WO1998031876A1

WO1998031876A1 - A method for forming a gravel covered upper surface along a railway bed section and an escavating arrangement adapted herefor

Info

Publication number: WO1998031876A1
Application number: PCT/SE1998/000079
Authority: WO
Inventors: Carl Anders Rosenqvist
Original assignee: A Rosenqvist Forvaltnings AB
Current assignee: A Rosenqvist Forvaltnings AB
Priority date: 1997-01-22
Filing date: 1998-01-20
Publication date: 1998-07-23
Anticipated expiration: 1999-07-22
Also published as: AU5787098A; SE510322C2; SE9700180L; SE9700180D0

Abstract

The invention relates to a method of forming a gravel-bed covered upper surface (1') along a section of a railroad bed, and of placing on this upper surface railroad sleepers (7) that are adapted to support and firmly hold parallel rails intended for railroad traffic. The upper surface (1') of the gravel bed is worked by a working machine with a fitted implement in a manner to form at least two parallel gravel-bed strings (10, 11). The distance (a) between gravel-bed strings is chosen to correspond to or at least essentially correspond to the distance between the rails. The sleepers (7) are placed along the gravel-bed strings (10, 11) at a pre-determined distance apart. Mutually opposite end-parts of respective sleepers (7) are rested on the uppermost surface of respective gravel-bed strings.

Description

TITLE OF INVENTION

A Method for Forming a Gravel Covered Upper Surface Along a Railway Bed Section and an Escavating Arrangement Adapted herefor.

FIELD OF INVENTION

The present invention relates primarily to a method of producing a gravel-covered top surface along a section of a railroad bed, and more particularly to a method that can be applied in repairing existing railroad sections och/or in the fabrication of new railroad sections .

More particularly, the inventive method involves positioning railroad sleepers , particularly concrete sleepers , that are adapted to support and firmly hold railroad tracks intended for railroad traffic, subsequent to preparing the gravel -covered top surface of said railroad bed .

The invention also relates to a so-called bulldozer or excavating means that functions to work the gravel-covered top surfaces of the railroad bed and which can be fitted to a working machine accordning to the method . BACKGROUND OF THE INVENTION

Various methods of working an at least partially prepared gravel-covered railroad bed such as to obtain a top surface of particular configuration along a railroad bed section are known to the art, and is also methods of placing on this top surface mutually parallel sleepers that are adapted to support and firmly hold parallel rail sections intended for railroad tra fic.

When practicing such known methods, it is endeavored to provide a top surface which is completely flat, or which is slightly inclined at curved sections, so that the sleepers can be placed on this top flat surface with the flat undersurface of the sleepers in direct abutment with the flat gravel-covered top surface of the railroad bed.

Rail sections along which railroad wagons or cars are propelled are now placed provisionally on the sleepers so as to enable rail sections to be laid one in front of the other, railroad sections to be secured to respective sleepers, and railroad beds and sleepers to be prepared for permanent use with railroad traffic, such as trains, especially express trains.

A number of constructions within this technical field are previously known, of which some are to be mentioned below.

DE-A1-2 624 212

This publication shows and describes a mobile machine adapted to continuously vibrate a railroad bed of gravel or macadam.

It is proposed to use a plough arrangement through which a groove is formed in the centre of the railroad bed. DE-C2- 2 633 605

This publication shows and describes an arrangement for the positioning of railroad sleepers for a section of a railroad.

CH-A5-593 399

This publication describes an arrangement, and a mobile unit, adapted to perform a replacement of railroad sleepers.

EP-A1-0 342 306

This publication shows and describes machine adapted to laterally shift a railroad section, with rails and sleepers.

SUMMARY OF THE INVENTION

TECHNICAL PROBLEMS

When taking into consideration the technical deliberations that a person skilled in this particular art must make in order to provide a solution to one or more technical problems that he/she encounters, it will be seen that it is necessary initially to realize the measures and/or the sequence of measures that must be undertaken to this end on the one hand, and to realize which means is/are required in solving one or more of said problems on the other hand. On this basis, it will be evident that the technical problems listed below are highly relevant to the development of the present invention.

