Rock anchor with integrated tension unit

Abstract

Disclosed is a rock anchor 200 with an inner stem 204 and outer stem 206 that are axially movable with respect to each other and when actuated cutting fingers 208 are flared outwards. The rock anchor

Description

The present invention relates to rock anchors, and specifically to groutless rock anchors having integrated tension units to ensure stability over the lifetime of the use of the rock anchor. The invention also relates to methods for installation and decommissioning of such rock anchors. Groutless rock anchors are known and may be seen described in, e.g., UK patent numbers GB2578948 and GB2579264. Figures 1A and 1B illustrate the working properties of such rock anchors, which generally have an inner stem 104 nested within an outer stem 106. Figures 1A and 1B show an installation of such a rock anchor 100 - in Figure 1A, an initial state is shown, illustrating that during installation, a rock anchor 100 is first drilled to a set depth in a substrate 102. Next, the inner stem 104 of the rock anchor 100 is pulled upwards (equivalent to “proximally” as used herein throughout). As the inner stem 104 is pulled proximally, a tapered portion 116 of the inner stem 104 is pulled towards and into a set of cutting fingers 108 located at the distal end of the outer stem 106. This interaction forces the cutting fingers 108 to flare outwardly. During this procedure, the outer stem 106 (or indeed the whole rock anchor 100) is rotated. This causes the cutting fingers 108 to cut as they flare outwardly, leading to an underreamed hole in the substrate 102, as shown in Figure 1B. The underreamed portion of the hole is wider than the anchor’s drilled diameter, as shown in Figure 1B. In this example, the inner stem 102 is pulled upwardly by use of a threaded portion 110 and nut 112. Rotating the nut 112 moves the nut 112 along the threaded portion 110, bearing downward (equivalent to “distally” as used herein throughout) on the top of the outer stem 106. This causes a relative axial motion between the inner 104 and outer 106 stems, specifically that the inner stem 104 moves axially proximally relative to the outer stem 106. In the abstract, this is equivalent to the outer stem 106 moving axially distally relative to the inner stem 104. However, since the rock anchor 100 is embedded in the substrate 102, which provides a convenient and consistent reference frame, this action is more commonly referred to as pulling the inner stem 104 upwardly or proximally. The tension within the anchor 100 is secured using the nut 112 which is mounted onto the threaded portion 110 on the inner stem 104. The contact surfaces between the nut 112 and of the upper end of the outer stem 106 each need to be flat since the rotational end position cannot be defined in advance of installation. The outer stem 106 is also provided with a tapered portion 116 which provides a reaction surface against which the upward force from the cutting fingers 08 and inner stem taper 116 impinges. This acts like a pair of jaws to grip the substrate 102. A cutter 118 is provided at the distal end of the inner stem 104 to allow the rock anchor 100 to drill the initial bore hole to arrive at the situation shown in Figure 1A. This design has the following technical shortfalls: • The arrangement provides only a relatively low amount of embedding of the anchor in the rock mass, resulting in relatively high losses of tension on installation. This in turn reduces the loading potential for the anchor. • In addition, during the anchor’s lifetime compression of the rock mass and / or wear / abrasion of the rock bearing surfaces can lead to further loss of tension in the inner stem (since motion in the substrate can cause the fingers to lose contact). This in turn can cause potential anchor failure, with the only mitigation being (expensive) regular re-tightening of the system. • The high stiffness typical of the inner stem means that even small movement of the tapers toward each other leads to catastrophic loss of tension. • Finally, it is difficult to lock the location of the nut because the final location is usually not known in advance. This leads to a risk that the nut accidentally untightens itself, particularly under highly fluctuating input loads, and tension in the inner stem is lost entirely. Again, this results in a failure of the anchor. The present invention aims to address some or all of the drawbacks set out above. Disclosed herein is a rock anchor extending along an axis from a proximal end to a distal end, the rock anchor comprising: an outer stem having one or more flareable cutting fingers disposed at a distal end; an inner stem, the inner and outer stems being moveable relative to Stowed includes stowable, and means that the fingers lie (or are able to be moved so that they lie) close to and roughly parallel with the axis.one another in the axial direction to selectively transition between a first configuration in which the cutting finger(s) is / are stowed and a second configuration in which the cutting fingers are flared outwardly; and an installation mechanism for selectively transitioning the inner and outer stems between the first and second configurations; and wherein the rock anchor further comprises an integrated tension unit, the integrated tension unit being arranged to exert a force to urge the relative axial positions of the inner and outer stems toward the second configuration. In this document, “outwardly” is used to mean generally in a direction away from the axis of extent of the rock anchor. The fingers may flare