SPORTS FIELD CONSTRUCTION

Abstract

A sports field has a stable, impermeable substrate, a water distributing layer provided over the substrate and an artificial turf layer over the water distributing layer. A bund defines a perimeter of the sports field and extends from the substrate to at least the height of the artificial turf layer. A drain channel having inlets at a height to communicate with the water distributing layer is provided such that water can flow from the water distributing layer into the drain channel and vice versa. As a result of this constructions, there is formed a containment, defined by the bund surrounding the field and by the substrate. Water can be held within the containment in the water distributing layer allowing for water attenuation and cooling of the sports field.

Claims

1-22. (canceled)

23. A method of cooling a sports field comprising an artificial turf layer on a porous water distributing layer within an impervious containment, the method comprising filling the impervious containment with water to a depth sufficient to immerse at least part of the artificial turf layer over the full area of the sports field and subsequently draining the water from the containment.

24. A sports field comprising: a stable, impermeable substrate; a water distributing layer provided over the substrate; an artificial turf layer over the water distributing layer; a bund defining a perimeter of the sports field and extending from the substrate to at least the height of the artificial turf layer; and a drain channel having inlets at a height to communicate with the water distributing layer such that water can flow from the water distributing layer into the drain channel and vice versa.

25. The sports field according to claim 24, wherein the drain channel is integrally formed with the bund.

26. The sports field according to claim 24, further comprising a water management facility arranged to control the height of the water within the drain channel to determine whether water flows from the water distributing layer into the drain channel or vice versa.

27. The sports field according to claim 24, wherein the drain channel extends below and above the water distributing layer.

28. The sports field according to claim 24, wherein the stable impermeable substrate comprises a stabilised soil substrate.

29. The sports field according to claim 24, wherein the stable impermeable substrate comprises an impervious membrane or coating.

30. The sports field according to claim 24, wherein the upper surface of the water distributing layer is substantially horizontal, preferably having no gradient greater than 1 in 100 and optionally less than 1 in 300.

31. The sports field according to claim 24, wherein the water distributing layer comprises recycled plastic granules and a binder.

32. The sports field according to claim 24, wherein the water distributing layer has a void ratio of between 20% and 70%, optionally around 45%.

33. The sports field according to claim 24, wherein the water distributing layer has a depth of between 10 mm and 100 mm, optionally around 40 mm.

34. The sports field according to claim 24, wherein the water distributing layer has a Young's modulus in compression of between 0.1 MPa and 50 MPa, preferably between 1 MPa and 10 MPa and more preferably between 2 MPa and 5 MPa.

35. The sports field according to claim 24, further comprising a resilient layer provided between the water distributing layer and the artificial turf layer.

36. The sports field according to claim 24, wherein at least the upper extremity of the bund comprises resilient material.

37. A method of constructing a sports field comprising: providing a stable, impermeable substrate; providing a water distributing layer over the substrate; installing an artificial turf layer over the water distributing layer; forming a bund defining a perimeter of the sports field and extending from the substrate to at least the height of the artificial turf layer; and providing a drain channel communicating with the water distributing layer such that water can flow from the water distributing layer into the drain channel and vice versa.

38. The method of claim 37, wherein providing the substrate comprises stabilisation of the existing on-site soil to a CBR of greater than 15 and preferably to a depth of at least 100 mm.

39. The method of claim 37, wherein forming of the substrate comprises providing an impermeable membrane or coating over a stabilised base.

40. The method of claim 37, wherein providing the water distributing layer comprises in-situ laying of a semi-fluid mass comprising recycled plastic granules and a binder, levelling the semi-fluid mass and allowing the semi-fluid mass to solidify to form a rigid porous layer.

41. The method of claim 37, wherein providing the water distributing layer comprises paving the substrate with pre-formed porous slabs of recycled plastic granules.

42. The method of claim 37, wherein forming the bund comprises installation of hollow curb-stones, to form an integral drain channel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The features and advantages of the invention will be appreciated upon reference to the following drawings of a number of exemplary embodiments, in which:

[0061] FIG. 1 shows a sectional view of a portion of a sports field according to the invention; and

[0062] FIG. 2 shows a cross-section through the sports field of FIG. 1 along line II-II showing the water management system.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Example

[0063] FIG. 1 shows a perspective sectioned view of a portion of a sports field 1 according to an example of the present invention. The sports field 1 comprises three main layers, namely a substrate 2, a water distributing layer 4 and an artificial turf layer 6. The whole is enclosed by a bund 8.

