EP2563975B1 - Molded wall having prefabricated cladding - Google Patents

Description

The present invention relates to the field of special works in the soil. It relates more particularly to a diaphragm wall, as well as to a method for producing such a diaphragm wall.

The molded wall according to the invention, and the corresponding production method, are particularly suitable for the construction of platforms, car parks, metro stations, tunnels, and more generally any structure in which the cladding of the wall is necessary.

Molded walls in the soil have been well known for a long time. An excavation of elongated shape, of width and depth equal to those of the wall that one wishes to obtain, is first formed in the ground. The stability of the trench during the drilling operation is obtained by filling the excavation with a liquid called "sludge", usually based on bentonite. This mud forms on the walls of the excavation a tight deposit which allows it not to percolate in the ground and to prevent the walls from collapsing. When the depth of the excavation has reached the desired level, a reinforcement cage is put in place, then the excavation is gradually filled with concrete using a dip tube, starting below the mud in the bottom of the excavation.

In some cases (wall integrated into the final structure, optimization of the thickness, special sealing requirements, regulatory aspects), the prefabricated walls offer an interesting alternative to the diaphragm walls. In particular, when access to the wall is impossible or dangerous, it is not possible to intervene on the diaphragm wall, after earthwork, to ensure the finish. Prefabricated walls, well known since the early 1970s, are a solution to this problem. According to the known methods, an excavation is carried out in the soil in the same manner as previously described for the diaphragm walls. The prefabricated panels were then lowered into the excavation, previously filled with drilling bentonite mud. A levitation device supported on guide walls allows the maintenance in place of prefabricated panels. The drilling mud is then replaced by a cement-based self-hardening grout that permanently bonds the prefabricated panel to the ground. Exemplary embodiments of such walls are known from the documents JP-A-03051416 and AT-B-330 677 .

The prefabricated walls have a level of finish such that they can in some cases constitute the final facing of the structure. No heavy finishing work is therefore necessary to obtain a satisfactory visual appearance on the visible part of the wall. However, the prefabricated walls have drawbacks that prevent their implementation in certain types of structures and in particular large structures. Indeed, there is currently no convenient way to join two prefabricated panels. The dimensions of the prefabricated panels are therefore limited by the capacity of the means of transport and lifting means, and they can be used with difficulty on high-rise structures. Moreover, given the weight of the panels, reinforcement of the concrete at anchorages can require a very dense and very complex reinforcement.

The present invention therefore relates to a wall that can be adapted to structures of large dimensions, resistant, and having, after execution, a sufficiently satisfactory visual appearance so that subsequent interventions of finishing are not essential.

• on forme dans le sol une excavation de forme allongée, à parois verticales, marquant la frontière d'une zone à déblayer,
• on positionne, dans l'excavation, une cage d'armatures à profil en L comportant une première partie de largeur adaptée à la largeur de l'excavation et destinée à être positionnée parallèlement au fond de l'excavation et une deuxième partie de largeur inférieure à celle de ladite première partie destinée à être adossée à la paroi longitudinale de l'excavation située du côté opposé à la zone à déblayer, de telle sorte qu'un espace libre est conservé entre ladite deuxième partie et la paroi longitudinale de ladite excavation située du côté de la zone à déblayer et,
• on positionne au moins un parement préfabriqué dans ledit espace libre, contre la paroi longitudinale de l'excavation située du côté de la zone à déblayer, et
• on coule du béton dans ladite excavation de manière à former une paroi moulée comprenant ledit parement préfabriqué.

In the first place, the subject of the invention is a method for producing a diaphragm wall according to claim 1, such that it comprises at least the following succession of steps:

• an elongated, vertical-walled excavation is formed in the soil, marking the boundary of an area to be cleared,
• an L-shaped reinforcement cage is positioned in the excavation having a first portion of width adapted to the width of the excavation and intended to be positioned parallel to the bottom of the excavation and a second part of smaller width to that of said first portion intended to be leaned against the longitudinal wall of the excavation located on the opposite side to the area to be cleared, so that a free space is maintained between said second portion and the longitudinal wall of said excavation located on the side of the area to be cleared and,
• positioning at least one prefabricated facing in said free space, against the longitudinal wall of the excavation located on the side of the area to be cleared, and
• pouring concrete into said excavation so as to form a molded wall comprising said prefabricated facing.

The method according to the invention combines the technique of the molded wall and that of the prefabricated wall. The molded wall thus obtained consists of a prefabricated facing, which covers part of one of its longitudinal faces, and a concreted part in situ, of general L-shaped profile, encasing the reinforcement cage, thus possibly waiting frames of prefabricated siding. This diaphragm wall thus benefits from the advantages of these two techniques. Executed conventionally by elementary panels, alternating or successive, it can be implemented over very long lengths. Moreover, because of the presence of prefabricated facing on one of the faces of the wall, a visible portion having the required visual appearance can be obtained from the execution of the wall, without the need for a subsequent heavy intervention. In some cases, it is also possible that in addition to its aesthetic function, the prefabricated element also takes up some of the forces exerted on the structure.

