EP0377541B1 - Process and apparatus for anchoring the shieldings of a reinforced-earth wall - Google Patents

Abstract

The process and apparatus which are the subject of the invention make it possible to repair particular reinforced-earth walls consisting of shieldings made of non-reinforced concrete. The shieldings (11) are anchored by means of plates (18) on which bear ties installed in the retained earth by way of a borehole starting from the centre of the shielding (40). The process involves retaining the shieldings (11) by means of a bearing plate (18) fixed to the head of the tie by a nut and pressed onto the shielding (11) at points equidistant from the centre of the shielding and arranged on the axes of symmetry or diagonals (38 and 39) of the shielding (11) and being greater than or equal to four in number. The device is a bearing plate (18) obtained by moulding, which has the general form of a star with four arms (34 to 37) terminating in pads (19) which allow the plate to bear on the shielding (11) at these points only. <IMAGE>

Description

The invention relates to a method and a device for anchoring the scales of a reinforced earth wall.

Some reinforced earth walls are made up of unreinforced concrete scales on their outside facing which hold the ground by means of metal reinforcements embedded in the ground, and moored to the scales. Certain walls thus constructed are threatened with ruin due to the oxidation of the frames embedded in the ground.

The subject of the invention is a method and a device making it possible to effectively repair such walls and to avoid their ruin.

We already know a way to repair these walls. The scales are anchored by means of support plates which retain them and which are properly anchored to the ground. The first plates used had a square shape, then a four-pointed star, as we can see, by reading the provisional document of SETRA, dated November 9, 1987 and entitled:
"Reinforcement of reinforced earth structures with stainless steel frames". The branches of these stars are suitably ribbed and directed each substantially 90 ° from the next. The central zone of these stars is pierced with a hole which allows the passage of the head of a tie rod and the support of the tightening nut. In addition, it comprises, on the side of the star support plane, a projecting crown and, on the opposite side, a hub, which constitutes, with the crown, a central sleeve. As these first plates are in contact with the scale supported over their entire surface, they do not make it possible to obtain the desired anchoring force in the tie rod. Indeed, cracks appear in the scale from this hole, whatever the dimensions of the support plate, while the force required in the anchor rod is not yet reached.

• TALOBRE (CH-A-448 941)
• DOHMEIER (FR-1 556 669)
• WILLIAMS (US-A-3 415 066).

Various devices have been devised in the past to support the rock walls:

• TALOBRE (CH-A-448 941)
• DOHMEIER (FR-1 556 669)
• WILLIAMS (US-A-3,415,066).

They do not make it possible to solve the problem posed, because they take into account neither the main axes related to the scale (axes of symmetry, diagonals), nor the mechanical behavior of these scales in unreinforced concrete of low thickness, which is very different from the behavior of a rock wall, nor from the need to move the bearing surfaces of the plate away from the hole drilled in the scale and to size them in order to avoid punching, nor to the low deformability that must present the support plate so that no new point of contact appears when exerting the force on the tie rod.

It is the same for the ROUMAGNOU device (FR-A-2-334 806) which does not move the bearing surfaces away from the hole drilled in the scale.

• on donne aux dites plaques d'appui une forme telle que chacune prenne appui sur l'écaille qu'elles retient au moyen de plusieurs patins ou pieds équidistants du centre de l'écaille et situés sur les axes de symétrie ou les diagonales de l'écaille,
• le nombre de patins est supérieur ou égal à 4,
• les patins sont les seuls points de contact entre l'écaille et la plaque d'appui,
• la plaque d'appui est solidarisée à la tête du tirant par un écrou.

According to the invention, the method according to which the scales of a reinforced earth wall are held in place by star-shaped bearing plates, by means of tie rods suitably anchored in the ground and the head of which passes through a hole previously drilled substantially in the center of the scale, is characterized in that:

• said support plates are given a shape such that each is supported on the scale which they hold by means of several skids or feet equidistant from the center of the scale and located on the axes of symmetry or the diagonals of the tortoiseshell,
• the number of skates is greater than or equal to 4,
• the pads are the only points of contact between the scale and the support plate,
• the support plate is secured to the head of the tie rod by a nut.

