IEEE Geoscience and Remote Sensing Magazine - September 2019 - 99

The first recorded underground test of advance-resistivity methods for a heading face began in 1991. The gradient
method using one fixed source was adopted by HCRI and was
tried to detect water-bearing structures ahead of the heading
face. In 1998, CUMT did an electric dipole profiling measurement in an underground borehole, which was used to check
the grouting effect of blocking karst water in limestone [53].
The principle of the source-fixed gradient method for advance
detection is based on the following assumptions: 1) anomalous geological bodies in front of the heading face would
distort the distribution of the point current source field even
in the rear of the roadway, and 2) such a distortion can be
measured by a pair of potential electrodes M and N. However, in the complicated environment of a coal mine, there
are other strong influences on the measurements, such as
coal and surrounding rock fractures, local water accumulation, excavating equipment, metal materials, stray industrial
currents, and geoelectrically anomalous bodies at the rear or
side of the roadway. To reduce these influences from the nonheading geological bodies, comparison and transformation
methods of measurements by adjacent sources and three- or
seven-electrode systems have been developed [17], [54], [55].
Liu et al. [56] studied the feasibility of a U-type observation
mode of resistivity methods inferred from the idea of the transient electromagnetic method. Systematic research on the recognition of abnormal laws, numerical simulation methods,
physical model experiments, and interpretation methods has
been discussed in several papers [50], [51], [57]-[62]. Qiang
et al. [63] and Cheng et al. [14] pointed out that the gradient
measurements of the fixed-source method have limitations in
advance detection. To suppress the effect of anomalous geological bodies at the rear end of the roadway, the focus-on
method of tunnel dc resistivity was proposed with the study
of its critical factors and measurement techniques [64]-[66].
Its feasibility and interpretation methods were studied by
Yang et al. [67], Zhang et al. [68], and Liu et al. [69]. A multisource array was proposed by Li et al. [70] to enhance the
signal-to-noise ratio of the focus-on resistivity method ahead
of a tunnel. A forward modeling model of borehole resistivity
and a reverse modeling method were developed by Su et al.
[71] for detecting a deep and complex geologic target.
Over the past 10 years, in situ monitoring of the deformation and movement of the overburden and floor strata
during mining procedures has drawn much attention by
providing an explanation of the mechanism of water burst.
Zhai [72] first introduced resistivity imaging techniques to
monitor the deformation of floor rock and the movement
of confined water in goaf; the electrodes and cable were preburied in the roadway, and the three-pole electrical sounding of a single roadway and a dipole perspective method between two roadways were applied to scan the conductivity
change within a certain time interval during mining. Liu et
al. [13], [73], [74] and Wang et al. [75] further developed the
monitoring technique of resistivity tomography between
roadways and boreholes in the floor of coal seams to describe the electrical variation characteristics of floor strata
SEPTEMBER 2019

IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE

during mining face movement. On the basis of the fracture
zone of a coal seam, a geoelectric model was established by
Su and Yue to study the anisotropic characteristics of water
conductivity fracturing in a coal seam [76].
MINE TRANSIENT ELECTROMAGNETIC METHOD
The application of MTEM in a coal mine began with the
detection of zones of water-rich sandstone in the roadway roof [77]. Chen et al. [78] adopted the transient electromagnetic method to detect hidden collapse columns
and check the grouting effect in the Renlou mine in the
northern area of Anhui Province. Then, this method was
widely expanded with success in exploring water-bearing
structures located in the roof or floor of coal seams in east
China. The techniques, instruments, applications, potentiality, and development trends of MTEM were summarized
by Yue and Jiang [79].
A series of inundation accidents occurred during 2004-
2005, including the "8.7" accident (named for the time of the
accident) in the Daxing coal mine, Meizhou City, Guangdong
Province, which was the largest one since the founding of the
People's Republic of China. Therefore, since 2005, CUMT has
carried out the research and development of MTEM in the
Wuyang, Tunliu, and Zhangcun coal mines in Luan, Shanxi
Province, during which time the experiments in the water-filling roadway at the Tunliu coal-mining area S2 (Figure 5) confirmed the adaptability of MTEM to forecast a water-bearing
area ahead of a roadway [80]-[84]. Guo et al. [85] adopted
MTEM to continuously track the geological anomalies ahead
of the roadway drilling face. Jiang [86] studied the mechanism
of MTEM for advance detection for a roadway heading face by
physical model experiments and numerical simulations. On
the basis of the study of the inductance effect for a multiturn
small loop source, Yang and others [23], [87], [88] simulated
a 3D whole-space transient electromagnetic response by using the finite difference method; the turn-off effect was also
considered. Yang et al. [24], [25] proposed a new type of coneshaped transmitter device and made a series of investigations
on the mutual inductance and transverse electromagnetic response characteristics of the device, especially on data processing and inversion interpretation.
The simulation algorithms of MTEM via the 2D and
3D finite-element methods, 2.5D and 3D finite difference
methods, and boundary element method have been developed at CUMT [81], [89]-[99], and some progress has been
made in the following aspects:
1) The receiving and transmitting characteristics of the
small multiturn coils and their effect on observation
results were summarized. Furthermore, the abnormal
responses of typical electric bodies were established,
which paved the way for qualitative interpretation.
2) The relationship between the orientation of the transmitter and receiver and the position of a geological anomaly
was investigated, and the law of time-depth conversion
was mastered, which provided the theoretical basis for
quantitative interpretations of measurements.
99

IEEE Geoscience and Remote Sensing Magazine - September 2019

Table of Contents for the Digital Edition of IEEE Geoscience and Remote Sensing Magazine - September 2019