MECHANICAL PARAMETER INVERSION AND EXCAVATION STABILITY OF THE SURROUNDING ROCK FOR BAIHETAN UNDERGROUND POWERHOUSE CAVERNS

In the study of the stability of the underground cavern chamber surrounding rock, the reasonableness of the selection of rock mechanical parameters is directly related to the correctness of the whole analysis and calculation. In this paper, the inverse analysis of the mechanical parameters of the surrounding rock during the construction period of the right bank underground plant cavern group of Baihetan Hydropower Station is carried out using the orthogonal design-BP neural network displacement inverse analysis method and based on the field monitoring data. The inverse parameters were used to study the stress and deformation evolution characteristics of the surrounding rocks of the cavern group during the construction period of the underground plant. The study shows that:the consistency between the finite element calculated displacement values and the field monitoring values is high, which verifies the reasonableness of the inversion method; the overall deformation of the surrounding rocks in the plant area is "phased", and the deformation growth is mainly caused by excavation and unloading, while the deformation produced by creep is relatively small; due to the influence of faults and fault zones, the overall stress in the surrounding rocks near the small pile number area of the plant is higher than that in the larger pile. The overall stress is greater in the area of small pile number, and the upstream displacement deformation is greater while the downstream side of the surrounding rock is more obvious stress concentration, so the monitoring of the deformation of the surrounding rock in this vicinity should be strengthened.