JP2009097151A - Permeable structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permeable structure with proper efficiency of water permeability, which facilitates cleaning for maintenance of an infiltration pipe. <P>SOLUTION: The infiltration pipe 20 is arranged in the ground through a bottom of a catch basin 10 for use in a drainage system which includes facilities for suppressing the outflow of water such as rainwater. One end of the infiltration pipe 20 includes an opening for taking in the rainwater at a predetermined distance from the bottom of the catch basin 10 when the infiltration pipe 20 is attached to the catch basin 10; its other end side is closed with a bottom cover 30; and its peripheral surface includes a plurality of infiltration holes 24a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water permeable structure comprising a water collecting basin used in a drainage system equipped with a rainwater outflow control facility, a permeation pipe, and a water guide layer provided around the permeation pipe in the ground. The present invention relates to a water permeable structure that is easy to clean and has good water permeable efficiency.

Conventionally, for the purpose of returning rainwater to the ground and draining water and cultivating plants, a drainage system in which a drainage ditch, a water collecting tank and a permeation pipe are combined is known (see Patent Document 1).
In this drainage system, the permeation pipe is buried in the ground and the upper part is attached to a water catchment. The water collected by the water catchment is taken from the top opening, and the water taken in is installed in the pipe wall. Infiltrate underground from the hole.
As a permeation pipe used in such a drainage system, one having a bottom lid provided with a bottom positioning member at its lower end is known (see Patent Document 2).

6 shows the lower end (bottom) of the permeation tube 20, FIG. 6A is a longitudinal sectional view showing a state where the bottom cover is attached to the permeation tube, and FIG. 6B is a plan view of the bottom cover. The bottom cover 30 is a disk-shaped member made of, for example, an iron-based material having a circular water-permeable hole 32 at the center as shown in the figure.
In this example, a rib-shaped bottom positioning member 34 and a pair of support pieces 36 to be attached to the lower end of the permeation tube 20 wound with the water-permeable sheet 20a are shown.

  The permeation tube 20 is propelled into the ground and placed upright in the casing with the water-permeable holes 32 of the bottom lid 30 placed on the foundation ground, and in this state, sand is introduced between the permeation tube 20 and the casing. Thereafter, the casing is buried in the ground by pulling the casing forward and backward.

  Water that has flowed into the buried permeation pipe 20 penetrates or permeates into the ground through the permeation hole or the water permeation hole 32 of the bottom bottom cover 30, but soil or sand that has flowed in along with rainwater while in use penetrates. It accumulates in the sand layer which constitutes the retaining wall inside and around the tube 20, and the permeation or water permeability effect is reduced. Since the deposits in the permeation tube 20 have properties similar to clay, it is not easy to remove them. Therefore, conventionally, cleaning with high-pressure water is regularly performed. That is, high-pressure water is injected into the permeation pipe 20 and drained from the permeation pipe 20 with a drain pump, and the sediment accumulated in the permeation pipe 20 and the sand layer is discharged together with the waste water to restore the original state.

  However, the bottom lid 30 at the bottom of the conventional osmotic tube 20 has a water-permeable hole 32 or does not have the bottom lid 30 (refer to FIG. 7: the bottom of the osmotic tube 20 has a rib-shaped bottom. Since only the positioning member 34 is provided (FIG. 7 is a bottom view thereof), the high-pressure water at the time of cleaning directly enters the bottom foundation ground of the permeation pipe 20 and disturbs the foundation ground, and the high-pressure water In this case, not only the foundation ground is destroyed, but also the earth and sand are sucked up from there, so that the permeation tube 20 may sink.

As described above, the permeation pipe 20 is attached to the catchment basin, and the catchment basin is attached to the sewer (side groove), and the slope of the sewer is set to flow to one side using a head. ing. The gradient is delicate and the height of the permeation tube 20 is required to be accurate to the millimeter. Therefore, when the permeation pipe 20 sinks and its height changes, the catchment and drainage ditch fixed to it also sinks and the inclination of the drainage groove changes, so that the set head cannot be maintained. It becomes impossible. Therefore, cleaning with high-pressure water must be performed carefully so as not to destroy the foundation ground. Moreover, even if it is performed carefully, when the drainage is performed, the earth and sand of the foundation ground may be sucked up and the permeation pipe 20 may sink.
Further, in the conventional osmotic tube 20, the foundation ground may be tightened by the water that permeates or permeates from the bottom during normal use, and the volume may shrink, and the osmotic tube 20 may sink accordingly.

