EP0096908B2 - Bulk material surface for football fields and method for its production - Google Patents

Abstract

1. Bulk material stratum (10) for athletic fields, notably soccer fields, comprising a multilayered top structure (12, 13, 15) pervious to water on a substratum (11) or substructure (11), wherein the covering layer (15) constituting the field surface and forming part of the top structure is pervious to water as well, characterized in that the covering layer (15) consists, at least in a predominant weight portion, of a substantially platelet-shaped bark material, the particles of which each have a maximum length of 100 mm as well as a thickness of less than 10 mm, which particles are compacted to form an essentially tread-resistant covering stratum of the bulk material stratum (10).

Description

The invention relates to a bulk material area for soccer fields. The invention further relates to a method for producing such a bulk material surface.

Sports fields are subject to very high loads when used as intended, especially if the sport is associated with high positive or negative accelerations in the movement of the athletes and / or sports shoes with studs are used. This is especially true for soccer fields.

However, the hardness of the covering, which is desirable per se because of such a load for reasons of resistance to damage, contradicts the requirement for a non-slip and preferably also fall-damping nature of the covering. This contradiction has so far not been satisfactorily resolved, at least not with reasonable economic outlay.

As a covering for football fields, natural grass with drainage of the field is considered optimal for the players; Regarding maintenance and care, turf is very problematic because the turf hub is very sensitive and requires a lot of time for regeneration (regrowth / replanting / transplanting).

Lawn pitches are therefore less suitable for regular and relatively frequent football training, and pitches that are less expensive to maintain are used, since the cover or covering layer consists of a mechanically compacted mineral material fill made of comparatively inexpensive particulate material, such as lava slag; Known bulk material surfaces for sports or football fields with a mineral surface layer, the so-called turf flooring, and the usual structure of a sub-base or substructure and a multi-layer superstructure are referred to as «turf surfaces» (DIN 18035) or hard courts, the surface layer of which is not necessarily water-permeable .

The balance of the disadvantages and advantages of bulk material surfaces with a water-permeable mineral cover or covering layer in the manner of tennis surfaces for training and betting is obvious: the grip is sufficient for low to medium loads, but usually fails at higher loads due to the curl of the particles the fill. The risk of falling injuries from abrasion / bruising is high. Maintenance, for example by smoothing and rolling, is much easier than that of a lawn.

The use of relatively soft bulk materials such as peat garbage and common, i.e. H. Flake-like wood bark waste, the particles of which have a maximum length of 100 mm and thicknesses of less than 10 mm, is known for various sports surfaces, such as riding and running tracks or play areas, and such surfaces are suitable for reducing the risk of falling injuries.

Such a bulk material is considered to be too soft for soccer fields and previous tests with wood bark material have shown that simple fillings, even after rolling, do not have sufficient tread strength for regular soccer games, because an essentially loose particle bed is obtained, the surface of which is loaded by parallel or Forces acting at an acute angle to the surface show practically no cohesion.

The object of the invention is to provide a bulk material area for football pitches, the cover layer of which consists at least predominantly of tree bark particles of the type mentioned and nevertheless has the stiffness required for regular game operation.

This object is achieved according to the invention by a bulk material surface with the features mentioned in claim 1.

It was by no means to be expected for the specialist in sports field construction that a top layer suitable for use as a football field without artificial binder can be obtained from particulate wood bark material; it was rather believed that an unbound bed of wood bark particles would not be able to cope with the surface loads that would occur when used as a regular football field, and the applicant's first attempts with single-layer beds of tree bark particles seemed to confirm this.

It was therefore surprising that with a multi-layer structure made up of differently structured sub-layers, a top layer of wood bark particles on bulk material surfaces for football fields that withstands the very high surface loads of the football game for regular operation and a technically and economically advantageous solution to the problems described above can be achieved.

The term "bulk material area" is used in the same way as the term "turf area" and basically means a multi-layer bulk material bed and not a two-dimensional "area" in the geometric sense.

Preferred embodiments of the bulk material surface according to the invention have the features specified in claims 2 to 9, the DIN or SNV standard reference referring to the respective German or Swiss standard regulations.