[0064] The substrate 2 is a soil stabilised layer having a depth of 300 mm as will be described in further below. Underneath the substrate 2 is the natural soil layer 10, which is also present behind the bund 8. On the upper surface of the substrate 2 is provided a bitumen coating 12, which imperviously seals the substrate 2 up to the bund 8.

[0065] The water distributing layer 4 is a 40 mm thick layer of a 50% by weight mixture of recycled plastic granules and rubber granules bound together with a polyurethane binder present at 14% by weight of the total. The resulting layer has a void ratio of around 45%.

[0066] The artificial turf 6 is a premier tufted third generation turf having a pile height of 60 mm and a rubber and sand infill available from Tiger Turf™ as Total Turf 60XQ.

[0067] The bund 8 is formed by interlocked hollow kerbstones 14 provided with a drain channel 16 and inlets 18. The kerbstones 14 are of 600 mm depth and the inlets 18 are slots of 50 mm length, extending to a level 100 mm below the top of the bund 8. The kerbstones 14 are set in a concrete haunch 20 and are sealed to each other by a mastic bead 22. The substrate 2, and the bund 8, together with the drain channel 16 form a containment 24 which is largely impervious and can retain water for a significant period. The drain channel 16 is connected to a water management facility 26, which controls inflow to and outflow from the containment 24

[0068] FIG. 2 shows a cross-section through the sports field 1 along the line II-II in FIG. 1 showing the substrate 2, the water distributing layer 4, the artificial turf layer 6 and the kerbstones 14. FIG. 2 also illustrates the water management facility 26, which comprises a chamber 28, connected to an outlet 30 from the drain channel 16. It will be understood that although a single outlet 30 is shown, there may be a plurality of such outlets 30 around the periphery of the sports field 1, connected to the chamber 28 by a ring drain or the like. Chamber 28 is further connected through a valve flow gate 32 to the storm water drainage system 34. In addition a water supply pipe 36 is attached to the top side of the chamber 28. In the illustrated example, this water supply pipe 36 is connected to the mains or another source of water such as a recycled water by a stop cock 38. It will be understood that the water supply pipe 36 may be connected to any suitable source of water such as a recycled water and that a pump arrangement may be provided rather than a stop cock. A controller 40 ensures control of the valve flow gate 32 and the stop cock 38, which may be automated or manually controlled.

[0069] Installation

[0070] Installation of the sports field 1 took place by first removing the existing top layer of turf and organic material from the site. The subsoil 10 was then analysed to determine the required soil stabilisation process. In the illustrated example, the soil was a relatively heavy clay soil. In order to dry out and granulate this soil it was mixed with a set dosage of lime to a depth of 300 mm. The process was carried out using a Wirtgen WR2500 SK integrated mixer to ensure that the mixed layer was consistent both in mix quality and also in the depth of the mixed layer. Following this first stage treatment the area was leveled by a laser levelling bulldozer and then rolled with a 20 tonne roller. The area was then left overnight so that the chemical reaction between the lime and the soil could take effect.

[0071] In a second stage of soil stabilisation, cement and water were introduced in amounts determined by the analysis in order to create a hydraulically bonded material. The Wirtgen mixer was again used whereby the machine controlled the precise amount of water and cement required. Cement was delivered from tanks inside the machine while water was fed from a browser in front of the machine. Again the soil was treated to a depth of 300 mm. During the process, samples of the mixed material were periodically tested to check that the material was behaving as predicted. Following soil mixing, the laser levelling bulldozer again graded and leveled the materials to a surface tolerance of +−10 mm over a 3 metre straight edge, while the 20 tonnes roller compacted the surface. After completion, in order to seal the finished surface of the substrate 2, it was sprayed with bitumen coating 12.

[0072] After 3 days the surface of the substrate 2 was CBR measured in 4 locations with the following results: [0073] Location 1—64% [0074] Location 2—30.8% [0075] Location 3—30.1% [0076] Location 4—37%

[0077] After 4-7 days of treatment, the substrate 2 was exceptionally stable, would carry heavy equipment and could be trafficked without any effect. CBR levels of around 60% were estimated over the whole surface.

