The tunnel had an existing 60-kilogram rail on timber-plated ballasted track, where the contact wire height was too low, with many sections measuring less than the standard 4.74 metres. Because of this issue, maintenance tamping was required but unable to be carried out, launching Sydney Trains Network Maintenance to seek a solution that improves track configuration and allows long-term maintenance.

SMEC was engaged by Rhomberg Sersa Australia (RSA) to complete the detailed design for the Coalcliff Tunnel for Sydney Trains. The chosen design solution involved the implementation of an Intelligent, Versatile, Efficient, Solid (IVES) track slab system to address the reliability of train operations and maintenance by improving Overhead Wiring (OHW) clearances, drainage, and track conditioning in the tunnel. The upgrade provides a sustainable solution to help proof the existing track’s longevity and minimise disruptions to services and track closures.

Implementing a long-term system

SMEC developed an innovative solution for the maintenance of the track, by upgrading the existing track configuration to the IVES track slab. The system has a ballastless composition that minimises maintenance tasks, creating fewer interruptions for trains passing through the tunnel along the whole Illawarra line. Utilising approved rail fastenings and structural elements to create efficiencies in its application and use, the system is highly adaptable and able to be developed, transported, and constructed in components, allowing it to be constructed for high-speed track usage in built-up areas. Along with improved drainage, the system significantly reduces groundwater contamination risks from oil, grease, and coal dust, and thoroughly mitigates any future environmental hazards, which may historically have posed disruptions to rail operations.

This solution holds promise for the broader rail industry faced with similar challenges, like reduced OHW height, short-track possessions, and restricted site access. Improving safety with better track quality, the system will create positive benefits on rail wear, rolling stock maintenance, and derailment risks in the heritage listed tunnel.

Roll-on impact for industry

SMEC’s comprehensive design incorporates the innovative track system, introduces new drainage solutions at the portal and within the tunnel. The implementation of a tunnel monitoring program aims to ensure a more reliable track, benefiting Sydney Trains and enhancing the experience for both passenger and freight stakeholders.

By embracing a design with minimal track reconditioning needs over the 120-year lifespan, the project will drastically reduce maintenance activities, positioning it as a sustainable, low-impact infrastructure solution. The system’s versatility allows for easy customisation to varying terrain and environmental conditions, ensuring seamless integration with existing infrastructure. Furthermore, its solid construction minimises wear and tear, reducing the frequency of repairs and replacements, thereby decreasing resource consumption and overall environmental impact. By prioritising the sourcing of localised materials and components from New South Wales, the detailed design negates the carbon emissions otherwise produced through inter-state and international transportation activities.

The outcomes of this project will benefit those who use the heritage listed tunnel, enhancing passenger safety and comfort by minimising rail wear, and reducing the risk of derailments. Phased construction during short maintenance windows will also have a beneficial impact on all involved in train operations. With minimised disruptions benefiting commuter convenience, the design makes it a viable solution for modernising rail infrastructure sustainably.

SMEC’s introduction of a versatile and adjustable track structure such as this, holds promise for the broader rail industry. The key benefits to the rail industry include the introduction of a new, flexible, and highly adjustable track structure. A rigorous type of approval process with an optimised track design for tunnel environments will guarantee a safe and reliable design to the currently available track systems (both ballasted and track slab). Future projects with similar challenges like reduced OHW height, short track possessions, and restricted access to site will greatly benefit from this highly adaptable track system. The relatively simple design of the track system will reduce the design works for following projects with review required only of the supporting layers (like asphalt) whilst allowing the main track components to remain the same. The system has an innovative construction method which allows for phased installations during short maintenance windows, eliminating prolonged tunnel closures and ensuring uninterrupted train operations.