Perturbation Solutions for Elasto-piastic Analysis of Circular Tunnel under Unequal Compression in Two Directions

In this paper, we have discussed the elasto-plastic problems of the circular tunnel under unequal compression in two directions. It is assumed that the materials may be idealized as elasto-perfectly plastic and the media in the neighborhood of the hole have been already in the plastic state.Using the Coulomb Yielding Criterion and considering the second order infinitesimal, the stress distribution and elasto-plastic interface are given. Unlike the results given by previous approximate methods, the research results in this paper indicate that the elasto-plastic interface is similar to ellipse and becomes circular when the angle of internal friction increases.