WO2018189565A1

WO2018189565A1 - An anchor assembly comprising a strand and an anchor unit

Info

Publication number: WO2018189565A1
Application number: PCT/IB2017/000598
Authority: WO
Inventors: Michel Rene MONBALLIU; Hong Shing TANG
Original assignee: Soletanche Freyssinet
Priority date: 2017-04-14
Filing date: 2017-04-14
Publication date: 2018-10-18
Also published as: EP3610093A1

Abstract

An anchor assembly comprising a strand (4) and an anchor unit (6) receiving said strand therethrough, the anchor assembly (2) being destined to be fixedly received in a hole (10) for anchoring said strand. The anchor unit (6) comprises a swage element (12) receiving the strand (4) therethrough, the swage element (12) being swaged onto the strand, thereby gripping said strand, the swage element being configured to let the strand slip therethrough upon exertion onto the strand of a removal tension force strictly greater than a maximum tension force the strand is configured to apply to the anchor unit (6) while the strand (4) is anchored and strictly inferior to an ultimate tensile force of the strand beyond which the strand breaks.

Description

An anchor assembly comprising a strand and an anchor unit

The invention pertains to the field of strands, in particular strands which are destined to be anchored in the ground, and to anchor units which may be used to have the strands fixedly received in the ground. Moreover, it relates to the removal of the strands which are so-anchored.

In the context of civil engineering, strands, which for instance include one or more wires such as steel wires, are often used to anchor pieces of equipment, such as dam elements, tunnel stabilization works, foundations of structures, etc.

To that end, the strands are connected to the corresponding load they are to anchor at one end, and are anchored by their other end, for instance in the ground.

For the anchoring of this particular end of the strands, anchor units may be used, which are fixedly received in a hole arranged in the ground. Some of these anchor units comprise an element swaged onto a strand which thereby grips it, thereby securing the strands to the ground.

In such a context, problems arise when the strands which are anchored are no longer needed. In fact, due to the units received in the holes needing to be fixedly received therein for the proper anchoring of the load, it may be that removing the grip anchor unit from its hole is not feasible. Once detached from their load, the unused strands may be left in their hole and tend to be a hindrance for the proper exploitation of the ground in which they are received and its vicinity.

To address this problem, a common approach lies in arranging one or more weaknesses along the length of strands, whereby portions of the strands may be ultimately separated from the rest of the strand through a breaking process.

However, this approach presents drawbacks, as it is generally undesirable to generate weaknesses in the strands, and the strands may not be removed entirely.

The invention seeks to improve this situation. To that end, the invention relates to an anchor assembly comprising a strand and an anchor unit receiving said strand therethrough, the anchor assembly being destined to be fixedly received in a hole for anchoring said strand, the anchor unit comprising a swage element receiving the strand therethrough, the swage element being swaged onto the strand, thereby gripping said strand, the swage element being configured to let the strand slip therethrough upon exertion onto the strand of a removal tension force strictly greater than a maximum tension force the strand is configured to apply to the anchor unit while the strand is anchored, and strictly inferior to an ultimate tensile force of the strand beyond which the strand breaks.

According to an aspect of the invention, the removal tension force is comprised between 30 % and 100 % of the ultimate tensile force of the strand. According to an aspect of the invention, the anchor unit further comprises an anchoring head receiving the strand therethrough, the swage element and the anchoring head being destined to cooperate in abutment with each other to anchor the strand.

According to an aspect of the invention, the anchor unit further comprises a sheath receiving the strand. According to an aspect of the invention, the sheath comprises at least one external corrugation destined to cooperate with walls of the hole or with a filling material filling the hole for keeping the anchor assembly fixedly arranged in the hole.

According to an aspect of the invention, the anchor unit further comprises an inner tube receiving the strand. According to an aspect of the invention, the inner tube and the sheath define a gap therebetween, said gap being filled with a filling material configured to mechanically couple the inner tube to the sheath.

According to an aspect of the invention, the strand comprises a free end extending beyond the swage element, the anchor unit further comprising a protection cap defining an inner chamber receiving said free end.

