In-situ stress state in critical areas of the Taiyuan pumped storage power station and its application in pivot project layout

The hydraulic fracturing in-situ stress testing technology was used to test two boreholes (500-meter and 520-meter deep) at the Taiyuan pumped storage power station in Shanxi Province. The in-situ stress state of critical areas was obtained, and the ground stress level, underground building layout, and lining form in the project area were analyzed. The results show that the maximum horizontal principal stress ranges from 10.98 to 18.09 MPa, the minimum horizontal principal stress from 6.79 to 11.32 MPa, and the vertical principal stress from 9.61 to 13.57 MPa. Compared with the high and low in-situ stress values at the north and south ends of Shanxi Province, respectively, the measured values are between; Compared with the simulated in-situ stress field in the Qinshui Basin, the test results are basically consistent. The vertical stress values are between the maximum horizontal principal stress values and the minimum horizontal principal stress values (S_H>S_v>S_h), which means the maximum horizontal stress at the measuring point is the maximum principal stress and is in the strike-slip stress state. Its lateral pressure coefficient K_av is between 0.92 and 1.09, reflecting that the tectonic action in the engineering area is not intense. In the range of 330–506 meters, the saturated uniaxial compressive strength of the two boreholes is betwwen 35 and 107 MPa, with an average of 63.79 MPa, and the ratio of the saturated strength to the maximum principal stress ($ {{R}_{\mathrm{b}}} $/σ_m) is between 3.54 and 5.81, belonging to the medium–high stress level. The direction of the maximum horizontal principal stress in the project area is NE 43° to NE 70.5°, and the average is NE 59.5°, consistent with the regional focal mechanism solution and GPS displacement data. From the perspective of in-situ stress orientation, the average direction of the maximum principal stress in the engineering area is NE 59.5°, and the direction of the long axis of the underground powerhouse is between NE 29.5° and NE 89.5°, which is conducive to the stability of the surrounding rock of the powerhouse. The maximum water head P_H of the underground hub project is about 4.62 MPa (i.e., P_H <σ₃). Based on the hydraulic splitting criterion, it can be seen that the rock mass can resist the maximum internal water pressure, and the reinforced concrete lining of the water transmission tunnel can satisfy the stability of the water transmission tunnel. The research results can be widely used in investigating and designing pumped storage power station projects.