Research On Damage Evolution Of Surrounding Rock Of Underground Powerhouse In Pumped Storage Power Station

The boom in hydropower construction of China is closely related to the rapid growth of energy demand.13^th Five-Year Plan of Hydropower proposes"accelerating the construction of pumped storage power stations".In the future nearly fifty pumped storage power station will be included in the construction plan with an additional generator capacity of 60 million kilowatts.The large-scale underground powerhouse caverns are built in deep buried mountains with complex geological conditions and crustal stress.The stability problem caused by the progressive damage evolution of the surrounding rock of the underground cavern is especially prominent.Further more,it also brings great security for the later operation safety.Therefore,it is of great significance to study damage evolution and stability of surrounding rock on excavation of pumped storage power station.This article focuses on the key scientific issue of the damage evolution and failure mechanism of surrounding rock on excavation of the large-scale underground powerhouse.Based on the microseismic monitoring project of underground powerhouse at Huanggou pumped storage power station for the first time,the initiation,development and agglomeration process of the rock micro-cracks during excavation were reproduced and its damage mechanisim was analyzed.Meanwhile from the perspective of the evolution of micro-fracture,the advantages of RFPA-SRM method in failure process analysis to reproduce the damage-induced failure process due to the strength degradation.The numerical simulation results are consistent with the microseismic monitoring results.And the safety factors and failure surface of surrounding rock of underground powerhouse are numerically obtained.Especially the damage evolution obtained with RFPA-SRM is significantly meaningful for the investigation of failure mechanism of underground powerhouse.It provides reference for the monitoring and evaluation of surrounding rock stability during the excavation process of underground powerhouse of pumped storage power station.The following major achievements are made in the paper:?1?microseismic monitoring system and recyclable sensor array were applied in pumped storage power stations.The P wave velocity was determined to be 5150 m/s with the error of source location less than 6 m.Through threshold setting,spectrum analysis and manual identification,effective identification of rock micro-fracture signals and rejection of noise signals ensures reliability of monitoring results.?2?Under the influence of construction disturbance,the damage evolution and its failure mechanism,the response regions of construction and the fault location are investigated on the basis of the temporal and spatial distribution regularity of the microseismic activity.The micro-fracture failure mechanism is explained by the source parameter E_S/E_P.Based on the comprehensive analysis of microseismic density and energy,the pile 0+20m to 0+80m of underground powerhouse are defined as the potential dangerous area of surrounding rock.?3?From the perspective of micro-fracture and stress field evolution,the damage progressive evolution and failure modes of the surrounding rock were reproduced by RFPA-SRM under the different fault locations and lateral pressure coefficients.The results show that the surrounding rock stress field of the underground cavern near the fault is easily degraded,which leads to the macroscopic instability damage caused by the progressive damage of the surrounding rock.The influence distance of the fault is 18m.The horizontal stress determines the damage evolution law and the potential failure mode of the surrounding rock of the underground powerhouse.When the side pressure coefficient K=1,the safety reserve coefficient of the surrounding rock stability is the largest.