Correlation of Electrical Resistivity with Different Condition

of the Soil

by

Mior Khairul Azinil Bin Mior Rarili

Dissertation submitted in partial fulfillment of

the requirements for the
Bachelor of Engineering (lions)
(Civil Engineering)

JUN1', 2010

Univcrsiti Tcknologi PETRONAS

Bandar Seri Iskandar
31750 'I'ronoh
Perak I)arul Ridzuan
 CERTIFICATION OF APPROVAL

Correlation of Electrical Resistivity with Different Condition of the Soil

By

Mior Khairul Azmil Bin Mior Razali

A project dissertation submitted to the

Civil Engineering Programme
Universiti Teknologi PE'IRONAS
in partial fulfilment of the requirement for the
BACHELOR OF ENGINEERING (lions)
(CIVIL ENGINEERING)

Approved by,

c_
ýýcýcý . ý..ý
ý
(Dr Syed Baharom)

UNIVERSITI TEKNOLOGI PETRONAS

TRONOI-1, PERAK
JUNE 2010

1
 CERTIFICATION OF ORIGINALITY

This is to certify that I am responsible for the work submitted in this project, that the

original work is my own except as specified in the references and acknowledgements,

and that the original work contained herein have not been undertaken or done by
unspecified sources or persons.

MIOR KI-IAIRUL AZMIL BIN MIOR RAZALI

2
 I
ABSTRACT

Assessments of slope stability using electrical parameters have least been

research by many scholars. The method is non destructive and very sensitive. It offers a

very attractive tool lbr describing the subsurfäce properties of the slope without
disturbing the physical characteristic of the soil. The method has been applied in various

contexts like groundwater exploration; landfill and solute transfer delineation,

agronomical management by identifying areas of excessive or soil horizon thickness

and bedrock depth.

The ranges of benefit of this method have attracted the author to do research on

the correlation between electrical parameter with some soil parameter. The experiments

were conducted in the laboratory using sand boxes specially designed using Perspex
material. Then to get the physical parameters of the soil, conventional Shear Box Test
has been used. Results and values obtained from both experiments were then analyzed
in order to establish some possible correlation.

From this research, the author sees a unique relationship exists between

electrical resistivity with percentage of moisture content for each variable of the soil

parameter. In general, Soils with higher percentage of moisture content and salt content

will have lower electrical resistivity. In addition soil with higher value of pI-I (alkaline)

will have lower electrical resistivity than lower value of pH (acidic).

3
 11
ACKNOWLEDGEMENTS

First and foremost, I am expressing my greatest praise and gratitude to Allah for

His guidance and blessings throughout the duration of my final year project (FYP).

The completion of this FYP would not have been possible without the support,

hard work and endless efforts from those who are involved directly or indirectly in this

report. I would like to thank to Dr. Sycd Baharom as project supervisor for delivering

many precious lessons on both technical and non-technical matters from my very first
days assigned for this research. Ills dedication and enthusiasm inspires me a lot and

working under his supervision was a great pleasure and valuable experience for me.

Loads of thanks to the UTP respective technicians such as Ms. Ema for

providing me sufficient and useful guidelines and lending an effortless compassionate

help, support and guidance so that I can complete my project on time towards the

successof FYP.

Besides, my deepest appreciation goes to my family and friends who offered

helps whenever I faced obstacles within the completion of this FYP. Their support

possibly makes me ongoing for my project progress. I hope that the outcome of this

report will bring beneficial output to others as well.

4
 III

TABLE OF CONTENTS

1. INTRODUCTION
1.1. Problem Statement 9
........................................................................
1.2. Objectives 10
.................................................................................
1.3. Scope of Study 10
............................................................................

2. LITERATURE REVIEW
2.1. Conventional Soil Properties Test and Electrical Resistivity Method............ 11

2.2. Soil Properties and Electrical Resistivity 13

.........................................................
2.3. Correlation between Electrical Resistivity with Moisture Content 13
...............
2.4. Correlation between Electrical Resistivity with Salt Content 15
.....................
2.5. Correlation between Electrical Resistivity with pH of the soil 16
....................
2.6. Electrical Resistivity Measurement 17
...................................................

3. METHODOLOGY
3.1 ResearchMethodology 21
..................................................................
3.1.1 Laboratory Works Test 22
........................................................
3.1.2 Analysis Data Method 23
.........................................................
3.2 Electrical Resistivity Testing Procedures 24
...........................................
3.2.1 Apparatus 24
........................................................................
3.2.2 Soil Type 24
.........................................................................
3.2.3 Preparation of Soil Sampling 24
.................................................
3.2.4 Equipment Setup 25
................................................................
3.2.5 Determining Resistivity of Soil 26
...............................................
3.2.6 Sample Integrity 26
.................................................................
3.3 Soil Shear Strength Testing Procedures 27
.............................................
4. RESULT AND DISCUSSION
4.1 Electrical Resistivity Result of Different Moisture Content 28
.......................
4.2 Electrical Resistivity Result of Different Salt Contcnt 31
..............................
4.3 Electrical Resistivity Result of Different pH Value of the Soil 36
....................

