WATER-PERMEABLE-RETENTIVE PAVEMENT STRUCTURE AND METHOD OF CONSTRUCTING THE STRUCTURE

Abstract

Provided is a water-permeable-retentive pavement structure that includes: a water absorption column formed by filling foam glass in a hole, the foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm, and the hole being formed through a roadbed to a depth below a groundwater level; a road subgrade formed on the roadbed, the road subgrade including the foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm; and a water-permeable pavement formed on the road subgrade.

Claims

1. A water-permeable-retentive pavement structure, comprising: a water absorption column formed by filling foam glass in a hole, the foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm, the hole being formed through a roadbed to a depth below a groundwater level; a road subgrade formed on the roadbed, the road subgrade including foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm; and a water-permeable pavement formed on the road subgrade; wherein the road subgrade includes: a lower layer made of foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm; an intermediate layer, on the lower layer, made of foam glass having a continuous pore structure with a grain diameter of 5.0 mm to 10 mm; and an upper layer, on the intermediate layer, made of foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm.

2. The water-permeable-retentive pavement structure according to claim 1, comprising foam glass laid evenly on the water-permeable pavement, the foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm.

3. The water-permeable-retentive pavement structure according to claim 1, wherein the water absorption column has a diameter of 100 mm to 300 mm.

4. The water-permeable-retentive pavement structure according to claim 3, wherein the number of the water absorption columns is one to five per 1 m.sup.2 of a plane.

5. The water-permeable-retentive pavement structure according to claim 1, wherein the water absorption column has a length of 1.5 m to 3.5 m.

6. A water-permeable-retentive pavement structure according to claim 1, wherein the lower layer has a thickness of 2 cm to 5 cm, the intermediate layer has a thickness of 10 cm to 30 cm, and the upper layer has a thickness of 2 cm to 5 cm.

7. A method of constructing a water-permeable-retentive pavement, the method comprising: forming a hole through a roadbed to a depth below a groundwater level; forming a water absorption column by filling the hole with foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm; forming a road subgrade on the roadbed with foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm; and forming water-permeable pavement on the road subgrade; wherein the road subgrade is formed by: configuring a lower layer by scattering foam glass, laying the foam glass evenly, and subjecting the foam glass to rolling compaction, the foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm; configuring an intermediate layer, on the lower layer, by scattering foam glass, laying the foam glass evenly, and subjecting the foam glass to rolling compaction, the foam glass having a continuous pore structure with a grain diameter of 10 mm to 50 mm; and configuring an upper layer, on the intermediate layer, by scattering foam glass, laying the foam glass evenly, and subjecting the foam glass to rolling compaction, the foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a cut-out cross-sectional perspective view showing a water-permeable-retentive pavement structure according to an embodiment of the present invention; and

[0019] FIG. 2 is a diagram showing suction of water in soil and water retention amounts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] FIG. 1 is a cut-out cross-sectional perspective view showing a water-permeable-retentive pavement structure according to an embodiment of the present invention.

[0021] As shown in FIG. 1, a water-permeable-retentive pavement structure 1 according to the embodiment of the present invention has a road subgrade 3 made of foam glass formed on a roadbed 2, and a water-permeable pavement 4 formed on the road subgrade 3. The water-permeable pavement 4 is at least water-permeable asphalt pavement, concrete pavement, interlocking blocks, or the like. In addition, the water-permeable pavement 4 may have water retentivity in addition to water permeability.

[0022] In addition, the water-permeable-retentive pavement structure 1 includes water absorption columns 5 formed by filling holes 10 each formed through the roadbed 2 to a depth below the groundwater level WL with foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm. The length of each water absorption column 5 depends on the depth of the groundwater level WL, but is set to a length that can correspond to the fluctuation range of the groundwater level WL, for example, 1.0 m to 3.5 m, preferably 1.5 m or more and 2.5 m or less. The diameter of the water absorption column 5 is 100 mm to 300 mm. There are one to five water absorption columns 5 provided per 1 m.sup.2 of a plane.

[0023] The road subgrade 3 is composed of: a lower layer 3A made of the foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm; an intermediate layer 3B, on the lower layer 3A, made of foam glass 12 having a continuous pore structure with a grain diameter of 5.0 mm to 10 mm; and an upper layer 3C, on the intermediate layer 3B, made of the foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm. Here, the foam glass 11 and 12 to be used in the water-permeable-retentive pavement structure 1 in the present embodiment has a specific gravity of 0.3 to 0.5 and a water absorption rate of 100% or more and 135% or less.

[0024] The lower layer 3A is formed to a thickness of 2 cm to 5 cm by scattering foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm, laying it evenly, and subjecting it to rolling compaction. The intermediate layer 3B is formed to a thickness of 10 cm to 30 cm by scattering foam glass having a continuous pore structure with a grain diameter of 10 mm to 50 mm on the lower layer 3A, laying it evenly, and subjecting it to rolling compaction. The upper layer 3C is formed to a thickness of 2 cm to 5 cm by scattering foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm on the intermediate layer 3B, laying it evenly, and subjecting it to rolling compaction.

