Process for obtaining hollow structures such as ducts, grain tanks or shelters.

The present invention relates to a process for obtaining hollow structures, having the shape of a cylinder resting on the ground by one of its generatrices or a similar curved shape.

Such structures are typically large section conduits, for example beyond traditional industrial manufacturing of the order of 2 m /, buried or not, used for the supply of water or other fluid under pressure or without pressure , or for cable passages and / or other conduits or the movement and parking of people or vehicles "

The invention is also applicable to conduits of smaller cross section, for example up to 1 m, 311e is also applicable to obtaining structures of similar or relatively short formas usable as cellars, silos or atomic shelters or others.

Although the invention is essentially described with reference to ducts of large section, it is therefore not limited to this technical field.

a Technical fields - have been used for the installation of conduits intended for water supply, oil transport, cable passages, or other conduits, etc. · .. "

The most frequent technique consists in using tubular sections, with circular section, which are put end to end and assembled by various methods. This technique has drawbacks - which increase with the diameter of the pipe, even if the length is decreased

07252 sections: manufacturing, transport, handling and installation. Anyway, in addition to the manufacturing problems, problems of congestion arise as soon as we approach an outside diameter of 2.50m which corresponds to the normal limit of road gauges .For large flows, we have to provide several conduits in parallel, which is an expensive solution, or else to construct the duct on site, using masonry construction techniques, or even gallery work, which is also expensive and takes a long time to manufacture or carry out.

On the other hand, the circular shape of the conduits is, as we know, the best suited to the case of high internal pressures. It is also the easiest to obtain when making sections corresponding to the entire section of the conduit . On the other hand, it has drawbacks in other uses. A circular duct creates stresses in the soil that supports its weight, which present a maximum marked in its middle region. It follows that, if the soil is loose, significant differential settlements can occur after installation. The circular shape does not lend itself to the use of space when it is congested as is often the case in urban areas. Finally, the weight of the duct is comparatively too indeed, the material is, in the case of unitary sections each covering the entire section, distributed uniformly over the entire periphery while the constraints are not. <

To solve these various problems, it has been proposed, see for example patent DE 215 71 91 to construct cross-sectional conduits of form a3

07252 flattened at the base, by assembly on site of longitudinal elements prepared in advance, each corresponding to a part of the cross section of the conduit, and made of corrugated sheet. Such elements have only a very low resistance to external stresses, which makes the conservation of the shape of the section and of the seal of the joints uncertain. In addition, the corrugations increase the resistance of the conduit to the circulation of fluids.

Also known from patent FR 733,098 or US patent 2,400,071, techniques consisting in assembling a large number of elements of small dimensions each provided with transverse flanges used for assembly with neighboring elements. The large number of elements makes it necessary to give them an identical shape, which leads to the adoption of a circular section, and in this case, the resistance to stresses requires that the junctions are alternated in the longitudinal direction. In US Patent 2,400,071, provision has been made to take account of some of the stresses exerted on the wall, and to use elements of lower resistance for the upper part of the section of a tunnel than for the lower part, but on the one hand an assembly with alternating joints of elements of different characteristics has an uncertain solidity, and on the other hand this introduces an additional complication in the assembly by assembling a large number of small elements, while such an assembly is difficult to · · have perfectly executed by low-skilled personnel.

Thus, it appears that there is an unresolved care be07252 of a process which makes it possible to obtain hollow, cylindrical structures, resting on the ground along a generative skirt, with a section of flattened shape at the base, in particular of ducts with a large cross section, or similar structures, this process making it possible to achieve structures having high mechanical strength with manufacturing cost prices, transport and installation considerably reduced compared to current techniques.

