Rainwater storage device

Abstract

To provide a rainwater storage device that has a large water storage capacity and is easy to construct.SOLUTION: A rainwater storage device of the present invention, comprising a crushed stone layer, comprises a rainwater storage tank and a sheet that envelops at least a portion of the crushed stone layer. Furthermore, the crushed stone layer is provided on both opposing sides of the rainwater storage tank, and the sheet envelops both the rainwater storage tank and the crushed stone layer provided on both sides of the rainwater storage tank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rainwater harvesting device. [Background technology]

[0002] Generally, a retarding basin (rainwater storage tank) that temporarily stores rainwater during rainfall is placed underground, and the amount of rainwater downstream is adjusted. Such rainwater storage devices are used as parks and school grounds by forming an artificial base on the surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-177414 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-132740 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the rainwater storage device described in Patent Document 1, the main components of the tank that stores rainwater are box culvert-type or U-shaped gutter-type perforated plate grooves, which requires large heavy machinery for construction and is not easy to install. Therefore, it is difficult to achieve both a large capacity for rainwater storage and ease of construction.

[0005] Furthermore, although the rainwater storage device described in Patent Document 2 is equipped with a means for preventing floating, the component for preventing floating does not have the function of storing rainwater, so the amount of stored water is not sufficient, resulting in a problem of increased costs relative to the amount of water stored.

[0006] An object of the present invention is to provide a rainwater storage device that has a large water storage capacity and is easy to install. [Means for solving the problem]

[0007] A rainwater storage device according to one aspect of the present invention is a rainwater storage device comprising a rainwater storage tank and a crushed stone layer, characterized in that it comprises a sheet that wraps the rainwater storage tank and at least a portion of the crushed stone layer. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a rainwater storage device that can store a large amount of water and is easy to install. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a rainwater storage device according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing a rainwater storage device including an inlet pipe and an outlet pipe according to a first embodiment of the present invention. [Figure 3] FIG. 4 is a cross-sectional view showing a rainwater storage device according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view showing a rainwater storage device according to a third embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view showing a rainwater storage device according to a fourth embodiment of the present invention. [Figure 6] FIG. 10 is a cross-sectional view showing a rainwater storage device according to a fifth embodiment of the present invention. [Figure 7] FIG. 10 is a perspective view of a main part of a rainwater storage tank used in a rainwater storage device according to a sixth embodiment of the present invention. [Figure 8] FIG. 1 is a perspective view of a quarter-sized rainwater retention block. [Figure 9] FIG. 2 is a plan view of the rainwater storage block. [Figure 10] 9 is a view seen in the direction of the arrow A1 in FIG. 8. [Figure 11] FIG. 10 is a perspective view of another rainwater storage block. [Figure 12] FIG. 10 is a perspective view of another rainwater storage block. [Figure 13] FIG. [Figure 14] FIG. 10 is a cross-sectional view of a rainwater storage tank according to a sixth embodiment of the present invention. [Figure 15] FIG. 10 is a perspective view of a rainwater storage block according to a first modified example. [Figure 16] FIG. 10 is a cross-sectional view of a rainwater storage tank according to a first modified example. [Figure 17] FIG. 10 is a cross-sectional view of a rainwater storage tank according to a second modified example. [Figure 18] FIG. 18 is an enlarged perspective view of a portion of the inspection hatch in FIG. 17. [Figure 19] FIG. 10 is a perspective view of a rainwater storage block according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) Hereinafter, a rainwater storage device 1 according to a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the rainwater storage device 1 includes a rainwater storage tank 2, a crushed stone layer 3, and a sheet 4 arranged around the rainwater storage tank 2 and the crushed stone layer 3.

[0011] The rainwater storage device 1 is provided underground and installed on top of a foundation 5 formed underground. An artificial base (not shown) is formed on the upper surface of the rainwater storage device 1, and is used as a park or school ground.

[0012] The rainwater storage tank 2 is a tank that stores rainwater when it rains. Specifically, when it rains, rainwater directly enters the rainwater storage tank 2 from the ground, whereby the rainwater is stored. Any conventionally known rainwater storage tank 2 can be used. For example, the rainwater storage tank 2 may have a structure in which a plurality of rainwater storage blocks (structural members) 6 are stacked, and may be constructed by laying a plurality of rainwater storage blocks 6 in the front-to-back and left-to-right directions and further stacking them vertically. In other words, the rainwater storage tank 2 may be constructed by arranging a plurality of rainwater storage blocks 6 along a horizontal plane and stacking them vertically.

[0013] The rainwater storage tank 2 in which such rainwater storage blocks 6 are stacked may be one described in detail in, for example, Japanese Patent Application Laid-Open Nos. 2011-132740, 2011-74692, 2017-14831, and 2014-240593.

[0014] The rainwater storage tank 2 is configured in a rectangular parallelepiped shape with predetermined lengths in the front-to-back, left-to-right, and up-to-down directions. Therefore, when the rainwater storage device 1 is viewed from above, the rainwater storage tank 2 is formed in a quadrilateral shape. The dimensions of the rainwater storage tank 2 may be determined appropriately based on the desired amount of water to be stored.

[0015] The crushed stone layer 3 is a layer made of crushed stone and has the function of storing rainwater. Specifically, crushed stone is filled underground and rainwater is temporarily stored in the gaps between the crushed stone. There are two types: a storage type and an infiltration type. Both types reduce the sudden inflow of rainwater into drainage facilities during heavy rain and contribute to preventing flood damage. They are also storage tanks that can be installed relatively inexpensively.

[0016] The crushed stone layers 3 are arranged on both the left and right side surfaces (opposite side surfaces) of the rainwater storage tank 2. Each of the crushed stone layers 3 is formed in a rectangular parallelepiped shape, and has a predetermined length in the front-to-back, left-to-right, and up-to-down directions. The lengths of the crushed stone layer 3 in the front-to-back, left-to-right, and up-to-down directions may be determined as appropriate, for example, by referring to the dimensions of the rainwater storage tank 2. In this embodiment, the lengths of the crushed stone layer 3 in the front-to-back direction (the direction toward the depth of the paper in FIG. 1) and up-to-down directions are equal to the lengths of the rainwater storage tank 2 in the front-to-back and up-to-down directions.

[0017] Each crushed stone layer 3 may be entirely wrapped in a sheet (not shown). This sheet may be either water-permeable or water-resistant, but using a water-permeable sheet is preferable because it is expected that the crushed stone layer 3 will have the rainwater storage function. Also, by wrapping a geotextile around the crushed stone layer 3, it is possible to improve the sheet's water permeability and strength.

