岩性特征对冲击地压震动波光栅监测影响机理研究

Study on influence mechanism of lithologic characteristics for rock burst shock wave grating monitoring

为了得出冲击地压震动波在岩石中传播时岩性特征的影响机理,借助光纤光栅对不同岩石载体中的震动波进行了监测,并从理论上分析了二者之间的耦合关系。以Housner的随机震动模型为基础,对震动波与光纤光栅之间的耦合机理进行了理论分析,结果表明,震动波可以改变光栅的周期Λ和有效折射率n eff,进而影响其初始波长,震动波幅值、相位及频率等参数与波长变化直接相关;震动波在岩石中传播的波速受岩性特征参数的影响,岩石的弹性模量、密度和泊松比以特定的形式影响光纤光栅的初始波长,且与波长变化呈余弦相关;对砂岩、石灰岩及大理石板分别进行了震动波传感监测实验,结果表明,3种岩石的岩性参数I与光纤光栅的初始波长值具有余弦函数对应关系,与理论分析的结果相一致。研究为煤岩冲击地压光纤光栅传感监测提供了理论依据及实践应用指导。

To obtain the influence mechanism of lithologic characteristics when rock bust shock waves transmit through rock,the shock waves in different rock supports were monitored with Fiber Bragg Gratings(FBG),and the coupling relationships between them were theoretically analyzed.Based on Housner′s random shock model,the coupling mechanism between shock waves and FBG was theoretically analyzed.The result showed that the shock wave can change the periodΛand effective refractive index n eff of FBG,thereby affecting their initial wavelength.Parameters such as vibration amplitude,phase,and frequency were directly related to wavelength changes.The transmitting velocity of shock wave in rock was affected by lithologic characteristics parameters.The elastic modulus,density and Poisson′s ratio of rock influence the initial wavelength value of FBG,and were cosine related to wavelength drifts.The experiments of shock waves sensing monitoring were carried out in sandstone,limestone and marble slabs,respectively.The result showed that the lithologic parameters of rock were cosine related to the initial wavelength value of FBG,which was consistent with the result of theoretical analysis.This study provided a theoretical basis and practical application guidance for coal or rock burst monitoring with FBG sensing.