The present invention therefore provides a process for obtaining cylindrical hollow structures, resting on the ground by a generator, with a section of flattened shape at the base, by assembly on site of longitudinal elements prepared in advance and each corresponding to a part of the cross section of the wall of the duct, and the elements of which intended for the lower part of the section have an overall transverse curvature that is smaller than the others, process which presents the particularity that one calculates in advance the stresses to which will be subjected in service said elements with lower transverse curvature and the other elements, and one prepares longitudinal elements without undulation whose material and / or 1-thickness are determined according to said constraints,

According to another interesting aspect of the invention, the latter provides a method for obtaining large cross-section ducts by assembling in situ longitudinal elements prepared in advance, each corresponding to only part of the cross section of the duct wall,

07252 and which presents the particularity:

- the optimal cross-sectional profile of the duct is determined by calculation, as a function of known parameters concerning the installation site, the conditions of use of the duct and its intrinsic characteristics:

- Said optimal sectional profile is divided into adjacent sections, each corresponding to a longitudinal duct element and together providing a substantially continuous interior surface; and

- The cross section of at least some of said elements is given a variable thickness to adapt it to the stresses exerted on the element considered.

Preferably, the shape of the longitudinal elements is determined so that at least some of the longitudinal joints between adjacent elements are located in the vicinity of the "stress nodes", that is to say points where the absolute value of the stresses transverse to the wall pass through a minimum.

In the generality of the cases, the structural joints according to the invention are not er. alternate arrangement. On the contrary, the longitudinal joints are an extension of each other on either side of each transverse joint.

The method according to the invention has a first advantage over the current technique, namely that the transport is facilitated. If it is indeed assumed that the maximum admissible dimension is 2.5m, the current technique only allows unit transport of sections.

07252 ons diameter, outside at most equal to 2.5 m.

If the elements according to the invention each correspond to a quarter of the section of conduit, this one may have, when finished, a diameter of about 3.5 m, that is to say a double face surO section, and if the elements correspond to a sixth of the section, this may have once finished a diameter of about 4.4 m, ie a surface of triple section. In addition, for the same height of 2.5 m, it will be possible to have, in the same volume, a considerable number of unit elements, stacked on each other, so that the same transport vehicle will be used at its expense. maximum useful. On the other hand, the total length of the junctions to be made, by welding or other means, is obviously increased. It should be noted that these are normally straight seals which are much easier to obtain or execute than circular seals, and that the number of the latter may on the contrary be reduced due to the larger size. unit length of the elements, permitted by their lower unit weight.

Another advantage of the invention results from the non-circular shape of the structure, the drawbacks of a circular shape have been indicated above.

In addition, thanks to the flattened cross section at the base, a considerable improvement in the distribution of the stresses generated in the underlying soil is obtained, and the movements thereof can be reduced very considerably. Another advantage of such shapes is a lower height with equal cross-section, which reduces excavation costs (earthworks,

07252 shields, drawdowns of groundwater, etc.). On the other hand, when the consistency of the bearing soil requires it (aquifer in particular) we can integrate into the pipe a ballast obtained by means of metal or concrete masses which come to hang, by an appropriate bolting, under the raft of said conduit. Of course, the weight of the ballast is calculated according to the data specific to the site concerned and each of the ballast elements can also be prefabricated. You can also anchor the conduit to the ground by this same bolting process which is made easier from the inside by the flattened shape of the raft.

On the other hand, the preliminary calculation of the constraints to which the elements of the pipe will be subjected, and the use of the result of this calculation to determine the thickness of each element, the variation of this thickness from one point to another of the section, the material of which each element is made and the location of the longitudinal joints, offer significant advantages ί

It is common, in fact, that the upper part of a conduit has only a protective role and is only subject to limited constraints. On the other hand, the weight of the fluid transported, when it acts of water or of another liquid / »obviously acts more at the lower part than at the top. In addition, the bare obte30 seal at the assembly joints allows the conduit to withstand internal pressures and, therefore, to be used in penstock. It will also be noted that, in its final form, the conduit constituting a homogeneous and mono07252 block assembly, it will not be necessary to make stops for changes of direction, generators of longitudinal thrusts. The possibility of adapting the thickness and the material of the element allows significant savings on the cost price and transport.

As mentioned above, the various elements can be of different thicknesses depending on the result of the stress calculation. They can also be made with different materials, provided however that, if necessary, the necessary precautions have been taken to avoid corrosion by the effect of electrochemical couples.

