JP3430292B2 - Rainwater storage facility and its construction method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rainwater storage facility which is usually used mainly for grounds and the like, and which can temporarily store rainwater in the ground when it rains.

[0002]

2. Description of the Related Art In a ground mainly composed of clay, which is used as a playground or various stadiums in schools, a stabilizer is mixed with ground surface soil to consolidate the surface, and at that time, a gradient is provided on the surface. Surface water is drained by introducing rainwater into drains provided around the ground. In addition, underground drainage is conducted using a culvert.

The pavement structure by the conventional method as described above is
By the time Japan was said to be the second wettest country in the world, efficient surface drainage was used to achieve the objective of preventing mud and frost damage.

However, in recent years, the city has become overcrowded,
In addition, due to the deterioration of the environment on a global scale, the heat island phenomenon occurs, and problems such as dust damage and the spread of allergic rhinitis due to the depletion of groundwater and a tendency toward low rainfall in the archipelago are becoming serious problems.

In fact, as a result of conducting a test excavation at 500 sites nationwide, it was confirmed that the surface soil was contaminated, and rainwater on the surface hardly penetrated into the ground and was drained to the surface.

The surface soil is solidified on the surface surface or in the ground 2
At ~ 3 cm, a suspension of silt and clay deposits, causing clogging and forming crusts.

The mechanism is as follows, according to Toshio Yawata, "Physics of Soil" (Univ. Of Tokyo, 1975). That is, the raindrops that begin to fall hit the aggregate of soil particles lined up on the surface of the ground, shake it, and
By rapidly immersing it in water, it causes slaking and loosens the bonds between particles (slaking means that when a dry mass of soil is rapidly immersed in water, the outside of the mass becomes saturated quickly, It is a phenomenon in which air is trapped inside, and the soil mass collapses due to the pressure). Subsequent raindrops create a very thin and slightly clogged crust on the surface of the earth's surface. As a result of this, the intrusion a little weakened, and rainwater gathered on the ground and became a little messy. The raindrops that fall there mix the rainwater with the dispersed soil particles. This creates a suspension of water in which most of the suspension is silt clay. Then, it is considered that it flows into the soil layer from fine cracks and thin crust areas.

[0008] Further, since the rainwater is drained to the surface as described above, the amount of water retention in the ground decreases, while the water level on the sea surface rises by several cm, and as a result, seawater evaporates more and more in the sea near Japan. The atmospheric pressure has dropped and many typhoons are occurring. It also has many rain typhoons and tends to concentrate in one place, but since rainwater does not penetrate into the ground as described above, disasters such as urban floods and debris flows frequently occur.

In order to solve the above problems, it is necessary to suppress the outflow of rainwater as surface drainage and temporarily store it in the ground.

As one of the solutions, a rainwater storage facility as shown in FIG. 1 has been proposed.

In this structure, a rainwater storage layer 2 made of crushed stone or the like is provided under the surface layer 1 of the ground, and a gutter 3 provided around the ground is connected to the rainwater storage layer 2 by a perforated pipe 4. . Rainwater directly permeates from the surface layer 1 into the rainwater reservoir 2, flows into the gutter 3, is introduced from the gutter 3 into the rainwater reservoir 2 through the perforated pipe 4, and is temporarily stored therein.
The rainwater that has been temporarily stored permeates into the underlying formation, and part of it is discharged to the outside by the underdrain drainage pipe 5 using a perforated pipe. It should be noted that the surface of the surface layer 1 is provided with a gradient to promote the inflow of rainwater into the gutter 3.

However, in such a structure,
Soil flows out from the surface layer 1 and flows into the perforated pipe 4 from the gutter 3, so that the relatively thin perforated pipe 4 and the rainwater reservoir 2 are apt to be clogged in a short period of time, and the perforated hole is buried in the ground. There is a problem that it is extremely difficult to dig out the pipe 4 and repair it.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and by temporarily storing rainwater in the ground, it is possible to prevent disasters such as floods and prevent daily dust damage. Moreover, the object is to provide a rainwater storage facility in which problems such as clogging are less likely to occur.

[0014]

In order to solve the above-mentioned problems, the rainwater storage facility according to claim 1 has a surface layer mainly made of clay and a rainwater storage layer provided below the surface layer. And the surface layer stabilizes the aggregate structure.
Made of water-resistant aggregate structure soil obtained by using
Water resistance of water reservoir obtained using aggregate structure stabilizer
A permeable stone part containing aggregated structure soil, which is adjacent to the surface layer and the rainwater reservoir and is filled with crushed stone, is provided in at least a part of the rainwater storage facility.
A permeable sheet is laid between the layer and the permeable part, and
It is assumed that a clogging prevention material is laid on the upper surface of the portion, and rainwater on the surface layer flows into the rainwater reservoir through the clogging prevention material, the water permeable portion and the water permeable sheet .

