JP2025028357A - Leachate collection pit, waste disposal facility, and method for constructing a leachate collection pit - Google Patents

Abstract

[Problem] To provide a leachate collection pit, a waste disposal facility, and a method for constructing a leachate collection pit that are capable of improving quality and shortening construction time. [Solution] A leachate collection pit (10) collects leachate generated in a storage tank (3), and includes a water storage structure (11) that is provided adjacent to the storage tank (3) at the intersection of the bottom surface (3c) and the slope (3b) of the storage tank (3) and has a water reservoir (21) into which leachate from the storage tank flows and is temporarily stored, a passage (13) that extends obliquely upward from the water storage structure (11) toward the outside of the storage tank (3), and a vertical shaft (17) that is connected to the passage (13) via a connecting structure (15) and extends upward from the connecting structure (15) to the ground surface, and the passage (13) and the vertical shaft (17) are constructed using a secondary concrete product. [Selected Figure] Figure 2

Description

The present invention relates to a leachate collection pit, a waste disposal facility, and a method for constructing a leachate collection pit.

A known technology in this field is a leachate collection pit at a waste disposal facility, as described in Patent Document 1 below. In this waste disposal facility, waste is stored in a landfill area in which a waterproofing structure is installed, and a leachate collection pit is provided adjacent to this landfill area. Leachate generated in the landfill area is collected at the bottom of this leachate collection pit through a collection pipe.

JP 2013-126638 A

When constructing this type of collection pit, the ground is excavated and the footing is relatively unstable, so it is often labor-intensive to repeatedly lay rebar, formwork, and concrete, and construction time tends to be long. In addition, it is desirable to further improve the quality, including water-stopping ability, of this type of leachate collection pit constructed underground. In view of these problems, the present invention aims to provide a leachate collection pit, waste disposal facility, and method for constructing a leachate collection pit that improves quality and shortens construction time.

The leachate collection pit of the present invention is a leachate collection pit that collects leachate generated in a mortar-shaped storage tank in a waste disposal facility that is dug down from the ground surface and stores waste to be disposed of by landfill. The pit is equipped with a water storage structure that is provided adjacent to the storage tank at the intersection of the bottom surface of the storage tank and the slope and has a water reservoir where leachate from the storage tank flows in and is temporarily stored, a passageway that extends from the water storage structure diagonally upward or horizontally outward from the storage tank, and a vertical shaft that is connected to the passageway via a connecting structure and extends upward from the connecting structure to the ground surface, and at least a portion of the water storage structure, the passageway, the connecting structure, and the vertical shaft are constructed using secondary concrete products.

The passageway and the shaft may be constructed using a secondary concrete product, and the water storage structure and the connecting structure may be constructed using cast-in-place concrete. The passageway may have a plurality of arch culverts connected in series, and the shaft may have a plurality of box culverts connected in series.

The passageway may also be constructed by continuously connecting multiple precast culvert members diagonally upward from the water storage structure to the connecting structure, and at least some of the precast culvert members may have anchor portions formed therein that extend in a direction intersecting the longitudinal direction of the passageway.

The waste disposal facility of the present invention comprises a cone-shaped storage tank excavated below the ground surface to store waste to be disposed of in a landfill, and any one of the leachate collection pits described above.

The method for constructing a leachate collection pit of the present invention is a method for constructing a leachate collection pit for collecting leachate generated in a mortar-shaped storage tank in a waste disposal facility that is dug down from the ground surface and stores waste to be disposed of by landfill. The leachate collection pit includes a water storage structure that is provided adjacent to the storage tank at the intersection of the bottom surface of the storage tank and the slope and has a water reservoir where leachate from the storage tank flows in and is temporarily stored, a passage that extends from the water storage structure diagonally upward or horizontally toward the outside of the storage tank, and a vertical shaft that is connected to the passage via a connecting structure and extends upward from the connecting structure to the ground surface. At least a part of the water storage structure, the passage, the connecting structure, and the vertical shaft are constructed using a secondary concrete product. Alternatively, the passage and the vertical shaft may be constructed using a secondary concrete product, and the water storage structure and the connecting structure may be constructed using cast-in-place concrete.

