JPH09296486A - Underground water storage tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent buckling from occurring to individual pile-up members and to ensure a large void content by a method wherein a load applied to a covering layer of a water storage space is sustained with a specified aggregate constructed of a number of pile-up members and installed to the water storage space. SOLUTION: An aggregate constructed of a number of pile-up members 2 arranged lengthwise and breadthwise and piled up in tiers vertically is installed to the inside of a water storage space formed underground in a pitlike shape, and load applied to a covering layer arranged on the aggregate is sustained with the aggregate B. Each of the pile-up members 2 is made of a polypropylene resin or the like and formed by integral molding into a shape wherein hollow cylindrical legs 23 respectively in equal length are provided in parallel with one another at corners 22... of a square link-shaped connecting rib 21 and reinforcing brackets 26 are arranged between each of the legs 23 and the connecting rib 21. Spigots 24 provided at the end of legs 23 of another pile-up member 2 are fitted into sockets 25 provided at the end of the legs 23, then the legs 23 of the pile-up members 2 are arranged vertically in the water storage space, and the aggregate is constructed with the pile-up members piled up vertically in tiers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground water tank, particularly a load applied to a coating layer arranged to cover a water storage space,
The present invention relates to an underground water tank which can be received by an assembly of a large number of stacked members loaded in the water storage space.

[0002]

2. Description of the Related Art An underground water storage tank of this kind is described in Japanese Patent Publication No. Hei 4-26648. FIG. 16 shows a stacking member loaded in the water storage space of the underground water storage tank described in this publication. As shown in FIG. 16, the stacking member 1 includes a rectangular bottom plate portion 11, an inclined side plate 12 that rises like an end from four side portions of the bottom plate portion 11,
The tilted side plate 12 has flanges 13 and 14 provided in a protruding shape at one end edge and the other end edge part in the up-down direction, respectively. Water passage 15 is opened.

As a stacking form when the stacking members 1 are stacked vertically in a water storage space of an underground water tank and loaded, for example, the stacking form shown in FIG. 15 is adopted.
In the stacking mode of the figure, the two stacking members 1, 1 stacked vertically are superposed with the two stacking members 1, 1 being turned upside down. Therefore, when a large number of the stacking members 1 ... Are lined up in the vertical and horizontal directions in the water storage space and stacked vertically, and loaded, and a coating layer for covering the water storage space is provided on the upper part thereof. , The load applied to the coating layer is received by an assembly of a large number of the stacking members 1, ... At that time, the inclined side plates 12 of the individual stacking members 1 stacked as shown in FIG. 15 resist the above loads. Acts like.

[0004]

However, since the slanted side plates 12 of the individual stacking members 1 stacked vertically are slanted in the shape of the end spread as described above, the load applied to the coating layer is When received by an assembly of a large number of the stacking members 1 ..., a large force is applied to the end-spreading inclined side plates 12 of the individual stacking members 1 in the direction of pushing and expanding it (that is, the direction in which the inclined side plates 12 are bent). When the inclined side plate 12 is likely to buckle and a partial crack is generated in the inclined side plate 12,
Even if the load applied to the inclined side plate 12 is not so large, the inclined side plate 12 may easily buckle from the crack point. In particular, when the stacking member 1 is integrally molded of synthetic resin and the inclined side plate 12 is made thin to some extent to reduce the weight of the stacking member 1, buckling as described above occurs. It is easy to occur. When the inclined side plates of the stacking member 1 cause buckling, the effect of the buckling extends over the entire number of stacking members loaded in the water storage space and is lined up vertically and horizontally and vertically. There is a problem that misalignment occurs between a large number of stacked stacking members and the overall balance of the stacked stacking members tends to be lost, and the underground water tank must be repaired at an early stage.

