ABSTRACT
Analyses of tunneling and mining excavations are frequently performed assuming elastoplastic properties for the ground. The paper describes a simple a priori estimate for the mesh size, which is required to achieve a desired target level of accuracy. In models of tunneling, for a given set of problem parameters, a certain zone size exists at which the mesh detects no plasticity. This zone size, which is easily found, can be used as a benchmark mesh size for elastoplastic analyses. In meshes that are finer than this benchmark, it is shown that the major source of error is the integration of the discontinuity in slope in the yield function at the elastic-plastic boundary. This causes the error convergence to be bounded by a line of O(h2), where h is the zone size. Therefore an upper bound on the error is known for small size zones whilst the error is known analytically at large (benchmark) zone sizes. Guidelines are given for use of the estimates for real tunnel problems and examples are given.
