EP0066478A1 - Method to assure the mechanical continuity between two adjoining panels of a reinforced concrete wall cast in the earth - Google Patents

Abstract

The invention relates to a method for ensuring mechanical continuity and the transmission of forces between two adjacent panels of a wall of reinforced concrete molded in the ground, which is characterized by the use of a plurality of jacks whose bodies (5n ) are embedded in the concrete of the panel (n) and the rods (6n) are embedded in the concrete of the panel (n + 1).

Description

The invention relates to the field of civil engineering and relates more particularly to a method for ensuring mechanical continuity and the transmission of forces between two adjacent panels of a reinforced concrete wall molded in the sul.

The various processes studied so far are based on the principle of the transmission of forces in concrete by covering the horizontal reinforcements of the ends of the cages of the adjacent panels. To this end, the end of the cage of a first panel is not concreted thanks to the installation of a partitioning system separating the concreted part of the panel from a space left free and then placed in communication with the excavation of a second neighboring panel, in order to allow the placement of the cage of the second panel with overlap with the cage of the first panel and thus to ensure continuity between the two panels after concreting.

The continuity between panels thus created is the same as in the case of resumption of concreting of a conventional concrete veil, the difficulty being to find a formwork allowing the reinforcements to pass under the conditions of execution of a diaphragm wall, that is to say several meters deep and under bentonite mud.

• - les longueurs de recouvrement des armatures horizontales sont limitées par les dimensions du système mis en oeuvre et ne sont, en général, pas suffisantes si l'on veut utiliser des diamètres de barres intéressants; le strict respect des règles de béton armé entraînerait un surdimensionnement de ces systèmes qui leur ferait perdre beaucoup de leur intérêt;
• - le procédé, de par sa nature, interdit la mise en place d'aciers transversaux de couture dans la zone de recouvrement des barres horizontales comme le réclament les règles de béton armé.

Aside from the complex nature of the formwork necessary for achieving this continuity of reinforcement and its difficulty of implementation which, in addition to the impact on the cost of the operation itself, slows down the rate of construction compared to a conventional wall, these methods have two serious drawbacks in the very design of the joint by covering the reinforcements:

• the overlapping lengths of the horizontal reinforcements are limited by the dimensions of the system used and are not generally sufficient if it is desired to use interesting bar diameters; strict compliance with the rules of reinforced concrete would lead to oversizing of these systems which would make them lose much of their interest;
• - the process, by its nature, prohibits the installation of transverse seam steels in the overlap area of the horizontal bars as required by the rules of reinforced concrete.

In addition, the use of a partitioning system with the necessary sealing means associated, considerably increases costs and is a nuisance from a practical point of view because of its size.

These prior methods aimed at ensuring the transmission of forces between two adjacent panels of molded wall by the realization of a continuity of the horizontal reinforcements by a device based on the classic principle and well known in reinforced concrete covering the bars. reinforcement, therefore do not provide a fully satisfactory solution to the problem posed both from the point of view of the application of the rules of reinforced concrete as from the point of view of economy and conditions of practical realization.

The object of the invention is to provide a new method for ensuring mechanical continuity and the transmission of forces between two adjacent panels of a reinforced concrete wall, molded in the ground, which is free from the above-mentioned defects and constitutes remarkable technical progress. .

According to the invention, this method consists in drowning in the concrete of a panel n in progress the bodies of a plurality of jacks distributed at intervals over the height of the panel and arranged at the end of said panel adjacent to the panel n +1 next to be produced, the rods of the jacks being in the retracted position and their ends being brought in the immediate vicinity of the shuttering means of the end of the excavation in which the panel n is poured, then, after sufficient setting of the concrete of this panel, execution of the excavation of the next panel n + 1 and removal of the formwork means provided at the end of the excavation of the panel n, to deploy the rods of the jacks so that they penetrate into the excavation of the next n + 1 panel to be produced and, finally, to concretize the excavation of said n + 1 panel, thus embedding the rods of the jacks in the concrete.

After the concrete has hardened, the jacks deployed act as reinforcements ensuring the transmission of forces from one panel to another.

In order to obtain the best possible anchoring of the cylinders in the concrete, it is advantageous to provide the cylinder body and the cylinder rod, at their opposite ends, with flanges or end plates. Alternatively, the body of the cylinder could be provided with protrusions intended to improve the adhesion between the concrete and the body of the cylinder, the rod being the only one provided with a flange or anchoring plate at its free end. According to yet another variant, the cylinder body could be fixed to irons or anchor bars which will themselves be embedded in the concrete.