The invention also relates to method of manufacturing an anchor assembly comprising a strand and an anchor unit receiving said strand therethrough, the anchor assembly being destined to be fixedly received in a hole for anchoring said strand, the anchor unit comprising a swage element, the method comprising: - engaging the strand through the swage element, the swage element being in a first configuration in which it allows the passage of the strand therethrough,

- swaging the swage element onto the strand, whereby the swage element is deformed to be brought in a second configuration in which the swage element grips the strand, in said second configuration, the swage element is configured to let the strand slip therethrough upon exertion onto the strand of a removal tension force strictly greater than a maximum tension force the strand is configured to apply to the anchor unit while the strand is anchored and strictly inferior to an ultimate tensile force of the strand at which the strand breaks.

According to an aspect of the invention, the anchor unit further comprises an inner tube receiving the strand and a sheath receiving the strand and the inner tube, the inner tube and the sheath defining a gap therebetween, the method further comprising filling said gap with a filling material.

According to an aspect of the invention, the method further comprises arranging the anchor unit in the hole and filling a space defined between walls defining the hole and the anchor unit with a material configured to mechanically couple the anchor unit to the walls of the hole. The invention also relates to a treatment method of an anchor assembly comprising a strand and an anchor unit receiving said strand therethrough, the anchor assembly being fixedly received in a hole for anchoring said strand, the anchor unit comprising a swage element receiving the strand therethrough, the swage element being swaged onto the strand, thereby gripping said strand, the swage element being configured to let the strand slip therethrough upon exertion onto the strand of a removal tension force strictly greater than a maximum tension force the strand applies to the anchor unit while the strand is anchored and strictly inferior to an ultimate tensile force of the strand at which the strand breaks, the method comprising : engaging the strand in a piece of equipment adapted to exert a tension force onto the strand,

- operating the piece of equipment to exert, onto the strand, a tension force equal or greater than the removal tension force so as to have the strand slip through the swage element until the strand is freed from the swage element.

According to an aspect of the invention, operating the piece of equipment comprises gradually increasing the tension force the piece of equipment exerts onto the strand until said tension force matches or becomes greater than the removal tension force.

According to an aspect of the invention, the anchor assembly comprises a plurality of strands, the piece of equipment being adapted to receive more than one strand at a given time and to exert respective tension forces onto said more than one strand, the piece of equipment being operated to exert on each strand a respective tension force equal or greater than the respective removal tension force of the considered strand. Further features and advantages of the invention will become more apparent by reading the following detailed description of the embodiments, which are given by way of non-limiting examples with reference to the appended drawings, in which:

Figure 1 is an illustration of an anchor assembly according to the invention;

- Figure 2 is an illustration of a swage element of the anchor assembly of Figure 1 ;

Figure 3 is an illustration of an anchor block of the anchor assembly of Figure 1 ; and Figure 4 is an illustration of a method of manufacturing an anchor assembly according to the invention, as well as of a method of treating an anchor assembly according to the invention. Figure 1 illustrates an anchor assembly 2 according to the invention.

The anchor assembly 2 is configured to anchor at least one strand 4, for instance in the ground, for the anchoring of a piece of equipment, such as civil engineering equipment, using the strand. For instance, the piece of equipment is a retaining wall, a dam, the foundation of a structure, tunnel stabilization works, etc. The anchor assembly 2 thus comprises one or more strand 4, as well as an anchor unit 6 destined to cooperate with the strand 4 to anchor the strand 4.

For instance, the anchor assembly 2 comprises from 1 to 20 strands, and advantageously from 1 to 5 strands.

In the context of the invention, the strand(s) 4 comprises one or more wires 8 (Figure 2). The wire(s) is for instance made of metal, such as steel. When the strand comprises a plurality of wires 8, the latter may be arranged together in a helical manner along the direction of the strand, as in Figure 2 over at least a portion of the length of the strand.

The strand may include a sheath which surrounds the wire(s) along all or part of the strand. It may further include a filling material, which fills at least part of the space defined between the sheath and the wires, and possibly part of spaces defined between the wires themselves. The filling material may have lubrication properties, and/or any properties which are sought given the specifics of the targeted application.

The strand 4 may form all or part of a tendon, or cable, which may comprise a single strand or a plurality of them. The strands of the cable may be in contact with one another along a portion of the length of the tendon, and are for instance spread apart in the vicinity of the anchor unit 6, for instance using any known means (which may form part of the anchor unit 6 itself). They may be arranged in parallel one relative to the other, as shown on Figure 1.

Each strand 4 exhibits an ultimate tension force, which corresponds to the maximum tensile force it can be subjected to without breaking. This ultimate tension force corresponds to a guaranteed ultimate tension force of the strand, and has a known value for a given strand. For instance, this value is provided by the manufacturer of the strand. In effect, when subjected to a tension force greater than this ultimate tension force, the strand is supposed to break.

