Seepage and stability analyses of slopes within landfill area

• Main Author: Ho, Kai Ling
• Other Authors: Harianto Rahardjo
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/59998
• Institution: Nanyang Technological University

Rainfall is identified as the factor for triggering slope failure and inducing leachate from a landfill, especially in countries that experience hot and humid climatic conditions like Singapore. Many soil slopes have a characteristic of a deep groundwater table with an unsaturated zone above the groundwater table. Infiltration of rainfall causes a decrease in matric suction and shear strength of the soil, resulting in slope failure. Pore-water pressures are negative in the unsaturated zone. The negative pore-water pressure or matric suction in unsaturated soil is highly affected by the flux boundary condition changes such as infiltration resulting from variations in climatic conditions. A change in matric suction causes a change in water volume, permeability and unsaturated shear strength of soil. Multistage saturated triaxial consolidated undrained (CU) and unsaturated triaxial consolidated drained (CD) tests were conducted to obtain the shear strength of the residual soils. The effective angle of internal friction, φ' of the residual soil, was found to be 29.0˚, the effective cohesion, c', was 5 kPa, and the φb angle was 29.0˚. Tempe cell and pressure plate tests were performed for the low pressure and high-pressure stage respectively to obtain the soil water characteristic curve (SWCC). The air-entry value (AEV) and the saturated volumetric water content, θs, were found to be approximately 60 kPa and 0.312, respectively. SWCC, permeability function and saturated and unsaturated shear strength of soil were used to analyze the variation of factor of safety of slope during rainfall that was shown to decrease with time.