DEVELOPMENT OF A NON-DESTRUCTIVE

TESTING APPROACH TO QUANTIFY

STRENGTH AND DEFORMATION
CHARACTERISTICS OF COHESIVE SOILS

Ali Hussnain Raza (2021-CIV-114)

Umais Murtaza (2021-CIV-119)
Muhammad Junaid (2021-CIV-127)
Muhammad Hadeed (2021-CIV-129)

PROJECT ADVISOR
DR. JAHANZAIB ISRAR

YEAR 2025

DEPARTMENT OF CIVIL ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGY
LAHORE, PAKISTAN
 DEVELOPMENT OF A NON-DESTRUCTIVE TESTING
APPROACH TO QUANTIFY STRENGTH AND
DEFORMATION CHARACTERISTICS OF COHESIVE
SOILS

A THESIS
presented to the University Engineering & Technology, Lahore in partial fulfillment
of the requirements for the degree of
Bachelors of Science
in
Civil Engineering

GROUP MEMBERS

Ali Hussnain Raza (2021-CIV-114)

Umais Murtaza (2021-CIV-119)
Muhammad Junaid (2021-CIV-127)
Muhammad Hadeed (2021-CIV-129)

INTERNAL EXAMINER EXTERNAL EXAMINER

DEPARTMENT OF CIVIL ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGY
LAHORE, PAKISTAN
 © 2025

All Rights Reserved

Any part of this thesis cannot be copied, reproduced or published without the written
approval of the Scholars
 DECLARATION

We declare the following to be our own work, unless otherwise referenced, as defined
by the University’s policy on plagiarism.
 ABSTRACT

This research develops an affordable, non-destructive method to estimate the shear

strength of clayey soils at the foundation level, using an electrical resistance megger.
While reliable, traditional soil tests like unconfined compression and triaxial tests
demand significant time, cost, and skilled labor. Existing non-destructive techniques,
including seismic and other geophysical methods, are often expensive and suit large-
scale projects, limiting their use in smaller or routine site investigations. To overcome
these limitations, this study proposes a practical approach: measuring the electrical
resistivity of clay soils to quickly estimate key shear strength parameters—
specifically cohesion and the angle of internal friction—at the foundation level. The
methodology involved preparing standard-sized soil samples with varying densities
and moisture contents under controlled laboratory conditions. We oven-dried these
samples for consistent testing and measured their electrical resistivity with a portable
electrical resistance megger. Simultaneously, we performed conventional unconfined
compression tests on companion samples to determine their shear strength parameters.
Statistical analysis revealed a clear linear relationship between soil resistivity and both
cohesion and the internal friction angle. This allowed us to develop empirical
correlations for estimating shear strength parameters directly from resistivity
measurements. The results demonstrate that this non-destructive technique predicts
shear strength values at the foundation level with an accuracy within ±10% of
conventional laboratory results. Moreover, the study shows that when the load applied
by a superstructure and the footing area are known, the estimated cohesion and
internal friction angle can be used to calculate the soil’s shear strength, aiding
foundation design decisions. This method offers a rapid, cost-effective, and user-
friendly solution for geotechnical engineers and contractors, especially in projects
where time and resources are limited.
 ACKNOWLEDGEMENT

We sincerely express our gratitude for the divine guidance and strength that have been
essential in completing this project. The lasting respect and admiration for Prophet
Muhammad ‫ ﷺ‬have continuously inspired and given deeper meaning to our work. We
are deeply thankful to Dr. Jahanzaib Israr, an exceptional mentor whose thoughtful
and motivating guidance has significantly influenced our academic path. His expert
mentorship and constant support have been crucial in managing the complexities of
this research. The genuine care and encouragement he provided energized our team to
overcome obstacles and reach the successful outcome we now celebrate. We also wish
to extend special thanks to the dedicated administrative staff, whose efficient
assistance ensured the smooth advancement of this project. Our heartfelt appreciation
goes to all participants who generously devoted their time despite demanding
schedules. Their unwavering dedication and hard work were key factors in navigating
the challenges of this research, leading to its completion. This collective effort reflects
the power of teamwork, determination, and shared commitment in the pursuit of
knowledge. We humbly acknowledge and appreciate everyone whose collaboration
and support have been vital to the success of this endeavor.
 TABLE OF CONTENTS
1 INTRODUCTION................................................................................................10
1.1 GENERAL...................................................................................................10
1.2 SIGNIFICANCE..........................................................................................10
1.3 OBJECTIVES..............................................................................................11
1.4 METHODOLOGY.......................................................................................11
1.5 SCOPE.........................................................................................................12
1.6 RESTRAINTS..............................................................................................12
1.7 RESEARCH OVERVIEW...........................................................................13
2 LITERATURE REVIEW.....................................................................................14
2.1 GENERAL...................................................................................................14
2.2 CONVENTIONAL METHODS..................................................................14
2.2.1 UNCONFINED COMPRESSION TEST............................................15
2.2.2 TRIAXIAL COMPRESSION TEST...................................................16
2.3 NON-INVASIVE METHODS.....................................................................18
2.3.1 SEISMIC & WAVE PROPOGATION METHODS...........................18
2.3.2 ELECTROMAGNETIC METHODS..................................................20
2.4 SUMMARY.................................................................................................21
3 METHODOLOGY...............................................................................................22
3.1 GENERAL...................................................................................................22
3.2 EXPERIMENTAL PHASES.......................................................................22
3.3 COLLECTION OF SAMPLES....................................................................22
3.4 SIEVE ANALYSIS......................................................................................23
3.5 SPECIFIC GRAVITY..................................................................................24
3.6 ATTERBERG LIMIT TEST........................................................................25
3.7 PROCTOR COMPACTION TEST.............................................................26
 3.7.1 STANDARD PROCTOR TEST..........................................................27
3.7.2 MODIFIED PROCTOR TEST............................................................28
3.8 SHEAR STRENGTH TESTS......................................................................29
3.8.1 UNCONFINED COMPRESSION TEST............................................30
3.8.2 TRIAXIAL COMPRESSION TEST...................................................32
3.9 RESISTIVITY MEASUREMENT..............................................................32
4 RESULTS AND DISCUSSIONS........................................................................35
4.1 GENERAL...................................................................................................35
4.2 PROPERTIES TESTS..................................................................................35
4.3 MOISTURE CONTENT..............................................................................35
4.4 SPECIFIC GRAVITY..................................................................................36
4.5 SIEVE ANALYSIS......................................................................................37
4.5.1 ORIGINAL CLAY SAMPLE..............................................................37
4.6 HYDROMETER TEST................................................................................38
4.7 ATTERBERG LIMITS................................................................................39
4.8 COMPACTION TESTS...............................................................................41
4.8.1 MODIFIED PROCTOR TEST............................................................41
4.9 SHEAR STRENGTH TESTS......................................................................42
4.9.1 UNCONFINED COMPRESSION TEST............................................42
4.10 RESISTIVITY MEASUREMENT..............................................................44
4.10.1 TRIAL TEST 1: DIRECT GROUND INSERTION METHOD..........44
4.10.2 TRIAL TEST 2: COPPER PLATE SUPPORTED CONFIGURATION
45
4.10.3 TRIAL TEST 3: STANDARD DRY SOIL SAMPLES......................46
4.11 DEVELOPMENT OF CORRELATIONS...................................................48
4.11.1 RESISTIVITY AND MOISTURE CONTENT...................................48
4.11.2 RESISTIVITY AND PLASTIC INDEX.............................................48
4.11.3 RESISTIVITY AND DRY DENSITY................................................49
4.11.4 RESISTIVITY AND COHESION (c).................................................50
4.11.5 RESISTIVITY AND ANGLE OF INTERNAL FRICTION(ϕ)..........51
5 CONCLUSIONS AND RECOMMENDATIONS...............................................52
 5.1 GENERAL...................................................................................................52
5.2 CONCLUSIONS..........................................................................................52
5.3 RECOMMENDATIONS.............................................................................53
6 REFERENCES ………………………………………………………………. 54

TABLE OF FIGURES
Figure 2-2 Unconfined Compression Test Apparatus Schematic Diagram.................15
Figure 2-3 Apparatus for CU Test Method..................................................................17
Figure 3-1 Proctor test apparatus.................................................................................27
Figure 3-2 Unconfined compression test apparatus.....................................................30
Figure 3-3 Schematic sketch of arrangement of apparatus for resistivity measurement
......................................................................................................................................33
Figure 3-4 Resistivity measurement of oven-dried clay sample..................................34
Figure 4-1 Specific gravity apparatus..........................................................................36
Figure 4-2 Sieve Analysis Gradation Curve of clay....................................................37
Figure 4-3 Hydrometer analysis gradation curve of clay.............................................39
Figure 4-4: Modified Compaction Test Curve.............................................................42
Figure 4-5: Unconfined compression test apparatus....................................................44
Figure 4-6: Trial Testing 1...........................................................................................45
Figure 4-7: Trial Testing 3...........................................................................................47

