EP0413676B1 - Process for fixing anchors - Google Patents

Description

• on réalise le trou foré en question en enfonçant ou en faisant forer dans le sol un tube de forage (2) comportant une tête de forage et on agrandit le diamètre du trou foré par injection sous pression d'un liquide,
• on utilise pour cela un tube de forage rotatif muni d'une tête de forage, on place dans l'axe central du tube de forage ledit équipement, la longueur de cet équipement correspondant sensiblement à celle du tube de forage, et, dans la phase finale, on laisse en place dans le sol l'équipement en question ci-dessus lors du retrait du tube de forage tandis que du coulis de ciment est injecté sous pression autour de l'équipement dans la cavité forée élargie formée. Un tel procédé est connu du document FR-A-2144079.

The present invention relates to a method of fixing anchors, bolts and equivalent equipment in the ground, by digging a hole drilled using a drilling head and by injecting a cement grout, according to which process (see preamble to claim 1 appended):

• the drilled hole in question is produced by driving a drilling tube (2) having a drilling head into it or drilling it into the ground and the diameter of the drilled hole is enlarged by injection of a liquid under pressure,
• a rotary drilling tube with a drilling head is used for this, said equipment is placed in the central axis of the drilling tube, the length of this equipment corresponding substantially to that of the drilling tube, and, in the phase Finally, the equipment in question above is left in place in the soil during the withdrawal of the drill pipe while cement grout is injected under pressure around the equipment into the enlarged drilled cavity formed. Such a method is known from document FR-A-2144079.

• a) Sous un angle de 0 à 90°, un trou de forage est réalisé dans le sol, éventuellement par utilisation d'un rinçage à l'eau et/ou d'air. Dans le cas de cette manipulation, un coulis peut être injecté;
• b) après l'exécution du trou foré, l'ancrage (boulons ou équipements) pourvu ou non de tubulures d'injection et/ou de moyens d'étanchéité est placé dans le trou foré;
• c) l'ancrage est fixé dans le trou foré, qui éventuellement aussi y a été élargi au moyen de ce que l'on appelle du taillage par jet ou de techniques de coulage, par injection dans le trou foré de produits durcissants, en majorité du ciment. Les produits durcissants, comme par exemple entre autres le ciment, peuvent être coulés sous pression dans le trou foré;
• d) par l'utilisation de certaines mesures, comme par exemple simultanément un vibrage (ou forage) et la fixation de l'ancrage, du boulon ou de l'équipement, l'ancrage est fixé dans le sol. Dans ce dernier procédé, on utilise les vibrations provoquées par le martelage et du coulis doit être pompé dedans sous une très haute pression;
• e) un trou agrandi peut aussi être réalisé, ce qui peut surtout être nécessaire dans des sols à très haute cohésion, un utilisant la technique de jet et coulis à hauteur de la racine de l'ancrage.

Equipment such as anchors and bolts, which can be placed in the ground vertically, horizontally or at any angle, have so far been fixed using one of the techniques described below:

• a) At an angle of 0 to 90 °, a borehole is made in the ground, possibly by using a rinse with water and / or air. In the case of this manipulation, a grout can be injected;
• b) after the execution of the drilled hole, the anchor (bolts or equipment) with or without injection pipes and / or sealing means is placed in the hole drilled;
• c) the anchor is fixed in the drilled hole, which possibly also has been widened there by means of what is called jet cutting or casting techniques, by injection into the drilled hole of hardening products, in majority cement. Hardening products, such as cement, for example, can be poured into the drilled hole under pressure;
• d) by using certain measures, such as simultaneously vibrating (or drilling) and fixing the anchor, bolt or equipment, the anchor is fixed in the ground. In the latter method, vibrations caused by hammering are used and the grout must be pumped into it under very high pressure;
• e) an enlarged hole can also be made, which may especially be necessary in soils with very high cohesion, using the spray and grout technique at the height of the root of the anchor.

The points a, b, cited above are similar to the technique described in patent FR-A-2,541,703 in the name of Bataille. Points a, b, c, d and e are similar to the technique described in patent application DE-A- 31 08 331 (see preamble to claim 4 appended) in the name of GKN Keller. Points a, b, c, e are similar to the technique described in the aforementioned document FR-A-2144079.

The methods cited above have several drawbacks. The methods described under b) and c) have the great disadvantage that their development is complicated and expensive. Important components used during drilling are lost and remain behind, in the ground with the equipment.

