Ground and Pile-Group Responses Due to Tunnelling

In urban areas, where many of the high-rise buildings are supported by pile foundations, the number of soft- ground tunnels has increased rapidly during recent years. To minimize the risk of damage as a result of tunnel construction the engineer who designs a tunnel needs to be able to make reliable predictions of the ground deformations induced by tunnelling and their effects on any adjacent pile foundations. In this paper, a closed form solution, developed by the authors, is used to assess the displacement field around the tunnel. The displacements estimated are then imposed on single piles and pile groups in simplified boundary element analyses to compute pile and pile group responses. The analytical method presented in this paper was verified with a case history and with numerical results obtained using FLAC3D computer software. Comparisons are made to evaluate the group action for various pile group configurations. The influence of various pile lengths and pile locations from the tunnel is also presented.