Generally, it can be considered that the positioning of the reinforcement cage inside the excavation does not need to be performed with great precision. On the other hand, to guarantee the aesthetics of the wall, it is important that the prefabricated facade (s) be (are) correctly positioned and, if necessary, aligned with each other.

According to the present invention, the reinforcement cage is therefore first lowered into the excavation (in a single section or in successive sections, as will be described in more detail below), and then, once the cage is positioned at the interior of the excavation, the prefabricated facing is lowered, separately, in the space preserved between the least wide part of the cage (ie the second part) and the longitudinal wall of the excavation located on the side of the zone to clear.

Thanks to these provisions, the positioning of the reinforcement cage inside the excavation is facilitated, particularly when the cage has a height and a high weight. Similarly, the facing, originally independent of the reinforcement cage, is more manageable, and can thus be positioned more easily in the trench.

According to one aspect of the invention, two guide webs materializing the desired implantation for the diaphragm wall are made in the soil to be excavated. The excavation is then carried out vertically between these two guide walls. The guide wall located on the side of the area to be cleared is generally removed after concreting of the molded wall. These guide walls constitute a precise reference for the execution, to support the positioning marks of the elements and for their positioning in height. They ensure the stability of the land surface and serve as support means for holding the reinforcement cage once it down in the excavation and other equipment.

According to an exemplary embodiment, the reinforcing cage and the facing are introduced into the excavation in the following manner: the cage is introduced into the excavation by supporting it with gripping loops provided on its upper part. It is temporarily stabilized in position in the excavation by means of bars passed in these handles and taking support transversely on the guide walls. Then we resume the maintenance of the reinforcement cage by means of a shaped rudder to clear the free space for the introduction of said prefabricated facing. Finally, the bars are removed, and the prefabricated facing is introduced into the free space of the excavation.

In the case of a structure of very great height, and in particular if the reinforcement cage formed in one piece is too heavy to be handled by the lifting gear, it may be advantageous for it to be formed of several sections descended successively in the excavation.

According to another aspect of the invention, the surface of the prefabricated facing intended to be oriented towards the zone to be cleared of a protection is coated before positioning the prefabricated facing in the excavation. This protection can be removed after clearing. It avoids the smearing of the visible face of the prefabricated facing, in particular by avoiding that concrete bypass comes to adhere to it.

According to an advantageous aspect of the invention, the lower part of the prefabricated facing is beveled lengthwise, and the prefabricated facing is positioned in the excavation so that the bevelled portion is oriented towards the inside of the molded wall. . This arrangement allows the concrete to flow more easily at the lower part of the prefabricated facing, and thus avoid poor contact between the concrete and the prefabricated facing in this area. In addition, the concrete tends to push the facing against the wall guide, towards the area to clear and not to the inside of the excavation. The probability that the siding deviates is, therefore, limited.

According to an advantageous aspect of the invention, the prefabricated facing comprises reinforcing bars on its lower end face and when the prefabricated facing is positioned in the excavation, these waiting frames are mixed with the reinforcements of the first part. of the reinforcement cage. This prevents a separation between the facing and the concrete portion of the molded wall.

According to one aspect of the invention, a formwork element is positioned at at least one end of the excavation, before concreting. The shuttering element may comprise, on its face facing the inside of the excavation, a groove extending over a height at least equal to the height of the molded wall and in which is inserted a sealing tongue making protruding outward. In this way, the portion of the tongue that protrudes outward is caught in the concrete during concreting. These arrangements make it possible to ensure a good seal between different panels constituting a molded wall, and in particular between two elementary panels molded successively in the ground (and in particular between the respective concrete portions of these two panels).

According to one aspect of the invention, waiting armatures protrude from the upper face of the molded wall after concreting. In addition, the prefabricated facing comprises, on its upper face, positioning members such as for example loops. To finalize the structure in the upper part, especially in the case of a dock, it is possible to make a crown beam on the upper face of the molded wall, so that the waiting armatures of the diaphragm wall and the prefabricated siding positioning are included in the crown beam.

According to one aspect of the invention, at least two prefabricated facings are positioned in the excavation. The first prefabricated facing to be positioned in the excavation has, on its lateral face oriented towards the inside of the excavation, a groove with a lock profile extending over the entire height of the facing, and the second facing intended to be positioned next to the first facing comprises a profile knife complementary to the groove, attached to the lower end of its side face facing the first facing. To connect the second prefabricated facing to the first facing, the knife of the second facing is progressively threaded into the groove of the first until the upper faces of the two faces are at the same height. The knife guides the second facing when introduced into the excavation, and position it precisely with respect to the first facing. This knife also allows the introduction of a seal connecting the grooves of the first and second facing.

In another aspect, after concreting, said first excavation is extended, at least at one of its ends, by a second excavation. In this case, the last facing of the first excavation, located at the end to be extended, comprises, on its lateral face facing this end, a lock profile groove extending over the entire height of the facing and closed by a friable or detachable protection. This protection makes it possible to prevent concrete from contaminating or closing the lock of the latter facing. The first facing to be positioned in the second excavation comprises him, a profile knife complementary to said groove, attached to the lower end of its side face facing the first excavation. In this way, it is possible to progressively slip the knife from the first facing of the second excavation into the groove of the last facing of the first excavation until the upper faces of the two facings are at the same height. The sliding of the knife into the lock of the last facing of the first excavation makes it possible to detach or destroy the protection of this lock.

