A SIMPLIFIED METHOD FOR IDENTIFYING THE

PREDOMINANT CLAY MINERAL IN SOIL

by

Eugene C. Mojekwu, B.S. in C.E.

A THESIS

IN

CIVIL ENGINEERING

Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirement for the Degree of

MASTER OF SCIENCE

IN

CIVIL ENGINEERING

Approved

Accepted

December, 1979

ACKNOWLEDGMENTS

I am deeply indebted to Dr. Warren K. Wray for his guidance

and counseling during this research. I am also grateful to Dr.

C.V.G. Vallabhan for his advice and useful criticisms.

Grateful acknowledgment is also made to the Civil Engineer-

ing Department of Texas Tech University for providing me with

financial support during this research.

Sincere appreciation is also extended to the following soil

sample contributors, viz, McClelland Engineering, Houston, Texas;

Southwestern Laboratories, Beaumont and Arlington, Texas; Amarillo

Testing Laboratory, Amarillo, Texas; East Texas Testing Laboratory,

Inc, San Antonio, Texas; Spencer J. Buchanan and Associates, Bryan,

Texas; Trinity Engineering and Testing Corporation, Austin, Texas;

and Rone Engineering, Arlington, Texas.

n

TABLE OF CONTENTS

Paae

ACKNOWLEDGMENTS ii

ABSTRACT...' V

LIST OF TABLES vi

LIST OF FIGURES vii

I. INTRODUCTION 1

1.1 The Problem 1 1.2 Purpose and Scope of Thesis 1 1.3 Review of Literature 2

1.3.1 Expansive Soils 2 1.3.2 Available Clay Mineral

Identification Methods 5 1.3.3 Atterberg Limits 6

1.4 Definition of Terms 10

II. MATERIALS AND TEST METHODS 13

2.1 Materials 13 2.2 Test Methods • 13

2.2.1 Cation Exchange Capacity 15 2.2.2 Atterberg Limits 15 2.2.3 Hydrometer Analysis 16

íll. RESULTS AND DISCUSSION 17

3.1 Test Results and Discussion on Cati on Exchange Capaci ty 17

3.2 Test Results and Discussion on Atterberg Limits 19

3.3 Correlation of Data 21

3.3.1 Analysis of Test Data 22 3.3.2 Discussion on Correlation of Data 24 3.3.3 Integrity of Correlation Equation 24 3.3.4 Summary 29

IV. CONCLUSIONS AND RECOMMENDATION 30

LIST OF REFERENCES 31

APPENDIX A: COUNTIES, GEOLOGY, AND CLIMATE OF THE CITIES AND THE DEPTHS FROM WHICH SOIL SAMPLES WERE OBTAINED 34

m

Page

APPENDIX B:

APPENDIX C

APPENDIX D

APPENDIX E

SIMPLIFIED PROCEDURE FOR DETERMINING CATION EXCHANGE CAPACITY USING A SPECTROPHOTOMETER (AFTER PEECH (10))

DETERMINATION OF ATTERBERG LIMITS

HYDROMETER ANALYSIS TEST PROCEDURE

43

46

52

TEST DATA FOR CATION EXCHANGE CAPACITY (CEC), ATTERBERG LIMITS (PLASTIC LIMIT (PL) AND LIQUID LIMIT (LL)), AND PLASTICITY INDEX 56

APPENDIX F: SUBROUTINE "INPUT" 59

APPENDIX G: PROCEDURE FOR REMOVING ORGANIC MATTER FROM SOIL 61

IV

ABSTRACT

Increased construction activity in sites that contain wery active

clay minerals has greatly expanded the necessity for engineering know-

ledge related to the type and amount of clay minerals in a given soil.

Presently, there are varying methods of predominant clay mineral iden-

tification. These methods are, however, frequently time consuming and

laborious and require expensive equipment that is not commonly found

in the ordinary commercial soils testing laboratories.

Pearring in 1968 and, later, Holt in 1970 developed a correlation

chart to aid in the identification of the predominant clay mineral in

a given soil. The two parameters involved are Cation Exchange Acti-

vity and Activity Ratio. These two parameters require the plasticity

index, the cation exchange capacity, and the percent of clay in the

soil fraction passing the No. 200 sieve. Presently, cation exchange

capacity determination is not devoid of expense and time problems.

These problems prompted this research which is intended to relate

the cation exchange capacity of a clay soil to the easily obtainable

Atterberg limits (plastic limit and liquid limit) and plasticity in-

dex.

A detailed study was made of selected soils of varying geographic

locations and geologic origins to establish data related to the chem-

ical (cation exchange capacities) and engineering index properties

of such materials. A study of the test results discloses that it is

possible to predict the cation exchange capacity of a soil and, hence,

the predominant clay mineral in the soil, using the plastic limit.

The result of the correlation study shows a strong relation to

exist between the cation exchange capacity and the plastic limit of

all soils tested. This relation may be approximated by the expres-

sion CEC = PL^*^^.

LIST OF TABLES

Page

1. Reproducibility of Cation Exchange as Determined by the Peech Method Using the "Spectronic - 20" 18

2. Comparison of Methods of Determining

Cation Exchange Capacity 18

3. Results of Regression Analysis 23

4. Comparison Betv/een Logarithmic Equations With and Without Intercepts 26

5. Comparison of Clay Mineral Identification Procedures 28

VI

LIST OF FIGURES

Pa^e

1. Correlation of Cation Exchange Activity, Activity Ratio, and Clay Minerals of Montmorillonitic and Latertic Soils (After Pearring and Holt) 7

2. Relationship Between Plasticity Index

and Clay Fraction (After Skempton (23)) 9

3. Location of Soil Samples Tested 14

4. Correlation Between Cation Exchange Capacity and Plastic Limit of Fifty-Five Soil Samples 25

v n

CHAPTER 1.

INTRODUCTION

Many methods are presently available that can be used to assess

the potential volume change characteristics of a soil. However, it

is frequently desirable to know the predominant clay mineralogy of

the soil in order to better assess its potential for shrink-swell

activity. Simple classification tests can only imply the soil acti-

vity whereas more sophisticated X-ray diffraction, infrared analysis,

and other tests are expensive and can require lengthy testing periods

This paper will present the results of a substantial testing program

that correlates such soil properties as Atterberg limits, cation ex-

change capacity, clay content, and activity into a simplified means

of identifying the predominant clay minerals of montmorillonite, ill-

ite, kaolinite, halloysite, and attapulgite without performing any

tests more sophisticated than the standard Atterberg limits and hydro-

meter analyses.

1.1 The Problem

The geotechnical engineer has frequently been faced with the

problem of identifying the predominant mineral in an active clay.

The basic solution to this problem has been based on experience and,

mostly, on the techniques available to him as well as the clay min-

eralogist and the soil physicist. The techniques commonly used in-

clude X-ray diffraction analysis, chemical analysis, electron micro-

scope resolution, differential thermal analysis, gravimetrical analy-

sis, and infrared analysis. These available methods are frequently

laborious, expensive, lengthy and require expensive,intricate equip-

ment that is, in general, too sophisticated and expensive to be

found in the ordinary commercial soils testing laboratory.

1.2 Purpose and Scope of Thesis

The purpose of this study is to find a simplified method of

identifying the predominant clay mineral in a soil. The correla-

tion chart developed by Pearring (9) and Holt (3) offered a simple

1

way of doing this except thatcation exchange capacity (CEC) is one

of the required parameters. Since the CEC is not typically evalua-

ted in normal practice, a simplified way to evaluate CEC was needed

without using the expensive equipment normally required to do so.

The Atterberg limits are easily obtainable and usually performed

and, hence, the objective of this study was to investigate the possi-

bility of a relation between CEC and Atterberg limits as a way to

avoid using the conventional tedious means of cation exchange capa-

city determination.

When the final relationship between CEC and Atterberg limits

was determined, a check of the overall method was made. The approach

was to arbitrarily identify some samples using the above method in

conjunction with Pearring-Molt correlation chart and then compare the

results to clay mineral identifications, on the same samples accom-

plished by X-ray diffraction analysis.

1.3 Review of Literature

The review of literature pertaining to this study v/as made

and is presented under the three headings: (1) Expansive Soils,

(2) Atterberg Limits, and (3) Available Methods for Clay Mineral

Identification.

1.3.1 Expansive Soils

The expansive soil problem has long instigated a lot of inves-

tigations which began as early as 1931 (3). Terzaghi (13) was the

first to look into the problem of expansive soils. In his work,

he concluded that swell is directly related to the electrical charge

on the clay mineral and the surface tension of the water it contains.

Since Terzaghi (13), other important contributions have been

made in the area of swelling soils and researchers (3, 13, 14, 22,

51) generally tend to agree that soil expansion is related to the

type and amount of clay mineral, the hydration rate of the adsorbed

ions, the amount of exhangeable cations the negatively charged min-

eral is capable of adsorbing (cation exchange capacity), and the a-

nount and composition of the pore water.

3

1.3.1-A The Effect of Clay Minerals on Expansion: Clay

minerals are the primary cause of soil volume changes (swelling and

shrinking). It has been reported that clay minerals are commonly

crystalline and contain chiefly silicon, aluminum, oxygen and water (12).

According to the combinations in which these constituents occur,

most of the minerals can be divided into three major groups: smec-

tite (montmorillonites being the most abundant), illite, and kaoli-

nite. Terzaghi and Peck (12) reported that these minerals have the

same laminated crystalline structure but wery different surface ac-

tivities. They also reported that kaolinites are the least active,

followed by illites. Smectites, they reported, are the most active

and have the capacity to swell by taking water molecules directly

into their space lattice. This type of swelling is referred to as

intramicellar swelling. The other type of swelling, intermicellar

swelling, occurs between clay minerals and is exhibited by all clay

minerals.

