The present invention relates to ground drainage apparatus, suitable for draining soils, e.g. to reduce pore water pressure behind retaining walls or within clay slopes. The present invention also relates to a method of installation of such ground drainage apparatus.

It is known in the art to use conduits such as “Wickdrains” to help drain water from soils. Such drains also increase soil strength in clay by increasing friction of slip planes and causing a reduction in the softening and lubrication of slip panels. Such drains comprise a corrugated plastic core with a geotextile sleeve. They are usually pushed vertically into the ground, up to a distance of 20m to 30m, typically to accelerate consolidation settlement on highways projects. It is also known in the art to use a ground anchor attached to a cable to secure cables in the ground.

GB2398808 presented ground drainage apparatus comprising: a ground anchor; and a length of conduit providing a drainage channel for water, wherein: the length of conduit is secured to the ground anchor in such a way that when the ground anchor is driven into the ground then the length of conduit is dragged through a passage in the ground formed by the ground anchor with the result that when the ground anchor is installed at a desired depth then the length of conduit provides a drainage channel in the ground. The conduit is connected to the ground anchor by the connecting wire.

The inventors have designed an improved ground drainage apparatus and associated method, defined in the appended claims. The ground drainage apparatus comprises a ground anchor; and a length of conduit providing a drainage channel for water. The ground anchor comprises a socket for locating a rod for driving the ground anchor into the ground using the rod. The length of conduit is secured to the ground anchor by securing means such that the length of conduit directly engages the ground anchor. When the ground anchor is driven into the ground in a driving direction, the length of conduit is dragged through a passage in the ground formed by the ground anchor.

The particular features described in the specific embodiment can be advantageous in the context of such a ground drainage apparatus in which the length of conduit directly engages the ground anchor.

For a better understanding of the invention, and to show how the same may be put into effect, reference will now be made, by way of example only, to the accompanying drawings in which:

Figure 1 shows a prior art ground drainage apparatus;

Figure 2 shows a schematic side view of a ground anchor according to the invention;

Figure 3 shows a top view of the ground anchor of Figure 2;

Figure 4 shows a front view of the ground anchor of Figure 2; and Figure 5 shows a rear view of the ground anchor of Figure 2. Figure 1 shows a prior art ground anchor 13, with a connecting wire 14, and a strip 15 of conduit connected to the ground anchor 13 by the connecting wire 14. In order to attach the strip 15 to the ground anchor, the wire 14 must be crimped at two locations 14a, 14b to form two loops in the wire 14. A first loop engages the ground anchor 13, while a second loop engages the strip 15. The manufacture of such an assembly is costly and slow. The prior art ground anchor 13 is sized and shaped for “load locking” (the process of rotating and so engaging the anchor with the ground so as to lock the anchor at a fixed location), rather than for the task of most appropriately deploying a length of conduit. The prior art apparatus has the problem of the strip 15 being damaged by contact with the ground through which the ground anchor 13 is driven.

A preferred embodiment of a ground anchor 100 is shown schematically in Figures 2 to 5.

As can be seen from Figure 2, the ground anchor 100 comprises: socket 117; a tapered front end 118; and securing means 120.

The securing means 120 is arranged to secure a length of conduit 15 to the ground anchor 100. In this way, the conduit 15 may be directly attached to the ground anchor without the provision of further components, such as the wire 14 of the prior art. The conduit 15 directly engages the ground anchor 100. The conduit 15 is preferably in the form of a strip. In which case, the strip preferably has a thickness of between 2mm and 5mm.

The tapered front end 118 is arranged for penetration into the ground by a force applied by a rod located in the socket 117.

The socket 117 is arranged to receive a rod for driving the ground anchor 100 into the ground using the rod. The socket 117 is a bore extending in a longitudinal direction of the ground anchor 100.

The socket 117 may be in the form of a blind bore.

