EP0263803B1 - Process and device for anchoring under tension - Google Patents

Abstract

The invention relates to a device for fixing a stressed anchorage in rock, comprising sealing components (7) to be sealed in place at the end of a predrilled hole (6) by the sealing material contained in a cartridge (2) fitted in the head of the device and protected by a perforated cap (5). When the device is put in place, the sealing head is fastened to the anchorage sleeve (11) by an unlockable connecting element (9, 10).

Description

The invention relates to a device for anchoring under stress in rock.

Similar anchorages are known, in particular for maintaining the vault of tunnels dug in the rock. They make it possible to stabilize the bolted rock and to exert a prestress on the walls of these tunnels, hence the possibility, given their ease of installation, of a very rapid and very safe advance of excavation works.

Various processes have been developed over the years for the implementation of this type of anchoring.

We distinguish, depending on the requirements to which they are subject, short type anchors generally not exceeding one to two meters and long type anchors reaching ten meters and beyond.

The short type anchors are generally of an elementary design but of an easy handling. Their length being limited, they are not designed for the application of real prestressing tensions. Furthermore, their operating principle is mechanically inapplicable to long type anchors. Among the short type anchors, one of the oldest is the Perfoo type bolt in which two perforated half-cylinders stuffed with mortar are joined and introduced into the cavity, the mortar then being driven out by percussion through the perforations. The known drawbacks of this system are due to its precarious results, given the small volume of mortar it contains and the insufficient control that there are anchoring conditions.

Selfix type tie rods have a breakable capsule with two compartments filled with two-component resin rigidly mounted on a metal rod of standardized length. After rupture of the capsule, a drill is mounted on the rod to give the latter a vigorous rotation intended to complete the mixing of the components. Such a principle is inapplicable to long anchorages because of the torque to be applied to the tie rod and the deformability of the tie rod.

It is also not possible to proceed with this method to a subsequent injection of a mortar grout.

The homogeneity of the mixture and therefore the regularity of hardening are always problematic.

The SWELLEX _@ anchoring is carried out by expansion under compressed air of an accordion tube, its principle is completely different from that of anchors sealed in place with synthetic cement.

All these anchoring devices only apply to limited tie lengths and are not designed to exert a real prestressing tension.

Long type anchors, generally of high capacity, have a part sealed at the bottom of a borehole connected by tie rods to an anchor head bearing against the orifice of this hole. Such anchors make it possible to exert prestressing tensions on the rock of several tens of tonnes, the sealed part being distant from the anchor head by ten meters and more.

Most of these anchoring methods or devices require either an injection or introduction of the sealing material prior to the installation of the tie rods, which obviously doubles the handling required, or the introduction of this sealing material after the setting in place of the anchoring device, a method which requires longer delays, as well as an elaborate, more expensive design that generates functional disturbances.

Dywidag @ type anchors use anchors consisting of threaded bars partially sleeved with a sealing sleeve, the end of which is sealed with resin. The sealing material is introduced before the anchor rods are put in place; these generally do not present the possibility of a subsequent injection of mortar.

However, patent FR-A 2 381 167 describes an anchoring device of the Dywidage @ type provided with means making it possible to subsequently inject cement grout over the length of the anchoring not sealed with resin. By such an injection of cement slurry, however, a blocked anchor is formed, the tension of which can no longer be controlled or adjusted.

These anchors use a two-component resin seal, the curing uniformity of which is always a function of the quality of the mixture in situ.

The anchoring devices described in patent application DE-B 1 101 324 also use a two-component resin seal and have the particularity that the traction element of the anchor can be detached and removed when it is desired, this traction element being a metal bar, one end of which is screwed into the sealing head.

Patent AT-B 342 277 describes a method and an anchoring device in which the constituents of the sealing material are mixed before the anchoring is placed.

