Integrated prediction for rockburst of underground powerhouse of Houziyan hydropower station

The underground powerhouse of Houziyan hydropower station under construction in southwest China has the characteristics of a large span and high sidewall. It lies in high geo-stress regions and its maximum measured geo-stress has reached to 36.43 MPa. The complete and hard limestone in this region has a high brittleness and provides a high energy storage condition, which is possible to result in dynamic geological disasters like rockburst because of the excavation disturbance. Based on the integrated prediction approach for rockburst, a research on rockburst tendency is conducted. Considering the strict simulation of topographical and geological conditions, a three-dimensional finite element model for Houziyan underground powerhouse is established. Then the step-by-step excavation process of underground powerhouse is simulated. And the initial geo-stress regression analysis is finished using method of back analysis. Wang Lansheng criterion is selected to evaluate the rockburst tendency. The rockburst tendency prediction of main powerhouse, main transformer chamber and tailrace surge chamber during step-by-step excavation process are analyzed. The results show that the light rockburst occurs during excavation of the underground caverns, and medium rockburst only happens in some areas. There are still some differences between the predicted results and the real situations. At the same time, a summary on various criteria of rockburst prediction and a discussion on the applicability of these criteria based on the existing engineering data are also carried out. It is indicated that there are some limitations using a single criterion to predict the actual projects. The predicted results by using five-factor rockburst criterion can reflect the actual situation more accurately.