ISSN 1000-3665 CN 11-2202/P

    深埋隧道孔内微震传感器与岩体耦合模型及其信号响应研究

    Coupling model and signal responses from borehole microseismic sensors with rock masses in deep-buried tunnels

    • 摘要: 微震传感器与围岩的耦合效果直接影响信号响应和监测的有效性,其信号有效频带的确定对深埋隧道微震监测的可靠性至关重要。文章建立了传感器-可回收式装置的多自由度振动模型,并基于此揭示了安装刚度对传感器频响特性的影响机制;选择西南某深埋隧道为工程案例,开展传感器-可回收式装置的原位试验,分析了该结构与注浆式安装对微震信号的响应差异;并对比了两种方案所采集微震信号的时频特征,探讨其对微震数据反演的影响。结果表明:(1)传感器-可回收装置轴向与 \theta _ y 方向振动解耦,而径向则与 \theta _z 、 \theta _ x 方向振动耦合,传感器与围岩的耦合程度受沿钻孔轴向和径向的等效振动刚度共同控制;(2)两种安装方案条件下微震信号采集效果接近:持续时间270~360 ms,上升时间10~150 ms,有效频带分析值分别为496 Hz和510 Hz(相差约2.7%),且微震事件的时空分布基本一致,释放能的时域演化虽存在差异但变化规律吻合。试验结果验证了文章所提的多自由度振动模型的有效性和传感器-可回收式装置的可靠性。本研究可为深埋隧道工程的微震监测传感器序列安装方案优化及监测预警提供量化依据和参考。

       

      Abstract: The coupling effect between microseismic sensors and the surrounding rock mass directly controls signal response and monitoring effectiveness, and the determination of the valid frequency band of signals is crucial to the reliability of microseismic monitoring in deep-buried tunnels. Firstly, a multi-degree-of-freedom vibration model for the sensor-retrievable device system was established, and based on this, the influence mechanism of installation stiffness on the frequency response characteristics of the sensor was revealed. Secondly, a deep-buried tunnel in Southwest China was selected as an engineering case, and in-situ tests of the sensor-retrievable device system were carried out to analyze analyzed the response differences of microseismic signals between this structure and the grout-filled method. Finally, the time-frequency characteristics of microseismic signals collected under two schemes were compared, and the impact on microseismic data inversion was discussed. The results indicate that the axial direction of the sensor-retrievable device is decoupled from the from the \theta _y directional vibration, while the radial vibration is coupled with the \theta _\textitz and \theta _x directional vibrations; The coupling degree between the sensor and the surrounding rock is jointly controlled by the equivalent vibration stiffness along the axial and radial directions of the borehole. Under the two installation schemes, the microseismic signal acquisition effects were found to be similar: the duration ranged from 270 to 360 ms, the rise time from 10 to 150 ms, and the effective frequency band analysis values were 496 Hz and 510 Hz, respectively (a difference of approximately 2.7%). The spatiotemporal distribution of microseismic events was essentially consistent, and although there were differences in the time-domain evolution of released energy, the evolution patterns agreed. The test results verified the validity of the proposed multi-degree-of-freedom vibration model and the reliability of the sensor-retrievable device. This study can provide quantitative basis and reference for optimizing the installation scheme of microseismic monitoring sensor arrays and for monitoring and early warning in deep-buried tunnel engineering.

       

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