1.3.1-B The Effect of lons on Expansion: Terzaghi and

Peck (12) reported that the surface of ewery soil particle carries

a negative electric charge. These negative charges, they reported,

attract the positive ions (or cations) in the adsorption complex.

These cations have been found to have appreciable effect on the

expansive character of clay. It is reported, by Holt (3), that

cations have varying hydration rates. In his work, Baver (14)

concluded that ions with the least ionic radii have the greatest

hydration rates and, thus, cause the greatest swell.

1.3.1-C The Relationship Between CEC and Expansion:

As Terzaghi and Peck reported, the surface of every soil particle

carries a negative electric charge. The intensity of the charge

depends largely on the mineral. Minerals are said to have high or

low surface activity, depending on the intensity of the charge.

The negatively-charged soil particle attracts cations which

have migrated from the surrounding liquid into the adsorbed layer

(water located within the charge's influence). These attracted

cations can be replaced by other cations that may migrate to the ad-

sorption complex (13).

The sequence of the replacing power of the common cations has not

yet been resolved. Way (15) concluded that the sequence of the repla-

cing power of the common cations was: sodium (Na), potassium (K),

calcium (Ca), magnesium (Mg), and ammonium (NH4). This means, for

instance, that ammonium will more easily replace calcium than

calcium will replace ammonium. However, as the study in cation re-

placeability was expanded, it became obvious that there was no univer-

sal replaceability series. The series varied depending on the experi-

mental conditions, on the cations involved.and on the type of clay

material (15).

The ease with which a cation replaces another depends on a number

of factors. As Grim (15) reported, the ability of a cation to replace

another increases as the concentration of the replacing cation is in-

creased. He also said that the nature of the valence of the cations

influence replaceability in that, all other things being equal, cations

with higher valences have greater replacing power and are more diffi-

cult to displace when already on the clay. For cations with the same

valence, he reported, replacing power depends on hydrated size; the

smaller the hydrated size of the ion, the greater the replacing power.

Grim also noted that replaceability depends on the nature of the anion

in the replacing solution. For instance, replaceability of sodium

cation from montmorillonite by calcium cation varies depending on

whether calcium sulphate or calcium hydroxide is used [sulfate (S0-~)

and hydroxide (0H~) are the anions involved].

The process of cations replacing other cations on the surface

of an active material, for example clay, is known as base exchange.

The amount of cations that the surface of the soil is capable of ad-

sorbing and exchanging is known as the cation exchange capacity, mea-

sured in milliequivalents (meq) per lOOg of sdil. A wery active surface

adsorbs more exchangeable cations. A high cation exchange capacity

value thus indicates a high surface activity and, thus, a high swell

potential. Grim (15) reported that montmorillonite, the most active

clay mineral, has CEC values in the range of 80-150 milliequivalents

per lOOg. The second most active, illite, has values ranging from

10 to 40 meq per lOOg and the least active, kaolinite, has a range of

3 to 15 meq per lOOg. These values, however, are for pure minerals

which are seldom found in nature.

1.3.1-D The Effect of Pore Water on Expansion: Water is a

known prerequisite for swelling. Yong and Warkentin (22) reported

that increases in the salt content of the pore water reduces swelling,

especially when monovalent ions prevail in the pore water. According

to Holt (3), water sorption follows the process of osmosis. If the

concentration in the pore water of the soil matrix is less than

that of the surrounding pore water sorption takes place, followed

by swelling. Adding salt to the surrounding pore water reduces its

concentration and, hence, swelling.

1.3.2 Available Clay Mineral Identification Methods

Many methods are presently available for identifying clay min-

erals in a soil in order to better assess its potential for shrink-

swell activity. The methods commonly used include X-ray diffraction,

chemical analysis, electron microscope resolution, differential ther-

mal analysis, gravimetrical analysis, and infrared analysis.

The available methods are frequently laborious and time consum-

ing and require expensive and intricate equipment that is, in general,

too sophisticated and expensive to be found in the ordinary commercial

soils testing laboratory.

In 1968, Pearring devised two parameters to aid in empirically iden-

tifying the predominant clay mineral in lateritic soils. The first para-

meter he called Cation Exchange Activity (CEAc) and defined as the ratio

of the cation exchange capacity to the percent clay content. The second

parameter he established was termed "Activity Ratio" and defined as the

ratio of the plasticity index to percent clay. This parameter is a mod-

ified "Skempton's Activity Ratio." Skempton (23) defined his activity

ratio as the ratio of the plast city index to the percent clay fraction.

Percent clay fraction as used by Skempton is the percentage by weight of

the whole sample that is less than 2vi. Pearring recognized the fact that

particles coarser than 2y impart some degree of plasticity to the soil and

defined percent clay content as the percent less than 2y of the soil

material passing the No. 200 sieve.

With the above two parameters, a correlation chart was devel-

oped to aid in identifying the common clay minerals of montmorillo-

nite (smectite), illite, kaolinite, halloysite, and attapulgite

(Figure 1). The horizontal and vertical lines of the several clay

mineral zones show the approximate ranges for the cation exchange

activities and activity ratios of the minerals making up the zone.

Pearring showed that this chart is applicable to lateritic soils

as depicted by the regression curve, A of Figure 1. In 1979, Holt

(3) further extended the correlation chart to include the montmoril-

lonite mineral group as shown by line B of Figure 1.

The parameter, cation exchange activity, is dependent on the

cation exchange capacity as well as the percent clay content. The

cation exchange capacity is an expensive and lengthy parameter to

obtain, and a quick and inexpensive way of doing this is needed to

help simplify the Pearring-Holt method even further.

1.3.3 Atterberq Limits

In 1911 Atterberg (16) proposed four different soil consis-

tencies for agricultural purposes. The consistencies proposed were

sticky, plastic, soft, and harsh. Casagrande (17) in 1932 modified

these consistencies for engineering purposes. He said that soil can

be divided into four states of consistency, namely, solid, semi-

solid, plastic and liquid. The boundary between the solid and semi-

solid state is the shrinkage limit. The boundary between the semi-

solid state and the plastic state is the plastic limit and the

boundary between the plastic state and the liquid state is the

liquid limit.

Atterberg's work was primarily concerned with the plasticity

of soil. He noted that the plasticity of soil was directly affected

by the presence of organic matter. Since Atterberg, researchers have

found that soil plasticity not only depended on the presence of or-

ganic matter, but also on the size, quantity, and type of predominant

clay mineral, water content, and the type of exchangeable cations

(3, 14, 23).

o < Ul o

o < Ul «9 < X u X UJ

< o

2.0

1.5

1.0

1.8

0.6

0.4

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IN

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ACTIVITY (Ac)

1.5 3.0

FIGURE 1 CORRELATION OF CATION EXCHANGE ACTIVITY, ACTIVITY RATIO, AND CLAY MINERALS OF MONTMORILLONITIC AND LATERITIC SOILS (AFTER PEARRIN6 (9) AND H0LT(3))

8

Holt (3), reported that while coarse-grained particles have no

plastic properties, flat-surfaced particles have a high degree of

plasticity and spherical grains exhibit a limited amount of plasti-

city. Hareens, et al., (3), concluded in their work that particle

size less than l.Oy (O.OOlmm) have pronounced effects on the liquid

and plastic limits which, in turn, highly influence plasticity.

The amount of clay particles have also been reported to in-.

fluence plasticity. Skempton's (23) work clearly depicts this

phenomenon. He found that the plasticity index increases as the

percentage clay fraction increases. In his work, Baver (14), also

concluded that plasticity increases as the percentage of clay frac-

tion increases and mathemetically expressed plasticity as a function

of the amount of clay thus:

Plasticity Index = 0.6 x (% clay) - 12 (1.1)

The rate at which plasticity increases, as percent of clay

increases, is dependent on the activity of the soil. Activity,

as defined by Skempton (23) is the ratio of the plasticity index

to the percentage by weight of the whole sample finer than 2y. As

is evident from Figure il, one can reasonably expect an active soil

to exhibit a higher plasticity than a soil that is relatively less

active. In support of Skempton's work, it has been reported (3)

that soils containing montmorillonite, the most active mineral,

exhibit higher plasticity than soils containing the same percen-

tage of kaolinite and illite.

As regards to the effect of ions on plasticity, Holt (3) re-

ported that soils saturated with univalent ions, generally, have

more plasticity than soils saturated with divalent ions.

The Atterberg limits, since their time of introduction, have

gained widespread acceptance as necessary parameters for engineering

knowledge related to soil properties. The procedures as originally

outlined by Atterberg have been greatly refined and specified in

sufficient detail so that persons anywhere can do the tests with

relative ease and in exactly the same manner. Some of the apparatus

100

UJ o fr UJ QL

x* UJ o

I -co <

80

60

40

20 -

\ 1 r (CLAY ACTIVITIES IN BRACKETS)

SHELLHAVEN (1.33)

LONDON CLAY (0.95)

WEALD CLAY (0.63)

HORTEN (0.42)

J-20 40 60 80

CLAY FRACTI0N«2Mm), PERCENT

100

FIGURE 2. RELATIONSHIP BETWEEN PLASTICITY INDEX AND CLAY FRACTION (AFTER SKEMPTON (23))

10

and procedures specified by the American Society of Testing and Mater-

ials (ASTM) have been found (24, 25, 26) to not be entirely satisfac-

tory because of excessive dependence on operator skill and judgment.

Extensive research by Ballard and Weeks (24) led to their conclusion

that plastic limit results reported on a single sample varied more be-

tween operators than results reported by a single operator. Thus, a

single operator has consistently reproducible results. Dawson (26) re-

searched and reported that liquid limits performed in accordance with

the ASTM method D423-59 varied considerably between laboratories and

in a particular case ranged from 58 to 71 percent. The results are,

however, reproducible within each laboratory. The works of Dawson,

Ballard and Weeks show that the plastic limit is more reproducible

between operators than the liquid limit, and, hence, the plastic

limit is a more dependable consistency parameter. Suggestions have

been made by researchers (24, 25, 26, 27, 28, 29) for changes of

techniques presently used for determining Atterberg limits, but as ,

of now the ASTM methods are still standard.

