Stability Analysis of Tunnel Face in Nonlinear Soil under Seepage Flow

Abstract

The face stability of tunnel may be decreased significantly due to the presence of seepage flow. In order to investigate effects of seepage flow, an original procedure is presented for face stability of a circular tunnel excavated by a pressurized shied, based on the discretization technique and the nonlinear failure criterion. A discretization technique is utilized to generate the latent failure mechanism by making use of point to point method. The collapsed blocks are decomposed into infinitesimal triangular elements. Each element is consisted of discretized points and adjacent radial to simplify the computed process. The upper bound solutions of retaining force are derived by equating the total rate of external work to the rate of internal energy dissipation. Pore water pressure is incorporated into energy calculation, according to the empirical distribution formula of hydraulic head which is derived by trial and error. The validity of the proposed method has been proved by making comparison with the published works. Agreement shows that the proposed method is effective. A parametric analysis is implemented to discuss the effects of seepage flow and soil nonlinearity on stability of tunnel face, and the concrete results are illustrated for practical use in engineering.