Three dimensional in-situ stress measurement and inversion analysis of deep buried large underground powerhouse area in Western Sichuan Plateau

The initial in-situ stress distribution is a critical factor influencing the stability of surrounding rock and the engineering design of underground powerhouses. Based on a large underground powerhouse project, this study employed the hydraulic fracturing method and the three-dimensional borehole deformation method for in-situ stress measurement. A three-dimensional visualization program was developed to achieve multi-dimensional and interactive visualization of the magnitude and direction of the principal stresses. A 3D numerical model for in-situ stress inversion was established, and an inversion parameter optimization program based on an improved Particle Swarm Optimization (PSO) algorithm was developed, enabling intelligent and rapid inversion and parameter optimization of the in-situ stress field. On this basis, accurate inversion and reconstruction of the in-situ stress field were accomplished. The research demonstrates that the self-developed 3D in-situ stress visualization system clearly reveals the spatial distribution of principal stresses, and the intelligent inversion optimization program significantly improves parameter fitting efficiency and inversion accuracy. The tectonic stress field in the underground powerhouse area is predominantly horizontal and falls within a medium to high stress category. Rockburst risk assessment of the tunnel surrounding rock indicates a potential for moderate rockburst during the construction period.