Rapidly Locating a Water–inrush Collapse Column in a Seam Floor: A Case Study

After a mine was flooded by water inrush, a suspected collapse column was speculated based on 3D seismic data, but was not found by drill holes. Seismic source positioning based on different signal arrival times was used to determine the position of the water-inrush point, permitting rapid and accurate grouting and mine restoration. The impact of the water on the roadway roof was used as a continuous and dynamic secondary seismic source, along with surface microseismic monitoring of microseismic events near the inrush collapse column, and two suspected inrush points were rapidly located, which provided the information needed for layout of surface directional detection boreholes. The drilling results indicated that one of the suspected inrush points was a collapse column; its positon had a planar error of 26 m compared to the collapse column controlled by drilling. The inrush point was located 77 m below the seam floor, and the size of the collapse column was 19 m × 7 m. Thus, microseismic monitoring holds promise for rapidly targeting grouting at similar sites.