Advantageously, provision is made for 4 points of support for the plates on the said scales, distributed substantially along the diagonals of the scales.

When operating in this way, it is possible, by means of a limited number of support plates, namely one per scale, to distribute and balance the support forces suitably on each scale, without deterioration thereof, and correctly retain the land, under very advantageous conditions of intervention cost.

The invention also relates to a device allowing the implementation of the above-mentioned method, and more specifically to a support plate having the general shape of a star with four suitably ribbed branches, each directed substantially at 90 ° from the next, and from a central area. This zone is pierced with a hole for the passage of the head of a tie rod and for the support of a tightening nut which fixes the plate to the tie rod. The central zone of the support plate comprises, on the side of the support plane of said plate, a projecting crown, and, on the opposite side, a hub which constitutes, with the crown, a central sleeve, as known from SETRA document mentioned above.

• chaque branche de l'étoile comporte respectivement, à son extrémité, un patin en relief (ces patins définissent le plan d'appui sus-visé),
• la couronne en saillie présente une section de diamètre extérieur sensiblement inférieur au diamètre du trou foré dans ladite écaille,
• ladite plaque est obtenue par moulage.

This support plate is characterized in that:

• each branch of the star respectively has, at its end, a raised pad (these pads define the abovementioned support plane),
• the projecting crown has a section of outside diameter substantially smaller than the diameter of the hole drilled in said scale,
• said plate is obtained by molding.

• la figure 1 est une coupe transversale faite au niveau de la tête d'un tirant mis en place à travers une écaille à soutenir, conformément au procédé de l'invention,
• la figure 2 montre, de façon schématique, un plan d'intervention sur un mur en terre armée menaçant ruine,
• la figure 3 montre une vue en coupe faite dans le plan III-III de la figure 2, illustrant schématiquement la mise en place des tirants ancrés dans les terrains,
• la figure 4 montre, en vue en plan, de l'extérieur, sensiblement selon la flèche IV de la figure 1, la forme de la plaque d'appui,
• la figure 5 montre, en vue perspective, une plaque d'appui vue de l'autre côté, sensiblement selon la flèche V de la figure 1.

The invention and its implementation will appear more clearly with the aid of the description which follows, made with reference to the appended drawings illustrating an embodiment and in which:

• FIG. 1 is a cross section made at the level of the head of a tie rod placed through a scale to be supported, in accordance with the method of the invention,
• FIG. 2 schematically shows an intervention plan on a wall of reinforced earth threatening ruin,
• FIG. 3 shows a sectional view made in plane III-III of FIG. 2, schematically illustrating the positioning of the tie rods anchored in the terrain,
• FIG. 4 shows, in plan view, from the outside, substantially along arrow IV of FIG. 1, the shape of the support plate,
• FIG. 5 shows, in perspective view, a support plate seen from the other side, substantially along arrow V of FIG. 1.

Referring first to Figure 1 there is illustrated in longitudinal section, at the level of the head of a tie rod, the positioning of a support plate making it possible to retain a scale of unreinforced concrete from the facing of the wall. in an armed land threatened with ruin. In 10, the terrain is referenced and in 11, a scale of the facing which is of substantially rectangular shape with recesses facilitating the staggered laying of these scales, as it appears more clearly in FIG. 2.

In FIG. 1, it can be seen that, in the unreinforced concrete scale 11, a hole 12 has been drilled substantially in the center of the scale, as also identified in FIG. 2. The hole 12 has been made at an angle determined by calculation, suitably inclined to the horizontal as it appears more clearly in figure 3. The drilling was done, through the scale and over a calculated length, in the ground. This length depends on the nature of the ground and the height of the embankment to be maintained. In the example of FIG. 3, it has been assumed that the length of the tie rod, at the level of the median scale 11 was of the order of 5 meters. For the 11 '' upper level scale, a tie and drill length of 4 meters may be sufficient, while at the underlying level 11 ', the calculation will indicate a tie length of 6 meters for example.

