GB2100314A

GB2100314A - Recoverable ground anchor having variable resistance to extraction

Info

Publication number: GB2100314A
Application number: GB8113462A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-05-01
Filing date: 1981-05-01
Publication date: 1982-12-22
Also published as: GB2100314B

Abstract

This has rigid anchoring bar(s) or fluke(s) 5 attached at one end by a hinge pin 6 to a rigid plate 1 having an earth-penetrating head 2 and a slot 3 aligned in its penetrative direction. Hinge pin 6 slides in slot 3. One edge of each fluke is a convex curve whose penetrating end 8 slides over shoulder 9 on the penetrating head, and whose following end terminates in a notch 13 engageable with the shoulder. The flukes are extended and retracted by lockable rod 15 attached to pin 6, rod 15 sliding in shaft 14. The flukes may be attached to flexible plates to increase resistance to extraction. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a method of and apparatus for anchoring This invention relates to improvements in methods of and apparatus for anchoring and is particularly concerned with providing an anchor in earth or ground. Such anchors are commonly referred to as earth anchors and are used in many and varied applications. Examples of the uses to which the present invention may be put include the securing of stay-ropes, or guys supporting masts or pylons or telegraph poies to secure earth retaining walls of inflateable structures or in permanent anchoring installations below the beds of rivers or seas.

Many method of anchoring at present in use involve earth-boring equipments for heavy drilling or screwing operations or for the excavation of holes in the ground and the burying of concrete blocks or metal plates to which the load to be anchored may be attached. All such anchors are expensive in labour and materials and equipment and are time-consuming to install. Moreover many such methods do not include an ability to retract the earth-pressure resisting element of elements of the mechanism, as and when required, after the installation of the anchoring mechanism into its operating attitude within a ground mass, thereby preventing a subsequent recovery of the anchor as, for example, on the completion of the purpose for which it was installed, or for re-use elsewhere.

It is an object of the present invention to provide an improved method of and apparatus for providing an anchor in earth or ground whereby the principle of movement of earth-pressure resisting surfaces or plates, along pathways of minimum resistance to movement of the said surfaces or plates within the otherwise undisturbed earth mass may, with advantage be used to provide and locate an earth-pressure resisting surface or plate within an earth mass in a position or attitude such that the said surface or plate will maximise its resistance to displacement or extraction from the earth mass by an extractive force acting upon the surface or plate after its installation into its operating position or attitude within the earth mass and means whereby the said surface or plate or a plurality thereof may be connected to the extractive force applied at or above the surface level of the ground mass.

It is a further object of the present invention to provide an improved method of and apparatus for providing an anchor in earth or ground which shall be easily recoverable as and when required from the earth or ground mass after the purpose for which the said anchor was installed has been completed the recovered anchor being thereafter available for a further anchoring use.

It is a further object of the present invention to provide an improved anchoring device which shall, as and when required, be retractable and recoverable from an earth mass in which it has been installed for further use and which shall be economic to manufacture and simple to install and robust in use.

It is a further object of the present invention to provide an improved anchoring device whose holding power or resistance to extraction within an earth mass may be varied or adjusted according to the known or predicted resistive properties and characteristics of the said earth mass.

It will be evident that a minimum resistance to movement of an earth-resisting surface or plate along a pathway within an otherwise undisturbed earth mass will obtain either when the said pathway is rectilinear or comprises an arc of a circle the requirement of minimum resistance to movement being, in either case, that all points on the surface or plate which lie transverse to the axis of movement of the surface or plate shall pass only along the same pathway.

The anchoring apparatus of the present invention comprises an anchoring mechanism support plate, or tie-bar, having an earth penetrating end, or head, and a slot which is coincident with, or parallel to, the longitudinal axis of the plate or the bar, the said slot being open-ended at the end of the plate which is remote from its penetrating head.

At least one rigid earth-pressure resisting element, or anchoring member, or fluke bar, is attached to the anchoring mechanism support plate, or tie-bar, by a pin, or bolt, or similar hinge piece, which passes through a hole near one end of the said anchoring member, or fluke bar, and the slot in the anchoring mechanism support plate within which the pin, or bolt, is free to slide.

