EP0774027A1

EP0774027A1 - Underground passage

Info

Publication number: EP0774027A1
Application number: EP95926410A
Authority: EP
Inventors: Alberto Ferreira
Original assignee: PREFAC BETON ENVIRONNEMENT
Current assignee: PREFAC BETON ENVIRONNEMENT
Priority date: 1994-07-28
Filing date: 1995-07-20
Publication date: 1997-05-21
Anticipated expiration: 2015-07-20
Also published as: FR2723116B1; AU3081295A; MA23541A1; FR2723116A1; EP0774027B1; WO1996003552A1

Abstract

An underground passage including footings (3) supporting prefabricated elements (5) such as shell halves for erecting an arch, said elements (5) being joined together at the keystone by means of a cast concrete tie beam. The length of the projections (11) integral with the elements (5) is such that the ends of said projections (11) are far enough apart in the assembled position to avoid ever touching one another when the shape of the shell halves (5) is changed during backfilling.

Description

"UNDERGROUND CONDUIT" The present invention relates to an underground conduit making it possible to arrange a passage for a traffic lane or for a watercourse, for example. It is well known to produce such an underground conduit by assembling prefabricated elements, these elements making it possible to constitute tubular sections of conduit which are arranged side by side along a longitudinal axis. In particular, it is known from the document entitled "Passages lower vaulted" from 1978, published by the general direction of inland transport of the French Ministry of Transport, to produce a structure presenting either a raft or two parallel support flanges, on which rest elements in the shape of vault.

For ducts of small section, the elements forming the roof of the structure can be of substantially hei-tubular section. On the other hand, as soon as the width at the base of the structure exceeds approximately five meters or its height exceeds approximately three meters, it becomes impossible to manufacture and transport such elements to the site. The vault is then made by assembling several elements. In general, a section of conduit is formed, in addition to the raft or the flanges, by two elements forming an arch, called "half-shells", the lower longitudinal edges of which are engaged in grooves provided in the raft and the upper longitudinal edges of which have outgoing frames and are assembled by keying and pouring a sill.

This document shows a possibility of assembling two half-shells, consisting of mounting scaffolding on the raft or between the flanges, in line with the keystone. This solution is not used in practice, because it would be extremely tedious to position the scaffolding over the entire length of the structure, to carefully place the two half-shells pressing simultaneously on this scaffolding, to operate the keying and pouring the sill, then removing the entire scaffolding.

The commonly used technique consists of placing the half-shells in abutment against each other with interlocking at their upper longitudinal edges, claving the outgoing reinforcements, projecting upwards, by means of longitudinal reinforcements, build a formwork around these reinforcements, and pour a concrete sill in this formwork. This technique has the drawback of being relatively complex and time-consuming to implement. In addition, the reinforcements and the sills for assembling the half-shells are situated outside the median curvature of the half-shells, at the level of which the stresses undergone are mainly exerted. As a result, the significant forces generated by the weight of the embankments are exerted in overhang on these sills, which can affect the assembly of the prefabricated elements and therefore the resistance over time of the structure.

In addition, it appears that particularly significant transverse forces are exerted on the sill when backfilling the sides of the structure. These stresses can lead to the creation of cracks in the sill, affecting its resistance in the long term.

British patent application GB 2 254 350 describes a half-shell structure assembled as a keystone by transverse tie rods and concrete pouring. Each half-shell includes a projecting spoiler, the two spoilers coming to bear against one another after assembly, to allow the clamping of the tie rods. The residual gap between the spoilers is sealed, before pouring the concrete, with a sealant.

The installation of the tie rods is relatively long and complex to carry out. In addition and above all, the aforementioned problem of cracking of the sill and the transverse forces exerted on it are not resolved.

Patent application No. FR 2 682 141 describes a process for producing a construction joint between two prefabricated elements, consisting in providing at least one of the elements with a spoiler projecting beyond its end surface, this spoiler being made of molded concrete in one piece with this element and delimiting one side of the joint area; having shims made of elastic material between the end surface of one element and looped reinforcements of the other element; placing the end of the spoiler of one element against the corresponding part of the other element, with interposition of sealing means; and to use a low shrinkage bond concrete.

The purpose of the shims is to obtain a "monolithism" without defect in the joints, by allowing, before setting of the concrete, a certain freedom of compaction of the elements to be assembled, thanks to the elastic shims. After the setting of the concrete, the forces are transmitted through the concrete, which is in homogeneous contact with the end surface of the elements.