[0018] In this embodiment, both the rainwater storage tank 2 and the crushed stone layer 3 are rectangular parallelepipeds, but the shape is not limited to this. For example, a protrusion that protrudes from the crushed stone layer 3 into the rainwater storage tank 2 may be provided on the side surface of the crushed stone layer 3 that contacts the rainwater storage tank 2.

[0019] In addition, a sheet 9 is provided at the boundary between the crushed stone layer 3 and the rainwater storage tank 2. The sheet 9 prevents crushed stone from entering the rainwater storage tank 2 from the crushed stone layer 3. In the illustrated example, the sheet 9 is provided over the entire boundary between the crushed stone layer 3 and the rainwater storage tank 2. A water-permeable sheet or a water-impermeable sheet can be used as the sheet 9. In addition to sheets made of various materials, the sheet 9 may also be made of geotextile. In order to prevent damage due to frictional force or the like, the tensile strength of the sheet 9 is preferably 5 kN / m or more.

[0020] In this embodiment, the rainwater storage tank 2 and the crushed stone layer 3 are enclosed by the sheet 4. Specifically, the sheet 4 is wrapped around the upper and lower surfaces of the rainwater storage tank 2, the upper and lower surfaces of both crushed stone layers 3, and the sides of the crushed stone layers 3 that are not in contact with the rainwater storage tank 2.

[0021] The sheet 4 may be a water-permeable sheet or a water-impermeable sheet. Furthermore, in order to prevent damage due to frictional forces and the like, the tensile strength of the sheet 4 is preferably 5 kN / m or more.

[0022] The sheets 4 and 9 used in this embodiment, and the sheet encasing the crushed stone layer 3, need to be made of different materials depending on the location where they are used. When using a water-permeable sheet, it is also possible to use a geotextile in addition to the water-permeable sheet. When using a geotextile in combination, the strength of the geotextile can protect other sheets used inside the rainwater storage tank 2. In particular, geotextiles are useful in the gap between the soil and the crushed stone layer (especially the top surface) because they are stronger than other sheets and allow water and other substances to pass through freely.

[0023] As the water-permeable sheet, for example, a nonwoven fabric such as a polyester long fiber nonwoven fabric can be used. As the water-impermeable sheet, for example, a sheet made of a thermoplastic elastomer, an ethylene vinyl acetate, a vinyl chloride resin, a vulcanized rubber, or the like can be used. Geotextiles are made of polyethylene, polypropylene, polyester filaments, and aramid fibers.

[0024] The geotextile may also be wrapped around the top and sides of the rainwater storage tank 2. In this case, it is effective to protect the surface of the rainwater storage tank 2 and other sheets, such as the sheet 4, wrapped around the rainwater storage tank 2.

[0025] One thing to note about sheets is that the material used needs to be different depending on whether the water you want to flow into the rainwater storage tank 2 is inflow water from a pipe or seepage water from the ground. In the case of inflow water from a pipeline, it is preferable that the sheet 9 covering the rainwater storage tank 2 and the crushed stone layer 3 is a water-impermeable sheet to prevent the inflow of water from sources other than the pipeline. On the other hand, in the case of infiltration water from the ground, it is necessary to use a permeable sheet on the top surface of the rainwater storage tank 2 to allow water to enter.

[0026] The foundation 5 may be configured to allow rainwater to permeate. For example, the foundation may be made of materials that allow rainwater to permeate, such as crushed stone or sand.

[0027] Moreover, the rainwater storage tank 2 preferably includes a pipe for receiving rainwater and a pipe for discharging rainwater. For example, as shown in Figure 2, an inlet pipe 10a and an outlet pipe 10b may be connected to the rainwater storage tank 2. The number and diameter of the inlet pipes 10a and outlet pipes 10b may be selected as appropriate. Note that in Figure 2, the crushed stone layer 3 and sheets 4 and 9 provided on one side of the rainwater storage tank 2 are omitted.

[0028] By providing the inlet pipe 10a, the method of storing water using the rainwater storage tank 2 is not limited to storing rainwater directly from the ground during rainfall (precipitation), but can also store water flowing in from the inlet pipe 10a. Furthermore, by providing the outflow pipe 10b, the water stored in the rainwater storage device 1 can be discharged to the outside of the device.

[0029] The inlet pipe 10a and the outlet pipe 10b may be connected to either the rainwater storage tank 2 or the crushed stone layer 3, and either or both of the inlet pipe and the outlet pipe may not be provided.

[0030] The rainwater storage device 1 of this embodiment has the above-described configuration, and can provide a rainwater storage device that can store a large amount of water and is easy to install. More specifically, the rainwater storage device 1 can store water in the rainwater storage tank 2 and the crushed stone layer 3, so that it can store a large amount of water. Furthermore, since the crushed stone layer 3 is less expensive than the rainwater storage tank 2, the amount of water stored in the rainwater storage tank 2 can be reduced by the amount of water stored in the crushed stone layer 3, thereby reducing costs accordingly.

[0031] Furthermore, while a common problem with rainwater storage tanks is that they may float up due to the buoyancy force caused by the groundwater level, in the rainwater storage device 1 of this embodiment, the rainwater storage tank 2 is integrated with the crushed stone layer 3, and the weight of the crushed stone layer 3 and the weight of the soil above the crushed stone layer 3 can function as a resistance force against the buoyancy force, preventing floating. In particular, the crushed stone layer 3 has a greater weight per unit volume than the rainwater storage tank 2, so it is effective as a resistance force against the buoyancy force.

[0032] Normally, the uplift force caused by the groundwater level is countered by increasing the soil cover on the rainwater storage device, thereby increasing the load of the soil above it, but this requires a storage device that is strong enough to withstand that amount of soil cover, which results in higher costs. In this embodiment, the mechanism for preventing such floating is simply the crushed stone layer 3 and the sheet 4, so there is no need to use large-scale heavy machinery for construction, which allows for cost reduction.

[0033] Furthermore, in the rainwater storage device 1 of this embodiment, even if force is applied to the upper part of the sheet 4, the sheet 4 will not be pulled out because it passes under the rainwater storage tank 2 and wraps around the rainwater storage tank 2 and the crushed stone layer 3. Therefore, there is also the advantage that there is no need to take the trouble of increasing the sheet area in the horizontal direction.