The method according to the invention for producing the new bulk material surface has the features specified in claim 10. On the superstructure produced in the usual way (see, for example, DIN 18035), at least two superimposed partial layers of different texture are formed as the top layer, preferably fresh or at least slightly rotten wood bark material particles being used as the wood bark material for all partial layers. A pre-orientation of the platelet-shaped particles when building up the partial layers can be achieved by ent speaking storage methods, e.g. B. scattering machines, with predominantly parallel particle delivery or by treating the deposited layer, for. B. with rakes can be achieved.

The necessary structuring of the top layer takes place by compacting the individual sub-layers, e.g. by isostatic rolling, typically compacting by in each case at least about 10% and for example about 30% of the thickness of the respective loose bed. In general, there is sufficient minimum resistance to treading when the top layer allows for at least one game without interruptions due to the surface under the usual load for professional football.

For the purposes of the invention, wood bark materials of various origins (deciduous or coniferous trees) and various types of extraction (manual or mechanical debarking) are initially suitable. Bark and bast material from hard-to-decompose woods, in particular hardwoods such as oak, and wood bark with a wood content of 10-30% by weight represent a preferred starting material.

In order to obtain a platelet-shaped wood bark material suitable for the invention - hereinafter referred to as a mixture for short - the raw material obtained during debarking, if necessary after comminution, can be obtained by known classification methods such as sieving, sifting and the like. The devices suitable for this are known to the person skilled in the art for the production of building material mixtures. Bark products of different origins can also be mixed before or after classification.

Suitable platelet-shaped parts or particles of the bark material are capable of forming a bed which, if necessary after prior orientation, can be compressed into a partial layer which, in vertical section, shows an orientation of the particles which is approximately parallel to the surface of the covering. This generally applies to particles with the maximum lengths and thicknesses mentioned above. Preferably, the wood bark material contains little or no fines, e.g. B. less than 10 wt .-% particles with maximum dimensions of less than 6 mm. Particles that are too long or narrow are less suitable, which is why the width-to-length ratio of a considerable (e.g. 50% by weight or more) fraction is at least 1: 4 and accordingly normally at most 1: otherwise the «widths »Dimension becomes the« length »dimension; finally, the smaller area dimension ("width") of an essential and usually at least 50% by weight part of the wood bark material should be at least three times larger than the thickness of the particles.

A certain proportion, preferably at least 20% and in particular at least 50% (in each case based on weight) of the wood bark material is preferably formed by particles which have a maximum thickness of approximately 3 mm and each have a total surface area of more than 300 mm ² .

The classification of particles suitable or preferred for the invention can generally be carried out according to known criteria for the assessment of particle sizes or particle shapes, as described in the relevant standard regulations and can be checked by visual inspection, sieving and the like methods.

Wood bark material particles are particularly advantageous which, according to SNV standard 670 / 120a, have a non-uniformity index C _" of 10-50 or / and a curvature index C _e of 1-3.

The invention is further explained with reference to the accompanying drawing, the only figure of which shows the schematic representation of the cross section of a preferred embodiment of the bulk material surface according to the invention.

The bulk material surface or bulk material bed 10 lies on a substructure 11, which is either the substrate, i.e. the naturally occurring soil, possibly improved, e.g. B. is by mechanical strengthening or with binder, or a substructure, d. H. a heap on the ground, which can also be improved.

The base or substructure 11 is leveled in the usual way with the flatness and inclination values customary for sports fields. The filter layer 12 lying above is the first bed layer that normally belongs to the superstructure, but can also be replaced by a geotextile layer. Any drainage devices (not shown) are usually located in or immediately below the filter layer, which is generally intended to prevent sub-surface or sub-construction material softened after frost periods or persistent rain from penetrating into the overlying base layer 13. This base layer should have a sufficiently stable grain structure in order to increase the load-bearing capacity of the covering and furthermore have a pore space which is sufficiently large for rain drainage of the layers above.

The installation of a dynamic layer 14 is optional; such layers normally serve mainly to increase the elastic compliance under vertical loads. Since the covering layer 15 according to the invention has a much higher elasticity than conventional turf coverings, the installation of a dynamic layer 14 is usually dispensed with; such a dynamic layer 14 can, however, form a granulometric transition between the covering layer 15 and the base layer 13 and have an additional water storage function.

In general, the substructure or substructure 11 and the surface layers 12, 13 and optionally 14 can be produced and constructed in practically the same way as that of conventional turf surfaces, apart from the covering of the latter. Find specific information about suitable thickness and compositions of layers 11-14 for example in relevant standards, e.g. DIN 18035 or the installation recommendations of the suppliers of geotextiles.