Consequently, the elements are directly in contact with each other, and this "monolithism" of the joints does not make it possible to solve the aforementioned problem of the transverse stresses exerted on a sill of assembly in keystone. Such a sill is, moreover, in no way described by this document. On the contrary, the elastic support of the elements is conceivable only for joints made on the sides of the structure. The present invention aims to solve the aforementioned specific problem of particularly large transverse forces exerted on a keystone sill, during the installation of embankments on the sides of the structure. The invention aims, in general, to provide an underground conduit perfectly resistant over time to the forces exerted on it by the embankments, while being simple and quick to build. The conduit that the invention relates to comprises, in a manner known per se, a slab or support flanges on which rest prefabricated elements, or "half-shells", making it possible to constitute a vault, these elements being assembled together. others longitudinally and transversely, at the level of the keystone, by a concrete sill cast in situ, and comprising outgoing reinforcements as well as projecting walls, or "spoilers", projecting from the elements on the interior side, these spoilers extending beyond the ends of the outgoing reinforcements, facing one another when these elements are placed in the assembly position and delimiting, with the upper longitudinal edges of the elements, a groove in which concrete can be poured to constitute the sill assembly. According to the invention, the length of the spoilers is such that the ends of these spoilers are located, after assembly, at a distance from one another sufficient to never come into contact with each other when the half-shells are deformed by the installation of embankments.

The Applicant has in fact found that the half-shells deform more or less upward when the embankments are placed on the sides of the structure. As a result, the half-shells act on the sill like levers around the bearing surfaces of the half-shells against each other, located below the sill.

Thanks to the invention, the spoilers do not come into contact with each other, so that the elements are not directly in abutment against one another. No leverage occurs when the elements are deformed, and no cantilevering force is transmitted to the sill by the elements.

The outgoing reinforcements and the longitudinal keying reinforcements are advantageously located in the extension of the wall of the elements, that is to say in the places where the forces resulting mainly from the stresses undergone by the elements are exerted, which ensures an assembly particularly solid and resistant over time.

Preferably, the outgoing frames form loops through which the longitudinal keying frames can be put in place by engagement.

Advantageously, studs forming spacers are inserted between the end faces of the spoilers. These studs make it possible to maintain a minimum space between these end faces, the time for the installation of the keying frames and for the casting of the sill. These items are then removed. According to a preferred embodiment of the invention, the elements are maintained in their assembly position, before keying in the reinforcements and pouring the sill, by means of one or more rigid longitudinal plates, which are fixed, with the possibility of game, spoilers and which connect them to each other. Preferably, the elements include threaded sockets embedded in their thickness substantially at the base of the spoilers, allowing the installation of screws ensuring the fixing of the said plate or plates. Furthermore, the lower longitudinal edges of the elements coming to bear on the raft or on the soles include support studs between which outgoing reinforcements protrude, in the extension of the wall of these elements, these studs and reinforcements being intended to be embedded in concrete poured on site, after possible installation of additional reinforcements, in order to constitute the raft or the footings.

Thus, a perfect connection with embedding is obtained between the arch elements and the raft or the support flanges.

Preferably, the studs comprise studs, projecting from their lower face, intended to be engaged in positioning holes arranged in the slab cast in situ, intended to support the conduit. The engagement of these pins in these holes allows precise provisional positioning of the lower ends of the elements, the time of pouring of the concrete coming to drown the studs and outgoing reinforcements. For a good understanding, the invention is again described below, with reference to the appended diagrammatic drawing representing, by way of nonlimiting example, a preferred embodiment of the underground conduit that it concerns. Figure 1 is a perspective view, partially broken away; and Figures 2 and 3 are sectional views, on an enlarged scale, of the assemblies between these constituent elements. FIG. 1 represents an underground conduit 2 making it possible to arrange a passage for a traffic lane or for a watercourse, for example.

The duct 2 comprises two support flanges 3 resting on a slab 4 and two elements 5, or "half-shells", constituting, when assembled, a vault supporting the embankments 6. 96/03552 PC17FR95 / 00981

The half-shells 5 are assembled to one another at the level of the keystone, and are assembled to the soles 3.

FIG. 2 represents the connection of the half-shells 5 to each other at the level of the keystone.

With reference to this figure, it appears that the assembly edge 5a of each half-shell 5 comprises outgoing reinforcements 10 forming loops, arranged in the extension of the wall of the half-shell 5, and comprises a wall, or "spoiler", 11 projecting from the half-shell 5 on the inner side, extending beyond the end of the outgoing frames 10.

In addition, each half-shell 5 comprises tapped sockets 12 embedded in their thickness substantially at the level of the base of the spoilers 11.

It appears in Figure 2 that the ends of these spoilers 11 are located, after assembly, at a certain distance from each other, explained below. FIG. 3 represents the connection of the half-shells 5 at the level of the support flanges 3.

As can be seen with reference to this figure and to FIG. 1, the lower longitudinal edges of the half-shells 5 comprise support pads 15 between which outgoing reinforcements 16 protrude, in the extension of the wall of the half-shells 5.

In addition, the underside of each stud 15 comprises a stud 17, projecting perpendicularly relative to it, while the slab 4 comprises positioning holes 18, in which the studs 17 can be engaged.

In practice, slab 4, made of lean concrete, is poured on site, after completion of adequate earthworks. The holes 18 are arranged during this pouring or drilled after the concrete has dried. The half-shells 5 are then positioned above the slab 4, so as to engage the pins 17 in the holes 18 and bring the ends of the spoilers 11 close to one another, as shown in the figure 2.