In this device, the drawbar and the sealing head which it carries at its end are arranged in a tube, a piston head is fixed to the pulling bar at the rear of the sealing head. The space between the tube and the sealing head is filled with sealing material before the installation of the device. After placing the device in a borehole, a push on the drawbar expels the sealing head and the surrounding sealing material from the tube, thereby sealing the head in the hole.

In BBRV _@ type anchors, the bundled cables are protected over part of their length by a sheath provided with a sealing sleeve. The sealing injection takes place under pressure via a specific member (injection tube) and is carried out after the anchor is placed in the cavity.

These different processes involve significant handling during installation.

One of the aims of the intention is the creation of a preloading anchoring device which can be put in place in a single operation.

Another object of the invention is an anchoring device where the factors of the sealing operation are closely controlled.

Another object of the invention is an anchoring device having the possibility of checking and rectifying the tension, even after subsequent sealing with mortar.

Another object of the invention is a prestressing anchor which can be tensioned very shortly after installation.

The subject of the invention is a method of producing anchors under stress in rocky terrain comprising the following steps: the prior drilling of a borehole, the making by extrusion of a cartridge of sealing material, the mounting of the said cartridge in an openwork protective cap at the head of an anchoring device comprising an anchoring sheath capable of being cemented in place surrounding a traction transmission element, a sealing head and unlockable connecting elements between the sealing head and anchoring sheath, introduction into the cavity of the anchoring device, checking the positioning of said device, unlocking the sealing head with the anchoring sheath, crushing of the sealant cartridge by acting on the traction transmission element, the hardening of the sealant, the tensioning of the device.

Preferably, the process also includes the following stages: the coating, prior to assembly, of the element intended to transmit traction using an organic compound capable of avoiding its adhesion to the cement and the injection, after tensioning of this element, a mortar grout in the anchor sheath, so that said grout fills the anchor sheath in its entirety and rises towards the surface on the periphery thereof.

• - une tête de scellement apte à être scellée dans la roche,
• - une tête d'ancrage mobile apte à prendre appui sur la paroi autour de l'embouchure du trou de forage,
• - un élément de traction apte à assurer une traction de contrainte entre la tête de scllement et la tête d'ancrage,
• - une gaine d'ancrage apte à être cimentée en place, entourant le dit élément de transmission de la traction.

Another object of the invention is a stress anchoring device in rocky terrain, intended to be placed in a borehole, comprising:

• - a sealing head capable of being sealed in the rock,
• - a movable anchoring head capable of bearing on the wall around the mouth of the borehole,
• a traction element capable of ensuring a tensile stress between the hoeing head and the anchoring head,
• - An anchoring sheath capable of being cemented in place, surrounding the said traction transmission element.

• - une cartouche de matière de scellement constituée d'une matière de scellement contenue dans une enveloppe aisément destructible montée à l'avant de la tête de scellement,
• - une coiffe de protection ajourée ou "crépine" fixée à la gaine d'ancrage et entourant la dite cartouche de matière de scellement,
• - un élément de liaison déverrouillable entre la tête de scellement et la gaine d'ancrage, le dit élément de liaison étant apte à être actionné par l'intermédiaire de l'élément de traction.

This device also includes:

• - a cartridge of sealing material consisting of a sealing material contained in an easily destructible envelope mounted at the front of the sealing head,
• - an openwork protective cap or "strainer" fixed to the anchoring sheath and surrounding said cartridge of sealing material,
• - An unlockable connecting element between the sealing head and the anchoring sheath, said connecting element being able to be actuated by means of the traction element.

According to an advantageous embodiment, the envelope surrounding the cartridge of sealing material is a film of polymer material.

As a sealing material, it is advantageous to use a synthetic mortar.

According to a preferred embodiment, the anchoring sheath is closed at its rear end by a nozzle mounted on the anchoring head; the anchor head is traversed by two openings communicating, respectively, with the internal volume of the sheath and with the volume of the borehole external to the sheath, these two volumes being placed in communication towards the front of the device by the perforations of the protective cap.

