GB2386882A

GB2386882A - Rail Track Arrangement

Info

Publication number: GB2386882A
Application number: GB0207474A
Authority: GB
Inventors: Charles Penny
Original assignee: Balfour Beatty PLC
Current assignee: Balfour Beatty PLC
Priority date: 2002-03-28
Filing date: 2002-03-28
Publication date: 2003-10-01
Also published as: GB0207474D0

Abstract

The arrangement has first and second rails 30, 32 of a first track and first and second rails 34, 36 of a second track. One rail of each track is positioned between the rails of the other track. This design provides one rail pair staggered with respect to the other, so that two different track designs can be provided, but over substantially the same area of ground. Each rail is held in a shell 26 embedded in a channel in a bed or slab of concrete 24.

Description

s 1 2386882

RAIL TRACK ARRANGEMENT

5 This invention relates to rail track arrangements, particularly in which more than one track is provided along a particular span, for example one track for freight traffic and another track for passenger traffic.

A conventional rail essentially comprises an I-beam, having a head, a narrow web and a 10 base. The rails are supported at regular intervals by sleepers, and span the spacing between sleepers. The I-beam structure provides the required vertical strength of the rail across these spans. An alternative rail design uses a continuous open channel to receive the rail. The rail has a substantially constant width, to enable it to be lowered into the channel. Any differences in width over the height of the rail are provided only 15 to enable a snap fit of the rail into the shell.

In either case, it may be desirable to provide different rail designs for different types of traffic. For example, passenger trains may have an axle load of around 20 tonnes, whereas freight trains may have an axle load of around 40 tonnes. Different damping 20 properties of the rail bed are ideally required for these different loads, and in the case of the embedded rail design, this can be achieved through appropriate selection of an elastic lining in the channel receiving the rail. For efficient use of material in the design of the rails, the rails will also have different dimensions depending on the load to be carried. The rails may also be of different hardness, different strength and different 25 materials or compositions.

Passenger and freight services also run at different speeds, so that ideally different cants (banking of the rails) is required at the comers. Furthermore, high and low speed rail designs will also require different maintenance programmer.

The provision of different track designs side by side for different services clearly requires additional space, and will not be possible through existing tunnels or over existing bridges.

According to the invention, there is provided a rail track arrangement comprising first and second rails of a first track and first and second rails of a second track, wherein first one rail of each track is positioned between the rails of the other track.

This design provides one rail pair staggered with respect to the other, so that two different track designs can be provided, but over substantially the same area of ground.

The cross sections of the rails of each track, perpendicular to the rail length, preferably 10 comprise a head portion and a supporting portion having substantially the same width.

The use of this rail cross section enables the first rails to be positioned close together and the second rails to be positioned close together. The two tracks may then pass through a single lane tunnel. For example, the lateral distance between the centres of the first rails of the first and second tracks and between the centres of second rails of the 15 first and second tracks may be less than 500mm, possibly less than 300mm.

The rails of the first track may have a first height, and the rails of the second track may have a second height which is greater than the first height. In this way, one track is designed for one load and the other is designed for a different load. The cant of the first 20 and second tracks in the region of a bend in the tracks may also be different, to allow for different speeds of service, and to improve wear and reduce corrugation.

One of the tracks may be used as an optional track during maintenance or renewal operations of the main track or in the event of a breakage in the main track.

The invention also provides a method of laying a rail track arrangement, comprising laying first and second rails of a first track and first and second rails of a second track, wherein one rail of each track is positioned between the rails of the other track.

30 Examples of the invention will now be described in detail with reference to the accompanying drawings in which:

Figure 1 shows a known rail cross section for use in the so-called "embedded flail Track" system; and Figure 2 shows a rail track arrangement using rails generally of the type shown in Figure 1.

Figure 1 shows an embedded rail design. The rail 20 is held in a shell 22 set in a bed or slab 24 of concrete. The shell 22 has an inner profile of an open channel to receive the rail 20 whilst also clamping the rail 20 in place. A resilient filler 26 is provided between the shell 22 and the rail 20.

The rail cross section comprises a head portion 20A and a supporting portion 20B. In the example shown in Figure 2, the top of the supporting portion 20B has a pinched part 28. To insert the rail 20 into the shell 22, the wider lower part of the supporting portion 20B has to pass through the pinched region of the fill 26, so that the rail must 15 effectively be sprung into the shell with a snap-action fit.

Despite this pinched part 28 of the rail cross section, the head portion 20A and the supporting portion 20B have substantially the same width. The only differences in width are provided to enable the snap-action fitting of the rail into the shell as described 20 above, and not to provide an Ibeam cross section as in more conventional rail designs.