Studs 20 made of hard polystyrene are inserted between the end faces of the spoilers 11, then longitudinal metal plates 21 are fixed to the spoilers 11, with the possibility of play, using screws 22 engaged in the tapped sockets 12.

After positioning of the plate 21, the spoilers 11 are held opposite one another and the half-shells 5 are placed in the assembly position. The spoilers 11 and the upper longitudinal edges 5a of the half-shells 5 then define a longitudinal groove.

A sealing strip 25 is placed in the bottom of this groove so as to cover the space existing between the two ends of the spoilers 11. Intermediate reinforcements 26 and longitudinal reinforcements 27 are then put in place by engagement in the loops that form the outgoing reinforcements 10, in order to carry out a keying thereof, then concrete 28 is poured into the groove to constitute an assembly sill. The pads 15 and frames 16 are then embedded in concrete poured on site to form the flanges 3, after installation of any additional frames.

Thus, once the half-shells 5 have been placed in their assembly position by fitting the studs 20 and the plate 21, it suffices to seal the groove using the strip 25, to connect the outgoing reinforcements 10 and pouring concrete 28 into this groove to assemble the half-shells 5. The distance between the ends of the spoilers 11 is sufficient so that these spoilers never come into contact with each other when the half-shells are deformed by the placement of embankments on the sides of the structure.

Thus, the half-shells 5 are not in abutment against one another. No leverage occurs during the deformation that the half-shells 5 undergo under the weight of the embankments 6, and no cantilevered force is transmitted to the sill 28 by them.

The outgoing reinforcements 10 and the keying reinforcements 26, 27 are also located in the extension of the wall of the half-shells 5, that is to say at the places where the forces resulting from the stresses undergone are mainly exerted. -this.

No scaffolding assembly and no particular formwork construction is necessary to pour the sill 28, so that the construction of the duct 2 is carried out in a simple and rapid manner. The studs 20 form spacers making it possible to maintain a minimum space between the end faces of the spoilers 11 while the keying frames 26,27 are in place and the sill is poured. They are normally removed, along with plate 21, after the concrete has dried. However, they can be left in place without hard spots being created between the half-shells 5, because of their material which is weakly resistant to compression.

The studs 15 and outgoing reinforcements 16, once embedded in the concrete poured on site intended to constitute the footings 3, ensure a perfect connection with embedding of the half-shells 5 and the support footings 3.

The engagement of the pins 17 in the holes 18 allows precise provisional positioning of the ends lower half-shells 5, the time that their assembly to one another and to the soles 3 is completed.

Claims

CLAIMS 1 - Underground conduit allowing the creation of a passage for a traffic lane, of the type comprising a slab or support flanges (3) on which rest prefabricated elements (5), or "half-shells", making it possible to constitute a vault, these elements (5) being assembled to each other longitudinally and transversely, at the level of the keystone, by a sill made of concrete poured in situ, and comprising outgoing reinforcements (10) as well as projecting walls, or "spoilers" (11), projecting from the elements (5) on the inner side, these spoilers (11) extending beyond the ends of the outgoing frames (10), coming opposite one another when these elements (5 ) are placed in the assembly position and delimiting, with the upper longitudinal edges of the elements (5), a groove in which concrete can be poured to constitute the assembly sill, conduit characterized in that the length spoilers (11) is such that the ends of these spoilers (11) are located, after assembly, at a distance from each other sufficient to never come into contact with each other when the half-shells (5) are deformed by the placement of embankments. 2 - Underground conduit according to claim 1, characterized in that the outgoing reinforcements (10) and the longitudinal keying reinforcements (26,27) are located in the extension of the wall of the elements.

3 - Underground conduit according to claim 1 or claim 2, characterized in that the outgoing reinforcements (10) form loops through which the longitudinal keying reinforcements (26,27) can be put in place by engagement.

4 - Underground conduit according to one of claims 1 to 3, characterized in that studs (20) forming spacers are inserted between the end faces of the spoilers (11).

5 - Underground conduit according to one of claims 1 to 4, characterized in that the elements (5) are maintained in their assembly position, before bonding of the reinforcements (10) and casting of the sill, by means of a or several rigid longitudinal plates (21), which are fixed, with the possibility of play, to the spoilers (11) and which connect them to one another. 6 - Underground conduit according to claim 5, characterized in that the elements (5) comprise threaded sockets (12), embedded in their thickness substantially at the base of the spoilers (11), allowing the installation of screws ( 22) ensuring the fixing of said plate or plates (21).

7 - Underground conduit according to one of claims 1 to 6, characterized in that the lower longitudinal edges of the elements (5) coming to bear on the base or on the flanges (3) comprise support pads (15) between which outgoing reinforcements (16) protrude, in the extension of the wall of these elements (5), these studs (15) and reinforcements (16) being intended to be embedded in concrete poured on site, after possible installation additional reinforcements, in order to constitute the raft or the soles (3).

8 - Underground conduit according to claim 7, characterized in that the studs (15) comprise studs (17), projecting from their underside, intended to be engaged in positioning holes (18) arranged in the slab (4 ) poured in place, intended to support the conduit (2).