EP0513461B1 - Method and apparatus for creating thin walls in the ground - Google Patents

Abstract

The invention relates to a method and apparatus for creating continuous thin walls in the ground, of the type in which a vertical beam or sheet pile, which comprises at its lower part a device for injecting a grout into the ground, which grout, after solidifying, forms the thin wall, is driven successively into the ground, along the route of the wall being built, using vibratory means. Method characterised in that at least one jet (12) of liquid at very high pressure, directed substantially in the plane of the wall to be built, is sent to the lower part of the beam (1). <IMAGE>

Description

The present invention relates to a new method for producing thin walls in the ground and to a device for implementing this method.

We know that we have to make thin grout walls in the ground to constitute in particular continuous watertight barriers.

Such walls can be less than ten centimeters thick and more than 10 meters high.

To make them, it is already known to use a beam or sheet pile having a generally H-shaped section which is driven into the ground using a vibrator along the path of the wall which it is desired to make. . At the same time, a grout based on cement or another hardening product is injected into the lower part of the beam in order to produce the thin wall in place of and in the vicinity of the beam. The injection can also be carried out during the ascent of the beam.

According to this known process, the grout is injected at a low pressure, for example of a few tens of kilos per cm², which is sufficient to maintain the ground and constitute the thin wall.

This method has the disadvantage of being relatively long to implement because it is necessary to beat or vibrate the beam in many successive positions which overlap, so that each threshing produces a width wall that is less than the width of the beam. In addition, the vibrations to which the beam is subjected can in certain cases disintegrate fine soils in the vicinity of the beam by creating pockets of debris in the wall which has just been produced and which therefore has a defective seal.

Another method is also known for producing thin walls which consists in driving from place to place along the path which the thin wall must occupy, a train of rods which is provided at its lower part with nozzles by which a grout of cement at very high pressure, for example at pressures between 200 and 600 kilos per cm², so as to cut in the ground by the technique called "jetting", a wall section which will be filled with a cement grout which, after hardening, will form the thin wall.

In this technique the jets of cement grout under high pressure are directed substantially in the plane of the wall to be produced, it being understood however that the jets sent from two neighboring boreholes must form a slight angle between them so as to overlap preferably substantially equidistant from the two piles.

This known method has the drawback that if a slight angular error occurs in the positioning of the piles, the continuity is lost, that is to say the tightness of the wall. In addition, it does not allow in practice to produce thin walls.

The subject of the present invention is a method which avoids the drawbacks of the methods mentioned above, and which makes it possible to produce thin walls in an efficient and economical manner.

The subject of the present invention is a new process for producing continuous thin walls in the ground of the type in which a vertical beam or sheet pile which has been successively pressed into vibrations in the ground, along the path of the wall to be produced. a thickness corresponding substantially to that of the wall to be produced and which comprises at its lower part a device for injecting into the ground a grout which, after solidification, constitutes the thin wall, a process characterized by the fact that the part is sent to the bottom of the beam or the sheet pile at least one jet of liquid at a very high pressure at least equal to two hundred kilos per cm² directed in the plane of the wall to be produced.

The very high pressure liquid is sprayed with a pressure which can be for example a few hundred kilos per cm².

The liquid which, according to the invention, is injected at very high pressure into the lower part of the beam can advantageously consist of a cement grout or another product which contains sufficient aggregate to harden it, allowing the wall to be produced. . This injection of liquid at very high pressure can be accompanied by an injection of gas and / or of another liquid at a relatively low pressure, for example of a few tens of kilos per cm 2.

According to a preferred embodiment of the method according to the invention, the spraying of the liquid at very high pressure takes place below the beam, from a nozzle which is located at the rear of the beam, (that is to say in the vicinity of the part of the wall which has already been produced) and in the direction of the part of the wall to be produced. We avoid as well as the terrain disintegrated by the vibrations of threshing comes to form pockets in the thin wall already produced and that the latter thus loses its continuity.

In another embodiment of the invention, a grout jet is sent to the already formed wall under very high pressure, possibly accompanied by an air jet of a nature to form the wall by hardening. This causes kneading of the grout which constitutes the upstream wall already formed and one thus destroys the pockets of ground debris which it could contain.

Alternatively, it is also possible to send downstream, in the opposite direction, a water jet under very high pressure, possibly accompanied by a grout jet and / or an air jet under relatively low pressures. .

In another variant, it is possible to send in the direction of the wall to produce a jet of grout under very high pressure, of a composition such that this grout can, after hardening, constitute the thin wall, accompanied by an air jet and optionally a jet of water under relatively low pressures.