5. CONCLUSION & FURTHER WORK

5.1 Conclusion 39
................................................................................
5.2 Further Work 40
..............................................................................

REFERENCES 41

APPENDICES 42
 IV

LIST OF TABLES

ITEMS DESCRIPTION
Soil Classification Based on pH from Corrosion Diagnostics
Table 2.5a Engineering
Table4.1a Electrical resistivity results for Different Moisture Content
Electrical resistivity results for Different Salt Content in 10%
Table 4.2a moisture Content
Electrical resistivity results for Different Salt Content in 30%
Table 4.2b moisture Content
Table4.3a Electrical resistivity results for Different pl-1value of Soil
Table5.1a Trend of Moisture Content Result
Table5.1b Trend of Salt Content Result
Table5.1c Trend of Salt Content Result

7
 V
LIST OF FIGURES

ITEMS DESCRIPTION

Figure2.1a Borehole Sampling Method

Relationship between the Volumetric Water Content and the
Figure2.3a Electrical Resistivity for Different Soil Types
Figure2.6a Principle of Electrical Operation
Figure3a Flow Chart of Research Methodology
Figure3.1.1a The Specification of the Sand Box
Figure3.1.1b The Shear Box Test Diagram
Figure 3.2.3a Laboratory soil mixture
Figure3.2.4a Equipments Setup for Laboratory Work Test of Soil Resistivity
Figure3.3a Direct Shear Box Test
Figure4.1a Graph Soil Resistivity vs. Moisture Content
Figure4.1b Graph Soil Cohesion vs. Moisture Content
Figure 4.1c Graph Friction Angle vs. Moisture Content
Figure4.2a.1 Graph Soil Resistivity vs. Salt Content in 10% Moisture Content
Figure4.2a.2 Graph Soil Cohesion vs. Salt Content in 10% Moisture Content
Figure 4.2a.3 Graph Friction Angle vs. Salt Content in 10% Moisture Content
Figure4.2b.1 Graph Soil Resistivity vs. Salt Content in 30% Moisture Content
Figure4.2b.2 Graph Soil Cohesion vs. Salt Content in 30% Moisture Content
Figure 4.2b. 3 Graph Friction Angle vs. Salt Content in 30% Moisture Content
Figure4.3a Graph Soil Resistivity vs. pH Value of the Soil
Figure4.3b Graph Soil Cohesion vs. pH Value of the Soil
Figure4.3c Graph Friction Angle vs. H Value of the Soil

8
 CHAPTER 1
INTRODUCTION

1.1 Problem Statement

The conventional method of doing the soil investigation (SI) is by borehole

sampling and involves laboratory testing of samples collected. The time required to do
the experiment on every sample at the lab is very long. The problem of time

requirement, field size and the field area that involved has lead to geophysical method
practice. One of the geophysical methods is electrical resistivity survey, which can be
conducted rapidly in the field.

The electrical resistivity survey that is being used today provides limited

information to be use for estimating the characteristics of the soil. The survey cannot
determine some of the important variable such as the strength parameters. mineralogy,

particle size, fabric, texture, salt content and percentage of organic content.

The general approach behind this quick assessmentsystem is to eliminate the usage

of physical soil parameters such as cohesion (c). internal frictional angle (0), and unit
weight (y) as is currently being practice for the calculation of FOS and replace these
physical parameters with their correlated electrical parameters such as resistivity,
conductivity, voltage etc.

9
 1.2 Objectives.

The primary objective of this study was to find possible correlation between

resistivity & some soil parameter with variation in different soil conditions. The
experiment will be focused on doing the laboratory test.

1.3 Scope of Study

Using electrical resistivity for slope stability study, authors must know electrical

resistivity depends on many factors such as porosity, electrical resistivity of the pore
fluid, composition of the solids, degree of saturation, particle shapeand orientation, and

pore structure.

The study of correlation between electrical resistivity and soil investigation is

divided by many portions. Because the research areas are really wide, this researchhas
been divide to several group. Authors have been more focused on doing the experiment
by determine on the three important variable that are:

a) Correlation against kaolin soil with different percentage of moisture content.

b) Correlation against kaolin soil with different percentage of salt content.

c) Correlation against kaolin soil with different pH value of the soil.

10
 CHAPTER 2
LITERATURE REVIEW

2.1. Conventional Soil Properties Test and Electrical Resistivity Method

Engineering properties of geomaterial are very important for civil engineers because

almost everything they build; tunnels, bridges, dams and others are in, on or with soils

or rocks. For geotechnical engineers, the strength, the stress-deformation behavior and

the fluid flow properties of earth materials are of primary concern and form the
conventional framework of the geotechnical discipline. Conventional techniques for the
determination of these engineering properties can be generally divided into three

categories; laboratory tests, in-situ tests and geophysical methods. Of these, geophysical

methods have been least developed as regards to their suitability for specific
quantification of soil properties.

