IEEE Geoscience and Remote Sensing Magazine - September 2019 - 98

Left Side

No.1

No.3 -30°
No.4 -60°

No.2

Coal Seam
Driving Face

No. 5

Roadway

Right Side No.11

No.10
No.9 30°
(a)

No. 6
No. 7

No.8 60°

Detection 1

Tx, Rx
Roadway

Floor

Driving Face

Roof

(b)

Detection 2

Coal Seam
Detection 3

Roadway

Floor

Driving Face

Roof
Coal Seam
Drill Hole
Tx1, Rx1

Txn, Rxn

(c)

FIGURE 4. The transient electromagnetic method for advance

detection of a heading face. (a) The device and the roadway side
are at different angles for a total of 11 directions (No. 1-No. 11). (b)
Azimuth scanning of a roadway section for a total of three directions. (c) The devices are laid in the borehole of the drilling head
and then moved forward in the borehole to observe sequentially.
2) Because the electric inhomogeneity of fractured rocks
seriously affects sounding curves, sectional sounding of the three-pole Schlumberger array with active
poles MN was proposed (with the development of
switch equipment of the electrodes and the 2D resistivity imaging method, which emerged in a mine
environment).
3) According to the working principle of digital electrical instruments, the square-wave comparative-reading
method, which can attenuate strong random noises, was
developed, and the problems involved in measurement
organization, electrode grounding, and mining and
transportation equipment interference on the surveying
results were solved properly.
4) The characteristics of electrical macro-anisotropy of coal
seams and the surrounding rocks provided theoretical
98

support for the design of electrode layouts and the arrangement of observation modes for advance detection
of spatially oriented objects.
5) The characteristics of free air in tunnels on the whole-space
distribution of the current were mastered, and the empirical correction formula of roadway influence was found.
6) Xi'an CCTEG developed the first domestic explosionproof digital dc electrical instrument, DZ-II [37].
To investigate the grouting effect of aquifers, mine audio-frequency electrical perspective technology [38], [39]
was developed. The Chongqing branch of CCTEG successfully developed multifunctional and explosion-proof
electrical instruments [40]. Since then, those achievements
summarized previously have been rapidly promoted and
applied in Chinese coal mines, and the inundation accidents caused by confined water in the floor of the coal
seams have been effectively controlled.
From 1991 to 1997, many scholars completed works
on mine-based dc electrical prospecting methods. They
proposed a 1D digital-filter algorithm forward-modeling
process for layered media in the whole space as well as the
3D finite difference method, 3D finite-element method,
and 3D boundary element method forward-modeling for
layered media with a roadway in the whole space. A large
number of physical model and underground surveying experiments have been carried out. On this basis, the theoretical framework of the whole-space current field under
the influence of the roadway was constructed, which can
be summarized as follows:
1) The roadway influence and whole-space effect are two
special problems inherent in mine-based dc exploration. The coal-bearing stratum with layer distribution
plays a decisive role in the distribution characteristics of
the whole-space current field.
2) The current field around the roadway tends to distribute into the whole space, and the anomalous geological
body in any orientation of the space can, in theory, be
reflected in the observation results.
3) The free air in the roadway has a distortion effect on
the distribution of the whole-space current field, which
causes the distribution of the current field around the
roadway to differ from that of either a real whole space
or half space.
4) The source electrodes deployed at the vertical or horizontal planes produce different field distributions because
their equivalent current loop satisfies different series and
parallel relations.
5) Because of the influence of free air in the roadway, the
measurements of mine-based resistivity methods mainly respond to the geological anomalies in the side where
the electrodes are located [34], [36], [41]-[48].
From 2005 to 2007, theoretical research on the tunnel resistivity method was carried out by Huang et al. on the background of metal mines using finite-element simulation,
which further verified and improved the theoretical results
of mine resistivity methods [49]-[52].
IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE

SEPTEMBER 2019

IEEE Geoscience and Remote Sensing Magazine - September 2019

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