The cover layer 15 typically has a thickness of 5-25 cm, but could also be thicker and is applied in at least two work steps, each work step being poured on with simultaneous or subsequent pre-orientation and compacting, e.g. B. with conventional rollers.

When the top layer 15 is built up according to the invention in at least two work steps, a comparatively “coarser” wood bark material (eg grain size according to SNV 670 812a to 60 mm, preferably up to 40 mm) is used for the lower layer 152 and a comparatively finer one for the upper layer 151 Wood bark material (for example grain size according to SNV 670812a up to 30 mm, preferably up to 15 mm) can be used in the upper partial layer 151 under its surface 150, for example a 5-10 cm and typically about 8 cm thick wood bark platelet layer with a finer texture and higher tread and To form surface shear strength or in the lower sub-layer 152, for example a 10-20 cm and typically 15 cm thick wood bark platelet layer with a coarser texture and higher water permeability.

In general, the platelet-shaped wood bark material to be used for the lower sub-layer 152 of the top layer 15 can first be loosely sprinkled evenly onto the layer 13 or 14; when using relatively smooth, i.e. this loose layer can already have a certain surface-parallel particle orientation when the pouring devices are not swirling strongly. If this is not the case, mechanical coarse screens can be used.

Then the loose bed of wood bark material for the lower sub-layer 152 is processed by compression, typically by about 10-40% and for example 30% of its loose bed height, e.g. with a smooth wheel roller of around 1 t / m drum width.

In the case of a two-layer structure of the top layer 15, a theoretical boundary layer 159 indicated by dash-dotted lines is formed, at which the two differently textured partial layers 151, 152 adjoin one another or merge into one another.

After the final compaction of the top layer 15 or the upper sub-layer 151, the entire top layer 15 is preferably saturated several times with water, which, depending on the weather, may require 1-4 liters / m ^{2 of} covering per day. Between the saturation phases, it is expedient to carry out repeated densification, expediently until a total pore volume of about 45-70% is reached and a water permeability value of 2, 10-3 cm / sec is not undercut. The optimum water content of the top layer 15 is approximately 45-50% by weight under normal conditions.

The bulk material surface 10 according to the invention is now ready for use as a soccer field. Test pieces taken from the edge of the top layer 15 made of wood bark material show a pronounced grain, i.e. Particle orientation, parallel to surface 150 of cover layer 15.

Known red-inhibiting substances can be added to the water used to saturate the top layer 15 or the wood bark material for forming the top layer 15. Elemental sulfur in powder form is a preferred additive for this, e.g. in amounts of 0.1-5%, in particular 0.5-3% and typically about 1% by weight of the bark material, but other substances are also suitable which are practically insoluble in water and which have a physiologically acidic action in layer 15 Produce pH of preferably 6 or less and in any case delay the microbiological degradation.

If necessary, artificial binders (eg an aqueous tar or PVC emulsion) can be added to the wood bark material or the water used to saturate layer 15. However, the use of such binders in considerable proportions is usually neither necessary nor advantageous and can have the disadvantage that the water permeability is reduced excessively. In general, the proportion of artificial binder in the cover layer should be less than 5% by weight, preferably less than 1% by weight. The resin, which is usually present in relatively high proportions in wood bark material, is often sufficient for sufficient top layer strength and is not included in the artificial binder.

In an analogous manner, the addition of special red-inhibiting substances to the top layer 15 is not particularly critical if it contains considerable amounts of bark material which contains a large amount of tannins or has a similar preservative effect ("Gerberlohe"), as is typical for hardwoods such as oak.

On the one hand, the invention offers advantages in terms of space construction and maintenance costs, since the bark material is comparatively cheap, but the covering produced with it is comparatively stable and generally does not require any particularly high maintenance expenditure. Detached covering parts can usually easily, e.g. B. with trawls or by rolling back in the layer and usually leave no holes, but comparatively harmless because of flat depressions.

Since the swellability of bark material is comparatively low, a cover layer 15 according to the invention does not lose its porosity due to swelling. In general, the finished top layer 15 z. Have as a according to DIN 18 035 Part 5, certain water-absorption value of at least 2.10- ³ cm / sec and a pore volume of 45-50 Vol .-%, which can be usually achieved with the above-mentioned beef materials or installation conditions.

