JP2022088757A - Construction method of storage tank - Google Patents

Abstract

To ensure that a waterproof resin material adheres a storage structure to a sheet covering the storage structure without allowing air bubbles to remain in a waterproof resin layer when the waterproof resin material is applied to the sheet to form the waterproof resin layer.SOLUTION: A construction method comprises: a first step of forming a foundation 1 having a storage tank installation surface 12a; a second step of applying a waterproof resin material 2 to the storage tank installation surface 12a to form a foundation waterproof resin layer 3; a third step of assembling a storage structure ST on the foundation waterproof resin layer 3; a fourth step of covering the side surfaces of the storage structure ST with a resin woven sheet 4 so that the lower part of the resin woven sheet 4 has an overlapping part of a predetermined width with the foundation waterproof resin layer 3 formed on the storage tank installation surface 12a; and a fifth step of applying the waterproof resin material 2 to the part covering the side surfaces of the storage structure ST of the resin woven sheet 4, the overlapping part of the resin woven sheet 4 and the foundation waterproof resin layer 3, and the exposed part of the foundation waterproof resin layer 3 having the predetermined width continuous with the overlapping part to form a side surface waterproof resin layer 5.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method of constructing a storage tank, and more particularly to a method of constructing a storage tank installed underground.

In order to suppress the outflow of rainwater during rainfall and reduce the damage caused by inundation, underground storage tanks are being installed in various parts of the country. As a method of installing a storage tank underground, a method of installing a formwork at the site and placing concrete and a method of assembling precast concrete at the site have been used so far, but in recent years, such a method has been used. Instead of the construction method using concrete, a storage structure is formed by stacking plastic storage blocks, and the outer circumference of this storage structure is covered with a water-impervious sheet to form a storage tank (hereinafter, "sheet impermeable"). It is sometimes referred to as "construction method"), which is attracting attention and becoming widespread because it can shorten the construction period, reduce costs, and save labor.

The applicant also constructed a plurality of storage tanks by the above-mentioned sheet impermeable method. As a result, it was found that the sheet impermeable process of covering the bottom surface and the side surface of the storage structure with three sheets (inner protective sheet + impermeable sheet + outer protective sheet) takes more time and labor than expected. In particular, a water-impervious sheet made of vinyl chloride or the like, which is wound around a rod-shaped core material in a roll shape, usually weighs several tens of kilograms. It took a lot of time and effort to install them side by side so that they overlap each other by about 10 cm to 15 cm. In addition, it takes time, effort, and attention to weld the overlapping parts of the juxtaposed geomembrane sheets, which have a total length of several tens to several hundreds of meters in the width direction, with hot air at about 600 ° C. Met. In addition, since the worker who performs the work is forced to bend down for a long time, the burden on the worker is heavy.

In addition, it is necessary to confirm the impermeable performance of the impermeable sheets that are juxtaposed and welded with hot air. In general, the work of confirming the impermeable performance is determined by blowing 0.1 MPa of air onto the hot air welded portion and checking whether the air pressure is 0.05 MPa or more, and the air pressure does not reach 0.05 MPa. It is determined that there is no continuity in the hot air welded portion of the impermeable sheet (the overlapping portion is not hot welded), and hot air welding is repeated until the air pressure becomes stable and becomes 0.05 MPa or more. It takes a lot of time and effort to confirm the impermeable performance and to repair the welding of the impermeable sheet.