In addition, when the bottom of the permeation tube 20 is open, if water permeation or permeation from the permeation tube 20 is performed, the opportunity to permeate into the ground through the permeation hole at the top of the permeation tube 20 is reduced. In some cases, the permeation area of the entire permeation tube 20 is decreased, and the permeation or water permeation efficiency is decreased. That is, since the water level in the permeation pipe is lowered early, permeation from the upper part of the permeation pipe is not performed, and the water pressure acting at the lower part of the permeation pipe is also lowered, so that the permeation rate (permeability coefficient) is lowered. Thus, it has also been found that the drainage of the permeation tube 20 may take time by providing a hole at the lower end (bottom surface) of the permeation tube 20.
JP 2006-118265 A JP 2007-177488 A

The present invention has been made in order to solve the above-mentioned problems of the conventional permeation tube. The first object of the present invention is to damage the substrate ground as in the past when the permeation tube is cleaned. It is an object of the present invention to provide an osmotic tube that can be safely and reliably cleaned without causing the tube to sink.
Moreover, the 2nd objective is preventing the water level in an osmosis | permeation pipe | tube falling early, and aiming at the improvement of osmosis | permeation or water permeation efficiency.

The invention of claim 1 is a water permeable structure, has a catchment used in a drainage system having a rainwater outflow control facility, an opening for taking in rainwater at the upper end, and has a rainwater infiltration hole on the peripheral surface. An infiltration pipe and a water guide layer provided around the infiltration pipe in the ground, the bottom of the infiltration pipe being closed, and the upper portion of the infiltration pipe protruding from the bottom surface of the water collection tank into the water collection tank It was made to be characterized.
According to a second aspect of the present invention, in the water-permeable structure according to the first aspect, the bottom of the permeation tube is closed with a lid, and the lid is formed to have a diameter equal to or larger than the diameter of the permeation pipe and equal to or smaller than the diameter of the water guide layer. It is characterized by being.
According to a third aspect of the present invention, in the water-permeable structure according to the first or second aspect, an upstanding edge having a predetermined height is formed at the upper and / or lower part of the periphery of the lid.
According to a fourth aspect of the present invention, in the water-permeable structure according to any one of the first to third aspects, the water guiding layer is formed of a granular material.
The invention of claim 5 is a water-permeable structure, and has a water collecting basin used in a drainage system provided with a rainwater outflow control facility, a hollow pipe having a water-permeable structure, and an opening for taking in rainwater at the upper end. And a permeation pipe constituted by a water-impervious structure water guide pipe attached to the upper end of the hollow pipe, the bottom of the hollow pipe being closed, and the upper part of the water pipe is connected to the top of the water collecting tank. It is characterized by protruding from the bottom into the catchment.
The invention according to claim 6 is the water-permeable structure according to claim 5, wherein the hollow tube is formed of a porous member.

According to the present invention, when washing the permeation tube, the high-pressure washing water does not enter the foundation ground from the bottom (bottom surface) of the permeation tube. Will never sink.
In addition, since osmotic water penetrates into the ground only from the peripheral surface of the osmotic pipe, the phenomenon that the water level in the osmotic pipe is lowered at an early stage is suppressed compared to the conventional case where water penetrates from the bottom of the osmotic pipe. Since the wider permeation surface provided on the peripheral wall of the permeation tube can be used effectively, rainwater can be efficiently permeated.

1st Embodiment of the water-permeable structure of this invention is described with reference to drawings.
FIG. 1 shows an osmotic tube used in the water-permeable structure of the present embodiment and a bottom cover attached thereto, FIG. 1A is a longitudinal sectional view thereof, and FIG. 1B is a plan view of the bottom cover.
The permeation tube 20 has basically the same configuration as the conventional one, and a water-permeable sheet 20a is wound around the permeation tube 20. The permeation pipe 20 has an opening provided with a filter 21 on the upper end side when buried in the ground, a water-impervious structure portion 22 having a predetermined length following the opening, and a circumferential surface following the water-impervious structure portion 22. And the other end portion (bottom portion) closed by the bottom cover 30.
Here, the osmotic tube 20 according to the present embodiment is different from the conventional osmotic tube 20 in that the bottom end 30 closes the underground side end (bottom).

