ANALYSIS OF THE EFFECT GROUNDWATER LEVEL FLUCTUATION ON SLOPE STABILITY IN THE COAL MINING PLAN

Based on geotechnical drilling activities carried out in the PT Battoman Coal mining plan area, it is known that the slope material is dominated by claystone. According to Chen (1975), claystone can be expansive when exposed to water, disrupting slope stability. The presence of the Sungai Putih tributary in the mining plan area can also affect slope stability. This research aims to analyze the influence of groundwater level fluctuations on slope stability in the PT Battoman Coal mining plan area based on actual conditions as a result of the research. Ground water level observations and measurements were conducted using the Casagrande piezometer method and observation wells in the high wall area. Slope stability analysis was carried out using the software Rocscience Slide V.6 using the Morgenstern Price method and the Mohr-Coulomb failure type by simulating slopes in actual conditions, the results of the highest and lowest groundwater measurements in the period September to October 2023, namely 4,26 meters and 28,45 meters from the ground surface. The analysis was carried out in pseudo-static conditions using mining area seismicity factors based on the Indonesian Seismic Zone Map according to the Ministry of PUPR in 2017. Overall slope area high walls in cross sections A-A' and B-B' are included in the critical to stable category with FK values between 0,901 to 1,782. Recommendation of overall slope designed by Kepmen ESDM 1827K/MEM/2018 so that it is obtained overall slope which is stable in saturated conditions with FK values between 1,176 to 1,245.