[0034] In this embodiment, the sheet 4 can also be wrapped around the crushed stone layer 5b and concrete layer 5a that form the foundation 5 of the rainwater storage device 1, and the weight of the crushed stone layer 5b and concrete layer 5a can also be used as a resistance to floating. The concrete layer 5a is heavier than permeable materials such as crushed stone, and is therefore sufficiently effective in resisting the uplift force. Furthermore, the foundation 5 made of concrete or the like is stronger than a foundation made of permeable materials such as crushed stone.

[0035] (Second embodiment) Next, a rainwater storage device 1A according to a second embodiment of the present invention will be described with reference to Fig. 3. This embodiment is a modified example of the first embodiment, and a description of the same parts will be omitted.

[0036] In this embodiment, the crushed stone layer 3A is provided on only one side surface of the rainwater storage tank 2. The sheet 4A is configured to encase the crushed stone layer 3A and the rainwater storage tank 2.

[0037] In this embodiment, as in the first embodiment, it is possible to provide a rainwater storage device that can store a large amount of water and is easy to install.

[0038] (Third embodiment) Next, a rainwater storage device 1B according to a third embodiment of the present invention will be described with reference to Fig. 4. This embodiment is a modified example of the first embodiment, and a description of the same parts will be omitted.

[0039] In this embodiment, the crushed stone layer 3B is formed with a predetermined thickness over the entire upper surface of the rainwater storage tank 2, and is formed on and above one side of the rainwater storage tank 2. That is, the crushed stone layer 3B is formed in an L-shape in cross section. The sheet 4B is configured to encase the crushed stone layer 3B and the rainwater storage tank 2.

[0040] In this embodiment, as in the first embodiment, it is possible to provide a rainwater storage device that can store a large amount of water and is easy to install. Furthermore, compared to the first embodiment, the crushed stone layer 3B is provided on the top of the rainwater storage tank 2, so that the resistance to the floating force is increased.

[0041] (Fourth embodiment) Next, a rainwater storage device 1C according to a fourth embodiment of the present invention will be described with reference to Fig. 5. This embodiment is a modified example of the second embodiment, and a description of the same parts will be omitted.

[0042] Unlike the second embodiment, the crushed stone layer 3C of this embodiment has a height length longer than the height length of the rainwater storage tank 2. Specifically, the crushed stone layer 3C is configured to protrude above and below the rainwater storage tank 2. The sheet 4C is configured to encase the crushed stone layer 3C and the rainwater storage tank 2.

[0043] In this embodiment, as in the first embodiment, it is possible to provide a rainwater storage device that can store a large amount of water and is easy to install. In this embodiment, the crushed stone layer 3C is provided on one side of the rainwater storage tank 2, but it may be provided on both opposing sides.

[0044] (Fifth embodiment) Next, a rainwater storage device 1D according to a fifth embodiment of the present invention will be described with reference to Fig. 6. This embodiment is a modified example of the first embodiment, and a description of the same parts will be omitted.

[0045] In this embodiment, the crushed stone layer 3D is formed so as to cover the upper surface and upper side portions of the rainwater storage tank 2. The sheet 4D is configured to encase the crushed stone layer 3D and the rainwater storage tank 2.

[0046] In this embodiment, as in the first embodiment, it is possible to provide a rainwater storage device that can store a large amount of water and is easy to install. Furthermore, compared to the first embodiment, the crushed stone layer 3D is provided on the top of the rainwater storage tank 2, so that the resistance to the lifting force is increased.

[0047] (Sixth embodiment) Next, a rainwater storage tank and a rainwater storage block used in a rainwater storage device according to a sixth embodiment of the present invention will be described with reference to FIGS.

[0048] [1. Structure of rainwater storage tank] As shown in Fig. 14, the rainwater storage tank 2A ​​of this embodiment is buried underground G1. The rainwater storage tank 2A ​​is covered with soil. In addition to the rainwater storage tank 2A, a crushed stone layer 3 (not shown) is provided. The rainwater storage tank 2A ​​is connected to upstream equipment 60, such as a drainage ditch and a manhole, and downstream equipment 65. The rainwater storage tank 2A, the upstream equipment 60, and the downstream equipment 65 are buried in the ground G1 around a building 70, such as a house.

[0049] The rainwater storage tank 2A ​​includes a stack of rainwater storage blocks 10 and a storage section 50. First, the rainwater storage block stack of rainwater storage blocks 10 will be described below. As shown in Fig. 7, the rainwater storage block stack 10 (rainwater storage tank 2A) has a configuration in which a plurality of rainwater storage blocks 11, 31a, 31b, 36 of this embodiment and a spacer 41 are arranged along a horizontal plane and stacked in a thickness direction Z (vertical direction) described later. Note that Fig. 7 does not show a portion of the spacer 41. For example, the rainwater storage block stack 10 (rainwater storage tank 2A) is constructed by arranging at least one of the rainwater storage blocks 11, 31a, 31b, 36, or multiple tier units 50a, 50b, 50c, 50d formed by spacers 41 so that the thickness direction Z is aligned in the vertical direction. Among the rainwater storage blocks 11, 31a, 31b, and 36, the quarter-size rainwater storage block 11 will be described below.

[0050] 8 to 10, the rainwater storage block 11 is a so-called quarter (1 / 4) size. The rainwater storage block 11 includes a plate unit 12 and a plurality of mountain units 17A, 17B, 17C, and 17D. The plate unit 12 has a plate-like body 13, a first ridge (ridge) 14, and a second ridge (ridge) 15.

[0051] 9, the plate-shaped body 13 is formed in a flat plate shape. In this embodiment, the plate-shaped body 13 has a square shape when viewed along the thickness direction Z of the plate-shaped body 13. When viewed along the thickness direction Z, the plate-shaped body 13 has four corners 13c, 13d, 13e, and 13f. The corners 13c, 13d, 13e, and 13f are arranged in this order counterclockwise when viewed from a first side Z1 (hereinafter simply referred to as the first side Z1) along the thickness direction Z. The plate-like body may have a polygonal shape such as a rectangle, a triangle, or a hexagon when viewed along the thickness direction Z.

[0052] Here, a first direction X and a second direction Y are defined along the main surface 13a facing the first side Z1 of the plate-like body 13. The first direction X and the second direction Y are directions perpendicular to each other.

