EP0585959B1 - Entrenched conduit - Google Patents

Abstract

The subterranean duct construction system consists of excavating a trench or cutting and laying the duct or tunnel in the bottom of it in the form of prefabricated sections (101 104) for the floor and arched sections (201-206) for the roof. The prefabricated roof and floor sections can be made in a wider variety of shapes, according to the dimensions requjred for the finished duct or tunnel, and they can be made in one or two basic widths, so that a series of roof sections can be used with a series of base sections, giving a wide range of interchangeable sections.

Description

The subject of the invention is a buried pipe cf. the preamble of claim 1, produced by assembly, on the site, along a longitudinal axis, of a plurality of prefabricated elements.

There are different types of buried pipes made by assembling prefabricated elements and made up in particular of aligned tubular sections end to end along a longitudinal axis. Each tubular section can be formed, for example, of a single element of tubular section. In that case, the tubular sections are generally provided with their part ends, respectively, in protruding and recessed, which fit one into the other to the laying of the elements and allow the solidarity of these.

For a large passage section, the circular sections have very heavy weights high and difficult to handle, transport and to set up.

This is why we also proposed to divide the wall of the duct in prefabricated elements, each tubular section consisting of a number of elements resting on each other so to constitute a closed section. We often use elements of a single type each covering an arc of circle of given length and therefore allowing make circular sections. House at also proposed to use prefabricated elements of different shapes for making sections of non-circular cross-section and, for example, having a flat bottom allowing better distribution on the ground the applied load.

In particular, the applicant has already described such structures, for example in the European patent EP 081.402 which shows different embodiments and, in particular, a conduit comprising, in section transverse, four elements, respectively one planar element to strike off, two side elements placed on either side of the raft and each provided a base allowing them to stand straight on the floor and a curved arch element resting on the upper edges of the side elements.

According to another arrangement described in the document EP-A-0296013 (cf. the preamble of claim 1), strike it out may be deleted, each side element consisting of a curved wall fitted at its base with an enlarged sole comprising two wings extending in console on either side of the wall. Thanks to this particular shape, the stability of the side element is ensured not only at the laying of this one but also during the operations of backfill, the widened sole preventing the element from side to flip inward.

After completion of the entire structure and of the backfill, each side element can collect individually the load applied by the fill on the corresponding arch element, this load being distributed over the entire width of the sole.

In another embodiment which makes the subject of patent EP 0188.487 by the same applicant, we have describes a conduit comprising, in cross section, only two elements, respectively one element lower forming a raft and an upper element in form of arch curved and resting, through its two longitudinal edges parallel, on supporting members arranged along on both sides of the raft.

According to one of the characteristics described in the EP 0188.487, the longitudinal support members formed on both sides of the raft consist of curved hollow bottom grooves in which engage the longitudinal edges of the element vault which each have a convex rounded profile of curvature slightly more marked than that of the groove so as to leave a slight clearance. Each support longitudinal thus presents a certain possibility articulation around an axis parallel to the axis longitudinal of the duct, each arch element can deform very slightly under load transmitted by the terrain that surmounts it. This is transmitted to the two lateral sides of the raft which consists of a solid shaped panel rectangular resting on the ground through a rigid bottom allowing to distribute well all the charges applied.

It appeared that such structures resist charges actively applied by mobilizing, moreover, the surrounding land to which a part of the applied load is transmitted by lateral deformation of the upper element, this the latter being thus unloaded in the key.

These peculiarities have led to the extension of possibilities of application of such conduits.

The invention relates to a buried conduit for the passage of a roadway or a river, formed by assembling elements on the site prefabricated placed one after the other along a longitudinal axis on the bottom of a trench, the whole then being covered with an embankment, said duct comprising in cross section to the axis, a upper element forming an arch and resting on two supporting elements discarded by means of organs longitudinal supports parallel to the longitudinal axis, each support element, having, on one side lower, a seat surface and, on one side upper, a longitudinal support part on which comes to rest a lower lateral edge of an element upper, said support elements having dimensional and structural characteristics determined to be able to withstand loads applied in service by the upper elements and to ensure a seat surface of sufficient width, taking into account said loads and the bearing capacity of the soil.

Supporting elements are fitted on their front faces with screws screw, pending reinforcements associated with reinforcements transverse, which intersect in a space left between the consecutive elements and are drowned, after installation, in a sealing binder to form a keyed joint, so that the set of several supporting elements connected together form a sill monobloc capable of distributing the load on the ground and to avoid differential settlements.

