AU2299800A - Pressurized liquid circulation duct and method for the production thereof - Google Patents

Description

1 This invention relates to a fluid circulation conduit, possibly buried under an embankment and more particularly intended for the circulation of fluid under high pressure, in the order of several bars. The invention relates more especially to the construction of conduits 5 having a very large transverse section, for example exceeding 2 M 2 , but may also be advantageous for the construction of conduits having more common dimensions. The invention also covers methods for constructing such conduits. A fluid transportation conduit can be made simply in the form of metal or 10 concrete pipe elements, butt jointed and whose ends are inserted into one another, with interposed joints. In case of sinking, some elements may come loose and therefore, to resist relatively high pressures, it is preferable to use metal pipes whose elements are welded at their adjacent ends, for instance, in the case of forced conduit for hydro-electrical plants. 15 In such a case, the conduit is composed of prefabricated pipe elements or of curved panels, which are transported to the site and welded there. At that moment, however, the pipe is not under pressure and may deform while taking an oval shape, which makes welding more difficult since the sheets would not be aligned.any longer. 20 Besides, such pipes must often be buried, for instance in the case of pipelines or gas-lines. When the pipe is under pressure, it can easily sustain the loads applied externally by the -embankment. But the pressure may vary and even become negative with respect to the outside. There is then a high risk of deformation of the pipe. 25 For all these reasons, the pipes performed by welding metal elements exhibit relatively limited section, most often smaller than 2 m 2 . The inventor has been studying for several years a new technique to produce conduits for the transportation of fluid under pressure, which do not exhibit such shortcomings. 30 With such a technique, the conduit is composed of a sealed thin-walled 2 pipe, normally a metal pipe, fastened to a rigid supporting body, usually made of reinforced concrete or preloaded concrete. Thus, the metal pipe enables the system to be sealed and to resist the internal pressure, whereas the thin wall is solely subjected to traction stresses, whereas the concrete body makes the 5 conduit rigid while bearing upon the laying surface on a widened surface enabling to distribute the loads applied and to better resist differential sinking. In the technique described in the document EP 0 767.881, the concrete supporting body consists advantageously of three sections, respectively a horizontal base bearing on the ground and two lateral bearing parts forming 10 vertical legs along each side of the pipe, whereby the assembly exhibits a U shaped profile surrounding the whole lower section of the pipe. The said pipe therefore consists, as a cross-section, of four panels, respectively a lower panel applied onto the base, two lateral panels applied respectively onto both lateral legs and an upper panel with two lateral edges which connect tangentially to 15 the corresponding ends of two side panels. The said side panels are held by both legs of the supporting body and their opposite edges can be thus perfectly aligned for welding purposes. Such a conduit can be easily made from prefabricated elements whose length is compatible with the transportation and handling capacities. 20 The inventor went even further in his studies with a view to simplifying the production technique of such a conduit, in particular to make the various prefabricated elements lighter and to facilitate their installation, while keeping the various advantages provided by the art so far. The invention therefore relates generally to a fluid circulation conduit, 25 comprising a sealed pipe fixed on a rigid supporting body forming a base bearing on a laying surface, said pipe having a longitudinal axis and being constituted of a thin resistant wall closed upon itself for forming a sealed tubular enclosure having an upper part and a lower part which is appreciated and fixed on an internal face of said supporting body. 30 According to the invention, the supporting body comprises, on either side 3 of the enclosure, a single-piece portion having, in cross-section, an L-shaped profile comprising a substantially vertical branch forming a lateral wing of the supporting body extending along the corresponding side of the lower part of the pipe and a substantially horizontal branch extending beneath the said lower 5 part of the pipe and forming at least a portion of the base of the supporting body resting of the laying surface. Particularly advantageously, at least over a certain length of the pipe, both lateral wings and the base of the supporting body form a U-shaped single piece. 