EP0028558B1 - Method of improving the sliding resistance of a civil engineering construction and its foundation - Google Patents

Abstract

A foundation for a retaining wall-type of structure acted upon by a principal force tending to slide same in a predetermined direction is anchored by a plurality of slide resisting walls. The slide resisting walls extend parallel to the predetermined direction in which the foundation tends to slide. The upper portions of the slide resisting walls are embedded in a concrete mass. The lower portions of the slide resisting walls project downwardly from the concrete mass into the earth, and are solely in engagement with the earth and not with concrete.

Description

The present invention relates to a method for improving the sliding resistance of a civil engineering structure, in accordance with the preamble of the main claim, which would risk moving due to the forces which it is called upon to bear, particularly when the efforts in question have a horizontal component.

The invention also relates to a foundation, in accordance with the preamble of claim 2, produced by the aforementioned method. The above-mentioned horizontal components appear, in particular when the structure under consideration is subjected on two opposite faces to different water pressures and thus plays a role of dam.

Similar horizontal forces appear when a structure built on the ground is subjected to an earth pressure.

In the two cases above, the structure risks slipping on the ground on which it rests. This risk is low, when it is a rocky soil or of good quality alluvium, with a satisfactory internal friction angle. It is different if the soil is more or less clayey or muddy.

The process of consolidating a foundation by one or more cross walls, which constitutes the object of the present invention, has a very general character and is already known from FR-A-2 088 676 or from FR-A-2 190 129. It will obviously take different forms depending on the type of work considered supporting horizontal forces, the foundation of which must be consolidated. Its application will be described in the case of the particular type of structure which is the subject of FR-A-2 190 129.

In this process, a platform is immersed in the water to rest it on two parallel sheet pile curtains sunk into the ground. The concrete is then poured under the platform so as to fill the space between the ground, this platform and the two curtains. This produces a concrete block which forms the foundation or the foundation of the body of the dam.

One of the sheet pile walls is located directly above the upstream face of the dam, while the other is placed along the downstream face. The strength of the foundations thus made depends in part on the strength of the two parallel curtains anchored in the ground. It will however be observed that these two curtains work perpendicular to their plane and are, therefore, liable to deform.

The object of the present invention is to provide a method making it possible to improve the slip resistance of the foundation of a civil engineering structure exposed to withstand forces having a horizontal component comprising a concrete block in contact with the ground.

According to the invention, this process is characterized in that beats in the ground of the metal pallet curtains parallel to the direction of the forces that the structure will have to bear, curtains which are called cross curtains and in that, after having beaten the sheet piles in the ground without driving them completely, the concrete constituting the concrete block is poured around the upper parts projecting from the ground of the split curtains so that they are embedded in said massive.

Because the upper parts of the split curtains are embedded in the concrete block, the sheet piles of these split curtains can not slide relative to each other under the action of a horizontal force exerted in the plane of the curtain in question. Put in the impossibility of sliding as it has just been said and hung to each other by their locks, they constitute a resistant and non-deformable monolithic wall which could only move in one piece.

As, in addition, the curtain of partition could not move in its plane compared to the ground only under the action of considerable efforts, higher than those which one must envisage, the solid mass of concrete will be solidly anchored in the ground.

Another object of the invention is to create a foundation exposed to withstand forces having a horizontal component, comprising a platform serving as formwork above a concrete block, this platform being stiffened on its underside by beaming and resting on two metal sheet pile walls threshed in the ground so that their upper parts protrude from the ground and arranged perpendicular to the horizontal component of the forces, the concrete filling the space between the ground, the platform and sheet pile curtains.

According to the invention, this foundation, characterized in that it also comprises cross-curtains constituted by metal sheet piles beaten in the ground parallel to the horizontal component of the forces and in that these cross-curtains are arranged under the beams and that their upper part, projecting from the ground is embedded in the concrete block, said block thus connecting the curtain curtains to the beams which stiffen the platform.

• La fig. 1 est une vue schématique transversale montrant une plate-forme conforme à l'invention reposant sur deux rideaux parallèles de palplanches, avant la constitution du massif de béton,
• la fig. 2 est une vue en coupe suivant le plan II-II de la fig. 1,
• la fig. 3 est une vue analogue à la fig. 1, montrant la coulée du béton sous la plate-forme,
• la fig. 4 représente, en coupe schématique, l'application de l'invention à la réalisation d'une fondation de barrage mobile.

Other features and advantages of the invention will appear in the description below.

• Fig. 1 is a schematic transverse view showing a platform in accordance with the invention resting on two parallel sheet pile walls, before the concrete block is formed,
• fig. 2 is a sectional view along the plane II-II of FIG. 1,
• fig. 3 is a view similar to FIG. 1, showing the pouring of the concrete under the platform,
• fig. 4 shows, in schematic section, the application of the invention to the production of a mobile dam foundation.

To make the submerged foundations at sea or in the river of a movable dam raft or the foundation of a civil engineering structure, dredging is optionally carried out, then a pile of soil is driven into the ground 1 palplan ches 2 so as to form two parallel curtains of sheet piles 3 and 4, substantially perpendicular to the direction F of the stream of water (see fig. 1). The curtain 3 is arranged upstream relative to the curtain 4 relative to the aforementioned direction F of the stream of water.

The sheet piles 2 of the curtains 3 and 4 are hooked to each other by their locks 2a, 2b, as shown in fig. 2.

The parallel curtains 3 and 4 are intended to serve as a support for a platform 5, the longitudinal edges 5a, 5b of which are folded down at 6 and 7.

