Numerical Simulation of Tunnel Advance using the Boundary Element Method

The aim of the project is to develop a novel software for the analysis of the displacements and stresses that occur due to tunnel construction. Particular emphasis is placed on the new Austrian tunneling method (NATM), where tunnel advance is by blasting and the primary means of support is shotcrete and rock bolts. The software is based on the Boundary Element Method (BEM), whose capabilities have been extended in order to allow the consideration of sequential excavation, the installation of ground support and visco-plastic material behaviour. The BEM has the advantage over the more commonly used FEM in that no mesh truncation is required and that the number of elements which needs to be used is reduced by an order of magnitude. BE meshes are also easier to generate and the solution is faster. The novel approach in this project, which makes the software extremely user-friendly, is the adaptive generation of internal cells for the integration of the volume integrals that occur when dealing with plasticity in the BEM. In addition a facility is implemented that allows to simulate the sequential excavation/construction processes that occur in NATM tunnelling. The resulting analysis software is intended to significantly reduce the effort for the three-dimensional numerical simulation of tunnel advance. As a consequence consulting bureaus will be able to perform these analyses on a routine basis. This is expected to contribute to an increase in tunnel safety.