EP0500444B1 - Underground tubular structure - Google Patents

Abstract

The subject of the invention is an underground tubular structure (1) of large dimensions built by assembling superimposed prefabricated longitudinal elements (2, 2') each having the shape of a box of U-shaped cross section, the said elements being laid one over the other and one after the other along a longitudinal axis, then covered with backfill (13). Each prefabricated element (2) is divided by a central wall (24), the structure (1) thus consisting of two tubular sections (S1, S2) placed side by side, on either side of a partition consisting of the central walls (24, 24'), which are superimposed and aligned, of the two elements (2, 2') of each pair. The height of at least one of the lateral and central walls of at least one of the superimposed elements may be adjusted depending on the applied loads and expected deformations in such a way that, in service, the loads are equally distributed over the three supports. The invention applies particularly to the building of roadways under backfill. <IMAGE>

Description

The subject of the invention is a buried tubular structure produced by assembling prefabricated longitudinal elements and having a large width with respect to its height, such a structure possibly having large dimensions and, for example, providing two parallel lanes of road traffic.

The invention is more particularly suited to the production of structures of rectangular section.

Various methods are known for producing buried structures of large cross section for the circulation of fluids at high flow rates, or else underground passages serving, for example, for the circulation of people, livestock or vehicles below a road or of a railway. Often, such passages are buried at a relatively small height and are therefore made on the bottom of a trench which is then backfilled.

The need for passages of this type being very great, in particular for the improvement of the road or rail network, we have been led to develop industrialized processes making it possible to reduce costs and very significantly reduce the exposure time. To this end, the inventor has already proposed different methods of making, from prefabricated longitudinal elements, structures buried under embankment which may have large sections.

European patent EP 081.402, in particular, describes a process for producing tubular structures which may have very large sections and made up of adjacent sections, each comprising, in a preferred embodiment, two side elements with vertical lateral wall, placed on the side and on the other of a raft, and on which is placed a curved element in the shape of a vault. Even for very large sections, such elements remain transportable if their width is limited to the road gauge because they can be stacked, lengthwise, on a road trailer. One must, however, have at least two molds, one for the side elements and the other for the arch elements, and possibly a mold to strike it.

In another embodiment described in European patent 0188.487, each section of the conduit is made up of two elements, respectively a lower element forming a raft which is raised on its edges to provide two longitudinal supports and an upper element in the form of a resting arch by its lateral edges on said supports. Such a method makes it possible to economically produce either conduits for the circulation of a fluid possibly under pressure, or underground passages for pedestrians, livestock or even vehicles.

The use of an upper arch-shaped element makes it possible to transfer part of the supported forces to the sides and, consequently, to reduce the thickness of the upper wall. However, this results in a relatively high overall height relative to the width.

However, in certain cases, the height of the passage must be limited when the upper level, for example that of a road or a railway, is determined and the level of the excavation is not to be lowered too low , for example to stay above the water table. It may be preferable, in this case, to use structures with a rectangular section or, in any case, whose upper part is relatively flat.

To this end, it is possible, for example, in the case of patent EP 081,402, to replace the arch element by a flat slab or, in the case of patent EP 188,487, to give the upper element the form an inverted U-shaped box comprising a flat central part and two lateral wings bearing on the raft.

However, when it is made up of a flat slab and a fortiori when it has a rectangular section, the upper element works on bending, since one no longer benefits from the arch effect and the part flat central unit forming the ceiling of the duct must therefore be reinforced. This leads to thicknesses and reinforcements which, for large sections, can make the elements untransportable. In practice, it is hardly possible to exceed a width of four meters which corresponds to that of a traffic lane.

Furthermore, to reduce the cost of the prefabricated elements, it is advantageous to produce them in series in different dimensions, and to give the upper elements and the lower elements, identical shapes so as to produce them in the same mold, the upper elements being simply turned over to be placed on the lower elements.

It had already been proposed, for example in document GB-A 476.316, to produce concrete conduits with several contiguous sections, consisting of prefabricated U-shaped elements and provided with intermediate partitions defining parallel grooves, each element being able to be covered. of the same element turned over so that the superimposed grooves form adjacent channels separated by the intermediate partitions.