The present invention provides a method for constructing a leachate collection pit, a waste disposal facility, and a leachate collection pit that improves quality and shortens construction time.

1 is a cross-sectional view showing a waste disposal facility of the present embodiment. This is an enlarged cross-sectional view showing the vicinity of the leachate collection pit at a waste disposal facility. FIG. FIG. 4 is an exploded perspective view showing a construction method for the passage portion. FIG. 13 is an exploded perspective view showing a construction method for the shaft section. 1 is a partially cutaway, enlarged perspective cross-sectional view showing the waterproofing structure of the joint between the connecting structure and the shaft section. FIG.

Below, an example of a leachate collection pit and waste disposal facility of this embodiment will be described in detail with reference to the drawings. The waste disposal facility 1 shown in FIG. 1 is a managed final disposal facility that disposes of waste by landfill. The waste disposal facility 1 is a type of waste disposal facility known as a "closed waste disposal facility" that has a roof 4 above a storage tank 3.

Waste to be disposed of at the waste disposal facility 1 includes commercial waste, and various waste materials, including organic and inorganic materials (salts, heavy metals), are dumped and disposed of in landfills at the waste disposal facility 1. Examples of waste materials include incineration ash and solidified fly ash generated at waste incineration facilities, organic sludge, inorganic sludge, wood chips, and slag. Before waste is disposed of in landfills, valuable materials are extracted from the waste and the waste is mixed.

In the waste disposal facility 1, which is a closed, managed disposal facility, water is sprayed and supplied to the waste layer S in order to stabilize the waste, so a relatively large amount of leachate is generated in the storage tank 3. This leachate is collected in a leachate collection pit 10, described below, and is ultimately sent to a separate leachate treatment facility (not shown) for purification treatment. The waste disposal facility 1 is decommissioned after landfilling is completed and the waste is stabilized.

The waste disposal facility 1 has a storage tank 3 for storing waste. The storage tank 3 is cone-shaped, with a slope 3b that extends at an angle from the ground surface to the bottom surface 3c of the storage tank 3. The storage tank 3 is formed, for example, with a cone-shaped recess formed by excavating the ground 100 downward from the ground surface 101, and a waterproof layer 2 applied to the entire inner surface of the recess. The concave space inside the waterproof layer 2 becomes the storage space 3a in which the waste is stored.

The water-shielding layer 2 is a layer that blocks water. The water-shielding layer 2 may be formed by laying a water-shielding sheet, a bentonite layer, a layer in which a water-shielding sheet is laminated on a bentonite layer, or any other structure that blocks water. A waste layer S made of waste is formed in the storage space 3a. In the storage space 3a, waste is piled up in layers and disposed of by landfill, so the waste layer S is composed of multiple layers. Since the storage space 3a is separated from the ground 100 by the water-shielding layer 2, the seepage water is confined within the storage space 3a by the water-shielding properties of the water-shielding layer 2 and does not leak into the ground 100.

A number of vertical pipes T are provided at predetermined intervals in the storage tank 3. The vertical pipes T are embedded in the waste layer S and extend vertically. The upper end of each vertical pipe T is exposed above the waste layer S, and the downstream end of each vertical pipe T is connected to a water collection pipe 6. The water collection pipe 6 is provided in the storage space 3a and installed above the water impermeable layer 2 along the bottom surface of the storage space 3a. The water collection pipe 6 is slightly inclined downward toward the lower end of the leachate collection pit 10 described later, and the downstream end of the water collection pipe 6 is connected to the lower end of the leachate collection pit 10.

