Municipal solid waste management (MSWM) has become a major challenge in Sri Lanka for post-conflict development activities. Many urban areas are facing severe problems in managing 10 to 50 metric tons of waste per day. However, limited research has been carried out to identify the key issues and policy gaps in MSWM. This research studies the existing complexities of MSWM processes, practices, and emerging challenges in three highly congested urban areas in the south-eastern coast of Sri Lanka. A mixed method strategy using field observations, semi-structured interviews and secondary data sources was employed for the data collection. The study revealed that, although the MSWM systems in the urban areas include all necessary elements, their effectiveness and efficiency are not satisfactory due to poor or non-segregation of waste at the source of generation; lack of resources; absence of regulation to reduce waste generation and control polluters; absence of regular collection schedule; and lack of technical know-how and initiatives. The recommendations drawn from the study include feasible solutions and immediate measures required to improve the MSWM before the related environmental and public health problems become a social catastrophe. The recommendations will also greatly contribute in the achievement of developing sustainable cities.

Static liquefaction of loose sands has been observed to initiate at stress ratios far less than the steady-state stress ratio. Different collapse surface concepts largely based on undrained triaxial test results have been proposed in the literature to explain the above instability phenomenon of loose sands. Studies of the instability behavior of fill material derived from residual soils remain limited. The present study investigated the instability behavior of a compacted residual soil using the conventional undrained triaxial tests and specially equipped constant shear triaxial tests. The test results were characterized in the p’: q: v space using the current state parameter with respect to the steady-state line for the residual soil. A modified collapse surface that has gradients varying with p’ and v was proposed for the loose residual soil to represent the instability states of undrained loading. Under constant shear stress conditions, the soil can mobilize stress ratios higher than those defined by the modified collapse surface. An instability surface was therefore presented for the instability states reached in static loading. Further, an alternative method of deducing the instability surface from the undrained stress paths was introduced.