Laboratory tests have the advantagesof directly measuring the specified engineering

properties under controlled boundary conditions and different environmental conditions.

However, soil samples are usually disturbed during the drilling and sampling processes,

which may make the measuredengineering properties, deviate from their actual values.

Figure 2.1a: Borehole Sampling Method

11
 The electrical resistivity method is one of the most useful techniques in Soil
investigation because the resistivity of a rock and soil is very sensitive to its water

content. In turn, the resistivity of water is very sensitive to its ionic content.

In general, it is able to determine the soil properties at the site and determine the

mineralogy without need to wait for the sample to be sent to the lab for experiment and
research.

Applications:

1. Water table depth.

2. Groundwater quality

3. Brine plumes.

4. Seawater intrusion

5. Well sitting.

6. Aquifer exploration
7. General stratigraphic mapping
Advantages:

1. Less costly than drilling.

2. Non disturbing.

Disadvantages:

1. Cultural problems because interference, e.g.. power lines, pipelines, buried

casings, fences.

2. Resolution.

12
 2.2. Soil Properties and Electrical Resistivity

Electrical conductivity and resistivity of soils have been investigated in a large

number of studies, which can be divided into three groups.

The first group includes laboratory studies of electrical conductivity and

dielectric constant of different dispersed media (including
soils) with electromagnetic
waves. These studies help to develop relationship between electrical parameters,
quantitative and qualitative compositions of electrolytic solutions. The relationships
were enhanced by the studies of soil electrical parameters with constant electrical field.
For some diluted soil solutions and groundwater. the methods are developed to calculate

electrical conductivity ii-om the solution compositions.

The second group of studies is devoted to laboratory measurements of' surface

electrical conductivity. The surface electrical conductivity is a major parameter

describing structure of' electrical double layer and its ion composition. There is only
limited special research with experimental measurements of' surface electrical
conductivity in soils.

The third group of studies includes measurementsof electrical conductivity of

soils, rocks, and sediments in situ with various geophysical methods.

2.3. Correlation between Electrical Resistivity with Moisture Content

In the literature the various models proposed to describe relationships between

electrical parameters and soil water content, temperature, or salt content. Electrical
conductivity and resistivity are usually measured as electrical parameters in laboratory
and field conditions. Relationships between soil water content and electrical parameters
were measured in field and laboratory conditions and mostly curvilinear models were
obtained. Curvilinear relationships were also proposed between electrical resistivity and
temperature. The researcher has been experiment and had proved that exponential

13
relationship between electrical resistivity, soil temperature, and water content based on

a series of experiments.

The assessment of soil water content variations more and more leans on

geophysical methods that are non invasive and that allow a high spatial sampling.
Among the different methods, Direct Current (DC) electrical imaging is moving
forward. DC Electrical resistivity shows indeed strong seasonal variations that

principally depend on soil water content variations. Although there are many studies
between electrical resistivity and water content of agricultural soils. on geotechnical or

engineering soils there are little attentions.

Electrical current in soils is mainly electrolytic, based on the displacement of

ions in pore water, and is therefore greater with the presence of dissolved salts. Thus,

electrical current in soils dependson the amount of water in the pores and on its quality.
In most studies concerning the water content, the electrical conductivity of the solution
is assumed to remain relatively constant to be neglected against its variation related to

water content variation. Prior to field surveys, preliminary calibration of the volumetric
water content related to the electrical resistivity is usually performed in the laboratory.
Figure 2.1 shows examples of laboratory calibration between the electrical resistivity

and the volumetric water content. The electrical resistivity decreaseswhen the water
content increases. It can also be seen that for water content below 15 percent. the
electrical resistivity rapidly decreaseswith increasing water content. The relationship
between the electrical resistivity and the water content has firstly been studied mainly in

the field of petroleum research.

14
 250
Cheshire Clay (McCarter 1984)
London Clay (McCarter 1984)
Loamy Clay Calsisol (Michot 2003)
200- Kibushi Clay (Fukue 1999)
ý.

ý
...
ý. 150-
ý ti 0
cn
in
a) "
100
U

ý
_,
w 50 ý ,.
y n'1
ýUII
: yQ
, ý
ý}ý yý ý,
) rflý L Lf L11 º
0
S 10 15 20 25 30 35 40 45 50
Volumetric water content (%)

Figure 2.3a: Relationship between the Volumetric Water Content and the Electrical

Resistivity for Different Soil Types

2.4. Correlation between Electrical Resistivity with Salt Content

Water and salt content distributions within the soil profile are the main properties

causing considerable variations in electrical resistivity or conductivity. The water

content and salt distributions in the soil are determined mainly by the saline
groundwater and also the different type of mineral of the salt itself.