The use of the jet of liquid at very high pressure in the direction of the wall to be produced has significant advantages over the already known technique of threshing the beam by vibro-driving.

First of all, this very high pressure jet avoids that under the action of the vibro-sinking of the beam, the ground which is below it does not flow back into the part of the thin wall which has already been performed, this due to the fact that the very high pressure jet tends to reject the ground downstream, in the direction of the thin wall which remains to be produced.

In addition, the action of the jet at very high pressure is exerted at a significant distance downstream of the beam, which makes it possible to increase the distance between the successive threshing positions of the beam. The excavation of the thin wall can even be carried out between two threshing positions only by the very high pressure jet, so that the distance which separates two successive threshing of the beam can be substantially greater than the width of the beam, so that in the known technique, it is less than or equal to this width.

Finally, the use according to the invention of the very high pressure liquid jet which disintegrates the ground at the bottom of the beam greatly facilitates the vibro-sinking of the latter which is faster and consumes significantly less energy.

According to the invention, it is possible to simultaneously use several jets at very high pressure which are sent in the plane of the wall which remains to be produced.

Thus it can be advantageous to use at the same time as a jet of grout at very high pressure directed upstream, a second jet at very high pressure downstream, that is to say say towards the wall that needs to be done.

The present invention also relates to an apparatus for producing continuous thin walls in the ground of the type comprising a vertical beam or sheet pile of reference H-section actuated by a vibro-beater, which has a thickness corresponding substantially to that of the wall to be produced and which is provided at its lower part with a device for injecting grout, this apparatus being characterized in that the beam or sheet pile comprises at its lower part at least one device for sending a liquid at a very high pressure at least equal to two hundred kilos per cm² in the plane of the thin wall being produced.

According to one embodiment of the invention, this device is advantageously located below and behind the lower end of the beam, so that the jet of liquid under very high pressure is sent below the beam, towards the wall to be made.

In a variant of this embodiment, the apparatus according to the invention further comprises a device for sending grout at very high pressure, which is placed at the lower part of the beam upstream, on the side of the part of the wall that is already made.

According to another embodiment, the device directs the grout jet under very high pressure only upstream, that is to say in the direction of the thin wall already produced.

The apparatus according to the invention may also include a device for sending a gas and / or a liquid under relatively low pressure, in parallel and in the vicinity of the jet of liquid at very high pressure.

• la figure 1 représente une vue schématique de la mise en oeuvre d'un procédé conventionnel de réalisation de parois minces dans le sol,
• la figure 2 est une vue à plus grande échelle de la partie inférieure d'un premier mode de réalisation de la poutre verticale selon l'invention,
• la figure 3 est une vue en coupe selon III-III de la figure 2,
• la figure 4 est une vue en coupe de la partie inférieure d'un deuxième mode de réalisation de la poutre verticale de l'invention,
• la figure 5 est une vue en coupe selon V-V de la figure 4,
• la figure 6 est une vue en coupe de la partie inférieure d'un troisième mode de réalisation de la poutre selon l'invention,
• la figure 7 est une vue en coupe selon VII-VII de la figure 6,
• la figure 8 est une vue de la partie inférieure d'un quatrième mode de réalisation de la poutre verticale de l'invention, et
• la figure 9 est une vue en coupe selon IX-IX de la figure 1.

In order to better understand the invention, we will now describe, by way of illustration and without any limiting character, several embodiments taken as examples and shown in the appended drawing in which:

• FIG. 1 represents a schematic view of the implementation of a conventional method for producing thin walls in the ground,
• FIG. 2 is a view on a larger scale of the lower part of a first embodiment of the vertical beam according to the invention,
• FIG. 3 is a sectional view along III-III of FIG. 2,
• FIG. 4 is a sectional view of the lower part of a second embodiment of the vertical beam of the invention,
• FIG. 5 is a sectional view along VV of FIG. 4,
• FIG. 6 is a sectional view of the lower part of a third embodiment of the beam according to the invention,
• FIG. 7 is a sectional view along VII-VII of FIG. 6,
• FIG. 8 is a view of the lower part of a fourth embodiment of the vertical beam of the invention, and
• Figure 9 is a sectional view along IX-IX of Figure 1.

There is schematically shown in Figure 1 a vertical beam or sheet pile 1 used to produce according to a traditional method a thin wall of cement grout or other curable materials.

To implement this known method, the beam 1 is driven into the ground using a vibrator 3 suspended from the end of the mast 4 of a lifting machine 5 and guided by a vertical mast 3 a .

At the lower part of the beam 1 is an injection device 6 shown diagrammatically which sends grout under a relatively low pressure to the base of the beam which is being threshing.

