THE HARMONIZING MINE PLANNING IN THE EAST KALIMANTAN COKING COAL MINE: THE CHALLENGES AND IMPROVEMENTS

THE HARMONIZING MINE PLANNING IN THE EAST KALIMANTAN COKING COAL MINE: THE CHALLENGES AND IMPROVEMENTS Ashabul Kahfi1*, Dwi P. Fransiskus2, Wijanarko K. Adi,3 Ahmad Prayogi, Luqman S. Purwosasongko4 1,2,3,4)Engineering Department, PT. Petrosea, Tbk. Artikel masuk : 31-01-2024 , Artikel diterima : 27-02-2024 ABSTRAK The coking coal mine at the research site is in the Pamaluan formation East Kalimantan. The condition of the mine has many complexities and challenges, such as natural slope condition (30º-35º), narrow pit area and low out pit dump capacity limited by land compensation issue, overburden material, geological structure, coal with very thin layers (<1 m) and consist multiple products in a layer, small number of strips and large number of blocks and high SR pit and SR balance in short range. Keywords: Challenges, Improvements, Mine Planning In mine planning at the research location, many improvements need to be made so that all aspects, starting with mine planning and operations, can run smoothly and profits can be as expected. Some of the improvements that have been made at the mine such as build mine planning concepts, build fleet allocation rules, structural and stratigraphical geology modelling and improve drill & blast plan, implementation dynamic mine planning and optimize mining digital product. By implementing these improvements, significant positive impacts have been achieved, such as Consistently maintain mine planning compliance (accuracy) >97%, Maintain fleet productivity performance in range of 95% - 110%, Consistently achieving production targets >97%, Able to maintain SR balance by achieving weekly coal plan with the range of 94 - 103%, Achieving blasting performance results with a value of >97% and Maintain work safety aspects with no accidents and loss time injury. Ashabul Kahfi: Doi : https://doi.org/10.36986/impj.v5i2.121 93 Indonesian Mining Professionals Journal Volume 5, Nomor 2, November 2023: 93 - 104 working with these challenges to maintain mining performance. BACKGROUND The goal of mine planning and design of any coal mining operation is to design an integrated coal exploitation system that will ensure that the coal is extracted and prepared to meet a desired market specification, at a minimum unit cost, within acknowledged safety, health, social, legal and regulatory constraints. A large number of specific engineering, scientific and economic disciplines contribute interactively to the overall mine planning and design process, thus making it a true multi-disciplinary activity (Spearing et al, 2023). THE CHALLENGES The condition of the mine has many complexities and challenges, such as natural slope condition, narrow pit area and low out pit dump capacity limited by land compensation issue, overburden material, geological structure, coal with very thin layers (<1 m) and consist multiple products in a layer, small number of strips and large number of blocks and high SR pit and SR balance in short range. Natural slope condition Coal is an organic material that forms in sediments from large volumes of vegetation as they die, regrow (frequently in swamps and wetlands) and are slowly buried over geological time becoming solidified due to increasing temperature and pressure. The swamp location is important as the dead vegetation does not always readily decay as the swamp is typically oxygen deficient, so peat is often formed and then converted to coal over several hundreds of millions of years. In the pit mining location, the relatively steep natural slope has an average slope of 35–50 degree. This is due to the presence of deposited coal, which is indeed located at the foot of the hill, so it is required to dig the hill to the top to get coal. Figure 1 shown the 2D section of the natural slope pit condition. With these conditions, challenges have been presented since exploration, where drill data collection is limited by natural slope conditions and continued during land clearing and mining operations, which greatly limit the ability of mining equipment with high slope degree. In addition, the hill also has bumpy hill face, with different conditions in each area. This site location has coking coal commodities in pamaluan formation East Kalimantan, that have unique characteristics that become challenges to mining. This paper shows all the challenges that exist in this coking coal mine and presents improvements by utilizing all aspects of literacy, methods and technology as part of Figure 1. Section 2D natural slope Narrow pit area and low out pit dump capacity limited by land compensation issue Moreover, the remaining area is still reduced by the land area that cannot be acquisitioned. This caused a very limited OPD capacity of only about 4.7 Mbcm, or less than 15% of the total disposal needs. The pit shell design is significantly influenced by the concession boundary on the west side and the permanent infrastructure area on the north side of the deposit area. The pit shell and concession boundary have a nearest distance between pit boundaries of 90 m and a longest distance of 550 m, and the pit shell and permanent infrastructure area have a distance about 250 m. Overburden Material The lithologic composition in the mining area is dominated by claystone and sandstone where the percentage of claystone is 65% and sandstone 35%. Claystone material has a unit weight (γn) of 16 KN/m3, saturated unit weight (γw) 19 KN/m3, cohesion 250 KN/m2, and friction angle 28º. The sandstone material has a unit weight (γn) of 18.1 KN/m3, cohesion of 600 KN/m2, and friction angle of 32º. Both overburden With the pit shell surrounded by the concession boundary, this also causes the area that can be used as an out-pit dump (OPD) area to be very limited. 94 Indonesian Mining Professionals Journal Volume 5, Nomor 2, November 2023: 93 - 104 materials can be categorized as very hard materials for overburden in coal mining areas which has the potential to cause difficult digging due to the hardness of the material. layering where it also forms lenses layer and pinch out. The sandstone lens layer has thickness from 1 4 m and interbedded the claystone layer. This indicates that the depositional environment of this layer is in a distributary channel complex Especially for sandstone material, it has a unique . Figure 2. Stratigraphical layer and depositional environment Geological Structure There are many geological structures found in the overburden layer in the mining area. Generally, geological structures found in sandstone layers are blocky structures that form blocky joints, gray- brown grain color, with a high number of natural cracks. Sandstone layers that have this structure are found in the upper sandstone layer which is 10 - 15 m thick. The geological structure is not only a weak layer for the stability of the mine slope, but also become a zone that causes energy loss in blast activity due to reduced gas propagation performance. This is (...truncated)