The effect of the quality (mineralization) of saturating water on the apparent

resistivity has been studied by many investigators. Resistivity measurementsconducted

by Sharapanov et al. (1974), showed indirect, two-segment, linear logarithmic

relationship between apparent resistivity and mineralization. For sands, the low gradient
segment corresponds to mineralization of up to about 2500 mg/I, whereas higher
mineralizations correspond to the higher-gradient segment. Other studies (e.g., Mares,
1984; Palacky, 1988; Kui, 1990; McNeill, 1990) although implying the direct

relationship between salinity and conductivity (or indirect for resistivity), however, the

15
nature of this relationship has not been discussed thoroughly. Moreover. Barker (1990)
showed that the relationship between chalk water conductivity and salinity
(experimentally determined) constructed on a bilogarithmic scale is not characterized by

a straight line, but rather by a parabola.

2.5. Correlation between Electrical Resistivity with pH of the soil

The pH provides a general guide to the nature of possible corrosion. Acidic soils are

corrosive. Neutral soils are optimal for the development sulphate-reducing bacteria.
Alkaline soils are generally benign; however, exceedingly high pH values can lead to

low electrical resistivity.

Development of acidity in soils is a result of the natural processesof weathering

under humid conditions. In regions of moderate rainfall, soluble salts do not accumulate
except where soil waters seepto lower levels and collect in depressions. However, in
regions of high rainfall, not only are soluble salts removed from the soil but the
absorbed basesnormally present in the colloidal materials of the soil are partially
removed, and result in increasedacidity. The processeseventually give rise to the
condition known as soil acidity. The depth to which this leaching of the basesoccurs
varies with rainfall, drainage, type of vegetation, and nature of the material present.

The degree of acidity or alkalinity of a soil is expressedas the pH, a value that

representsthe logarithm of the reciprocal of the hydrogen ion concentration. A pH value

of 7 indicates neutrality; lower values, acidity; and higher values, alkalinity. Terms used
for soil classification basedon pI-I are defined as follows.

16
 I-ligh alkalinity lowers electrical soil resistivity and increase soil corrosivity.
Certain corrosive substancesin the medium (e.g., chloride ions) and mechanical effects

can destroy surface films locally, leading to intensive local corrosion such as pitting and
stresscorrosion.

Soil Classification Based on pH

Extremely Acid Below 4.5
Very Strong Acid 4.5 to 5.0
Strongly Acid 5.1 to 5.5
Medium Acid 5.6 to 6.0
Slightly Acid 6.1 to 6.5
Neutral 6.6 to 7.3
Mildly Alkaline 7.4 to 7.8
Moderately Alkaline 7.9 to 8.4
Strongly Alkaline 8.5 to 9.0
Výrr t1,11
1I, I. Aline 9.1 and Higher

Table 2.5a Soil Classification Based on pH from Corrosion Diagnostics &

Engineering

2.6. Electrical Resistivity Measurement

Soil resistivity data is the key factor in designing a grounding system for a

specific performance objective. All soil conducts electrical current, with some soils
having good electrical conductivity while the majority has poor electrical conductivity.

The resistivity of soil varies widely throughout the world and changes dramatically

within small areas. Soil resistivity is mainly influenced by the type of soil (clay, shale,

etc.), moisture content, the amount of electrolytes (minerals and dissolved salts) and
finally, temperature.

When designing a grounding system for a specific performance objective, it is

necessaryto accurately measurethe soil resistivity of the site where the ground is to be
installed. Grounding system design is an engineering process that removes the

17
guesswork and "art" out of grounding. It allows grounding to be done "right, the first

time". The result is a cost savings by avoiding change orders and ground
-enhancements. -

The best method for testing soil resistivity is the Wenner Four Point method. It

uses a 4-pole digital ground resistance meter, probes, and conductors.

It requires inserting four probes into the test area. The probes are installed in a

straight line and equally spaced (Figure 2.2). The probes establish an electrical contact
with the earth.

Figure 2.6a: Principle of Electrical Operation

The four pole test meter injects a constant current through the ground via the
tester and the outer two probes. The current flowing through the earth (a resistive
from the
material) develops a voltage/potential difference. This voltage drop resulting
current flow is then measuredbetween the two inner probes.

The meter then knows the amount of current that is flowing through the earth

and the voltage drop across the two center probes. With this information the meter uses
ohms law (R=V/1) to calculate and display the resistance in ohms.

18
 This displayed resistance value is in ohms and must be converted to ohms-

meter, which are the units of measure for soil resistivity. Ohms-meter is the resistance
of a volume of earth that is one meter by one meter by one meter. or one cubic meter.

To convert from the displayed ohms to ohms-meter, the meter reading is

multiplied by 2 and the result multiplied times the probe spacing. The following shows
the calculation in a formula.

p(ohms-m) =2xRxA

p= soil resistivity in ohm-m (em)

2 is constant
R= digital readout in ohms (Q).
A= distance between electrodes in ft.

