GB2134573A

GB2134573A - Railway track maintenance

Info

Publication number: GB2134573A
Application number: GB08400095A
Authority: GB
Inventors: James Cooper
Original assignee: D Wickham and Co Ltd
Current assignee: D Wickham and Co Ltd
Priority date: 1983-01-04
Filing date: 1984-01-04
Publication date: 1984-08-15
Also published as: GB2134573B; GB8400095D0

Abstract

A railway track is maintained by raising the sleepers (as by apparatus 8), placing beneath them packing layers of settable plastics material or fibrous concrete (as from a tank 14 through line 16) and lowering the sleepers onto the packing layers as soon as these have sufficiently set to support the sleepers. Where the material of the packing layer is initially readily flowable, flow can be restrained by reducing the porosity of the adjacent ballast (as by applying sheet material or by using device 10 to inject a chemical bonding agent into the ballast). <IMAGE>

Description

SPECIFICATION Railway track maintenance This invention relates to the maintenance of railway tracks.

A railwardy track comprising rails secured by fasteners to sleepers or cross-ties is conventionally supported by ballast resting on a substrate. The ballast invariably settles under the loads imposed by trains running on the track, and because of such factors as the non-uniform consistency of the ballast, variations in the substrate, and centrifugal forces generated at curved track positions, this settlement is uneven, so that the rails lose alignment. Alignment can be restored by tamping the ballast between the ties to consolidate it. However, the slip planes in the ballast which have allowed re-positioning by the tamper also allow a return to the position of lost alignment, which can be regarded as a "natural" position or profile from which the tamping has effected a distortion, necessarily for only a limited time, after which the tamping operation has to be repeated.

In order to increase the time between necessary re-alignment operations, the ties can be lifted and stones (pea gravel) thus placed beneath them either manually with a shovel or by blowing stones carried in an air stream. The desired rail alignment can be obtained in this way with the ballast in its "natural" profile but the stones used to pack the cross-ties are inconvenient to handle and are moreover themselves subject to settlement.

The invention therefore provides a method of maintaining a railway track having rails carried by cross-ties, the method comprising the steps of raising a cross-tie, providing packing to support the cross-tie at a desired position and lowering the cross-tie onto the packing, in which settable material is employed to provide stabilized support for the lowered cross-tie.

The invention also provides a method of maintaining a railway track having rails carried by cross-ties supported on ballast, the method comprising the steps of lifting a cross-tie, forming a packing layer of settable material on the ballast beneath the raised cross-tie, and lowering the cross-tie onto the packing layer.

The invention also provides a method of realigning a railway track comprising rails secured to cross-ties, the cross-ties resting on ballast on a substrate, the method comprising the steps of raising a length of the track to separate at least one cross-tie from the ballast, forming on the ballast beneath the lifted cross-tie a packing layer of a material which is initially flowable but which will subsequently set, and lowering the track so that the cross-tie rests on the packing layer in a desired position when the material has set.

The settable material of the packing layer may be a liquid applied by injection. Alternatively, concrete can be employed. Besides the usual ingredients of concrete, namely cement, sand, aggregate and water, additives to effect fast setting can be included. The volume of material applied can be calculated beforehand to give a packing layer of a desired thickness to afford correct alignment of the rails when the cross-tie is lowered and the material has set. The packing layer when set is advantageously resilient, as resilience of the layer serves to prolong the life of the cross-tie or sleeper.

To confine a highly flowable packing layer material to the required region, which is normally a cavity in the ballast in which the cross-tie has previously been received, measures to limit flow of the material can be adopted. Thus, the porosity of the adjacent ballast may be reduced by chemical bonding of the ballast particles or a sheet or film of non-pourous material is applied to the surface of the ballast defining the region in which the packing layer is to be formed. Such restraint will not be needed if the material resists flow or is extremely quick setting, as may be achieved for example by use of a synthetic resin material to which a hardener or accelerator is added shortly before the mixture is deposited in the desired region.

Instead of currently relatively expensive synthetic polymer material, concrete can be employed, preferably with the addition of fibres to enhance its mechanical properties. Such a fibrous additive provides for control of the flow of the material into the interstices of the ballast. The fibrous additive could comprise long chain polymers, such as cellulose from paper or cotton waste.

The invention also provides a railway track having rails secured to cross-ties supported on ballast, at least one cross-tie being supported by means of an intermediate packing layer formed of settable material.

