A weight factor-based backward method for estimating ground stress distribution from the point measurements

Shear stress component often can be much smaller than the normal stress in in-situ stress testing, which will lead to large errors in the inversion results. A new back-analysis method of in-situ stress field by considering stress weighting factor (SWF) was proposed. Firstly, through the macro-analysis of the regional geological structure, topographic features, and the surrounding rock failure phenomenon of the exploration adit by combining stereographic projection analysis, some representative measured data that can reflect the in-situ stress distribution characteristics of the project area were obtained. Secondly, an objective function of in-situ stress field inversion by considering SWF was established. Thirdly, a comprehensive evaluation method (CEM) of in-situ stress field inversion was constructed. Thereafter, a three-dimensional numerical model was developed to invert the stress field of the project area by the finite difference method. Then, the calculated in-situ stresses under different values of SWF were obtained. Finally, based on the CEM, the inversion accuracy of the in-situ stress field was evaluated to determine the optimal SWF and the corresponding in-situ stress field. To verify the reliability and rationality of the proposed method, the proposed method was applied to back-analysis of the in-situ stress field of Wudongde Hydropower Station. The calculated results show that when SWF is 0.2, the calculated in-situ stresses are in good agreement with those measured, and the inversion accuracy of the stress vector is significantly improved. The research results can provide more accurate in-situ stress field for highly stressed deep buried projects with strong tectonic movements.