عنوان مقاله [English]
In this paper, an analytical-numerical model for the analysis of tunnels below groundwater table in plain strain axisymmetric condition is presented. A new numerical procedure, using finite difference method, is proposed for calculating the distribution of stresses, radial displacements and pore pressures around a circular tunnel excavated in a generalized Hoek-Brown rock mass. Considering strain-softening behavior and several seepage patterns, an elasto-plastic model is proposed for analysis of underwater circular tunnels. Comparing various seepage models, the most accurate one have been selected and used in this research. For the strain-softening behavior, it is assumed that all the strength parameters are a linear function of deviatoric plastic strain, which is different from the function used by Brown-Bray. As the derived differential equations have no explicit analytical solutions for the plastic zone, the finite-difference method (FDM) is used in this study. On the other hand, analytical expressions are derived for the elastic zone. Two examples are given demonstrate the performance of the proposed solution for dry and wet conditions. The results show the effects of dilatancy angle, deviatoric plastic strain as the factor of strain-softening, elastic strain increments. It can be observed that both elasto-plastic radius and convergence of the tunnel are increased by raising the groundwater level. Meanwhile, variations of dilatancy angle also have significant effect on ground response curve and elasto-plastic radius.