Inversion analysis method for in-situ stress field of rock mass considering the influence of layered structure characteristics

Layered rock mass and the interlayer shearing fracture zone have complex influences on the magnitude and direction of local stress field in underground engineering areas. Obtaining the initial in-situ stress field under complex geological conditions is a prerequisite for analyzing the surrounding rock stability of underground caverns in layered rock mass. Firstly, aiming at the influences of complex valley evolution process, topography and tectonic action, a lateral pressure coefficient method based on the strata denudation simulation is proposed for the first-stage inversion and obtain the initial ground stress field of big model. Secondly, based on the influence of layered rock mass on local stress field, a second-stage inversion model of layered rock mass is established. The equivalent tectonic load is obtained by the stress field calculated by interpolation from the big model, and the second-stage inversion analysis method based on equivalent tectonic load is presented. Combined with the first and the second inversion methods, the optimal inversion analysis method of the three-dimensional initial in-situ stress field of layered rock mass is formed. Finally, the in-situ stress field of Guiyang pumped storage hydroelectric plant area is inverted on account of the measured in-situ stress data. The secondary inversion results indicate that the inversion results of the in-situ stress field can meet the requirements of point coincidence at measured points and field coincidence reflecting the valley evolution process and influences of layered rock mass. The local stress field in underground engineering areas is significantly affected by the interlayer shearing fracture zone, which is mainly manifested in the following aspects :1) the local stress value increases slightly near interface and releases in the soft rock layer; 2) the local stress field direction deflects differently due to the changes of the rock stratum occurrence. Using the method, the influences of anisotropic mechanical properties of layered rock mass and boundary conditions on the magnitude, direction and disturbance range of local in-situ stress field are deeply analyzed.