Failure mechanism of large-diameter shield tunnels and its effects on ground surface settlements

A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented. The technique is based on a velocity field model using more different truncated solid conical blocks to clarify the multiblock failure mechanism. Furthermore, the shape of blocks between the failure surface and the tunnel face was considered as an entire circle, and the supporting pressure was assumed as non-uniform distribution on the tunnel face and increased with the tunnel embedded depth. The ground surface settlements and failure mechanism above large-diameter shield tunnels were also investigated under different supporting pressures by the finite difference method.