According to an advantageous embodiment, the traction transmission element has, vis-à-vis its sheathing, a low coefficient of adhesion.

According to a preferred embodiment, the element for transmitting the stress is a greased-sheathed cable.

According to a particular embodiment, the greased-sheathed cable is stripped of its sheathing over part of its length.

According to a preferred embodiment, the sealing head comprises several modular sealing elements provided with a profile capable of promoting the transmission of their anchoring force via the rock sealing material, threaded on the cable.

According to an advantageous embodiment, the unlockable fixing mechanism of the sealing head is a bayonet mount.

An advantageous embodiment of the protective cap is that of an openwork grid.

• - grâce à sa simplicité d'emploi, le dispositif d'ancrage selon l'invention peut être utilisé de façon très souple, avec un matériel minimum et même en faisant appel, le cas échéant, à un personnel peu expérimenté;
• - lors de sa mise en place, la cartouche est protégée mécaniquement pour éviter son ouverture prématurée. La localisation et le moment de l'ouverture sont donc parfaitement contrôlés; en particulier, il est possible de retirer la cartouche en cours d'opération en cas d'imprévu;
• - la possibilité d'une injection complémentaire d'un coulis sous pression confortant, d'une part, le scellement de l'ancrage et améliorant, d'autre part, les qualités de la roche encaissante par remplissage des fissures éventuelles;
• - même après injection complémentaire de ce coulis de ciment, l'ancrage selon l'invention garde la possibilité d'une remise sous tension à tout moment ainsi que celle d'un contrôle permanent de cette tension;
• - de par la configuration du dispositif et de par la forme des éléments de scellement, la matière de scellement est sollicitée en compression, ce qui est un facteur avantageux;
• - une très grande facilité de mise en oeuvre; tout comme certains ancrages courts, le dispositif d'ancrage de l'invention forme avec la cartouche de matière de scellement un ensemble complet, la tête de scellement s'introduisant, après montage de la cartouche de matière de scellement en une seule opération, dans le trou d'ancrage foré au préalable;
• - il est possible de régler avec beaucoup de facilité la longueur libre d'ancrage en dénudant partiellement l'élément de traction; de même,
• - il est aisé de moduler la longueur scellée avec la matière de scellement en modifiant, lors du montage de l'ancrage, le nombre d'éléments de scellement utilisés; enfin,
• - l'utilisation d'un câble souple permet l'usage d'ancrages de longueur supérieure au diamètre de la galerie et procure une grande facilité de transport sur site.

Among the advantages of the invention over the conventional methods of the existing technique, the following may be mentioned in particular:

• - Thanks to its simplicity of use, the anchoring device according to the invention can be used in a very flexible manner, with minimum equipment and even by calling, if necessary, on inexperienced personnel;
• - during its installation, the cartridge is mechanically protected to avoid its premature opening. The location and the time of opening are therefore perfectly controlled; in particular, it is possible to remove the cartridge during operation in the event of the unexpected;
• - the possibility of an additional injection of a grout under pressure consolidating, on the one hand, the sealing of the anchor and improving, on the other hand, the qualities of the host rock by filling in any cracks;
• - Even after additional injection of this cement grout, the anchoring according to the invention retains the possibility of re-energizing at any time as well as that of permanent control of this tension;
• - By the configuration of the device and by the shape of the sealing elements, the sealing material is stressed in compression, which is an advantageous factor;
• - great ease of implementation; just like certain short anchors, the anchoring device of the invention forms with the cartridge of my sealing face a complete assembly, the sealing head being inserted, after assembly of the cartridge of sealing material in a single operation, in the anchoring hole drilled beforehand;
• - It is possible to easily adjust the free length of anchoring by partially stripping the traction element; likewise,
• - It is easy to modulate the length sealed with the sealing material by modifying, during the mounting of the anchor, the number of sealing elements used; finally,
• - the use of a flexible cable allows the use of anchors longer than the diameter of the gallery and provides great ease of transport on site.

