Rockburst Risk Evaluation for Stage Excavation of Underground Powerhouse

The main powerhouse is the most important one for a hydropower station. It usually located in complex geological environment with high geostress. So that rockburst risk evaluation is very significant for actual construction. Stage excavation is very common in the building of underground powerhouse. It has practical significance to forecast rockburst according to the firstly excavated stage. Numerical simulations were done to analysis the distribution of the secondary stress field in order to evaluate the rockburst risk. The results show that rockburst would occur at the bottom angles of the later stage if rockburst occurred in the earlier stage, and rockburst risk of the sidewall would be weaker. Rockburst would also be weaker in the firstly excavated stage at the same time. Because of stress of the arch increased, support of the arch should be enhanced during the following construction.