TABLE OF TABLES

Table 4-1 Moisture Content Calculation......................................................................35

Table 4-2 Specific gravity of Clay Sample..................................................................36
Table 4-3 Sieve Analysis Results of Clay....................................................................37
Table 4-4 Hydrometer test results of clay....................................................................38
Table 4-5 Liquid Limit Analysis..................................................................................39
Table 4-6 Plastic Limit Analysis..................................................................................40
Table 4-7 Atterberg limits............................................................................................40
Table 4-8 Modified Compaction Test results...............................................................41
Table 4-9 Unconfined Compression Test results.........................................................43

CHAPTER 1

1 INTRODUCTION

1.1 GENERAL
Introducing a non-destructive testing (NDT) approach to assess the strength and
deformation characteristics of cohesive soils represents a significant advancement in
geotechnical engineering. This innovative technique aims to estimate crucial soil
properties, such as shear strength and cohesion, without relying on traditional, often
invasive, methods. By leveraging electrical resistivity measurements, this approach
offers real-time, accurate insights into in-situ soil behavior under natural conditions.
Such innovations not only streamline the testing process, reducing time and costs, but
also minimize environmental disturbances associated with conventional sampling. As
research on electrical resistivity-based NDT methods continues to evolve, it paves the
way for more dependable and sustainable geotechnical practices, ultimately enhancing
foundation design and construction outcomes. This study endeavors to bridge the gap
between laboratory-based testing and field evaluations, contributing to a more
efficient, reliable, and environmentally friendly approach to soil characterization and
geotechnical design.

1.2 SIGNIFICANCE
This research introduces an innovative non-destructive testing (NDT) technique
developed to address the increasing demand for precise and practical soil evaluation
methods in geotechnical engineering. By leveraging electrical resistivity
measurements, the study creates a novel approach for assessing the strength and
deformation characteristics of cohesive soils directly in the field. A key achievement
is establishing a reliable correlation between soil resistivity and critical geotechnical
properties, such as cohesion and angle of internal friction. We rigorously validated
this correlation by comparing it with conventional laboratory tests and further refined
it through field calibration, ensuring accuracy across diverse soil conditions. The
proposed method offers a minimally invasive, cost-effective alternative to traditional
testing, promoting sustainability without compromising precision. This advancement
enables real-time soil behavior analysis, ultimately enhancing foundation design
practices and contributing to the development of more efficient, environmentally
conscious geotechnical engineering solutions.

1.3 OBJECTIVES
 Formulate a comprehensive non-destructive testing (NDT) protocol that
employs electrical resistivity to precisely determine the in-situ shear strength
and deformation characteristics of cohesive soils.
 Examine the efficacy of various measurement configurations within the NDT
framework to enhance the accuracy and dependability of soil property
assessments.
 Investigate electrical resistivity's potential as an innovative, non-invasive
metric for quantifying key geotechnical parameters like shear strength and
deformation.
 Establish a clear correlation between electrical resistivity measurements
obtained from an electrical resistance megger and the shear strength and
deformation characteristics of cohesive soils.
 Validate the proposed NDT method through extensive comparisons with both
conventional laboratory and field-testing techniques, emphasizing its accuracy
and practicality.
 Calibrate and refine the derived correlation to ensure consistent accuracy and
broad applicability across diverse soil types and field conditions.
 Evaluate the applicability, advantages, and constraints of the electrical
resistivity-based NDT approach in various soil environments and site
conditions.

1.4 METHODOLOGY
This study's methodology introduces an innovative non-destructive testing (NDT)
framework to address the demand for efficient and practical soil evaluation, offering
an alternative to traditional geotechnical practices. This approach integrates
compaction and compression tests, providing a comprehensive, cost-effective, and
rapid means to assess the in-situ shear strength and deformation characteristics of
cohesive soils.
A core element of this methodology involves establishing a reliable correlation
between soil resistivity and essential soil properties—specifically shear strength and
deformation characteristics. We achieve this by measuring soil resistivity with a
precise electrical resistance megger. To ensure accuracy, this relationship is validated
by comparing NDT results with those from conventional laboratory tests.
Once validated, the methodology includes calibrating the developed relationship,
accounting for factors that might influence soil resistivity. This calibration enhances
the approach's robustness and reliability, making it suitable for practical use at
foundation levels.

1.5 SCOPE
This thesis presents a specialized non-destructive testing (NDT) methodology focused
on evaluating the shear strength and deformation characteristics of cohesive soils
using electrical resistivity measurements. Integrating conventional compaction and
compression tests within the NDT framework, the research emphasizes innovative
techniques for capturing soil resistivity data using an electrical resistance megger.
Central to the investigation is the development of a dependable correlation between
soil resistivity and key mechanical properties, thoroughly calibrated to ensure
accuracy and reliability.
Prioritizing validation, the research rigorously compares the proposed NDT results
with those obtained from traditional geotechnical tests, ensuring both consistency and
practicality. The study systematically examines the applicability of this approach
across a range of cohesive soil types under varying environmental conditions,
highlighting the method’s adaptability and relevance to real-world geotechnical
settings.
This comprehensive assessment significantly advances the field of geotechnical
engineering by offering a reliable, efficient, and cost-effective alternative to
traditional methods. In essence, the research offers a detailed exploration into the
development and implementation of an innovative NDT methodology, aiming to
refine practices in soil strength and deformation characterization at the foundation
level.

1.6 RESTRAINTS
While developing a non-destructive testing (NDT) methodology for assessing the
shear strength and deformation characteristics of cohesive soils using electrical
resistivity, it is essential to consider several constraints. The precision of the
measuring equipment requires careful management to ensure reliable data. Variations
in soil composition, particularly the presence of sand, silt, or gravel, can affect the
method’s accuracy. Environmental factors such as moisture content, temperature, and
electrical interference can also impact resistivity measurements, necessitating
additional attention.
Furthermore, achieving consistent and accurate measurements often requires oven-
drying soil samples—a step that may not be feasible in all field conditions. The need
for thorough calibration and standardization, as well as the dependence on specialized
equipment, can limit the method’s immediate application in resource-constrained
environments. Despite these challenges, this research seeks to refine the NDT
approach for effective implementation across diverse geotechnical scenarios.

1.7 RESEARCH OVERVIEW

Chapter 1 introduces the core problem addressed by this thesis, emphasizing the
importance of the study. It outlines the research objectives, offers a brief summary of
the methodology, and defines the scope and limitations of the investigation.

Chapter 2 presents an extensive review of existing literature, focusing on identifying

gaps and limitations in previous non-destructive testing techniques. This review forms
the foundation for proposing a novel method inspired by earlier research.

In Chapter 3, the research methodology is thoroughly described, detailing the

procedures followed to meet the study’s objectives. The chapter includes an overview
of the experimental work conducted, ensuring adherence to established standards and
protocols.

Chapter 4 discusses the experimental results related to the development of a non-

destructive approach for in-situ soil density measurement. The analysis highlights key
findings and their implications for improving the NDT method.

Finally, Chapter 5 summarizes the overall research outcomes, drawing conclusions

and providing recommendations for future studies and potential improvements.
CHAPTER 2

2 LITERATURE REVIEW

2.1 GENERAL
The evaluation of in-situ soil strength and deformation characteristics through
accurate and non-invasive methods has become an increasingly important area of
study in geotechnical engineering. Conventional testing techniques, while widely
adopted, often involve intrusive procedures that disrupt the natural soil structure and
may not yield sufficiently precise results for detailed analysis. The advancement of
non-destructive testing (NDT) techniques represents a significant paradigm shift,
offering the potential for improved accuracy while preserving the integrity of the soil.
Existing literature highlights the inherent limitations of traditional methods such as
the Standard Penetration Test (SPT) and the Cone Penetration Test (CPT), particularly
in their ability to reliably capture the mechanical behavior of soil in situ. As a result,
there is growing interest in the development and application of alternative approaches
that reduce disturbance and enhance measurement accuracy. Various NDT methods,
including seismic testing, ground-penetrating radar (GPR), and other geophysical
techniques, have been investigated for their capacity to provide a more nuanced
understanding of soil strength and deformation properties. These studies emphasize
both the technical challenges involved in in-situ characterization and the potential of
NDT technologies to transform current assessment practices. In light of the increasing
demand for sustainable and performance-driven geotechnical solutions, the
development of reliable non-destructive methods for evaluating soil strength and
deformation remains a critical focus of ongoing research and innovation.
2.2 CONVENTIONAL METHODS

Conventional methods are widely used for the mechanical characterization of

cohesive soils. The two most common tests include the Unconfined Compression Test
and Triaxial Compression Tests.