The anchor unit 6 is configured to anchor the strand(s) 4, for instance in the ground.

To that end, it is destined to cooperate with the or each strand 4, and to be fixedly received in a hole, or cavity 10. The hole 10 is for instance arranged in the ground using any known means, such as a drill.

In the context of the invention, the anchor unit 6 is preferably a swage grip anchor unit. In other words, it is destined to cooperate with the strand(s) 4 by gripping the latter using a swage element which is swaged onto the strand. In reference to Figure 1 , the anchor unit 6 comprises a swage element 12, an anchor block, or head, 14, an inner tube 16, and a sheath 18.

The swage element 12 is configured to receive the strand therethrough and grip the strand 4. As detailed below, this configuration is the result of a swaging operation whereby the swage element is swaged onto the strand, i.e. radially deformed inwardly so as to come in contact with the strand and be locked in relative position with the strand. The swage element 12 is also configured to cooperate with the anchor block to anchor the strand.

In the context of the invention, advantageously, the anchor unit 6 comprises a swage element 12 for every strand 4 the anchor unit 6 anchors. Each swage element 12 is associated to a single strand 4 and grips the corresponding strand for its anchoring. In reference to Figure 2, the swage element 12 presents a cylindrical configuration.

In the context of the invention, for instance, each wire of the strand has a diameter of about 5 mm. The strands 4 have a diameter between 5 mm and 25 mm. The swage element 12 has a diameter between 10 and 50 mm a length between 20 and 100 mm.

For instance, in an example, for a strand of 16 mm in diameter, the associated swage element 12 has a diameter of 37 mm and length of 50 mm before swaging, and a diameter of 32 mm and a length of 60 mm after swaging. In another example, for a strand of 16 mm in diameter, the swage element has a diameter of 33 mm and length of 60 mm before swaging, and a diameter of 28 mm and a length of 76 mm after swaging.

The swage element 12 comprises a main portion 20 having a cylindrical shape and which gives the swage element its overall shape. The longitudinal extremities of the main portion are for instance perpendicular to the axis of the main portion. Optionally, at least one may include a bearing structure, such as a ring, protruding therefrom. This structure is for instance destined to come in contact and more specifically in abutment with the anchor head 14.

It further comprises an opening 22 arranged in the main portion 20. It receives the corresponding strand 4. For instance, the opening 22 stretches along the axis of the swage element 12, advantageously in the center of the main portion 20.

The material from which the main portion 20 is made may be a metal, such as steel. For instance, it is made of a high strength steel, such as a grade 900 MPa steel. Preferably, the main portion 20 is made of a ductile material, in that it has the ability to be plastically deformed without breaking.

Additionally, the swage element may comprise an inner spring 24 arranged along the walls of the opening 22. The inner spring comprises spires, which may optionally be in contact with one another. The inner spring may stretch along the length of the entire opening, or only part of it.

For instance, the inner spring is made of metal, such as steel. It is advantageously made of a steel having a high hardness and a high tensile strength, whereby it can deform, typically cause an indentation, both the strand 4 and the main portion 20 of the swage element 12 so as to allow the swage element 12 to grip the strand 4. The steel is for instance a grade 2200 MPa steel,

The hardening of the steel may be obtained using a quenching process.

In addition, due to its hardness and brittle nature, the inner spring may easily break when subjected to a force which tends to deform it. In effect, the length over which the inner spring stretches may thus easily be modified, advantageously through a process in which spires of the inner spring are removed so as to have the inner spring stretch over the desired length of the central opening 22.

In the context of the invention, in its gripping configuration, i.e. when it has been swaged onto the corresponding strand, at least one of the swage elements 12 of the anchor unit 6 is configured to allow the strand to slip through it upon exertion on the strand of a removal tension force which is strictly greater than a maximum tension force the strand 4 is configured to apply to the anchor unit while the strand 4 is anchored by it.

In other words, once swaged onto the strand, the swage element is configured to allow the strand to slip in its central opening if a sufficient tension force is applied, this tension force being configured to be strictly higher than a maximum value of the tension force the strand is destined to apply to the swage element due to its being anchored, i.e. due to its taking up efforts of the load it is to anchor by its other end.

In the context of the invention, the removal tension force is a longitudinal traction, i.e. a traction exerted longitudinally onto the strand relative to the direction of the strand, at least locally in the region of the anchor assembly.