1.4 Definition of Terms

The aim of this section is to prevent unnecessary expansion

of the text and to eliminate confusion in the use of scientific •

terms.

The definitions that follow are as found in literature and

are those considered to be most acceptable and offer a source of

ready reference for the reader.

Absorption: The taking up of water by clay particles through capillary suction (3).

Activity Ratio (Ac): The ratio of the plasticity index to the percentage clay content (23). In this manuscript the percentage clay content is defined as the per-centage less than 2y of the soil material passing the U.S. No. 200 sieve (9).

n Adsorbed Layer:

Adsorption:

Adsorption Complex;

Cation Exchange:

Cation Exchange Activity (CEAc):

Caton Exchange Capacity (CEC):

Clay:

Clay Minerals:

Exchangeable Cation

Water located within the zone of influence created by the negative charge on a soil particle.

The adhesion of water molecules on the surface of clay minerals by the process of chemical bonding (3).

The adsorption complex is constituted by the attracted cations that enter the adsorbed layer.

The interchange between a cation in solution and another cation on a surface active material (3).

The ratio of the cation exchange capacity to the percentage clay content (9). Percent clay content is as defined in activity ratio.

The total amount of exchangeable cations that a soil is capable of adsorbing, measured in milliequiva-lents per 100 grams of soil.

The soil particles smaller than 2y which arederived from the chemical decomposition of rock. It consists, chiefly, of clay minerals but small amounts of quartz, feldspar, organic matter, soluble salts and amorphous materials are also present.

The extremely small crystalline hy-drous aluminum silicates found in clay material. Clay minerals com-prise a small family of minerals of which the most abundant are kaolinite, halloysite, illite, chlorite, vermi-culite,and smectite (the most abundant of this group is montmorillonite (9).

A cation that is capable of being exchanged with another cation in an adsorption complex.

12

Liquid Limit (LL): The water content, expressed as a percentage of the weight of the dry soil, at the boundary between the liquid and plastic states. The water content at this boundary is defined as the water content at which a groove, Imm wide, cut in the soil sample with a standard gooving tool, closes for a length of 1/2-inch when a brass dish containing the soil is dropped 25 times, at the rate of 2 drops per second, through a distance of 1 cm on a standard hard rubber base.

Plastic Limit (PL) The water content, expressed as a percentage of the dry weight of the soil at which the soil becomes crumbly and ceases to be plastic. The water content is defined as the water content at which the soil just begins to break apart and crumble when rolled, by hand, into threads one-eighth of an inch in diameter.

Plasticity Index (PI):

X-Ray Diffrac-tion Analysis

The difference between the greater moisture content of the liquid limit and the less moisture content of the plastic limit. It is de-fined as the range in water con-tents through which the soil remains in the plastic state.

A technique used to identify clay minerals. It can be applied to clay mineral identification through the application of Bragg's Law (37) which states that:

where.

nx = 2dsinø

n = order of relection

X = wave length of X-ray beam

d = distance between two like planes

e = angle of diffraction.

The distance, d, can be calculated and used to identify the predominant clay mineral when the wave length, X, and the angle of diffraction, e, are known

CHAPTER 2.

rWERIALS AND TEST METHODS

2.1 Materials

The undisturbed soil samples, taken from depths of 1 to 11 feet,

were obtained from practicing geotechnical engineering firms and tes-

ting laboratories located in a number of Texas cities. The cities

include: Abilene, Amarillo, Arlington, Austin, Bartlett, Beaumont,

Bryan, Corpus Christi, Corsicana, Crowel, Dallas, Deer Park, Groves,

Hemphill, Houston, Irving, Jefferson, Lewisville, Longview, Lubbock,

Lufkin, Marshall, Nacogdoches, Nederland, New Braunfels, Orange, Pecos,

Port Arthur, San Antonio, Sugarland, Tyler, Universal City, Waco,

White House, and Winnie (see Figure 3).

The cities were selected to provide a wide variation in geologic

origin as well as climate to prevent local prejudice (see Appendix A).

A total of fifty-five samples, enough to ensure reliable correlation

between the parameters to be obtained, were tested.

2.2 Test Methods

All laboratory testing of soils were performed on the campus of

Texas Tech University located at Lubbock, Texas. The Geotechnical

Engineering Laboratories of the Civil Engineering Department were

utilized for the chemical tests (cation exchange capacities) and the

consistency tests (Atterberg limits). The laboratory personnel of

the Plant and Soil Sciences Department performed flame photometer

analyses on six random samples to determine the cation exchange ca-

pacities of each material using the Coleman Model 21 Flame Photo-

meter. The Geology Department performed X-ray diffraction analyses

on three of the six random samples to determine the predominant clay

minerals in each material.

The writer, with the assistance of laboratory personnel in the

Geotechnical Engineering Laboratories, performed all chemical tests

to obtain data related to such tests and to familiarize himself with

test procedures and equipment.

13

14

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15

The consistency tests and the hydrometer analyses were performed

by the Geotechnical Engineering Laboratory personnel.

2.2.1 Cation Exchange Capacity

Cation exchange capacity is a measure of the amount of exchange-

able cations an active surface is capable of adsorbing and depends,

primarily, on the activity of the predominant clay mineral. A wery

active clay has a high cation exchange capacity and a relatively

lesser active clay has a lower cation exchange capacity (3).

The cation exchange capacity was determined on the soil fraction

passing the U.S. No. 40 sieve. The testing program was accomplished

using the Bausch and Lomb "Spectronic - 20" spectrophotometer by the

procedure of Peech (10) (see Appendix B). In general, the Peech

method determines the amount of ammonium cations that can be replaced

by magnesium cations on the soil surface. Although Way's (15) re-

placeability series asserts that ammonium cations more easily replaces

magnesium cations, the concentration of magnesium cations added was

such that the ammonium cations were "crowded-off," thus, assuring

easy replaceability by the magnesium cations.

2.2.2 Atterberg Limits

The Atterberg l im i t s (p las t ic l i m i t and l i qu i d l i m i t ) were deter-

mined on a l l f i f t y - f i v e samples with d i s t i l l e d water as the wett ing

agent.

In accordance with ASTM procedure D423-66, the liquid limits were

determined on the soil fraction passing the U.S. No. 40 sieve. The

liquid limit tests were run on samples that had been tempered in a

moisture room of 72-76°F temperature and humidity of 97% for approxi-

mately 24 hours. In general, this method involves finding the mois-

ture content at which a groove cut in the wet sample with a standard

grooving tool closes when a brass dish containing the sample is drop-

ped 25 times, at the rate of 2 drops per second, through a distance

of lcm on a hard rubber base (see Appendix C).

In accordance with ASTM D424-59 procedure, the plastic limits

were determined on the soil fraction passing the U.S. No. 40 sieve.

In general, this method involves finding the moisture content at

which the wet soil just begins to crumble or break apart when rolled

by hand, into threads one-eighth of an inch in diameter (see Appen-

dix C).

2.2.3 Hydrometer Analysis

Hydrometer analysis is used for grain-size distribution of soils

where appreciable quantities of the soil pass the U.S. No. 200 sieve.

This test procedure was that given by ASTM D422-63. This method uti-

lizes the relationship between the velocity of fall of a sphere in

a fluid, the diameter of the sphere, the unit weights of the sphere

and of the fluid, and the viscosity of the fluid to classify the

woil particles under different diameter catagories (see Appendix D

for detailed procedure.)

16

CHAPTER 3.

RESULTS AND DISCUSSION

3-1 Test Results and Discussion on Cation Exchanqe Capacity

The values for the cation exchange capacities of all soils tested

are reported in Appendix E. The values ranged from a low of 16.23 meq/

lOOg to a high of 72.8 meq/lOOg.

The cation exchange capacities of the soils tested reflect the

type of predominant clay minerals present.

The testing program was accomplished by the procedure of Peech

(10) using the Bausch and Lomb "Spectronic - 20" spectrophotometer.

The "Spectronic - 20" is susceptible to certain errors, the most com-

mon of which are: (a) wrongly positioning the test tube in the "Spec-

tronic - 20," (b) using even a drop more of any reagent than required,

and (c) parallax in reading the transparency scale.

To insure that the aforementioned errors were kept to a minimum,

the cation exchange capacities of five random samples were repeated.

Table 1 shows a comparison between the initial tests and the repeated

tests. The values compare favorably and depict a minimal human factor

in the values of the cation exchange capacities obtained.

The Peech method, if followed carefully, compares very well with

other methods for cation exchange capacity determination. To check

the integrity of the Peech method, the cation exchange capacities of

six samples were independently determined by the Plant and Soil Sci-

ences Department using the flame photometer method. Table 2 compares

the results obtained by the flame photometer to the results obtained

by the Peech method. The values compare favorably, showing that the

Peech method is sufficiently accurate for determining cation exchange

capacity.

The correlation chart of Pearring and Holt are based on cation

exchange capacities of soil samples free of organic material. In

general, the organic material occurs in clay minerals as discrete

particles of wood, leaf matter, spores, etc.,; it may also be pre-

sent as organic molecules adsorbed on the surface of the clay mineral

particles (15). The discrete organic particles may be present in any

17

18

TABLE 1. REPRODUCIBILITY OF CATION EXCHANGE AS DETERMINED BY THE PEECH METHOD USING THE "SPECTRONIC - 20".

