MINE DRAINAGE FACILITY PLANNING AT WASTE DUMP COAL MINE OF PT XYZ

• Main Author: Ernasari, Meilia
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86382
• Institution: Institut Teknologi Bandung

PT XYZ is an open-pit coal mining company that produces overburden material, which must be stockpiled according to the mining plan. This stockpiling is influenced by natural factors, such as hydrological conditions and the characteristics of the overburden material. In the eastern zone, PT XYZ has a waste dump composed of peat material that is highly water-saturated and capable of retaining large amounts of water. Due to the absence of drainage facilities, movement has occurred at the foot of the dump, necessitating efforts to manage runoff and design drainage facilities to address this issue. The design of drainage facilities begins with a frequency analysis of daily rainfall data from 2010-2023 using a partial duration series. The selection of probability distribution is performed through the Chi-Square test and the Smirnov-Kolmogorov test to determine the planned rainfall value. The planned rainfall intensity is then calculated using the Mononobe formula. A topographic analysis is conducted to determine the characteristics of the catchment area (CA), including its size, length, and slope. Using the data above, a Soil Conservation Service (SCS) hydrograph is constructed to obtain the peak runoff discharge. Due to the water-absorbing nature of peat, cumulative infiltration analysis is also conducted using the Green-Ampt method, utilizing physical data of the peat such as hydraulic conductivity, effective porosity, and suction head. Based on the probability distribution fit test, Log Pearson Type III was selected, resulting in a planned rainfall intensity of 38.28 mm/hour for a 1-hour duration and 42 mm/hour for 5- and 10-year return periods. The planned CA areas are 1.94 m³ for void A3 and 0.97 m³ for void B North. The SCS hydrograph shows a peak runoff discharge of 11.50 m³/s from CA void A3 and 9.57 m³/s from CA void B North, with a cumulative peat infiltration of 1.48 cm for a 1-hour rainfall. Required drainage facilities include open channels (trapezoidal, 2-2.2 m bottom width, 1-1.2 m height), drop structures (1 m height, 5-20 drops), culverts (1-1.2 m diameter, 4 lines), and drainage basins (CA A3_2, CA B North_1, CA B North_3). Retention ponds require capacities of 41,358.67 m³ (void A3) and 22,060.13 m³ (void B North) for an outlet discharge of 1 m³/s, and 33,157.27 m³ (void A3) and 16,811.97 m³ (void B North) for an outlet discharge of 2 m³/s.