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C <br />A computer was 'developed to solve the three-dimensional equation <br />presented in Tsur-Lavie, at als analytical elasticity solution. This computer program is. cat)abI <br />of evaluating the differential settlement caused by voids at depth. The input variables <br />program consist of the following: <br />• The void size (defined by L. x 4 x D); <br />0 The soil thickness over the void (T); and, <br />0 Poisson's ratio of the subsiding material. <br />The computer program was verified by comparing its output with the characteristic curve <br />presented in Tsur-Lavie, at. al's paper. <br />Assumpkns. Three basic assumptions were made to modal the deformation of a surface dut <br />to the presence of a void at depth. These assumptions are as follows: <br />• The liner surface is stress free; <br />• Differential settlement on a horizontal plane is projected to a graded surface; an( <br />• A constant Poisson's ratio. <br />Each of the assumptions listed above is further discussed in the following sections. <br />&-e-ss Free Surface, A stress free surface is one of the assumptions made in the solutior <br />of the Elastic Model. This is a conservative assumption because the strains at the finer sr - - <br />are reduced by the arching effect of the material, i.e., waste, overlaying it. Mathematk-,y, <br />incorporating the waste• above the liner could reduce the magnitude of the settlement b) <br />approximately half. <br />Overburden <br />OCI-Y <br />Sand <br />`00 <br />C; <br />.C;" <br />ana Dropped <br />rupture trapdoor Ruptures <br />0 na ne rro ire > 0 <br />Ifullal Bend,ng Initial Bending <br />stress stress stress stress <br />Figure 2 Influence of overburden on lateral stress level <br />(After Jessberger and Stone, 1991) <br />1503 - Vancouver. Canada - Geosynthedcs 93 <br />