As is known in the art, a rod may be inserted into the socket 117 in the ground anchor 100 and then a driving tool used to drive the anchor 100 via the rod, in a percussive or pushing manner into the ground, dragging behind it a length of conduit 15. Once the anchor 100 has been driven deep enough then the rod will be removed from the anchor 100 and the ground to leave the anchor 100 in place with the length of conduit 15 extending backwards from the anchor 100 to another location, such as the surface of the soil.

As shown in Figure 3, the ground anchor 100 may be divided in the longitudinal direction into the front end 118, a mid-section 130, a rear section 140. The rear section 140 extends to the mid-section 130, and the mid-section extends to the front section 118. The securing means 120 is within the mid section 130. The tapered front end 118 is the leading end as the anchor 100 is driven into the ground.

A variety of shapes are possible for the tapered front end 118. However, it is preferable that the tapered front end 118 comprises two opposing concave-curved sides 118b, an upper ridge surface 118c and a lower surface 118d as shown in Figure 4.

The lower surface preferably extends laterally outwardly beyond the maximum width of the upper ridge surface 118c.

Preferably, the upper ridge surface 118c and the lower surface 118d meet along a flat driving edge 118a extending in the lateral direction. The flat driving edge 118a may be sharpened to a chisel point.

The flat driving edge 118a have a width of between 30% to 50% of the width of the ground anchor 100 (both measured in the lateral direction). By way of example, the width of the flat driving edge 118a may be from 40mm to 70mm, preferably 55mm, and the width of the ground anchor 100 may be from 100mm to 180mm, preferably 140mm.

The concave-curved sides 118b extend rearwardly from the ends of the flat driving edge 118a.

The outward curve of the concave-curved sides 118b can act to compress the ground outwardly laterally (i.e. in the direction in which the flat driving edge 118a extends) as the ground anchor 100 is driven into the ground under the action of a driving rod inserted into the socket means 117. The compression can stabilise the hole formed by the passage of the ground anchor 100 preventing, or lessening, the inward collapse of the hole onto the length of conduit 15 attached secured to the ground anchor 100. When the length of conduit 15 is in the form of a strip, this can prevent the potentially fragile edges of the strip from being damaged.

Collectively, the rearmost edge 118c’ of the upper ridge surface 118c’, the rearmost edges 118b’ of the concave-curved sides 118b, and the rearmost edge 118d’ of the lower surface 118d, define an outer profile 118’.

Preferably, the outer profile 118’ defines the perimeter of the ground anchor 100 when viewed along the longitudinal direction, which corresponds to the direction in which the socket 117 extends.

The mid-section 130, when viewed along the longitudinal direction, does not extend outside of the outer profile 118’ defined by the tapered front end 118. In other words, the mid-section 130 has a cross-sectional profile perpendicular to the longitudinal direction that does not extend beyond the outer profile 118’ defined by the tapered front end 118. The mid-section 130 may have a constant profile along its length (its length being defined in the longitudinal direction). The securing means 120 forms part of the mid-section 118. The length of conduit 15 is secured to the securing means 120 such that it does not extend outside of the outer profile 118’ defined by the tapered front end 118. Preferably, the securing means 120 is located such that the length of conduit 15 secured thereby is spaced from the outer profile 118’. the securing means is located such that the length of conduit 15 secured thereby is within the outer profile.

The securing means 120 is spaced from the rearmost edge 118c’ of the upper ridge surface 118c’ such that there is a gap therebetween perpendicular to the longitudinal direction (and perpendicular to the lateral direction). This can assist in preventing the ground from engaging the top of the conduit 15 close to the securing means 120.

The preferred form of securing means 120 is a clamp. The clamp comprises a clamping surface 122b of the ground anchor 100 and a clamp plate 122a. The conduit 15 may be held between the clamping surface 122b and the clamp plate 122a. Fixings may be provided to hold the clamping surface 122b and the clamp plate 122a together to grip the conduit 15.

For example, aligned apertures 124a, 124b may be formed in the clamping surface 122b and the clamp plate 122a for fixings such as screws or bolts. The apertures 124a, 124b may be located far enough apart that the conduit 15 can extend between them. Flowever, in order to maximise the width of the conduit 15 that may be secured by the securing means 120, holes may be formed in the conduit 15 for the fixings to pass through when inserted into the apertures 124a, 124b.

