INVESTIGATION OF THE CONSOLIDATION AND
SHEAR STRENGTH CHARACTERISTICS

OF TWO CLAY MINERALS

The“: 509 the Degree of M. S.
MICHIGAN STATE UNIVERSITY
Murl Harry Webster

1959

 

This is to certify that the

thesis entitled

IIWESTIGATIUN OF THE CONSOLIDATION AND
SHEA 'l STRENGTH CHA {ACTEII STI CS
OF TWO CLAY I‘EINSRALS

presented by

MURL HARRY WEBSTER

has been accepted towards fulfillment
of the requirements for

MASTER OF SCIENCE degree in CIVIL ENGINEERING

W

Major professor

 

Date May 13, 1959

 

0-169

 

LI 8 R A R Y
Michigan Stare
University

 

 

w-~_fi‘4

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INVESTIGATION OF THE CONSOLIDATION AND SHEAR
STRENGTH CHARACTERISTICS OF TWO

CLAY MINERALS

by

Murl Harry Webster

AN ABSTRACT

Submitted to the College of Engineering
Michigan State University of Agriculture and
Applied Science in partial fulfillment of
the requirements for the degree of

MASTER OF SCIENCE
Department of Civil and Sanitary Engineering

June 1959

Approved: EZQ§¢f32L¢<Lf ,

 

MURL HARRY WEBSTER ABSTRACT

This paper is concerned with the effect of the sodium
and calcium ions on the consolidation, orientation, and
shear strength of the clay minerals grundite and kaolinite.

Experiments were conducted with the clay minerals
saturated with sodium or calcium ions. The clays were
artifically sedimented and consolidated to various pressures.
The shear strengths, consolidation characteristics, and
orientation were then studied at these various pressures.

The optical studies showed that particle orientation
is increased by consolidation. From the consolidation tests,
it was found that the sodium clay showed a higher void
ratio than the calcium clay at the same pressures.

The strength tests showed that the ions affect the
shear strength. Sodium clays are found to have less
strength than calcium clays.

The remolded strength of a soil is much less than
the undisturbed strength. This may be explained by the

high initial pore pressure in the remolded soil.

INVESTIGATION OF THE CONSOLIDATION AND SHEAR
STRENGTH CHARACTERISTICS OF TWO
CLAY MINERALS

by

Murl Harry Webster

A THESIS

Submitted to the College of Engineering
Michigan State University of Agriculture and
Applied Science in partial fulfillment of
the requirements for the degree of

MASTER OF SCIENCE

Department of Civil and Sanitary Engineering

June 1959

.’; l. .11 x: A:
t ‘ I ‘.
.4 ‘ I.» J

Liege

ACKNOWLEDGMENTS

The author would like to express his sincere thanks
to his major professor, Dr. T. H. Wu, Associate Professor
of Civil Engineering, Michigan State university; for his
guidance in the study and for his careful checking of the
manuscript. Gratitude is also extended to the National
Science Foundation for their support of this project and
to the Department of Civil Engineering for the use of its

facilities.

11

TABLE OF CONTENTS _
Page

ACKNOWLEDGMENTS. . . . . . . . . . . . . 11
LIST OF FIGURES. . . . . . . . . . . . . iv
LIST OF TABLES . . . . . . . . . . . . . vi
LIST OF SYMBOLS. . . . . . . . . . ‘. . . v11
Chapter
I. DEVELOPMENT OF CURRENT KNOWLEDGE. . . . 1
II. METHOD OF INVESTIGATION. . . . . . . 6
III. RESULTS . . . . . . . . . . . . 12
Iv. SUMMARY OF RESULTS . . . . . . . . 16
APPENDIX-~Figures . . ., . . . . . . . . . ' 19
Tables . . . . . . . . . . . . 39

BIBLIOGRAPHY. . . . . . . . . . . . . . 42

iii

13.

14.

15.

16.

17.

