Pile settlement zones above and around tunnelling operations

H. G. Poulos

This paper describes briefly the method of analysis of the response of a pile to tunnelling-induced movements, including estimation of the loss of axial capacity. The various pile settlement “zones” computed from this analysis are compared with those measured experimentally for tunnels in sand by Jacobsz et al. (2001). Some theoretical differences are identified between the cases of tunnels in sand and in clay. Finally, for an example case of a structure over a tunnel, a comparison is made between the performance of three alternative foundation types, a piled foundation, a piled raft foundation and a raft foundation without piles. It is shown that the tunnelling induced movements have less influence on the latter two foundation types than on the fully piled foundation.