2.2.1 UNCONFINED COMPRESSION TEST

o ASTM STANDARD: D2166

The Unconfined Compression Test is a simple and quick method used to determine
the unconfined compressive strength of cohesive soil samples. In this test, a
cylindrical soil specimen is loaded axially until failure without any lateral
confinement.
Although the test is cost-effective and does not require complex equipment, it does
not replicate the actual stress conditions experienced in the field. This limits its
applicability in more advanced or realistic engineering analyses.

Figure 2-1 Unconfined Compression Test Apparatus Schematic Diagram

The unconfined compression test is performed in accordance with ASTM D2166. The
procedure begins by preparing a cylindrical soil specimen with a height-to-diameter
ratio of 2:1, typically 76 mm in height and 38 mm in diameter. The ends of the
specimen are trimmed smooth and made perpendicular to the vertical axis to ensure
uniform load distribution. The specimen is then placed vertically between the plates of
a compression testing machine without any lateral confinement. Care is taken to align
the specimen properly to avoid eccentric loading. A vertical axial load is applied at a
constant strain rate, generally between 1% and 2% per minute, while the load and
corresponding deformation are recorded continuously. The loading is continued until
the specimen fails, and the unconfined compressive strength is calculated as the
maximum axial stress the soil sample can withstand during the test.

2.2.2 TRIAXIAL COMPRESSION TEST

o ASTM STANDARD: ASTM D2850/ASTM D4767

Triaxial compression tests provide more comprehensive information about the

strength of soils under controlled conditions. These tests simulate different field stress
states by subjecting a cylindrical specimen to axial and confining pressures. The two
main types used for cohesive soils are Consolidated Undrained (CU) and
Consolidated Drained (CD) tests.
The triaxial compression test is conducted according to ASTM D2850 (for
unconsolidated undrained tests) or ASTM D4767 (for consolidated undrained or
drained tests). The procedure begins by preparing a cylindrical soil specimen with a
height-to-diameter ratio of 2:1, commonly 76 mm in height and 38 mm in diameter.
The specimen is encased in a thin rubber membrane and placed between two porous
stones inside a triaxial chamber. The chamber is then filled with water, and a
confining pressure is applied uniformly around the specimen to simulate in-situ stress
conditions. Depending on the test type, the specimen may be allowed to consolidate
under this pressure. After consolidation (if applicable), axial loading is applied
through a loading piston at a constant strain rate, while the confining pressure is
maintained. Throughout the test, measurements of axial load, axial deformation, and
in some cases pore water pressure is recorded. The test continues until the specimen
fails, and the resulting data are used to determine shear strength parameters, such as
cohesion and angle of internal friction, under controlled drainage and stress
conditions.

2.2.2.1 CONSOLIDATED UNDRAINED TEST (CU TEST)

In the CU test, the soil specimen is first consolidated under a confining pressure that
simulates in-situ stress conditions. Following consolidation, the sample is sheared
without allowing drainage. As a result, pore water pressure develops during shearing,
and this pressure is measured to estimate effective stresses. CU tests are commonly
used in geotechnical engineering because they replicate the undrained conditions that
occur during short-term events such as earthquakes or rapid construction.

Figure 2-2 Apparatus for CU Test Method

2.2.2.2 CONSOLIDATED DRAINED TEST (CD TEST)

In the CD test, the soil specimen is also consolidated under a confining pressure.
However, unlike the CU test, the CD test allows drainage during the shearing phase.
This prevents the buildup of excess pore water pressure and results in a more accurate
estimation of effective stress over a longer time frame. Although the CD test provides
valuable insights into long-term soil behavior, it requires significantly more time than
the CU test.

Figure 2-4 Apparatus for CD Test

Despite the richness of data provided by these tests, they are destructive in nature,
require strict laboratory controls, and may not accurately reflect the conditions
encountered in the field.

2.3 NON-INVASIVE METHODS

In geotechnical engineering and construction, the precise assessment of in-situ soil
strength and deformation behavior is of critical importance, and non-destructive
testing (NDT) methods have emerged as essential tools in this domain. These
approaches provide efficient and reliable means of evaluating the mechanical
properties of soil without altering its natural structure or conditions. This research
seeks to explore the broad range of NDT techniques utilized in geotechnical
engineering for the assessment of soil strength and deformation characteristics. From
advanced technologies such as seismic wave propagation and surface wave analysis to
more established methods like electrical resistivity and acoustic techniques, this study
examines the practical applications, benefits, and limitations of each approach. By
highlighting the capabilities and constraints of these NDT methods, the investigation
offers a comprehensive perspective on non-invasive soil characterization in varying
geological and environmental settings. Ultimately, this work aims to enhance the
accuracy, safety, and efficiency of geotechnical investigations and to support more
informed decision-making in construction and foundation design.

2.3.1 SEISMIC & WAVE PROPOGATION METHODS

Seismic methods are widely utilized in geotechnical engineering to evaluate the
stiffness characteristics of soils, primarily through the measurement of shear wave
velocity (Vs). These techniques are particularly effective for assessing small-strain
stiffness, which refers to the soil’s response to very minor deformations, typically less
than 0.001% strain. This parameter is essential in the design of foundations, retaining
structures, embankments, and earthquake-resistant systems, as it governs the soil’s
behavior under initial loading and vibrational conditions.

Spectral Analysis of Surface Waves (SASW) and Multichannel Analysis of Surface

Waves (MASW) are commonly used surface-based seismic methods. These
techniques rely on the generation and analysis of surface wave dispersion, where
wave velocity varies with frequency due to soil layering. By analyzing dispersion
curves, engineers can derive shear wave velocity profiles, which are used to calculate
the small-strain shear modulus (G₀), a fundamental measure of soil’s initial stiffness.

Cross-hole and Down-hole Seismic Testing are borehole-based methods that offer
more precise and depth-specific measurements. In cross-hole testing, seismic waves
are generated in one borehole and recorded in another, allowing for direct
measurement of wave travel time between points at the same depth. In downhole
testing, a surface-based source generates waves that are recorded at multiple depths
within a single borehole. These methods enable the determination of both shear (S-
wave) and compressional (P-wave) velocities, which are used to compute key elastic
moduli such as shear modulus (G), bulk modulus (K), and Young’s modulus € under
small-strain conditions.
Despite their effectiveness in evaluating stiffness at low strains, seismic methods have
limitations when it comes to assessing soil strength at medium to large strains, which
are more relevant during failure or significant loading events. At these levels, soil
behavior becomes nonlinear and is influenced by factors such as pore water pressure,
plasticity, and strain history—none of which can be captured by wave velocity alone.
Therefore, additional empirical correlations, in-situ tests like the Standard Penetration
Test (SPT) or Cone Penetration Test (CPT), and laboratory tests are often required to
supplement seismic data for accurate strength analysis.

With advancements in instrumentation, data processing, and geotechnical modeling,

seismic methods are increasingly being integrated with other subsurface investigation
techniques to create more comprehensive ground models. When combined with
numerical simulations and site-specific calibration, they offer powerful capabilities
for seismic site classification, liquefaction potential assessment, and the design of
resilient geotechnical systems.

Figure 2-5 Schematic diagram of seismic reflection method

Figure 2-6 Schematic sketch of seismic refraction test

2.3.2 ELECTROMAGNETIC METHODS

Electrical and electromagnetic techniques are used to infer properties such as moisture
content, density, and clay fraction, all of which influence soil strength and behavior.

2.3.2.1 ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT)

It is a method that maps subsurface resistivity variations, helping to detect soft clay
zones and structural heterogeneity. Factors like pore water conductivity, void ratio,
and soil fabric influence the resistivity readings.
2.3.2.2 GROUND PENETRATING RADAR (GPR)
Ground Penetrating Radar (GPR) is a non-destructive testing method commonly used
in geotechnical investigations to examine subsurface conditions without disturbing the
ground. It operates by sending high-frequency electromagnetic waves into the soil and
recording the signals that reflect back from different underground features. These
reflections occur due to contrasts in material properties, such as moisture content,
density, or the presence of voids and buried objects. While GPR does not directly
measure strength or deformation characteristics, it helps identify soil layers, detect
irregularities, and assess site conditions that influence mechanical behavior. Its ability
to deliver quick, detailed subsurface profiles with minimal disruption makes GPR a
valuable tool for supporting geotechnical assessments and guiding further testing.

