EP1087063A1 - Device for drilling and anchoring and method for installing ground anchors - Google Patents

Abstract

The anchor for a building guy cable has a drill tube (8) and a drill tip (12) at one end of the tube. Multiple tension cables (4) are attached to the drill. The rill head is placed in a sealing case (7) formed by injection of cement into the soil surrounding the anchor hole. The anchor tube is removed to leave the dill head and cables embedded in the cement.

Description

The present invention relates to an anchoring device and a method of setting in place of anchor rods intended to ensure the stability of a structure by with respect to land, involving the drilling of a hole into an area anchoring in the ground, the introduction of cables and / or other reinforcements pulling in the borehole, and the injection by said borehole of a suspension of cement so as to form a sealing body in said anchoring area.

The usual processes of this type require, for the formation of the body of sealing, several cement injections, for example by means of injections by cuffs, these injections having to be spaced in time and thus generally requiring several days for the formation of the body of sealing. On the other hand, the strength of use remains limited, especially in clay or loamy soils, due in particular to the transverse dimensions restrictions of the sealing body achievable by known methods, poor control over the formation of this body of its composition which remains essentially constituted by the injected cement.

The document EP-A-0413676 describes a process of the aforementioned type according to which tool is used which has a drilling tool part and has a axial channel extending an injection channel, a valve being arranged at the inlet of said axial channel so as to allow said inlet to be closed before injection of a suspension of pressurized cement through the central channel and said channel axial.

The document EP 0 770 734 describes a method according to which drilling is carried out by means of a tube provided, at its front end, with a drilling tool and injection tube, this tube forming a cement injection channel and said tool having at least two side nozzles oriented in directions opposite, and comprising a drilling tool part having an axial channel extending said injection channel, a valve being disposed between the inlet of said axial channel and said nozzles, so as to close said inlet before injection of the pressurized cement suspension, which is injected said cement suspension in the surrounding ground through said nozzles, radially to said tube, with a pressure greater than about 40 MPa (400 bars), by rotating this tube around its axis and raising it, by continuously or discontinuously, over a determined sealing length, that the injection is then stopped and the tube is completely reassembled, the said cables and / or other tie rods being introduced into the borehole, before the cement hardens, right down to the sealing body training.

This process considerably shortens the time required for the setting up tie rods and making a good anchorage.

The invention aims to provide an anchoring device and a method of positioning improved anchor rods, in particular a device and a method, respectively, of the aforementioned type where the anchoring is further improved and the operation of setting up anchor rods simplified and faster.

To this end, the method according to the invention comprises the operation of performing the drilling by means of a drilling column comprising a drilling tube provided, at its front end, an injection tool and a drilling tool coupled to the injection tool, this tube forming a cement injection channel and said tool injection system comprising at least one or more nozzles allowing injection of a suspension of pressurized cement in the surrounding ground to form a sealing body, characterized in that the drilling tool is attached to one or more tie rods or other tie rods, as said cement suspension is injected into the surrounding soil and around tie rods and the drilling tool, and that the tube is reassembled entirely leaving the drilling tool in the sealing body.

The drilling and anchoring device comprises a column comprising a tube drill, a drill tool mounted at the end of the tube and one or more cables and / or other tie rods, characterized in that the cables and / or other tie rods are attached to the drilling tool, so that the tool drilling remains in a sealing body formed by the injection of cement in the surrounding terrain of the drill hole.

The injection tool is preferably provided with at least two side nozzles oriented in opposite directions and at least one end nozzle oriented obliquely towards the central axis of the tube in which the cables and / or other tie rods. The drilling tool has a part coupling which slides axially in the tube axially separable.

During the drilling operation, pressurized water is brought in through a channel axial to the drilling tool. The axial channel can be formed by a tube inside coaxial with the drill pipe. The inner tube can be fitted with a valve, for example in its upper part, to control the supply of water under drilling tool pressure during drilling operation and during operation of the ascent of the drill string after formation of the body of sealing.

The space between the drill pipe and the inner pipe can form the channel cement injection.

The end nozzle is tilted at an acute angle to the direction axial, for example at 30 °, so that the cement suspension jet exiting this nozzle applies a force component in the direction axial on the drilling tool. This allows the drilling tool to be separated from the tube drilling during the formation of the sealing body. On the other hand, this nozzle ensures that cables and / or other tie rods are completely embedded in the sealing body.