Advantageously, all the swage elements 12 of the anchor unit 6 exhibit this property. The removal tension force associated to a given swage element 12 may differ from that of another swage element.

Advantageously, the removal tension force is inferior or equal to the ultimate tension force of the strand, whereby the slipping of the strand through the swage element 12 will occur before the strand breaks. This allows the entire strand to be removed without having the strand break, as detailed below.

Advantageously, the removal tension force is strictly inferior to this ultimate tension force.

For instance, the removal tension force is included in a range having an upper boundary corresponding to 100% of the ultimate tension force, and advantageously in a range having an upper boundary corresponding to 95% of the ultimate tension force. Alternatively, this upper boundary is lower, and may correspond to 90%>, 85%, or 80%. This increases the overall safety of the removal of the strand, as it ensures the strand will not break upon removal.

The lower boundary may greatly vary according to the considered application, as may be as low as 30%) of the ultimate tension force, or even lower. It may however be greater than 40%>, 50%>, 60 % or higher, such as greater than 70%, 80% or 90%.

To the end of having the swage element allowing the strand to slip therethrough, i.e. of appropriately "calibrating" the swage element, different approaches may be used, either separately or in combination. For instance, one approach relies on choosing the length of the swage element. In effect, the greater the contact surface between the swage element and the strand, the higher the gripping effect of the swage element on the strand.

The length may be chosen as a function of one or more parameters among the diameter of the swage element (such as its diameter before swaging and/or after swaging), the material it is made of, the pressure which is applied to the swage element to swage it onto the strand, etc.

Another approach may be to adjust the length of the inner spring 24 of the swage element within the central opening 22.

For instance, this length is adjusted prior to the swaging of the swaging element onto the strand. Due to its configuration, the inner spring 24 plays an important role in the gripping effect of the swage element on the strand. Shorter lengths will therefore result in lower grips. As such, the length of the spring 24 can be used as a prominent finely controllable way to adjust the gripping effect of the swage element.

Another approaches lies in choosing the material of the swaging element. For instance, the ductility of the swage element may be chosen specifically, or even a material other than steel may be chosen, whereby the deformation of the swage element will be different and will translate into different grips for a given pressure applied to the swage element for its swaging. Other properties may be chosen specifically such as the ultimate tensile strength of the main portion of the swage element, and/or its yield strength. For example, for a strand having an ultimate tensile strength of about 1860 MPa and a diameter of about 16 mm, a swage element having the desired gripping effect can be obtained. This swage element for instance measures a few tens of millimeters in length, and its inner spring has a few tens of spires made of steel.

As indicated, these approaches may be combined together to obtain the desired gripping effect of the swage element on the strand, the details of the designing operations of an appropriate swage element using such approaches being within reach of the man skilled in the art.

In effect, for instance, a given material having the desired ductility is chosen for the main portion of the swage element, and a given material is chosen for the inner spring. Then, the number of spires of the inner spring is adjusted to obtain the desired gripping effect after swaging using a predetermined swaging configuration (in particular in terms of deformation of the swage element). The anchor block 14, which may also be referred to as an anchor head, is configured to cooperate in abutment with the swage element 12 to retain the swage element within the hole 10.

The anchor head 14 presents any shape, such as disc -type shape. It may be made of any material. For instance, it is made of steel.

The anchor head 14 presents regions 26 destined to cooperate with the swage elements 12. The respective portions of the regions 26 which form part of the surface of the anchor head facing away from the opening of the hole are advantageously planar. These portions are destined to be in contact with the swage elements and oppose any longitudinal movement of the strand toward the opposing end of the latter.

The regions may be surrounded at least in part by a shoulder 28 having an inner shape which is complementary to the shape of outer wall of the corresponding swage element, thereby preventing sliding of the swage element relative to the anchor head.

In addition, the anchor head 14 includes reception openings 31 each destined to receive one strand 4.

The dimensions of the opening may be complementary to that of the strands, whereby the strand comes in contact with the walls defining the reception openings. Alternatively, they may be greater so as to prevent such contacts.

As shown in Figure 1 , the anchor head 14 and the sheath 18 are in a fixed relative position. For instance, to that end, the anchor head 14 is secured to the sheath 18, for instance using any known means (which may take the form of a dedicated element, whereby the head 14 and the sheath 18 may not be in direct contact).

