GB2342376A

GB2342376A - Method of levelling a railway sleeper and panel for use in the method

Info

Publication number: GB2342376A
Application number: GB9821908A
Authority: GB
Inventors: Robin S Cope
Original assignee: Amey Railways Ltd
Current assignee: Amey Railways Ltd
Priority date: 1998-10-09
Filing date: 1998-10-09
Publication date: 2000-04-12
Also published as: GB9821908D0

Abstract

The method of levelling a railway sleeper resting on a bed of stone ballast comprises inserting beneath the sleeper one or more pre-formed height-adjusting panels 18 comprising a layer of stone ballast particles 19 bonded together by an adhesive. The bonded layer of particles may be self-supporting but the particles are preferably bonded onto a backing sheet 17. Each panel includes a standard quantity of ballast, thus avoiding the necessity of measuring out quantities of loose particles on site. It is also easier to insert the panels beneath the sleeper than it is to insert loose particles in a controlled manner.

Description

"Method and device for levelling railway sleepers" The invention relates to the levelling of railway sleepers.

As is well known, the spaced parallel rails of a railway track are supported on transverse sleepers which are spaced apart at regular intervals along the length of the track. The sleepers are normally supported in a bed of aggregate stone particles or chippings (ballast) which are tightly packed beneath and around the sleepers.

When a section of track is first laid or subsequently renewed, the sleepers are laid on a bed of ballast which has been compacted so as to be perfectly flat, and further ballast is then packed between and around the sleepers. Initially, therefore, the heads of the rail are smoothly profiled. With use, however, there may be some settling of the ballast beneath the sleepers and voids may appear beneath the sleeper. As a result undulations may appear in the rails mounted on the sleepers.

As is well known, the rail heads may be transversely canted, and/or on a gradient, and/or have a curved horizontal profile. References herein to the ballast being"flat"or to"levelling"of the track therefore refer only to the conditions needed to ensure that the rail heads are generally co-planar and have a smooth longitudinal profile, and do not imply that the rail heads necessarily lie in a horizontal plane.

In order to level uneven track it is necessary to dig out the ballast surrounding a sleeper down to the level of the bottom of the sleeper and then to introduce more ballast beneath the sleeper in order to raise it. Although machinery is commonly employed to lift sleepers to the correct level and re-pack existing ballast beneath them, the introduction of further ballast beneath a sleeper is generally carried out by hand and this is a time-consuming process. An attempt can be made to control the introduction of further ballast by specifying that it should be introduced beneath the sleeper in multiples of a measured standard quantity. It can then be estimated how many standard quantities of the ballast are required to raise the level of the sleeper by the necessary amount to level the rail. Nevertheless, this existing method does not allow particularly accurate control of the quantity of ballast introduced below the sleeper, partly because the method of manually introducing the ballast beneath the sleeper, with a shovel, is awkward and difficult to control.

In the existing method, as described above, the measuring out of the ballast and its subsequent distribution beneath the sleeper is a particularly time-consuming element of the process. The present invention therefore provides an improved method for disposing further ballast beneath a railway sleeper and a component for carrying out the new method.

According to the invention there is provided a method of levelling a railway sleeper resting on a bed of particulate material, the method including the step of inserting beneath the sleeper at least one pre-formed height-adjusting panel comprising a layer of discrete particles bonded in position by an adhesive.

Since each panel is preformed, it may contain a standard quantity of particles.

An appropriate number of panels may therefore be used, depending on the height by which the sleeper is to be raised, thus avoiding the necessity of measuring out quantities of loose particles on site. Furthermore, since the particles are preformed into a panel, it is a simple matter to insert the panel beneath the sleeper from one side. The use of the panel therefore automatically ensures that the particles are distributed evenly across the under-surface of the sleeper and the even distribution does not depend on the skill of the person introducing the particulate material, as is the case when loose material is introduced on a shovel. The method according to the invention is therefore much more controllable, as well as being easier, quicker and less costly than the method currently employed.

Preferably the particles are bonded one to another by the adhesive, and in this case the layer of bonded particles may be self-supporting. Altematively or additionally, however, the layer may have a backing sheet applied to at least one face thereof to provide extra strength to the panel and/or to facilitate manufacture of the panel. The layer of particles may be bonded to the backing sheet by an adhesive, which may be the same adhesive which bonds the particles together. The backing sheet may be formed from synthetic plastics or any other suitable material. For example, on occasions a membrane is laid between the underside of the ballast and the natural material below it, and the backing sheet of the layer of particles may therefore comprise such membrane material.

Preferably the particles are so bonded in position as to leave voids between the particles, whereby water may permeate through the layer. In the case where a backing sheet is provided, the backing sheet may then be formed with holes through which water may pass. In some cases the backing sheet may provide only temporary support for the particle layer, being stripped from the particle layer before the panel is inserted beneath the sleeper.

