Strain softening and permeability evolution model of loaded rock and experimental verification

To predict the strain softening behaviors and permeability evolution of the loaded rock, according to the tri-axial compression experimental results of Gebdykes dolomite, the effects of the confining pressure on the elastic modulus, failure strain, peak strength, strength degradation process, residual strength and dilatancy are analyzed. The whole deformation process of loaded rock is divided into three stages. The strength degradation index, brittle modulus coefficient and dilatant index are employed to improve the SS model (strain softening model) in FLAC, and a new strain softening model with the effects of confining pressure is proposed. According to the test data analysis of the permeability VS volumetric strain obtained including the coal of Huainan Panyi mine, tuff, sandstone of Balikun mine, mudstone of Anjialing, a permeability evolution model based on the enhanced permeability of volumetric strain is established. Based on the improved SS model, the strain softening and permeability evolution model of loaded rock is set up. The processes of the tri-axial compression, permeability evolution and dilatancy of Anjialing mudstones and Gebdykes dolomite are numerically modeled using the proposed model. The results show that (1) The permeability evolution model of the enhanced permeability of volumetric strain can better describe the relationship between the permeability and the volumetric strain. (2) The proposed model can better numerically model the effects of confining pressure on the residual strength, strength degradation process, dilatancy and permeability evolution of loaded rock.