矿井瞬变电磁法三维时域有限差分数值模拟.pdfVIP

第 2 2卷 第 6期 地 球 物 理 学 进 展 Vol_22 NO．6 2007年 12月(页码：1904～1909) PR0GRESS IN GE0PHYSICS DeC． 2007 矿井瞬变电磁法三维时域有限差分数值模拟 岳建华， 杨海燕， 胡 搏 (中国矿业大学 资源与地球科学学院，徐州 221116) 摘 要 给出了矿井全空间瞬变电磁场的时域有限差分法(FDTD)算法，并推导了Mur吸收边界条件．利用Mur吸 收边界条件，选用均匀全空间电偶极源作为初始激发源，模拟了均匀介质中巷道底板岩层内部和层状介质中三维低 阻异常体的全空间响应特性，分析了瞬变电磁场在均匀介质中1．9 s和27．6 s两时刻的传播规律及在层状介质中 1．2 s和0．023 ms两时刻的传播规律．结果表明：巷道对电场的影响在初期并不明显，在2O s后才表现出来；瞬变 场能较好地分辨低阻层，对高阻层的穿透能力强，并且对低阻体反映灵敏；吸收边界条件只有在场域较大、网格节点 较多时才能产生明显的效果．所研究成果为矿井瞬变电磁法资料的解释提供了理论依据． 关键词 瞬变电磁场，矿井，时域有限差分法，吸收边界条件，模拟 中图分类号 P631 文献标识码 A 文章编号 1004—2903(2007)06～1904—06 3 D finite difference time domain numerical simulation for TEM in--mine YUE Jian—hua， YANG Hal—yan， Hu Bo (School of Resource and Earth Science，China University of Mining~~Technology，Xuzhou 221116，China) Abstract A 3D finite difference time domain(FDTD)solution was presented and Mur absorbing boundary condition was deduced．The whol~space response characteristics for three dimensiona1 conductive body 1ocated in the floor of the mine drift either in homogeneous medium or in layered medium was simulated，with using Mur absorbing bounda— ry condition and taking a electrical dipole source in homogeneous whole space as a initial source；the diffused regulari— ty of the transient field in homogeneous medium at 1．9 s and 27．6 s，and in layered medium at 1．2 s and 0．023 ms was discussed．Simultaneously，the results indicate that，it is not visible tO electric field affected by laneway at early times，this influence displays after 20“s；transient field has a high resolution capability tO low—resistivity layer，and also has a high penetrative capability tO high—resistivity layer；Therefore，it is s