Figure 2-7 GPR Method

2.3.2.3 ELECTROMAGNETIC INDUCTION (EMI)

Electromagnetic Induction (EMI) is a non-destructive testing technique used in
geotechnical applications to assess subsurface soil conditions by measuring variations
in electrical conductivity and magnetic susceptibility. The method involves generating
a low-frequency electromagnetic field using a transmitter coil, which induces eddy
currents in the ground. These currents create secondary magnetic fields that are
detected by a receiver coil. Changes in the measured response are interpreted to
identify differences in soil properties such as moisture content, salinity, compaction,
and material composition. Although EMI does not directly determine strength or
deformation parameters, it provides valuable indirect information about soil
heterogeneity and conditions that influence mechanical behavior. Its non-invasive
nature, rapid data collection, and ability to cover large areas make EMI a practical
tool for preliminary site investigations and for supporting more detailed geotechnical
analyses.

Figure 2-8 EMI Method

2.4 SUMMARY
Although current non-destructive testing (NDT) techniques have significantly
contributed to advancements in geotechnical engineering, they still present several
drawbacks, such as high costs and operational complexity. There is a growing
recognition of the need for methods that offer greater precision, cost-effectiveness,
and user-friendliness. This literature review highlights the demand for more practical
solutions to in-situ soil density assessment, particularly in addressing the limitations
of existing approaches. By critically examining these shortcomings and considering
the real-world challenges encountered in geotechnical practice, it becomes evident
that a more efficient and adaptable method is required. The objective is to develop a
technique that not only resolves the current issues but also meets the practical
requirements of field engineers, delivering accurate and dependable results under
diverse site conditions.
CHAPTER 3

3 METHODOLOGY

3.1 GENERAL
The research work was conducted in several phases to thoroughly evaluate Non-
Destructive Testing (NDT) methods for measuring in situ soil density. Initially, soil
samples were collected from diverse sites, chosen to ensure a comprehensive and
representative test matrix. This diversity in sampling was crucial for the robustness of
the study, allowing for the examination of NDT methods across various soil types and
conditions. Following the sample collection, various traditional laboratory methods,
including Proctor compaction tests and permeability tests, were applied to these soil
samples. These traditional methods provided a necessary and reliable set of baseline
data, which was essential for comparing and validating the results obtained from the
NDT methods.

3.2 EXPERIMENTAL PHASES

The experimental phase of the research work consisted of the following phases:
1) Collection of soil samples
2) Sieve analysis
3) Specific gravity test
4) Atterberg limits test
5) Proctor compaction test
6) Shear strength tests
7) Resistivity measurement

3.3 COLLECTION OF SAMPLES

Soil samples of sand and clay were carefully collected from the geotechnical
engineering lab of the Civil Engineering Department at the University of Engineering
& Technology, Lahore. These samples came from different areas of the city, ensuring
a varied and representative selection of soil types. Including different soil types, each
with unique physical and chemical properties, was done to improve the relevance and
applicability of the research findings. By using a wide range of soils, the study aimed
to create an approach that could be applied to soils with different characteristics. This
variety in soil samples was essential for making sure that the results would be useful
and applicable in real-world situations, thereby increasing the reliability and
usefulness of the developed NDT methods for in situ soil density measurement.

3.4 SIEVE ANALYSIS

o ASTM Standard: C136 / C136M

Sieve analysis stands as a pivotal technique in assessing both the composition and
distribution of particles within a given material sample, offering invaluable insights
into its engineering properties. An in-depth comprehension of the particle size
distribution of these materials holds paramount importance as it directly dictates their
behavior under various conditions, including load-bearing capacities, permeability,
compaction characteristics, and overall soil performance.

Apparatus:
 Stack of sieves (4.75 mm (No. 4) to 0.075 mm (No. 200))
 Sieve Shaker
 Balance
 Sample Splitter
 Brush
 Pan
 Oven

Procedure:
1. Dry the sample in an oven at 105°C to 110°C until a constant weight is
achieved.
2. Allow the sample to cool to room temperature in a desiccator.
3. Weigh the dried sample and record the weight (W1).
4. Arrange the sieves in decreasing order of size with the pan at the bottom.
5. Place the sample on the top sieve of the stack.
6. Place the sieve stack in the sieve shaker and secure it.
7. Shake the stack for a specified duration (usually 10-15 minutes).
8. After shaking, weigh each sieve and the pan with the retained material.
9. Record the weights of each sieve and the pan.
10. Calculate the weight of material retained on each sieve by subtracting the
weight of the empty sieve from the weight of the sieve with the retained
material.
11. Calculate the cumulative weight retained by adding the weight of material
retained on each sieve to the sum of the weights retained on all coarser sieves.
 12. Calculate the percentage retained on each sieve by dividing the weight of
material retained on each sieve by the total sample weight (W1) and
multiplying by 100.
13. Calculate the percentage passing through each sieve by subtracting the
cumulative percentage retained from 100.
14. Plot the grain size distribution curve on a semi-logarithmic graph with sieve
sizes on the x-axis (log scale) and the percentage passing on the y-axis (linear
scale).

3.5 SPECIFIC GRAVITY

o ASTM Standard: D-854

The specific gravity test for soil is a fundamental procedure in geotechnical

engineering that determines the specific gravity (Gs) of soil solids. Specific gravity is
defined as the ratio of the density of the soil particles to the density of water at a
specified temperature. This parameter is essential for calculating various soil
properties, including porosity, void ratio, and soil classification. Accurate
determination of the specific gravity of soil solids provides insights into the mineral
composition of the soil, which directly influences its mechanical behavior and
suitability for various engineering applications.
Apparatus:
 Pycnometer
 Balance
 Vacuum Pump
 Thermometer
 Distilled Water
 Drying Oven
 Desiccator
 Spatula
 Funnel

Procedure:
1. Dry the soil sample in an oven at 105°C to 110°C for 24 hours to remove all
moisture.
2. Cool the dry soil sample in a desiccator to avoid moisture absorption from the
air.
3. Weigh an empty pycnometer (W1).
4. Fill the pycnometer with a known mass of the dry soil sample (about 50 grams
for fine-grained soils or 100 grams for coarse-grained soils) and weigh it (W2).
5. Add distilled water to the pycnometer containing the soil sample until it is
about half full.
 6. Agitate gently to ensure the soil is fully wetted and no air bubbles remain.
7. Use a vacuum pump to remove any entrapped air from the soil-water mixture.
Continue this process until no more air bubbles appear.
8. Fill the pycnometer completely with distilled water and ensure there are no air
bubbles.
9. Weigh the filled pycnometer with the soil-water mixture (W3).
10. Empty the pycnometer, clean it, and fill it with distilled water only. Ensure it
is filled to the same level as before and weigh it (W4).
11. Measure the temperature of the water in the pycnometer and note it down.
12. Use the following set of formulas to find out the specific gravity.

Ms=W 2−W 1

M w=W 4−W 1

M ws=W 3−W 1

M wd=M ws−M s

Gs=M s/ M wd

3.6 ATTERBERG LIMIT TEST

o ASTM Standard: D-4318

The Atterberg Limits Test is a widely used method in geotechnical engineering to

determine the moisture content at which a fine-grained soil transitions between
different states of consistency, defined by the Atterberg limits: liquid limit (LL),
plastic limit (PL), and shrinkage limit (SL). This test provides valuable insights into
the engineering properties and behavior of soils, particularly their plasticity and
potential for volume change. Its primary purpose lies in assessing the plasticity and
consistency characteristics of fine-grained soils, aiding in soil classification and
predicting soil behavior under varying loading and environmental conditions.

Apparatus:
 Liquid Limit Device
 Plastic Limit Dish
 Balance
 Oven
 Moisture cans or containers
 Spatula
 Water
Procedure:
1. Liquid Limit Test:
 Prepare a representative soil sample and place it in the liquid limit
device.
 Gradually add water to the soil while mixing until a uniform
consistency is achieved.
 Rotate the device and determine the moisture content at which the soil
begins to flow.
 Repeat the test with different moisture contents until consistent results
are obtained.
 Record the number of blows required for soil transition and calculate
the liquid limit.
2. Plastic Limit Test:
 Take a small portion of the soil sample from the liquid limit test and
place it on the plastic limit dish.
 Mold the soil into a thread of uniform diameter.
 Roll the thread into a ball and continue rolling until it crumbles.
 Repeat the process with different moisture contents until the soil no
longer forms a cohesive thread.
 Record the moisture content at which the soil crumbles and calculate
the plastic limit.

3.7 PROCTOR COMPACTION TEST

The Proctor Compaction Test is a widely used laboratory method for determining the
compaction characteristics of soil. Developed by R.R. Proctor in the 1930s, the test
identifies the optimal moisture content at which a soil type will reach its maximum
dry density. The primary purpose of the Proctor Compaction Test is to establish the
relationship between soil moisture content and dry density. By doing so, it helps
determine the ideal moisture content that allows for maximum compaction of the soil.
 Figure 3-3 Proctor test apparatus

3.7.1 STANDARD PROCTOR TEST

o ASTM STANDARD: D-698

This process involves compacting soil using a 5.5 lb. (2.5 kg) rammer dropped from a
height of 12 inches (305 mm). The soil is compacted in three layers, with each layer
receiving 25 blows from the rammer. This method ensures uniform compaction and
simulates the conditions the soil will experience in the field, providing a reliable
measure of its density and stability.

