CONSTITUTIVE MODEL OF ROCKS CONSIDERING DILATANCY-BULKING BEHAVIOUR AND ITS CALIBRATION

The rock dilatancy-bulking deformation characteristics under high geostress unloading condition are critically important to understand the stability evolution and control mechanism of deep roadways,and to evaluate the stability of surrounding rocks.Using the triaxial unloading tests on the rocks sampled from the Gubei colliery,the evolution characteristics of the typical stresses with confining pressure are first studied.The criterion of rocks approaching pre-peak damage dilatancy and post-peak bulking deformation under critical condition is proposed.Then,the damage and degradation process of mechanical parameters of rocks during unloading are considered,and a progressive failure constitutive model is subsequently constructed.Finally,the distinct element code UDEC is embedded into the model to realize nonlinear numerical calculation.Simulation results of triaxial unloading tests show that the proposed model is suitable for describing the rock dilatancy-bulking deformation characteristics.Besides,the proposed model is used to evaluate the excavation damaged zone(EDZ) around a deep roadway.Compared with classical Mohr-Coulomb strain softening model,the performances of the proposed model are suggested to be applicable for practical engineering,and helpful for stability analysis and maintenances of deep roadways.