During the process of subsidence, the ground surface is changed as a result of the excavation of the underlying coal unit. The final surface profile is determined by a multitude of factors, such as extracted coal thickness, width of the opening, depth, overburden lithology, mine design, and mining method. An anlysis of the typical subsidence profile reveals that almost every point of the surface over the mining area will be displaced both horizontally and vertically. Furthermore, mining operations have often been accused of causing local water wells to become dry or polluted. The impact on water can be of major proportions in such areas as the western United States, where underground aquifers represent a major source of water for populated areas, and in the Midwest, where slight alterations in surface drainage could radically affect the agriculture industry. The Bureau of Mines subsidence research program is focusing on providing the mine operator with the ability to predict surface movements and effects on ground water as a function of mining method and geologic context. The program is designed for coal basins where high mining activity may impact land use requirements. These areas have been delineated via consultations with industry and other government agencies. Eventually, all coal basins and mining methods will be addressed. Data sets are now available from the Eastern Interior, and Rocky Mountain Coal Provinces for full-extraction mining methods (longwall and/or room-and-pillar with retreat mining).
Proc. 88th Annu. Gen. Mtg. Canadian Inst. of Min. & Met., Montreal, Canada, May 11-15, 1986, 14 Pp