Further, as shown in FIG. 17, the uppermost stacking member 1 forming the aggregate is arranged upside down with its bottom plate portion 11 facing upward, and is covered thereon. The layers must be arranged. However, in doing so, a space S is inevitably formed between the uppermost stacking members 1 and 1 that are adjacent to each other in the vertical direction or the horizontal direction. This void S must be filled in some way,
If a means of filling and filling the void S with gravel is adopted, the load applied to the coating layer is applied in the direction in which the inclined side plate 12 of the stacking member 1 is bent through the gravel layer, so that the inclined side plate 12 is very easily buckled. It is not preferable because it will be put in a situation. As another means, when a wedge-shaped member for filling the space S is provided, when the wedge-shaped member is pressed downward by the load applied to the coating layer, the wedge-shaped members are adjacent to each other in the vertical direction or the horizontal direction. It is not preferable because the whole shape of the aggregate tends to collapse in an attempt to expand the interval of 1,1.

The present invention has been made in view of the above problems, and is an assembly composed of a large number of stacking members that are loaded in the water storage space to apply a load applied to the coating layer disposed so as to cover the water storage space. Basically, the stacking member is basically configured to receive the load by devising the shape or configuration of the stacking member so that the individual stacking members that form the aggregate that receive the load applied to the coating layer are less likely to buckle. The purpose is to provide an underground water tank.

Another object of the present invention is to provide an underground water storage tank in which the shape of the whole assembly is less likely to be destroyed by the load applied to the coating layer.

Further, the present invention provides an underground water storage tank which can have a larger space ratio than the water storage space of the underground water storage tank using the stacking members described in FIGS. 15 and 16. To aim.

A further object of the present invention is to provide an underground water storage tank using a stacking member that is easier to make lighter than the stacking member described with reference to FIGS. 15 and 16.

[0010]

The underground water storage tank according to the present invention is vertically and horizontally arranged and vertically stacked inside a water storage space formed in a recess in the ground. In an underground water tank, in which an aggregate consisting of a large number of stacking members is loaded, a coating layer is disposed on the upper part of the aggregate, and the load applied to the coating layer is received by the aggregate, the stacking member is , A plurality of leg rods arranged in parallel with each other and a connecting bone for mutually connecting these leg rods are integrally provided, and a fitting portion is provided at one end of each of the leg rods, and The other end of the leg rod is a synthetic resin integrally-molded body in which a fitted portion having a shape and dimensions that can be fitted to the fitting portion is provided, and the assembly is stacked vertically. Between the two stacking members, one stacking section The fitting portion of the leg rod is fitted to the fitted portion of the leg rod of the stacking member of the other stage, and the stacking member of each of the stacking members constituting the aggregate is The foot rod is vertically arranged in the water storage space.

In such an underground water tank, the load applied to the coating layer when a person walks on the coating layer or an automobile runs on the coating layer depends on the load of the individual stacking members constituting the aggregate. It acts mainly in the direction of vertically compressing the vertical rod, and does not apply so much force in the direction in which the rod is bent.

Further, since the stacking member which constitutes the above-mentioned assembly has a skeleton structure formed by a plurality of the above-mentioned leg rods and the above-mentioned connecting bones, the above-mentioned assembly in the above-mentioned water storage space The volume occupied by the body is kept small. As a result, it becomes possible to store a large amount of water by increasing the porosity of the water storage space. In addition, since the stacking member has the frame structure described above, it is easy to achieve weight reduction of the stacking member.

In the underground water storage tank of the present invention, the leg rod of the uppermost stacking member forming the aggregate rises from the connecting bone of the stacking member, and one end of the leg rod is formed. The fitting portion provided on the lid body made of a plate-shaped frame is fitted to the fitting portion provided on the lid body, and the lid body is disposed on the uppermost stacking member, and the lid body is placed on the lid body. It is preferable to employ a configuration in which the coating layer is provided. By doing so, no void is formed in the mutual rods of the stacking members adjacent to each other in the longitudinal direction and the transverse direction at the uppermost part of the above assembly, so that the stacking members can be spread by the load applied to the coating layer. Absent.