10 According to another embodiment, at least over a certain length of the pipe, the supporting body comprises two L-shaped profile pieces whose horizontal branches connect on either side of the medium plane of the pipe passing through the longitudinal axis, in order to form a continuous base. Normally, the supporting body is made of reinforced concrete and the 15 reinforcement can be made conventionally to sustain the loads applied, in particular, loads tending to spread the lateral sections apart. However, according to another particularly advantageous feature, the reinforcement may be made of at least one curved sheet, embedded in the concrete supporting body and having two branches, respectively horizontal and vertical, extending 20 each into the corresponding branch of each L-shaped portion of the supporting body. Preferably, to ensure transmission continuity of the loads, each L-shaped lateral part of the supporting body comprises an internal face for application and fixation of the enclosure, whose orientation varies gradually between a 25 substantially horizontal lower section and a substantially vertical upper section. Other advantageous features are the subject matter of the sub-claims. But the invention will be understood better by the following description of certain embodiments given for exemplification purposes and represented on the appended drawings, 30 Figure 1 is a schematic view, as a transversal and perspective section, of ar: 33 01 53 04 % uu 4 a portion Of a conduit according to the invention. Figure 2 shows schematically the deformation conditions of a conduit, in case of depression with respect to the outside. Figure 3 Shows an another embodiment. Figure 4 is a detailed view of the lateral part of the supporting body. 5 Figure 5 is a transversal sectional view of another embodiment. Figure 5 is a t ed vew of a means for joining the pipe to the supporting shows schematically the execution and the transportation of the Io prefabricated elements. Figure 8 shows an another embodiment with an interconnection crossbeam. d 10 illustrate embodiments enabling to change the direction Figures 9 an of the conduit axis. presentation, in perspective, of a portion of a conduit Fccording to the invention consisting, generally, of a pipe A associated with a concrete supporting body B. The pipe A consists of curved metal panels, welde aongrteir adupt edges, whereas the number of panels depends on welded along their adjacent tinoebu ersi the passage section to be provided. For a passage section of about 2 metres in 20 width, the pipe A may comprise two panels only, respectively a lower panel I 0 ontituting the lower part of the tubular enclosure and an upper panel 2 constituting the upper part, said panels 1, 2 being 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 conduit, a length L depending on 25 the transportation possibilities. The panels la, ob, 2a; 2b of two successive sections of the pipe, are welded along their opposite transversal edges 12a, 12b, 22a, 22b, in order to constitute a sealed tubular enclosure A resisting an internal pressure. plied onto a supporting body B which The tubular enclosure A is apple onto bits a U-shape comprising 30 surrounds its whole lower section and ar: 33 01 53 04 64 00 HP a 5 a base 3 and two lateral wings 31, 3' going up vertically along both lateral sides of the enclosure A. The assembly is symmetrical with respect to a vertical medium plane I passing through the longitudinal axis 0, 0'. Both wings 31. 31' of the base B extend up substantially to the level of 5 the horizontal diametrical plane P2 of the pipe, passing through the axis 0, 0' and, even, slightly above this plane in the embodiment represented on Figure Both lateral sides 13, 13' of the lower panel 1 of the enclosure A may still reach above the plane P2 since they are stiffened by both wings 31, 31' of the 10 base and their longitudinal edges are therefore held parallel and aligned 10 wbasetad therongidial edges of tion of the conduit already provided, with the corresponding edges of the poe Iding of the upper panel 2. The lower which facilitates the installation and the we the 18*, with a re-entrat panel 1 then covers an angular sector greater than angle, whereas the upper panel 2 covers the complementary angular sector, a5eTheupersart of the pipe I made of the upper panel 2 and of the sides 15 The upper pnel 1 which connect tangentially, exhibits 13, 13' of the lower panel I, ofaclne revolution centred on the advantageously the shape of a sector Of a cylinder of Thuthe entre A is axis 0, o', at least down to the diametrical plane P2. Thus, the enclosure A is able to resist the loads applied in best conditions. Indeed, the application of an 20 internal pressure solely determines the traction loads in the metal wall which is easily calculated and whose thickness may be relatively Snals- it should be noted that the semicrcular shape of the wall 2,13, t enables the latter to resist in best conditions, not only an internal pressure but also external loads, for instance, in the case of a conduit buried under an embankment before 25 pressurising the fluid inside