Apparatus:
 Proctor Mold.
 Manual Rammer (2.5 kg for standard proctor test)
 Sample Extruder
 Precision Balance
 Straight Edge.
 Mixing Tools
 Moisture Cans
 Controlled Oven

Procedure:
1. Gather approximately 10 lb (4.5 kg) of air-dried soil in a mixing pan, ensuring
it passes through a No. 4 sieve by breaking any lumps.
2. Add water to the soil to increase its moisture content by approximately 5%,
ensuring even distribution throughout the sample.
3. Measure the weight of the empty Proctor mould (M4) without the base plate
and collar.
 4. Securely attach the collar and base plate to the Proctor mould.
5. Place the first portion of soil into the mould and compact it with 25 blows
using a hammer. Repeat this process for other two layers, ensuring each layer
is compacted evenly.
6. Scratch each compacted layer with a spatula to ensure uniform energy
distribution. Compact each layer with 25 blows.
7. Ensure the final layer of soil extends slightly above the mould's rim with the
collar attached. Carefully remove the collar, then use a straight edge to level
the excess soil.
8. Determine the weight of the mould with the moist soil (M5). Extrude the
sample and collect a portion from the middle for water content determination.
9. Weigh an empty moisture can (M1) and weigh it again with the moist soil
sample (M2) obtained from the extruded sample. Place this can in the oven for
water content determination.
10. Break the remaining compacted soil by hand to ensure it passes through a No.
4 sieve. Adjust the moisture content by increasing it by 2%. Repeat steps 4 to
11, maintaining 25 blows for each layer with a hammer weight of 2.5 kg
dropping from a height of 30.5 cm.
11. Record the volume of the compaction mould, the empty mould weights (after
cleaning), the weight of the mould after soil compaction, and the water content
of the soil specimen. Utilize a balance sensitive to 0.01 g and 1 g for weighing
samples.
12. Oven-dry the soil samples at 110 ± 5°C for 24 hours to obtain dry weights.
Record the mass of the mould without the base and collar (M4), the mass of the
mould with moist soil (M5).

3.7.2 MODIFIED PROCTOR TEST

o ASTM STANDARD: D-1557

This version utilizes a heavier 10 lb. (4.5 kg) rammer dropped from a height of 18
inches (457 mm). The soil is compacted in five layers, with each layer receiving 25
blows from the rammer. The Modified Proctor Test is employed in scenarios requiring
higher compaction efforts, making it suitable for applications where enhanced soil
density and stability are critical. This test ensures that the soil can withstand greater
loads and provides a more robust evaluation of its compaction characteristics under
rigorous conditions.

Apparatus:
 Proctor Mold.
 Manual Rammer (3.54 kg for modified proctor test)
 Sample Extruder
 Precision Balance
  Straight Edge.
 Mixing Tools
 Moisture Cans
 Controlled Oven

Procedure:
1. Gather approximately 10 lb (4.5 kg) of air-dried soil in a mixing pan, ensuring
it passes through a No. 4 sieve by breaking any lumps.
2. Add water to the soil to increase its moisture content by around 5%, ensuring
even distribution throughout the sample.
3. Determine the weight of the empty Proctor mould (M4) without the base plate
and collar.
4. Attach the collar and base plate securely to the Proctor mould.
5. Place the first portion of soil into the mould and compact it with 25 blows
using a hammer. Repeat this process for subsequent layers, ensuring each layer
is compacted evenly.
6. Scratch each compacted layer with a spatula to ensure uniform energy
distribution. Compact each layer with 25 blows.
7. Ensure the final layer of soil extends slightly above the mould's rim with the
collar attached. Carefully remove the collar, then use a straight edge to level
the excess soil.
8. Determine the weight of the mould with the moist soil (M 5). Extrude the
sample and collect a portion from the middle for water content determination.
9. Weigh an empty moisture can (M 1) and weigh it again with the moist soil
sample (M2) obtained from the extruded sample. Place this can in the oven for
water content determination.
10. Break the remaining compacted soil by hand to ensure it passes through a No.
4 sieve. Adjust the moisture content by increasing it by 2%. Repeat steps 4 to
11, increasing the compaction effort by introducing 25 blows for each five
layers with a hammer weight of 10 lbs dropping from a height of 18 inches.
11. Record the volume of the compaction mould, the empty mould weights (after
cleaning), the weight of the mould after soil compaction, and the water content
of the soil specimen. Use a balance sensitive to 0.01 g and 1 g for weighing
samples.
12. Oven-dry the soil samples at 110 ± 5°C for 24 hours to obtain dry weights.
Record the mass of the mould without the base and collar (M 4), the mass of the
mould with moist soil (M5).

3.8 SHEAR STRENGTH TESTS

Shear strength tests are essential in geotechnical engineering to evaluate the ability of
soil to resist shear stress. Two common shear strength tests, the Direct Shear Test
(DST) and the Unconfined Compression Test (UCT), offer valuable insights into soil
behavior. Soil density, including dry density and bulk density, significantly influences
shear strength, making its measurement crucial. Higher density soils exhibit greater
shear strength due to increased particle interlock, reduced void ratio, and improved
cohesion. Denser soils have tightly packed particles, enhancing frictional resistance
and stability, while lower void ratios reduce deformation potential under stress. In
cohesive soils, increased density improves particle contact and cohesion, further
enhancing shear strength. Thus, understanding the relationship between shear strength
and soil density is vital for developing effective compaction and densification
strategies.

3.8.1 UNCONFINED COMPRESSION TEST

o ASTM Standard: D2166 / D2166M – 16

The Unconfined Compression Test (UCT) is a fundamental laboratory procedure

utilized in geotechnical engineering to determine the unconfined compressive strength
(qu) of cohesive soils, particularly clays. This test, known for its simplicity and
efficiency, provides valuable insights into the mechanical behavior of cohesive soils
under load. Unlike other compression tests, the UCT is performed without any
confining pressure, making it particularly suitable for undrained conditions where
lateral support is limited. This test allows the direct measurement of the maximum
compressive stress the soil can withstand without confinement.

Figure 3-4 Unconfined compression test apparatus

Apparatus:
 Unconfined Compression Device
 High-Precision Load and Deformation Dial Gauges
 Specialized Sample Trimming Equipment
 Precision Balance
 Moisture Cans or Containers

Procedure:
1. Carefully extrude the soil sample from the Shelby tube sampler. Cut the soil
specimen to ensure the length-to-diameter ratio (L/d) is approximately
between 2 and 2.5.
2. Measure the exact diameter of the top of the specimen at three equidistant
locations (120° apart). Repeat the measurements at the bottom of the
specimen.
3. Calculate the average of these measurements and record it as the diameter on
the data sheet.
4. Measure the exact length of the specimen at three equidistant locations (120°
apart).
5. Calculate the average of these measurements and record it as the length on the
data sheet.
6. Weigh the soil specimen accurately and record the mass on the data sheet.
7. Calculate the deformation (∆L) corresponding to 15% strain (ε) using the
formula:

Δ𝐿 = 𝜖×𝐿0

8. Carefully place the specimen in the compression device, ensuring it is centred

on the bottom plate.
9. Adjust the device so that the upper plate just makes contact with the specimen,
then set the load and deformation dials to zero.
10. Apply the load at a rate producing an axial strain between 0.5% to 2.0% per
minute.
11. Record the load and deformation dial readings at every 20 to 50 divisions on
the deformation dial.
12. Continue applying the load until one of the following conditions is met:
 The load (as indicated by the load dial) significantly decreases.
 The load remains constant for at least four successive deformation dial
readings.
 The deformation significantly exceeds the 15% strain calculated in step
5.
13. Draw a detailed sketch to depict the mode and nature of the sample failure,
noting any observable features.
 14. Carefully remove the sample from the compression device.
15. Obtain a representative sample for water content determination and follow
standard procedures to measure the water content accurately.