In order to increase the number of storage tanks constructed by the sheet impermeable method in the future, it is necessary to reduce the work labor in the sheet impermeable process, improve the impermeable performance, and shorten the construction period. Therefore, a method has been proposed in which the bottom surface and side surfaces of the storage structure are covered with a sheet such as a non-woven fabric, and a waterproof material is applied to the sheet (for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2013-167137 JP-A-2017-206950

According to the proposed construction method, it is considered that the work labor in the sheet impermeable process can be reduced as compared with the conventional sheet impermeable construction method. However, when a liquid waterproof material such as a polyurethane resin is spray-applied to the sheet, the waterproof material is generally heated to a liquid temperature of about 60 ° C. to 90 ° C. and spray-applied. At this time, if the sheet covering the storage structure is a non-woven fabric as in the proposed method, the air contained in the non-woven fabric expands due to the high-temperature waterproof material, and the waterproof resin formed on the surface of the non-woven fabric. It may remain as bubbles in the layer. If air bubbles remain in the waterproof resin layer, stress due to earth pressure from the surroundings of the buried storage tank may be concentrated around the air bubbles in the waterproof resin layer and become the starting point of deterioration of the waterproof property of the sheet. be.

Further, if the thickness of the nonwoven fabric used in the proposed construction method is thin, the thickness of the nonwoven fabric varies due to the tensile force applied when attaching the nonwoven fabric to the side surface of the storage structure, and the waterproofness of the sheet becomes high in the thin portion. It may decrease. Therefore, the thickness of the nonwoven fabric used in the proposed construction method is required to be at least 4 mm (paragraph (0023) of Cited Document 2 and the like). However, if the thickness of the non-woven fabric is 4 mm or more, when the liquid waterproof material is spray-applied from the outside by covering with the non-woven fabric of the storage structure, the waterproof material cannot pass through the non-woven fabric and reach the storage structure, and the non-woven fabric cannot be reached. And the storage structure cannot be bonded by a waterproof material.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a waterproof resin layer when forming a waterproof resin layer by applying a waterproof resin raw material to a sheet covering a storage structure. It is an object of the present invention to provide a method for constructing a storage tank capable of adhering a storage structure and a sheet with a waterproof resin raw material without leaving air bubbles.

The method for constructing a storage tank according to the present invention that achieves the above object is a method for constructing a storage tank to be installed underground, that is, a first step of forming a foundation having a storage tank installation surface, and the storage tank installation surface. The second step of applying a waterproof resin raw material to the base waterproof resin layer to form a basic waterproof resin layer, the third step of assembling a storage structure composed of a plurality of storage blocks on the basic waterproof resin layer, and the lower part of the resin woven cloth sheet. A fourth step of covering the side surface of the storage structure with the resin woven cloth sheet so as to have an overlapping portion having a predetermined width with the basic waterproof resin layer formed on the storage tank installation surface, and the resin weaving. A portion of the cloth sheet that covers the side surface of the storage structure, the overlapping portion of the resin woven cloth sheet and the basic waterproof resin layer, and an exposed portion of the basic waterproof resin layer having a predetermined width continuous with the overlapping portion. It is characterized by having a fifth step of applying a waterproof resin raw material to the surface to form a side waterproof resin layer.

In the construction method having the above configuration, the waterproof resin raw material is preferably a non-foaming polyurethane resin raw material.

Further, in the construction method having the above configuration, it is preferable that the waterproof resin layer is applied by spray application.

Further, in the construction method having the above configuration, the resin woven fabric sheet is preferably a polyolefin-based woven fabric sheet.

Further, in the construction method having the above configuration, the thickness of the resin woven fabric sheet is preferably in the range of 0.2 mm or more and 0.6 mm or less.

Further, in the construction method having the above configuration, when the side surface of the storage structure is covered with the resin woven fabric sheet, the resin woven fabric sheet is applied to the storage structure while applying a tension of 50 N or more and 200 N or less to the resin woven fabric sheet. It is preferable to attach it.

According to the method for constructing a storage tank according to the present invention, the waterproof resin raw material is applied to the sheet covering the storage structure to prevent bubbles from being generated in the waterproof resin layer, and the waterproof performance of the sheet is stable for a long period of time. And be maintained. Further, by applying the waterproof resin raw material to the sheet, a waterproof resin layer is formed on the sheet surface, and at the same time, the storage structure, the sheet and the waterproof resin raw material are integrally adhered to form a high-strength composite waterproof film.