As reinforcement cages will most often be placed in excavations before pouring concrete, it is convenient to attach or suspend the bodies of the jacks to the reinforcement cage in order to ensure their distribution over the height of the panel to achieve. If the fixing of the body to one of the bars of the cage is sufficiently solid, it can at the same time ensure the anchoring of the body to the concrete after pouring of the latter, without the need to provide a flange or end plate on the cylinder body.

Of course, in the case of the use of reinforcement cages, it is necessary to provide in these free volumes intended to receive the rods of the jacks during their deployment.

Thus each reinforcement cage can carry a series of jacks at one of its ends and be provided with adequate free volumes at the other end to receive the rods of the jacks of the adjacent cage during their deployment. As a variant, one out of two reinforcement cages can carry a set of jacks at each of its ends, the adjacent cages being, for their part, provided with adequate free volumes. In this latter embodiment, the jacks provided at the two ends of the jacking cages can be connected two by two by a connecting member, such as a steel bar, ensuring their anchoring.

As usable cylinders, single acting or double acting cylinders can be used. In the case of single-acting cylinders, care must be taken that when deploying ment of the rods, for example under the effect of compressed air pressure or another pressurized fluid, the piston of each cylinder comes into abutment against the bottom of the cylinder in order to be certain that the forces will be well transmitted from the rod to the cylinder body and vice versa. In the case of double-acting cylinders, it is possible to exert a prestress, after hardening of the concrete, in order to put in tension the rod of the jack. The durability of this prestressing will be ensured by the use as pressurizing fluid of the jack of a curable fluid, such as a cement grout without shrinkage, which will take hold in the cylinder of the jack. Such a curable fluid can also be used in the case of a single-acting cylinder. The anchoring zones of the body and of the rod of the jack may be reinforced transversely by steels provided for this purpose in the cages, so as to respect the uses in terms of concrete.

The cylinders can be of very ordinary quality, or even inferior, since they are intended to operate only once.

The jacks can be placed horizontally and parallel to the faces of the diaphragm wall or in any other direction desirable from the point of view of the transmission of forces. The cylinders can be positioned in the middle plane of the panels if it is a question of transmitting a simple traction. In the case of the transmission of a bending force, it is possible to provide a series of jacks offset relative to the mean plane of the panels when the force is always exerted in the same direction or two series of jacks each positioned on either side 'other of the average plane of the panels when the force is exerted alternately in both directions.

The rods of the cylinders will advantageously be protected from corrosion when crossing the joint. We could, for example, provide an anti-corrosion coating on the rod of each cylinder.

The cylinders will be sized according to the forces to which they will be subjected, as is obvious.

The description which will follow with regard to the appended drawing, given by way of nonlimiting example, will make it clear how the invention can be implemented, the features which emerge both from the drawing and from the text of course forming part of said invention.

Figures la to le are schematic plan views illustrating the method of the invention. Figure 2 is a schematic sectional view along line E-E of Figure 1e; and Figure 3 is a schematic view illustrating a variant of the method of the invention.

Figures 1a to 1e and 2 illustrate the implementation of the method of the invention. In Figure la, we see an excavation In carried out in a conventional manner under bentonite mud, in which will be poured the panel n of the diaphragm wall. At the end of this excavation next to the future n + 1 panel, a 2n profiled formwork is put in place. In excavation 1n, a reinforcement cage 3m is put in place (very simplified) to which are fixed a plurality of single-acting cylinders 4n in the retracted position.

The jacks 4n comprise a body 5n and a rod 6n carrying at their opposite ends flanges or anchoring plates 7n and 8n, respectively. The 4n cylinders are positioned at intervals, for example, regular over the height of the cage and in the region of the cage next to the formwork 2n. The cylinders of the jacks are supplied with pressurized fluid through a conduit 9n. The cage carrying the jacks being in place, a light blow of compressed air is sent into the jacks so that the plates 8n come into abutment against the formwork 2n, then we proceed to concreting the excavation 1n (Figure 1b).

During this concreting, the cage 3n, the conduit 9n, the bodies 5n of the jacks and their plates 7n are embedded in the concrete, while only a small portion of the rods 6n is coated, the plates 8n flush with the concrete.

