Clay soil posses a great threat causes problem on civil engineering structures due to its tendency to swell when it is in contact with water and shrinks when they dry out. Stabilization using chemical admixtures is the oldest and popular method of soil improvement. In this study, an investigation was conducted to explore the possibility of using processed termite mound as a stabilizing admixture to improve clay soils. This investigation involves the determination of the swelling potential of expansive soil in its natural state as well as when mixed with varying proportion of termite dust from (0 to 30%). The processed termite mound in this experimental work is obtained from termite mound (anthill), dried and ground followed by sieving through sieve no.36. Consistency limits, specific gravity, swelling properties were determined for the samples. Addition of processed termite mound decreases liquid limit, plasticity index, plastic limit, shrinkage limit, shrinkage index, specific gravity and activity. Experimental results also showed that the swelling percentage decreased while rate of swell increased with increasing percentage of processed termite mound content. The rates of swelling and swelling percentage of the stabilized specimens were also affected by curing in a positive direction such that the effectiveness of the stabilizer increased with termite mound content. The CBR and UCS values obtained also increases with stabilizer content. Based on results obtained from the study, the use of 25%-30% termite mound is recommended for the improvement of clay as sub-grade material.
TABLE OF CONTENTS
Approval page i
Certification page ii
CHAPTER ONE: INTRODUCTION 9
1.1 Background of the Study 9
1.2 Aim of Study 9
1.3 Significance of Study 9
1.4 Scope of Work 9
CHAPTER TWO: LITERATURE REVIEW 12
2.1 Clay Soils 12
2.2 Clay Mineralogy and Major Groups 12
2.3 Mechanism of Swelling 13
2.4 Factors Affecting Swelling 16
2.5 Termites 16
2.6 Design and Analysis of Experiments 17
2.7 Model Derivation 18
2.61 Least Squares Estimation of the Model Parameters. 20
CHAPTER THREE: MATERIALS AND METHOD 22
3.1 Sample Collection and Preparation 22
3.2 Experimental Tests 22
3.2.1 Plastic Limit 23
3.2.2 Liquid Limit 24
3.2.3 Plasticity Index 24
3.2.4 Compaction Test 25
3.2.5 California Bearing Ratio Test 25
3.2.6 Unconfined Compressive Strength Test 26
CHAPTER FOUR: RESULTS AND DISCUSSION 27
4.1 Identification of Soil and Processed Termite 28
4.2 Compaction Characteristics 29
4.3 Consistency Limits 29
4.4 California Bearing Ratio 30
4.5 Unconfined Compressive Strength 31
4.6 Response Surface Methodology of Processed Termite Stabilized
Soil and Model Verification 35
4.6.1 Optimum Moisture Content 37
4.6.2 Maximum Dry Density 39
4.6.3 California Bearing Ratio (Unsoaked) 40
184.108.40.206 California Bearing Ratio (Soaked – 4 Days) 42
4.6.4 Unconfined Compressive Strength (4-Days) 43
4.7 Model Verification 44
CHAPTER FIVE: CONCLUSIONS 54
5.1 Recommendations 56
Some partially saturated clayey soils are very sensitive to variations in water content and show excessive volume changes. Such soils, when they increase in volume because of an increase in their water contents, are classified as expansive soils. Problem of clayey soils has appeared as cracking and breakup of pavements, railways, highways, embankments, roadways, building foundations, channel, irrigation systems, etc. (Wayne et al. 1984).
It is reported that damage to structures due to clayey soils has been the most costly natural hazard in some countries. In the United States damage caused by clayey soils exceeds the combined average annual damage from floods, hurricanes, earthquakes, and tornadoes. (Jones and Holtz, 1973). Documented evidence of the problems associated with clayey soils is worldwide, having occurred in such countries as the United States, India, China, Canada and regions in Europe. (Popescu, 1986). It is reasonable that studies on the problem of clayey soils become more important day by day if the durative deficit of World resources and economy is taken into consideration. (Ipek, 1998). When geotechnical engineers are faced with clay soils, the engineering properties of those soils may need to be improved to make them suitable for construction. (Muntohar and Hantoro, 2000).
1.1 BACKGROUND OF THE STUDY
Clayey soil is a term used for soils which exhibit moderate to high plasticity, low to moderate strength and high swell and shrinkage characteristics (Holtz and Gibbs, 1956). They are often considered a potential natural hazard, likely to cause extensive damage to structures, roads etc if not adequately treated. These soils are more difficult to deal with than collapsible soils because collapsible is a one way process, whereas clayey soils can shrink and swell as the case may be. Such soils swell when given an access to water and shrink when they dry out (Al-Rawas et al. 2002). Some saturated clayey soils are partially very sensitive to variations in water content and show excessive volume changes. Such soils increase in volume as a result of an increase in water content.
Generally, they have high plasticity and are relatively stiff or dense. Its nature is most obvious near the ground surface where the profile is subjected to seasonal and environmental changes. The pore water pressure is initially negative and the deposit is generally unsaturated. These soils often have some montmorillonite clay mineral present. The higher the amount of monovalent cations absorbed to the clay mineral (e.g. sodium), the more severe the soil problem (Fredlund and Rahardjo, 1969).
Termite clay is obtained from termite mound, while mound is a pile of earth made by termite resembling a small hill. It is made of clay whose plasticity has further been improved by the secretion from the termite while being used in building the mound ( Minjinyawa et al. 2007) It is therefore a better material than the ordinary clay in terms of utilization for moulding lateritic bricks ( Minjinyawa and Odumodu et al. 2007) and this type of clay has been reported to perform better than ordinary clay in dam construction ( Yohanna et al. 2003). The clay from the termite mound is capable of maintaining a permanent shape after moulding because of its plasticity; it is also less prone to crack when compared with ordinary clay. In addition, it has low thermal conductivity and expectedly reduced solar heat flow and temperature fluctuation within an enclosure( Minjinyawa et al. 2007).
The problem of these soils has appeared as cracking and break-up of pavements, railways, highway embankments, roadways, building foundations slab-on-grade members, channel, reservoir linings, irrigation systems, water lines and server lines ( kehew 1995). Detailed and documented evidence of the problems associated with soils that are clayey in nature is worldwide. It occurs in most of these countries such as India, Canada, Australia, China, United states, regions in Africa and Europe ( Popescu 1986).
It is important and reasonable that, studies regarding the problem of clay soils become imperative day by day if the durative deficit of the world resources and economy is taken into consideration. When geotechnical engineers are faced with clay soils, the engineering properties of these soils need to be improved to make them suitable for construction ( Okafor et al. 2009). To study the model of strength determination of soil to the processed termite stabilized soil using Scheffe’s second degree polynomials, to check the empirical models results and compare it to the experimental results in the absence of strenuous laboratory results, to check the unconfined compressive strength ofprocessed termite and the CBR values of expansive soil. The purpose of this experimental study is to investigate the potential ofprocessed termite as a stabilizing agent for expansive soil.
1.2 AIM AND OBJECTIVE OF STUDY
- To investigate the potentials of processed termite mound as a stabilizing agent in clay soils.
- To determine if there exist, a relationship between processed termite mound model and the experiment.
1.3 SIGNIFICANCE OF STUDY
- To develop empirical models that can be used to predict the behaviour of soil processed termite mound stabilization.
- It will help reduce pressure on the use of cement for soil stabilization thereby conserving the country foreign reserve.
- To cut-down the cost of unsuitable materials in road construction.
1.4 SCOPE OF WORK
This research work, only covers soils that are clayey in nature.
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