Study on the Mechanism of Fault Slip Instability and Energy Release Law Induced by Mining
In order to study the mechanism of mining-induced fault slip instability and energy release law,the production distribution of fissures and joints are obtained by in-site investigation,and the basic mechanical parameters of the surrounding rock are obtained by experimental tests with the rock cores from in-site borehole drilling.The Hoek-Brown strength criterion is used to determine the mechanical parameters of the rock mass with different depths.By importing the fissures and joints into FLAC3D software in the form of discrete fracture network(DFN),a refined numerical model is built and numerical analysis has been carried out.The results indicate that the coulomb failure stress increment(ΔCFS)value of the rock mass can be used as a quantitative criterion to predict the slip instability region of the fault.When the principal stress is rotated in the direction of the upper plate of the fault,the ΔCFS value decreases with the increase of the rotation angle and the dip angle of the fault,and the rock mass around the fault is not easily damaged.When the principal stress is rotated in the direction of the lower plate of the fault,the ΔCFS value increases with the increase of the rotation angle and the dip of the fault,and the damage of the rock mass around the fault increases.The slip instability of the fault is divided into three stages:the slip accumulation energy stage,the stable slip stage and the slip weakening stage.The strain energy density concentration area of the rock mass around the fault is the location of energy release during fault slip instability,and the strain energy density distribution of the rock mass shows the phenomenon of accumulation-downward diffusion-re-accumulation.Using the energy formula for fault slip instability,the magnitude of energy release during fault slip instability can be estimated.
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