It is a process drawing which shows an example of the construction method of the storage tank which concerns on this invention. It is a process drawing which shows an example of the construction method of the storage tank which concerns on this invention. It is a perspective view which shows an example of the spray coating apparatus of a waterproof resin raw material.

Hereinafter, the method of constructing the storage tank according to the present invention will be described in more detail, but the present invention is not limited to these embodiments. In addition, in this specification, "-" means that the numerical values before and after it are included as the lower limit value and the upper limit value.

An example of the construction method of the storage tank according to the present invention will be described for each step based on FIGS. 1 and 2.

(First step)
As shown in FIG. 1A, first, as a first step, a foundation portion 1 having a storage tank installation surface 12a is formed. Specifically, at the planned burial site of the storage tank, a region larger than the outer shape of the storage tank S (shown in FIG. 2C) in a plan view is excavated by a shovel car or the like, and the height of the storage tank S is higher than the height of the storage tank S. Dig a hole as deep as 0.5m to 2.0m. Then, after the bottom surface of the hole is leveled substantially horizontally, a foundation crushed stone layer 11 of about 10 cm to 20 cm is usually constructed, and a leveling concrete layer 12 is constructed on the foundation crushed stone layer 11. In the present embodiment, the foundation crushed stone layer 11 and the leveled concrete layer 12 constitute the foundation portion 1 of the present invention, and the upper surface of the leveled concrete layer 12 is the storage tank installation surface 12a. If the bottom surface of the hole is a sturdy bedrock or the like, the foundation crushed stone layer 11 may not be provided. The outer shape of the foundation portion 1 in a plan view is set to be larger than the outer shape of the storage structure ST. Specifically, it is desirable that the length L1 (shown in FIG. 2A) between the end portion of the foundation portion 1 and the end portion of the storage structure ST in a plan view is approximately 200 mm or more. Further, it is desirable that the width L2 (shown in FIG. 2A) of the overlapping portion 41 of the resin woven fabric sheet 4 and the basic waterproof resin layer 3 described later is about 30 mm or more.

(Second step)
Next, as shown in FIG. 1 (b), as a second step, the waterproof resin raw material 2 is applied to the storage tank installation surface 12a of the leveled concrete layer 12 to form the basic waterproof resin layer 3. The waterproof resin raw material 2 that can be used here includes a non-foaming polyurethane resin raw material, a non-foaming polyurea resin raw material, a urethane rubber-based resin raw material, an acrylic rubber-based resin raw material, a chloroprene-based resin raw material, a rubber asphalt-based resin raw material, and an FRP resin raw material. And so on. Among these, a non-foaming polyurethane resin raw material is preferably used because the liquid viscosity of the raw material is low, spray coating is possible, and curing is quick. The non-foaming polyurethane resin raw material contains a polyol, isocyanate, and a catalyst, and a non-foaming polyurethane resin layer (waterproof resin layer) is formed by the reaction of the polyol and isocyanate.

Conventionally known coating methods such as spray coating and roller coating can be used to apply the leveling concrete layer 12 of the waterproof resin raw material 2 to the storage tank installation surface 12a, but the work labor can be reduced and the work time can be shortened. Spray coating is preferably used because it is possible. When a non-foaming polyurethane resin raw material is used as the waterproof resin raw material 2 for spray coating, it is preferable to use, for example, the spray coating apparatus SP shown in FIG. In the spray coating apparatus SP shown in FIG. 3, isocyanates and polyols are supplied from the drum can 61 and the drum cans 62 to the apparatus main body 60, respectively, and the isocyanates and the polyol adjusted to a predetermined pressure in the apparatus main body 60 are sprayed via the heating hose 63. It is supplied to the gun G. Then, in the spray gun G, the isocyanate and the polyol are mixed and sprayed on the object to be coated (storage tank installation surface 12a or resin woven fabric sheet 4). For example, the discharge pressure from the device main body 60 of the spray coating device SP at the time of spraying is about 14 MPa to 24 MPa, and the maximum hydraulic pressure temperature is about 90 ° C. As such a spray coating device SP, for example, "H-XP3 reactor" manufactured by GRACO is preferably used.

