In mine areas, ground movement such as surface subsidence and landslide is frequently caused by the influence of mining work in the past or at present. It is of great importance to assess the hazard of the disaster to reduce the consequent damage from it. This study aims to assess the surface subsidence hazard of a mining area by numerical simulation. For a case study, a limestone mine in South Korea was selected where sinkhole type subsidence and local landslide took place during its operation. In a FLAC3D model, the topography, geological features and mined galleries of the mine site were considered according to the mining maps and site surveys. Then, the strength reduction method was applied to simulate the ground movement. The proposed numerical method reasonably simulated the sinkhole and landslide that occurred in the area in terms of location, extent and shape of the ground movement. The methodologies and results of the study can be used for analyzing the stability of a mining area and determining appropriate reinforcement methods.
In Korea, the anual limestone production is estimated to be 97 million tons as of 2014 (Statistics Korea, 2014). It takes about 90 percent of the total amount of the annual mineral production in Korea. Open pit mining method has been commonly applied in limestone production since 1950's, while underground mining method has been applied in parallel since the latter half of 1980's. For underground production, room-and-pillar mining method has been widely used in Korea. In the method, mine excavation often deviates from the predetermined layout to produce richer orebodies resulting in irregular shape and position of the pillars. This mining practice often makes it hard to assess the hazard of roof collapse and surface subsidence at limestone mines due to the irregular and complicated shape of the mined cavities.