the enclosure A. The lower portion I does not to be seBi-eircular and may even be flat since the base 3 of the concrete supporting body 3 and the reinforcements thereof can be calculated in order to resist the bending stresses. In the embodiment described in the previous patent application 30 EP 0 767 861 of the same inventor, the supporting body consisted of three 6 sections, respectively a base extending beneath the lower section of the enclosure and two lateral bearing parts which maintain the sides of the enclosure and which are pushed against the lateral faces of the base by preloaded tie rods. 5 In such a disposition, the junction between both lateral bearing parts and the base of the supporting body works as an articulation. In the present invention, conversely, at least the lateral portion 31 of the supporting body B placed on either side of the enclosure A, is constituted of a single-piece portion having, as a transversal section, an L-shaped profile which 10 comprises a substantially vertical branch 32 extending along the corresponding side of the enclosure A and a substantially horizontal branch 33 extending beneath the pipe to form at least a portion of the base 3 bearing on the ground. Such a layout enables to guarantee the transmission continuity of the loads, whereby the spreading stresses applied by the lateral sides 13, 13' of the 15 enclosure A on both wings 32, 32' of the supporting body B are absorbed by the base 3 of the said body. Thus, it is possible to remove the preloaded tie rods which were tightened in the previous embodiment, into the base, the latter being thus subjected to high compression stresses. According to the invention, the base is 20 solely subjected to bending stresses resulting from the spreading tendency of the sides 32, 32' which are, besides, compensated for by the weight of the pipe A and the application of the pressure onto its lower face 14. The base 3 of the supporting body can then be made lighter and it is possible, even for very large sections, for instance, a diameter in the order of 3 25 metres, to execute a single-piece supporting body such as represented on Figure 1; The supporting body B will, normally, consist of reinforced concrete, for instance as indicated as a partial section on Figure 1. The reinforcement 5 must then exhibit the desired U-shaped and may consist, conventionally, of 30 longitudinal reinforcing steel rods 51 associated with transversal reinforcements 7 52. The lower face 14 of the tubular enclosure may have a curvature radius greater than that of the upper face 2 and can even be flat. However, the lower face 14, substantially horizontal, and the lateral sides 13, 13', substantially 5 vertical, of the panel 1, are applied against the inside face 38 of the L-shaped part 31 of the body B and it is preferable to provide a gradual transition between the vertical 32 and the horizontal 33 branches in order to guarantee transmission continuity of the stresses without any angular point. For exemplification purposes, Figure 2 represents schematically, as a full 10 line, a conduit according to the invention comprising a metal pipe A associated with a concrete base B and, as a mixed line, the deform A', B', determined by calculation in the case of an excess pressure from the outside with respect to the inside of the conduit, for example under the weight of an embankment. Obviously, the scale of deformations has been amplified to make them 15 more visible but it can be seen that, thanks to continuous transmission to the base 3, 33, 33' of the spreading stresses applied to the wings 32, 32', of the concrete supporting body B, the latter deforms gradually, whereby both wings 32, 32' maintain the rigidity of the tubular enclosure at the sides 13, 13' of the said enclosure without any risk of breakage at the junction with the concrete 20 supporting body B. Thanks to the excellent distribution of the stresses over the whole volume of the single-piece concrete supporting body B, the mass of the said body can be reduced considerably with respect to the embodiments known previously. 25 To make the structure still lighter, "high performance concrete" can advantageously be used, with compression and traction resistance far greater than that of the ordinary concrete, for example above 40 MPa. Such a resistance stimulates interconnection and co-operation between the metal pipe A and the concrete supporting body B. On the other hand, increasing the 30 performances of the concrete enables to use high resistance steel. The 8 thickness of the metal wall can then be reduced and, consequently, the global weight of the elements as well. Moreover, as indicated on Figures 3 and 4, it is possible to improve the junction between the metal wall A and the supporting body B using angle iron 7, 5 7', each forming at least one angle with a side 71 covering the upper face 30' of each wing 32, 32' of the supporting body B and a side 72 extending upwards and tangent to the external face of the corresponding lateral side 13, 13' of