EP0381547B1 - Method for laying an entrenched conduit - Google Patents

Abstract

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

Description

The subject of the invention is a system for producing buried conduits of various shapes and sizes each made up of a plurality of prefabricated elements by assembly on site, along a longitudinal axis and also covers the elements. prefabricated and the way they are presented.

Reference is made to Divisional Application EP 0585.959 published on March 9, 1994.

There are different types of buried conduits produced by assembling prefabricated elements and made up in particular of tubular sections aligned end to end along a longitudinal axis. Each tubular section may consist, for example, of a single element of circular section. In this case, the tubular sections are generally provided at their ends with parts, respectively, projecting and recessed, which fit into one another when the elements are installed and allow the latter to be joined.

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

This is why it has also been proposed to divide the wall of the duct into prefabricated elements, each tubular section being made up of a certain number of elements bearing on each other so as to constitute a closed section. Often, elements of a single type are used, each covering an arc of a given length and therefore making it possible to produce sections of circular section. However, it has also been proposed to use prefabricated elements of different shapes making it possible to produce sections of non-circular cross section and, for example, having a flat bottom allowing better distribution of the applied load on the ground.

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

In another embodiment which is the subject of French patent n ° 84 16811 by the same applicant, a duct has been described comprising, in cross section, only two elements, respectively a lower element forming a raft and an upper element in shape curved vault in an arc of a circle and resting, by means of its two parallel longitudinal edges, on support members formed along the two sides of the raft.

According to one of the characteristics described in patent FR 84 16811, the longitudinal support members formed on both sides of the slab consist of grooves with a curved hollow bottom in which engage the longitudinal edges of the arch element which have each a rounded convex profile of curvature slightly more marked than that of the groove so as to leave a slight clearance. Each longitudinal support thus presents a certain possibility of articulation around an axis parallel to the longitudinal axis of the conduit, each element arch can be deformed very slightly under the load transmitted by the terrain which surmounts it. This is transmitted to the two lateral sides of the raft which is made up of a massive rectangular panel resting on the ground by means of a fund rigid allowing to distribute well all the applied loads.

It appeared that such structures resist the loads applied in an active way by mobilizing, moreover, the surrounding grounds to which a part of the applied load is transmitted by lateral deformation of the upper element, the latter being thus unloaded with the key .

An article in the review "TRAVAUX" n ° 620 - April 1987 - Pages 46-53 (cf. the preamble of claim 1), explains the advantages of this new technique of making buried conduits and, in the case of the conduit four elements described in patent EP 081,402, indicates the possibility of making conduits of various shapes, either raised or lowered, by combining side elements belonging to a typical conduit of a certain dimension with basic elements and elements vault belonging to a standard duct of another dimension.

It is thus possible, using existing molds, to modify the general profile of the conduit so as to better adapt to needs, but the possibilities of adaptation remain limited.

These features have led to extending the possibilities of applying such conduits.

In fact, the arrangements described in the preceding patents, in particular EP No. 081 402 and FR 84 16811 were intended essentially for the production of ducts of very large section, which could even go as far as road gauges. In this case, given the very high cost of the entire structure, it is profitable to determine with precision, as required, the dimensions and the different characteristics of the elements, to calculate their resistance, for example by applying the method described in patent EP No. 081 402, and to make special molds or, in all cases, adaptable to the desired dimensions.

However, it has been found that structures of this type have such advantages that it could be advantageous to produce in this way conduits of medium section, which, until now, usually consist of tubular sections of circular section.

The invention, which applies to conduits with two elements, respectively a raft and a vault, gives, in fact, very wide possibilities of choice, thanks to an original system allowing to realize on demand and in a particularly fast way and economical, conduits having various shapes and dimensions and whose constitution and, in general, many characteristics can be determined as required with great flexibility of adaptation.

The system according to the invention applies to the production of buried conduits of the type described in particular in patent FR 84.16811 and each consisting of a series of contiguous sections placed one after the other, along a longitudinal axis , on the bottom of a trench, each section comprising, in cross section, a base element resting on the laying surface and an upper element forming an arch and resting on the base element by means of longitudinal support members parallel to the longitudinal axis and formed respectively on the lateral sides of the base element and of the upper element, said elements, respectively basic and superior which can have different shapes.

According to the invention, the system comprises an assortment of basic elements and superior elements immediately available from stock or capable of being immediately manufactured in a desired number, and whose dimensional and structural characteristics have been defined in advance, said elements being distributed in a certain number of series of basic elements each corresponding to a width between supports and in the same number of series of upper elements corresponding to the same widths between supports, each series comprising a certain number of basic elements or of superior elements differing from the apostles, in each series, by the shape and by at least one of the parameters determining the resistance of the element, such as the cross-sectional profile, the thickness and the constitution, the elements base and the upper elements compatible with each other, which can be combined in pairs so as to form, for each width between supports, a certain number of standard sections each corresponding to a passage section and to a maximum admissible load, the number of series and widths between supports being determined so as to cover, almost continuously, thanks to the choice of profile, a wide range of passage sections.

