Substrate intended to act as a cultivation support and use for the preparation in particular of sport surfaces

0001The present invention relates to a substrate intended to serve as a growing medium, in particular for natural turf, in particular for producing a sports surface made of natural turf intended for the sporting practice of football, rugby, or horse sports such as galloping running. trot, polo, jumping and dressage, for example.

0002The surface conventionally used for these many sports is the grass, more specifically the natural grass: it is recognized as the ideal surface in the summer, but which has the disadvantage of being sensitive to climatic conditions and not not support intensive attendance without deteriorating when conditions are not favorable, especially in case of precipitation or freezing.

0003To overcome this disadvantage, it was thought to replace natural grass with artificial surfaces and in particular artificial turf for football or rugby and, for tracks or rides or horse careers, with synthetic surfaces based on sand, in particular siliceous, possibly associated with elements such as lattice, fibers, ash, crushed synthetic elements, paraffin and any elements designed to increase the cohesion of the track or reduce its sensitivity to frost and its need for watering.

0004However, these surfaces have significant disadvantages compared to natural grass surfaces, both ecologically and from the point of view of the economy, the comfort of use, the approval of the players and the neighborhood and of security of the game

0005In fact, the natural grass participates, like all other plants, in the environment by photosynthesis, acts like a true solar energy air conditioner, by maintaining the soil temperature at about 20 ° C while the temperature of the synthetic surfaces reaches 60 ° C in the sun, and finally participates in the purification of air and water by absorbing fine dust; Conversely, synthetic surfaces do not trap dirt or dust, but produce them, drop products into the environment, smell bad in summer and pose a recycling problem. Also economically, the price of a turf sports surface, reduced to the hour of use, is advantageous because the investment is lower and more durable than for synthetic surfaces, which must be changed. after 10 years. Another very important advantage of the turf over synthetic surfaces is the enjoyment and safety of the players: the turf, on the one hand, makes the soil firm enough to be wearing and restoring energy and cleaning thus the muscles of the sportsmen and, on the other hand, allows the ground to remain sufficiently flat and bouncing and simultaneously flexible enough to dampen the race and to spare the joints of the sportsmen. The turf thus helps the muscles of the sportsmen and / or animals.

0006Despite the disadvantages described above in comparison with natural grass in ideal conditions, substitute surfaces for natural grass grow to the detriment of the latter, with "synthetic turf" for football fields, sands and fibers or textiles or shredded for quarries and rides: indeed, the natural turf has the disadvantageous prohibition of not being in all circumstances in a correct state. This inconvenience is today perceived as an unacceptable handicap and weighs more heavily than all the other benefits (economic, ecological and health) of natural grass in comparison with artificial surfaces.

0007To overcome these disadvantages of lack of turf resistance in humid periods, it has already been proposed to add many elements to turf growing substrates including plastic fiber lattices and coarse synthetic fibers and finally, recently, fibers. synthetic "fine".

0008In the same way that the concrete was reinforced and reinforcement by mesh with large mesh (reinforced concrete) then by the addition of relatively fine synthetic fibers (with a diameter greater than or equal to 100 microns) then by so-called micro fibers -fibers (with a diameter greater than or equal to 50 μμ), similarly, proposals for the addition of fibers have been made for turfgrass substrates with strips of polypropylene fillets (such as those marketed under the trade mark Netlon) and then by the addition of increasingly fine fibers, those which are more precisely available on the market because used to arm the concrete.

0009In addition, to improve the resistance of a substitute soil to the grass consisting essentially of sand, it has already been proposed to incorporate finer fibers than those used in concrete. It is for example known (document<patcit id="pcit0001" dnum="FR270703A"><text>FR-A-2.707.03</text></patcit>) artificial turf athletic soil, shear-resistant, can be obtained by a mechanism similar to that of grass root resistance, by the incorporation of a 1 to 5 dose weight fibers of fine section (5 to 20 μ) and relatively short length (4 to 75 mm) in a substantially sandy substrate with a particle size of between 10 microns and 20 mm with a dose of between 1 and 5 ‰ in weight assay.

0010These additions are more and more effective in "arming" a soil of substitution, like concrete: we obtain indeed a soil reaching good performances in terms of shear resistance, but, unfortunately, this improvement of the resistance is reached at the expense of flexibility.

0011To overcome the disadvantage of a gel sol and also to provide more flexibility to the turf surface, it has recently been proposed the addition of cork granules and especially cork baked in coarse grain size (> 3 mm). ) in medium granulometry (500 μμ to 3 mm) and in fine granulometry (<500 μμ) to confer on a growing substrate in which it is incorporated improved characteristics of frost resistance by the double effect of the insulating nature of cork and its resilience which allows him to "cash in" the increase in the volume of water under the effect of frost and under the effect of permeability conferred by coarse particles of cork. At the same time, cork has the advantage of giving the substrate lightness, flexibility and resistance to compaction by its density and resilience. Moreover, if coarse grains improve the permeability of the substrate, the small cork grains, which are non-swelling, also offer a high capacity for capillary water retention due to the strong surface tension of the cork and the ratio between their surface area. and their volume.