the thin wall A, at the outlet of the supporting 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, 10 13' which is thus stiffened and held against the wing 32, 32' of the supporting body B, which enables to avoid any risk of separation liable to cause, for instance, water ingress. The angle iron 7, 7' is fitted with sealing parts 73 and may advantageously cover the external edge of the upper face 30' of the supporting 15 body B to reduce the risks of concrete cracking. Preferably, the angle iron 7, 7' extend along the whole face 30' of the supporting body B, but they can also consist of simple sealing tabs, at a distance from one another. According to another particularly advantageous feature, continuous 20 transmission of the stresses in the supporting body B enables to simplify the execution of the reinforcement, as represented on Figures 3 and 4. In such a case, indeed, the reinforcement can also consist essentially of a simple sheet 54 which is bent with the same curvature as the wall 1 of the enclosure A and the inside face 38 of the body B, said sheet 54 being 25 embedded in the concrete 30. Perforations 55 provided over the whole surface of the sheet 54 guarantee the penetration of the concrete for better interconnection. Moreover, as indicated on Figure 4, the sheet 54 can also be provided, on both its faces, with protruding elements 56 for complete interconnection. 30 Both parallel sheets 1 and 54 connected by the concrete 30 co-operate 9 together as a curved crossbeam in order to absorb the spreading stresses of the lateral sides 32, 32'. To avoid cracking, it suffices to place in the angles of the supporting body B, a light reinforcement 5', for example a welded wire netting, in particular along the 5 external faces of the supporting body. Thanks to the simplification of the reinforcement, as shown on Figure 4, it is possible to provide, at each angle of the supporting body, a free space in which are placed pipes 58 butt jointed which can be involved in the resistance of the body B and delineate a longitudinal space for the passage, for instance, 10 of electric cables, of ducts or of longitudinal preloaded bars. According to another advantageous feature represented on Figure 4, the concrete 30 can be a fibre concrete comprising, as already known, a plurality of metal fibres 57 distributed regularly in the supporting body of the concrete and oriented randomly. Thus, the concrete supporting body B can also 15 be made lighter. Generally, for allowing a random repartition of the metallic fibres 57, a fibre concrete is executed with small ballast, the bigger elements being practically less than 8 mm. Moreover, adjuvants are often used, particularly with high performance concrete, for improving the fluidity, Thus, during casting, 20 such a concrete may flow easily into the reinforcement, so that vibration is often not necessary. According to another very advantageous feature of the invention, for ensuring interlocking of the concrete body with the metallic sheet A, it is foreseen to fix on the external face of the latter, a waved junction piece which is 25 preferably constituted of a metallic wire netting 8 having longitudinal bars 81 and transversal bars 82. Such wire netting is to be found on the market and may be waved, for example by passing it between rolls having imbricated grooves, the waves being parallel to the longitudinal bars 81. Such a waved wire netting can be easily deformed in the transversal direction and thus may 30 be applied on the section 14 of the external face of the enclosure A on which is par: 33 01 53 04 64 00 10 then be electrically applied the concrete body. The tops 8 3 1 of the waves ma th iechfrmsa weledina known manner, on the external face 14 of the wall 1 which forms a welded, in 6a ndwcae on te exta concrete with fine granulation is used, lost mould as indicated on Figure 6., the latter may penetrate in the particularly a high performance fibre concrete,en the top 83 so that the wire 5 parts 84 of the wire netting extending betwe the matter setting, a perfect netting is totally embedded in the concrete and bring te B. a phownct interlocking between the enclosure A and the concrete body t. As shown on Figre , o th uper eve ofthe concrete body B, the junction May be still Figure 6, on the upper level Of th cneetting 8 having an adequate profile improved by a prolongation 85 of the wir netin te enclosure A and the 10 Thus, all risks of penetration of water between th scribed angle iron 7 may concrete body B may be avoided and the previously de be omitted. f fibre concrete, the other previously Moreover, thanks to the ueoafbrcoctthohrpevus de drefoements 52, 54, may be omitted. Such a feature still improve , described reinforcementsu, 15 the flexibility of the structure.. the execution of the prefabricated elements and Thanks to the invention, f odit may be simplified. their implementation for the construction of a condu may consist, even for The lower portion 1 of the tubular enclosure A May cist evie great sizes, of sheet panels which are pressbent or rollbent in order to provide 20 the requested curvature. As shown schematically on Figure 7, to execute a prefabricated element of the conduit, the panel I is turned over and placed at the bottom of a mould 6 in order to constitute a lost mould. The panel 1 has been provided in advance, on the extrados side, with interconnection elements 53 such as welded profiles or a means for joining the pipe to the supporting 25 body as in the case of Figure 6. After installing the lateral faces 61 of the mould and the reinforcement 5, the concrete is cast up to the requested provide the necessary thickness to the shape reinforcement of Figures 3 and It should be noted that the sheetshaped dincemon the panel 1. 