MXPA00009666A - Pressurized liquid circulation duct and method for the production thereof - Google Patents

Abstract

The invention relates to a liquid circulation duct comprising a pipe (1) that is fixed to a solid, rigid support (B) in order to form a base that rests on a standing surface (C). The pipe (A) is made of a thin resistant wall that forms a tight tubular enclosure. On each side of the longitudinal axis (O, O'), the solid, rigid support (B) is provided with a single-piece component (31, 31') having an L-shaped profiled cross-section comprising a substantially vertical branch (32) that extends along a corresponding side of the enclosure (A) and a substantially horizontal branch (33) that extends underneath the latter, forming at least one part of the base (3) of the solid support (B) that rests upon the ground.

Description

CIRCULATION DUCT OF LIQUID UNDER PRESSURE AND METHOD FOR ITS PRODUCTION The present invention relates to a fluid circulation duct, possibly buried below a shaft and more particularly provided for the circulation of fluid under high pressure, of the order of several bars. The invention relates more particularly to the construction of ducts having a very large cross section, for example greater than 2 m 2, but it can also be advantageously applied to the construction of ducts having more common dimensions. The invention also covers methods for the construction of these ducts. A fluid transport duct can be made simply in the form of metal or concrete tube elements, juxtaposed together and whose ends are inserted one inside the other, with interposed joints. In case of collapse, some elements may come loose and therefore, to withstand relatively high pressures, it is preferable then to use metal tubes whose elements are welded to their adjacent ends, for example, in the case of forced duct for hydro plants. -electrical. In this case, the pipeline is composed of prefabricated pipe elements or curved panels, which are transported to the site and welded there. At that time, however, the tube is not under pressure and can deform as it acquires an oval shape, which makes the welding more difficult since the sheets would no longer be aligned. In addition, such pipes must often be buried, for example in the case of pipes or pipelines. When the tube is under pressure, it can easily withstand the loads applied externally by the embankment. But the pressure can vary and even become negative with respect to the outside. There is then a high risk of tube deformation. For these reasons, the tubes formed by welded metal elements exhibit a relatively limited section, very often smaller than 2m2. The inventor has studied for several years a new technique to produce pipelines for the transport of fluid under pressure which do not exhibit such drawbacks. With such technique, the pipeline is composed of a thin-walled sealed tube, usually a metal tube, secured to a rigid support body, usually made of reinforced concrete or prestressed concrete. Thus, the metal tube allows the system to be sealed and able to withstand internal pressure, while the thin wall is only subjected to tensile stress, and while the concrete body gives rigidity to the pipeline while resting on the surface lying on an enlarged surface allowing distributing applied loads and better resist differential sinking. - In the technique described in WO96 / 00867, the concrete support body advantageously consists of three sections, respectively: a horizontal base resting on the ground and two supporting lateral parts that form vertical extremities along each contour of the tube, whereby the assembly exhibits a U-shaped profile that encircles the entire lower section of the tube. Said tube therefore consists, as a straight section, of four panels, respectively a lower panel applied on top of the base, two side panels applied respectively above both lateral extremities and an upper panel with two lateral edges which connect tangentially to the corresponding ends of two side panels. Said panels. The sides are supported by both ends of the support body and their opposite edges can thus be perfectly aligned for welding purposes. Such a duct can easily be made from prefabricated elements whose length is compatible with the transport and handling capacities. The inventor went even further in his studies visualizing the simplification of the production technique of such a pipeline, in particular to make the different prefabricated elements lighter and to facilitate their installation, while preserving the various advantages offered by the technique up to that time. The invention therefore relates, in general terms, to a fluid circulation duct, comprising a sealed tube fixed on a rigid support body forming a base resting on a positioning surface, said tube having a longitudinal axis and is constituted by a strong thin wall closed on itself to form a sealed tubular enclosure having an upper part and a lower part, said tube is applied and fixed on an internal face of said support body. According to the invention, the support body comprises, on one side or the other side of the tubular enclosure, a single-piece portion having, in cross-section, an L-shaped profile comprising a substantially vertical branch