  That is, in the conventional osmotic tube 20, an opening is provided in the central portion of the bottom cover 30 in order to promote the penetration of rainwater into the ground. In this embodiment, however, no opening is provided as shown in FIG. 1B. It is not provided, and the diameter is not less than the diameter of the permeation tube and not more than the diameter of the water guide layer. The other configuration is basically the same as that of the conventional bottom lid. In FIG. 1A, reference numeral 36 denotes a pair of support pieces for inserting and bolting the lower end of the permeation tube 20, as shown in FIG. 1B. They are provided at intervals of 90 ° (in addition, the attachment structure of the permeation tube 20 and the bottom cover 30 is not limited to this, and other known attachment means can be applied). Although not shown, a rib-like bottom portion positioning member is provided around the bottom lid 30 every 90 °, for example, as in the prior art.

  FIG. 2 is a cross-sectional view schematically showing an enlarged portion of the water collecting basin 10 in which the osmotic pipe 20 is arranged. For example, a structure in which the osmotic pipe 20 is arranged in the water collecting basin 10 provided along the road. Is shown. Here, the rainwater collected in the catchment tank 10 through the side groove 12 is infiltrated into the ground through the permeation pipe 20 installed in the catchment tank 10.

  The drainage basin 10 has a substantially rectangular shape made of concrete, and is connected to the side groove 12 by an arbitrary means (not shown) such as a bolt. The upper portion is covered with a water collecting lid (grating) 14 and rainwater is formed from a plurality of openings 14 a provided in the water collecting lid 14 together with the side grooves 12. Is also configured to flow in.

  When the permeation tube 20 is attached to the catchment basin 10, a filter 21 for separating dust flowing into the catchment basin 10 together with rainwater is attached to the opening at the upper end of the osmosis tube 20. The lower portion is buried in the ground while leaving a predetermined length H of the impermeable structure portion 22 in the water collecting basin 10 through the opening 10a provided in the ground. Thus, sand or the like is precipitated up to a depth H in the water collecting basin 10 and is not taken into the permeation tube 20.

The permeation pipe 20 is disposed on the foundation ground G composed of crushed stones or the like thrown into the bottom, and the periphery is a water-conducting layer that guides the water that has permeated from the permeation pipe 20 into the ground, that is, a charged granular material. It is supported by a certain sand wall or sand layer S and buried or standing in the ground.
In this structure, rainwater flowing in from the opening 14a of the water collecting lid 14 or the side groove 12 is collected in the water collecting basin 10 and collected therein. When rainwater reaches a predetermined depth H from its bottom surface in the catchment basin 10, it begins to flow into the infiltration tube 20 from the upper opening through the filter 21 of the infiltration tube 20 installed at that position. That is, among the rainwater collected in the catchment basin 10, the initial rainwater inflow is stored in the catchment basin 10 as it is, and only the supernatant of the further inflow is permeated into the ground through the permeation pipe 20.

Here, since the bottom part (bottom face) side of the main permeation pipe 20 is closed, the permeation or water permeation from the bottom part (bottom face) is not performed unlike the conventional permeation pipe. Therefore, apart from the case where rainwater overflowing from the infiltration pipe 20 flows, if the inflow of normal rainwater, the bottom of the infiltration pipe 20 is blocked by the bottom lid 30, so the rainwater is blocked at the bottom, The internal water level is higher than that of the conventional permeation tube 20 having an opening at the bottom.
In the conventional permeation tube 20, rainwater permeates into the ground (or water permeates) from the bottom, so that the permeation efficiency seems to be high at first glance, but it is difficult to permeate conversely, as is apparent from the results of experiments described later. I found out that That is, it has been found that the permeation efficiency as a whole increases rather when the water is temporarily stored in the permeation pipe to increase the permeation pressure and the permeation pipe 20 has a wider permeation area.
In the osmotic tube 20 according to the present embodiment, rainwater is blocked at the bottom as described above and the water level in the tube rises, so that temporary water is stored in the tube, and the osmotic pressure at the lower portion of the osmotic tube increases. This is advantageous in that a wider permeation area of the permeation tube 20 can be used.

