An application of CSAMT to geological investigation at the changlinggang railway tunnel

Controlled-Source Audio Magnetotelluric (CSAMT) method is of a frequency domain sounding by using a controlled source. The method, characterized by efficiency, high lateral resolution, weak shielding effect from resistive beds and moderate detection depth, in recent years, it played an important role in engineering geological investigation. This paper presents a successful application of the CSAMT to the detection of geological hazard bodies in bedrock near the shoulder line of a deep-buried tunnel. The method has been successfully adopted for quickly mapping hidden fracture zones and structural framework, as well as geological stability assessment. This application case shows that the CSAMT is an effective method for investigating geological structure and formation water saturation near the deep-buried tunnel, and providing useful information for selecting borehole location and tunnel design and construction.