Engineering properties of soil/solid waste at closed unlined landfill - A case study

The design and rehabilitation of landfills require performing comprehensive geotechnical analysis to demonstrate that all landfill systems have been designed to be consistent with long-term performance requirements. A geotechnical-testing program was conducted to evaluate the engineering properties of aged solid waste samples retrieved from a closed, unlined landfill located in Al-Adan area in Kuwait. The conducted tests included water content, specific gravity, Atterberg limits, grain size distribution, consolidation, triaxial and direct shear tests. Compression Index values, C,, derived from small scale (63.5 mm in diameter), one-dimensional consolidation tests were between 0.1 and 1.13 for a void ratio range of about 1.0 to 3.0. The friction angle from triaxial tests ranged from 21 to 30 degrees. None of the samples exhibited cohesive property in the triaxial test. Results from direct shear tests at different levels of horizontal displacements indicated that the value of the friction angle increased with the displacement level while cohesion remained essentially constant. Effective friction angles, phi', of 26.7 degrees to 50 degrees with cohesion of 7.43 to 35 kPa were evaluated from direct shear tests. The results indicate that anticipated settlement of the landfill site would be a major constraint on the rehabilitation and structural development of the site.