WO2000017456A1

WO2000017456A1 - Tubular structure

Info

Publication number: WO2000017456A1
Application number: PCT/FR1999/002231
Authority: WO
Inventors: Marcel Matiere
Original assignee: Societe Civile De Brevets Matiere
Priority date: 1998-09-22
Filing date: 1999-09-20
Publication date: 2000-03-30
Also published as: AU5630499A; DE69905479D1; ATE232931T1; JP2002526693A; ES2190656T3; JP4382987B2; EP1119663A1; TR200100804T2; OA11909A; AP2001002124A0; CA2344225A1; MY121095A; EP1119663B1; PT1119663E

Abstract

The invention concerns a tubular structure comprising, in cross-section transverse to its axis (O), at least three prefabricated elements, respectively two side wall elements (32, 32') resting on the setting surface and at least one upper element (31) with a curved profile resting, along two longitudinal joints (36), on the upper edges of the two side wall elements (32, 32') and tangentially connected thereto to form a continuous vault for transmitting loads on the bases (33) of said side walls (32, 32'). The invention is characterised in that at least some of the side wall elements (32, 32') are shaped so as to possess sufficient rigidity for carrying the applied loads without lateral support on an embankment covering the structure.

Description

Tubular piping

The invention belongs to the field of construction and public works. It relates to an underground passage structure, more particularly intended for the circulation of vehicles.

The invention also covers prefabricated pedestal elements, specially adapted for the production of such a structure.

A road and, a fortiori, a rail traffic lane must have a fairly regular longitudinal profile, avoiding too steep slopes. It is therefore not possible to constantly follow the profile of the terrain, the platform being, in certain sections, either above or below the level of the natural terrain. On the other hand, it is desirable, at crossings, to pass one lane below the other by means of an underground passage.

When the difference in level between the laying surface of an underground passage and the natural ground is not too great, it is advantageous to make an open trench, the bottom of which is placed at the desired level to allow the construction in the open of the structure which is then covered with an embankment to restore the level of the natural ground.

The inventor has developed, in recent years, a particularly advantageous technique for constructing works of this type, which is described in particular in document EP-A-0.081.402 or document US-A-4,836,714.

In this technique, the structure consists of prefabricated wall elements arranged one after the other on a platform formed in the bottom of the trench. In an embodiment described in particular in document EP-A-0.081.402, the structure comprises, in cross section with the axis, an upper element forming a vault resting on two pedestals placed on either side of a slab . Preferably, the upper longitudinal joints between the arch element and the upper edges of the two pedestals are formed by articulations which give the structure relative flexibility, in particular when the embankment is being made. In addition, the pedestal elements advantageously have a curved upper part which tangentially connects to the upper element, so as to form a continuous arch. Between the bases of the two pedestals can be arranged a radiant element, prefabricated or cast in place, which is connected to the internal sides of the bases of the pedestals by concrete joints forming a rigid longitudinal connection, the assembly thus forming a flat base allowing distribute the load over a large area.

In certain cases, however, in particular when the span of the structure is very large, the raft can be removed, each pedestal resting on the ground by an enlarged base whose dimensions are calculated according to the loads to be supported and the capacity bearing of the ground. Such an arrangement is described in particular in document US-A-4,836,714.

In a particular embodiment, it is possible to build very large structures, consisting of several adjacent passage sections, for example for the construction of an underground highway with several traffic lanes. In the case of a structure having two passage sections, these are separated by a central pedestal on which rest two arch elements which, on the outside, each rest on a lateral pedestal. This technique has undergone significant development because it allows very large sections to be produced particularly quickly and economically.

In fact, the entire supporting structure is made up of prefabricated elements which can be produced economically and under the best possible safety conditions, in a specially equipped prefabrication factory or in a fairground workshop installed near the structure when this is important. It is thus possible to rigorously control the manufacturing conditions and, in particular, the composition of the concrete and its water content, the positioning of the reinforcements and the surface quality after formwork removal. We can even, in some cases, use high performance concrete.

