The Civil Engineering Contractor June 2018 | Page 16

ON SITE The massive piles will comprise about 40t of rebar to support the huge weight above. The good soil that comes from the excavations will be used on other projects, while the rest will be disposed of in municipal dumps. Devan continues: “Presently, we have completed the bulk excavation, by and large, with one section remaining. How we sequenced the earthworks was by starting from the northern face, working towards the southern face, creating the excavation platforms that we required for the piling to get underway.” The piling operations had literally started on the day of the site visit, with the first pile in progress. Dan Alford, contracts manager at Mega Pile Inland, says that Mega Pile Inland is responsible for the major lateral support works and piling works within the four parking basements. His response to comment on the large puddles of water possibly being 14 - CEC June 2018 from groundwater seepage is: “The significant water on the site was not from water seepage, but from the substantial rain experienced over the past week,” Alford assures and adds: “We have had about 0.5 metres of rain since the start of the project. Despite this, we are still on track with meeting the deadline, although the rain causes logistical problems with trucks moving in and out of the site. We were concerned about encountering groundwater at the base of our excavation, but fortunately, we have not found any.” When asked about the number of piles, he says with a grin: “96 piles in total. I think this was intentional, as this is 96 Illovo.” The piles are various diameters, ranging from 500mm to 1.2 metres — BIG piles, with heavy steel, to support massive loads. The concrete used in the piles amounts to about 700 cubic metres, with about 40 tons of rebar. The 13-metre-high basement’s retaining walls are made of wet Shotcrete, Alford explains: “Previously, dry Shotcrete was used. This new wet Shotcrete is an innovation; it reduces wastage massively and also produces a more consistent mix and wall finish. “In the old conventional system, using dry Shotcrete (gunite), the process was to add the water at the nozzle, whereas wet Shotcrete is already mixed. By adding water at the nozzle, the emerging concrete spray can be inconsistent, dependent on the consistency/pressure of the water spray. Now we use ready-mix, which goes straight through the nozzle. This gives uniform quality and moisture consistency, which also reduce wastage considerably. Air entrainment