Stress inversion based on microseismic monitoring and its engineering application

Determining the stress field environment of rock mass in engineering is the basis of disaster monitoring, disaster warning and its application. A joint iterative inversion method is used to retrieve the stress field based on the focal mechanism. The method uses instability coefficient I as a constraint and combines it with the classical linear inversion method to retrieve the stress field, which can effectively avoid the negative influences of the fuzziness of the two fault planes on the inversion results and improve the accuracy of the results. To determine the optimal friction coefficient of rock mass, the friction coefficient which can produce the maximum instability coefficient is selected as that of rock mass through multiple inversion. The concept of the main fault plane is defined by the friction coefficient and stress. A typical case of rock fracture microseismic location event is presented and analyzed. Firstly, the source mechanism is analyzed, the type of fracture and the orientation of the fracture surface are obtained, and the time evolution of the fracture is predicted. Secondly, the error of the stress inversion results with different levels of noise is analyzed, and the results are presented. Finally, the distributions of stress filed are analyzed, and the results show that the azimuth angle and inclination angle of the maximum principal stress axis are 229.86º and 48.57º. The azimuth angle and inclination angle of the intermediate principal stress axis are 353.89º and 26.28º. The azimuth angle and inclination angle of the minimum principal stress axis are 100.08ºand 29.44º. The distribution of stress axes is consistent with the P/T axes of the focal mechanism. The orientation of the main fault plane is in great agreement with the actual monitoring results.