In the example of Figure 1 , the anchor head 14 is shared by all the strands of the anchor assembly, i.e. the anchor assembly 2 solely comprises a single head 14 destined to cooperate with the respective swage elements associated to all the strands 4 to anchor unit 6 anchors. As illustrated, in Figure 3, the reception openings may then be evenly distributed angle-wise around a central region of the anchor head.

Alternatively, the anchor assembly may comprise a plurality of such anchor heads 14, which each receive one or more strand. The anchors heads are in fixed position relative to the sheath 18, and may be secured to the latter to that end. They may optionally be secured to one another. Still in reference to Figure 1, the inner tube 16 is configured to define an inner volume 30 within which at least one strand is received.

Preferably, as illustrated in Figure 1, the anchor assembly includes one inner tube for each strand 4, a given inner tube receiving an associated strand therein. Alternatively, the anchor unit comprises one or more inner tube receiving a plurality of strands . For instance, the anchor unit then includes a single inner tube received all the strands.

In a general manner, advantageously, the inner tube is configured so that the inner tube and the strand(s) received therein are not in contact while the strand is in operation. Alternatively, they are in contact. The inner tube 16 is in a fixed position relative to the anchor head 14, and for instance is secured to the latter to that end. For instance, it is secured to the face of the anchor block 14 which is opposite the face of the block 14 which is in contact with the swage elements 12.

For instance, the inner tube 16 presents itself in the shape of a hollow cylinder. It stretches along a direction which is advantageously substantially parallel to that of the local direction of the strands.

Advantageously, the inner volume 30 does not contain any dedicated filling material, such as a pliant and/or lubricant material. It may be filled with a gas such as air.

The inner tube may be made of any material, such as a metal, for instance steel.

Still in reference to Figure 1 , the sheath 18 is configured to allow the reception of the anchor unit in the hole 10 in a fixed manner. In other words, it is configured to fixedly retain the anchor unit in the hole 10, and in particular to mechanically couple the anchor unit and thereby the strands to the walls 32 of the hole.

To that end, its outer surface is destined to come in contact with the walls 32 which define the hole 10, or with a material 33 which fills the hole and mechanically couples the anchor unit to the walls of the hole 10.

In case it is present, the material 33 is configured to mechanically couple the anchor unit to the walls of the hole 10, and in particular to lock them in a fixed relative position, whereby the material 33 anchors the anchor unit to the walls of the hole 10.

For instance, the material 33 comprises a cement matrix, such as a grout, a mortar or a concrete. The sheath 18 presents an overall cylindrical hollow shape. It is mechanically coupled to the anchor head 14 and is in a fixed position relative thereto. For instance, it is secured to the anchor head.

The sheath 18 stretches along an axis which is substantially parallel to the local direction of the strands.

Advantageously, it is arranged so as to form a tube which is arranged outwardly relative to the inner tube(s), i.e. to form an outer shell for the anchor unit. It defines an inner cavity 34 within which the strands and the one or more inner tube are arranged.

Advantageously, it exhibits a diameter which is equal or greater than the diameter of the circle defined onto the surface of the anchor head in which the reception openings 31 are inscribed. In other words, its diameter is sufficient to encapsulate all the strands. Its diameter may for instance correspond to that of the anchor head.

The sheath 18 may be made of any material, in particular a metal. For instance, it is made of steel. Alternatively, it may be made of plastic. Advantageously, the space of the inner cavity 34 defined between the inner face of the sheath 18 and the outer face of the inner tube(s) is filled with a filling material 36. The material 36 is configured to mechanically couple the inner tube to the sheath to allow transmission of efforts therebetween.

The filling material is preferentially hardenable. The filling material may comprise a cement matrix, and is for instance a grout. For instance, the filling material is a high strength cement grout, or a regular cement grout.

Advantageously, the space of the inner cavity which is defined between the sheath and the inner tube is tight.

In particular, this space is advantageously tight on the side of the anchor block, so as to prevent the material 36 from escaping the cavity 34 between the sheath and the anchor block. A joint between the sheath and the anchor head may thus be used to that end.

In addition or in parallel, the cavity may be tight on its side opposite to the anchor head 14. For instance, a lid or a cover may thus be used to seal the cavity 34.

It should be noted that no specific element may be used to close the cavity. In fact, the material 36 may itself form a sealing barrier once hardened. In another embodiment, no specific precaution may be taken to seal the cavity on its side opposite to the anchor head. In other words, the cavity may not be tight.