[0078] In order to install the kerbstones 14, a circular saw was used to cut the substrate 2 cleanly with a 75 mm gap to the front of the bund 8. The kerbstones 14 were then joined to each other with a mastic bead 22 to ensure a watertight seal. Once the kerbstones 14 were installed and set, the water distributing layer 4 was laid. First, the plastic and the rubber granulates were metered in equal amounts using a SMG MixMatic M6008 with additional hopper to add the granules to a 14 wt % PU feed. Then the area was paved using a SMG PlanoMatic P936 to a depth of 40 mm and at a rate of 20 kg of mixed material to 2.8 kg of PU binder per m.sup.2. The final surface tolerance of the paved layer was +−10 mm over a 3 metre straight edge. After 48 hrs of curing the water distributing layer 4 layer was tested using a Deltec™ club tester. The average results from 10 test locations were the following: [0079] Force Reduction—50.2% [0080] Surface Deformation—5.4 mm [0081] Energy Restitution—35.8%

[0082] Once the water distributing layer 4 was fully cured, the turf 6 was installed in a conventional manner, and filled with a mixture of rubber granules and sand. The turf 6 was laid up to the bund 8 at all sides and to the same level.

[0083] Strain Testing

[0084] A sample of water distributing layer 4 manufactured to the same specification as the example described above was laboratory strain tested in compression to determine its Young's modulus. The sample size was 250 mm square, having a nominal thickness of 40 mm. The nominal density of the sample was 520 kg/m3. An Instron compression machine was utilised, with a load cell of 10 kN capacity. The loading plates were: 100 mm top compression plate, 300 mm bottom compression plate.

[0085] The test protocol was as follows; [0086] 1. Compression rate set at 5 mm/minute. [0087] 2. A small seating load of 50N was applied to the sample at the start of the test to ensure good contact, and the deformation gauge set to 0 mm. [0088] 3. The sample was subjected to two pseudo-static load cycles. A further cycle was used to evaluate the effects of a maintained load (creep) test. [0089] a. The sample was compressed up to the pre-set load of 2500N. The load was then removed and the sample examined for any signs of damage. [0090] b. The sample was compressed up to the pre-set load of 5000N. The load was then removed and the sample examined for any signs of damage. [0091] c. The sample was compressed to the pre-set load of 2500N and the load maintained for a period of 7 hours. [0092] 4. The samples were observed during the compression and the real-time Load vs Deformation behaviour observed.

[0093] The vertical strain at 2500N was estimated at approximately 10%. The gradient of the force versus deformation graphs permitted an estimate of the sample (spring) stiffness to be in the range of 600 kN/m. The stress/strain data suggests an (elastic) stiffness modulus of approximately 3.2 MPa.

[0094] The test was repeated with a 24 mm thick sample having the same composition as that of the previous sample. This had a nominal density of 490 Kg/m3. The vertical strain at 2500N was approximately 17% and the gradient of the force versus deformation graph permitted an estimate of the sample (spring) stiffness to be in the range 570 kN/m. The stress/strain data suggests an (elastic) stiffness modulus of approximately 2 MPa.

[0095] Operation

[0096] Operation of the sports field 1 will now be described with reference to FIGS. 1 and 2. During use, rain water falling on the sports field 1 percolates through the artificial turf layer 6 into the water distributing layer 4. The level surface of the substrate 2 allows the water to distribute across the whole of the sports field 1, assisted by capillary action within the water distributing layer 4 and its open structure. The inlets 18 to the drain channel 16 are at the height of the bitumen coating 12 at the upper surface of the substrate 2 and allow the water to escape into the drain channel 16 from where it can flow through the outlet 30 to the chamber 28 and through the valve flow gate 32 to the storm water drainage system 34. If desired, the valve flow gate can be closed, whereby water will back-up within the drain channel 16 until it reaches the level of the inlets 18. Any further rainfall will remain within the containment 24. The valve flow gate 32 may be controlled to keep the level of water at a predetermined level within the water distributing layer 4 or may be set to slowly release it into the storm water drainage system 34 to allow for attenuation.

[0097] During warm periods, additional water may be introduced into the water management facility 26 through the water supply pipe 36 to cause the water level in the containment 24 to rise above the level of the water distributing layer 4. By increasing the water level to completely or partially flood the artificial turf layer 6, the sports field 1 can be quickly cooled. Subsequently draining the water from the containment 24 allows the designated sport to be practiced, while the artificial turf layer 6 may continue to evaporate moisture thereby keeping the sports field 1 cool. It is noted that although not illustrated in the present design the water management facility 26 may be provided with a buffer reservoir having a capacity equal to the size of the containment or at least the part of the containment above the water distributing layer 4, allowing this portion of the sports field 1 to be filled and emptied prior to play commencing.

[0098] Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art. In particular, the arrangement of sub-base construction and its design may be based on local geological conditions and materials available. Thicknesses and ratios of granulated materials of the water distributing layer, kerb size and shape, drainage hole frequency, size and shape water inlet and outlet points attenuation and water flow rates, and water input and extraction facilities may all be dependent on performance requirements and may be distinct from the schematically illustrated design.

[0099] Many modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.