The device and method according to the invention thus make it possible to achieve a very good anchoring with very few operations and great speed.

The invention also makes it possible to avoid problems which may be linked to the reintroduction of tie rods in the process borehole conventional.

In addition, the attachment of the tie rods to the drilling tool and the insertion beforehand in the drill pipe, that is to say before the drilling operation, allow to optimize the density of reinforcements placed in the axial channel of the tube.

Attachment of the drilling tool to the end of the tie rods improves also the retention of these reinforcements in the sealing body.

La Fig. 1 est une vue en coupe schématique d'un tirant d'ancrage placé dans un terrain;

la Fig. 2 est une vue, en coupe axiale, d'une extrémité frontale d'un dispositif de forage et d'ancrage;

la Fig. 3 est une vue, en coupe axiale, d'une partie de fusible mécanique, à proximité de la tête d'injection, d'un dispositif de forage de l'invention;

la Fig. 4 est une vue en coupe selon la ligne IV-IV de la Fig. 3; et

la Fig. 5 est une vue simplifiée, en coupe axiale, d'un dispositif de forage selon l'invention.

Characteristics, aims and advantages of the method according to the invention will emerge more clearly from the description given below by way of example, illustrated in the appended drawings in which:

Fig. 1 is a schematic sectional view of an anchor rod placed in a ground;

Fig. 2 is a view, in axial section, of a front end of a drilling and anchoring device;

Fig. 3 is a view, in axial section, of a part of a mechanical fuse, near the injection head, of a drilling device of the invention;

Fig. 4 is a sectional view along the line IV-IV of FIG. 3; and

Fig. 5 is a simplified view, in axial section, of a drilling device according to the invention.

According to the schematic representation of FIG. 1, a work to anchor 1 rests on a part of land 2 and is stabilized by an anchor, designated as a whole by the reference 3.

This anchoring tie comprises, in a known manner, for example cables of pulling 4 constituted by strands of which one end is fixed in a head of pulling 5 in support on the structure 1.

The tie cables 4 are arranged in a borehole 6 on a certain free length and are integral with a sealing body 7 in the form of a bulb formed around the lower part of the borehole by injection of cement under high pressure in the surrounding terrain. Fig. 1 gives that a schematic representation of an example of a tie rod, the technique anchor being well known in itself.

The present invention consists in using, for example, a drill stand comprising a drilling tube 8 provided with an injection tool 9 coupled to a tool drilling 12 according to FIG. 2 to drill, at first, hole 6 on a length corresponding to the desired free length and the length of sealing which is essentially that of bulb 7 of FIG. 1. The borehole 12 is attached to the ends of the tie cables 4, for example by welds 17 or by mechanical clamping means such as keys. The drilling tool 12 and the tie cables 4 are threaded into the channel central 10 of an inner tube 21 coaxial with the drilling tube 8, before the drilling operation. The drill pipe 8 has a length, without partitions, at the less equivalent to the length of the tie rods. The drilling tool 12 is coupled to the injection tool 9, axially separable, by teeth complementary 18, or other known mechanical means allowing driving in rotation of the drilling tool 12 by the injection tool 9. The tool drilling 12 preferably comprises a part of tube 19 which threads into the central channel 10 to allow its radial positioning and retention by compared to the injection tool 9.

The drilling operation is accompanied by an injection of water or a mixture of water and air through the central channel 10 and its extension 11 in the tool injection. Water is injected into the borehole through one or more channels 20 extending axially through the drilling tool.

When the drilling is finished, a suspension of cement at a very high pressure, for example 450 bar, through one or more several end nozzles 16 inclined and two or more side nozzles 13, 14 of small diameter, ie 1.5 to 2 mm, communicating with one or more axial channels 15 in the injection tool 9. The injection channels 15 are connected to an injection channel 15 'formed between the wall of the drill pipe 8 and the wall of the inner tube 21. A valve (not shown) is arranged in the part upper part of the drill pipe to close the central channel 10 during injection cement. During this operation, the tube is rotated around its axis and is withdrawn slowly, so that the jets produced by the nozzles 13 and 14 in opposite radial directions enter the ground creating an essentially cylindrical bulb, as shown in FIG. 1.