LIST OF FIGURES

Particle Size‘Distribution Curve. . . . .

Typical Time-Consolidation Curve. . . .
Optical Axes Diagram. . . . . . .
Triaxial Cell . . . . .. . . . . .
Consolidation Curves Kaolinite .

. Consolidation Curves Grundite. . . . I. ..

Typical Consolidation Curve of Sedimented
Clay Consolidated and Rebounded, Precon-
»solidation Pressure Determined by

Caesagrande’s Graphical Method . . . . .

Void Ratio Permeability KaOIinite .

‘Void Ratio PermeabiIity Grundite. . .
Calcium Grundite Photomicrographs . . .
Calcium Kaolinite Photomicrographs .

Typical Unconfined Compression Test
StresséStrain Curves .. .. .. . . . . .

Graphical Construction for the Determination
of g; and Plot of Mohr' s Envelopes. . . .

Stress-Strain and Porgwater Pressure~Strain
Curves, Po - A kg/bm , c 0.25.kg/Cm2 . .

Stress-Strain and Porewater Pressure~8train

Stress—Strain and Porewater Pressure-Strain
Curves, Po 2 u kg/bme, a 1.5 kg/bmz . ..

Stress-Strain and Porewater Pressure-Strain
Curves, Po 2 A/kg/bm.2, a A. O kg/th a .

iv

'Page

19
2O
21
‘22

23 .
24

25
26
27
~28

3O

31

.32

33

3h

35

Figure Page

18. Graphical Construction for the Determination
of the True Cohesion. . . . . . . . . 36

19. Typical Triaxial Quick Test with Porewater
Pressure Measurements . . . . . 37

20. Water Content vs.Undisturbed Shear Strength . 38

Table

LIST OF TABLES

Atterberg Limits and Activity. .

Preconsolidation-Pressure and Orientation
Factor . . . . . . . . . .

Void Ratio and Permeability .

Tabulation of Po, 0, Crem: C/PO and w for

Kaolinites. . . . .

Tabulation of Po, C, Crem’ C/PO and w for

Grundites .

vi

Page
39

39
AD

41

Al

LL
PI
PL

qu

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a an.

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“I

LISTING OF SYMBOLS
electrical attractive force per unit area
coefficient of compressibility (l/gms.)
undisturbed shear strength (kg/Cm2)
remolded shear strength (kg/Cm2)
coefficient of consolidation (cm3/sec).
deviator stress (kg/Cme)
compression dial reading at zero time
compression dial reading at 50% primary compression
compression dial reading at 100% primary compression
void ratio
permeability (cm/Sec)
liquid limit
plasticity index
plastic limit
preconsolidation pressure (kg/Cm2)
unconfined compression strength (kg/Cme)
electrical repulsive force per unit area
porewater pressure (kg/Cm?)
water content %
total normal stress (kg/bme)
effective normal stress (kg/Cme)
major principle stress (kg/bme)
minor principle stress (kg/Cm?)
shear stress on a plane (kg/bm2)

true angle Of internal friction (degrees)
vii

I. DEVELOPMENT OF CURRENT KNOWLEDGE

Soil Structure

Soil structure is a property that has been recognized
to be of importance for many years [TerZaghi 1925,
Cassagrande 1932, and Hvorslev l938‘(6)*]. Originally the
structure of a soil referred only to the arrangement of the
particles. However, at present, when referring to a clay
soil, structure encompasses the particle arrangement as
well as the electrical forces acting between particles.
Baver (1) states that both chemical and physical properties
seem to be controlled by the surface activity Of the soil

particles.

Forces Acting Between Soil Particles

 

The forces between soil particles may be divided into
three main groups; primary valence bonds, hydrogen bonds,
and secondary valence bonds.

Primary valence bonds are defined as the forces that
hold the atoms together in the basic mineral units. This
group is further subdivided into three subgroups; ionic
bonds, covalent bonds, and heterpolar bonds.