One edge of the rigid earth-pressure resisting element, or anchoring member, or fluke bar, is shaped to a curve the end of which, remote from the hinged pin-joint of the member, bears against a deflecting surface, or edge, incorporated into the penetrating head of the mechanism support plate, the relationship of the axis of the slot in the plate and the curved edge of the anchoring member and the deflecting surface, or edge, of the penetrating head being geometrically such that when the pin or bolt connecting the anchoring member to the mechanism support plate is caused to slide in the direction of the penetrating head of the plate within its slot, the leading or penetrating end of the anchoring member is deflected outwardly, relative to the longitudinal axis of the mechanism support plate, by the curved edge of the anchoring element sliding over the deflecting surface or edge of the penetrating head, and along the pathway within the earth mass which offers a minimum resistance to the outward movement of the anchoring member or fluke bar.

The end of the curved edge of the anchoring elment which is remote from the leading or penetrating end of the member, terminates in a notch, or identation, in the edge of the member which will engage with the deflecting surface or edge on the penetrating head of the anchor mechanism, when the anchoring member has been deflected outwardly from the anchoring mechanism support plate into its earth-pressure resisting, anchor operating attitude. Thereafter an external force or load applied to the anchor mechanism support plate will be resisted by the extended earth-pressure resisting member acting through its notch, engaged with the penetrating head of the plate, and the pin or bolt restraining its following end.Where the material of a ground mass into which the anchoring mechanism is to be installed does not possess a sufficiently high extractive resistance, the anchoring mechanism may, with advantage, include a plurality of anchoring member or fluke bars, as heretofore described, arranged to extend alternately on opposite sides of the anchoring mechanism support plate, the plurality of fluke bars being connected to the plate by a pin or bolt which is common to them all.

Additionally the leading or penetrating ends of each set of fluke bars on opposing sides of the mechanism support plate may with advantage be connected to the leading or penetrating ends of flexible earth-resisting pressure plates which span the spaces between the anchoring flukes and which are initially elongate and lie against the sides of the support plate during the initial installation of the anchoring mechanism into a ground mass and which subsequently are drawn outwardly from the plate by the fluke bars along the same pathway of minimum resistance to movement within the earth mass as that followed by the penetrating ends of the fluke bars.

According to one aspect of the present invention there is provided a method of producing an earth anchor which comprises the steps of driving an anchoring apparatus as heretofore described into the ground to the extent that the slot in the anchoring mechanism support plate or tie bar is below ground level and displacing outwardly from the longitudinal axis of the said tie bar at least one rigid earth-pressure resisting element or anchoring member or fluke bar by the application of force on the pin or bolt hinging the said fluke bar to the slotted tie bar thereby causing the pin or bolt to slide forward in the direction of penetration of the mechanism within its slot, the aforesaid force being applied to the pin or bolt by way of a bar or rod which is free to slide in the open-ended slot in the mechanism support plate and to bear upon or be attached to the pin or bolt, within the slot.

Preferably a plurality of rigid earth-pressure resisting elements or anchoring members or fluke bars are conjointly hinged upon a pin or bolt which is slidable within the slot of the anchor mechanism support plate the said flukes being arranged on both sides of the plate and with their curved edges bearing upon deflecting surfaces or edges alternately on opposite edges of the penetrating head, so that when the pin or bolt is caused to slide within the slot in the anchor mechanism support plate in the direction of penetration of the mechanism, the fluke bars are caused to be deflected outwardly from the initial penetrative axis of the mechanism alternately on opposite sides of the axis.

According to another aspect of the present invention there is provided an anchoring device comprising an anchoring mechanism substantially as heretofore described and, preferably, incorporating a plurality of rigid earth-pressure resisting elements or anchoring members or fluke-bars, conjointly hinged upon a pin or bolt which is free to slide within an open-ended slot in an anchor mechanism support plate or tie-bar whose leading or penetrating end incorporates a penetrating head having opposing deflecting surfaces or edges against which the curved edges of the anchoring members or fluke bars bear and by means of which the said members or fluke bars may be deflected outwardly relative to the longitudinal axis of the anchoring mechanism support plate when the pin or bolt to which their following ends are hinged is caused to move within the slot in the mechanism support plate in the direction or penetration of the said support plate.