outwardly by virtue of one or more pivotable connections (per finger), for example, meaning that while a portion remains as close to the axis throughout, other parts are forced further outward than this. In this framework, a stowed configuration is one in which each finger is substantially aligned with the axis so that they fit within a cylindrical envelope, while flared fingers are angled to form a cone shape. As used herein, stowed also includes stowable, in the sense that when the fingers move toward the flared configuration, they are usually forced outwardly by some mechanism, yet there is not always a corresponding mechanism to force the fingers towards the stowed mechanism (although there is also no resistance to stowing motions either, hence “stowable”). While other existing systems have specialised tools for installing, which involve external machinery to apply tension to the anchor, these tend to be large and expensive, so are removed once an anchor has been successfully installed so that the installation equipment may be used elsewhere. This means that should such known anchor types lose tension during their lifetime (for example due to shifting or compression of the rock mass), the only remedy is to bring back the large and expensive installation equipment. By contrast, here, the tension unit is integrated, meaning that it forms part of the anchor and in particular remains in place for the lifetime of the anchor. The action of the tension unit is to exert a force to compensate for any loss of tension, thereby effectively maintaining the tension without intervention and extending the lifetime of the anchor. The term “tension unit” is used because the effect of the unit is to hold a portion of the anchor in tension, as a means to continue exerting a force to drive the anchor increasingly far toward the second configuration. In otherwords, the present invention stores some tensioning potential in the integrated tension unit, and thereby is able to dynamically compensate for compression or shifting of the rock, without an external installation unit being required. This can extend lifetime and reduce maintenance complexity. The tension unit may allow for the maintenance of almost constant tension in the anchor, allowing the cutting fingers to be held against the rock surface and resulting in deeper embedding. In particular an advantageous effect of this arrangement is the maintenance of sufficient tension to ensure integrity of load holding of the installed rock anchor. The current system means that relatively large motion of the upper and lower portions toward each other can be compensated for, i.e. without losing tension. When installed, the rock into which the anchor is embedded may fracture and compress under load, rock fatigue effects could occur, or movement of the cutting surfaces of the anchor when installed could erode rock. All of these may lead to relaxation of the pre-tension and it is important to mitigate these risks so that the operations and maintenance burden of the anchoring system is reduces as much as possible. Note that the force urges the fingers "toward" (rather than e.g. "into") the second configuration because the fingers are being pressed in an outward direction, but there may not be (initially at least) any actual motion because the fingers already bear on a rock mass. Because an installed anchor already has flared fingers, the force acts to push the fingers outwardly against the rock. The biasing therefore allows the fingers to move more outwardly as and when this becomes possible, while maintaining contact with the rock. This leads to a retention of tension in the system and avoids the need for re-tightening of the anchor. The integrated tension unit may include sensors or visual markings to indicate the level of tension currently maintained in the system. This can allow an operator to inspect the anchor and determine the status of the anchor. Additional tightening can be applied if needed, but this can be limited to only anchors which need maintenance (as identified by the sensor and / or visual markings), thereby making the process more efficient. The integrated tension unit may include a spring arranged to exert the force. This is a simple and passive approach to maintaining tension. The spring may include one or more leaf springs, one or more coil springs, etc. Other examples include active tensioning units, such as mechanical, pneumatic, hydraulic or electrical systems can be used to exert a continuous or controllably varying force. The integrated tension unit may be located at a proximal end of the rock anchor. This can allow for easy inspection of the unit prior to and after installation, as well as easy access to the unit to increase tension during installation, because the proximal end of the anchor remains above the substrate. The integrated tension unit may include a housing, the housing enclosing a biasing means for exerting the force. This allows for the biasing means to be protected from the environment while exerting its force, thereby improving lifetime. The installation mechanism may include a threaded portion at the proximal end of the inner stem and wherein a nut coupled to the threaded portion of the inner stem is operable to urge the outer stem distally with respect to the inner stem. Optionally, activation of the installation mechanism also causes the integrated tension unit to increase the force exerted. This means that tension is applied via the integrated tension unit during the installation of the anchor, while also installing the anchor by underreaming a hole in the substrate. Any