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(11) | EP 0 004 150 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Improvements in and relating to an embeddable anchor and to a method of embedding such anchors |
| (57) An embeddment anchor (1) comprises a tie rod (2) on which is mounted, at one end,
thereof, anchoring means (3) which may be of fluke-like form. Also mounted upon the
tie rod is a thrust member (5) which, in one embodiment, is movable along part of
the length of the tie rod (2). The anchoring means (3) are designed to provide a substantial
proportion of the resistance of the anchor (1), when embedded, to uplift forces whilst
the thrust member (5) provides a substantial proportion of the resistance of the anchor
(1) when embedded, to lateral forces. The thrust member (5) may be so formed that
it supports the tie rod (2) whilst the latter is being embedded. |
[0001] This invention relates to an embeddable anchor for use in anchoring a structure, and especially to an embeddable anchor for use in anchoring a marine platform to the sea bed. The invention also relates to a method of embedding such an anchor.
[0002] One major difficulty in devising embeddable anchors and embedding processes is that one is faced with providing such anchors and processes for several different soil types. As a result some processes and anchors, although perfectly satisfactory in themselves, are only applicable to one or a small number of selected soil types. There are several disadvantages in having a different anchor for each soil type, not the least of which is the high cost of providing extra equipment and stock to cope with different soil conditions. It is therefore considered desirable to try to develop an anchor and process which has application, with little or no variation, in all soil types.
[0003] In the case of marine embeddable anchors and embedding processes, further constraints may be placed on the installation procedure. Thus, first it may be desirable that the anchor should be capable of being embedded by surface operations only except, perhaps, disconnection of temporary lines which could be done from a diving bell or mini-submarine. Secondly, the equipment required should be presently available or at least be in the process of rapid development.
[0004] A further desirable point is the ability to provide anchors of different capacities within a fairly wide range simply by scaling some or all of the variables of the anchor configuration.
[0005] Throughout this Specification, the term "earth" should be interpreted to mean the outer layer(s) of the Earth's crust and so includes the soil on dry land and the sand or other sea bed material under the seas.
[0006] The present invention provides a method of embedding an embeddable anchor in the earth, the anchor comprising a tie rod on which is mounted a thrust member adapted to provide a substantial part of the resistance to lateral movement of the anchor when embedded comprising the steps of positioning the anchor above the surface of the earth and then driving the anchor into the earth until the thrust member is lodged therein.
[0007] The present invention also provides a method of embedding an embeddable anchor in the earth, the anchor comprising a tie rod on which is mounted, for movement along part at least of the length of the tie rod, a thrust member adapted to provide a substantial part of the resiz- tance to lateral movement of the anchor when embedded comprising the steps of placing the thrust member on the surface of the earth and driving the tie rod into the earth.
[0008] In the method referred to in the preceding paragraph, the thrust member may be driven into the earth either before, after or during the driving of the tie rod into the earth.
[0009] The present invention provides a method of embedding an embeddable anchor in the earth, the anchor comprising a thrust member, a tie rod having a container or longitudinal passage between its ends or being in the form of a hollow shaft or tube, and means for embedding the anchor in the earth, the method comprising positioning the anchor substantially vertically above the surface of the earth and driving the anchor into the earth until the thrust member is lodged in the earth, wherein binding material is disposed in the container, passage or tube prior to driving, which material is forced out of the passage or tube when the thrust member is lodged in position.
[0010] The present invention further provides a method of embedding an embeddable anchor in the earth, the anchor comprising a thrust member, a tie rod having a container or longitudinal passage between its ends or in the form of a hollow shaft or tube, and means for embedding the anchor in the earth, the anchoring means comprising a plurality of members having a closed or collapsed condition and an open or expanded condition, means being provided for holding the members in their collapsed condition, the method comprising positioning the tie rod substantially vertically above the surface of the earth, driving the anchor into the earth until the thrust member is lodged in the earth, and moving the said members from their collapsed to their expanded condition, said movement being achieved, at least in part, by forcing binding material from the container, passage or tube.
[0011] According to the invention, an embeddable anchor comprises a tie rod and, mounted upon the tie rod, a thrust member adapted to provide a substantial part of the resistance to lateral movement of the anchor when embedded.
[0012] In one embodiment of the invention the thrust member is movable along at least a part of the length of the tie rod.
[0013] The present invention further provides an embeddable anchor comprising a tie rod, a thrust member for providing a substantial part of the resistance to lateral movement of the anchor when in position, and means for anchoring the anchor in the earth, the anchoring means being secured to the tie rod at or adjacent one end thereof for providing resistance to upward movement of the anchor when in position and the thrust member being mounted on the tie rod for relative movement along the tie rod over at least part of the length of the latter.
[0014] The anchoring means may take the form of separate anchoring devices secured to the tie rod at spaced- apart points along the length of the tie rod. Such separate devices may include one at the end of the tie rod. In this way, the resistance of the anchor to uplift forces i.e. forces tending to lift the anchor from its embedded position is increased.
[0015] The separate anchoring devices may be of a form requiring movement of components of the devices to positions in which the devices develop maximum resistance to uplift forces. Such components may be actuated individually to such positions or they may be linked to a common actuator which is able to move or allow the movement of all of the components to said positions at the same time.
[0016] The present invention further provides a method of embedding the said anchor, which has a thrust member mounted on the tie rod for relative movement along part at least of the length of the tie rod, in the earth, the method comprising positioning the tie rod substantially vertically and partially lodging the thrust member in the earth, driving the anchoring means into the earth, until the thrust member is at the other end of the tie rod, and then driving the thrust member into the earth.