Before the installation of this platform 5 on the curtains 3 and 4, a series of sheet piles 8 is driven into the ground 1, between the parallel curtains 3 and 4, so as to form curtains 9, 10. ., said to be split, perpendicular to the curtains 3 and 4. These sheet piles 8 are hooked to each other by their locks 8a, 8b, while the ends 9a, 9b, 10a, 10b, of these curtains 9, 10 are preferably connected to the two parallel curtains 3 and 4. The grooves 20 of the various curtains open alternately in opposite directions.

In the case of the embodiment shown, the platform 5 has on its lower surface 5a, a beam which gives the sheet the necessary rigidity, beam which is represented schematically by the beams 11. The sheet piles 8 of the split curtains 9, ..., are driven into the ground until the dimension of their upper edges 12 is located slightly below that of the flanges 13 of the beams 11.

After the platform 5 has been placed on the curtains 3 and 4, alluviums 14 are formed along the latter and against the edges 6 and 7 of the platform 5, so as to close off the space between the ground 1 and these edges 6 and 7.

Concrete 15 is then poured into the substantially closed space situated between the platform 5, the ground 1 and the massive embankments 14 (see fig. 3), as described in FR-A-2 190 129. This operation can be carried out by means of concrete injection nozzles 16 which are engaged in openings 17 made in the platform 5.

Once the concrete mass 15 has hardened, the platform 5 is securely fixed to the concrete by the beam which stiffens it.

On the other hand, the mass of concrete 15 completely covers the upper part of the sheet piles 8, which constitute the cross-sections 9, 10 ...

The foundation thus obtained can then serve as a base for a dam body or constitute the raft of a movable closure system with valve 19 (see fig. 4) as described for example in FR-A-2 458 633.

The dividing curtains 9, 10, ..., arranged between the upstream 3 and downstream 4 curtains considerably increase the sliding resistance of the foundation, sliding which could result from the forces exerted by the pressure of the water in a direction perpendicular to these upstream 3 and downstream 4 curtains.

This resistance results on the one hand from the connection of the cross curtains 9, 10, ..., with the ground 1 and on the other hand from the connection of these curtains 9, 10, ..., with the concrete block 15 integral with the raft.

The dividing curtains 9, 10 ... each offer, thanks to the grooves 20 formed by the juxtaposed sheet piles 8 considerable resistance and even practically infinite resistance to displacement in a direction parallel to their plane.

The slip resistance of the foundation with respect to a force applied parallel to the cross curtains 9, 10 ... increases with the number of curtains 9, 10 ... It is all the more important as the distance L (see fig. 2) between two adjacent cross curtains 9, 10 ... is lower. Between two cross curtains, the raft constitutes a beam whose height corresponds to a significant fraction of the span.

Furthermore, good conditions for anchoring the concrete slab 15 relative to the ground 1 are achieved when the upper part of the sheet piles 8 making up the cross-curtains 9, 10, etc. is embedded in the concrete 15 over a height H included. between 0.30 and 1 m.

Of course, the invention is not limited to the example which has just been described and many modifications can be made to it without departing from the scope of the invention.

Thus the invention can also be applied to the case of non-submerged foundations, resting on a slippery floor and liable to be subjected to significant forces comprising a horizontal component such as that which could result from a push of the earth.

In such non-submerged foundations, the use of the platform 5 for pouring concrete 15 is of course not necessary. Frequently, the light curtains can also be removed.

Furthermore, to build a solid, non-deformable, monolithic crosswall, one could not use metal sheet piles, but use the well-known technique of walls molded into the ground, to directly build a reinforced concrete wall.

Claims (4)

1. Method for improving the resistance to sliding of the foundation of a civil engineering structure destined to withstand forces having a horizontal component and comprising a massive concrete structure (15) which is in contact with the ground (1) or attached to this latter by any means known per se, characterized in that metallic sheet-pile walls (9, 10) which are parallel to the direction of the forces to be resisted by the structure are driven into the ground, said sheet-pile walls (9, 10) being known as cross-walls, and that, after the sheet piles have been driven into the ground without being driven-in completely, the concrete constituting the massive concrete structure (15) is placed around the top portions of the cross-walls (9, 10) which project with respect to the ground, with the result that these latter are embedded in said massive structure (15).

2. Foundation which is destined to withstand forces having a horizontal component, comprising a platform (5) which serves as a top shuttering element for a massive concrete structure (15), this platform (5) being stiffened on its bottom face by a system of girders (11) and supported on two metallic sheet-pile walls (3, 4) which are driven into the ground so that their top portions project with respect to the ground (1), and disposed at right angles to the horizontal component of the forces, the space formed between the ground, the platform (5) and the foundation sheet-pile walls (3, 4) being filled with the concrete (15), characterized in that the structure further comprises cross-walls (9, 10) constituted by metallic sheet-piles driven into the ground in a direction parallel to the horizontal component of the forces and that these cross-walls (9, 10) are placed beneath the system of girders (11) and that their top portion which projects with respect to the ground (1) is embedded in the massive concrete structure (15), the cross-walls (9, 10) being thus joined by said massive structure (15) to the system of girders (11) which stiffens the platform (5).

3. Foundation in accordance with claim 2, characterized in that the distance (L) between the cross-walls (9, 10) is substantially comprised between 5 and 10 times the distance (D) comprised between the two sheet-pile cross-walls (3, 4) which are driven-in first.

4. Foundation in accordance with claim 3, characterized in that the upper portion of the cross-walls (9, 10) is embedded in the concrete (15) to a depth (H) comprised between 0.30 and 1 m.

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