Method for waterproofing railway bridges and waterproofing material for carrying out said method

Abstract

A method for waterproofing of bridges (1) and similar structures aimed at railway traffic is described, the structures comprising an arch or deck structure, on which there is placed a ballast (M) of gravel or crushed stone (2) upon which the tracks (6) extend between the two ends of the bridge (1). The waterproofing is obtained first by the removal of the tracks (6) and a reduced layer (S) of gravel or crushed stone (2), leaving in place the remaining part of gravel or crushed stone (2), and then by laying one or more sheets (10) of cured rubber on the remaining part of gravel or crushed stone (2). The thickness of the rubber is such as to be sufficiently resistant to perforation by the gravel or crushed stone (2), which is subsequently placed thereon to complete the ballast, Finally, the previously removed tracks (6) are set in place again. According to the method, a joint is made between the sheets (10) by means of a connection of mechanical type, with a positive locking shape fit, or a chemical bond using a suitable adhesive.

Claims

1. A method for waterproofing of a section of railway line or railway bridge or structure that supports rail traffic on a plurality of tracks (6), including a ballast (M) that includes gravel or crushed stone (2) upon which at least one track (6) extends, with waterproofing (10) placed between the ballast (M) and a support surface of the section of railway line or railway bridge (1) or structure that supports rail traffic, the method comprising: removing the at least one track of the plurality of tracks (6) of the section of the railway line or railway bridge (1) or structure that supports rail traffic; removing a layer (S) of gravel or crushed stone (2) forming the ballast (M), up to a greater depth with respect to a depth normally achieved by periodic mixing of said gravel or crushed stone (2), during maintenance operations of the plurality of tracks (6), leaving in place any remaining portion of gravel or crushed stone (2); laying at least one sheet (10) of cured rubber on the remaining portion of gravel or crushed stone (2) of the ballast (M), said sheet (10) having such a thickness as to be sufficiently resistant to perforation by the gravel or crushed stone (2) situated below, as well as by that which is subsequently placed on top to complete the ballast; and repositioning the previously removed gravel or crushed stone (2) on the at least one sheet of cured rubber (10) and the previously removed at least one track of the plurality of tracks (6) of the section of railway line or railway bridge or structure that supports rail traffic, wherein said section includes a first track (6a) and a second track (6b), parallel to each other, the method including: removing a section of said first track (6a) and of any associated ties; removing a layer (S) of gravel or crushed stone (2) forming the ballast (M), from a side of said first track (6a) and beyond a midline plane of said ballast (M), up to the greater depth with respect to the one normally achieved by periodic mixing of said gravel or crushed stone (2) during maintenance operations of the plurality of tracks (6), leaving in place any remaining underlying portion of gravel or crushed stone (2); installing a first vertical shoulder (51), along a whole extension of the section to be waterproofed, laying at least one first sheet (101) of cured rubber on the underlying portion of gravel or crushed stone (2) of the ballast (M), from the side of said first track (6a), said first sheet (101) having such a thickness as to be resistant, on both faces, to perforation by the gravel or crushed stone (2), keeping a first edge (101a) of said first sheet (101) raised against a wall of said first shoulder (51); installing a second vertical shoulder (52), situated beside the first shoulder (51), keeping said first edge (101a) between said first shoulder (51) and said second shoulder (52); repositioning the removed gravel or crushed stone (2) on the at least one first sheet of cured rubber (101), of said first track (6a) and the associated ties of the previously removed section of the first track (6a); removing a section of said second track (6b) and of any associated ties; removing a layer (S) of gravel or crushed stone (2) forming the ballast (M), from a side of said second track (6b), up to the greater depth with respect to the one normally achieved by periodic mixing of said gravel or crushed stone (2) during maintenance operations of the plurality of tracks (6), leaving in place any remaining underlying portion of gravel or crushed stone (2); removing said first shoulder (51); laying at least one second sheet (102) of cured rubber on the underlying portion of gravel or crushed stone (2) of the ballast (M), from the side of said second track (6b), having a same characteristic type of cured rubber as said first sheet (101), keeping a second edge (102a) of said second sheet (102) beside said first edge (101a) of said first sheet (101); joining said first (101a) edge and second edge (102a); repositioning the removed gravel or crushed stone (2) on the at least one second sheet of cured rubber (102), of said second track (6b) and the associated ties of the previously removed section of railway line; and removing said second shoulder (52).