In the preferred embodiment of the anchoring device the anchoring mechanism as heretofore described is securely connected to the leading or penetrating end of a tube or hollow shaft by the end of the mechanism support plate which is remote from its penetrating end the said tube or hollow shaft being used to initially drive the mechanism into an earth mass by a percussive effort applied to the following end of the shaft.

Within the driving shaft a rod or bar in contact with or secured to, the pin or bolt connecting the fluke bars to the anchor mechanism support plate is free to slide within the hollow shaft and also within the open ended slot in the support plate.

After the anchoring mechanism has been initially installed into an earth mass by means of its driving shaft a force applied to the upper or following end of the bar or rod will cause the forward movement of the pin or bolt and its associated fluke bars in the direction of penetration of the anchor and thereby effect the outward movement of the fluke bars along their pathways of minimum resistance to movement and into their anchoring attitudes.

It will be evident that a plurality of anchoring members or fluke bars may be arranged between or on both sides of more than one anchor mechanism support plate so that the resistance of the earth pressure over an enlarged bearing area may be shared between the plurality of support plates and excessive shear stresses avoided in the pin or bolt connecting the fluke bars to the support plates; such arrangements having the added advantage of an anchoring mechanism assembly from standard parts and pin diameter to suit a wide range of earth resisting characteristics.

Where ground conditions make it necessary for the anchoring mechanism to deploy an earthpressure resisting anchoring area such that the mechanism requires to incorporate more than one anchor mechanism support plate, the parallel plurality of plates may be connected at their penetrating ends by a common penetrating head and their following ends, or ends remote from their penetrating end, connected by a bridge or saddle or band to which the hollow anchor driving shaft may be attached and through which the fluke pin actuating bar or rod may also pass.

Embodiments of the invention will now be described by way of example, reference being made to the accompanying drawings in which: Fig. 1 is a part sectional and part elevational view of an anchoring device according to the present invention, whose anchoring mechanism is positioned for the initial installation of the anchor into a ground mass.

Fig. 2 is a part sectional and part elevational view of the anchoring device shown at Fig. 1, when viewed from its side.

Fig. 3 is a part sectional and part plan view of the anchoring device shown in Fig. 1.

Fig. 4 shows the end of the anchor mechanism support plate which is remote from its penetrating end and illustrates the open-ended slot therein within which the fluke bar hinge pin or bolt is connected to the slidable activating bar or rod, the driving tube being omitted.

Fig. 5 is a part sectional and part elevational view of an anchoring device according to the present invention with a plurality of earthpressure resisting elements or anchoring members or fluke bars and attached flexible earth-pressure resisting plates, extended outwardly from their anchoring mechanism support plate within a ground mass.

Fig. 6 is a part sectional and part elevational view of the anchoring device shown at Fig. 5, when viewed from its side.

Fig. 7 shows successive positions of the penetrating end of a fluke bar for associated positions of its actuating slideable pin or bolt within the slot of an anchor mechanism support plate or tie-bar; and, by way of example, the design concept of a fluke bar to be initially circumscribed by the periphery of a mechanism support plate having a width of "D", the said penentrating end of the fluke bar having moved through a circular arc subtending 90 degrees at the centre of a circle of radius "R" in moving outwardly from the mechanism support plate along its pathway of minimum resistance to movement within a ground mass.

The anchoring device illustrated in Figs. 1 to 4 comprises a mechanism support plate or tie-bar 1 having an earth penetrating end 2 and a slot 3 which is open-ended at the end 4 of the plate 1 which is remote from its penetrating end 2. A plurality of rigid earth-pressure resisting elements, or anchoring members or fluke bars 5 are connected at one end to a pin or bolt 6 about which the fluke bars 5 are free to rotate, the pin or bolt 6 also passing through the slot 3 within which it is free to slide. One edge 7 of each fluke bar 5 is shaped to a curve whose leading or penetrating end 8, being the end of the fluke bar 5 remote from its pin-jointed end 6, bears against a deflecting surface or edge 9 incorporated into a penetrating head 10 either attached to, or forming an integral part of, the penetrating end 2 of the anchor mechanism support plate 1.