According to another aspect of the invention, after the concreting of the molded wall and the possible realization of a crown beam, the area to be cleared is cleared so as to at least partially discover the surface of the prefabricated facing facing the area to be cut. clear.

Secondly, the subject of the invention is a diaphragm wall made according to the process according to claim 1.

• les figures 1A à 1F, 2, 3 et 4 sont des vues schématiques de différentes étapes du procédé de réalisation d'une paroi moulée selon un mode de réalisation de l'invention ;
• la figure 5 illustre une variante de réalisation du procédé de réalisation d'une paroi moulée selon l'invention ;
• la figure 6 illustre l'exécution d'une paroi moulée selon l'invention par panneaux successifs ;
• la figure 7 montre l'extrémité supérieure d'un parement préfabriqué pouvant être utilisé dans la présente invention ;
• la figure 8 montre l'extrémité inférieure du parement préfabriqué de la figure 7 ;
• la figure 9 illustre un exemple de coffrage pouvant être utilisé dans la présente invention ;
• la figure 10 illustre un exemple de joint pouvant être utilisé dans la présente invention ;
• la figure 11 illustre la liaison entre deux parements préfabriqués ;
• la figure 12 représente un quai réalisé avec le procédé de la présente invention ;
• les figures 13A, 13B et 13C illustrent une variante de réalisation du procédé de réalisation d'une paroi moulée selon la présente invention ;
• la figure 14 illustre encore une autre variante de réalisation du procédé de réalisation d'une paroi moulée.

Other features and advantages of the invention will emerge on reading the following description of exemplary embodiments of the invention. given by way of illustration and not limitation. This description refers to the attached drawing sheets in which:

• the Figures 1A to 1F , 2 , 3 and 4 are schematic views of different steps of the method of producing a molded wall according to one embodiment of the invention;
• the figure 5 illustrates an alternative embodiment of the method for producing a molded wall according to the invention;
• the figure 6 illustrates the execution of a molded wall according to the invention by successive panels;
• the figure 7 shows the upper end of a prefabricated siding that can be used in the present invention;
• the figure 8 shows the lower end of the prefabricated siding of the figure 7 ;
• the figure 9 illustrates an example of formwork that can be used in the present invention;
• the figure 10 illustrates an example of a seal that can be used in the present invention;
• the figure 11 illustrates the connection between two prefabricated facings;
• the figure 12 represents a dock made with the method of the present invention;
• the Figures 13A, 13B and 13C illustrate an alternative embodiment of the method of producing a diaphragm wall according to the present invention;
• Figure 14 illustrates yet another alternative embodiment of the method of producing a molded wall.

For example, a molded wall 10 according to the present invention may be used for producing the platform as shown in FIG. figure 12 . The invention may, however, be implemented in any other suitable work, and in particular in any work requiring a good finish visible parts of the walls.

The steps of the method for producing a molded wall 10 according to one embodiment of the invention will now be described with reference to the Figures 1A to 1F , and 2 to 4 .

A first step of the process, illustrated on the Figure 1A consists in producing guide walls 12a, 12b making it possible to materialize the implantation of the future molded wall. In the example, two guide walls 12a, 12b, parallel to each other, define a space of constant width I corresponding to the desired width for the future molded wall. These guide walls 12a, 12b are generally made of reinforced concrete and have a height of about 1 to 1.50 meters. Their function is to ensure the stability of the surface lands, constitute leveling marks, and serve as support for the lifting gear required during the execution of the wall. Guide walls 12a, 12b are most often temporary structures, intended to be destroyed once the wall 10 is completed.

In a second step, an excavation 14, of height H and width I corresponding to those desired for the molded wall 10, is hollowed vertically between the two guide walls 12a, 12b. The excavation 14 has an elongated shape which extends over a length L. As illustrated in FIG. figure 2 the excavation comprises two longitudinal walls 16a, 16b spaced a constant distance, each of them extending vertically in the extension of one of the two guide walls 12a, 12b. The excavation 14 marks the future location of the diaphragm wall. 10, and therefore delimits an area to be cleared 18. In the case of a wharf, the area to be cleared 18 extends from the longitudinal wall 16b of the excavation 14 oriented towards the body of water, in the direction of this plane of water.

Depending on the terrain and specifications, various tools may be employed to dig the excavation 14, for example, skips, skips on Kelly, drivelines, etc.

To ensure the stability of the excavation 14 during the drilling operation and in particular to prevent the walls 16a, 16b from collapsing, the excavation 14 is filled, during drilling, with a mud 24 generally based on bentonite.

Thirdly, as illustrated on the Figure 1B , an L-shaped reinforcement cage 26 is progressively introduced into the excavation 14 by means of a hoist 28.

The reinforcement cage 26 is illustrated in more detail on the figure 2 , where it appears that it comprises a first portion 30 of width substantially corresponding to the width I of the excavation 14, surmounted by a second portion 32 of smaller width.

Hoists 34 of the hoist 28 hold the reinforcement cage 26 at gripping loops 36 provided at the upper end of its second portion 32.