Advantageously, the sheath 18, and more particularly its outer surface, comprises at least one corrugation 38 destined to cooperate with the walls of the hole 10 or with the material 33. For instance, this corrugation 38 takes the form of a protrusion which stretches outwardly from the rest of the sheath (relative to the axis of the sheath), i.e. from the outer surface of the rest of the sheath. As such, the corrugation is external.

For instance, the corrugation 38 presents itself in the form of a band of matter. It may stretch over all or part of the outer face of the sheath, for instance in a helical manner relative to the axis of the sheath.

The corrugation may be integral with the rest of the sheath, or may be added to the rest of the sheath.

In effect, the corrugation is designed to increase the mechanical aspect of the fixed position of the anchor unit 6 relative to the walls of the hole 10, in particular longitudinally. The sheath may comprise a plurality of such corrugations. For instance, it comprises two or more such corrugations, which for instance present themselves in the form of respective bands of matter which are parallel to one another and stretch helically along the axis of the sheath.

In addition to the elements described above, the anchor unit 6 may further comprise one or more protection cap 40. In effect, as depicted in Figure 1 , each strand has a free end which extends beyond the anchor head 14 and the corresponding swage element 12. Each cap 40 is configured to protect at least the free end 42 of at least one strand 4.

Advantageously, the anchor unit comprises a single cap 40 receiving the free ends of all the strands. Alternatively, as shown in Figure 1, the anchor unit includes at least one cap receiving the free end of a single strand, and for instance includes as many such caps as there are strands.

In a preferred configuration, the anchor unit includes a single cap which receives the free ends of all the strands.

The (or each) protection cap 40 is secured to the anchor head 14 (or to another element which is fixed relative to the anchor head). The protection cap 40 defines an inner chamber 44 in which the corresponding free end(s) 42 is received. For instance, the inner chamber 44 is tight, such as water and/or air tight, and protects the free end from corrosion.

Advantageously, the inner chamber comprises a protective material filling at least part of the inner chamber 44, such as wax or grease.

In some embodiments, the anchor unit includes a protection cap for each strand, each protection cap forming a chamber receiving one free end. Alternatively, a given cap may receive a plurality of free ends. The anchor unit may include a single cap receiving all the free ends of the strands 4 of the assembly 2. The operating principle of the anchor assembly is as follows.

While in operation, the strands take up efforts which are produced by the load they are anchoring. These efforts translates into a tension force applied by the strand to the swage element, this force being transferred to the anchor head then the inner tube(s) and the sheath trough the material 36, then the walls of the hole 10 through the material 33, whereby the energy applied to the strands by the load is dissipated and the anchor unit remains in place in the hole due to the mechanical coupling of the anchor unit to the walls of the hole.

The transfer of the efforts between these components may mainly involve shearing effects.

A method of manufacturing an anchor assembly 2 according to the invention will now be described in reference to the Figures. In general, the method includes swaging the swage element associated to a given strand so as to have the swage element 12 allow the strand to slip therethrough upon exertion onto the strand of the removal tension force which is greater than the maximum tension force the strand is destined to apply to the swage element and the anchor unit as a whole during its operational lifetime, i.e. to anchor the load whose efforts it is to take up. To that end, during a step SI, the strand 4 is engaged through the swage element 12 which is destined to be swaged onto the strand. Initially, the swage element 12 is in a first configuration in which it allows the passage of the strand 4 through its central opening without exerting any gripping effect on the latter, or at least with a grip much lower than in operation. For instance, in this configuration, the strand may be inserted in the swage element through any known process, such as manually. In a step S2, the swage element 12 is swaged onto the strand so as to come to a second configuration in which the swage element 12 grips the strand 4. In this second configuration, the swage element is configured to let the strand slip therethrough upon exertion onto the strand of the removal tension force defined above. In effect, during this step, the swage element is deformed radially in a plastic manner so that the inner spring 24 and/or the walls of the central opening 22 come in contact with the strands and exert a gripping effect on the latter.

As described above, this results from a previous calibration of the swage element given the pressure it is to be submitted to in step S2. The means used for this step may include a swaging jack, or a press with a hollow die.

In a step S3, the anchor assembly is assembled together using the strand and the swage element 12 which has been swaged onto the strand 4. More particularly, the strand 4 is inserted through the anchor head 14, the swage element 12 being placed in abutment against the anchor head 14 which is fastened to the sheath (either before or after). The inner tube(s) is secured to the anchor head as well, the strands being received therein. The protection cap(s) 40 is arranged on the anchor head so as to receive the free end of the strand(s), wherein a process of filling the inner chamber may be carried after the protection cap has been arranged on the anchor head.