Another type of bond that can be classified as a

primary bond is that of electrostatic attractions and

 

*Numbers in parentheses are references listed at the
end of this paper. '

1

repulsions. Clay particles are negatively charged along
their plates and may or may not be positively charged along
the edges. Thus, if cations are present they will be
attracted to the plate. These ions are called adsorbed
ions or counterions. Water mOlecules will also be adsorbed
by the clay particles. This happens because the water
molecule is a dipole. The adsorption of water takes place
‘in the presence of cations and the adsOrbed water layer is
affected by the presence of the ions.

Secondary valence bonds, also known as van der Naals
forces, arise from electrical moments within the existing
units. It should be noted that the net effect is attraction.

Since the clay particles have a net negative charge,
the particles repel each other. Using the Gouy Chapman
theory, an expression for the electrical repulsion can be
written. However, the actual case is not so simple, as
secondary valence forces also act. By combining repulsive
and attractive forces chemists have developed expressions
relating the potentialand the net repulsion to the inter-
particle spacing. This information was published recently
by Krutz,1952 and Bolt,1955(6).

The Gouy Chapman theory assumes that the charges are
distributed evenly over the entire particle. If the
charges on the edges are ignored the theory shows that
flocculation with parallel orientation results if the

attractive forces exceed the repulsive forces. However,

not all flocculation will produce parallel orientation.
This is because of the fact that often the edges carry
a plus charge, thus tending to cause flocculation in an

edge to plate array.

Volume Changes in the Soil

 

For volume changes to take place, a particle rearrange-
ment must take place. If the soil is loaded and the
rearrangement of the particles takes place, decreasing the
volume, the rearrangement must have forced the partiCles
into a more orderly array. When a volume decrease takes place
due to compression as above, it is largely non-recoverable.

Consider now the hypothesis of equilibrium presented
by Lambe (6). To maintain equilibrium the externally applied
intergranular stress ('5' ) plus the electrical attraction
(A) must equal the electrostatic repulsion (R). Now if a
pressure increase is applied (.57?' ), for equilibrium to
be maintained the colloidal particles must move closer
together with an increase in the net repulsion. Some water
between the particle is forced out by this movement. Now
examine the case when the load is removed from the mass.

For equilibrium there must be an increase in the distance
between particles to allow the net repulsive force to
decrease by the amount (4—0" ). This type of volume increase
is almost the sole contributor to the rebound of a soil,

as was stated by Bolt (3).

 

Shear Strength

When considering the shear strength of a soil one
usually recalls the Coulomb equation S = C + tan ‘E. It
states that the strength is made up of two parts, cohesion
and internal friction. When one examines the shear strength
of a system of clay particles, one must consider the same
forces that are discussed under "VOlume Changes in the Soil,"
( 5*), (A) and (R). As was stated earlier for equilibrium
( 0- + A = R) must exist,

According to Lambe (6),shear strength.of a colloid
is primarily determined by the electrical forces acting
between particles; however, he also mentions four factors
other than electrical that have some effect. They are
respectively: (a) particle spacing, (b) orientation, (c)
external loads ( €- ), and (d) characteristics of the water
system.

In natural clays a decrease in particle spacing
increases the shear strength. This supports Leonards,

1955 (9) and Rutledge,19u8 (7), who state that the closer
the particle spacing the denser the soil and the greater

the shear strength.

Orientation of Clay Particles

 

Under the topic of strength was mentioned orientation
of clay particles. Generally one associates a random type
of orientation with flocculation. It is also possible to

have parallel orientation in a flocculated material,

depending upon the forces that are responsible for floccu-
lation.

In 1956 Mitchell (10) published an extensive article
on a study of the fabric of clays. This article showed
that the improvement in orientation by remolding increases

with increasing sensitivity of the clay.