which forms a lateral wing of the support body extending along the corresponding side of the lower part of the tube and a substantially horizontal branch extending below said lower part of the tube and forming at least a portion of the base of the body of support that rests on the recumbent surface. It is of particular advantage, at least over a certain length of the tube, that both lateral wings and the base of the support body form a single U-shaped part. According to another embodiment, at least over a certain length of the tube , the support body comprises two pieces of L-shaped profile whose horizontal branches connect on one or the other side of the median plane of the tube passing through the longitudinal axis, in order to form a continuous base. Normally, the support body is made of reinforced concrete. The reinforcement can be conventionally made to support the applied loads, in particular the loads that tend to extend the lateral sections apart. However, according to another particularly advantageous distinguishing feature, the assembly can be made of at least one curved sheet, embedded in the concrete support body and having two branches, respectively horizontal and vertical, each extending within the corresponding branch of each L-shaped portion of the support body. Preferably, to ensure the continuity of transmission of the loads, each L-shaped side part of the support body comprises an internal face for the application and fixing of the enclosure, whose orientation varies gradually between a substantially horizontal lower section and an upper section. substantially vertical. Other useful features are the subject of the subclaims. But the invention will be better understood by the following description of certain preferred embodiments which are given by way of example and are represented in the appended drawings, wherein: Figure 1 is a schematic, cross-sectional and perspective view of a portion of a duct according to the invention; Figure 2 schematically shows the deformation conditions of a duct, in case of depression with respect to the outside; Figure 3 illustrates another preferred embodiment; Figure 4 is a detailed view of the other preferred embodiment of Figure 3; Figure 5 is a cross-sectional view of yet another preferred embodiment; Figure 6 is a detailed view of a means for joining the tube on the support body; Figure 7 shows schematically the manufacture and transport of the prefabricated elements; Figure 8 shows another embodiment with an interconnecting crossbeam; Figures 9 and 10 illustrate modalities permitting the change of direction of the duct axis. Figure 1 is a schematic representation, in perspective, of a portion of a duct according to the invention and consisting, generally, of a tube A associated with a concrete support body B. The tube A consists of metal panels curved, welded along their adjacent edges, while the number of panels depends on the section of passage to be provided. For a passage section of about 2 meters in width, the tube A may comprise two panels only, a lower panel 1 constituting the lower part of the tubular enclosure and an upper panel 2 constituting the upper part, respectively, said panels 1 , 2, which are welded along their longitudinal adjacent edges 11, 21, 11 ', 21'. Each panel 1, 2 covers, in the direction of the longitudinal axis 0, 0 'of the duct, a length L that depends on the transport possibilities. The panels Ia, Ib, 2a, 2b of two successive sections of the tube are welded along their opposite transverse edges 12a, 12b, 22a, 22b to form a sealed tubular enclosure A which resists an internal pressure. The tubular enclosure A is applied above a support body B which encircles its entire lower section and therefore exhibits a U-shape comprising a base 3 and two side wings 31, 31 'which rise vertically along both lateral sides of the enclosure A. The assembly is symmetrical with respect to a vertical median plane Pl that passes through the longitudinal axis 0, 0 '. Both wings 31, 31 'of the base B extend upwards substantially at the level of the horizontal diametrical plane P2 of the tube, which passes through the axis 0, 0' and still, slightly above this plane in the preferred embodiment shown in FIG. Figure 1. Both lateral sides 13, 13 'of the lower panel 1 of the enclosure A can still reach above the plane P2 since they are stiffened by both wings 31, 31' of the base and their longitudinal edges 11, 11 'are therefore held parallel and aligned with the corresponding edges of the portion of the duct already provided, which facilitates the installation and welding of the top panel 2. The bottom panel 1 then encompasses an angular sector greater than 180 °, with an angle of -entrant, while the upper panel 2 covers the complementary angular sector. The upper part of the tube 1 made of the upper panel 2 and the sides 13, 13 'of the lower panel 1, which connect tangentially, advantageously exhibits the shape of a sector of a cylinder of revolution centered on the axis 0, 0'. , at least down to the diametrical plane P2. Thus, the enclosure A is able to withstand the loads applied in the best conditions. Incidentally, the application of an internal pressure only determines the tensile loads in the metal