[0015] method of constructing 請 Motomeko 2 rainwater storage facilities mainly has a rainwater storage layer provided under the top layer and the surface layer made of clay, a construction method of the rainwater storage facility ground, construction Excavating the soil at the site, screening it,
Separation into fine-grained soil and coarse-grained soil, and stable aggregate structure in the coarse-grained soil
Add a chemical agent and knead to obtain aggregate-structured soil.
A rainwater reservoir is formed using aggregated soil obtained from
Aggregate structure stabilizer is added to the fine-grained soil, a surface layer is formed on the rainwater reservoir using the aggregate structure soil obtained by kneading, and the surface layer and the rainwater reservoir are adjacent to each other. To form a water permeable part filled with crushed stone, and at that time, the surface layer and rainwater
A permeable sheet is laid between the reservoir and the permeable section,
It consists of laying a clogging prevention material on the upper surface of the water part .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically with reference to the drawings, but the present invention is not limited thereto.

FIG. 2 is a schematic sectional view showing a rainwater storage facility which is an embodiment of the present invention.

In the figure, reference numeral 10 is a surface layer of the ground, 20 is a rainwater reservoir, 30 is a gutter, 31 is a gutter lid,
40 is a water permeable part, 41 is a clogging prevention material, 50 is a water permeable sheet, 60 is a culvert drainage pipe, 61 is crushed stone, and 62 is a water permeable filter.

In the rainwater storage facility shown in this figure, the surface layer 1
A rainwater storage tank 20 is provided below the water tank 0, and a water permeable portion 40 is provided so as to contact both of them. The surface layer 10 is preferably made of water resistant aggregate structure soil, and the rainwater storage tank 20
Consists of crushed stone and / or aggregate structure soil,
Is filled with crushed stone. These will be described later.
A side groove 30 is provided further outside the water permeable portion 40, and a lid 31 is provided on the side groove 30.

The surface layer 10, the rainwater storage tank 20, and the water permeable portion 40
A water-permeable sheet 50 is laid between the and. A clogging prevention material 41 is laid on the water permeable portion 40.

Below the rainwater storage tank 20, a groove is formed and a drainage pipe 60 is arranged, and a crushed stone 61 is filled around the drainage pipe 60. The drainage pipe 60 is a perforated pipe and is connected to an external drainage facility.

In the rainwater storage facility having the above structure, rainwater flows on the surface layer 10 while partially penetrating into the surface layer 10 as shown by the arrow in the figure, and reaches the water permeation section 40. In the case of normal rainfall, most of the rainwater flows into the water permeable portion 40, but the amount of rainfall per unit time is particularly large, and if the permissible amount of inflow to the water permeable portion 40 is exceeded, the surface of the water permeable portion 40 It passes through and flows into the gutter 30.

The rainwater that has penetrated into the surface layer 10 in the above is
As it continues to permeate downward, it flows into the rainwater storage tank 20 and is temporarily stored therein. The rainwater that has flowed into the water permeable portion 40 also permeates or flows into the surface layer 10 and the rainwater storage tank 20 via the water permeable sheet 50. Part of the rainwater stored in the rainwater storage tank 20 gradually penetrates into the underlying formation and is naturally dissipated, and part of the rainwater is drained to the outside through the underdrain pipe 60.

As in the prior art, it is preferable to provide an appropriate gradient on the surface of the surface layer 10 so that rainwater can flow smoothly. The magnitude of the gradient is usually about 0.5 to 0.7 °.

According to the above structure, since rainwater flows into the rainwater storage tank 20 through the water permeable portion 40 filled with crushed stone, it is less likely to be clogged than the prior art using a relatively thin perforated pipe. It becomes much smaller, and even if it becomes clogged, it is easy to repair it because it is only necessary to excavate the water permeable portion 40.

Moreover, since the clogging prevention material 41 is laid on the water permeable portion 40, the clogging prevention material 41 can be replaced as needed to almost completely prevent the water permeable portion 40 from being clogged. .

As the soil constituting the above-mentioned surface layer 10,
Aggregated soil is preferably used. When aggregated soil is used, it has excellent water permeability, so rainwater penetrates into the ground in a short time after rainfall, and the ground becomes usable,
Since water retention is imparted to the surface layer 10, the daily dust damage prevention effect is remarkable. Further, since appropriate elasticity is imparted, the impact on the human body from the ground is mitigated, and the injury due to the fall or the like during exercise can be prevented.