3.8.2 TRIAXIAL COMPRESSION TEST

o ASTM Standard: D2850 (Unconsolidated Undrained), D4767 (Consolidated
Undrained), D7181 (Consolidated Drained)
The Triaxial Shear Test is a sophisticated laboratory method used to evaluate the
shear strength and stress-strain characteristics of soils under controlled confinement.
Unlike the Unconfined Compression Test (UCT), this method applies controlled
radial pressure (σ₃) while axially loading the specimen, simulating in-situ stress
conditions more accurately. The test determines two critical geotechnical parameters;
Cohesion (c) and Angle of internal friction (φ).
The test can be conducted under three primary conditions.
 Unconsolidated Undrained (UU) – Simulates rapid loading (e.g.,
earthquakes, immediate construction loads).
 Consolidated Undrained (CU) – Models partially drained conditions (e.g.,
staged embankment construction).
 Consolidated Drained (CD) – Represents fully drained, long-term loading
(e.g., slow-moving slopes).

3.9 RESISTIVITY MEASUREMENT

The use of an electrical resistance megger to measure soil resistivity provides a
reliable, non-invasive means of evaluating the strength and deformation properties of
cohesive soils. Parameters such as shear strength are largely governed by factors
including moisture content, clay composition, pore arrangement, and saturation levels
—all of which influence the electrical conductivity of the soil.
In this method, resistivity readings are taken under varying moisture and densities,
and are then correlated with mechanical properties obtained from standard laboratory
tests such as unconfined compressive strength, triaxial shear, and consolidation tests.
Likewise, as cohesive soils undergo strain, internal changes—such as the
redistribution of pore water or alteration of the soil structure—can cause
corresponding shifts in resistivity. By examining these electrical responses alongside
stress-strain data, it becomes possible to formulate empirical models that relate
resistivity to mechanical performance. This technique offers a valuable alternative or
compliment to traditional geotechnical testing, especially in conditions where direct
sampling is impractical or may disturb the soil structure.
 Figure 3-5 Schematic sketch of arrangement of apparatus for resistivity measurement

Apparatus:
 UCS (Unconfined Compression Strength) mould
 Electrical Resistance Megger
 Precision balance
 Compacting tools
 Flat, stable surface
 Water container
 Mixing tools

Procedure:

1. Accurately measure 160 grams of the soil sample using a precision

electronic balance.
2. Adjust the moisture content of the sample by adding a pre-calculated
quantity of water, ensuring thorough mixing for uniform distribution.
3. Compact the moistened soil into an unconfined compression strength
(UCS) mould, taking care to achieve even compaction and uniform
density.
4. Gently extract the compacted sample from the UCS mould to avoid
disturbance or deformation.
5. Place the extracted specimen upright on a stable, level surface, such as a
laboratory bench, ensuring it remains undisturbed during measurement.
6. Determine the weight of the specimen using a precision balance to
calculate its bulk density.
7. If the sample exhibits high moisture content, oven-dry it at 105°C for 24
hours. For adequately dry samples, this step may be omitted.
8. Insert the megger probes into the specimen following the schematic layout,
ensuring correct and stable probe placement.
9. Power on the megger and take resistivity readings at a maximum voltage
setting of 1000V.
10. Record the measured resistivity values and compute the average to obtain a
representative value.
11. Document any observations that may influence measurement accuracy,
such as visible soil inconsistencies or ambient environmental factors.
12. Repeat the procedure for additional soil specimens prepared with varying
moisture contents and compaction levels.
13. Ensure all samples are prepared and tested under consistent laboratory
conditions to maintain reliability and comparability of results.

Figure 3-6 Resistivity measurement of oven-dried clay sample

CHAPTER 4

4 RESULTS AND DISCUSSIONS

4.1 GENERAL

After completing the tests, we carefully analysed the collected data to evaluate the
engineering properties of various soil samples. The Maximum Dry Density and
Optimum Moisture Content were determined using both the Standard Proctor test
(ASTM D698) and the Modified Proctor test (ASTM D1557). Additionally, we
evaluated the soil's shear strength through Direct Shear tests (ASTM D3080) and
Unconfined Compressive Strength (UCS) tests (ASTM D2166), which provided
insight into the soil’s resistance to deformation and failure under load. By thoroughly
following each testing procedure and interpreting the results, we developed a detailed
understanding of the soil’s behaviour, supporting well-informed decisions in
geotechnical design and construction planning.

4.2 PROPERTIES TESTS

Comprehensive property tests were performed on the collected soil samples, and the
resulting data were thoroughly analysed and examined. The analysis emphasizes the
importance of each tested property and discusses their relevance to the study’s core
objectives. These tests offered critical insights into the soil’s composition, structure,
and behaviour, thereby enhancing our overall understanding of the soil characteristics
vital to the research.

4.3 MOISTURE CONTENT

Natural moisture content of cohesive soil is a crucial parameter for cohesive soils. The
moisture content of the procured cohesive soil was determined by standard oven-dry
method. The results obtained are as follows:

Moisture Content
Weight of Empty Can W1 15.34
Weight of Can+soil W2 38.72
Weight of Can+soil after oven dry W3 35.89
% Moisture Content M.C. 13.7713

Table 4-1 Moisture Content Calculation

4.4 SPECIFIC GRAVITY

The specific gravity test is a fundamental component of soil analysis, offering vital
information about soil density and composition that significantly supports non-
destructive testing (NDT) techniques for determining in-situ soil density. By applying
the pycnometer method to accurately measure specific gravity, we gain insight into
the soil’s mineral content, porosity, and level of compaction. These measurements are
essential for calibrating NDT equipment and establishing reliable correlations
between soil characteristics and NDT outputs, such as electrical resistivity. Specific
gravity plays a key role in interpreting NDT data, ensuring the accuracy and reliability
of in-situ density evaluations. Integrating specific gravity into NDT models improves
their precision and predictive power, enabling accurate, non-invasive assessments of
soil conditions critical for geotechnical engineering tasks such as foundation analysis
and slope stability evaluation.

Figure 4-7 Specific gravity apparatus

Specific Gravity

Wt. of volumetric flask W1 25.5g

Wt. of volumetric flask + soil W2 60.3g

Wt. of volumetric flask + soil + water W3 90.5g

Wt. of volumetric flask + water W4 77.54g

Temperature T 18°C

Temperature Correction Factor α 0.9988

Specific Gravity GS 2.707

 Table 4-2 Specific gravity of Clay Sample

4.5 SIEVE ANALYSIS

Sieve analysis was carried out on the samples of clay. Distribution curve b/w the sieve
size and percentage passing has been plotted.

4.5.1 ORIGINAL CLAY SAMPLE

Sieve Sieve Wt. Cumulative % Wt. % Passing

No. Size Retained Wt. Retained Retained
mm grams grams
3/4" 19.05 0 0 0 100
4 4.75 3 13.11 13.11 86.89
10 2 4.98 34.86 21.76 65.14
40 0.425 2.6 46.22 11.36 53.78
100 0.15 4.89 67.58 21.36 32.42
200 0.075 7.42 100 32.42 0

Table 4-3 Sieve Analysis Results of Clay

Sieve Analysis
Clay Sample
120.00%
Percent Finer by Weight (%)

100.00%

80.00%

60.00%

40.00%

20.00%

0.00%
100 10 1 0.1 0.01
Grain Size (mm)

Figure 4-8 Sieve Analysis Gradation Curve of clay

 4.6 HYDROMETER TEST
Hydrometer analysis is a laboratory technique used to determine the particle size
distribution of fine-grained soils, especially silt and clay particles that are too small to
be analyzed by sieve analysis. It measures the relative density of a soil-water
suspension over time, using a hydrometer.

Corr.
Act. Corr. % for
T Reading Reading Finer Meniscus L L/t K D
Time °C - - % - cm cm/min - mm
min 17 33 27.3 53.99% 33 8.4 8.4 0.01408 0.04081
1 17 29 23.3 46.08% 29 9.2 4.6 0.01408 0.0302
2 17 25 19.3 38.17% 25 9.9 3.3 0.01408 0.02558
3 17 22 16.3 32.24% 22 10.4 2.6 0.01408 0.0227
4 17 21 15.3 30.26% 21 11.4 1.425 0.01408 0.01681
8 17 15 9.3 18.39% 15 12.2 0.813 0.01408 0.0127
15 17 12 6.3 12.46% 12 13.3 0.443 0.01408 0.00937
30 17 9 3.3 6.53% 9 14.8 0.247 0.01408 0.00699
60 17 6 0.3 0.59% 6 15.5 0.129 0.01408 0.00506

Table 4-4 Hydrometer test results of clay

Figure 4-3: Hydrometer Test Apparatus

 Hydrometer Analysis
Original Clay Sample
60.00%

PERCENT FINER BY WEIGHT (%)

50.00%
40.00%
30.00%
20.00%
10.00%
0.00%
-10.00%
0.10000 0.01000 0.00100
GRAIN SIZE (MM)

Figure 4-9 Hydrometer analysis gradation curve of clay

4.7 ATTERBERG LIMITS

Atterberg Limits are a set of standardized tests used to describe the critical water
content at which fine-grained soils change their behavior and consistency. They
include three main limits:

 Liquid Limit (LL): The water content at which soil changes from a plastic to
a liquid state.
 Plastic Limit (PL): The water content at which soil changes from a semi-solid
to a plastic state.

