AU656435B2 - Reinforced turf - Google Patents

Description

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i 1 656435

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPE C I F I C ATION FOR A STANDARD PATENT nr

ORIGINAL

Name of Applicant: GEORGE F. BARNES George F. Barnes Actual Inventor: Address for Service: SHELSTON WATERS Clarence Street SYDNEY NSW 2000 Invention Title: "REINFORCED TURF" Details of Associated Provisional Application No: PK9Ct1 dated November, 1991 The following statement is a full description of this invention, including the best method of performing it known to me:-

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2 The present invention relates to turf, and in particular to reinforced turf and a method for the preparation thereof.

The invention has been developed primarily for use in establishing grassed areas for drainage lines and other areas of concentrated water flows such as stream banks and will be described hereinafter with reference to that application. However, it will be appreciated that the invention is not limited to that particular field of 1 0 use and is also applicable to erosion prevention and soil stabilisation of grassed areas used for residential and sporting purposes.

Turf is generally grown and harvested at a location remote from an intended prepared site and subsequently transported and laid on that site. Once laid, the turf is allowed to establish itself to provide a grassed area. Where the site is steep, or where reasonably large quantities of water flow, the roots will not be able to readily establish anchorage with the underlying soil, and S 20 as such the turf is liable to be moved or damaged, or S "both. Moreover, in the event of a storm or the like the newly laid turf is likely to be disturbed and the underlying soil eroded.

In partial answer to these problems, a three dimensional matting has been laid over the prepared site, and onto this the turf is laid. Once established, the matting adds cohesion to the area of turf. However, such matting is expensive, and the turf laid above it will not 1 9r 3 be satisfactorily anchored to the underlying soil for four to six weeks. Subsequently, in the event of disturbance during this initial establishment period, the turf is likely to be broken up and moved, resulting in an unstable surface which is much more susceptible to erosion and less aesthetically pleasing.

It is an object of the present invention, at least in its preferred embodiment, to overcome or substantially ameliorate at least one of these deficiencies of the prior art.

According to one aspect of the invention there is provided reinforced turf characterised in that the reinforcing is a durable two dimensional flexible mesh, said mesh including strands comprised of two or more knitted filaments wherein said strands are alternatively entwined to two adjacent like strands to form a plurality of mesh cells which are subdivided by a first loosely woven filament.

Preferably also, the filaments are nylon and the cells are generally square, having a cell dimension in the range of 5mm to 40mm and more preferably 10mm to In a preferred form, the turf includes a second mesh adjacent the first and having a cell dimension in the range of 10mm to Preferably, at least one of the meshes includes a plurality of perpendicularly extending loosely knitted strands which intersect within said cells.

4- More preferably, the loosely knitted strands divide the cells into four substantially equal sub-cells.

According to a second aspect of the invention there is provided a method for producing reinforced turf including the steps of: preparing a site for growing turf, the site including a first soil layer exposed by prior harvesting; bringing a first durable two dimensional flexible mesh into contact with the first soil layer, said mesh including strands comprised of two or more knitted filaments wherein said strands are alternatively entwined to two adjacent like strands to form a plurality of mesh cells which are subdivided by a loosely woven filament; growing a grass layer from the soil layer, the grass layer including a stolon layer extending across the soil layer for entangling and retaining the mesh and a leaf layer extending from the stolon layer; and harvesting the turf.

Preferably, a plurality of adjacent meshes are Splaced above the first soil layer, each of the meshes having cells of different dimensions.

Preferably also, at least one of the meshes is at least partially buried in the soil layer for allowing the roots extending from the grass layer to entangle and retain the mesh. More preferably, after bringing the mesh into contact with the first soil layer the burying \U is effected by placing a second soil layer over the iz/ kJ 4a mesh. Even more preferably, the second soil layer includes compost.

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a cross-section of reinforced turf according to the invention; i k i I io I i YI 5 Figure 2 is a top view of mesh included in the turf of Figure 1; Figure 3 is a cross-section of an alternative embodiment of the invention; and Figure 4 is a top view of an alternative mesh for ise in the turf of Figure 1 or Figure 3.

Referring to Figure i, a reinforced turf 1 includes a durable two dimensional mesh 2 lying along a ground horizon 3. A grass layer 4 extends across horizon 3 and retains mesh 2. Roots 5 extend downwardly from horizon 3 into soil layer 6 and terminate at a lower horizon 7 formed when turf 1 was harvested.

Referring in particular to Figure 2, mesh 2 includes a plurality of strands 8, 9, 10, 11, 12 and 13 each being formed from two open knit nylon filaments.