In the underground water tank of the present invention, the connecting bone of the stacking member has a polygonal annular shape, and each of the plurality of leg rods of the stacking member and the polygonal annular connecting bone are formed. It is possible to adopt a configuration in which the connecting bones of the stacking members, which are crossed at a right angle and are aligned in the vertical direction and the horizontal direction, are butted against each other in the vertical direction and the horizontal direction. By doing so, the many stacking members arranged adjacent to each other in the vertical and horizontal directions are unlikely to be displaced in the vertical and horizontal directions due to the abutment of the polygonal annular connecting bones.

In the underground water storage tank of the present invention, the connecting bone has a polygonal annular shape, and each of the plurality of leg rods intersects the polygonal annular connecting bone at a right angle. When adopting, it is possible to select a square ring or an isosceles triangle ring as the polygon ring.
When the rectangular ring is selected, it is desirable that the above-mentioned leg rods are provided on each of the four corner portions of the connecting bone, and when the isosceles triangular ring is selected, each of the three corner portions of the connecting bone is selected. It is desirable that the above-mentioned leg rod is provided on the. By doing so, the installation state of the individual stacking members forming the aggregate is stable.

In the underground water storage tank of the present invention, between the at least two stacking members that are adjacent to each other in the vertical direction and the horizontal direction in the assembly, the leg rod of one stacking member and the stacking of the other stacking member. It is preferable that the leg rods of the member are connected by a connecting tool that keeps the relative positions of the leg rods constant.

With this arrangement, the positional displacement between the stacking members can be prevented more reliably.

In the present invention, if the leg rod is made to be a hollow cylinder, a large bending strength is imparted to the leg rod, so that the buckling thereof is less likely to occur. Further, if a reinforcing bracket is provided between the leg rod and the connecting bone in the stacking member, the boundary rod between the leg rod and the connecting bone is reinforced by the reinforcing bracket, so that the leg rod is It is unlikely that a situation such as breaking at the root or impairing the right angle between the leg rod and the connecting bone will occur.

[0019]

1 is a vertical sectional view schematically showing an underground water storage tank A which is an embodiment of the present invention. The underground water storage tank A has a water storage space 3 formed in a recess in the ground by digging down the ground. Inside the water storage space 3, the water storage space 3 is arranged vertically and horizontally and vertically. An assembly B made up of a number of stacked stacking members 2 is loaded, a coating layer 5 is arranged on top of this assembly B, and the load applied to this coating layer 5 is received by the assembly B. Has become. The configuration for disposing the coating layer 5 on the uppermost stacking member 3 of the assembly B will be described later.

The covering layer 5 in the illustrated example is formed by laying gravel or cobblestone to form a water permeable layer 52, and a lawn 53 or the like is vegetated on the surface of the covering layer 5. It is also possible to build a walking path or a car parking lot on the surface of the covering layer 5. Since the coating layer 5 has water permeability, the water that has permeated the coating layer 5 enters the water reservoir space 3. A side groove 31 for collecting water and a side groove 32 for draining water are provided in the water storage space 3. A trap 33 is interposed between the water collecting side groove 31 and the water storage space 3, and rainwater flowing into the side groove 31 is trapped by the trap 33.
It is designed to flow into the water storage space 3 via. Therefore, if solid matter such as soil or sand is mixed in the rainwater flowing into the gutter 31, the solid matter is trapped in the trap 33.
Removed by. On the other hand, an overflow weir 32 is installed between the drainage gutter 32 and the water storage space 3. Therefore, when the water level in the water storage space 3 tries to rise above the overflow weir 32, water overflows the overflow weir 32 and flows out to the gutter 32. A water infiltration facility 35 for infiltrating water into the ground is connected to the gutter 32. Also,
A drain pipe 36 leading to a river or the like is also connected to the gutter 32. In addition, a manhole 37 that penetrates the coating layer 5 and reaches the bottom of the water storage space 3 is provided.