  In addition, even when a high-pressure water flow is injected into the permeation pipe 20 during cleaning, it is blocked by the bottom cover 30, so that the high-pressure jet does not directly enter the foundation ground as in the past. Even if the washing water pressure is increased, the foundation ground will not be destroyed. In addition, drainage is performed from the inside of the permeation pipe with the drainage pump in accordance with the jet of the water flow, but even if the drainage capacity is increased, there is no possibility of sucking up earth and sand from the foundation ground of the permeation pipe 20. Therefore, not only the inside of the permeation pipe 20 but also the deposit that flows out of the permeation pipe 20 and is deposited on the retaining wall portion (water conveyance layer) made of the sand layer around the permeation pipe 20 can be easily sucked and discharged. be able to.

3A to 3C are longitudinal sectional views of the bottom lid that closes the bottom of the permeation tube 20, and show an embodiment different from the bottom lid 30 according to the first embodiment described above.
That is, FIG. 3A is a second embodiment in which a peripheral wall extending upward is formed at the peripheral edge of the bottom lid, and FIG. 3B is a third embodiment in which a peripheral wall extending downward is formed at the peripheral edge of the bottom lid. Further, FIG. 3C shows longitudinal sectional views of a fourth embodiment in which a peripheral wall portion extending in the vertical direction is formed on the periphery of the bottom lid.

  In the bottom cover 30 of the second embodiment shown in FIG. 3A, since the peripheral wall 33 rises upward from its peripheral edge and extends as a standing edge, it is made of sand thrown around the permeation tube 20 as described above. When the retaining wall is configured, by making the diameter of the bottom cover 30 larger than that of the permeation pipe 20, there is an advantage that the retaining wall is supported by the sand on the side surface and the bottom surface to reinforce the retaining wall. It is done.

  In the bottom cover 30 according to the third embodiment shown in FIG. 3B, the peripheral wall 35 extends as an upstanding edge standing downward from the peripheral edge thereof. By extending the peripheral wall 35 in this way, it is possible to prevent water that has permeated from the peripheral surface of the permeation tube 20 from entering the ground. That is, when the permeated water descending from the periphery of the permeation tube 20 wraps around and enters, for example, earth and sand of the foundation ground, the permeation pipe 20 may sink to compact the earth and sand and reduce the volume of the foundation ground. By providing the peripheral wall 35 extending downward on the peripheral edge of the bottom cover 30, such a phenomenon can be prevented.

In the bottom cover 30 according to the fourth embodiment shown in FIG. 3C, the peripheral wall 37 extends from the peripheral edge as an upstanding edge that stands up and down. With this configuration, the advantages of the second and third embodiments can be obtained simultaneously.
The bottom cover 30 according to each of the above embodiments can be appropriately selected in consideration of the retaining wall and the ground when the permeation tube 20 is embedded.

Next, the water permeable structure which concerns on the 2nd Embodiment of this invention is demonstrated.
FIG. 4 is the same as FIG. 2, and is a cross-sectional view schematically showing an enlarged portion of the water collecting basin 10 in which the second permeation pipe (herein simply referred to as the permeation pipe) 40 is arranged. A structure in which a permeation pipe 40 is arranged around a water collecting rod 10 provided along a road is shown.
Rainwater collected in the catchment basin 10 through the side groove 12 is infiltrated into the ground through the permeation pipe 40 installed in the catchment basin 10.

  The water collecting basin 10 and the side groove 12 are the same as those already described, and here, the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the substantially central portion of the catchment basin 10, the main body of the water permeable structure is disposed in the ground, leaving a tip portion of the permeation tube 40 (water guide tube 46 described later) at a predetermined height H from the bottom surface. ing.

As shown in the figure, the permeation tube 40 is made of a material such as sand or gravel having a hole 42 in the center as appropriate, or made of porous concrete, that is, a cylindrical tube 44 as a hollow tube having a water-permeable structure ( The shape is not limited to this, and may be, for example, a square tube) and a water-impervious structure water guide tube 46 inserted and fixed to the upper end portion thereof. The water conduit 46 is formed as a pipe made of synthetic resin, which is a water-impermeable material, for example, similarly to the water-impermeable structure portion 22 of the permeation tube 20 of the first embodiment. The filter 21 is attached to the upper end portion of the water conduit 46.
The outer diameter of the cylindrical tube 44 is formed to be approximately the same as the outer diameter of the water guide layer in the first embodiment, and the inner diameter is formed to be approximately equal to that of the permeation tube 20 of the first embodiment. Therefore, the cylindrical tube 44 also has the function of the water guiding layer in the first embodiment. Since the permeation tube 40 has the above-described configuration, it is not necessary to form a water-conducting layer of sand or the like around the permeation tube 20 as in the first embodiment, or even if it is formed, the width is formed thin. That's enough.

