For the first time in more than two decades, on November 9, 2018, a South African company received the Award of Excellence at the International Concrete Repair Institute Awards, which took place in Omaha, Nebraska, in the US.
The Award of Excellence was presented to Sanika Waterproofing Specialists for its professional concrete repair and waterproofing of Anglo American Coal’s mine ventilation shaft at its Goedehoop colliery, in Mpumalanga.
The ventilation shaft is about 60 m deep and more than three decades old.
Sanika explains that the shaft experienced ingress of water over the past 35 years, with a notable increase in the last couple of years through the joint interface, resulting in potential flooding and deterioration to the existing concrete shaft liner.
“The excessive leaks were being pumped out on a daily basis as part of a routine operation which was required for the normal running of the mine; how- ever, over the years, the underground water levels increased, exacerbating the potential for significant leakages and flooding of the mining levels.”
Early in 2017, the underground build-up of water broke through the concrete ventilation shaft, leading to excessive water penetration into the mine.
A solution to the water penetration into the shaft (about 7 000 ℓ per minute) was necessary, failing which the possibility of closing the affected shafts was inevitable.
There were numerous water ingress points along the entire depth of the shaft, with the primary water ingress area located between 19 m and 25 m below ground level.
As a ventilation shaft, access would require the manufacture and installation of “elaborate” custom-made access equipment for both personnel and equipment, which was undertaken by Sky Jacks.
“Even after extensive panel tests by various contractors, none were able to apply a product that could withstand the immense negative pressure exerted by the water in the mine shaft,” Sanika recalls.
Semane Consulting Engineers, which specialises in mining infrastructure, contacted Sanika; the company had previous successful dealings with a South African platinum miner, the company reports. Sanika specialists were asked to undertake the specialised and complex remedial measures to initially abate and eventually eliminate the ingress of water into the shaft.
Semane Consulting Engineers, as well as Sky Jacks, was actively involved throughout the project, Sanika comments.
Numerous tests were carried out to determine the most effective procedures to access the mine to investigate the concrete damage below water level and confirm structural integrity as well as safety.
The scope of work focused on the main water ingress points that were in urgent need of concrete repair and jointing detail, as well as surface waterproofing applications.
Based on all information gathered during the investigation stage, Sanika concluded that the Kryton Leak Repair System was the best course of action for a project of this magnitude.
“The very first obstacle to overcome was that of access . . . 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,” Sanika states.
The inspection and preparation of the site were imperative and a borehole had to be sunk to the depth of the major water ingress and camera equipment lowered into the borehole to accurately investigate the ingress from the positive side. “A scan of the concrete in the affected areas was conducted to ensure safety and that the integrity of the structure was still intact.”
With information gathered by visuals, a Krytonit Swelling Waterstop was introduced into the positive side to reduce the water flow to a manageable level.
The Kryton Krystol application over the entire surface of the concrete structure resulted in the growth of crystals throughout the concrete mass, preventing any further water or air ingress into the concrete, and thereby transforming the concrete into a waterproof barrier.
The growth of these crystals into the concrete and subsequent waterproofing of the concrete will retard any further deterioration of the concrete structure through water ingress and substantially extend the life span of this structure.
“The overall result is a safe, dry and useable structure,” the company affirms.