Performance of Residual Soil as Cover System for a Sanitary Landfill in Singapore

A large amount of construction waste creates problems related to cost and space for disposal, especially for countries with limited land like Singapore. Therefore, it is important to choose a suitable landfill management system (e.g., cover system) for optimization of landfill area in Singapore. In this paper, the performance of a cover system for minimizing rainwater infiltration into a sanitary landfill in Singapore is presented. The cover system was designed using principles of unsaturated soil mechanics. In this study, a residual soil from Old Alluvium with a low coefficient of unsaturated permeability was used in the cover system. Comprehensive geotechnical instrumentation was installed in the landfill area to monitor the pore-water pressure changes within the cover system and landfill during and after rainfall. Laboratory tests were conducted to characterize the index and engineering properties of the residual soil for the cover system under saturated and unsaturated conditions. The finite-element seepage analyses were carried out to study the effect of climate change on the soil cover system. The results from the seepage analyses showed good agreement with those obtained from the field measurements. The results also showed that the residual soil from Old Alluvium can be used as a landfill cover system to prevent rainwater infiltration into the waste material.