The leachate in the waste layer S flows into the vertical pipe T, through which it flows into the collection pipe 6, and is then guided to the collection pipe 6 and collected in the leachate collection pit 10. Some of the leachate in the waste layer S flows directly into the collection pipe 6 and into the leachate collection pit 10. Note that the vertical pipe T is not limited to a structure that extends vertically, and may be branched out and extend vertically and horizontally within the waste layer S.

For example, the vertical pipe T is composed of a high-density polyethylene pipe with many holes, a gravel layer formed by filling gravel (e.g., broken granules) around the high-density polyethylene pipe, and a corrugated pipe that separates the gravel layer from the waste layer S. For example, the water collection pipe 6 is composed of a high-density polyethylene pipe with many holes, a single-grained crushed stone layer formed around the high-density polyethylene pipe, a gravel layer formed by filling gravel (e.g., broken granules) around the single-grained crushed stone layer, and a polyethylene net that surrounds the gravel layer.

Next, the leachate collection pit 10 will be described in more detail with reference to Figures 2 to 5. The leachate collection pit 10 is constructed in the ground 100 on the side of the storage tank 3, and extends from near the bottom of the storage tank 3 to the ground surface 101. The leachate collection pit 10 is constructed in the ground at a position outside the storage tank 3 from the slope 3b. The body of the leachate collection pit 10 includes a water storage structure 11, a passage 13, a connecting structure 15, and a vertical shaft 17. The water storage structure 11 is located at the intersection of the bottom surface 3c of the storage tank 3 and the slope 3b, and is provided in a hollow shape adjacent to the storage tank 3. A part of the outer wall 11a of the water storage structure 11 extends at an angle so as to form a part of the slope 3b, and a water shielding layer 2 exists between this outer wall 11a and the storage space 3a.

The water storage structure 11 has a water reservoir 21 recessed at a position lower than the bottom surface 3c of the storage tank 3. Meanwhile, the downstream end of the water collection pipe 6 is inserted into the water storage structure 11, penetrating the water shielding layer 2 and the outer wall 11a, and the leachate discharge port 6a at the downstream end of the water collection pipe 6 is located above the water reservoir 21. The leachate in the storage tank 3 is discharged from the leachate discharge port 6a through the water collection pipe 6 and flows into the water reservoir 21 where it is temporarily stored. A pump 23 for pumping up the leachate is submerged below the liquid level of the leachate in the water reservoir 21.

For example, by increasing the pressure in the leachate collection pit 10 using a specific device installed in the leachate collection pit 10, air can be forced to flow back into the collection pipe 6 through the leachate outlet 6a. By sending air into the collection pipe 6, air can be supplied to the waste layer S in the storage space 3a via the vertical pipe T, etc. The air supplied to the waste promotes aerobic reactions by aerobic bacteria in the waste, promoting the stabilization of the waste.

The passage 13 is cylindrical and extends in a straight line from the water storage structure 11 diagonally upward outward from the storage tank 3. That is, the passage 13 is provided so as to be inclined with respect to the horizontal plane. The passage 13 is inclined in a direction that becomes higher as it approaches the outside of the storage tank 3, similar to the slope 3b, but the inclination of the passage 13 is smaller than that of the slope 3b. The connecting structure 15 is interposed between the passage 13 and the vertical shaft 17. The connecting structure 15 is formed, for example, in a rectangular parallelepiped shape with a horizontal bottom surface, with one end of the passage 13 connected to one side of the rectangular parallelepiped, and the lower end of the vertical shaft 17 connected to the upper surface of the rectangular parallelepiped. The vertical shaft 17 is in the shape of a square tube and extends vertically from the upper surface of the connecting structure 15 to the ground surface 101. In addition, a building 19 is provided to cover the above-ground opening of the vertical shaft 17.

This leachate collection pit 10 is provided with a transfer pipe 29 for transferring the leachate in the water reservoir 21 to the outside. The transfer pipe 29 starts at the pump 23 and extends along the inner wall surfaces of the water storage structure 11, the passage 13, the connecting structure 15, and the vertical shaft 17. The leachate temporarily stored in the water reservoir 21 is pumped up by the pump 23 and transferred to the outside of the building 19 through the transfer pipe 29, and then transported from near the building 19 to a leachate treatment facility (not shown).