2. The method as claimed in claim 1, further comprising: after said removing the layer of gravel or crushed stone forming the ballast (M) from the side of said first track (6a), installing a plurality of first under track crossties (55) under said second track (6b), and fastening the plurality of first under track crossties to said first shoulder (51); after or at the same time as said repositioning of said first track (6a), installing a plurality of second under track crossties (56) under said first track (6a), and fastening the plurality of second under track crossties to said second shoulder (52); after or at the same time as said removal of said second track (6b), removing said first under track crossties (55); and after said repositioning of said second track (6b), removing said second under track crossties (56).

3. The method as claimed in claim 1, further comprising: after said positioning of a first vertical shoulder (51), installing a safety rail (53); at the same time as said removal of said first shoulder (51) and said second shoulder (52) removing said safety rail (53).

4. The method as claimed in claim 1, wherein external parts of a surface covered by said at least one sheet of rubber (10,101,102) extend from side to side and beyond a limit defined by containment walls (3), (4) of the ballast (M), and in vertical or sloping extension also over the containment walls (3), (4), to define a containment basin.

5. The method according to claim 1, wherein several sheets (10,101,102) are laid out and adjacent sheets of the several sheets (10,101,102) are joined by a bond of mechanical type, obtained by a positive locking fit.

6. A method for waterproofing of a section of railway line or railway bridge or structure that supports rail traffic on a plurality of tracks (6), including a ballast (M) that includes gravel or crushed stone (2) upon which at least one track (6) extends, with waterproofing (10) placed between the ballast (M) and a support surface of the section of railway line or railway bridge (1) or structure that supports rail traffic, the method comprising: removing the at least one track of the plurality of tracks (6) of the section of the railway line or railway bridge (1) or structure that supports rail traffic; removing a layer (S) of gravel or crushed stone (2) forming the ballast (M), up to a greater depth with respect to a depth normally achieved by periodic mixing of said gravel or crushed stone (2), during maintenance operations of the plurality of tracks (6), leaving in place any remaining portion of gravel or crushed stone (2); laying at least one sheet (10) of cured rubber on the remaining portion of gravel or crushed stone (2) of the ballast (M), said sheet (10) having such a thickness as to be sufficiently resistant to perforation by the gravel or crushed stone (2) situated below, as well as by that which is subsequently placed on top to complete the ballast; and repositioning the previously removed gravel or crushed stone (2) on the at least one sheet of cured rubber (10) and the previously removed at least one track of the plurality of tracks (6) of the section of railway line or railway bridge or structure that supports rail traffic, wherein several sheets (10,101,102) are laid out and adjacent sheets of the several sheets (10,101,102) are joined by a bond of mechanical type, obtained by a positive locking fit and wherein the positive locking fit, comprises a male-female type, and includes an edge of one of the adjacent sheets of the several sheets (10,101,102) being provided with a shaped extension (12) situated along a midline of a junction side (11), and an edge of an adjacent sheet (10,101,102) having a receiving seat (13), matching with the shaped extension (12), the receiving seat (13) configured to receive the shaped extension (12) to obtain said positive locking fit.