19
 CHAPTER 3
METHODOLOGY

Start
Definition
ofproblem
Define of thesoil
iStudythe
thevariables

to the
effectofthevariables
electrical
resistivityandalsosoilstrength_
Experimental
TestinGeotechnical_Lab
NotSatisfy

Data
Collective ý-

Satisfy
ý7
Results
anddiscussion
Satisfy
Conclusion

Figure 3a: Flow Chart of ResearchMethodology

20
3.1 Research Methodology

This studies was divided into two main phases which are phase one and phase
two.

For the phase one concentration was more on research information details such

as the fundamental concepts of these studies, find the related information and research
especially the journals and paper works for the electrical resistivity in the soil and
includes preparation of soil sample for the laboratory test. The soil will be tested on

three soil sample, there are; pure sand, pure silt and pure clay. The soil sample must be
totally pure soil without mix with any type of soil.

The second phase of this study was on the laboratory test. The tests were conducted in

the soil laboratory with special instruments and equipments for testing the soil sample

about electrical resistivity with the soil water content. The laboratory works have been

tested for each three different parameters of the soil with different values. The shear

strength parameters of the soil sample were determined to correlate with the electrical

resistivity in soil sample. The data were then elaborate to find the correlation about the

electrical resistivity with the soil water content. At the end of these studies, the result

were summarized to come out with the relationship of the between electrical resistivity

with particle size distribution of the soil and soil shear strength parameters.

21
3.1.1 Laboratory Works Test

Sand Box

For the lab method on determine electrical resistivity change with different

parameters,the authors use sand box apparatusthat have been designed to ease
handling, save time, cost and give more accurate data. The sand box iwas designed by

referring to the Wenner method. The Wenner method is suitable for horizontal
structures such as sand box and also will give greater strength signal. Below is the
specification of the sand box:

40mm

99- ' r
A- 40mm
200mm

Figure 3.1.1a: The Specification of the Sand Box

Shear Box Test

The shearing resistance offered by the soil as one portion is made to slide on the

other is measuredat regular intervals of displacement. Failure occurs when the shearing
resistancethe maximum value which the soil can sustain. The author carry out the shear
box test through all set of experiments (water content, salt content, and pl-I) under

22
dil7erent normal pressures,the cohesion (c) and internal frictional angle ((1) of the
soil
sample can he determined.

Teststo measure o"

1. Sh6ar Box
: Test

M...
REM=$
/ ///////i
i®//

® -ýýý % Loadcell 1
ureI : '/. ý measure
0- I III'= ý_
iýL
A. pl, ShearForce
i/
/:. .ýý ý()] i ý. %
/
ýi
ý%%///////////////%%%/.: V1"1.

zxi. qrzzzzzzzz

RIN
w.

Measure relative "

verticaldisplacementof top platen.dy
Figure 3.1.1b: The Shear Box Test Diagram

3.1.2 Analysis Data Method

After the laboratory experiment, all the data were analyzed to get the final result.
The author have conducted graphical and table method in order to correlate relation
between the electrical resistivity with the strength of the soil. The graphs were created

using Microsoft Excel.

23
3.2 Electrical Resistivity Testing Procedures

3.2.1 Apparatus

" Four terminal probes.

" Null balancing ohmmeter or multimeter capable of four wire resistance

measurementsfrom one to one million ohms.

" Four insulated wire conductors

" Soil box

" Measuring tape

3.2.2Soil Type

In this researchthe author conduct experiment only to one type of soil which is
determine as Kaolinite Sand of grade K200. The basic properties of the soil are as
below:

" Particle Size Distribution(PSD) : 0.250mm- 2.000mm

" Specific Gravity (SG) : 2.6

" Liquid Limit (I.,L) : 36.1%

" Plastic Limit (PL) : 33.7%

" Plasticity Index (PI) : 2.4%

" pl I: 4.41

3.2.3 Preparation of Soil Sampling

The soil samples were put into the oven for 24 hours to ensure the soil sample

totally dried and free from water content. After 24 hours, the soil were taken out from
the oven and exposed to the room temperature for 15 minutes. The soil sample were
weighted approximately 5000g for each test.

24
 The 5000g of the soil sample were added with change of moisture
content, salt
content or pH value dependson parameter value need to be determined. The soil sample
were mixed up using soil mixture (Figure 3.2) to ensure it will be mix perfectly.
E_ý ýýý

Figure 3.2.3a: Laboratory soil mixture

3.2.4 Equipment Setup

Soil box was rinsed with deionised water before starting test. The wires were

connected to the multi meter. A standard soil box have four probes at either end or a
pair of electrode pins spaced out between the probes (Figure 3.3). The current source
from the ohmmeter was connected to the outer probes, and the potential was measured
between the pins.

