INFLUENCE OF CLAY CONTENTS ON DRAINED SHEAR STRENGTH PARAMETERS OF RESIDUAL SOIL FOR SLOPE STABILITY EVALUATION

Consolidated drained triaxial compression tests (CD) were conducted to determine the compression properties of remolded samples collected from hillslope in residual soil. The test results showed that the effective drained shear strength of residual soil was primarily affected by the degree of weathering according to depth, parent rock material, and clay contents and also influenced by initial moisture content. These samples were classified as silt soils of high to low plasticity. CD tests were performed on samples prepared under 100 and 200 kPa remolding pressure with three different confining pressures of about 50, 100 and 150 kPa. Predicted results showed that the soil strength increased with increasing samples’ density for those who prepared with a higher remolding pressure. According to the soil composition, a clear decrease in soil cohesion was observed for samples collected at a deeper depth, while a further increase in the effective internal friction angle was observed for samples collected with a lower depth. However, this explains the significant influence of clay contents that can be represented as a relevant relation. Therefore, the results indicated that the studied residual soils have physical and geotechnical properties that are highly dependent on the clay and initial water contents. Then, the concept of long-term stability analysis of hillslope of Balai Cerap area (in UTM/ Malaysia) was presented in the form of factors of safety as discussed later in this study by employing Geo-Studio program (SLOPE/W application) with Limit Equilibrium Method.