0012However, if the incorporation of cork improves the flexibility and the good behavior in case of frost, especially in the case of addition of coarse particles, this is done to the detriment of the cohesion and the shear strength of the substrate , especially in the case of addition of coarse particles. The document<patcit id="pcit0002" dnum="US2003230027A"><text>US-2003230027</text></patcit> discloses a substrate to serve as a culture support.

0013One of the aims of the present invention is therefore to provide a substrate intended to be used as a crop, in particular for natural turf, which makes it possible to produce a sports surface, in particular a natural grass that is acceptable for any sporting discipline.

0014Another object of the present invention is to provide such a very strong substrate, very flexible, highly draining, frost resistant and unaffected by very heavy precipitation.

0015These and other objects which will become apparent are attained by a substrate for use as a culture support which is characterized according to claim 1.

0016Advantageously, the hard particles of the first part are grains of siliceous sand.

0017Preferably, the resilient particles P_R from the first part are cork seeds.

0018Advantageously, the corpuscular elements of the second part consist of clay, silt, sand whose particle size is less than 100 microns, organic material, fine porous elements such as zeolite powder, coral powder or diatoms.

0019Preferably, the corpuscular elements of the second portion having a size of less than 20 μm represent less than 60 g / l of substrate and the corpuscular elements having a dimension of less than 100 μm represent less than 300 g / substrate.

0020According to an alternative embodiment, the corpuscular elements of the second portion having a dimension of less than 80 μm represent less than 45 g / l of substrate.

0021Advantageously, the fine fibers of the third part are polyester hollow fibers with a diameter of between 10 μm and 20 μm.

0022Preferably, at least 20% of the fibers of the third part are coated with a hydrophobic lubricant, such as, for example, silicone.

0023Advantageously, more than 50% of the weight of the fine fibers of the third part consists of fine fibers whose diameter is less than 10% of the average particle size of the hard particles of this substrate.

0024Preferably, the PV volume proportion of the P-resilient particles_{R> 100} in the substrate is greater than 5% and less than 60%, and more than 50% of the weight of the fine fibers of the third part is constituted by fine fibers whose diameter is less than 10% of the mean particle size of the hard particles.

0025In the case where the hard particles are sand grains, on the one hand, more than 80% by weight of these grains has a particle size of between 200 μm and 400 μm, and, on the other hand, the fine fibers of the third part are hollow fibers of polyester, with a diameter of between 12 and 30 microns and silicone surface.

0026A substrate according to the present invention allows the realization, possibly in situ, of sports surfaces, terrace surfaces, medium for the transplantation of plants or grass turf culture.

0027According to a preferred embodiment, the sports surface consists of juxtaposed trays, limited by walls, and filled with the substrate at a height at least equal to that of these walls.

0028The following description, which is not limiting, will enable those skilled in the art to better understand not only the advantages of the present invention, but also its implementation and its applications.

0029A substrate according to the present invention intended to serve as a culture support, in particular a turf, comprises:<ul id="ul0001" list-style="dash" compact="compact"><li>a first part constituting the backbone of the substrate and representing more than 70% of the total volume of the substrate, composed of particles P_>100 with a particle size greater than 100 μm, all of these particles consisting of hard particles P_{D> 100} and / or resilient particles P_{R> 100}. these resilient particles P_{R> 100} constituting a volume proportion PV between 0% and 100% by volume of this first part;</li><li>a second part of corpuscular elements P_<100 smaller than 100 μm, this part constituting from 0 to 450 grams per liter of the substrate;</li><li>a third part constituting from 0 to 200 grams per liter of the substrate, composed of fine fibers having a length of between 3 mm and 100 mm and a diameter of between 5 μm and 35 μm;</li><li>a fourth part constituting from 0 to 200 grams per liter of the substrate, composed of other elongated and / or surface inclusions, each of these elongate or surface inclusions having at least one of their dimensions much greater than the particle size of the particles of the first part, and the sum of the doses of the third part and the fourth part being greater than 3 grams per liter of the substrate.</li></ul>

0030It will be recalled here that the present invention must make it possible to respond to the following different conditions:<ul id="ul0002" list-style="dash" compact="compact"><li>the substrate must have a poral volume of large pores corresponding to gravity water as large as possible, which is obtained with large particles but at the same time a useful water reserve as large as possible which is achieved by small elements with high surface tension;</li><li>fiber available in sufficient quantity and at a price compatible with the application;</li><li>fibers satisfying the requirements of the precautionary principle with regard to health risks if there is inhalation of micro-fibers;</li><li>fibers which participate, where appropriate, in the increase of the capillary water reserve useful for the emergence then the growth of the turf or plants cultivated in the substrate.</li></ul>

0031Surprisingly, it has been shown that a soil compatible with lawn cultivation, which is relatively satisfactory in terms of cleanliness and very satisfactory for a soil with a particle size of less than 20 μm in particle size, is obtained. at 60 gram / liter of substrate and whose particle size of a particle size less than 100 microns is less than 300 gram / liter of substrate: the surface thus obtained has a relative permeability.

