Microseismic Activity Characteristics of Surrounding Rock Under Shaft Excavation Disturbance at Yebatan Hydropower Station

The high geostress and complex geological structure of underground powerhouse at Yebatan Hydropower Station frequently result in surrounding rock failure which delay construction schedule. Based on the microseismic monitoring technique, the microseismic activity characteristics of surrounding rock failure is analyzed under excavation disturbance in the intersection area of the shaft and the 2# drainage gallery. The results show that the microseismic events are concentrated in the failure area of surrounding rock, the cumulative energy is stably increasing and then rapidly increasing, the apparent stress contour illustrates the distribution of stress concentration. The evolution law of the energy index is continuously increasing and maintaining a high level, then suddenly decreasing, last increasing again and the cumulative apparent volume is continuously increasing and suddenly increasing. In addition, it discusses the failure evolution and mechanism of surrounding rock. Finally, the results can provide important reference and technical support for construction.