矿井富水区陷落柱成像研究

Research on karst collapse pillar imaging of water-rich area in coal mine

  • 摘要: 针对目前矿井富水区超前探测瞬变电磁法常用的时域有限差分(FDTD)方法时间步长选取受限于Courant-Friedrich-Lewy稳定性条件的问题,同时为进一步提高电磁计算效率和富水区成像分辨率,提出将逆时偏移成像算法和Crank-Nicolson时域有限差分(CN-FDTD)方法应用于矿井富水区陷落柱成像研究。首先介绍了逆时偏移成像算法和CN-FDTD方法基本原理;然后建立了矿井富水区陷落柱三维空间模型,研究了激励源线圈频率和角度对成像分辨率的影响,并得出了矿井富水区陷落柱成像结果;最后分析了CN-FDTD方法的计算效率。试验结果表明:当激励源线圈峰值频率为65 MHz且激励源线圈平行于xoz平面时,富水区陷落柱成像分辨率较高;基于CN-FDTD逆时偏移成像算法的矿井富水区陷落柱成像与实际模型相符;CN-FDTD方法较传统FDTD方法计算效率高,内存占比小。

     

    Abstract: In order to solve the problem that selection of time step was limited by Courant-Friedrich-Lewy stability condition in current finite-difference time-domain(FDTD) method commonly used in advanced detection transient electromagnetic method of water-rich area in coal mine, and further improve electromagnetic calculation efficiency and imaging resolution of water-rich area, reverse time migration imaging algorithm and Crank-Nicolson finite-difference time-domain(CN-FDTD) method were applied to research of karst collapse pillar(KCP) imaging of water-rich area in coal mine. Firstly, basic principles of reverse time migration imaging algorithm and CN-FDTD method were introduced. Then a three-dimensional KCP model of water-rich area in coal mine was established. Influence of frequency and angle of excitation source coil on imaging resolution was researched, and imaging results of the KCP were obtained. Finally, computational efficiency of CN-FDTD method was analyzed. The experimental results show that when peak frequency of excitation source coil is 65 MHz and the excitation source coil is parallel to xoz plane, imaging resolution of the KCP is high. The KCP imaging of water-rich area in coal mine based on CN-FDTD reverse time migration imaging method is consistent with the actual model. Compared with traditional FDTD method, CN-FDTD method has higher computational efficiency and smaller memory proportion.

     

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