Soil

Sample

13 - 04

72 - 06

82 - 08

83 - 08

86 - 08

Cati on Exchange Capaci

Test 1

50.9

71.2

14.6

60.0

50.0

ty (meg/lOOg)

Test 2

52.4

72.8

16.9

58.4

50.0

TABLE 2. COMPARISON OF METHODS OF DETERMINING CATION EXCHANGE CAPACITY

Soil

Sample

01 - 01

31 - 02

53 - 05

72 - 06

73 - 06

86 - 08

Ca-

Fl

tion

ame

Exchar ige Capa Photometer

21.1

28.2

14.7

71.4

21.6

45.0

city imeq/lUUgm, Spectronic •

20.2

26.2

7.0

72.8

18.9

50.0

;

- 20^

^Bausch and Lomb "Spectronic - 20" Spectrophotometer.

size from large chunks easily visible to the naked eye to particles

of colloidal size (15). Although it may be possible for a mineral-

organic complex to have a higher CEC than for the mineral by itself,

a number of investigators have reported that the presence of organic

compounds in any quantity have a reductive effect on the value of

the CEC (31, 32, 33, 34). One explanation given for this is that

the organic molecules react with the negative charge sites or phy-

sically cover the sites, thus hindering the number of exchange

locations (31). Whatever the effect on CEC, reductive or elevative,

organic matter should be removed from the soil sample prior to tes-

ting if it appears to an appreciable extent. Detection of organic

matter is usually accomplished by vision or smell or by a compari-

son between the Atterberg limits of the undisturbed sample and those

of the air-dried sample in which case a large demacation between the

values suggests the presence of organic matter. A simple procedure

for removing organic matter is presented in Appendix G. The samples

used in this study, as determined by visual and odor observations,

were devoid of much organic matter and tests were run on the virgin

samples.

3.2 Test Results and Discussion on Atterberg Limits

The data for the Atterberg limits (plastic limit and liquid

limit) and plasticity indices of all samples tested are presented

in Appendix E. The liquid limits ranged from a low of 22.0% to

a high of 82.4%. The plastic limits ranged from 13.97% to 32.52%

The plasticity indices ranged from 7.7% to 51.5%.

Since the Atterberg limits (plastic and liquid limits) are de-

pendent on the type and amount of clay in a soil, they are extremely

helpful parameters in recognition of the nature of the clay fraction

of a soil (20). Casagrande (20) showed that each blow required to

close the standard groove is equivalent to 1 gm/cm^ of shear strength.

Seed, et al. (20) reported that the liquid limit of a soil is equiva-

lent to the shear strength of the clay-water mixture. This means

that the sand-water mixture does not contribute to the liquid limit

and, hence, the liquid limit is influenced, primarily, by the clay

fraction in the soil.

19

20 The plastic limit, like the liquid limit, is primarily deter-

mined by the clay fraction in the soil. When rolled to a thread,

the soil thread will crack through the clay component and the plas-

tic limit will essentially be determined by the characteristics of

the clay fraction (20).

The ASTM D424-59 procedure for determining plastic limit re-

quires a lot of operator judgment as to the diameter of the soil

thread. The difference in results vary more between operators than

with a single operator (24). This fact was acknowledged in this

study by limiting the number of operators to one and to further

limiting possible errors, a one-eighth inch rod was readily avail-

able to the operator for comparison with the soil thread diameter.

The conventional ASTM D423-66 method for liquid limit deter-

mination is besieged with many errors. Grooving tool motion,

tempering of sample, drying history of sample and different appara-

tus and operators, among other factors, influence the liquid limit

values (27, 28, 26, 31).

Grooving tool motion substantially affects the value of liquid

limit. However, there is no statement in the literature as to

which direction of tool motion is to be preferred (towards or away

from operator). For all samples tested for liquid limit in this

study, grooving tool motion was toward the operator to insure con-

sistency.

Tempering alters the liquid limit considerably; that is, a

soil thoroughly mixed with water and allowed to temper for a period

of time will have a different liquid limit than a soil tested immedi-

ately after mixing (26). Although the ASTM D423-66 procedure does

not address tempering, the samples used in this investigation were

tempered for 24 hours in a moisture room of 72-76°F temperature and

a relative humidity of 97%. The reason for this was to insure proper

mixture of soil and water so as to prevent dry friction between sample

and brass dish and to prevent "tearing" of sample during the testing

process.

Moum and Rosenquist (21) have shown the effect of drying condi-

tions on liquid limits. They reported that while the liquid limit

of a natural clay was 62.5%, the liquid limit of the same clay, 21

stored for 14 days at 60°C in the absence of air, was 61% and the

liquid limit was 73.3% v/hen the clay was stored for 14 days at

20°C in the presence of air. It is, thus, evident that the drying

history of a soil prior to testing can influence the liquid limit

value. The ASTM method D423-66 calls for the liquid limit test to

be conducted on samples that had been previously air-dried so all

tests in this investigation were performed on samples with a com-

mon drying history. Drying samples in air or any other condition,

however, does not assure common drying history since soils react

differently to similar drying conditions. If the procedure of

air-drying samples introduced any errors in the liquid limits ob-

tained in this investigation, they were unavoidable in maintaining

test procedure consistency.

Errors due to the standard apparatus arise as a result of the

resiliency of the base, height of blow adjustment and position of

device on table. If the resiliency of the standard base introduced

any errors, they were unavoidable in complying with the ASTM speci-

fications. Height of blow adjustment probably did not contribute

any errors since the apparatus was properly calibrated prior to

each test.

3.3 Correlation of Data

A method to determine the predominant clay mineral which re-

quires only the amount of clay fraction, the plasticity index (PI)

and the cation exchange capacity (CEC) was developed by Pearring

(9) and extended by Holt (3). The method requires two simple tests

that are commonly performed by most testing laboratories to deter-

mine the amount of clay fraction and the PI. The test for the

third parameter, the CEC, is difficult to perform and is not typi-

cally accomplished by the ordinary practitioner. Finding a rela-

tionship between one or all of the Atterberg limits and the CEC

would assist the engineer even more since it would eliminate the

need for the CEC test.

The purpose of this section is to present a study of the corre-

lation between the chemical (CEC) and engineering (Atterberg limits)

22 properties of the soils tested. The parameters involved in the

correlation are: (1) cation exchange capacity, and (2) Atterberg

limits.

3.3.1 Analysis of Test Data

A computerized numerical analysis of the data resulting from

the testing program as herein outlined in this manuscript was made

using the Hocking-LaMotte-Leslie Select Regression Analysis (35, 36)

(see Appendix F for supporting subroutine "input" used). The analy-

sis produces the statistically optimum regressions on subsets of the

independent variables of size 1 to n<80. The result is either a

linear equation of the form:

y = a^ + a . x^ + a^x^ + a . x . (3.1)

or a logarithmic equation of the form

y ^ a ^ x , " ! x^^z x../i-1 x.^- (3.2)

where

y = dependent variable

X = independent variable

a = constant

b = regression coefficient or power.

The logarithmic equation was used in this study to analyze the

gathered data and the form of the resulting equation was that of

Eq. (3.2).

The cation exchange capacity was the dependent variable while the

Atterberg limits (plastic and liquid limits) and the plasticity index

were the independent variables.

The results of the regression analysis is as shown in Table 3.

The dependent and independent variables along with the corresponding

equations and the multiple correlation coefficients are listed. The

23

multiple correlation coefficient, expressed as "R-squared," measures

how well the regression model fits the data. R-squared values near

zero are expected for completely random data, whereas, an R-squared

value of 1.00 would imply all data to be falling on a straight line,

i.e., the best possible fit. R-squared values for the regression

equations as listed in Table 3 indicate the equations provide rela-

tively good fits.

TABLE 3. RESULTS OF REGRESSION ANALYSIS

3.3 CEC^ P L ^ L L S P I ^ CEC - Pl°-'''ll''-'''Pl'-°'' °-''''

3.4 CEC PL.LL CEC = piO-^&\iOA7^ O.9946

3.5 CEC PL.PI CEC = PL°-9°*PI°-245 0.9946

3.6 CEC LL CEC=LL°-512 0.9942

3.7 CEC PL CEC = PL -'' 0.9941

^Cation Exchange Capacity

''Plastic Limit

'^Liquid Limit

''piasticity Index

As is evident from Table 3, there are five possible equations

but, although it has the least R-squared value, Eq. (3.7) is pre-

ferred by the writer due to its simplicity. The differences between

the R-squared value of Eq. (3.7) and the R-squared values of the

other equations are not significant and the fact that the plastic

limit is apparently a more reproducible parameter than the liquid

limit justifies the preference of Eq. (3.7) from a practical stand-

point. The cation exchange capacity (CEC) can thus be estimated

by the "correlation equation:"

CEC = (PL)^-^^ (3.7)

3.3.2 Discussion on Correlation of Data

The most significant aspect of the equations in Table 3 is that

they were forced through the origin. Other models were attempted,

including linear models (with and without intercepts) and logarith-

mic models with intercepts, but the R-squared values obtained from

these efforts were disappointing. Table 4 shows a comparison between

the logarithmic models with and without intercepts. In each of the

five cases compared, the equation forced through the origin has a

better R-squared value, depicting a better fit of the data.

Figure 4 shows a plot of the data points and the line of best

fit,

CEC = (PL)^-"'^ (3.7)

The plastic limits used in the regression analysis ranged from

13.97% to 32.52% and any use of plastic limits outside of this range

for estimating the CEC from Eq. (3.7) should be done with caution.