[0017] The present invention further provides a method of embedding the said anchor, which has a thrust member mounted on the tie rod for relative movement along at least part of the length of the tie rod, in the earth, the method comprising positioning the tie rod substantially vertically, driving the thrust member into the earth until it is partly or fully lodged in position, and driving the anchoring means into the earth until the thrust member is at the other end of the tie rod and completing the lodgement of the thrust member if necessary.
[0018] The present invention further provides an embeddable anchor comprising a thrust member, a tie rod and means for anchoring the device in the earth, the anchoring means comprising at least two members in the form of plates which are pivoted to the tie rod and movable between a first or collapsed condition in which the plates are substantially parallel and a second or expanded condition in which they extend transversely relative to the axis of the tie rod, means being provided for holding the plates in their collapsed condition.
[0019] The thrust member is of a form such that it provides a substantial part of the resistance to lateral movement of the anchor when in position. The anchoring means provides resistance to upward movement of the anchor when in position.
[0020] The present invention further provides a method of embedding the aforesaid anchor comprising the said plates, the method comprising driving the anchor into the earth until the thrust member is lodged in position, releasing the holding means, and moving the plates from their collapsed to their expanded condition.
[0021] The present invention further provides a method of embedding an embeddable anchor in the earth, the device comprising the thrust member, a tie rod and the means for anchoring the anchor in the earth, the method comprising forming a substantially vertically extending hole in the earth and inserting the anchor into the hole.
[0022] The invention further provides a method of embedding an embeddable anchor having the features of any two or more of the methods defined aforesaid.
[0023] The invention further provides an embeddable anchor having the features of any two or more of the anchors defined aforesaid.
[0024] The invention further provides a method of embedding an embeddable anchor having the features of any two or more of the anchors defined aforesaid.
[0025] An advantage of having binding material in the container, passage or tube prior to driving is that it is not necessary to provide a separate line for filling the container, passage or tube after installation.
[0026] An advantage of using binding material to release the holding means and move the said members from their collapsed to their expanded condition is that in at least most applications binding material is required, in any event, to hold the anchoring means in position.
[0027] An advantage of having a thrust member which is relatively movable along part at least of the length of tie rod is that when the thrust member is partially lodge- in the earth it provides a guide for the tie rod as the latter is driven into the earth.
[0028] All the anchors constructed in accordance with the invention may comprise, and all the methods according to the invention may use, an anchor comprising a tie rod having a container or a longitudinal passage between its ends or in the form of a hollow shaft or tube. The tie rod may be in the form of a solid rod. In such a case, the rod may have one or more external longitudinal grooves along its length through which a mechanism for releasing the movable members comprising the anchoring means.
[0029] All the embeddable anchors constructed in accordance with the invention may comprise, and all the methods according to the invention may use, an anchor with anchoring means comprising a plurality of members having a closed or collapsed condition and an open or expanded condition and means for holding the members in their collapsed condition. The means may comprise one or more explosive bolts which hold the members in the closed or collapsed state until movement to the open position is required. The explosive charge or charges is or are then set off and then either the members are forced to their open positions by the explosion or are released to be moved to those open positions by some other mechanism. The explosive material in the bolt or bolts may be set off by a triggering device mechanically operated by a suitable mechanism operated by remote control or by a control signal, for example a radio signal or an ultra sonic signal. Alternatively, the members may be so shaped that, after they have been released, further embedding movement of the anchor causes the members to move into their open positions.
[0030] All the embeddable anchors constructed in accordance with the invention, except that device having a thrust member mounted on the tie rod for relative movement along part at least of the length thereof, may comprise, and all the methods according to the invention, except that using the relatively movable thrust member, may use an anchoring device comprising, a thrust member which is secured to that end of the tie rod remote from the anchoring means.
[0031] In all the methods according to the invention binding material may be forced from the container, passage or tube to release the holding means. Alternatively, the holding means can be released by an explosive charge or by a cutting operation. The explosive charge may be set off by a signal transmitted from a position remote from the anchor. The signal may be a radio signal or a signal at an ultra-sonic frequency.
[0032] In all the methods according to the invention binding material may be used to effect the total movement of the said members. Alternatively, the holding means may be released before driving is complete, the members being partially moved towards their expanded condition by completing the driving operation and then being moved into their expanded condition by the binding material.
[0033] Holding means may be provided for holding the members in the open or expanded condition. The holding means may be self-locking when the members are in the condition just mentioned.
[0034] In all the methods according to the invention, reinforcing material, for example in the form of a helical winding of reinforcement, may be arranged in the container, passage or tube and forced out by the binding material. The reinforcement serves to reinforce the bulb formed around the anchoring means.
[0035] In all the methods according to the invention except where the binding material is used to provide at least part of the movement of the said members from their collapsed to their expanded condition the method may further comprise releasing the holding means, for example by an explosive charge or by a cutting device, prior to completion of the driving operation, and moving the said members from their collapsed condition by completion of the driving operation. This method is of particular advantage when the members are constituted by the said plates.
[0036] In all the methods according to the invention an explosive charge may be used to effect partial movement of the said members from their collapsed to their expanded condition.
[0037] In all the methods according to the invention except where the binding material and/or driving is usedto move said members, an explosive charge may be used to effect the total movement of the said members.