Summary
The foregoing discussion indicates that the consoli-

dation and shear strength characteristics are controlled to
a very large extent by the physical chemical forces that
act between the particles. The review also brought out the
fact that outside of the fundamental laws on potential

and repulsive forces between partiCles, little is known
about these forces and their effects on consolidation and

shear strength characteristics.

II. METHOD OF INVESTIGATION

Objective

The primary objective of this research was to attempt
to evaluate the physical-chemical forces that are important
to the mechanical properties of clays. The consolidation
characteristics, the undisturbed and remolded shear strengths
and their relationships with the adsorbed ion and with the
particle orientation were studied. Two minerals, kaolinite
and grundite, and two ions sodium and calcium, were chosen.
Consolidation studies were made on laboratory sedimented
clays. The shear strengths were measured by the unconfined
compression test and the triaxial test, performed on clays
preconsolidated to various pressures. From this data the
ratio of the Shear strength to the preconsolidation pressure,
C/PO was computed. The orientation of the clay particles
were studied by examination of thin sections with a petro-

graphic microscope.

Soil Studied

 

This study used two clay minerals, kaolinite and
grundite. The grundite is a mineral of the illite family,
which has a general formula
(OH)A Ky (s18_y ~A1) ( A14° Fen ' Mgu 'Mg6) 023 (A).

The grundite has a slightly more expanding structure than

6

the Fithian illite. Illite being a general term proposed
by Grim, gt a}, (A) in 1937 for a mica like clay commonly
found in the state of Illinois.

The grain size characteristics of the clays are shown
in Figure 1. Table 1 is a tabulation of the Atterberg
Limits of the clays studied.

Preparation Of the Clay Minerals

 

The general procedure used in the preparation of both
clay minerals was identical. First the clay was put into
suspension with a standard Waring blender. Approximately
100 grams of soil was mixed with 1 liter of distilled water.
After the suspended soil had flocculated, the clear water
on top of the soil was poured off. Next the container, a
3 liter beaker, was filled with 1 normal HCl. The clay
was vigorously stirred until all clay was in suspension.
Again the clay was allowed to flocculate and the liquid
poured off. This procedure was repeated until no green
color was observed in the liquid above the soil. At this
point all the exchangeable ions had been replaced with '
hydrogen ions. The HCl washes were discontinued, and the
clay was washed with distilled.water approximately five
times. After completion of the washings, the clay was
poured onto a number fifty filter paper inzn118.5 centimeter
Buchner funnel. The Buchner funnels were supported by
4 liter vacuum flasks which were evacuated by a vacuum pump.

Enough clay was poured on the filter paper to form a pat

approximately one-eighth of an inch thick. During this
phase a continual wash Of distilled water was run through
the Clay until no chlorine ions could be detected in the
wash water. The silver nitrate test was used to detect
chlorine ions.

After completion of the washing the clays were titrated
with a base until pH7 was maintained. .This usually required
7 to 10 days. The two bases used were sodium hydroxide
[NaOH] and calcium hydroxide [Ca(0H)2]. The titration pro-
duced clays saturated with Na and Ca ions. In the remainder
of this paper the clays will be referred to as sodium
kaolinite, calcium kaolinite, Sodium grundite or calcium

grundite.

Consolidation Tests

 

The clay was mixed into a dilute suspension
(w = 800% to 1200%) and placed in a modified consolidometer
fitted with a tall lucite standpipe. In a matter of about
24 hours the clay had floccUlated to allow clear water to
be decanted off the top and the standpipes refilled.” This
was repeated until 6 to 8 inches of flocculated material had
accumulated at the bottom of the standpipe. After 72 hours
Ia porous stone was lowered to the top of the clay. At this
point standard consolidation loading was started. The first
load was 0.04 kg/bmz.

The sodium grundite when mixed in a dilute suspension

remained dispersed so it was treated slightly differently.

Instead of mixing the clay into a dilute suspension it was
mixed into a thin paste (w = 400% to 601%) and placed in the
apparatus. The procedure followed henceforth was identical
to the procedure Just described.