• 1. Les mesures à prendre pour l'obtention de la fixation d'un ancrage, d'un boulon ou d'un équipement sont très chères. Par le vibrage, tout le composant qui est utilisé à cette fin dans le sol est perdu de sorte que les avantages que ce procédé devrait normalement fournir sont réalisés pour rien;
• 2. en présence de pierres dans le sol, de concrétions dures, de matériaux de remplissage et/ou de sous-sol de pierre, il n'est pas possible de pénétrer le sous-sol sans mesures accessoires. Dans de telles circonstances géologiques, ce que l'on appelle "des avant-trous" sont forés de sorte que le coût de ce procédé est considérablement augmenté;
• 3. en présence de pierres et d'autres obstacles du même genre, des déviations inadmissibles peuvent être déterminées lors du forage, par rapport à la direction théorique. L'ancrage ne présente effectivement aucune stabilité suffisante pour surmonter de telles difficultés et pour conserver la direction imposée.

The process described in d) has the following drawbacks:

• 1. The measures to be taken to obtain the fixing of an anchor, bolt or equipment are very expensive. By vibration, all the component that is used for this purpose in the soil is lost so that the benefits that this process would normally provide are realized for nothing;
• 2. in the presence of stones in the ground, hard concretions, filling materials and / or stone basement, it is not possible to penetrate the basement without additional measures. In such geological circumstances, so-called "pilot holes" are drilled so that the cost of this process is considerably increased;
• 3. in the presence of stones and other similar obstacles, unacceptable deviations may be determined during drilling, compared to the theoretical direction. The anchoring does not actually have sufficient stability to overcome such difficulties and to maintain the imposed direction.

The object of the invention is therefore to propose a method which overcomes the known drawbacks and to propose a new and original method by which equipment can be placed and fixed in the ground in a remarkable manner, whatever may be also the geological structure of the soil. The method according to the invention in fact allows the installation of equipment in all kinds of alluvial soils, without taking into account that it is sand, clay or silt. Also soils which contain a rocky bottom, stones filled with filling, saturated or not saturated with water and / or grounds containing stones stones can be worked. This also applies to the type of equipment, whether we consider anchoring, bolting or the introduction of any equipment.

In order to apply the process according to the invention in the best circumstances and from the in the most economical way possible, this method is further characterized in that the drilling tube is constituted by a rotary double-walled drilling tube providing a concentric space connecting on the one hand to at least two spraying and on the other hand to a pressurized liquid supply inlet, said tube being provided with a drilling head comprising axially an end orifice and having laterally said spraying nose, the diameter of the tube and of the end orifice of the drilling head being of such a size that said equipment can be slid along their central axis, said end orifice of the drilling head being fitted with a removable plug constituting an element lost during withdrawal of the drilling tube, said plug being left in the ground with the above-mentioned equipment in the latter's cement jacket.

The invention also relates to a device for implementing the method according to the invention and comprising the characteristics according to claim 4. Advantageous methods of the method according to the invention are the subject of claims 2 and 3 and of the provisions preferred of the implementation device are the subject of claims 5 and 6.

Other details and advantages will emerge from the following description of a method for fixing anchors, bolts and equivalent equipment in the ground and of the device used on this subject according to the invention. This description is given only by way of example and in no way limits the invention as defined by the claims. The references relate to the annexed drawings below.

Figures 1 to 3 schematically illustrate three successive steps of the method according to the invention.

Figure 4 is a schematic side view, with partial section, of the device used for the application of the method according to the invention.

The process illustrated in Figures 1 to 3 includes the following steps.

A hole drilled in the ground 1 is dug using a double-walled drilling tube 2. A quay wall or a similar block is indicated by the reference 3. In general, the equipment in question is indeed applied through a quay wall for anchoring this structure. The actual drilled hole is not represented in the schematic figures because the method consists precisely in working the drilled hole into an enlarged drilled hole 4. This is achieved by the injection under pressure of a fluid by the drilling head 5. In this regard, it can be done use water, but also a cement grout can be applied for this. Details of the structure of the double-walled drill pipe 2 and the drill head 5 follow below. The drilling head 5 is in fact equipped with a plug 6 which closes an orifice in the drilling head 5. This plug 6 is abandoned in the ground when this orifice must become free to allow passage to the equipment 7.

In FIG. 2, it is in fact noted that the drilling tube 2 and the drilling head 5 are gradually extracted from the enlarged drilled hole 4. The equipment 7 nevertheless remains in place and is surrounded by the mass of cement grout 8 injected under pressure.

Finally, schematic figure 3 shows the state in which the equipment 7 is completely surrounded by cement grout 8 in the enlarged drilled hole 4. The double-walled drilling tube is completely removed therefrom from the drilled hole.

It is obvious that for a better anchoring of the whole and according to the geological structure of the ground, one can provide locally, for example at the end of the drilling, an even larger diameter of the drilled hole. This possible variant is not shown in the figures.

The device for the implementation, in the most economical and technically most reliable circumstances, of the method is represented in FIG. 4 where the double drill pipe is indicated by the general reference 2. The double drill pipe 2 comprises effect an outer jacket 9 which concentrically surrounds an inner cylinder 10. Between the outer jacket 9 and the inner cylinder 10 there is a space 11. The space 11 is connected to two or at least two spray noses 12 while at the 'opposite end this space 11 is connected in the washing head 13 with an inlet 14 for the supply of pressurized water, possibly in cement slurry.