3.3.3 Integrity of Correlation Equation

To check the applicability of the correlation equation in clay

mineral identification, identification of clay minerals were performed

on three random samples. The first identification procedure was by

X-ray diffraction analysis, independently performed by the Geology

24

100

90

80

70

60

50

25

O o

8 40

E

u hJ U ^ 30

u < u hJ O

U bj 2 0 z o I -< u

± 1 10 20 30

PLASTIC LIMIT (PL), PERCENT 40 50

FIGURE 4 . CORRELATION AND PLASTIC

BETWEEN CATION EXCHANGE CAPACITY LIMIT OF FIFTY-FIVE SOIL SAMPLES

26

TABLE 4. COMPARISON BETWEEN LOGARITHMIC EQUATIONS WITH AND WITHOUT INTERCEPTS

Model Equation R^ Value

Forced Through Origin CEC = PLO-646^^0.353^^0.067 0.9946

With Intercept CEC = 2.47 {pi^'^'^n-^-^^pi^'^^^) o.468

Forced Through Origin CEC = PLO-^^^LL^*^^^ 0.9946

With Intercept CEC = 1.05 [pi^'^\i^'^'^^) o.463

Forced Through Origin CEC = ^^0-904^^0.245 0.9946

With Intercept CEC = 1.49 (pi^''^'^^pi^''^^^) o.466

Forced Through Origin CEC = LL°*^^^ 0.9942

With Intercept CEC = 1.71 (LL°*^^^) 0.430

Forced Through Origin CEC = PL^*^^ 0.9941

With Intercept CEC = 1.15 (PL^*^^^) 0.409

27

Department. The second procedure was to identify the clay minerals

using the CEC values, obtained by the Plant and Soil Sciences Depart-

ment using the flame photometer, in conjunction with the Pearring-

Holt correlation chart. Lastly, identification was accomplished by

using the CEC's obtained from the correlation chart. The purpose

of these efforts was to facilitate comparison between identification

accomplished by the correlation equation and those accomplished by

other more sophisticated and more expensive methods as shown in

Table 5.

For the flame photometer identification procedure, the activity

ratio and the cation exchange activity area as defined by Pearring,

viz:

Activity Ratio: Ac = J - Q Y ^ (^•S)

rcr Cation Exchange Activity: CEAc = o^ ^-^ (3.9)

where

PI = Plasticity Index

CEC = Cation Exchange Capacity (determined by the flame photometer)

and

% CLAY = Percentage less than 2y of the soil material passing the No. 200 sieve.

For the correlation equation identification procedure, the activity

ratio remains as defined by Pearring while the cation exchange acti-

vity is defined by:

(PL)^-''^ Cation Exchange Activity: CEAc - ^ (-.| — (3.10)

28

u I

to

w u "

I I I

Q UJ O O DH O -

U W w

í S I

is S t

<C

UJ

ca: _ j o

o to DH <c o_ s : o o

LO

«a:

l ^

co

u. »— O

csi

co CNJ

.«c IM

té

5 ^

3

00

m

Pi

o m

.— (M tn f -

l O

r

«

O

s s «c

29 where

1.17 (PL) = CEC

and

PL = Plastic Limit.

As is evident from Table 5, the correlation equation method

identifies the same clay mineral as the other, more sophisticated

and more expensive methods. The correlation equation can, thus,

be authoritatively said to be a viable and simplified aid in clay

mineral identification.

3.3.4 Summary

The work of first Pearring and then Holt have shown that the

activity ratio and the cation exchange activity of a soil can be

useful in identifying the predominant clay mineral in the soil.

Their work has been further simplified by this study which shows

that the tedious step of determining cation exchange capacity can

be eased by a relationship between cation exchange capacity and

plastic limit. This relationship, which is limited to plastic

limits in the range of 13.97% to 32.5%, is expressed as:

1.17 CEC = (PL) (3.7)

CHAPTER 4.

CONCLUSIONS AND RECOMMEflDATION

4.1 Conclusions

Three important conclusions may be reached from an investigation

of the data obtained under the testing conditions of this study:

(a) The Peech method using an inexpensive spectrophotometer produces reliable measurements of cation exchange capa-city as evidenced by its comparison to flame photometer results.

(b) A strong relation exists betv;een the cation exchange capa-city and the plastic limit for all soils tested. This re-lationship can be approximated, for soils with plastic limits in the range of 13.97% to 32.5%, by the expression:

CEC = (PL)^-"^^ (3.7)

(c) This expression can be used in conjunction with the Pear-ring and Holt Correlation Chart to easily and quickly identify the predominant clay mineral in a soil.

4.2 Recommendation

It is recommended that additional research be undertaken to

extend the applicability of the correlation equation to soils with

plastic limits outside the range of 13.97% to 32.5% used in this

investigation.

30

LIST OF REFERENCES

!• Chen, F. H., Foundations on Expansive Soils, Elsevier Scientific Publishing Co., New York, NY, 1975, p. 123, pp. 263-270.

2. Franzmhier, D. P., and Ross, S. J., "Soil Swelling: Laboratory Measurement and Relation to Other Soil Properties," Pro-ceedings, Soil Science Society of America, Vol. 32, No. 4., July-August, 1968, pp. 573-577.

3. Holt, J. E., "A Study of the Physio-Chemical, Mineralogical, and Engineering Properties of Fine-Grained Soil in Relation to Their Expansive Characteristics," Dissertation presented to Texas A&M University, College Station, Texas, in 1967 in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy.

4. Jones, D. E., and Holtz, W. G., "Expansive Soils—The Hidden Disaster," Civil Engineering-ASCE, Vol. 43, No. 8, New York, NY, August, 1973, pp. 49-51.

5. Jumikis, A. R., Soil Mechanics, D. Van Nostrand Co., Inc, Prince-ton, New Jersey, 1966, pp. 67-69.

6. Lytton, R. L., "The Characterization of Expansive Soils in Engi-neering," Presented at the December 1977, American Geophy-sical Union Conference, held at San Francisco, CA, pp. 63.

7. McKeen, R. G., "Characterizing Expansive Soils for Design" Pre-sented at the October, 1977, Joint Meeting of the Texas, New Mexico and Mexico Sections of ASCE, Albuquerque, NM, pp. 23.

8. Mitchell, J. K., Fundamentals of Soil Behavior, John Wiley & Sons, Inc, New York, New York, 1976. pp. 169-185.

9. Pearring, J. R., "A Study of the Basic Mineralogical, Physical-Chemical, and Engineering Index Properties of Laterite Soils," Dissertation presented to Texas A&M University at College Station, Texas, 1968, in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy.

10. Peech, M., "Determination of Exchangeable Cations and Exchange Capacity of Soils - Rapid Micromethods Utilizing Certrifuge and Spectro-Photometer," Proceedings, Soil Science Society of America, Vol. 1, 1945, pp. 25-38.

11. Van Der Merwe, D. H., "The Prediction of Heave from the Index and Percentage Clay Fraction of Soils," The Civil Engineer in South Africa, June, 1964, pp. 103-107.

31

32 12. Terzaghi, K., and Peck, R. B., "Soil Mechanics in Engineering

Practice," John Wiley & Sons, Inc, New York, NY, 1948, pp. 10-13.

13. Terzaghi, K., "The Swelling of Two Phse Systems," Colloid Chemistry (J. Alexander), Vol. 3, D. Van Nostrand Co., New York, NY, 1931, pp. 65-88.

14. Baver, L. D., Soil Physics, John Wiley & Sons, Inc, New York, NY,

1956.

15. Grim, R. E., Clay Mineraloqy, McGraw-Hill, 1953, pp. 188-224.

16. Atterberg, A., "Die Plastizitat der Tone," Internationale Mittei-lungen fur Bodenkunde, Vol. 2., 1912, pp. 149-188.

17. Casagrande, A., "Research on the Atterberg Limits of Soils," Public Roads, Vol. 13, No. 8, 1932.

18. Wray, W. K., "Development of a Design Procedure for Residential and Light Commercial Slabs-on-Ground Constructed Over Ex-pansive Soils," Dissertation presented to Texas A&M Univer-sity at College Station, Texas, 1978, in Partial Fulfill-ment for the Degree of Doctor of Philosophy.

19. Bowles, J., "Engineering Properties of Soils and Their Measure-ment," McGraw-Hill Book Company, New York, NY, 1979, pp. 4U51.

20. Seed, H., Woodward, R. J., and Lundgren, R., "Fundamental Aspects of the Atterberg Limits," Proceedings, Soil Mechanics and Foundation Division, ASCE, SM6, November, 1964, pp. 75-104.

21. Moum, J., and Rosenqvist, I., "On the Weathering of Young Marine Clay," Proceedings, Fourth International Conference on Soil Mechanics and Foundation Engineering, London, Vol.l, 1957, pp. 77.

22. Yong, R. N., and Warkentin, B. P., Introduction to Soil Behavior, The MacMillan Company, New York, NY, 1966.

23. Skempton, A. W., "The Colloidal Activity of Clays," Proceedinqs, Third International Conference on Soil Mechanics and Founda-tion Engineering, Vol. 1, Switzerland, 1955, p. 57.

24. Ballard, G. E. H., and Weeks, W. F., "The Human Factor in Deter-mining the Plastic Limit of Cohesive Soils," Materials Re-search and Standards, MTRSA, Vol. 3., No. 9, September, 1963, pp. 726-729.

25. Sowers, G. F., "Introduction," Proceedinqs of the ASTM Symposium on Atterberg Limits, Special Technical Publication (STP), No. 254, pp. 159.

33

26. Dawson, R. F., "Investigations of the Liquid Limit Test on Soils," Proceedings of the ASTM Symposium on Atterberq Limits, Special Technical Publication (STP), No. 254, pp. 199-195.

27. Mitchell, J. E., "Liquid Limit Results from Various Types of Groov-ing Tools," Proceedings of the ASTM Symposium on Atterberg Limits, Special Technical Publication (STP), No. 254, pp7 197-200.

28. Morris, M. D., Ulp, R. B., and Spinna, J. R., "Recommendation for Changes in the Liquid Limit Test," Proceedinqs of the ASTM Symposium on Atterberq Limits, Special Technical Publication (STP), No. 254, pp. 202-211.

29. Nuyens, T. A. E., and Kockaeitz, R. F., "Reliable Techniques for Determining Plastic Limit," Materials Research and Standards, Vol. 7, No. 7, 1967, pp. 295-299.