For all consolidation tests a complete record of
time-consolidation readings was kept. A plot of a typical

time-consolidation curve is shown in Figure 2.

Study of Optical Properties

The fabric of the clays was studied in various states
of consolidation. The unconsolidated clay was allowed to
flocculate in small glass Jars (P0 = 0). To impregnate the
clay the porewater was displaced by a 1:3 solution of
carbowax and water. The flocculated soil was kept in this
dilute carbowax solution for about a week at a temperature
of 650C. Then the water was allowed to evaporate and after
another week the specimen was removed from the oven and the
carbowax allowed to solidify. .

The study also includes consolidated clays. One speci-
men being preconsolidated to l kilogram per square centimeter
(P0 = l kg/cmE), and the other preconsolidated to 43 kilo-
grams per square centimeter (Po 2 40 kg/Cme). The impreg-
nation of the consolidated clays for thin sections was
identical with that described by Mitchell,l956 (11), A piece of
the clay was placed in a bottle containing liquid carbowax
and placed in an oven at 650C for a period of two weeks- At
the end of this time the carbowathad replaced all of the

porewater in the clay. Following this the bottles were removed

10

from the oven, allowing the carbowax to solidify. When
cooled. the clay was_ready to be sliced into thin sections.
The thin sections were prepared by Mr.-George Rev of

Columbia University.

Optical Studies

 

The thin sections were studied under the petrographic
microscope. Using a vertical section of a clay with parallel
orientation, four alternate stages of illumination and
extinction could be Observed when placed between crossed
nicol prisms. (Light passed through crossed nicols vibrates
in two planes only.) The horizontal sections showed no
illumination because the al and a2 axes lie in all directions.
(See Figure 3A In a vertical section, random oriented
particles show no illumination or extinction as none of the
axes of the individual particles are oriented in a particular
direction.

The method used by Wu (1h) to measure the degree of
orientation is as follows: the light transmitted at both
extinction and illumination is measured by the use of a
photo tube attached to the petrographic microscope eyepiece.
Then she ratio of the light at illumination to that at

extinction is designated as the orientation factor.

Strength Tests

 

Unconfined compression tests. The clays were con-

 

solidated to a certain pressure, extracted from the

consolidometer and specimens one inch square and two inches
long were trimmed from the cake. Both the undisturbed and
remolded clays were tested using approximately 2% strain

per minute.

Drained triaxial tests. For the determination of the

 

true angle of internal friction the drained triaxial test
was used. ‘The specimen Of remolded soil was placed into

the rubber membrane supported by the membrane Jacket. A
specimen one inch in diameter and three inches in length
was obtained. Two sets of three samples each were used.

One set had an initial water content of 71% and the second
set an initial water Content of 61%. The chamber pressures
used were 0.25 kg/Cme, 0.50 kg/bme, 1.0 kg/bme, 1.50 kg/Cme,
and A.0 kg/bme. I

Consolidated quick triaxial tests. The procedure
for preparation of the undisturbed specimens for the con-
solidated quick test was similar to that used in the con-
solidation tests. In this case standpipes with a 4 inch
inside diameter were used. The specimens were consolidated
to 4.0 kg/bmg before being trimmed for the test. A standard
triaxial cell modified for porespressure measurements

(Figure A) was used.

Quick triaxial tests. Preparation of the undisturbed

 

specimen used in the triaxial quick test was identical to

the procedure followed for the consolidated quick tri xial

test.

III. RESULTS

Consolidation Tests

Pressure-Void ratio curves obtained from the con-
solidation tests are presented in Figures 5, 6, and 7. It
will be seen that the adsorbed ions, exerts an effect on
the pressure-void ratio curves. At a given void ratio the
curves for both the sodium grundite and sodium kaolinite
show higher pressures than their calcium counterparts. This
means that thenet repulsive forces between particles is
greater in the sodium clays than it is in the calcium clays.
This is in agreement with the results of theoretical
calculations by Bolt (3).

