Stability analysis of surrounding rock in underground pumping station caverns under complex geological conditions

Abstract

The Banmiao underground pumping station in the Gongming Reservoir Qinglinjing Reservoir Connection Project has a large scale of underground caverns, and complex geological conditions, which pose many challenges to the excavation and support design of the project. Numerical simulation method were used to investigate the excavation construction, support parameters, key blocks, and other aspects of the underground pumping station caverns. The numerical result showed that the geostress in the underground pumping station caverns is relatively low, and the direction of σ₁ intersected with the long axis side wall of the pump room by about 14 °. After applying systematic support, the deformation and plastic zone of the surrounding rock around are significantly reduced. Reducing the density of bolt(spacing of 1 m × 1 m → 1.5 m × 1.5 m) has a certain impact in the area of fault F1, but it is not significant in other areas; The areas with high stress on bolts and cables are mainly located in the areas of fault F1 and alteration zones; Based on the joints' information in boreholes, it is found that all of the potential blocks belong to infinite blocks using the Block Stereographic Projection Method. Seven large(> 180 m³) random blocks were found during the search, and all random blocks had a safety factor greater than 2.0 after considering anchoring support measures, meeting the requirements for the block safety factor.

Keywords

Banmiao underground pumping station / complex geological conditions / erosion zones / stability analysis of underground caverns / block stability