Royal Bafokeng Platinum is investing in the establishment of a new chairlift decline at Bafokeng, aimed at enhancing safety and improving production speed.
Royal Bafokeng Platinum is investing in the establishment of a new chairlift decline at its Bafokeng Rasimone Platinum Mine (BRPM) north shaft, aimed at enhancing safety and improving production speed. The project can be described as innovative, quick and low on capital costs thanks to contractors SSIS and G4 Civils’ design/build contract writes Laura Cornish.
In June 2014, every underground miner at the Western Limb situated BRPM will access the mine’s north shaft via a new decline chairlift. It will accommodate 550 people per hour travelling to their respective work area and ensure their journey is a safe one. “Once complete, we will be able to increase tonnage output while providing our employees with improved and faster access to the underground workings,” says Paul van Wyk, section manager at BRPM.
Undertaking a project of this nature, in spite of poor platinum demand and weak platinum prices, has led to a design and build contract which is nothing short of impressive, from every aspect.
Together with EPCM contractor DRA Mining, multi-disciplinary engineering firm SSIS and civil engineering construction company G4 Civils presented BRPM with turnkey package for the installation of a tunnel that not only opposes traditional development methodologies but is still quick to deliver and substantially lower in cost.
“Unlike typical tunnel development, blasting and cement lining a decline, this project entails the construction of a box cut and the installation of a patented corrugated steel 80 m long tunnel structure which has taken only a few months to complete,” explains SSIS director, Mark Webb. Once the tunnel is installed, the box cut will be filled, leaving no evidence of the tunnel other than its entrance.
The contract (to develop the boxcut) was awarded in January 2013 and subsequently the tunnel in March. In October, 10 months since project start, the tunnel development contract was completed.
G4 Civils mining director Quintin Badenhorst explains the first critical project step and outlines its importance. “Bulk earthworks to establish the box cut with temporary support were the first essential steps in the project. It is the necessary foundation required to install the tunnel. Compared to a permanent box cut which is prone to weathering, watering and requires lateral support upkeep, a closed box cut is more viable and cost effective in the long term.”
“The design of the box cut is critical to the overall project as it must support and accommodate the tunnel in terms of angle, length and support,” Badenhorst adds.
Installation of the tunnel was a short three day process. The 1.2 m long steel segments are pre-erected, transported to site and ‘inserted’ onto the demarked tunnel area using an overhead crane. A small Bobcat excavator pulls the segments into place and aligns them. SSIS is the African distributer for the steel product which is manufactured in the States by Atlantic Industries Limited (AIL) – an expert in the development of efficient infrastructure solutions in corrugated metal structures. “The structures, fully imported from AIL, are quick and cheap to assemble and install and are stronger than conventional concrete or cement tunnel structures because it is not prone to negative arching. It is the reason we are able to fulfil our goal in meeting quick deadlines at minimal cost, thereby delivering clients with true value engineering,” Webb outlines.
Tunnel statistics and details
- 80 m tunnel length connecting directly with underground workings
- Multi-plate corrugated structural steel
- 200 x 55 mm corregation profile
- 1.22 m segment lengths
- 13 segments each comprising three rings
- 39 rings in total with five plates per ring (circumference)
- 3.97m inside tunnel span
- 3.38m inside rise
- Decline Slope Angle: 16.5°
- 18.83m maximum height cover
While the overall project can be described as a relatively seamless process, SSIS and G4 Civils did have to contend with a few challenges.
“Unlike a traditional decline which ranges at a dipping angle of between 7 and 10⁰ and a traditional chairlift decline which dips at about 12⁰, the BRPM north shaft chairlift decline is at an extremely deep 16.5⁰ angle. The reason for this can be attributed to unstable ground conditions and the need to reach more stable bedrock material as well as the requirement to align the tunnel with the underground workings,” SSIS engineer Frikkie Rautenbach points out.
The final project element, prior to the installation of the chairlift, is backfilling the box cut – a major engineering feat in its own right. “80 m long with a 23 m highwall, the shape of the box cut was designed to accommodate the tunnel’s shape, ensuring it provides support once filled, especially with the added steepness pressure. And filling it will was also performed according to a specific design plan. A mixture of the removed box cut soil and concrete will be poured in equal amounts at the same time on both sides of the tunnel to ensure it does not roll or move out of position,” Badenhorst outlines.
Completed in October, Van Wyk says the project has achieved excellent safety results and remains well within budget and timeframe, “thanks to solid working relationships, full transparency between parties and common goal.” Installation of the chairlift will proceed. It will connect to the mine’s 5 Level, and directly to an underground chairlift.
“We are extremely proud of this project and what we have achieved for our client. It also leads the way forward in working together on future projects to deliver turnkey solutions,” Webb and Badenhorst conclude.
Other SSIS and G4 Civils projects
SSIS has completed projects similar in nature to the BRPM tunnel. Both larger in terms of tunnel dimensions and length, Sasol Mining’s two new mines Thubelisha and Impumelelo both access underground via an SSIS pre-constructed tunnel. The company’s Shondoni brownfields expansion project also includes an SSIS tunnel.
G4 Civils boasts a similarly impressive work portfolio. The company is currently underway with numerous civils, earthworks and constructuion mining-related projects for Xstrata South Africa, Impala Platinum, Anglo American Platinum and Shanduka.
RB Plat holds a 67% interest in BRPM, with partner Anglo American Platinum holding the rest. The mine has a 4E resource base of 72.4 Moz (57.6 Moz, measured and indicated).
It is predominantely a Merenksy reefmine, supplemented by additional UG2 ounces. Operational since 2008, it still has decades of life remaining. It has full mining and concentrating infrastructure on site, with a 200 000 tpm nameplate capacity.