Can No. 38 77-B 21 65

Wt. of wet soil + can W1 g 26.84 20.6 26.52 23.74
Wt. of dry soil + can W2 g 23.94 18.38 24.07 21.18
Wt. of can W3 g 13.26 10.99 16.13 15.29
Wt. of dry soil WS g 10.68 7.39 7.94 5.89
Wt. of moisture WW g 2.9 2.22 2.45 2.56
30.04 30.86 43.46
Water content ω 27.15%
% % %
No. of blows N 19 24 34 35
L.L 33.36

Table 4-5 Liquid Limit Analysis

 Liquid Limit
Moisture Content vs No. of Blows Curve
Trendline
30.00%
Moisture Content W (%)
29.50%
29.00%
28.50%
28.00%
27.50%
27.00%
10
No. of Blows (N)

Figure 4-5: Liquid Limit Curve

Can No. 98 115 50 212

Wt. of wet soil +
W1 g 15.44 53.84 33.85 14.18
can
Wt. of dry soil +
W2 g 14.91 49.36 30.55 13.9
can
Wt. of can W3 g 14.12 32.84 14.11 12.88
WS = W2 -
Wt. of dry soil g 0.79 16.52 16.44 1.02
W3
WW = W1 -
Wt. of moisture g 0.53 4.48 3.3 0.28
W2
67.09 27.12 20.07 27.45
Water content ω
% % % %
Plastic Limit P.L. 35.43%

Table 4-6 Plastic Limit Analysis

Sample Liquid Limit Plastic limit Plasticity index

Clay 33.36 35.43 33

Table 4-7 Atterberg limits

4.8 COMPACTION TESTS
Modified Proctor test is vital for determining the Maximum Dry Density of cohesive
soils and crucial for geotechnical analysis. By compacting soil samples at varying
moisture contents and energy levels, these tests simulate real-world conditions,
offering insights into soil compaction characteristics essential for construction
practices. Relating to non-destructive testing (NDT), the Maximum Dry Density
values obtained from Proctor tests serve as key reference points for calibrating NDT
methods.

Figure 4-5: Compaction Test Lab Apparatus

4.8.1 MODIFIED PROCTOR TEST

The modified proctor test was performed on the procured cohesive soil sample as per
standard procedure by ASTM D1557-12. The obtained results are shown as follows:

SAMPLE TEST MAXIMUM DRY OMC

DENSITY
g/cc %
Clay Modified compaction 1.95 12.5

Table 4-8 Modified Compaction Test results

 Modified Compaction
Test
Compaction Curve
Polynomial (Compaction Curve)
Zero Air Void Curve
24
23
22
Dry Density yd (kN/m3)

21
20
19
18
17
16
15
5.00% 7.00% 9.00% 11.00% 13.00% 15.00% 17.00%
Moisture Content w (%)

Figure 4-10: Modified Compaction Test Curve

4.9 SHEAR STRENGTH TESTS

The shear strength test determines the maximum shear stress that soil can resist before
failure occurs. Shear strength is a critical property for evaluating the stability of
slopes, foundations, and retaining structures. It depends on factors like soil type,
moisture content, and loading conditions.
Shear strength is influenced by cohesion (c) and internal friction angle (φ), and is
typically expressed using the Mohr-Coulomb failure criterion:

τ =c +σ∗tan(φ)

4.9.1 UNCONFINED COMPRESSION TEST

The unconfined compression test (UCS) was performed on 2 samples of cohesive
soils of different origins and the results were found to be quite comprehensive and
accurate.
 Mohr-Coulomb Failure
Envelope
Shear Stress (kPa) Kasur Sample Nandipur Sample
350.000
300.000
f(x) = 304.031664155867
250.000
200.000
150.000 f(x) = 176.572235721292
100.000
50.000
0.000
0.000 100.000 200.000 300.000 400.000 500.000 600.000 700.000

Normal Stress (kPa)

Figure 4-5: Unconfined Compression Test

Clay Sample Cohesion

kPa
Kasur 176.57
Nandipur 304.03

Sample Peak axial Peak shear

stress stress

Clay kPa kPa

353.14 176.57

Table 4-9 Unconfined Compression Test results

 Figure 4-11: Unconfined compression test apparatus

4.10 RESISTIVITY MEASUREMENT

Multiple trials were conducted to measure resistivity accurately and ensure the
reliability of the results. During testing, several challenges arose, mainly due to the
influence of real-world conditions. These difficulties required modifications and
improvements to the testing procedure. A detailed discussion of the testing process,
the obstacles encountered, and the solutions applied is provided in detail below:

4.10.1 TRIAL TEST 1: DIRECT GROUND INSERTION METHOD

The preliminary experiment represents the most basic and uncomplicated approach to
testing the electrical properties of soil. In this setup, two metal knobs are inserted
directly into the ground's surface. These knobs are positioned at shallow depth merely
2 mm beneath the surface guaranteeing minimal soil disturbance while still allowing
for the establishment of a conductive pathway. This experiment is conducted using
three varying distances between the electrodes. These varying separations seek to
assess how the spacing between electrodes affects the electrical readings obtained,
such as potential difference, current flow, or resistivity.

The simplicity of this setup provides a clear, immediate link to the earth. Because
there are no structural or material supports such as plates or containers the data
obtained from this setup are greatly affected by the soil's natural properties during the
test. Factors such as humidity, soil makeup, density, and temperature can significantly
influence the results. A damp, loamy soil may show reduced resistance due to
enhanced ionic movement, while dry or sandy soils might reveal increased resistance
readings. Moreover, the restricted insertion depth indicates that only the upper layer
of the soil is involved in the measurement, which may not accurately represent the
properties of deeper subsurface layers.
Utilizing different spacing intervals offers valuable insights into the changes in
electric field distribution or soil resistance with varying distances. As separation
increases, the current path extends, and resistance is anticipated to increase
correspondingly, assuming consistent soil conditions. However, in natural soil,
fluctuations can disrupt this pattern, making these experiments useful for mapping soil
resistivity in the field or identifying buried objects and anomalies.

Figure 4-12: Trial Testing 1

4.10.2 TRIAL TEST 2: COPPER PLATE SUPPORTED CONFIGURATION

The second trial presents a more regulated and technically sophisticated experimental
configuration aimed at enhancing the consistency, precision, and dependability of
electrical measurements in soil. In contrast to the initial trial that involved directly
inserting the knobs into the ground, Trial 2 uses vertical copper rods that are first
placed into the soil. The measuring terminals or knobs are then firmly connected to
these rods. This structural modification signifies a notable improvement compared to
the earlier trial.
The copper rods fulfill several significant roles. To begin with, copper serves as an
outstanding electrical conductor, guaranteeing that the signals or current flowing
through the knobs are conveyed with little resistance and signal loss. Secondly, the
arrangement stabilizes the contact point by embedding the rods into the ground and
connecting the knobs to them, minimizing the likelihood of inconsistent readings due
to uneven insertion or environmental factors like vibrations or shifting soil.
All tests in this trial employ the same spacing setups as Trial 1: 100 mm, 200 mm, and
300 mm intervals between rods (and consequently the connected knobs). The knobs in
this instance are located 10 mm above the ground level, affixed to the vertical rods.
This height adds a vertical aspect to the experiment, slightly raising the measurement
area above the ground level, which is crucial for examining electric field interactions
just above the surface or imitating elevated electrode setups seen in real-world
applications (such as buried cable surveillance or ground-penetrating sensors).
This controlled environment probably minimizes the variability induced by elements
like soil surface texture, organic matter, and moisture loss that often impact shallow or
surface electrodes. Additionally, employing copper rods guarantees a more profound
and stable ground connection, offering a clearer electrical path and aiding in the
measurement of more reliable field values.
Through the analysis of data gathered at various spacing intervals, researchers can
gain insights into how electrode distance relates to voltage drop, electric field
intensity, or soil resistivity. The raising and backing of the electrodes further aid in
mimicking more authentic field scenarios, particularly in modeling underground
setups or electrode configurations utilized in precision farming, soil cleanup, or
geophysical exploration.

