EVALUATING SEISMIC IN-SOIL ISOLATION OF MSW LANDFILL USING GEOSYNTHETIC LINERS IN SHAKING TABLE TEST: CASE STUDY OF TEHRAN KAHRIZAK LANDFILL

Seismic loads may damage municipal solid waste landfills (MSWLF) through the relative movements within the waste, bottom-lining system, cover system, foundation, and interfaces. These movements can disrupt the performance of drainage and gas
collection systems, thereby resulting in environmental pollutions. The smooth synthetic materials might be placed beneath the structures to provide seismic protection by absorbing the imparted energy of earthquakes through the sliding mechanism. It has been found that a high-strength geomembrane placed over the other smooth and lubricated geomembrane sheets (e.g., geomembrane/geomembrane) constitutes a liner that is well suited for this application. In the present study, experimental investigations were conducted in order to evaluate the role of in-soil base isolation on seismic response of the Kahrizak MSW landfill with more than 7000 tons waste disposal daily in Tehran, Iran.Results of geophysical and geotechnical investigations in the landfill site are presented in detail. Shaking table tests were conducted on the MSW embankment isolated by semielliptic shaped liners and subjected to harmonic sinusoidal base excitations. Two types of base isolation system were employed in the experiments. The results of the isolated and non-isolated cases are compared in terms of permanent displacement and seismic response. It has been observed that, at all elevations, the spectral accelerations within the waste decreased by base isolation, especially for the more intense excitations. Although the fundamental period of the embankments significantly increased by increasing the amplitude of input motion, the base isolation mechanism did not affect the system period. In fact, isolation liners can significantly reduce
the seismic shear forces and accelerations transmitted to the landfill crest. The sliding displacement that is required to provide efficient soil isolation is in the range of permissible displacements for MSW landfills. Results of the present study demonstrate a suitable application of geosynthetic liners for seismic retrofitting of landfills.