The curved edge 7 of each of the fluke bars 5 is of a geometric form such that when the pin or bolt 6 connecting together the said fluke bars is caused to move towards the penetrating end 2 of the anchor mechanism support plate 1 within the slot 3, the leading or penetrating end 8 of each fluke bar 5 is caused to move outwardly or away from the longitudinal axis of the plate 1 by the curved edge 7 sliding over its associated deflecting surface or edge 9 on the penetrating head 10, the said leading or penetrating end 8 following the pathway of minimum resistance to movement of the fluke bar 5 within the earth mass.

With the advantage the earth-pressure resisting area bounded by the fluke bars 5, after their deflected passage through the earth mass, outwardly from the plate 1, may be increased by one or more flexible pressure plates 11 attached to at least the penetrating ends 8 of the fluke bars 5 by bolts or studs or by the locking bar 12 or by similar securing means, the said flexible plate 11 being elongate and lying against its associated edge of the plate 1 during the initial installation of the anchoring mechanism into a ground mass, and thereafter following the same or a similar pathway of minimum resistance to movement within the earth mass as that followed by the fluke bars 5 during their movement outwardly from the plate 1 as heretofore described.

The end of a fluke bar curved edge 7 which is remote from its leading or penetrating end 8 is terminated in a notch or indentation 13 which will engage with its associated surface or edge 9 on the penetrating head 10, when the outward passage of the fluke bar 5 has been completed and the actuating pin or bolt 6 is at, or near to, the leading end of the slot 3. Thereafter an earth resisting pressure upon the extended fluke bars 5 or upon their supported flexible pressure plate or plates 11, induced by an extractive force "F" applied to the anchoring mechanism, will be transmitted by the fluke bars 5 to the mechanism support plate 1 as a reaction between the engaged notch 13 and the edge 9 and by the pin or bolt 6.

The following end 4 of the anchor mechanism support plate 1 is joined, by welding or a bolted or similar connection, to a shaft or hollow tube 14, by which the anchor mechanism may be initially driven into the ground.

A fluke activating rod or bar 1 5 is free to slide within the shaft 14, the said bar 15 having a leading end 1 6 shaped so that it will clear the following ends of the fluke bars 5 and allow the bar 1 5 to also slide within the slot 3, the said leading end 1 6 being secured to the pin or bolt 6 within the slot 3 by a welded joint 17, or by a similar attachment.

It will be evident that following the initial driving of the anchoring mechanism into the ground the pin 6, together with its hinged fluke bars 5, may be driven along the slot 3 in the direction of penetration by a force applied from above ground surface level to the fluke activating bar 1 5 thereby causing the outward movement of the fluke bars 5 and flexible pressure plates 11 as heretofore described. When the outward driving of the fluke bars 5 has been completed, and their notches 8 are engaged with their associated edges 9, the activating rod or bar 15 may, with advantage, be secured to the anchor shaft 14 by a pin 18 passing through both bar and shaft, or by a similar locking device.

Figs 5 and 6 illustrate the anchoring mechanism in its operating or earth resisting attitude, that is to say with its fluke bars 5 and pressure plates 11 extended into an earth mass and with an extractive force "F" applied to the anchor shaft 14, the numbering and nomenclature of the anchor parts being as heretofore described.

On the completion of the anchoring purpose for which the anchor was installed into a ground mass, the anchor may be recovered for re-use elsewhere by first disconnecting the activating bar 1 5 from the anchor shaft 14 by the removal of the locking pin 18. The anchor mechanism support plate 1, and penetrating head 2 may then be driven sufficiently further into the ground by a force applied to the shaft 14, to disengage the notches 8 in the curved edges 7 of the fluke bars 5 from their associated surfaces or edges 9 on the penetrating head 2.An extractive force thereafter applied to the actuating bar 1 5 will cause the movement of the pin or bolt 6 towards the end 4 of the mechanism support plate 1 and the withdrawal of the fluke bars 5 from their extended positions in the earth mass, and into the positions they occupied during the initial installation of the anchor. On the completion of the aforesaid retraction of the fluke bars 5 the anchoring mechanism may be withdrawn from the earth mass by an extractive force applied to the anchor shaft 14.