• la Fig. 1 est une vue schématique du dispo sitif d'ancrage selon l'invention;
• la Fig. 2 est une vue en coupe schématique du même dispositif introduit dans le trou d'ancrage;
• la Fig. 3 est une vue du dispositif d'ancrage après écrasement de la cartouche de matière de scellement;
• la Fig. 4 est une vue du dispositif a près durcissement de la matière de scellement et mise sous tension;
• la Fig. 5 est une vue en cours d'injection du coulis de remplissage;
• la Fig. 6 est une vue latérale plus détaillée d'un élément de scellement;
• la Fig. 7 est une vue en coupe en perspective d'un manchon de l'élément de liaison du câble à sa gaine d'ancrage;
• la Fig. 8 est une vue en perspective du serre-câble correspondant au manchon de raccordement décrit à la Fig. 7;
• la Fig. 9 est une vue en coupe en perspective d'une autre exécution du manchon de raccordement;
• la Fig. 10 est une vue en perspective du serre-câble correspondant au manchon montré à la Fig. 9;
• la Fig. 11 est une vue en coupe plus détaillée de la tête d'ancrage, et
• la Fig. 12 est une vue de la tête de scellement du dispositif d'ancrage où les éléments enfilés sur le câble ont été dissociés.

Other features and advantages of the invention will emerge from the detailed description of a preferred embodiment described below with reference to the attached drawings, in which:

• Fig. 1 is a schematic view of the anchoring device according to the invention;
• Fig. 2 is a schematic sectional view of the same device introduced into the anchoring hole;
• Fig. 3 is a view of the anchoring device after crushing the cartridge of sealing material;
• Fig. 4 is a view of the device after hardening of the sealing material and tensioning;
• Fig. 5 is a view during injection of the filling slurry;
• Fig. 6 is a more detailed side view of a sealing element;
• Fig. 7 is a perspective sectional view of a sleeve of the cable connecting element to its anchoring sheath;
• Fig. 8 is a perspective view of the cable clamp corresponding to the connection sleeve described in FIG. 7;
• Fig. 9 is a perspective sectional view of another embodiment of the connection sleeve;
• Fig. 10 is a perspective view of the cable clamp corresponding to the sleeve shown in FIG. 9;
• Fig. 11 is a more detailed sectional view of the anchoring head, and
• Fig. 12 is a view of the sealing head of the anchoring device where the elements threaded on the cable have been separated.

Figs. 1 to 5 show schematically the different phases of use of the anchoring device according to the invention.

In Fig. 1, the anchoring device 1 is provided with its cartridge of sealing material 2, the components of which are mixed on site, prior to introduction. After preparation and extrusion, the cartridge of sealing material 2 is put in place at the head of the device, abutting against the spun sleeve 3 crimped at the end of the greased-sheathed cable 4. An openwork cap 5 (also called strainer) protects the cartridge 2 during its introduction into the borehole 6.

The sealing elements 7 (the role of which will be explained below) are mounted on the cable 4 below the spun sleeve.

The set of sealing elements 7 and the spun sleeve 3 mounted at the end of the cable 4 form the sealing head 8.

The sealing head 8 is fixed by means of the unlockable connecting elements 9, 10 (shown in more detail in FIGS. 7, 8, 9 and 10) to the anchoring sheath and to the perforated cap 5.

Fig. 2 is a schematic sectional view of the anchoring device 1 introduced into the hole 6 previously drilled. The anchoring sheath 11 and the greased-sheathed cable 4 form an assembly of sufficient rigidity so that the sealing head 8 can be inserted without difficulty into the borehole 6, as if it had been mounted at the end of a perch. The set is however flexible enough to accommodate irregularities and can bend according to the dimensions of the site; in particular, it is perfectly possible to place an anchor whose length is greater than the diameter of the gallery where the work is carried out.

