Seismic stability and permanent displacement of landfill cover systems

A set of equations are formulated to determine the seismic stability and permanent displacement of cover soil in a solid-waste containment system. The formulation considers a two-part wedge mechanism with the soil-geosynthetic interface acting as the plane of weakness. In the absence of seismic forces, these equations degenerate to those proposed by Koerner and Hwu. Parametric studies indicate that the soil-geomembrane interaction coefficient has a significant effect on the stability and permanent displacement of the cover soil. The geosynthetic force required to restore stability of the cover soil can be two to three times larger under seismic loading as compared to static loading. Under otherwise identical conditions, the resulting permanent displacement calculated through an infinite slope can be more than two to three times larger than that obtained for a finite slope. The results of this study indicate that a rational seismic design of soil cover system should be based on a finite slope formulation.