The bed or slab 24 is lower on one side of the rail than on the other side, to allow the passage of the flange of a wheel of the railed vehicle. However, the shell 22 provides support for most of the height of the rail 20 on both sides of the rail. In particular, the 25 shell 22 provides support for at least part of the head portion 20A on both sides of the rail, and over the entire height of the supporting portion 20B on both sides.

The rail design of Figure 1 is described in greater detail in WO 99/63160. The shell 22 defines a continuous supporting structure for the rail 20, rather than the discontinuous 30 sleeper arrangement of more conventional rail designs.

The invention provides a track layout which is particularly suitable for this type of rail cross section, in particular as this rail does not require a wide supporting base. Figure 2

shows the track layout in accordance with the invention, and which is economic in cost and space.

The rail track arrangement of Figure 2 comprises first and second rails 30,32 of a first S track and first and second rails 34,36 of a second track. The first rail 30 of the first track is positioned on one side of the first rail 34 of the second track (to the left in Figure 2), and the second rail 32 of the first track is positioned on the same side of the second rail 36 of the second track. The two tracks are interleaved with each other so that one rail of each track is between the rails of the other track. Thus, one rail pair is 10 arranged to one side of the other rail pair, but with the rails overlying substantially the same area of ground.

Clearly, only one track can be used at any one time, and the track to be used will depend on the service (for example freight or passenger) being supported. The traffic will be 15 directed onto one or other track using turnouts and switches in known manner.

Typically, the passenger traffic will have a lower load but will run at higher speeds.

The second Hack 34,36 in Figure 2 has smaller height and is the passenger rail. High speed rails also require more frequent maintenance, and whilst one track is being 20 maintained or replaced, the other track can be used, although a running at a reduced speed if required.

The damping of the embedded rail design is a function of the elastic fill 26, and different fill compositions may be used for the different tracks, in particular to take 25 account of the different speeds and loads. Thus, when the passenger train is running on the freight track because of maintenance of the high speed line, a reduced speed may be required as a result of the different damping properties.

The cant (the slope) of the first and second tracks may also be different, to allow for 30 different speeds around corners. This cant will be determined by the shape of the bed 24. Furthermore different inclinations may be provided for different rails, again through design of the bed 24, specifically the channels in the bed 24.

The use of the embedded rail design enables the first rails 30,34 and the second rails 32,36 to be positioned close together. The two tracks may then pass through a single lane tunnel. This avoids the need to have mixed traffic in tunnel areas on one pair of rails. For example, the lateral distance 38 between the centres of the first rails of the 5 first and second tracks and between the centres of second rails of the first and second tracks may be less than SOOmm for example 300mm or less. The distance 38 is limited only by how closely the rails can be held together.

Although the specific example above uses embedded rails, the invention can be applied 10 to conventional rail designs, and the invention is not restricted to any specific rail design. Various modifications will be apparent to those skilled in the art.

Claims

C AIMS

1. A rail track arrangement comprising first and second rails of a first track and first and second rails of a second track, wherein one rail of each track is positioned 5 between the rails of the other track.

2. An arrangement as claimed in claim 1, wherein the first and second tracks have substantially the same gauge.

10 3. An arrangement as claimed in claim 1 or 2, wherein the cross sections of the rails of each track, perpendicular to the rail length, comprise a head portion and a supporting portion having substantially the same width.

4. An arrangement as claimed in claim 3, wherein the cross sections of the rails of 15 each track, perpendicular to the rail length, further comprise a base portion having substantially the same width as the head and supporting portions.

5. An arrangement as claimed in claim 4, further comprising a shell for each rail, which receives the respective rail.

6. An arrangement as claimed in claim 5, wherein each shell is embedded in a respective channel in a support structure.

7. An arrangement as claimed in any preceding claim, wherein the rails of the first 25 track have a first height, and the rails of the second track have a second height which is greater than the first height.

8. An arrangement as claimed in any preceding claim, wherein the cant of the first and second tracks in the region of a bend in the tracks is different.

9. An arrangement as claimed in any preceding claim, wherein the lateral distance between the centres of the first rails of the first and second tracks and between the centres of second rails of the first and second tracks is less than 500mm.

10. An arrangement as claimed in claim 9, wherein the lateral distance is less than 300mm. 5 11. A method of laying a rail track arrangement, comprising laying first and second rails of a first track and first and second rails of a second track, wherein one rail of each track is positioned between the rails of the other track.