After that, one digs, following the excavation 1n, an excavation 1n + 1, in which the panel n + 1 will be molded, then the formwork 2n is extracted (FIG. 1c). Alternatively, the formwork could be extracted before digging the 1n + ₁ excavation, provided that the concrete of the panel n has become firm enough to support itself.

In the next step (Figure 1d), we put in the excavation 1n + 1 a reinforcement cage 3n + 1 similar to the cage 3n, whose end close to the panel n is provided with free volumes 10 _{n +1} corresponding to the location occupied by the rods 6n with their plates 8n once deployed, while its opposite end carries a plurality of cylinders 4n + ₁ (not shown).

Finally (FIG. 1e), a fluid under pressure is injected into the conduit 9n in order to release the rods 6n from the grip of the concrete and deploy them until the portion of each jack comes into abutment, at the end of the stroke. , against the bottom of the cylinder. If desired, one could use a conventional double shutter injection tube inserted into the conduit 9n and which would be brought successively opposite each of the branches serving the jacks, in order to be sure that the deployment of the jacks is effective. It should be noted that it is fairly easy to release the rods from the concrete footprint, the latter enclosing only a short, smooth section of each rod if care has been taken to apply the 8n plates against the formwork end. After that, there is only to concrete the excavation 1n + 1. Of course, we will proceed in a similar manner to what has just been described to achieve the junction between the panels n + 1 and n + 2

Thanks to the presence of the flanges or plates? N and 8n the body and the rod of the jacks are firmly anchored in the concrete, which excludes any risk of slipping.

FIG. 3 illustrates the variant of the method of the invention in which double-acting cylinders 14 are used instead of single-acting cylinders 4. In this variant, jacks are used, the cylinder of which has two chambers which can be pressurized by the conduits 9n and 11n respectively, and the procedure is as described with reference to FIGS. 1 and 2, except that in the sequence illustrated by FIG. 1e, the rods are not fully deployed but a certain residual stroke is left, for example by providing a stop 12n on the rod of each cylinder, and that, after setting the concrete poured into the excavation n +1, the rod of each of the jacks is put in traction by injecting through the conduit 11n a hardenable fluid under pressure, such as a cement grout without shrinkage, the grip of which will ensure the durability of the traction force applied to the rod of each of the cylinders. FIG. 3 illustrates the jacks after they have been pulled.

Claims (9)

1. A method for ensuring mechanical continuity and the transmission of forces between two adjacent panels of a reinforced concrete wall, molded in the ground, characterized in that it consists in drowning in the concrete of a panel n being making the bodies (5n) of a plurality of jacks distributed at intervals over the height of the panel and arranged at the end of said panel adjacent to the next n + 1 panel to be produced, the rods of the jacks being in the retracted position and their ends being brought to the immediate vicinity of the formwork means (2n) of the end of the excavation into which the panel n is poured, then, after sufficient taking of the concrete from this panel, execution of the excavation of the next panel n + 1 and removal of the formwork means provided at the end of the excavation of the panel n, to deploy the rods (6n) of the jacks so that they penetrate into the excavation of the panel n + 1 according to be produced and, finally, to concreting the excavation of said n + 1 panel in a core ant the rods of the cylinders in the concrete. 2 _o A method according to claim 1, characterized in that the cylinders bodies are attached to a frame cage placed in the trench n before concreting the excavation. 3. Method according to claim 1 or 2, characterized in that cylinders are used whose body and rod are provided, at their opposite ends, flanges or plates. 4. Method according to claim 1, 2 or 3, characterized in that single acting cylinders are used. 5. Method according to claim 1, 2 or 3, characterized in that double-acting cylinders are used, and in that the rods of the cylinders are put in traction after setting of the concrete poured into the excavation n + 1 , by injecting a hardenable pressure fluid into the cylinders. 6. Method according to any one of claims 1 to 5, characterized in that there is provided a plurality of jacks at each end of a panel on two. 7. Method according to claim 6, characterized in that the bodies of the jacks provided at the two ends of a panel are connected in pairs by a connecting member. 8. Method according to any one of claims 1, 2, 4, 5 and 6, characterized in that the bodies of the jacks carry protrusions. 9. Method according to any one of claims 1, 2, 4, 5 and 6, characterized in that the cylinders bodies are fixed to irons or anchor bars embedded in the concrete.

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