Fig. 3 is a schematic sectional view of the anchoring device 1 after crushing the cartridge 2. When the end of the sealing head 8 abuts against the bottom of the hole, the operator unlocks the connecting elements 9, 10 ( in this case, united by a bail mount) which makes the sealing head 8 and the anchoring sheath 11 integral. To do this, a twist is exerted on the cable 4 so as to release two lugs 29 from bent grooves at right angles 32, formed on the side face of a cylindrical cable clamp 9 (Fig. 7 and 8).

After unlocking, the sealing head 8 and the cable 4 can slide longitudinally with respect to the anchoring sheath 11. It suffices to apply to the cable 4 a push to pierce the cartridge of sealing material 2, the contents of which spread in the cavity, creeps through the openings of the protective cap 5 and drowns the sealing elements 7.

These latter elements contribute significantly to the effectiveness of the anchoring device according to the invention. They are shown in more detail in FIG. 6.

The anchoring device 1 is left to stand for the time necessary for the setting of the sealing material (for example a few hours for synthetic mortar), after which it can be put directly under tension.

Fig. 4 shows the anchoring device 1 after power-up. An anchor plate 12 is disposed on the orifice of the borehole. A key pot 13 is mounted on the anchor plate 12, this assembly forming the anchor head. The application of a jack allows the tensioning of the cable which is then kept under tension in the key pot 13 by keys 14. The centering of the key pot 13, relative to the drilling axis, is ensured by the presence of a ball joint assembly 15. A more detailed view will be shown in FIG. 11. At this stage, the anchoring device can be used as it is, the cable 4 remaining free in its anchoring sheath 11, which provides it with a first protec tion. This protection can however be reinforced by injecting a cement mortar grout into the cavity 6, which is done in a controlled manner thanks to the design of the anchoring sheath 11 and the anchoring plate 12, as will be seen. referring to FIG. 5.

Fig. 5 is a schematic sectional view of the anchoring device 1 during the injection of the filling mortar 16.

Two openings are drilled in the anchor plate 12. A first opening 17 opens out inside the anchor sheath 11. A second opening 18 opens out in the borehole 6 outside the anchor sheath 11.

A cement mortar grout 16 is injected under pressure through the opening 17. This mortar grout 16 flows along the anchoring sheath 11 and reaches the level of the perforated protective cap 5.

The length of the perforated protective cap 5 is such that its rear end emerges from the mass taken in the sealing material.

The cement mortar grout 16 injected under pressure creeps in through the openings of the remaining length of the cover 5 and flows back from the outside of the anchoring sheath 11 to the opening 18, thus attesting to the continuity of the coating. This grout 16, once hardened, consolidates the rock around the anchoring device 1, provides a second protection of the latter and strengthens the sealing of the sealing head 8.

Thanks to its coating of grease, the cable 4 can continue to play freely relative to its sheath 19, even after injection of the mortar 16. The cable 4 can therefore continue to freely exert the prestressing tension on the surrounding rock.

According to the requirements of the site, one can also provide a cable 4 devoid of all or part of its length of its coating and its sheath 19, so that it is found, after pouring the mortar 16, partially immobilized in its gangue mortar 16, which gives it an additional anchoring length and modifies the anchoring characteristics accordingly.

Fig. 6 is a more detailed side view of a sealing element 7. As has been specified above, the sealing head 8 comprises a number of elements 7 varying according to the constraints imposed on the anchoring and the quality of the rock. Optionally, these sealing elements 7 are extended, at the rear, by a male part and, at the front, by a female part of corresponding shape.

During assembly, the male part 20 of each element 7 engages in the female part 21 of the next element, so that the sealing head 8 has no discontinuity.

A support ring 22 is mounted between the first element 7 and the spun sleeve 3 so as to distribute the pressure exerted by the latter. The presence of this ring is justified by any irregularities appearing on the front surface 23 of the sealing elements 7 depending on their embodiment; the support ring 22 may, if necessary, be omitted. The sealing element 7 shown here is made of machined metal, but it can also be made of molded metal, concrete or synthetic materials, such as resin or plastic.