Such an arrangement was however only provided for small conduits intended for the passage of cables or pipes, the prefabricated elements being able to be simply manipulated by hand. We could hardly imagine that we could achieve in an analog way gue elements of dimensions large enough to constitute real works of art such as underpasses for vehicles. It is indeed necessary, in this case, that the elements remain fairly light despite their very large dimensions and can be handled and installed with a crane.

The subject of the invention is a provision making it possible to economically solve all of these problems and to produce tubular structures of large dimensions, having a flattened section, preferably rectangular, and made up of elements of a single type, which can be made in the same mold, such structures can be buried under an embankment to constitute, for example, underground passages for vehicles or very large nozzles for the passage of a river or the evacuation of floods, for example when crossing a valley by a highway or a railroad laid on an embankment.

However, it was noted that, in the case of very large buried structures, the use of box elements comprising two lateral supports and a central support posed problems of load distribution between the three supports which could lead to cracks or ruptures of an overly loaded support, in particular of the central support.

To solve such problems, which were negligible in the case of known conduits of small dimensions, the invention proposes various solutions.

The invention therefore relates to a large buried tubular structure, in particular for the passage of at least two vehicle traffic lanes, produced by assembling prefabricated longitudinal elements constituting adjacent sections placed end to end, each section being constituted , in cross section, of two substantially identical molded elements, in the form of an open box comprising a flat central part, two side walls and a central wall, substantially perpendicular to the flat central part, respectively a lower element resting on the ground by its part central and an upper upturned element supported by the ends of its side walls and central on the corresponding ends respectively of the side and central walls of the lower element, so as to constitute three separated supports each consisting of a pair of superimposed walls, the walls of two a then resting directly on one another and covering a fixed height, and the third support being associated with means of at least temporary adjustment of the height of the two superimposed walls, capable of ensuring an equal distribution of the stresses applied on the three supports depending on the applied loads, foreseeable deformations and settlements.

In a particularly advantageous manner, the means for adjusting the height of the third pair of walls comprise an intermediate support device, of adjustable thickness, interposed between the ends facing said walls for adjustment, at least temporarily , the distance between them and the height of said third support.

Such devices can be of a known type used for the recovery of the foundations of a building under construction and described for example in documents JP-A-60,119,827 or US-A-4,191,496.

Preferably, each intermediate support device consists of at least one hydraulic or mechanical jack, comprising two parts which are movable axially with respect to one another and which bear respectively one on the lower element and the another on the upper element of the structure. However, it is also possible to use an elongated inflatable envelope extending at least over part of the length of the joint between the ends facing the walls of the two superimposed elements.

Thanks to such arrangements, after the upper elements have been placed on the lower elements, the distance between the ends facing the two walls can be adjusted so as to obtain a determined distribution of the support pressures between the three supports. longitudinal and, after assembly of the elements, realization of the embankment and stabilization of the whole of the conduit and the distribution of the stresses, a final blocking of the ends is carried out opposite the longitudinal support of adjustable height and the the intermediate support device is removed.

According to another equally advantageous characteristic, the two superposed elements, respectively lower and upper, have substantially identical profiles and are made of concrete in the same mold, and two of the longitudinal supports have ends with inverted profiles, respectively hollow and projecting , capable of engaging one another when the upper element is placed on the lower element, the opposite ends constituting the third longitudinal support being symmetrical with respect to a median plane passing through the other two longitudinal supports.

For example, the end of the wall constituting the third symmetrical support can have a crenellated longitudinal profile comprising at least two longitudinal parts respectively placed at two symmetrical levels relative to the median plane and having in cross section inverted hollow and projecting profiles , the upper element being offset longitudinally at installation with respect to the lower element so that the crenellated ends facing the two elements of each pair engage one in the other.

In another embodiment, at least one of the three longitudinal supports formed by the superimposed side and central walls has an intermediate bar interposed between the ends of the corresponding walls, the latter being shorter than the other two walls so as to leave between the said ends when the elements are installed, a space in which the bar is placed, the latter having a height equal to or slightly greater than that of the said space, that is to say double the distance between the end of the wall and the plane passing through the lateral supports.