  When the permeation tube 40 is embedded in the ground, after the excavation hole is excavated and the foundation ground G is formed at the bottom thereof in the same manner as in the first embodiment, the permeation tube 40 is stood in the excavation hole. The bottom surface (bottom portion) of the permeation tube 40 is closed, including its central hole 42, by impregnating or applying cement, adhesive, paint, and the like, thereby blocking the passage of rainwater.

In this structure, rainwater flowing in from the opening 14a of the water collecting lid 14 or the side groove 12 is collected in the water collecting basin 10 and accumulated therein as in the first embodiment. When rainwater reaches a predetermined depth H from its bottom surface in the catchment basin 10, it begins to flow into the permeation tube 40 from the upper opening through the filter 21 of the permeation tube 40 installed at that position.
Here, since the bottom portion of the osmotic tube 40 is closed by the closed portion 48, the permeation or water permeation from the bottom portion is not performed unlike the conventional osmotic tube 40. Therefore, apart from the case where rainwater overflowing from the permeation tube 40 flows, if the inflow of normal rainwater, the rainwater is blocked at the bottom and the water level inside the permeation tube 40 having an opening at the bottom is conventional. Goes up.

In this way, a wider permeation area of the permeation tube 40 can be used, which is advantageous for drainage.
In addition, even when a high-pressure water flow is injected into the permeation tube 40 during cleaning, the water flow is blocked by the closed portion 48, so that the high-pressure jet does not directly enter the foundation ground as in the prior art. Even if the pressure of the washing water is increased, the foundation ground of the permeation tube 40 is not destroyed. In addition, drainage is performed from the inside of the permeation pipe 40 by the drainage pump in accordance with the jet of the water flow. In this case, even if the drainage capacity is increased, there is no possibility of sucking up earth and sand from the foundation ground G of the permeation pipe 40. As with the form, cleaning can be performed efficiently.

FIG. 5 shows the permeation pipes (referred to as the first and second permeation pipes, respectively) in the first and second embodiments, with the same structure (open side) and the bottom face (bottom part) fully opened, or The comparison result of the water permeability coefficient performed by comparing with each permeation pipe which made the side water-proof structure in the state where the bottom face was fully opened is shown.
In the experiment, water was poured into a 200 mm inner diameter osmosis tube installed under the same conditions, and after about 15 to 15 minutes, the amount of water level decreased after the water became full at a water depth of 1200 mm was obtained, and the respective hydraulic conductivity was obtained. Compared.
The water level was measured 2.5 hours and 16 hours after full water, and the respective hydraulic conductivity (the rate at which water moves through the soil cm / sec) was determined. The figure is a graph showing the hydraulic conductivity based on the average value, and the vertical axis indicates the hydraulic conductivity.

In the figure, 1-1 is a water-impervious structure in which the periphery of the permeation pipe around the permeation pipe with the bottom face (bottom) of the permeation pipe (peripheral surface opening) of the first embodiment fully open is covered with a steel pipe. It is the graph which showed the penetration efficiency of.
1-2 is a graph showing the permeation coefficient of the permeation tube of the first embodiment of the present invention.
1-3 is a graph showing a permeation coefficient in a state where the bottom surface of the permeation tube of the first embodiment is fully opened.
As is apparent from the above graphs, when the permeation tube 20 of the first embodiment (that is, the bottom surface of the permeation tube is closed by opening the side surface), the perimeter of the permeation tube is impermeable. The permeability coefficient is not only higher than the permeability coefficient (1-2) of the fully open bottom surface and the permeability coefficient (1-3) of the fully open bottom face with the peripheral surface being permeable structure, It shows that it is higher than the water permeability coefficient when adding both, that is, 1-1 and 1-3.