In addition, workers can enter and exit the leachate collection pit 10 from the outside through the building 19, and can access the water reservoir 21 by moving through the shaft 17, the connecting structure 15, the passage 13, and the water storage structure 11. The workers can then inspect the water reservoir 21, the pump 23, the transfer piping 29, and the like. A staircase 27 is provided connecting the building 19 to the connecting structure 15 to allow the workers to move around. In addition, the connecting structure 15 is provided with a vertical space for lifting and lowering equipment, etc., parallel to the side of the staircase 27. In addition, since the passage formed in the passage 13 is not a staircase but a simple slope, it is easy to transport equipment through the passage 13. In addition, in the passage formed in the passage 13, a staircase and the above-mentioned slope may be provided in parallel.

In the leachate collection pit 10 described above, the passage section 13 and the vertical shaft section 17 have a relatively simple structure, being cylindrical and extending in a straight line. Therefore, the passage section 13 and the vertical shaft section 17 of the leachate collection pit 10 are constructed using secondary concrete products (for example, precast culvert members in this case). As will be described in more detail later, an arch culvert 31 (see Figure 4) is used for the passage section 13, and a box culvert 41 (see Figure 5) is used for the vertical shaft section 17.

The arch culvert 31 and the box culvert 41 are precast concrete products made of reinforced concrete, and are manufactured in a factory and then transported to the construction site of the leachate collection pit 10. Here, a general-purpose arch culvert is used as the arch culvert 31, and a general-purpose box culvert is used as the box culvert 41, in order to reduce construction costs. In contrast, the water storage structure 11 and the connecting structure 15, which have shapes that are more complex than the passageway 13 and the shaft 17, are constructed from cast-in-place concrete.

[Passage section]
3 and 4, the passage portion 13 has a plurality of arch culverts 31 continuously connected in the longitudinal direction of the passage portion 13. That is, the passage portion 13 is constructed by continuously connecting a plurality of arch culverts 31 obliquely upward from the water storage structure portion 11 to the connecting structure portion 15.

When constructing the leachate collection pit 10, at least the ground 100A (see FIG. 2) above the leachate collection pit 10 is excavated, and the support surface 35 for supporting the passage section 13 is exposed. When constructing the passage section 13, as shown in FIG. 4, the arch culverts 31 are lowered one by one from above by a crane, installed on the support surface 35, and connected to adjacent arch culverts 31. In addition, the arch culverts 31 are connected to each other by a known general-purpose method, such as sandwiching a water-stopping material 33 such as water-stopping rubber between them and fastening them with a PC steel rod inserted between the arch culverts 31. The length of each arch culvert 31 may be set appropriately based on, for example, the installation position and lifting capacity of a crane that can be installed at the construction site.

Among the multiple arch culverts 31 that make up the passageway 13, some arch culverts 31 (hereinafter referred to as "arch culverts 31A") that have a different configuration from the others are mixed in at a specified interval. These arch culverts 31A have anchor bars 39 (anchor sections) that protrude in a direction perpendicular to the longitudinal direction of the passageway 13. Specifically, the arch culvert 31A has two rectangular column sections 37 that protrude approximately horizontally on both sides from the lower end of the main body of the arch culvert 31A, and the anchor bars 39 are provided so that two of them extend downward from the underside of each rectangular column section 37.

The arch culvert 31A may be manufactured by attaching the square column portion 37 and the anchor bar 39 to a general-purpose arch culvert 31, for example, using a resin anchor. The arch culvert 31A may be hung above the support surface 35 in a prefabricated state as illustrated in FIG. 4, or the square column portion 37 and the anchor bar 39 may be attached to the arch culvert 31 after it is installed on the support surface 35. The anchor bar 39 of the arch culvert 31A is inserted into the ground 100 below the support surface 35 to generate a shear force, so that at least some of such arch culverts 31A are mixed in, thereby preventing the passage portion 13 from sliding on the support surface 35 during construction. Note that all of the arch culverts 31 constituting the passage portion 13 may be arch culverts 31A having the anchor bar 39.