When considering the present standpoint of techniques as described above, it will be seen that a technical problem is one of realizing the significance of and the advantages afforded by shaping and/or working the top surface of the gravel bed, by means of a working machine and a thereto applied implement, in a manner which will enable the aforesaid drawbacks to be eliminated or at least greatly reduced in a simple manner and considerably cheapen in comparison with a mobile unit adapted to a preparation of the gravel bed belonging to the railroad bed.

Another technical problem is one of forming in said gravel bed "hard-packed" regions that lie close to the rails and that are able to take-up loads exerted by the weight of so-called "provisional" railroad traffic by means of an implement belonging to a working machine.

By provisional railroad traffic is meant the traffic that is involved in preparing the railroad bed, laying-out railroad sleepers, laying-out rail sections, fastening the rail sections to underlying sleepers with the aid of clips and/or final preparation of the railroad bed.

This type of railroad traffic differs from the traffic applicable in more permanent use of the railroad, including heavy goods trains and/or passenger train traffic.

In this respect, it will be seen that a technical problem is one of realizing the significance of levelling-off the upper surface of the gravel bed so as to form two mutually parallel strings consisting of loose gravel, and of spacing the strings apart at a distance which corresponds to, or at least essen- tially corresponds to, the distance between the rails, wherewith the sleepers may be placed along the strings at a pre-determined distance apart.

It will also be seen that a technical problem resides in working and compacting the gravel strings to a flat state and to a uniform degree of compaction that will enable said strings to withstand the loads exerted by said provisional railroad traffic.

Another technical problem in this context is to realize the significance of working the gravel strings, such as compacting said strings, with the aid of a working machine wherewith the wheel span of the machine is adapted to the distance between said strings, and wherewi^'th the wheel pressure is adapted to a pre-determined value.

Another technical problem is one of realizing the significance of and the advantages that are afforded by permitting solely opposite end-parts of said sleepers to rest on the upper surface of a respective string of loose gravel that has been compacted by the wheels of said working machine.

Another technical problem is one of realizing the significance of using the blade of the implement to form on a loose-gravel or compacted-gravel bed two loose-gravel structured bed strings and to compact said strings with the aid of all wheels on the working machine in sequence, and to enable these string sequences to be fabricated readily with the aid of a single working machine that has an implement, with a specially configured excavation blade or dozer blade, fitted thereto.

It will also be seen that a technical problem is one of realizing the significance of laying railroad sleepers on the thus formed and compacted gravel-bed strings with the aid of a working machine that has sleeper laying gear mounted thereon.

Another technical problem is one of realizing the significance of further compacting the gravel strings with the wheels of a working machine as said machine ^■ lays the sleepers on said strings.

Another technical problem is one of realizing the significance of and the advantages afforded by compacting the gravel-bed strings to a height of between 5 and 10 cm above an intermediate surface.

Another technical problem is one of realizing the significance of and the advantages afforded by giving each of said strings a smallest width of between 20 and 40 cm. Another technical problem is one of realizing the significance of and the advantages afforded by enabling each of the sleepers to be pressed down into the gravel strings with the aid of apparatus that is adapted to provide a fine-adjustment of intermediate distances between mutually adjacent sleepers, and to fasten rails on respective sleepers with the aid of appropriate fasteners, such as clips.

Another technical problem is one of realizing the significance of being able to provide between the gravel strings a loose- gravel bed that will loosely support the central region of respective sleepers.

Another technical problem resides in providing a so-called bulldozing arrangement or excavating means that will function to level-out and selectively compact said gravel strings, in addition to creating said strings.

Another technical problem is one of realizing the significance of providing a so-called bulldozing arrangement which will function to provide desired gravel strings, by removing gravel from between said strings.

