Electromagnetic Response Analysis of Tunnel Full Space 3D Forward Numerical Simulation

Taking Chongqing Rail Transit Line 9 as the engineering background, this paper used ground penetrating radar to forecast the surrounding rock characteristics in front of the tunnel. It is considered that the geological conditions within 0–30 m in front of the tunnel face are complex, the structure is loose, the groundwater is developed, and the self stability of rock and soil is poor, which seriously affects the construction progress and the safety of life and property. Based on this, the reasonable construction and reinforcement measures are put forward, and the electromagnetic response analysis of the full space 3D forward modeling is carried out by using ANSYS software. It is considered that: the 3D forward modeling results of no unfavorable geological bodies show that the "water wave effect" of eddy current and electromagnetic induction intensity occurs in the whole space, which indicates that the results of numerical solution and analytical solution are similar, which provides the basis for further exploration of electromagnetic response characteristics of transient electromagnetic method. The 3D forward modeling results of typical water bearing unfavorable geological body show that the maximum eddy current is formed in the poor geological body, and the transient electromagnetic method is more sensitive to the low resistivity body. The results of 3D forward modeling of water filling of unfavorable geological bodies show that the greater the water filling, the stronger the electromagnetic response, while the abnormal characteristic response of semi water filled karst cave is relatively weak.