Once the reinforcement cage 26 is positioned in the excavation 14, its first portion 30 is positioned parallel to the bottom 38 of the excavation 14, at a sufficient distance from the bottom 38 so that the end fittings of the cage 26 may be properly coated during the concreting of the excavation 14 which will be described in more detail later in this description.

The second portion 32 of the reinforcement cage 26, which extends above said first portion 30, is, it, leaned against the longitudinal wall 16a of the excavation 14 located on the opposite side to the area to be cleared. .

A free space 40 is thus preserved above the first portion 30 of the reinforcement cage 26, between the second portion 32 and the wall 16b of the excavation 14 located on the side of the area to be cleared 18.

In the illustrated example, the first portion 30 has a width I1 and a length L1 substantially corresponding to the width I and the length L of the excavation 14, and a height H1. The second portion 32 has a width 12, less than I1, the same length L1 as the first portion 30, and a height H2. In this embodiment, the reinforcement cage 26 is made in one piece. Other examples of embodiments will be described below, in particular with reference to Figures 13A, 13B and 13C .

As indicated above, it is necessary for the reinforcement cage 26 to remain at a certain distance from the bottom 38 of the excavation 14 and not to bear against this bottom 38, in order to prevent it from being deformed and to subsequently allow a satisfactory coating of its frames in the lower part.

For this, in a fourth step, as illustrated on the figure 1C the reinforcement cage 26 is provisionally stabilized in position in the excavation 14 by means of bars 42 passed in its grip handles 36 and bearing transversely on the guide walls 12a, 12b. The establishment of the bars 42 allows the holding cage in position 26 once its gripping handles 36 released from the lines 34 of the hoist 28.

The disadvantage of the bars 42 extending transversely from one guide wall to the other above the excavation 14 is that they prevent access to the excavation 14 for elements of great length. However, as will be described in more detail later in the present application, a prefabricated facing 44 of length substantially identical to that of the excavation 14 must be lowered into the free space 40 of the excavation 14 located above of the first part 30 of the reinforcement cage 26 and between the second part 32 of this cage 26 and the wall 16b of the excavation situated on the side to be cleared 18.

To allow the insertion of this prefabricated facing 44 (shown in FIG. figure 1F ), it installs in a fifth time, on the guide walls 12a, 12b, a rudder 46 of length greater than the length L of the excavation 14, positioned so that its two feet 46a, 46b are sufficiently spaced one of the other so as not to obstruct the opening of the excavation 14 ( figure 1D ). The rudder 46 has the function of keeping the cage 26 in position by means of hoists 48, for example, connected to the handles 36. Once the cage 26 taken up by the rudder 46, it is possible to remove the bars 42 gripping handles 36 of the cage 26, and thus completely clearing the opening of the excavation 14 to allow the introduction of the prefabricated facing 44 ( figure 1E ).

In a sixth time, as represented on the figures 1F and 2 , the prefabricated facing 44 is brought above the excavation 14 to be introduced into the free space 40 defined between the second portion 32 of the reinforcement cage 26 and the wall 16b of the excavation 14 located on the the area to be cleared 18, and be placed there against the guide wall 12b on the same side.

In reality, as illustrated on the figure 2 , a flat iron wedge 50 is advantageously provided at the upper end of the guide wall 12b to allow fine positioning of the prefabricated facing 44 relative to the guide wall 12b. This flat iron wedge 50 is supported on the upper face of the guide wall 12b and extends at right angles along the longitudinal face of the wall 12b facing the excavation 14. It has a very small thickness, 1 centimeter order, and allows to keep sufficient clearance with the prefabricated facing 44 so that the destruction of the guide wall 12b, after execution of the wall 10, does not lead to deterioration of the visible face of the facing 44 (ie its face located on the side of the area to be cleared 18).

An example of prefabricated facing suitable for the present invention is illustrated in more detail on the Figures 7 and 8 .

The figure 7 shows the upper end of the prefabricated facing 44, from which projecting reinforcements 52 project whose function will be described in detail with reference to the figure 4 and positioning members 54 allowing the handling of the facing 44 by the lifting apparatus 28. These positioning members may be handles, as illustrated in FIG. figure 7 , or other types of hangers.

The figure 8 , which shows the lower end of the prefabricated facing 44, highlights a beveled portion 56 in the direction of the length of the facing. When it is introduced inside the excavation 14, the prefabricated facing 44 is positioned so that this beveled portion 56 is oriented towards the inside of the excavation 14 and not towards the area to be cleared 18.

It is also apparent from figure 8 that the prefabricated facing 44 comprises waiting reinforcement 58 on its beveled lower end face 56. When the prefabricated facing 44 is positioned in the free space 40 of the excavation 14, resting against the flat iron wedge 50 , with its upper face substantially at the same level as the guide walls, these waiting frames 58 are found mixed with the reinforcements of the first part 30 of the reinforcement cage 26, as shown in FIG. figure 3 .