[0038] In all the methods according to the invention, except that method where the tie rod is prefilled with binding material, binding material may be passed down the hollow shaft or passage after the anchoring device has been installed.
[0039] In all the methods according to the invention including the step of embedding the anchor into the earth, that step can be replaced or supplemented by forming a substantially vertically extending hole in the earth and inserting the anchor into the hole. If the hole is made deep enough, then no driving will be required but if the length of the hole is less than the length of the tie rod, then driving may be required to complete installation of the anchoring device after it has been inserted into the hole. Preforming a hole in this way may be necessary, for example where the anchoring device is to be installed in rocky terrain. If necessary the base of the hole may be under-reamed.
[0040] The holding means may comprise locking bolts which can be sheared by cutting when required to be released. Such locking bolts may be used if the said members are in the form of flukes or plates (which may be pivoted to the tie rod).
[0041] Alternatively, the said members may together define a hollow, for example a tubular chamber, the said members being frangibly connected together, for example by lines of weakening. In this case, of course, the holding means is constituted by the frangible connections which may be broken by the pressure of the binding material or by explosion of an explosive material in the hollow chamber.
[0042] Whenever any of the methods according to the invention is used for marine application, it is preferred that the embedding operation is accomplished by an underwater hammer. This allows the anchor to be embedded almost entirely by surface operations.
[0043] Further, for marine application, it is preferable if anchor cable(s) are attached to the device before driving so that the device would be ready for service as soon as the anchoring means is properly installed. The cable(s) may be attached by connections including universal joints or other means which permit a required degree of movement of the cable. However, for certain applications, the cable may be connected after installation of the anchor.
[0044] The binding material may be mortar, concrete and/or an epoxy resin. When the binding materLal is stored in the passage or tube it may include an agent for retarding the rate of setting of the material.
[0045] In all the anchors and methods according to the invention one or more further anchoring means may be arranged along the length of the tie rod.
[0046] It is preferred if the thrust member is of generally cylindrical form and may be open-ended. Other forms may be used, for example frusto-conical or conical, but a cylindrical thrust member provides better displace- ment/load characteristics for the device. To facilitate manufacture, a thrust member of polygonal, for example hexagonal, form when seen in plan and also open-ended and constructed from plates may represent a practical approximation to a cylinder. The shape of the thrust member in conjunction with the shape of other components of the embeddable anchor may also be determined by the expected direction of application of the load to be supported by the anchor when embedded. The interior of the thrust member may be divided up into cells by dividing walls which may extend radially from the centre line of the thrust member. The dividing walls also act as stiffeners.
[0047] Advantageously to assist lodging of the thrust member in the earth it is provided with a cutting edge or edges.
[0048] It is of particular advantage if the thrust member is of open lattice or cellular construction. Such a construction gives a better rigidity/weight ratio.
[0049] The lattice or cells are so arranged that earth passes through during embeddment which is thus made easier. The lattice or cell size is preferably such that earth becomes packed inside the thrust member and so tends to become retained therein.
[0050] Preferably, if the thrust member is mounted on the tie rod for relative movement along part at least of the length of the tie rod, the thrust member is releasably secured to the tie rod near to the anchoring means. The thrust member may frangibly be connected to the tie rod, the connection being broken by an explosive charge or may be connected by other releasable means for example explosive bolts.
[0051] A method using such a thrust member would then include the further step of releasing the thrust member from the tie rod. The thrust member may be released when it has been partially lodged in the earth. In this case it is preferred if the thrust member is frangibly connected to the tie rod so that it can be released from the tie rod by initial driving of the anchoring means which breaks the frangible connection. Alternatively the thrust member may be completely lodged in the earth by driving the tie rod and anchoring means and the thrust member then released from the tie rod to allow completion of driving of the tie rod and anchoring means.
[0052] If desired or found to be necessary, the thrust member may again be connected to the tie rod after the anchor has been fully embedded in the earth. Connection may be achieved by the use of wedging surfaces or by locking means either self-actuating or requiring actuation from a remote point, or by the use of explosive charges which deform the thrust member or a part thereof to lock the member to the tie rod.
[0053] When the anchoring means comprises two plates they may be held together simply by bolts which may be released by explosion or by cutting. The plates can then be held in their expanded condition by forcing binding material into the space below the plates. Alternatively, and with advantage, however, a linkage is provided which so connects the plates together that they are also held in their expanded condition by the linkage. The linkage may be self-locking to hold the plates in their expanded condition.
[0054] The present invention further provides a support structure for supporting the anchor during driving, the structure comprising a tower for supporting and/or guiding the tie rod, the tower being secured to a base for positioning the tower on the earth.
[0055] Such an installation is particularly useful for marine application, since when the base is properly positioned on the sea-bed accurate driving can be accomplished which is not affected by underwater currents, etc. and driving can be started more quickly than with normal pilinq and continue in rough weather since accurate station keeping of the support vessel is not necessary.
[0056] Although the tower can have external guides it is preferred if the tower is in the form of a hollow shaft for supporting and/or guiding the tie rod.
[0057] The support structure may be employed with any of the anchoring devices constructed in accordance with the invention and/or in any of the processes according to the invention.
[0058] The support structure is particularly useful, however, with an anchor, or in a method which employs an anchor, having a thrust member which is mounted in the tie rod for relative movement along part at least of the length of the tie rod, the thrust member being releasably secured to the tie rod near to the anchoring means. In this case the anchor can be arranged on the said structure with the tie rod supported by tower and with the thrust member disposed beneath the base. When the structure is lowered on to the earth its weight (together with the weight of the anchor) can be used to force the thrust member into the earth until the base itself is supported on the earth. Proper positioning of the base on the earth may be assisted by driving the structure. The anchor can then be embedded by driving it into the earth, the thrust member being partially or completely lodged in the earth before it is released from the tie rod.
