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BRAY, RATHJE, AUGELLO AND MERRY D Seismic Design for Lined Solid-Waste Landfills <br />221GEOSYNTHETICS INTERNATIONAL S 1998, VOL. 5, NOS. 1-2 <br />Figure 12. Cover liner sliding displacements. <br />0.0 0.2 0.4 0.6 0.8 1.0 <br />0.01 <br />0.1 <br />1 <br />10 <br />100 <br />1000 <br />10000 <br />ky /kmaxCover liner sliding displacement,U(mm)Mw =6.25 <br />Mw =7.0 <br />Mw =8.0 <br />Mw = 6.25, median and 16% <br />probability of exceedance <br />Mw = 7.0, median and 16% <br />probability of exceedance <br />Mw = 8.0, median and 16% <br />probability of exceedance <br />ment results. Analytical results indicate that for a wide range of landfill heights, waste <br />fill properties, and input rock motions, the calculated base sliding permanent displace- <br />ments for the rock site case are less than approximately 150 mm (with about a 10% <br />probability ofexceedance) when the yield acceleration coefficient is 60% of kmax (Bray <br />and Rathje 1998). Hence, 60% of kmax (=MHEA/g) may be used as the seismic coeffi- <br />cient in pseudo-static analyses of base sliding in combination with conservative dy- <br />namic strength properties and a factor of safety of one. However, the engineer must <br />decide whether 150 mm of permanent displacement along the landfill/liner interface <br />is tolerable. <br />Geosynthetic and soil materials comprising the base liner and cover systems are sus- <br />ceptible todamagebyseismically induced deformationsthat canproducetensile strains <br />in the materials. Geosynthetic material performance can be evaluated it terms of its <br />yield strain compared to induced tensile strains (e.g. Koerner 1998). In evaluating the <br />induced tensile strain in a geosynthetic layer, the zone over which strains can accumu- <br />late may be small (Zornberg 1994). Hence, small deformations may damage or even <br />rupture a geomembrane. The compacted clay liner’s integrity can be assessed in terms <br />of the potential for shear or tensile zones to develop within the layer (e.g. Singh 1992). <br />Finally, transient stresses and deformations within the waste containment system may <br />affect performance; however, validated analytical procedures to estimate these are not <br />currently available.