In addition, the invention covers many variants which are the subject of the subclaims and which will be described in detail in the description which will follow, with reference to the accompanying drawings.

Figure 1 shows an embodiment of a known type of conduit.

Figure 2 shows, in cross section, a conduit according to the invention, buried under an embankment.

Figure 3 is a longitudinal section of the Figure 2 conduit at its end opening into an embankment.

Figure 4 is a partial side view representing a particular embodiment of longitudinal support between an upper element and a basic element.

Figure 5 is a partial top view representing, in a particular embodiment, a interlocking transverse joint between two elements consecutive basic.

Figure 6 is a view of detail representing an embodiment of the connection between two consecutive support elements.

Figure 7 is a detail view showing an embodiment of connection between two consecutive supporting elements, and not the subject of the invention as claimed.

Figure 8 shows, by way of example, two series III, III ', of supporting elements.

Figure 9 is a cross-sectional view of another embodiment.

Figure 10 is a schematic view, in perspective, of the conduit of Figure 9.

In Figure 1, there is shown in section transverse to the axis, an example of a pipe section of the type described in patent EP 0188.487 and constituted of two types of elements, respectively an element of base 10 forming a raft placed on the ground and a upper element 2 in the shape of a curved arch resting on the raft element 10. Elements 10 and 2 are made by molding, normally in concrete reinforced or prestressed, or fiber concrete, but other moldable materials can be used.

The duct 1 is placed at the bottom of a trench B which is open to a laying surface flattened and packed A placed at the desired level, leads it being, after installation, covered with fill C. conduit thus buried is therefore subject, on the one hand, to the load of the embankment which essentially depends on the height of the latter and, on the other hand, to loads applied for example on a pavement D on the embankment.

The basic element comprises a bottom 10 constituted a massive reinforced concrete panel rectangular provided, along its two lateral sides 11, of two longitudinal supports which, in the example shown, consist of grooves at the bottom curved 72 placed substantially at the level of the face top of bottom 10.

The arch element 2 has a cylindrical shape in semicircular, centered on a longitudinal axis O which can be placed either in the horizontal plane of grooves 72, i.e. at a height h above the face upper 13 of the raft 10. For example, in the mode embodiment of Figure 1, the arch element 2 has two planar sides 21 tangent to the part circular 20 which allow the axis O to be raised the same height.

Maintaining the semicircular shape of the vault, it is thus possible to vary the total height H of the duct by modifying the height flat parts 21 of the roof element 2.

Each end 22 of the upper element 2 of arch has a rounded convex edge 71 which engages in the concave groove 72 corresponding to the level of the upper face 12 of the basic element 1. The rounded edge 71 has a slightly more curvature accentuated than that of the groove 72 so as to play a light game allowing the parties lower 25 of the arch element to pivot very slightly on either side of the vertical plane P passing through the bottom of each groove 72. it constitutes thus, on each lateral side, a support member 7 articulated around an axis parallel to the axis O of the drove.

Therefore, as described in the EP patent 0188.487, the roof element 2 can deform very slightly thanks to its articulated supports 7, 7 ', under the action of the applied loads and this results in a some reduction in constraints to the key, a part of the load being taken up laterally by the embankment C.

Each articulated support 7 must however be held laterally. For this purpose, each groove 72 is limited by raised edges 14 which, in the case shown in Figure 1, where the grooves are placed at the level of the upper face 13 of the raft, have a height of not more than 5 cm, which allows to make the raised edges 14 when pouring concrete without using a special mold. The elements of write off 13 can therefore be molded quickly and economically.

It is also possible, as described in patent EP 0188.487, to apply the edges 22 of the vault in the grooves 72 by means of tie rods 25 energized by relying on parts 24 of the vault, a seal being interposed between the edges 71 and the bottom of the grooves 72.

By varying the height h of the parts lower planes 21 of the arch element, one can modify the total height H of the structure as well as the passage section S inside the duct.

But for the same width between supports, we can also reduce the height H of the duct by giving the vault a lowered form in basket handle. Good heard, in this case, the passage section S is also reduced. If you have to respect a height maximum, we can increase the width of the raft and, therefore, the distance between supports L so that ensure a defined passage section.

