WO2007061289A1

WO2007061289A1 - Sport field

Info

Publication number: WO2007061289A1
Application number: PCT/NL2006/000584
Authority: WO
Inventors: Arnold Jan Knottnerus; Adriaan Johannes Markusse
Original assignee: Arcadis Regio B.V.
Priority date: 2005-11-22
Filing date: 2006-11-21
Publication date: 2007-05-31
Also published as: EP1951960A1

Abstract

The invention relates to a sport field or artificial grass. Below the artificial grass there is a draining, load spreading and bearing structure of unbound material granules, o.a. sand. Below this structure there are drain tubes. Within this structure there is minimally 3 cm below the artificial grass layer a water permeable, interrelated, light weight layer with resilient/elastic properties. This sport field has the sport technical properties of a natural grass field.

Description

Title: Sport field.

This invention relates to a bound (e.g. athletics track at asphalt layer), partly bound (e.g. artificial grass) and/or unbound (e.g. natural grass) sport field, e.g. for football, tennis or hockey. This invention is by the way also applicable for different outdoor sport accommodations, e.g. an athletics track, possibly with a water permeable top layer (artificial sport mat) of e.g. plastic/polymer material, founded onto e.g. a freezing/frost damage free package (un) bound granules stone like material. The invention also relates to the method for making such outdoor sport accommodation and/or keeping it in proper condition, e.g. frost free.

Without limitation, the invention is in the following however described by way of an artificial grass field.

At this moment the construction of an artificial grass field in Netherlands is as follows: Drainage tubes are at lowest level. Immediately or at some distance there above an unbound sand package with thickness of approximately 38 cm is present. On top of it there is a so called sport technical unbound layer with thickness of approximately 8 cm (e.g. a mixture of sand and/or rubber and steagran or lava stone) . On top of that the artificial grass fabric (semi-bound since loose rubber granules and/or sand is spread into it) approximately 1-6 cm thick. The sport technical layer is sufficient permeable for water and provides a level and stable substrate for the grass fabric. The sand package provides sufficient water drainage and goes sufficient deep to provide a frost free structure. In Netherlands the structure is frost free if at 20 degrees Celsius frost, at a depth of 50 cm no frost is present or the prevailing frost and the possible consequences of it are acceptable.

To install such artificial grass field, it is typically required to dig a construction pit. Generally, the grass field will be flush with the earth surface, such that a pit of approximately 50 cm deep must be dug.

The costs for constructing an artificial grass field is ever increasing and complicated since, a.o., an increasing shortage of convenient raw materials such as sand for the sand package and the increasing requirements for processing the soil that comes free with digging the pit.

The object of this invention is to at least partly solve one or more of the disadvantages of the prior art.

It is thus proposed to provide below the artificial grass fabric a layer of thermally isolating material. This layer can be immediately below the grass fabric, or at a distance there below, e.g. onto, within or below the sport technical layer or onto, within or below the sand package; thus preferably within the construction height. By applying the thermally isolating layer it is now possible to decrease the height of the frost free structure such that digging can be decreased or even avoided, and less raw material is used.

It is appreciated that the thermally isolating capacity of the layer of thermally isolating material is substantially better (e.g. at least 2, 3, 4, 5 or 10 times) then that of unbound sand or different granule like, stone like material such as nowadays applied below an artificial grass fabric. Preferably said capacity is substantially equal to or within the same order of magnitude as that of mineral wool, cork or a different isolating material that is typically use in home building. Preferably the thermal isolation coefficient of this layer is at most 0.1 or 0.08 or 0.06 W/mK (for comparison the figures for the following materials : soil 0.6; glass wool 0.04; air 0.025) . By applying this isolating layer the sand package will, if the construction height or frost damage freedom is kept equal, become substantially thinner, e.g. at least 10 or 15 or 20 or even 30 cm thinner. Preferably the isolating material contains more then 50 or 60 volume percentage air. Its layer thickness is preferably at least 5 or 10 mm, possibly at most 40 or 50 mm.

