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Design of Liner Systems Under Vertical Expansions: An Atternadve to <br /> Geogrids <br /> 4 <br /> D.J. Jam <br /> Golder Asociates Inc., USA <br /> C. Montei 9 = <br /> Golder As iates Ines; USA •>_ =c`� �` •' <br /> ABSTRACT <br /> Acquiring and rmitting new landfill sites is often a dif&ult task. An attractive <br /> alternative to present Ifu dfill owners is to permit expansions to existing landfills. This option <br /> often involves the desigr and pemitting of vertical expansions aver old landfiff areas that were <br /> constructed before line and Ieachate collection systems wera required: At present, the <br /> literature on vertical expa nsions suggests that linass and wHection systems overlaying old landfill <br /> areas require some type 4 f 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 bJ' <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 modc I is to define the shape of the deformed. surface, and to predict the <br /> actual tensile strains on the 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 in (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 in. els, which may be used to evaluate void-induced settlement, 'arc <br /> briefly discussed in this p per. This paper illustrates how one of these models, which is based <br /> on an elastic solution, rn y be applied to the evaluation:and design of a liner and leachate <br /> collection system over an misting landfill that is proposed to be expanded vertically. <br /> Geo-syndie=. '93-Vancouver,Canada-1497 <br />