The invention also covers a method of making a buried pipe from prefabricated elements of the system.

In accordance with the invention, for each typical section which can be formed from a base element and an upper element of the system which are compatible with each other, the maximum distributed load admissible by the standard section considered under various conditions of use and, for the production of a duct which must have a passage section and a given size and subject to a given load, a standard section is chosen having an admissible load greater than the load to be applied to the duct and whose profile, taking into account the width between supports, makes it possible to optimally respect the passage section and the space required, and elements are taken from stock or manufactured in a desired number and upper sections presenting the profile, dimensions and structural characteristics of the element of the lower part and of the upper part of the selected standard section, then we co nstruct the conduit by assembling said elements.

In a particularly advantageous manner, in order to check the maximum admissible load by each typical section, the upper elements and the basic elements chosen from said series are produced in full size corresponding respectively to the different seat widths, each element of a series being produced , for each width, in a number corresponding to the possibilities of combination with the elements of another series and the base elements and the upper elements are associated in pairs so as to produce the standard sections envisaged, then subject each standard section thus formed in a load test applied to the key until the section ruins to deduce therefrom, by application of safety coefficients, the maximum distributed load admissible by the section considered.

The invention also covers the prefabricated elements distributed in several series and the profiles of the standard sections produced from said elements.

According to an advantageous characteristic, for the determination of the cross-sectional profiles of the basic elements, the height of the longitudinal support is varied in each series relative to the bottom of the element, each longitudinal support being provided, ie at the level of the upper face of the raft, or the upper part of a pedestal extending along each lateral side of the base element, perpendicular to the bottom and over a variable height.

But it is also possible, in the same series of basic elements, to produce elements of varied profiles having various useful characteristics such as, for example, projecting parts formed on the underside of the base of the raft to ensure the anchoring of this in the laying surface or else tubular recesses made in the thickness of the bottom parallel to the axis so as to produce internal channels extending over the entire length of the structure and through which can pass, for example electrical pipes or prestressing cables.

In addition, the bottom of the raft must have a sufficient bearing surface to collect the load supported but is not necessarily flat and, for example, it can provide an axial wedge projecting from the underside and engaging in a corresponding recess in the laying surface.

Similarly, in each series of arch elements corresponding to a determined width between supports, it is possible to vary the curvature of the element and in particular the ratio between the arrow and the width between supports; for example, it is possible to produce, for each width between supports, arch elements having a semicircular curvature, lowered elements having a basket handle curvature and raised elements having an ovoid curvature.

Furthermore, it is particularly advantageous to group together all the characteristics of the standard sections, in a catalog indicating the widths between supports of the different series of raft and arch elements available and, for each width between supports, the profiles of the sections types with indication of the cross-section and the maximum admissible load.

The invention also covers such a presentation of the construction possibilities.

In addition, the invention covers numerous variants which will be described in detail in the description which follows, with reference to the accompanying drawings.

FIG. 1 represents a first embodiment of a semicircular vault duct.

FIG. 2 represents a duct with a lowered vault in the basket handle.

FIG. 3 represents a duct with raised supports.

FIG. 4 shows by way of example two series of elements for implementing the method.

Figure 5 shows some examples of typical achievable sections.

Figure 6 schematically shows a failure test.

Figure 7 is a partial side view showing a particular embodiment of the longitudinal support between an upper element and a raft element.

Figure 8 is a partial top view showing, in a particular embodiment, a transverse joint interlocking between two consecutive raft elements.

Figure 9 shows, in cross section an alternative embodiment of a conduit according to the invention.

Figure 10 is a longitudinal section of the conduit of Figure 9 at its end opening into an embankment.

Figure 11 and Figure 12 are detail views showing two embodiments of the connection between two consecutive support elements.

FIG. 13 represents, by way of example, two series III, III ′ of support elements.

Figure 14 is a cross-sectional view of another embodiment.

FIG. 15 is a schematic perspective view of the conduit of FIG. 14.

In Figure 1, there is shown in cross section to the axis, a first example of a pipe section consisting of two types of elements, respectively a basic element 1 forming a raft placed on the ground and an upper element 2 in form of curved arch resting on the raft element 1. The elements 1 and 2 are made by molding, normally in reinforced or prestressed concrete, or in fiber concrete but other moldable materials can be used.

The conduit is placed in the bottom of a trench B which is open up to a leveled and compacted laying surface A placed at the desired level, the conduit being, after installation, covered with an embankment C. The conduit thus buried is therefore subject on the one hand to the load of the embankment which essentially depends on the height of the latter and, on the other hand, to loads applied, for example, on a roadway D fitted on the embankment.