The grout thus injected serves to facilitate the descent of the beam and, during the ascent, to fill the void left by the depression of the beam 1.

To make the wall, successive sinking of the beam 1 is carried out by moving it to the right at most a distance corresponding to its width. In practice, the beam can only be moved to the right for a new threshing by a distance less than its width so as to obtain an overlap of the footprints left by the beam in the ground.

There is shown in Figures 2 and 3 a first embodiment of the lower part of the beam according to the invention.

As can be seen in Figure 3, the beam 1 has an H-shaped section having a core 7 joining two wings 8 and 9. A its lower part the beam 1 is reinforced by extra thicknesses 7 a , 8 a and 9 b making it possible to make an imprint in the ground with dimensions greater than those of the current section of the beam.

In the present case, the lower end of the beam 1 also has on its left part a fin 10 located in the extension of the core 7. This fin is intended to engage in the part of the wall which has been produced. during the previous threshing of the beam.

In accordance with the invention, a nozzle 11 has been placed at the lower part of the beam, making it possible to send a jet of grout 12 at very high pressure substantially horizontal in the plane of the thin wall, that is to say in the plane of the core 7 of the beam 1.

The composition of this grout based on water, cement and aggregates (sand, gravel, limestone powder etc.) is such that it can, after solidification, constitute the thin wall.

This grout projected under very high pressure at 12 causes cutting of the ground below the beam 1 and on the right beyond this beam in the plane of the wall which must be produced.

The very high pressure grout is supplied by a tube 14 disposed along the wing 9.

The implementation, in accordance with the invention, of sending the grout under very high pressure to the lower part of the beam 1 has the multiple advantage of pushing back the ground which is falling apart under the beam 1 by preventing it from engage to the left in the part of the wall that has already been made, to facilitate the insertion of the beam 1, which makes it easier to work and save energy, and to achieve a flat cavity downstream of the beam 1, that is to say on the right as seen in FIG. 2, cavity which is used for the subsequent molding of the planar wall.

Thus, thanks to the invention, it is not necessary that, during two successive driving of the beam 1, the footprints overlap. On the contrary, it is possible to carry out successive threshing of the beam 1 by spacing them a distance which is greater than the width of the beam 1, the cavity intended to receive the thin wall between two successive imprints of the beam 1 being produced by the jet 12 a at high pressure.

In a variant not shown in Figures 2 and 3, one can send an air jet in the vicinity of the grout jet at very high pressure, which facilitates the penetration of the grout into the ground.

The second embodiment of the invention which is shown in Figures 4 and 5 differs from the embodiment of Figures 2 and 3 by the fact that the nozzle for sending liquid, for example water, very high pressure is located on the right part 8 a of the lower end of the beam 1, so that the nozzle 11 a projects a jet 12 a at very high pressure only downstream of the beam 1, that is to say - say in the part of the ground which has not yet been worked by the driving in of beam 1.

The nozzle 6 supplied by the pipe 15 provides the base 1 of the beam 1 of the grout which, after solidification, will ensure the formation of the thin wall.

It is conceivable under these conditions that, while one proceeds to the vibro-threshing of the beam 1 by injecting grout below the beam, as is conventionally known, one also proceeds by spraying liquid at very high pressure according to the jet 12 a to a vertical cutting of the ground which is upstream of the beam 1. It is thus possible to produce the thin wall in this slot, either with the liquid projected by the nozzle 11a when this liquid is curable grout, or by filling this slit with the grout sent at 6 with a volume and a pressure sufficient to occupy the space produced by the water jet 12 a under very high pressure. This space can still be filled during the subsequent beating of the beam 1 which, as explained above, can be carried out at a certain distance from the previous footprint of this same beam.

In the embodiment shown in FIGS. 6 and 7, there is disposed on the left side of the lower part of the beam, a nozzle 17 for sending grout at very high pressure which projects a jet 18 into the part of the thin wall which has already been made during previous threshing, which has the advantage of eliminating any pocket of land which could remain in this part of the thin wall.

The grout thus injected arrives via line 19.

In this embodiment, a very high pressure water jet 12 is also sent via the nozzle 11 and the pipe 14 which is directed downstream to the part of the wall which remains to be produced. We also send through the nozzle 11b, a compressed air jet 12 b which comes via line 14 b and which opens in the immediate vicinity of the water jet 12, which facilitates the penetration of the latter in the soil.

Finally, as in the embodiment of Figures 4 and 5, the nozzle 6 brings the grout under relatively low pressure to occupy the cavity formed in the ground by the high pressure water jet 12 and form the wall after hardening.

The fourth embodiment according to FIGS. 8 and 9 comprises a nozzle 11 for projecting water at very high pressure downstream, towards the part of the wall which is not yet produced, as well as a nozzle projection of grout at very high pressure 17 upstream, in the opposite direction.

