FR2777924A1 - PROCESS FOR THE CONSTRUCTION OF A STRUCTURE UNDER A SUPPORT SLOPE OF A RAILWAY OR A PAVEMENT - Google Patents

Abstract

The procedure is carried out by constructing or laying a flat guide platform (2) on at least one side of the embankment excavation to support a concrete tunnel structure or frame (13) and connecting it to traction cables (6) inserted through channels in the platform. One end of each cable is connected to a fixed anchoring point (12) on the platform, while the other is connected to a power cylinder (21) which enables the structure to be slid into position inside the embankment excavation on a layer of a lubricating agent between the structure's base slab (14) and platform.

Description

The present invention relates to a method for producing a

  passage or tunnel reserved for the movement of pedestrians or vehicles under a railroad or an active road or motorway roadway, which requires only a limited interruption in time of traffic on this track, the structure defining the passage to be built being prefabricated, if necessary carried out next to the track before the latter is momentarily cut to allow the excavation of the ground forming the embankment for supporting this track, said structure then being placed in the excavation thus created before the track or the pavement is reconstructed on top of this structure The invention relates more particularly to a process which allows, once the excavation is cleared after sectioning the track, to bring the structure under the location of the latter within extremely short deadlines, while allowing remarkable precision of its positioning, the sub-layers or the ballast being then reconstituted on the structure before the track is reformed, allowing

the immediate resumption of traffic.

  More particularly still, the invention relates to a construction method in which the structure to be put in place under the track is made up of one, or even two, hollow and concrete frames, developed in situ, the frame being arranged in the first case on one side of the slope carrying the track and in the case of two homologous frames symmetrically one from the other on each side of the median plane of this slope, parallel to the track, the frame single being placed transversely in the excavation or else the two frames meeting in the median plane so as to ensure the continuity of the passage under the track

from one frame to another.

  We know from European patent EP-A-0 611 848 in the name of the applicant, a so-called autoripage process, allowing the delivery of a work prepared in situ in reinforced concrete through a slope supporting a railway, a roadway

  road or motorway in activity.

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  This method uses, to move bridges or structures developed in situ in reinforced concrete, at least one flat support and guide raft for a concrete frame. The frame is carried by the raft and is provided laterally with anchoring points for traction cables. The traction cables are secured at the front of the guide raft to at least one fixed anchoring point, while the other end is engaged with jacks carried by the frame, so that the traction force exerted on the cables by the jacks results, as a result of reaction, of a

  sliding of the frame on the raft, then on the ground.

  The main drawback of this process lies particularly in the fact that it is insufficient for the movement of works of large mass. Indeed, the anchor points which are located laterally and at the front of the guide raft in a spade, tend to bend and tear from the ground under the effect of the traction of the jacks and due to friction important reigning between the faces in contact respectively of the frame, the

write off, then off the ground.

  The present invention therefore aims to overcome this drawback, by proposing a method which allows on the one hand, to distribute the tensile force over multiple anchor points judiciously distributed at the end of the front of the raft of guidance in at least one spade buried in the ground perpendicular to the axis of traction, and on the other hand to distribute using a mattress of fluid, contained between the slab of the structure and the sole of the raft or the soil, the pressure of this structure

on the support.

  To this end, the process considered, consisting of temporarily cutting the track to the right of the location provided in the embankment supporting this track for the passage to be carried out, and carrying out an excavation by excavating the ground in this location, is characterized in that it consists of previously manufacturing or having, on at least one side of the excavation, at least one flat guide raft supporting at least one raft of the frame of the concrete structure, to be placed under the hollow frame inside reservation grooves made in the guide raft, at least one traction cable, this cable being secured to one end of a fixed anchor point linked to the guide apron, while the other end is in engagement with at least one jack carried by the raft of the frame, so that the tensile force exerted on the cable by the jack results, as a result of the reaction on the anchor point, by a pushing effect on l e to erase the frame which gradually slides on the guiding apron, then on the ground of the excavation, to ensure its direct penetration into it, in front of said

guide base.

  In a preferred embodiment of the method according to the invention, the flat guide base is arranged so as to make it comprise at least one boss or solid mass constituting the passive anchoring point of the traction cables, this boss being arranged in the vicinity of the end of the guide raft facing inwards

  of the excavation, at at least one transverse spade.

  Similarly, at the rear of the frame raft, at least one boss or bulkhead is arranged constituting the active anchoring point of the jacks which cooperate with the

traction cables.

  Under these conditions, the method consists in associating, via passive and active anchoring points, each structure supported by the raft of the frame with at least one or more parallel cables, extending below the latter at the level of longitudinal passages made at

within the guide slab.

