A three-dimensional hybrid boundary element method for non-linear analysis of a weak plane near an underground excavation

A three-dimensional hybrid boundary element method is developed for the analysis of non-linear behaviour of weak planes near underground excavations. The hybrid model adopts the fictitious stress method for the simulation of underground excavation and the displacement discontinuity method for the weak planes. Besides, the hybrid model employs linear elastic behaviour for the rock and the Barton-Bandis non-linear model for the weak plane. The developed model was verified and applied to analyze the Problem of a tunnel penetrating a weak plane, in which the geometrical and material parameters were adopted from a tunnel project in central Taiwan. For the problem with the strike of the weak plane perpendicular to the tunnel mis, the numerical results show that: (1) the smaller the approaching angle, between the tunnelling direction and the dip direction of the weak plane, the larger the failure zone and the roof deformation; (2) the larger the RMR value, the smaller the deformation and failure zone; and (3) the larger the K (=sigma(h)/sigma(v)) ratio the larger failure zone will occur around the tunnel. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.