Such an underground water storage tank A can be used for avoiding a situation in which the water level of a river suddenly rises and causes flooding when it is hit by heavy rainfall. For example, if the water pool 3 is emptied in advance by a warning of heavy rain, and the water level of the river is rising due to the heavy rain, a part of the rainwater flowing over the surface of the river and flowing into the river If the stored water in the water storage space 3 is discharged to the river when the water level in the water storage space 3 is temporarily stored by flowing into the water storage space 3 and the torrential rain has subsided, the water level in the water storage space in the water storage space 3 is suddenly increased. It is possible to avoid flooding due to rising. When an emergency such as a fire is required, a fire hose or pumping pipe 38 is inserted from the manhole 37 into the water storage space 3, and the pumping pipe 3 is inserted.
It is also possible to pump up the stored water in the water storage space 3 through 8 or the like and use it as fire prevention water. Normally, the water storage space 3
The water can be used for irrigating plants, and for that purpose, it is preferable to separately lead the water drawing port from the water storage space 3.

In the above-mentioned underground water tank A, the water storage space 3
The wall 39 forming the wall may be an impermeable layer such as clay, concrete, or an impermeable sheet, or may be an impermeable layer laid with gravel, cobblestone, or a permeable sheet. Then, the water in the water storage space 3 can be gradually released into the ground.

FIG. 2 is a schematic perspective view of the stacking member 2 when viewed obliquely from above, FIG. 3 is a schematic perspective view of the stacking member 2 of FIG. 2 that is inverted and viewed obliquely from above, and FIG. FIG. 5 is a plan view of the stacking member 2, FIG. 5 is a back view of the stacking member 2,
FIG. 6 is a side view of the stacking member 2 in an inverted state,
FIG. 7 is a sectional view taken along the line VII-VII of FIG.

This stacking member 2 is a square annular connecting bone 2.
Each of the four corners 22 ... Is provided with an equal-length leg rod 23 made of a hollow cylinder. These four rods 23
… Are arranged parallel to each other, and these rods 23…
Are connected to each other by the connecting bones 21. The connecting ribs 21 are provided with ribs 27 ... Which extend diagonally. Each leg rod 23 and the connecting bone 21 intersect each other at a right angle, and a reinforcing bracket 26 is provided between each leg rod 23 and the connecting bone 21. The reinforcing bracket 26 serves to prevent the squareness between the leg rod 23 and the connecting bone 21 from being damaged by the load applied to the leg rod 23.

A fitting portion 24 is attached to one end of each of the rods 23.
Is provided, and the fitting portion 24 is provided at the other end of the leg rod 23.
A fitted portion 25 having a shape and dimensions that can be fitted to is provided. In this embodiment, the shape and dimensions of the fitted portion 25 are determined so that the fitted portion 24 can be fitted into the fitted portion 25. The shape and size of the fitted portion 25 may be set so that the fitting portion 24 can be fitted outside. Also,
In this embodiment, the connecting bone 21 is formed by a plate-shaped frame, and only the fitted portion 25 of the leg rod 23 projects to one side of the plate-shaped frame, and the portion of the leg rod 23 excluding the fitted portion 25 thereof. Is projected on the other side of the plate-shaped frame.

In the stacking member 2, the length of the leg rod 23 is 20 to 80 cm, preferably 30 to 50 cm.
cm is appropriate, and the outer diameter of the above-mentioned leg rod 23 is 2 to 5
cm is appropriate. If the length of the leg rod 23 is too long or the outer diameter is too small, the bending strength of the leg rod 23 becomes too low, which is not preferable. Further, the vertical dimension and the horizontal dimension of the connecting bone 21 are appropriately 30 to 80 cm.
As can be seen from this, it is preferable that the stacking member 2 has a cubic shape close to that of the stacking member 2 as a whole. By doing so, the stacking member 2 can be arranged in the water storage space 3 side by side in the vertical direction and the vertical direction. Improves workability when stacking.

The stacking member 2 described above is integrally formed of synthetic resin such as polypropylene resin or polyvinyl chloride resin.