further embedment of the anchor is then compensated by the integrated tension unit, forcing the cutting fingers to stay in contact with the rock. In other examples, an integrated tensioning unit may be used to continually exert a tensioning force (e.g. via springs or other biasing means), which may interface with a screw thread, or a series of grooves or other portions to which the tensioning unit may grip. Where the rock anchor operates in the manner illustrated above (Figures 1A and 1B), the integrated tension unit can be situated between the upper end of the outer stem and the nut coupled to the threaded portion of the inner stem. The tensioner is then arranged to store energy to exert a force. The force acts between the nut and the outer step, pushing the nut relatively upward and / or the outer stem relatively downward. Since the nut is coupled to the inner stem via the threaded portion, this has the effect of pulling up the inner stem to cause the fingers to be forced outwardly. The stored energy (e.g. via the springs) exerts a continuous force to cause contact between the fingers and the rock, even if the rock shifts. The installation mechanism may be lockable to inhibit motions which cause a transition towards the first configuration. This prevents the anchor from reverting toward the stowed configuration. Optionally, locking the relative motion of the inner and outer stems is achieved using a form fit arrangement. Note that in the configuration shown in Figures 1A and 1B a locking form fit cannot be used to lock the drive mechanism as it is not possible to control the pre-tension within acceptable limits as limited nut rotation will result in a significant loss of pre-tension due to the high stiffness in the system. In the present arrangement, as set out in more detail below, the force exerted by the tension unit can hold the system in a stable configuration by resisting loosening. Where the system is analogous to that in Figures 1A and 1B (but for the inclusion of the tension unit), a hydraulic bolt tensioner or other direct tensioning mechanism can be used to tension the anchor. In addition, it is possible to integrate an interlock or other form fit at the axial contact surface of the nut, preventing the nut from accidentally rotating and untightening itself due to vibrations etc. The capability of the springs to compensate the movement when the nut makes untightening motions means that the risk of losing too much pre-tension is avoided. It will be appreciated that other locking mechanisms may be employed to achieve the same effect, of course. Optionally the inner stem further includes a cutter at its distal end. This can be used to bore a hole into which the underreaming is to be cut. The outer stem may have a tapered portion at its proximal end for gripping a rock mass, optionally wherein the tapered portion has a cutter or abrasive surface. This provides a gripping action between the fingers and the upper end of the outer stem. Also disclosed herein is a tensioning unit for a rock anchor having an outer stem having one or more flareable cutting fingers disposed at a distal end; an inner stem, the inner and outer stems being moveable relative to one another in the axial direction such that a distally directed motion of the inner stem relative to the outer stem selectively transitions towards a first configuration in which the cutting finger(s) is / are stowable and proximally directed motion of the inner stem relative to the outer stem selectively transitions towards a second configuration in which the cutting fingers are flared outwardly, the inner stem having a threaded portion at its proximal end; and wherein a nut is coupled to the threaded portion of the inner stem, operable to urge the outer stem distally with respect to the inner stem, the tensioning unit comprising: biasing means disposed between the nut and the outer stem and arranged to exert a force to urge the relative axial positions of the inner and outer stems toward the second configuration. This exerts a downward (distally directed) force on the outer stem and / or an upward (proximally directed) force on the inner stem to compensate for changes in rock mass configuration. The tensioning unit can be retrofitted to existing rock anchors to provide the various advantages set out above in terms of retaining tension in the anchor. The various features disclosed above regarding the operation of the tension unit may also be applied to this tensioning unit. Also disclosed herein is a method of tensioning a rock anchor, comprising the steps of: (a) providing a rock anchor of the type discussed above in a bored hole;; and (b) actuating the integrated tension unit to cause the integrated tension unit to exert a force to urge the inner and outer stems into the second configuration. Steps (b) and (c) are optionally performed simultaneously. This allows the anchor to be installed into the substrate with tension applied by the tension unit, to retain the fingers in contact with the rock. Step (a) may include the steps of: (a1) providing the rock anchor in a bored hole; and (a2) actuating the installation mechanism while rotating the rock anchor to flare the cutting fingers outwardly thereby underreaming a portion of the bored hole. This provides a convenient manner of providing the rock anchor in the bored hole. The method may further comprise using a cutter at the distal end of the inner stem to bore the bored hole prior to step (a). As noted above, the installation mechanism and the integrated tension unit may be actuated by a single action. The single action