The Tutupan Coal Mine in South Kalimantan, Indonesia has an annual production capacity of 41 million tonnes of coal. It is reputed to have coal reserves amounting to 3 billion tonnes of thermal coal, making it one of the largest coal reserves in Asia and the world.
Adaro Indonesia planned to develop a multi-seam deposit of low-ash, low-sulphur, bituminous coal along an 18 km strike length. The planned mining depth of 300 m would extend some 280 m below the water table.
As is typical for coal mines in Indonesia, the presence of uncemented sands and mudstone required careful design of the low and high walls to reduce any possibility of landslide, which could disrupt or curtail mining or even result in fatalities. Both the footwall and highwall materials included the uncemented sands and mudstone, which were also common in the interburden units forming the mine floor.
An evolving mine design appropriate to the conditions was informed by our geotechnical investigations, which also extended to other crushing, plant, stockpiles, load-out facilities and an 80 km haul road over very soft swamp materials up to 24 m thick with high peat content.
We conducted extensive and continuous hydrogeological investigations to assess dewatering requirements and groundwater-related stability issues. Our team undertook hydrogeological drilling, test pumping of production dewatering bores and the analysis, design and implementation of dewatering systems for the footwall sandstone aquifer.
We continued to assist our client with analysis and engineering reporting. We visited the site quarterly to check the mine condition against our design recommendations. In addition, our team trained Adaro’s engineer on site so that our client could continue some aspects of the work independently into the future.
Due to our extensive involvement in the project over 18 years, our client was able to achieve its goal of mining deeper while minimising the risk of catastrophic wall failure.