A metal interference correction method of tunnel transient electromagnetic advanced detection

Abstract

Water inrush during tunnel excavation severally threatens the mining safety as blind water-bearing structures may develop in front of the working face. The transient electromagnetic method (TEM) has been widely applied in the advanced detection of tunnel water-bearing structures. However, the metal interference of both supports and tools in the tunnel has become a bottleneck that reduces the forecast accuracy of this method. In this paper, we analyse the effect of metal interference on TEM data and propose a novel set of an observation and correction method under metal interference based on the ratio of anomalous and background apparent resistivity. Flume model experiments both with and without metal interference are carried out, showing that this interference can affect TEM measurements significantly and result in false anomalies, and that our proposed method can remove this ambient noise caused by metal interference appropriately. The practical application further proves that this method can effectively reduce low-resistivity interference introduced by the support and other metal tools inside the tunnel. By applying this correction method, the location of water-rich anomalies can be detected more precisely during the excavation process of the same tunnel, which is of high application value of reducing exploration difficulty and tunneling risk.

Numerical simulation on transient electromagnetic response of separation layer water in coal seam roof

“…Zhang et al 16 studied the three-dimensional full-space response characteristics of vector finite element mine transient electromagnetics and discussed the shut-off effect, the influence of roadway, and the response law in the case of water accumulation and goaf. Based on the finite volume method, Zhou et al 17 explored the interference effect of metal body in tunnel on TEM data and proposed a correction method under the interference of metal body. Chen et al 18 used the integral equation method to simulate the multi-component transient electromagnetic response characteristics of the coal seam floor aquifer and discussed the response law of the horizontal and vertical components observed in the borehole.…”

Fast Advanced Prediction of water-filled Structure using Transient Electromagnetic Method based on Deep Learning

“…For instance, the targets from different positions symmetrically along the receiving coil may cause the same TEM response at the receiving coil (Figure 1). In such a case, the use of a fanshaped detection method with measuring points distributed in detection direction from -90°to 90° (Tang et al,2018;Zhou et al, 2020), makes it difficult to distinguish the location of the abnormal target. Secondly, due to the limited deployment of measuring points, the progress in two-dimensional and threedimensional tunneling TEM inversion is slow, resulting in weak constrains on the full-space inverted parameters (Yu et al, 2017).…”

Feasibility of Tunnel TEM Advanced Prediction: A 3D Forward Modeling Study

“…Among them, electromagnetic methods have the unique advantage that they are more sensitive to the composition of heading rocks rather than the distribution of geologic interfaces [7]. More explicitly, electromagnetic surveys can help find water-bearing faults and karsts with relatively high electric conductivity [8]. Thus, they play a crucial role in preventing water inrush disasters and protecting lives and property during the tunnel excavation process.…”