As shown in FIG. 3, the arch culverts 31B arranged at both ends of the passage section 13 among the arch culverts 31 have one end surface 31t inclined with respect to the extension direction of the passage section 13 in order to connect to the vertical connection ports of the water storage structure section 11 and the connecting structure section 15. In addition, some of the arch culverts 31 may have a different longitudinal length of the passage section 13 from the others in order to fine-tune the length of the passage section 13 that is finally completed. In addition, the arch culverts 31 each have small parts such as steps for joints between the arch culverts 31, holes and fixing boxes for PC steel rods, grooves for installing water-stopping materials 33, and anchors for hanging bolts, as necessary, but illustrations and detailed explanations of these are omitted.

[Shaft section]
5, the shaft section 17 has a plurality of square box culverts 41 continuously connected in the longitudinal direction (vertical direction) of the shaft section 17. That is, the shaft section 17 is constructed by continuously connecting a plurality of box culverts 41 vertically upward from the connecting structure section 15 to the ground surface 101. Note that the box culverts 41, which are general-purpose products, are primarily connected in the horizontal direction when originally used, but in this embodiment, they are connected in the vertical direction.

The construction of the shaft section 17 is carried out after the completion of the connecting structure section 15. Specifically, as shown in FIG. 4, the box culverts 41 are lowered one by one from above with a crane, connected in sequence, and stacked on the upper surface of the connecting structure section 15. The box culverts 41 are connected to each other by a known, general-purpose method in which the box culverts 41 are fastened together with PC steel bars inserted between them while a water-stopping material 43 is sandwiched between them.

[Water storage structure and connecting structure]
The construction of the water storage structure 11 and the connecting structure 15 shown in FIG. 2 is performed in a state where the ground 100A (see FIG. 2) above the seepage water collection pit 10 is excavated. As described above, the water storage structure 11 is constructed by cast-in-place concrete. Specifically, the water storage structure 11 is constructed by a known cast-in-place concrete casting method, in which reinforcing bars are installed at the construction position of the water storage structure 11, a concrete formwork is assembled, and concrete is poured into the formwork. The connecting structure 15 is constructed in the same manner. In addition, water-stopping material and wrapping concrete are applied to the joint 12j between the water storage structure 11 and the passage 13, the joint 14j between the passage 13 and the connecting structure 15, and the joint 16j between the connecting structure 15 and the shaft 17, respectively, to ensure water-stopping at each of the joints 12j, 14j, and 16j. In addition, a bentonite-based water-stop material or a waterproof seal may be used for the water-stop structure of each of the joints 12j, 14j, and 16j.

An example of the water-stopping structure of the joints 12j, 14j, and 16j will be described. FIG. 6 is a perspective cross-sectional view showing the water-stopping structure of the joint 16j between the connecting structure 15 and the shaft 17, partially cut away and enlarged. As shown in the figure, inside the concrete covering 45 of the joint 16j, the lower end surface of the lowest box culvert 41 constituting the shaft 17 abuts against the upper end surface of the connecting structure 15. Around the corner 47 where the outer wall surface of the box culvert 41 and the upper end surface of the connecting structure 15 intersect, a primer-coated area 49 of a predetermined width is set as shown by a dashed line in the figure. The primer-coated area 49 is then surface-cleaned and then coated with a primer.