In 13, the tie rod has been identified, which may be constituted by a steel bar comprising, at its head 14, a thread for placing a tightening nut over a support washer 16 and a gasket 17 (for example, made of Shore hardness rubber 80) holding the support plate 18 which comes to bear, by its pads 19, on the outer surface of the scale 11.

In FIG. 1, it can also be seen that the support plate 18 has, on its internal face turned towards the terrain, a sort of crown 20 towards the rear and a hub 41 towards the front forming a central sleeve, the whole inclined along an axis 42 on the horizontal and therefore, at an angle to the general support plane of the plate 18. On the crown 20, a tube 21 made of suitable plastic such as PVC is engaged. Over the tube 21 is engaged another section of plastic tube of similar quality 22, comprising a truncated cone 22a uniting a part of reduced diameter 22b which encloses the tube 21 and a part 22c of enlarged diameter fitting, with a certain clearance, inside the borehole 12. In this section 22c of enlarged diameter, is also received a third section of tube 23 of similar quality. The total length of the three sections engaged end to end 21, 22, 23 is chosen so as to correspond substantially to the thickness of the scale 21. These sections can be joined together, for example, by gluing or heat sealing, and the tube 21 can be fixed, for example, by gluing to the crown 20.

Still in FIG. 1, we can see, towards the free end of the last section 23 of plastic tube, a seal 24 made of plastic foam held in place around section 23 by a strip, wire or the like 25. As it clearly appears in the drawings, the seal 24 carries, inside the drilled hole, on the scale, ensuring the tightness at this level.

Referring to Figures 4 and 5, we can more clearly see the general shape of the support plate 18, formed in a 4-pointed star with 4 support pads 19, and, the 3 sections 21, 22, 23 of tube plastic received on the crown 20 of the plate as well as the foam gasket 24.

We will now describe the method of setting up the device according to the invention.

• par un rond plein, les tirants d'une longueur déterminée, par exemple de 5 mètres,
• par un rond marqué d'une croix, les tirants déterminés d'une longueur inférieure, par exemple de 4 mètres,
• par un rond clair, les tirants d'une longueur supérieure, par exemple de 6 mètres,
• etc...

First of all, we will have determined, by calculation, at the level of each scale, the length and direction of the drilling that will have to be carried out through each scale of the facing of the wall to be repaired. These indications can be schematically transferred to the intervention plan in Figure 2, indicating:

• by a solid circle, tie rods of a determined length, for example 5 meters,
• by a circle marked with a cross, determined tie rods of a shorter length, for example 4 meters,
• with a clear circle, tie rods of a greater length, for example 6 meters,
• etc ...

At each scale, we will then drill, substantially at the center of each scale, a hole of diameter and length determined for the passage of the tie rod 13 and its anchoring to the ground. After drilling the hole through the flake and fitting the tie rod 13, it will be sealed in the conventional way, with a filling cement grout as shown in 26. This grout, after refusal of the land, will take on a substantially horizontal orientation , as illustrated in FIG. 1. Of course, the tie rod 13 has been put in place so that its head 14 protrudes sufficiently above the scale 11, so that one can then pass over it. support plate 18, the washers 16 and 17 for positioning, and that one can tighten the nut 15 for tensioning.

When the cement grout 26 has sufficiently solidified, the support plate 18 provided with the three tube sections 21, 22, 23 and the seal 24 is put in place, over the head 14 of the tie rod. , until proper positioning, that is to say until the pads 19 come to bear against the scale 11. And in parallel, care has been taken to engage a tube 27 in the borehole 12 which will come out, behind the seal 24, in the space, for the moment left empty, above the grout 26 for sealing the tie rod. We have identified at 27a the point where the opening of the filling tube 27 opens into this space. We can then introduce, by this tube, the additional grout used to finish the anchoring and to protect the head of the tie rod, which grout will fill all the free space between the tie rod 13 and the casing formed by the inside of the tube sections 21, 22, 23 and also the free gap between the crown 20 and the head of the tie rod . We have figured and hatched, in 28, this additional grout. The operation of placing the additional grout is facilitated by the provision of a vent hole 29, directed radially outwards from the support plate in its hub 41 and in its lower part; This vent can, moreover, communicate with a vent pipe 30, for the recovery of the surplus additional grout. In 31, 32 there are shown shims for the proper functioning of the plate 18 fixed to its tube 21, 22, 23 for fitting and proper sealing.

