Variation of the internal friction angle and cohesion of the plastic softening zone rock in roadway surrounding rock

In order to study the variation law of the internal friction angle and cohesive force of rocks in the plastic sof- tening zone of roadway (tunnel),Based on the results of 18 published experimental studies,the variation properties of internal friction angle and cohesion in the post-peak phase of full stress-strain curve of the rock are analyzed in combi- nation with the Mohr-Coulomb criterion. The results show that the change of the internal friction angle in the post-peak peak stage is small and can be considered to be unchanged. According to the four-stage and three-stage strain softening models which are widely used,the constant property of the cohesive modulus and the linear relationship between the cohesion of surrounding rock and the circumferential strain are obtained. The result reveals the calculation method of the internal friction angle and cohesion of the rock in the plastic softening zone of the surrounding rock,and the chan- ging law of cohesion and softening modulus of cohesion,which lays a reference for the study of deformation zoning of soft rock roadway in coal mine.