The lateral surface of the sealing elements 7 has reliefs 24 capable of improving their seating in the cavity 6. The reliefs 24 shown in the figure have the shape of a helical projection, but it is obvious that they can have a profile d 'Any attachment compatible with their embodiment and the material used.

Fig. 7 shows a perspective sectional view of the connection sleeve 10 which forms the first part of the connecting element 9, 10 between the anchoring sheath 11 and the sealing head 8 described in FIG. 1.

The end of this sleeve 10, facing the sealing head 8, is hollowed out with a rebate 25 intended for the insertion of the protective cap 5.

The other end of the sleeve 10 is extended by a tip 26 provided with reliefs 27 suitable for securing the sleeve 10 to the anchoring sheath 11.

The sleeve 10 is pierced with two diametrically opposite openings 28 in which pins 29 are fixed projecting from the inner part of the sleeve 10.

Fig. 8 shows, in perspective, the cable clamp 9 corresponding to the connection sleeve 10 shown in FIG. 7. This cable clamp 9 is fixed to the cable 4 downstream of the sealing elements 7 by a pressure screw 30 resting here on a split ring 31. The lateral face of the cable clamp 9 carries two grooves 32 bent at an angle straight consisting of a rectilinear part 33 parallel to the axis of the cable clamp 9 and a curved part 34, over approximately 90 _° , along the perimeter of the cable clamp.

Fig. 9 is a sectional view, in perspective, of a variant of the connection sleeve 10, more particularly adapted to a mode of manufacture by molding. The embodiment is distinguished in particular by the shape of the lugs 35 reinforced longitudinally.

Fig. 10 is a perspective view of the cable clamp 9 corresponding to the connection sleeve described in FIG. 9.

The curved part 34 of the bent groove 32 is wider, in relation to the increased dimension of the pins 35, and has at its end part a widening 36 intended to prevent the pins 35, under the effect of the stresses, from coming out of their accommodation.

Fig. 11 is a more detailed view, in section, of the device for tensioning the anchoring device 1.

The anchor plate 12 carries claws 37 intended to distribute the thrust on the wall.

The mouth of the borehole is closed by a closure piece 38 comprising a tip cylinder 39 intended to be pressed into the end of the sheath 11 and a seal 40 applying against the rock wall around the drilling hole 6. Two openings 17, 18 pass through the anchor plate 12 and open, respectively, at the end of the end cylinder 39, in the interior volume of the anchor sheath 11, and at the periphery of the borehole 6, in the volume outside the anchoring sheath 11.

Maintaining the cable 4 under tension is ensured by the wedging of the keys 14 in the key holder 13. The alignment of the holding device 13, 14 with the axis of the cable 4 takes place automatically by the presence of the ball joint 15 Thanks to the key pot 13, the tensioning ("bolting") of the anchoring device 1 is simplified since this fastening system does not require to move a nut by rotation while the tensioning cylinder exerts a traction on an anchor rod.

Fig. 12 is a view of the head of the anchoring device 1 where all the elements threaded on the cable 4 have been separated.

There are, progressing towards the end, successively mounted, the anchoring sheath 11, the connection sleeve 10, the protective cap 5, the cable clamp 9, two sealing elements 7, the support ring 22 , finally the end piece here consisting of a spun sleeve 3 which is integral with the cable 4 and transmits the prestressing stress to the whole of the sealed mass.

It is obvious that the spun sleeve 3, although providing an elegant technical solution to the anchoring according to the invention, can be replaced by any other equivalent technical solution such as bolted sleeves, a crimped part or any dead anchoring of dimensions compatible with the diameter of the borehole.

Likewise, sealing can be obtained using different sealing materials and in particular synthetic mortars, such as resin-based mortars (for example based on epoxy resins or acrylic resins).

Furthermore, it is possible to use to join the unlockable connecting elements 9 and 10, without departing from the scope of the invention, other assembly systems ensuring the same function, such as, for example, a thread of appropriate form.