The thickness of the basic waterproof resin layer 3 is not particularly limited as long as it exhibits the waterproof function, but is usually preferably in the range of 1.5 mm to 5.0 mm, and more preferably in the range of 2.0 mm to 2.5 mm. .. If the thickness of the basic waterproof resin layer 3 is too thin, the waterproof function and strength are insufficient, while if the basic waterproof resin layer 3 is too thick, the raw material cost becomes high and it is not economical.

The coating area of the basic waterproof resin layer 3 is larger than that of the storage structure ST in a plan view, and is larger than the overlapping portion 41 (shown in FIG. 2A) between the resin woven cloth sheet 4 and the basic waterproof resin layer 3 described later. It is set large. Normally, the basic waterproof resin layer 3 is applied to the entire upper surface of the leveled concrete layer 12.

(Third step)
As a third step, as shown in FIG. 1 (c), a storage structure ST composed of a plurality of storage blocks SB is assembled on the basic waterproof resin layer 3. The storage structure ST is formed by stacking a plurality of storage blocks SB. One layer of the storage structure ST having the laminated structure of FIG. 1 (c) has a matrix of 8 × 4 in the XY directions in which the convex portions of the quadrangular pyramid are orthogonal to each other in the plan view. The storage blocks SB provided in the above are arranged side by side in a predetermined number in the XY directions. Then, the storage blocks SB adjacent to each other in the vertical direction are rotated by 90 degrees in the XY plane and stacked alternately. The size of one storage block SB is, for example, a square shape with an X direction and a Y direction of 900 mm to 1100 mm, and a height in the range of 200 mm to 400 mm. The porosity of the storage structure ST composed of such a storage block SB is preferably 80% or more, more preferably 92% or more, and further preferably 95% or more. As the material of the storage block SB, a resin material such as polypropylene, polyethylene, or polyethylene terephthalate is preferable because it is lightweight and has a predetermined strength. The storage block SB that can be used in the present invention is not limited to such a form, and conventionally known ones can be used.

(4th step)
As a fourth step, as shown in FIG. 2A, the side surface of the storage structure ST assembled on the basic waterproof resin layer 3 is covered with a sheet. One of the important points here is that the sheet covering the side surface of the storage structure ST is the resin woven fabric sheet 4. As described above, in the conventional method, the non-woven fabric is used as the sheet covering the side surface of the storage structure ST. Therefore, when the waterproof resin raw material 2 is applied to the outer surface of the non-woven fabric, bubbles are generated and bubbles remain in the waterproof resin layer. The waterproof resin raw material 2 could not pass through the non-woven fabric and reach the storage structure ST, and the non-woven fabric and the storage structure ST could not be adhered by the waterproof resin raw material 2. On the other hand, in the present invention, since the resin woven cloth sheet 4 is used as the sheet covering the side surface of the storage structure ST, no bubbles are generated when the waterproof resin raw material 2 is applied to form the side surface waterproof resin layer 5. .. Further, the thickness of the resin woven fabric sheet 4 can be reduced while maintaining a predetermined strength as compared with the non-woven fabric, and a part of the waterproof resin raw material 2 passes through the resin woven fabric sheet 4 and reaches the storage structure ST. By adhering the resin woven fabric sheet 4, the storage structure ST, and the waterproof resin raw material 2, a high-strength composite waterproof film can be formed.

