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i <br /> A=maglh A computer -program was ..developed to solve the three-dimensional equation. <br /> Presented in Tsur-Lav=e, et at's analytical elasticity solution. This computer P program is-can; <br /> Of evaluating the differential settlement caused by voids at depth. The input variables <br /> y- program consist of the following: <br /> • The void size (defined by 1, x L�, x D); <br /> • The soil thicImess over the void M; and, t <br /> • Poisson's ratio of the subsiding material. <br /> - <br /> The computer program was verified by comparing its output with the characteristic curve <br /> presented in Tsur-LaAe, et. al's paper. <br /> Assum129ns Three basic assumptions were made to model the deformation of a surface dui <br /> to the presence of a void at depth. These assumptions ane as follows: <br /> i <br /> • <br /> The linea surface is stress-free; <br /> • Differential settlement on a horizontal plane is projected to a graded surface; anc <br /> • A constant Poisson's ratio. <br /> l _ <br /> Each of the assumptions listed above is further discussed in the following sections. <br /> St r-ess Free Surl�ce. 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 /> are reduced by the arc' irrg effect of the material, i.e., waste, overlaying it. Mathemati —y, <br /> incorporating the waste- above the liner could reduce the magnitude of the settlement by <br /> approximately half. <br /> Overburden <br /> 10 Clay <br /> Sand <br /> crack <br /> and t3ropped <br /> ruolwe <br /> 1r3060or Ruplwes <br /> .., .,e .., ♦...<0 .., s ..,. to.>O <br /> ♦ a + s <br /> ♦ ♦ [\4 <br /> (n.t.al Dendwq Inual BendkV . <br /> Stress Stress Siress Stress <br /> Figure 2 Influence of overburden on lateral stress level <br /> (After Jessberger and Stone, 1991) <br /> 1502-Vancouver.Canada-Geosyndiedes'93 <br />