Among the preferred materials, mention may be made, for their low price and their ease of obtaining and assembly by welding and / or other means, ductile iron, but other materials can be envisaged alone or in combination, such than steel, aluminum alloys, other metals, plastics reinforced or not by fibers, reinforced concrete or not, prestressed or not. In these last two. In the latter case, it is obvious that the welds mentioned above are to be replaced by suitable connections.

In the case where the duct elements are produced by one-piece molding or else by continuous section profiling, in particular by spinning, of materials such as ductile iron, steel, reinforced concrete, resins, etc. a mold or tool is advantageously used, the cross section of which is profiled so as to reproduce, by acting on the internal surface. of the duct element, the above variations of optimal profile and also the dirty cross-over variation of the thickness.

Directional changes are obtained by precast elements, curved or cut sections, specially calculated and adapted to the imposed geometry,

The construction of a conduit according to the invention, that is to say by elements which correspond only to a part of the section but which can, by compensation, be of considerable length, poses specific problems at the time. assembly; these problems could be solved by the following assembly process, which is therefore in close connection with the main object of the invention. According to this method, the elements are initially assembled by connecting them both longitudinally and transversely by means allowing limited relative displacement of the adjacent elements and by inserting between them a seal made of flexible material, and then proceed to the final and rigid assembly of the elements together when the surrounding terrain and the entire duct have stabilized. Preferably, the initial assembly of the elements with each other is made by means of bolts passing through at least one of the elements through a hole widened accordingly.

However, other joining methods may prove to be more advantageous, in particular in joints where the high stresses impose significant wall thicknesses.

In these cases, it is preferable to operate according to one or more of the following methods.

- to make the longitudinal junction and possibly the transverse junction

07252

Θ duct elements, hollow or protruding parts are placed in the^z~ zones of the corresponding edges and able to cooperate by conjugation of shapes and / or forces for the creation of the necessary longitudinal and transverse joints;

- For the creation of longitudinal joints, a rib is formed on each of the edges of two elements to be joined and distributed along the two ribs thus formed locking means; ,

- The clamping means are rigid or elastic stirrups;

- The stirrups are fixed using risid or elastic pieces fitted between the inner surface of the stirrup and the side of the corresponding rib or else by elastic deformation of the stirrups themselves;

seals, of a profiled section corresponding to the edges of the longitudinal and transverse joints, are interposed between said edges and their tight tightening is ensured using said stirrups or else using collars, straps, prestressing cables or other means;

- In cases where the elements are formed of weldable or sealable materials, the longitudinal and transverse joints are made by adding material 'welding or corresponding sealing.

According to an advantageous modality, to facilitate the establishment and stabilization of the pipe, stabilizing elements with triangular longitudinal section are provided, on the sides of the underside of the pipe, these elements have a horizontal plane face. which is roughly at the bottom of

07252 the pipe, a flat face roughly vertical or inclined., and a face which matches that of the pipe. These stabilizing elements are preferably discontinuous and located from place to place along the pipe to prevent the lower element from tilting on its longitudinal axis after its installation *

These stabilizing elements can be fixed by bolting, welding or other on the

10. element of pipe structure. If it is obtained · by molding (concrete) they can also be one with it.

In addition to their interest in stabilizing the entire pipe, the stabilizing elements are advantageous in the case where the pipe is formed of elements some of which constitute the bottom and others side walls with a general-vertical orientation: by providing that the stabilizing elements are fixed beforehand on the side wall elements, or else are in one piece with these elements, these become capable of standing upright when resting on the ground, which facilitates the obtaining their junction with the background elements laid in pre25 mier. Then, the elements forming the top · can be put in place by placing them on the side wall elements.

In the case where the section of the hollow structure is relatively small, for example p a duct of 1 to 4 m approximately, it can be provided that the section of the duct is formed by only two elements, one of which corresponds to the lower part and alongside the conduit and the other forms a cover, These elements, or at least one par12

07252 tie of them can be made of concrete or other molded material.