Undesirably, when the fixings penetrate the conduit 15, they define areas of highest stress in the conduit 15. In order that the tearing strength of the conduit 15 is not limited by the use of such fixings, the clamping surface 122b and the clamp plate 122a are preferably provided with complementary non-planar surfaces for gripping the conduit 15 therebetween.

For example, the clamping surface 122b and the clamp plate 122a may comprise one or more of: complementary inter-fitting grooves 126b and ridges 126a; and complementary inter-fitting cavities 126b and protrusions 126a.

The clamping plate 122a may have a thickness T of between opposing major surfaces, with the grooves 126b, ridges 126a, cavities 126b and/or protrusions 126a extending into or out of one of the major surfaces. The thickness T is preferably between 5mm and 30mm, preferably 15mm.

Although shown with the ridges 126a formed in the clamping plate 122a and grooves in the clamping surface 122b, the opposite is possible. Preferably, any grooves 126b and ridges 126a will extend in the lateral direction (i.e., perpendicular to the longitudinal direction). The complementary ridges 126a and grooves 126b may be configured such that when the clamping plate 122a and clamping surface 122b are spaced apart by a predefined gap G, the same gap G exists between the ridges 126a and grooves 126b. The gap G may match the thickness of the conduit 15. In this way, the conduit 15 can be held by the ridges 126a and grooves 126b without too high a pinching force, which could in some cases otherwise shear the conduit 15.

Preferred ridges 126a and grooves 126b are V-shaped in cross-section. The height of the V-shape may be from 5mm to 10mm, preferably 7mm.

Although not essential, in some embodiments, the ground anchor 100 may include a slot 128b at the forward end of the clamping surface 122b for receiving a hooked end 128a of the clamping plate 122a. If desired, the gap G discussed above may also be provided between the hooked end 128a and the slot 128b to accommodate the conduit 15.

In some embodiments, if extra drainage capacity is required, more than one conduit 15 may be secured to the ground anchor 100.

When the conduit 15 is formed as a strip, multiple conduits may be held by the securing means 120 as layers. In which case, at least one of the layers contacts the ground anchor clamping surface 122b.

When the conduit 15 is formed as a strip, it may be folded around the clamping plate 122a with two lengths of the same conduit 15 extending back from the fold in order to provide twice the capacity.

That is, a plurality of strips 15 may be stacked (in layers) and clamped in a single ground anchor 100, and one or more of these strips 15 may be wrapped around the clamping plate 122a to provide two tailing lengths of strip 15 for extra drainage.

As shown in Figure 5, the rear section 140, when viewed along the longitudinal direction, does not extend outside of the outer profile 118’ defined by the tapered front end 118.

The rear section 140 includes a rear surface 142 angled relative to the longitudinal direction. The rear surface 142 extends from the underside 144 of the ground anchor 100. The underside 144 is opposite the clamping surface 122b. The underside preferably is defined as a longitudinal extension of the rearmost edge 118d’ of the lower surface 118d of the tapered front end 118.

The rear surface 142 has formed therein the opening of the socket 117.

The rear surface 142 is sloped from the rear end of the underside 144 to the clamping surface 122b such that the rear end of the underside 144 extends further rearwardly in the longitudinal direction than the rear end of the clamping surface 122b. This can assist in preventing the ground from engaging the underside of the conduit 15 close to the securing means 120.

When secured, the conduit 15 overlaps the ground anchor 100 in the longitudinal direction and directly contacts the ground anchor 100. Since the conduit 15 is secured by the securing means 120 such that it is within, or spaced from the outer profile 118’, as it is drawn through the hole in the ground formed as the ground anchor 100 is driven by the driving rod in socket 117, the conduit 15 remains entirely within the cross-section of the hole in the ground without engaging the edge with any significant force that could damage the conduit 15.