The face of the prefabricated facing 44 intended to be oriented toward the area to be cleared 18 is advantageously covered with a protection 60, for example in the form of a self-adhesive sheet, before the facing 44 is lowered into the excavation 14 The face of the facing 44 is obviously perfectly cleaned before being covered with said self-adhesive foil 60. This protection prevents circumferential concrete from contaminating the visible part of the facing 44. As illustrated on FIG. figure 12 it is removed after concreting of the excavation 14 and excavation of the area to be cleared 18.

Other characteristics of the facing represented on the Figures 7 and 8 will be described in detail in the following description.

In a seventh time, once the facing 44 positioned in the free space 40, a formwork 62 is positioned at each end of the excavation 14.

An example of adapted formwork 62 is described in more detail with reference to the figure 9 . This formwork 62 comprises a profiled central portion 64 whose profile corresponds to the impression, here concave, which it is desired to impart to the end of the molded wall 10, two plane lateral wings 66a, 66b located on both sides. another of the central portion 64, and an L-shaped iron 68 welded along the junction line between the central portion 64 and the lateral flange 66a intended to be positioned facing the end of a facing. The function of this L-shaped iron will be described in more detail with reference to the figure 5 . In the example, the formwork 62 comprises a groove 67 on the face of its central portion 64 oriented towards the inside of the excavation 14, said groove 67 extending over the entire height of the formwork 62. In this groove 67 is inserted a sealing tongue 70 projecting towards the interior of the excavation 14, the function of which will appear better in the light of the figure 6 which illustrates a molded wall according to the invention executed by successive panels. The sealing tongue is indeed intended to seal between two successive panels of such a diaphragm wall.

In the eighth step, once the formwork elements have been put in place at the ends of the excavation 14, the concrete 72 is cast, starting under the bentonite mud 24, at the lower end of the excavation 14, according to the technique of the concreting to the dip tube under the mud. The concrete 72 thus progressively encapsulates the reinforcing bars of the reinforcing cage 26, as well as the waiting armatures projecting from the bevelled lower face 56 of the prefabricated facing 44, until the concreted part in situ 74 reaches the level of the upper face of the prefabricated element. The beveled portion 56 of the cladding 44 makes it possible to avoid poor contact between the concrete 72 and the prefabricated facing 44 in this zone. Furthermore, under the effect of this beveled shape, the concrete 72 has a tendency to push the facing 44 towards the guide wall 12b, thus avoiding the deflection of the facing 44 towards the inside of the excavation 14.

In general, and in particular when the upper end of the molded wall 10 must have a good finish, it is necessary, as illustrated in FIG. figure 4 , to overcome the diaphragm wall 10 of a beam of coronet 76 of reinforced concrete, of width corresponding to that of said wall 10. In this case, it is expected that the reinforcing bars 78 of the reinforcement cage 26 protrude from the upper face of the concrete portion 74 of the molded wall 10, after concreting. Thus, the coping beam 76, cast on the upper face of the molded wall 10, encompasses these holding armatures 78, those 52 provided on the upper face of the prefabricated element 44 (as described with reference to FIG. figure 7 ) and finally the positioning loops 54 of the same prefabricated element 44.

This crown beam 76, which is generally necessary for the structure, also makes it possible to improve the finishing of the structure, and to complete the mechanical joining of the prefabricated facing 44 and the concrete portion 74 of the diaphragm wall 10.

According to another exemplary embodiment, as an alternative to the crown beam 76, it is also possible to provide, at the upper end of the prefabricated facing 44, that the waiting frames 52 are bent at 180 ° and oriented towards the excavation, so as to plunge into the concrete portion 74. These expectations frames allow better attachment of the prefabricated facing 44 to the concrete portion 74 of the diaphragm wall 10, and avoid any detachment.

In the exemplary embodiment described with reference to Figures 1A to 4 , the molded wall 10 comprises a single reinforcement cage 26, and a single prefabricated facing 44, both of a length substantially equal to that of the excavation 14.

As an alternative, a number N1 of L-shaped reinforcing cages can be lowered into the excavation, and a number N2 (equal to or not equal to N1) of prefabricated facings can be introduced into the free space kept between these N1 cages. reinforcement and the side wall 16b of the excavation 14 located on the side of the area to be excavated 18.

According to an embodiment illustrated on the figure 5 two reinforcing cages 261, 262 are successively positioned in the excavation 14. Each reinforcing cage 261, 262 has an L-shaped profile similar to that of the reinforcement cage 26 described with reference to FIGS. Figures 1A to 4 but a length substantially equal to half the total length L of the excavation 14.

As in the embodiment described above, each reinforcement cage 261, 262 is positioned in the excavation 14 so that its first portion extends substantially along the bottom of the excavation 14, and that its second portion is leaned against the wall 16a of the excavation 14 located on the opposite side to the area to be cleared 18. Two prefabricated facings 441, 442 are then positioned successively in the excavation 14, one next to the other, in the free spaces respectively defined by the reinforcement cages 261, 262. In the example of the figure 5 , wherein the molded wall 10 is a straight wall, the two faces 441, 442 are positioned substantially in the same plane.

As illustrated on the figure 5 each prefabricated facing 441, 442 comprises, on each of its lateral faces, a cavity (or reservation) 80, here in the form of a groove with a "keyhole" profile and extending over its entire height. One of these cavities 80, facing the end of the excavation 14, is closed by a protection, such as a layer of polystyrene 84, for preventing the concrete from contaminating said cavity during concreting.