By way of example Fig. 7 defines one geometric profile of one form of fluke bar curved edge 7 having a nominal or parametrical radius "R", for the case of one or more extended fluke bars moving outwardly from the anchor mechanism support plate 1 into a position where the tangent to the leading or penetrating ends of the fluke bar 5 is at right angles to the axis of penetration of the anchoring mechanism.

It will be apparent that the number and size, and shape and length of extended pathway, of the fluke bars 5 and their associated pressure plates 11 may be varied to suit the characteristics of a ground mass in which they are to operate, and that one of the economies of the mechanism as heretofore described in the standardisation of component parts of the mechanism which may be assembled to best suit a particular ground condition.

Claims (Filed on 4 May 1982) 1. An anchoring device comprising a plate or frame having therein a slot aligned in the direction of its longitudinal axis and terminating proximate to an earth-penetrating head the said head having at least one shoulder or ledge engageable with the curved convex edge of at least one rigid earthpenetrating anchoring bar or fluke attached to the said plate by a hinge pin or bolt which is rotateable within a hole near to the end of the said fluke remote from its earth-penetrating end, and slidable within the slot in the said plate or frame to whose end remote from its penetrating end is attached a tubular driving shaft or similar means whereby the aforesaid anchoring device may be installed into earth or ground, at least to the extent that the said slot is below ground level and with the said hinge pin restrained in the said slot at such position remote from its penetrating end that the leading or penetrating end of said convex curved edge of the fluke is engaged with the said shoulder or the earth-penetrating head, by a rod or bar secured to the said hinge pin and slidable within the said driving shaft and thereafter by means of the said rod to move the said hinge pin and its associated fluke in the direction of the said earth-penetrating head to the extent that the said fluke is deflected outwardly relative to the longitudinal axis of the said plate or frame by the convex curved edge of the said fluke sliding over the shoulder of the said earthpenetrating head.

2. An anchoring device according to Claim 1 in which the geometrical relationship between the slot in the plate or frame and the shoulder on the earth-penetrating head and the convex curved edge of the fluke is such that the said fluke when deflected outwardly relative to the longitudinal axis of the said plate will penetrate the earth or ground mass along a pathway presenting a minimum resistance to its movement therein.

3. An anchoring device according to Claim 1 or 2 in which the convex curved edge of the fluke extends from its penetrating or leading end to a notch or indentation in the said edge remote from its said penetrating end said notch being engageable with the said shoulder or ledge of the earth-penetrating head to form a locked connection therewith after the outward travel of the fluke has been completed.

4. An anchoring device according to Claim 1 or 2 or 3 in which the rod or bar secured to the hinge pin may be selectively locked to the driving shaft by a slidable pin passed through opposing holes in the said driving shaft and through one of a pair of holes in the said rod.

