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In order to real time monitor and analyze the rock fracturing due to continuous construction and consolidation at the left slope of Jinping I hydropower station, southwest of China, a microseismic monitoring system was conducted and an optimal design for the sensor arrays was investigated. The sensor array was designed on the basis of P method and Powell algorithm. The artificial fixed blasting tests were applied to adjust the positioning accuracy of the monitoring system. The results show that the location error of seismic source is less than 12 m in the scope of the sensor array, which demonstrates the monitoring system has high positioning g accuracy. The contour of source location shows that the location errors near the main tunnels at the left bank slope is below 6 m. Signals from 689 microseismic events with moment magnitude ranging from -2.1 to -0.2 were recorded during the first year monitoring period from June 15, 2009. The spatial distribution of microseismicity can identify and delineate the potential failure at the left bank slope, which provides some references for the future excavation and consolidation of the hydropower station.

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The dam of Guanyinyan hydropower station is composed of a concrete gravity dam in the left bank and a rockfill dam in the right bank. During the operation of the hydropower station, several surface cracks occurred in the concrete gravity dam, which threatened the stability of the dam. To evaluate the evolution trend of the cracks and forecast the potential risk of the dam, the microseismic (MS) monitoring technique and finite-element method were used. First, the concrete three-point bending field test was performed to prove the reliability of the MS technique in monitoring the concrete cracks. The MS monitoring results were consistent with the simulation results. Then, the MS monitoring system was installed in the dam body. By analysing the MS activities before and after the impoundment, the evolution trend of the cracks and potential risk of the dam were evaluated and forecasted. The simulation results were also consistent with the monitoring results. These results can provide significant references for the operation safety of the dam and also present a new thought for the risk evaluation of similar dam engineering.

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