Abstract: Using the obtained parameters of field shear velocity test, static and cyclic triaxial tests, the finite element method based analysis approach is presented for the seismic stability of extended municipal solid waste (MSW) landfill, and the seismic stability of extended MSW along internal circular sliding surfaces, along interface between extended and existing MSW as well as along back and base liners is analyzed respectively by the finite element method. During the earthquake, the extended MSW more tends to be failure along the interface between extended and existing MSW if the water level of the leachate in extended MSW is low. For the dynamic stability of the extended MSW along internal circular sliding surfaces, the computed dynamic factor of safety of the conventional total stress method will be larger than the real one due to that is cannot take into account the softening of MSW induced by the increasing dynamic pore water pressure during the earthquake. The permanent diplacements of six landfills with different vertical and horizontal extensions are computed by the Newmark method for two kinds of input accelerograms with different maximal horizontal accelerations. Results show that logarithm of seismic permanent displacement of extended MSW along interface between the existing and extended MSW is roughly linear to the ratio of the yield acceleration and the maximal horizontal acceleration.

Key words: extended landfill, seismic response, stability, permanent displacement