wall which is easily calculated and whose thickness can be relatively small. It will be observed that the semicircular shape of the wall 2,13,13 'allows the latter to resist under the best conditions, not only an internal pressure but also external loads, for example, in the case of a duct buried under an embankment before pressurizing the fluid within the enclosure A. The lower portion 1 should not be semi-circular and may still be flat since the base 3 of the concrete support body B and the reinforcements thereof can be calculated in order to resist the bending efforts. In the preferred embodiment described in the prior patent application EP 0 767 861 of the same inventor, the support body consisted of three sections, respectively a base that extends below the lower section of the enclosure and two lateral support parts that hold the sides of the enclosure and which are pushed against the side faces of the base by bars of pre-tensioned ties. In an arrangement of this type, the connection between both lateral support parts and the base of the support body functions as a joint. In the present invention, conversely, at least the lateral portion 31 of the support body B placed on either side of the enclosure A is constituted by a single piece portion having, as a cross-section, an L-shaped profile which it comprises a substantially vertical branch 32 extending along the corresponding side of the enclosure A and a substantially horizontal branch 33 extending under the tube to form at least a portion of the base 3 that rests on the floor. Said arrangement makes it possible to guarantee the continuity of the transmission of the loads, whereby the extension efforts applied by the lateral sides 13, 13 'of the enclosure A on both wings 32, 32' of the support body B are absorbed by the base 3. of said body. Thus, it is possible to remove the pre-tensioned tie bars that were placed in the previous mode in the base, the latter subjected to high compression efforts. According to the invention, the base is subjected only to bending stresses resulting from the tendency to expand the sides 32, 32 'which are, moreover, compensated by the weight of the tube A and the application of the pressure on its lower face 14. The base 3 of the support body can then be made lighter and it is possible, even for very large sections, for example with a diameter of the order of 3 meters, to execute a single-piece support body such as depicted in Figure 1. The support body B will normally consist of reinforced concrete, for example as indicated as a partial section in Figure 1. The assembly 5 has then to exhibit the desired U-shape and can conventionally consist of the longitudinal reinforcing steel bars 51 associated with the transverse reinforcements 52.

The lower face 14 of the tubular enclosure may have a greater radius of curvature than that of the upper face 2 and may even be flat. However, the lower face 14, substantially horizontal, and the lateral sides 13, 13 ', substantially vertical, of the panel 1, are applied against the inner face 38 of the L-shaped part 31 of body B and it is preferable to provide a gradual transition between the vertical 32 and the horizontal 33 branches in order to guarantee the continuity of transmission of the stresses without any angular point. For purposes of exemplification, Figure 2 schematically represents, as a solid line, a duct according to the invention comprising a metal tube A associated with a concrete base B and, as a dot-segment line, the deformed A ' , B ', determined by calculation in the case of an excess pressure from the outside with respect to the interior of the duct, for example under the weight of an embankment. Obviously, the scale of the deformations has been amplified to make them more visible but it can be seen that, thanks to the continuous transmission to the base 3, 33, 33 'of the extension efforts applied to the wings 32, 32' of the body of concrete support B, the latter is gradually deformed whereby both wings 32, 32 'maintain the rigidity of the tubular enclosure on the sides 13, 13' of said enclosure without any risk of breakage at the junction with the concrete support body B. Thanks to the excellent distribution of stresses over the entire volume of the single-piece concrete support body B, the mass of said body can be considerably reduced with respect to the previously known preferred embodiments. To make the structure even lighter, "high performance concrete" can be advantageously used, with compression and tensile strength much higher than that of ordinary concrete, for example above 40 MPa. Such resistance stimulates interconnection and cooperation between the metal tube A and the concrete support body B. On the other hand, increasing the performances of the concrete allows the use of high strength steel. The thickness of the metal wall can then be reduced, and consequently, the overall weight of the elements likewise. On the other hand, as indicated in Figures 3 and 4, it is possible to improve the connection between the metal wall A and the support body B using the angle iron 7, 7 ', each forming at least one angle with a side 71 covering the upper face 30 'of each wing 32, 32' of the support body B and a side 72 