Sequential portions of each strand are alternately knitted to corresponding portions of adjacent strands to form a plurality of mesh cells 14. For example, strand 11 is joined to strand 10 at portions 15 and to strand 12 at portions 16.

The length of strand 11 extending between portions and 16 is referred to as the cell dimension and is preferably in the range of 5mm to 40mm, and more preferably in the range of 10mm to 30mm. A preferred mesh is produced by Sarlon Industries Pty Ltd and marketed as product number 62211, which is produced from a HDPE monofilament knitted to form generally square cells having a cell dimension of I r ba-- 6 6 Referring to Figure 4, an alternative mesh 21 is substantially similar to mesh 2 with corresponding features being denoted by corresponding reference numerals. Mesh 21, however, includes additional loosely knitted filaments 22 which intersect within respective cells. Filaments 22 divide the cells into four substantially equal sub-cells. The inclusion of these additional filaments allows more secure retention between the mesh 21 and the turf while also allowing the mesh to remain flexible. If required, the cell size can be increased and a number of separate loosely knitted filaments included to divide the cells into a greater number of sub-cells.

Filaments 22 are threaded through the mid point of strands 8 to 13 and are intended to provide sites for additional entanglement with the grass. The overall strength of the reinforcing is provided by stands 8 to 13.

Meshes 2 and 21 are stable when exposed to ultraviolet light, and as such, even if they do become 20 exposed through wear or removal of the associated turf, they will continue to provide a reinforcing for any regrowth. Additionally, the high strength of the mesh (which is greater than 60 Tex high density polyethlene or nylon) results in any exposed portion being resistant to tearing or damage.

Grass layer 4 includes a layer of runners or stolons 17 and leaf layer 18 extending upwardly from the stolon 17. The cell dimension of mesh 2 enables a 4_L~i~

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7 sufficient proportion of stolons 17 to entangle with the mesh without hindering their growth across horizon 4.

Stolons 17 are also able to grow between individual filaments due to the open knit configuration which furthers the anchorage of turf 1 to mesh 2. Both of these features effect increased integrity throughout turf 1.

The reinforced turf is grown in the same time as it takes to grow turf that is not reinforced because of the two dimensional nature of mesh 7. Moreover, when harvesting the reinforced turf cutting depths are generally the same as those for unreinforced turf.

The flexible nature of mesh 2 does not prevent or hinder harvested turf strips from being formed into rolls which.are easily transported to and positioned on the new site.

Once positioned on such a site, roots 5 at horizon 7 are immediately adjacent underlying soil.

Subsequently, root growth will effect anchorage of turf 1 to the new site. Mesh 2 effectively provides a binding force throughout the turf and in the event of water runoff or wear turf 1 will be less likely broken up or removed from the site both during and after the initial establishment period. Once established, turf 1 is capable of withstanding flows in excess of 4m 2 /sec and thereby prevent erosion and increase soil stability.

From the above it is evident that the invention provides a reinforced turf, which alleviates the need for

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I b 8 either an underlying matting, or an overlying mesh. The reinforced turf need simply be laid on the prepared surface, or if steep slopes or high water flows are encountered, pegs are driven into the turf to engage the mesh and securely retain the turf in a fixed position.

Where turf 1 is to be laid in areas subject to extreme conditions, two or more flexible meshes are included along horizon 3. Preferably, the meshes have different cell dimensions or have similar dimensions but are spaced such that cells 14 overlap at least two cells on an adjacent mesh. Stolons 17 entangle and entwine with both meshes to effect a more secure reinforcing. If required the separate meshes are able to be physically joined by way of ties or the like.

An alternative embodiment of the invention is illustrated in Figure 3 where corresponding features are denoted by corresponding reference numerals. Mesh 2 lies intermediate soil layer 6 and along horizon 20 and is entangled and retained by roots 5. That portion of 20 layer 6 disposed above horizca 20 is either on both topsoil or compos which was spread over mesh 2 to encourage plant growth during the initial growing period. If required an additional mesh can be included along horizon 3.

After a layer of turf is harvested from a site, the roots contained within the soil below horizon 7 (along which harvesting took place) continue to grow and will form a new grass layer in due course. Subsequently,

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9 after harvesting mesh 2 is placed over the site to allow entanglement as stolons 17 and leaf layer 18 grow.

If required, once mesh 2 is positioned on the site a 5mm to 10mm layer of soil or organic matter is placed on the mesh such that roots 5 will grow and entangle the mesh to form a reinforcing layer below stolons 17. A second and even third mesh layers are included for entanglement by stolons 17 previously described if the application demands a turf of increased integrity.