[0053] The plate-like body 13 has a side extending along the first direction X and a side extending along the second direction Y. A plurality of through holes 13b are formed in the plate-like body 13. In this example, the plurality of through holes 13b have a rectangular shape when viewed along the thickness direction Z. The arrangement of the plurality of through holes 13b will be described later. The shape of the plurality of through holes 13b is not limited to this. Note that through holes or notches (not shown) are formed in the plate-like body 13 at portions where mountain units 17A, 17B, 17C, and 17D (described later) are arranged when viewed along the thickness direction Z. These through holes or notches are formed in shapes corresponding to the mountain units 17A, 17B, 17C, and 17D.

[0054] Each of the first ridges 14 is formed in a strip shape with the thickness direction of the first ridge 14 being in the second direction Y. The multiple first ridges 14 extend in the first direction X and are arranged at intervals from one another in the second direction Y. Each of the first ridges 14 protrudes from the plate-like body 13 toward the first side Z1. Each second ridge 15 is formed in a strip shape with the thickness direction of the second ridge 15 being the first direction X. The multiple second ridges 15 extend in the second direction Y and are arranged at intervals from one another in the first direction X. Each second ridge 15 protrudes from the plate-like body 13 toward the first side Z1.

[0055] Here, the side opposite to the first side Z1 in the thickness direction Z is defined as a second side Z2 in the thickness direction Z (hereinafter simply referred to as the second side Z2) (see FIG. 8).

[0056] The multiple through holes 13b are formed so as to avoid the multiple first ridges 14 and the multiple second ridges 15. When viewed along the thickness direction Z, the multiple through holes 13b are formed in the center of plate pieces (reference numerals omitted) in the plate-like body 13 that are partitioned by the multiple first ridges 14 and the multiple second ridges 15. In this example, only one through hole 13b is formed in each plate piece.

[0057] In this embodiment, the configuration of the mountain unit 17A is the same as that of the mountain units 17B, 17C, and 17D. Therefore, the configuration of the mountain unit 17A is indicated by adding the capital letter "A" to the number or number and lowercase letter of the symbol. The configurations of the mountain units 17B, 17C, and 17D that correspond to the mountain unit 17A are indicated by adding the capital letters "B," "C," and "D" to the number or number and lowercase letter of the symbol of the mountain units 17B, 17C, and 17D. This avoids redundant explanations. For example, a mountain portion 18A of the mountain unit 17A, which will be described later, and mountain portions 18B, 18C, and 18D of the mountain units 17B, 17C, and 17D, which will be described later, have the same configuration.

[0058] The mountain unit 17A has a mountain portion 18A, a first protrusion 19A, a gate mark 20A, and a second protrusion 21A. The peaks 18A protrude from the plate-like body 13 toward the first side Z1. In this example, the peaks 18A are formed in a truncated quadrangular pyramid shape with the surface on the second side Z2 as the bottom surface and the center of the bottom surface being open. That is, when viewed along the thickness direction Z, the peaks 18A have a rectangular shape. The length of the peaks 18A in the second direction Y is longer than the length of the peaks 18A in the first direction X. 10, in this example, the draft angle 18dA for the mold of the ridge portion 18A is set to 8°. However, the draft angle 18dA is not particularly limited as long as the rainwater storage block 11 can be molded. The peaks may be in the shape of a polygonal truncated pyramid or a truncated cone (see a rainwater storage block 11A according to a modified example shown in FIG. 15) as long as the center of the bottom surface is open.

[0059] As shown in Figures 9 and 10, recesses 18aA are formed on each side surface of the peak portion 18A. Each recess 18aA is recessed toward the inside of the peak portion 18A. Each recess 18aA extends in the thickness direction Z along the side surface. For example, the depth to which each recess 18aA is recessed from the side surface is constant regardless of the position in the thickness direction Z. The width of each recess 18aA (for example, the length in the second direction Y of the recess 18aA formed on the side surface facing the first side in the first direction X) gradually narrows toward the second side Z2. An end of each recess 18aA on the first side Z1 is continuous with an end face 18bA of the first side Z1 of the peak 18A. An end of each recess 18aA on the second side Z2 is continuous with the plate-shaped body 13.

[0060] 9, the peaks 18A are disposed near the corners 13c of the plate-like body 13. When viewed along the thickness direction Z, the distance L1 between the center 18cA of the peaks 18A and the center 13g of the plate-like body 13 is longer than the distance L2 between the center 18cA of the peaks 18A and the corners (vertices) 13c of the plate-like body 13. The corners 13c are the vertices (corners) of the polygonal plate-like body 13 that are closest to the center 18cA of the peaks 18A (i.e., the nearest vertex). The center of the peak 18A may be the intersection of the diagonal lines of the rectangular peak 18A. The recess 18aA may be formed on at least one side surface of the peak 18A. The distance L1 may be equal to or less than the distance L2.

[0061] 9 and 10, the first protrusion 19A is provided on an end surface 18bA of the mountain portion 18A. In this example, the first protrusion 19A is formed in a cylindrical shape. The gate mark 20A is provided on the first protrusion 19A. In this example, the gate mark 20A is provided on the end surface of the first side Z1 of the first protrusion 19A. The gate mark 20A is a mark provided on the rainwater storage block 11 at a position corresponding to the gate of the mold. The gate mark 20A is a gate mark. The gate is an entrance for pouring resin into the space in the mold where the rainwater storage block 11 is molded. During injection molding, the rainwater storage block 11 is molded while connected to a runner, for example. In this case, when the rainwater storage block 11 is separated from the runner, a convex protrusion may be formed on the rainwater storage block 11 at the separation point. For example, this protrusion becomes the gate mark 20A. The second protrusion 21A is formed on the bottom surface of the recess 18aA facing the first direction X. The second protrusion 21A is spaced in the second direction Y from the surface of the recess 18aA facing the second direction Y. An end of the second protrusion 21A on the first side Z1 is located closer to the second side Z2 than the end surface 18bA of the mountain portion 18A. An end of the second protrusion 21A on the second side Z2 is continuous with the plate-shaped body 13.

[0062] As shown in FIG. 9, the peaks 18B, 18C, and 18D are disposed at positions near the corners 13d, 13e, and 13f of the plate-shaped body 13, respectively. The end of the second side Z2 of the peak portion 18A is connected to the inner peripheral edge of a through-hole or notch formed in the plate-shaped body 13 corresponding to the peak portion 18A. The length of the peak portion 18B in the second direction Y is longer than the length of the peak portion 18B in the first direction X. The peak portions 18C and 18D are similar to the peak portion 18B.

