Subsidence and reclamation in coal mine areas of China

Underground coal mining accounts for 97 percent of total coal production in China. About 21 million ac of land has been affected by mine-related subsidence. Ln areas of active mining, where nominal total extraction is practiced, subsidence is essentially contemporaneous with mining. Mine subsidence can be divided into two types: (1) subsidence caused by longwall mining and (2) subsidence caused by ground-water withdrawals in areas of active mining. Ground deformation resulting from subsidence has damaged structures by simple tension and compression transferred by friction and adhesion to the undersides of foundations. Differential settlement and intensified pressures on soil-structure are equally significant in some coal mine areas of China. Mine reclamation has been practiced in some large mining areas since the early 1980s. Engineering reclamation, such as backfilling mines with gangue, coal ash, and garbage, and biological reclamation, such as soil improvement, plant breed screening and vegetation technology, are commonly used.