extending upwards and tangent to the external face of the corresponding lateral side wall 13, 13 'of the thin wall A, at the outlet of the support body B. The side 71 is sealed in the concrete and the side 72 is welded on the external face of the lateral side 13, 13 'which is thus stiffened and held against the wing 32, 32 'of the support body B, which allows to avoid any separation risk subject to causing, for example, water ingress. The angle iron 7, 7 'is fitted with the sealing parts 73 and can advantageously cover the outer edge of the upper face 30' _ of the support body B to reduce the risk of concrete cracking. Preferably, the angle iron 7, 7 'extends along the entire face 30' of the support body B, but may also consist of simple sealing tabs, at a distance from one another. According to another particularly advantageous distinguishing feature, the continuous transmission of the forces in the support body B makes it possible to simplify the fabrication of the assembly, as shown in Figures 3 and 4. In this case, of course, the assembly can also consist essentially of a simple sheet 54 that is bent with the same curvature as the wall 1 of the enclosure A and the inner face 38 of the body B, said sheet 54 being embedded in the concrete 30. The perforations 55 provided over the entire surface of the sheet 54 guarantees the penetration of the concrete for a better interconnection. further, as indicated in Figure 4, the sheet 54 can also be provided, on both sides, with protruding elements 56 for complete interconnection. Both parallel sheets 1 and 54 connected by the concrete 30 cooperate, together with a curved transverse beam to absorb the separation forces of the lateral sides 32, 32 '. To avoid cracking, it is sufficient to place a light reinforcement 5 'at the corners of the support body B. For example a welded wire net, particularly along the outer faces of the support body. Thanks to the simplification of the reinforcement, as shown in FIG. 4, it is possible to provide at each angle of the support body a free space in which tubes 58 attached to the stop are placed which can be involved in the resistance of the body B and delineate a longitudinal space for the passage, for example, of electrical cables, ducts or longitudinal bars pre-tensioned. According to another advantageous feature shown in FIG. 4, the concrete 30 can be a fiber concrete comprising, as already known, several metallic fibers 57 distributed regularly in the concrete support body and oriented randomly. Thus, the concrete support body B can also be lighter. In general, to allow a random distribution of the metal figures 57, a fiber concrete with small particle size is made, the larger elements being practically less than 8 mm. In addition, adjuvants are frequently employed, particularly in the case of high performance concrete, to improve fluidity. Thus, during casting, a concrete of this type can easily flow into the reinforcement in such a way that there is often no need to apply vibrations. According to another very advantageous feature of the invention, in order to ensure an interconnection of the concrete body with the metal sheet A, it is contemplated to fix on the external face of the latter, a corrugated connecting piece preferably constituted by a metal wire mesh. having longitudinal bars 81 and transverse bars 82. Said wire mesh is obtained in the market and can be formed in a wavy manner by passing it, for example, between rollers having overlapping grooves, the corrugations are parallel to the longitudinal bars 81. Said mesh of corrugated wire can be easily deformed in the transverse direction and therefore the section 14 of the external face of the enclosure A where the concrete body is applied can be applied. The upper parts 83 of the corrugations can then be electrically welded, in a known manner, to the external face 14 of the wall 1 which forms a lost mold in accordance with that indicated in figure 6. If a concrete with fine granulation is used, particularly a high-performance fiber concrete, the latter can penetrate the portions 84 of the wire mesh that extends between the upper parts 83 in such a way that the wire mesh is fully integrated into the concrete and provides, after setting, a perfect interconnection between the enclosure A and the concrete body B. As shown in figure 6, at the upper level of the concrete body B, the connection can still be improved through an extension 85 of the wire mesh 8 that has an adequate profile. Thus, all risks of water penetration between the enclosure A and the concrete body B and the iron profile 7 previously described can be omitted. In addition, thanks to the use of a fiber concrete, the reinforcements 52, 54 previously described can be omitted. This feature continues to improve the flexibility of the structure. Thanks to the invention, the manufacture of the prefabricated elements and their implementation for the construction of a duct can be simplified. The lower portion 1 of the tubular enclosure A may consist, even in the case of large sizes, of sheet panels bent by pressing or bent by roll in order to provide the required curve. As shown schematically in Figure 7, to make a prefabricated element of the duct, the panel 1 is turned