In the embodiments described up to present, the lower part was made up one-piece prefabricated elements forming a slab continued. It is possible, however, to replace each basic element 10 by two support elements spaced 30 so as to constitute two support lines 3 separated by a free space.

Such a provision, which has been shown on Figures 2 and 3 could be useful, for example, for very large sections for which monobloc basic elements would become not transportable. Indeed, the support elements 30 form insulated soles whose width can be designed to provide sufficient support surface. In particular, in the case of soils with good resistance, the width of the sole 32 could be scaled down.

Such elements, which are identical and can be stacked easily, are lighter and less bulky than one-piece elements covering the whole the width of the duct.

In the embodiment shown in the Figures 2 and 3, each upper element 20 has the shape a curved arch resting on the supporting elements 30 by its lower lateral edges, the latter having a convex rounded profile and each inserting in a groove 31 in the form of a concave chute formed on the upper face of each element support 30. This produces two support members longitudinal with some possibility of articulation of the upper element 20 relative to to the two support elements 30.

Replacement of a monobloc lower element by two separate support elements does not change substantially the maximum admissible load because it basically depends on the resistance of the arch, the role of the raft being essentially of transmit the load applied to the roof to the ground and sealing down.

The space between the two support elements separated 30 may, as the case may be, be left free or well closed anyway adequate corresponding to the use of the conduit.

In Figure 2, for example, the part lower 4 of the duct consists of a layer of base 41 in compacted aggregates, placed between the sides internal lateral 33 of the support elements 30 and covered with a slab 42 which can be formed of prefabricated elements or else cast in place in covering the upper faces 34 of the elements support 30.

We can thus, as shown on the Figure 3, pass between the two support lines 3 pavement 43 and we see that one of the advantages of this provision resides in the fact that the roadway 43 can be carried out continuously and classic inside and outside the duct, while lower concrete elements would impose a connection with the roadway outside, with the risk of lag due to differential settlements and expansions.

In addition, the plans of the transverse joints 23 between two consecutive arch elements 20 can be offset longitudinally from the plane of transverse joints 35 between the support elements 30. In this way, the load applied by each element upper 20 is distributed over two support elements consecutive, on both sides of the joint plane.

Advantageously, we can also, as we have shown schematically in Figure 5, spare the along the two transverse edges 8 of each element basic protruding parts 81 which engage in recessed portions 82 formed on the edge transverse opposite the adjacent element.

In this way, we ensure a relative centering of the consecutive elements to avoid risks misalignment when the structure is subjected to a lateral shifting effect, for example in curves.

A longitudinal shifting effect can also appear, for example, when the structure is performed on a surface inclined with respect to the horizontal.

In this case, as shown for side in Figure 4, each support member longitudinal 7 has a niche profile. The convex profiled part 71 formed on each edge lower 22 of the upper element 2 indeed extends alternately on two different levels so that understand, for example, a central part in projection 71 framed by two recessed parts 73 which engage in inverted parts arranged in hollow 74 and projecting 75 on the upper edge of the basic element and which are provided with a groove longitudinal.

Such a niche profile ensures the longitudinal support of each upper element 2 relative to the corresponding base element.

Of course, other similar provisions, comprising offset and projecting parts offset longitudinally could be used.

Cross joints between two elements 30 consecutive can be achieved from different manners.

In Figure 6, for example, a sealed joint 5 between two consecutive elements 30, 30'. The latter are provided, on their faces front facing waiting frames 51 which intersect in a space 50 left between the two elements 30 and 30 'and which are associated with transverse irons 52, the assembly being embedded in a sealing mortar 53. The sealing joint 5 thus produced between the two consecutive elements 30 and 30 'constitutes a real keying in the sense longitudinal. By joining together a certain number of consecutive elements, we realize, over a length determined, a monobloc sill which allows distribute the load on the ground and avoid differential settlements.

An embodiment not covered by the invention, is represented in Figure 7. According to this mode, the ends are placed facing two consecutive elements 30 and 30 ', connecting members 54, 54 ', which fit one in the other and can be connected by a pin 55. The two consecutive elements 30 and 30 'are thus linked together by an articulated connection giving each element a slight possibility of deviation by relation to the elements that surround it.

The dimensions of the support elements 30, and in particular the width L 'of their seating surface and their height H ', will be chosen according to the circumstances of use, including charges and the bearing capacity of the soil.