Overall, the invention offers remarkable loading Advantages of use: a typical cover layer 15 of 5-20 cm thickness produced according to the above information has a comparatively high resilience and is still practically completely sturdy, so that all movement sequences typical of football and comparable sports remain unimpeded. The risk of bumping and crushing injuries when falling can be significantly reduced compared to hard or hard lawns and the risk of abrasions can be almost eliminated. Another considerable advantage of the invention, particularly in the case of soccer fields, is that raining immediately before or during the game does not normally lead to a deterioration in playability, that is to say no “heavy ground” arises; it may even be expedient to spray water on a football field according to the invention immediately before a game.

Claims (11)

1. Bulk material stratum (10) for soccer fields having a water-pervious multilayered top structure (12, 13, 15) on a substratum (11) or substructure (11), wherein the covering layer (15) constituting the field surface and forming part of the top structure is pervious to water as well and wherein the covering layer (15) consists, at least in a predominant weight portion, of a substantially platelet-shaped bark material, the particles of which each have a maximum length of 100 mm and a thickness of less than 10 mm, characterized in that the surface (150) of said bulk material stratum (10) is made tread-resistant by forming said covering layer (15) of at least two superimposed partial layers (151, 152) of differing textures, wherein the one layer (151) which forms the surface (150) consists of a compacted finer tree bark material and the other layer (152) consists of coarser tree bark material that has been compacted prior to compaction of the layer (151) forming the surface (150) for producing a substratum (152) which has a coarser structure and a". higher water permeability than the superimposed layer (151).

2. Bulk material stratum according to claim 1, characterized in that the particles of the bark material of both partial layers (151,152), in a predominant part, are oriented approximately parallel to the surface (150) of covering layer (15) and, in a predominant weight portion, have thicknesses of not more than 5 mm.

3. Bulk material stratum according to claims 1 or 2, characterized in that the bark material of both partial layers (151, 152) comprises (a) not more than 10%, based on its weight, of particles having maximum dimensions of less than 6 mm, (b) at least 50%, based on its weight, of particles having a width: length ratio of at least 1 :4, and (c) at least 50%, based on its weight, of particles having a width that is at least three times greater than the thickness of each particle.

4. Bulk material stratum according to any of claims 1 to 3, characterized in that both partial layers (151, 152) consist substantially completely of bark material.

5. Bark material stratum according to any of claims 1 to 4, characterized in that the covering layer (15) contains less than 5% and preferably less than 1%, based on its weight, of a synthetic binder.

6. Bulk material stratum according to any of claims 1 to 5, characterized in that a portion of at least 20%, preferably at least 50%, by weight, of the bark material consists of particles each having a maximum thickness of 3 mm and a surface area of more than 300m².

7. Bulk material stratum according to any of claims 1 to 6, characterized in that the bark material particles meet at least one of the following criteria: (d) the particles have a non-uniformity index C_", according to SNV 670/120a, of 10-50; (e) the particles have a curvature index C_c, according to SNV 670/120a, of 1-3.

8. Bulk material stratum according to any of claims 1 to 7, characterized in that the covering layer has a water absorption value, determined according to part 5 of DIN 18035, of at least 2·10^-3 cm/sec and a pore volume of 45 to 50%, by volume.

9. Bulk material stratum according to any of claims 1 to 7, characterized in that the bark mixture comprises rind and bast portions of rot-resistant trees, notably of broadleaf trees, and contains rind having a wood content of not more than 50%, by weight, preferably 10-30%, by weight, and/or comprises a rot inhibitor additive, preferably elemental sulphur.

10. Method for producing the bulk material stratum according to any of claims 1 to 9, characterized in that the covering layer (15) of the top structure (12,13) is formed by bulk deposition of the top structure (12, 13) is formed by bulk deposition of the bark mixture by first forming the lower partial layer (152) by compacting a first bulk deposit of a relatively coarse bark material to produce a waterpermeable layer having a relatively coarse texture, and by subsequently compacting upon said lower layer a second bulk deposit of a relatively fine bark material forming the partial layer (151) constituting said tread-resistant surface (150) to such an extent that the water permeability of partial layer (151) is lower than that of partial layer (152), wherein the particles are preoriented, in the course of the deposition or subsequently, parallel to the horizontal plane, and by mechanically compacting the preoriented loose deposition.

11. Method according to claim 10, characterized in that each upper partial layer (151) is formed of a bark material having a sieve number that is smaller than that of the bark material used forthe respective lower partial layer (152).

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