4 could be fastened in advance, at the requested distance, d and turned over. 30 After setting, the assembly is removed from the mou ar: 33 01 53 04 64 00 kA 11 To handle the prefabricated element thus provided the former must obviously be provided with anchoring points such as rings 40 sealed in the concrete at the upper portion of the wings 32, 32' and enabling slings to be hooked to the latter. if needed. the rings 40 can also be welded to the angle 5 iron 7 sealed on the upper face 30' of the supporting body . sily to the Such prefabricated elements can be transpoted easile to the construction site, for example on a trailer 62, as indicated on Figure 6. It is thus possible to transport elements of very large sizes by road if the height h of the element, added that of the trailer, remains compatible with the road gauge. 10 indeed, it suffices to delineate the length L of the prefabricated element so that, the latter being placed transversally on the trailer, the whole does not exceed the authorized width. stin of bent sheets, can be simply The upper panels 2 of the pipe, consi 9 stacked for their transportation to the site- after having prepared the installation 15 For the execution of the conduit, ae one behind the other along surface C, the prefabricated elements are placed e and the positioning so that the longitudinal axis 0, 0' while adjusting the levels B1 to be installed the lateral edges 11a, 11b of the panels Ia, plb of the element oB em ntale and of the element B already installed, are placed in the alignment of one 20 another, whereby the corresponding transversal edges 12a, 12b contact each o The upper panel 2a can then be installed and the assembly can .be welded along the joints, respectively longitudinal 1,21 and transversal 12,22. At each longitudinal end of the prefabricated element, the concrete 25 supporting body B is stopped slightly recessed from the sheet I in order to leave between two consecutive elements Be, B2, a space 34 which males the installation of the element and the welding of the sheets easier. The longitudinal reinforcement 51 is provided with standby portions that cross one another in this space 34 and are then embedded in a sealing mortar. 30 The execution of the conduit is therefore particularly easy, since the 12 elements can be prefabricated in factory and then transported to the building yard. However, for very large sizes, it is also possible to execute the elements on sitc. The sheets 1, 2 can Indeed be formed in the workshop and dWAked on 5 a trailer to be delivered to the yard, which only needs to be fitted with the necessary moulds 6, whereby the latter are particularly simple. In the case of a large conduit, the element can then be constructed close to the yard on mobile prefabrication units. Obviously, if the supporting body B can be made lighter, it must, 10 however, be calculated in relation to the circumstances of use. For instance, when the conduit is located inside the groundwater table, the concrete supporting body advantageously operates as ballast and its mass is therefore determined accordingly. But the invention is obviously not limited to the details of the 15 embodiments that have just been described, since other embodiments may be contemplated without departing from the scope defined by the claims. For instance, to make the supporting body still lighter, it would be possible, as indicated on Figure 3, to give a circular profile to the tubular enclosure A which resists then by itself the internal pressure, without applying 20 any bending stresses onto the base 3 which provides essentially for the rigidity of the enclosure, in particular during assembly, and serves to distribute the load over a great surface. However, the total height H of the element is increased and, for a large passage section, the embodiment with flattened base of Figure 1 will be, generally, preferable. 25 Moreover, the construction, according to Figure 7, of a tubular enclosure in two parts is particularly interesting for conduits having very large cross sections but, thanks to the obtained advantages, the invention may be applied for conduits having more common dimensions, for example from a diameter of 0,5 metres. In this case, it is more advantageous to execute directly closed 30 pipes.

