Research On The Influences Of Reservoir Impounding On Fault Activity Behavior And Their Induced Seismicity Effect

As important artificial water conservancy facilities,reservoirs play an irreplaceable role in impoundment and power generation,flood control and irrigation,domestic water supply,inland water navigation and other aspects;thus,reservoirs have become a key factor to the improvement of the national economy and people's livelihoods.However,one cannot ignore the series of disasters that have been induced during the construction and operation of reservoirs;in particular,the reservoir-induced seismicity is more severe with the characteristics of great harmfulness,weak controllability,complicated causes,less predictability,etc and arouses great attention among the governments and community which puts forward more urgent requirements on the research of reservoir-induced seismicity.According to the analysis and discussion on the research status of several aspects for reservoir-induced seismicity sunch as formation conditions,genetic mechanism,prediction and evaluation,prevention and control,etc,this study summs up the experience and shortage,especially during the research for the correlation analysis between the fillings of a reservoir and the induced seismicity and the cause mechanism of reservoir-induced seismicity,besides proposes a comprehensive research ideas that can be summarized as “Data-Appearance-Mechanism-Model-Method”.The main content of the thesis includes:(1)Research of the correlation between reservoir impounding and induced seismic frequency,environmental factors and seismic magnitude based on Copula: based on the data souces of the reservoir-induced seismicity,the filling processes of the reservoir,the tectonic context and from the appearance of reservoir-induced seismicity,this study proposes to utilize copula theory to build correlation models from single factor and multiple factors to analyze the correlation between the induced seismic factors and reservoir-induced seismicity,and perform the risk analysis,in order to reveal the basic spatial and temporal characteristics from the appearance.(2)Research of the responsive mechanism of fault activity behavior to the reservoir impounding: due to the special behavior of fault activity in reservoir area under the impact of impounding,based on the theoretical foundation of rock mass mechanics,elastic mechanics,effective stress principle,rock failure criterion,this paper builds the reservoir seepage and rock mass structure(fluid-structure)coupled model and uses finite difference method to simulate the stress distribution on the fault resulted from the reservoir.Then,the stress changes caused by the reservoir water are analyzed,and the responsive mechanism of fault activity behavior to the reservoir impounding is quantitatively extracted from the viewpoint of mechanical analysis to reveal the mechanism of reservoir-induced seismicity from internal physical mechanism.(3)Research of the model of fault activity behavior changes to induce seismicity and its application: according to the responsive mechanism of fault activity behavior to the reservoir impounding and Coulomb-Navier failure criterion,this study discusses the influences of fault activity behavior change on the condition of fault crack and instability determine the main controlling factors that impact the fault activity behavior changes caused by reservoir water and builds the earthquake triggering and delaying model of fault activity behavior changes.Based on earthquake triggering and delaying model,this paper analyzes the induced seismicity mechanism of the object reservoir to explore the main risk sources and controlling factors and then to propose the corresponding measures to decrease and prevent the induced earthquake effect from two aspects: project management and dispatch management.This study illustrates the correlation between the induced seismic factors and reservoir-induced seismicity from the formation condition,and reveals the mechanism of reservoir-induced seismicity from internal physical mechanism.Furthermore,the conclusions in this paper can provide new theoretical and methodological supports for the prediction and evaluation of water induced seismic risk and making the specific risk prevention and control measures.