Abstract:
The surface transient electromagnetic method (TEM) is a geophysical technology normally
used in detecting water-enriched zones. However, with an increase of mining depth, the accuracy and
reliability of surface detection is gradually reduced, and surface TEM cannot meet the requirements of high-
precision detection for coal mine production safety. In this study, surface-to-coal mine roadway TEM is
proposed to detect water-enriched zones in coal mines. The resolution of this method in detecting targets,
however, is still unknown. Based on a 1-D layered model, the surface-to-coal mine roadway TEM response
is numerically simulated using the nite-difference time-domain method (FDTD). The results show that
the surface-to-coal mine roadway TEM has higher resolution of the target above the underground receiving
point and weaker resolution of the target below the receiving point. 3-D geo-electric models for typicalwater-
enriched zones such as a water- lled mining goaf, a water- lled fault and a water- lled collapse column are
established. The surface-to-coal mine roadway TEM responses are numerically simulated and compared
with the surface TEM responses. The results show that for the goaf model, the surface-to-coal mine roadway
TEM response is more sensitive than the surface TEM response. For fault and collapse column models,
the surface-to-coal mine roadway response is more sensitive than surface response in the early delay stage
but less sensitive in the late delay stage. The present study provides theoretical support for device selection
and for data processing interpretation in actual work.