Preferably the adhesive bond is such as to be capable of breaking down under the loads to which the panel is subjected when in use under the sleeper. In this case, under the effect of such loads, the panel of bonded particles will respond in just the same way as a layer of loose particles, and the adhesive itself will not provide any significant resistance to such loads.

The particles may be of generally the same type as the particles in the bed of material on which the sleeper is laid. For example, they may comprise stone ballast particles. However, the invention does not exclude methods where particles in the panel are of a different material. For example, the particles may be formed from synthetic plastics material or an inorganic natural material.

The layer of particles may be generally one particle deep or may be several particles deep. Two or more panels may be inserted, one on top of another, beneath the sleeper to achieve a required depth. The panels may be of any appropriate size.

Preferably, however, each panel may be of substantially the same width as a standard railway sleeper. The panel may be of any convenient length and two or more panels may be arranged side-by-side beneath the sleeper.

A number of panels of different thicknesses and/or lengths may be supplied, in order to provide a variety of modes of adjustment of the height of the sleeper.

The invention includes within its scope a panel, for use in the above-described methods, comprising a layer of discrete particles bonded in position by an adhesive.

The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which: Figure 1 is a diagrammatic section through part of a railway track, Figure 2 is a plan view of one form of height adjusting panel for use in the invention, and Figure 3 is a section on the Line 3-3 of Figure 2.

Referring to Figure 1, there is shown diagrammatically a conventional section of railway track in which the two parallel rails 10 are mounted on spaced transverse sleepers 11 which are embedded in a body 12 of ballast.

When the track is originally laid, the sleepers 11 are laid on the flat upper surface, indicated in dotted lines at 13, of a main body of particulate material 14, usually comprising crushed stone ballast. The surface 13 is tamped and compacted so as to be perfectly smooth before the sleepers 11 are placed on the surface. An upper layer of ballast 15 is then packed around the sleepers 11. The material in the upper layer 15 may be the same as that in the base layer 14, or may be a different material.

As previously explained, over a period of time there is a tendency for the sleepers 11 to move in the bed of material in which they are embedded. This may be partly due to the very heavy loads to which the track is subjected by traffic in use, and also in part due to shifting of the ground material. Differential settling of the sleepers 11, as a result of such effects, may cause twisting and undulation of the rails 10. From time to time, therefore, it is necessary to level the sleepers 11.

This is achieved by digging out the upper layer of embedding material 15 to the depth of the sleeper, as indicated diagrammatically by the chain line at 16. The sleeper 11 is then temporarily raised and additional ballast is introduced beneath it, from one side or from both sides, the sleeper then being lowered on to the newly introduced ballast.

The quantity of ballast to be introduced may be estimated or determined more accurately by survey. Accordingly, in the conventional method used hitherto, the appropriate amount of ballast is measured out and then is introduced beneath the sleeper 11 using a shovel. The estimation of the amount of material to be used assumes that the material is distributed evenly beneath the sleeper 11. However, it is inherently difficult to introduce loose material beneath the sleeper 11 with a shovel, and even more difficult to ensure that the material is evenly distributed over the whole area beneath the sleeper.

As a consequence, the process is time-consuming and may have to be repeated later to compensate for any uneven settlement resulting from the ballast material having been unevenly spread, leading to subsequent redistribution under load.

According to the present invention, the ballast is not introduced beneath the sleeper as loose particles"but is first preformed into standard self-supporting panels of material such as is shown in Figures 2 and 3.

Each panel comprises a backing sheet 17 to which is bonded, by use of a suitable adhesive, an evenly distributed layer 18 of particles 19 which may conveniently be the same type of particles, such as stone chippings, used in the original base layer 14.

The particles 19 may be pre-coated in the glue and then evenly spread over the backing sheet 17 so that the particles stick to one another and to the backing sheet.

Alternatively, the particles may be first spread over the backing sheet, the liquid glue then being sprayed or otherwise distributed over the covered sheet so as to glue the particles to one another and to the backing sheet. The glue may be an epoxy resin.

The disposition of the particles on the sheet is such that there are voids between the glued particles to allow the permeation of water between them. The backing sheet 17, which may for example be formed from a suitable geotextile, may be formed with perforations so that water will also permeate through the backing sheet, in use. For example, the backing sheet might comprise a mesh-like plastics material.

Alternatively, if the strength of the adhesive bond between the particles 19 is surdent to make the layer 18 self-supporting, the backing sheet 17 may be omitted, or it may be used only for the manufacture, transport and storage of the panel, being stripped off the layer of particles 18 prior to use.

In use, the preformed panel of particulate material is simply slid beneath the underside of the sleeper 11. The panel may be of the same width as a standard sleeper.