may further be lockable. Also disclosed herein is a method of decommissioning a rock anchor installed according to the methods above, the decommissioning method comprising: (d) actuating the installation mechanism to transition the rock anchor toward the first configuration; and (e) pulling the rock anchor out of the bored hole. Where the anchor has a locking mechanism, there is optionally an additional step where the anchor is first driven more toward the second configuration using an external actuator, to reduce forces on the locking mechanism, to allow it to be easily released. Subsequently method operates as set out above in terms of decommissioning. The invention will now be described, by way of example only, with reference to the accompanying Figures, in which: Figure 1A shows a prior art rock anchor part-way through an installation process; Figure 1B shows the prior art rock anchor of Figure 1A at a later stage in the installation process; Figure 2A shows a portion of an example rock anchor as disclosed herein, comprising an integrated tension unit in a slack configuration; Figure 2B shows the view of Figure 2A, but with the integrated tension unit in a tensioning configuration; Figure 2C shows alternate locations at which the integrated tension unit may be located; Figures 2D and 2E illustrate a locking mechanism in place between the integrated tension unit and a nut; and Figure 2F illustrates the locking mechanism of Figures 2C and 2D showing the nut in a disassembled state. Examples of the novel features of this disclosure may be seen in Figures 2A to 2G. Starting with Figures 2A and 2B, which show the upper portion of a rock anchor 200 with an integrated tension unit 220 in place. These Figures are loosely analogous to Figures 1A and 1B, and corresponding features are labelled with similar reference numerals. Although not shown, a set of flareable cutting fingers is located at the distal end of the rock anchor 200, which operate in a corresponding manner to that in Figures 1A and 1B. Similarly, a cutter and tapered portion or other means for flaring the fingers may be included on the inner stem 206 in the same way as shown in Figures 1A and 1B. Figure 2A shows the anchor 200 at an early stage in the installation process in which the integrated tension unit 220 is storing little or no energy, while Figure 2B shows a later step in the installation in which the integrated tension unit 220 stores energy and applies tension to the inner stem 204. During installation, similar to the anchor 100 shown in Figures 1A and 1B, the installation process is actuated in this example by driving a nut 212 along a threaded portion 210 of the inner stem 204. However, here, the nut 212 presses against the integrated tension unit 220, rather than pressing directly against the outer stem 206. This has the effect that, in addition to pulling the inner stem 204 proximally, energy is stored in the integrated tension unit 220 which in turn exerts a force on the inner stem 204 to maintain tension in the inner stem 204. The integrated tension unit 220 includes a two-part housing 222a, 222b and a spring 224. The two part housing has a first part 222a which interacts with the nut 212 and acts like a piston, compressing the spring 224. The first part 222a also surrounds the spring 224 to retain the spring 224 in position. The second part 222b of the housing surrounds the first part 222a and also clips onto the outer stem 206 to ensure correct alignment of the integrated tension unit 220. The first 222a and second 222b parts of the housing are moveable relative to one another in an axial direction. This means that the second part 222b is coupled to the outer stem 206 and does not move relative to the outer stem 206. The first part 222a is driven downwards by the nut 212, to compress the spring 224, thereby moving the first part 222a downward relative to the second part 222b. Although this example shows a specific arrangement of features, various alterations may be made while providing broadly the same advantages. For example, the integrated tension unit may be actuated by a different procedure from that which is used to flare the fingers as part of the underreaming. For example this may allow the installation to proceed as normal in a first procedure, and then separately tension can be applied to the inner stem using a second, distinct procedure operating on the integrated tension unit. This may be advantageous, because decoupling the two aspects of the procedure can allow the tensioning to be applied separately and thereby in a more controlled manner focussing on the specific requirements of that installation (e.g. due to differences in rock type between locations), albeit at the cost of a more complex installation procedure than the combined drive system discussed above. For an may be anchor in a hole, a template structure can be placed over multiple anchors concurrently and then pre-tension applied atop the template structure over the whole pile group at the same time, bearing against the lower taper of each individual pile Another variation is to supply the tension unit separately, for example for retrofitting to existing legacy anchors. In this case (consider Figures 1A and 1B), the tension unit can be installed by removing the nut 112 entirely, fitting the tension unit to the top of the outer stem 106, and replacing the nut 112 so that it is able to bear against the first part of the housing of the tension unit. The tension unit may also be located in a different location from that shown at the top (proximal) end of the anchor. Figure 2C illustrates