Transient electromagnetic detection method and device for three-component holes of underground large loop in coal mine

Abstract

The invention relates to a transient electromagnetic detection method and device for the three-component holes of an underground large loop in a coal mine. According to the method and the device, a loop is arranged around a working face to form an emission source, and an induced eddy current is generated inside a target body by manually controlling the establishment and disappearance of a static magnetic field. According to the equivalent eddy current theory, the induced eddy current can be replaced by a current loop associated with the shape of the target body. The induced eddy current radiates an induced magnetic field in space, sensors are arranged in a borehole to receive a three-component induced magnetic field, and the position and shape parameters of the target body can be obtainedthrough current loop interpretation on the data. As the loop emission source is arranged on the working face and is close to the detected target body, a stronger excitation effect can be obtained at the target body. Meanwhile, a receiving device is arranged in the borehole, and the distance loss of the induced field is minimized due to the close distance to the target body.

Description

technical field [0001] The invention relates to a transient electromagnetic detection method and system, belonging to the technical field of geophysical exploration, in particular to a transient electromagnetic detection method and device in a three-component hole of a large loop line in a coal mine. Background technique [0002] In the process of coal mine production, safe production is very important, which requires a full understanding and mastery of the underground geological structure, hydrogeological conditions, location and scale of abnormal bodies, etc. The geological conditions are particularly important. A large loop three-component hole transient electromagnetic detection method applied underground in coal mines is a new type of method for detecting abnormal objects inside the working face and its roof and floor. The working method is to surround the working face or in adjacent roadways and Conductive cables are arranged in the alley to form an ungrounded emissio...

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Problems solved by technology

The transmitting device used in this type of method is a small loop device placed near the borehole in the roadway. The coil is not larger than the section size of the roadway. It is generally a square loop with a side length of 2m. The transmitting magnetic moment is small, and the magnetic field energy is mainly concentrated in the transmitting Near the coil, as the distance between the receiving device and the transmitting coil increases, the signal attenuates sharply, the signal-to-noise ratio decreases, and the ability to detect abnormal objects decreases

In addition, due to the use of multi-turn coils, there will be strong self-inductance and mutual inductance, which will adversely affect the acquisition of secondary field signals

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