Figure 3.2.4a: Equipments Setup for Laboratory Work Test of Soil Resistivity

25
 3.2.5 Determining Resistivity of Soil

Samples were placed (5000 grams approximately) in a soil box. Fill soil box to

top taking care to leave no voids and striking excess off top of box. Fill level must be

more than the distance between the probes. This is the resistivity or the resistivity of the
soil in its present condition. Soil box was filled up and then the resistivity results were

obtained. The same process was repeated until the resistivity stops dropping or starts to
rise again. The result for the test was the average resistivity obtained during this
process. Report results in ohm (a).

3.2.6 Sample Integrity

The soil box was washed with distilled water after each sample to avoid

contamination between samples. Clean tools have been used for gathering samples and
never transport or store samplesin open containers.

3.3 Soil Shear Strength Testing Procedures

26
 After testing the electrical resistivity of the soil sample, the soil samples were

taken out from the soil box and put into the pan. The soil sample were tested on shear

strength parameters by Direct Shear Box Test Method. The procedures of the testing
method were conducted as same as British Standard procedures. Figure 3.4 shows the
equipments of Direct Shear Box Test.

Figure 3.3a: Direct Shear Box Test

CHAPTER 4

27
 RESULT AND DISCUSSION

In this chapter. the results were analyzed. discussed and presented in the sub-

topic below:

4.1 Electrical Resistivity Result of Different Moisture Content

The experiments were conducted by change the moisture content into four

diflercnt values which are 10%. 15%, 25% and 30%. The results show as below:

Water Content (%) 10 15 25 30

Electrical 615.25 325.50 97.79 58.53
Resistivity, p (LZm)
Cohesion, c (kN/mz) 0.8855 1.7645 10.0462 12.2108
Friction angle, (I) ('") 26.49 30.13 27.3 24.89

Table 4.1a: Electrical resistivity results for Different Moisture Content

In order to look at the possible correlation ofelectrical resistivity obtained and

the various soil parameters, the results of the electrical resistivity can be refer to the

plotted graph. Graph for electrical resistivity versus water content, cohesion and friction
angle are given in Figures 4.1a, 4.1 b, and 4.1c.

28
 Electrical Resistivity, p (0m)
700

600

500

400
Electrical Resistivity, p
300
(0m)
200

100

0
0 10 20 30 40

Figure 4.1a: Graph Soil Resistivity vs. Moisture Content

Cohesion, c (kN/m2)
14

12

10

6/ Cohesion, c (kN/m-)

0
0 10 20 30 40

Figure 4.1 b: Graph Soil Cohesion vs. Moisture Content

29
 Friction angle, D (°)
35

30

25

20

15 Friction angle, (D

10

0
0 10 20 30 40

Figure 4.1c: Graph Friction Angle vs. Moisture Content

From the result given in Figure 4.1 a, it is clear that electrical resistivity of the

soil decrease with increment of water content. Figure 4.1b indicates that when the
electrical resistivity decreases, the cohesion of the soil increases. It shows that the
cohesion of the soil sample increases as well as increasing of the water content in soil
sample. For internal frictional angle result, the angle of friction decreases when the
electrical resistivity decreasesas shown in Figure 4.1c.

The data above show the strength of the soil increases with incremental of the moisture

content. This correlation was expected, as the strength of a soil will decrease with
tillage, due to breakdown of natural aggregates and pores. The water will fill pore
inside the soil and reduce the effect of tillage.

30
 4.2 Electrical Resistivity Result of Different Salt Content

The experiments were conducted in two conditions, 10% and 30% of moisture

content (salt + water content) with three different values of salt content

respectively. The value of salt content are 1.6%. 1.9%, and 2.2% for 10% of

moisture content 6%, 7.5% and 9% for 30% of moisture content. The results show

as below:

Salt Content (% 1.6 1.9 2.2

Electrical 0.9393 0.8245 0.7089
Resistivity, (fim
Cohesion, c (kN/mz) 2.00 1.97 1.39
Friction angle, (°) 26.1 24.7 27 75
.

Table 4.2a: Electrical resistivity results for Different Salt Content in 10% moisture
Content

Salt Content (% 6 7.5 9

Electrical 0.3394 0.3093 0.2775
Resistivity üm
,p
Cohesion, c (kN/m2 16.7 17.5 15.4
Friction angle, D (°) 21.29 28.47 25.81

Table 4.2b: Electrical resistivity results for Different Salt Content in 30% moisture

Content

In order to look at the possible correlation of electrical resistivity obtained and

the various soil parameters, the results of the electrical resistivity can be refer to the

plotted graph. Graph for electrical resistivity versus salt content, cohesion and friction
angle are given in Figures 4.2a. 1,4.2a. 2,4.2a. 3,4.2b. 1,4.2b. 2 and 4.2b. 3 for 10% and
30% moisture content respectively.

