Quarry dust is a by-product of rubble crusher units and is a commonly available material, due to the vast usage of crusher metal in the construction industry. This product can be used to improve engineering properties of high plasticity silty (MH) soils, in order to develop a cost effective method for highway sub-grade construction. As such, research reported in this paper illustrates the effect of using of quarry dust' as an admixture to improve the engineering properties of high plasticity silty soils with combination of cement. High plasticity silty soils which were rejected by one of the main road construction projects in Sri Lanka, were selected as the test samples. These high plasticity silty soils were mixed in the laboratory with different percentages of quarry dust and 2% of cement, on the weight and left to harden for a period of seven days. Further, shear strength behavior of soil-quarry dust mixes were presented in this paper. The results of the subsequent tests revealed that even mixing with only quarry dust, caused appreciable improvement in engineering characteristics of poor quality soils. It was found that this improvement can be significantly enhanced with the addition of 2% of cement. Therefore, problems associated in the construction of highways over clayey sub grade, can be reduced significantly by mixing with quarry dust and cement.

Due to formation of shrinkage cracks in landfill clay liners in dry zone of Sri Lanka leads to infiltration of leachate into ground during the rainy season. Therefore, in this research study, shrinkage behaviour of expansive soil available in dry zone of Sri Lanka, which is used to develop compacted clay liners, were evaluated using laboratory desiccation plate tests. Circular desiccation plates with different thicknesses were used for the experiments. A series of tests have been carried out with unamended soil and soil amended with different percentages of bentonite. Further, shrinkage behaviour was studied by amending oleic acid and coconut coir fibers into the soil. Digital image processing technique has been used to determine the Crack Intensity Factor (CIF). Crack initiation time under different configuration was recorded. Based on visual observations, it can be seen that all samples produce predominantly orthogonal crack patterns leading to sub division of crack area in to smaller cells. Higher desiccation rate was observed for smaller thickness of soil specimen. In addition, higher CIF was recorded for the bentonite amended soil. It was noted that shrinkage cracks can be controlled by amending soil with coconut coir fibers.

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Soil nailing is a technique which is used to reinforce and strengthen the existing ground conditions. This is done by installing closely spaced, passive, structural inclusions known as nail into the soil and these nails helps to improve the overall shear strength of soil. The nail pullout resistance is the shear stress at the grout-soil interface. The soil-nail pullout resistance depends on many parameters. Among the factors influencing the soil-nail pullout resistance, degree of saturation of the soil is an important factor. As degree of saturation of soil mass change with the moisture content of the soil, the pullout resistance may decrease during the intense rainfall. However, verification of pullout tests on soil-nail are not conducted under the worst condition. Hence, measured pullout resistance may not be a safe parameter for design. As such, in this research study, the effect of degree of saturation on pullout resistance was studied by conducting a series of laboratory tests using a laboratory pullout box. Especially designed waterproof cap was used to apply back pressure to saturate the soil within the pullout box. Variation of earth pressures close to the grouted nail were observed during the tests. It was evident from the results that higher the degree of saturation, lower the pullout resistance. Maximum pullout resistance was observed when the degree of saturation is near the optimum moisture of the soil. When the soil is sufficiently dry, lower pullout resistance was observed due to low bond strength between grout surface and surrounding dry soil.

Disposal of Municipal Solid Waste (MSW) has become a serious problem all over the world which is affected by the rising population and rapid urbanization. Most of the developed countries tend to proceed with engineered landfilling or incineration of solid waste while developing countries continue with open dumping. Most of these open dump sites are located on marshy lands or low lying land areas due to the high demand for prime lands in city areas, and they are expanded in vertical direction, saving the horizontal spaces. Therefore, physical, chemical and shear strength properties of MSW are timely important to overcome the stability failures of the dump sites during the operational period and after the closure of the dump sites. In this study, engineering properties of MSW were investigated using several laboratory experiments for disturbed waste samples collected from Meethotamulla dump site. In order to represent the aging effect of MSW, samples were extracted at different depths and variation of geotechnical properties with aging was analysed. Based on the laboratory test results, it can be noted that MSW in open dump sites in wet zone of Sri Lanka mainly consists of fine residue, aggregated soil, polythene and textiles. Further, higher shear strength parameters were obtained for MSW due to presence of textiles within the waste body. As such, it can be concluded that, it is necessary to consider the influence of textiles in analyzing the stability of open dump sites.