ICGCM Papers:
Roof Mapping and Void Detection
 
 
Problems in "Void" Detecltion in Coal Mine Water Hazards
23rd International Conference on Ground Control in Mining
Problems in "Void" Detecltion in Coal Mine Water Hazards
by
Francis Kendorski, Agapito Associates, Inc., Lombard
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[Conference] 23rd International Conference on Ground Control in Mining
[Price] Free  [Comments] 0
[Topical Area] Roof Mapping and Void Detection
[Author] Francis Kendorski, Agapito Associates, Inc., Lombard
[Abstract] One ofthe most dangerous events in underground coal mining is unexpectedly encountering water inrushes from undetected abandoned mines in the same seam. The surest and most confident method is probe drilling either from the mine or from the surface. However, drilling is expensive and may even miss the suspected mine voids entirely by drilling through pillars. Many operators rely upon one or more of several remote sensing techniques for detecting mine voids. However, mine "voids" often are not air- or water-filled open cavities, but are collapsed, rubble-filled chimneyed columns in the strata. Geophysical techniques, such as seismic reflection and refraction, electrical resistivity, magnetics, ground-penetrating radar, and others, often assume a continuous or fractured rock mass that has varying properties which provide the signatures that allow discrimination of one strata from another, or of strata from voids. However, a rubble-filled cavity has rock block-to-rock block contact throughout its volume and can still respond as a continuous rock mass with the rock blocks allowing signal transmission or mass detection, rather than a void space. Hydraulically, a rubble-filled cavity is essentially as transmissive to water as an open mine void. Thus, the problem of detecting a mine void with confidence is significantly compounded.