基于微震监测的大岗山高拱坝坝踵蓄水初期变形机制研究

 混凝土高拱坝坝踵是蓄水初期阶段拱坝安全的重点关注部位。通过构建国内首套高拱坝坝踵微震监测系统，实现对蓄水初期阶段大岗山拱坝坝踵区微破裂的实时监测，探究坝踵蓄水初期变形机制及其与微震活动性的关系。采用人工敲击试验确定坝踵等效P波波速为4 300 m/s，系统定位误差小于8 m。对系统获取的事件波形进行噪声滤除，并在自动定位基础上进行人工二次校核，提高定位精度，验证了微震监测技术应用于大体积混凝土工程的可行性。分析认为：蓄水初期阶段，大岗山高拱坝坝踵区微震活动性与库水位密切相关，微震事件聚集区实现从坝踵向坝趾的转移，坝踵压缩变形减小，而坝趾区变形量增加。此外，通过拱坝坝踵区微震变形演化过程，揭示了导流洞下闸蓄水前940 m高程基础廊道拱顶裂缝产生的根本诱因。研究成果可为混凝土高拱坝微震监测和真实工作性态研究提供参考。

Deformation mechanism of the dam heel of Dagangshan high arch dam based on microseismic monitoring during initial impoundment

The safety of the heel of the concrete high arch dam is highly concerned during the initial impoundment. The microseismic monitoring system was installed for the first time in China at the high arch dam heel. The real-time monitoring of the micro-cracks was achieved in the heel zone of the Dagangshan arch dam during the initial impoundment. The deformation mechanism of the arch dam heel and its relationship with the microseismic activities were investigated. The P wave velocity was determined using the manual tapping test and was 4 300 m/s with the error of system positioning less than 8 m. The event waveforms were denoised. The automatic positioning results were manually verified for better accuracy. The results proved the feasibility of applying the microseismic monitoring technology in the large-scale concrete structures. During the initial impoundment period，the microseismic activities of the high arch dam heel were closely related to the water level of reservoir. The accumulation area of micro-cracks was transferred from the dam heel to the dam toe. The deformation of the toe area of dam increased and of the heel area decreased. The process of microseismic deformation of the dam heel zone revealed the inducement of the crack at the base corridor vault at the elevation of 940 m. The results can provide reference for the studies on the microseismic monitoring of concrete high arch dams as well as the dam working performances.