[0059] Preferably, the support structure is designed for use with an underwater hammer, guides being provided on the tower for the hammer.
[0060] Advantageously, to assist recovery of the support structure, buoyancy chambers may be incorporated, preferably attached to or forming part of, the base, which can be filled with water for lowering and driving and into which air may be pumped, after driving has been completed, to allow the support to be lifted from the sea bed.
[0061] Anchors and an anchor support structure constructed, and embedding methods performed, in accordance with the invention, will now be described, by way of example only, with reference to accompanying drawings, of which:-
Fig. 1 is a side view of a first embodiment,
Fig. 2 is a plan view of a part of the first embodiment,
Fig. 3 is a side view of another part of the first embodiment,
Fig. 4 is a front elevation of the part shown in Fig. 3,
Figs. 5 and 6 are plan and front elevation respectively of further part of the embodiment of Fig. 1,
Fig. 7 is an elevation partly in section of the parts of Figs. 2-6 in assembled form,
Fig. 8 is a section on the line VIII-VIII of Fig. 7,
Fig. 9 is a view in the direction of arrows IX in Fig. 7,
Figs. 10 and 11 are schematic illustrations of different stages of an embedding process,
Figs. 12 and 13 are, respectively, side elevation and plan view of a piling rig with an anchor in position prior to an embedding operation, and,
Fig. 14 is a side view of a second embodiment.
[0062] Referring first to Figs. 1-9 of the accompanying drawings, a first embodiment of the invention comprises an embeddable anchor indicated generally by reference 1. The anchor has a tie rod 2 in the form of a hollow shaft or tube to the lower end of which is secured anchoring means 3 shown in Fig. 1 in a closed position. Movable relatively to the tie rod 2 between the anchoring means 3 and a flange 4 secured at the upper end of the tie rod is a thrust member 5.
[0063] The thrust member 5 comprises a lower part 6 0f cylindrical form with a series of internal ribs 7 extending from a central hollow tube 8 through which the tie rod 2 extends as shown in Fig. 1. The tube 8 extends only partly through the cylinder, the lower edges of the ribs 7 thus being angled as shown. Alternate ones of the ribs 7 extend upwardly from the lower part 6 and support the upper part of the tube 8 to whose upper end is secured a flanged collar 9. The upper ends of the other ribs 7 are flush with the upper edge of the part 6.
[0064] Thus, the ribs 7 divide the interior of the thrust member into a series of cells and also provide a degree of stiffness and rigidity to the cylindrical structure.
[0065] The lower edges of the ribs 7 and that of the lower part 6 may be formed as cutting edges cr be fitted with such edges to facilitate movement of the member into the earth during an embedding operation as will be described below.
[0066] The anchoring means 3 comprise two anchor flukes 10. 11 (Fig. 7) with spade-like, flat surfaces 12, 13, each with integral ribs 14 located within a recess formed by the flat surface and two further parallel ribs 15 joined at their lower ends by a transverse wall 16 whose lower surface is bevelled and wedge-shaped as can be seen from Figs. 3 and 4. As can be seen from Figs. 3 and 4 the ribs 14 and 15 extend for a short distance beyond the upper edges of the surfaces 12, 13.
[0067] There are three ribs 14 in side-by-side, spaced parallel relationship, the two outer ribs being formed with gear teeth 17 on an arcuate upper surface of the ribs. At their lower ends, the ribs 14 are joined by a spindle 18.
[0068] The lower edge 19 of each surface 12, 13 is pointed and bevelled as indicated at 20, the bevel in the centre of the lower edge being extended, at 21, to meet the lower edge of the transverse member 16.
[0069] The two flukes are pivotally attached to a hinge block 22 (Figs. 5 and 6) by means of bolts 23, 24 respectively which pass through holes 25, 26 respectively in the upper parts of the ribs 14 and 15 and also through corresponding holes 27, 28 in each of four mounting arms 29 extending from the base 30 of the block 22. The hinge block 22 is fixed to the lower end of the tie rod 2.
[0070] Extending downwardly from the base 30 of the tie block 22 and centrally between the flukes 10, 11 is a lock bar 31 to whose lower end plates 31a are welded to support a transverse pin 32 on which are pivotally mounted the lower ends of links 33 whose other ends are pivotally attached to the spindles 18.
[0071] The lock bar 31 passes through an aperture 34 in the base 30 of the hinge block 22 and through a pair of wedges 35 movable with the lock bar 31 with respect to a second pair of co-operating wedges 36 secured to the base 30.
[0072] A spine assembly comprising parallel plates 37 joined at their upper ends to the outer arms of the arms 29 of the hinge block and at their lower ends to a transverse plate 38, the lower parts of the plates 37 being enlarged to facilitate attachment of the plate 38.
[0073] The transverse members 16 of the flukes are apertured at 39 to receive an explosive bolt (not shown) of conventional form designed to resist a predetermined tensile load and to break clearly at a shear notch located on the stem of the bolt.
[0074] The tie rod 2 may be of Grade 50 steel fully welded at its lower end to the base 30 of the anchor bloc÷< itself a mild steel annealed casting. The thrust member and its ribs 7 may be fabricated from mild steel plate. The flukes 10, 11 may also be mild steel annealed castings as is the hinge block 22. The links 33 may be of high tensile steel as may be the anchor lock.
