Westlink M7
Sydney, New South Wales, Australia
The Westlink M7 project is a 40km dual carriageway motorway in western Sydney, connecting the M5 motorway at Prestons to the M2 Motorway at Baulkham Hills, including a major interchange with the M4 at Eastern Creek. It provides 40km of dual carriageway in each direction and has been designed to accommodate future public transport in the wide central median.
The project has a significant geographical span and includes:
- 17 interchanges
- 20 km of local road upgrades
- 47 km shared pedestrian and cycle paths
- 7 million m3 of excavation, and
- 142 bridges.
The two major interchanges with the M4 and M5 Motorways were challenges to the design and construct team. They involved the construction of more than 20 separate ramps at up to five different levels over some of the busiest sections of motorway in Australia. A major driving force in the selection of the construction techniques was the requirement to minimise impacts on the existing motorway.
The contract for works was signed in February 2003 with a contract construction period of 42 months and a construction price of US$1.09 billion.
Bridges
The project included the construction of 142 bridge structures, which comprise a significant proportion of the overall project costs. Their timely construction was a critical programming constraint on the completion of the project and the early opening of the motorway.
Standardisation of the bridges has been a major aim of the design. Conventional pretensioned precast concrete beam designs were chosen for bridges with spans up to 35m and precast segmental box girder bridges for the longer span bridges and motorway overbridges.
Span by span box girder designs incorporating dry joints and external tendons have been designed for the motorway viaducts and overbridges. Balanced cantilever segmental boxes incorporating epoxy joints and internal tendons have been designed for the longer span bridges at the major motorway interchanges and major road crossings.
There are also a number of pedestrian bridges that form an architectural feature of the project. These include steel truss bridges with spans of up to 66 m, ‘V’ girder pedestrian bridges using precast prestressed girders, and precast ‘boardwalk’ bridges used for where the shared cycleway / footpath crosses environmentally sensitive areas.
