ENGINEERING GEOLOGICAL MAPPING AND SLOPE STABILITY ANALYSIS USING LIMIT EQUILIBRIUM METHOD ON SIDE WALL FINAL DESIGN AT OPEN PIT MINE IN DAMAI DISTRICT, WEST KUTAI, EAST KALIMANTAN

• Main Author: Lanang Adhyananda, Nizar
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/48561
• Institution: Institut Teknologi Bandung

A Mining activity at the open pit coal mine in Damai District, West Kutai, East Kalimantan will be still operating for years ahead. However, with recent geotechnical conditions, the side wall final design of this pit has not been reaching the optimum condition for the reason that the slope angle was made the same from highwall to low wall. Thus, the side wall final design of this pit can be optimized to reach the optimum production. The aims of this study are to identifiy the geotechnical conditions of the pit and to get a safe and optimum side wall final design using limit equilibrium method, which is to find the failure plane with the lowest safety factor. Open pit mine area in Damai District consists of five rock/soil units, which are claystone 1 unit, claystone 2 unit, sandstone unit, residual soil unit, and debris unit. This area has a relatively north-south strike with dip ranging from 10° – 20°. There is an angular unconformity which acts as a boundary between the claystone 2 unit and the sandstone unit. There are two thrust faults named thrust fault 1 and thrust fault 2 which has orientation respectively N255°E/40°NW and N240°E/40°NW. Erosion and landslide were found as an exogenic process in the study area. Due to the relatively low of shear strength, sandstone from sandstone unit (c=30 kPa, ?=27,25°) and claystone from claystone unit 2 (c=262 kPa, ?=13,45°) can be a threat to the mining activity, especially when these materials are acting as a dump. The Side wall final design has to be changed to get a safe and the most optimum condition, which has the steepest slope but still fulfills minimum safety factor and maximum failure probability criteria for both static and dynamic conditions. Slopes on cross section A and B has to perform layback until the slopes have respectively 24° and 30° slopes angle to get the standard criteria, while slopes on cross section C, D, E, and F can perform cutback until the slopes have respectively 35°, 59°, 81°, and 63° slopes angle to get more coal reserves.