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moach• A Computer .program was 'developed to solve the throe-dimensional equatic*�. <br /> presented in Tsur-Lavie, et al's analytical elasticity solution. This computer program is.cap. <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 LY z 4 x D); <br /> • The soil thickness over the void M; and, <br /> • 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, et. al's paper. <br /> Ammpt ons Three basic assumptions were made to model the deformation of a surface due <br /> to the presence of a void at depth. These assumptions ane as follows: <br /> • The liner 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 /> Each of the assumptions listed above is further discussed in the following sections. <br /> Stress 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 use the strains at the liner sr- - <br /> e reduced by the arching effect of the material, i.e., waste, overlaying it. athemath...._.y, <br /> incorporating the waste- above the liner, could reduce the magnitude of the settlement by <br /> approximately half. <br /> Overborden <br /> �I Clay <br /> Sand <br /> cracks <br /> arw CD/opped <br /> wpw.e trapdoor Ruptures <br /> ..• ..e ..• • u,<0 r,o ere rro oe>O <br /> • z + s <br /> ♦ ♦ <br /> HA r.\ <br /> (n.trat 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 /> 1502-Vancouver.Canada-Geosyntheties'93 <br />