WO1999009254A1

WO1999009254A1 - Structure of ground surface portion

Info

Publication number: WO1999009254A1
Application number: PCT/JP1997/002878
Authority: WO
Inventors: Katsuyuki Ogura; Yoshio Aihara
Original assignee: Dyflex Corporation; Ay Chemical Co., Ltd.
Priority date: 1997-08-20
Filing date: 1997-08-20
Publication date: 1999-02-25

Abstract

Formed on a substrate roadbed layer (4) is a cushioning layer (5) having a thickness of 50 mm to 200 mm and composed of elastic chips, which are formed by an elastic material to have a size of 7 mm to 0.05 mm, preferably 2 mm to 0.5 mm and a specific gravity of 1.8 to 3.5, alone or a mixture of the elastic chips and sand. The cushioning layer (5) contains elastic chips in 3 wt.% or more. The elastic chips are formed by blending a material selected from synthetic rubber, natural rubber and synthetic resin with a specific gravity adjusting material, which is composed of inorganic grains having a specific gravity of 3 or more.

Description

Description Structure of ground surface Technical field

The present invention mainly relates to a structure of a ground surface such as a dirt course on a racetrack, a ball court, a tennis court, an athletic track, and a general athletic field.

: Technology

On dirt courses at racetracks, a river sand layer is usually formed on an underground roadbed layer, taking into account drainage and impact mitigation, and this river sand layer is used as a cushion layer on the ground surface.

The disadvantage of this cushion layer is that, when used for a long period of time, river sand is pulverized by the impact of a horseshoe kick and settles at the bottom of the cushion layer, forming a rigid plate-like layer, In addition, poor drainage occurs due to deterioration of the performance, and the actual thickness of the cushion layer is reduced, causing an accident such as horseshoe kicking the above-mentioned hard plate layer and damaging the horse leg. That is.

Therefore, chip rubber (mainly discarded tire rubber) and plastics used in general sports facilities such as track and field sports are mixed with river sand and the like, and the cushion layer of the dirt course is formed. It was proposed to be composed.

However, the specific gravity of such rubber and plastic chips is about 1.1 to 1.5, and when sand is blended, the chips float on the surface of the cushion layer due to the difference in specific gravity with sand. Therefore, the homogeneity of the cushion layer cannot be maintained. In addition, the function to prevent the pulverization (siltation) of sand during the use process has not been sufficiently studied. The present invention has been made based on the above circumstances, and one of its objects is to achieve uniform stabilization of the cushion layer in the structure of the ground surface portion and to suppress the pulverization of the cushion layer. It is in.

Further, another object of the present invention is to provide a ground surface portion having good mobility (that is, capable of effectively obtaining a propulsive force during walking or running: so-called good foot clearance). Is to provide a structure. Disclosure of the invention

In order to achieve the above object, according to the present invention, an underground material having a specific gravity of 1.8 to 3.5, which is made of an elastic material and has a size of 7 mm to 0.05 mm, preferably 2 mm to 0.5 mm. The cushion layer is formed by using elastic chips alone or mixed with sand.

The elastic material can be formed by blending a material selected from synthetic rubber, natural rubber, and synthetic resin with a specific gravity adjusting material made of inorganic powder having a specific gravity of 3 or more.

The cushion layer preferably contains an elastic chip of 3% or more by weight. In this way, by using an elastic chip having a specific gravity close to that of sand alone or by mixing it with sand at an appropriate ratio, the cushion layer is homogenized (including homogenous stability over time). It is possible to suppress the pulverization of the cushion layer.

The thickness of the cushion layer can be appropriately set according to the intended use. For application to a horse racetrack dart course, 50 to 200 mm is preferable. If the thickness is less than 500 mm, it tends to be difficult to obtain good cushioning properties for racehorses. If the thickness exceeds 200 mm, the economic efficiency tends to decrease.

Compact the sand or soil to a thickness of 20 Omm to 30 Omm or 50 mm to 7 Om with the construction of asphalt concrete or concrete. The cushion layer can be formed on the roadbed layer having a thickness of 0 mm. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic sectional view illustrating an embodiment of the present invention.

FIG. 2 is a graph showing test results according to the present invention.

