Numerical investigation of the effectiveness of a bored pile wall for the minimisation of settlement resulting from tunnel driving / Numerische Untersuchung der Wirkungsweise einer Bohrpfahlwand zur Minimierung der Setzungen infolge Tunnel

Bored pile walls can be constructed between buildings and tunnel alignments to protect sensitive buildings from settlement resulting from tunnelling. The aim of the research work presented here was to evaluate the effectiveness of such a bored pile wall with FE calculations and identify influential parameters. Two methods of predicting settlement were investigated with the programme ABAQUS: The GAP method, where the deformations of the tunnel contour are prescribed, and the stress reduction method, with which the support pressure at the tunnel contour is reduced. The ground is modelled as linear-elastic, ideal-plastic with a Mohr-Coulomb failure criterion as well as with a hypoplastic constitutive law. The contact surface between wall and ground was modelled with complete bonding as well as with a contact law with friction.
The simulation results with the stress reduction method and the hypoplastic material model show the best results qualitatively. The predict settlements agree well with empirical methods and centrifuge tests from the literature. The simulations show that the effectiveness of the wall is significantly influenced by the contact properties in the boundary surface. It achieves the best protection effect when frictionless.