Tunneling adjacent to a row of loaded piles.

摘要

Much new construction for public transport in congested urban areas will involve underground excavation (tunnels and cut and cover) adjacent to existing building foundations and services due to the lack of surface space. Careful assessment of structure-soil-tunnel interaction situations is relatively new and only limited information is currently available. This research presents numerical and physical model studies of (i) the behaviour of an individual pile and an independent tunnel to set the basic responses and (ii) the pile and soil response for various tunnel locations as the volume loss is increased. It presents possible influence lines for the pile-soil-tunnel interaction situation, and potential failure mechanisms are presented for a single pile, an independent deep pile and for the pile-soil-tunnel interaction problem. The numerical investigation of the deformation behaviour between the pile and the tunnel used the FEA with the CRISP package. The laboratory model tests were idealised two dimensional studies using a multi-sized rod material for the particulate material and close range photogrammetry for obtaining detailed displacement data. The soil deformation patterns and strain data from the FE output are shown to compare well with the equivalent physical model tests. Admissible stress fields and the failure mechanisms are presented and used to develop upper and lower bound values for the minimum support pressure within the tunnel. The FE program was found to suffer serious convergence problems with non- associated flow rules during passive pile loading. In contrast, unloading from the pile working load to failure due to tunnelling produced acceptable results provided that a careful choice of the soil properties was made. Users of FE programs must be aware of the limitations imposed by (i) the coding adopted for the soil behaviours (i.e. the relationship between &phis; and psi) and (ii) the incorporation of slip elements and boundary conditions into the mesh generation.