The injection pressure is preferably between 500-800 bars. During injection, the injection nozzles 13, 14, 16 may become blocked by impurities or coarse elements in the cement causing overpressures in the injection channel 15 '. The cement injection pump can have a solenoid valve to trigger the pump during a overpressure. However, during a very sudden increase in pressure, it is the solenoid valve may not have time to fire sufficiently early to avoid crushing the inner tube. To deal with this problem, the drill string is provided with a mechanical fuse part 22 comprising a part of drilling tube 8 'and a part of inner tube 21' forming between they an injection channel 15 '. The mechanical fuse part 22 is arranged at proximity to the injection head 23, so that in the event of deformation, the fuse can be easily exchanged without removing the drill string from the hole before the end of the cement injection operation. The inner tube portion 21 'of the fuse part 22 has a smaller wall thickness than the inner tube 21 of the drill string or some other weakening, so that the part of inner tube 21 'crashes more easily than inner tube 21. The crushing of the part of the inner tube 21 causes the escape of the pressure in the central channel 10, preventing damage to the inner tube main 21.

When reassembling the drill pipe 8, including the inner pipe 21, the tool 12 and the tie cables remain in place and become integral with the bulb 7 during hardening thereof.

To this end, the inclined end nozzle 16 projects a jet against the drilling tool 12 so that the tool is pushed towards the bottom of the borehole for that the injection tool 9 is reassembled, thus separating the drilling tool from the tool injection. The end nozzle being inclined towards the central channel 10, it also ensures very good filling of the borehole with cement injected, so the tie cables are completely embedded in the body sealing. In addition, the drilling tool attached to the ends of the cables pulling improves their anchoring.

When the sealing body has been formed to the desired length, we extract the drill hole injection tool.

As mentioned above, the present invention allows in all application cases to shorten and simplify the implementation procedure places tie rods, while providing reliable, well-controlled anchoring and with great resistance in all types of terrain.

Claims (10)

Method of placing anchor rods according to which one performs drilling by means of a tube (8) provided, at its front end, with a tool injection tube (9) and a drilling tool (12) coupled to the injection tool, this tube having a cement injection channel (15, 15 ') and said injection tool comprising at least one or more nozzles (13, 14, 16) allowing the injection of a suspension of pressurized cement in the surrounding ground to form a sealing body (7), characterized in that the drilling tool is attached to a or several tie rods (4) or other tie rods, which are injected said suspension of cement in the surrounding ground and around tie rods and the drilling tool, and that the tube is reassembled entirely leaving the drilling tool in the sealing body. Method for installing anchor rods according to claim 1, characterized in that the drilling tube (8, 8 ') is rotated about its axis central during reassembly. Drilling and anchoring device comprising a drilling tube (8), a drilling tool (12) mounted at the end of the tube and one or more cables (4) and / or other tie rods, characterized in that the cables and / or other tie rods are attached to the drilling tool, so that the tool drilling remains in a sealing body (7) formed by the injection of cement in the surrounding land of a borehole (6). Drilling and anchoring device according to claim 3, characterized in that it has an inner tube (21, 21 ') coaxial with the drilling tube, forming between them a cement injection channel, and the inner tube forming a central channel (10) in which the cable and / or other reinforcements extend tie rods. Drilling and anchoring device according to claim 4, characterized in that it comprises a mechanical fuse part (22) provided with a part of drilling tube (8 ') and an inner tube part (21') coaxial with the part of drill pipe, the inner pipe part (21 ') of the fuse part having a lower mechanical resistance to crushing than the inner tube (21). Drilling and anchoring device according to the preceding claim, characterized in that the mechanical fuse part (22) is arranged at proximity to the injection head (23) of the device. Drilling and anchoring device according to one of claims 3 to 6, characterized in that the drilling tool (12) is coupled to a tool for injecting axially separable, the injection tool comprising injection nozzles cement (13, 14, 16). Drilling and anchoring device according to the preceding claim, characterized in that there are at least two of said cement injection nozzles which are arranged radially opposite in the injection tool. Device according to the preceding claim, characterized in that said radially opposite injection nozzles are directed so that the cement is injected in one direction basically orthogonal to the central axis of the drill pipe. Drilling device according to one of claims 7 to 9, characterized in that at least one of the injection nozzles (16) is directed towards the drilling to facilitate the separation of the injection tool from the drilling tool during cement injection.

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