According to another method of obtaining usable joints, in the case where the elements are made of concrete or other molded material, there are provided, on the edges of the longitudinal elements, angles of weldable or bondable material on which one fixes, after installation and, preferably after stabilization, flat parts for sealing in a material compatible with that of the angles.

In certain cases, in particular when it is a question of transporting or storing dangerous fluids, or for the construction of atomic shelters, it is advisable to obtain a perfect sealing even in the event of ground movements or explosion nearby, and if the elements are constructed of concrete or other material which could crack or lose its watertightness in another way, provision is made for a waterproof interior lining or lining, ... integral, or not elements of the structure.

In some cases, this covering can constitute a part of lost formwork for the elements of the structure. If the covering is in sheet metal or other metallic or non-metallic material weldable or stickable, flat pieces of the type indicated above can be welded or glued on the joints of this coating, or you can directly weld or glue the coating parts together at the points ”

If the structure, duct or shelter, is made up of concrete elements, this provides resistance to crushing, while an interior coating of sheet metal or not or plastic, welded, glued or applied by any coating provides an absolute seal against contamination or infiltration, radioactive or other, even if movements of the ground or due to an explosion have

C7252 distorted the structure.

The examples below relate essentially to ducts of large cross section, but it is easy to see that what is said there also applies to silos, shelters or similar structures.

In the case of a prefabricated atomic shelter, longitudinal wall elements are put in place, which can be made in the same way as for ducts of large section, and the shelter is closed at its ends by flat or curved transverse walls. Preferably, the shelter is given a substantially flat bottom, and the base or side elements are provided with lateral stabilization elements, integrated during manufacture or added later, so as to prevent the tilting of the shelter around its longitudinal axis.

Advantageously, a waterproof interior covering is provided, especially if the shelter is constructed of concrete.

The shelter can be set up very quickly, because it is made up of separate elements which can be easily transported to be assembled on site. It can be placed in a dig, which is then plugged in, or even, in some cases, simply placed on the ground. It will be noted that the flat base form provides improved resistance to the effects of blast, compared to a masonry shelter of cylindrical or parallelepiped shape.

The invention will now be described in more detail using non-limiting exemplary embodiments, illustrated by the drawings among

07252 which :

Figs. 1 to 3 are schematic cross sections of conduits according to the invention.

* Fig. 4 is a partial section illustrating an assembly method.

Fig. 5 is a schematic perspective view of a duct, the various sections of which are formed of longitudinal elements, the longitudinal and transverse assembly joints of which are highlighted,

Fig. 6 represents an example of duct elements having a gradual reduction in radial thickness towards the center,

Fig. 7 shows an example of duct elements having a gradual increase in transverse thickness from left to right.

Fig. 8 is a cross section of a longitudinal joint showing an assembly method with ribs and stirrups,

Fig. 9 shows an example of an interlocking profile of the corresponding edge of two duct elements to form a longitudinal ou'transversal joint.

Fig, 10 shows another example of profiling the edges of elements to form a longitudinal or transverse joint.

Fig. 11 shows yet another example of profiling the edges of elements to form a longitudinal or transverse joint.

Fig. 12 shows an example of an interlocking transverse joint whose sealing is ensured by an annular joint of special profile which is compressed using a ± 5

07252 appropriate strapping.

Fig. 13 is a cross section of the duct of FIG. 12, showing the strapping of the seal,

Fig. 14 shows the establishment of a joint in the case of reinforced concrete elements.

Fig. 15 is a diagram illustrating the results of stress calculations.

Fig. Here is a section of a hollow structure section in reinforced concrete corresponding to the calculation in Figure 16.

Fig. 17 shows another exemplary embodiment, specially adapted to conduits of small section.

Fig. 18 shows a method of obtaining the seal of the seal.

Fig. 19 shows a method of tightening the joint. .

Fig. 20 shows another mode of obtaining tightness.

Figure 1 shows, in solid lines, the section of a conduit 1 obtained by the method of the invention, and for comparison in dashes, the section of a circular conduit 2 of the same section.