SOLUTION

With the intention of solving one or more of the aforesaid technical problems, the present invention takes as its starting point a method of forming a gravel-bed upper surface along a section of a railroad bed and of placing on said surface railroad sleepers that are adapted to support and firmly hold mutually parallel rails intended for railroad traffic.

In accordance with the invention, the upper surface of the gravel bed is worked or levelled in a way to form at least two mutually parallel gravel strings, wherein the distance between selected strings is made to correspond to, or to essentially correspond to, the distance between the rails, wherein the sleepers are placed along the gravel strings at a pre-deter- mined distance apart, and wherein the mutually opposite ends of the sleepers are caused to rest against at least respective upper surfaces of the respective gravel strings.

The present invention specifically teaches that the leveling of the gravel bed and the formation of said two gravel strings is achieved with the aid of a working machine which has an implement with a specially designed dozer blade or excavating blade fitted thereto.

As proposed embodiments, falling within the scope of the present invention, it is taught that the dozer blade is to be positioned close to the working machine and that a supporting wheel is located in front of said dozer blade as seen in the forward driving direction.

According to one embodiment, sleepers are placed on the gravel strings with the aid of a working machine fitted with a sleeper laying gear belonging to an implement.

According to one preferred embodiment of the invention, the gravel strings have a height of between 5 and 10 cm above an intermediate surface.

It is also proposed that the gravel strings will have a smallest width of between 20 and 40 cm when the gravel bed is comprised of washed shingle having a stone or pebble size of 22-64 mm. If a smaller stone or pebble size is chosen 15-25 mm could be used in some applications.

It is also proposed in accordance with the invention that each of the sleepers can be pressed down slightly into the strings with the aid of suitable means, such as apparatus that will function to finely adjust the distance between mutually adjacent sleepers and to secure the rails to said sleepers with the aid of appropriate fastener means, such as clips. It is also proposed that a further gravel bed is applied between the gravel strings, to support the central region of respective sleepers.

It is also proposed that the loose-gravel strings are compacted in one or more stages with the aid of the front and rear wheels of the working machine and/or that the loose-gravel strings are further compacted by an other working machine.

It is also proposed within the scope of the invention that there is used when practicing the inventive method a so-called bulldozing arrangement that has a dozer blade which is comprised of number of blade sections and positioned transversely to the section of the railroad bed being worked.

In this respect, a centrally positioned blade section of a dozer blade belonging to an implement is adapted to extend slightly beneath laterally orientated blade sections and therewith function to form gravel strings on each side of the centrally positioned blade section and that a guiding or supporting plate, or similar, is adapted to rest on the railroad bed.

According to proposed embodiments, two laterally positioned blade sections are angled to the direction in which the machine is driven.

At least one supporting wheel is positioned in front of the centrally positioned blade section.

The wheel will preferably be raisable and lowerable, so as to enable the excavating depths of the centrally positioned blade section to be adjusted.

An implement attachment for a working machine is mounted on one side (behind) of said centrally positioned blade section, and said wheel is positioned on the other side (in front of) said centrally positioned part, as seen in the forward driving direction.

The implement attachment may also be raisable and lowerable so as to enable the excavating depth of the centrally positioned blade section to be adjusted.

Two wheels are positioned at the opposite edge-regions of the centrally positioned blade section.

The supporting or guiding plate is adapted to be able to rest on an excavated section.

ADVANTAGES

Those advantages that are primarily afforded by an inventive method and an inventive bulldozing arrangement are found in the provision of conditions which, by means of a working machine with a thereto connected impelement, enable gravel-bed strings to be formed on a railroad bed and to be compacted by the working machine adjacent the end-parts of railroad sleepers laid thereon and positioned to receive and support associated railroad rails, thereby ensuring bearing resistance for concrete sleepers with reduced risk, or with no risk, of the sleepers needing to absorb high punctilinear or distributed compression forces from railroad traffic within the central regions of said sleepers.