Examples of the resin woven fabric sheet 4 that can be used in the present invention include a polyolefin-based woven fabric sheet and a polyester-based woven fabric sheet. Among these, a polyolefin-based woven fabric sheet is preferable, and a polypropylene woven fabric sheet is more preferable. The thickness of the resin woven fabric sheet 4 is 0.2 mm to 0. From the viewpoint that the side waterproof resin layer 5 can be stably formed on the outer surface and a part of the waterproof resin raw material 2 can pass through the resin woven fabric sheet 4. A range of 6 mm is preferred. Further, when the resin woven fabric sheet 4 has such a thickness, it has flexibility, and the work of attaching the storage structure ST to the side surface becomes much easier than in the case of the non-woven fabric.

Another important thing when covering the side surface of the storage structure ST with the resin woven fabric sheet 4 is the basic waterproof resin layer 3 in which the lower portion of the resin woven fabric sheet 4 is formed on the storage tank installation surface 12a. And to have an overlapping portion 41 of a predetermined width (see the enlarged view of FIG. 2A). By having the overlapping portion 41 between the resin woven fabric sheet 4 and the basic waterproof resin layer 3, in the next step, the outer surface of the resin woven fabric sheet 4, the overlapping portion 41, and the overlapping portion 41 have a predetermined width w continuous. When the waterproof resin raw material 2 is applied to the exposed portion of the basic waterproof resin layer 3 to form the side waterproof resin layer 5, the lower end of the resin woven cloth sheet 4 is shown in the lower left partially enlarged view of FIG. 2 (c). The part is sandwiched between the basic waterproof resin layer 3 and the side waterproof resin layer 5 to form a sealing structure, and the water and earth and sand from the surroundings surrounding the storage tank S are surely invaded into the storage tank S. It can be prevented.

As shown in the partially enlarged view at the lower left of FIG. 2A, the width L2 of the overlapping portion 41 between the resin woven fabric sheet 4 and the basic waterproof resin layer 3 at the lower part of the resin woven fabric sheet 4 is in the range of 30 mm to 100 mm. preferable.

When the side surface of the storage structure ST is covered with the resin woven fabric sheet 4, it is desirable that the resin woven fabric sheet 4 is attached so as to be in contact with the side surface of the storage structure ST. When the resin woven fabric sheet 4 is in contact with the side surface of the storage structure ST, the waterproof resin raw material 2 that has passed through the resin woven fabric sheet 4 in the next step of applying the waterproof resin raw material 2 to the resin woven fabric sheet 4. This is because a part of the above acts to fix the storage structure ST and the resin woven fabric sheet 4 at the contact portion between the storage structure ST and the resin woven fabric sheet 4. In order to attach the resin woven fabric sheet 4 so as to be in contact with the side surface of the storage structure ST, the resin woven fabric sheet 4 is woven with a known fastener such as staples at a pitch of 300 mm to 2000 mm while applying a tension of 50 N to 200 N. It is preferable to attach the cloth sheet 4 to the storage structure ST.

(Fifth step)
As a fifth step, as shown in FIG. 2B, a portion of the resin woven fabric sheet 4 covering the side surface of the storage structure ST, an overlapping portion 41 of the resin woven fabric sheet 4 and the basic waterproof resin layer 3 The waterproof resin raw material 2 is applied to the exposed portion of the basic waterproof resin layer 3 having a predetermined width w continuous with the overlapping portion 41 to form the side waterproof resin layer 5. What is important here is not only the portion of the resin woven fabric sheet 4 that covers the side surface of the storage structure ST, but also the overlapping portion 41 of the resin woven fabric sheet 4 and the basic waterproof resin layer 3 and the overlapping portion 41. The waterproof resin raw material 2 is applied to the exposed portion of the basic waterproof resin layer 3 having a continuous predetermined width w. By applying the waterproof resin raw material 2 to the overlapping portion 41 and the exposed portion to integrally form the side waterproof resin layer 5, the inside of the storage tank S for water or earth and sand due to water pressure or earth pressure from the surroundings surrounding the storage tank S. It is possible to reliably prevent intrusion into.