0032According to another embodiment of the invention, the corpuscular elements of the second part having a dimension of less than 80 μm represent less than 45 g / l of substrate: the surface thus obtained has a high permeability

0033To respect the precautionary principle, and to pose no risk to the health of the people handling them for the formation of the substrate and throughout the life cycle of the substrate, it is known that a micron diameter of fiber greater than 3 microns is considered the maximum diameter that can be inhaled, that a diameter of 6 microns is the diameter above which the current legislation does not classify fibers according to a potential health hazard: it has been considered preferentially that a diameter of 10 microns makes it possible to maintain a large margin of safety. Not only the size of the fibers incorporated but also their fate in time and how they may or may not break down into finer fibrils. In this respect, the already known polyester fibers can not be broken down into smaller fibers because of their manufacturing method and are recognized as being harmless with respect to the environment and health: they make it possible to respect the principle precautionary. Polyester fibers with a diameter greater than 10 μm are compatible with these precautionary measures and are widely available on the market. A conservative minimum diameter of 10 μm corresponds to a hollow polyester fiber with a titration of 1.15 dtex and a minimum diameter of 6 μm corresponds to a titration of 0.4 dtex.

0034To allow a fiber to move before stretching in a poral network during shearing, two possibilities are possible:<ul id="ul0003" list-style="dash" compact="compact"><li>either the grains are in rigid sand, so it is necessary in section that the diameter of the fiber is smaller than the diameter of the hole between three contiguous grains in the plane formed by the center of these three grains (like the wire which passes in the cat of a needle): if a fiber has a diameter greater than 1/5 the diameter of three contiguous grains, these grains must deviate to let the fiber pass without crushing it and there is no degree of freedom for the fiber under these conditions.</li><li>either the grains between which the fiber is coated are in resilient grains and in particular if it is cork grains: the condition of size of the fiber with respect to the size of the cork grain is not necessary in the as the fiber pressing the resilient grain will crush it without opposing the shearing movement and the whole resumes its place after the effort.</li></ul>

0035However, as the particle size of the substrates according to the invention is not homometric and as a fiber, which is very long compared to the size of a grain of sand, passes through many pores on its path and as the diameter the fiber must allow it to not be "hooked" too often on its path, it takes a significant difference in diameter between the passage defined by three grains and the diameter of a fiber (to fix the ideas, a fiber 3 cm in length corresponds to 100 times the size of a sand grain of 300 μμ). This depends not only on the diameter of the fiber, but also on its flexibility (which increases when the diameter decreases) and its lubrication and of course the statistical distribution of the dimensions of the passages in the porosity as a function of the particle size distribution of the sand; if it is possible to easily give a diameter in a homometric medium beyond which it is known that the fiber is jammed, it is not easy to theoretically determine a diameter below which the fiber will slide in the porosity before being stretched and block the movement.

0036The tests conducted have surprisingly shown that a satisfactory macroscopic effect can be obtained when at least 50% of the fibers have a diameter less than D50 / 10, and very satisfactory for a diameter of less than D50 / 20, D50 being the diameter of grain below which 50% of the grains of sand of the substrate are present, that is to say that all the hard particles smaller than D50 represent half the weight of all the hard particles: in other words, more than 50% of the weight of the fine fibers of the third part consists of fine fibers whose diameter is less than 10% of the mean particle size of the hard particles. This condition is particularly advantageous in the case where the PV volume proportion of the P-resilient particles_{R> 100} in the substrate is greater than 5% and less than 60%.

0037For the aspect of flexibility and for the blocking efficiency of the fiber, it is preferable to have a diameter as small as possible; but the longer the fiber, the harder it is to maintain flexibility, the easier it is to block the substrate and the harder it is to incorporate the fiber into the substrate.

0038We start to have a significant efficiency for a fiber length equal to 5mm but, it is better to have a length greater than 20mm and the results improve when the length of fiber increases. A 60mm fiber is very effective and it would be desirable to have fiber lengths of up to 100 or 200mm or maybe even more, but it has not been possible to incorporate them in the recent tests because the incorporation of fibers is more and more difficult when the length increases.

0039Other tests have shown, surprisingly, that a satisfactory macroscopic effect can be obtained for a fiber with a diameter of less than D30 / 10 and very satisfactory for a diameter of less than D30 / 20, D30 being the grain diameter. below which there is 30% by weight of the hard grains of the substrate.

0040Preferably, a small fiber diameter is preferred to provide better blocking and flexibility at the same time; but it is found that the smaller the diameter, the more difficult it is to separate the fibers between them and to mix with the substrate, which reduces the effectiveness of the fibers.

0041In view of these elements, experience shows that a satisfactory result is obtained in a sand with a particle size of between 200 μm and 1000 μm for a hollow polyester fiber having a diameter of between 12 and 30 μm, corresponding to a titration between 1.6 dtex and 34 dtex.

0042Silicone fibers have the advantage of better "sliding" in the porosity of sand through a "sleeve" of droplets that results from the hydrophobicity induced by the silicone coating: it is a positive effect for the flexibility of the substrate for a given fiber diameter. In contrast, however, sliding better, they are therefore less effective in maintaining the sand.

0043It is therefore preferable to use the silicone fibers only in the case of long fibers, preferably for fibers longer than 3 cm.

0044In addition, the silicone fiber does not retain water by capillarity and the fact of using such a silicone fiber should therefore in principle reduce the useful reserve.

