Analisis Kestabilan Lereng Lowwall Pit 4 Menggunakan Finite Element Method pada Site DMP PT Cipta Kridatama Sumatera Selatan

Abstract

The west-south CK-DMP pit 4 lowwall slope often experiences landslides. The upper slope contains unexposed land and also unexposed coal seam B, so slope stability analysis is required. This study aims to obtain the results of Rock Mass Rating (RMR) analysis of claystone material, analyze the results of slope safety factor calculations using the Finite Element Method (FEM) with slope stability software, and design an appropriate slope model for the west-south lowwall pit 4 RL 60 in accordance with the safety factor criteria specified in the Kepmen ESDM RI No. 1827 K/30/MEM/2018. Primary and secondary data were processed to obtain the Bieniawski 1989 RMR value. The RMR value was used to determine the Generalized Hoek-Brown failure parameter, which was then analyzed using the Finite Element Method (FEM) in slope stability software. The basic principle of FEM is to reduce the cohesion and internal shear strength values. FEM analysis yields the Strength Reduction Factor (SRF) and total displacement. The SRF value is assumed to be equal to the Safety Factor. The RMR value for claystone material is 45, categorized as Category III Good Rock. The Generalized HoekBrown parameters , ,and 𝑎 are 0.074, 0.0002, and 0.511. The slope is analyzed in static (without disturbance) and dynamic (with seismic load) conditions. The results of the FEM analysis of actual slope in static and dynamic conditions are SRF and total displacement values of 1.01 and 0.0627041 meters, and 0.92 and 0.134001 meters. This indicates that the slope is unsafe due to discontinuities, so slope geometry recommendations are provided. The recommended slope geometry is an 8 meter bench height, a 5 meter bench width, and a 25° slope angle. The FEM analysis of the recommendations yielded SRF values and total displacements in static 1.43 and 0.352504 meters and dynamic 1.32 and 0.845934 meters.