13 For example, in a known manner, a thin sheet with a big length may be biased rolled, the adjacent helicoidal sides being welded for constituting a tubular closed enclosure which is cut in pieces having a length consistent with the possibility of handling and transporting. 5 Such a tubular piece may be placed between two lateral walls of a mould having, on either side of the pipe, two bottoms which are placed on the adequate level, for example on the middle of the pipe. Interlocking means, for example a waved wire netting 8 are then fixed on the upper convex portion of the pipe. As previously indicated, concrete may then be cast in the mould thus 10 constituted until a level above the upper part of the pipe for giving the prescribed thickness to the concrete body. On the other hand, it is particularly advantageous to execute a U-shaped single-piece concrete supporting body, but it would be possible, also, as represented on Figure 5, to provide two L-shaped portions 36, 36' having 15 horizontal branches 33, 33' which connect in the medium plane P1 of the conduit. The enclosure would then be constructed in order to leave between the opposite faces of both branches 33, 33' a free space 37 in which standby reinforcements of both elements cross one another and co-operate with longitudinal reinforcements, whereby the assembly is embedded in a sealing 20 mortar to provide the continuity of the base. Besides, the level of the longitudinal joints 11, 21 can be varied as well as the height (h') of the lateral sides 32, 32' but the latter must remain sufficient to maintain the rigidity of the sides 13, 13' and resist a crushing stress of the conduit when subjected to a depression with respect to the outside. 25 Obviously, the concrete supporting body B must be resistant enough to enable handling, transportation and installation of prefabricated elements. Indeed, thanks to the interlocking between the metallic wall A and the concrete body B, the rigidity of the whole is improved. However, to make the supporting body B as light as possible, it will be, sometimes, more interesting to strengthen 30 it using a linking crossbeam fixed on the upper ends of both wings 32, 32' in 14 order to provide for the rigidity of the lower element during handling operations. This back-up crossbeam can be fastened removable, in order to be removed after installation of the lower element, in order to mount the upper panel 2. However, such a linking crossbeam can also exhibit advantages after the 5 construction of the conduit. Indeed, as indicated on Figure 8, it can be shaped as a cradle 41 of mechanical-welded construction, spanning the conduit and exhibiting an inner profile 42 identical to that of the upper wall 2. Such a cradle 41 can also be fastened in advance to the upper panel 2 if the supporting body B is sufficiently resistant for handling operations. The cradle 41 then provides 10 for the external protection and reinforcement of the panel 2 whose thickness can be reduced, whereas the said thickness can be calculated solely in relation to the traction loads caused by internal pressure. The panel 2 thus reinforced by one or several cradles 41, will better resist crushing when the conduit is depressurised with respect to the outside. 15 A conduit according to the invention exhibits other advantages still. For example, in curved portions of the conduit, the successive concrete elements can be linked to one another in order to prevent the conduit from slipping. As indicated on Figure 9, the prefabricated elements can easily be constructed so that the transversal jointing plan Q in which are placed the 20 transversal edges 12, 22 of the enclosure A is tilted with respect to the longitudinal medium plane P1 of each prefabricated element in order to enable, gradually, a change of direction. The successive elements can then be interconnected by preloaded tie rods 43 which can advantageously be inserted into the tubes 58 desuUibod previously with reference to Figure 4 and whose 25 ends bear upon bosses 35 provided, externally, at the ends of each element B1, B2. In a similar way, as indicated on Figure 9, the jointing plane Q can be tilted with respect to the horizontal axis in order to suit any pitch variation of the laying surface C. 30 As indicated above by reference to Figure 6, for ensuring the interlocking 15 between the concrete body B and the pipe A, it is particularly advantageous to fix on the latter a waved wire netting 8 which is inexpensive and may be easily executed. However, such a perforated panel allowing the penetration of the concrete and able to be waved could be executed in another manner, for 5 example by using a grating forming a kind of lattice or a caillebotis obtained by stretching a thin plate split into blades. Moreover, the nature and the characteristics of the wall constituting the pipe A must be obviously adapted to the fluid transported and the pressure applied. 10 Then, it should be noted that the particular constitution of the conduit allows the reducing of the thickness of the wall of the pipe in comparison with the common metallic conduits. Thus, it may be interesting to execute the pipe in a special metal, for example stainless steel, the increasing of the cost being compensated by the suppression of the lining which is usually necessary in the 15 improving of the flowing conditions. In such a case, it will be particularly advantageous to improve the interlocking between the pipe and the concrete by means of a waved wire netting as shown on Figure 6. The reference signs inserted after the technical characteristics 20 mentioned in the claims are aimed solely at facilitating the understanding thereof and do not limit their scope in any way.