By the internal side of the internal cylinder 10, the space 15 is partially occupied by the equipment 7 which rests there. The term "equipment" also takes into account what may be referred to here as a bolt or anchor. The space 15 is in connection with an entry 16 for the addition of cement or water grout. Cement grout or water can therefore flow under pressure from the inlet 16, through the space 15, towards the drilling head 5 which is closed by a plug 17. The plug 17 has the form of a point and is provided with non-return valves and is therefore intended, on the one hand, to close the orifice 18 of the drilling head 5 and, on the other hand, to facilitate penetration into the ground.

Referring again to schematic figures 1 and 3 and to the explanation of the process connected thereto, the advantages and the great technical simplicity of the process and of the device are perfectly highlighted.

The device therefore makes it possible, by using the combination of techniques known to a certain extent, to seed equipment with cement in kinds of soils with the most disparate geological structures.

Although the schematic figures show horizontal bores, it is obvious, as elsewhere emphasized at the beginning, to adapt this technique by drilling in the vertical direction. Bores which appear at angles between 0 and 90 ° can also be very well executed by this.

The invention is however not limited to the embodiment described above and many modifications can be made without departing from the scope of the invention as defined by the appended claims.

Claims (6)

1. Method for fixing anchorages, bolts and equivalent equipments in the bottom by boring a drill hole by means of a drill bit and by injecting cement grout, according to which method :

   - the drill hole in question is effected by driving or boring a drill pipe (2) including a drill bit in the bottom and the diameter of the drill hole is enlarged by injecting a liquid under pressure,

   - use is made hereto of a rotating drill pipe provided with a drill bit, said equipment is placed in the central axis of the drill pipe, the length of this equipment corresponding substantially to the one of the drill pipe, and, in the final phase, the equipment in question hereinabove is left in place in the bottom when withdrawing the drill pipe while cement grout is injected under pressure around the equipment in the formed enlarged drill cavity,

   characterised in that said drill pipe (2) is composed of a double wall (9, 10) rotating drill pipe providing a concentric space (11) connected, on the one hand, to at least two spray nozzles (12) and, on the other hand, to an inlet (14) for supplying liquid under pressure, said pipe being provided with a drill bit (5) including axially an end orifice (18) and presenting laterally said spray nozzles (12), the diameter of the pipe and of the end orifice (18) of the drill bit being of such a size that said equipment (7) may be slid according to their central axis, said end orifice (18) of the drill bit being equipped with a removable stopper (6, 17) forming an element which is lost upon withdrawal of the drill pipe (2), said stopper being left in the bottom with aforesaid equipment (7) in the cement jacket of this latter.
2. Method according to claim 1, characterized in that use is made of cement grout as liquid when enlarging the diameter of the drill hole.
3. Method according to claim 1, characterized in that use is made of water as liquid when enlarging the diameter of the drill hole.
4. Device for carrying out the method according to any one of the claims 1 to 3, comprising a drill pipe (2) provided with a drill bit (5), the drill bit including axially an end orifice (18) and presenting laterally at least two spray nozzles (12) for injecting a liquid under pressure, the diameter of the pipe and of the end orifice of the drill bit being of such a size that an equipment (7), such as a bolt or an anchorage, may be slid according to their central axis, characterized in that said drill pipe is a rotating drill pipe composed of a double wall (9, 10) pipe so as to provide a concentric space (11) connecting, on the one hand, to the spray nozzles (12) and, on the other hand, to an inlet (14) for supplying liquid under pressure, both for enlarging the diameter of the drill hole as for putting a jacket in cement into place around aforesaid equipment (7), and in that said end orifice (18) of the drill bit is equipped with a removable stopper (6, 17) forming an element which is lost upon withdrawal of the drill pipe (2), said stopper being left in the bottom with aforesaid equipment (7) in the cement jacket of this latter.
5. Device according to claim 4, characterized in that in aforesaid double wall drill pipe (2), aforesaid spray nozzles (12) are in communication with the concentric space (11) between the two walls of the double wall drill pipe (2), which is composed of an outer sleeve (9) and an inner cylinder (10).
6. Device according to either one of the claims 4 or 5, characterized in that aforesaid double wall drill pipe (2) is provided on the extremity which is opposed to the drill bit (5) with a cleaning head (13) including at least two inlets (14 and 16), the first inlet (14) being in communication with the space (11) between the outer sleeve (9) and the inner cylinder (10) while the other inlet (16) is in communication with the space (14) wherein aforesaid equipment (7) is slid in, and communicates moreover with the orifice (18) of the drill bit (5).

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