Construction World December 2017

Category B: Specialist Contractors or Suppliers

2 PYBUS ROAD, SANDTON In August 2014 a project was initiated for a new office space in Sandton at the 2 Pybus Road site. The site faces the Sandton city shopping centre and is therefore in a prime location.

PROJECT INFORMATION

to run in parallel with one another. The concrete bases now required additional resources in the form of hydraulic hammers to be brought to site in order to break up the concrete. The congestion in an already resource-saturated site increased, amplifying the risk of a safety incident. Extended shifts, micro planning and management of resources was implemented and the nett effect was that the main contractor had partial access to the site on the date as originally promised. Yet again, meticulous planning and execution as well as the experience in dealing with these types of challenges, proved to be the secret to the success of this project. The lateral support was designed using the observational method. Conventional geotechnical design requires conservative soil parameters to be used due to the large variability of soils and rock in general. The application of the observational method allows the design to be optimised without additional risk to be taken and results in a cost-effective lateral support solution. Multi disciplines were running in parallel with the lateral support activities, these including bulk earthworks and foundation piling. All disciplines were planned to a micro level to ensure all contractors could work simultaneously in a crowded and space restricted environment. From both a technical and management aspect Franki showcased the optimum solution, bringing the ultimate goal of a successful project to the client that entrusted them with this responsibility. • Company entering: Franki Africa • Value: R14,5-million • Start date: January 2017 • End date: May 2017 • Main contractor: Franki Africa • Architect: GLH & Associates • Principle agent: S.I.P • Quantity surveyor: Brian Heineberg and Associates • Earthworks: Zero Azania • Demolition: Phoenecian

Highly Commended

important elements had to be determined upfront. Firstly, the approval by the neighbouring property owner to have work done in their basement and secondly, the precise location of concrete slabs, services and any possible obstructions that could be affected by the drilling works into the 90 Rivonia basement, had to be resolved. Accurate anchor positions were set out on site from the new basement end and the drilling operations implemented with resounding success. The existing four-storey building with a 3 metre deep parking basement fell over 80% of the site footprint and this presented a unique set of challenges. No demolition of this structure could happen without first anchoring back an existing concrete retaining wall that formed part of the parking structure. This retaining wall sat on the boundary with the adjacent property and together with the services in the servitude and the limited headroom for the rigs to install the anchors from the operation proved to be a significant challenge. The accuracy of as-built information of the services has proved to be, on numerous occasions, inaccurate and therefore risky for the contractor installing any form of ground anchors. After the pinning back of the retaining wall was concluded, the slabs propping the interphase between the building and this wall were saw cut and separated, and the building demolition work commenced. The demolition was effectively concluded within the anticipated programme period and the rubble removed off site, thus allowing the lateral support and bulk earthworks to commence. As the lower portion of the site neared final excavation level, large concrete bases varying between 1 to 1,8 metres deep were encountered. In order for a successful completion of the programme, the bulk earthworks, lateral support and the foundation piling activities would need

At conceptual stage, the project seemed to be relatively straight-forward with no major challenges, but, as work commenced, the unknowns rose to the surface and tested the Franki design and site teams extensively. Challenges included unknown location of services, concrete obstructions covered by soil and retaining neighbouring property structures/basements as well as time constraints necessitated in unconventional construction methods and solutions being applied. The close proximity of the neighbouring property structure comprising of the 90 Rivonia Road parking basement required that a different approach be implemented to retain the soil wedge between the two properties. To add to this complication, unknown services at different depths ran in this shared servitude. The narrow servitude prevented the conventional soil nails approach from being installed as there would be insufficient bond stress to retain the new gunite walls. The most sensible solution would therefore be to ‘tie’ the two walls together. In order to carry out this proposal, two

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