The above-mentioned stacking members 2 are arranged vertically and horizontally in the water storage space 3 described with reference to FIG. A mode in which the stacking members 2 are stacked vertically is shown in FIG. That is, between the two stacking members 2 and 2 stacked in the vertical direction in the assembly B, as can be seen in FIG.
The fitting portions 24 of the leg rods 23 of the book are individually fitted to the fitted portions 25 of the four leg rods 23 of the stacking member 2 of the other stage. Further, FIG. 9 shows a form in which the stacking members 2 are arranged in the vertical and horizontal directions. That is, in the stacking members 2 ... Arranged in the vertical direction and the horizontal direction, the connecting ribs 21 ... Abut each other in the vertical direction and the horizontal direction. Further, as shown in FIG. 10, between the four stacking members 2 which are adjacent to each other in the vertical direction and the horizontal direction, four leg rods 23 which are adjacent to each other have their legs. They are connected by a connecting tool 6 that keeps the relative positions of the rods 23 ... This connecting tool 6 has a clamp portion 61 which can be fitted into and removed from the leg rods 23 in the radial direction, and by only fitting the clamp portion 61 to the leg rods 23, as shown in FIG. The function of keeping the relative positions of the four leg rods 23 ...

The leg rods 23 of the respective stacking members 2 ... Which constitute the above-mentioned aggregate B stand vertically in the water storage space 3.

In the embodiment described above, the connecting bone 21 of the stacking member 2 is formed in a square annular shape, but this point may be formed in an isosceles triangular annular shape as shown in FIG. In the stacking member 2 in which the connecting bone 21 is formed in the shape of an isosceles triangle as described above, the leg rods 23 may be provided in each of the three corners of the connecting bone 21. In FIG. 11, FIGS.
The same reference numerals as those given to the above are given to indicate the same or corresponding portions. Stacking member 2 as shown in FIG.
Is formed into a rectangular shape as a whole by abutting the bottom portions of the connecting bones 21 as shown in FIG. Other matters are the same as those described in FIGS.
The connecting bone 21 may be formed in another polygonal ring such as a hexagon.

FIG. 13 shows an example in which the leg rod 23 is H-shaped. When such an H-shaped rod rod 23 is adopted, the fitting portion 24 at one end portion of the leg rod 23 becomes H-shaped, so that the fitted portion 25 at the other end portion of the leg rod 24 (see FIG. 13). In the figure, the fitted portion 25 of another stacking member 2 is shown), or an H-shaped recessed portion having the same shape as the fitting portion 24 is formed, or a rectangular recessed portion (not shown) is formed. It is preferable that the above-mentioned H-shaped fitting portion 24 be fitted into the rectangular recessed portion.

As described above with reference to FIG. 1, the underground water storage tank A which is an embodiment of the present invention has the water storage space 3 which is formed in the ground by digging down the ground. An aggregate B composed of a large number of the stacking members 2 arranged in the vertical and horizontal directions and stacked in the vertical direction is loaded inside the water storage space 3, and a coating layer 5 is provided on the upper portion of the aggregate B. The assembly B is arranged so that the load applied to the coating layer 5 is received by the assembly B.

By the way, as shown in FIG.
When the stacks are stacked, the leg rods 23 of the individual stacking members 2 project upward at the uppermost portion (uppermost layer) of the assembly B. In such a case, it is desirable to attach the lid body by using the fitting portion 24 provided at the end portion of the leg rods 23 ... As this lid, on one side of a rectangular plate frame,
It is possible to use a fitting provided with a mounting portion having the same shape and size as the fitted portion 25 described above, and such a lid body is used to connect the fitted portion 25 of the stacking member 2 shown in FIG. It can be easily made by cutting and removing the leg rod 23 while leaving 21 and 21. The lid body thus made is assembled B by fitting its mounting portion (corresponding to the fitted portion 25) to the fitting portion 24 of the leg rod 23 protruding upward.
Mounted on top of. It is also possible to use a synthetic resin molding for such a lid. When the lid is attached to the uppermost part of the assembly B in this way, for example, a water-permeable sheet and a non-woven fabric may be laid on the lid, and the coating layer 5 described above may be disposed thereon. .
In FIG. 1, the arrangement position of the lid body is indicated by reference numeral 51.