FIG. 3 is a schematic diagram showing an outline of an apparatus used for a test for obtaining the test results of FIG. BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, as shown in FIG. 1, as a dirt course of a racetrack, for example, a layer 1 of cut crushed stone is formed to a thickness of 250 mm, and a layer 2 of volcanic gravel is formed thereon to a thickness of 50 mm. Then, a layer 3 of Cinder is formed to a thickness of 50 mm on top of it, and a pile of sand (grain size: 2 mm to 0.5 mm, for example) is compacted on top of it. A subbase layer 4 having a thickness of preferably 200 mm to 300 mm is formed, and further thereon a 7 mm (3 mesh) to 0.05 mm (300 mesh), preferably 2 mm The cushion layer 5 made of an elastic chip having a specific size of 1.8 to 3.5 and having a specific gravity of 1.8 to 3.5 with a size of 10 mm (10 mesh) to 0.5 mm (40 mesh) is formed. It is formed to a thickness of 200 mm. The size of the elastic tip is within the above range if it passes through the corresponding coarse mesh size sieve described in the above range but does not pass through the corresponding fine mesh size sieve. Is defined as In the present invention, it is most preferable that all the elastic chips included in the cushion layer are within the above range, but a small amount outside of these ranges is small (for example, within 10% by weight of the total elastic chips, preferably Is within 5% by weight, more preferably within 2% by weight, and most preferably within 1% by weight. As the cushion layer 5, a mixture of the above elastic chip and sand, preferably river sand (particle size: for example, 2 mm to 0.5 mm) may be used. In this case, it is preferable to mix at least 3% by weight or more of elastic chips with the sand. The effectiveness of this elastic tip will be described in detail in the following embodiments.

The shape of the elastic chip is, for example, a flake shape or a granular shape, but is not limited thereto. The size of the elastic chip is preferably about 2 mm to 0.5 mm, which is close to the size (grain size) of mountain sand or river sand in consideration of homogeneous mixing with sand.

The elastic material is selected from synthetic rubber such as ethylene-propylene rubber and urethane rubber, natural rubber, or a material selected from general-purpose synthetic resins such as vinyl chloride resin, vinyl acetate resin, polystyrene, polyethylene, and polypropylene. It is made by blending inorganic powder materials such as titanium oxide, barium sulfate, barium carbonate, lithium oxide, iron oxide, lead oxide, antimony oxide, and zinc oxide (preferably having a specific gravity of 3 or more). ing.

As the elastic chip, for example, a material having a specific gravity of 2.5, which is obtained by mixing 400 parts by weight of barium sulfate with 100 parts by weight of EPDM (ethylene-propylene rubber) can be used.

[Example]

An elastic tip made of a material with a specific gravity of 2.5, which is a mixture of 100 parts by weight of EPDM and 400 parts by weight of barium sulfate, with a grain size of 2 mm to 0.5 mm is used. Then, a test of pulverization of the cushion layer 5 was performed.

As an example of a cushion layer, the above elastic chip was blended in river sand (particle size: 2 mm to 0.5 mm; the same applies hereinafter) at a 3% weight ratio (97: 3). At a 10% weight ratio (9: 1) Case 2, case 3 where elastic chips were blended with river sand at a 20% weight ratio (8: 2), and a comparative example (conventional example) where river sand was 100% were used.

The method of this pulverization test is as follows. A 150 mm diameter container is filled with each sample to a thickness of 70 mm (weight: about 150 g), and a 50 mm diameter and 4.5 kg iron rod is placed. This method is to drop naturally from a height of 4 25 mm, perform this drop 100 times, then separate fine powder with a No. 100 mesh sieve, and measure the amount of separated fine powder. .

The results of the micronization test are shown in Table 1 below.

table 1

In conclusion, micronization is halved with more than 10% of elastic chips mixed with 100% sand. In other words, it can be seen that the elastic tip absorbs the impact energy and significantly reduces sand damage.

In addition, the impact energy mitigation test for the cushion layer has obtained the results shown in Figure 2. In this test, the above sample was filled into a container with a thickness of 40 mm as shown in Fig. 3 and a rod with a contact surface of 40 mm x 40 mm was used. Is compressed. From the graph in Fig. 2, it can be seen that the compressive displacements in Cases 2 and 3 were significantly increased as compared with the comparative example, and exhibited high cushioning properties.