7. A method for waterproofing of a section of railway line or railway bridge or structure that supports rail traffic on a plurality of tracks (6), including a ballast (M) that includes gravel or crushed stone (2) upon which at least one track (6) extends, with waterproofing (10) placed between the ballast (M) and a support surface of the section of railway line or railway bridge (1) or structure that supports rail traffic, the method comprising: removing the at least one track of the plurality of tracks (6) of the section of the railway line or railway bridge (1) or structure that supports rail traffic; removing a layer (S) of gravel or crushed stone (2) forming the ballast (M), up to a greater depth with respect to a depth normally achieved by periodic mixing of said gravel or crushed stone (2), during maintenance operations of the plurality of tracks (6), leaving in place any remaining portion of gravel or crushed stone (2); laying at least one sheet (10) of cured rubber on the remaining portion of gravel or crushed stone (2) of the ballast (M), said sheet (10) having such a thickness as to be sufficiently resistant to perforation by the gravel or crushed stone (2) situated below, as well as by that which is subsequently placed on top to complete the ballast; and repositioning the previously removed gravel or crushed stone (2) on the at least one sheet of cured rubber (10) and the previously removed at least one track of the plurality of tracks (6) of the section of railway line or railway bridge or structure that supports rail traffic, wherein several sheets (10,101,102) are laid out and adjacent sheets of the several sheets (10,101,102) are joined by a bond of mechanical type, obtained by a positive locking fit and wherein the adjacent sheets (10,101,102) are joined by a chemical bond, obtained by providing a recess (15) along edges of the sheets (10,101,102) to be joined, by raising upper borders (16) which delimit a recess (15) along each of the adjacent sheets (10,101,102), when said two sheets (10,101,102) are being joined and laying a strip (18) of the same or different material onto a lower border (17) of each recess (15), which are juxtaposed or almost juxtaposed, and by releasing said upper borders (16) so as to obtain said positive locking fit.

8. A method for waterproofing of a section of railway line or railway bridge or structure that supports rail traffic on a plurality of tracks (6), including a ballast (M) that includes gravel or crushed stone (2) upon which at least one track (6) extends, with waterproofing (10) placed between the ballast (M) and a support surface of the section of railway line or railway bridge (1) or structure that supports rail traffic, the method comprising: removing the at least one track of the plurality of tracks (6) of the section of the railway line or railway bridge (1) or structure that supports rail traffic; removing a layer (S) of gravel or crushed stone (2) forming the ballast (M), up to a greater depth with respect to a depth normally achieved by periodic mixing of said gravel or crushed stone (2), during maintenance operations of the plurality of tracks (6), leaving in place any remaining portion of gravel or crushed stone (2); laying at least one sheet (10) of cured rubber on the remaining portion of gravel or crushed stone (2) of the ballast (M), said sheet (10) having such a thickness as to be sufficiently resistant to perforation by the gravel or crushed stone (2) situated below, as well as by that which is subsequently placed on top to complete the ballast; and repositioning the previously removed gravel or crushed stone (2) on the at least one sheet of cured rubber (10) and the previously removed at least one track of the plurality of tracks (6) of the section of railway line or railway bridge or structure that supports rail traffic, wherein several sheets (10,101,102) are laid out and adjacent sheets of the several sheets (10,101,102) are joined by a bond of mechanical type, obtained by a positive locking fit and wherein the adjacent sheets of the several sheets (10,101,102) are joined in complementary reduced thickness areas along borders of the adjacent sheets of the several sheets (10,101,102) by superimposing the reduced thickness areas when joining, with interposition of an adhesive substance (23), so as to obtain said positive locking fit.

9. A method for waterproofing of a section of railway line or railway bridge or structure that supports rail traffic on a plurality of tracks (6), including a ballast (M) that includes gravel or crushed stone (2) upon which at least one track (6) extends, with waterproofing (10) placed between the ballast (M) and a support surface of the section of railway line or railway bridge (1) or structure that supports rail traffic, the method comprising: removing the at least one track of the plurality of tracks (6) of the section of the railway line or railway bridge (1) or structure that supports rail traffic; removing a layer (S) of gravel or crushed stone (2) forming the ballast (M), up to a greater depth with respect to a depth normally achieved by periodic mixing of said gravel or crushed stone (2), during maintenance operations of the plurality of tracks (6), leaving in place any remaining portion of gravel or crushed stone (2); laying at least one sheet (10) of cured rubber on the remaining portion of gravel or crushed stone (2) of the ballast (M), said sheet (10) having such a thickness as to be sufficiently resistant to perforation by the gravel or crushed stone (2) situated below, as well as by that which is subsequently placed on top to complete the ballast; and repositioning the previously removed gravel or crushed stone (2) on the at least one sheet of cured rubber (10) and the previously removed at least one track of the plurality of tracks (6) of the section of railway line or railway bridge or structure that supports rail traffic, wherein external parts of a surface covered by said at least one sheet of rubber (10,101,102) extend from side to side and beyond a limit defined by containment walls (3), (4) of the ballast (M), and in vertical or sloping extension also over the containment walls (3), (4), to define a containment basin, said method further comprising fastening a border (24) of the at least one sheet to a containment wall of the containment walls (3), (4) by means of screws or nails (26) driven into the sides of the containment wall, and providing flashing (25) on the containment wall, in such a way as to rise above edges of the border (24) to prevent passage of water below the border (24).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The characteristics of the invention, which have not appeared from what has been previously said, will become evident from the following description, with reference to the enclosed drawing tables, in which:

(2) FIG. 1 and FIG. 2 show an arch bridge and the conformation of the waterproofing system according to the traditional modality of the prior art, in lateral and top views, respectively, with some parts removed so as to better point out the implementation of the waterproofing system according to the prior art;

(3) FIGS. 3 and 4 show an arch bridge and the conformation of the waterproofing system according to the invention, with the bridge seen from the side and in cross section, respectively;

(4) FIG. 5 shows the bridge of FIGS. 3 and 4 in plan view, with some parts removed to better point out the implementation of the waterproofing system proposed by the present invention;

(5) FIGS. 6A to 6C illustrate the details, in section view, of a characteristic point of the waterproofing system proposed by the present invention;

(6) FIGS. 7A to 7D illustrate the details, in section view, of the bridge and waterproofing system according to the invention;

(7) FIG. 8 shows a detail of the system obtained in accordance with the invention;

(8) FIGS. 9A to 9F illustrate as many working steps of a different embodiment of the invention, particularly suitable for multi track railway, by which the train traffic must not be interrupted completely.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(9) With reference to the above mentioned Figures, reference numeral 1 indicates, by way of example, an arch bridge (FIG. 3), which has been subjected to maintenance to restore the waterproofing system. As already said, the considerations made for an arch bridge will be valid also for the bridges with decks, if not otherwise specified.

(10) In accordance with the method proposed by the present invention, the operation on the track can be advantageously carried out in automatic way, by the machines already used for alignment (not shown in the drawings).

(11) First the tracks 6 are sectioned in pieces of 18-20 meters by cutting with oxyacetylene torch, along each span C of the bridge 1 (FIGS. 3 and 5).

(12) Then, the tracks are moved to the side, in an area which is not involved in the restoration; the tracks are moved by a machine called loading platform. The loading platform, which lifts, and a mechanical shovel, which shifts and moves away, remove a layer of crushed stone 2 to the extent necessary for the method under discussion. Such extent exceeds a little the depth of the layer normally removed for the ordinary maintenance of the tracks, but not more than that. The removal depths typically acceptable are comprised between 50 and 80 centimetres.

(13) Afterwards, the material of cured rubber in sheets 10 is laid in one layer, without any concrete support layer or covering/protection layer of bitumen conglomerate.

(14) The quality of the used rubber, which includes a particular compound, prepared on purpose to give resistance to the perforation, relieves from the necessity of using concrete support levels below and layers of bituminous conglomerate above, since it is self-protected and avoids perforations, tearing, cracks, etc.

(15) This allows the maintenance operation with the restoration of the waterproofing system to be carried out in few hours for those bridges for which the traditional system required a few days.

(16) Since the crushed stone 2 has rather irregular forms, it is to be expected that the rubber must adapt itself assuming shapes that correspond to the shapes of the crushed stone lying thereon and to the shapes of the crushed stone situated under it.

(17) With reference to FIGS. 6A-6C, the joint 11 between the various sheets 10 is made without using glues or adhesives and this also helps save time for the restoration of the waterproofing system. In fact, the sheets 10 are separated and, in case, pre-assembled in the material production site or in another specially provided place, and then put in place by unrolling them from rolls (not shown), on which they have been previously rolled up to be transported.

(18) If the transversal and longitudinal dimensions of the bridge do not allow reasonably the assembly, transport and subsequent laying of a single sheet, smaller sheets are produced, rolled up and transported to the place. They must be subsequently joined to one another and to the sides of the railway line of the bridge, along which they must be installed.

(19) A first possible joint (FIG. 6A) includes a joint of mechanical type, obtained by a positive locking fit, for example male-female, with the edge of one of the sheets 10 provided with a shaped extension 12, for example drop-like, situated along the midline of the joining side, and with a receiving seat 13 being complementary to the shaped extension 12, grooved in the side of the adjacent sheet. The coupling and introduction between the shaped extension 12 and the receiving seat 13 is certainly capable of maintaining the sheets 10 joined one to another assuring also the tightness.