The conduit according to the invention is obtained by assembling five elements of the same length.

Two basic elements 3 are substantially planar; two side elements 4 have a greater variable curvature downwards than upwards; the profile is completed by an upper element 5, with a circular arc section. The example shown corresponds, for information purposes, to a section of 10 m. The total height H is

2.40 m and the width L of 5.00 m, compare with

07252 the diameter D of the corresponding circular duct, which is 3.57 m, the excavation necessary for the duct according to the invention is plys wider at the base than for the circular duct, but it is less deep; and in total, the volume to be excavated can be lower and the work easier to do.

FIG. 2 shows another form of conduit according to the invention, in which the elements of the bottom 3a are slightly curved, and which comprises two upper elements 5a instead of one.

Figure 3 shows yet another embodiment, which has the particularity that the bottom element 3b forms a central wedge 6 * It is expected that the wedge is in the middle of the element 3b and is slightly flared so that elements are identical and stackable for transport, but of course other arrangements are possible. According to the conventional technique, the addition of a cunette poses an almost insoluble problem. *.

FIG. 4 illustrates an example of the mode of junction between two elements 4,. 5 placed as elements 4a and 5a in FIG. 2.

The element 4 is in a first phase provided with a connection plate 7, fixed by a weld 8, which can be executed in the factory or on site. This plate 7 has enlarged holes 9 which, during assembly, come into correspondence with enlarged holes 10 of the element 5.

At the time of assembly / insert between element 5 and plate 7 a

07252 flexible seal 11 made of elastomer or the like, then the joining is carried out using a screw 12 and a nut 13.

When the set of elements corresponding to the next section of the duct is mounted, slight relative movements of the elements 4 and 5 may appear, for example under the effect of variations in the level of the bottom of the excavation. Slight movements can also be the consequence of the compaction of the underlying soil.

All these movements are made possible by the widening of the holes 9 and 10. When these movements have ceased to occur, the elements can be definitively joined by welding 15 14. The screw 12, and the nut 13 can furthermore be removed, and the holes 9 and 10, or only one of the two, can be closed by welding.

In Figure 5, there is shown in schematic perspective view a conduit obtained by implementing the method according to the invention. This conduit comprises longitudinal elements such as Al, Bl, Cl, etc. for the first section A'1, S'1, Cl, .etc ... for the second section, and so on; these elements are linked together by longitudinal joints, JL1, JL2, JL3, JL4, etc ... and by transverse joints JT1, JT2, JT3, JT4, etc ...

The method according to the invention consists in a first step of determining in a known manner by calculation the optimal section profile of the duct as a function of the known parameters concerning the installation site, the intrinsic characteristics of the duct itself and its conditions. 'use. In the calculation we

C7252 involves forces stressing the conduit, in particular:

- the self-weight of the duct,

- the weight of the fluid passing through the conduit,

- the pressure to be established in the pipe, (forced pipe in particular),

- possible overpressures resulting from the use of hydraulic devices (valves, etc ...)

- the hydrostatic pressure of a sheet of water in which the conduit may possibly be embedded, s

- the charge of the fillings or the conduit is buried,

- fixed overloads possibly existing on the backfills,

- mobile overloads possibly requesting embankments,

- variations in temperature and humidity,

- support reactions, etc.

As indicated in the preamble, it is interesting to arrive at a profile whose lower part is fairly flattened and whose upper part corresponds to a curve resulting from the optimization of the computation of the stresses.

The second step consists in dividing the optimal section profile thus obtained into adjacent sections, each corresponding to a longitudinal element, * such as Al, Bl, etc., and together providing a substantially continuous interior surface, designated by S in the figure. 5.

The third step consists in giving the cross section of at least some of said elements a variable thickness to adapt it to the stresses exerted at the different points.

