M6 Junctions 6-7 Gravelly Hill to Thornbridge Viaduct

Background

A £26.5m contract for the Highways Agency to undertake major maintenance on the M6 motorway between junctions 6 – 7 in the Birmingham area.

Works involved deck repairs, full road and drainage reconstructions. Two of the slip roads at junction 6 were included, as well as box girder repairs to the Gravelly Hill viaduct substructure that carries the M6 motorway. The viaduct crosses Lichfield Road, Aston Expressway and is adjacent to and spans a river, railway and canal.

Roadworks, over a 3.3km length of the M6, entailed carriageway reconstruction to an approximate depth of 400mm and associated works such as kerbing, safety barriers, drainage and ironware. The removal and replacement of the motorway lighting system and lighting columns foundations were also included.

Bridge deck works involved 680m length of M6 viaduct, including Witton Viaduct and College Road Bridge, on a composite steel / concrete deck slab approximately 225mm thick and 900m length of viaduct to two slip roads at junction 6 on Gravelly Hill interchange. These works comprised the:

• Removal and replacement of all existing bituminous materials, including waterproofing and all the expansion joints
• Removal and replacement of lighting, safety barriers, columns cables, plain and reinforced concrete and kerbs in the central reservation
• Refurbishment of steel parapet rail components
• Provision of road marking and drainage ironware
• Concrete repairs to reinforced concrete deck where required. Concrete was removed by mechanical tools and high-pressure water jetting and replaced with repair concrete in a specified sequence

Steel box girder strengthening and repairs to the pier crossbeams comprised the fixing of additional stiffeners inside and outside of the boxes and augmenting existing welds at certain locations. The repair part of the works was instructed after the boxes had been shotblasted internally, and the existing welds inspected and tested.

On all parts of the works, we installed and maintained traffic management and the provision of recovery vehicles to facilitate the work.

Achievements

• Development of new deck repair material with a key supplier has significantly improved the application performance of available flowable repair materials in addition to introducing needed competition into the market
• Development of all year round deck repair techniques, where we have combined controlled environment protection with heated repair materials
• Development of new steelwork repair techniques removed the need for lane closures during many operations
• New initiatives with Supply Chain Partners in assessing and sharing risk and resources and incorporating incentivised and transparent target cost elements on approximately half of all sub contracts placed
• Repeat use of Supply Chain Partners from previous Major Maintenance Contract for approximately 97 per cent of value of sub contract elements
• Savings of £2m as a result of a series of innovations including Traffic Management; alternative pavement options; recycling; and Varioguard barrier use
• Shared risk management allowed Interserve and our supply chain to score the highest mark for our Quality submission and better our nearest competitor’s price by over 20 per cent