巷道边界条件下矿井瞬变电磁响应研究

Research on Response of Transient Electromagnetic Field in Underground Mine with Boundary Condition of Laneway

研究了巷道对瞬变电磁场的影响，模拟了全空间中介质的瞬变电磁响应特征．提出了适用于矿井三维全空间瞬变电磁法时域有限差分计算的新的巷道边界条件，通过将该边界条件离散为差分格式，并结合时域有限差分法进行计算，研究了1μs到0．8ms之间巷道的存在对瞬变电磁场的影响特征，以及巷道对巷道顶、底板内部的低阻异常体响应的影响、结果表明，由于巷道的高阻作用，使置于巷道中间的发射源，在0．5ms时在巷道两迎头处感应出2个相同的新源，而当发射源置于巷道一端迎头时，在另一迎头处逐渐感应出1个新源，在0、1ms后巷道的边界能清楚的显示出来、另一方面，巷道的延迟作用使低阻体响应的位置在20μs时落后其实际位置6～8m．

The effect of laneway on transient electromagnetic field was studied, and the response of transient electromagnetic field in medium in whole-space was simulated. A new boundary condition of roadway was proposed, which was suitable to calculation of time domain finite difference method （FDTD） for the three dimension whole-space transient electromagnetic method （TEM） in underground mine. By combining with time domain FDTD, the effects of 1μs-0.8 ms laneway on characteristics of electromagnetic field and the response of anomalous bodies in surrounding rocks were investigated. The results indicate that a transmitter source placed in middle location in laneway, inducted two new sources in two turning ends of laneway at 0.5 ms because of the high resistivity of laneway. When the source is placed in one turning end, a new source is inducted in the other end, and boundaries of laneway are displayed obviously at 0.1 ms. The location of response of anomalous bodies is 6-8 m behind the actual location at 20 μs because of the delay effect of laneway.