alternative proposed locations for the integrated tension unit. A first region 226a is located along the length of the nested inner and outer stems. The advantage of placing the integrated tension unit here is that there is a long extent over which to exert forces and build up tension. The second region 226b is at the cutting fingers. This can operate to directly press the fingers outwardly, thereby achieving the desired effect, without needing to actually tension the inner stem, since the outward force is applied directly to the fingers, and not via the tapered portion on the inner stem. In addition, both alternative locations are located below the substrate surface, which protects the tension unit from damage due to external objects. This comes at the expense of it being harder to access and control the tension. The alternative tensioners themselves may make use of springs, hydraulics, ratchets and so forth to provide the desired tension. These elements may be actuated as the inner stem is pulled up, or by a separate mechanism. An additional variation on the arrangement of Figures 2A and 2B is to allow the position of the nut 212 to be lockable. This is illustrated in Figures 2D to 2F. Here the nut 212 and the first part of the housing 222a are provided with corresponding and interlocking projections 228a and indents 228b to allow a form fit arrangement. Figures 2D and 2E show these portions in an interlocked arrangement, while Figure 2F shows the nut 212 and the first part of the housing 222a separately. It will be appreciated that the purpose of this arrangement is to prevent loss of tension in the inner stem 204 due to the nut 212 loosening. Therefore, the form of the projections 228a and indents 228b should be chosen to resist rotational motion of the nut 212 in the “untightening” direction. They can, for example be shaped so as to allow a ratchet effect, in that tightening the nut 212 is possible as the projections 228a ride over the indents 228b, but motion in the untightening direction locks the projections 228a into the indents 228b. In addition, the upward force on the first part of the housing 222a pushes the first part of the housing 222a into the nut 212, thereby increasing friction and reducing the likelihood of the nut 212 coming undone. The shape of the projections 228a and indents 228b can be any suitable shape, but it will be apparent that certain forms are better than others. For example forms with projections 228a and indents 228b having surfaces extending radially will resist untightening motions well. Similarly, having a repeated pattern having rotational symmetry is desirable because even if the nut 212 does slip and start to rotate, it will necessarily rotate into another stable locked arrangement after a rotation of N degrees, where N = 360 / n and n is the order of rotational symmetry. For these reason it can be seen in Figure 2F that the specific form fit chosen uses twenty projections 228a (and correspondingly twenty indents 228b, not shown), each extending generally radially. Other means of locking the nut 212 may also be used, of course. The anchor 200 itself is installed in a very similar manner to that in Figures 1A and 1B. Specifically, a hole is bored into the substrate 202 and the anchor 200 positioned inside the hole. The nut 212 or other installation mechanism is actuated to force the cutting fingers to flare outwardly and cut an underream into the bored hole. This step may include rotating the outer stem 206 to cause the cutting fingers to cut a conical underream. Simultaneously or separately, the integrated tension unit 220 is actuated to exert a force to keep the fingers pressed against the rock at the interior surface of the underream. As in the above examples, the anchor may be provided with a cutter at the lower end of the inner stem to be used to bore the initial hole. Where a form fit arrangement is used as discussed above, the installation process may simply rotate the nut 212 until the form fit locks into place. In other examples, in addition to rotating the nut, a separate hydraulic, pneumatic, or electric actuation may be used to push the first part of the housing 222a downwards and compress the spring 224. Simultaneously the nut 212 can be tightened until it bears against the integrated tension unit 220. Further tightening of the nut 212 pulls the inner stem 204 upward and flares the fingers. Once the fingers have flared as far as desired, the separate actuation can be relaxed and the form fit engaged to prevent rotation of the nut 212. Decommissioning the anchor 200 is achieved in substantially the same way, by enacting the steps in reverse. First the nut 212 is undone to allow the fingers to relax. This may require use of the separate hydraulic, pneumatic, or electric actuation to push the first part of the housing 222a downward and disengage the form fit, where a form fit is used, prior to undoing the nut. Usually it is not possible to force the cutting fingers back to the stowed configuration (unless using a linkage based finger system in which the finger flaring is coupled to the relative motion of the inner 204 and outer 206 stems, for motion in both directions) using features present on the anchor alone. However, if the nut 212 is loosened and the inner stem 204 pushed downward, then the fingers are not prevented from returning to the stowed position. Therefore, pulling upward on the outer stem 206 will make the underreamed rock surface push the fingers, and align them closer to the axis. Repeated pulling will eventually lead to the anchor 200 being fully removed from the hole.