  According to a particular characteristic, the cable anchoring bosses are formed in the front part of the guide raft, as close as possible to the sides of the excavation in the embankment, the traction jacks being mounted on the

strike out of the frame.

  Advantageously, the active anchoring bosses comprise, at the level of the zones for securing the jacks, orifices whose penetration axis is inclined

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  with respect to the horizontal by an angle a, by means of deflectors, so as to deflect the traction cables towards the bottom of the raft of the frame, in

  the grooves for reserving the guide raft.

  Advantageously similarly, the passive anchoring bosses situated in the zone forming the "spade" of the guide raft, at the zones of attachment of the end of the cables, comprise orifices whose penetration axis is inclined relative to horizontally by an angle B, so as to deflect the traction cables running in the guide slab towards the

"spade" area.

  Preferably, the cables used are multi-wire cables, the strands of which are secured at one of their ends to a support plate which abuts on the face.

opposite of the anchoring boss.

  Other characteristics of a process for the construction of works under a railroad and means for the implementation of this process will become apparent from

  through the following description of an example of

  embodiment, given by way of nonlimiting indication, with reference to the appended drawings in which: - Figure 1 is a perspective view of a device allowing the implementation of the method, object of the invention; - Figure 2 is a sectional view in side elevation of a device for implementing the method, object of the invention; Figure 3 is a sectional view in front elevation of Figure 2; - Figure 4 is a sectional view and a top view of the raft of the frame; - Figure 5 is a sectional view in side elevation, on a larger scale, of the raft of the frame; - Figure 6 is a sectional view in side elevation, on a larger scale, from another point of detail

to write off the frame.

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  According to the invention, the realization of such a passage is carried out in the following manner, the example given below relating to the implementation of a passage consisting of two precast concrete frames, homologous and arranged symmetrically on either side of the slope, these frames substantially joining in the median longitudinal plane of this slope extending parallel to the track. Of course, the method applies just as well when the passage to be made is constituted by means of a single frame which extends entirely across the slope to form

alone the passage in question.

  Firstly, on both sides of the slope, two support and guide rafts 1,

  these rafts being arranged opposite one another opposite

screw in the middle plane of the track.

  Each guide raft 1 consists of a flat concrete base 2, preferably cast in situ and comprising projecting parts such as extending under this sole 2 to form spades 3 for immobilizing the base 1 in the ground . If necessary, the raft is associated with anchor rods, one end of which is secured to the edge of the raft and the other of which, which is buried in the ground, is blocked with respect to the latter by being embedded in a solid mass of concrete. On its lateral sides, the sole 2 includes

  ledges 4 whose role will be explained later.

  The sole 2 is provided with a plurality of reservation grooves 5 which are capable of allowing the passage of traction cables 6. These reservation grooves 5 are arranged along the longitudinal axis of the guide raft 1, they allow horizontal routing traction cables 6 between the two ends 7, 8 opposite deflectors 9, 10 coming respectively from points

11 and passive 12 anchor points.

  Secondly, there is on each guide raft 1 thus produced and immobilized on the ground, a hollow frame 13 forming the framework of the concrete structure, generally of rectangular cross section and comprising

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  a lower slab 14, lateral sides 15 and an upper slab 16, parallel to the lower slab 14, the width of the frame 13 being substantially equal to that which

  separates, on the guide raft 1, the edges 4 of the latter

  ci, so that, once the frame has been poured onto the guide slab 1, this frame 13 can slide on the latter 1, this sliding being able to be facilitated in particular by an injection between the sole 2 and the slab 14, between their faces opposite, a lubrication agent, in particular a bentonite grout or other similar product, providing lubrication which may be useful during the relative movement of the frame 13 on the guide base 1, then on the ground, in front of the base as and as

  the frame 13 moves by moving away from it

  ci, as explained below.

  The lubrication agent injection wells open into a plurality of n-sections placed in a direction substantially transverse to

  in the direction of movement of the work.

  According to an advantageous characteristic of the invention, an annular belt 17 is produced on the slab 14 of the raft of the frame 13, at the level of the opposite face of the guide raft 1. This is intended to receive a bladder 18 or chamber preferably made of a deformable material, in particular of the plastic material type, under

the action of a pressurized fluid.

  Thus, during the development by pouring of the lower slab 14 of the raft of the frame 13 of the concrete structure, the reserve of material forming the annular belt 17 is filled by a chamber 18 which is filled with a fluid under pressure incompressible of the water type, so as to expand it in the volume of the annular belt 17 and to conform a mattress which will be able to withstand the compressive forces during the pouring of concrete of

  the work on the raft of the frame 13.

