AN ANALYTIC SOULUTION OF ELASTO-PLASTIC PRESSURE TUNNEL CONSIDERING MATERIAL SOFTENING AND DILATANCY

Based on the unified strength theory proposed by Yu, an analytical elasto-plastic solution of stresses and displacements around pressure tunnel is developed. The characteristics of softening and dilatation of geomaterial are considered and a tri-linear softening model is adopted. The discriminant equation is given on the basis of the displacement or the inner pressure. Thus, the development of plastic zones around the tunnel can be determined. It is shown that the existing solutions such as the Kastner equation, the Airey equation and so forth are the particular cases of the present solution. The influences of dilatancy, softening and different strength models on the results are studied through examples.