The structure of the ground surface with such high cushioning properties is particularly effective when adopted for a racetrack dart course, and the feature of using an elastic tip is that the mobility Good (that is, there is less occurrence of elastic chips and sand escape [flow] when stepping on Propulsion can be obtained effectively, and so-called stepping-out is improved). Such characteristics are even more remarkable when synthetic rubber or natural rubber is used as the material of the elastic chip, or when synthetic resin having a high degree of rubber is used.

In addition, the cushion layer with 20% elastic chip mixed in Example 3 and the cushion layer with tire rubber chips (specific gravity of 1.1 to 1.5) used as elastic chips (mixed at 20% weight ratio). As a result, the following conclusions were obtained as a result of a visual comparison test on the stability over time of the homogeneity of the mixed material in the cushion layer. That is, both were laid at a thickness of 50 mm in a busy passage and left for 2 months, and visually observed that the former according to the present invention did not change at all on the surface, but the latter A considerable amount of the mixed material (tire rubber chips) was released from the river sand and floated on the surface, indicating that the above-mentioned stability of the cushion layer was reduced. From this, the significance of the specific gravity adjustment by the specific elastic tip in the present invention became clear.

In the above embodiment, the structure of the ground surface portion of the present invention is adopted for a dirt course of a racetrack, but other exercise facilities, for example, a tennis court, a volleyball court, other ballparks, Of course, it can be applied to the structure of the surface of the ground, such as a track and field stadium, a multipurpose open space, a school yard, and a playground.

In this case, depending on the application, soil may be used for the roadbed layer in addition to sand, and it may be formed to a thickness of, for example, 50 to 70 mm by asphalt concrete or concrete construction. May be adopted.

As described above, according to the present invention, the elastic material having a specific gravity of 1.8 to 3.5 made of an elastic material and having a size of about 7 mm to 0.05 mm, preferably about 2 mm to 0.5 mm. The chip layer is formed by laying the chip alone or mixed with sand, preferably in a thickness of 50 to 200 mm, so that the cushion layer on the ground surface portion which is repeatedly stepped on can be used with time. This makes it possible to stabilize the composition homogeneously and suppress the pulverization of the cushion layer. Also, the elastic tip By using it, it becomes possible to obtain the propulsive force of walking or running effectively, and the motility on it becomes good. Industrial applicability

As described above, the structure of the ground surface according to the present invention can be used for dirt courses on racetracks and other sports facilities, such as tennis courts, ball courts, other ball fields, athletics fields, multipurpose plazas, and schools It can be used for the structure of the ground surface such as schoolyards and playgrounds.

Claims

The scope of the claims

1. Cushion layer on the underground with elastic chips of 7 to 0.05 mm in size and made of elastic material and having a specific gravity of 1.8 to 3.5 alone or mixed with sand The structure of the surface of the ground, characterized in that the surface is formed;

2. The structure of the ground surface portion according to claim 1, wherein the size of the elastic tip is 2 mm to 0.5 mm.

3. The structure of the ground surface portion according to claim 1, wherein the elastic material is formed by blending a specific gravity adjusting material with a material selected from a synthetic rubber, a natural rubber, and a synthetic resin.

4. The structure of the ground surface portion according to claim 3, wherein the specific gravity adjusting material is made of an inorganic powder having a specific gravity of 3 or more.

5. The structure of the ground surface portion according to claim 1, wherein the cushion layer includes the elastic chip in a weight ratio of 3% or more.

6. The structure of the ground surface part according to claim 1, wherein the thickness of the cushion layer is 50 mm to 200 mm.

7. The ground has a roadbed layer formed by compacting sand or soil or by asphalt concrete or concrete, and the cushion layer is formed on the roadbed layer. The structure of the ground surface portion according to claim 1, wherein:

8. The structure of the ground surface portion according to claim 7, wherein the thickness of the roadbed layer formed by squeezing the sand or soil is 200 mm to 300 mm.

9. The structure of the ground surface portion according to claim 7, wherein the thickness of the roadbed layer formed by the asphalt concrete or concrete application is 50 mm to 70 mm.