  During the shifting phase of the apron of the frame 13 relative to the guide apron 1, the fluid contained in the

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  bladder 18 is expelled and is replaced by a gaseous fluid

under pressure (compressed air).

  According to another characteristic, the face of the bladder 18 facing the face of the guide raft 1 has a plurality of raised zones 19, so as to conform a lip which retains the fluid which is injected between the

  sole 2 and lower slab 14.

  It is thus possible, by virtue of this bladder 18 filling the annular belt 17, to contain between the sole 2 and the lower slab 14, a substantially constant thickness of a fluid mattress of a lubricating agent, intended to support the work on the slab guide 1, then on the ground, during the sliding of the structure, and this without risk of lateral leaks of lubricant given the

presence of lips.

  The pressure of the structure on the guide slab 1, then on the ground, taking into account the order of magnitude of the facing surfaces, is maintained, by virtue of this device, within a very reasonable range, of the order of 0.3 to 1.5 bars, which allows the lifting of the structure for a fluid injection pressure, on the one hand inside the chamber 18 (of the order of 1.5 to 2 bars), and on the other hand between the lower slab 14 and the sole 2, the intensity of the injection pressure of the

  lubrication being of the order of 0.3 to 1.5 bars.

  In order to prevent the lubrication agent from escaping through the reservation grooves 5 made in the guide raft 1, there are in the areas of intersection between the reservation grooves 5 and the injection wells of the lubricating agent, a plate 20 partially closing the section at n at this level. The cables 6 can, depending on the case, be manufactured on site or even be prefabricated and brought already formed on the site. The lateral sides 15 of each frame 13 may optionally also include external bosses 11, disposed above the edges of the guide raft 1 when the frame 13 rests thereon, in these conditions being substantially opposite. screw and in the extension of the passive anchoring bosses 12 of this guide raft 1, provided at the end of the flanges at the end of the

strike off facing the slope.

  The active bosses 11 of the frame 13 are arranged so as to allow the mounting and the support of hydraulic jacks 21, intended to cooperate with traction cables 6 such that, each of the cables possibly lateral and cables situated between the raft of the frame 13 and the guide raft 1, respectively along the lateral sides and the front edge of the frame, having one end fixed on the one hand on the corresponding passive anchor 12 buried in the ground at the spade 3 and being engaged on the other hand with the jack 21 so that the tensile force on the cable 6 exerted by this jack 21 causes, by reaction on the frame 13, a corresponding displacement of the latter with respect to the guide base

1 towards the slope.

  The cables 6 are multi-wire cables, formed from a plurality of strands arranged in such a way that, at the end of the cable in the passive anchor 12, they open out in a recess of the latter in order to be fixed to the means of locking keys on a support plate 22, ensuring an adequate distribution of the forces

  created by the corresponding traction cylinder 21.

  The blooming zone of the cable 6 inside an orifice 23 formed in the passive anchoring 12 takes place within a trumpet 24. The main axis of this orifice 23 is inclined at an angle B relative to the horizontal axis, this angle being between 5 and 15 and

preferably close to 10.

  Likewise, at the level of the bosses of the frame 13 constituting the active anchoring points 11, provision is made for each orifice 24 through which each traction cable 6 opens, is inclined at an angle a with respect to the horizontal axis, this angle being between 5 and 15 and

preferably close to 10.

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  In addition, each of the orifices 23, 24 produced within the active 11 and passive 12 anchor points is provided with a diverter 23 '. This deflector 23 'is produced from

  a tube, in particular a metal tube, which is additionally bent.

  It thus forms a guide sleeve for each of the traction cables 6 between the anchoring points 11, 12 and the reservation grooves 5 made in the raft of

guidance 1.

  The frame 13 cast on its guide raft 1, with a similar arrangement on each side of the slope in the example more especially considered, being again reminded that the same process can be carried out with a single frame and a single raft fitted out with 'one side of the slope, we then proceed to the momentary sectioning of the track and the realization through the slope of a excavation whose dimensions transversely are substantially those of the frames which, once put in place in this excavation,

  will delimit the passage under the track.

  Each of these frames 13 is gradually and mutually ripped towards each other on the guide rafts 1 which support them, until these cables, which run horizontally within the reservation grooves 5, meet in the median plane of the slope, ensuring the continuity of the passage; the sub-layers or the ballast on top of the upper slab 16 of each frame 13 can be quickly replaced, before the track is reconstituted so as to allow the resumption of traffic which has only been interrupted during

  shifting operations of the frames 13, as indicated above

above.