The installation of the forms 62 at the ends of the excavation 14 after placement of the prefabricated facings 441, 442 allows the lateral flange 66a of each formwork to be correctly pressed against the adjacent polystyrene layer 84. As is apparent from the figure 5 , the iron L 68 of each formwork 62 is then positioned in front of the polystyrene layer 84 covering the end of the adjacent prefabricated facing. The L-shaped iron makes it possible for the concrete tongue formed during concreting at the level of the polystyrene layer to be sufficiently weak to be broken during stripping.

It will be noted, however, that the locks 80 of the prefabricated face or faces provided at the ends of the excavation are only applicable if the same facings are intended to be connected to other similar facings subsequently introduced into adjacent excavations. This case will be described in more detail with reference to the figure 6 .

Each prefabricated facing 441, 442 further comprises, at the lower end of one of its lateral faces, a metal knife 82 of complementary profile to that of the cavities 80. An illustration of such a knife 82 is given to the figure 8 . In the example, and for reasons that will be explained in the following, the second facing 442 has a metal knife 82 at the lower end of its side face to be positioned next to the first cladding 441.

After the first cladding 441 has been introduced into the excavation 14 with its polystyrene-coated lateral face 84 facing the end of the excavation 14, the second cladding 442 is placed above the free space adjacent to the first facing 441, then descended into this free space (as shown in figure 11 ) so that its knife 82 is threaded progressively into the groove 80 of the first facing 441, and until the upper faces of the two faces 441, 442 are found at the same height.

The knife 82 has a guiding and positioning function of the second cladding 442. It also makes it possible to slide a seal 86 between the two cladding 441, 442, in particular an inflatable "water-stop" type seal. Such a seal 86, positioned in the cavities 80 of two adjacent facings, is shown in detail on the figure 10 . It comprises two inflatable hollow tubes 88a, 88b, each being intended to be introduced into a cavity 80, and an intermediate portion connecting these two flanges 88a, 88b. Sealing is ensured when a cement grout is injected into each flange until it swells sufficiently to achieve close contact between the concrete and the joint.

For a better understanding of the general principles of the method according to the invention, the description up to now has been limited to the case of a molded wall 10 comprising a single panel. In the vast majority of structures, the desired dimensions of the diaphragm wall will be such that it must be executed conventionally by elementary panels, either successive or alternating.

The execution of a wall molded by successive elementary panels will now be described in connection with the figure 6 .

As shown on the right side of the figure 6 , a primary panel 101 has been made in a first excavation 141, according to the method described above with reference to the figure 5 and a second excavation 142 was dug to the left of the first excavation 141. The formwork 62 was removed to the left of the first excavation 141, after the excavation 142 had been dug. As shown in the figure, the primary panel 101 presents, at this end, a continuous concave overall impression over its entire height. This concave end face protrudes the sealing tongue 70 of the formwork 62 (previously described with reference to FIG. figure 9 ), secured to the first panel 101 during the setting of the concrete.

As for the primary panel 101, two reinforcing cages 261 ', 262' and two prefabricated facings 441 ', 442' have been positioned in the second excavation 142. A formwork 62 identical to that shown in FIG. figure 9 has been placed at the end of the second excavation 142 opposite to the primary panel 101. A single formwork 62 is necessary here since, on the other side, the second excavation 142 is delimited by the concrete end face of the primary panel 101 .

As previously described in connection with the figure 5 , the facing 442 of the first excavation 141, an end face of which adjoins the second excavation 142 (ie here the second facing 442 of the first excavation 141) comprises, on this end face, a groove 80 with a lock profile. extending over the entire height of the facing 442 and closed by a layer of polystyrene 84.

The first facing 441 'to be positioned in the second excavation 142 comprises, him, a metal knife 82 identical to that described with reference to figures 8 and 11 attached to the lower end of its lateral face facing the first excavation 141. In this way, the knife 82 of the first facing 441 'of the second excavation 142 can be progressively threaded into the cavity 80 of the last facing 442 of the first excavation 141 until the upper faces of the two facings 441 ', 442 are at the same height. In reality, before starting to thread the knife 82 into said cavity 80, an operator manually "scratches" the upper end of the polystyrene layer 84, in order to unclog the lock 80. The sliding of the knife 82 in the lock 80 allows to detach or destroy the rest of the protection 84 over the entire height of the facing 442. The protection will then be evacuated with the sludge.

Protections such as the polystyrene layer 84 illustrated on the Figures 5, 6 and 7 are mainly intended to prevent concrete from circumventing, during the concreting operation, soil a lock 80 in which the knife 82 of an adjacent facing must be inserted later. Conversely, when two facings are already interconnected at the time of concreting, in particular by a seal of the type described above, such protection is no longer necessary.

We understand, in the example of figure 6 , that the first facing 441 'of the second excavation 142 has no protection on any of its end faces, since it will be connected to the two adjacent faces 442 and 442' before the concreting operation. The second facing 442 'of the second excavation 142, on the other hand, must be protected by a layer of polystyrene 84 to prevent the cavity 80 provided on its lateral face facing the formwork 62 from being soiled by the concrete during the operation. concreting, which would make impossible the connection with an additional facing placed in a possible third excavation located in the extension of the second excavation.