30. Eden, W. J., "Use of a One-Point Liquid Limit Procedure," Proceed-ings of the ASTM Symposium on Atterberg Limits, Special Tech-nical Publication (STP), No. 254, pp. 168-75.

31. Harter, R. D., "Reaction of Minerals with Organic Compounds in Soil," Chapter 20, Minerals in Soil Environment, Editors Dixon, J. B., and Weed, S. B., Soil Science Society of Ameri-ca, Madison, WI, 1977.

32. Ensminger, L. E., and Gieseking, J. E., "The Adsorption of Proteins by Montmorillonite Surfaces: Ethylene Glycol," Soil Science Society of America, Vol. 51, 1941, pp. 125-132.

33. Kown, B. T., and Ewing, B. B., "Effects of the Counter-Ion Pairs on Clay lon-Exchange Reactions, Soil Science of America, Vol. 108, 1969, pp. 231-240.

34. DeSilva, J. A., and Loth, S. J., "Cation Exchange Reactions, Elec-trokinetic and Viscometric Behavior of Clay-Organic Complexes," Soil Science Society of America, Vol. 97, 1964, pp. 63-76.

35. Hocking, R. R., and Leslie, R. N., "Selection of the Best Subset in Regression Analysis," Technometrics, Vol. 9, 1967, pp. 531-540.

36. LaMotte, L. R., and Hocking, R. R., "Computational Efficiency in the Selection of Regression Variables," Technometrics, Vol. 12, 1970, pp. 83-93.

37. Resnick, R., and Halliday, D.. "Physics," John Wiley & Sons, Inc, New York, NY, 1966, pp. 1140-1143.

APPENDIX A

COUNTIES, GEOLOGY, AND CLIMATE OF THE CITIES AND THE DEPTHS FROM WHICH SOIL SAMPLES WERE OBTAINED

34

35

Sample No.

001-01

003-01

004-01

005-01

008-01

010-01

011-01

012-01

013-01

015-04

017-04

021-04

026-02

028-02

029-02

030-02

033-02

035-02

036-03

038-03

040-03

041-03

042-03

044-03

046-03

047-03

048-03

049-07

050-07

055-05

057-05

058-05

059-05

061-05

Location (City)

Sugarland, TX

Deer Park, TX

Deer Park, TX

Houston, TX

Houston, TX

Houston, TX

Port Arthur, TX

Port Arthur, TX

Amarillo, TX

Amarillo, TX

Amarillo, TX

Amarillo, TX

Port Arthur, TX

Nederland, TX

Winnie, TX

Groves, TX

Beaumont, TX

Nederland, TX

Dallas, TX

Irving, TX

Dallas, TX

Crowell, TX

Crowell, TX

Arlington, TX

Arlington, TX

Amarillo, TX

Amarillo, TX

Bryan, TX

Bryan, TX

Whitehouse, TX

Diboll, TX

Hemphill, TX

Diboll, TX

Jefferson, TX

County(ies)

Fort Bend

Harris

Montgomery

Harris

Harris

Harris

Jefferson

Jefferson

Potter/Randall

Potter/Randall

Potter/Randall

Potter/Randall

Jefferson

Jefferson

Chambers

Jefferson

Jefferson

Jefferson

Dallas

Dallas

Dallas

Foard

Foard

Tarrant

Tarrant

Potter/Randall

Potter/Randall

Brazos

Brazos

Smith

Angelina

Hemphill

Angelina

Jefferson

Depth (feet)

0.5

3.0

9.5

4.5

3.5

11.5

2.5

9.0

2.5

15.0

5.0

10.0

2-4

1-4

7-9

8-10

4-6

6-8

0.5-1.0

3-4

4-5

4-5

6-7

2-3

2-3

1-2

9-10

6-8

1-4

3-5

5-7

1-3

5-7

3-5

36 Sample

No.

062-05

063-05

065-05

068-06

069-06

071-06

072-06

073-06

074-06

075-06

077-06

078-08

080-08

081-08

084-08

085-08

086-08

087-08

Location (City)

Hemphill, TX

Lufkin, TX

Jefferson, TX

San Antonio, TX

San Antonio, TX

San Antonio, TX

San Antonio, TX

San Antonio, TX

New Braunfels, TX

New Braunfels, TX

Universal City,

Waco, TX

Corpus Christi,

Abilene, TX

Abilene, TX

Bartlett, TX

Corpus Christi,

Austin, TX

TX

TX

TX

County(ies)

Hemphill

Angelina

Jefferson

Bexar

Bexar

Bexar

Bexar

Bexar

Comal

Comal

Bexar

McClennan

Nueces

Taylor

Taylor

Williamson

Nueces

Travis

Depth (feet)

5-7

1-3

8-10

7.5-8.5

4-5

7.5-8.5

1-2

7.5-8.5

7.5-8.5

2.5-3.5

10-11

5-6.5

3-5

6.5-8

6-7.5

1.5-3

8-9.5

4-5

Anqelina County

Geology:

Climate:

37

The geological formation from which most of the soils in the Angelina County are derived belong to the Mio-cene period of the Tertiary era.

The greater part of the deposits in the area consist of gray, white, and blue sands. The principal bed underlying these sands, and the one probably forming the greater proportion of the whole group, is a heavy bed of dark-blue clay.

No weather bureau stations are located within the limits of this county, nor are there any stations having records covering a sufficient time to have established normals. The average temperature of 67.0°F and average precipitation of 39 inches for Trinity, which is a country adjacent to Angelina, could well be typical values for Angelina County.

Bexar County

Geology:

Climate;

The soils of Bexar County developed over cherty lime-stone. The soils consist of one or more formations that contain limestone, chalky limestone, chalk, shaly clay, marly clay, sandy clay, calcareous clay, sand, and sandstone.

Rainfall in Bexar County is fairly well distributed throughout the year. Evaporation is high and rain-fall seldom wets below the root zone. This has caused great leaching of calcium carbonate from upper zones of some soils but not from their lower horizons. Con-sequently, many of the soils have a layer in which calcium carbonate has accumulated.

Brazos County

Geology:

Climate:

Brazos County has soils that have a large number of parent materials which include old sediments deposited by floodwaters of the Brazos River, alkaline to weakly calcareous clay, sand clay, water lain unconsolidated loamy sands, acid shaly clay and acid sandy clay loam.

Brazos County has a warm temperature, humid, continen-tal climate. Annual precipitation which averages 30 inches, is relatively uniform throughout the county. Droughts of varying duration and severity occur in summer. They are the result of a high rate of evapor-ation, low humidity, and low water-holding capacity of the soils.

Comal County

Geology;

Climate;

In addition to the alluvial and coalluvial material occurring in the valleys, the rocks which make up the soils in this area are largely of marine sedi-mentary origin.

Mean annual temperature is about 67°F, while mean annual precipitation is about 28 inches.

38

Chambers County

Geology:

Climate;

Old alluvium and marine sediment laid down by ancient streams and the Gulf of Mexico are the main parent materials of most soils in this county. These materials consist primarily of clay and sandy clay mixed with some clay loam, silt and sand.

The climate of Chambers County is humid subtropical and is characterized by warm summers. The proximity of the Gulf of Mexico and the bays results in a pre-dominantly marine climate. Average annual tempera-ture is 77.7°F. Rainfall is abundant, averaging 51.55 inches annually.

Dallas County

Geology:

Climate:

The soils and subsoils of Dallas County are charac-teristically calcareous.

Warm, temperate climate. The summers are long, with rather high temperatures during most of the time. The winters are short and mild. Mean temperature is 64.9°F. Mean annual precipitation is 38.04; this is fairly well distributed throughout the year.

Foard County

Geology: The soils of Foard County developed in residuum de-rived from permian shale, permian sandstone, permian limestone, and permian gypsum; in sandy and clayey outwash, or acient alluvium, and recent alluvium.

Foard is underlain by the geological formation known as the permian red beds. This red bed consists of sediments that, according to geologists, were laid down in an old sea some 200 million years ago.

Climate: Foard County has a subhumid, warm temperate, conti-nental-type climate. The permian rocks have been broken down into residuum, from which soils have formed, by temperature changes and by the action of water. A wetter climate in past geologic ages was responsible for the disposition of the parent mater-ial of all of the soils formed in outwash and allu-vium. Water has leached calcium carbonate from the profile of the sandy soils and moderately coarse textured soils. Also, rainwater has moved clay particles downward in this profile.

Wind, too, is an outstanding factor in the develop-ment of soils in the area. It deposited sand over the pre-existing permian red beds.

Fort Bend County

Geology: Fort Bend County soils are of three geologic for-mations--lissie (range from sands to sandy clays), beaumont (overlies the lissie in areas between streams contains limy clay, sandy clays, clayey sands, and fine sands) and recent (mainly calcar-eous materials deposited by the Brazos River).

Climate: Humid, warm-temperate, continental-type climate.

Harris County

Geology: In Harris County the parent material consists of un-consolidated sediment of holocene, pliestocene, and pliocene age. In general, the soils are sedimentary and consist of material that has been deposited by water. In some areas, terrace or beach deposits of non-calcareous unconsolidated material range from sand to clay. Some of the soils developed from calcareous clayey sediment.

Climate: Humid, warm and moist.

Hemphill County

Geology: Most of the soils of Hemphill County formed on de-posits of the Cenozic era. The thick deposits of the High Plains or Ogallala were deposited in the Tertiary period. The soils are alkaline to calcar-eous, loamy and sandy earths.

Climate: Warm and semi-arid. Soil development has been re-tarded by low rainfall in the county.

39

40

Jefferson Countv

Geology: Old alluvium and marine sediments laid down by ancient streams and the Gulf of Mexico are the chief parent materials of most soils in this country.

The materials consist primarily of clay and sandy clay mixed with some clay loam, silt and sand. They ori-ginated from a multitude of soils, rocks, and unconsol-idated sediments that existed throughout the flood plains of the ancient streams.

Climate: Jefferson County has a mixture of tropical and temper-ate climate.