  This ensures the realization of a passage under a railway or if necessary a roadway or other, in a simple, fast and efficient manner, with a time of interruption of traffic on this track as limited as possible. The guidance of the frames and their sliding on the two rafts is made very easy by the design of the latter and in particular the presence of the lateral flanges which they comprise, making it possible to obtain a positioning

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  very precise frames towards each other as they come together. In addition and as already specified, their sliding can be facilitated if necessary by suitable lubrication of the base of the raft and the lower slab of the frames, but in all cases without requiring the use through the excavation of sills or other rails support as used in conventional solutions and whose implementation is long and delicate, and therefore requires greater interruption of the

traffic.

  In addition, since the tensile forces of the jacks on the cables 6 are distributed in a transverse plane of the spade 3, there is no longer any risk

  tearing and sagging thereof.

  It is thus possible, thanks to this process, to put in place precast concrete structures of considerable mass, due to the joint action of a plurality of action points which must exert the displacement of the structure and of a joint. annular which allows to maintain between the sole 2 and the slab 14 a mattress of a lubricating agent supporting the weight of the structure during its sliding, the force exerted on the frame 13 being exerted in a distributed manner on a sill beforehand buried in the ground. Note further that, the ground pressure due to the frames 13 sliding on their guide rafts 1 being less than that created by the mass of soil removed in the excavation, the risks of soil compaction as encountered in a process of shifting of the frames on stringers previously made across this excavation, are eliminated, which allows a placement

safer frames.

  Of course and as follows from the above, the invention is not limited to the example of implementation more especially described above with reference to the accompanying drawings; on the contrary, it embraces all

  variants within the scope of the claims below

  afterwards, in particular when the passage to be built under the track is formed by means of a single frame and no longer as above using two homologous frames joining

  in the median plane of the slope in the middle of the excavation.

Claims (7)

  1 - Process for the construction of a structure under an embankment supporting a railroad track or a carriageway, consisting in temporarily cutting the track at the right of the location provided in the embankment supporting this track for the passage to carry out, and to carry out an excavation by excavation of the ground in this location, characterized in that it consists in previously manufacturing or having, on at least one side of the excavation, at least one flat guide raft (1) supporting the at least one slab of the frame (13) of the concrete structure, to be placed below the hollow frame (13) inside the reservation grooves (5) made in the guide slab (1), at least a traction cable (6), this cable being secured! at one end of a fixed anchor point (12) linked to the guide base (1), while the other end is engaged with at least one jack (21) carried by the base base (13), so that the tensile force exerted on the cable (6) by the jack (21) is translated, as a result of the reaction on the anchor point (12), by a pushing effect on the raft of the frame ( 13) which slides progressively on the guide base (1), then on the ground of the excavation, to ensure its direct penetration into it, forward of said guide raft (1).   2 - Method according to claim 1, characterized in that there is arranged within a lower slab (14) of the concrete structure and opposite the sole (2) of the guide raft, an annular belt ( 17) containing a bladder (18) deformable under the action of a pressurized fluid, then the latter is filled with a fluid so as to form a seal between the sole (2) of the guide base (1) and the lower slab (14), the bladder (18) now dilated, between the lower slab (14) and the sole (2), a mattress of a lubricating agent previously introduced through the slab (14), during the sliding of the frame (13) of the structure with respect to the guide raft (1), then on the ground. 13 2777924   3 - Method according to one of claims 1 or 2,   characterized in that, in line with the raft of the frame (13), uniformly distributed over its width, there are bosses, providing active anchoring points (11) for cylinders (21) for pulling the cables (6 ). 4 Method according to claim 3, characterized in that there are fitted within the bosses providing the active anchoring points (11), orifices (24) opening out inclined at an angle a with respect to the horizontal axis, this   angle being between 5 and 15.   - Method according to claim 4, characterized in that the orifice (24) is inclined at an angle a neighbor of 10.   6 - Method according to one of claims 1 or 2,   characterized in that there is fitted, in line with the spade (3) of the guide raft (1), buried in the ground, uniformly distributed over its width, bosses, providing passive anchor points (12) for   the end of the traction cables (6).   7 - A method according to claim 6, characterized in that there is arranged within the bosses providing the passive anchor points (12), orifices (23) opening out inclined at an angle B relative to the horizontal axis , this   angle being between 5 and 15.   8 - Method according to claim 7, characterized in that one inclines the orifice (23) at a neighboring angle B of 10.   9 - Method according to any one of claims   previous, characterized in that there is incorporated within the orifices (23, 24) formed within the active (11) and passive (12) anchor blocks of the deflectors (9, ) curved.   - Method according to any one of the claims   previous, characterized in that the deflectors (9, 10) are used as guide sleeves for each of the traction cables (6), between the anchoring points (11, 12) and the reserve grooves (5 )   made in the guide slab (1).