Claims

1. A rock anchor extending along an axis from a proximal end to a distal end, therock anchor comprising:an outer stem having one or more flareable cutting fingers disposed at a distal end;an inner stem, the inner and outer stems being moveable relative to one another in the axial direction to selectively transition between a first configuration in which the cutting finger(s) is / are stowed and a second configuration in which the cutting fingers are flared outwardly; andan installation mechanism for selectively transitioning the inner and outer stems between the first and second configurations; and whereinthe rock anchor further comprises an integrated tension unit, the integrated tension unit being arranged to exert a force to urge the relative axial positions of the inner and outer stems toward the second configuration.

2. The rock anchor according to claim 1, wherein the integrated tension unitincludes a spring arranged to exert the force.

3. The rock anchor according to claim 1 or claim 2, wherein the integrated tensionunit is located at a proximal end of the rock anchor.

4. The rock anchor according to any one of the preceding claims, wherein theintegrated tension unit includes a housing, the housing enclosing a biasing means for exerting the force.

5. The rock anchor according to any one of the preceding claims, wherein theinstallation mechanism includes a threaded portion at the proximal end of the inner stem and wherein a nut coupled to the threaded portion of the inner stem is operable to urge the outer stem distally with respect to the inner stem.

6. The rock anchor according to any one of the preceding claims, whereinactivation of the installation mechanism also causes the integrated tension unit to increase the force exerted.

7. The rock anchor according to claim 6, wherein the installation mechanism islockable to inhibit motions which cause a transition towards the first configuration.

8. The rock anchor according to claim 7, wherein locking the installationmechanism is achieved using a form fit arrangement.

9. The rock anchor according to any one of the preceding claims, wherein theinner stem further includes a cutter at its distal end.

10. The rock anchor according to any one of the preceding claims, wherein theouter stem has a tapered portion at its proximal end for gripping a rock mass, optionally wherein the tapered portion has a cutter or abrasive surface.

11. A tensioning unit for a rock anchor having an outer stem having one or moreflareable cutting fingers disposed at a distal end; an inner stem, the inner and outer stems being moveable relative to one another in the axial direction such that a distally directed motion of the inner stem relative to the outer stem selectively transitions towards a first configuration in which the cutting finger(s) is / are stowable and proximally directed motion of the inner stem relative to the outer stem selectively transitions towards a second configuration in which the cutting fingers are flared outwardly, the inner stem having a threaded portion at its proximal end; and wherein a nut is coupled to the threaded portion of the inner stem, operable to urge the outer stem distally with respect to the inner stem, the tensioning unit comprising:biasing means disposed between the nut and the outer stem and arranged to exert a force to urge the relative axial positions of the inner and outer stems toward the second configuration.

12. A method of tensioning a rock anchor, comprising the steps of:(a) providing a rock anchor according to any one of claims 1 to 10 installed in a bored hole;; and(b) actuating the integrated tension unit to cause the integrated tension unit to exert a force to urge the inner and outer stems into the second configuration.

13. The method of claim 12, wherein step (a) includes the steps of:(a1) providing the rock anchor in a bored hole; and(a2) actuating the installation mechanism while rotating the rock anchor to flare the cutting fingers outwardly thereby underreaming a portion of the bored hole.

14. The method of claim 13, wherein steps (a2) and (b) are performedsimultaneously.

15. The method of any one of claims 12 to 14, further comprising using a cutter atthe distal end of the inner stem to bore the bored hole prior to step (a).

16. The method of any one of claims 12 to 15, wherein the installation mechanismand the integrated tension unit are actuated by a single action.

17. The method of claim 16, wherein the single action is lockable.

18. A method of decommissioning a rock anchor installed according to the methodof any one of claims to 12 to 17, the decommissioning method comprising:(d) actuating the installation mechanism to transition the rock anchor toward the first configuration; and(e) pulling the rock anchor out of the bored hole.15

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