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BRAY, RATHJE, AUGELLO AND MERRY D Seismic Design for Lined Solid-Waste Landfills <br />209GEOSYNTHETICS INTERNATIONAL S 1998, VOL. 5, NOS. 1-2 <br />Figure 3. Shear wave velocity profiles for municipal solid-waste (after Kavazanjian et <br />al. 1996). <br />0 100 200 300 400 500 <br />0 <br />15 <br />30 <br />45 <br />60 <br />75 <br />Shear wave velocity,Vs (m/s)Depth (m) <br />Average profile <br />Recommended <br />range <br />GeoSyntec Consultants 1996;Augello etal. 1998)haveproposedshear modulusreduc- <br />tion and damping relationships based upon the OII landfill recordings. Figure 4 shows <br />the various shearmodulus reduction and damping curves proposedformunicipal solid- <br />waste. In general, analytical results are more sensitive to the choice of damping curves <br />compared tothechoice ofshear modulusreduction curves. The Poisson’sratio ofwaste <br />fill wasfoundtobeapproximately 0.3.Thedynamic strengthofwastefill wasback-cal- <br />culated to be at least equal to the static strength recommended by Kavazanjian et al. <br />(1995) (i.e. cohesion intercept,c = 24 kPa and internal friction angle,¬=0_for a total <br />normalstress,¹n <30kPa;andc =10kPaand¬=33_for ¹n >30kPa),and areasonable <br />back-calculated range of dynamic friction angles for the Southern California landfills <br />is 33 to 38_(Augello et al. 1997). <br />2.5 Dynamic Responses of Geomembranes and Geomembrane Interfaces <br />Geomembranes made of HDPE, polypropylene (PP), and polyvinyl chloride (PVC) <br />are often used as low-permeability layers within MSWLF units. The primary function <br />of a geomembrane is to minimize the migration of leachate through the base liner or <br />the infiltration ofwater throughthe coversystem. Geomembranes, unlike geogrids, are <br />rarely designed asstructural members that carry loads. Rather, the desired response for <br />a geomembrane is to deform without failure. To maintain system integrity, the ability <br />ofageomembrane toelongate inresponsetothedesignloads,including additional seis- <br />mic forces, without failure is of paramount importance. For design calculations, the <br />stress-strain response of a geomembrane is often based on wide-strip tension tests per- <br />formed at a specified strain rate of typically, 1%/minute.