The inventive method and bulldozing arrangement may also reduce the time required to lay railroad tracks in relation to known techniques.

The primary characteristic features of the inventive method are set forth in the characterizing clause of the following Claim 1, while the primary characteristic features of an inventive bulldozing arrangement are set forth in the characterizing clause of Claim 10.

BRIEF DESCRIPTION OF THE DRAWINGS

A number of preferred embodiments of apparatus required to form the upper surface of a gravel-bed along a section of a railroad bed, placing railroad sleepers along said section, and allowing railroad sleepers to firmly hold railroad track intended for railroad traffic will now be described in more detail with reference to the accompanying drawings, in which

Figure 1 is a perspective illustration of a working machine levelling a prepared, but loose gravel bed, with the aid of a first embodiment of an implement with an inventive bulldozing or excavating arrangement;

Figure 2 is a perspective view of sleeper laying apparatus;

Figure 3 is a perspective view of apparatus for pressing sleepers against the gravel bed of the railroad bed, said apparatus being adapted to adjust the position of the sleepers relative to one another and relative to the railroad tracks;

Figure 4 is an enlarged perspective view of the apparatus shown in Figure 2 and is intended to illustrate laying of sleepers along the gravel-bed strings of the railroad bed section more clearly;

Figure 5 is a cross-sectional view of the upper surface of a gravel bed, said surface including two gravel strings compacted by the whels of the working machine which support a sleeper that has been laid on said^' strings with the aid of the apparatus shown in Figure 2;

Figure 6 is a cross-sectional view showing a sleeper pressed down into the compacted strings with the aid of apparatus according to Figure 3 among other things and carrying two mutually parallel rail sections, where depression into the gravel strings caused hereby ensures enhanced bearing capacity of the railroad bed immediately beneath the tracks or rails;

Figure 7 is a side view of another embodiment of an inventive bulldozing arrangement belonging to an implement;

Figure 8 is a front view of the bulldozing arrangement shown in Figure 7;

Figure 9 is a horizontal view which illustrates certain parts of the bulldozing arrangement shown in

Figure 7 ; and

Figure 10 is a cross-sectional view of a railroad sleeper placed on compacted gravel strings by means of the apparatus shown ^■ in Figure 3 among other things and supporting two mutually parallel rail sections.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates primarily to a method of preparing the upper surface of the gravel covering of a railroad bed section, such as to enable railroad sleepers adapted to support and firmly hold the parallel rails of railroad tracks intended for railroad traffic to be placed thereon.

Figure 1 is a perspective view of a first embodiment of a so- called bulldozing arrangement belonging to an implement for a working machine 2. The bulldozing arrangement is shown while levelling a prepared loose-gravel bed with the aid of a specially configured dozer blade.

By preparing is meant, for instance, levelling and/or compacting a gravel bed that consists of washed shingle with a stone or pebble size of up to about 70 mm, such as 22-64 mm.

Figure 2 is a perspective view of sleeper laying apparatus, with sleepers being placed successively along the levelled gravel bed 1' of Figure 1 at a pre-determined distance therebetween.

Figure 3 is a perspective view of apparatus 15 for lifting sleepers against the rails when applying fastener elements, and pressing of the sleepers against the gravel bed.

Figures 1 to 3 are intended to illustrate three different consecutive and important preparatory sequences prior to allowing provisional railroad traffic to pass along railroad tracks .

The first working sequence shown in Figure 1 comprises shaping a prepared gravel bed 1 in accordance with the invention, using a bulldozing arrangement that includes a working machine 2 and an implement, with a specially designed dozer blade 3, fitted thereto.

Figure 2 illustrates a second working sequence, in which sleepers are laid with the aid of a sleeper laying apparatus 5 and also with the aid of a working machine 6, not shown in detail in the figure. Figure 2 shows a last sleeper 7 placed on the uppermost surface of the gravel bed 1 ' .