[0063] The rainwater storage block 11 is made of synthetic resin. Examples of synthetic resin include polyolefin resin (for example, polypropylene resin (PP), polyethylene resin (PE), polyethersulfone resin (PES)), polyester resin, polyvinyl chloride resin, etc. Furthermore, a polyolefin resin having a functional group may be used as the synthetic resin. By using a modified resin as the synthetic resin, the rigidity and chemical resistance of the rainwater storage block 11 are improved. Furthermore, reinforcing fibers may be mixed with the synthetic resin. The reinforcing fibers may be, for example, glass fibers, carbon fibers, etc. When reinforcing fibers are mixed with the synthetic resin, the rigidity of the rainwater storage block 11 can be improved. Recycled materials may be mixed with the synthetic resin, for example, recycled container and packaging materials as specified by the Container and Packaging Recycling Law.

[0064] The rainwater storage blocks 31a and 31b are what is called half (1 / 2) size. As shown in FIG. 11, for example, the rainwater storage block 31a is configured by arranging two rainwater storage blocks 11 in a first direction X and connecting the two rainwater storage blocks 11 to each other by a first connecting member (not shown). The first connecting member is made of the same material as the rainwater storage block 11. In this embodiment, the fact that the two members are made of the same material may mean that the main components of the two members are the same. For example, if recycled materials are mixed into the synthetic resin that forms the rainwater storage block 11, the components of the synthetic resin that forms the rainwater storage block 11 will vary depending on the recycled materials mixed in. Even in such a case, if the main component of the synthetic resin that forms the rainwater storage block 11 and the main component of the synthetic resin that forms the first connecting member are the same, the first connecting member may be made of the same material as the rainwater storage block 11. Note that the first connecting member does not have to be made of the same material as the rainwater storage block 11. For example, the rainwater storage block 31b is configured by arranging two rainwater storage blocks 11 in the second direction Y and connecting the two rainwater storage blocks 11 to each other with a second connecting member (not shown). The second connecting member is made of the same material as the rainwater storage block 11.

[0065] 12, the rainwater storage block 36 is a so-called full-size. For example, the rainwater storage block 36 is configured by arranging two rainwater storage blocks 31a in the second direction Y and connecting the two rainwater storage blocks 31a to each other with a second connecting member.

[0066] For example, if a full-size rainwater storage block 36 manufactured by injection molding is used as is, the rainwater storage block 36 can be obtained. On the other hand, after manufacturing the rainwater storage block 36 by injection molding, if an operator of the injection molding machine cuts the rainwater storage block 36 at the position of the second connecting member, two half-sized rainwater storage blocks 31a are manufactured. After manufacturing the rainwater storage block 36, if an operator cuts the rainwater storage block 36 at the position of the first connecting member, two half-sized rainwater storage blocks 31b are manufactured. Furthermore, after the two rainwater storage blocks 31a are manufactured, the worker cuts each of the rainwater storage blocks 31a with the first connecting member, whereby four quarter-sized rainwater storage blocks 11 are manufactured.

[0067] Assuming that the length of one side of the plate unit 12 of the full-size rainwater storage block 36 is 1, as in this embodiment, the rainwater storage blocks 11, 31a, 31b, 36 may be configured as the rainwater storage block 36 (full) which is 1 x 1, the rainwater storage blocks 31a, 31b (half) which are 0.5 x 1, and the rainwater storage block 11 (quarter) which is 0.5 x 0.5. The rainwater storage tank 2A ​​may be formed by combining these rainwater storage blocks 11, 31a, 31b, 36. Furthermore, for example, the number of ridges 18A, 18B, 18C, and 18D of the half-size rainwater storage blocks 31a and 31b may be half the number of ridges 18A, 18B, 18C, and 18D of the full-size rainwater storage block 36. The number of ridges 18A, 18B, 18C, and 18D of the quarter-size rainwater storage block 11 may be one-fourth the number of ridges 18A, 18B, 18C, and 18D of the full-size rainwater storage block 36.

[0068] In the rainwater storage blocks 11, 31a, 31b, and 36, the plate unit 12 and the multiple mountain units 17A, 17B, 17C, and 17D may be molded as a single unit, or the plate unit 12 and the multiple mountain units 17A, 17B, 17C, and 17D may be molded as separate parts and then formed into a single unit by, for example, fitting, joining, welding, etc. Furthermore, a reinforcing member (cover) (not shown) may be provided on the rainwater storage blocks 11, 31a, 31b, 36. The reinforcing member may be attached to the plate-like body 13 and may cover at least a portion of the peaks 18A, 18B, 18C, 18D. The reinforcing member may cover, for example, a portion of the peak units 17A, 17B, 17C, 17D or the plate unit 12, where stress is likely to concentrate.

[0069] 13, the spacer 41 is formed in a flat plate shape as a whole. The spacer 41 has a plurality of first protrusions 42 and a plurality of second protrusions 43. Each of the first protrusions 42 is formed in a strip shape with the thickness direction of the first protrusion 42 extending along the second direction Y. Each of the first protrusions 42 extends in the first direction X. The multiple first protrusions 42 are arranged at intervals from one another in the second direction Y. Each second protrusion 43 is formed in a strip shape with the thickness direction of the second protrusion 43 extending along the first direction X. Each second protrusion 43 extends in the second direction Y. The multiple second protrusions 43 are arranged at intervals from one another in the first direction X.

[0070] The multiple first protrusions 42 and the multiple second protrusions 43 are arranged in a lattice pattern. A through hole 44 is formed between two first protrusions 42 adjacent to each other in the second direction Y and between two second protrusions 43 adjacent to each other in the first direction X. The spacer 41 is made of the same material as the rainwater storage block 11. For example, when viewed along the thickness direction Z, the outer shape of the spacer 41 is the same as the outer shape of the rainwater storage block 11.

[0071] The number of row units constituting the rainwater storage block stack 10 is not limited. 7, for example, tier unit 50a is the tier unit arranged lowest among tier units 50a, 50b, 50c, and 50d. tier units 50a, 50b, 50c, and 50d are arranged in this order from bottom to top. For example, the row unit 50a has four rainwater storage blocks 36 arranged in a grid pattern, with two in the first direction X and two in the second direction Y. The directions shown in Fig. 7 are based on the row unit 50a.

