金属干扰环境下矿井瞬变电磁有限元正演模拟研究  

Finite-element forward modeling of transient EM in mines under metal interference

作　　者：朱姣 姜志海[1] 殷长春[2] 邱长凯 李毛飞 高兆丰 ZHU Jiao;JIANG Zhihai;YIN Changchun;QIU Changkai;LI Maofei;GAO Zhaofeng(School of Resources and Geoscience,China University of Mining and Technology,Xuzhou 221116,China;College of Geoexploration Science and Technology,Jilin University,Changchun 130026,China;Development and Research Center,China Geological Survey,Beijing 100037,China)

机构地区：[1]中国矿业大学资源与地球科学学院,江苏徐州221116 [2]吉林大学地球探测科学与技术学院,吉林长春130026 [3]中国地质调查局发展研究中心,北京100037

出　　处：《煤炭学报》2024年第11期4578-4589,共12页Journal of China Coal Society

基　　金：国家自然科学基金青年资助项目(42304085);江苏省自然科学基金资助项目(BK20231086);国家自然科学基金资助项目(42030806)。

摘　　要：金属干扰一直以来都是影响矿井瞬变电磁探测数据可靠性的关键因素之一。不仅给数据解释带来误判、错判,甚至导致接收信号彻底无效,因此系统研究金属环境下的瞬变电磁响应特征至关重要。可采用三维矢量有限元法实现金属干扰环境下的瞬变电磁正演模拟。利用精细化四面体网格对全空间计算区域进行空间离散,同时引入二阶后退欧拉时间离散格式,将直接求解器MUMPS用于线性方程的求解,最终获得高精度的数值解。在验证算法精度的基础上给出金属干扰环境下的矿井瞬变电磁响应,证明非结构有限元法对交界面电阻率差异巨大、磁导率参数较大的含金属模型依然能够进行较好的模拟。为系统分析金属干扰环境下瞬变电磁响应规律,设计切合实际尺寸的典型块状金属和金属工字钢模型。以精细化四面体网格拟合金属模型界面并提取数值模型的电磁扩散剖面,分析金属体与接收线圈距离及金属体尺寸对响应信号的影响。非结构有限元法数值模拟结果表明:巷道内金属的存在使得电磁场信号产生畸变,感应电动势曲线在晚延时产生异常高值。并且金属体尺寸越大、距离越近,则感应电动势响应幅值更大、影响范围越广,甚至淹没目标含水地质体的信号。可移动的块状金属与连续的工字钢在响应特征上具有相似的规律,因此在工程实践中可通过调整距离等方式对其处理。Metal interference has always been one of the key factors affecting the reliability of transient electromagnetic(TEM)data in mines.Not only does it cause misjudgment in data interpretation,but it also can lead to ineffective signal.It is crucial to comprehensively study the TEM response characteristics under the influence of metal environment.Thus,it is necessary to adopt the 3D vector finite-element(FE)method to realize a TEM forward modeling.Using refined tetrahed-ral grids for the spatial discretization of the computational domain,utilizing the second-order backward Euler scheme to discretize the governing equation,and applying the direct solver MUMPS for the solution of the linear equations,so that the high-precision numerical solutions can be obtained.After verifying the accuracy of the algorithm,comparing the res-ults of mine TEM responses in metal interference environments,it proves that the unstructured FE method can get good results for the metal-containing full-space models even with significant resistivity contrast and large permeability paramet-ers.To analyze the TEM responses under a metal interference environment,typical block-shaped metal and I-beam mod-els that are suitable for actual sizes are designed,the EM diffusion profiles are displayed for different models with refined tetrahedral mesh to fit interface,and the influences of the distance between the metal object and receiving coil and the size of the metal on the response are discussed.The numerical results of unstructured FE method indicate that the metal in the roadway distorts the EM fields,the electromotive force(EMF)curve generates abnormally high values in the late time.The larger the metal size is,or the closer the metal is from the coils,the larger the amplitude of the EMF and the influence area,even submerging the signal of the target water bearing geological body.For the block metal and the continuous I-beam having similar response characteristics,its influence can be weakened by adjusting their distance.

关 键 词：矿井瞬变电磁法 金属干扰 三维正演模拟 矢量有限元 全空间 

分 类 号：TD713[矿业工程—矿井通风与安全]