Ground subsidence in abandoned mine areas can cause loss of lives and serious property damage. In Korea, ground subsidence in abandoned mine area takes place in different forms from sinkhole type to a large scale trough type subsidence. For the prevention of serious damage, it is of importance to predict the ground movement. In this study, some typical cases of mining-induced ground subsidence are reviewed. The reinforcement and monitoring methods for ground subsidence in abandoned mine areas in Korea are discussed. In addition, management of mining subsidence in Korea was briefly introduced. Finally, some new technologies related to the prevention of mining-induced subsidence in Korea are introduced.
Mining-induced hazards have adverse effects to public safety and cause damage to the surrounding environment. There are many kinds of mining-induced hazards, such as ground subsidence, contaminated mine drainage, forest destruction, dust, noise, seismicity, indirect soil pollution, slope failure and so on. Recently, GIS-based modeling and assessment of mining-induced hazards were overviewed in Korea (Suh et al., 2017).
Subsidence is the lowering behavior of ground surface following underground extraction of an orebody, and is produced by almost all types of underground mining (Brady and Brown, 2004). In Korea, about 98.5 percent of coal mines and 96.4 percent of metal mines have been closed in the past decades (Jeon, 2016). There are numerous abandoned mines have potential security risks. Mine Reclamation Corporation (MIRECO) was founded in 2005, reorganizing from Korea Coal Industry Promotion Board (KCIPB). MIRECO has set a long-term goal of completing the plan of mining-induced hazards prevention within 20 years (Jeon and Jeon, 2014).
There are mainly two types of ground subsidence occurring in the abandoned mines, that is, sinkhole type and trough type as shown in Fig.1. Sinkhole type subsidence is an abrupt local depression at the surface due to underground mining. Sinkhole occurs due to the collapse of overburden into a limited mine opening. On the other hand, trough type subsidence usually occurred when longwall mining or caving mining method is adopted, where pillars fail by crushing or punching into the mine roof. The roof becomes bended, so the tensile failure by bending action causes the trough subsidence (Hunt, 2007). The comparison of sinkhole type and trough type subsidence in terms of slope of the slide, scope, degree of subsidence, occurrence speed, period, depth of goaf etc. is shown in Table 1.