0045On the contrary, it has surprisingly been found that the use of hydrophobic fibers such as silicone fibers is an extremely effective means of retaining water in the porosity when the diameter of the drop of water on the hydrophobic surface of the fiber is greater than the size of the passage between three grains of sand decreased by the diameter of the fiber, because the water that enters this cavity and regroups in the form of a large drop due to the hydrophobicity of the fiber can no longer emerge through the passage taken by the fiber.

0046In practice, it has surprisingly been found that a hydrophobic fiber, for example a silicone fiber, in a sand whose D50 is less than 500 μm, confers on the substrate a water behavior that is particularly favorable to the development of the turf.

0047Thus, a silicone fiber in a sand of D50 &lt;500 μm and more particularly in a sand of D50 &lt;350 μm, has the double interest of a lubrication allowing the incorporation of the fiber to the porosity of this sand, this incorporation being all the more difficult as the sand is fine and create a completely new synergy between a porosity of hydrophilic granules and a hydrophobic surface fiber to trap water in the porosity, this water being very easily used by the root of plants growing in the substrate.

0048Given these elements, experience shows that we obtain a particularly satisfactory result both mechanically and in terms of grass growth, given a good useful reserve and a good capillarity in sand having a particle size of between 200 μm and 400 μm and for a hollow silicone polyester fiber having a diameter of between 12 and 30 μm.

0049Experience shows that even better results are obtained with a non-silicone fiber but that it is more difficult to incorporate well and that the efficiency drops if it is not well incorporated. For lengths of fibers of less than 80 mm, however, the choice of non-silicone fibers is an interesting possibility if one has particularly effective means of incorporation.

0050Polyester fiber from industrial recovery can also be used with cotton fabric.

0051It is possible to remove cotton which does not play a significant positive mechanical role and even less of a durable positive mechanical role, because it is biodegradable. But surprisingly, cotton, being extremely hydrophilic, brings a very interesting water reserve at the beginning of the life of the substrate, at the crucial moment of implantation of the sod by sowing or implantation of plants on a terrace or for transplanting large trees.

0052Similarly, it has surprisingly emerged that the fibers, which are not individualized, are less effective for the originally intended role of mechanically reinforcing the substrate. But these non-individualized fibers that appeared unexpectedly in the manufacturing process in the form of small balls unattractive, have proved interesting to give a kind of substrate structure that resembles the structuring of clods of a natural soil.

0053If the fibers are hydrophilic but also, more unexpectedly, if they are not hydrophilic but silicone, the balls have surprisingly proved to be very effective in creating useful water reserves in which the young radicles are primarily concentrated at the same time. a seedling; and, moreover, it has unexpectedly appeared that these balls effectively oppose the penetration of a crampon for example, as the hair buns protected the warriors by preventing a saber even sharp cut neck. It has also been found, unexpectedly, that these balls occupy a large volume, likely to collapse on itself and resume its volume: they finally constitute a kind of light particle, insulating, aerated, with a strong reserve of water and resilient.

0054Too many, however, these balls or surface elements, in addition to being particularly unsightly on the surface, make especially extremely difficult the establishment of the substrate and the equalization of the surface; and, moreover, they may eventually reduce the cohesion of the assembly if continuous sliding surfaces can be formed from one ball to another. In addition, with a mechanical efficiency almost zero compared to that of individualized fibers, these fiber clod, if they are more than necessary increase the price of the substrate without mechanical advantage.

0055Therefore, according to the present invention, the dosage of these surface elements must not represent more than 75% of the dosage (D_F + D_al) of all inclusions of Parts Three and Four.

0056Surprisingly, it has been found that the maximum fiber dose that can be mixed with the substrate is considerably higher if the substrate comprises a preponderant share of cork or material resilient to sand; and it has even been realized, even more surprisingly, that it is possible to form a substrate in which cork constitutes the essential part, sand being either absent or very largely in the minority in volumetric dosage (for example sand dose less than 30%): this cork-based substrate is, against all odds, for the same fiber dosage even more resistant to shear than a substrate composed mainly of sand.

0057Thus, it has been found, totally unexpectedly, that a substrate consisting essentially of cork can admit a much higher fiber dose, because the fiber does not block the machine that mixes fiber and cork by creating a shear thanks to the resilience of cork that crashes to pass where the sand would block in the manufacturing process.

0058In such a mixture, according to the invention, thanks to the cork grains which separate the fibers (which otherwise agglomerate and compact), these constitute, in mixture with cork, and in the same way as the latter, a integral component of the substrate, lightweight, insulating, resilient, capable of retaining capillary water.

0059It has been found that, even more surprisingly, the cork and the fiber, partly in ball and partly in individualized strands, constitute, with possibly a little sand, an extraordinary matrix, whose behavior with respect to the plants is that of a ground but which behaves on the macroscopic scale like a tatami of judo for example, ie like an elastic solid.

0060This substrate can be molded and compressed to its equilibrium thickness and can be walked or jump on its edge without destroying it: the slice can crash locally under the weight of several centimeters and immediately resume its place.

