ELASTOPLASTIC ANALYSIS OF CIRCULAR OPENINGS IN STRAIN-SOFTENING ROCK MASSES
ZHANG Qiang,WANG Shuilin,GE Xiurun
(State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,Hubei 430071,China)
Abstract:Geotechnical materials are generally performed with strain-softening mechanical behaviors. Considering post-strength surface shrinkage characters during strain softening process,it is assumed that the rock mass material parameters keep unchangeable in sufficiently small region. In this way,the rock mass is divided into multi-plastic rings after failure. Based on the plane strain condition and Mohr-Coulomb criterion,the quasi-strain softening elastoplastic closed-form expressions are obtained. Considering the rock mass strength evolution law,the multi-plastic radii can also be obtained using rock mass rupture conditions on the adjacent plastic rings. It is generally known that the ground reaction curve(GRC) is a very important basis for the underground lining design. The rock mass deformation parameters are also deteriorated with the increase of plastic deformation. So,the influences of deteriorated degree of shear modulus on rock mass deformation,softening radius and residual radius are analyzed. Finally,the analytical method is validated by an example;and the results can provide meaningful theoretical foundations for underground engineering optimization design and its stability analysis.