Mining is a backbone of the South African economy, and the Anglo American Coal company has been a key catalyst in creating a safer, stronger, healthier and more sustainable South Africa since its inception in 1917.
One of the key requirements of a mine is to ensure that provisions are made for adequate ventilation. This includes airways for the air to flow down the mine to the working areas. The primary ventilation system consists of an intake (downcasts) through which the fresh air passes to the mine working areas, and an exhaust (or upcasts) where the air passes after having bene ventilated. Any interference with the ventilation system would have a direct impact on the safety and operational capacity of the mine.
The Goedehoop Colliery Block 7 mine ventilation downcast shaft is approximately 60m deep and was constructed in the 1980’s. The shaft consists of a segmented ring liner arrangement with an interlocking joint connection between the different shaft segments. The shaft had experienced an ingress of water over the last 35 years with a notable increase in the recent years through the joint interface, posing potential flooding and deterioration to the existing concrete shaft liner.
Early in 2017, the underground build-up of water broke through the concrete ventilation shaft, allowing excessive water penetration into the mine. The situation was so dire that the ingress of water into the shaft had increased to the rate of ~7000 litres per minute. To run the mine on a normal schedule, excessive leaks had to be pumped out daily. Repair was vital, failing which closing the shafts was not short of inevitable.
Hired to repair the mine, Sanika Waterproofing Specialists, the exclusive distributors for Kryton products in South Africa, found it critical that the entire structure be accurately rejuvenated, repaired and waterproofed using Kryton’s Crystalline Krystol® Technology, which has a proven record of success in similar projects worldwide for the last 40 years.
The first obstacle to overcome was that of access to the 7m deep diameter shaft, which was riddled with leaks. After numerous discussions and on-site tests, Sky Jacks, the appointed access company devised a cradle system to safely lower workers into the shaft. The cradle also needed to be stabilised against the sides of the shaft to reduce movement for the work at hand.
The inspection and preparation of the site was imperitive to this project. A borehole was equipped with a camera and sunk into the ingress to accurately investigate the ingress from the positive side. A scan of the affected concrete was conducted with GPRS equipment to ensure that the safety and integrity of the structure was still intact. With the information gathered, it was determined that the Krytonite™ Swelling Waterstop and the Krystol Leak Repair System were the best solutions to repair leaks of this size.
To prepare the site for the application of Kryton products, the damaged sections of concrete were cleaned and prepared using a dustless sandblasting and ultra-high pressure cleaning system. Chisels and concrete cutting machines were used to chip chases along the entire length of all water ingress points, construction joints and cracks.
As part of the Krystol Leak Repair System, Krystol Repair Grout is a crystalline concrete waterproofing product that stops the flow of water to permanently repair leaking cracks, holes and joints in concrete, and can also be used to resurface and waterproof defective, damaged or deteriorating concrete. The grout employs advanced fiber technology and shrinkage controlling additives to prevent cracking.