EP0169872B1

EP0169872B1 - Ground anchoring system

Info

Publication number: EP0169872B1
Application number: EP85900713A
Authority: EP
Inventors: Peter Alsop
Original assignee: Individual
Current assignee: Scourmat Ltd; Seabed Scour Control Systems Ltd
Priority date: 1984-01-30
Filing date: 1985-01-29
Publication date: 1988-06-15
Also published as: EP0169872A1; NO853862L; JPS61501404A; DE3563366D1; IT1202134B; DK156993B; ZA85476B; GB2162562A; BR8505004A; AU3887685A; CA1239006A; DK156993C; GB2162562B; FI853771L; ES292838Y; AU575621B2; FI83982C; MX162095A; IE56388B1; OA08109A

Abstract

An anchor plate for use in a groundanchoring system includes a flap (17) projecting rearwardly from a trailing edge (18) of the plate (10), the flap (17) being retained in a cocked position inclined at a first angle (1) to the plate when the plate is engaged by the driving rod (22) of a driving tool, and being released from its cocked position so that it lies at a second greater angle (2) to the plate (10) when the rod (22) is withdrawn, the rear edge (24) of the flap (17) thereby engaging the side of the hole (25) to resist reverse upward movement of the plate (10) and providing a fulcrum about which the plate pivots to a skew position.

Description

In my published UK Patent Application GB-A-2,085,386 there is described a ground anchoring system in which a generally flat anchor plate includes transverse slots for receiving and retaining one end of a flexible anchoring web or strap, the plate being driven edge-first into the ground by a driving tool with the other end of the web or strap connected to the object being anchored.
When the driving tool is removed and a lifting force is subsequently applied to the flexible web or strap, the plate tends to skew across the hole and thereby resist extraction from the ground.
On the whole this system works satisfactorily, but I have found that there is often a significant delay before the plate is skewed after a lifting force is applied to the line. During this period, the plate can be pulled some distance back up the hole, and the anchored object may not then be firmly anchored in its desired position. This problem is particularly troublesome when anchoring objects to the river or sea bed. For example, when anchoring a frond mat to the sea bed to combat erosion of the bed beneath structures such as oil or gas pipelines, any "lifting" of the mat after it has been anchored can seriously affect subsequent performance of the mat under operating conditions.
It is also known from FR-A-2470823 and US-A-4003169 to provide an anchor plate with a fixed tail flap intended to assist the turning of the plate into a skew position after it has been driven into the ground. However the comparatively high angle of these flaps not only provides substantial resistance when driving the plates into the ground but also form an entry channel in the ground which is wide in relation to the anchor plate. This increases the risk of the anchor being pulled some distance back up the channel when the anchor line is tensioned.
An alternative locking mechanism is shown in US-A-3888057 in which a movable fluke is secured to the anchor line, the fluke being pulled from a position substantially parallel to the anchor plate to a position transverse to the plate when the anchor line is tensioned. This arrangement has the disadvantage that the lifting force is applied directly to the movable fluke when the anchor line is tensioned.
An object of the present invention is to provide an anchor plate which overcomes the above problem but without substantially increasing the resistance of the plate when being driven downwardly into the ground.
According to the present invention there is provided a ground anchoring system comprising an anchor plate which, in use, is driven edge-first into the ground by a driving tool, the plate having a projecting tail flap and transverse slot means for receiving and retaining one end of a flexible anchoring strap or web, characterised by an elongate socket for receiving the driving tool, the socket being disposed toward the leading edge of the plate beneath the transverse slot means such that the plate is aligned with the tool while being driven into the ground, the tail flap being retained by a cooperating portion of the tool in a first cocked position offering minimum drag resistance when the tool is located in the socket but being biased for movement into a second position inclined at a greater angle to the plate when the tool is withdrawn from the socket.
In its cocked position (i.e. the position from which it can be released) the tail flap is generally aligned with the plate, the angle being generally in the range of 0 to 15° and preferably less than 10°. It therefore offers minimal resistance to the downward movement of the plate into the ground. In its released position, on the other hand, the angle increases and generally lies in the range of 20° to 60° with a preferred range of 30° to 45°.
The increased angle brings the trailing edge of the tail flap into contact with the side of the channel cut by the plate when driving it into the ground. The flap therefore provides a fulcrum about which the plate pivots into a skew position across the channel when the anchor line is tensioned.
The tail flap is preferably resiliently biased but may alternatively fall freely into the released position under the force of gravity when the driving tool is removed from its socket. It may comprise a deformable strip projecting from the trailing edge of the plate, or it may be hinged to the trailing edge.
By way of example only, an embodiment of the invention will now be described with reference to the accompanying drawings, in which:-

Fig. 1 is a front elevation view of an anchor plate fitted with an anchoring strap;
Fig. 2 is a side elevation of the plate and strap;
Fig. 3 shows the plate being driven into the ground by a driving tool; and
Fig. 4 shows the skew position of the plate when the strap is subsequently tensioned after driving the plate into the ground.