0061The smaller the sand portion, the stronger the grain portion of resilience, particularly cork, and the lower the density of the substrate and the higher the insulation coefficient.

0062For a substrate whose cork represents more than 50% by volume, the mechanical characteristics of the substrate are almost unaffected by the gel. It has even been found that a turf implanted in a substrate according to the present invention with a cork share of more than 75% remains flexible, while other soils are frozen and hard as stone.

0063For such a substrate according to the invention, of which the cork in large granules represents more than 20% and preferably more than 50%, and whose sandy part has a D10 greater than 200 μμ, the permeability is such that the substrate "drinks and at the end of the worst rainfall, only the water retained by capillarity.

0064The combination of the water retained by capillarity and the thermal insulation makes it possible to preserve very long and until the surface a reserve of water available for the sowing.

0065A substrate according to the present invention can be characterized whatever the formulation, as follows:<ul id="ul0004" list-style="dash" compact="compact"><li>on the one hand by the initial volume proportion of each component of the mixture, with the exception of fibers, defined as the heap volume of the component before its incorporation divided by the sum of the heap volumes of all components before incorporation (to the exception of fibers); and,</li><li>on the other hand by a weight density of the fiber in the mixture defined as the weight of the fiber divided by the sum of the heap volumes of all the components before their incorporation into the mixture, with the exception of the fibers.</li></ul>

0066In the usual way, in a soil analysis, the proportions by weight (in dry weight) of the various fractions are considered in a mixture because the dry weight of the mixture is equal to the sum of the dry weights of the constituents, whereas the volume of a mixture It is not necessarily equal to the sum of the initial volumes of the constituents, because of the swelling or packing of the mixture, the small particles being able to "disappear" in the porosity of the large particles.

0067Practically, however, for the constituents other than the fiber, the initial volume proportions as defined above are used to characterize the substrate, so that the sum of the initial volume proportions of all the constituents does well. 100%.

0068The advantage, in the context of the present invention, of expressing the composition of the substrate in initial volume proportions is threefold:<ul id="ul0005" list-style="dash" compact="compact"><li>on the one hand, the constituents used are chosen non-swelling, which means that the volume of the pile of each constituent remains the same, whether the component is wet or dry, while the weight of the pile varies considerably depending on the content of water. The heap volume, and not the heap weight, is therefore proportional to the dry weight of the element under consideration.</li><li>on the other hand the sand and cork dosing process, as practiced in the context of the invention, is done by the heap volume and not by the weight</li><li>lastly, and above all, the densities of the constituents being very different from each other since for example the sand is 20 times denser than the cork, a hypothetical initial volume proportion of 75% of cork would give a weight proportion of 15% of cork then that 3/4 of the volume is occupied by cork and that it is this occupation of the space which makes that the cork imposes its mechanical behavior (density of the mixture, capacity of absorption, resilience, thermal insulation, etc.) which is therefore more related to the initial volume proportion than to the weight proportion.</li></ul>

0069In another version of the dosing process, the control of the beginning of the sand is controlled according to the variation of the weight of sand in a hopper and one could express the relation between the volume of cork and the weight of sand, but it is more telling for the man of the art to consider the volume ratio between cork and sand; if we know the weight of the sand, it is enough to divide the weight by the density of sand even if this density is chosen arbitrarily or conventionally, to convert the weight of the sand in volume and to be reduced to a volume composition in this which concerns sand and cork components.

0070As regards the fibers, on the contrary, the initial volume of the fibers is not used because the volume of the same quantity of fibers can vary in a ratio of more than 10 depending on the packaging of these fibers which can compress strongly and occupy a small volume or on the contrary open and occupy a very large volume. For a given type of fiber, it is therefore the weight of fiber that is the most practical parameter to know the amount of fiber incorporated.

0071A substrate according to the present invention certainly has for main application the realization, possibly in situ, sports surfaces, but also terrace surfaces or medium for the transplantation of plants or lawn turf culture.

0072The improvement of the characteristics of flexibility, less sensitivity to compaction and thermal insulation is detectable when the volume proportion of the resilient particles in the substrate is greater than 5% and the diameter of the fine fibers is less than 10% of the particle size of the hard particles of the first part. This improvement is naturally accentuated as the proportion of resilient particles increases But the concomitant increase in the cost price and the difficulty of maintaining such a good cohesion beyond 60% make formulas more than 60% volume of resilient elements are rather reserved for growing substrates for terracing; the sports field formulas preferably contain less than 60% by volume of resilient elements.

0073Given these elements, the substrate according to the invention is available in several different formulations depending on the applications.

0074Several elements make it possible to define the formulation according to needs.

0075The cost price is increasing very significantly with the increase of the proportion by volume of cork PV, which is a first element of cork limitation for economic reasons. Moreover, if the cork brings flexibility, it is necessary that the grounds keep, according to their destination, a certain performance and a sufficient rebound: the ground is faster for the race or for the balloon when it is harder; it is necessary for example a sufficient rebound of soccer ball or tennis ball: this is a reason of limitation of the cork for technical reason.

0076For one year, experiments were conducted to improve the product and test the formulations.

0077To improve the product, various sources of fibers were sought and it was found that one obtains completely different results in terms of mechanical behavior with relatively little different fibers and exactly equivalent formulations elsewhere.