McClennan County

Geology: The soils of McClennan County are underlain by many parent materials, viz, marine sediments of marl, chalk, or calcareous clay; marine sediments of fri-able marl or chalk; old alluvial sediments of calcar-eous clay; and soils of stream terraces.

Climate: Warm, temperate, humid continental climate. The summers are long, with rather high temperatures much of the time. The winters are short and mild.

Navarro County

Geology: Navarro County soils formed in five kinds of parent materials, namely: (a) clay and marl, (b) limestone caps over clay, (c) clay and shale, (d) sandy clays to clayey sediment, or old alluvium, and (3) recent alluvium.

Climate: Navarro County has a humid, subtropical climate. Rainfall is fairly evenly distributed throughout the year and averages 36.96 inches annually. Summer tem-peratures are hot and winter temperatures are mild. The mild climate has promoted rapid soil development,

Nueces County

Geology: The geologic materials from which the soils of this county formed are Beaumont clay and material of the lissie formation and of the recent epoch. The recent materials are alluvial sediments of streams and eloian sands that were blown from beaches along the Gulf of Mexico.

Climate: The climate in Nueces County is intermediate between that of the humid, subtropical region to the north-east along the coast of Texas and that of the semi-arid region to the west and southwest.

41

Smith County

Geology:

Climate:

The subsoils in this county have been derived from beds of heavy clay, calcareous clays, and alluvial deposits.

The climate of Smith County is characterized by rela-tively mild winters and long, warm summers, with a gradual transition from one season to the other.

The mean precipitation of 38 inches is well distri-buted throughout the year.

Tarrant County

Geology:

Climate:

The parent materials of the soils in this county are calcareous clays, lime carbonate, soft chalky material, and hard limestones.

Summers are long and winters are short. Mean annual temperature is 65°F, of summer, 82.2°F; and, that of fall, 66°F. Rainfall in this county is distributed throughout the year, but somewhat unevenly.

Taylor County

Geology:

Climate:

Parent material in Taylor County consists of permian shale and clay, permian sandstone, recent deposits of alluvium, outwash from cretaceous formations, and clayey sediment over limestone.

Taylor County lies roughly on the boundary between the humid climate of East Texas and the semi-arid climate of the west and north.

Some soils in the county have accumulated a lot of calcium carbonate caused by water leaching the solu-ble material to a certain depth.

Because Taylor County has mild winters and hot summers, micro organisms continuously decompose residue from plants and animals. This contributes to the high or-ganic content found in some Taylor County soils.

42

Jravis County

Geology:

Climate:

The soils of Travis County are formed in several kinds of parent material. In the western part of the county, the parent material was mainly limestone, dolomite, interbedded limestone and marl, and clay. In the cen-tral part of the county, it was chalk, marl, limestone and marly limestone. In the eastern part of the county it was clay, chalky marl, and silty clay. Along the Colorado River the parent material was alluvium.

Travis County has a humid, subtropical climate. Win-ters are usually short and mild; summers are long, with hot days and warm nights.

Randall Count.y

Geology:

Climate:

The parent materials of the soils of Randall County are dominantly strongly calcareous and moderately alkaline, unconsolidated sandy and silty clay mater-ial. It was derived mostly from loessal deposits and from rocky mountain outwash.

Precipitation, temperature and wind have been important in the development of soils of Randall County. The wet climate of past geologic ages influenced the deposition of parent materials. Later, rainfall was limited, and it seldom wet below the root zone.

Williamson County

Geology:

Climate:

In Williamson County, there are three major soil pro-vinces, each of which is underlain by a characteristic variety of rock formation; namely, the blackland prairie underlain by marl of very highly calcareous clays and chalks; the East Texas timber country, underlain by sands and sandy clays containing no carbonate of lime; and the Grand Prairie, underlain by clays.

Moderately humid and warm-temperate. It is continen-tal in type and is characterized by irregularity of rainfall, sudden changes in temperature, and a com-paratively dry atmosphere. Mean annual temperature is 67.2°F and mean annual precipitation is 31.80 inches.

APPENDIX B

SIMPLIFIED PROCEDURE FOR DETERMINING CATION EXCHANGE CAPACITY USING

A SPECTROPHOTOMETER (AFTER PEECH (10))

43

44

The cation exchange capacity of a soil may be determined by com-

parative means in the standard spectrophotometer device. This simpli-

fied procedure is:

1. Place 10 grams of clay soil in a beaker and 100 ml of neutral

1N_ ammonium acetate (NH^Ac) is added. The solution is allowed to

stand overnight.

2. Filter the solution of Step 1 by washing through No. 42 filter

paper with 50 ml of NH^Ac

3. Wash the material retained on the filter paper of Step 2 with

two 150 ml washings of isopropyl alcohol, using suction. The isopropyl

alcohol wash fluid should be added in increments of approximately 25 ml

and the sample allowed to drain well between additions. Discard wash

solution.

4. Transfer the soil and filter paper to a 800 ml flask. Add 50

ml MgClo solution and allow to set at least 30 minutes, but preferably

24 hours.

5. Under suction filter the fluid resulting from Step 4. Store in

stoppered flask.

6. Prepare a standard curve by using lOyg of NH^-N/ml standard

solution in a 50 ml volumetric flask. Adjust the volume to approxi-

mately 25 ml, add 1 ml of 10% tartrate solution, and shake. Add 2 ml

of Nessler's aliquot with rapid mixing. Add sufficient distilled

water to bring the total volume to 50 ml. Allow color to develop for

30 minutes.

7. Repeat Step 6 for 1.0, 2.0,4.0 and 8.0 ml of aliquots of

standard solution (Note: 72.2yg, 57.70yg, 28.88yg, 14.44yg and 7.22yg

of aliquots were used in this investigation.)

45

8. Insert the standard solution form Steps 6 and 7 into the

spectrophotometer. Record readings and plot the transparency read-

ings against the corresponding NH^-N/mL strengths to construct a

standard curve. (The spectrophotometer is calibrated before hand

with 1 ml of 10% tartrate, 2 ml Nessler and distilled water.)

9. Extract 2.0 ml of sample aliquot (wash solution of Step

5) and add 25 ml of distilled water in a 50 ml volumetric flask.

Add 1 ml of 10% tartrate and shake. Add 2 ml of Nessler's aliquot

with rapid mixing. Add sufficient distilled water to bring the

total volume to 50 ml. Let the solution stand for 30 minutes and

then insert into the spectrophotometer and record the transparency

reading:

10. Typical calculations:

Weight of dry soil = 10.85 gm

Spectrophotometer = 78.6%

= 44yg/g from standard curve.

Conversion:

44yq 50ml^ 50ml^ x "" x "* x IQQom 2ml/aliquotc ^ 1 ml ^ 10.85gm lOOOyg/mg ^ 14mg/meq ^ '"^^m

= 36.21 meq/lOOgm.

total volume of solution from Step 9

volume of MgCL^

^volume of sample aliquot.

APPENDIX C

DETERMINATION OF ATTERBERG LIMITS

46

LIQUID LIMIT

The liquid limit was determined in accordance with the ASTM D423-66.

47

ratus

(a)

(b)

(c)

(d)

(e)

(f)

• •

Evaporating dish

Spatula

Liquid limit device

Grooving tool

Containers (moisture cans)

Balance.

Sample:

About 100 g of so i l from the thoroughly mixed portion of the

material passing the No. 40 sieve:

Procedure:

1. Adjust the liquid limit device.

2. Place soil in evaporating dish and mix with 15 to 20 ml of

distilled water by alternately and repeatedly stirring, kneading, and

chopping with a spatula. Make further addition of water in increments

of 1 to 3 ml. Thoroughly mix each increment of water with the soil,

as previously described, before adding another increment of water.

3. Place a portion of the mixture in the liquid limit device

cup above the spot where the cup rests on the base, when enough water

has been added to produce a consistency that will require 30 to 35

drops of the cup to cause closure. With the spatula, level the soil

and at the same time trim it to a depth of 1 cm at the point of maxi-

mum thickness, care being taken to prevent entrapment of air in the

mass. Divide the soil in the cup by firm strokes of the grooving

48

tool along the diameter through the centerline of the cam follower

so that a clean, sharp groove of the proper dimensions will be formed.

4. Lift and drop the cup by turning the liquid limit device

crank, at the rate of 2 rps, until the two halves of the soil cake

come in contact at the bottom of the groove along a distance of 1/2

inch. Record the number of drops.

5. Remove a slice of soil approximately the width of the spatula,

extending from edge to edge of the soil cake at right angles to the

groove and including that portion of the groove in which the soil

flowed together, and place in a suitable tared container. Weigh

and record the weight. Over-dry the soil in the container to a con-

stant weight at 230 ± 9F and reweigh as soon as it has cooled. Re-

cord this weight. Record the loss in weight due to drying as the

weight of water.

6. Transfer the remaining soil from the cup to the evaporating

dish. Wash and dry cup and grooving tool, and reattach the cup to

the device in preparation for the next trial.

7. Repeat the above operation for at least two additional

trials, with the soil collected in the evaporating dish, to which

sufficient waster has been added to bring the soil to a more fluid

condition. The object of this procedure is to obtain samples of

such consistency that the number of drops required to close the

groove will be above and below 25. The number of drops should be

less than 35 and exceed 15. The test shall always proceed from the

dryer to the wetter condition of the soil.

8. Calculation:

(a) Water Content, W^ =

(weight of water/weight of oven dry soil) x 100

49

(b) Plot a "flow curve" representing the relationship

between water content and corresponding number of

drops on a semilogarithmic graph with the water

content as abscissae. The flow curve is a straight

line drawn as nearly as possible through the plotted

points.

(c) The water content corresponding to the intersection

of the flow curve with the 25-drop ordinate is the

liquid limit, reported to the nearest whole number.