The layer of thermally isolating material must have sufficient compression strength to be substantially incompressible with the typical loads it will encounter when applied below the artificial grass fabric (e.g. generally the weight of the material layers resting on top of it and locally the load from standing, walking, jumping, etc. of individuals as point loads) . It has come out that by using a thermal isolating layer the frost damage free construction (sport layer (top layer) , sport technical layer, isolating layer, sand package) can be designed with a height between approximately 15 and 30 cm, such as approximately 20 cm (in stead of the usual 50 cm) .

Excellent results were obtained with the following materials (supplied by Akzo Nobel) : Enkaflex 20; Enkaspacer 5025; Enka underlay 10. These have a layer thickness between 1 and 2 cm. They have a sandwich structure with parallel thin (less than 5 mm thick) skin layers of geotextile, spaced by a random pattern of in the direction of the thickness extending thick threads of polymer material of the surprising airy (more than 80 volume percent air) core. Until now, these materials were applied as shock absorbing layer below an artificial sport layer installed onto, e.g., a rocky substrate. Obviously the invention is not limited to application of these isolating materials.

A non-limiting example of the invention is as follows: The artificial fabric bears onto a sport technical layer that bears onto a thermally isolating layer that bears onto a sand package below which drainage tubes are present. The sport technical layer is comprised of an unbound granule mixture of stone like material of large and small granules, e.g. with a diameter substantially in the range from 1 mm to 20 mm. Thus this layer is comprised of an unbound stable mineral skeleton with load spreading and bearing capacity wherein the unavoidable space between larger granules is taken up by the smaller and still smaller granules while the water permeability is ensured. Rubber granules are added. The sand package consists of an unbound granule mixture of stone like material of small granules, e.g. with a diameter substantially in the range smaller than 2 or 3 mm. Layer thicknesses are preferably as follows: sport technical layer 5 to 10 cm; isolation layer 2 to 5 cm; sand package 0, 5 or 10 cm minimum and/or 10, 15, 20 or 25 cm maximum. One or more of these layers can possibly have a different layer thickness or be absent. The sport field can be constructed as follows: First a pit is dug, then the drainage is provided, then the layers are provided in succession. Possibly digging can be limited to making trenches in which the drainage tubes are placed. The complete frost damage free structure is then located on top of the earth surface. In another situation the frost damage free structure will be partly sunk in the ground, e.g. by partly digging a pit. Alternatively the proposal is to, in combination with the above or independent there from, flow a temperature controlling gas or liquid below the natural or artificial grass fabric, for which convenient means can be provided, such as a gas or liquid pump. Preferably said gas or liquid is flown through a layer that is intended for that, which is e.g. the layer of thermally isolating material . It is preferably provided that the concerning gas or liquid is limited to a predetermined layer by making the top and/or bottom thereof gas or liquid impermeable. In case of a relatively thin layer, a substantially two dimensional flow of the gas or liquid is provided. Preferably use is made of a feature, such as a spreading or collecting element, such that gas or liquid flows to/from a central supply or discharge line, respectively, into/from the layer below the grass fabric and general processing of the grass layer is possible, e.g. heating the grass layer with a view to e.g. frost protection. Homogeneous tempering is then the object.

In a preferred embodiment the fluid is flown at a level above (e.g. immediately above) a layer of thermally isolating material (e.g. the layer of Enkaflex 20 or a different above discussed thermally isolating layer) . With thermal isolation below the thermally active fluid, loss of energy towards the substrate can be limited. For some cases it can further be advantageous, to install pipelines below the grass layer through which the thermal active fluid is flown. The fluid can be galvanic or magnetic flow, etc.

Also the surprising understanding that by providing the layer of thermally isolating material at some distance below the top layer, the sport technical properties (e.g. energy release/damping during running) increases substantially, belong to the invention. The durability of these properties also increases. It is already known to provide a cohesive resilient/elastic layer immediately below the top layer (i.e. the (artificial) grass layer or such layer), e.g. of rubbery material, o.a. with a view to load spreading and flatness action. In practise, this yields unpleasant running experiences.

It has come out that this effect of the thermally isolating layer can also be obtained with a different convenient material layer with preferably minimally one of the following properties: light weight, cohesive, (resilient) elastic. Examples are foam materials, bound rubber granules, sheets of polystyrene. The thickness of this layer is preferably between approximately 0.5 and 5 cm. This layer is preferably present minimally 2, 3 or 5 cm below the top layer and preferably not further than 20 or 30 cm below the top layer. Most preferably this layer is between 10 and 15 or 20 cm below the top layer. Between this layer and the top layer, preferably unbound (fine or coarse) granule like material is present, such as of sand, lava, steagran. This layer can be on top, within or below the so called sport technical (unbound) layer.