31
 Electrical Resistivity, p (C)m)
1
0.9
0.8
0.7
0.6

0.5 Electrical Resistivity, p

0.4 (Uni)
0.3
0.2
0.1
0
0 0.5 1 1.5 2 2.5

Figure 4.2a. 1: Graph Soil Resistivity vs. Salt Content in 10% Moisture Content

Cohesion, c (kN/m2)
2.5

1.5

1 Cohesion,c (kN/m2j

0.5

0 0.5 1 1.5 2 2.5

32
 Figure 4.2a.2: Graph Soil Cohesion vs Salt Content in 10% Moisture Content

Friction angle, D (°)

28

27.5

27

26.5

26 / Friction angle, m (")

25.5

25

24.5
0 0.5 1 1.5 2 2.5

Figure 4.2a.3: Graph Friction Angle vs Salt Content in 100,

'o Moisture Content

Electrical Resistivity, p (Om)

0.4

0.35
0.3

0.25

0.2 Electrical Resistivity, p

(Om)
0.15
0.1
0.05
0
ý24ý8 10

Figure 4.2b. 1: Graph Soil Resistivity vs. Salt Content in 309%Moisture Content

33
 Cohesion,c (kN/m2)
18

17.5

17

16.5
Cohesion,c (kN/m2)
16

15.5

15
024 6 8 10

Figure 4.2b.2: Graph Soil Cohesion vs. Salt Content in 30% Moisture Content

Friction angle, D (°)

30

25
20
a
i=
15
X
Q
10 Friction angle, 0 (')

0
02468 10

Axis Title

Figure 4.2b. 3: Graph Friction Angle vs. Salt Content in 30% Moisture Content

34
 From the result given in Figure 4.2a. 1 and Figure 4.2b. I. it is clear that electrical

resistivity of the soil decreaseswith increment of salt content. Figure 4.2a.2 and Figure
4.2b.2 indicates that when the electrical resistivity decreases,the cohesion of the soil
decreases.It shows that the cohesion of the soil sample increases as well as decreasing

of the salt content in soil sample. For the internal frictional angle result, the angle of
friction decreaseswhen the electrical resistivity increasesas shown in Figure 4.3.

The data above show the strength of the soil increases with incremental of the salt

content. This correlation was expected, as the strength of a soil will decrease with
tillage, due to breakdown of natural aggregates and pores. The condition is same with

moisture content. The particle of the salt will fill pore inside the soil and reduce the
effect of tillage.

35
 4.3 Electrical Resistivity Result of Different pH Value of the Soil

The experiments were conducted by change the pH value of the soil into three
different range values which are 4.02.5.87 and 8.02. The result show as below:

pH Value of Soil 4.02 5.87 8.02

Electrical 58.525 52.32 27.652
Resistivity, p (am)
Cohesion, c (kN/m2) 11.426 9.0636 11.422
Friction angle, °) 25.07 25.17 31.82

Table 4.3a: Electrical resistivity results for Different pH value of Soil

In order to look at the possible correlation of electrical resistivity obtained and

the various soil parameters, the results of the electrical resistivity can be refer to the
plotted graph. Graph for electrical resistivity versus water content, cohesion and friction
angle are given in Figures 4.3a, 4.3b, and 4.3c.

36
 Electrical Resistivity, p (0m)
70

60

50

40
Electrical Resistivity, p
30
(Om)
20

10

02468 10

Figure 4.3a: Graph Soil Resistivity vs. pH Value of the Soil

Cohesion, c (kN/m2)
12

10

6
Cohesion, c (kN/m2)
4

02468 10

Figure 4.3b: Graph Soil Cohesion vs. pH Value of the Soil

37
 Friction angle, D (°)
35

30

25

20

15 Friction angle, m (')

10

0
024G8 10

Figure 4.3c: Graph Friction Angle vs. p11Value of the Soil

From the result given in Figure 4.3a, it is clear that electrical resistivity of the soil

decreases with increment of pH value. Figure 4.3b indicates that when the electrical

resistivity decreases, the cohesion of the soil still the same. It shows that the cohesion of

the soil sample remain same although the water content in soil sample is increasing. For
internal frictional angle result, the angle of friction increases when the electrical

resistivity decreases as shown in Figure 4.1 c.

The data above show the strength of the soil remain the same with incremental of the

salt content. This correlation was expected, as the increasing pl l value of the soil did

not increases or decreases the pores inside the soil. The effect of tillage will be the

same.

38
 CHAPTER 5
CONCLUSION & FURTHER WORK

5.1 Conclusion

The objective to establish correlation between electrical resistivity with different

condition of the soil was reached by the author. The three types of test condition by the
author in this research show significant result to the value of electrical resistivity of the

soil. The trend for all the soil testing in laboratory results behaves as follows:

PARAMETERS ELECTRICAL RESISTIVITY

Water Content, T P, J,
Cohesion, '(` p,
Frictional Angel, 4, p,

Table 5.1a: Trend of Moisture Content Result

PARAMETERS ELECTRICAL RESISTIVITY

Salt Content, 'I` p, "'
Cohesion, j, p, .L
Frictional Angel, '(` P, "L

Table 5.1b: Trend of Salt Content Result

PARAMETERS ELECTRICAL RESISTIVITY

WaterContent, p, 4,
Cohesion, = p, 4,
Frictional Angel, 'j` p, 4,

Table 5.1c: Trend of Salt Content Result

39
5.2 Further Work

Further work can be done to correlate the soil strength value with electrical

resistivity of the soil in the appropriate procedure. After that, the result should be
compare with field work method to make sure the data are applicable to be use during
the soil investigation.