Advantageously, such an intermediate bar can be limited by two longitudinal edges with a convex profile, the end of the central wall having a corresponding concave longitudinal profile which allows, to admit slight displacements or deformations of the two elements one compared to the other, for example as a result of differential settlements.

• La Figure 1 est une vue en coupe transversale d'une structure selon l'invention.
• La Figure 2 est une vue schématique d'un moule pour la réalisation d'un élément.
• La Figure 3 est une vue de détail montrant une variante de réalisation.
• La Figure 4 est une vue en élévation, partiellement en coupe longitudinale, d'une structure munie d'un dispositif d'appui intermédiaire réglable.
• Les Figures 5 et 6 sont des vues de détail, respectivement en coupe longitudinale et en coupe transversale d'une variante du dispositif d'appui intermédiaire.
• La Figure 7 et la Figure 8 montrent, respectivement en coupe longitudinale et en coupe transversale, un autre mode de réalisation de l'invention.
• La Figure 9 montre schématiquement, en perspective, la mise en place des éléments des Figures 7 et 8.
• La Figure 10 montre, en perspective, un autre mode de réalisation de l'invention.
• Les Figures 11 et 12 montrent encore d'autres modes de réalisation de l'appui central.
• La Figure 13 représente une structure à face supérieure inclinée.

However, the invention also has many other advantages which will appear in the following description of certain embodiments given by way of example and shown in the accompanying drawings.

• Figure 1 is a cross-sectional view of a structure according to the invention.
• Figure 2 is a schematic view of a mold for the production of an element.
• Figure 3 is a detail view showing an alternative embodiment.
• Figure 4 is an elevational view, partially in longitudinal section, of a structure provided with an adjustable intermediate support device.
• Figures 5 and 6 are detailed views, respectively in longitudinal section and in cross section of a variant of the intermediate support device.
• Figure 7 and Figure 8 show, respectively in longitudinal section and in cross section, another embodiment of the invention.
• Figure 9 shows schematically, in perspective, the placement of the elements of Figures 7 and 8.
• Figure 10 shows, in perspective, another embodiment of the invention.
• Figures 11 and 12 show still other embodiments of the central support.
• Figure 13 shows a structure with an inclined upper face.

In Figure 1, there is shown, in cross section, a structure according to the invention comprising two adjoining sections for the passage of vehicles.

The structure 1 is placed on the bottom 11, leveled and packed, with a trench 12 and covered with an embankment 13 on which one can pass below a track 14 of road or rail traffic.

The structure 1 can, as shown in Figure 1, be used for the passage of vehicles or of a river, for example in a valley, for the evacuation of floods.

Structure 1 is made up of prefabricated reinforced concrete elements, produced industrially and assembled on site, and comprises, for each cross section, a pair of superimposed elements, respectively a lower element 2 and an upper element 2 '. These two elements have identical shapes, the upper element 2 'being simply turned over before being placed on the lower element 2.

Each element 2 is molded in one piece and has a flat central part 21 bordered on its two sides by two vertical side walls 22, 23, and in the middle of which rises a central wall 24, the whole of the box having thus a double U section which opens upwards for the lower element 2 resting on the ground 11 by its base 21, and which opens downwards for the upper element 2 'turned over, and therefore comprises a flat central part 21 'bordered by two side walls 22', 23 ', and divided in two by a central wall 24'.

The two elements 2, 2 ', having identical sections, after turning over, the upper element 2' rests by the ends 4 ', 3', of its side walls 23 ', 22', respectively on the ends 3, 4, side walls 22, 23, of the lower element 21, the central walls 24 ', 24, bearing one on the other by their ends 5', 5.

Each pair of superimposed elements 21, 21 ′ therefore constitutes a gallery section comprising two contiguous sections S1, S2, and, by placing one after the other, along a longitudinal axis x'x, a certain number of pairs of elements A, A '; B, B '; CC' ; ..., one can constitute a tubular structure comprising two adjoining sections S1, S2, and having a rectangular section the width L of which can be large relative to the height H and, for example, exceed double thereof.

For a determined passage section, necessary, for example, to ensure a certain flow rate in the case of a fluid transport pipe, it is possible to reduce the height H of the structure.

It is thus possible to pass two separate traffic lanes under a motorway or a railway track by reducing to a minimum the height H 'of the trench while limiting the range between supports of the flat parts 21' to the value just necessary for the passage of a track, that is to say not exceeding four meters.