An embodiment of the invention is described below by way of example with reference to the drawings in which Figure 1 schematically shows a railway train for maintaining a railway track in accordance with the process of the invention; and Figure 2 is a schematic longitudinal, vertical section through a sleeper of the railway track and part of the ballast supporting it.

Figure 1 shows rolling stock which may be towed along a railway track comprising rails 1 secured by suitable fasteners to sleepers or crossties 2 supported by ballast 4 on a substrate (not shown), for the purpose of effecting re-alignment of the rails after a period of use.

The rolling stock illustrated comprises a carriage 6 housing track lifting apparatus 8 arranged to engage beneath the rails 1 and sleepers 2 so that as the carriage moves along the track a short length of the rails, together with the associated sleepers, is lifted from the ballast 4 and returned to it. The carriage 6 also houses a device 10 for injecting into the ballast 9 a chemical bonding agent which is capable of filling the interstices between the ballast particles so as to render the region treated non-porous or at least to substantially reduces its porosity.

Adjacent the carriage 6 is a second carriage 12 containing a storage tank 14 for a flowable, settable, material, and a motor 1 5 for example a diesel motor for feeding the material in the tank 14 onto the ballast 4, through a line 16.

In use of the illustrated track maintenance equipment, the carriages 6, 12 are advanced slowiy along the track. The rails 1 and sleepers 2 are raised by the lifting apparatus 8 and whilst each sleeper is suspended above the ballast 4, the device 10 is operated to inject the chemical bonding agent into a region 1 8 of the ballast extending below and around the cavity or recess 20 in the ballast top surface in which the sleeper 2 was previously received. As soon as the porosity of the ballast 4 in the region of this recess has been appropriately reduced in this way, the flowable material in the container 14 is fed by way of the line 1 6 into the recess 20 where it forms a layer 22, being restrained against flow into the adjacent ballast by the loading agent in the region 18. The quantity of the material supplied is selected so that the layer 22 has a thickness sufficient to raise the sleeper 2, on its return to the recess 20, to a position in which rail alignment is achieved.

It will be evident that the invention can be carried into effect in other ways than as described with reference to the drawing.

Claims

1. A method of maintaining a railway track having rails carried by cross-ties supported on ballast, the method comprising the steps of lifting a cross-tie, forming a packing layer of settable material on the ballast beneath the raised crosstie, and lowering the cross-tie onto the packing layer.

2. A method as claimed in claim 1 comprising forming the packing layer by depositing settable material and allowing the settable material to set at least sufficiently to support the cross-tie before the cross-tie is lowered.

3. A method of re-aligning a railway track comprising rails secured to cross-ties, the crossties resting on ballast on a substrate, the method comprising the steps of raising a length of the track to separate at least one cross-tie from the ballast, forming on the ballast beneath the lifted cross-tie a packing layer of a material which is initially flowable but which will subsequently set, and lowering the track so that the cross-tie rests on the packing layer in a desired position when the material has set.

4. A method as claimed in claim 3 wherein the track is lowered when the material has sufficiently set to support the cross-tie in substantially the desired position.

5. A method as claimed in claim 1, 2, 3 or 4, wherein the settable material is injected in liquid form.

6. A method as claimed in claim 1, 2, 3 or 4 wherein the settable material comprises concrete with or without an additive to modify the setting and/or mechanical properties thereof.

7. A method as claimed in any preceding claim having the step of providing means to limit movement of the settable material into the'ballast.

8. A method as claimed in claim 7 wherein movement of the settable material is limited by chemically bonding together particles of the ballast adjacent the packing layer.

9. A method as claimed in claim 7 wherein movement of the settable material is limited by sheet or film material.

10. A method as claimed in claim 7 wherein movement of the settable material is limited by concrete with or without an additive to modify the behaviour thereof.

1 A method as claimed in claim 6 or 10 wherein the concrete includes a cellulose or other fibrous additive.

12. A method of maintaining a railway track having rails carried by cross-ties, the method comprising the steps of raising a cross-tie, providing packing to support the cross-tie at a desired position and lowering the cross-tie onto the packing, a settable material being employed to provide stabilized support for the lowered crosstie.

1 3. A method of maintaining a railway track substantially as herein described with reference to the accompanying drawing.

14. A railway track having rails secured to cross-ties supported on ballast, at least one crosstie being supported by means of an intermediate packing layer formed of settable material.

15. A railway track as claimed in claim 10 wherein the packing layer is resilient.

1 6. A railway track substantially as hereinbefore described with reference to the accompanying drawing.