Britpave: The British In-Situ Concrete Paving Association

Cast-in Sleeper

The rail is mounted on a sleeper by means of resilient baseplate (e.g. Vossloh System 300). The sleeper is cast into a concrete track slab.

This system has been widely used for construction of high speed lines around the world, with examples being the Rheda and Züblin systems.

Rheda track was first installed in Germany in the 1970s and the system has been developed and optimised.

Rheda 2000 has been used successfully on high speed lines in Germany, Holland, Spain and Taiwan. Rheda 2000 has been installed in the Hibel & Prestbury Tunnels near Macclesfield in the UK.

Turnouts, crossovers and rail expansion joints are available for Rheda slab track (or ballastless track).

System Components

The system typically consists of the rail mounted on a pre-cast concrete sleeper via a resilient baseplate assembly (Vossloh System 300).

The traditional Rheda track form used a mono-block sleeper, while Züblin, as installed on the Cologne-Frankfurt Line used twin-block sleepers.

Rheda 2000 represents an optimised form of cast-in sleeper track with “skeleton” pre-cast sleepers set in a reduced depth slab. The sleepers are linked together via longitudinal reinforcing bars and placed in a concrete trough or base slab. The sleepers are then surrounded with concrete. The fastener/baseplate assembly provides all elasticity in the system.

System Performance

The cast-in sleeper system has been used extensively throughout the world for high speed lines, and has proven reliability in service over many years.

The problem reported with traditional Rheda was that sleepers worked loose due to vibration and lost their bond with the concrete surround. The development and optimisation of the system over the years leading to Rheda 2000 has largely eliminated this problem. However, careful design of the track slab reinforcement is necessary to mitigate against cracking, particularly where the track is installed in the open.

Construction Issues

The installation of cast-in sleeper track systems can be fully mechanised. This was successfully done on the Cologne-Frankfurt High Speed and the Dutch HSL-Zuid.

The base slab or trough section is slip-formed. Track panels with the rail mounted on the sleepers are then set up and longitudinal reinforcement threaded through. Additional lateral reinforcement is placed, if required.

The adjustment for line and level can be mechanised with adjustment screws through the sleepers holding the track in position prior to placing the concrete fill. Final adjustment is carried out by hand prior to concrete placement.

Concrete is placed between the sleepers and finished by hand. Good compaction of concrete beneath the sleepers must be ensured.

Rate of installation depends on concrete supply: Where concrete is supplied as a pump mix, typical installation would be around 120 to 130 metres of track completed in a 12 hour shift. On the HSl-Zuid, up to 300 metres was achieved in an 8 hour shift.

Maintenance Issues

The Vossloh System 300 fastener has the capacity for adjustments of 30mm vertical and 20mm lateral adjustment.

Acoustic Performance

The acoustic performance of cast-in sleeper systems is well documented, with installations having been in place for over 30 years.

Trials have been carried out to mitigate air-borne noise by applications of surface treatment to the slab and use of absorptive noise barriers.

For control of ground-borne noise and vibration, the ability to “tune” performance is limited by the Vossloh System 300 fastener. Since the resilient layer is provided beneath the rail seat, there is limited scope to adjust the softness of the pad, without affecting rail stability.