over and placed in the bottom of a mold 6 in order to form a lost mold. The panel 1 has been provided in advance, on the side of the top, with interconnection elements 53 such as for example welded profiles or a means for joining the tube on the support body as in the case of figure 6. After the installation of the side faces 61 of the mold and the reinforcement 5, casting is carried out in concrete up to the level required to provide the necessary thickness to the base B. It should be noted that the sheet-form reinforcement of Figures 3 and 4 can be fastened forward, at the requested distance, in panel 1. After fixing, the assembly is removed from the molding and is turned over. To manipulate the prefabricated element thus provided, it must obviously be provided with anchor points such as the rings 40 sealed in the concrete in the upper portion of the wings 32, 32 'and allowing slings to be hooked to the latter. If necessary, the rings 40 can also be welded to the angle iron 7 sealed on the upper face 30 'of the support body B. Such prefabricated elements can be easily transported to the construction site, for example on a trailer 62, such as indicated in Figure 6. It is thus possible to transport elements of very large sizes by road if the height h of the element, added to that of the trailer, remains compatible with the road gauge. Incidentally, it is sufficient to delineate the length L of the prefabricated element such that, when the latter is placed transversely in the trailer, the total width does not exceed that authorized. The upper panels 2 of the tube, consisting of bent sheets, can simply be stacked for transport to the place of use. For the production of the duct, after having prepared the installation surface C, the prefabricated elements are placed one behind the other along the longitudinal axis O, O 'while adjusting the levels and the positioning such that the lateral edges lia, llb of the panels 1 a, Ib of the element Bl to be installed and of the element B already installed, are placed in alignment with one another, whereby the corresponding transverse edges 12 a, 12 b contact each other. The upper panel 2 a can then be installed and the assembly can be welded along the lengthwise, longitudinal, 11, 21 and transverse junctions 12, 22. At each longitudinal end of the prefabricated element, the concrete support body B is stopped slightly hollowed out of the sheet 1 so as to leave between two consecutive elements bl, b2, a space 34 that makes the installation of the element and welding of the sheets easier. The longitudinal reinforcements 51 are provided with standby portions that are traversed with each other in this space 34 and are then embedded in a sealing mortar. The manufacture of the duct is therefore particularly simple, since the elements can be prefabricated in the manufacturing plant and then transported to the construction yard. However, for very large sizes, it is also possible to run the elements in the terrain site. The sheets 1, 2 can certainly be formed in the workshop and stacked on a trailer to be delivered to the patio, which only needs to be adjusted with the necessary moldings 6, so the mentioned ones are particularly simple. In the case of a large duct, the element can then be constructed near the yard on mobile prefabrication units. Obviously if the support body B can be made lighter, it must be calculated in relation to the circumstances of use. For exampleWhen the duct is located within the horizontal groundwater stratum, the concrete support body advantageously operates as a ballast and its mass is accordingly determined accordingly. But the invention is obviously not limited to the details of the preferred embodiments that have been just described, since other preferred embodiments can be contemplated without departing from the scope defined by the claims. For example, in order to make the support body even lighter, it would be possible, as indicated in Figure 3, to provide a circular profile to the tubular enclosure A which then resists the internal pressure by itself, without applying bending stresses. some above the base 3 that provides essentially for the rigidity of the enclosure, in particular during the assembly, and that serves to distribute the load over a large area. However, the total height H of the element is increased and, for a large passage section, the preferred embodiment with flattened base of Figure 1 will generally be preferable. In addition, the construction, according to Figure 7, of a tubular enclosure in two parts is particularly interesting for ducts having very large cross sections but, thanks to the advantages obtained, the invention can be applied in the case of ducts having dimensions most common, for example, with a diameter of 0. 