Claims (20)

1. A conduit for the circulation of fluid, comprising a sealed pipe (A) fixed on a rigid supporting body (B) forming a base (3) bearing on a laying surface (C), said pipe having a longitudinal axis and being constituted of a thin 5 resistant wall closed upon itself for forming 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 supporting body (B), wherein the supporting body (B) comprises, on either side of the longitudinal axis (0, 0') of the tubular enclosure (A), a single-piece portion 10 (31,31') having, in cross-section, an L-shaped profile comprising a substantially vertical branch (32) extending along the corresponding side of the lower part of the pipe (A) and a substantially horizontal branch (33) extending beneath the latter for forming at least a portion of the base (3) of the supporting body (B) resting on the ground (C). 15

2. A conduit according to claim 1, wherein at least over a certain length, the supporting body (B) is cast as a single piece, whereas the horizontal branches (33,33') of both L-shaped portions (31,31') meet to form the base (3) of the supporting body (B).

3. A conduit according to claim 1, wherein at least over a certain 20 length, the supporting body (B) is constituted of two L-profiled portions (36,36') with horizontal branches (33,33') whose opposite ends are interconnected in the medium plane (P1) of the enclosure (A) passing by the longitudinal axis (0,0') in order to constitute a continuous base.

4. A conduit according to one of the preceding claims, wherein the 25 supporting body (B) is made of reinforced noncroto.

5. A conduit according to one of the preceding claims, wherein each L-shaped section (31) of the supporting body (B) comprises an internal face (38) for application and fixation of the enclosure, whose orientation varies gradually between a substantially horizontal lower section and a substantially 30 vertical upper section. 17

6. A conduit 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 curvature radius which varies continuously, without any angular point. 5

7. A conduit according to any one of the preceding claims, wherein each vertical branch (32,32') of the supporting body (B) is covered at least partially with a metallic piece (7,7') forming at least one re-entrant angle with one side (71) sealed on the upper face (30') of the branch (32,32') of the supporting body (B) and one side (72) tangent to the lateral side (13,13') of the 10 enclosure (A), at the outlet of the supporting body (B), and welded onto the latter.

8. A conduit according to any one of the preceding claims, wherein the supporting body is made of reinforced fibre concrete.

9. A conduit according to claim 1, wherein the supporting body (B) is 15 made of high performance concrete, with compression resistance in excess of 40 MPa.

10. A conduit according to one of the preceding claims, wherein at least in each L-shaped portion (31, 31'), the supporting body (B) is constituted of concrete with a reinforcement (52) embedded inside the concrete (30) and 20 having two branches, respectively horizontal and vertical, each extending in the corresponding branch (32,33) of the L-shaped portion (31) of the body (B).

