GB2116222A

GB2116222A - Inserting ground anchors; reinforcing waterside banks

Info

Publication number: GB2116222A
Application number: GB08205773A
Authority: GB
Inventors: Douglas Jesse Tupper
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-02-26
Filing date: 1982-02-26
Publication date: 1983-09-21

Abstract

The anchor comprises a soil- penetrating rigid member 13 which resists extraction by an upward pulling force on a flexible connector 10. A driving-tool (Fig. 3) is releasably engaged to the member, and is disengaged when the member is totally buried. The connector is secured to the anchor in such a way as not interfere with the driving- tool. Various types of anchor and tool are disclosed. An anti-erosion web is held in place on a waterside bank by anchors driven into the bank, and into the bottom beneath water-level. <IMAGE>

Description

SPECIFICATION Improvements relating to the staking or anchoring of bodies to the ground This invention relates to the anchoring of objects to the ground. The invention may be used on dry land or underground, e.g. to anchor antierosion matting or fronds to the ground.

A known method of preventing erosion of the sea-bed around the feet of structures such as oil rigs is to plant a bed of artificial reeds or fronds around the feet. Such beds can also be planted in coastal waters to prevent erosion of the coast by creating artificial sandbank barriers, or by stabilising existing sandbanks.

In general the fronds or reeds are first secured at spaced intervals to a matting e.g. of plastics webbing such as (Trade Mark) Paraweb, and this matting is then staked to the sea-bed.

Antierosion matting can be used to revet the beds or banks or canals. In this case the constant down draw of water as ships pass up and down the canal can produce considerable viscous drag on the matting. Also crumbling of the bank is often caused by traffic. Conventional methods of staking the matting using stakes or piles manufactured from wood, plastics or metal provide a limited retention force which is not always sufficient to counter this drag.

Higher retention forces can be obtained by using surface screw anchors but these are difficult to insert and at least in certain soils can be pulled out of the ground if a lifting force is applied directly along the line of the screw.

However the anchor or the method of anchoring according to the invention can be used in a variety of applications, e.g. in water engineering, civil engineering, and the construction industry. The anchors can be used e.g. in anchoring pylons or mobile homes or trees and other vegetation.

According to one aspect of the invention there is provided an anchor arranged to be driven into the ground, with a flexible connector attached to it, to a totally submerged position with the aid of a driving tool and comprising a rigid member shaped so as to facilitate entry into, and passage through, the soil and to resist extraction by an upward pulling force on the connector, the member comprising a soil piercing formation at a front end, means for removably engaging a driving tool such as to enable the driving tool to be disengaged in a submerged position of the anchor by withdrawal, and means enabling securement of the connector without interference with the driving tool.

In one form of anchor, at least a portion thereof is pivotable from a first position offering minimum resistance to the passage of the anchor through the ground and a second position offering a substantially greater resistance, such that the member adopts its first position when being driven into the ground and automatically pivots to its second position when the member is embedded in the ground and a pulling force is applied to the connector.

This form of anchor may comprise a generally flat plate provided with a tool-engaging surface, a soil piercing formation at a front end and attachment means for the connector at a region intermediate the ends whereby a pulling force on the connector causes the anchoring member to pivot towards a position in which the plate lies transversely to the connector.

The flexible connector may be a strap and the plate may include a slot for receiving the strap.

There may be two parallel slots through which one end of the strap is (in use) woven to form a secure attachment. The pulling end of the strap preferably enters through the lower slot.

The front end of the anchor may be bent backwards providing a tool-engaging surface at the inner angle of the bend.

Another form of anchor comprises a stake having a soil piercing projection at a front end and a connector receiving means at or adjacent a rear end, and having at least two blades, each blade being pivotably coupled to the stake towards the front end and being movable between a rearwardly folded position lying generally parallel to the stake and an open position extending outwardly from the stake.

Preferably the connector receiving means comprises a pair of oppositely disposed rings and two opposed blades cover the rings in the closed position.

Yet another form of anchor comprises a rod having a helical formation at the front end terminating in a point, an axially extending shank at the rear of the helical formation, the shank terminating in a head for receiving a rotating tool, a connector securing means being rotatably mounted to the shank and being shaped to allow passage through the soil.

