Construction World December 2017

Category C: Professional Services: Consulting Engineers

MOUNT EDGECOMBE INTERCHANGE UPGRADE SMEC South Africa was appointed by SANRAL Eastern Region to provide consulting engineering services in 2009 for the upgrade of 21 km of the N2/26 from the Mount Edgecombe Interchange to the Tongaat Toll Plaza. Construction only commenced in May 2013. Winner

The initial Traffic Study on the capacity improvements of the N2 and site observations revealed that the northbound off-ramp to the Mount Edgecombe Interchange was a major safety concern, as traffic backed up onto the N2 during peak periods. Similar delays were experienced on the cross road (M41) during peak periods. An in-depth traffic demand and micro- simulation study revealed that major improvements were required at the Mount Edgecombe/M41 interchange beyond the scope of works originally envisaged. This would entail the design and construction of a free-flow interchange facility catering for high traffic volumes through the interchange, as well as a grade-separated pedestrian bridge and footway facilities to meet the demand of a large number of pedestrian movements. In addition, to facilitate the future traffic demand, the interchange upgrade further includes the widening of the N2 to five lanes in each direction to the South of the interchange. This ties in with current planning that underway to upgrade the outer ring portion of the N2 past Durban to five lanes per direction. The space constraints were overcome by clever geometric design and the use of PROJECT INFORMATION • Company entering: SMEC South Africa • Client: South African National Roads Agency SOC Limited Eastern Region KZN Department of Transport • Start date: May 2013 (commencement of construction) • End date: April 2017 • Consulting engineer: SMEC South Africa • Civils contractor: CMC di Ravenna South Africa (Italian) • Geotechnical: Franki Africa (Cased Auger Piles, Dynamic Compaction and Lateral Support) • Equipment: Bauer BG28 rig, Casagrande oscillator rig • Specialist subcontractor: VSL Construction Solutions • Suppliers: Natal Portland Cement, Ital Concrete, Conchem Construction Chemicals • Laboratory: Matrolab Group

a four-way directional stack interchange configuration. This would provide for full-width directional ramps in all directions, while keeping the geographical footprint of the interchange as small as possible, and within the restraint of the road reserve. The extreme skew angle of the M41 to the N2 meant that a small portion of land belonging to Tongaat Hulett had to be expropriated to accommodate the full extent of the upgrade. Traffic counts and congestion was evidence of the current interchange having reached its design capacity. This would impact heavily on the provision and design of temporary deviations during construction. In-depth studies were undertaken to ensure traffic could be deviated within the constraints of the interchange with the minimum disruption to the traveling public. The south-east quadrant of the interchange acts as an attenuation pond for the stormwater runoff from the commercial and light industrial areas surrounding the interchange. This presented designers with a unique problem. As part of the environmental requirements, the attenuation pond had to remain in place, and could not be encroached upon. Currently not only the largest interchange project in South Africa, this project is also located in one of the fastest-developing areas in the country, among some of the wealthiest and most prestige develop- ments countrywide. These factors played a major role in the conceptual design of this upgrade, ensuring that the interchange would aesthetically suit, and complement, its fast- pace, modern surroundings. but also stand the test of time in terms of lifespan, and a unique ability to deal with the ever-growing vehicle demands. The project consists of nine new road bridges, one new pedestrian bridge (432 m), nine mechanically-stabilised earth walls (1 880 m), three soil-nail retaining walls (770 m), and more than 11 km of piling. The project’s wide range of concrete finishes, state-of-the-art construction methods, clever and innovative use of precast and in situ concrete elements, along with its many unique features, exemplifies its benchmark excellence.

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