When the two minerals are compared one finds that the
void ratio of the grundites is always greater than that
of the kaolinites.

One may also consider the activity of the minerals.
Activity is defined as the plasticity index divided by
the per cent finer than 2 microns. Referring to Table 1,
one sees that the grundite is more active than the kaolinite.
The activity of a mineral is indicative of the net charge
of the clay particles and the magnitude of the surface
forces. Thus, it can be concluded that the activity of the
mineral reflects accurately the consolidation characteris—
tics of the clay mineral.

12

13

Figure 2 is a representative time-consolidation curve
and illustrates the calculation of the coefficient of
consolidation and permeability by the Logarithmic method.
The relationship between the permeability and void ratio
for the four soils are plotted in Figures 8 and 9.

Optical Studies

The orientation of the soils as measured through the
petrographic microscope is given in Table 2. The optical
studies indicate a definite trend for the orientation ratio
to increase with increased consolidation pressure. This is
reasonable and is expected because the clay particles are
forced closer together and are slightly rearranged during
consolidation. Average values are given in the tables.
The kaolinites exhibit a considerable range in orientation.
The calcium kaolinites, at P0 = l kg/Cm2, has a range from
1.5 to 2.2, while at P0 = no kg/cm2 the range is from 1.4
to 2.0. As can be seen from this data the orientation is
initially improved but after consolidation to l kg/cm2
little improvement can be expected. The range in measured
orientation for the two grundites is very small and the
average values in the table are representative of a fairly
uniform condition throughout the specimens. Figures 10 and
11 Show photomicrographs of the thin sections at both

illumination and extinction.

14

Strength Tests

Unconfined compression tests. Tables 4 and 5 give the
results of the unconfined compression tests on undisturbed
and remolded soils. One can see that the adsorbed ion ‘
effects the C/Po ratio considerably less than does the
mineral itself. Again it can be concluded that the clay
mineral has a.much greater effect upon the characteristics
of the soil than do the exchangeable ions. Figure 12
shows typical unconfined compression stress-strain curves

for both undisturbed and remolded soils.

Drained triaxial tests. The drained triaxial tests

 

were performed on remolded sodium kaolinite. From the
results obtained, the true angle of internal friction was
determined. In Figure 13 is plotted the water content at
failure vs. the chamber pressure 0'; . Directly below this
Mohr's envelops are drawn. The graphical construction to
compute mg is also shown in the figure. The value of as

is found to be 15 degrees.

Consolidated quick triaxial tests. Consolidated quick

 

triaxial tests were performed on laboratory sedimented and
consolidated specimens of sodium kaolinite. The stress?
strain and porewater pressure-strain curves are shown in
Figures 14 to 17. From the test results the effective
normal stress and the shear stress on the failure plane were

computed and are plotted in Figure 18. The true cohesion

15
2 2
of the soil ranged from 0.03 kg/bm to 0.10 kg/bm .

Quick triaxial testp. Triaxial quick tests with pore-

 

water pressure measurements were performed on the sodium
kaolinite. An undisturbed specimen preconsolidated to

4.0 kg/cm2 was tested. After this the specimen was remolded
and tested again. The stress and porewater pressure vs
strain.curves are shown in Figure 19. One sees that the pore
pressure in the undisturbed test is abOut equal to the
chamber pressure. ‘This is expected of=a saturated clay when
placed in a triaxial cell. As the deviator stress is in-
creased, the pore pressure decreaSed Slightly. This may be
due to movement of sell-particles along the failure plane
causing a slight expansiOn of the struCture.