As previously explained, the jet 12 of water at very high pressure cuts the ground where the wall is to be made, while the jet 18 of grout 18 at very high pressure, mixes the grout in the wall which has just been carried out to eliminate pockets of ground which could remain in the grout.

The nozzle 11 a sends a jet of grout 12 a , preferably at high pressure, to fill with grout the cavity produced by the very high pressure water jet 12, and the nozzle 11 c sends in the vicinity of the jet of grout 12 a , a jet of compressed air 12 c which arrives via the line 14 c .

The mixing of the air with the grout jet 12 a allows a better distribution of the grout and a better penetration of the jet 12 a .

As can be seen, the invention makes it possible, by simple means, to considerably improve the productivity of an apparatus for producing thin walls in the ground while increasing the quality of these walls.

It is understood that the embodiments which have been described above have no limiting character and that they can receive any desirable modifications without departing from the scope of the invention.

In particular, it is clear that the configuration of the lower part of the beam 1 or sheet pile can be modified according to the opportunities, insofar as the retention at the lower part of the vertical beam is maintained. a jet of liquid sent at very high pressure in the plane of the wall to cut a cavity and / or avoid that pockets of ground remain in the volume which the thin wall must occupy.

Finally, it is understood that according to the invention, the liquid sent at very high pressure can for example be water and / or grout, and that a gas such as air, can be injected in the vicinity of or injection points for very high pressure liquids.

Claims (15)

1. Method for the production of continuous thin walls in the ground, of the type wherein there is driven successively into the ground by vibrations, along the course of the wall constructed, a vertical beam or sheet pile which has a thickness corresponding substantially to that of the wall to be constructed and which comprises at its lower part a device for injecting into the ground a grout which, after solidification, constitutes the thin wall, this method characterised in that there is delivered at the lower part of the beam (1) or sheet pile at least one jet (12, 12a, 18) of liquid at a very high pressure at least equal to two hundred kilos per cm² which is directed substantially in the plane of the wall to be produced.
2. Method according to claim 1, characterised in that the grout is injected with a relatively low pressure of some tens of kilos per cm².
3. Method according to any one of the preceding claims, characterised in that the liquid is projected at a very high pressure of about some hundreds of kilos per cm².
4. Method according to any one of the preceding claims, characterised in that the liquid at very high pressure is constituted by a grout containing cement or another hardening product, as well as aggregates, the said grout constituting the thin wall after solidification.
5. Method according to any one of claims 1 to 3, characterised in that the liquid at very high pressure is water.
6. Method according to any one of the preceding claims, characterized in that a gas under pressure, such as air, is injected in the vicinity of the point of injection of the liquid at very high pressure.
7. Method according to any one of the preceding claims, characterized in that the jet of liquid at very high pressure is directed downstream, in the direction of the part of the wall which is still to be produced.
8. Method according to any one of the preceding claims, characterized in that the jet (12) of liquid at very high pressure is situated below the beam (1).
9. Method according to any one of the preceding claims, characterised in that a jet of grout is projected at very high pressure at the lower part of the beam in the upstream sense, in the direction of the wall which has already been produced.
10. Method according to any one of the preceding claims, characterized in that the jet at very high pressure is projected substantially horizontally.
11. Apparatus for the production of thin walls in the ground by the method according to any one of claims 1 to 10, of the type comprising a vertical sheet pile or beam preferably of H-form section actuated by a vibratory driving, device, which beam or sheet pile has a thickness corresponding substantially to that of the wall to be produced and is provided at its lower part with a device for injecting grout, this apparatus being characterized in that the beam or sheet pile comprises at its lower part at least one device (11, 11a) for projecting a liquid at a very high pressure at least equal to two hundred kilos per cm² in the plane of the thin wall being produced.
12. Apparatus according to claim 11, characterised in that the device (11) for projecting a liquid at very high pressure in the plane of the wall is arranged below and rearwardly of the lower end of the beam (1), such that the jet of fluid at very high pressure (12) is delivered downstream, below the beam.
13. Apparatus according to any one of claims 11 and 12, characterized in that it comprises a device (11a) for projecting liquid at very high pressure situated at the lower part of the beam (1) at the side corresponding to the part of the wall which is not yet produced.
14. Apparatus according to any one of the preceding claims, characterised in that it comprises a device (7) for the projecting of grout at very high pressure which is directed towards the portion of the wall already produced.
15. Apparatus according to any one of claims 11 to 14, characterised in that it comprises a device for injecting air in the vicinity of the jet of liquid at very high pressure.

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