[0072] For example, the stage unit 50b is made up of one rainwater storage block 36, two rainwater storage blocks 31a, two rainwater storage blocks 31b, and four rainwater storage blocks 11. When viewed along the thickness direction Z, in the step unit 50b, the rainwater storage blocks 11, 31a, 31b, 36 are all arranged so that the long side direction of the peak portions 18A, 18B, 18C, 18D is perpendicular to the long side direction (second direction Y) of the peak portions 18A, 18B, 18C, 18D of the four rainwater storage blocks 36 in the step unit 50a (first direction X in the step unit 50a).

[0073] In the tier unit 50b, the rainwater storage block 36 is arranged above the four rainwater storage blocks 36 of the tier unit 50a so as to straddle the four rainwater storage blocks 36. The rainwater storage blocks 36 of the tier unit 50b are arranged at an angle of 90° around an axis along the thickness direction Z relative to the four rainwater storage blocks 36 of the tier unit 50a. The four rainwater storage blocks 11 are arranged at the four corners of the step unit 50b. Each rainwater storage block 31a is disposed between adjacent rainwater storage blocks 11 in the second direction Y, above the two rainwater storage blocks 36 of the tier unit 50a, so as to straddle the two rainwater storage blocks 36. Each rainwater storage block 31b is disposed between adjacent rainwater storage blocks 11 in the first direction X, above the two rainwater storage blocks 36 of the tier unit 50a, so as to straddle the two rainwater storage blocks 36. The tier unit 50b may be inverted upside down in the thickness direction Z, as in the modified rainwater storage tank 2B shown in Fig. 16. In this case, it is preferable that the rainwater storage blocks 36 of the tier unit 50b are not rotated 90° around an axis along the thickness direction Z relative to the four rainwater storage blocks 36 of the tier unit 50a.

[0074] The row unit 50c has the same configuration as the row unit 50a. The row unit 50d is composed of a plurality of spacers 41. The plurality of spacers 41 are arranged side by side in the first direction X and the second direction Y. The plurality of spacers 41 are arranged above the four rainwater storage blocks 36 that make up the row unit 50c.

[0075] There are no limitations on the storage section 50 as long as it can store the rainwater storage block stack 10. As shown in Fig. 14, for example, the storage section 50 has a storage body 51 and a lid 56. The storage section 50 may function as the sheets 4, 9. The storage body 51 is made of a water-impermeable sheet. An opening 52 is formed in the upper part of the storage body 51. The storage body 51 houses the rainwater storage block stack 10. The lid 56 is made of a water-permeable sheet and seals the opening 52 of the storage body 51.

[0076] As shown in FIGS. 17 and 18 , the rainwater storage tank 2C may be provided with an inspection hatch 86. The inspection hatch 86 is a space formed by, for example, not disposing the rainwater storage block stack 10 over the entire height of the rainwater storage tank 2C in the thickness direction Z. The inspection hatch 86 is a space for inspecting the condition inside the rainwater storage tank 2C and the level of the stored rainwater, for example. A manhole 89 is provided above the inspection hatch 86. The manhole 89 penetrates the cover 56 from the ground surface and communicates with the inspection hatch 86. As shown in FIG. 18 , the inspection hatch 86 is formed by a plurality of rectangular frames 87 arranged at predetermined intervals in the thickness direction Z. The edges of each rectangular frame 87 are supported by the edges of the row units 50a, 50b, 50c, and 50d that are located at the same height as the rectangular frame 87. Support columns 88 are inserted along each of the four inner corners of the rectangular frame 87. The support columns 88 are connected to the four corners of the rectangular frame 87 with bolts 82. Note that, among the frame members 87a that make up the rectangular frame 87, a reinforcing frame 87d may be fixed between the inner surfaces of the ends that face each other at right angles of the frame members 87a that are connected to each other at right angles. This reinforcing frame 87d may also serve as scaffolding. Furthermore, diagonal braces 83 may be provided between adjacent support columns 88.

[0077] A construction method for the rainwater storage tank 2A ​​configured as above (hereinafter simply referred to as construction method) will be described. For example, in the construction method, a rainwater storage tank 2A ​​having a configuration in which a plurality of rainwater storage blocks 11, 31a, 31b, and 36 are stacked in the thickness direction Z is constructed. At this time, the rainwater storage blocks 11, 31a, 31b, and 36 may be stacked while changing their orientation around an axis along the thickness direction Z.

[0078] Next, the operation of the rainwater storage tank 2A ​​configured as above will be described. As shown in Figure 14, rain that falls on the ground surface G2 flows into the rainwater storage tank 2A ​​as rainwater W through, for example, the upstream equipment 60 or the cover 56 of the rainwater storage tank 2A. The rainwater storage tank 2A ​​functions as a tank that temporarily stores the rainwater W, especially during heavy rain. The rainwater W is stored between the row units 50a, 50b, 50c, 50d, etc. in the rainwater storage block stack 10 in the storage section 50. The rainwater W stored in the rainwater storage tank 2A ​​is discharged to the downstream equipment 65 at a constant flow rate.

[0079] [2. Consideration of specifications to solve the problem] The following describes the results of examining specifications for the rainwater storage block 36 to solve the problem of "reducing mass while maintaining rainwater storage performance." As shown in Tables 1 and 2, the ridge ratio, porosity, ridge height, short-term allowable stress, and long-term allowable stress were examined for rainwater storage blocks 36 from Sample No. 1 to Sample No. 8.

[0080] [Table 1]

[0081] [Table 2]

[0082] The peak ratio here refers to the number of peaks 18A, 18B, 18C, and 18D relative to the area of ​​the plate-like body 13 when viewed along the thickness direction Z (number / m 2 The void ratio means the ratio of the space other than the rainwater storage block 36 within the rectangular parallelepiped circumscribing the outer shape of the rainwater storage block 36 to the volume of this rectangular parallelepiped. The height of the peaks 18A, 18B, 18C, and 18D referred to here means the distance between the plate-shaped body 13 and the end face 18bA of the peak 18A on the first side Z1, for example.

[0083] The short-term allowable stress here refers to the allowable stress level (the limit of the resistance force generated by each component) against short-term loads and external forces such as earthquake force and wind pressure. The short-term allowable stress (allowable stress level) in the table is calculated as "(maximum stress) x (deemed proportional limit coefficient) / (material variation coefficient)." Here, maximum stress refers to the maximum stress observed when "1. Storage Structure Strength Test Method" in the appendix of the "Technical Guidelines for Plastic Underground Storage and Infiltration Facilities (Draft) [Revised Edition, 2018]" (Publisher: Rainwater Storage and Infiltration Technology Association, Public Interest Incorporated Association, Publication Date: April 1, 2018) is conducted. The deemed proportional limit coefficient is, for example, 0.7. The material variation coefficient is, for example, 1.3. In actual products, the short-term allowable stress in the table is the upper limit of short-term allowable stress.