Furthermore, three layers of butyl-based waterproof seals 51, 52, and 53 are layered on top of the applied primer and installed along the corner 47. The waterproof seals 51 to 53 are strip-shaped sealants of the same width, and are layered and installed with their positions shifted from each other in the width direction. The waterproof seal 51 is attached on the primer so as to bridge the gap between the box culvert 41 and the connecting structure 15 at the corner 47 and close the gap. The waterproof seal 52 is attached so as to overlap the waterproof seal 51 in a position shifted from the waterproof seal 51 toward the connecting structure 15, and the waterproof seal 53 is attached so as to overlap the waterproof seals 51 and 52 in a position shifted from the waterproof seal 51 toward the box culvert 41. In FIG. 6, the waterproof seals 51 to 53 are shown partially broken away in the longitudinal direction, but the waterproof seals 51 to 53 extend over the entire length of the gap between the box culvert 41 and the connecting structure 15 at the corner 47.

These three layers of waterproof seals 51-53 waterproof the gap between the box culvert 41 and the connecting structure 15 at the corner 47. Furthermore, a waterproof structure is constructed for the joint 16j by applying concrete lining 45 around the corner 47 to cover the primer application area 49 and the waterproof seals 51-53. Note that while an example of the waterproof structure for the joint 16j has been described here, similar waterproof structures are also constructed for the joints 12j and 14j.

After the water storage structure 11, passageway 13, connecting structure 15, and shaft 17 are completed in the manner described above, the ground 100A is formed by backfilling and filling with soil, completing the structure of the leachate collection pit 10 in the ground 100.

Next, the above-mentioned leachate collection pit 10, its construction method, and the effects of the waste disposal facility 1 will be described. In general, structures constructed using secondary concrete products have higher water-stopping reliability than structures constructed with cast-in-place concrete. That is, because separators remain inside cast-in-place concrete, these separators can become a passageway for water. In addition, with cast-in-place concrete, the quality of concrete filling and compaction can affect the water-stopping ability of concrete joints.

In contrast, secondary concrete products avoid the possibility of reduced watertightness caused by separators and joints as described above, so structures constructed using secondary concrete products can achieve relatively reliable watertightness. At least a portion (here, the passageway 13 and the shaft 17) of the leachate collection pit 10 of the waste disposal facility 1 is constructed from secondary concrete products. Therefore, the passageway 13 and the shaft 17 have higher watertightness than cast-in-place concrete, and as a result, the watertightness of the leachate collection pit 10 as a whole is improved compared to when the entire leachate collection pit 10 is constructed from cast-in-place concrete.

Furthermore, if the passageway 13 and shaft 17 were constructed using cast-in-place concrete, the work load could increase because rebar, formwork, and concrete pouring would have to be repeated on sloping ground with unstable footing. Furthermore, the structure and construction sequence of the waterstops would become complicated depending on the concrete pouring lot allocation, and curing would also be necessary after the concrete was poured, which could result in a longer construction period. Furthermore, the need for lifting work on narrow sloping ground or working at height would place a strain on measures to ensure work safety.

In contrast, by using a secondary concrete product in the leachate collection pit 10, construction time is shortened and quality (homogeneity, strength, and aesthetic appearance) is improved compared to constructing the entire leachate collection pit 10 with cast-in-place concrete. In addition, construction using secondary concrete products reduces the labor load compared to casting concrete in place, allows the work to be done by a smaller number of people, shortens work hours, and improves safety as a result.

In addition, concrete preforms generally have relatively high strength due to the manufacturing process, such as steam curing, that is not used in cast-in-place concrete. Therefore, the passageway 13 and shaft 17 constructed with the concrete preform have a higher strength than those constructed with cast-in-place concrete.

On the other hand, the water storage structure 11 and the connecting structure 15 have a more complex shape than the cylindrical passage 13 and the shaft 17. Therefore, it would be difficult and likely to be more costly to construct the water storage structure 11 and the connecting structure 15 using secondary concrete products, and therefore they are constructed using cast-in-place concrete. Because the water storage structure 11 and the connecting structure 15 are constructed on a flat supporting surface, the labor load is relatively small even if they are constructed using cast-in-place concrete.