These result obtained are the possible preliminary crude correlation between

electrical resistivity and some soil parameters with various soil condition. More detail
researchneed to be conducted to enhance result and to have more detail correlation.

40
 REFERENCES

1. Zeyad S.Abu-Hassanein, Craig H. Benson and Lisa R. Blotz, (1996)

"Eectrical Resistivity of Compacted Clays"
2. R.J. Kalinski, Member ASCE and W. E.KeIly (1994) " Electrical-Resistivity
Measurements for Evaluating Compacted Soil Liners"
3. William E. Kelly, M. ASCE (1985) " Electrical Resistivity for Estimating Ground

Water Recharge"

4. Rosemary Knight (1991) "Hysteresis in The Electrical Resistivity of Partially

Saturated Sandstones"

5. Andrew Binley, Siobhan Henry-Poulter and Ben Shaw (1996) " Examination of

solute transport in an undisturbed soil column using electrical resistance

tomography"
6. G. Keller and Friskhknecht (1996) "Elctrical Method in Geophysical Prospecting"

7. D. I-Iuntley (1986) " Relationship Between Permeability and Electrical Resistivity in

Granular Aquifers"

8. P.Jackson (1975) "An Electrical Resistivity Method for Evaluating the in-situ
Porosity of Clean Marine Sand

41
 APPENDICES

Appendices 1: Electrical Resistivity Test Equipment

Appendices 2: Shear Box Test Equipment

42
Electrical Resistance Data Experiment: Moisture Content

10%0Moisture Content

Vs Vr Ir R
30 4.2 0.0011 3818.18
20 2 0.0006 3214
10 0.5 0.0001 5000
Average 4010.73

15% Moisture Content

Vs Vr Ir R
30 5.02 0.003 1673.33
20 2.2 0.0013 1692.31
10 0.9 0.0003 3000
Average 2121.88

25% Moisture Content

Vs Vr Ir R

30 8.02 0.0131 612.21

20 5.09 0.0081 628.4
10 2.15 0.0032 671.88
Average 637.5

30% Moisture Content

Vs Vr Ir R

30 6.966 0.0181 384.86

20 4.5466 0.0121 375.75

10 1.9966 0.0052 383.96

Average 381.52

43
Electrical Resistance Data Experiment: Salt Content

1.6% Salt Content (10% Moisture Content)

Vs
Vs Vr
Vr Ir R

15 13.151 1.9084 6.8911

10 6.4941 1.1685 5.5576
5 3.028 0.5114 5.921
Average
Average 6.1232

1.9% Salt Content (10% Moisture Content)

Vs
Vs Vr
Vr Ir R

30 5.1789 0.9378 5.5224

20 3.6805 0.6507 5.6562
10 1.7853 0.361 4.9454
Average 5.3747

2.2% Salt Content (10% Moisture Content)

Vs Vr Ir R

30 5.294 1.2758 4.1496

20 3.5323 0.8144 4.3373
10 1.8537 0.3447 5.3777
Average 4.6215

44
Electrical Resistance Data Experiment: Salt Content (continue)

6% Salt Content (30% Moisture Content)

Vs Vr Ir R

15 3.3519 1.573 2.1309

10 2.2483 0.9883 2.2749

5 0.9814 0.4396 2.2325

Average 2.2128

7.5% Salt Content (30% Moisture Content)

Vs Vr Ir R

15 3.2678 1.3859 2.3579

10 1.9767 0.9969 1.9828

5 0.7043 0.4124 1.7078

Average 2.0162

9% Salt Content (30% Moisture Content)

Vs Vr Ir R

15 3.1544 1.5676 2.0123

10 1.8794 1.0505 1.789

5 0.6554 0.403 1.6263

Average 1.8092

45
Electrical Resistance Data Experiment: pH value of Soil

pH 4.02

Vs Vr Ir R

30 6.966 0.0181 384.86

20 4.5466 0.0121 375.75

10 1.9966 0.0052 383.96

Average 381.52

pH 5.87

Vs Vr Ir R

30 7.308 0.0213 343.1

20 4.7023 0.0138 340.75

10 2.0361 0.006 339.35

Average 341.07

pH 8.02

Vs Vr Ir R

30 7.397 0.0399 184.93

20 4.6266 0.0253 182.87

10 1.8337 0.0106 172.99

Average 180.26

46