Different profiles can also be planned. For example, for making pavements underground, at least one of the support lines 3 could consist of 30 shaped elements of so as to present an upper face 34 'substantially horizontal and placed above the level of the floor 4 so as to create a sidewalk of pedestrian traffic.

According to another variant represented on the Figures 9 and 10, the conduit is intended for passage liquid, for example from a river. In this case, the bottom 6 of the duct can advantageously be formed a series of plates 61 of cast iron, sheet metal or plastic material, having a width equal to that of duct and covering the space between the two elements 30, going up on the upper faces 34 thereof up to the joints 31. As indicated on the Figure, the plates 61 can limit a profile in hollow, for example for the passage of a channel and the height H 'of the support elements 30 can be increased so as to raise the average water level, the bottom 6 thus limiting a sufficient section for flow rates means. Seals can be placed between the upper parts 31 of the support elements 30 and the upper edges 62 of each plate 6 of so as to allow the water level to rise above of the level of the edges 62 by filling more or minus the conduit, in the event of a flood. The conduit can even be pressurized if the lower edges 21 of the arch 2 are applied in the bottom of the grooves 31 by tensioned tie rods.

In addition, as shown in the view in perspective of Figure 10, the plates 61 can advantageously overlap each other in the way of a stabilizer, the transverse end 63 of a plate facing downstream, in the direction of circulation of the liquid, covering the front end 64 of the following plate 61 ', with the interposition of a sealing cord.

Other methods of bottom coating could obviously be employed. It is possible, in some cases that the longitudinal axis (O) of the duct is inclined to the horizontal and the support elements 30 may then tend to riper. To avoid it, it will be interesting to plan, on the lower faces 32 of the elements 30, hooking notches 37 which can be made at concreting or, as shown in the Figure 10, being housed on a cast iron plate 38 sealed on the underside of each element support 30.

As shown in Figure 10, in case of strong slope, the seat faces 32 of the support elements 30 could form steps, the laying surface A constituting steps A2 of corresponding width.

To avoid any danger of slipping, the elements 30 can be anchored in the ground by beams transverse forming keys. The same is true of upper elements 2 which can be keyed by compared to the basics.

According to another advantageous arrangement shown in Figures 3 and 10, we add to the upper elements 2 of the head pieces 9 placed at each end of the conduit.

Indeed, the conduit is buried under an embankment C and leads at each end into a slope C 'which must be held by the two lateral sides. For avoid unnecessarily prolonging the leads to the outside of embankment C, we will advantageously use head pieces each comprising a wall vertical 9 of triangular or trapezoidal shape, associated with a sole 90.

In Figures 3 and 10, for example, the sole 90 consists of one or more support elements 39 identical to those 30 which support the elements of vault 20. Each head piece is then formed of a plate 9 comprising a horizontal side 91 which rests on the upper part 31 of the element corresponding support 39, a vertical side 92 placed in the extension of side 24 of the last element upper 25 of the duct, and an inclined side 93 of which the inclination corresponds to the natural angle of the slope VS'.

The wall 9 can be maintained by a sealing between the vertical sides 92 and 24 opposite or by nesting of parts suitable sealed in the facing faces of said sides 91, 24.

In addition, the wall 9 is supported in the direction longitudinal, on a stop 94 closing the chute 31 in which engages the horizontal side 91.

But we could also make pieces of head each provided with a sole 90 forming a body with the vertical wall 9, so as to produce a freestanding element.

You can choose the dimensions and the profile of prefabricated elements to vary the section of passage and size, in particular the width L and the height H of the duct, depending on the circumstances, including conditions of use and the construction site.

In particular, the dimensional characteristics and structural elements such as the thickness of the vault, the nature of the concrete and the constitution of the reinforcement will have to be determined according to the constraints applied by the embankment and by operating expenses.

In addition, without changing the profile of the vault, we can also raise the level of supports 7, for example when the conduit is used when passing a height of water not exceeding, normal service, the height of the supports 7. Such provision keeps the water out of the water longitudinal supports as long as the flow transported by the duct is normal.

But other characteristics could also be modified or added, depending on needs and some accessories may also be added to basic items or items superiors.

The arch elements 2 can also make variants of which some have already been described.

We can therefore determine in advance different forms of upper elements and elements basic which can be combined in any way possible.

In addition, for each profile, we can also vary the parameters determining the resistance concrete, like the thickness of the vault, the nature of the concrete used and the constitution of the reinforcement, reinforcements can also be prestressed.

