煤系地层弹性波阶段性衰减特性分析  

Analysis of phased attenuation characteristics of elastic wave in coal measure strata

作　　者：李全贵[1,2] 凌发平 胡千庭[1,2] 李楠[3] 姜志忠 钱亚楠 刘荣辉[1,2] 李文禧 LI Quangui;LING Faping;HU Qianting;LI Nan;JIANG Zhizhong;QIAN Yanan;LIU Ronghui;LI Wenxi(State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400044,China;School of Resources and Safety Engineering,Chongqing University,Chongqing 400044,China;State Key Laboratory of Coal Resources and Safe Mining,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China;College of Mining,Guizhou University,Guiyang,Guizhou 550025,China)

机构地区：[1]重庆大学煤矿灾害动力学与控制国家重点实验室,重庆400044 [2]重庆大学资源与安全学院,重庆400044 [3]中国矿业大学煤炭资源与安全开采国家重点实验室,江苏徐州221116 [4]贵州大学矿业学院,贵州贵阳550025

出　　处：《中国矿业大学学报》2023年第3期466-477,共12页Journal of China University of Mining & Technology

基　　金：国家自然科学基金项目(52074049)。

摘　　要：微震监测技术在矿山动力灾害预警、水力压裂增透效果评价等方面发挥着显著作用.煤系地层是典型的层状介质,介质各向异性和层间界面是弹性波在煤系地层中传播和衰减的重要影响因素.结合弹性波传播理论,采用有限元数值模拟为手段,研究了层状介质中弹性波传播的阶段性衰减特征.研究结果表明:相同试验条件下,层状介质中弹性波传播的信号幅值随着传播距离的增加呈指数衰减.由于层间界面的反射和透射作用,雷克子波速度幅值在100~400 Hz频带内显著衰减,在低频段(100~200 Hz)内的垂直衰减系数约为水平衰减系数的1.5倍,测点有效监测范围为8~12 m.雷克子波作用1个周期内,穿层方向的垂直应力场在近震测点(距离≤13 m)范围内具有相同的波动规律,应力响应表现出传递特性;随震源作用时间和传播距离增加,层间不连续界面阻断弹性波应力传递过程,弹性波幅值在主应力方向表示出阶段性衰减规律,应力状态呈现“正—负—正”交替变化特征.通过数据拟合分析发现,层状介质中的衰减系数介于单层介质吸收衰减系数的最小值与最大值之间.The microseismic monitoring technology plays a significant role in the early warning of mining dynamic disasters,and the evaluation of the scope of hydraulic fracturing.Coal measure strata are typical layered media.Media anisotropy and interlayer interface are important factors affecting the propagation and attenuation of elastic wave in coal measures.Combined with the theories of elastic wave propagation,the phased attenuation characteristics of elastic wave propagation in layered medium by means of finite element numerical simulation were studied.The results show that under the same experimental conditions,the signal amplitude of elastic wave propagation in layered medium decreases exponentially with the increase of propagation distance.Due to the reflection and transmission of the interface between layers,the Ricker wavelet velocity amplitude is significantly attenuated in the 100—400 Hz frequency band,and the vertical attenuation coefficient of elastic wave velocity in low frequency band(100—200 Hz)is about l.5 times that of horizontal attenuation coefficient,and the effective monitoring range of measuring points is 812 m.The vertical stress field of elastic wave has the same fluctuation characteristics in near-seismic measuring point(≤13 m)within one period of Ricker wavelet,the stress response exhibits transfer characteristics.With the increase of the source action time and propagation distance,the discontinuous interface between layers break the elastic wave stress transfer process,and the elastic wave amplitude shows a phased attenuation law in the principal stress direction,and the stress state presents a"positive-negative-positive"alternating change characteristic.Through data fitting analysis,it is found that the attenuation coefficient in layered medium is between the minimum and maximum value of absorption attenuation coefficient in single medium.

关 键 词：弹性波传播 阶段性衰减 层状介质 微震 数值模拟 

分 类 号：O347.41[理学—固体力学]