The basic element 1 comprises a bottom 10 consisting of a solid reinforced concrete panel of rectangular shape provided, along its two lateral sides 11, with two longitudinal supports which, in the example shown, consist of grooves with curved bottom 72 placed substantially at the level of the upper face of the bottom 10.

The arch element 2 has a semicircular cylindrical shape, centered on a longitudinal axis (O), which can be placed either in the horizontal plane of the grooves 72, or at a height h above the upper face 13 of the strike off 1. For example, in the embodiment of FIG. 1, the arch element 2 is provided with two plane sides 21 tangent to the circular part 20 which make it possible to raise the axis O by the same height.

By retaining the semicircular shape of the arch, it is thus possible to vary the total height H of the duct by modifying the height of the flat parts 21 of the arch element 1.

Each end 22 of the upper arch element 2 is provided with a convex rounded edge 71 which engages in the corresponding concave groove 72 at the level of the upper face 12 of the base element 1. The rounded edge 71 a a slightly greater curvature than that of the groove 72 so as to provide a slight clearance allowing the lower parts 25 of the arch element to pivot very slightly on either side of the vertical plane P passing through the bottom of each groove 72. One thus constitutes, on each lateral side, a support member 7 articulated around an axis parallel to the axis (O) of the duct.

Therefore, as described in patent FR 84 16811, the arch element 2 can deform very slightly, thanks to its articulated supports 7.7 ′, under the action of the loads applied and it results therefrom a certain reduction in the stresses to the key, part of the load being taken up laterally by the embankment 32.

Each articulated support 7 must however be held laterally. To this end, each groove 72 is limited by raised edges 14 which, in the case shown in FIG. 1, where the grooves are placed at the level of the upper face 13 of the raft, have a height not exceeding 5 cm, this which allows the raised edges 14 to be produced when the concrete is poured without using a particular mold. The raft elements 13 can therefore be molded quickly and economically.

It is also possible, as described in patent FR 84 16811 to apply the edges 22 of the arch in the grooves 72 by means of tie rods 25 tensioned by bearing on parts 24 of the arch a joint seal being interposed between the edges 71, and the bottom of the grooves 72.

By varying the height h of the flat lower parts 21 of the arch element, it is possible to modify the total height H of the structure as well as the passage section S inside the duct.

But for the same width between supports, it is also possible to reduce the height H of the duct by giving the arch a lowered shape in the shape of a basket handle, as shown in FIG. 2. Of course, in this case, the section of passage S is also reduced. If it is necessary to respect a maximum height, the width of the raft can be increased and consequently the distance between supports L so as to ensure a determined passage section.

In addition, without modifying the profile of the vault, it is also possible to increase the passage section S of the duct by using, as shown in FIG. 3, a box-shaped radiating element comprising, along the two lateral sides, two sides 15 extending vertically over a variable height h1. Such an embodiment makes it possible to raise the level of the longitudinal supports 7 relative to the bottom 13 and will be suitable, for example when, the conduit is used for the passage of a height of water not exceeding, in normal service, the height of the supports 7. Such an arrangement makes it possible to keep the longitudinal supports out of the water as long as the flow transported by the conduit is normal, a greater flow, for example in the event of a flood, being supported by the entire conduit which can be pressurized if the roof 2 is connected to the raft 1 by the tie rods 25 and is supported by seals.

Figures 1,2 and 3 therefore show how one can choose the dimensions and the profile of the prefabricated elements to vary the passage section and the size, in particular the width L and the height H of the duct, according to the circumstances, including the conditions of use and the construction site.

In particular, the dimensional and structural characteristics of elements such as the thickness of the roof, the nature of the concrete and the structure of the reinforcement must be determined according to the constraints applied by the embankment and by the operating costs.

However, other characteristics could also be modified or added, as required.

For example, in Figures 1, 2 and 3, there are shown three types of rafts. In FIG. 1, the support members 7 are placed substantially at the level of the upper face 13 of the base element 1. In FIG. 2, on the contrary, the support members 7 are slightly raised and placed at the upper part of the sides 15 whose internal face 15 ′ is rounded so as to facilitate the flow of the transported liquid and to avoid deposits.

In FIG. 3, the sides 15 are still raised and the base element 1 has a box or shell shape of rectangular section, the upper element 2 having a semicircular shape. But we could also give the upper element 2 the same box shape, as shown in Example 205 of Figure 4, the entire duct then having a rectangular section.

Some accessories can also be added to the basic elements or to the upper elements.

Thus, in Figure 1, there is shown a basic element 1 having a flat bottom 15 which allows the installation on a surface A simply flattened and packed.

In FIG. 2, another example of a basic element 1 has been shown, the bottom 10 of which is provided, in its central part, with a wedge 17 formed in the axis and projecting from the underside 16 In this case , the laying surface A is provided with a recess A1 of section corresponding to that of the cunette, the two parts of the lower face 16 placed on either side of the cunette 17 obviously having to have a width sufficient for the transmission applied forces on the ground.