In the remolded speCimen an initial porewater pressure
of 0.03 kg/cm2 at zero chamber pressure was measured. When
the chamber pressure of 0.50 kg/cm2 was applied the pore
pressure increased by an amount equal to the chamber pressure.
Thus it is evident (refer to Figure 18) that the effective
stress a: is negatiVe. If Figure 18 is referred to one
sees that the remolded teSt falls mostly in the second
quadrant. The failure pOint pIOts in the first quadrant
with 1: equal to 0.033 kg/cm2, This indicates that the re-
molding of the soil destroys the structure such that an
initial porewater pressure is set up. It can be concluded
that the ranolded strength of a soil is low because no

internal friction is active.

IV. SUMMARY OF RESULTS

Consolidation of the Soils

From the information gathered on the consolidation of
the soils certain general conclusions may be drawn. In
Figures 8 and 9 and Table 3 the permeability vs. void ratio
relationships are given. The data from the grundite shows
that the permeability of the sodium clay is always smaller
than that Of the calcium clay. This is also true of the
kaolinites when the void ratios are less than 1.3. However,
as the void ratios increase the reverse takes place. The
small difference can be explained by the fact that the
kaolinite has so small an ion exchange capacity that the
material does not adsorb many ions. Therefore, the small
number of ions have little effect on the permeability. The
reason the sodium clay has the smaller permeability can
be explained by the fact that it is more active than the
calcium clay. The double layer that contains the adsorbed
ions and adsorbed water has a greater thickness in the
sodium clay. Since the adsorbed water is immobile, its
greater thickness reduces the void space open to flow of
water. When the clay thus surrounds itself with this
thick water layer its permeability is consequently reduced.

It is interesting to note the general relationship
of the permeability to the PI. From Tables 1 and 3 one sees

16

17

that the sodium clay has higher PI values than the calcium
clay; the permeabilities of the sodium clays are lower than

the calcium clays.

Orientation of Clays

In Table 2 are given the orientation factors for the
calcium kaolinite and grundite. These results show that
in general consolidation increases orientation of the clay
particles. However, the kaolinite seems to reach an optimum

orientation at a preconsolidation pressure of l kg/cme.

Shear Strength Of Clays

In Figure 20 the shear strengths measured by the un-
confined compression test are plotted against the water
content of the specimens. It shows that at equal water
contents the calcium clays possess greater strength than
the sodium clays. Also the grundites have a greater strength
than the kaolinites. If the influence of the adsorbed
ions are considered one finds that the sodium clays with
the thicker double layer has less strength. From this one
may conclude that the shear strength does not depend upon
the thickness of the adsorbed water. Furthermore the
shear strength is controlled by factors other than those
that control the permeability and consolidation character-
istics.

An interesting point can be seen from the quick
triaxial test data presented in Figure 19. From this data

18

a possible explanation as to the reason for the low remolded
strengths can be presented. It was found that the remolded
soil had such a high porewater pressure that the effective
normal stress on the failure plane was negative for the
greater portion of the test. At failure the 5': was
positive, but the strength developed approximated the true
cohesion value for the clay. Thus the conclusion is that

a remolded soil only develops the cohesive component of

the shear strength.

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TABLE |
CLAY ACTIVITY L.L. PL. RI.
SODIUM GRUNDITE 0.8I4 84.2% 23.2% CH.
CALCIUM GRUNDITE 0.077 74 'I. 28.7% 453%
SODIUM KAOLINITE 0.267 50.3% 20% 24.91
CALCIUM KAOLINITE 0202 47.51. 29.5% l8.0’/.
TABLE 2
CLAY PRECONSOLIDATION ORIENTATION
PRESSURE Ks/r-m‘ FACTOR
CALCIUM GRUNDITE 0 LOO
CALCIUM GRUNDITE I LBO
CALCIUM cannons 40 230
CALCIUM KAOLINITE 0 LOO
CALCIUM KAOLINITE I L70
CALCIUM KAoLINITE 40 Leo

 

 

 

 

 

 

 

 

TABLE 3

 

CLAY vow RATIO PERMEABILIT v I: I0" CHI/sec

CALCIUM GRUNDITE

SODIUM GRUNDITE

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SODIUM KAOLINITE

 

