Stability control for surrounding rock of the underground powerhouse of Baihetan hydropower station in China

Abstract

The geological conditions of Baihetan hydropower station are very complex, under which the stability control of surrounding rock encounters two major challenges: stress-induced large deformation and brittle failures, and dislocation deformation along interlayer shear zones. Brittle failure control is achieved through proper excavation sequence and fine excavation method to reduce the damage of excavation and avoid the superposition of the stress concentration area, and pre-treatment measures are applied for key parts of the powerhouse to control the excavation shape, with proper support sequence and parameters being used to strengthen support in stages and thus limit the development of fractures. Dislocation deformation control is achieved through the use of concrete replacement tunnels to promote shear resistance, proper excavation sequences to avoid rapid stress relaxation, and targeted supports on hanging wall to reduce rock mass relaxation to limit shear displacement and promote the stability of surrounding rock. The data obtained from visual appearance observation, displacement measurement, and acoustic testing show that such measures are effective.