It has already been indicated, with reference to FIG. 3, that the basic element 1 can be provided on its sides with piers 15 making it possible to raise the longitudinal supports 7 by a variable height. This figure also shows , for example, a bottom 16 on which have been provided protruding parts 18 which form asperities for anchoring the raft 1 in the ground, for example to oppose side shifting effects.

The roof elements 2 can also be subject to variants, some of which have already been described.

We can thus determine in advance different forms of upper elements 2 and basic elements 1 which can be combined in any possible way.

Furthermore, for each profile, it is also possible to vary the parameters determining the strength of the concrete, such as the thickness of the vault, the nature of the concrete used and the construction of the reinforcement, the reinforcements possibly being prestressed.

In this regard, it may also be advantageous, as shown in FIG. 1, to provide, in the thickness of the base elements 1, tubular recesses 19 which are placed in alignment with each other when laid. elements 1 so as to form longitudinal channels in which it is possible to pass prestressing reinforcements then secured, in a conventional manner, by pouring a mortar.

Such channels 19 could also be used for example for the passage of pipes or electrical or telephone cables.

Advantageously, it is also possible, as shown diagrammatically in FIG. 8, to spare along the two transverse edges 8 of each base element 1 of the protruding parts 81 which engage in recessed parts 82 formed on the transverse edge facing the raft element 1 'adjacent.

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

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

In this case, as shown in side view in Figure 7, each longitudinal support member 7 has a slot profile. The convex profiled part 71 formed on each lower edge 22 of the upper element 2 in fact extends alternately on two different levels so as to include, for example, a projecting central part 71 framed by two recessed parts 73 which s 'engage in inverted parts formed in hollow 74 and projecting 75 on the upper edge of the raft element 1 and which are provided with a longitudinal groove 72.

Such a niche profile ensures the longitudinal maintenance of each upper element 2 with respect to the corresponding base element 1.

Of course, other similar arrangements, comprising hollow and protruding parts offset longitudinally, could be used.

It was thus necessary to define the characteristics of a certain number of profiles of upper elements and basic elements which, as shown in FIG. 4, can be classified in series each corresponding to a width between support.

The first series I of basic elements 1 therefore comprises a certain number of elements of the same width between supports L1 but having different profiles, dimensions, reinforcements, etc..

By way of example, in FIG. 4, the series I of basic elements comprises an element 101 in which the support members 4 are in the plane of the upper face 13 of the raft and one or more elements 102, 103 wherein the support members 4 are formed at the upper part of the corners 15 whose height h1, but also the shape, can vary. For example, the element 104 is provided with internal faces 105 which are curved so as to be tangentially connected to the bottom.

Furthermore, these basic elements can also be provided with accessory members such as, longitudinal conduits 19 or else notches 18 for anchoring formed on the underside 16 of the raft. Such accessories have been shown by way of example on the element 104 but could be provided on the other elements.

Similarly, the series II of upper elements 2 may include, for example, an element 202 lowered into a basket handle, an element 203 raised on flat side walls, an element 204 raised in ovoid shape, an element 205 in rectangular shell, element 206 in the form of a slab, etc.

Other characteristics such as thickness e, the nature of the concrete or the reinforcement may vary. For example, it is possible to produce elements having a reinforcement in one or two plies or elements made of concrete reinforced with fibers or in another moldable and resistant material.

For another distance between supports L2, a second series I ′ of basic elements will be produced in which a certain number of characteristics are varied such as the profile, the height of the longitudinal supports with respect to the bottom, the thickness, etc., and a second series II ′, of arch elements having different profiles, thicknesses or reinforcements.

We can thus define the characteristics of a certain number (a) of series I of basic elements and II of upper elements, each series corresponding to a width between supports, so as to cover as continuously as possible but in economically profitable conditions, a wide range of passage sections to meet customer needs. In practice, it is possible, for example, to define four series of base elements and of upper elements whose widths range between 1 m and 2.50 m, which makes it possible, depending on the profile adopted, to create passage surfaces from 0.35 m ² to 6 m ² , approximately.

The upper and base elements thus defined are all made in full size and in sufficient number to be able to be associated two by two in all possible and desirable ways, by forming a certain number of standard sections of the same width and whose profiles and passage section are significantly different.

Of course, the associated elements must be compatible and, for example, we will combine together arch elements and basic elements having thicknesses and reinforcements allowing them to withstand forces of the same order.

This produces, for each width between supports, different standard sections T ₁ , T ₂ , T ₃ .... corresponding to heights, passage sections and different resistances and some of which have been shown, by way of example , in Figure 5.