These operations being completed, it is possible, when the tie rod 13 is properly anchored, securely tighten the nut 15 for tensioning the system.

Referring again to Figures 4 and 5, we will describe more precisely the particular configuration of the star support plate 18 used in the example described.

The concrete scales being rectangular, the support plate 18 is in the form of a star with 4 ribbed branches, marked 34 to 37, oriented at 90 ° from each other, and positioned on each scale such that 11, so that the support pads 19, located at the ends of each branch, are on the diagonals 38, 39 of the scales, at a certain distance from their center 40, where the orifice 12 was drilled the passage of the tie. The pads 19, located at the ends of the branches 34 to 37 of the star which are supported at this location on the scale 11, therefore distribute support forces in 4 zones located on the diagonals of the scale. In the illustrated embodiment, the scales such as 11 were of a substantially square shape 1.50 m on a side, while the 4-pointed star 18 was inscribed substantially inside a 40 cm square side, a distance from pad 19 to pad 19, opposite on the same diagonal, of the order of 50cm. Advantageously, the plate 18 is made of cast iron, as well as the pads 19 which are part of this plate.

The comparison of Figures 1 and 4 makes it possible to clearly see the ribbed configuration of the star, allowing the repair of reinforced earth walls for a reduced weight, and, avoiding, in the position of use against the wall, that water coming from the bad weather can stagnate on the hub 41 of the plates 18.

In FIGS. 1, 4 and 5, we can also see, on the internal face side of the support plate 18, the projecting crown 20, inclined at an angle relative to the general support plane of the pads 19, and on which may easily attach the composite plastic tube 21, 22, 23 described above, which facilitates the positioning of the plates on the wall.

The abovementioned support plates make it possible to limit, to precise regions of the unreinforced concrete flakes 11, the rigid support contacts, which allows the abovementioned scales to withstand, in much better conditions, the forces brought by the anchors.

Claims (6)

1. Repair process for reinforced earth walls made up of non reinforced concrete shielding. This shielding is held in place using star shaped pressure plates and pull rods suitably anchored in the ground. The pull rod end passes through pre-drilled holes in the centre of the shielding. It is characterised by:

   - the form given to the said pressure plates (18), the form is such that each plate applies pressure to the shield (11) which it retains by means of several pads or feet (19) equally distanced from the centre of the shielding (40) and placed along the symmetric axes or the diagonals of the shielding,

   - the number of pads is equal or superior to 4,

   - the pads are the only contact points between the pressure plate and shielding,

   - the pressure plate is held in place by means of a nut (15) screwed onto the end of the pull rod (14).
2. Process in accordance with the claims made in 1, characterised by:

   - the number of pads (19) being 4,

   - the pads are placed along the diagonals of the shielding (11).
3. The pressure plate used for the application of any of the above claims is designed in the form of a star having four branches (34 to 37) suitably corrugated and places at angles of 90° from one another, the central zone has a hole drilled in it for passage of the end (14) of the pull rod (13) and for the application of the tightening nut (15) used to join the pressure plate and the pull rod. The central zone of the pressure plate bears on the pressure plane side a crown (20) standing off and on the opposite side a hub (41) made up of a crown with central sleeve, characterised by:

   - each branch of the star comprises, respectively, at the end, a protruding pad (19) (these pads determine the pressure plane of the plate on the shielding),

   - the standing off crown has an exterior diameter which is considerably inferior to that of the drilled hole in the said shielding,

   - the said pressure plate is manufactured by moulding.
4. Pressure plate according to the claims in 3 characterised by the fact that the axis of the crown is bias inclined in respect to the pressure plane of the pads (19).
5. Pressure plate according to the claims in 3 and 4 characterised by the fact that the hub bears at least one opening (29) directed largely radially and in connection with the interior of the central sleeve.
6. Pressure plate according to any one of the claims from 3 to 5 characterised by the fact that it is made of cast iron.

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