[0075] A ring bolt or other suitable securing means (not shown) is attached to the upper end of the tie rod 2 or to the thrust member to enable a mooring cable or chain to be secured to the anchor.
[0076] As has been stated above, the thrust member 5 is movable relatively to the tie rod 2 and can be located in a position adjacent the flukes so that it can act as a template which guides the tie rod during the initial stages of embedding the anchor in the earth. If desired, the thrust member may be temporarily fixed to the tie rod in the position just described, the fixing being broken during the internal movement of the tie rod.
[0077] Fig. 10 shows in diagrammatic form only, the anchor in position on the sea bed prior to the commencement of an embedding operation.
[0078] Before embedding the device in the sea bed, the anchor with the thrust member 5 in the position shown in Fig. 10, is hoisted over the side of a barge 39. The upper end of the tie rod 2 is connected to a detachable, extension driving shaft 41 of an underwater hammer 42. The whole system is then lowered to the sea bed.
[0079] The weight of the device forces the thrust member 5 into the top layer(s) of the sea bed material. To facilitate entry of the thrust member 5 it may have a lower cutting edge 43. The device is now in the position shown in Fig. 11. The hammer 42 is now used to drive the tie rod 2 into the earth, the thrust member 5 serving to guide the tie rod 2 during its downward movement. If the thrust member 5 is attached to the tie rod 2 initial driving of the latter shears this connection so that the tie rod 2 is then free to pass through the thrust member 5.
[0080] Driving continues until the flange 4 on the tie rod 2 engages the thrust member 5. Both the tie rod 2 and the thrust member 5 are then driven into their final position below the sea bed. The thrust member 5 may be driven below the surface of the sea bed but it could be left flush or slightly proud thereof depending on the consistency of the sea bed material. The rigid mounting of the thrust member 5 in the sea bed is facilitated by the open cellular form of the member.
[0081] The explosive bolt holding the flukes 10, 11 together is fired just before the anchor reaches its final position and the further movement of the anchor into that position opens the flukes. The opening movement of one fluke is synchronised with that other because the gear teeth 17 on the ribs 14 move into meshing engagement and thereafter the flukes move in unison. Once in their fully opened positions, the flukes are locked therein by the anchor lock mentioned above, the links 33 being in a straight line configuration.
[0082] It will be understood that, if desired, the thru±. member 5 could be driven at least partly into the sea bed before the driving of the tie rod commences. It is possible to drive the thrust member into its final lodgement position in the sea bed before driving of the tie rod commences. This method may be adopted in cases in which the apparatus for embedding the anchor is not sufficiently powerful to drive both thrust member and tie rod at the same time.
[0083] It will be appreciated that there may be circumstances in which the anchor is required to resist loads which are applied to the anchor from one side only i.e. loads which are substantially lateral and do not contain any substantial uplift load i.e. a load applied in such a direction that there is an uplift force on the anchor tending to lift it from the ocean bed. In such circumstances, it is possible to dispense with the anchoring means so that the anchor comprises, basically, merely a rod on which the thrust member is mounted.
[0084] The form of the thrust member will be determined by the factors referred to above, and for example, a thrust member of the form of the member 5 shown in Fig. 1 may be employed.
[0085] The thrust member may be permanently fixed to the tie rod or it may be movable along at least a part of the length of the tie rod. As described above, the thrust member may be detachably fixed to the tie rod so as to be movable therewith when required and, once the connection between the thrust member and the tie rod is broken, relative movement between these two components can then take place.
[0086] Thus, in its basic form, the anchor may take a form comprising the tie rod 2 (Fig. 1) with a thrust member of the form shown in Figure 1, the lower end of the tie rod being pointed as indicated by the dotted line 52 to facilitate movement of the tie rod into the earth, the anchoring means 3 being absent.
[0087] It is not essential that the thrust member be movable along the tie rod. The member may be secured permanently at some point along the length of the tie rod, for example at the upper end adjacent the flange 4.
[0088] Choice of the dimensions of the anchor and of its component parts, for example, the thrust member, and the depth to which the components are buried are embedded will depend upon the nature of the earth in which the anchor is to be embedded, the magnitude of the load to be applied to the anchor and its direction of application.
[0089] The shape of the thrust member in conjunction with the shape of the other components of the embeddable anchor may also be determined by the expected direction of application of the load. A frusto-conical or cylindrical thrust member has the advantage that it will withstand load from any direction and over a wide range of inclination. To facilitate manufacture, a thrust member of polygonal, for example hexagonal, form when seen in plan and constructed from plates may represent a practical approximation to a cylinder. The thrust member may be made in two or more parts and subsequently assembled round the tie rod. Where the load is from a given direction only and with a particular inclination a simpler form of thrust member, for example a plate or sheet form, may be adopted.
[0090] In addition, where a number of embedded anchors are used to anchor a structure, the size and shape of the components of each such anchor may also be determined, at least in part, by the number of such anchors and the disposition of each anchor relative to the structure. In particular, the shape of the thrust member may be determined by the factors just mentioned.
[0091] An embeddable anchor embodying the invention comprises a tie rod whose length is 70 feet and whose diameter is 3 feet which has, at one end, a cylindrical thrust member of 25 feet diameter and 12 feet depth, and, at the other end, and anchoring means about 10 feet long and providing flukes having a horizontally-projected area of 80 sq. ft..
