核磁共振测深进行隧道超前地质预报的可行性

Feasibility of using magnetic resonance sounding in prediction of water bearing structures in front of a tunnel face

针对隧道掌子面前方含水构造有效探测问题,提出了采用核磁共振测深技术进行隧道超前地质预报。以均匀全空间模型为基础,计算了均匀导电全空间中回线源形成的谐变电磁场,模拟了核磁共振超前探测时的扳倒角分布。结果显示隧道核磁共振超前探测时含水体能够产生明显核磁共振响应,但信号较弱。针对地下探测空间的特殊性,提出了以阶跃波代替现有余弦波激发源、以磁探头代替线圈作为接收装置进行改进的建议。核磁共振测深直接找水有望成为一种非常有潜力的探测掌子面前方水体并区分水与泥的有效方法。

The use of magnetic resonance sounding in prediction of water bearing structures in front of a tunnel face was proposed in order to realize the effective detection of water in front of a tunnel face. A homogeneous conductive full space was used as the basic model. The distribution of harmonic electromagnetic response was calculated. Distribution of the magnetic resonance toppled angles in magnetic resonance sounding（MRS） detection on tunnel face was also sim- ulated. The modeling result showed the obvious MRS response from the water in front of a tunnel face, while the ampli- tude was very small. According to the characteristics of MRS detection in tunnels, it was proposed that the currently co- sine excitation source could be replaced with step source and the current receiver coil could be replaced with magnetic probe. MRS is a potential method to detect water and distinguish water and mud.