Claims (12)

1. Process for placing anchorages under tension in rocky grounds, comprising the following steps:

- predrilling of a bore-hole (6),

- making up by extrusion on site of a cartridge of sealing material (2), contained in an easily destructible casing,

- fitting of the said cartridge (2) in a perforated protective cap (5) at the head of an anchorage device (1) comprising an anchorage sleeve (11) able to be cemented on the spot surrounding a component (4) for transmitting a traction and a sealing head (8) and connecting unlockable components (9, 10) between the sealing head (8) and the anchorage sleeve (11),

- introduction of the anchorage device (1) in said cavity (6),

- checking the correct position of said device (1),

- unlocking the sealing head (8) from the anchorage sleeve (11),

- crushing the cartridge of sealing material (2), by exerting a pressure on the component (4) for transmitting a traction,

- hardening of the sealing material,

- placing of the device (1) under tension.

2. Process according to claim 1, characterized in that it further comprises, the following steps:

- prior to assembly, coating of the component (4) suitable to exert a traction, with a substance suitable to prevent its adherence to the mortar,

- injection, after placing this component (4) under tension, of a liquid filling of mortar (16) in the anchorage sleeve (11), so that the said liquid filling fills up the said anchorage sleeve (11) and rises round its periphery.

3. Anchorage device under tension (1) in rocky grounds intended to be placed in position in a bore-hole (6) comprising:

- a sealing head (8) suitable to be sealed in rock,

- an anchorage head (12, 13, 14) suitable to rest against the wall around the mouth of the bore-hole (6),

- a traction component (4) suitable to ensure a traction under tension between the sealing head (8) and the anchorage head (12, 13, 14),

- an anchorage sleeve (11) suitable to be cemented in place, surrounding the said traction component (4) characterized in that it further comprises:

- a cartridge of sealing material (2) contained in an easily destructible casing fitted at the front of the sealing head (8),

- a perforated protective cap (5) fixed to the anchorage sleeve (11) and surrounding the said cartridge of sealing material (2),

- unlockable connecting components (9, 10) between the sealing head (8) and the anchorage sleeve (11), the said components (9, 10) being suitable to be activated via the traction component (4).

4. Anchorage device according to claim 3, characterized in that the casing enclosing the cartridge of sealing material (2) is a thin sheet of polymer material.

5. Anchorage device (1) according to any one of claims 3 and 4 characterized in that the anchorage sleeve (11) is closed at its rear end by an end piece fitted on the anchorage head (12, 13, 14), which anchorage head is crossed by two openings (17, 18) connecting, respectively, with the inner volume of the sleeve (11) and with the volume of the bore-hole (6) outside the sleeve (11), these two volumes being placed in contact, towards the front of the anchorage device (1), by the perforations of the protective cap (5).

6. Anchorage device (1) according to any one of claims 3, 4 and 5 characterized in that the traction component (4) is provided with a coating suitable to prevent its adherence to cement (19).

7. Anchorage device (1) according to claim 6, characterized in that the traction component (4) is a single strand sleeved greased cable.

8. Anchorage device (1) according to claim 7, characterized in that the single strand sleeved greased cable (4) is bared of its sleeving (11) and the grease with which it is covered along part of its length.

9. Anchorage device (1) according to any one of claims 3 to 8 characterized in that the sealing head (8) comprises strung along on the traction component (4) several modular sealing components (7) having a profile suitable to assist the transmission of their anchorage force to the rock via the sealing material.

10. Anchorage device (1) according to any one of claims 3 to 8 characterized in that the connecting component (9, 10) between the sealing head (8) and the anchorage sleeve (11) is a bayonet fitting.

11. Anchorage device (1) according to any one of claims 3 to 10 characterized in that the protective cap (5) of the sealing cartridge (2) is a perforated grille.

12. Anchorage device according to any one of claims 3 to 11 characterized in that the end of the traction component (4) is fitted with a threaded sleeve (3).

Images