Figure 4-7: Trial Testing 2

4.10.3 TRIAL TEST 3: STANDARD DRY SOIL SAMPLES

The third trial is the most advanced of all and represents a completely regulated
laboratory experiment in which external variables are reduced. In this setup, a
cylindrical soil specimen is created and employed as the measurement medium. The
cylinder measures 3.6 cm in diameter and 7.2 cm in height. This sample is detached
from the outside environment, facilitating consistent compaction, moisture
distribution, and structural uniformity. The aim is to examine the electrical
characteristics of soil in strictly regulated conditions, removing the unpredictability
linked to in-situ field assessments.
After the soil is compressed into the cylinder, the knobs are placed into the sample at
designated spots. In two configurations, the knobs are positioned 2 mm within the
cylindrical side walls, located directly across from each other at the cylinder's mid-
height. This side placement mimics the flow of current through the sample's
horizontal cross-section and is perfect for assessing uniformity, conductivity, and the
distribution of the electric field within the soil. In the third variation, the knobs are
embedded into the top and bottom surfaces of the cylinder, forming a vertical
electrode arrangement. This arrangement allows for the examination of current flow
or electric field intensity throughout the height of the soil column, providing insights
into vertical resistivity or stratification influences. This regulated method is ideal for
calibration, material assessment, or comprehensive analyses of particular soil
responses to electric fields.
The measurements recorded in this experiment are generally more precise and
dependable due to the contact between the electrodes and soil being clear, stable, and
uniform. In a lab environment, temperature, humidity, and external vibrations can be
closely monitored or managed, unlike in-field methods. The outcomes from this trial
can serve to verify models or to evaluate field equipment.

Figure 4-13: Trial Testing 3

Figure 4-8: Pictorial Representation of Electrode Configuration

4.11 DEVELOPMENT OF CORRELATIONS
The relationship between different soil parameters and resistivity is established
through a series of carefully developed formulas. Based on extensive testing of
various soil samples, the research team formulated and refined these equations to
ensure accuracy. The step-by-step derivation of this correlation is thoroughly
explained in the sections that follow. By applying these formulas systematically, the
study seeks to shed light on the intricate link between different soil parameters and
resistivity.

4.11.1 RESISTIVITY AND MOISTURE CONTENT

The resistivity values were analysed for accuracy and relevance in soil density
assessment, while the moisture content as provided. Using our device, we determined
resistivity values, while moisture content was measured using conventional methods.
This dual approach allowed us to evaluate the performance and reliability of our non-
destructive testing device as a benchmark for comparison. This integrated
methodology ensures precise and contextually relevant data, advancing non-
destructive soil testing.

Figure 4-9: Resistivity-Moisture Content Curve

4.11.2 RESISTIVITY AND PLASTIC INDEX

The graph illustrates a clear inverse relationship between soil resistivity and plasticity
index, showing that as resistivity increases, the plasticity index generally decreases. In
contrast, soils like pure sand, which have low plasticity and little moisture retention,
exhibit very high resistivity. The regression line and the moderate R2 value supports
this trend, suggesting that while plasticity influences resistivity, other factors such as
moisture content and mineral composition may also play a role. Overall, the graph
effectively demonstrates how soil composition impacts its electrical behavior.

Y =−0.0104 x +38.403
2
R =0.3875
 Figure 4-10: Resistivity-Plasticity Curve

4.11.3 RESISTIVITY AND DRY DENSITY

The graph shows a positive relationship between dry density and resistivity, indicating
that as the resistivity of the soil increases, its dry density also tends to increase. This
trend is reflected by the upward-sloping regression line, suggesting a moderate
correlation. The data points reveal that clay-rich soils generally have lower dry
densities and lower resistivity, likely due to their higher porosity and moisture
retention, which reduce particle packing and enhance electrical conductivity. In
contrast, the sand sample, which displays the highest resistivity, also shows the
highest dry density, reflecting its compact and less porous structure that restricts ionic
movement and leads to greater electrical resistance. Although the correlation is not
extremely strong due to the influence of other factors such as moisture content,
mineral composition, and soil texture, the graph supports the general idea that denser
soils particularly non-cohesive ones like sand tend to exhibit higher resistivity.

Y =0.0002 x +1.6413
2
R =0.333

Figure 4-11: Resistivity-Dry Density Curve

4.11.4 RESISTIVITY AND COHESION (c)
The relationship between resistivity and the cohesion of the soil was established using
two different standard tests, which are discussed separately as follows:

4.11.4.1 UNCONFINED COMPRESSION TEST

The unconfined compression test on cohesive soil sample verified the trend as
highlighted in previous studies.

Y =0.4601 x – 314.4
2
R =1

Figure 4-12: Resistivity-Cohesion Curve 1

4.11.4.2 TRIAXIAL COMPRESSION TEST

The triaxial compression test on cohesive soil sample verified the trend as highlighted
in previous studies.

Y =0.4601 x – 314.4
2
R =1
 Figure 4-13: Resistivity-Cohesion Curve 2

4.11.5 RESISTIVITY AND ANGLE OF INTERNAL FRICTION(ϕ)

The relationship between resistivity and the angle of internal friction of the soil was
established using through triaxial compression tests, which are discussed separately as
follows:

Y =0.1417 x+22.718
2
R =1

Figure 4-14 Resistivity-Angle of Internal Friction Curve

CHAPTER 5

5 CONCLUSIONS AND RECOMMENDATIONS

5.1 GENERAL
In this chapter, a succinct summary of the key findings and conclusions drawn from
the data presented in earlier chapters is provided. Furthermore, the limitations
encountered in the course of the study are highlighted, and recommendations for
potential avenues of future research on the subject are proposed.

5.2 CONCLUSIONS
1. By applying the correlation developed in this study, the shear strength of
cohesive soils can be estimated by measuring soil resistivity. This
measurement, in turn, helps establish relationships between resistivity,
moisture content, dry density, plasticity index, cohesion, and internal friction
angle.

2. By applying the sequence of equations established and validated through

experimental work in this study, the shear strength of cohesive soils can be
determined.

c=0.4061∗R−314.4
Φ=0.1417∗R+22.718
б =Applied Load /Footing Area

т=c+б∗tan(ϕ )

3. The developed correlation applies to all cohesive soils containing minimal

amounts of sand, silt, and their combinations at the foundation level. However,
it does not apply to soils with significant gravel content.

4. Environmental factors such as soil moisture, proximity to electrical

installations, vegetation, and temperature changes can affect the reliability of
soil resistivity readings. Variations in moisture levels can influence the soil's
conductive properties, thereby altering measurement results. Additionally,
 electrical currents from nearby power lines, underground cables, or pipelines
can generate stray currents in the soil, causing interference with the testing.
Fluctuations in temperature may also affect the calibration of the measuring
device, impacting the accuracy of the recorded data.

5. Depending on empirical correlations to link electrical measurements with soil

properties naturally brings some degree of uncertainty, as these models are
often tailored to specific soil types and conditions. Differences in soil
composition, such as variations in mineral content and the presence of organic
matter, can affect the precision of these correlations.

6. The design, configuration, and interaction of the probe with the soil are key
factors influencing the accuracy of measurements. Maintaining consistent
contact between the probe and the soil is essential to obtain reliable data. Any
inconsistency in contact can lead to measurement errors.

5.3 RECOMMENDATIONS
1. Conduct minimum conventional geotechnical tests at the foundation design
depth to confirm and support the findings obtained through the non-destructive
testing methods outlined in this study.

2. Perform on-site calibration of the measurement instruments, adjusting for

actual soil characteristics and environmental conditions to improve data
accuracy.

3. Combine non-destructive testing results with traditional testing data to provide

a more thorough and reliable evaluation of soil properties for foundation
design.

4. Consider site-specific variables such as soil heterogeneity and environmental

influences during data analysis, and adapt testing methods accordingly to
ensure reliable outcomes.

5. Implement a comprehensive quality control program that includes cross-

validation of NDT results with traditional testing, ensuring data integrity and
enhancing confidence in soil property assessments for foundation engineering.
 6. REFERENCES
1. ASTM D2166 / D2166M – 16: Standard Test Method for Unconfined
Compressive Strength of Cohesive Soil.
2. ASTM D2850: Standard Test Method for Unconsolidated-Undrained Triaxial
Compression Test on Cohesive Soils.
3. ASTM D4767: Standard Test Method for Consolidated Undrained Triaxial
Compression Test for Cohesive Soils with Pore Water Pressure
Measurements.
4. ASTM D698: Standard Test Method for Laboratory Compaction
Characteristics of Soil Using Standard Effort (12,400 ft-lbf/ft³ or 600
kN-m/m³).
5. ASTM D1557: Standard Test Method for Laboratory Compaction
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m/m³).
6. ASTM D4318: Standard Test Methods for Liquid Limit, Plastic Limit, and
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7. ASTM D854: Standard Test Methods for Specific Gravity of Soil Solids by
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8. ASTM C136 / C136M: Standard Test Method for Sieve Analysis of Fine and
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9. ASTM D3080: Standard Test Method for Direct Shear Test of Soils Under
Consolidated Drained Conditions.
10. ASTM D7181: Standard Test Method for Consolidated Drained Triaxial
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