Thus, it is possible to produce in a single mold, as shown very schematically ment in Figure 2, elements comprising a flat central part, two side walls and a central wall, and capable of constituting the upper element and the lower element of a section of double gallery.

To ensure the centering of the two superimposed elements on one another, it is advantageous to provide on the ends 3, 4, side walls 22, 23, parts, respectively hollow and projecting, for example a longitudinal boss 31 and a groove 41 of corresponding shapes, the arrangement of which is reversed on the inverted element, and which can therefore engage one into the other in the manner of a tenon and mortise interlocking. It is preferable, however, to leave, between the nested parts 31, 41, a certain clearance which allows the deformations of the elements under the action of the applied loads, the two extreme supports 3, 4 'and 4, 3', being able to admit slight swivels around horizontal axes.

As shown schematically in Figure 2, the two superimposed elements 2 and 2 'can be cast in the same mold 14, easy to design, and consisting for example of a fixed base on which are fixed formwork walls 15 making it possible to give the element 2 the desired shape and dimensions, inserts 16 being provided for the shuttering of the ends 3, 4, 5, of the vertical walls 22, 23, 24.

It will be noted, however, that even using a single mold 14, slight differences between the two superimposed elements 2 and 2 ′ can be admitted insofar as these differences result in limited modifications to the mold. Thus, in the example shown in Figure 3, there is provided, at the base of the lower element 2, an outward enlargement of the planar portion 21 which allows to increase the seating surface and can be produced by means of a simple auxiliary formwork.

Similarly, it is possible, without significant modification of the mold, to vary the heights h, h ', of the lower element 2 and of the upper element 2'.

To allow the molding of the two superimposed elements in the same mold, the latter must have a symmetry allowing the inversion. This is why the end 5 of the central wall 24 must be symmetrical with respect to the plane passing through the two lateral supports 3, 4. In the simplest embodiment shown in FIG. 1, the end 5 has a flat support face 50 which is placed in this plane.

If we refer to Figure 1, we see that, in service, the three supports 3, 4, 5, may not be loaded in the same way. In particular, the box is more rigid on its edges than in its central part and it is necessary to take into account the loads transmitted by the backfill, overloads and, possibly, differential settlements.

Instead of giving the side walls 22, 23 and the central part 24 of the heights strictly equal with respect to the base 21, it will be possible, on the contrary, in a simple embodiment, to slightly modify the height of one of the supports , for example the central support, taking into account the distribution of loads and overloads as well as foreseeable deformations so that, in service, the three supports are also loaded

During the molding of each element, the relative levels of the three supports 3, 4, 5, can therefore be adjusted according to the heights calculated in advance.

Such an embodiment is particularly simple, but assumes, however, that one can know exactly the loads applied and their distribution on the three supports. This is why the invention proposes other more elaborate embodiments making it possible to ensure the correct distribution of the loads.

Figure 4, which is a longitudinal section of a gallery consisting of several adjacent cells A, A '; B, B '; CC' ; ..., shows such a particularly advantageous embodiment of the central support.

As can be seen, in fact, on cell B, B ', which has been represented in section by a longitudinal plane, the central walls 24, 24', of the two elements 2, 2 ', have a height slightly less than that side walls 22, 23, so that the ends 5, 5 'of the central walls 24, 24' are separated by a space e when the upper element 2 'is placed on the lower element 2. Furthermore , recesses 51 are arranged along the end 5 of the central wall 24 so as to form, when the upper element 2 ′ is turned upside down, a housing consisting of two recesses opposite 51, 51 ', and in which a hydraulic cylinder 52 can be placed, the two elements of which bear, in opposite directions, on the ends 5, 5', of the two walls 24, 24 '.

Depending on the length d of the elements 2, it is possible to provide either a single jack 52 placed in the transverse median plane of the element, or several jacks distributed over the length of the wall 24.

The jacks 52 thus constitute, between the central walls 24, 24 ′, of the two elements 2, 2 ′, superimposed, an intermediate support device of adjustable thickness which, after having placed the upper element 2 ′ on the lower element 2, to act on the distance e between the ends 5, 5 ', of the central walls so as to modify the distribution of the stresses on the three supports 3, 4'; 5.5 '; 4, 3 ', for example to ensure an equal distribution or, if preferred, to increase the stresses applied on the central support in th loading the lateral supports.

