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Design of Liner Sys ms Under Vertical Expansions. An Alternative to <br /> Geogrids <br /> D.-J. Janill <br /> Golder As.,--ociates Inc., USA <br /> C. Monteilo - <br /> Golder As iates Inc:; USA •�' c ;. :. <br /> ABSTRACT <br /> Acquiring and rinitt ng new landfill sites is often a dzficult task. An attractive <br /> alternative to present la dfill awners is to permit expansions to ezist3ng landfills. This option <br /> often involves the desigr and permitting of vertical expansions over old landfilf areas that were <br /> constructed before line and leachate collection systems were required: At present, the <br /> literature on vertical expa nsions suggests that liners and collection systems overlaying old landfill- <br /> areas require some type of reinforcement. The purpose of the reinforcement is to minimize th� <br /> tensile strains in overlaying liner and leachate collection systems assuming a void, created by <br /> progressive degradation and sudden collapse of large objects buried in the old landfill areas, <br /> Occurs. <br /> This paper presents the results of a model study -aimed to analyze and define the <br /> expression of a void occu 'ng at depth, on the surface of a liner and leachate collection system. <br /> The purpose of.the model is to define the shape of the deformed surface, and to predict the <br /> actual tensile strains on tite liner surface. The model in this paper suggests that given a finite <br /> void size, excessive tensile strains will not occur; unless the object collapsing and creating a void <br /> is assumed to be in very lose proximity to the liner. The model presented in this paper shows <br /> that if large objects likely to decay and create a void, are not present within 1.8 to 3 m (6 to 10 <br /> feet) (depending on the void size and the material properties used in the analysis) underneath the <br /> Liner system, excessive tensile strains are not created and reinforcement of the liner is not <br /> necessary. <br /> Four analytical m. els, which may be used to evaluate void-induced settlement, are <br /> briefly discussed in this p2 per. This paper illustrates how one of these models, which is based <br /> on an elastic solution, m y be applied to the evaluation ;and design of a liner and leachate <br /> collection system over an xisting landfill that is proposed to be expanded vertically. <br /> GeosyndrAws'93-Vancouver,Canada-1497 <br />