In this underground water storage tank A, the coating layer 5
The load applied to the coating layer when a person walks on the vehicle or when the vehicle is parked compresses the vertical rods 23 of the individual stacking members 2 forming the aggregate B in the vertical direction. It mainly acts on the direction. For this reason, since a great force is not applied in the direction in which the leg rod 23 is bent, the possibility that the leg rod 23 is bent or buckled is small. Further, since the large number of stacking members 2 ... Constituting the aggregate B all have a skeleton structure formed by a plurality of the leg rods 23. The volume occupied by the above-mentioned aggregate in 3 is suppressed small. As a result, the porosity of the water storage space 3 increases, so that a large amount of water can be stored in the water storage space 3. Moreover, since each of the stacking members 2 ... Has the above-mentioned frame structure, it is easy to achieve the weight saving of the stacking members.

In addition, since the connecting ribs 21 of the stacking members 2 arranged in the vertical direction and the horizontal direction are butted against each other in the vertical direction and the horizontal direction, the stacking members 21 ... It is in a state where it is difficult to shift the position laterally. In addition, the leg rods 23 of the stacking members 2 ... Which are adjacent to each other arranged in the longitudinal direction and the lateral direction
Since the connecting members 6 are connected to each other, the stacking members 21 ... Are more difficult to be displaced in the vertical and horizontal directions.

The underground water tank A of FIG. 1 has a gutter 31 for collecting water.
A trap 33 is interposed between the water storage space 3 and the water storage space 3 so that rainwater flowing into the side groove 31 flows into the water storage space 3 via the trap 33. Such a structure is effective in the case where surface water having no dead leaves or sediment is allowed to flow into the gutter 31, such as the ground surface of a tennis court or an asphalt pavement surface. However, when a ditch for collecting water is provided in a place where dead leaves and organic matter are mixed in rainwater, such as in a park, a screen 31a is provided in the ditch 31 as shown in FIG. It is desirable to allow the rainwater after removal to flow into the water storage space 3.

[0037]

INDUSTRIAL APPLICABILITY The underground water tank according to the present invention has a large number of stacking members forming an aggregate by the load applied to the covering layer when a person walks on the covering layer or a car is parked. Since it is unlikely that the leg rods will buckle, the durability of the underground water tank will be improved as compared with the underground water tank using the conventional stacking members described in FIGS. 15 and 16. The cover layer can be used as a passage for heavier objects. Further, since the stacking member has a frame structure, it is easy to reduce the weight of the stacking member, and moreover, a large amount of water can be stored for the size of the water storage space.

In the underground water storage tank of the present invention, in the case where the lid rod of the plate-like frame is attached to the leg rod of the uppermost stacking member forming the aggregate, at the uppermost portion of the aggregate. Since no gap is formed in the mutual rods of the stacking members that are adjacent to each other in the vertical direction and the horizontal direction, the stacking members are prevented from being expanded by the load applied to the coating layer.

In addition, according to the present invention, it is possible to prevent displacement of a large number of stacking members that are arranged adjacent to each other in the vertical direction and the horizontal direction and to stabilize the installation state of each stacking member.

In addition, according to the present invention, the height of the aggregate is adjusted by cutting the leg rod of the stacking member and adjusting the length of the leg rod so that the uppermost level of the aggregate is adjusted to the water level. Ground level around the storage space (ground level)
The effect is that it can be easily adjusted to.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view schematically showing an underground water storage tank according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view of a stacking member used in the underground water storage tank when viewed obliquely from above.

FIG. 3 is a schematic perspective view of the stacking member of FIG. 2 when inverted and viewed from diagonally above.

