Construction World January 2018

PROJECT PROFILE

compared to the conventional method of installing the pressure pipe through a tunnelled concrete ‘sleeve’. During 2016, a total of 1 200 m of pipeline was installed successfully with a high degree of precision, ahead of programme and within budget, using micro- tunnelling. An average of 16 m/day was achieved during a typical 9-hour day. A total of eight drives were done from shafts measuring 6 m x 4 m with the longest drive being 218 m. CSV Construction’s Herrenknecht AVN 800 XC TBM is the first of its kind to be owned and operated by a Southern African company. The project team is confident that the micro-tunnelling technology will form a crucial role in the successful implementation of future pipeline projects located in congested urban areas of Southern Africa. The environment The construction of the CF3-2 was undertaken through residential areas. Therefore social and environmental considerations were prioritised by the project team. A full-time Community Liaison Officer was appointed for the duration of the contract, who updated residents regularly of activities on-site, and addressed general queries and complaints. AECOM also appointed an Environmental Control Officer, who conducted monthly audits, and reported on any findings relating to the Construction Environmental Management Programme. Due to the use of the micro-tunnelling method of construction a much smaller impact was made on the areas involved requiring less disturbance and rehabilitation. The equipment used during the micro- tunnelling process is all silenced machines preventing noise pollution to the surrounding areas. Health & Safety Due to the nature of this project, there were many safety risks that had to be managed daily on-site. The core project team and the contractor’s workforce were reminded regularly not to become complacent when it came to health and safety matters, and to ensure all work practices on-site complied with the Occupational Health and Safety Act and Construction Regulations. Despite the many risks on-site associated with deep-trench excavation, installing large-diameter concrete pipes, and using heavy machinery, there were no major construction-related incidents on-site. 

CSV operators in the microtunnelling control room.

Construction of the rising main discharge chamber with barometric loop.

construction route relatively quickly. In areas close to structures or existing services, the sheet piles were installed using vibration-free hydraulic press silent piling machines. Micro-tunnelling The 5,3 km CF3-2 route traverses a densely-populated area of Cape Town, where significant sections of the pipeline would need to be installed beneath narrow and busy roadways. On some of the road crossings sensitive existing services had to be crossed with minimal clearances. CSV Construction offered micro-tunnelling as an option, in terms of technical and financial feasibility, with the ultimate goal of reducing the social and environmental impact during construction. Micro-tunnelling is a specialised pipe- jacking operation, preceded immediately

by a Tunnel Boring Machine (TBM) that removes soil mechanically from the jacking face using a slurry process. The TBM is operated remotely from a control centre on the ground surface. No human into the tunnel is required. Following extensive technical and financial evaluation, it was found that micro-tunnelling some challenging sections of the CF3 2 would not only mitigate social and environmental impacts, but would also offer the CCT a financially feasible alternative, with reduced risk and higher end-product quality. A contributing factor favouring micro- tunnelling was the recent introduction of ductile iron jacking pipes to the market, which is a pressure pipe that can be jacked directly into the ground behind a TBM. Therefore this offered a more cost-effective and operationally-sustainable system,

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CONSTRUCTION WORLD JANUARY 2018