(20) The bottom of the receiving seat 13 could be recessed with respect to the profile of the shaped extension 12, which could be flattened in its outermost part, in such a way as to leave a cavity 14, once the coupling has been obtained, aimed at being filled with a hardening and sealing liquid injected in a subsequent moment.

(21) A second possible solution, illustrated in FIG. 6B, includes a recess 15, made along the edges of the sheets to be joined, for example equal to about a third of the thickness of the sheet 10 and situated centred along its midline. When the two sheets 10 are put one beside another, the upper borders 16 which delimit the recesses 15 of the two adjacent sheets are lifted, and a strip 18 of the same material is laid onto the two lower, almost juxtaposed, borders 17. The thickness of the strip 18 corresponds to that of the recesses 15 and its width is such to extend for the most part of the two opposite recesses.

(22) The lower surface of the connecting strip 18 can be pre-glued and covered with a protection film (not shown), which is removed on the application. Also the upper surface can be pre-glued and protected with a film, likewise removed when, in the end, the upper borders 16 of the recesses 15 are released.

(23) The possible interspace 19 that remains between the two borders of the upper recesses 16 can be closed by the introduction of the polymer putty 20, so as to improve and assure the waterproofness.

(24) Another solution, illustrated in FIG. 6C, includes a reduction of the thickness along the borders of the sheets 10 to be joined. In a complementary way, the sheet 10 presents, on one of its sides, a reduction of the thickness and a reduced thickness area 21 with lowering of the upper surface, while the opposite sheet presents a reduction of the thickness and a reduced thickness area 22 with lifting of the lower surface. The reduced thickness areas 21, 22 that extend for some centimetres or few tens of centimetres toward the inside of the relative sheets of rubber 10, are then overlaid on the joint, with the interposition of an adhesive substance 23, recomposing the whole thickness and obtaining the tight join.

(25) Once the joint between the various sheets of rubber 10 has been realized and the impermeable carpet has been obtained, it is necessary to fasten the borders 24 thereof to the containment walls 3, 4 of the ballast 2 (FIGS. 4 and 7B). In order to avoid lateral water infiltrations, the carpet must extend beyond the limits defined for the ballast by the containment walls 3, 4 and vertically or diagonally along the surface of the same walls. The borders 24 of the carpet are fastened to the walls 3, 4 by mechanical means, for example plates (not shown) with through screws driven into the side of the walls.

(26) The tightness between the borders 24 and the walls 3 is usually sufficient to prevent water passage, if there are plates situated over the border of the impervious carpet. In another case, as illustrated in a detailed way in FIG. 8, or if the tightness must be assured, along the borders 24 joined to the walls 3, 4, after the border 24 has been fastened with screws or nails 26, the flashings 25 are applied, likewise fastened for example by screws or nails 26 driven into the wall 3, which rise above the same borders 24, preventing the water passage under them.

(27) Apart the joint 11 between the various sheets of cured rubber as well as the joint of the impervious carpet with the containment walls 3, 4 of the ballast, it is necessary to provide for required inclinations (FIG. 7A), so that the water is collected in points, from which it can be easily drained later on, in order to avoid useless filling of the basin formed by the carpet. As illustrated in FIGS. 7C and 7D, in the collecting points, the water is accumulated and drained by means of inlets 27 tightly joined to the sheets and pipes 28, which originate from the sheets 10 of rubber and empty outside of the ballast M and of the bridge 1.

(28) In the optimal embodiment, the discharge pipes finish in a water removal system (not shown) in accordance with the method that will be obvious for those skilled in the art.

(29) In the bridges with decks the inclination provided for the bridge during construction can be enough. On the other hand, in case of the arch bridges, it is necessary to remove the crushed stone 2 from the ballast to such an extent and with such a distribution as to obtain just an inclined configuration of the surface of the sheets 10 of rubber.

(30) In both cases, a slight inclination toward one or both ends of the bridge 1 can be provided, in such a way as to collect the water in a corner area R of the impermeable carpet, i.e. the area in which the inlets 27 and the water collecting pipes are situated.

