Errors in Pore Pressure Predictions Associated with Two Dimensional Modeling

Mine stability is often dictated by the effective stress distribution, which depends in part on the pore pressure distribution.  It is common practice to use two dimensional flow models in either Cartesian or radially-symmetric coordinates to estimate pore pressure distributions through mine cross sections. It is clear that two-dimensional representations cannot capture the effects of anisotropy, heterogeneity, and flow system geometry.  Even in the absence of these complications, there are limitations to these two-dimensional models.  Specifically, Cartesian representations can account for background gradients, but do not represent convergent flow adequately.  Radially-symmetric representations can account for convergent flow, but cannot consider a background gradient. We examine the effects of these limitations for estimating steady state pore pressure distributions around a dewatered pit in a homogeneous, isotropic medium using a three dimensional model as a control.  The results identify locations that are most subject to under prediction of pore pressure using two-dimensional models to represent this three-dimensional flow system.