Analisis Subsidence dan Kestabilan Lereng pada Disposal Area Sump Batutegi di Site North Tutupan, PT Adaro Indonesia

Abstract

This research focuses on the Batutegi Sump Disposal Area at Site North Tutupan of PT Adaro Indonesia, a coal mining company with a large and growing production target. This production growth results in an increase in the volume of overburden that must be removed and stockpiled. However, the problem faced is the presence of large amounts of mud in the bottom layer of the disposal, which can cause land subsidence in the disposal area. This study uses primary and secondary data. The primary data used were Unconfined Compressive Test (UCT) results from overburden and mud soil samples. This data, along with the initial topography of the Batutegi Sump area, the design of the Batutegi Sump Stage 7 Disposal Area, and material properties, were used for modeling the disposal using Minescape and Rockscience Slide software. The analysis was conducted using the Limit Equilibrium Method in the form of the Bishop, Janbu, and Morgenstern-Price Methods. The results showed that the average subsidence was about 2.34 cm, with the factor of safety before subsidence ranging from 1.23450 to 2.09151, depending on the method used. After subsidence, the factor of safety decreased, but not significantly. Across the three methods, the effect of subsidence on the factor of safety of the disposal ranged from 0.52% to 38.38%. These findings suggest that the use of laboratory compressive strength tests in measuring subsidence at the Batutegi Sump Disposal Area may require review, as the assumptions used in the factor of safety analysis appear to have a high degree of uncertainty. In addition, the trendline shows that the greater the subsidence, the smaller the factor of safety. This highlights the importance of managing and addressing subsidence issues in large coal mining operations, such as those faced by PT Adaro Indonesia.