Moreover, the portion of the inner cavity which surrounds the inner tube(s) 16 is filled with the material 36, and the extremity of this cavity may be closed if required. After that, the material 36 is left to harden, and comes to mechanically couple the inner tube(s) 16 and the head 14 to the walls of the sheath 18. Once assembled, in a step S4, the anchor assembly, and more particularly the anchor unit 6, is arranged in the hole 10. The hole may have been excavated beforehand, for instance in parallel to any one of steps SI to S3, or may be so after step S3.

During a step S5, the volume of the hole which surrounds the anchor unit is filled with the material 33. After that, the material is left to harden, and comes to mechanically couple the anchor unit to the walls of the hole 10.

Thereafter, during a step S6, the strands of the assembly 2 are connected to the piece of equipment they are to anchor in the ground by their opposing end. From there on, through the anchor unit 6, the strands 4 anchor the piece of equipment to the ground, as described above. This is so until they are no longer needed, at which point they are disconnected from their load.

During a removal process following thereafter, the strands 4 are removed from the anchor unit 6. More particularly, they are entirely removed, and are so without being broken. To that end, during a step S7, each strand 4 is engaged in a piece of equipment, such as a piece of machinery, which is adapted to exert a tension force onto the strand.

For instance, this piece of equipment is a hollow jack. It should be noted that the jack may be a monostrand jack, i.e. a jack adapted to receive a single strand at a given time. Alternatively, it may be a multistrand jack, i.e. a jack adapted to receive a plurality of strands simultaneously, for instance all of them. From there on, the removal of the strands may be carried out simultaneously or sequentially, depending on the jack to be used.

During a step S8, the piece of equipment is operated to exert a tension force onto the strand(s) 4. The tension force is increased so as to match or become greater than the removal tension force described above, whereby the strand is allowed to slip through the corresponding swage element 12 and is progressively released from the swage element. The tension force is for instance maintained until the strand 4 is freed from the swage element. The respective tension forces exerted onto the various strands may be different.

As indicated above, this may be for instance done for each strand separately, or simultaneously for all the strands.

Advantageously, during step S8, the tension force exerted by the piece of equipment is gradually increased, for instance through increasing the pressure in the jack. Advantageously, this increase is made in a continuous fashion rather than through jerks.

Advantageously, during this step, protective measures may be implemented to prevent the strands from flying out of the anchor unit 6. For instance, a protection apparatus is arranged behind the jack and defines a cavity within which the strand will be retained if it were to fly. The protection apparatus may then also act as a shock absorber.

The invention presents several advantages. In particular, it allows the complete removal of anchoring strands efficiently, and without the need to dispose of additional components specifically designed to that end. In addition, this property has no impact on the operation capabilities of the anchor assembly.

Moreover, this property may result from various parameters which may be selected to obtain this result, whereby this method is highly adaptable depending on the targeted application.

In the description above, the anchor assembly has been described as being destined to be arranged in the hole 10. It may be that several such assemblies may be arranged in a same hole 10. For instance, they are then arranged in a staggered configuration, each assembly being distant from the adjacent assembly/assemblies along the local direction of the strands. In addition, in some embodiments, the strands may be coupled to a sealing element 46 configured to seal the corresponding inner tube 16 to prevent the material 33 from penetrating therein.

For instance, the elements each form a sleeve engaged on the extremity of the inner tube and around the corresponding strand, as illustrated in Figure 1.

For instance, the sealing elements are made of a heat-shrinkable material, and are thus heated during the process. Preferentially, this is done prior to the anchor unit 6 being installed in the hole 10.

The sealing element(s) may include a flexible filling material alternatively or additionally. The filling material is for instance solely located at the mouth of the inner tube(s). It may be used as the only sealing element if the inner tube has an important radius, for instance if the anchor unit includes a single inner tube. For instance, the filling material is a silicon-based material.