07252 of the section of the element considered. Thus we have highlighted in Figures 6 and 7 cross sections of conduit elements showing how can vary the thickness of material, This characteristic ca5 is extremely important, both for manufacturing as for transport and assembly of the element since the quantity of material, and consequently the weight and the cost price are defined, in the most exact manner possible, according to the parameters governing the production of the final duct. If we consider the application of the invention to the construction of pipelines, aqueducts, etc., of long lengths, we can easily see the influence of weight gain on the final profitability of execution of the work.

The duct elements according to the present invention can be made of different materials and be manufactured, in correspondence, by different methods. Thus it is possible to envisage the manufacture of elements such as Al, Bl, Cl, etc. of a metal such as ductile iron, spheroidal graphite iron, steel, aluminum alloys, etc. For such materials, it is possible to practice different methods such as, for example, casting piece by piece, continuous casting, spinning, forging, differential rolling, etc. All these processes make it possible to carry out homogeneously hollow or projecting parts to be used later, during assembly of the elements, for establishing longitudinal and transverse joints, as will be explained below,

It is also possible to realize

07252 duct elements made of materials other than metals, in particular reinforced concrete, plastics or resins reinforced or not with fibers, etc. In such conditions, the elements are produced by molding using molds or formwork, which also make it possible to obtain the above-mentioned projecting and recessed parts.

All the methods of using the materials defined above for the production of the duct elements according to the invention involve tools, molds, formwork, etc., which must take account of the characteristics of the method of obtaining con15 products according to the invention under the following conditions:

- the inner surface of the manufactured duct element must correspond to the optimal section profile of the duct, determined by calculation according to known parameters concerning the type of installation, the conditions of use of the duct and its intrinsic characteristics.

The expression `` optimal profile '' means, in the case of a pipe where the external conditions vary little, an average profile applicable to this pipe over a certain length,

- each element must have the overall dimensions allowing it to be assembled with the other elements of the conduit and the different thick21

252 their elements must be calculated to allow them to resist the constraints to which they are subjected,

The final waterproofing is obtained by different means appropriate to each material used, it is created from inside the duct, after final stabilization (compaction, compensation for expansion, compaction, etc.).

We will now describe how the various elements are assembled to form a conduit, with reference to FIGS. 8 to 12 which give some examples of the construction of longitudinal joints and transverse joints. Thus there is shown in cross section in Figure 4 a longitudinal joint established between the two conduit elements A1 and Bl, In this case there is provided, on either side of the points defined by the two surfaces 71,72 of elements A1, Bl, respective external longitudinal ribs 73, 74 which extend over the entire length of the corresponding duct elements. These ribs may be formed during the casting, spinning, rolling, or molding of the corresponding elements, or they may also be added by welding, in which case they may be discontinuous. These two ribs allow, as shown in FIG. 8, the simple and effective fixing of a locking stirrup 79, by means of wedges 76, 77 which are fitted in position between the stirrup and the corresponding rib by operating for example by hammering or any other similar process.

In order to absorb the reactions occurring in a direction perpendicular to the cross-sectional profile of the duct, it is suitable to give the lateral delimitation surfaces of the duct elements A1, Bl, etc., shapes allowing them to absorb the constraints in the best possible way, given all the parameters having

07252 relates to the conditions of manufacture and use of the conduit, and also of the material of which it is made. Thus, by way of nonlimiting examples, we have given in FIGS. 8, 9 and 10^& some models of profiles of said lae teraies surfaces for delimiting the duct elements. In Figure 8, the delimiting surfaces 71 and ~ 2 are inclined relative to the plane perpendicular to the profile · of the section of the conduit. Such profiling of the joint surfaces is suitable for example when the static loads exerted on the duct are predominant.

In FIG. 9, the two lateral delimitation surfaces of the duct elements A1, B1 which are designated by 79 and 80, have corresponding rounded shapes so as to absorb reactions exerted in both directions in said plane perpendicular to the profile section.

In FIG. 10, delimitation surfaces 82 and 83 have been shown which form steps making it possible to produce an interlocking.

In Figures 11, there are shown profiles 33 and 34 defining a cell 35 which can be filled with a sealing material for example of a cast resin.