[0025] The foam glass having a continuous pore structure with a grain diameter of 10 mm to 50 mm in forming the intermediate layer 3B is pulverized by rolling compaction to be the foam glass 12 having the continuous pore structure with a grain diameter of 5.0 mm to 10 mm. Contrarily, the foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm in forming the lower layer 3A and the upper layer 3C is not pulverized so much by the rolling compaction, to have the grain diameter remaining almost unchanged. Therefore, the foam glass becomes the foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm.

[0026] In the water-permeable-retentive pavement structure 1 having the above configuration, the foam glass 11 in the water absorption columns 5, which is the foam glass 11, having a continuous pore structure, filled in the holes 10 formed through the roadbed 2 to a depth below the groundwater level WL, allows a capillary action to suck up the groundwater. This allows the foam glass 11 and 12 of the road subgrade 3 to absorb and retain the water. When the temperature of the road surface rises due to sunshine or the like, the water passes through the water-permeable pavement 4 formed on the road subgrade 3, rises, gasifies on the road surface, and evaporates into the atmosphere. The evaporation heat at this time reduces the temperature rise of the road surface.

[0027] In addition, water supplied to the road surface through rainfall, sprinkled water, etc. passes through the water-permeable pavement 4 and is absorbed by and retained in the foam glass 11 and 12 in the road subgrade 3 and the water absorption columns 5. The foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm has a very large water permeability coefficient of about 1?10.sup.?1 (m/s), and the water permeability is as high as clean gravel, so that water easily passes from the water absorption columns 5 to the bottom of the roadbed 2. Then, the foam glass 11 in the water absorption columns 5 and the groundwater are brought into contact and mixed to be integrated. Thereafter, water in the groundwater is constantly sucked up through capillary action, and is absorbed by and retained in the foam glasses 11 and 12 in the road subgrade 3.

[0028] In addition, the water-permeable-retentive pavement structure 1 of the present embodiment has the water absorption columns 5 each having a diameter of 100 mm to 300 mm. This allows constantly keeping groundwater sucked up to the road subgrade 3 through the water absorption columns 5. Furthermore, one to five water absorption columns 5 arranged per 1 m.sup.2 of a plane allows constantly keeping an appropriate amount of groundwater sucked up to the road subgrade 3 through the water absorption columns 5.

[0029] The above water-permeable-retentive pavement structure 1 is formed, for example, by the following procedure.

[0030] (1) The water absorption columns 5 are formed by excavating from the roadbed 2 to a depth of 1.0 m below the groundwater level WL (=about 0.4 to 0.7 m) with an auger of ?100 to 300 mm, and filling the foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm in the excavated holes 10 up to the opening 10A. At this time, the number of water absorption columns 5 to be formed per 1 m.sup.2 of a plane is one to five, for example.

[0031] (2) The lower layer 3A made of the foam glass 11 having a continuous pore structure, for example, with a grain diameter of 1.0 mm to 2.0 mm and a thickness of 2 cm, is formed by scattering foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm on the roadbed 2, laying it evenly, and subjecting it to rolling compaction. The intermediate layer 3B made of the foam glass 12 having a continuous pore structure, for example, with a grain diameter of 5.0 mm to 10 mm and a thickness of 10 cm, is formed by scattering the foam glass 12 having a continuous pore structure with a grain diameter of 10 mm to 50 mm on the lower layer 3A, laying it evenly, and subjecting it to rolling compaction. The upper layer 3C made of the foam glass 11 having a continuous pore structure, for example, with a grain diameter of 1.0 mm to 2.0 mm and a thickness of 3 cm, is formed by scattering the foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm on the intermediate layer 3B, laying it evenly, and subjecting it to rolling compaction. In this way, the road subgrade 3 is formed.

[0032] FIG. 2 is a diagram showing suction of water in soil and water retention amounts. Sample A in FIG. 2 is the foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm after rolling compaction. Sample B is the foam glass 12 having a continuous pore structure with a grain diameter of 5.0 mm to 10 mm after rolling compaction. Sample C is foam glass having a continuous pore structure with a grain diameter of 1.0 to 10 mm, formed by mixing foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm and foam glass having a continuous pore structure with a grain diameter of 10 mm to 50 mm at a ratio of 3:7 and subjecting the mixture to rolling compaction. As shown in FIG. 2, only the foam glass 11 of sample A having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm had three times the water retention amount of the foam glass 12 of sample B having a continuous pore structure having a grain diameter of 5.0 mm to 10 mm. In addition, sample C had a water retention amount approximately twice that of sample B. However, if the road subgrade 3 is composed only of the foam glass 11 with a small grain diameter, the construction unit price will be high. Therefore, the upper layer 3C with a thickness of 3 cm and the lower layer 3A with a thickness of 2 cm are made of the foam glass 11 having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm, and the intermediate layer 3B with a thickness of 10 cm is made of the foam glass 12 with a continuous pore structure having a grain diameter of 10 mm to 50 mm.