Therefore, compared to a formwork construction and concreted on site, the use of prefabricated elements makes it possible to reduce their thickness relative to their span and, consequently, to lighten them. Even for large spans, the prefabricated elements can therefore be handled and put in place by the lifting devices usually available on a site. To build such a structure, after having dug a trench, the bottom of which is leveled to the desired level, the side elements which are designed to stand straight by themselves are laid successively, then the upper elements which rest, at their ends, on two side elements, the assembly then being covered with an embankment. According to one of the characteristics of this technique, the embankment contributes to the resistance of the whole. In fact, since the elements can be particularly thin and the reinforcement can be produced with great precision, the elements have a certain flexibility and can yield slightly when the structure supports the embankment and the overloads, which reduces the forces applied to the key, the structure bearing laterally on the embankment.

It is particularly advantageous to use such a technique for the bypassing of agglomerations or the passage of a road or rail way in a protected area, because the structure can be made in open trench over a long length, even near dwellings , then be covered by an embankment so as to restore the level and the natural aspect of the ground while ensuring, moreover, an almost perfect sound insulation.

However, it is not always easy to carry out, on either side of the structure, an embankment liable to withstand lateral forces. This is the case, in particular, in urbanized areas when the structure passes close to existing constructions, for example, the foundations or cellars of a building, or even a sewer. In addition, in a tight space, it may be necessary to pass pipes near the structure and it may therefore be necessary, for maintenance or replacement, to reopen the embankment.

The object of the invention is to remedy such drawbacks by means of a new embodiment. such a structure making it possible to avoid the creation of a lateral embankment capable of withstanding lateral forces in particular, in urban areas and in cases where the traffic lane is, in whole or in part, above the level of the natural land.

The invention therefore relates to the production of tubular structures consisting of prefabricated wall elements arranged one after the other on a platform so as to form a resistant structure having at least one tubular passage section centered on a longitudinal axis and resting on the platform by a flattened base, the structure comprising, in cross section with the axis, at least three elements, respectively two side elements forming piers each having a substantially vertical wall having an edge upper and a base with a flat lower face resting on the platform, and at least one upper element with a curved profile resting on the upper edges, respectively, of the two pedestal elements, along two longitudinal joints and tangentially connecting to the upper parts of said pedestals so as to form a continuous arch for the transmission of loads on the bases of said pedestals oits.

According to the invention, at least certain pedestal elements, placed on the outside of the structure, are shaped so as to have sufficient rigidity to collect and transmit the loads applied, without lateral support on an embankment covering the structure.

In a preferred embodiment, each pedestal element is provided with at least one stiffening rib extending over at least one face of its side wall and capable of opposing a deformation thereof under the effect of the loads applied by the upper element.

Furthermore, each upper element can advantageously be provided, along at least one lateral side placed on the outside of the structure, with a rigid veil extending upward for stable maintenance of a minimum thickness of embankment above the upper element. The invention also covers the prefabricated wall elements thus produced.

The invention therefore constitutes an extension of the known technique for producing tubular structures which has numerous advantages and makes it possible to adapt to particular situations.

Indeed, it was admitted, until now, that the construction of underground passages was necessary only in the case where, precisely, the platform of circulation is below the level of the natural ground. When, on the other hand, the ground drops below the level of the platform, it must be built on an embankment or a viaduct to restore the desired level. This raises the problem, in urban areas, of the noise caused by vehicle traffic and the discomfort caused to the environment, and noise barriers which often are expensive, unattractive and sometimes ineffective must often be produced.

The invention also remedies such drawbacks by ensuring, under the best conditions, environmental protection over the entire length of the traffic lane. In fact, thanks to the arrangements according to the invention, the structure can be produced, at least in part above the level of the natural terrain. This is first covered with a first embankment having an upper part in the form of a platform to constitute the laying surface and, after the laying of the elements, the entire structure and the first embankment which supports it. is covered with a second embankment which connects to the natural ground on either side of the structure so as to form an artificial hill, the flattened base of the structure having a width determined according to the bearing capacity of the first embankment of so as to transmit to it the loads applied without risk of excessive compaction.