(31) A different embodiment of the method according to the invention is illustrated in FIGS. 9A to 9F, and takes up again the most general principle of the invention in the specific case of railway lines or bridges with two or more tracks. The method applicable to a double track line will be described in the following, but it is obvious that it can be advantageously applied to lines or bridges with more parallel tracks.

(32) The railway line or the section of line included in a railway bridge 1, comprises a first track 6a and a second track 6b, parallel to each other. The method for waterproofing according to the invention includes the following working steps, some of which have common characteristics with the working steps of the method according to the already described embodiment.

(33) The beginning situation of the line or bridge 1 is illustrated in FIG. 9A, which points out an upper layer S of the ballast M, whose depth is certainly bigger with respect to the depth of the ordinary maintenance operations, during which a top layer of the crushed stone or gravel 2, that forms the ballast M, is removed and substituted, or even only moved and re-positioned. Usually the depth of the upper layer S, as already defined, is in the range of 50 to 80 centimetres.

(34) In accordance with the method described herein, first of all a piece of the first track 6a is removed, together with the ties, in case there are any.

(35) Then, the layer S of gravel or crushed stone 2 that forms the ballast M is made with the normal equipment, provided to the maintenance staff, from the side of the first track 6a and little beyond the centreline plane of said ballast M, up to a greater depth with respect to that normally achieved by periodic mixing of said gravel or crushed stone 2 during maintenance operations of the aforementioned tracks 6, thus leaving in place the possible remaining underlying portion of gravel or crushed stone 2 (see FIG. 9B).

(36) After the above described step, in which the upper layer of the ballast from the side of the first track 6a is removed (however the operation can be carried out also before), a plurality of first under track crossties 55 are installed below the second track 6b.

(37) Then a first vertical shoulder 51 is installed (still FIG. 9B), along the whole extension of the section of line to be waterproofed. The shoulder 51 can be made with wood, metal or another material having suitable mechanical characteristics. The first under track crossties 55 are then fastened to the first shoulder 51. Moreover, a safety rail 53 is fastened to the shoulder 51 in order to protect the site.

(38) Then a first sheet 101 of cured rubber is spread on the underlying part of gravel or crushed stone 2 of the part of ballast M, from the side of the first track 6a (FIG. 9C). Like in the previous embodiment of the invention, the first sheet 101 has a thickness, and in general good mechanical tensile stress, extension and penetration characteristics, such as to be sufficiently resistant, on both faces, to perforation by the gravel or crushed stone 2.

(39) The first sheet 101 is laid while keeping a first edge 101a of the above mentioned sheet 101 raised against the wall of the first shoulder 51.

(40) Then, a second vertical shoulder 52 is installed, beside the first shoulder 51, keeping the first edge 101a contained between the shoulders first 51 and second 52.

(41) The gravel or crushed stone 2 removed previously, is subsequently repositioned on the first sheet 101 of cured rubber (FIG. 9D); afterwords, the above mentioned first track 6a and the possible ties of the previously removed section of railway line are restored.

(42) After or at the same time with the aforesaid step, in which the first track 6a is repositioned, a plurality of second under track crossties 56 are installed under the first track 6a. The second under track crossties 56 are also fastened to the second shoulder 52 in order to ensure that it remains in position also after the stresses imposed by trains passing on the first track 6a.

(43) The subsequent step includes removal of a section of said second track 6b and of its ties possibly present (FIG. 9E). At the same time, the first under track crossties 55, which at this time have finished their task, are removed.

(44) In accordance with a procedure similar to that already described in relation to the first track 6a, a layer S of gravel or crushed stone 2, which constitutes the ballast M, is removed from the side of the second track 6b, up to a greater depth with respect to the one normally achieved by periodic mixing of said gravel or crushed stone 2 during the maintenance operations of the aforementioned tracks 6, leaving in place any possible remaining underlying portion of gravel or crushed stone 2.

(45) Then, the first shoulder 51 is removed, leaving only the second shoulder 52 to support the stresses transmitted on the opposite side of the ballast M.

(46) The same way as already described, a second sheet 102 of cured rubber is laid on the underlying part of gravel or crushed stone 2 of the part of the ballast M from the side of said second track 6b. The second sheet has the same characteristics as the first sheet 101, and a second edge 102a of the second sheet 102 situated beside the first edge 101a of the first sheet 101 is kept raised.