The invention also includes a method of anchoring an object to the ground in which a flexible connector to which the object is connected or to be connected is attached to a rigid anchoring member and the anchoring member with the connector attached is removably engaged with a driving tool and driven into the ground to a totally submerged position, the anchoring member being shaped so as to facilitate entry into and passage through the soil and to resist extraction by an upward pulling force on the connector, the driving tool, after full submersion, being disengaged from the anchoring member and withdrawn.

In another aspect of the invention includes a method of anchoring an object to the ground comprising the steps of securing an anchoring member to an end of a flexible connector, connected or to be connected to the object, at least a portion of the anchoring member being pivotable between a first position offering minimum resistance to movement of the member through the ground and a second position offering substantial resistance, engaging the anchoring member with a mechanical driving tool, forcibly driving the tool into the ground with the anchoring member in its first position until a predetermined length of the line is embedded below ground level; disengaging the tool from the anchoring member; and extracting the tool from the ground; whereby a lifting force subsequently applied to the line rotates the anchoring member or the said portion of the anchoring member into its second position to resist extraction of the anchoring member from the ground.

The invention is also inclusive of a method of reinforcing a waterside bank in which an antierosion web is held in place at least partly with the aid of anchors as described herein before, driven into the bank to a depth of at least two meters, and into the bottom beneath water level.

The length of the flexible connector or anchor line and the depth the anchor is driven into the soil, naturally depends upon the soil mechanics of the bed together with the acting forces exerted by the anchoring body. The advantages of the present invention are as follows. The apparatus has a high retention characteristic which may be readily justified by altering the length and width of the anchor plate, thereby presenting greater or lesser surface areas as demanded by engineering requirements. The anchor line may be of low weight in bulk for ease of handling. Equipment for installing in or out of the water is readily available.

The cost is low compared to other systems, both the materials and installation.

Embodiments of the invention are hereinafter described with reference to the accompanying drawings, in which Fig. 1 is a cross-section through an anchoring assembly, Fig. 2 is a bottom plan view of the anchoring plate in the assembly of Fig. 1, Fig. 3 is a side view of a driving tool for use with the assembly of Fig. 1, Fig. 4 is a side view of a coupling for coupling the tool of Fig. 3 to a pneumatic hammer, Fig. 5 is a sectional view on the line A-A of Fig. 4, Fig. 6 is a side elevation view of one component of the coupling, Fig. 7 is a front elevation view of an alternative anchoring member providing a higher retention force, Fig. 8 is a side elevation of the anchoring member of Fig. 8, Fig. 9 is a plan view of an alternative form of anchor plate in its flat state, Fig. 10 is an elevational view of the plate of Fig. 9 in its finished state, Fig. 11 is a plan view of another form of anchor plate in its flat state; Fig. 12 is an elevational view of the plate of Fig. 11 in its finished state, Fig. 1 3 is a perspective view of another form of anchor plate, Fig. 14 is an elevational view of a helical form of anchor according to the invention, Fig. 1 5 is a plan view of the anchor of Fig. 14, and Fig. 1 6 is a perspective view of a strap connector for attachment to the anchor of Fig. 14.

Referring first to Figs. 1 and 2, a flexible anchor line 10 in the form of a synthetic web or strap is threaded through the slots 11 and 12 of an anchor plate 13. The web or strap 10 may consist, for example, of a polyester fibre encases in polyalkylene plastics material e.g. Trade Mark Paraweb.

The front end of the plate 13 is bent back as a hook 14 to provide in the angle of the bend a toolengaging surface which in use, is engaged by a driving tool so that the plate 13 and strap 10 can be driven into the ground (in the direction shown by the arrow) with the strap 10 lying substantially parallel to the plate 13 as shown in Fig. 10.

The plate is generally driven into the ground to a depth of 1 to 3 metres, but possibly as much as 6 metres, depending on soil characteristics. When the driving tool is then removed and the strap 10 is pulled in the reverse direction, the plate 13 will tend to rotate anticlockwise (as viewed in Fig. 1) about the slot 11 (the slot 11 being offset frontwardly from the centre of the plate 13) so that the front end rotates towards the direction of pull and the plate tends to a position transverse to the line.

