Civil Engineering August 2021 | Vol 29 No 7

activities as the natural beauty of the area must be preserved. At the end of 2020, Grinaker-LTA completed the construction of seven foundations for a new RopeCon as well as the concrete sliding of a silo that will feed the second RopeCon. The second RopeCon will span 2.8 km, transferring ore from the mine’s Merensky shaft to the central silo, where it will in turn be transferred again to the southern processing plant. The biggest concrete foundation that Grinaker-LTA con- structed for the second RopeCon is termed Tower 2, which has a 230 m 3 base with a 350 m 3 plinth that sits on top of that base. 4 200 T ROM ORE SILOS Of the three silos constructed by Grinaker-LTA in recent years, the tallest is 37.42 m high with an outside diameter of 14.8 m. Both the second and third silos’ wall slides finished ahead of programme, with the second wall slide reaching a height of 30.56 m within 10 days. This was achieved with concrete slip forming which is a fast paced, continuous construction process where concrete, rebar and cast-in items are placed 24 hours a day for the entire construction duration, while the slip forming shutter is jacked up at a continuous pace. All three silos have a storage capacity of 4 200 tons and will feed the two RopeCon conveyors with ore. THE NORTH DRIVE STATION The North Drive Station constructed by Grinaker-LTA is a concrete foundation and support structure for the RopeCon’s drive units. The nearly 900 m 3 base of the drive station resists the momentum generated by the drive unit when it propels the RopeCon over long distances. The drive station is located on a steep hill, and due to access constraints at the time, the 900 m 3 of concrete for the base was pumped through a 51 m long static line that ran uphill at a nearly 45° angle. Grinaker-LTA executed the drive station base pour over three days with a concrete supply averaging 16 m 3 /hour. This was the second drive station base constructed by Grinaker-LTA on the Booysendal Mine. CENTRAL COMPLEX WORKS Also noteworthy is the infrastructure that Grinaker-LTA constructed at the Booysendal Mine’s central complex. This infrastructure includes an 8.5 Mℓ reservoir which had no major leaks. The reservoir’s 12.2 m high walls were com- pleted in 16 pours and finished a month ahead of programme. Another noteworthy pour was the vent shaft deck that was constructed on a platform next to the face of the mountain, 56 m higher in elevation than the central terrace area. For this pour, concrete was pumped from one concrete pump on the central terrace into another concrete pump that was at a higher platform. This second concrete pump fed into a static line that spanned the last of the distance to the slab. The pour was planned and executed successfully by Grinaker-LTA, like many others. PROSPECTS Grinaker-LTA has a very good relationship with both DRA and Northam – something the company is proud of and strives to maintain. Grinaker-LTA will continue to deliver safe and quality projects to clients for many more years to come. For more information www.grinaker-lta.com +27 (0)11 923 5000 Chris Tshivhidzo General Manager: Civil – Structures chris.tshivhidzo@grinaker-lta.co.za Civil Engineering August 2021 5 The nearly 900 m 3 drive station base resists the momentum generated by the RopeCon The 8.5 Mℓ reservoir at the mine’s central complex Mountainous topography and underlying rock and boulders presented a challenge