t ransmission e l e c t r o n microscope d a t a
it i s e v i d e n t t h a t t h e elect roc he mica^ t r e a t m e n t w i t h KCL s o l u t i o n

i s e f f e c t i v e i n a l t e r i n g 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 of Montmoril-

l o n i t e s and t h e r e b y r e d u c i n g t h e expansive p r e s s u r e o f t h e s o i l .
T h i s evidence, b o t h x-ray and e l e c t r o n micrographic, i n d i c a t e s t h a t ,
g e n e r a l l y , t h e environment o f t h e C h i n l e C l a y ' s p a r t i c l e s i n t e r l a y e r
s p a c e has been a l t e r e d which, o f c o u r s e , s i g n i f i c a n t l y a f f e c t s t h e
engineering properties of the clay.
A s t o t h e e f f e c t s on t h e l a t t i c e s t r u c t u r e o f t h e c l a y , i . e . d i a -

g e n e s i s , t h e s e i s no c o n c l u s i v e e v i d e n c e wihch c l e a r l y shows t h a t
s i g n i f i c a n t amounts o f t h e Chinle Clay a r e e l e c t r o c h e m i c a l l y conv e r t e d i n t o an i l l i t i c c l a y .

(3)

Based on p r e v i o u s work it is a p p a r e n t t h a t t h e lower t h e m o i s t u r e
c o n t e n t a t t h e b e g i n n i n g o f t r e a t m e n t t h e more e f f e c t i v e t h e t s e a t -

(4)

The h i g h e r t h e p e r c e n t a g e o f M o n t m o r i l l o n i t e t h e more e f f e c t i v e t h e
treatment.

(5)

The most e f f e c t i v e e l e c t r o d e c o n f i g u r a t i o n f o r f i e l d i n s t a l l a t i o n
i s one i n which b o t h t h e anode and cathodes a r e p l a c e d i n a h o r i z o n t a l

position.

(6)

Potassium c h l o r i d e i s a w a t e r s o l u b l e m e t a l l i c s a l t t h a t w i l l e f f e c t i v e l y reduce t h e s w e l l i n g o f Montmorillonite

(7)

I t i s recommended t h a t t h e average v o l t a g e g r a d i e n t ( p o t e n t i a l /

d i s t a n c e between e l e c t r o d e s ) f o r f i e l d p r o j e c t s l i e between 0 . 2
volts/cm and 0 . 4 volts/cm.
is prohibitive.

Below 0 . 2 v o l t s / c m t h e t i m e requirement

Above 0 . 4 v o l t s / c m t h e r e i s a n o t i c a b l e h e a t i n g o f

t h e s o i l which i s an i n d i c a t i o n o f h i g h energy l o s s and waste a s s o c i a t e d with t h i s l o s s .

(8)

Because of t h e i n h e r e n t l y random n a t u r e o f t h e e l e c t r o c h e m i c a l proc e s s when used On heterogeneous m a t e r i a l , l i k e C h i n l e Clay, it i s
necessary t o c o n s t r u c t a very f i n e n e t o f s o l u t i o n wells t o s a t i s f a c t o r i l y i n u n d a t e t h e s o i l w i t h a s t a b i l i z i n g chemical.

I t was

found t h a t t h e n e t as used on t h i s p r o j e c t , i . e . ,

6" (l5.24cm) p o s t

h o l e s on 8 ' (2.4m)

Moreover, t h e

c e n t e r s , was n o t f i n e enough.

f i n e n e s s 0 6 t h e s o l u t i o n w e l l n e t w i l l be a f u n c t i o n o f t h e s o i l
c h a r a c t e r i s t i c s and hence must be d e t e r d n e d by l a b o r a t o r y t e s ts

(9)

E l e c t r o c h e ~ c a ls o i l s t a b i l i z a t i o n i s most e f f e c t i v e on a h i g h l y
l o c a l i z e d c l a y mass which h a s h i g h s w e l l p o t e n t i a l .

(PO)

The n u c l e a r m o i s t u r e m o n i t o r i n g gauge h a s proven i t s e l f t o b e a

u s e f u l t o o l i n m o n i t o r i n g long-term m i s t u r e changes i n subgrade

.

o r base m a t e r i a l s .