In this position the force required to pull the plate 1 3 out of the ground is substantially increased. It has been found that, with a 4 inch long plate, such a system can provide a retention force of up to 600 kilogrammes. Moreover, the full anchoring effect is obtained immediately the tool is removed, and there is virtually no reverse movement of the anchor strap once it has been anchored.

The free end 1 5 of the strap 10 is secured in any desired manner to the member being anchored. This may be done either before or after the anchor plate 13 is driven into the ground. The end 1 5 may be attached to anti-erosion matting for lining the banks or beds of canals, or at spaced intervals to the wires or ropes threaded through the discrete blocks of a flexible concrete mat used for lining the banks of a waterway, canal, embankment, or shoreline. Moreover such mats are normally secured by means of surface screw anchors, the time required to secure each anchor being in the region of 10 to 1 5 mins. In contrast, the anchor of Fig. 1 can be secured in about 1020 seconds. In practice, a roll of such matting may be provided with a number of the straps 10 secured at spaced intervals such that, as the matting is unrolled along the bank or bed of the canal, the straps appear consecutively in front of the advancing roll. A particular advantage of the latter application is that the straps 10, when embedded in the canal bank, provide ties which reinforce and hold together the bank soil.

Fig. 3 illustrates an extension member for use with a pneumatic hammer. It consists of a solid metal rod 1 6 having a flattened end 17 which engages the tool-engaging surface in the angle of the hook 14 of the anchor plate 13 (Fig. 1 ) with locating projections 1 7a projecting at each end of the tool-engaging surface. The other end of the rod 16 is formed with a square or hexagonal section solid block 1 8. To secure the tool to the mole or stem of a pneumatic hammer, the block 18 is inserted into one end of the bore 19 of a box-section coupling member 20. The other end of the bore 1 9 receives the hammer or mole or stem so that blows imparted to the mole by a reciprocating hammer are transmitted to the block 18.The tool is retained in the coupling 20 by means of a retaining member 22 (Fig. 6) held in place by a split pin 21 (Fig. 5). For clarity, the retaining member 22 has been omitted from Fig.

5 but, as illustrated in Figs. 4 and 6, it consists of a cross-piece 24 connected to a pair of upstanding spaced apart pins 25 by a flat plate 23. The cross-piece 24 engages behind a pair of flanges 27 depending from the coupling member, while the two pins 25 receive the rod 16 and locate behind the block 18 at the end of the rod.

The anchoring member of Figs. 7 and 8 consists essentially of a stake 50 in the form of a solid metal bar pointed at the front end. A pair of rings 51 are welded to the stake near the rear end for attachment to the flexible anchor line. In addition, a pair of opposed blades 52 are pivotably mounted on respective pins 53 extending between a pair of metal plates 54 welded to opposing faces of the stake adjacent the front end of the stake in section. The blades 52 are curved and can pivot from the closed position shown in full outline in Fig. 8 in which they extend rearwardly to cover the rings 51 to the open or extended position shown in dashed outline. When in their closed position, the blades offer minimum resistance to movement of the stake through the ground.The stake is preferably driven into the ground to a depth of at least 3 metres using an electrically controlled hydraulically actuated percussive hammer and a driving tool similar to that illustrated in Figs. 3 to 6 except that the blade 1 7 is replaced by a socket capable of receiving the top end of the stake 50.

The anchor blade of Figures i and 2 is (in its unbent state) generally pentagonal in plan having a sharply tapered point at its front end, a blunt rear end and a maximum width nearer the rear end than the front end. It can be observed that the maximum width of the anchor is rearward of the front slot.

Figures 9 and 10 show an alternative form of anchor which in its unbent state is in the form of a generally square plate 60 with one corner 61 forming the front end and slots 62, 63 extending on opposite sides of the transverse diagonal. As shown in Figure 10 the front end is prior to use bent over as in Figure 1 to provide the toolengaging surface at 64. The opposite corner 65 is in use bent obliquely e.g. at an angle of about 300 away from the plane of the plate oppositely to the hook as shown in Figure 1 0. This ensures that when a pull is taken in the direction of the arrow in Figure 10, the plate will immediately pivot sharply due to entry of the pointed end 65 into the soil.