When the desired distribution of forces has been obtained, the intermediate support 5, 5 ′ can be locked in this position for example by interposing shims between the ends 5, 5 ′, or, simply, by carrying out a concrete bonding , the ends 5, 5 ′, which can optionally be provided, as shown in FIG. 5, with reinforcements 53 which are embedded in a mortar using suitable formwork elements.

After setting or blocking, the cylinders 52 can be removed.

This adjustment of the distribution of the stresses on the three supports can be carried out either at the installation of each cell, or after the installation of several cells covering a significant length and, possibly, of the whole of the structure. For example, this adjustment can be made after the embankment 13 has been made so as to take account of the differential settlements which have occurred and, if necessary, to correct them.

The intermediate support device can be produced in different ways. For example, as shown in Figures 5 and 6, the cylinders 52 may be replaced by an elongated inflatable envelope 54 interposed between the ends 5, 5 ', and extending over almost the entire length of the central wall 24, 24 ′, leaving the two ends of the parts 55, possibly provided with waiting frames 53, which can be wedged and concreted after adjusting the height of the support, the inflatable envelope 54 then being removed and the corresponding space possibly concreted.

In the examples which have just been described, the intermediate supports 5, 5 ', are perfectly symmetrical and therefore make it possible to produce the two elements 2, 2', of each cell in the same mold.

However, other embodiments can be envisaged, in particular when, to simplify the structure, it is not desired to use an adjustable intermediate support.

Thus, in the example shown in Figures 7, 8, 9, the central wall 24 has a crenellated profile, its end 5 consisting of two longitudinal parts 56, 57, placed at different levels symmetrical with respect to at plane P passing through the two lateral supports 3, 4, the part 56 being below this plane and the part 57 above.

In addition, the two parts 56 and 57 are provided, respectively, at their end, with a longitudinal boss 25 and a groove 26 having corresponding projecting and recessed profiles.

As before, to make a cell, two identical elements 2, 2 ′ are superimposed, produced in the same mold, the lateral supports 3, 4, and 4 ′, 3 ′, being inverted and their hollow parts 31 and projecting 41 committing to each other.

However, the upper element 2 'must be offset longitudinally by a distance corresponding to the length of the parts 56, 57, so that the short part 56' of the central wall 24 'of the upper element 2' is superimposed on the long part 57 of the central wall 24 of the lower element 2, their hollow ends 26 and projecting 25 engaging one in the other.

Generally, the length of the elements being fairly short compared to their width L, only two parts 56, 57, of different levels will be provided on the central wall 24. But one could also, for a longer length, provide several offset parts 56, 57, in even number, constituting a crenellated profile.

In Figure 10, another example of a symmetrical intermediate support is shown. In this case, the central wall 24 is, over at least part of its length, shorter than the side walls 22, 23. Thus, when the two elements 2, 2 ', are superimposed, the ends 5, 5', of the two central walls 24, 24 ′, are separated by a space in which an intermediate bar 6 can be placed ensuring the transfer of the forces and of height equal to that of said space, that is to say twice the distance between the end 5 of the central wall 24 and the plane P passing through the lateral supports 3, 4. The height of the bar 6 can also be slightly greater so that, after installation, the central support is more loaded than lateral supports.

To facilitate the positioning of the bar 6, the two longitudinal edges 61, 62 of the latter have a transverse profile forming a projection 25 and engage, when laying, in the ends 5, 5 ′, of the walls 24, 24 ', these being provided with grooves 26 having a corresponding hollow profile.

In the case shown in FIG. 11, the bar 6 is given an olive shape bounded by two longitudinal edges 61, 62, having a convex circular profile, the ends 5, 5 ′, of the central walls 24, 24 ′, having a concave circular profile with the same curvature.

In this way, the olive bar 6 can be oriented slightly relative to the two superimposed elements 2, 2 ′, which makes it possible to take into account displacements or deformations due, for example, to differential settlements and to avoid stress concentrations which could cause cracking.