It should be noted that all of these shapes of the lateral surfaces delimiting the duct elements can be perfectly produced by any of the aforementioned manufacturing methods. To establish a good seal, there is provided in each case, between the corresponding surfaces of the aforementioned longitudinal joints, coatings, sealants, fillings. Or au07252 very sealants, in particular rubber, natural or synthetic, as indicated respectively at 8 in figure 8, at 81, in figure 9 and at 84 in figure

10, « »

It should be noted in this regard that these seals provide a pressure seal.

In Figure 14, there is shown a longitudinal joint which is established between two elements 10 of conduit A1, B1 made of reinforced concrete. The respective reinforcements of the elements Al, El have been designated by 20 and 21. To achieve the junction, the frames 20, 21 are allowed to protrude during the molding of the elements and, once these latter have been put in place in the positions provided at the place of installation of the conduit, the parts are connected together extremes protruding from the respective reinforcements, as indicated in 22, then using suitable cover elements such as 26, a sealing mortar is poured at 23 in the existing interval in order to achieve the envisaged longitudinal joint.

In FIG. 14, angular and hollow profiles 25 have been highlighted at 24 and 25 from the connection edges of the elements Al, Bl.

These profiles are intended on the one hand to facilitate the attachment of the sealing mortar 23 and on the other hand to perfect the sealing of the joint by creating discontinuities serving to suppri30 mer localized leakage paths. 27 and 28 have designated shuttering holding members 26 which are fixed in position using nuts 29, 30.

07252 ·

In Figure 12, there is shown an embodiment of a transverse joint between two sections of conduit constituted respectively by elements such as AÏ, ... and 5 elements such as A'1 ... etc ... The boundaries of the transverse joint have been designated by 15 and 16. In the example considered, there is provided a peripheral seal designated as a whole by 1T and comprising on the one hand a radial mold which comes to fit in the gap existing between the surfaces 15, 16 and on the other hand by a peripheral ring whose internal surfaces are applied against the external surfaces of the respective duct elements, said ring comprising on its external peripheral surface raised portions 19, intended to be flattened by compression using a strapping or collar 18A, 18B, as shown in FIG. 9 which is a transverse section of the conduit of FIG. 12. In the example considered, given without limitation , the raised parts 19 may have a dovetail profile and include partitions in their notches in order to create a joint of the labyrinth rinth type. The flattening strapping is made • in two parts ISA, 18B connected together by tensioners 31, 32 which are actuated for final tightening.

It should be noted that, although all the exemplary embodiments of joints between duct elements do not involve bolting, such a process is absolutely not excluded and that it is possible to form or fix on the elements parts analogous to ledges

25'

07252

V f 'et'dés flanges. who. would then be assembled using bolts or the like.

In certain applications, it is possible, within the framework of the invention, to adopt. for the duct a mixed structure, that is to say on the one hand of elements formed of a first material, for example reinforced concrete, in a first part of the duct, for example in the lower part between 10 longitudinal joints JL1 and JL4 in FIG. 5, and on the other hand elements formed from a second material, for example a metal or a plastic material reinforced or not with fibers, in the remaining part of the duct. Such a mixed structure can be recommended in an open trench water supply structure, that is to say without high loads on the top of the duct, in a remote region where it is profitable to manufacture the lower part in molded reinforced concrete and the upper part in thin elements, prefabricated in the factory · 'and transported to the site.

• There figure 15 shows, in full line '.

'' the shape of the neutral fiber · of a section of conduit according to the invention (curve I), in dashes 25 (curved II) the distribution of the bending moment corresponding to the vertical thrust of the earth and in alternating lines (-curve III) the distribution of the bending moment corresponding to the lateral thrust of the earth. The complete calculation also includes the determination of a certain number of analogous curves, corresponding, for example, to the internal pressure of the dead weight of the pipe, etc. The calculation then comprises the combination of the results corresponding each

07252 to a type of constraint.

We observe.-that the complete profile of the • 9 section includes four zones of nodes ”, located one in the lower part of the pipe, the other towards its upper part.