Having defined the dimensional characteristics of the elements that will be available, it is possible to calculate the reinforcement and the resistance by applying known calculation methods. However, according to one of the features of the invention, it will be preferable, in certain cases, to check the resistance of the elements by subjecting each typical section thus formed to a rupture test in an installation shown diagrammatically in FIG. 6 by a press P, any other system which can be used insofar as it makes it possible to apply to the key 23 of the arch element 2 a vertical force of variable intensity.

For each typical section, the load applied to the key 23 is gradually increased until the element fails. The breaking load of the considered standard section is thus determined.

However, for a given profile and arch thickness, it is possible to calculate the ratio between the bending moments resulting from the application of a point load to the key and a load distributed over the width of the element.

We can therefore determine, from the point load having caused the rupture, the distributed load which would have had the same consequence and, by applying a weighting coefficient easy to define between the service stress and the stress of rupture, we determine the maximum permissible load in service for the typical section tested.

Of course, all the characteristics, curvature profile, thickness, reinforcement, etc. of the two elements of each section have been noted.

All the sections T ₁ , T _2, etc. are thus subjected to a rupture test, which it is possible to constitute, for each width between supports, from the elements of the two series I of basic elements and II of upper elements and it is possible to draw up a table indicating for each width between supports and for each experimental section the passage section S and the maximum admissible load.

On this table, we can also add other characteristics allowing to define each element, for example its thickness, a profile drawing etc.

All this information is advantageously brought together in a catalog showing on the one hand the profiles of all the standard sections which can be produced and which have been subjected to a rupture test and giving on the other hand, in the form of a table, the 'set of useful characteristics and, for example, references making it possible to find, for a given standard section, all the characteristics of the elements which constitute it.

Such a catalog can be presented to the customer who first of all defines his needs and the conditions of use, in particular the desired passage section S, the overall dimensions in width L and in height H which must be respected and, of course, the characteristics of the construction site, in particular the height of embankment H1 above the duct.

We then determine, depending on the height and nature of the embankment and operating loads, the maximum load that will be applied in service on the duct, as well as the width between supports allowing to best respond to the space requirements to be observed and the various standard sections are indicated in the catalog, corresponding to an admissible load greater than the service load previously calculated and making it possible to ensure, under the best conditions, the desired passage section. The customer then chooses the section type allowing to meet, in an optimal way, all of its needs.

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

If the necessary elements are not in stock, they can however be made very quickly because all their dimensional and structural characteristics are already defined and we normally have the molds that were used to make the elements subjected to the preliminary tests. the customer orders elements having other accessory characteristics, such as internal pipes or anchoring members, or even slight variations in dimensions due to implantation requirements, the mold is simply adapted to obtain the casting, of these additional characteristics, all the other characteristics remaining well fixed.

The prefabricated elements are then produced in a desired number either in a factory or on the site and they are assembled to build the conduit.

In what follows, the statements relating to the replacement of each basic element by two separate support elements are not part of the invention

In the embodiments described so far, the lower part 1 consisted of one-piece prefabricated elements forming a continuous raft. It is possible, however, to replace each base element 1 with two spaced support elements 30 so as to constitute two support lines 3 separated by a free space.

Such an arrangement, which has been shown in Figures 9 and 10, could be useful, for example, for very large sections for which one-piece basic elements would become untransportable. Indeed, the support elements 30 form insulated soles whose width can be provided to provide a sufficient support surface. In particular, in the case of soils having good resistance, the width of the sole 32 could be reduced.

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

In the embodiment shown in Figures 9 and 10, each upper element 20 has the shape of a curved arch resting on the support elements 30 by its lower lateral edges, the latter having a rounded convex profile and fitting each in a groove 31 in the form of a concave chute formed on the upper face of each support element 20. This produces two longitudinal support members having a certain possibility of articulation of the upper element 20 relative to the two elements support 30.

As already described for the upper elements 2 and the basic elements 1, it is possible to produce at least a series III of support elements inside which a certain number of dimensional characteristics are varied. and structural such as, for example, the width of the seat surface, the height of the element, the shape of the support members 31, the nature of the concrete used and the constitution of the reinforcement, etc ....

For example, in Figure 13, there is shown schematically two series III, III ′ of support elements each corresponding to a width L ′ ₁ and L ′ ₂ of the seat surface and in which we have varies the shapes of the elements.

In addition to the series, I, I ′ .... of basic elements 1 and II, II ′ .... of upper elements 2, there is thus at least one additional series III of basic elements and, as required, it is therefore possible to combine the arch elements 20 chosen from the corresponding series, either with elements of the raft corresponding to the same width between supports, or with isolated support elements chosen from an additional series III, III ′ having a seating surface compatible with the bearing capacity of the ground.

The replacement of a monobloc lower element by two separate support elements does not significantly change the maximum admissible load because it depends essentially on the resistance of the arch, the role of the raft being essentially to transmit to the ground the load applied to the arch and provide a downward seal.

The space existing between the two separate support elements 30 may, as the case may be, be left free or else closed in any suitable manner corresponding to the use of the conduit.