[0092] Such an anchor buried vertically in clay to a depth such that the upper surface of the thrust member is about 25 feet below the surface of the sea bed is calculated to have an ultimate load capacity in the upward direction of 2003 tonf approximately in the short term and about 1595 tonf in the long term, and in the horizontal direction a long term capacity of about 960 tonf. In the case for load applied intermittently, cyclically or repeatedly, the ultimate load capacity is 1598 tonf approximately.
[0093] In sand, the corresponding values are, in the upward direction, about 3737 tonf for both short and lonq term, about 1467 tonf in the horizontal direction, and about 1967 tonf for the cyclic load.
[0094] If the anchor is buried vertically in stiffer clay to a depth such that the upper surface of the thrust member is buried about 10 feet below the surface of the sea bed is calculated to have an ultimate load capacity in the upward direction of 2830 tonf approximately in the short term and 2019 approximately tonf in the long term, ard, in the horizontal direction a long term capacity of 1642 tonf approximately. In the case of a load applied intermittently, cyclically or repeatedly, the ultimate load capaci.ty is about 2014 tonf.
[0095] In sand, the corresponding values are about 2795 tonf for both long and short term, about 800
the horizontal direction, and about 1381 for the cyclic load.
[0096] It should be borne in mind that the above example is merely one embodiment of the embeddable anchor in specified soil conditions and that other different configurations and relative sizes may be required in othe= soil conditions.
[0097] The major components of the anchor, i.e. the thrust member, tie rod and flukes may be fabricated separately in a range of sizes from which can be assembled an anchor capable of dealing with a specified loading or range of loadings in a specified direction or range of directions and in a specified soil structure.
[0098] Once in position, the anchoring means, i.e. the flukes contribute substantially to the resistance offered by the anchor to upward movement whilst the thrust member provides a substantial part of the resistance offered by the anchor to lateral movement. In addition, however, the composite mass of the thrust member together with its frictional resistance to movement also contribute to the resistance offered by the anchor to upward movement. If additional resistance to upward movement is required, the anchor may have one or more additional anchoring means which may be of a construction similar to that of the means 3 described above. Such additional anchoring means will be secured to the tie rod at a point spaced from the lower end of the tie rod.
[0099] Where such additional anchoring means are provided, it is normally preferable that movement to the open position thereof is effected at the same time.
[0100] It will be appreciated that other embedding techniques may be adopted than the one described above with reference to Figs. 10 and 11.
[0101] For example, the step of embedding the anchor into the earth may be replaced or supplemented by forming a substantially vertical hole in the earth and locating the anchor in the hole. The depth of the hole may be determined by the nature of the terrain through which it is formed. For example, a hole may be pre-formed through a rocky layer overlying sub-soil into which the anchor can be driven. In this case, the depth of the hole is less than the overall length of the anchor. If necessary, the base of the hole may be under-reamed to allow outward movement of the flukes.
[0102] The anchor may also be embedded at a desired location by means of a piling rig. If the location is on the sea bed, the rig is conveyed to the location by a barge or ship and is then lowered over the side on to the sea bed. Alternatively, the rig may be launched from a substantially horizontal position on a deck of the barge or ship into a vertical position and then lowered to the sea bed.
[0103] Yet again, the rig may be accommodated in a special hold in a ship adapted to carry out anchor embedding operations. When required, the rig is lowered to the sea bed through an access opening in the hull of the ship.
[0104] Figs. 12 and 13 are a side elevation and plan respectively of one form that the piling rig might take, the rig and associated components being shown in diagrammatic form only.
[0105] The rig comprises an open lattice tower 44 supported by three legs 45 each pivotally mounted upon the tower 44. The lower ends of the legs 45 are fitted with shoes 46 which may include levelling devices to locate the tower 44 in a vertical position.
[0106] Within the lattice tower is located the driving mechanism for a hammer 47 to which reciprocating movement is imparted via a cable 48 from the driving mechanism. A lifting cable 49 secured to the upper end of the tower 44 enables the rig to be lowered into a desired location.
[0107] The hammer 47 is guided by guide surfaces on the tower 44 and applies blows to the anchor 1 via a driving follower 50 that allows the anchor to be embedded below the surface if required. Desirably, the follower extends upwardly within the hammer because this improves the stability of the hammer action. The upper end of the follower is fitted with a protective helmet and interposed between the helmet and the end of the follower is a timber "cushion". The cushion is found to reduce somewhat the peak value of the hammer impact but it also increases the duration of the impact and this gives quicker driving. The cushion also reduces distortion of the upper end of the follower.
[0108] The follower is not essential and hammer blows could be imparted to the shaft directly or through the protective helmet and timber cushion just described.
[0109] The piling rig is used in the conventional manner having been conveyed to the desired location and placed in position at the anchor site. When the anchor has been embedded, the rig is withdrawn for use in another embedding operation.
[0110] The rig may, if desired, incorporate buoyancy tanks which enable the rig to be floated to a desired location at sea. When the location is reached, the tanks are flooded and allow the rig to sink to the sea bed. The rig may be floated in a horizontal position and, at the location, the tanks are selectively flooded to bring the rig into a vertical orientation either before or during the sinking operation. When the anchor has been embedded, the tanks are filled with air to facilitate return of the rig to the surface.