As shown in Figure 4, by using an arch culvert 31 as the secondary concrete product for the passageway 13, a passageway 13 that is more resistant to earth pressure from the ground 100A and waste layer S, etc., can be obtained compared to when a box culvert is used. For comparison, consider an inspection gallery of a dam constructed within a concrete embankment using precast culverts. In this case, the weight of the dam's embankment is borne by the strength of the embankment itself, so the pressure that the precast culvert receives from the embankment is relatively small.

In contrast, in the leachate collection pit 10, a relatively large earth pressure from the ground 100A etc. acts on the passageway 13, so there is a high need to strengthen the passageway 13 compared to the above-mentioned dam inspection gallery etc. Therefore, for example, it is preferable to adopt a thick-walled arch culvert as the arch culvert 31 from among general-purpose arch culverts. The wall thickness etc. of the arch culvert 31 may be appropriately selected according to the earth pressure from the ground 100A and the waste layer S etc.

In addition, the arch culverts 31 that make up the passageway 13 include some arch culverts 31A with anchor bars 39. As mentioned above, the passageway 13 is installed at an angle, so that the passageway 13 undergoes construction on the support surface 35, and as a result of its own weight, a force is generated that causes the passageway 13 to slide diagonally downward in the longitudinal direction on the support surface 35. In contrast, the anchor bars 39 of the arch culvert 31A are embedded in the ground 100 below the support surface 35, and generate a shear force against the ground 100. Therefore, as described above, it is possible to suppress the passageway 13 undergoing construction from sliding on the support surface 35.

In addition, because the passageway 13 is inclined, an axial force caused by its own weight acts on the passageway 13 itself during construction. Such axial forces are not originally anticipated in the general-purpose arch culvert 31, and may cause a deterioration in quality. However, the presence of the anchor bars 39 reduces such axial forces. Furthermore, even after the leachate collection pit 10 is completed, the presence of the anchor bars 39 suppresses axial displacement of the passageway 13 in the ground 100.

The leachate collection pit 10 employs a structure in which the passage 13 is inclined so that the connecting structure 15 side is higher than the water storage structure 11 side. As can be understood geometrically, this structure allows the connecting structure 15 to be located at a shallow position and the shaft 17 to be shortened, and the amount of soil excavated from the ground 100A is reduced, thereby reducing construction time and costs.

On the other hand, the greater the gradient of the passage 13, the greater the force that tends to cause the passage 13 to slide, as described above. Furthermore, if the inclination of the support surface 35 becomes greater, the arch culvert 31 installed on the support surface 35 becomes less stable during construction, and construction becomes more difficult. Furthermore, if the gradient of the passage 13 is large, the axial force acting on the passage 13 itself due to its own weight, as described above, also becomes large, which is undesirable. From this perspective, it is necessary to suppress the gradient of the passage 13, and it is preferable to keep the gradient of the passage 13 to 20% or less. In other words, ultimately, it is preferable to keep the gradient of the passage 13 between 0 and 20%.

In addition, because the passageway 13 is linear, general-purpose arch culverts 31 can be connected together using general-purpose methods, and there is no need to use special materials or methods. Furthermore, the structure of simply connecting the arch culverts 31 in a straight line is simple, which reduces the possibility of a decrease in water-stopping properties, etc.

The leachate collection pit 10 is constructed underground at a position outside the storage tank 3 relative to the slope 3b. Therefore, compared to a leachate collection pit constructed along the slope 3b of the storage tank 3, the overall structure of the leachate collection pit 10 can be designed more freely. As a result, the design freedom of the equipment (e.g., pumps, passages, piping) installed inside the leachate collection pit 10 is also increased, making such equipment easier to use. In addition, the leachate collection pit 10 is simultaneously equipped with equipment installed inside as described above, such as an inspection path for inspecting the water reservoir 21, etc., transportation equipment for transporting heavy objects (e.g., submersible pump 23, etc.), transport piping 29 for transporting leachate to the outside, and ducts used for ventilation and for sending atmospheric air to the waste layer S in the storage space 3a through the water collection pipe 6, etc.