In FIG. 9, for example, the lower part 4 of the duct consists of a base layer 41 of compacted aggregates, placed between the internal lateral sides 33 of the support elements 30 and covered with a slab 42 which can be made up of prefabricated elements or else cast in place by covering the upper faces 34 of the support elements 30.

We can thus, as shown in Figure 10, pass between the two support lines 3 a roadway 43 and we see that one of the advantages of this arrangement lies in the fact that the roadway 43 can be carried out without discontinuity and in a conventional manner inside and outside the duct, while lower concrete elements would require a connection with the outside pavement with the risks of offset due to differential settlement and expansion.

Furthermore, the planes of the transverse joints 23 between two consecutive arch elements 20 can be offset longitudinally relative to the plane of the transverse joints 35 between the support elements 30. In this way, the load applied by each upper element 20 is distributed on two consecutive support elements, on either side of the joint plane.

The transverse joints between two consecutive elements 30 can be made in different ways.

In Figure 11, for example, there is shown a sealed joint 5 between two consecutive elements 30, 30 ′. The latter are provided, on their front faces opposite, waiting frames 51 which intersect in a space 50 left between the two elements 30 and 30 ′ and which are associated with transverse irons 52, the assembly being embedded in a sealing mortar 53. The sealing joint 5 thus produced between the two consecutive elements 30 and 30 ′ constitutes a real keying in the longitudinal direction. By thus joining a certain number of consecutive elements, a monobloc sill is made over a determined length which makes it possible to distribute the load on the ground and to avoid differential settlement.

However, it is also possible, as shown in FIG. 4, to place at the opposite ends of two consecutive elements 30 and 30 ′, connecting members 54, 54 ′ which fit one into the other and can be connected by a pin 55. The two consecutive elements 30 and 30 ′ are thus connected to each other by an articulated connection giving each element a slight possibility of deviation from the elements which surround it.

Of course, the dimensions of the support elements 30 and in particular the width L ′ of their seating surface and their height H ′ will be chosen according to the circumstances of use, and in particular the loads supported and the bearing capacity of the ground.

Different profiles may also be provided. For example, for the production of underground pavements, at least one of the support lines 3 could consist of elements 30 shaped so as to have an upper face 34 ′ substantially horizontal and placed above the level of the pavement 4 so as to create a pedestrian traffic sidewalk.

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

For example, the internal side of the elements 30 could be provided with parts arranged to constitute or receive circulation rails of a trolley or gantry facilitating the assembly and / or maintenance of the structure.

According to another variant shown in Figures 14 and 15, the conduit is provided for the passage of liquid, for example from a river. In this case, the bottom 6 of the duct may advantageously consist of a series of plates 61 of cast iron, sheet metal or plastic, having a width equal to that of the duct and covering the space between the two elements 30, in going up on the upper faces 34 of these, up to the joints 31. As indicated in the figure, the plates 61 can limit a hollow profile, for example for the passage of a channel and the height H ′ support elements 30 can be increased so as to raise the level of the seals 31 to above the average water level, the bottom 6 thus limiting a sufficient section for average flow rates. Seals can be placed between the upper parts 31 of the support elements 30 and the upper edges 62 of each plate 6 so as to allow the water level to rise above the level of the edges 62 by filling more or less the conduit, in case of flood. The duct can even be pressurized if the lower edges 21 of the roof 2 are applied to the bottom of the grooves 31 by tensioned tie rods.

In addition, as shown in the perspective view of FIG. 6, the plates 61 can advantageously overlap each other in the manner of a covering, the transverse end 63 of a plate facing downstream, in the direction of flow of the liquid, covering the front end 64 of the next plate 69, with the interposition of a sealing bead.

Other methods of coating the bottom could obviously be used. It is possible in certain cases, that the longitudinal axis 10 of the duct is inclined relative to the horizontal and the support elements 30 may then have a tendency to slip. To avoid this, it will be advantageous to provide on the lower faces 32 of the elements 30, hooking notches 37 which can be produced during concreting or else, as shown in FIG. 6, be formed on a plate. cast iron 38 sealed on the underside of each support element 30.

As indicated in FIG. 15, in the event of a steep gradient, the seat faces 16 of the base elements 1 or 32 of the support elements 30 could form steps, the laying surface A constituting steps of corresponding widths.

To avoid any danger of skidding, the elements 30 can be anchored in the ground by transverse beams forming keys. The same applies to the upper elements 2 which can be keyed in relation to the basic elements 1.

According to another advantageous arrangement shown in Figures 10 and 15, is added to the upper elements 2 of the head pieces 9 placed at each end of the conduit.

Indeed, the conduit is buried under an embankment C and opens at each end in a slope C ′ which must be maintained by the two lateral sides. To avoid unnecessarily prolonging the conduit outside the embankment C, head pieces are advantageously used, each comprising a vertical wall 9 of triangular or trapezoidal shape, associated with a flange 90.