[0111] The anchoring means may take forms other than the flukes described above. For example, a hollow bulb may be attached to the lower end of the tie rod, the interior of the bulb communicating with the interior of the tie rod 2. The bulb is formed with lines of weakness defining a series of two or more prongs which may be of fluke-like form.
[0112] The bulb is shaped to facilitate its movement into the earth during an embedding operation. When a required depth of embeddment is reached, the bulb is fractured along the lines of weakness and the prongs splayed outwardly into the adjoining soil.
[0113] The fracturing and splaying out may be accomplished by an explosive charge inside the bulb, or by pumping a fluent substance down the tie rod into the bulb. The substance may be liquid concrete, liquid mortar or an epoxy resin.
[0114] The fluent substance may be contained within the bulb and/or tie rod and pressurised to effect fracturing of the bulb and release of the substance which then sets to form a solid mass round the prongs and thus an effective anchoring means. Alternatively, the substance may be pumped down into bulb via a supply line connected either directly to the bulb or to the tie rod.
[0115] It is possible to effect fracturing and splaying-out of the prongs by means of an explosive and then pump the fluent substance into the fractured bulb to for:, the solid mass referred to in the preceding paragraph.
[0116] Splaying-out of the prongs could be effected in part by an explosive charge and in part by movement of fluent substance into the bulb. Alternatively, an explosive charge could be used to fracture the lines of weakness in the bulb without causing any substantial movement of the resultant prongs, that movement being effected by the fluent substance.
[0117] Fig. 14 shows schematically an anchor after the anchor has been embedded and the bulb fractured to produce splayed-out prongs 50 and fluent substance has been pumped into the bulb to form a mass 51 round the prongs.
[0118] Further reinforcement, in the form for example of a helical winding of flexible wire or rod, could be arranged in the tie rod and forced out with the fluent substance.
[0119] The fluent material may be an aggregate which is forced out to fracture the bulb and so form the prongs, grout is then pumped down into the voids in the aggregate to form a solid mass round and within the prongs.
[0120] If desired, a fluent binding substance could be used in conjunction with the fluke-like anchoring means of the anchor described above with reference to Figs. 1-9. At the conclusion of the embedding operation and after the flukes have been moved outwardly, the substance is pumped into the space between the flukes and, on setting, forms a solid wedge therebetween and holds the flukes in their extended positions.
1. An embeddable anchor comprising a tie rod, and, mounted upon the tie rod, a thrust
member adapted to provide a substantial part of the resistance of the anchor to lateral
movement when embedded.
2. An anchor as claimed in claim 1 in which the thrust member is movable along at
least part of the length of the tie rod.
3. An anchor as claimed in claim 2 in which a releasable device is provided for holding
the thrust member in a predetermined position on the tie rod.
4. An anchor as claimed in claim 1, 2 or 3 in which the lower end of the tie rod is
formed to facilitate embedding the anchor in the earth.
5. A method of embedding an anchor as claimed in claim 1 comprising the steps of positioning
the anchor above the surface of the earth and then driving the anchor into the earth
until the thrust member is lodged therein.
6. A method of embedding an anchor as claimed in claim 2 comprising the steps of partially
or completely lodging the thrust member in the earth and then driving the tie rod
into the earth.
7. An embeddable anchor comprising a tie rod, a thrust member for providing a substantial
part of the resistance to lateral movement of the anchor when embedded, and anchoring
means for providing a substantial part of the resistance to upward movement of the
anchor when embedded, the anchoring means being secured to the tie rod at or adjacent
one end thereof and the thrust member being mounted upon the tie rod for relative
movement along at least a part of the length of the tie rod.
8. An anchor as claimed in claim 7 in which the anchoring means comprise at least
two members movable between a first position in which the members lie in a closed
formation and a second position in which the members lie in an open formation to provide
the substantial part of the resistance to upward movement of the anchor when embedded.
9. An anchor as claimed in claim 8 in which the members are of fluke-like form and
are pivotally mounted.
10. An anchor as claimed in claim 9 in which the members are pivotally mounted upon
the tie rod.
11. An anchor as claimed in claim 9 in which the members are pivotally mounted upon
a component attached to the tie rod.
12. An anchor as claimed in claim 11 in which the component is attached to the said
one end of the tie rod.
13. An anchor as claimed in any one of claims 8-12 in which the members are interconnected
in a manner such that they move in synchronism.
14. An anchor as claimed in any one of claims 9-13 in which releasable holding means
are provided for holding the members in the first position.
15. An anchor as claimed in claim 14 in which the releasable holding means comprises
one or more bolts.
16. An anchor as claimed in claim 15 in which the bolt or each of some of the bolts
is an explosive bolt and in which means are provided for firing the explosive charge
or charges to release the members for movement to the second position.
17. An anchor as claimed in claim 15 in which the bolt or each of some of the bolts
is a bolt so positioned as to be exposed to a load during embeddment of the anchor
and adapted to release the members for movement to the second position when the load
exceeds a predetermined value.
18. An anchor as claimed in any one of claims 8-17 in which holding means are provided
for holding the members in the second position.
19. An anchor as claimed in claim 18 in which the holding means self lock when the
members are in the second position.
20. An anchor as claimed in any one of claims 8-19 and which further includes an arrangement
for moving the members from the first to the second position.
21. An anchor as claimed in claim 8 in which the members form, in the first position,
part at least of the wall of a container, means being provided for separating the
members partially from one another or from the wall.
22. An anchor as claimed in claim 21 in which each member is defined by a line of
weakness in the wall, the means for separating operating to separate the members along
the lines of weakness.