Other advantageous provisions of the invention are the subject of the claims and will emerge from the description which follows of certain particular embodiments, given by way of nonlimiting examples and represented in the appended drawings, in which:

Figure 1 is a schematic view, in longitudinal section, of the assembly of a structure produced according to the invention. Figure 2 is a cross-sectional view along line II-II of Figure 1.

Figure 3 is a cross-sectional view along line III-III of Figure 1.

Figure 4 is a schematic overview, in perspective.

Figure 5 is a detail view of the base of a pedestal.

Figure 6 shows, in cross section the realization of a structure with two adjoining sections. Figure 7 shows a particular embodiment of such a work.

Figures 8 and 9 show, respectively in side view and in top view, the exit of a structure crossing a slope at an angle.

In Figure 1, there is shown schematically, in longitudinal section, part of a traffic lane produced according to the invention on relatively uneven terrain whose longitudinal profile is indicated by line 10 which therefore corresponds to the section of the natural terrain 1 by a vertical plane P passing through the longitudinal axis of the taxiway. This is provided on a platform A which includes a portion 11 located below the level of the natural terrain and a portion 12 located above it.

Consequently, the part 11 of the platform A is formed in cut on the bottom of a trench B while the part 12 is formed on the top of an embankment C.

In the excavated part 11, the platform A constituting the traffic lane is covered, in a conventional manner, with a tubular work D constituting an underground passage which is first produced in the open air, then buried under an embankment E to restore level 14 of the natural terrain.

Such an arrangement is particularly advantageous for bypassing urbanized areas because it ensures perfect sound insulation and restores the environment, the embankment E can be planted.

In an embodiment described in patent EP-0.081.402, the tubular wall D consists of successive sections placed end to end and each comprising, in cross section, at least three elements, respectively a curved upper element 21 resting on two side pedestals 22, 22 'each provided with a flat base allowing them to be placed upright on the ground. The internal sides of the bases of the two pedestals can be connected, by concrete longitudinal joints, to a fourth element forming a raft. In this way, all of the load applied to the tubular wall is transmitted to a very large base.

However, it is also possible to delete the deletion. As shown in FIG. 2, each lateral pedestal 22, 22 ′ then comprises an enlarged base 23 having two wings, respectively internal and external, which give the element a sufficient seating surface, and a side wall 24 having an upper part 25, curved inwards, which tangentially connects to the upper element 21 so that the assembly forms, in cross section, a substantially semicircular arch centered on a longitudinal axis 0.

In addition, the longitudinal joints 26 between the upper element 21 and the upper edges of the two side pedestals 22, 22 'are formed by articulations centered on planes PI, P'1, in which are placed the centers of curvature of the 'upper element 21 and upper parts 25 of the sides 22, 22'. Preferably, these joint planes are inclined at 45 ° relative to the vertical.

In this known arrangement, the loads applied to the upper element 21 are transmitted tangentially to the two lateral pedestals 22, 22 '. The latter are supported on the ground by their base 23 but, due to the flexibility of the structure and the use of the articulated joints 26, the upper element 21 tends to bend slightly by spreading the side pedestals 22, 22 ' which also flex and bear laterally on the embankment E. This must therefore be made in a particular way to participate in the resistance of the entire structure by taking the lateral thrusts applied by the two sides 22, 22 '.

As indicated, it is not possible, in some cases, to lean laterally on the surrounding land.

According to the invention, the side walls which must then resist by themselves to the loads applied by the upper element are formed so as to be rigid enough not to bend under the load. For this purpose, as shown in FIG. 3, each pedestal element 32 is provided with a stiffening rib 37 placed on the outer side of the wall 34 and extending between the base 33 and the upper joint 36. The pedestal 32 thus stiffened can therefore transmit the loads in a substantially vertical direction, without lateral support on the embankment 5.

Such an embodiment of the side walls is particularly advantageous in the case shown in FIG. 1, of relatively uneven natural terrain. Usually, in fact, when the level of the platform 11 joins the natural level of the terrain 1, at point 13 of the longitudinal profile 10, the arched structure 2 covered with an embankment is stopped and the rest of the traffic lane A is performed in the sky open on the upper part of a C slope or, even, on a viaduct. This results in discomfort for the environment and, in urbanized areas, it is often necessary to build noise barriers along both sides of the platform A. Such an achievement is expensive and unattractive.