In the figure, reference numeral 2-1 shows a state in which the bottom surface of the permeation tube (peripheral surface opening) of the second embodiment is fully opened, and the periphery of the permeation tube (cylindrical tube 44) is covered with a steel pipe to form an impermeable structure. It is the graph which showed the water permeability coefficient.
2-2 is a graph showing the water permeability coefficient of the permeation tube (peripheral surface open and bottom surface occlusion) of the second embodiment of the present invention.
2-3 is a graph showing the water permeability when the bottom surface of the permeation tube of the second embodiment is fully open.
As is apparent from the above graphs, when the permeation tube 40 of the second embodiment is used, the permeation coefficient (2-2) and the perimeter surface of the permeation tube whose permeation surface is impermeable structure are permeated. Not only is the permeability coefficient (2-3) higher than the permeability coefficient of the structure whose bottom is fully open, but it is even higher than the permeability coefficient when both are added, that is, 2-1 and 2-3. Is shown.

  From the above experimental results, comparing the hydraulic conductivity calculated from the water level drop, it can be seen that the bottom impervious type is about 7 to 9 times better than the side impervious. In addition, and "peripheral surface impervious" (having a water permeable part only on the bottom surface: 1-1 and 2-1 in the figure) and "None" type without any water permeable part (both peripheral and bottom surfaces) In the type having the permeation surface: 1-3, 2-3) in the figure, the permeation amount is reduced and the water permeability coefficient is lower than the bottom impermeability (1-2, 2-2). I understood. This is presumed to be due to the fact that the pressure in the ground due to temporary storage is low because the in-hole water level does not rise temporarily by not suppressing infiltration from the bottom.

FIG. 1A is a longitudinal sectional view of an osmotic tube according to an embodiment of the present invention, and FIG. 1B is a front view of a bottom lid. It is sectional drawing of 1st Embodiment which expanded and showed typically the part of the water collecting tank which attached the osmosis | permeation pipe | tube. Fig. 4 shows a different embodiment of the bottom lid. 3A is an embodiment in which a peripheral wall extending upward is formed at the peripheral edge of the bottom lid, FIG. 3B is an embodiment in which a peripheral wall extending downward is formed at the peripheral edge of the bottom lid, and FIG. Each longitudinal cross-sectional view of embodiment with which the peripheral wall extended in the up-down direction was formed in the peripheral part of the bottom cover is shown. It is sectional drawing of 2nd Embodiment which expanded and showed typically the part of the water collecting tank which attached the osmosis | permeation pipe | tube. It is the graph which showed the permeation | transmission efficiency when rain water was filled with each infiltration pipe | tube in full. FIG. 6A is a longitudinal sectional view showing a bottom portion of an osmotic tube having a conventional bottom lid, and FIG. 6B is a plan view of the bottom lid. It is a figure similar to FIG. 6B of the conventional osmosis | permeation pipe | tube without a bottom cover.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Water collecting trough, 12 ... Side groove, 14 ... Water collecting lid, 20 ... Permeation pipe, 20a ... Water-permeable sheet, 21 ... Filter, 22 ... Water-impermeable structure part 24 ... underground penetration part, 24a ... penetration hole, 25 ... bolt through hole, 30 ... bottom lid, 33, 35, 37 ... peripheral wall, 40 ... (second) Osmosis tube.

Claims (6)

Catchment used in drainage system equipped with rainwater outflow control facility,
A permeation pipe having an opening for taking in rainwater at the upper end and having a rainwater permeation hole in the peripheral surface;
A water conduction layer provided around the permeation pipe in the ground,
The permeation tube is closed at the bottom and has a top projecting from the bottom of the catchment into the catchment. In the water-permeable structure according to claim 1,
The permeation tube is closed at the bottom with a lid,
The water permeable structure is characterized in that the lid body is formed to have a diameter equal to or larger than that of the permeation tube and equal to or smaller than the diameter of the water guide layer. In the water-permeable structure according to claim 1 or 2,
A water permeable structure, wherein an upstanding edge having a predetermined height is formed on an upper and / or lower side of the periphery of the lid. The water-permeable structure according to any one of claims 1 to 3,
The water permeable structure is characterized in that the water guide layer is formed of a granular material. Catchment used in drainage system equipped with rainwater outflow control facility,
A water-permeable hollow tube, and an osmotic tube composed of a water-impervious water guide tube attached to the upper end of the hollow tube having an opening for taking in rainwater at the upper end,
The hollow pipe is closed at the bottom, and has a water permeable structure in which an upper portion of the water conduit is protruded from the bottom surface of the water collecting basin into the water collecting basin. In the water-permeable structure according to claim 5,
The water permeable structure is characterized in that the hollow tube is formed of a porous member.

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