In Figures 2 and 6, for example, the sole 90 consists of one or more support elements 39 identical to those 30 which support the arch elements 20. Each head piece then consists of a plate 9 comprising a horizontal side 91 which rests on the upper part 31 of the corresponding support element 39, a vertical side 92 placed in the extension of the side 24 of the last upper element 25 of the duct, and an inclined side 93 whose inclination corresponds at the natural angle of slope C ′.

The wall 9 can be held in place by sealing between the vertical sides 92 and 24 facing each other or by fitting suitable parts sealed in the facing faces of said sides 91, 24.

In addition, the wall 9 is supported, in the longitudinal direction, on a stop 37 closing the chute 31 in which the horizontal side 91 engages.

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

Consequently, it is also possible to add to the series III, III ′ of upper and lower elements, a series of head pieces having different thicknesses, heights and possibly inclinations so as to be able to adapt to different cases of the best way.

In general, moreover, one could imagine other variants and other accessory arrangements, for example to make the bottom or the upper part of the duct differently.

Claims (20)

1. System for producing underground conduits with various shapes and sizes comprising each a series of joined sections placed one after the other along a longitudinal axis (0) on the bottom (A) of a trench (B), each section comprising in cross section a base element (1) resting on a laying surface (A) and an upper element (2) forming a vault and resting on the base element (1) via longitudinal bearing members (7,7') parallel to the longitudinal axis (0) and arranged respectively on the lateral sides (11) (21) of the base element (1) and of the upper element (2), said elements respectively the base element (1) and the upper element (2) being liable to have various shapes, characterized in that it comprises a plurality of various base elements (1) and upper elements (2) immediately available in stock or liable to be made immediately according to the required members and for which the dimensional and structural characteristics have been previously defined, said elements being distributed according to a certain number (a) of series (I,I'...) of base elements (1) corresponding each to an inter-bearing width (L₁,L₂...) and a same number (a) of series (II,II'...) of upper elements (2) corresponding to the same inter-bearing widths (L₁,L₂...) , each series (I,II...) comprising a certain number of base elements (101, 102...) or upper elements (201, 202...) differing each other, in each series, by the shape and by at least one parameter determining the strength of the element such as the profile in cross section, the thickness and the construction, the base elements (101, 102...) and the upper elements (201,202...) compatible each other being liable to be associated two by two in order to make for each inter-bearing width (L₁, L₂...) a certain number of standard sections (T₁,T₂,T₃...) corresponding each to a flow section and to a maximum safe load, the number (a) of series and inter-bearing widths (L₁,L₂...) being determinated so as to satisfy quasi-continously a great range of flow sections because of the choice of the profile.
2. System for producing conduits according to claim 1, characterized in that each series (I, I') of base elements (1) corresponding to a determined inter-bearing width (L) comprises at least elements formed from a rectangular panel forming a bottom (10) provided along its lateral sides (11) with elevated parts forming side walls (15), each provided, at its lower part, with a bearing part (72) of the upper element, the level of which, relative to the bottom, may vary from one element to the other within each series (I) (I').
3. System for producing conduits according to one of claims 1 and 2, characterized in that some of the base elements (1) of the series (I)(I') are provided on their lower face (16) with projecting parts (18) for anchoring the element to the laying surface (A).
4. System for producing conduits according to one of claims 1 to 3, characterized in that the foundation surface (16) of the base elements (1) forms tiered steps capable of being laid on top of stairs arranged on the laying surface A when the longitudinal axis (O) of the conduit slants.
5. System for producing conduits according to one of claims 1 to 4, characterized in that each series (I, I') of base elements (1) corresponding to a determined inter-bearing width (L) comprises at least one element whose bottom (10) is provided with an axial low water channel (17).
6. System for producing conduits according to claim 5, characterized in that the lower face (16) of the bottom (10) has a central part projecting relative to the lower level of the lateral sides (11) of the base element (1) and engaging in a corresponding recess (A1) arranged in the laying surface (A).
7. System for producing conduits according to claims 1 to 5, characterized in that each series (I, I') of base elements (1) corresponding to a determined inter-bearing width (L) comprises base elements provided, along their edges (8,8') transverse to the axis of the structure, with centering parts, projecting (81) and recessed (82) respectively, the projecting (81) and recessed (82') parts of two consecutive base elements (1, 1') fitting into each other when the said elements are laid.
8. System for producing conduits according to one of claims 1 to 7, characterized in that at least some base elements (1) are provided with one tubular recess (19) arranged in the thickness of the bottom (10) and parallel to the axis (O) such that the aligned tubular recesses (19) of several consecutive base elements (1) form an internal channel extending over the entire length of the structure.
9. System for producing conduits according to one of claims 1 to 7, characterized in that each series (II) of upper elements (2) corresponding to a determined inter-bearing width comprises elements (201, 202) having at least two different profiles selected from among various types of profiles, a surbased profile (202) with a three-centered curvature, a circular profile (20), an ovoidal elevated profile (204), a rectangular-box profile (205) and a plane-slab profile (206) respectively.
