The Stability Study On The Dagangshan Hydropower Station High Arch Dam Using Microseismic Monitoring In Impounding Period

The stress state and deformation mechanism of the high arch dam due to firstimpoundment relate to the working behavior and long-term safety.The mechanism of stress redistribution and the evolution of progressive failure process of arch dams can be studied by investigating the stress redistribution of arch dams,which can provide references for the safe operation of arch dams.Therefore,taking the high arch dam of Dagangshan as the research object,the full size three-dimensional numerical model of Dagangshan high arch dam is established in the ANSYS software,and the model is loaded into the RFPA3 D software after imposing the loads under different working conditions.The RFPA3 Dsoftware simulates the non-homogeneous property of the material by Weibull random distribution function,and uses this function as a fundamental theory to calculate the three-dimensional elastic damage evolution of the Dagangshan arch dam model.In this paper,the stress state and deformation of Dagangshan high arch dam under different storage height conditions during impoundment period are studied.From the perspective of stress state and deformation,the influence of variation of reservoir water level on arch dams is simulated and analyzed,combined with micro-seismic monitoring results.The calculated distribution of the high stress area of the dam coincides with the field microseismic monitoring result,which provides a reference for similar projects afterwards.This paper focuses on the numerical computation of arch dam models from the following aspects.1.The stresses and deformations of the arch dam due to different water levels of the reservoir are studied.Numerical results indicate that,(1)Based on the geological conditions of the Dagangshan high arch dam area,the RFPA3 D software is used to simulate the stress state and deformation of the arch dam in the initial stage of water storage.After the analysis of the numerical results,the dame area where high stresses and large deformations emerge at different reservoir water levels in the early water storage are determined.(2)The in-site spatial distribution of microseismic events in Dagangshan high arch dam basically consistent with that of numerical simulation using RFPA3 D.The spatial distribution of microseismic events is in the view of "cluster" distribution on the transverse direction of the river.With the increase of water level,the stress distribution in the bottom area of arch dams is uneven,and micro cracks emerge as a result.(3)Due to the arch dam's self weight and upstream water load,the deformation of dam during the initial stage of water storage is in conformity with designing codes,and the symmetry is good.In this process,the deformation of the dam is positively correlated with the storage level.With the uplift of the reservoir water level,the deformations along longitudinal and transverse river directions continue to increase,and both of these two deformations are not beyond the reasonable range.2.Optimization of sensor network for micro seismic monitoring technology of arch dam.Through the calculation results of the RFPA3 D software numerical simulation and the potential danger zone of the dam identified with this results,the sensor candidates and hypocentral location for micro seismic monitoring technology of arch dam is selected.Further more,the existing Dagangshan microseismic monitoring system network is optimized and the validity is verified.The contents of the study are summarized as follows.(1)The theory of optimization and evaluation for microseismic sensor network based on RFPA3 D simulation is proposed.(2)Based on the RFPA3 Dsoftware,the progressive failure process of Dagangshan arch dam under over-load conditions is simulated,and the fracture position and type of fracture in the concrete dam are analyzed according to the acoustic emission distribution.(3)Based on the RFPA3 D numerical calculation,the positioning accuracy and the weight coefficient of the sensor network are determined,and the new RFPA3 Dnumerical simulation software is used to optimize the sensor network scheme.