23. An anchor as claimed in claim 21 or 22 in which the tie rod is a hollow shaft
and the container is hollow, the shaft being in communication with the interior of
the container.
24. An anchor as claimed in claim 21, 22 or 23 in which the container is adapted to
contain an explosive charge positioned to effect separation of the members.
25. An anchor as claimed in claim 21, 22 or 23 in which the container is adapted to
contain an explosive charge positioned to effect separation of the members and movement
thereof to the second position.
26. An anchor as claimed in any one of the preceding claims in which a releasable
device is provided for holding the thrust member in a predetermined position on the
tie rod.
27. An anchor as claimed in claim 26 in which the thrust member is releasably held
in a position adjacent the anchoring means.
28. An anchor as claimed in claim 26 or 27 in which the releasable device is such
that it is capable of re-locking the thrust member to the tie rod after movement of
the thrust member from the predetermined position.
29. An anchor as claimed in claim 26 or 27 in which a locking device is provided for
locking the thrust memberto the tie rod after movement of the thrust member from the
predetermined position.
30. An anchor as claimed in any one of the preceding claims in which the thrust member
is of plate-like form.
31. An anchor as claimed in any one of claims 7-29 in which the thrust member is of
cylindrical form.
32. An anchor as claimed in claim 31 in which the cylinder has a cross-section transverse
to its length that is polygonal.
33. An anchor as claimed in any one of claims 7-29 in which the.thrust member is of
tubular form.
34. An anchor as claimed in claim 33 in which the tube has a cross-section transverse
to its length that is polygonal.
35. An anchor as claimed in any one of claims 31-34 in which the thrust member is
open at both ends.
36. An anchor as claimed in any one of claims 31-34 in which the thrust member has
a plurality of internal walls that divide the interior of the thrust member into a
plurality of cells.
37. An anchor as claimed in claim 35 in which the thrust member has a plurality of
internal walls that divide the interior of the thrust member into a plurality of open-ended
cells.
38. An anchor as claimed in claim 33 or 34 in which the thrust member has a central
tubular member through which the tie rod passes and an outer member of tubular form
to which the central tube is secured.
39. An anchor as claimed in claim 38 in which the outer member is secured to the central
tube by a series of ribs extending radially from the tube.
40. An anchor as claimed in claim 39 in which the tube projects from one end of the
outer member and in which some at least of the ribs extend along the length of the
projecting part of the tube.
41. An anchor as claimed in any one of the preceding claims in which the thrust member
has or is formed with a cutting edge to facilitate movement of the thrust member into
the earth during an embedding operation.
42. A method of embedding an anchor as claimed in claim 7 comprising the steps of
securing the thrust member to the tie rod at a position adjacent the anchoring means,
and driving the tie rod relatively to the thrust member into the earth.
43. A method as claimed in claim 42 which also includes the step of driving the thrust
member into the earth after the tie rod has been driven into the earth.
44. A method of embedding an anchor as claimed in claim 7 comprising the steps of
partially or completely lodging the thrust member in the earth and then driving the
tie member relatively to the thrust member into the earth.
45. A method of embedding an anchor as claimed in claim 14 including the steps of
driving the anchor into the earth, releasing the said releasable holding means when
the anchor is at a predetermined depth and then continuing to drive the anchor into
the earth to move the members to the second position.
46. A method of embedding an anchor as claimed in claim 16 including the steps of
driving the anchor into the earth to a predetermined depth and then firing the explosive
charge or charges to release the members for movement and then continuing to drive
the anchor into the earth to move the members to the second position.
47. A method as claimed in claim 42 or 43 which includes the further step of moving
the members from the first to the second position.
45. A method as claimed in claim 47 which includes the further step of locking the
members in said second position after movement thereof into that position.
49. A method of embedding an anchor as claimed in claim 21 which includes the steps
of embedding the anchor in the earth and then effecting separation of the members.
50. A method as claimed in claim 49 for embedding an anchor as claimed in claim 21
in which separation of the members is effected by forcing a fluent substance into
the container.
51. A method as claimed in claim 50 which includes the step of forcing a fluent substance
into the container to effect separation of the members and their movement to the second
position.
52. A method as claimed in claim 51 in which the fluent substance is one capable of
retaining the members in the second position.
53. A method as claimed in claim 49 in which separation of the members is effected
by firing an explosive charge.
54. A method as claimed in claim 49 in which separation of the members and their movement
to the second position is effected by firing an explosive charge.
55. A method as claimed in claim 53 in which movement of the members to the second
position is effected by forcing a fluent substance between the members.
56. A method as claimed in claim 55 in which the fluent substance is one capable of
retaining the members in the second position.
57. A method as claimed in claim 50 for embedding an anchor as claimed in claim 23
comprising the steps of loading the hollow shaft with a fluent substance prior to
embedding the anchor and then, when the anchor is embedded, forcing said substance
from the shaft into the container to effect separation of the members.
58. A method as claimed in claim 50 for embedding an anchor as claimed in claim 25
when appended to claim 23 including the steps of loading the hollow shaft with a fluent
material prior to embedding the anchor, and then, after the anchor is embedded, firing
the explosive charge to separate the members and forcing the fluent material from
the shaft to move the members to the second position.
59. An embeddable anchor substantially as described herein with reference to and as
illustrated by Figs. 1-9 of the accompanying drawings.
60. An embeddable anchor substantially as described herein with reference to and as
illustrated by Fig. 14 of the accompanying drawings.