0078The thickness of the fibers is an important element, as well as its surface condition and its length has proved decisive. If the fibers, all things being equal, are too short in relation to the grain size, the stabilizing effect is very weak, sometimes even non-existent; the longer the length increases and the more the fibers are effective, for the same dosage of fibers, provided they succeed in keeping them unraveled, which is more and more difficult when the length increases.

0079To improve the formulation and to incorporate fibers as effective as possible, it was necessary to improve the defibration system, which aims to separate the fibers, to keep them separated and to introduce them well separated in the granular medium, at the strategic meeting point in the mixing process.

0080In view of these improvements, it was possible to test many formulations with well-defibrated fibers by installing on a checkerboard and then testing the mechanical behavior of different formulations obtained, for different types of fibers, by varying the concentration of fibers along one axis of the checkerboard and the concentration of cork along the other axis.

0081In particular, tests were carried out with 40 mm fiber lengths which proved effective but too short for good efficiency, 70 mm fibers which proved to be very effective in obtaining a flexible and stable substrate and 140 mm in diameter. proved even more effective, especially with the most corky substrates.

0082Preferably, it has been found that other elongated or surface inclusions that can be added to the fibers to stabilize the substrate are more effective if they have a larger dimension at least greater than 10 times their smaller dimension and at least 10 times greater the average particle size of the particles constituting the backbone of the substrate.

0083In the examples studied, it was necessary to choose a description of the mixtures, taking into account what is measurable and the relationship between the density of cork and that of sand. A process for the formulation and control of the manufacture of the mixtures has been developed, characterized by the fact that three dispensing members are known whose flow rate is known, a sand dispensing member, a cork distributor member and a fiber dispensing member and that the different rates are adjusted to obtain a formulation equal to the proportion of the distribution rates of the elementary components.

0084In this process, the flow of sand is characterized by the measured weight of sand passing per unit of time while the cork flow is characterized by the measured volume of cork passing per unit of time and the fiber flow is characterized by the weight of fibers passing per unit of time.

0085It has been decided to characterize the granular medium by the proportion of the respective volumes of sand and cork, but a difficulty arises for the sand, the volume of which depends on the state of compaction and of which only the weight is known.

0086Given the weight uncertainties due to the water attached to the sand, we measure the weight of wet sand passing per unit of time and we consider in the manufacturing process and evaluation an arbitrary volume of sand calculated from of its weight, arbitrarily deciding that the "arbitrary volume" of sand is that corresponding to the measured weight, for an arbitrary density chosen, for example 1.4 kg / liter of sabie; the volume proportion between sand and cork is then characterized by considering that the proportion of sand is the ratio between the arbitrary volume of sand and the sum of the arbitrary volume of sand and the measured volume of cork, the sum of the volume proportions of sand and cork being equal to 100%.

0087The dosage of the fibers is considered in grams per liter of mixture: the ratio between the weight of the fiber supplied and the arbitrary volume of the mixture equal to the sum of the arbitrary volume of sand and the measured volume of cork in the same unit of time.

0088What is called the fiber weight in relation to the volume of the mixture is in fact the ratio between the weight of fibers supplied and the arbitrary volume of aggregates defined by the sum of the arbitrary volume of sand and the measured volume of cork.

0089The process developed is then characterized by the fact that on the one hand the flow of sand is adjustable and continuously measured by the weight variation measurement of a sand circulation member, for example by mounting this member on precision weighers and on the other hand that there is a computer program of servocontrol flow rates allowing, depending on the desired formulation, enslave cork and fiber flows to this sand flow measurement and also continuously accelerate or decelerate the flow of sand to maintain it at its expected flow rate, despite flow irregularities related to irregularities of internal friction in the circuit.

0090In view of the progress made in terms of defibration on the one hand, choice of fibers on the other hand and accuracy of the mixtures finally, it has been possible to systematically test numerous formulations. Surprisingly, the results are very significantly different from the preliminary results obtained with less suitable fibers, less well defibrated and mixed with less precision.

0091Surprisingly, the progress made on the choice of fibers and the method of defibration completely upset the results previously obtained, as shown by some examples of subsequent tests.

0092Many tests have been carried out on the various mixtures and relate to the mechanical aspect, the agronomic and hydric aspect and the adaptation of the product to different uses.

0093In particular, accelerometric tests make it possible to test the elasticity and the kinetic energy dissipation modes while other tests make it possible to measure the cohesion and the internal friction angle of the substrate.

0094The disadvantage of these tests is that they give measurements that characterize the substrate well, but without giving any effectiveness threshold, whether minimum threshold or maximum threshold.

0095In addition to scientific measures of characterization, we have been able to define a qualitative test of the minimum threshold of effectiveness, which is very simple and seems relevant because it is simple to carry out, discriminates and reproduces, and correlates with the objective of stability sought. This test consists, for a given substrate, in spreading it over a small height and a small surface, compacting it and then trying to push in a spade: for a fiber dosage lower than a certain dosage which defines the threshold efficiency demonstrated by this test, it is possible to push the spade, while above this dosage, it becomes very difficult and impossible to do, as soon as we exceed a little this threshold efficiency ; although dependent in absolute terms on compaction methodology and moisture or how to drive a spade, this test, carried out in a summary way by compacting with the feet, proved perfectly reproducible, even if is not of great precision and it was therefore used to determine the minimum threshold of fibers to be incorporated in the various granular mixtures tested.