In particular, when the aggregate structure stabilizing material (hydraulic binder) made of a raw material containing alumina or the like is used for aggregation, water resistance is imparted to the aggregate structure to maintain the aggregate structure for a long period of time. To do. Therefore, the effects such as the water permeability are maintained, and the surface soil is less likely to flow out together with the rainwater, so that the risk of clogging of the water permeable portion or the rainwater reservoir is further reduced.
The type of the aggregate structure stabilizing material is not particularly limited, but a material obtained from tap water (purified water) sludge of a water purification plant can be preferably used for effective use of waste. Among them, those having an aggregate structure imparted to the aggregate structure stabilizing material itself are preferable, and such aggregate structure stabilizing material includes, for example, dehydration of tap water sludge
The dried dehydrated cake is crushed and then put into an agglomerating sieve sorter, and sieved while agglomerating. It is obtained by doing.

The thickness of the surface layer 10 is usually 30 to 100.
mm, and preferably about 70 to 100 mm. The rainwater reservoir 20 can be formed by laying crushed stones as in the prior art, but instead of crushed stones, or coarse crushed aggregate structure soil described below can be used together with crushed stones. In that case, use of crushed stones Not only can the amount be reduced, which is economically advantageous, but the elasticity of the ground is also improved.

The rainwater reservoir 20 usually has a thickness of 100 to 5
It is about 00 mm.

As a material for forming the surface layer 10 and the rainwater storage layer 20, it is preferable to use aggregated structure soil obtained by using degraded soil of the ground, as described below, for environmental protection and cost saving. Are particularly preferred.

That is, the deteriorated soil excavated from the construction site is first sieve-sorted while being agglomerated using an agglomerating-sieve sorter to separate it into fine-grained soil and coarse-grained soil. A water-resistant aggregate-structured soil can be obtained by adding an aggregate-structure stabilizer to each of the obtained fine-grained soil and coarse-grained soil and kneading them with a kneader. The fine-grained aggregate structure soil obtained from the fine-grained soil is on the surface layer 10,
The coarse-grained aggregate structure soils obtained from the coarse-grained soils are used for the rainwater reservoir 20, respectively. As described above, the rainwater reservoir 2
For 0, it is also possible to use a mixture of coarse-grained aggregate structure soil and small stones or crushed stones.

It is an essential requirement that the water permeable portion 40 be provided so as to be in contact with both the surface layer 10 and the rainwater storage layer 20 so as to ensure the above-mentioned flow of rainwater. Therefore,
The thickness is determined by the thicknesses of the surface layer 10 and the rainwater storage layer 20, and in the present embodiment, the bottom surface thereof has substantially the same height as the bottom surface of the rainwater storage layer, and the top surface thereof has substantially the same height as the surface of the surface layer 10. However, the present invention is not limited to this, and the bottom surface thereof can be made higher than this.

The width of the water permeable portion 40 may be determined within the range in which the object of the present invention is achieved, but it is usually 200 to 300.
It is about mm.

Further, the installation place, the number of installations, and the length are not particularly limited, and they are individually determined according to the amount of rainfall and the conditions of the ground. That is, it may be provided along the entire periphery of the ground, but normally it may be provided along the most appropriate portion of the periphery. For example, when the ground is a quadrangle and is entirely inclined, it may be provided only on one side located on the lower side, or may be provided on two sides or three sides including this one side. When the ground has a circular shape or an irregular shape, the length and the number necessary for achieving the purpose may be provided centering on the low portion.

The size of the crushed stone forming the water permeable portion 40 is usually about 20 to 40 mm (No. 4 to 5) and 30 to 30 mm.
About 40 mm is preferable. The effective porosity is usually 2
It is set to about 5 to 40%, preferably about 30%.

The water-permeable sheet 50 is used for preventing clogging between the surface layer and the rainwater storage layer and the water-permeable portion, and is composed of, for example, a filter of one layer or multiple layers of non-woven fabric. Specific examples thereof include Green Sheet KP12-300 and KP12-6 manufactured by Takiron Co., Ltd.
00, KPY12-400 and the like.

The clogging preventing material 41 is laid on the upper surface of the water permeable portion 40 for preventing clogging, and for example, a polyethylene planar drainage material having a three-layer structure as shown in FIG. 3 is suitable. Used. The polyethylene sheet drainage material shown in FIG. 3 is obtained by forming a band 42 of high-density polyethylene into a corrugated shape and arranging a plurality of rows in parallel, and covering both sides with a filter material 43 made of polyethylene net. Specific examples of polyethylene surface drainage materials include T manufactured by Tota Kogyo Co., Ltd.
AC mendren and the like can be mentioned.

