Solution includes the building of a temporary road to ease traffic flow during construction of the new embankments.
01/10/2001
The first phase of a major road improvement scheme over the Rochdale Canal was completed recently with the opening of a temporary route to carry traffic diverted off the A664 Kingsway. Piling, together with a Basal Reinforced Platform (BRP) constructed using the ParaLink strip system from Maccaferri Ltd, specialists in retaining structures, slope reinforcement and erosion protection, have been used in building the new road which carries traffic over the Rochdale Canal.
The route will remain in use during the main construction work which will see the old concrete viaduct replaced with an integral bridge and embankments. This bridge, built around 70 years ago, carries traffic taking the Kingsway route through Rochdale over the Rochdale Canal and crosses difficult terrain comprising layers of peat overlying soft clays. Over the years the concrete support columns had been repaired a number of times and in the late 1990s Rochdale MBC took the decision to replace the structure.
The project was tendered based on a design proposed by Engineers at Rochdale MBC Technical Services Department. The design included supplementing the existing bridge support piles with additional mini-piles and demolishing the existing viaduct. Embankments supported by a load transfer structure to include a double layer of unprotected woven polyester geotextile were planned to carry the new road.
The proposed construction was complicated by the very restricted site, with an area of unusable land to the South East and a garden centre in the South West. To the North West, houses had been constructed close to the end of the bridge. These restrictions were further complicated by a suspected live gas main located within the existing structure causing the western parapet and footpath to be retained within the new permanent structure.
The need to provide a temporary diversionary road to ease traffic congestion during construction of the permanent structure added a further element to an increasingly complex project.
The main contract was won by Galliford Northern, with the piling work awarded to specialist contractor, Stent. Having worked closely with Stent on previous contracts of a similar nature, Maccaferri was invited to submit alternative proposals for the basal reinforced platform during the tender process. In discussion with Gallifords site team and Stent, Maccaferri Engineers agreed that the Paralink Strip System would provide a more effective load transfer structure which could adapt to the modular nature of the phased construction.
The need to retain part of the existing bridge was a significant factor in this decision. The location of new piling, together with the requirement for proposals to include designs for the temporary road BRP and permanent road BRP to be continuous under both structures was a key factor in determining the final solution. In the words of Maccaferri design Engineer, Niall Corney, this was a bit like “threading the eyes of several needles with a single thread at the same time.”
The first phase of construction is now complete with Paralink strips overlaying essential new piling to create an effective load transfer platform. The temporary road bridge over the canal opened to traffic on 16 August.
Work on the second phase has now commenced, replacing the old viaduct with an integral bridge and permanent embankments over the piled BRP.
Maccaferri developed its ParaLink Strip System, also referred to as a Basal Reinforced Platform (BRP) as an alternative to the geotextiles which have been the industry standard for a number of years and which were included in the initial design by Rochdale MBC. ParaLink strips are high strength, high modulus polyester based geogrid strips. Available in a range of strengths from 100kN/m up to 1250kN/m and custom-made to meet precise design specifications, ParaLink offers superior uni-directional strength.
For the strip system ParaLink strips are located only along the line of the pile caps. Carrying the load between adjacent pile caps, the Strip System reduces the amount of materials required and the time consumed in constructing the embankment, offering significant advantages to the contractor.
The UK arm of the Maccaferri Industrial Group, headquartered in Italy, Maccaferri Ltd specialises in gabions, geotextiles, geogrids and geomats. In addition to a full range of products for retaining structures, slope reinforcement and erosion protection, the company offers an in-house design and consulting service.
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