(47) The two edges, first 101a of the first sheet 101 and second 102a of the second sheet 102 are subsequently joined to each other in accordance with one of the above described techniques, or with another known joint technique, in such a way as to make the coupling of the first and second sheets stable and impervious.

(48) The previously removed gravel or crushed stone 2 is subsequently repositioned on the second sheet 102 of cured rubber. Then, the above mentioned second track 6b and the ties possibly present of the previously removed section of railway line are repositioned.

(49) Finally, the second under track crossties 56, the second shoulder 52 and the safety rail 53 are removed.

(50) The outer lateral borders of the sheets 101,102 are fastened to the containment walls 3,4 of the line or bridge 1 according to what has been described in relation to the previous embodiment of the method.

(51) At this point, the section of railway line or bridge 1 are perfectly waterproofed and the procedure can be applied to a subsequent section of line or another bridge to be waterproofed.

(52) The above described embodiment of the invention advantageously allows waterproofing operations of the section of line or bridge 1 without the necessity to interrupt completely the traffic on the railway line, thus allowing the trains to transit alternatively on one of the tracks 6a or 6b, although at reduced speeds.

(53) According to an advantageous version, which has not been illustrated in the enclosed drawings and which can be applied to all the above described embodiments of the invention, the whole extension of the carpet of rubber that must be placed in the ballast to restore the waterproofing system, considering a not too long bridge, can be assembled in a suitable seat, thus solving all the complications deriving from the necessity to connect the various sheets. The so obtained carpets can be wound on big rolls, transported to the working site and then applied to the bridge, from which the layer of ballast of the required thickness has been removed.

(54) The obvious advantage of this way of constructing the carpet derives from the considerable reduction of time required for applying the sheath, since the positioning of the sheets 10 and their joint are not necessary. In fact, in this case it is sufficient to spread the sheath, possibly composed of two or more big sheets, if required by the bridge dimensions, and, after the borders have been fastened along the containment walls 3, 4, to place again the crushed stone 2 and tracks.

(55) According to another advantageous version of the covering used for the waterproofing, a fabric or cloth is embedded in the sheets of rubber, in a known way, so as to further increase the resistance of the sheets 10 to tearing and perforation. In this way, the thickness of the sheet can be reduced with respect to that of a sheet 10 constituted only by cured rubber. For example, a total thickness that can be assumed for such covering, can be of about 3-4 millimetres.

(56) Yet more advantageously, in the case of installation on a particularly busy railway line, or with a particularly heavy load traffic, the sheet 10 can be formed by overlaying two suitably stabilized sheets of the aforesaid rubber reinforced with canvas. The stabilization can be obtained by gluing of the two overlaying sheets, or by a subsequent vulcanization.

(57) The thickness of the layer S (FIG. 4) removed for the positioning of the sheets of rubber is only a bit bigger than that of the layer normally removed for the regular ordinary maintenance of the tracks and is typically included between 50 and 80 centimetres. On one hand, the result is the reduction of time necessary for the removal and repositioning of the material, and, on the other hand, the possibility of continuation of the normal maintenance of the railway line without the risk to jeopardize the waterproofing system.

(58) An interesting consequence of the practical application of the present invention is the possibility of reutilization of the material already used and stocked in warehouses. In particular, this is the case of the rubber deriving from the enormous quantity of discarded tyres, which at present remain simply stored in very large areas, perhaps to be partly reutilized in one way or another. The method proposed by the present invention allows a reutilization in massive way of this polluting material, difficult to dispose of, even though it is used as a part of the total quantity of material being used, thus assuming also an ecologic value of primary importance.

(59) Another advantageous effect of the invention derives from the fact that the vibrations transmitted by trains which pass on the bridge to the bridge structure can be reduced. The layer of rubber situated inside the ballast could form a shock absorber which avoids the direct transmission of the vibrations. The beneficial effect on the bridge structure and on the production and diffusion of noise appears obvious.

(60) It is understood that what has been written above is a pure example and is not limiting, therefore possible versions of the method under discussion are considered within the protection field of the invention, as claimed hereinafter.