According to the invention, instead of being stopped at the outlet of trench B, the tubular structure 2 is extended by a structure of the same nature 3 which is shown in FIG. 3, this being a cross section, according to the line III-III of figure 1.

To this end, a first embankment 4 is constructed, in the extension of the part 11 of the platform A, the upper part 41 of which is leveled so as to form a platform 12 on which the tubular structure 3 is placed.

In Figure 4, which is a perspective view of the assembly, there is shown, for simplicity, a single section of the tubular structure 3 which comprises, in cross section with the axis O, at least three elements, respectively a curved upper element 31 resting on two lateral pedestals 32, 32 'along longitudinal joints 36. These prefabricated wall elements preferably have exactly the same profile as the elements 21, 22, 22' of the structure 2 and are placed therefore as an extension of these. The longitudinal joints 36 are therefore placed in alignment with the longitudinal joints 26 of the structure 2 and also constitute joints giving the structure relative flexibility.

In addition, each pedestal 32 is provided with a base 33 bearing on the platform 12. After the installation of the elements constituting the structure 3, in the extension of the structure 2, the assembly is covered with a second embankment 5, the surface 50 of which gradually connects to the natural ground 1 and to the surface 14 of the embankment E, of so as to create an artificial hill which can advantageously be planted to restore an aesthetic environment.

It is clear that, in this way, an almost perfect sound insulation is achieved, even in the parts where the platform A is at a level higher than the natural terrain.

In addition, the traffic on the platform A thus covered is no longer visible from neighboring constructions F.

These essential advantages can compensate, in urbanized areas, the additional cost due to the construction of the structure 3 and the second embankment 5. As for the structure 2, each lateral pedestal 32, 32 ′ preferably includes an enlarged base 33 and a curved side wall 34 which tangentially connects to the upper element 31. The upper elements 31 and the sides 32 have the same profile as the similar elements 21, 22 of the structure 2 and can therefore be cast on the same molds , these being slightly modified to produce the stiffening ribs 37.

The width of the base 33 of each pedestal 32 must be determined taking into account the bearing capacity of the first embankment 4 which is likely to be less than that of the platform 11 formed in the bottom of the trench B, that is to say on natural ground. However, as indicated above, the prefabricated elements of this type, even for a large span, can be produced at a site remote from the site and transported by road, each element being able to be placed lengthwise on a trailer.

For large dimensions, it is therefore interesting to calculate the elements so as to lighten them as much as possible and, since a stiffening rib is added to a pedestal, it may be preferable to reduce the width of the sole by providing for a possibility of widening it, after installation, to give it the necessary seating surface.

To this end, as shown in FIG. 5, provision can be made, during the manufacture of the wall elements, to allow protruding reinforcements 42a on the two sides, respectively external 33a and internal 33b, of the base 33 , 42b. Thus, the weight of the pedestal element can be reduced so as to remain compatible with the transport capacities. After the elements have been laid, it is possible, using appropriate formwork, to pour extensions 44a, 44b on each side of the base 33 so as to widen the latter to reduce the loads applied to the embankment 4. In thus reducing the width of the sole 33, it is possible to compensate for the increase in weight due to the rib 37. Furthermore, longitudinal reinforcements 45 covering several successive pedestal elements can be threaded into the waiting reinforcements 42 so as to produce a longitudinal beam connecting the elements, allowing them to better resist differential settlements. To further increase the seating surface 30, it is also possible to pour, between the internal sides of the bases 33, 33 'of the two pedestal elements 32, 32', a raft 43 provided with the necessary reinforcement and in which the reinforcements are embedded. waiting 42b.

