Macro-micro mechanical response and energy mechanism of surrounding rock under excavation disturbance

In order to reveal the disturbance stress redistribution characteristics and energy evolution mechanism of roadway excavation under different stress environments,the semi-circular arch mudstone roadway model is established by discrete element program of PFC,and the dynamic evolution curve of macroscopic stress field and full-section deformation of the roadway surrounding rock are obtained. Based on the distribution characteristics of micro-stress field,the general law of acoustic emission and energy evolution of roadway excavation is revealed. The influence of confining pressure and lateral pressure coefficient on different energy characteristics is explored,and the strain energy release rate is used to characterize the excavation energy release. The results show that after the roadway excavation,the radial stress and the tangential stress all go through four stages:"pressure relief-recovery-fluctuation-stability". In the pressure relief stage,the stress is released rapidly,and the closer to the free surface,the more intense the stress re lease. The simulation results of radial stress and tangential stress at different depths of the vault are in good agreement with the analytical solution,which shows that the simulation results can better reflect the stress distribution law of the surrounding rock after the roadway excavation. When λ=1.0,the maximum displacement of the roadway is approximately linearly positively correlated with the vertical stress. The micro contact forces such as particle adhesion force and linear force increase with the increase of vertical stress and lateral pressure coefficient. During the excavation disturbance,the cracks are mainly produced in the stage of stress increase,concentrated at the bottom corner of the roadway and the vault. The strain energy,kinetic energy and friction energy of surrounding rock increase with the increase of vertical stress and lateral pressure coefficient. Under the same lateral pressure coefficient,the strain energy is proportional to the square of the confining pressure. The relationship between strain energy and confining pressure is quantitatively revealed. The release rate of strain energy increases with the increase of surrounding rock stress level,which indicates that the release rate of strain energy in high stress roadway is more intense,which leads to the significant increase of surrounding rock kinetic energy and friction energy.