Another modification of plate 70 is shown in Figures 11 and 12. In this case the anchor plate in its unbent state is again generally pentagonal as in Figures 1 and 2, but the rear end is squared off at 71 and the corner section at the front end 72 is cut away. The front end is bent backwards as in the embodiments of Figures 1 and 9 and the rear end portion 71 bent obliquely away from the plane of the plate e.g. at about 300. In Fig. 12 the portion 71 is shown bent in the direction of the hooked front end. The pull will then be taken in the direction of the arrow shown in full lines. The reason is that in plates of the type of Fig. 10 there is a tendency at low depths for the direction of insertion to curve around away from the direction of the hook due to the drag of the oblique corner 65 and this is more pronounced when this is of greater size as in Figure 11.Forming the rear angle in the same direction as the hook tends to counteract this tendency but the plate may alternatively be formed with the rear edge as shown in broken line so that the pull is in the direction of the arrow also in broken lines.

As indicated by broken lines,the slots may be replaced by two holes to receive a threaded cable e.g. of steel. The cable end may be looped through the holes and crimped to the main length of the cable.

Fig. 13 shows a heavier form of plate 80 in which rear edge portions 81 at each side of the axis are bent obliquely away from the direction of pull indicated by the arrows at an angle e.g. of about 300. A re-entrant 82 is formed in a central part of the bent portion to provide a tool engaging surface 83 perpendicular to the plane of the plate. Although the central portion may be cut away, it is preferable to cut and fold the central portion as shown at 84 so that the tool-engaging surface 83 is double the plate thickness. The plate of Figure 13 is utilised with an extension tool the front end of which is bifurcated to fit around the tool engaging surface 83.

The plates may be of BS 42 steel of 3 or 4 mm thickness, although those of Figures 11 to 13 are preferably of the greater thickness.

By way of example, an anchor plate as shown in Figure 9 and 10 cm width was found to resist a pull of up to 1 tonne in wet sand at a depth of 1 m.

A 14.5 cm width plate as in Figure 11 at a depth of 1 T m was found to resist a pull of up to 3200 Ibs (1452 kg) with a lift of O to 1 T inches.

The above plates were of 4 mm thickness.

A similar 4 mm plate as in Figure 11 was found to hold a pull of up to 300 Ibis (1361 kg) art a depth of 1 m.

A 3 mm plate as in Figure 11 was found to hold up to 3200 Ibs (1452 kg) at a depth of 3 feet with a lift of O to 12 inches.

A 3 mm plate as in Figure 11 at a 12 m depth in softer soil was found to resist a pull of up to 1800 Ibs (817 kg) with a lift of 4 to 6 inches before final holding.

The above were retained by woven synthetic fibre straps.

The following tests were carried out using 8 mm steel cable.

On a different soil a 3 mm plate as in Figure 11 was found to resist a pull of up to 3800 Ibs (1724 kg) at a depth of 1 T m.

On very firm soil a 3 mm plate as in Figure 11 was found to resist a pull of up to 3100 Ibs (1407 kg) with a lift of O to 1 T inches at a depth of 2 feet.

Clearly the depth of use will depend upon the compaction of the soil and in general the anchor plates should be buried as deep as practical, especially where the soil is loose or sandy.

The extension members should preferably be of 12 mm steel rod (specification EN 43 J) hardened to 81 tons per square inch (128 kg/mm2) Another form of anchor which is also useful within the general context of the invention is shown in Figures 14 and 1 5. This comprises a rod 90 having a helical formation 91 at its front end, terminating at a point 92 and an axially extending shank 93 at the rear of the helical formation, the shank terminating in a head 94 for receiving a rotating tool. A flexible connector securing means is rotatably mounted to the shank and shaped to allow penetration into the soil. In the embodiment illustrated this comprises a plate 95 arranged with the shank 93 lying in the plane of the plate, the plate having a central hollow enlargement 96 to receive the shank.

The plate 95 is welded from two individual plates 95a, 95b which can be individually pressed to define hemi-cylindrical recesses which together form the cylindrical opening 96 for receiving the shank.

The shank, as shown bisects the plate to define two wings 96 each having an opening 97 e.g. a 10 mm bore for connection to the flexible connector or anchor line.