To simplify Figure 3, there is shown a work carried out on natural terrain 1 substantially horizontal in cross section. In practice, however, the slope line of the ground, in a direction orthogonal to the longitudinal axis of the structure, can be more or less inclined relative to the horizontal, between an upstream slope 16 and a downstream slope 15. As shown, by way of example, in FIG. 6, it follows that, in the zone or the platform 11 passes above the level of the natural terrain 1, the side of the structure turned from the the downstream side must be placed on an embankment 61, while the upward-facing side rests on the bottom of a trench 62 made of cuttings. The structure according to the invention is particularly suitable for such a situation. Indeed, as indicated above, the use of prefabricated pedestals bearing on a very wide sole and on which the upper element rests by means of a longitudinal articulation makes it possible to resist particularly well the differential settlements which may result. of such asymmetrical support.

In Figure 6, there is shown, by way of example, a structure with two arches of the type described in document EP-A-0.202.256, which is particularly suitable for the construction of motorways and comprises at least two lanes traffic SI, S2 on either side of a central pedestal 63 on which rest two upper elements, respectively 64, 64 ', which bear outwards, each on a lateral pedestal, respectively 65 on the upstream side and 65' on the downstream side. The embankment 5 which covers the whole of the structure and connects to the natural ground in the manner indicated in FIG. 6, is asymmetrical, but this does not affect the stability of the structure, the loads being transmitted vertically by the legs 65, 65 ', made rigid by the ribs 37.

Figures 3 and 6 show another improvement of the invention. Indeed, the second embankment 5 which is formed over the first embankment

4, can be subjected to sliding and that is why it is advantageous, as indicated in FIG. 3, to provide on the lateral side of each upper element 31, a concrete veil 38 which extends upwards so to retain the upper part 51 of the embankment covering the structure. Thus, the latter is always covered with a sort of earth cap whose weight increases the stability of the assembly and which is not likely to collapse if the downstream part 52 of the embankment 5 tends to slide.

Preferably, the retaining veil 38 is perpendicular to the lateral side of the wall element 31 and, therefore, parallel to the joint plane PI.

In the case of a single-section structure shown in FIG. 3, the upper element 31 can be provided with two webs 38, 38 ′ formed on each of its sides. On the other hand, in the case of a structure with two sections, each upper element 64, 64 ′ is provided with a retaining veil 38 only on its external side resting on a lateral pedestal ld

65, 65 ', the internal sides of the two elements 64, 64' resting symmetrically on the central pedestal 63.

It should be noted that the prefabricated elements which have just been described have numerous advantages which justify their application to various situations.

For example, through the use of reinforced piers as described above, the backfill no longer has to be made in a particular way and can therefore be reopened if necessary. Therefore, one can pass there conduits 67 which can be laid even after completion of the work.

This advantage is particularly interesting in urban sites because it frees up space on each side of the structure. Such piers can therefore advantageously be used, even for a structure produced, in a conventional manner, on the bottom of a trench. However, in the case represented in FIG. 6 of a structure produced on an asymmetrical ground, the part of the embankment comprised between the upstream pedestal 65 and the slope 16 can be carried out so as to collect the lateral thrusts. The pedestal 65 could therefore have been made without a rib, like a pedestal 22 of the structure 2.

FIG. 7 shows another embodiment of a structure with two traffic lanes in the case of an oblique exit in inclined natural terrain. It may then be advantageous to first stop the S'2 section of the structure located on the downstream side and to extend for a certain period the S'1 section located on the upstream side and which is alone covered with a slope 51 '. This one is advantageously stopped by an inclined veil 38a formed on the side facing the slope of the upper element 66 which rests on the central pedestal 63 '. The latter may consist of a solid wall or a row of pillars surmounted by a sill and comprising, on the upstream side, a single support member 36 for the upper element 66 covering the section S'1. On the downstream side, the upper part of the central element 63 ′ advantageously constitutes an inclined face 39a for supporting the retaining veil 38a.

Similarly, the rib 37 of each pedestal element 65 ′ closing the section S ′ 2 towards the outside can be provided, at its upper end, with an inclined face 39 having the same orientation as the web 38 ′ associated with the 'upper element 64' so as to constitute a bearing face of said web 38 '.

