隧道瞬变电磁超前预报平行磁场响应探测方法

ADVANCED GEOLOGY PREDICTION WITH PARALLEL TRANSIENT ELECTROMAGNETIC DETECTION IN TUNNELLING

通过三维数值试验和模型试验研究,分析平行磁场的响应特征,发现一些新的现象和规律,提出隧道瞬变电磁超前预报平行磁场响应探测方法。数值试验结果表明:(1)与掌子面平行的磁场响应对于判识掌子面前方的含水构造具有非常明显的响应特征;(2)对于垂直磁场响应无法识别的含水构造,平行磁场响应仍然具有很明显的响应特征。(3)当大规模含水构造距离掌子面较近时,平行磁场响应存在2次电动势反向的现象,可直接用于工程中水体的判识。采用数值方法计算TBM开挖隧道进行瞬变电磁超前预报时的响应特征曲线,提出的新探测方法有望应用于TBM开挖隧道的超前预报工作。

The parallel electromagnetic responses were studied through three-dimensional numerical and physical modelling respectively. Abnormal electromagnetic responses at the planes ahead of and parallel to the tunnelling front were found, leading to the identifying of the existence of water bearing structures. Some water bearing structures being not detected by the electromagnetic responses perpendicular to tunnel front were detected by the parallel one. When large water bearing structures were very near to the tunnelling front, the paralleled electromagnetic field induced twice occurring of the back electromotive force in the fixed time windows, which can be used directly for the identification of water body in real engineering practice. These findings indicated that the parallel electromagnetic responses could be a useful method for advanced geological prediction.