Construction World December 2018

FNB PALACE PARKADE With the dire need for safe and secure parking in the Johannesburg CBD, an opportunity presented itself for the construction of a four basement and 12 storey parking facility on the corner of Rissik and Pritchard Street. The first phase entailed the excavation and the lateral support to form the basement for the multi-storey structure to be shoe horned into.

T he scope of works entailed 42 000 m³ of bulk excavation, 2 800 m² of lateral support walls and the removal/demolition of existing concrete structures. The anticipated project duration was five months, with the builder’s break accommodated in between. The lateral support works can be further broken down into the installation of 258

PROJECT INFORMATION

• Company entering: Franki Africa • Client: Eris Property Group • Project value: R17,7-million • Start date: November 2017 • End date: May 2018 • Main Contractor: Franki Africa • Project Manager: Morta Project Management • Structural Engineers: WSP • Quantity Surveyors: Vusela Quantity Surveyors • Architect: I.C.M. • Subcontractors: Zero Azania (Bulk Earthworks), Diamond Cutting & Coring (Concrete Saw Cutting and Coring)

no. hollow bar anchors ranging in capacity from 300 to 450 KN, 146 no. percussion and hollow bar micropiles to 6,5 metres below ground level, 400 no. soil nails and 2 800 m² of gunite walls reinforced with two layers of weldmesh.

The earthworks volume finished up at 42 000 m³ of material to spoil, with a further 1 400 m³ of rubble that was sent to a recycling site to be crushed and reused. The project demanded a level of innovation, creativity and technical expertise that is not often required on projects of a similar nature. Located in the heart of the Johannesburg CBD, the Franki design and works teams were faced with ageing infrastructure/services immediately surrounding the positions of the lateral support walls. As-built information of the existing services is non-existent and/or highly inaccurate. A time-consuming exercise was undertaken by Franki Africa prior to the commencement of the lateral support system in an attempt to expose the existing services and numerous discrepancies were encountered. Design parameters were altered to suit Franki’s findings necessitating in tricky installation alternatives. Not only did the soil anchors have to miss a myriad of services at different positions and levels, but these also had to accurately installed to ensure no damage to services. Furthermore, the anchors had to provide sufficient force to prevent the movement in the soil faces. The outcomes were successfully achieved as no damages were recorded to council services. The lateral support design incorporated percussion drilled micropiles around the site perimeter. These were installed as the first operation after the services investigation was completed. Approximately 80% were successfully installed but a challenge developed in the form of unknown concrete rubble obstructions below ground level. Despite numerous attempts at installing the conventional system, an alternative was urgently sought so as to prevent programme delays. The revised system necessitated in machine modifications and urgent materials procurement. 

Construction WORLD

2 18 BEST PR O JECTS

45