However, i t s h o u l d n o t b e used i n t h e presence

o f s i g n i f i c a n t concentrations of neutron poisons, i . e . , those e l e ments w i t h a h i g h n e u t r o n a b s o r p t i v e c r o s s s e c t i o n .
Recommen d a t i o n s
E l e c t r o c h e m i c a l s o i l s t a b i l i z a t i o n i s recommended f o r use whenever a
h i g h l y l o c a l i z e d mass o f h i g h - s w e l l c l a y i s encountered.

I n such c a s e s i t

i s quick a c t i n g , e f f i c i e n t and has long l a s t i n g e f f e c t s .
This s t u d y has produced s e v e r a l o p e r a t i o n a l t e c h n i q u e s t h a t w i l l f a c i l i t a t e
t h e f i e l d t r e a t m e n t of expansive c l a y s over which a roadway i s b u i l t t o reduce
the swelling p o t e n t i a l .

I t i s recommended t h a t t h e p r o c e s s be implemented

u s i n g t h e f o l l o w i n g procedure :
(1)

Execute p r e l i m i n a r y sampling p l a n a s given i n Chapter I 1 of t h i s
report.

(2)

A f t e r i d e n t i f i c a t i o n o f degree o f s w e l l i n g determine depth of
s t a b i l i z a t i o n r e q u i r e d based on t h e e x p a n s i v e p r e s s u r e i f i n - s i t u
material,

T h i s w i l l range from 3' (. 912m) t o 5 ' (1. Sm) .

A typical

design f i g u r e would be 4 ' o r about 1 . 2 m e t e r s .
(3)

Determine volume o f s o i l t o b e t r e a t e d .

Based on t h i s f i g u r e

o b t a i n e d r e q u i r e d amount o f KCL by u s i n g a design f i g u r e o f 1 . 6 % 2% KCL p e r u n i t weight o f s o i l .
(4)

P r e p a r e s i t e f o r e l e c t r o c h e m i c a l t r e a t m e n t u s i n g 6" (15.24~111) d i a m e t e r a u g e r h o l e s sunk approximately 6 ' (l,8m) below s u r f a c e on
4 ' (1.2m) t o 8 ' (2.4m) c e n t e r s (Note: The e x a c t c e n t e r i n g d i s t a n c e
can o n l y b e d e t e r ~ n e dby s o l u i i o n movement t e s t s i n s o i l s a m p l e s ) ,
S l e e v e a u g e r h o l e s w i t h 6" ( I S . 24cm) 0 . B. s t e e l p i p e w i t h a 10"
(25.4cm) d i a m e t e r p l a t e w i l l have a 1.5" (3.8lcm) d i a m e t e r h o l e i n
c e n t e r t o p e r m i t t h e i n t r o d u c t i o n o f KCL s o l u t i o n .

The p i p e s h o u l d

have a l e n g t h which i s t h e depth o f t h e b a s e course p l u s 6" (15,24cm).

(5)

P l a c e h o r i z o n t a l s anodes and cathodes and make e l e c t r i c a l connections.

(6)

P l a c e s o l u t i o n i n w e l l s t w i c e a day f o r 30 days.

(7)

A t t h e end o f 30 days t u r n on a v o l t a g e g r a d i e n t o f 0 . 2 v o l t s / c m

and c o n t i n u e o p e r a t i o n with a p p l i e d v o l t a g e g r a d i e n t f o r 3 t o 4
weeks depending on e l e c t r o d e p o l a r i z a t i o n phenomena,
(8)

C o l l e c t s u f f i c i e n t p o s t - t e s t samples t o determine e f f e c t i v e h e s s
of e l e c t r o c h e m i c a l t r e a t m e n t .
A flow c h a r t i l l u s t r a t i n g t h e e s s e n t i a l procedure s t e p s , compris-

i n g an e l e c t r o c h e m i c a l t r e a t m e n t , i s given i n Figure 61.
(9)

To a v o i d m o i s t u r e measurement e r r o r s d u r i n g t h e o p e r a t i o n o f
Nuclear Moisture Monitoring gauges i n ' an environment c o n t a i n i n g
elements w i t h a h i g h Neutron Absorption c r o s s s e c t i o n , i . e .

,

10 b a r n s , c o n t i n u a l c a l i b r a t i o n of t h e gauges r e l a t i v e t o t h e
chemically i n u n d a t e d s o i l must b e c a r r i e d o u t .