[0033] (3) The water-permeable pavement 4 is formed on the road subgrade 3. Note that the water-permeable asphalt serving as the water-permeable pavement 4 has so many pores that water retained in the foam glass 11 and 12 of the roadbed 2 and the road subgrade 3 does not rise to the pavement surface. Therefore, it is desirable to scatter foam glass having a continuous pore structure with a grain diameter of 1.0 mm to 2.0 mm on the water-permeable pavement 4 and lay it evenly. This allows capillary action in the pores on the surface of the water-permeable pavement 4, so that the pores on the surface of the water-permeable pavement 4 can also exhibit a water retention function and promote gasification on the road surface. This allows further reducing the temperature rise of the road surface.

EXAMPLES

[0034] The water-permeable-retentive pavement structure 1 in the above embodiment was subjected to test construction, and a temperature comparison was made with conventional pavement using a normal temperature asphalt mixture (Remifalt (trade name) manufactured by NIPPO CORPORATION).

[0035] Examples 1 to 4 use water-permeable-retentive interlocking blocks as the water-permeable pavement 4. Examples 5 to 7 use water-permeable-retentive asphalt pavement as the water-permeable pavement 4. The test results are shown in Tables 1 and 2, respectively.

[0036] <Water-Permeable-Retentive Interlocking Blocks>

TABLE-US-00001 TABLE 1 Number of Temperature water difference absorption Number of compared to columns construction Color of Sensor Remifalt (columns/m.sup.2) (columns) block position pavement (? C.) Example 1 4/4 m.sup.2 White Part ?11.4 1 immediately above water absorption column Example Green Part ?11.1 2 immediately above water absorption column Example 2 8/4 m.sup.2 White Part outside ?13.5 3 of water absorption column Example White Part ?13.5 4 immediately above water absorption column

[0037] (1) The water-permeable-retentive interlocking blocks had the largest temperature difference from the Remifalt pavement in Examples 3 and 4, and the difference was ?13.5? C.

[0038] (2) Examples 1 and 2 shows that the white interlocking blocks had a temperature lower by 0.3? C. between the colors.

[0039] (3) Examples 1 and 4 shows that the interlocking blocks with two water absorption columns per m.sup.2 had a temperature 2.1? C. lower than those with one water absorption column per m.sup.2. A comparison during the daytime (9:00 to 18:00) also showed the interlocking blocks with two water absorption columns per m.sup.2 had lower values (maximum 2.6? C.) in all sections.

[0040] (4) Examples 3 and 4 showed there was no difference between a part of an interlocking block (white) immediately above the water absorption column and a part outside thereof.

[0041] <Water-Permeable-Retentive Asphalt Pavement>

TABLE-US-00002 TABLE 2 Temperature Number of difference water compared to absorption Number of Remifalt columns construction Surface Sensor pavement (columns/m.sup.2) (columns) layer position (? C.) Example 1 4/4 m.sup.2 Water- Part ?7.9 5 permeable- immediately retentive above water pavement absorption column Example Water- Part outside ?6.2 6 permeable- of water retentive absorption pavement column Example 2 8/4 m.sup.2 Water- Part ?9.9 7 permeable- immediately retentive above water pavement absorption column

[0042] (1) The water-permeable-retentive asphalt pavement had the largest temperature difference from the Remifalt pavement in Examples 7, and the difference was ?9.9? C.

[0043] (2) Examples 5 and 6 shows that there was almost no temperature difference as small as 1.7? C. between a part immediately above a water absorption column and a part outside thereof.

[0044] (3) Examples 5, 6, and 7 shows that the water-permeable-retentive asphalt pavement with two water absorption columns per m.sup.2 had a temperature 2.0? C. lower than the pavement with one water absorption column per m.sup.2. A comparison during the daytime (9:00 to 18:00) also showed a tendency in which the water-permeable-retentive asphalt pavement with two water absorption columns per m.sup.2 had lower temperature.

INDUSTRIAL APPLICABILITY

[0045] The present invention is useful as a water-permeable-retentive pavement structure having water permeability and water retentivity and a method of constructing the structure, and is particularly suitable as a water-permeable-retentive pavement structure capable of reducing a temperature rise of the road surface utilizing groundwater and a method of constructing the structure.

REFERENCE SIGNS LIST

[0046] 1 water-permeable-retentive pavement structure [0047] 2 roadbed [0048] 3 road subgrade [0049] 3A lower layer [0050] 3B intermediate layer [0051] 3C upper layer [0052] 4 water-permeable pavement [0053] 5 water absorption column [0054] 10 hole [0055] 11, 12 foam glass