In all the examples described above, the armature cage 26, 261, 262 has been described as being formed in one piece. In some cases, however, the desired dimensions for the molded wall 10 are too large for the reinforcement cage 26, 261, 262 to be lowered in one section. It is possible, therefore, that each armature cage 26, 261, 262 of the type described above consists of several sections descended one after the other in the excavation. In this case, the positioning of the reinforcement cage is carried out in the manner described in the Figures 13A and 13B . In this embodiment, the armature cage 26 consists of two sections 90, 92. It will be readily understood that the same method can be used for any number of sections.

In the example, the first section 90 of the reinforcement cage 26 actually corresponds to the first portion 30 of the reinforcement cage 26, which has a width substantially equal to that of the excavation 14, while the second section 92 corresponds to the second portion 32 of the cage 26, of smaller width than the first portion 30 and intended to be leaned against the wall 16a of the excavation 14 located opposite the area to be cleared 18.

The first section 90 is first inserted into the excavation 14 until its upper end is positioned substantially at the guide walls 12a, 12b. Following the same method as described in connection with the figure 1C , this first section 90 is temporarily held in position by means of bars 42 placed transversely and resting on each of the guide walls 12a, 12b. With the aid of a hoist, the second section 92 is brought directly above the first section 90, and the first and the second section 90, 92 are secured by ligation or welding of the reinforcements waiting for the two sections. The assembly formed by the first and the second section is then lowered into the excavation 14 until reaching its final position.

As in the examples described above, the prefabricated facing is then positioned in the free space preserved between the second portion 32 and the longitudinal wall of the excavation 14 located on the side of the area to be cleared 18 (see FIG. figure 13C ).

According to another example illustrated in FIG. 14, the prefabricated facing 44 may be secured to the section of the reinforcement cage 26 intended to be inserted last in the excavation so as to limit the number of lifting operations during the execution of the wall. Thus, after having introduced the first part 30 of the reinforcement cage into the excavation (in one or more sections, where appropriate), the assembly formed by the last section 32 and the facing 44, finishing thus the L-shaped structure of the reinforcement cage. It will generally be provided, in this case, that the second part 32 of the reinforcement cage (ie the one, finer than the base of the L extending parallel to the bottom of the excavation, leaned against the wall of the excavation opposed to the zone to be breached) consists of a single section, so that the facing 44 can fill the empty space between the second part of the reinforcing cage and the wall of the excavation located on the side of the area to be knocked down.

Advantageously, the prefabricated facing 44, previously secured to the last section 92 (ie to the second portion 32) of the reinforcement cage 26, may be molded (ie cast) with the section 92 of the reinforcement cage 26 intended to be last introduced in the excavation 14. According to another embodiment, the facing 44 may comprise waiting frames, and these waiting frames can be ligated to reinforcements of the last section 92 of the reinforcement cage 26 , so as to secure the two elements. In all the exemplary embodiments illustrated, the base of the diaphragm wall is substantially at the level of the working platform (ie at the guide walls). But the invention also allows make molded walls with low base, several meters under the working platform if necessary. In this case, each prefabricated facing is extended by a post at each of its ends, said posts having a height sufficient to reach the working platform once the prefabricated facing positioned in the excavation, and the positioning members of the prefabricated facing (handles, threaded bars, etc.) are also lengthened accordingly. The lock-shaped cavities of the prefabricated facings and the protections, for example made of polystyrene, covering these cavities extend over the entire height of the posts. These posts are intended to be destroyed after concreting.

Claims (15)

1. A method of making a diaphragm wall (10), comprising at least the following succession of steps:

   · forming in the ground an excavation (14, 141, 142) of elongate shape, having vertical walls, marking the frontier of a zone (18) to be dug away;

   · positioning, in the excavation (14, 141, 142), a reinforcing cage (26, 261, 262) of L-shaped profile having a first portion (30) of width matching the width of the excavation (14, 141, 142) and intended to be positioned parallel to the bottom (38) of the excavation (14, 141, 142), and a second portion (32) of width less than the width of said first portion (30) and intended to be backed against the longitudinal wall (16a) of the excavation (14, 141, 142) that is situated on its side remote from the zone (18) to be dug away, in such a manner that an empty gap (40) is retained between said second portion (32) and the longitudinal wall (16b) of said excavation (14, 141, 142) situated beside the zone (18) to be dug away; characterized in that it comprises afterwards the step of