5 meters. In this case, it is more profitable to make closed tubes directly. For example, in a known manner, a thin sheet with an important length can be rolled in an inclined manner, adjacent helical sides are welded to form a tubular enclosure that is cut into pieces that have a length consistent with the possibility of handling and transport. Said tubular piece can be placed between two side walls of a mold having, on both sides of the tube, two bottoms placed at the appropriate level, for example at the middle of the tube. Interconnection means, for example a corrugated wire mesh 8 are then fixed on the upper convex portion of the tube. As previously indicated, concrete can be cast into the mold, formed in this way up to a level above the top of the tube to provide the prescribed thickness to the concrete body. On the other hand, it is particularly advantageous to execute a U-shaped single-piece concrete support body, but it would also be possible, as shown in Figure 5, to provide two L-shaped portions 36, 36 'having ramifications. horizontal 33, 33 'that are connected in the median plane Pl of the duct. The enclosure would then be constructed to leave between the opposite faces of both branches 33, 33 'a free space 37 in which they would cross each other with longitudinal reinforcements, whereby the assembly is embedded in a sealing mortar to provide continuity of base. Additionally, the level of the longitudinal joints 11, 21 can be varied as can the number of the panels constituting the tube A. However, the height (h ') of the lateral sides 32, 32' must remain sufficient to maintain the rigidity of the sides 13, 13 'and of resisting a breaking stress by compression of the duct when it is subjected to a depression with respect to the outside. Obviously, the concrete support body B must be strong enough to allow the handling, transport and installation of prefabricated elements. In fact, thanks to the interconnection between the metal wall A and the concrete body B, the rigidity of the assembly is improved. However, for the support body B to be as light as possible, it will sometimes be more interesting to strengthen it by using a transverse link beam fixed at the upper ends of both wings 32, 32 'in order to ensure the stiffness of the lower element during handling operations. This support crossbar can be tightened removable, in order to be removed after the installation of the lower element, in order to mount the upper panel 2. However, such a link crossbar can also exhibit advantages after the construction of the duct. Incidentally as indicated in figure 8, it can be shaped like a tundish frame 41 of mechanical-welded construction, encompassing the duct and exhibiting an internal profile 42 identical to that of the upper wall 2. Such a frame 41 can also be affirmed previously to the upper panel 2 if the support body B is sufficiently resistant for the handling of the operations. The frame 41 then provides for the external protection and the reinforcement of the panel 2 whose thickness can be reduced, as long as said thickness can be calculated only in relation to the tensile loads caused by the internal pressure. The panel 2, reinforced in this way by one or more frames 41, will better withstand compression breaking when the pipe is depressurized with respect to the outside. A duct according to the invention still exhibits other advantages. For example, in the curved portions of the pipeline, successive concrete elements can be linked together to prevent the pipe from slipping. As indicated in Figure 8, the prefabricated elements can be easily constructed such that the transverse joint plane Q on which the transverse edges 12, 22 of the enclosure A are placed is offset from the median longitudinal plane Pl of each prefabricated element. in order to allow, gradually, a change of direction. The successive elements can then be interconnected by pre-tensioned tie bars 43 which can be advantageously inserted into the tubes 58 previously described with reference in Figure 4 and whose ends fall on the protuberances 35 provided, externally, at the ends of each element Bl , B2. Similarly, as indicated in Figure 9, the joint plane Q can be inclined relative to the horizontal axis in order to accommodate any variation of inclination of the positioning surface C. As indicated above with reference to the 6, to ensure the interconnection between the concrete body B and the tube A, it is particularly advantageous to fix in the latter a corrugated wire mesh 8 which is economical and can be easily realized. However, said perforated panel allows the penetration of the concrete and allows ripples to be formed in another way such as, for example, by using a grid forming a type of lattice obtained by stretching a thin plate divided into sections. In addition, the nature and characteristics of the wall constituting tube A must obviously be adapted to the fluid transported and to the applied pressure. In addition, it should be noted that the particular constitution of the tube allows the reduction of the wall thickness of the tube in comparison with the common metallic ducts. Thus, it can be interesting to manufacture the tube of a special metal such as stainless steel, the cost increase can be compensated by the elimination of the lining that is usually necessary to improve the flow conditions. In this case, it is particularly advantageous to improve the interconnection between the tube and the concrete through a corrugated wire mesh as shown in Figure 6. The reference signs inserted after the technical features mentioned in the claims have only the purpose to facilitate the understanding of the invention and not to limit its scope.

