Vehicle-Borne Transient Electromagnetic Numerical Characteristic Parameter of Water-Bearing Body behind Tunnel Linings

Abstract

The water-bearing body (WBB) behind tunnel linings has been some of the main causes of damage in operational tunnels. The WBB directly affects the serviceability state of tunnel linings; thus, determining a method to detect this problem is a widely studied issue regarding tunnel maintenance. In this paper, a vehicle-borne transient electromagnetic method (VBTEM) is put forward for the first time to detect WBB behind tunnel linings, and the aim is to fully investigate the transient electromagnetic response and numerical characteristics of the WBB behind tunnel linings. Firstly, the transient electromagnetic response curves of the WBB and surrounding rock are obtained and compared in detail by using the finite element method. Then, taking the distance, thickness, radius, and resistivity of the WBB as variable parameters, the parametric sensitivity rule of the response curve of the WBB is analyzed. Finally, a dimensionless response curve is proposed, a mathematical extraction equation is established, and seven numerical characteristic parameters are proposed and extracted. Based on seven numerical characteristic parameters, the technical parameters of the VBTEM equipment are put forward. The results illustrate that the transient electromagnetic response of the WBB is obviously different from that of surrounding rock. The seven numerical characteristic parameters of the dimensionless curve of the WBB can represent the entire response curve of the WBB. The results reveal that the first time gate of the VBTEM equipment needs to be less than 0.05 μs for short-distance problem, and the time span needs to reach four time spans at least. The research results can provide valuable technical references for the application of VBTEM.

Theoretical and Experimental Investigation of Vehicle-Mounted Transient Electromagnetic Method Detection for Internal Defects of Operational Tunnels

“…Tunnel structural defects are usually manifested on the lining surface, such as lining cracking, water leakage, concrete peeling, and convergence deformation [1,3,[10][11][12]. The Appl.…”

“…Tunnel structural defects are usually manifested on the lining surface, such as lining cracking, water leakage, concrete peeling, and convergence deformation [1,3,[10][11][12]. The occurrence of these defects is usually a superficial characteristic, but it is closely related to the internal conditions of surrounding rocks.…”

“…Tunnel defects are a prominent problem in railway, highway, and underground engineering all over the world, especially the high-speed railway tunnels in China [1]. Due to the influence of various factors, such as geology, climate, design, and construction conditions, a variety of defects appear during the normal operation of tunnels, including water leakage, cavity, crack, and insufficient thickness of tunnel linings [2,3]. Therefore, tunnel defects are a worldwide hot problem, especially in the mountainous area of southwest China.…”

“…The transient electromagnetic method (TEM) is widely used in various fields, such as coal mine and tunnel construction exploration, deep-sea metal mineral exploration, and ground exploration [6,7]. Based on the identification performance of the low-resistivity body of TEM technology, the vehicle-borne TEM has been preliminarily proposed to rapidly detect tunnel defects behind tunnel linings [3], and the adaptability of this rapid detection method was also investigated [8,9]. Qian et al [3] adopted the numerical simulation method to investigate the variation rule of the transient electromagnetic response curve of a low-resistivity water-bearing body at the condition of short-distance and whole-space, and revealed the transient electromagnetic digital characteristic parameters that can reflect the regular physical parameters of a low-resistivity water-bearing body.…”

“…Based on the identification performance of the low-resistivity body of TEM technology, the vehicle-borne TEM has been preliminarily proposed to rapidly detect tunnel defects behind tunnel linings [3], and the adaptability of this rapid detection method was also investigated [8,9]. Qian et al [3] adopted the numerical simulation method to investigate the variation rule of the transient electromagnetic response curve of a low-resistivity water-bearing body at the condition of short-distance and whole-space, and revealed the transient electromagnetic digital characteristic parameters that can reflect the regular physical parameters of a low-resistivity water-bearing body. Liang et al [8] used the combination of a least square support vector machine and particle swarm optimization algorithm to study the three-dimensional fast inversion of a short-distance low-resistivity water-bearing body, and realized the prediction of physical parameters of a low-resistivity water-bearing body.…”