Although the panels may be introduced beneath any part of the sleeper, packing is generally required under the parts of the sleeper which carry the rails, in order to provide support for the rails.

In order to minimise the occurrence of settling, the particles are preferably sieved, before manufacture of the panels, so as to lie within a comparatively narrow range of sizes, and avoiding the presence of fine particles which might otherwise filter downwards through the layer of larger particles.

The ballast initially employed to support the sleepers may be angular crushed stone of nominal 50mm dimension. Small ballast is of nominal 3540mm dimension.

Chippings are angular crushed stone of 20mm or less dimension. The particles 19 used on the panels according to the present invention may be chippings. Different types of panel may have different sized chippings, e. g. of 6mm, 12mm, 15mm or 20mm dimension. Preferred sizes are 6mm and I Omm.

Since the panel may be manufactured with a standard thickness and density of particles 19, the use of a standard panel will raise the sleeper by a standard amount. The sleeper may be raised by greater distances by inserting two or more panels stacked one upon another. However, the panels may also be made in different standard thicknesses so that a single thicker panel may be used, when required, rather than a number of thinner panels. The particles 19 may be arranged in substantially a single layer of minimum thickness on the panel, or may be layered to a greater depth.

Preferably the adhesive used to bond the particles 19 together is sufficiently strong to make the panel self-supporting, but is weak enough to cause the bond between the particles to break down when the panel is in position beneath the sleeper and is subjected to the working loads on the track The particles then can move relatively to one another and act to distribute the load on the underside of the sleeper in exactly the same way as they would if they had been introduced beneath the sleeper as separate loose particles.

Claims

1. A method of levelling a railway sleeper resting on a bed of particulate material, the method including the step of inserting beneath the sleeper at least one preformed height-adjusting panel comprising a layer of discrete particles bonded in position by an adhesive.

2. A method according to Claim 1, wherein the particles are bonded one to another by the adhesive.

3. A method according to Claim 2, wherein the layer of bonded particles is self-supporting.

4. A method according to any of Claims 1 to 3, wherein the layer of particles has a backing sheet applied to at least one face thereof.

5. A method according to Claim 4, wherein the layer of particles is bonded to the backing sheet by an adhesive.

6. A method according to Claim 2 and Claim 5, wherein the layer of particles is bonded to the backing sheet by the same adhesive which bonds the particles together.

7. A method according to any of Claims 4 to 6, wherein the backing sheet is formed from synthetic plastics.

8. A method according to any of the preceding claims, wherein the particles are so bonded in position as to leave voids between the particles, whereby water may permeate through the layer.

9. A method according to any of the preceding claims in which a backing sheet is provided, wherein the backing sheet is formed with holes through which water may pass.

10. A method according to any of the preceding claims in which a backing sheet is provided, wherein the backing sheet provides only temporary support for the particle layer, being stripped from the particle layer before the panel is inserted beneath the sleeper.

11. A method according to any of the preceding claims, wherein the adhesive bond is such as to be capable of breaking down under the loads to which the panel is subjected when in use under the sleeper.

12. A method according to any of the preceding claims, wherein the particles are of generally the same type as the particles in the bed of material on which the sleeper is laid.

13. A method according to any of Claims 1 to 11, wherein the particles are formed from synthetic plastics material or an inorganic natural material.

14. A method according to any of the preceding claims, wherein the layer of particles is generally one particle deep.

15. A method according to any of the preceding claims, wherein the layer of particles is several particles deep.

16. A method according to any of the preceding claims, wherein two or more panels are inserted, one on top of another, beneath the sleeper to achieve a required depth.

17. A method according to any of the preceding claims, wherein each panel is of substantially the same width as the railway sleeper beneath which it is laid.

18. A method according to any of the preceding claims, wherein two or more panels are arranged side-by-side beneath the sleeper.

19. A panel, for use in the methods according to any of the preceding claims, comprising a layer of discrete particles bonded in position by an adhesive.

20. A panel comprising a layer of stone ballast particles bonded to one another and/or to a backing sheet by an adhesive.

21. A panel according to Claim 20, wherein the particles are bonded to a backing sheet formed from synthetic plastics.

22. A panel according to any of Claims 19 to 21, wherein the particles are so bonded in position as to leave voids between the particles, whereby water may permeate through the layer.

23. A panel according to any of Claims 19 to 22 in which a backing sheet is provided, wherein the backing sheet is formed with holes through which water may pass.

24. A panel according to any of Claims 19 to 23, wherein the layer of particles is generally one particle deep.

25. A panel according to any Claims 19 to 23, wherein the layer of particles is several particles deep.

26. A method of levelling a railway sleeper resting on a bed of particulate material, substantially as hereinbefore described with reference to the accompanying drawings.

27. A panel for use in levelling a railway sleeper resting on a bed of particulate material and substantially as hereinbefore described with reference to the accompanying drawings.