11. A conduit according to any one of the preceding claims, wherein the supporting body (B) is constituted of concrete with a reinforcement composed of at least one curved sheet (53) embedded in the concrete (30) and 25 substantially parallel to the lower section (1) of the enclosure (A), the said sheet (53) going up into the vertical branches (32,32') of the supporting body (B).

12. A conduit according to any one of the preceding claims, wherein it is associated with a number of spaced cradles (41) distributed along the conduit and having an internal face (42) surrounding the upper section (2) of 30 the tubular enclosure (A). 18

13. A conduit according to any one of the preceding claims, wherein it is composed of prefabricated juxtaposed elements, each extending over a certain length of the conduit and each comprising a pipe element (A) forming a tubular enclosure closed in cross-section and having an external face (14) with 5 a section forming a lost casing for moulding an element of the concrete body B.

14. A conduit according to claim 13, wherein each pipe element (A) is constituted by at least two curved panels of metallic sheet, respectively a lower panel (1) having two longitudinal parallel sides (11,11') and at least an upper panel (2) having two lateral sides (21,21') welded on the longitudinal sides 10 (11,11') of the panel, the concrete body (B) being moulded on a section of the panel (1) between the longitudinal sides (11,11').

15. A conduit according to one of claims 13, 14, wherein each pipe element (A) is interlocked with the element of the body (B) by a junction means constituted of a perforated metallic panel (8) which is formed for having waves 15 and is applied on the moulding section (14) of the external face (14) of the pipe element (A), said waves each having a top (83) welded on said external face and a projecting part (84) between two consecutive tops, the body element (B) being constituted of concrete which is caste on said moulding section (14) and penetrates inside said waves for entirely embedding the perforated panel B. 20

16. A conduit according to claim 15, wherein the perforated panel (8) is a panel of wire netting having rectilinear longitudinal bars (81) parallel to the longitudinal axis of the pipe (A) and transversal undulated bars (82).

17. A conduit according to claim 15, wherein the perforated panel is a metallic grating which is formed for presenting waves parallel to the longitudinal 25 axis of the pipe (A).

18, A conduit according to claim 14, wherein at least two successive elements (B1,B2) are terminated, at their adjacent ends, by transversal jointing planes (Q) tilted with respect to the axis (0,0') of the pipe (A), in order to ensure a change of direction of the axis (0,0') of the conduit. 30

19. A method for constructing a conduit constituted of prefabricated 19 elements according to one of claims 14 to 18, wherein, for each element, at least two sheet panels are previously formed with the predetermined curvature, respectively a lower panel (1) and an upper panel (2), projecting interconnection elements (53, 8) are welded on an external face of the lower 5 panel (1), said panel (1) is placed at the bottom of a mould (6), the convex external face being upward turned, the necessary reinforcement is installed and concrete is caste overpassing above the upper level of the turned panel by a minimal height and, after setting the concrete and removing, the conduit element thus prefabricated is turned and the upper panel (2) is then welded on 10 the upper sides of the panel (1) for closing the pipe, the prefabricated elements thus executed being placed on the laying surface and joined together for constituting the conduit.

20. Method for constructing a conduit constituted of prefabricated elements according to claim 13, wherein a metallic pipe is continuously 15 executed by biased rolling of a thin sheet having a great length and welding the adjacent helicoidal edges for constituting a closed pipe, said pipe is cut in tubular pieces having a length consistent with the handling and transporting pQssibilities, interconnection means (53,8) are welded on a moulding section (14) of each piece, said piece is placed in a mould (6) by turning the moulding 20 section (14) upward, said mould (6) having two lateral walls (61) parallel to the longitudinal axis of the piece, and extending upwards on either side of the latter, each lateral wall (61) of the mould (6) being connected to the wall of the pipe (A) by a plate forming a bottom which is placed at an intermediate level determining the height of the lateral part of the body, concrete is then cast in 25 the mould thus formed until a level overpassing the upper level of the moulded section (14) by a minimal height and, after setting of the concrete and removing, the element thus prefabricated is turned and may be placed on a laying surface for constructing the conduit,