50 PLASTIC LIMIT

Plastic limit was determined in accordance with ASTM D424-59.

Apparatus:

(a) Evaporating dish

(b) Spatula

(c) Surface for rolling - A ground-glass plate or piece

of glazed or unglazed paper on which to roll.

(d) Containers

(e) Balance.

Procedure:

1. Place about 15 g of the air-dried soil sample passing the No.

40 sieve in an evaporating dish and thoroughly mix with distilled water

until the mass becomes plastic enough to be easily shaped into a ball.

Take about 8 g of this ball for the test sample.

2. Squeeze and form the 8 g test sample into an ellipsoidal-

shape mass. Roll this mass between the fingers and the ground-glass

plate or a piece of paper lying on a smooth horizontal surface with

just sufficient pressure to roll the mass into a thread of uniform

diameter throughout its length. The rate of rolling shall be between

80and90 strokes/min, counting a stroke as one complete motion of the

hand forward and back to the starting position again.

3. When the diameter of the thread becomes 1/8-in., break the

thread into six or eight pieces. Squeeze the pieces together between

the thumbs and fingers of both hands into a uniform mass roughly ellip-

soidal in shape, and reroll. Continue this alternate rolling to a

thread 1/8-in. in diameter, gathering together, kneading and rerolling,

until the thread crumbles under the pressure required for rolling and

the soil can no longer be rolled into a thread. The crumbling may

occur when the thread has a diameter greater than 1/8-in. This shall

51

be considered a satisfactory end point, provided the soil has been

previously rolled into a thread 1/8-in. in diameter.

4. Gather the portions of the crumbled soil together and place

in a suitable tared container. Weigh the container and the soil and

record the weight. Oven-dry the soil in the container to constant

weight at 230 ± 9F. Record this weight. Record the loss in weight

as the weight of the water.

5. Calculate the plastic limit, expressed as the water content

in percentage of the weight of the oven-dry soil, as follows:

Plastic limit = (weight of water/weight of oven-dry soil) x 100.

APPENDIX D

HYDROMETER ANALYSIS TEST

PROCEDURE

52

53

Grain size analysis of the less than No. 200 sieve material was

accomplished by the hydrometer using the ASTM D422-63 procedure.

Apparatus

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

Procedure

• •

Balance

Stirring apparatus

Hydrometer (152 H model)

Sedimentation cylinder

Thermometer

Water bath

Beaker

Timing device.

•

1. Take exactly 50 g of oven-dry, well-pulverized soil and mix

with 125 cu cm of 4 percent sodium metaphosphate solution. The 4 per-

cent solution can be prepared by adding 40 g of dry sodium metaphos-

phate to 1000 cu cm of water. This solution should be freshly mixed,

but, in many cases, should not be over 1-month old.

2. Allow the mixture to stand for about 16 hours. Transfer the

mixture to a special dispersion cup and add distilled or dimineralized

water until the cup is more than half full. Stir for a period of 1

minute.

3. Immediately after dispersion, transfer the soil-water slurry

to the glass sedimentation cylinder and add distiller or demineralized

water until the total volume is 1000 ml.

4. Using the palm of the hand or a rubber stopper over the open

end of the cylinder, turn the cylinder upside down and back for a period

of 1 minute to complete the agitation of the slurry. At the end of 1

minute set the cylinder in a convenient location and take hydrometer

54

readings at the following intervals of time, or as many as may be

needed; 2, 5, 15, 30, 60, 250, and 1440 minutes.

5. When it is desired to take a hydrometer reading, carefully

insert the hydrometer about 20 to 25 secs before the reading is due

to approximately the depth it will have when the reading is taken.

As soon as reading is taken, carefully remove the hydrometer and

place it with a spinning motion in a graduate of clean distilled or

demineralized water. Readings shall be taken at the top of the menis-

cus formed by the suspension around the stem, since it is not possible

to secure readings at the bottom of the meniscus.

6. After each reading, take the temperature of the suspension

by inserting the thermometer into the suspension.

7. Calculat ions:

(a) Calculate percentage of soil remaining in suspension

for hydrometer 152 H as follows:

P = (Ra/w) X 100

where a = correction factor to be applied to the hydro-

meter reading (listed in most lab manuals)

R = corrected hydrometer reading

= actual -zero reading + C^

(C. = temperature correction; listed in most soil laboratory manuals)

apd w = oven-dry weight of soil in a total test sample

represented by weight of soil dispersed, grams.

(b) The diameter of a particle corresponding to the percentage

indicated by a given hydrometer shall be calculated ac-

cording to Stoke's law:

55

D =/[30n/980 (G-G^)] x L/T

which may be written as:

D = K / L/T

where

G = Specific gravity of soil particles

G^ = Specific gravity (relative density) of

suspending medium

n = Coefficient of viscosity of suspending medium.

D = Diameter of particle, mm

K = Constant depending on temperature of suspension

and specific gravity of the soil particles

(values are listed in most soil laboratory

manuals).

L = Distance from the surface of the suspension to

the level at which the density of the suspension

is being measured, cm. This distance is known

as effective depth and is listed in most soil

laboratory manuals.

T = Interval of time from beginning of sedimenta-

tion to the taking of the reading, min.

8. When the hydrometer analysis is performed, a graph of the test

results shall be made, plotting the diameters of the particles on a loga-

rithmic scale as the abscissa and the percentages smaller than the corres

ponding diameters to an arithmetic scale as the ordinate.

APPENDIX E

TEST DATA FOR CATION EXCHANGE CAPACITY (CEC), ATTERBERG LIMITS (PLASTIC LIMIT (PL) AND LIQUID LIMIT (LL), AND PLASTICITY INDEX

56

Sample No.

001-01

003-01

004-01

005-01

008-01

010-01

011-01

012-01

013-04

015-04

017-04

021-04

026-02

028-02

029-02

030-02

033-02

035-02

036-03

038-03 040-03

041-03

042-03

044-03

046-03

047-03

048-03

049-07

050-07

055-05

057-05

058-05

059-05

061-05

LL

28.80

25.40

34.43

53.31

34.30

36.20

43.96

32.00

44.30

36.70

47.97

32.42

53.94

51.42

62.80

30.29

82.42

43.15

47.60

72.20 41.40 *

48.35

28.95

49.56

57.60

52.13

35.33

39.80

72.72

52.80

59.12

62.70

65.80

33.67

PL

18.48

15.48

15.79

19.32

17.01

16.39

18.46

15.23

23.10

19.37

19.18

14.95

17.06

25.11

20.70

16.66

30.94

18.41

18.84

31.17

20.49

21.63

13.97

22.84

24.30

19.89

15.05

16.70

22.37

22.59

20.02

20.83

21.49

15.55

PI

10.32

9.42

19.64

33.99

17.30

19.81

25.30

16.77

21.20

17.18

28.79

17.47

35.54

26.31

42.08

13.34

51.48

24.74

28.76

41.03

20.91

26.72

14.98

26.72

33.30

32.24

20.28

23.10

50.35

30.21

39.10

41.87

44.31

18.12

CEC

20.20 17.66

29.20

48.40

35.90

23.24

27.57

23.52

52.40

27.87

26.34

19.40

35.43

36.70

50.30

26.66

44.87

38.90

54.95

49.00

38.40

28.70

16.23

34.50

51.24

43.56

31.24

27.75

46.54

20.29

42.20

32.00

34.64

22.54

57

58

Sample No.

062-05

063-05

065-05

068-06

069-06

071-06

072-06

073-06

074-06

075-06

077-06

078-08

080-08

081-08

083-08

084-08

085-08

086-08

087-08

LL PL PI CEC

46.88

60.00

32.40

50.05

51.85

52.57

74.27

54.80

22.00

55.45

54.84

38.75

54.48

32.19

81.06

31.90

44.38

61.53

38.46

18.95

20.12

16.67

22.59

20.39

18.53

32.52

18.36

14.34

24.80

21.61

18.31

18.26

17.97

29.57

13.33

18.02

25.10

21.79

27.93

39.88

15.73

27.46

31.46

34.04

41.75

36.44

7.66

30.65

33.23

20.44

36.22

14.22

51.57

18.57

26.36

34.90

16.55

36.20

32.80

15.94

30.00

34.14

31.56

72.80

18.90

24.80

50.00

26.70

23.20

27.14

28.20

58.40

34.40

49.00

50.00

29.10

APPENDIX F

SUBROUTINE "INPUT"

59

60 SUBROUTINE INPUT

IMPLICIT REAL*8(A-H,0-Z,$)

DIMENSIØN D(6)

CØMMØN|BLK2|Z'(80),1FMT(180),NVAR, MØD,CHK

DATA END|'END'|

READ(5,1FMT) (D(I),I=1,NVAR),CHK

IF (CHK.EQ.END) RETURN

X=D(1)

Z(1)=DL0G10(X)

B=D(2)

Z(2)=DL0G10(B)*3.25

C=D(3)

Z(4)=DL0G10(P)*2.19

RETURN

END

Note: Z(l) is the dependent variable

Z(2), Z(3), Z (4) are the independent variables. The Z vectors

used in this investigation are not standard but depend on the

nature of the problem.

APPENDIX G

PROCEDURE FOR REMOVING ORGANIC MATTER FROM SOIL

61

62

Apparatus:

(a) 600 ml glass beaker

(b) Clorox

(c) Hydrochloric acid {HCÍL)

(d) pH meter.

Procedure:

1. Pour about 450 ml of clorox (sodium hypochlorite) into beaker.

Check pH (should be about 12-13).

2. Add HCA a little at a time, with constant mixing, until pH

becomes about 9.

3. Place enough soil in the solution. Allow soil to remain in

beaker for about 30 minutes, with occasional stirring.

4. Filter solution through No. 42 Whatman filter paper.

5. Wash soil with distilled H2Q until wash solution registers

neutral PH (=7.0).

6. Soil sample is now ready for testing.