IEEE Geoscience and Remote Sensing Magazine - September 2019 - 97

Driving Face

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pe
n-

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ff
C

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If geological targets are in the roof or
floor of coal seams, then the parallel
Ventilation Roadway
or axial dipole array can be used [15].
Roof
The electromagnetic wave toWorking Plane
mography method (also known as
Goaf
the radio-imaging method) is a highTransportation Roadway
frequency electromagnetic-imaging
Electrode
technology based on the theory of inAn
A1 A2 A3
Floor
traslit radio wave penetration, which
(a)
is mainly used for structural detection
Ventilation Roadway
in a coal-mining face. The operating
Roof
frequencies of the transmitting and
An
receiving antennas are generally 0.3,
Working Plane
Goaf
0.5, or 1.5 MHz. They are arranged in
A1 A2 A3 Electrode
different roadways, and the normal
Transportation Roadway
direction of the antenna plane is generally consistent with the direction of
Floor
(b)
the roadway. Under the theoretical asRoof
sumption of the straight-line propagation of radio waves, the algebraic
Coal Seam
reconstruction algorithm is adopted
Drill Hole
to invert the absorbing coefficient
Roadway
planar image of the radio wave passAn
A1 A2 A3
ing through the coal seams.
Electrode
In the advance detection of a coalmining face, the coincident loops or
Floor
(c)
separate loops at the roof, floor, or
side of the roadway are mainly applied
in the underground transient electro- FIGURE 2. The working principle of the resistivity methods for advance detection. (a) The
magnetic method. These measurement electrodes are laid on the middle axis of the roadway floor. (b) The electrodes are laid along
points are deployed along the roadway, the midline of the roadway side, forming a shape similar to the letter U. (c) The electrodes are
and the coincident loop system is usu- laid in the borehole of the drilling head.
ally chosen to attain the maximum
electromagnetic coupling response, with the normal direction
of the transmitter coil being toward the detecting targets.
HISTORY OF RESEARCH DEVELOPMENT
More than 20 fatal coal mine inundation accidents occurred
in 1985, which prompted geophysicists to focus their attention into the research and development of mine-based
geophysical prospecting technologies. The Xi'an Branch of
the China Coal Technology Engineering Group (CCTEG),
Hebei Coal Research Institute (HCRI), and China University of Mining and Technology (CUMT) carried out a series
of technical experiments. With the reform of techniques
and conditions for coal mining, the underground electrical methods for advance detection have gone through several different stages: evaluation of a water burst from a coal
seam floor, detection of a water-rich zone in roof sandstone,
advance detection for the heading face, mined-out area delineation, and in situ monitoring of the stability of roof and
floor rocks. All these studies focused on two typical workplaces: the coal-mining face and the heading face. Advancedetection systems related to resistivity methods, the transient
electromagnetic method, electromagnetic wave tomography,
and GPR have now become more and more sophisticated.
SEPTEMBER 2019

IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE

r
Tx

Rx
(a)

(b)

FIGURE 3. The device mode of the advance transient electromagnetic method for a driving face. Rx: receiver; Tx: transmitter.

MINE-RESISTIVITY METHODS
Since 1988, the electrical research group of CUMT has cooperated with the Huaibei Mining Bureau Surveying Department to carry out a series of comprehensive underground
experiments of mine-based geophysical methods.
1) The contrast test of different electrode arrays around the
symmetrical quadrupole, dipole, and combined threeelectrode along with other profile methods allowed the
reservation of asymmetric and multielectrode distance
configurations to improve the resolution and solve the
problems of data processing and geological interpretation.
97

IEEE Geoscience and Remote Sensing Magazine - September 2019

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