Stability Analysis of Yebatan Underground Cavern Surrounding Rock based on Crack Evolution Theory

The deformation properties of rock are closely related to the effect of crack closure, generation and expansion in the rock. In this paper, the stress-crack strain evolution constitutive model is used to determine the relaxation damage zone of the surrounding rock based on the change regulation of the crack closure ratio during the whole process of surrounding rock damage, and the model is embedded into FLAC3D software, and then the stability evaluation of the surrounding rock of the cavern group under unsupported and supported conditions is carried out for the underground plant of Yebatan hydropower station. The excavation simulation shows that the displacement of the cavern surrounding rock increases with the excavation step, and the influence of the fault on the displacement of the surrounding rock is very significant. The high stress concentration area is distributed in the arch top of the plant, the tailwater connection hole, the arch top and the bottom of the tail chamber, and the tensile stress area is mainly distributed in the high side wall of the underground plant and the tail chamber. The crack closure ratio index was used to quantitatively evaluate the degree of relaxation damage of the surrounding rock, indicating that the relaxation damage area is influenced by the fault, and the volume of the surrounding rock damage area under the system support is significantly reduced compared with the unsupported working condition, showing the effectiveness of the support measures.