0096These tests have shown a sensitivity to fiber for low dosages but with a minimum dosage that increases with the amount of fiber.

0097It has been observed that it is preferable to have at least 0.5 g / l of fiber to observe a fiber effect.

0098It is preferable to have at least 0.5 g / l of fiber and at least 1 g / liter of the sum of fibers plus inclusions to obtain a visible result with a cork dose greater than 5% and less than 60%.

0099It is preferable to have at least 1 g / l of fibers and at least 2 g / liter of the sum of fibers plus inclusions to obtain a visible result with a dose of cork greater than 60%.

0100Preferably, maximum efficiency is obtained for a substrate having a cork dose of less than 60% for a dosage of fibers plus elongated or surface inclusions of between 2 g / liter and 80 g / liter.

0101Preferably, a maximum efficiency is obtained for a substrate having a cork dose greater than 60% for a dosage of fibers plus elongated or surface inclusions of between 5 g / liter and 200 g / liter.

0102On the side of the maximum threshold of usable fiber in a mixture, it was not possible to find an objective test as for the minimum threshold and it is necessary, to determine the maximum preferable dose of the non-intrinsic criteria which are essentially the possibility and the interest to put more fibers in each granular mixture.

0103It has become obvious that the more cork there is, the more it is possible to integrate large amounts of fiber without "blocking" the mixing machine and the more it is useful to add to stabilize the mixture.

0104The disadvantages of putting too much are:<ul id="ul0006" list-style="dash" compact="compact"><li>first of all the difficulty of incorporating the fiber without stalling the mixing machine</li><li>and the difficulty of keeping a homogeneous mixture that is compacting well,</li><li>then the material cost increase</li><li>and the decrease in the pace of manufacture,</li><li>then the difficulty of spreading the mixture and keeping it flat</li><li>and lastly the increased difficulty of subsequently avoiding the segregation of fibers in over-number and poorly mixed.</li></ul>In general, however, the tests have not shown obvious intrinsic disadvantage unacceptable for a too high fiber dosage, as soon as it is possible to incorporate them; With the improvements of the production tool, it was possible to mix doses much more important than what had been imagined previously, without reaching an assay revealing a behavioral defect, even if, when the dose of fibers increases too much :<ul id="ul0007" list-style="dash" compact="compact"><li>the substrate becomes more and more difficult to put in place</li><li>the substrate becomes more and more difficult to compact,</li><li>the substrate requires more and more water and mechanical stress to be compacted</li><li>the substrate deviates more and more drying,</li><li>the substrate is more and more subject to drying segregation, with the fibers detaching in time on the surface of the substrate</li><li>the substrate has degraded agronomic characteristics.</li></ul>

0105It is noted that beyond a certain dosage the substrate no longer appears as a granular matrix with fibers circulating around the grains and separated from each other by these grains but evolves continuously towards a fibrous matrix in which are incorporated aggregates which are attached to the fibers by electrostatic or hydraulic cohesion forces and which continues to present itself as a culture substrate but with continuously changed characteristics and in less interesting for economic reasons, density.

0106It therefore appears from the view of these new tests that there is no maximum threshold test as there is a minimum threshold test but that there is simply a gradual degradation of the interest to increase the dosage. fiber, both economically and technically. Taking into account these new observations, no test allowed to fix a maximum intrinsic threshold not to exceed, even if the economic considerations or the difficulties of manufacture in the current state or of absence of observed advantage to increase the dosage of fibers beyond a certain limit makes it possible to set a maximum dosage which is preferable for the various tests carried out.

0107It is therefore not necessary to set a maximum dosage, although it is however desirable, preferably, not to exceed a maximum dosage for sports ground uses, and particularly for high sand content assays because:<ul id="ul0008" list-style="dash" compact="compact"><li>on the one hand, beyond a certain threshold, the soil becomes more and more difficult to adjust when the fiber dose increases</li><li>and because on the other hand the price increases (price of fiber and mixing time) without it being possible to observe in return a significant advantage in terms of stabilization.</li></ul>

0108For a cork dosage of less than 60%, it is preferable to have a fiber dosage of less than 80 g / liter.

0109Beyond 60% of cork and especially more than 75% and up to 100% of cork, we realized, with new tests carried out on the one hand for use in grass substrate for parking or for vehicular roads and secondly in light substrate for terrace cultivation that these uses make interesting an important fiber dosage but with maximum intrinsic limits that have appeared.

0110In the case of terraces, the preferable cork assays are between 60% and 95% (100% cork substrates were used but the substrate is less and there is a high segregation of the fibers above 90% ).

0111When we tried to increase the dosage of fibers beyond 200g / m3 for 95% cork assays, we found that it was more interesting to add 5% of sand and to return to a 90% cork and 10% sand substrate than to add 70 g / m3 of fibers because it is substantially equivalent in terms of compacted substrate density at most but with a sandy substrate that is better compacted and then stands in place while the increase in the weight of fibers increases the density of the substrate, but gives a substrate that is compacted less well and is then less well for a cost very much higher.

