EFFECTS OF SOIL RECOMPACTION ON PERMEABILITY
Presence of water changes the properties of soil such as dry density, shear strength, swelling-shrinkage and permeability. In this research, the effects of recompaction on permeability of laterite soil extracted from the Faculty of Engineering in Universiti Teknologi Malaysia was investigated in the design of liners and covers used as hydraulic barriers in sanitary landfills. Landfill liner needs to have sufficiently low permeability value so that it impedes migration of leachate through the compacted soil which causes groundwater contamination. The falling head permeability method of testing was adopted in the experimentation. Laterite soil samples were first mixed with water and compacted using Standard Proctor compaction. The same samples were then remixed at higher water contents and recompacted. The compacted and recompacted soil samples were subjected to falling head permeability tests. Based on the tests results, the permeability value of 2.24 x 10-8 m/s for recompacted laterite soil at 40% moulding water content was lower than the permeability value of 5.95 x 10-8 m/s for compacted sample at the same moulding water content. The laterite soil was observed to contain low fines content and is susceptible to crushing.