Three-Dimensional Face Stability Analysis of Circular Tunnels by Numerical Simulations

The face stability analysis of shallow circular tunnels driven by the pressurized shield is investigated by three-dimensional numerical simulations. Both the active and passive soil failures of the tunnel face are considered in the analysis. A comparison is performed between (i) the present numerical solutions of the ultimate pressure of the tunnel face, (ii) the results of the multiblock mechanism of the kinematical approach in limit analysis and (iii) the values of the ultimate tunnel pressure obtained from centrifuge model tests. The shortcomings of the multiblock failure mechanism are presented and discussed.