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Design of Liner Sys ms Under Vertical Expansions, An Alternative to <br /> Geogrids <br /> D.-J. Jan <br /> Golder Associates Inc., IDSA <br /> C. Mont r <br /> Golder Am ociates Inc= USA ->- <br /> ABSTRACT <; <br /> Acquiring and rmittitlg new landfill sites is often a diff ult task. An attractive <br /> alternative to present landfill awners is to permit expansions to existing landfills. This option <br /> often involves the desigr and permitting of vertical expansions aver old landfill-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 the <br /> tensile strains in overlay ng 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 lia.er 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 a liner surface. The model in this paper suggests that given a finite <br /> void size, excessive temile strains will not occur; unless the object collapsing and creating a void <br /> is assumed to be in very close 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 vo d 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 in els, which may be used to evaluate void-induced settlement, are <br /> briefly discussed in this p r. This paper illustrates how one of hese 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 /> - Geesynthetics'93-Vancouver.Canada-1497 <br />