Although the gutter 30 and the lid 31 thereof are not essential in the present invention, when they are installed, they may be constructed in the same manner as conventional ones, and rainwater in the gutter 30 is discharged to the outside by a drain pipe or other suitable means. Allow it to be discharged.

The surface layer 10, the rainwater storage layer 20, the water permeable portion 40, and the water permeable sheet 50 are installed in the order that the water permeable portion 40 is provided first, and the water permeable sheet 50 is provided on the side surface of the water permeable portion 40. And the surface layer 10 may be provided in order,
Alternatively, the rainwater storage layer 20 and the surface layer 10 may be provided first, the water permeable sheet 50 may be provided on the side surface thereof, and then the water permeable portion 40 may be provided.

[0041]

According to the rainwater storage facility of the first aspect, the rainwater is temporarily stored in the rainwater storage tank, thereby preventing a disaster such as a flood and preventing daily dust damage due to drying. . And since rainwater is stored in the rainwater reservoir through the water permeable part filled with crushed stone, it is less likely to cause troubles such as clogging due to soil flowing out from the surface layer as compared with the conventional one using a perforated pipe. Even if it happens, it is easy to repair. Further , maintenance (replacement of the clogging prevention material) is extremely easy.

And obtained by using an aggregate structure stabilizer
By using the water resistant aggregate structure soil , the permeability of the surface layer is secured and the outflow of soil from the surface layer is suppressed.

Further, by improving the moisturizing property and elasticity, the dust damage preventing effect is further improved, and the impact on the human body from the ground is mitigated, and the injury at the time of falling can be prevented .

According to the construction method of the second aspect , not only a rainwater storage facility that achieves each of the above effects can be obtained, but also waste can be effectively used.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a conventional rainwater storage facility.

FIG. 2 is a schematic sectional view showing an embodiment of the present invention.

FIG. 3 is a perspective view showing a clogging prevention material (polyethylene surface drainage material).

[Explanation of symbols]

1 ... Surface 2 ... Rainwater storage tank 3 ... Gutter 4 ... Perforated tube 10 ... Surface 20 …… Rainwater storage tank 30 ... gutter 31 ... Lid 40 ... Permeable part 41 ... Clogging prevention material 42 …… High-density polyethylene belt 43 ... Filter material 50 ... Water-permeable sheet 60 ... Underdrain drainage pipe 61 …… Crushed stone 62 ... Permeable filter

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-102569 (JP, A) JP-A-3-208903 (JP, A) JP-A-11-71789 (JP, A) JP-A-8- 311938 (JP, A) JP 58-207412 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) E03F 1/00 E01C 13/00

Claims (2)

(57) [Claims] 1. A rainwater storage facility having a surface layer mainly composed of clay and a rainwater storage layer provided below the surface layer , wherein the surface layer is water resistant obtained by using an aggregate structure stabilizing material.
It consists of aggregated structure soil, and the rainwater reservoir was obtained using aggregated structure stabilizer
A water- permeable part containing water resistant aggregate structure soil, which is adjacent to the surface layer and the rainwater reservoir and is filled with crushed stone, is provided in at least a part of the rainwater storage facility. Water-permeable sheet between layer and water-permeable part
Is laid and a clogging prevention material is laid on the upper surface of the water-permeable part.
Is, rainwater said purpose clogging prevention material on the surface, the permeability section and
A rainwater storage facility, characterized in that it flows into the rainwater storage layer through a permeable sheet . 2. A method for constructing a ground rainwater storage facility having a surface layer mainly made of clay and a rainwater storage layer provided below the surface layer, which comprises excavating soil at a construction site, screening the soil. , Separate into fine-grained soil and coarse-grained soil , add aggregate structure stabilizing material to the coarse-grained soil, and knead to aggregate
A structured soil is obtained, a rainwater reservoir is formed using the aggregated soil obtained from the coarse-grained soil, a aggregate-structure stabilizing material is added to the fine-grained soil, and the aggregate is obtained by kneading. A surface layer is formed on the rainwater reservoir by using a grain structure soil, and a water-permeable part formed by filling crushed stone is formed adjacent to the surface layer and the rainwater reservoir, and at that time, the surface layer and the rainwater reservoir. layer
A method for constructing a rainwater storage facility , comprising laying a water-permeable sheet between the water-permeable portion and a water-permeable portion, and laying a clogging prevention material on the upper surface of the water-permeable portion .