Presentations and Papers
Summary - Transit Space - The Art of Fitting the Square Peg in the Round Hole - Applied to Perth New MetroRail Tunnels
Presenter: Andrew Matthews and John Chugh
The Southern Suburbs Railway will connect Mandurah to the City of Perth and the northern suburbs.
A key aspect of the implementation of the new railway was the construction of tunnels taking the railway from the Narrows Bridge, under the city, and connecting to the existing Northern Suburbs Railway.
Transit Space diagrams were used to optimise the size of the bored tunnel and cut-and-cover tunnel early in the design process. Transit Space diagrams allocate spaces within the tunnel for track, overhead electrification, signalling and tunnel systems. These spaces are configured within the tunnel such that the overall tunnel size is minimised without conflicting with the space required for the dynamic train envelope and electrical clearances.
In the case of the bored tunnel both the track bed design and overhead electrification design have a major bearing on the tunnel diameter. For the cut-and-cover tunnel and open dive structures the need to provide for signalling system assets and overhead electrification weight tensioning equipment increased the complexity of determining the final Transit Space allocations.
Efforts were made early in the design to anticipate the space required for the various components. However, these issues had to be balanced with the desire to minimise the tunnel diameter to reduce costs and also reduce potential ground settlement above the tunnels. The tunnel diameter had to be locked in well before details of the track, overhead electrification, signalling and tunnel systems were fully developed and so tunnel sizing had to be based on preliminary, but workable designs in these areas.
Later in the design process it became apparent that, with the chosen tunnel diameter and the preliminary systems designs used, there would be very little spatial flexibility and so designers would still be faced with a challenge to ‘make things fit’. To compound the complexity of the transit space design, some of the tunnel equipment was designed, supplied and installed under a separate contract.
This paper details the design process, problems encountered and how these were resolved. It provides some lessons learned that might benefit future projects.
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