In this regard, it can also be interesting as shown in Figure 1, to spare, in the thickness of the basic elements, recesses tubular which are aligned with each other others to lay the elements so as to form longitudinal channels in which we can do pass the integral prestressing reinforcement then, in a conventional manner, by pouring a mortar.

Such channels may also be used, for example example, for the passage of pipes or cables electric or telephone.

The parallel European patent application N ° 90.400.144.3 of which the present request is a Division, describes a system for carrying out buried conduits according to which one defines in advance the characteristics of a number of profiles of superior and basic elements which can be classified into series each corresponding to a width between supports.

We can thus define the characteristics of a certain number (a) of series I, I ', ... of basic elements and II, II', ... of superior elements, each series corresponding to a width between supports, so as to cover as continuously as possible, but under economically profitable conditions, a wide range of passage sections to meet the needs of customers. In practice, it will be possible, for example, to define four series of base elements and of upper elements whose widths range between 1 meter and 2.50 meters, which allows, depending on the profile adopted, to produce surfaces passage from 0.35 m ² to around 6 m ² .

In the same way, it is possible to realize at minus a series III of supporting elements inside from which we vary a number of dimensional and structural characteristics like, for example, the width of the seat surface, the height of the element, the shape of the supporting members 31, the nature of the concrete used and the constitution of the reinforcement, etc ...

For example, in Figure 8, we have schematically represented two series III, III ', supporting elements each corresponding to a width 1 and 2 of the seating surface and in which the shapes of the elements have been varied.

In addition to series I, I '... of basic elements 1 and II, II '... upper elements 2, we have thus at least one series III of basic elements and, according to the needs, we can therefore associate the arch elements 20 selected from the series corresponding to selected isolated support elements in a series III, III ', presenting a surface seat compatible with the bearing capacity of the ground.

The superior and basic elements thus defined can be combined in any way possible and desirable, by forming a number of standard sections of the same width and whose profiles and the passage section are significantly different.

Of course, the associated elements must be compatible and, for example, we will associate together arch elements and basic elements having thicknesses and reinforcements allowing them to bear similar efforts.

We can have in stock a certain number elements of several widths presenting significantly different characteristics with regard to concerns the profile, thicknesses and reinforcement and corresponding to the most common needs. If the necessary items are in stock, they can immediately be delivered to the job site.

If the necessary elements are not found in stock, they can however be made very quickly because all their characteristics dimensional and structural are already defined and we normally have the molds that were used for realization of elements subjected to preliminary tests. When the customer orders items with other accessory features, such as internal piping or anchoring devices, or many slight variations in dimensions due to installation requirements, we simply adapt the mold for obtaining, at the casting, these additional features, all others characteristics remaining well fixed.

The elements are then produced in a desired number prefabricated either in a factory or on the site, and we assemble them to build the drove.

Other prefabricated accessories could moreover be advantageously added to the series supporting elements 30.

For example, the inner side of the elements 30 could be fitted with parts designed to build or receive traffic rails of a trolley or gantry facilitating assembly and / or maintenance of the structure.

We can also add to the series of elements upper and lower, a series of head pieces with thicknesses, heights and, possibly different inclinations so to be able to adapt to different cases of the best way.

Generally speaking, moreover, we could imagine other variants and other arrangements accessories, for example to achieve differently the bottom or the top of the duct.

The reference signs, inserted after the technical characteristics mentioned in the claims are intended only to facilitate the understanding and limiting them in no way the scope.

Claims (14)