Claims (18)

1. CLAIMS A duct for the circulation of fluid, comprising a sealed tube (A) fixed in a rigid support body (B) forming a base (3) that rests on a placement surface (C), said tube having a longitudinal axis and is constituted by a thin resistant wall closed on itself to form a sealed tubular enclosure having an upper part and a lower part (1), which is applied and fixed on an internal face (38) of said support body (B), wherein the support body (B) comprises, on both sides of the longitudinal axis (0, 0 ') of the tubular enclosure (A), a one-piece portion (31, 31') having, in section transverse, an L-shaped profile comprising a substantially vertical branch (32) extending along the corresponding side of the lower part of the tube (A) and a substantially horizontal branch (33) that extends below this lower part of the tube to form at least a portion of the base (3) of the support body (B) that rests on the floor (C).
2. A duct according to claim 1, wherein at least over a certain length, the support body (B) is cast as a single piece, while the horizontal branches (33, 33 ') in both L-shaped portions ( 31, 31 ') join to form the base (3) of the support body (B).
3. A duct according to claim 1, wherein at least over a certain length, the support body (B) comprises two L-shaped shaped portions (36, 36 ') with horizontal branches (33, 33') whose opposite ends they are interconnected in the median plane (Pl) of the enclosure (A) that passes along the longitudinal axis (0, 0 ') in order to constitute a continuous base.
4. A duct according to any of the preceding claims, wherein the support body (B) is made of reinforced concrete.
5. A duct according to any one of the preceding claims, wherein each L-shaped section (31) of the support body (B) comprises an internal face (38) for applying and fixing the enclosure, whose orientation varies gradually between a lower section substantially horizontal and a substantially vertical upper section.
6. A duct according to claim 5, wherein the internal face (38) of both branches (32, 33) of each L-shaped section (31) as well as the corresponding sections of the tubular enclosure (A) have a curve radius which varies continuously without any angular point.
7. A duct according to any of the preceding claims, wherein each vertical branch (32, 32 ') of the support body (B) is at least partially covered with a metal part (7, 7') that forms at least one reentrant angle with one side (71) sealed on the upper face (30 ') of the branch (32, 32') of the support body (B) and one side (72) tangent to the lateral side (13, 13 ') of the enclosure (A), at the exit of the support body (B), and welded in the latter.
8. 8. A duct according to any of the preceding claims, wherein the support body is made of reinforced fiber concrete.
9. 9. A duct according to claim 1, wherein the support body (B) is made of a high performance concrete with a compressive strength greater than 40 MPa.
10. A duct according to one of the preceding claims, wherein at least in each L-shaped portion (31, 31 '), the support body (B) is constituted of concrete with a reinforcement (52) integrated within the concrete (30) and having two branches, respectively horizontal and vertical, each extending into the corresponding branch (32, 33) of the L-shaped portion (31) of the body (B).
