Mining-Induced Ground Subsidence

Underground mining created voids or mine-out areas that cause changes in the magnitude and orientation of the in-situ stress field and induce earth fractures and ground subsidence. Although some subsidence incidents are anticipated in mining areas, they can strike with little or no warning. Mine subsidence is a geohazard that can result in catastrophic and costly damage and even fatalities. Ground movement is typically swift and sudden for pit subsidence, while trough subsidence, which can develop over mines of any depth, appears as a gentle depression in the ground and can spread over an area as large as several square kilometers. Many factors including mining method, depth of extraction, size and configuration of openings, rate of advance or extraction, coal thickness, topography, lithology, structure, hydrology, in situ stresses, and rock strength and deformational properties affect the initiation and maximum lateral extent of subsidence; the most important ones are extraction width, coal thickness, and mining depth.