[0084] Long-term allowable stress is the allowable stress (1m 2 permissible creep load per unit area). The long-term allowable stress is determined, for example, by the following method. First, the target long-term allowable stress (1m 2 Set the allowable creep load per unit area. Also, the allowable displacement δmax is calculated from the short-term compression test. The allowable displacement δmax is calculated by multiplying the corrected displacement at 70% of the maximum stress by 1m 2 The difference between the displacement at the allowable creep load (target long-term allowable stress) per m 2 The difference between the displacement at the allowable creep load and the short-term compression test is determined by the short-term compression test method specified in "1. Test method for storage structure strength" in the appendix. Furthermore, the expected displacement δ over 50 years is determined from the creep test. In the creep test, the target long-term allowable stress is applied. The creep test is the test method specified in "2. Long-term creep test method for storage structures" in the above-mentioned appendix. If δmax≧δ×(material variation coefficient), the target long-term allowable stress can be considered to be a stress that satisfies the conditions. The material variation coefficient is, for example, 1.3. The long-term allowable stress in the table is the upper limit of the stress that satisfies the conditions. In actual products, the long-term allowable stress in the table is the upper limit of the stress that is allowed over the long term.

[0085] For example, for sample No. 1, the peak ratio is 30 / m 2 The porosity was 93%, the height of the ridges 18A, 18B, 18C, and 18D was 22 cm, and the short-term allowable stress was 200 kN / m 2 and the long-term allowable stress is 70kN / m 2 is.

[0086] The peak ratio is 20 pieces / m 2 If it is less than this, the size (height) of the peaks 18A, 18B, 18C, and 18D will be large, and the mass of each rainwater storage block 36 may become heavy. The peak ratio is 40 pieces / m 2 The peak ratio is preferably 40 / m or less. 2 If the thickness exceeds this value, the size of the peaks 18A, 18B, 18C, and 18D will be small, and the thickness of the peaks 18A, 18B, 18C, and 18D will be thin, which may result in insufficient strength.

[0087] If the porosity is less than 92%, the 3 On the other hand, if the porosity exceeds 96%, the amount of synthetic resin required to store rainwater will increase, which may result in higher costs. 3 If the amount of synthetic resin required to store the rainwater is too small, the rainwater storage tank 2A ​​may not be strong enough. If the height of the peaks 18A, 18B, 18C, and 18D is less than 15 cm, 3On the other hand, if the height of the peaks 18A, 18B, 18C, and 18D exceeds 25 cm, the amount of synthetic resin used will be reduced due to the height of the peaks 18A, 18B, 18C, and 18D, which may result in a decrease in strength. Alternatively, if the thickness of the rainwater storage blocks 36 is maintained, the height of the peaks 18A, 18B, 18C, and 18D will increase the weight, which may result in an increase in costs or a decrease in workability.

[0088] Short-term allowable stress is 90kN / m 2 If the stress is less than 300 kN / m, it may be impossible to install facilities on top of the rainwater storage tank 2A ​​or to perform crane work on top of the rainwater storage tank 2A. On the other hand, the short-term allowable stress is 300 kN / m 2 If the thickness exceeds 1000 nm, the strength is high, that is, the amount of synthetic resin is large, which may result in high costs.

[0089] Long-term allowable stress is 70kN / m 2 If the strength is less than 90 kN / m, it may be impossible to install facilities on top of the rainwater storage tank 2A ​​or to perform crane work on top of the rainwater storage tank 2A. On the other hand, the long-term allowable stress is 90 kN / m 2 If the thickness exceeds 1000 nm, the strength is high, that is, the amount of synthetic resin is large, which may result in high costs.

[0090] For example, if the peak ratio is 20 / m 2 If the peak ratio is 20 / m or more, the evaluation is "Good". 2 If it is less than this, the evaluation will be "× (Bad)". In sample No. 1, the peak ratio was evaluated as "○". Similarly, in sample No. 1, the porosity was evaluated as "○", the height of peaks 18A, 18B, 18C, and 18D was evaluated as "○", the short-term allowable stress was evaluated as "○", and the long-term allowable stress was evaluated as "○". A sample with a peak ratio evaluation of "○" and a porosity evaluation of "○" is given an overall evaluation of "○" or "◎ (Very Good)." A sample with a peak ratio evaluation of "×" or a porosity evaluation of "×" is given an overall evaluation of "×."

[0091] From the above, in order to solve the problem of "reducing mass while maintaining rainwater storage performance", it is necessary to set the peak ratio of the rainwater storage block 11 to 20 pieces / m 2 As a result, it was found that a porosity of 90% or more is necessary.

[0092] The mass of the rainwater storage blocks 36 is preferably 6 kg or more and 9 kg or less per block. If the mass is less than 6 kg per piece, the mass is light, i.e., the amount of synthetic resin is small. Therefore, there is a risk that the strength will be insufficient to install facilities above the rainwater storage tank 2A ​​or to perform crane work above the rainwater storage tank 2A. On the other hand, if the mass is more than 9 kg per piece, the mass will be too heavy and construction may be difficult.

[0093] The planar dimensions of the rainwater storage block 36 are preferably 700 mm or more and 1100 mm or less per side. If the planar dimensions of the rainwater storage blocks 36 are less than 700 mm, the number of products required to build a rainwater storage tank 2A ​​of a given size increases, which may result in a longer construction period. On the other hand, if the planar dimensions of the rainwater storage blocks 36 exceed 1100 mm, the weight of each rainwater storage block 36 increases, which may result in poor workability. The planar dimensions of the rainwater storage block 36 may be less than 700 mm per side. For example, when actually constructing the rainwater storage block 36, it is conceivable that the size (planar dimensions) of the rainwater storage block 36 will need to be adjusted to match the shape and size of the rainwater storage tank 2A. In this case, if it is preferable that the planar dimensions of the rainwater storage block 36 be less than 700 mm per side, the planar dimensions of the rainwater storage block 36 may be less than 700 mm per side. However, even in cases other than this, the planar dimensions of the rainwater storage block 36 may be less than 700 mm per side. Furthermore, the planar dimensions of the rainwater storage block may be shorter than the planar dimensions of the full-size rainwater storage block 36, such as half the length of the planar dimensions of the full-size rainwater storage block 36. In this case, the full-size rainwater storage block 36 can be cut and used as the rainwater storage block.

