Ground Stress Characteristics of Underground Caverns in Yebatan Hydropower Station

Abstract

Ground stress is the primary load acting on the support structures of large underground engineering projects, directly affecting the stability of the cavern's surrounding rock. Therefore, determining the characteristics of ground stress is the main issue to be resolved in the design of underground engineering. To investigate the ground stress characteristics of underground caverns in Yebatan hydropower station, the aperture deforming method is adopted to measure the ground stress. The results show that the magnitude of maximum principal stress (i.e. σ1) is 16.51 - 37.57 MPa. And its orientation ranges from N82°E to N54°W, which is close to the direction of the regional tectonic principal compressive stress. Meanwhile, ground stress field of underground caverns is mainly horizontal tectonic stress. Furthermore, the formation of disk-shaped rock cores can be found in the drilling holes of PD08 exploratory adit, indicating that the underground caverns are located in high ground stress area. Finally, the location of spalling is concentrated in upstream spandrel, providing significant validation for the ground stress characteristics within the underground caverns of Yebatan hydropower station.