Figure 3 shows apparatus 15 which performs a working process when fastening a rail 8 to a sleeper 7' with the aid of clips 9.

The fundamental features of the apparatus 15 are described and illustrated in more detail in Swedish Patent Application 9303695-2 (Swedish Patent 501 761), and a method that can be applied when using the apparatus 15 is described and illustrated in more detail in Swedish Patent Application 9601965-8, filed on the 23rd May 1996.

The contents of this latter patent application shall be considered to constitute part of the present patent application.

Figure 4 is principly an enlarged illustration of the area shown in Figure 2, from which it will be seen that the upper surface la of the loose gravel bed 1 has been worked at 1 ' by the working machine 2 and the dozer blade 3 or plough blade in a manner to form two mutually parallel loose-gravel strings 10, 11 and an intermediate flat region 12.

The configuration of the gravel-bed strings 10, 11 and the intermediate region 12 are determined by the bottom configuration of the dozer blade 3. Thus,- the bottom edge 3a of the blade is substantially straight, or slightly angled, and includes two recesses 3b and 3c that are adapted to form the gravel-bed strings 10, 11, said strings therewith being formed from loose gravel.

The distance "a", measured between central sections of the gravel-bed strings 10, 11 is chosen to correspond to or to corresponding generally to a chosen distance between mutually parallel rails 8, 8'. The sleepers 7, according to Figure 2, are laid at a pre-deter- mined distance apart, by ^'coupling the implement or apparatus 5 ( the sleeper laying apparatus ) to a working machine 6 in the excavator attachment. The sleeper laying apparatus 5 is therewith fully rotatable and tiltable.

The apparatus 5 can load up to eight sleepers at a time, as they lie side-by-side in a stack, and then lay the sleepers at the correct distance apart with the aid of an adjustable, built-in length measuring system, and by resting the sleepers one at a time on the uppermost surfaces 10a, 11a of the gravel- bed strings 10, 11.

This enables the sleepers 7 to be placed with the bottom surfaces of respective end-parts 7a, 7b of said sleepers resting on the uppermost surfaces 10a, 11a of respective gravel-bed strings.

The gravel bed can be levelled and said two gravel-bed strings formed with the aid of a working machine 2 that is equipped with a specially designed dozer blade 3 ( includes recesses ) for forming the strings 10, 11, although the bed may be levelled and said strings formed more beneficially with a bulldozing arrangement illustrates in Figures 7 to 10.

It will be noted in particular that the gravel-bed strings 10, 11 formed by the dozer blade 3 shall be immediately compacted by causing the wheels 2a, 2b of the working machine 2 to pass along the strings and therewith compact the gravel material, irrespective of the design of the dozer blade and the construction of the bulldozing arrangement used.

In this regard it is necessary for the distance between the wheels of one and the same axle to correspond to the distance between the rails 8, 8' of the railroad track, and for the compacting pressure achieved through the tyres of said wheels to correspond to a pre-determined value. This value can be adapted by using different tyre dimensions for different working machines.

The gravel is conveniently compacted in several stages.

For instance, a first stage of compaction can be effected by the front wheels 2a of the machine 2 and a second compaction station via the rear wheels 2b of said machine. A third compaction stage can be effected when laying-out the sleepers by the machine carrying the apparatus 5.

The invention is based on the gravel-bed strings (of loose gravel or compacted gravel) having a height "h" over an intermediate surface 12 of about 5 and 10 cm, a greater height in the case of loose gravel than in the case of pre-compacted gravel .

The gravel-bed strings, such as the string 10, may have a width "b" of between 20 and 40 cm in the case of a dozer blade according to Figure 1, although the string 10 may have a much greater width in accordance with the invention.

As illustrated in Figure 6, each of the railroad sleepers can be pressed down into the gravel strings 10, 11 by means of the apparatus 15, so as to finely adjust the intermediate distance between adjacent sleepers and fastening of the rails to respective sleepers with the aid of appropriate fastener elements, such as clips.