The present invention can be implemented in various forms, including the above-described embodiment, with various modifications and improvements based on the knowledge of those skilled in the art. It is also possible to construct modified versions by utilizing the technical matters described in the above-described embodiment. The configurations of each embodiment, etc. may be used in appropriate combination.

For example, the waste disposal facility of the present invention is not limited to a closed waste disposal facility 1 having a roof 4, but may be a waste disposal facility in which the roof 4 is omitted. In addition, it is not essential that the passage section 13 is provided at an incline, and the passage section 13 may extend horizontally. In addition, the precast culvert that constitutes the passage section 13 may be a box culvert instead of the arch culvert 31. In addition, the water storage structure section 11, the passage section 13, the connecting structure section 15, and the shaft section 17 may all be constructed using secondary concrete products.

1...waste disposal facility, 3...storage tank, 3c...bottom surface, 3b...slope, 100...ground, 101...surface, 11...water storage structure, 13...passageway, 15...connecting structure, 17...vertical shaft, 21...water reservoir, 31...arch culvert (secondary concrete product), 41...box culvert (secondary concrete product), 39...anchor bars (anchor section).

Claims (7)

A leachate collection pit for collecting leachate generated in a mortar-shaped storage tank in a waste disposal facility, the storage tank being excavated from the ground surface and used to store waste to be disposed of in landfill, comprising:
a water storage structure having a water reservoir section that is provided adjacent to the storage tank at an intersection between a bottom surface of the storage tank and a slope and into which the leachate from the storage tank flows and is temporarily stored;
A passage portion extending from the water storage structure portion toward the outside of the storage tank, diagonally upward or horizontally;
A vertical shaft portion connected to the passage portion via a connecting structure portion and extending upward from the connecting structure portion to the ground surface,
A leachate collection pit, wherein at least a portion of the water storage structure, the passageway, the connecting structure, and the shaft are constructed using a secondary concrete product. The leachate collection pit according to claim 1, wherein the passage and the shaft are constructed using the secondary concrete product, and the water storage structure and the connecting structure are constructed using cast-in-place concrete. The leachate collection pit according to any one of claims 1 to 2, wherein the passage portion has a plurality of arch culverts connected in series, and the shaft portion has a plurality of box culverts connected in series. The passage portion is
A plurality of precast culvert members are continuously connected diagonally upward from the water storage structure to the connecting structure,
A leachate collection pit as described in any one of claims 1 to 3, wherein at least a portion of the precast culvert member is formed with an anchor portion extending in a direction intersecting the longitudinal direction of the passage portion. A mortar-shaped storage tank that is dug below the surface of the earth to store waste to be disposed of in a landfill;
A waste disposal facility comprising the leachate collection pit according to any one of claims 1 to 4. A method for constructing a leachate collection pit for collecting leachate generated in a mortar-shaped storage tank in a waste disposal facility, the storage tank being excavated from the ground surface and used to store waste to be disposed of in a landfill, comprising the steps of:
The leachate collection pit is
a water storage structure having a water reservoir section that is provided adjacent to the storage tank at an intersection between a bottom surface of the storage tank and a slope and into which the leachate from the storage tank flows and is temporarily stored;
A passage portion extending from the water storage structure portion toward the outside of the storage tank, diagonally upward or horizontally;
A vertical shaft portion connected to the passage portion via a connecting structure portion and extending upward from the connecting structure portion to the ground surface,
A method for constructing a leachate collection pit, comprising constructing at least a portion of the water storage structure, the passage, the connecting structure, and the shaft using a secondary concrete product. The method for constructing a leachate collection pit according to claim 6, wherein the passage and the shaft are constructed using the secondary concrete product, and the water storage structure and the connecting structure are constructed using cast-in-place concrete.

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