The invention can thus also be applied to only improve the sport technical property of the field. The invention thus also relates to a field with a typical construction (e.g. top layer, sport technical layer, sand package) and construction height, with an added cohesive layer, possibly thermally isolating, at some distance below the top layer.

Possibly the layer that improves the sport technical properties and/or thermal isolation is minimally approximately 3 or 4 cm below the top layer and/or is unbound. This layer, or its core, preferably contains minimally approximately 80, 90 or 95 volume percent air/gas. This layer can be connected to a venting system or an edge part of it can extend upwards until e.g. below the top layer for immediate venting.

In addition to the above or alternatively one or more of the following can be obtained with the invention: saving rubber; avoiding collapsing of the field; environment friendly. The invention can also be applied to so-called horse tracks in which case the top layer of (artificial) grass is absent or replaced by a different top layer, typical for horse tracks.

Different embodiments also belong to the invention, e.g. obtained by combining one or more aspects (or equivalent (s) of it) of the one herewith disclosed embodiment with one or more aspects (or equivalent (s) of it) of one or more different herewith disclosed embodiments . All described features make as such or in arbitrary combination the subject of this invention, also independent from their arrangement in the claims .

Claims

1. Sport field, comprising a the top layer providing artificial grass layer; at a level there below an unbound, water permeable layer of a stable skeleton providing granule mixture and a durable auxiliary layer with resilient/elastic and/or thermal isolating properties .

2. Sport field according to claim 1, wherein the auxiliary layer is at some distance below the top layer, preferably minimally

2. 3, 5 or 10 and/or maximally 20 or 30 or 40 cm below the top layer .

3. Sport field according to claim 1 or 2, wherein the auxiliary layer comprises a foam material such as polystyrene or polyurethane, or cohesive/bound rubber granules.

4. Sport field according to claim 1, 2 or 3, wherein between the top layer and the auxiliary layer an unbound, water permeable fine and/or coarse granule like layer of e.g. stone like material, such as sand, lava and/or steagran, is present

5. Sport field according to any of claims 1-4, wherein below the auxiliary layer a granule like package, e.g. sand package, possibly with drain, is present.

6. Sport field according to any of claims 1-5, wherein the auxiliary layer is bound and/or cohesive; and/or wherein the auxiliary layer is between 5 and 50 or 100 mm thick.

7. Sport field according to any of claims 1-6, comprising one or more of the following: a sport technical, load spreading and/or bearing layer; a layer with a thickness between 5 and 10, 15 or 20 cm; a layer with added elastic granules of e.g. rubber; a freezing/frost free bearing structure with drainage elements, e.g. tubes; a between 10 cm and 25 cm thick, water permeable layer of an unbound granule mixture stone like material;

Stone like material with a diameter substantially smaller than

2 or 3 mm; or substantially between 1 en 20 mm; a cohesive, light weight layer with resilient/elastic properties; a cohesive, light weight layer minimally 5 or 10 cm and/or maximally 20 or 30 cm below the top layer; a cohesive layer comprising minimally 60, 70 or 80 volume percent air; a cohesive layer with a thickness between 5 en 50, 75 or 100 mm; a cohesive layer having a coefficient of thermal isolation of at the most 0.2 or 0.1 or 0.08 or 0.06 W/mK; wherein one or more of the layers can be integrated; such that this sport field e.g. imitates the sport technical properties of a natural grass field substantially completely and is free from collapsing.

8. Sport field according to any of claims 1-7, wherein the cohesive layer has a sandwich structure with parallel thin skins and there between a very airy core with more then 80 volume percent air and preferably in the thickness direction extending threads of e.g. polymer material.

9. Sport field according to any of claims 1-8, wherein an cohesive resilient/elastic, light weight layer immediately below the top layer is absent.

10. Sport field according to any of claims 1-9, wherein above the draining tubes an water impermeable of badly permeable layer is absent.