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3.87 IZI
2.27 6.26
I .7I 6.09
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4.43 ‘95
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I . IS 393
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TABLE 4 ..
KAOLINITE
P C ' C. C.
N 0 PC!" /
IO Isa/ant “9/“, W In“, F3. W %
SODIUM 2.0 0.084 0.0IBI 0.042 44.3
2.0 0.073 0.0l8I 0.038 44.3
4.0 0.098 0023 0.025 43.0
8.0 0. 37 0.0393 0.046 40.:
5b 0. 5'8 0.0440 0.012 40.:
CALCIUM LO 0.074 0.027 0.074 . '50.:
\.O 0.059 0027 0.059 50.5
TABLE 5'
GRUNDITE
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CALCIUM I . 0 0. I69 0.047 0. m9 56. 4
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2. 0 0.360 0.7.30 0. I80 44.4
Somum I. 0 0.095 0.070 0.095 17. o
2.0 0.2IO 0487 0405 59-8

 

 

 

 

 

 

 

 

 

 

10.

11.

BIBLIOGRAPHY

Baver, L. D. Soil Ph sics. New York: John Wiley and
Sons, Inc., e . C 6, p. IOff.

Bjerrum, L. Theoretical and Experimental Investigations
on the Shear Strength of Soils, Morwegion Geo-
technical Institute, Publication NR5, Oslo 1954.

Bolt, Gerard H. Physico-Chemical Properties of the
Electric Double Layer on Planar Surfaces, Phd
thesis Cornell University, 1954, p. 9-13, 64.

Grim, R. E. Cla Mineralo , McGraw-Hill Series in
Geology. ew YorE: ficGraw-Hill Book Co., Inc.,
01953; P. 161ff.

Grim, R. E. Some Fundamental Factors Influencing the
properties of Soil Materials, Proceedings of the
Second International Conference on Soil Mechanics
and Foundations Engineering, V3, p. 8, 1948.

Lambe, T. William. The Structure of Compacted Clay,
Journal of the Soil Mechanics and Foundations
Division, Proceedings ASCE, No. 1654, vol. 84,
no. SM2, part 1, May 1958.

Lambe, T. William. The Engineering Behavior of.Com-
pacted Clay, Journal of the Soil Mechanics and
Foundations Division, Proceedings ASCE, No. 1655,
vol. 84, no. 8M2, part 1, May 1958.

Lambe, T. William. Soil Testing for Engineers. New
York: John Wiley andJSons, Inc., c1951.

 

Leonards, G. A. Strength Characteristics of Compacted
Clays, Transactions ASCE, Vol. 120, 1955, p. 1420.

Mitchell, James K. The Fabric of Natural Clays and
its Relationship to Engineering Properties,
Proceedings Highway Research Board, Vol. 35,

p. 393. 1956.

Salas Jimenez, Jose A. and Trollope, D. Hugh. Discus-
sion on the Engineering Behavior of Compacted
Clay, Journal of the Soil Mechanics and Founda-
tions Division, Proceedings ASCE, Vol. 85, no.
SMl, part 1, February, 1959.

42

12. Trollope, D. Hugh. Discussion on the Engineering
Behavior of Compacted Clay, Journal of the Soil
Mechanics and Foundations Division, Proceedings
ASCE, V01. 85, SMl, part 1, February 1959.

13. Trollope, D. Hugh. Discussion on the Structure of
Compacted Clay, Journal of the Soil Mechanics
and Foundations Division, Proceedings ASCE,
Vol. 85, SMl, part 1, February 1959.

14. Wu, T. H. Geotechnical Properties of Glacial Lake
Clays, Journal of the Soil Mechanics and
Foundations Division, Proceedings ASCE, Vol. 85,
SM3, part 1, August 1958.

 

umIIIMIMI”:wumwullluIrwin“I

206