It can be seen that the invention can be the subject of numerous variants and is not limited only to the details of the embodiments which have just been described.

For example, to obtain a good distribution of the stresses between the supports, the jacks constituting an intermediate support of adjustable height could be interposed between the ends of the side walls, the central support being fixed.

One could also imagine other ways of achieving an intermediate central support having a symmetry allowing the prefabricated element to be turned over. For example, as shown in FIG. 12, the end 5 of the central wall 24 could be provided with a lateral boss 27 giving it, in cross section, a stepped profile. After turning over, the two lateral bosses 27, 27 ′ are placed on either side of the longitudinal median plane and engage with each other ensuring the centering of the end 5 ′ on the end 5 of the lower wall 24.

The bosses 27 may extend over the entire length of the wall 24 or else over a part of the latter, alternately on either side of the median plane, which ensures a better centering effect.

Furthermore, the invention applies, in general, to the production of structures of great width with respect to their height and having a flattened section, but this is not necessarily rectangular.

Thus, in the case of fluid circulation conduits, it would be advantageous to give each passage section a rounded profile in the corners, as shown in FIG. 1.

In addition, if it is preferable to give the elements 2 a rectangular section, this could also be, for example, trapezoidal, the side walls 22, 23, being inclined relative to the bottom 21.

It should also be noted that, if the central support 5, 5 ', is theoretically placed in the plane P passing through the two lateral supports 3, 4'; 4, 3 ', which is normally horizontal, this arrangement is not imperative. As we have seen, it may indeed be interesting to slightly raise the central support 5, 5 ′, so that it is more loaded and, even in the case where there are no intermediate cylinders 52 , it is possible to obtain such a result by simply giving the central wall 24 a greater height so that the support 5 is a little above the plane P passing through the lateral supports 3, 4.

One can also advantageously interpose between the faces bearing one on the other a damping strip of slightly compressible material, for example neoprene or lead. Such a strip can play the role of a seal against infiltration but also makes it possible, when the central support 5, 5 ′, is raised, to absorb vibrations and to remove hard spots for 'passing vehicles above the structure on a taxiway 14 which, more often than not, is very close to the upper face 21 'of the structure 1.

The invention also makes it possible, thanks to the use of two superimposed double U elements, to optionally adapt the inclination of the upper face 21 ′ to that of the track 14 passing over the structure 1. By Indeed, if it is preferable that the lower face 21 resting on the ground be horizontal, one can however play on the relative heights of the lateral supports 3, 4 '; 4, 3 ', by slightly pivoting the upper element 2' around the central support 5, 5 ', which, as we have seen, has been provided for this purpose. As shown in Figure 13, it suffices, for example, to give different heights to the damping strips 27 interposed between the two lateral supports so that the upper face 21 'is inclined relative to the lower face 21 , this inclination corresponding to that of track 14.

The reference signs, inserted after the technical characteristics mentioned in the claims, have the sole purpose of facilitating the understanding of the latter and in no way limit their scope.

Claims (15)

1. High size underground tubular structure, particularly for the passage of at least two vehi- cules traffic ways, made by assembling prefabricated longitudinal elements constituting adjacent sections located end to end, each section comprising in cross-section two substantially identical molded elements (2)(2') having the shape of an open box comprising a plane central part (21)(21'), two lateral walls (22, 23)-(22', 23') and a central wall (24)(24') substantially perpendicular to the plane central part (21), respectively a lower element (2) bearing on the ground by its central part (21) and a turn over upper element (2') bearing by the ends (4', 3', 5') of its lateral walls (23', 22') and its central wall (24') on the corresponding ends (3, 4, 5) respectively of the lateral walls (22, 23) and central wall (24) of the lower element (2) in order to provide three spaced supports having each a pair of superposed walls, the walls of two supports (22, 23', 23, 22') bearing directly one on another and covering a fixed height and the third support (24, 24') cooperating with at least temporary adjusting means (52, 54, 6) of the height of the two superposed walls, liable to provide an equal distribution of the stresses induced on the three supports according to the applied loads, the foreseeable deformations and the settlings.

2. Underground tubular structure according to claim 1, characterized in that the height adjusting means of the third pair of walls (24, 24') comprise an intermediate support (52, 6) having an adjustable thickness interposed between the ends (5, 5') facing said walls (24, 24') in order to adjust at least temporary the length between said latter and the height of said third support.