Figure 16 shows the half-section of a conduit formed by four reinforced concrete elements.

observe that the thickness (h ^, hg) in the most

On zones which correspond to the strong constraints of figure 15, that is to say in the center of the base and on the sides is approximately

50% greater than the thickness hg at the top. The junctions JL1, JL2 between elements have been established in the zones, of nodes of constraint. In this figure, the reference designates the reinforcing bars embedded in the concrete of the elements prepared in advance and fg designates the anchoring bars, which have been folded over one another before being embedded in the concrete during construction of the structure.

FIG. 17 shows an exemplary embodiment adapted to ducts of relatively small cross section: 1.5 · to 4 m approximately. For the sake of simplification, the section of the pipe is divided into two elements which can be transported separately without special difficulties due to their · small dimensions. The lower element 40 is made of concrete, and produced by molding, it comprises the base ^ with a flat bottom and the sides. We also observe that it has stabilizing elements-41, which are one with it, and which allow its easy installation in a flat-bottom excavation. These stabi27 elements

252 Readers are volumes with a generally triangular cross-section, with a horizontal underside, these stabilizing elements not extending over the entire length of the element 40 for the purpose of lightening, The upper element 42 of the pipe is simpler in shape because it has the shape of an inverted gutter,

M with low curvature. It can be produced either by molding or by extrusion. In the case where the lower element 40 is produced by extrusion, it is clear that the stabilizing elements 41 are fixed later, but before the installation of the pipe, by screwing, welding or any suitable means. In FIG. 16, a stabilizing element 41 is shown in dashed lines. This figure highlights another advantage of this stabilizing element in the case of a structure whose section is formed of more than two elements. It is indeed seen that the side element A2, provided with the external stabilizing element 41 can remain alone in the final position. There is therefore no need to provide temporary support during the completion of the JL2 junction with the base element A3.

It will also be noted that in the case of a structure placed on the ground, the stabilizing element increases the resistance to lateral forces tending to overturn the structure, which is a risk in the case of an atomic or other shelter, which would be placed on the ground and exposed to the effects of breath.

FIG. 18 shows an embodiment of tight seals in the case where the elements

<img file="OA7252A_D0001.tif" />

C7252 elements are made of neither weldable nor stickable material, for example concrete:

Each element A1, A2 carries on its edges ü angles 43 of weldable or adhesive material, 5 for example of ferrous metal, put in place during molding if the element is obtained in this way. Flat elements 44 or other flat connecting elements made of weldable or stickable material on the angles 42 are welded or glued on these, possibly after stabilization of the ground.

FIG. 19 shows another means of assembling the structures according to the invention.

One of the elements Al, has a threaded hole

45, which can be provided in an insert 46. This hole. threaded being directed approximately perpendicular to the plane of the joint. The other element A2 has a shoulder 47 · pierced with a hole 48 in which a screw 49 is inserted which is screwed into the hole 45 through 20, making the hole 48 play with play.

FIG. 20 shows another embodiment of joint sealing, in which the elements A1, A2 of concrete, are provided internally with a sealing coating 50 made of sheet metal, for 25 mant lost formwork. An inner flat element 44 is then welded directly onto this covering 50. An angle iron, similar to that of FIG. 18, can be provided on the other edge of the elements A1, A2.

It is pointed out that a certain number of assembly arrangements described above are used for the installation of the duct and are not intended to contain alone, essentially, the hydrostatic pressures in the case of 'use in penstock, these hydrostatic pressures being partly compensated by the thrust of the embankments.

07252

To better secure the elements of a conduit, shelter or other and facilitate the realization of the joints, one can optionally provide, in addition to the prestressing cables forming the strapping, cables or prestressing bars connecting together adjacent longitudinal elements in the sense of length from each other. These cables or bars can each interconnect at least two consecutive elements ", for example, an element can be connected to the element which follows it by a set of cables or bars, to the element" which precedes it by a similar clearance, which allows to operate the prestress gradually as the installation progresses. Provision may also be made for each pre-stress cable or bar to connect three or more consecutive elements together.