高频大地电磁法在慈母山隧道勘察中的应用

Application of High Frequency Magnetotelluric Method in Chimushan Tunnels

慈母山隧道是重庆市城市快速干道之"三横线"的关键节段工程,隧址区地形地质条件复杂,隧道涌突水、断层破碎带、煤系地层与瓦斯成为工程的主要不良地质和施工地质灾害问题。为查明上述不良地质,沿隧道轴线采用高频大地电磁测深(EH-4电导率系统)方法开展地球物理探测,并根据探测结果,圈定了低阻异常区,与隧道施工开挖对比分析表明,发生涌水的位置、断层的位置均处于低阻异常范围内。实践表明该方法探测深度大、精度较高,有助于查明隧道富水条件、断层带等不良地质体,提高隧道宏观超前地质预报准确性。

Chimushan tunnels are key project of ＂San transverse lines＂ expressway in Chongqing city, their to- pography and geomorphology are very complex in the project region, the gushing water, fault fracture zone, coal measure strata and gas are the main unfavorable geological conditions and construction geology disasters in the tunnel project, it uses the high frequency magnetotelluric method （EH-4 system} to finding out these unfavorable geological conditions. According to the result of detecting, the anomaly area of low resistance is analyzed and determined, com- parative analysis of the result with reality conditions after tunnel excavation shows that the site of occurring gushing water and fault fracture zone are in range of low resistance anomaly area. The merits of high frequency magnetotelluric method （EH-4 system） are its ability in detecting great depth and high accuracy; the practice shows that it is advan-tageous to finding out unfavorable geological conditions, such as the site with rich water, fault, to improving accuracy of advanced geological prediction in tunnel.