Referring first to Figs. 1 and 2, a generally flat, wedge-shaped anchor plate 10 includes a pair of slots 11, 12 for receiving a flexible anchoring strap or web 13. A looped end 13a of the strap 13 is inserted through the lower slot 12 from the rear side (as viewed in Fig. 1), and is then fed back through the upper slot 11. A split elongate retaining ring 14 receives the looped end and prevents the strap being withdrawn from the slots.
An elongate socket 15 is welded to the front side of the plate 10 for receiving an extended driving rod 22 (Fig. 3) of an hydraulic hammer tool (not shown) such that the leading edge 30 of the plate can be driven downwardly into the ground. As shown in Fig. 3, the rod 22 fits into the socket with a loose push fit and maintains the plate 10 aligned with the rod in a substantially vertical orientation when driving the plate into the ground.
A flap 17 projects rearwardly from the trailing edge 18 of the plate 10. A longitudinally split hollow tube 19 is welded to the trailing edge 18 and pivotally mounts a spindle 20 secured to a central portion 21 of the flap. The flap 17 is thereby hinged to the trailing edge 18 and is movable through an angle determined by the width of the slit in the tube 19. It is resiliently biased by springs 23 into the position shown in full outline in Fig. 2, the angle 6₂ being approximately 40°. The other extreme position is shown by the chain-dot outline in Fig. 2, the angle 6, being approximately 5°.
The operation of the system is illustrated in Figs. 3 and 4. The object being anchored (not shown) is attached to the top end of the strap 13. The driving rod 22 of the hammer tool is then inserted into the socket 15. To insert the rod into the socket, the hinged flap 17 must first be moved back against its resilient bias into the cocked position shown in full outline in Fig. 3. The rod 22 once inserted in socket 15 then holds the flap 17 in its cocked position against the bias of spring 23, the rod being accommodated by the recess 31 (Fig. 1) in the rear edge of the flap.
The hammer is then actuated to drive the plate 10, strap 13 and rod 22 into the ground, the location of rod 22 in socket 15 maintaining the plate aligned in the rod with a generally vertical orientation as shown in Fig. 3.
Once the plate and strap have been driven to the required depth, say 1-2 metres, the rod 22 is withdrawn from socket 15 and the flap 17 automatically springs into the position shown in chain-dot outline in Fig. 3. In this position the serrated rear edge 24 of the flap digs into the side of the hole 25 and thereby resists reverse upward movement of the plate. Moreover it immediately provides a fulcrum about which the plate 10 is forced to pivot to a skew position as shown in Fig. 4 when the strap 13 is subsequently tensioned by lifting forces applied to the object being anchored. This action ensures that the plate is immediately locked in its skew position and cannot be pulled back up the hole.
The centre of gravity of the plate 10 is positioned above the lower slot 12 so that the plate will tend to rotate in the direction shown by the arrows in Fig. 4 when the rod 22 is withdrawn from socket 15. This further assists in urging the serrated edge 24 of flap 17 into engagement with the side of the hole 25.
Moreover, a short bar 26 welded to the ring 14 spaces the strap 13 from the rear face of the plate 10 so that an additional turning moment is applied in the direction of the arrows shown in Fig. 4 when the strap 13 is tensioned. In practice the forces on the plate are such that it continues to rotate into a generally horizontal locked position as the rear edge 24 of the flap 17 digs further into the side of the hole.

Claims

1. A ground anchoring system comprising an anchor plate (10) which, in use, is driven edge-first into the ground by a driving tool (22), the plate (10) having a projecting tail flap (17) and transverse slot means (11, 12) for receiving and retaining one end of a flexible anchoring strap or web (13), characterised by an elongate socket (15) for receiving the driving tool (22), the socket being disposed toward the leading edge of the plate (10) neneath the transverse slot means (11, 12) such that the plate is aligned with the tool while being driven into the ground, the tail flap (17) being retained by a cooperating portion of the tool (22) in a first cocked position offering minimum drag resistance when the tool is located in the socket (15) but being biased for movement into a second position inclined at a greater angle to the plate (10) when the tool (22) is withdrawn from the socket (15).

2. A system according to claim 1 in which the tail flap (176) is inclined to the plate at an angle not exceeding 15° in its first cocked position.

3. A system according to claim 2 in which the tail flap (17) in its second position is inclined at an angle to the plate of between 20° and 60°.

4. A system according to any one of the preceding claims in which the strap or web (13) extends upwardly from one side of the plate (10) for connection to the object being anchored, and the socket (15) is welded or otherwise secured to the opposite side of the plate.

5. A system according to any one of the preceding claims in which the trailing edge of the tail flap (17) is serrated.

6. A system according to any one of the preceding claims in which the tail flap (17) is hinged to the trailing edge (18) of the anchor plate (10).

7. A system according to claim 6 in which the hinge comprises a split hollow tube (19) secured to the trailing edge (18) of the plate, the tail flap (17) having an associated spindle (20) rotatable within the tube.

8. A system according to any one of the preceding claims in which a portion (31) of the trailing edge (24) of the tail flap (17) is recessed to accommodate the driving tool (22) when the tool is located in the socket (15).