   · positioning at least one prefabricated facing element (44, 441, 442) in said empty gap, against the longitudinal wall (16b) of the excavation (14, 141, 142) situated beside the zone (18) to be dug away, and casting concrete into said excavation (14, 141, 142) in such a manner as to form a diaphragm wall (10) including said prefabricated facing element (44, 441, 442).
2. A method of making a diaphragm wall according to claim 1, characterized in that after concreting, the zone (18) to be dug away is dug away so as to uncover at least part of the surface of the prefabricated facing element (44, 441, 442) that faces towards the zone to be dug away.
3. A method of making a diaphragm wall according to claim 1 or claim 2, wherein said reinforcing cage (26, 261, 262) of L-shaped profile is made up of a plurality of segments lowered successively into said excavation (14, 141, 142).
4. A method of making a diaphragm wall according to any one of claims 1 to 3, characterized in that two guide strips (12a, 12b) marking the desired location for the diaphragm wall (10) are made in the form of low walls in the ground to be excavated, and the excavation (14, 141, 142) is then excavated vertically between these two guide strips (12a, 12b).
5. A method of making a diaphragm wall according to any one of claims 1 to 4, characterized in that said reinforcing cage (26, 261, 262) includes grip loops (36) at its top portion, and in that said cage (26, 261, 262) is inserted into said excavation (14, 141, 142) while supporting it via said loops (36), it is temporarily stabilized in position in said excavation (14, 141, 142) by means of bars (42) passed through said loops (36) and bearing transversely on said guide strips (12a, 12b), support of the reinforcing cage (26, 261, 262) is taken over by means of a lifting beam (46) shaped to leave clear said empty gap in order to insert said prefabricated facing element (44, 441, 442), said bars (42) are withdrawn, and said prefabricated facing element (44, 441, 442) is inserted.
6. A method of making a diaphragm wall according to any one of claims 1 to 5, characterized in that, prior to positioning the prefabricated facing element (44, 441, 442) in the excavation (14, 141, 142), the surface of said prefabricated facing element that is to face towards the zone (18) to be dug away is covered by a protection (60), preferably an adhesive sheet.
7. A method of making a diaphragm wall according to claims 2 and 6, characterized in that the protection (60) is removed after digging away.
8. A method of making a diaphragm wall according to any one of claims 1 to 7, characterized in that the bottom portion of the prefabricated facing element (44, 441, 442) is chamfered lengthwise, and the prefabricated facing element (44, 441, 442) is positioned in the excavation (14, 141, 142) in such a manner that the chamfered portion (56) faces towards the inside of the diaphragm wall (10).
9. A method of making a diaphragm wall according to any one of claims 1 to 8, characterized in that the prefabricated facing element (44, 441, 442) includes starter bars (58) on its bottom end face, and in that when the prefabricated facing element (44, 441, 442) is positioned in the excavation (14, 141, 142) said starter bars (58) extend between the reinforcing bars of the first portion (30) of the reinforcing cage (26, 261, 262), whereby said facing element (44, 441, 442) is prevented from becoming detached from the concreted portion (74) of the diaphragm wall (10).
10. A method of making a diaphragm wall according to any one of claims 1 to 9, characterized in that, prior to concreting, a shuttering element (62) is positioned at at least one end of the excavation (14, 141, 142).
11. A method of making a diaphragm wall according to any one of claims 1 to 10, characterized in that, after concreting, starter bars (78, 52) project from the top face of the diaphragm wall (10), in that the prefabricated facing element (44, 441, 442) includes positioning members (54) on its top face, and in that, after concreting, a capping beam (76) is made on the top face of the diaphragm wall (10) in such a manner that said starter bars (78, 52) of the diaphragm wall (10) and said positioning members (54) of the prefabricated facing element (44, 441, 442) are included in said capping beam (76).
12. A method of making a diaphragm wall according to claim 3 and any one of claims 1 to 11, characterized in that at least the guide strip (12b) situated beside the zone (18) to be dug away is removed after the diaphragm wall (10) has been concreted.
13. A method of making a diaphragm wall according to any one of claims 1 to 12, characterized in that at least two prefabricated facing elements (441, 442) are positioned in said excavation, in that the first prefabricated facing element (441) to be positioned in the excavation (14, 141, 142) includes, on its side face facing towards the inside of the excavation (14, 141, 142), a slot (80) having a keyhole-shaped profile extending over the full height of said facing element (441), in that the second facing element (442) intended to be positioned beside the first facing element (441) includes a blade (82) of profile complementary to said slot (80) and fastened to the bottom end of its side face facing towards said first facing element (441), and in that in order to connect the second prefabricated facing element (442) to the first facing element (441), the blade (82) of the second facing element (442) is engaged progressively in the slot (80) of the first facing element (441) until the top faces of the two facing elements are at the same height.
14. A method of making a diaphragm wall according to any one of claims 1 to 13, characterized in that, after concreting, said first excavation (141) is extended at at least one of its ends by a second excavation (142), in that the last facing element (442) of the first excavation (141) that is situated at the end that is to be extended includes, on its side face facing towards said end, a slot (80) of keyhole-shaped profile extending over the entire height of the facing element (442) and closed by breakable or detachable protection (84), in that the first facing element (441') to be positioned in the second excavation (142) includes a blade (82) of profile complementary to said slot (80) and fastened to the bottom end of its side face facing towards the first excavation (141), and in that the blade (82) of the first facing element (441') of the second excavation (142) is engaged progressively in the slot (80) of the last facing element (442) of the first excavation (141) until the top faces of the two facing elements are at the same height, thereby removing said breakable or detachable protection (84).
15. A diaphragm wall (10) made in accordance with the method of any one of claims 1 to 14.

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