Deformation measurements and a stability analysis of the slope at a coal mine waste dump

Abstract This study surveyed and investigated the deformation of the coal waste dump slope and the natural ground slope under the waste dump at Dogye village in Samcheock city, Gangwon Province, Korea. Multiple sets of south-north tension cracks were observed at the crest of the coal waste dump slope. These cracks were greater than 100 m in length, and the resulting drop head averaged 1.0–1.5 m. To investigate the behaviors of the waste dump slope and the natural slope under the waste dump, wire sensors and a rain gauge were installed at the crest of the waste dump slope, and inclinometers were installed in the natural slope of the ground under the waste dump. According to the monitoring results, the deformation at the crest of the waste dump slope steadily increased and then converged over time due to the effect of the infiltration of rain into the ground after rainfall. In addition, the horizontal deformation of the natural slope under the waste dump was affected by the accumulated precipitation. The basis of this effect is that the rate of increase of the maximum horizontal deformation tends to show increasing or convergent behavior according to the precipitation. The slope stability analysis showed that the safety factor of the natural slope before the discharge of the waste was 2.14. Meanwhile, the safety factor of the waste dump slope, including the natural slope in the dry season was 1.66 and the safety factor in the rainy season was 0.98. The natural slope before the discharge of the waste and the coal waste slope, including the natural slope remained stable during the dry season but became unstable during the rainy season, especially when the ground water level in the waste dump slope becomes rising as a result of infiltration by rainwater. The waste dump slope and the natural slope under the waste dump experienced deformation due to the increasing weight placed on the waste dump by the infiltration resulting from rainfall.