欠阻尼中心回线瞬变电磁效应

Transient electromagnetic effect of the underdamped center loop

瞬变电磁法经过近百年的发展,在各行各业都有广泛的应用,常规的瞬变电磁法对于天线的选择都尽可能选取临界阻尼天线,以减少过渡过程的影响.基于地震波检波器原理的启发,地震波检波器采集震动信号的过程,实质上是震动衰减转换为电磁振荡阻尼过程,欠阻尼瞬变电磁接收回线采集电磁波的过程,其实质也是电磁振荡衰减过程,两者接收都是感应电压信号,因此,欠阻尼中心回线的采集原理和地震检波器相同.本文利用欠阻尼中心回线研究探测砼结构的瞬变电磁效应,同时和过阻尼天线进行对比,说明欠阻尼天线在特点条件下探测结构体具有较强的探测能力及较高的异常分辨能力,其拟地震波图谱显示便于对异常体形状的判译.这种装置将揭开瞬变电磁法在混凝土结构探测中新的应用方向.

After nearly a century of development, the Transient Electromagnetic Method(TEM) has been widely used in various fields. To reduce the influence of the transition process, conventional selection of antenna for the transient electromagnetic method is to select critical damping antenna as far as possible. Inspired by the principle of the seismic geophone, the process of seismic geophone collecting vibration signal essentially is the process of vibration attenuation converting into electromagnetic oscillation damping, meanwhile, the process of electromagnetic wave acquisition by an underdamped transient electromagnetic receiver essentially is the process of the electromagnetic oscillation attenuation, both of them are receive induced voltage signal. Therefore, the collection principle of the underdamped center loop is the same as that of the seismometer. In this paper, the underdamped center loop is used to study the transient electromagnetic effect in the detection of concrete structure, and the effect is compared with using overdamped antenna. It was concluded that the underdamped antenna under the characteristic condition of detection structure has strong ability, and abnormal high discernibility, and fitting seismic wave map shows that it is easy to distinguish abnormal body shape. The device will uncover new application direction of TEM in the detection of concrete structure.