Claims

16 CLAIMS

1. An anchor assembly comprising a strand (4) and an anchor unit (6) receiving said strand therethrough, the anchor assembly (2) being destined to be fixedly received in a hole (10) for anchoring said strand, the anchor unit (6) comprising a swage element (12) receiving the strand (4) therethrough, the swage element (12) being swaged onto the strand, thereby gripping said strand, the swage element being configured to let the strand slip therethrough upon exertion onto the strand of a removal tension force strictly greater than a maximum tension force the strand is configured to apply to the anchor unit (6) while the strand (4) is anchored, and strictly inferior to an ultimate tensile force of the strand beyond which the strand breaks.

2. The anchor assembly according to claim 1, wherein the removal tension force is comprised between 30 % and 100 % of the ultimate tensile force of the strand (4).

2. The anchor assembly according to claim 1, wherein the anchor unit (6) further comprises an anchoring head (14) receiving the strand therethrough, the swage element (12) and the anchoring head (14) being destined to cooperate in abutment with each other to anchor the strand.

3. The anchor assembly according to claim 1 or 2, wherein the anchor unit (6) further comprises a sheath (18) receiving the strand.

4. The anchor assembly according to claim 3, wherein the sheath (18) comprises at least one external corrugation (38) destined to cooperate with walls of the hole or with a filling material filling the hole for keeping the anchor assembly fixedly arranged in the hole.

5. The anchor assembly according to any one of the preceding claims, wherein the anchor unit further comprises an inner tube (16) receiving the strand.

6. The anchor assembly according to claims 4 and 5, wherein the inner tube (16) and the sheath (18) define a gap therebetween, said gap being filled with a filling material (36) configured to mechanically couple the inner tube to the sheath.

7. The anchor assembly according to any one of the preceding claims, wherein the strand comprises a free end (42) extending beyond the swage element (12), the anchor unit further comprising a protection cap (40) defining an inner chamber (44) receiving said free end.

8. A method of manufacturing an anchor assembly comprising a strand (4) and an anchor unit (6) receiving said strand therethrough, the anchor assembly (2) being destined to be fixedly received 17 in a hole (10) for anchoring said strand, the anchor unit comprising a swage element (12), the method comprising:

- engaging (S I) the strand (4) through the swage element (12), the swage element (12) being in a first configuration in which it allows the passage of the strand therethrough, - swaging (S2) the swage element (12) onto the strand (4), whereby the swage element is deformed to be brought in a second configuration in which the swage element (12) grips the strand (4), wherein in said second configuration, the swage element (12) is configured to let the strand slip therethrough upon exertion onto the strand of a removal tension force strictly greater than a maximum tension force the strand is configured to apply to the anchor unit while the strand is anchored and strictly inferior to an ultimate tensile force of the strand at which the strand breaks.

9. The method according to claim 8, wherein the anchor unit (6) further comprises an inner tube (16) receiving the strand (4) and a sheath (18) receiving the strand (4) and the inner tube (16), the inner tube and the sheath defining a gap therebetween, the method further comprising filling said gap with a filling material (36).

10. The method according to claim 8 or 9, the method further comprising arranging the anchor unit in the hole (10) and filling a space defined between walls defining the hole (10) and the anchor unit (6) with a material (33) configured to mechanically couple the anchor unit (6) to the walls of the hole (10)

11. A treatment method of an anchor assembly (2) comprising a strand (4) and an anchor unit (6) receiving said strand (4) therethrough, the anchor assembly (2) being fixedly received in a hole (10) for anchoring said strand, the anchor unit comprising a swage element (12) receiving the strand therethrough, the swage element (12) being swaged onto the strand (4), thereby gripping said strand, the swage element being configured to let the strand slip therethrough upon exertion onto the strand of a removal tension force strictly greater than a maximum tension force the strand applies to the anchor unit while the strand is anchored and strictly inferior to an ultimate tensile force of the strand at which the strand breaks, the method comprising : engaging (S7) the strand in an piece of equipment adapted to exert a tension force onto the strand,

operating (S8) the piece of equipment to exert, onto the strand (4), a tension force equal or greater than the removal tension force so as to have the strand (4) slip through the swage element (12) until the strand (4) is freed from the swage element (12). 18

12. The treatment method of claim 11, wherein operating the piece of equipment comprises gradually increasing the tension force the piece of equipment exerts onto the strand until said tension force matches or becomes greater than the removal tension force.

13. The treatment method according to claim 11 or 12, wherein the anchor assembly comprises a plurality of strands, the piece of equipment being adapted to receive more than one strand at a given time and to exert respective tension forces onto said more than one strand, wherein the piece of equipment is operated to exert on each strand a respective tension force equal or greater than the respective removal tension force of the considered strand.