层状全空间介质中重叠回线的瞬变电磁响应

采用第一类修正贝塞尔函数积分对回线源的瞬变电磁场进行求解，应用法拉第电磁感应原理得到柱坐标系下的瞬态值，研究一维全空间介质的层状递推公式和均匀全空间瞬变电磁场的扩散规律，分析不同回线尺寸大小、经典模型的全空间响应特征，并应用于实测数据。结果表明，回线源产生的瞬变电磁场在空间上具有一定的方向性；回线尺寸增加不影响早期的响应强度，但延后了响应对应的延时时间。均匀全空间层状解的相对误差小于4%，具有较高的精确度；回线半径小于层厚时，低阻层的畸变表现基本在同一时刻，反之则增加。半径减小，使得晚期响应强度明显降低，但扩大了晚期应用范围，增强了纵向分辨率。补充了重叠回线瞬变电磁的理论内容，为矿井全空间观测的工作参数提供参考。

Transient Electromagnetic Response for a Coincident Loop in a Full-space Layered Medium

The transient electromagnetic field of loop sources is solved by using the first kind of modified Bessel function integral, and the transient value in cylindrical coordinate system is obtained by using Faraday electromagnetic induction principle. The layered recursive formula of one-dimensional whole-space medium and the diffusion law of uniform whole-space transient electromagnetic field were studied, and the whole-space response characteristics of different loop sizes and classical models were analyzed and applied to the measured data. The results show that the transient electromagnetic field generated by the loop source has a certain directionality in space, and the increase of loop size does not affect the early response strength, but delays the corresponding delay time. The relative error of the whole-space layered solution is less than 4%, which has high accuracy, and when the loop radius is less than the layer thickness, the distortion of the low resistivity layer is basically at the same time, otherwise it increases. The reduction of radius significantly reduces the late response intensity, but expands the late application range and enhances the longitudinal resolution. The theoretical content of the coincident loop TEM is complemented, and reference for the working parameters of the whole space observation is put forward.