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APP-F4aC-h._.. A computer .program was ..developed to solve the three-dimensional equatir,^. <br /> presented in Tsur-Lavic, et al's analytical elasticity solution. This computer program is.caD: <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 Ll x 4 X D); <br /> • The soil thicimess over the void (D; and, <br /> • Poissonys ratio of the subsiding material. <br /> The computer program was verified by comparing its output with the characteristic curve <br /> presented in Tsur-L. 41e, et. al's paper. <br /> Asstrrr► tions Three basic assumptions were made to model the deformation of a surface dot <br /> to the presence of a void at depth. These assnptions are as follows: <br /> • The Iinef surfacd is stress'free; <br /> • Differential settlement on a horizyontal plane is projected to a graded surface; ane <br /> • A constant Pei-sson's ratio. <br /> Each of the assumptions listed above is further discussed in the following sections. <br /> Stress Free Svrfkr, 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 liner sr- " <br /> a-r-e reduced by the arclring effect of the material, i.e., waste, overlaying it. Mathemath—,y, <br /> incorporating the waste above the liner. -could reduce the magnitude of the settlement by <br /> approximately half. <br /> ovedwrden <br /> G,ay <br /> Sano <br /> Cracas <br /> ano Dropped <br /> worwc trapdoor Auptdres <br /> .r♦ .re .rp s ry<0 ry res rep 4 ere>O <br /> ♦ s + <br /> e ♦ 4 4 <br /> (ntai Ben" tnitiat Bending <br /> stress stress dress stress <br /> Figure 2 Influence of overburden on lateral stress level <br /> (After Iessberger and Stone, 199 1) <br /> 1502-Vancouvrs.Canada-Geosynthctics 93 <br />