Rail sleeper and ballast-free track structure

Abstract

According to one aspect of the invention there is provided a prefabricated rail sleeper [10] suitable for use in erecting a track structure [30]. The rail sleeper [10] comprises an elongate body portion [12] for supporting rails [14], the body portion [12] including a top surface [12,1], a bottom face [12.1] and at least two side faces [12.3], and terminating at least at one end thereof in a transition joint formation [16] dimensioned matingly to engage a complimentarily dimensioned transition joint formation [16] of an adjacent rail sleeper [10] in use so as to form a substantially continuous track structure. The sleeper [10] also includes a series of block formations [20], each of which is at least partially outwardly flared and extending beyond the side faces [12.3] of the body portion [12] so as to increase shear interlock of the sleeper [10] with the track bed to reduce longitudinal creep; as well as a series of transverse drainage ducts [26] extending underneath the rail sleeper [10] for allowing rainwater drainage between different side faces [12.3] of the body portion [12] and away from the rail sleeper. The invention extends to a ballast-free track structure [30] comprising at least two rail sleepers [10] according to the invention wherein the sleepers are located in spaced parallel orientation on a ballast-free track bed so as to define a centre drain [32] between the sleepers; and including a mesh [34] located between the sleepers [10] for reinforcing the centre drain [32].

Description

TECHNICAL FIELD [0001] This invention relates to a ballast-free track structure suitable for carrying railway rails, and to a rail sleeper for use in such a structure. BACKGROUND ART [0002] Conventional methods for laying a railway track involve placing large wooden, reinforced concrete or steel sleepers on a ballasted track bed, after which rails are fastened to the sleepers. The purpose of the ballast is to provide a free-draining foundation with high shear strength and good elastic (resilient) properties. [0003] However, for over a century there has been very little fundamental improvement in the design and construction of conventional, ballasted railway track. Consequently, some serious and persistent problems have never been completely resolved. In particular, the progressive degradation of the track structure under repeated loading remains problematic. This degradation is manifest in several ways, including loss of geometric stability (the ballast spreads and settles, resultin...

AI Technical Summary

Benefits of technology

[0009] It is an object of the present invention to provide a rail sleeper suitable for use in erecting a railway track that will overcome or at least minimize some of the problems associated with the prior art and which will facilitate rapid installation and replacement of railway tracks.

Problems solved by technology

However, for over a century there has been very little fundamental improvement in the design and construction of conventional, ballasted railway track.

Consequently, some serious and persistent problems have never been completely resolved.

In particular, the progressive degradation of the track structure under repeated loading remains problematic.

This degradation is manifest in several ways, including loss of geometric stability (the ballast spreads and settles, resulting in loss of vertical and horizontal alignment); loss of resilience (the ballast degrades and becomes contaminated by finer material resulting in increased dynamic damage to track structure (corrugations) as well as to rolling stock); and pumping of sub-grade (caused by dynamic loading, and resulting in ballast fouling and destruction of formation).

The control of these problems is expensive due to heavy ongoing maintenance requirements as well as foreshortened track and rolling stock life spans.

A major disadvantage of this system is that it still relies on a ballasted formation and so remains susceptible to the problems described hereinbefore.

A further disadvantage associated with this system is that it is often characterised by poor load dispersal and weak resistance to longitudinal creep movement of the sleepers.

One of the disadvantages associated with this method is the relatively extensive time involved for construction, maintenance and reconstruction of the track, because of curing times of the concrete.

Other disadvantages include the logistics and complexity of construction, and accompanying difficulties associated with site quality assurance and control.

Images