10. System for producing conduits according to one of claims 1 to 9, characterized in that each articulated longitudinal bearing member (7) comprises two profiled parts, convex (71) and concave (72) respectively, arranged projecting and recessed respectively along the opposite lateral sides (21) (11) of the upper element (2) and of the base element (1) of each section.
11. System for producing conduits according to claim 10, characterized in that the profiled parts, convex (71) and concave (72) respectively, extend alternately on two different levels so as to form, along each base element (1) and each upper element (2), profiles with inverted crenellations comprising, on the base element (1), recessed (74) and projecting (75) parts in which engage reversed parts arranged projecting (71) and recessed (73) respectively on the lateral sides (21) of the upper element (2) .
12. System for producing conduits according to one of the preceding claims, characterized in that it comprises at least one series of plates (61) having respectively widths substantially equal to each inter-bearing width (L₁,L₂...) and liable during the making of a conduit of being placed one after another so as to form the bottom (6) of the conduit, the said plates being made from moldable, injectable or rolled material such as metal, concrete or plastic materials.
13. System for producing conduits according to claim 12, characterized in that during the making of a conduit, the plates (61) are overlapping each other in a manner of a sequence of roofing tiles, the downstream end (63) of one plate (61) overlapping the upstream end (66) of the following plate (61').
14. System for producing conduits according to one of the preceding claims, characterized in that it comprises a plurality of head pieces (9) at least of one standard liable to be placed at each end (25) of a conduit protruding from a backfill (c') in the extension of the two sides (26) of the upper element of the last section of the conduit and comprising each a lateral wall element (9) having a substantially trapezoidal or triangular shape comprising a horizontal side (91) resting on the bearing footing (90), a vertical side (92) placed along the corresponding side (24) of the upper element (25) and an inclined side (93) whose inclination corresponds to the natural angle of the slope (C') of the backfill covering the conduit.
15. System for producing conduits according to claim 14, characterized in that it comprises a series of head pieces (9) in wich at least one of the parameters has been varied, such as the thickness of the wall (9), the height of the vertical side (92), the inclination of the inclined side (93) and the width of the bearing footing (90).
16. Method for producing an underground conduit from previously made elements of the system according to one of the preceding claims, characterized in that for each standard section (T₁,T₂...) liable to be produced from a base element (101, 102...) and an upper element (201, 202...) of the system mutually compatible, the maximum safe load for the standard section (T₁,T₂...) in question in various conditions of use is determined and for producing a conduit which is to have a flow cross-section (S) and a given size and is subjected to a given load, a standard section (T₁,T₂) is selected having a safe load greater than the load which is to be applied to the conduit and the profile of which, taking into consideration the inter-bearing width (L₁,L₂) enables the required flow cross-section and size to be respected optimally and base (1) and upper (2) elements are taken from a stock or manufactured in the desired number having the profile, the dimensions and the structural characteristics of the element of the lower part and of the upper part of the standard section selected, and the conduit is then constructed by assembling the said elements.
17. Method according to claim 16, characterized in that in order to check the maximum safe load for each standard section (T₁,T₂), the upper elements (201, 202) and the base elements (101, 102), selected from the said series (I, II) and corresponding to the various widths (L₁,L₂...) respectively, are made to their actual size, each element of a series being made, for each width, in a number corresponding to the possible combinations with the elements of another series and the base elements and the upper elements are combined in pairs so as to form the envisaged standard sections (T₁,T₂) and then each standard section (T₁,T₂) thus formed is subjected to a test where a load is applied to the soffit until the destruction of the section in order to deduce therefrom, by reapplying factors of safety, the maximum safe distributed load for the section (T_1,T₂) in question.
18. Method according to one of claims 16 and 17 characterized in that side walls (15) are arranged along the two lateral sides (11) of each base element (1) and perpendicular to the bottom (10) and the height of which is varied within the series (1) so that various levels (h₁) for the longitudinal bearing part (2) are available.
19. Method according to one of claims 16 to 18, characterized in that the curvature of the element, and in particular the ratio between the hog and the inter-bearing width, is varied in each series (II) of upper elements (2) corresponding to a determined inter-bearing width (L).
20. Method according to one of claims 16 to 19, characterized in that all the characteristics of the standard sections (T₁,T₂...) are grouped together in a booklet indicating, in particular, the inter-bearing widths (L₁, L₂...) and the widths and the foundation of the various series (I,I') of base elements (1) and (II, II') of upper elements (2) produced and, for each inter-bearing width (L₁, L₂...), the profiles of the standard sections (T₁, T₂...) with the flow cross-section and the maximum safe load indicated.

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