Civil Engineering April 2021 | Vol 29 No 3

On the cover That the Harbour Arch is set to become an iconic landmark in Cape Town is not disputed. Developed by the Amdec Group which boasts, among others, The Yacht Club, Melrose Arch and Evergreen Lifestyle in its portfolio, the Harbour Arch project is set to be the largest mixed- use precinct in the ‘Mother City’ CBD. Consisting of six individual towers, the development will offer a 360-degree view of the city, Table Mountain, the harbour and beyond. Keller’s contracts engineer, Daryn Cloete, explains how the approximately 11 m deep three-level basement was constructed. The excavation consisted of loose sandy soils, stiff clays, and hard rock material, all amounting to 66 000 m³ of material to be removed to spoil sites. “The project comprised both lateral support and foundation piles. The lateral support was essentially a triple basement, constructed by means of soldier piles, jet grout columns, anchors and gunite arches with dewatering included in the scope of works. The foundation piles comprised large diameter temporary cased augered piles, which were socketed into hard rock,” explains Daryn. NOT WITHOUT CHALLENGES One of the major challenges the team had to contend with was the disruptive nature of the Covid-19 pandemic. The site handover for the start of the project was on 22 January 2020. After mobilising on site and commencing the lateral support piling in February 2020, Covid-19 struck, halting operations for three months from March to May, before work could resume in June 2020. “Apart from Covid-19, concrete ob- structions and old foundation footings as well as the relocation of services presented major challenges and necessitated rese- quencing of the works, including building of a cable tray capping beam on top of the lateral support piles to house the relocated services,” explains Daryn. “The jet grouting proved to be a winner with regards to sealing off the Keller supports Amdec Group’s Harbour Arch project Leveraging its experience of executing technically challenging geotechnical projects with accelerated programmes, Keller, formerly known as Franki Africa, once again proved its mettle at the Harbour Arch project in Cape Town. 4 April 2021 Civil Engineering Day 1 on the Harbour Arch project