5. An anchoring device according to any of Claims 1 to 4 in which the rod or bar connected to the hinge pin incorporates a screwthreaded length remote from its said connection to receive a nut which is caused to bear against the end of the driving tube, remote from its penetrating end and by means of which said nut and rod the said hinge pin may be returned to its position in its slot remote from the earth-penetrating head and its associated fluke retracted from an extended position within an earth mass.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. bars 5, may be driven along the slot 3 in the direction of penetration by a force applied from above ground surface level to the fluke activating bar 1 5 thereby causing the outward movement of the fluke bars 5 and flexible pressure plates 11 as heretofore described. When the outward driving of the fluke bars 5 has been completed, and their notches 8 are engaged with their associated edges 9, the activating rod or bar 15 may, with advantage, be secured to the anchor shaft 14 by a pin 18 passing through both bar and shaft, or by a similar locking device. Figs 5 and 6 illustrate the anchoring mechanism in its operating or earth resisting attitude, that is to say with its fluke bars 5 and pressure plates 11 extended into an earth mass and with an extractive force "F" applied to the anchor shaft 14, the numbering and nomenclature of the anchor parts being as heretofore described. On the completion of the anchoring purpose for which the anchor was installed into a ground mass, the anchor may be recovered for re-use elsewhere by first disconnecting the activating bar 1 5 from the anchor shaft 14 by the removal of the locking pin 18. The anchor mechanism support plate 1, and penetrating head 2 may then be driven sufficiently further into the ground by a force applied to the shaft 14, to disengage the notches 8 in the curved edges 7 of the fluke bars 5 from their associated surfaces or edges 9 on the penetrating head 2.An extractive force thereafter applied to the actuating bar 1 5 will cause the movement of the pin or bolt 6 towards the end 4 of the mechanism support plate 1 and the withdrawal of the fluke bars 5 from their extended positions in the earth mass, and into the positions they occupied during the initial installation of the anchor. On the completion of the aforesaid retraction of the fluke bars 5 the anchoring mechanism may be withdrawn from the earth mass by an extractive force applied to the anchor shaft 14. By way of example Fig. 7 defines one geometric profile of one form of fluke bar curved edge 7 having a nominal or parametrical radius "R", for the case of one or more extended fluke bars moving outwardly from the anchor mechanism support plate 1 into a position where the tangent to the leading or penetrating ends of the fluke bar 5 is at right angles to the axis of penetration of the anchoring mechanism. It will be apparent that the number and size, and shape and length of extended pathway, of the fluke bars 5 and their associated pressure plates 11 may be varied to suit the characteristics of a ground mass in which they are to operate, and that one of the economies of the mechanism as heretofore described in the standardisation of component parts of the mechanism which may be assembled to best suit a particular ground condition. Claims (Filed on 4 May 1982)

1. An anchoring device comprising a plate or frame having therein a slot aligned in the direction of its longitudinal axis and terminating proximate to an earth-penetrating head the said head having at least one shoulder or ledge engageable with the curved convex edge of at least one rigid earthpenetrating anchoring bar or fluke attached to the said plate by a hinge pin or bolt which is rotateable within a hole near to the end of the said fluke remote from its earth-penetrating end, and slidable within the slot in the said plate or frame to whose end remote from its penetrating end is attached a tubular driving shaft or similar means whereby the aforesaid anchoring device may be installed into earth or ground, at least to the extent that the said slot is below ground level and with the said hinge pin restrained in the said slot at such position remote from its penetrating end that the leading or penetrating end of said convex curved edge of the fluke is engaged with the said shoulder or the earth-penetrating head, by a rod or bar secured to the said hinge pin and slidable within the said driving shaft and thereafter by means of the said rod to move the said hinge pin and its associated fluke in the direction of the said earth-penetrating head to the extent that the said fluke is deflected outwardly relative to the longitudinal axis of the said plate or frame by the convex curved edge of the said fluke sliding over the shoulder of the said earthpenetrating head.

6. An anchoring device according to any of the

Claims 1 to 5 in which a plurality of rigid earthpenetrating anchoring bars of flukes are attached to the plate or frame by the hinge pin, the convex curved edge of each said fluke being engageable with an associated shoulder or ledge provided at the earth-penetrating head.

7. An anchoring device according to Claim 6 in which the plurality of anchoring bars or flukes are arranged to extend into an earth mass in alternate opposing directions relative to the longitudinal axis of the plate or frame and on opposing sides thereof.

8. An anchoring device according to any of the preceeding Claims in which a flexible plate is attached to one or more rigid earth-penetrating anchor bar or fluke, the said flexible plate being elongate and situated transversely to the edge of the plate or frame during the initial installation of the said anchoring device into a ground mass into which the said flexible plate is thereafter moved by the said extended fluke or flukes.

9. An anchoring device according to Claim 8 in which a plurality of flexible plates are attached to a plurality of rigid earth-penetrating anchoring bars or flukes.

10. An anchoring device constructed, arranged and adapted to operate substantially as herein described with reference to and as shown in the accompanying drawings.