Redpath Mining Africa, a provider of comprehensive shaft-sinking and underground mining services, will present its latest raiseboring technology, and two recently-completed key projects, at Investing in African Mining Indaba 2017.
One of these projects was a world-first decline sand tunnel for Gem Diamonds at its Ghaghoo diamond mine, near the south-eastern border of the Central Kalahari game reserve, a remote area characterised by its expansive and up to 80 m-deep sand cover.
The scope of work involved a 6 m-diameter decline tunnel development to 112 m below surface through shifting Kalahari sand at an 8° inclination. Phase one saw a 25 m-deep, 171 m-long box cut in the Kalahari sand to provide safe and secure access to the underground mine.
This was followed by excavation work using an open face tunnel shield for the concrete-lined segmented sand tunnel, of which 403 m was in pure sand, and 121 m transitioning from sand to basalt, said Redpath Mining Africa.
The 95 t open face tunnel shield acted as a cylindrical shield to protect workers and equipment underground, and also provided the necessary support to install the required 845 concrete segments for the tunnel. While such technology or methodology is not new, it had never been used in a decline before.
Within South Africa, Redpath Mining Africa has also achieved great success with the rehabilitation of Phakisa number 3 ventilation shaft for Harmony Gold. A shale band about 80 m thick (starting from 120 m from surface) had swollen, and broken out the shaft lining into the shaft cavity, causing a serious reduction and restriction in the ventilation flow within the workings. The fast-track rehabilitation of the collapsed vent shaft barrel was critical to sustain production output.
The rehabilitation method saw inflatable lightweight balloon-type bags lowered into the shaft-equipped compartments to a depth of about 210 m from surface. The bags, guided by a camera, formed a plug in the shaft barrel just below the damaged area.
After the plug in the shaft was established, the shaft barrel and cavity were filled with aerated foam cement. This stabilised the area, and enabled the team to mine through the aerated cement and pour a new lining to stabilise the shaft. The project was completed without a single injury, achieving 504 accident-free days.
“These two projects highlight our innovative solutions and expertise in developing custom solutions for our clients’ specific needs,” Redpath Mining Africa marketing and business infrastructure manager Davlin Richardson comments.
“We want to reach out to all of the key players and stakeholders who will be present at Mining Indaba 2017, with the message that we can play a critical role in developing cost-effective and safe solutions to help unlock the continent’s mining potential,” Richardson explains.