3. Underground tubular structure (1) according to claim 2, characterized in that each pair of elements respectively upper (2') and lower (2) bearing one on another is associated with intermediate support (52)(6) interposed between the ends (5, 5') of the central walls (24, 24').

4. Underground tubular structure (1) according to claim 2, characterized in that each pair of elements, respectively upper (2') and lower (2) bearing one on another is associated with at least an intermediate bearing device (52)(6) interposed between the ends of at least a pair of lateral walls (22, 23) on at least one side of the structure (1).

5. Underground tubular structure (1) according to one of claims 2 to 4, characterized in that each intermediate bearing device comprises at least an hydraulic or mechanical jack (52) having two axially moveable parts one with respect to the another and bearing respectively one on the lower element (2) and the other on the upper element (2').

6. Underground tubular structure (1) according to one of claims 2 to 4, characterized in that each intermediate bearing device comprises an inflatable elongated jacket (54) extending at least on a part of the length of the joint between the ends (5, 5') facing the walls (24, 24') of the two superposed elements (2, 2').

7. Underground tubular structure according to one of claims 2 to 6, characterized in that the intermediate bearing device (52, 6) is associated with final blocking means (53) of the ends (5, 5') facing the walls (24, 24') constituting the third support after adjustment of the height of said latter, the intermediate bearing device (52, 6) being removed after the blocking.

8. Underground tubular structure (1) according to one of the preceding claims, characterized in that the two elements, respectively lower (2) and upper (2') of each pair have substantially identical profiles and are made of concrete in the same mold, in that two of the longitudinal supports have ends (3, 4) with inverted hollow (31) and protruded (41) profile liable to engage one into another during the fitting of the upper element (2') upon the lower element (2) and in that the ends (5, 5') facing each other constituting the third longitudinal support are symetrical with respect to a plane (P) running through the two others longitudinal supports (3, 4' ; 4, 3').

9. Underground tubular structure (1) according to claim 8, characterized in that the end (5) of the wall (24) constituting the third symetrical support has a crenellated longitudinal profile comprising at least two parts (56, 57) the longitudinal edges of which (26, 25) are located respectively at two symetrical levels with respect to the plane (P) running through the two others supports and having in cross section inverted hollow and protruded profiles, the upper element (2') being offset longitudinally during the fitting with respect to the lower element (2) in order that the crenellated ends facing the two elements (2, 2') of each pair engage one on another.

10. Underground tubular structure (1) according to claim 8, characterized in that at least one of the three longitudinal supports (3, 3' ; 4, 4' ; 5, 5') constituted by the superposed central and lateral walls comprises an intermediate bar (6) interposed between the ends (5, 5') of the corresponding walls (24, 24'), said latter being shorter than the two others walls (22, 23) in order to provide between said ends (5, 5') during the fitting of the elements, a space in which is located the bar (6), said latter having a height at least equal to those of said space.

11. Underground tubular structure (1) according to claim 10, characterized in that the intermediate bar (6) has a height slightly upper to the twice of the distance between the end (5) of the central wall and the plane (P) running through the lateral supports (3, 4).

12. Underground tubular structure (1) according to claim 10, characterized in that the bar (6) is delimited by two longitudinal edges (61, 62) with convexe profile and in that the end (5) of the central wall (24) has a corresponding concave longitudinal profile in order to allow small displacements or deformations of the two elements (2, 2') one with respect to another.

13. Underground tubular structure (1) according to one of the preceding claims, characterized in that the end (5) of the central wall (24) is located at a height slightly upper the level of plane P running through the two lateral supports in order that the central support (5, 5') is more loaded than the two lateral supports (3, 4')(4,3').

14. Underground tubular structure (1) according to one of the preceding claims, characterized in that a strip (27) in a slightly compressible material is interposed between at least the lateral supports (3, 4')(4, 3').

15. Underground tubular structure (1) according to claim 13, characterized in that at least by wedging, the two lateral supports (3, 4')(4, 3') have different heights in order that the central part (21') of the upper element (2') is slightly slanted with respect to the central part (21) of the lower element (2) bearing on the ground.

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