The flexible connector may be a strap e.g. of (Trade Mark) Paraweb fitted to a special adaptor as shown in Figure 1 6. This comprises a U-shaped hook member 100 of steel rod around the web 101 of which is wrapped the end of the strap 102, the wrapped end of the strap being bonded to the main portion so that the strap is firmly secured to the U-shaped member 100. The limbs 102 of the member 100 are bent upwardly into hooks which can engage through the openings 97 of the securing means 95.

The helical rod and shank are preferably of 12 mm round rod of EN 1A steel with a galvanised finish. The head may be welded on with Oerlikon Inox DW welding rod. The head is preferably 22 mm square having been drilled to receive the shank prior to welding. In one embodiment the helix was of 75 mm diameter with 221 turns. The plate forming the strap receiving means was, when finished, of 3 mm thickness, of 25 mm width and 75 mm length i.e. substantially the same as the diameter of the helix. The receiving apertures 97 are e.g. 10 mm diameter.

The U-shaped member of the adaptor was of 8 mm round steel of EN 1 A specification.

The anchor of Figure 1 5 may be driven into the ground by a hand brace to which an extension rod as previously described can be fitted, the extension rod terminating in a female connection for matching the head 94. Alternatively and preferably it is driven in by means of an electrical or hydraulic rotating tool. The extension of a rod should be of tempered steel as previously described.

The advantage of the screw anchor at depth is that it is relatively cheap to produce and manufacture and has a very high retention at depth, where the soil is generally more compact due to the imposed pressure of the material above. Very much higher pull resistances can be achieved than with surface screw anchors. It is relatively easily installed by hand tools or mechanical tools. For deep insertion, a number of extension rods can be linked together as required and easily recovered. The dimensions of the helix can be varied virtually at will to obtain optimum holding power in different soils. It is relatively easy to insert the anchor at different angles to obtain an instantaneous holding and this holding is obtained at virtually any angle of pull.

Submerged screw anchors as described are particularly useful in the anchoring of webbing or matting to canal or river banks where they can be quickly and deeply insertcd e.g. horizontally underneath a road or burm surface where there is substantially greater compaction of soil and where the length of line reinforces the antierosion properties of the mat by holding the soil together at depth.

Since these anchors are inserted by a rotary action, and have virtually no withdrawal tolerance before purchase is achieved, the strap may be preattached to the mat and anchored straight in under tension, without the danger and of any subsequent loosening.

Claims

1. An anchor arranged to be driven into the ground with a flexible connector attached to it, to a totally submerged position with the aid of a driving tool and comprising a rigid member shaped so as to facilitate entry into, the passage through, the soil and to resist extraction by an upward pulling force on the connector, the member comprising a soil piercing formation at a front end, means for removably engaging a driving tool such as to enable the driving tool to be disengaged in a submerged position of the anchor by withdrawal, and means enabling securement of the connector without interference with the driving tool.

2. An anchor according to claim 1 wherein at least a portion of the anchor is pivotable from a first position offering minimum resistance to the passage of the anchor through the ground and a second position offering a substantially greater resistance, such that the member adopts its first position when being driven into the ground and automatically pivots to its second position when the member is embedded in the ground and a pulling force is applied to the connector.

3. An anchor according to claim 2 comprising a generally flat plate provided with a tool-engaging surface, a ground piercing formation at a front end and attachment means for the connector at a region intermediate the ends whereby a pulling force on the connector causes the anchoring member to pivot towards a position in which the plate lies transversely to the connector.

4. An anchor according to claim 3 in which the flexible connector is a strap, and the plate includes a slot for receiving the strap.

5. An anchor according to claim 4 including two parallel slots through which an end of the strap is (in use) woven to form a secure attachment.

6. An anchor according to claim 5 wherein the pulling end of the strap enters through the lower slot.

7. An anchor according to any of claims 3 to 6 wherein the front end of the anchor is bent backwards providing a tool-engaging surface at the inner angle of the bend.

8. An anchor according to claim 1 comprising a stake having a soil piercing projection at a front end and a connector receiving means at or adjacent a rear end, and having at least two blades, each blade being pivotably coupled to the stake towards the front end and being movable between a rearwardly folded position lying generally parallel to the stake and an open position extending outwardly from the stake.

9. An anchor according to claim 8 wherein the connector receiving means comprises a pair of oppositely disposed rings and two opposed blades cover the rings in the closed position.

