A Case Study of Subsidence over an Abandoned Underground Limestone Mine

Abstract

ABSTRACT Mining is a dynamic operation, and the instability of mine openings is mainly due to structurally controlled gravity fallouts and stress induced rock mass failures. The surface damage due to subsidence is an inevitable consequence of underground mining, which may be immediate or delayed for many years. The surface damage in an abandoned underground limestone mine in Korea is observed to be of different forms from simple sinkhole formation to a large scale landslide of the ground in the subsided area. For the prevention of damage, it is very important to predict an extent of ground movement. Therefore, in this study, the cause, extent and forms of subsidence have been analyzed and the mechanism of subsidence in the study area has also estimated based on the given information. A probabilistic approach based on a simple predictor model is applied to a subsidence case. Geological and mining parameters can affect the magnitude and extent of sinkhole subsidence. These influence factors should be evaluated to predict and mitigate subsidence hazards. The model needs geometrical parameters and mechanical properties and these measurements can imply random errors. Therefore, Monte Carlo simulation is used to consider the effects of random errors on the modified model. A number of the sets realized from the simulation, which are combined of depth of subsided ground, bulking factor and angle of repose, are used to calculate the extent of subsidence.