It should be noted that the slope 51 can be stopped at the level of the web 38 ′, the lower part 52 of the embankment 5 being eliminated. The structure is then covered with a simple earth cap and the ribs 65 'ribs remain visible from the outside, providing sound protection by themselves. This gives an interesting aesthetic effect. Furthermore, even in the case of a work carried out in a trench and entirely covered with an embankment, it may be advantageous to provide rib pedestals at the outlet of the work, in particular when the latter is arranged at an angle with respect to to the embankment that covers it.

By way of example, there is shown in FIGS. 8 and 9 the outlet of such a structure passing through an embankment E on which is formed a track circulation 14, the longitudinal direction of which makes a non-right angle with the axis 70 of the structure 7.

In current section, the structure consists, like the structure 2 of FIG. 2, of successive sections each comprising an upper element 21 resting on two lateral pedestals 22, 22 ′ which can take lateral support on the embankment E covering the work. However, the embankment E, which has been removed in FIG. 9, is limited by an inclined slope E 'whose edge, along the structure is indicated in phantom. Usually, at the outlet 7 of the structure, the side walls 72, 72 ′ of the last section 71 are extended by prefabricated walls 73, 74 having the same inclination as the slope, for the maintenance of the land.

It can be seen that, in particular on the side closest to the bottom of the slope, the pedestal 72a cannot bear on the embankment, the height of which is insufficient. In this case, to collect the lateral thrusts applied by the upper element 71, the two side elements must sometimes be connected to their base by a connecting beam extending between the two flanges 73, 73 '. This can have drawbacks, for example for the construction of a road passing inside the structure and these drawbacks can be avoided by using, at the two ends where the height of the ground is insufficient, ribbed pedestals of the type described. previously and which collect by themselves the loads applied without the need to take lateral support on the embankment.

As shown in FIG. 9, the adjacent pedestals 72a, 72b of the last two sections are then provided with ribs 37 while, on the other side, only the extreme pedestal 72'a is rib, the pedestal 72 'b of the penultimate section resting on a slope of sufficient height to absorb the thrust and being, therefore, identical to the current pedestal 22' .

It therefore appears that the prefabricated elements which have just been described can be used in various ways. In addition, the invention is obviously not limited to the details of the embodiments which have just been described by way of example, other variants, other improvements and other uses which can be imagined without departing. of the protective framework defined by the claims. In particular, it is advantageous to use, for the construction of the structure, wall elements with an enlarged sole, but it may be preferable to connect the bases of the two pedestals, by a concrete slab allowing the load to be distributed on a base. unique with a very large seating area.

On the other hand, as indicated above, in the embodiments described in the previous patents, the sidewalls were dimensioned and scrap so as to present a certain flexibility by leaning laterally on the embankment. In the invention, on the other hand, the entire applied load is transmitted by the pedestal on its sole and this results, for the same passage section, an increase in the compressive stresses applied to the concrete. Therefore, in order not to be obliged to increase the thickness of the side wall and, consequently, the weight of the walls, it may be advantageous to produce the elements in one high performance concrete with significantly increased compressive strength.

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

1. Tubular work consisting of prefabricated wall elements arranged one after the other on a platform (A) so as to form a resistant tubular structure (D) having a longitudinal axis (O) and comprising , in cross section with the axis (O), at least three elements, respectively two side elements (32, 32 ') forming piers each having a substantially vertical wall (34) having an upper edge and a base

(33) with flat lower face resting on the platform (A), and at least one upper element (31) with curved profile resting on the upper edges respectively, of the two pedestal elements (32, 32 ') along two joints longitudinal (36, 36 ') and tangentially connecting to the upper parts (35, 35') of said sides (32, 32 ') so as to form a continuous arch for the transmission of loads on the bases (33, 33') of said pedestals (32, 32 '), characterized in that at least some of the pedestal elements (32, 32') are shaped so as to have sufficient rigidity to collect and transmit the loads applied without lateral support on an overlapping embankment the book.

2. Tubular structure according to claim 1, characterized in that at least some of the pedestal elements (32, 32 ') are each provided with at least one stiffening rib (37) extending over at least one face. of the side wall

(34) and capable of opposing a deformation thereof under the effect of the loads applied by the upper element (31).

