ANALYSIS OF GROUNDWATER TABLE FLUCTUATION IMPACT ON THE SLOPE STABILITY DESIGN OF DISPOSAL XYZ AT PT. BUKIT ASAM TBK. WITH MORGENSTERN-PRICE METHOD

Abstract

Disposal areas are crucial in open-pit mining as locations for overburden material dumping. However, the stability of disposal slopes is highly influenced by the geotechnical properties of the material and groundwater table (GWT) fluctuations. This study was conducted at Disposal XYZ of PT Bukit Asam Tbk. with the objectives of analyzing the geotechnical conditions of the material and GWT elevation, assessing the effect of GWT fluctuations on slope safety factors, and providing technical recommendations to maintain slope stability. The research method utilized secondary data such as topographic maps and material mechanical properties, as well as primary data obtained from monitoring wells. The analysis was carried out using GeoStudio software (Seep/W and Slope/W) with the Morgenstern-Price method, Mohr-Coulomb failure criteria, steady-state seepage analysis, and from-parent condition analysis. The results showed that rising GWT levels decrease the slope safety factor (SF). Under low GWT conditions, SF values are greater than 1.3 (safe), while under saturated conditions, the SF decreases to approximately 1.1 (critical). The proposed technical recommendations include the construction of surface and subsurface drainage systems, groundwater monitoring with automatic water level recorders, and revegetation.