CRCP solution for Gonubie Main Road upgrade
“The Buffalo City Metropolitan Municipality (BCMM) advised CBM Africa in August 2011 that funds had been secured through allocation from National Treasury for not only the preliminary design, but also construction over the next three financial years,” explains CBM Africa Consulting Engineers associate, Ian Swartz.
“BCMM had already engaged iTEPA (local traffic engineer) to prepare a traffic model that would assist in predicting potential traffic volumes and movements along GMR. This information was needed to be able to design the junctions and intersections along the road - design progressed and tender documentation was prepared,” he continues.
Swartz outlines the scope of works as:
- the widening of GMR from three lanes to four lanes (3.4 m) with a central median (2.61 m) that contains a precast concrete barrier
- a1 m hard shoulder on both sides of the road
- a 1.4 m verge between the carriageway and a 1.5 m wide footpath,on the south side
- a 1.9 m concrete V-drain narrowing down to interface with the existing 3-m wide foot/cycle path, on the north side
- outside of the footpath, a 600mm width to the shoulder break point to contain potential public lighting
- incorporation of five junctions (four of which are to be 40-m diameter roundabouts and the fifth a T-junction with the existing Quenera Link Road
- the surface is to be a continuously reinforced concrete pavement (CRCP).
We are only three months into the 18-month contract, and so far have widened 39% of the road, relocated services and installed Telkom ducts,” explains Basil Read project manager, Barry Leech.
“One of the significant challenges on the R150 million contract is to maintain two-way traffic at all times, as the road is extremely heavily trafficked at all times,” he continues.
Swartz adds that issues with privatelyowned land adjoining the road alignment may hinder construction as “technically the road can be contained between the existing fence lines; however, this would require the footpath and verge to be removed from the existing scope of the works.”
In addition, junctions 4 and 5 may not be constructed at all as land has not been secured beyond the existing fence.
“This is not too critical as these junctions do not service any existing access points and are only required for future access when the proposed service lands come into existence,” points out Swartz.
The BCMM has engaged with valuation processes and is hoping for a willing buy/willing seller before the scope of works can be reduced.
“The road bed preparation will be compacted to 93% of Mod AASHTO and layer works. The layer works comprise a lower 150 mm selected subgrade layer of G9 material compacted to 95% Mod AASHTO and 150 mm upper selected layer of G7 material, also compacted to 95% Mod AASHTO,” explains Leech.
“Following on from the selected layers, two 125 mm G6 stabilised sub-base layers to conform to C4 are to be constructed to bring the widening up to level with the existing surfacing on the existing road. Running concurrently with the earthworks and layer works, a suite of four Telkom ducts are being installed alongside the four existing fibre optic cable ducts for the whole length of the contract (3 800 m), along with associated manholes and junction boxes,” he continues.
“On completion of the surfacing work, a 180 mm layer of CRCP will be machine paved along and across the entire road, including the widened sections.”
Basil Read recently received two commendations at this year’s Fulton Awards for the CRCPon the N12 highway project in Johannesburg - one in the Civil Engineering Structure category and the other in the Innovative Construction category.
“The same Wirtgen SP 500 paver equipment will be used on the upgrading of GMR contract,” explains Basil Read contracts director, Paul Walker.
“To the professional teams’ knowledge, this is the first time this technology will be used within the BCMM boundaries.”