Modelling of ground support in tunnelling using the BEM

Ground support plays an important role in tunnelling. The New Austrian Tunnelling Method (NATM) relies on the interaction between the overall arching effect in the rock mass due to the tunnel excavation and the supporting system. Thus, the timing of the installation of ground support and its accurate numerical representation is a crucial aspect. While the numerical simulation of ground support measure like shotcrete, steel arches and pre-cast segments has already been the subject of extensive research, the presented project deals with the efficient simulation of rock boltsendons and pipe roofings. In the project a new Boundary Element based macro-scale approach for the numerical calculation of ground support in tunnelling will be developed and integrated into an existing boundary element program code. The advantage of the new method compared to existing approaches is twofold. Since a BEM disretisation is used for the infinite ground the computational costs are reduced drastically compared with the domain discretisation of a FEM approach. The second improvement is owed to a novel approach using a cell mesh instead of a sub-region technique. This will introduce no further unknowns by the presence of supports. The iterative scheme used will produce only little computational overhead because it will go along with the plasticity algorithm which will be run at the same time. Special focus is laid on the efficiency which is guaranteed by the semi-analytical treatment of the appearing volume integrals.