3. Tubular structure according to one of claims 1 and 2, characterized in that each longitudinal joint (36, 36 ') between a pedestal element (32) and the upper element (31) constitutes a joint with a longitudinal axis .

4. Tubular structure according to claim 3, characterized in that each longitudinal articulation (36) is centered on a joint plane (PI) inclined relative to the vertical.

5. Tubular structure according to one of the preceding claims, characterized in that each pedestal element (32) has an enlarged base (33) extending on either side of a substantially vertical side wall (34) having an upper part (35) curved on the side of the axis (O) of the structure, so as to be tangentially connected to the corresponding side of the upper element (31) and that at least one stiffening rib (37) is formed on the outside of the side wall (34) and extends from the base (33) substantially to the level of the longitudinal joint (36).

6. Tubular structure according to one of the preceding claims, characterized in that the platform (A) is made, at least in part (12), above the level of the natural ground (1), the latter being first covered with a first embankment (4) having an upper part (41) forming a platform (12) to constitute the laying surface of a resistant structure (3) and that, after the laying of the elements (31, 32), the entire structure (3) and the first embankment (4) which supports it is covered with a second embankment (5) which is connected to the natural ground (1) on either side of the structure to form an artificial hill, the structure (3) resting on a seat surface (30) having a width determined as a function of the bearing capacity of the first fill (4) so as to transmit to the latter the loads applied without risk of excessive compaction.

7. Underground structure according to claim 6, characterized in that, the natural terrain (1) on which the structure is built being inclined in a direction transverse to the longitudinal axis (O) of the structure (3) between an upstream slope (16) and a downstream slope (15), the platform (A) is made asymmetrically and comprises a part (18) made of cuttings in the bottom of a trench (62), on which the pedestals (65) of the structure turned on the upstream side (16), and a part (17) made of embankment (61) above the natural ground (1) and on which the pedestals (65 ') of the structure turned towards the downstream side (15), at least said downstream pedestals (65 ') being provided with a reinforcing rib (37).

8. Tubular work according to one of the preceding claims, characterized in that the base (33) of at least some of the pedestal elements (32) is provided, on at least one lateral side (33), with reinforcements on standby (42) capable of being embedded in poured concrete after the element has been laid in order to widen (44) the seating surface (30).

9. Tubular structure according to claim 8, characterized in that it comprises a raft (43) extending between the bases (33, 33 ') of the pedestal elements (32, 32') and secured to the internal sides (33b) of said bases (33, 33 ') so as to constitute a seat surface (30) of the structure (3).

10. Tubular work according to one of the preceding claims, characterized in that each upper element (31) is provided, along at least one side facing outwards, with a rigid veil (38) s' extending upward from said side to maintain an earth cap (51) consisting of a minimum thickness of fill at least partially covering the structure.

11. Tubular structure according to claim 10, characterized in that the rigid web (38) formed on one side of an upper element (31) rests on a bearing face (39) of the same orientation formed at an upper end of each stiffening rib (37) of the corresponding pedestal element.

12. Tubular structure according to one of claims 10 and 11, characterized in that the embankment partially covering the structure is stopped at the level of the retaining veil (38), the rib rib elements (65 ') remaining visible from outside.

13. Tubular structure according to one of claims 10 to 12, comprising at least two sections (SI, S2) joined on either side of at least one central pedestal (63), each section comprising an upper element (64 ) resting, on one side on the central pedestal (63) and on the other on a lateral pedestal (65), characterized in that, at the exit of a ground whose surface is at an angle to the longitudinal direction of the structure, one of the sections (S'1) is extended relative to the other (S'2) and is covered by an element upper (66) provided, on the side bearing on the central pedestal (63 '), with a rigid veil (38a) extending upward to maintain an embankment (51') up to the level of the pedestal central (63 '), the upper part of the latter forming, on the upstream side, a support (36) for the upper element (66) and, on the downstream side, an inclined face (39a) for supporting the web (38a ) to maintain the embankment (51 ').