1. Underground conduit for a traffic carriageway or river to pass through made by assembling on site prefabricated elements placed one after the other along a longitudinal axis (0) on the bottom (A) of a trench, the assembly being covered with a backfill (C), said conduit comprising in cross-section to the axis (0) an upper element (2) forming a roof and resting on two spaced bearing elements (30) through longitudinal bearing members (7) arranged parallel to the longitudinal axis (0), each bearing element (30) having on a lower face a foundation surface (32) and on an upper face (34) a longitudinal bearing part (72) on which rest a lateral lower edge (71) of an upper element (2), the said bearing elements (30) having structural and dimensional features so as to be capable of resisting the loads applied in service by the upper elements (2) and of ensuring a foundation surface (32) of sufficient width (L'), the said loads and the soil bearing capacity being taken into consideration,
      characterized in that the consecutive bearing elements (30,30') are provided on the opposed front faces thereof with projecting reinforcements (51) associated with transverse reinforcement (52), crossing in a space (50) provided between the consecutive bearing elements (30,30') and embedded after laying them in a sealing compound (53) so as to form a keyed joint such that the assembly of several consecutive bearing elements (30,30') thus interconnected forms a one-piece sill liable to distribute the load on the ground and to avoid differential compressing.
2. Underground conduit according to claim 1, characterized in that each upper element is made so as to be deformed under the action of the applied loads by slightly pivoting around bearing members (7,7').
3. Underground conduit according to one of claims 1 and 2, characterized in that each bearing element (30) has a substantially trapezoidal cross section comprising a large lower face (32) providing a foundation surface and an upper face providing a bearing part (72), the height H' of the bearing element (30) and the width L' of the foundation surface being determined according to the applied loads and the soil bearing capacity.
4. Underground conduit according to one of the preceding claims, characterized in that it comprises, between the two lines (3) of bearing elements (30), a sequence of intermediate elements (61) bearing against the inner parts (34) of the bearing elements (30) of the two lines (3) so as to form the bottom (6) of the conduit (1).
5. Underground conduit according to claim 4, characterized in that the intermediate elements (61) are made of a moldable, injectable or rolled material such as metal, concrete or plastic materials.
6. Underground conduit according to one of claims 4 and 5, characterized in that the bottom (6) of the conduit (1) provides a channel for a liquid flow and in that the intermediate elements are made of plates (61) covering substantially the entire internal width of the conduit and overlapping each other in a manner of a sequence of roofing tiles, the downstream end (63) of one plate (61) overlapping the upstream end (66) of the following plate (61') .
7. Underground conduit according to one of claims 1 to 3, characterized in that when the conduit (1) is used for a traffic carriageway (43) to pass through, the latter is made without any discontinuity between the two lines (3,3') of bearing elements (30).
8. Underground conduit according to one of the preceding claims, characterized in that the bearing elements (30) are each provided on the lower face (32)thereof with projecting parts (37) for anchoring the element to the laying surface (A).
9. Underground conduit according to one of the preceding claims, characterized in that the foundation surface (32) of the bearing elements (30) forms tiered steps capable of being laid on top of stairs (Az) arranged on the laying surface (A) when the longitudinal axis (0) of the conduit slants.
10. Underground conduit according to one of the preceding claims, characterized in that at least some base elements (30) are provided with at least one tubular cavity arranged in the thickness of the element and parallel to the axis (0) such that the aligned tubular cavities of several consecutive base elements (30) form an internal channel extending over the entire length of the structure.
11. Underground conduit according to one the preceding claims, characterized in that each longitudinal bearing member (7) (7') comprises two respectively convex (71) and concave (72) profiled parts which are arranged, projecting and recessed respectively, along the opposite lateral sides (21) (31) of the upper element (2) and of the two base elements (30) of each section so as to form a link.
12. Underground conduit according to claim 11, characterized in that the profiled parts, convex (71) and concave (72) respectively, extend alternately on two different levels so as to form, along each base element (30) and each upper element (2), profiles with inverted crenellations comprising on the base element (30), recessed (74) and projecting (75) parts in which engage projecting (71) and recessed (73) reversed parts which are respectively arranged on the lateral sides (21) of the upper element (2).
13. Underground conduit according to one of the preceding claims, characterized in that, the conduit being covered with a backfill (C) limited by a slope (C'), each end (25) of the conduit opening out into the slope (C') is equipped with two head pieces (9) placed in the extension of the two sides of the conduit respectively and each comprising a lateral wall element (9) with a slanting shape resting on a bearing footing (90) and capable of being placed in the extension of the two lateral sides (24) respectively of the upper element (25) placed at the end of the conduit, each lateral wall element (9) having a substantially trapezoidal or triangular shape comprising a horizontal side (91) resting on the bearing footing (90), a vertical side (92) placed along the corresponding side (24) of the upper element (25) and an inclined side (93) whose inclination corresponds to the natural angle of the slope (C') of the backfill covering the conduit.
14. Underground conduit according to claim 13, characterized in that a series of head pieces (9) are available in which at least one of the parameters such as the thickness of the wall (9), the height of the vertical side (92), the inclination of the inclined side (93) and the width of the bearing footing (90), has been varied.

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