FIG. 4 is a plan view of the stacking member.

FIG. 5 is a back view of the stacking member.

FIG. 6 is a side view of the stacking member in an inverted state.

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 4;

FIG. 8 is a partial side view showing a form in which stacking members are stacked vertically.

FIG. 9 is a schematic plan view showing a form in which stacking members are arranged in a vertical direction and a horizontal direction.

FIG. 10 is a partial schematic plan view showing a state in which the leg rods of the stacking members arranged in the vertical direction and the horizontal direction are connected by a connecting tool.

FIG. 11 is a schematic perspective view of a stacking member including connecting bones that form an isosceles triangular ring.

12 is a schematic plan view of a combination of the stacking members of FIG.

FIG. 13 is a schematic partial perspective view showing a modified example of the fitting portion and the fitted portion of the leg rod.

FIG. 14 is a vertical cross-sectional view showing a modified example of the gutter for collecting water.

FIG. 15 is a schematic perspective view of a stacking member used in a conventional underground water storage tank.

16 is a partial side view showing a stacked state of the stacking member of FIG.

FIG. 17 is an explanatory view showing the form of the uppermost part of the assembly used in the conventional underground water tank.

[Explanation of symbols]

 A underground storage tank B assembly 2 stacking member 3 water storage space 5 coating layer 6 connector 21 connecting bone 23 leg rod 24 fitting part 25 fitted part 26 reinforcing bracket 51 position of lid

Claims (8)

[Claims] 1. An assembly of a large number of stacking members arranged vertically and horizontally and stacked vertically is loaded inside a water storage space formed in a concave shape in the ground. In an underground water tank, in which a covering layer is arranged on the upper part of the aggregate and the load applied to the covering layer is received by the aggregate, the stacking member includes a plurality of leg rods arranged in parallel with each other. An integrally provided connecting bone connecting these leg rods to each other, a fitting portion is provided at one end portion of each of the leg rods, and the fitting portion is provided at the other end portion of the leg rods. It is a synthetic resin integrally molded body provided with a fitted portion having a shape and dimensions that can be fitted, and the above-mentioned assembly is provided between the two above-mentioned stacked members which are vertically stacked. The fitting portion of the leg rod of the stacking member is the same as that of the other step. The leg rods of the stacking members that are fitted to the fitted portions of the leg rods of the lifting member and that constitute the aggregate are vertically arranged in the water storage space. An underground water tank that is characterized. 2. A leg rod of the uppermost stacking member forming the aggregate rises from the connecting bone of the stacking member, and the fitting provided at one end of the leg rod. The mounting portion provided on the lid body made of a plate-like frame is fitted to the portion, the lid body is arranged on the uppermost stacking member, and the covering layer is arranged on the lid body. The underground water tank according to claim 1. 3. The connecting bone of the stacking member has a polygonal annular shape, and each of the plurality of leg rods of the stacking member intersects the polygonal annular connecting bone at a right angle. The underground water tank according to claim 1, wherein the connecting bones of the stacking members arranged in the vertical direction and the horizontal direction are butted against each other in the vertical direction and the horizontal direction. 4. The connecting bone is formed in a square ring shape,
The underground water tank according to claim 3, wherein each of the four corners of the connecting bone is provided with the leg rod. 5. The underground water tank according to claim 3, wherein the connecting bone is formed in an isosceles triangle annular shape, and the leg rods are provided at each of three corners of the connecting bone. 6. The leg rods of one of the stacking members and the leg rods of the other of the other stacking members are arranged between the stacking members that are adjacent to each other in the vertical or horizontal direction in the aggregate. The underground water tank according to claim 1, wherein the underground water tank is connected by a connecting tool that keeps the relative positions of the leg rods constant. 7. The underground water storage tank according to claim 1, wherein the leg rod in the stacking member is a hollow cylinder. 8. The underground water tank according to claim 4, wherein a reinforcing bracket is provided between the leg rod and the connecting bone of the stacking member.