This provides conditions for further compaction of the regions 10b and lib immediately beneath the rails 8, 8^', so as to ensure sufficiently high bearing capacity of the railroad bed for withstanding the load that the provisional railroad traffic and the normal railroad traffic will generate along the parallell railroad tracks. The intermediate region 12b is still loose and does not support against the centrally located bottom surface of the sleeper 7 ' , as shown in Figure 6.

However, in practice a certain supportive function may also be found in this region.

In accordance with the invention, a gravel bed 1" is then applied at least between the gravel-bed strings 10, 11, so as to supplement supporting of the central region of the sleepers and to adapt to normal train traffic.

The space 12' formed by the intermediate surface 12 and the sleepers 7' is also suitable for facilitating the function of the apparatus 15.

Figures 7 to 10 illustrate an alternative implement-related bulldozing arrangement 30.

This arrangement is comprised of a frame structure 31 which carries at one end (its front end) two wheels 32, 32a which can be raised and lowered with the aid of an adjusting device 33. The illustrated wheel adjusting device 33 comprises a crank 33a which co-acts with a spindle or screw threaded rod 33b that turns in a nut-part 33c attached to the frame structure 31.

The frame structure 31 also carries a dozer blade 34 which is comprised of a number of blade sections. A central blade section is referenced 34a.

As will be evident from Figure 8, the central blade section 34a has a lowermost edge-part 34a' that extends beneath the lowermost edge-parts of remaining blade sections through a distance

Positioned on each side of the blade section 34a is a respective blade section 34b and 34c, these blade sections being fixed at an angle (b) of 165° with the apex of the angle being located in the direction of forward travel. Angular values in the range of 170-150° are also considered suitable.

Edge-related blade sections 34d and 34e are rotatably connected to the blade sections 34b and 34c by means of vertical pivot shafts 35, 36.

The position to which the blade sections 34d and 34e are pivoted or rotated can be regulated with the aid of known means 37 and 38. Although the illustrated means comprises an adjuster rod, it will be understood that hydraulic means may alternatively be used.

The length of the blade section 34d corresponds to one third of the length of the blade section 34b.

The blade section 34d (34e) is angled (c) forwardly at an angle of 150° in relation to the blade section 34b. Angular values of between 100 and 250° are also considered suitable.

Edge-parts 34d'and 34e' may also be angled downwards, in accordance with the broken lines in Figure 8.

Behind the dozer blade section 34a and the blade sections 34b and 34c, as seen in the forward driving direction, there is a horizontally positioned supporting plate 41. The underneath side of the supporting plate 41 coincides with the lowermost edge-parts 34b^', 34c' of the blade sections 34b and 34c and this supporting plate 41 is intended to lean or support on formed gravel-bed strings and thereby leveling the same. The supporting plate can bear on a worked gravel-bed surface.

Figure 10 is a cross-sectional view (similar to the view of Figure 6) of a railroad bed where the gravel bed has been worked with a bulldozing arrangement according to Figures 7 to

9, and it will be evident from said figure that the excavated gravel-bed region (12') has been brought outside the railroad bed as loose gravel. In this case, the railroad bed is compressed to a lesser extent than in the case of the Figure 1 application.

This bulldozing arrangement is particularly adapted for use with an inventive method and has a dozer blade which is divided into a number of parts or blade sections that extend across the whole of the section of the bed. A centrally positioned blade section 34a is adapted to extend beneath the laterally positioned blade sections, such as to form gravel-bed strings 10', 11' on respective sides of the centrally positioned blade section.

At least one wheel 32 is located at the centrally positioned blade section and placed in front of said blade section 34a, as seen in a forward driving direction.

The wheels 32, 32a can be raised and lowered so as to adjust the excavating depth of the centrally positioned blade section 34a.

An implement attachment 40 for a working machine ( 2 ) is mounted on one side of the centrally positioned blade section 34a and said wheel 32 is mounted on the other side of said centrally positioned blade section 34a, as seen in the forward driving direction.