Once grass layer 4 is sufficiently established, 'turf 1 is harvested along horizon 7 and formed into rolls. These rolls are generally from 15mm to thick, 0.45 meters to 1.2 meters wide and 2.4 meters to meters long, however, many other sizes are able to be produced. The mesh strength enables turf to be cut and formed into rolls of at least 250kg which are able to cover at least 15m 2 The rolls are subsequently }j .transported to the desired site and placed to produce a S* grassed area which will quickly establish anchorage with the underlying soil and remain interconnected across a large area due to the integral mesh.

The prior methods of laying turf and three dimensional mesh have required the preparation of a site which includes the digging of trenches about the periphery of that site for burying the edges of the mesh. The mesh is then laid over the site and pegged into position, with an overlap between adjacent meshes of approximately 10cm being required. Thereafter the trenches are filled and compacted to retain the mesh about the periphery and further topsoil is spread to fill the mesh. The turf is then laid onto the mesh and topsoil layer and pegged into position.

Laying turf 1, however, simply requires that the preparation of a suitable topsoil layer on which the turf is to be laid. If required, pegs can be used to positively locate the laid turf. There is neither need to overlap the turf nor to bury the outermost edges.

This procedure saves substantial amounts of time and labour, while also resulting in a reinforced turf which quickly establishes roots within the underlying soil.

The invention provides a cheap and simple reinforced turf which alleviates the problems of the prior art. Turf 1 both grows and establishes natural anchorage on a predetermined site in the same time as unreinforced turf. However, the integral mesh ensures that no covering or additional measures are necessary to artificially anchor the turf during or after the initial 20 period.

Moreover, the reinforcing remains embedded within the turf after it becomes established to provide additional integrity and resistance to wear.

Consequently, the resultant turf exhibits enhanced wearing properties while also resisting water damage.

The mesh is ideally non-metallic to provide greater flexibility and to avoid corrosion problems.

Furthermore, the flexible mesh, when cut by a turf 11 harvester, does not leave sharp protrusions which may injure the persons handling the turf.

The invention is particularly suited for producing a reinforced turf grown from couch or kikyu grass, however, other grasses or mixtures of grasses are also 1 suitable.

The placement of the mesh or meshes between the roots and stolons allows the grass plants to effect a more stable and secure entanglement with the mesh. That is, the stolons are generally stronger than the roots and allowing the mesh to be entangled with these stolons increases the resultant binding force. Ideally, the mesh would be entangled by both roots and stolons.

Although the present invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

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Claims (11)

1. 2. A method according to claim 1 wherein a plurality of Sadjacent meshes are placed above the first soil layer.
2. 3. A method according to claim 2 wherein each of the meshes have cells of different dimensions.
3. 4. A method according to claim 1 wherein said two dimensional flexible mesh is at least partially buried in the soil layer for allowing the roots extending from the grass layer to entangle and retain the mesh. A method according to any one of the preceding claims wherein said cells are generally square and have a cell dimension in the range of 5 mm to 40 mm.
4. 6. A method according to claim 5 wherein said cell ,NT I 7C~Ji7; 13 dimension is in the range of 10 mm to 30 mm.
5. 7. A method according to any one of the preceding claims including maintaining a second durable two dimensional flexible mesh adjacent the first wherein said second mesh has a cell dimension in the range of 10 mm to 80 mm.
6. 8. A method according to any one of the preceding claims wherein at least said first mesh is produced from a non-metallic material.
7. 9. A method according to claim 9 wherein said material is HDPE. Reinforced turf produced in accordance with any one of claims 1 to 9.
8. 11. Reinforced turf characterised in that the reinforcing is a durable two dimensional flexible mesh, said mesh including strands comprised of two or more knitted filaments wherein said strands are alternatively entwined to two adjacent like strands to form a plurality of mesh cells which are subdivided by a first loosely woven filament.
9. 12. Reinforced turf according to claim 11 wherein said first filament intersects within said cells a second substantially perpendicularly extending like filament.
10. 13. A reinforced turf substantially as herein described with reference to Figure 4.
11. 14. A method for producing reinforced turf substantially as herein described with reference to Figure 4. DATED this 1st Day of November, 1994 GEORGE F. BARNES Attorney: LEON K. ALLEN Fellow Institute of Patent Attorneys of Australia Aof SHELSTON WATERS L2 ABSTRACT A reinforced turf includes a durable two dimensional mesh lying along a ground horizon A grass layer extends across horizon and retains mesh Roots extend downwardly from horizon (3) into soil layer and terminate at a lower horizon (7) formed when turf was harvested. Also disclosed is a method for growing reinforced turf ooeUo p:LI i 0kf