STABILITY ANALYSIS OF UNDERGROUND LIMESTONE MINE USING A THREE-DIMENSIONAL LASER SCANNER

Due to complex geological settings and structures, underground limestone mines generally require accurate surveying performance, and geological modeling adopting laser scanning devices has become a routine site investigation process. At some mines however, information on the geologic structures at the mining site are still recorded and processed based on two-dimensional drawings. As a result, there is a risk of fatal accidents, and safety and environmental issues are still remaining. Recently, underground limestone mining is rapidly increasing in Korea due to the environmental regulations and resource depletion at shallow depth, and specialized and systematic guidelines for mine opening design securing the underground stability. Laser scanners of high performance capability are used at some mimes to construct accurate geospatial information, which can increase the safety and efficiency of the mine operation.

In this study, stability of pillars of an underground limestone mine was analyzed using a three dimensional laser scanner. Laser scanner used in the study is Trimble X7, which is a compact and lightweight system with automatic calibration and infield registration capability to increase efficiency and provide reliability in the field. The test bed mine has been developed with three drifts, 9~12m wide and 6m high. In drift no. 3, two pillars of major stability concern are located, and laser scanning was performed to obtain point-cloud data. A total of 581 discontinuities were extracted and statistically treated using the obtained point-cloud data, and a discrete fracture network was simulated and applied to the numerical analysis model. The stability, based on the safety factor and displacement, was evaluated for two pillars located in large underground openings using the numerical analysis model. The results showed that the safety factor tended to decrease from the center of the pillar to the side wall. The maximum displacement occurred in a part of the pillar side wall. However, it was concluded to be insignificant compared to the size of the pillar.