0112The preferred maximum dosage for a proportion of cork greater than 60% is 300 g / liter.

0113In the case of car parks or roads, it first appeared that increasing the proportion of cork promotes friction and the anti-shearing effect but that a minimum sand density is useful for the principle of Action-reaction and the preferable cork dosage is between 40 and 70%.

0114It then appeared in the same way that the density of fibers should be as large as possible to create a maximum of links and an anti-shear efficiency as great as possible but that its increase comes up against the disadvantage that the surface does not remain more compact because the water is necessary to compact the volume but that drying there is again abundance and destabilization.

0115It also seemed preferable not to exceed a dosage of 300 g / liter arbitrary granulate.

0116For a football sports field, it is preferable to keep a very low cork formulation at the entry level for economic reasons; but it is preferable to have between 5% and 20% of cork to improve flexibility; for high-end land, it is preferable to be between 20 and 40% cork, with a fiber dosage of between 7 and 15% for normally-intensive land and up to 20g / l for land. training very used. So that the ball bounces sufficiently, one must not exceed 60% of cork and to keep a fast ground while improving the flexibility for the sportsmen, it seems that 40% of cork is a good compromise.

0117For a golf green, the advantage of a substrate according to the invention is to allow a dense surface that remains aerated, bearing and hard, and decompacted conducive to the cultivation of the lawn with sufficient water reserve easily usable. To accelerate the green, that is to say the speed of the ball on the green, which is generally sought, the proportion of cork will have to be reduced but the other aspect is to have greens of a speed similar to the others golf greens, so that the proportion of cork will preferably be between 10% and 40%, depending on whether one seeks the performance of the green considered or the homogeneity with respect to the other existing greens.

0118Similarly for tennis, the amount of cork has an influence on the type of games; by increasing the proportion of cork, we obtain a higher comfort but a lower rebound and a lower rebound speed, which brings the behavior of the surface closer to that of a clay ground copiously watered while a substrate according to the The invention with a low proportion of cork will make it possible to obtain a surface approaching grass lawn on dry land. Depending on the objectives, the preferred proportion of cork will be 0 to 20% for a very fast surface, between 20% and 40% for a comfortable and slower surface type clay and up to 60% for a very hard surface. comfortable with a slow game, suitable for tennis practiced for pleasure rather than for competition.

0119For a rugby pitch, flexibility and durability matter more than the rebound of the ball and the best compromise is technically between 40 and 60% cork with 15 to 20 g / liter of substrate or between 20% and 40%. % cork with 10 to 15g / liter of fiber for a lower budget training ground.

0120The football and rugby fields may have a substrate layer according to the invention 10 to 15 cm thick or a substrate layer according to the invention 3 to 7 cm at the surface, resting on a sub-layer of sand of permeability at least equal.

0121At a time when there is concern for both sustainable development and heating the lawns, for their sporting use in winter, cork has a great advantage because of its isothermal nature: it gives the ground the capacity to withstand more intense cold without freezing and to stay longer warm enough to allow the grass to sprout or grow; in addition to this isothermal nature, the resilient appearance of the cork allows the soil to accommodate the possible expansion of water between 4 ° C and 0 ° C when the water turns into ice: the soil does not become hard and taken together in the case where the water present in the substrate becomes ice, especially since the substrate according to the invention has a very high permeability and retains a small amount of water by capillarity; most of the water present in the porosity is very quickly evacuated by gravity if the substrate is laid, as it should be, on a surface with effective drainage.

0122Thus, the substrates according to the invention make it possible to make a sports field that can be used in the winter without heating while other terrains are hard like stone and also makes it possible, if a heating of the substrate is put in place, to obtain a more stable temperature. important for much lower energy consumption. Tests have shown that, for the same heating energy distributed in the same way at the same time, the substrate according to the invention tested had a temperature 10 ° C higher than that of the control substrate.

0123Regarding gallop courses must be of both a lot more flexible because the horses used to run on wet grass in which their feet sink several centimeters, and very resistant to avoid having to put the clods back in place, as is currently the case, this work represents a very important cost. As a result, the desirable formulations comprise a minimum proportion of cork, of between 40 and 60% and preferably an even higher proportion, of between 60 and 80%, especially in the most sensitive areas, such as obstacle reception, with thicknesses of such a substrate comprised at least between 15 and 20 cm.

0124For the obstacle courses, they must be flexible, but not too much, and must especially restore the energy: a proportion between 10% and 40% of cork would be indicated on the technical level.

0125Surfaces for polo or trotting must be harder and the proportion of cork may advantageously be between 5% and 20%.

0126When the sports field, or sports surface, consists of juxtaposed bins, limited by walls, they are filled with a substrate according to the present invention over a height at least equal to that of these walls.

0127When the level of the substrate exceeds the level of these walls by a few centimeters, the preferred substrate is a substrate comprising more than 50% of cork because the lower density of the substrate and its elastic solid behavior allow the vertical edges exceeding the level of the walls. and the play surface to hold well, while ensuring the flexibility of the substrate.