The implement attachment 40 can be raised and lowered so as to adjust the excavating depth (a) of the centrally positioned blade section.

The centrally positioned blade section 34a is fixed in relation to remaining blade sections and to the frame structure 31.

It will be understood that the invention is not restricted to the aforedescribed and illustrated embodiments thereof and that modifications can be made within the scope of the inventive concept as illustrated iri the following claims.

Claims

1. A method of forming a gravel-covered upper surface along a section of a railroad bed and placing on said upper surface railroad sleepers that are adapted to support and firmly hold parallel rails intended for railroad traffic; working the upper surface of said gravel bed in a manner to form at least two mutually parallel gravel-bed strings; causing the distance between chosen gravel-bed strings to correspond to or corre- sponding at least essentially to the distance between said rails; placing railroad sleepers along the gravel-bed strings at a pre-determined distance apart; and resting the mutually opposite end-parts of respective sleepers on the uppermost surface of a respective gravel-bed string, characterized by working the gravel bed and forming said two gravel-bed strings with the aid of a working machine fitted with an implement with a dozer blade.

2. A method according to Claim 1, characterized by positioning the dozer blade close to the working machine and locating a supporting wheel, belonging to said implement, in front of said dozer blade as seen in the forward driving direction.

3. A method according to Claim 1 or Claim 2, characterized by laying-out said sleepers and forming said gravel-bed strings with the aid of a working machine fitted with sleeper laying apparatus.

4. A method according to Claim 1, characterized by forming the gravel-bed strings to a height of between 5 and 10 cm above an intermediate surface.

5. A method according to Claim 1, characterized by giving the gravel-bed strings a width between 20 and 40 cm.

6. A method according to Claim 1, characterized by pressing each of said sleepers down into said gravel-bed string with the aid of apparatus for finely adjusting the intermediate distance between adjacent sleepers and fastening rails to respective sleepers with the aid of appropriate fastener elements, such as clips.

7. A method according to Claim 6, characterized by applying a further gravel bed between the gravel-bed strings for supporting the central region of respective sleepers.

8. A method according to Claim 1, characterized by compacting the gravel-bed strings with the aid of the wheels of a first working machine.

9. A method according to Claim 8, characterized by further compacting the gravel-bed strings with the aid of the wheels of a second working machine.

10. A bulldozing arrangement adapted for use with a method according to any one of the preceding claims and having posi- tioned across the railroad bed section a dozer blade that is divided into a number of blade sections, characterized in that a centrally positioned blade section of a dozer blade belonging to an implement is adapted to extend beneath laterally positioned blade sections and therewith form gravel-bed strings on respective sides of the centrally positioned blade section and that a supporting plate, or similar, is adapted to rest on the railroad bed.

11. An arrangement according to Claim 10, characterized in that the two laterally positioned blade sections are angled in a direction towards the driving direction.

12. An arrangement according to Claim 10 or Claim 11, characterized in that at least one supporting wheel is mounted in front of a centrally positioned blade section.

13. An arrangement according to Claim 12, characterized in that said wheel can be raised and lowered to adjust the excavating depth of the centrally positioned blade section.

14. An arrangement according to Claim 10, characterized in that an implement attachment for a working machine is mounted on one side of said centrally positioned blade section, and in that said wheel is mounted on the other side of said centrally positioned blade section as seen in the driving direction.

15. An arrangement according to Claim 14, characterized in that the implement attachment can be raised and lowered to adjust the excavating depth of said centrally positioned blade section.

16. An arrangement according to Claim 12, characterized in that two wheels are mounted on mutually opposite edges of the centrally-positioned blade section.

17. An arrangement according to Claim 10, characterized in that the centrally positioned blade section is fixed relative to remaining blade sections.

18. An arrangement according to Claim 10, characterized in that saidguiding plate or supporting plate is adapted to rest on a worked railroad bed section.