Abstract
To study the influence of metal supports in roadways on the detection of mines using the transient electromagnetic method, authors treated metal supports including anchor nets as a thin metal layer. According to the finite differences principle, the characteristics of the full-space transient electromagnetic response under the thin metal layer’s influence were calculated using a non-uniform grid. The thin metal layer’s presence slowed the electromagnetic field’s diffusion rate and hindered the overall diffusion. The transient electromagnetic response curve observed under the thin metal layer’s influence was higher than that without the supports. Thicker metal layers resulted in higher early response values and slower decay rates. The decay rate increased as a function of time, gradually approaching that of the curve without metal supports. The simulation of the transient electromagnetic response to the model of water-containing low-resistance structures showed that the metal roadway support reduced the sensitivity of the transient electromagnetic method and weakened its response to low-resistance anomalies.
Highlights
With increasing coal mining depth, the hydrogeological conditions of mines are becoming increasingly complex, and coalmine water inrush disasters are a serious threat to the safe operation of coal mines (Wu, 2014)
Transmission and receiving devices used by the mine transient electromagnetic method are located in underground roadways and the received signal is a superposition of various low-resistance electromagnetic induction signals within the detection range
By using a numerical simulation method to simulate the effect of metal support on TEM detection, the following conclusions are drawn
Summary
With increasing coal mining depth, the hydrogeological conditions of mines are becoming increasingly complex, and coalmine water inrush disasters are a serious threat to the safe operation of coal mines (Wu, 2014). Studying the influence of metal supports in the roadway on mine transient electromagnetic detection is important for eliminating metal interference and determining the distribution range of water-containing anomalies. The transient electromagnetic field under the influence of the metal roadway support can be derived based on the finite-difference equation.
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