Level Crossing Removal Project – Design Process for a Rail Underpass in a DC Traction Environment

Paper No. 130
Mr Adrian Vinnell1, Dr Ulf Kreher1 – 1Aurecon, Docklands, Australia

Abstract

A number of level crossing removal projects are currently underway across metropolitan Melbourne. These major construction projects are being undertaken to remove road level crossings from the suburban train network in order to improve traffic flow and reduce hazards to drivers or pedestrians. The construction methodology used on these projects have been either lowering the rail below the road and constructing a road bridge across the cutting, or constructing a long via-duct style rail bridge along the rail alignment over the road crossing. This paper will focus on the rail-under-road type of level crossing removal structure which utilises piled retaining walls.

The Victorian surburban train network is a DC traction system that operates at 1500V DC and has the potential to cause corrosion of nearby structures and assets such as pipelines through stray current (electrolysis) corrosion. These corrosion issues need to be carefully considered during the design and construction of any asset that makes changes to the rail network itself or is constructed nearby. However, while corrosion issues can be a critical feature of the design it is rare within the rail environment that the requirements of the corrosionist can be satisfied in isolation; there are other considerations such as personnel safety, operational requirements, architectural appearance and physical site constraints that may need to take priority and be considered alongside corrosion mitigation design.

This paper will include a case study that follows the design development of a recently completed level crossing structure based on the piled retaining wall design. It will commence with a summary of key features of the structure, how an initial assessment of likely corrosion impacts was undertaken, and a short discussion of the possible mitigation strategies proposed to reduce these impacts.

As the design progresses, the structure and interfaces become increasingly complex as more engineering disciplines become involved and the basic concept is updated. The design now includes, station electrical systems, geotechnical considerations, traction power systems, signalling power systems and access considerations for members of the public and maintenance personnel.

The paper will outline the approach to corrosion management in the now more complex design with many constraints applied. Several of the constraints were incompatible with the initial corrosion management strategy and the paper will conclude with discussion on how a cooperative team was critical in identifying and implementing design solutions to ensure a compromise which captured critical requirements of each discipline including management of the corrosion risks.