[0094] The thickness of the rainwater storage block 36 is preferably 1.5 mm or more and 5.0 mm or less. The thickness here refers to the thickness of each component of the rainwater storage block 36. If the thickness is less than 1.5 mm, the wall thickness is too thin and the rainwater storage tank 2A ​​may not be strong enough. On the other hand, if the thickness is more than 5.0 mm, the thicker wall thickness increases the amount of synthetic resin, which may increase costs or the weight may become heavy, which may make installation difficult. The cycle time of the rainwater storage block 36 becomes longer, which may make it difficult to manufacture the rainwater storage block 36.

[0095] 3. Effects of this embodiment As described above, in the rainwater storage blocks 36 of this embodiment, for example, the first side Z1 is arranged upward, and the plate-like body 13 of one rainwater storage block 36 is arranged above the multiple peaks 18A, 18B, 18C, 18D of another rainwater storage block 36. Then, rainwater W can be stored in the gaps formed by these multiple rainwater storage blocks 36. At this time, since the porosity of the rainwater storage block 36 is 90% or more, the rainwater W storage performance can be maintained. The peak ratio is 20 pieces / m 2 As a result, the size of each of the plurality of peaks 18A, 18B, 18C, and 18D can be prevented from increasing, and the mass of the rainwater storage block 36 can be reduced.

[0096] The mountain unit 17A has a first protrusion 19A and a gate mark 20A. For example, when manufacturing the rainwater storage block 36 by injection molding, molten synthetic resin is injected into a mold through a gate located in a portion corresponding to the gate mark 20A. At this time, the synthetic resin accumulates in the portion of the mold corresponding to the first protrusion 19A, thereby preventing the pressure of the synthetic resin near this gate from becoming too high. Distance L1 is longer than distance L2. Therefore, even if rainwater storage block 36 is formed to be small, for example, when a worker places his / her feet on the center of plate-like body 13 to work, ridges 18A, 18B, 18C, and 18D can be prevented from interfering with the worker.

[0097] Recesses 18aA are formed on the side surfaces of the peaks 18A, which increases the strength of the peaks 18A with the recesses 18aA formed therein compared to the strength of the peaks 18A without the recesses 18aA formed therein. The end of the recess 18aA on the second side Z2 is continuous with the plate-like body 13. Therefore, the strength of the peak 18A in which the recess 18aA is formed can be further increased.

[0098] The second protrusions 21A are formed on the bottom surfaces of the recesses 18aA facing the first direction X. Therefore, the second protrusions 21A can increase the strength of the mountain portions 18A in which the recesses 18aA are formed. The plate unit 12 has the first ridges 14 and the second ridges 15. Therefore, the bending strength of the rainwater storage block 36 (rainwater storage block 11) around an axis that intersects with the thickness direction Z can be increased.

[0099] Furthermore, the rainwater storage tank 2A ​​of this embodiment can be configured by stacking the rainwater storage blocks 11, 31a, 31b, and 36, which have reduced mass while maintaining rainwater storage performance. Furthermore, in the construction method of this embodiment, the rainwater storage tank 2A ​​can be constructed by stacking the rainwater storage blocks 11, 31a, 31b, and 36, which have reduced mass while maintaining the rainwater storage performance.

[0100] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments and can be modified in various ways. For example, in the above embodiment, examples have been described in which the rainwater storage tank is provided on both opposing sides, one side, or one side and the top, but it may also be provided on all six sides of the rainwater storage tank.

[0101] 19 shows a modified rainwater storage block 11B, and the side panels P may be installed on the rainwater storage block 11B. In this modified example, the side panels P are attached between adjacent mountain units 17A, 17B, 17C, and 17D. In the illustrated example, one side panel P is provided between the mountain unit 17A and the adjacent mountain units 17B and 17D along each of the two sides extending from the corner where the mountain unit 17A is located. However, one side plate P may be provided between mountain unit 17C diagonally opposite mountain unit 17A and mountain units 17B and 17D adjacent to each other along two sides extending from the corner where mountain unit 17C is located (at the position P1 indicated by the dashed line in FIG. 19). In other words, the side plate P may be provided around the entire outer periphery of plate unit 12 of rainwater storage block 11. The side wall A can, for example, improve the strength of the rainwater storage tank 2A ​​and prevent soil and sand from entering. [Explanation of symbols]

[0102] 1, 1A, 1B, 1C, 1D Rainwater storage device 2,2A,2B,2C Rainwater storage tank 3,3A,3B,3C,3D,5b Crushed stone layer 4, 4A, 4B, 4C, 4D, 9 seats 5 Basics 5a Concrete layer 6, 11, 11A, 11B, 31a, 31b, 36 Rainwater storage blocks 10a Inflow pipe 10b Outflow pipe

Claims

1. A rainwater storage device comprising a rainwater storage tank and a crushed stone layer, A rainwater storage device comprising the rainwater storage tank and a sheet that encases at least a portion of the crushed stone layer.

2. The crushed stone layers are provided on opposite side surfaces of the rainwater storage tank, 2. The rainwater storage device according to claim 1, wherein the sheet encases the rainwater storage tank and the crushed stone layers provided on both sides of the rainwater storage tank.

3. 2. The rainwater storage device according to claim 1, wherein the crushed stone layer is provided only on one side of the rainwater storage tank.

4. 2. The rainwater storage device according to claim 1, wherein the crushed stone layer is provided on the top surface and the side surface of the rainwater storage tank.

5. The crushed stone layer is provided on one side or both opposing sides of the rainwater storage tank, 2. The rainwater storage device according to claim 1, wherein the vertical height of the crushed stone layer does not match the vertical height of the rainwater storage tank.

6. 2. The rainwater storage device according to claim 1, wherein the crushed stone layer is formed above the top surface and sides of the rainwater storage tank.

7. The rainwater storage device according to any one of claims 1 to 5, characterized in that the sheet is a water-permeable sheet.

8. 7. The rainwater harvesting device of claim 6, wherein the sheet comprises a geotextile.

9. 2. The rainwater storage device according to claim 1, wherein the rainwater storage tank is configured by arranging a plurality of rainwater storage blocks along a horizontal plane and stacking them vertically.

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