11. A duct according to any of the preceding claims, wherein the support body (B) is constituted of concrete with a composite reinforcement - of at least one curved blade (53) integrated in the concrete (30) and substantially parallel to the lower section (1) of the enclosure (A), said sheet (53) reaches up to the vertical branches (32, 32 ') of the support body (B). .
12. A duct according to any of the preceding claims, wherein it relates to a number of spaced trough frames (41) distributed along the duct and having an internal face (42) surrounding the upper section (2) of the enclosure tubular (A). .
13. A duct according to any of the preceding claims, consisting of juxtaposed prefabricated elements, each extending over a certain length of the duct and each comprising a tube element (A) forming a tubular enclosure closed in cross section and having an outer face (14) with a section forming a lost envelope for molding an element of the concrete body (B). .
14. A duct according to claim 13, wherein each tube element (A) is constituted by at least two curved metal sheet panels, respectively a lower panel (1) having two parallel longitudinal sides (11, 11 ') and at least one top panel (2) having two side sides (21, 21 ') welded on the longitudinal sides (11, 11') of the panel, the concrete body (B) is molded into a section of the panel (1) between the longitudinal sides (11, 11 ').
15. 15. A duct according to any of claims 13, 14, wherein each tube element (A) is interconnected with the body member (B) by a joining means consisting of a perforated metal panel. (8) formed having undulations and applied on the molding section (14) of the external face (14) of the tube element (A), said corrugations each having an upper part (83) welded on said external face and a part of projection (84) between two consecutive upper parts, the body element (B) is constituted by concrete that is cast in said molding section (14) and that penetrates within said corrugations to completely cover the perforated panel 8.
16. A duct according to claim 15, wherein the perforated panel (8) is a wire mesh panel having rectilinear longitudinal bars (81) parallel to the longitudinal axis of the tube (A) and transverse corrugated bars (82). ).
17. 17. A duct according to claim 15, wherein the perforated panel is a metallic grid formed in such a way that it presents undulations parallel to the longitudinal axis of the tube (A).
18. 18. A duct according to claim 14, wherein at least two successive elements (Bl, B2) terminate, at their adjacent ends, by transverse connecting planes (Q) inclined relative to the axis (0, 0 ') of the tube (A), in order to ensure a change of direction of the axis (O, O ') of the duct. A method for constructing a duct constituted of prefabricated elements according to any of claims 14 to 18, wherein, for each element, at least two sheet panels are previously formed with the predetermined curve, respectively a lower panel (1) and a upper panel (2), protruding interconnecting elements (53, 8) are welded on the outer face of the lower panel (1), said panel (1) is placed on the bottom of a mold (6), the external convex face is turned upwards, the necessary reinforcement is placed and a concrete casting is applied that exceeds the upper level of the inverted panel by a minimum height and, after the setting of concrete and removal, the prefabricated conduit element is flipped over and the upper panel (2) is welded on the upper sides of the panel (1) to close the tube, the prefabricated elements made in this way are placed on the laying surface and joined together to constitute r the pipeline. A method for constructing a duct constituted of prefabricated elements according to claim 13, wherein a metallic tube is continuously manufactured by inclined lamination of a thin sheet having a long length and by welding the adjacent helical edges to form a closed tube, said tube is cut into tubular pieces that have a length consistent with the handling and transport possibilities, interconnection means (53, 8) are welded in a molding section (14) of each piece, said piece is placed in a mold (6), by turning the molding section (14) upwards, said molding (6) has two side walls (61) parallel to the longitudinal axis of the piece, and extend upwards on both sides of the latter, each side wall (61) of the molding (6) is connected to the wall of the tube (A) by a plate forming a bottom that is placed at an intermediate level that determines the height of the lateral part of the body, a concrete casting is applied in the mold thus formed up to a level that exceeds the upper level of the molded section (14) by a minimum height and, after the setting of the concrete and removal, the element thus manufactured is turned over and can be placed on a surface of application to build the pipeline .