A Metal Interference Elimination Method for Transient Electromagnetic Response of Tunnel Advance Geological Prediction

Abstract

The invention provides a method used for eliminating metal disturbance in tunnel advance geology forecast transient electromagnetic response. The method comprises the steps that (1) transient electromagnetic response values of a tunnel background field and a metal body and a detection coil in different coupling conditions through field test; (2) the resistance limit values of two transient electromagnetic responses in the step (1) are calculated respectively, and resistance limit functions under different coupling conditions of the metal body and the detection coil are further acquired; (3) the resistance limit value of the low-resistance geology anomalous body transient electromagnetic response of each measure point is acquired; and (4) an inversion objective function is established by using the low-resistance geology anomalous body resistance limit value as an eigenvalue, and the cover depth and size of a low-resistance geology anomalous body are calculated. According to the invention, the interference of a metal body to the detection result of a transient electromagnetic method can be effectively eliminated; misjudgment is reduced; and the tunnel geology forecast accuracy is improved.

Description

technical field [0001] The invention relates to the field of tunnel space transient electromagnetic method detection, in particular to a metal interference elimination method for tunnel advanced geological prediction of transient electromagnetic response. Background technique [0002] During tunnel excavation, low-resistance unfavorable geological bodies such as water-rich faults and water-filled karst caves are often encountered in front of the tunnel face, which are important safety hazards during tunnel construction. The successful prediction of low-resistance unfavorable geological bodies in front of the tunnel face has become an important measure to ensure the safe construction of tunnels. For this reason, people have introduced the transient electromagnetic method into the advanced geological prediction of tunnels. However, the tunnel space detection environment is complex, and there are often a large number of metal interference objects. Previous studies have shown th...

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Problems solved by technology

However, the tunnel space detection environment is complex, and there are often a large number of metal interference objects. Previous studies have shown that these metal objects have a greater impact on the detection data and interpretation results, and sometimes even lead to misjudgment.

[0003] At present, some scholars have conducted research on the metal interference body of the mine transient electromagnetic method, but there are still limitations in the field application of the existing method, such as: for a given metal body and detection device, the transient electromagnetic response of the metal body The time spectrum also depends on its coupling with the coil; when there are multiple low-resistance bodies, there is mutual inductance between each low-resistance body, and the transient electromagnetic response value is not a simple addition or subtraction of a single low-resistance body; shielded probes are only suitable for The center loop and the overlapping loop with a strong response to geological anomalies are not suitable, and because the magnetic field line is a closed curve, the shielding effect of the receiving magnetic probe on the rear signal needs to be further verified

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