10. An anchor according to claim 7 wherein the anchor plate (in its unbent state) is generally pentagonal in plane having a sharply tapered point at its front end, a blunt rear end and a maximum width nearer the rear end than the front end.

11. An anchor according to claim 10 wherein the maximum width of the anchor is rearward of the front slot.

12. An anchor according to claim 7 wherein the anchor plate (in its unbent state) is generally square in plan with one corner forming the front end and slots extending on opposite sides of the transverse diagonal, the rear cover being (in use) bent obliquely away from the direction of pull.

1 3. An anchor according to claim 7 wherein the anchoring member (in its unbent state) is generally pentagonal in plane having a sharply tapered point at its front end and a maximum width at its rear end, an edge portion of the rear end prior to use being bent obliquely away from the direction of pull.

14. An anchor according to claim 3 wherein a rear edge portion of the plate is bent obliquely away from the direction of pull and a reentrant is formed in a central part of the bent portion to provide a tool-engaging surface perpendicular to the plane of the plate.

1 5. An anchor according to claim 14 wherein the central part is cut and folded flat to provide a tool-engaging surface of double the plate thickness.

1 6. An anchor according to claim 1 comprising a rod having a helical formation at the front end terminating in a point, an axially extending shank at the rear of the helical formation, the shank terminating in a head for receiving a rotating tool, a connector securing means being rotatably mounted to the shank and being shaped to allow passage through the soil.

1 7. An anchor according to claim 1 6 wherein the securing means comprises a plate arranged so that the shank lies in the plane of the plate, the plate having a central hollow enlargement to receive the shank.

1 8. An anchor according to claim 7 wherein the shank bisects the plate to define two wings and the connector is connected to openings in the wings.

1 9. An anchor according to any of claims 1 6 to 1 8 in combination with a rod-like extension member enabling the anchoring member to be drawn into the ground to a depth of at least one meter.

20. A method of anchoring an object to the ground in which a flexible connector to which the object is connected or to be connected is attached to a rigid anchoring member and the anchoring member with the connector attached is removable engaged with a driving tool and driven into the ground to a totally submerged position, the anchoring member being shaped so as to facilitate entry into and passage through the soil and to resist extraction by an upward pulling force on the connector, the driving tool, after full submersion, being disengaged from the anchoring member and withdrawn.

21. A method of anchoring an object to the ground comprising the steps of securing an anchoring member to an end of a flexible connector, connected or to be connected to the object, at least a portion of the anchoring member being pivotable between a first position offering minimum resistance to movement to the member through the ground and a second position offering substantial resistance; engaging the anchoring member with a mechanical driving tool, forcibly driving the tool into the ground with the anchoring member in its firstmqosition until a predetermined length of the line is embedded below ground level; disengaging the tool from the anchoring member in its first position until a the ground; whereby a lifting force subsequently applied to the line rotates the anchoring member or the said portion of the anchoring member into its second position to resist extraction of the anchoring member from the ground.

22. A method according to claim 21 wherein the anchoring member comprises an anchor according to any of claims 3 to 13.

23. A method according to claim 21 or 22 wherein the tool is a pneumatic or hydraulic reciprocating tool having a reciprocating stem and an extension member is filled to engage the stem and the anchoring member enabling the anchor member to be driven into the ground to a depth of at least one meter.

24. A method according to claim 23 wherein the extension member is adapted to an anchor according to claim 7 and comprises a shank having a stem engaging means at a rear end and a blade at the front end, the blade having a transverse front edge portion for engaging the tool-engaging surface and locating projections on each side of the front edge portions.

25. A method according to claim 20 wherein the anchoring member comprises an anchor according to any of claims 16 to 19.

26. A method according to claim 25 wherein an extension tool according to claim 23 is utilised the front end of which is bifurcated to fit around the tool-engaging surface.

27. An anchor according to claim 1 substantially as described herein with reference to any one of the embodiments.

28. A method according to claim 20 substantially as described herein with reference to any one of the embodiments.

29. A method of reinforcing a waterside bank in which an anti-erosion web is held in place at least partly with the aid of anchors as claimed in any of claims 1 to 19 or 27, driven into the bank to a depth of at least two meters, and into the bottom beneath water level.