The predetermined width w (shown in FIG. 2C) of the exposed portion of the basic waterproof resin layer 3 continuous with the overlapping portion 41 of the resin woven cloth sheet 4 and the basic waterproof resin layer 3 to which the waterproof resin raw material 2 is applied is The range is not limited as long as it can prevent water and earth and sand from entering the storage tank S from the outside, but is usually preferably in the range of 50 mm to 150 mm.

As the waterproof resin raw material 2 used here, the same one used for forming the basic waterproof resin layer 3 can be used. The thickness d (shown in FIG. 2C) of the side waterproof resin layer 5 formed by applying the waterproof resin raw material 2 is not particularly limited as long as it exhibits the waterproof function, but is usually 1.5 mm or more. The range of 5.0 mm is preferable, and the range of 2.0 mm to 2.5 mm is more preferable.

(others)
A predetermined resin top plate material and a water permeable protective sheet are attached to the upper surface of the storage structure ST. Alternatively, the resin woven fabric sheet 4 is also attached to the upper surface of the storage structure ST, and if necessary, the waterproof resin raw material 2 is applied to form the waterproof resin layer. Further, an inflow pipe and a discharge pipe (not shown) are attached to the storage tank S.

The prepared storage tank S is in a state of being buried underground with soil backfilled in the surrounding space and the upper surface. Then, an overburden is placed on the storage tank S, and a covering layer is constructed depending on the intended use, so that it can be used as, for example, a park or a parking lot.

According to the method for constructing the storage tank according to the present invention, when the side waterproof resin layer 5 is formed by applying the waterproof resin raw material 2 to the resin woven cloth sheet 4 covering the storage structure ST, the side waterproof resin layer 5 is formed. It is possible to bond the storage structure ST and the resin woven cloth sheet 4 with the waterproof resin raw material 3 without leaving air bubbles in the storage structure ST.

1 Foundation 2 Waterproof resin raw material 3 Basic waterproof resin layer 4 Resin woven cloth sheet 5 Side waterproof resin layer S Storage tank 11 Foundation crushed stone layer 12 Leveling concrete layer 12a Storage tank installation surface 41 Resin woven cloth sheet and basic waterproof resin layer Overlapping part SB storage block SP spray coating device ST storage structure

Claims (6)

It is a construction method of a storage tank installed underground.
The first step of forming a foundation having a storage tank installation surface,
The second step of applying a waterproof resin raw material to the storage tank installation surface to form a basic waterproof resin layer, and
The third step of assembling a storage structure composed of a plurality of storage blocks on the basic waterproof resin layer, and
A fourth covering the side surface of the storage structure with the resin woven fabric sheet so that the lower portion of the resin woven fabric sheet has an overlapping portion having a predetermined width with the basic waterproof resin layer formed on the storage tank installation surface. Process and
The portion of the resin woven fabric sheet that covers the side surface of the storage structure, the overlapping portion between the resin woven fabric sheet and the basic waterproof resin layer, and the basic waterproof resin layer having a predetermined width continuous with the overlapping portion. A method for constructing a storage tank, which comprises a fifth step of applying a waterproof resin raw material to an exposed portion of the surface to form a side waterproof resin layer. The method for constructing a storage tank according to claim 1, wherein the waterproof resin raw material is a non-foaming polyurethane resin raw material. The method for constructing a storage tank according to claim 1 or 2, wherein the application of the waterproof resin layer is spray application. The method for constructing a storage tank according to any one of claims 1 to 3, wherein the resin woven fabric sheet is a polyolefin-based woven fabric sheet. The method for constructing a storage tank according to any one of claims 1 to 4, wherein the thickness of the resin woven fabric sheet is in the range of 0.2 mm or more and 0.6 mm or less. Any of claims 1 to 5 for attaching the resin woven fabric sheet to the storage structure while applying a tension of 50 N or more and 200 N or less to the resin woven fabric sheet when the side surface of the storage structure is covered with the resin woven fabric sheet. Construction method of the storage tank described in Crab.

Images