Leachate collection pit, waste disposal facility, and method for constructing a leachate collection pit

Abstract

To provide a leachate water-collection pit whose quality can be improved and whose construction period can be shortened, a waste disposal facility, and a method of constructing a leachate water-collection pit.SOLUTION: A leachate water-collection pit 10 for collecting leachate generated in a storage tank 3, comprises: a water storage structure unit 11 comprising a water storage 21 disposed adjacent to the storage tank 3 on the intersection of a bottom face 3c and a slope face 3b of the storage tank 3 to temporarily store leachate flowing thereinto from the storage tank; a passage 13 extending from the water storage structure unit 11 toward outside of the storage tank 3 in the obliquely upward direction; and a vertical shaft 17 connected to the passage 13 via a link structure unit 15 to extend upward from the link structure unit 15 to the ground surface, with the passage 13 and the vertical shaft 17 being constructed using secondary products of concrete.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a leachate collection pit, a waste disposal facility, and a method for constructing a leachate collection pit. [Background technology]

[0002] A known technology in this field is the leachate collection pit at a waste disposal facility described in Patent Document 1 below. In this waste disposal facility, waste is stored in a landfill area where a waterproofing work is installed, and a leachate collection pit is installed 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-126638 Summary of the Invention [Problem to be solved by the invention]

[0004] When constructing this type of collection pit, the ground is excavated and the footing is relatively unstable, requiring a great deal of labor to repeatedly install reinforcing bars, formwork, and concrete, which often results in a long construction period. Furthermore, for this type of leachate collection pit constructed underground, it is desirable to further improve the quality, including watertightness. In view of these problems, the present invention aims to provide a leachate collection pit, a waste disposal facility, and a method for constructing a leachate collection pit that improves quality and shortens the construction period. [Means for solving the problem]

[0005] The leachate collection pit of the present invention is a leachate collection pit that collects leachate generated in a bowl-shaped storage tank in a waste disposal facility that has been dug down from the ground and constructed to store waste to be landfilled, and comprises a water storage structure that is located adjacent to the storage tank at the intersection of the bottom 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 diagonally upward or horizontally from the water storage structure 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, and at least a portion of the water storage structure, passage, connecting structure, and vertical shaft are constructed using secondary concrete products.

[0006] The passageway and the shaft may be constructed using a prefabricated 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 continuously connected arch culverts, and the shaft may have a plurality of continuously connected box culverts.

[0007] In addition, the passageway may 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 that extend in a direction intersecting the longitudinal direction of the passageway.

[0008] The waste disposal facility of the present invention comprises a mortar-shaped storage tank excavated from the ground surface to store waste to be disposed of in a landfill, and any one of the leachate collection pits described above.

[0009] 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 cone-shaped storage tank excavated from the ground surface and storing waste to be landfilled at a waste disposal facility. The leachate collection pit includes a water storage structure disposed adjacent to the storage tank at the intersection of the bottom surface and the slope of the storage tank and having a water reservoir into which leachate from the storage tank flows and is temporarily stored, a passage extending diagonally upward or horizontally from the water storage structure toward the outside of the storage tank, and a vertical shaft connected to the passage via a connecting structure and extending upward from the connecting structure to the ground surface, wherein at least a portion of the water storage structure, the passage, the connecting structure, and the vertical shaft are constructed using a precast concrete product. Alternatively, the passage and the vertical shaft may be constructed using a precast concrete product, and the water storage structure and the connecting structure may be constructed using cast-in-place concrete. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a leachate collection pit, a waste disposal facility, and a method for constructing a leachate collection pit that improves quality and shortens construction time. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a waste disposal facility of the present embodiment. [Figure 2] This is an enlarged cross-sectional view showing the vicinity of the leachate collection pit at a waste disposal facility. [Figure 3] FIG. [Figure 4] FIG. 10 is an exploded perspective view showing a construction method for the passage portion. [Figure 5] FIG. 10 is an exploded perspective view showing a construction method for the vertical shaft section. [Figure 6] FIG. 10 is an enlarged perspective cross-sectional view showing the waterproof structure of the joint between the connecting structure and the shaft section, partially cut away. DETAILED DESCRIPTION OF THE INVENTION

[0012] An example of a leachate collection pit and a waste disposal facility according to this embodiment will be described in detail below with reference to the drawings. The waste disposal facility 1 shown in Figure 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.

[0013] The waste disposal facility 1 also handles commercial waste, and various types of waste, including organic and inorganic materials (salts and heavy metals), are dumped and disposed of in a landfill. Examples of waste 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 a landfill, valuable materials are extracted from the waste and the waste is mixed.

[0014] At the waste disposal facility 1, which is a closed, controlled disposal facility, water is sprinkled and supplied to the waste layer S in order to stabilize the waste, which causes a relatively large amount of leachate to be generated in the storage tank 3. This leachate is collected in a leachate collection pit 10, which will be described later, and is ultimately sent to a separate leachate treatment facility (not shown) for purification treatment. After the landfill is completed and the waste is stabilized, the waste disposal facility 1 is decommissioned.

[0015] 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 toward the bottom surface 3c of the storage tank 3. The storage tank 3 is formed, for example, by a cone-shaped recess formed by excavating the ground 100 downward from the ground surface 101, and a water-impermeable layer 2 applied to the entire inner surface of the recess. The concave space inside the water-impermeable layer 2 becomes the storage space 3a where the waste is stored.

[0016] The water impermeable layer 2 is a layer that blocks water, and may be formed, for example, by laying a waterproof sheet, or may be a bentonite layer, or may be a layer in which a waterproof sheet is laminated on a bentonite layer, or may have any other structure as long as it is a layer that blocks water. A waste layer S made of waste is formed in the storage space 3a. Note that, since the waste is piled up in layers in the storage space 3a and disposed of by landfill, the waste layer S is made up of multiple layers. Since the storage space 3a is separated from the ground 100 by the water impermeable layer 2, the leachate is confined within the storage space 3a by the waterproofing properties of the water impermeable layer 2 and does not leak into the ground 100.

[0017] A plurality of vertical pipes T are provided at predetermined intervals within 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 within the storage space 3a and is 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 below, and the downstream end of the water collection pipe 6 is connected to the lower end of the leachate collection pit 10.

[0018] The leachate in the waste layer S flows into the standpipe T, passes through the standpipe T to the collection pipe 6, and is then guided to the collection pipe 6 and collected in the leachate collection pit 10. In addition, some of the leachate in the waste layer S flows directly into the collection pipe 6 and then into the leachate collection pit 10. The standpipe T is not limited to a structure extending vertically, but may be a structure in which it branches out within the waste layer S and extends vertically and horizontally.

[0019] For example, the standpipe T is made up 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 separating the gravel layer from the waste layer S. For example, the water collection pipe 6 is made up of a high-density polyethylene pipe with many holes, a single-grain crushed stone layer formed around the high-density polyethylene pipe, a gravel layer formed by filling gravel (e.g., broken granules) around the single-grain crushed stone layer, and a polyethylene net surrounding the gravel layer.

[0020] 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 to 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 outward of the storage tank 3 from the slope 3b. The body of the leachate collection pit 10 comprises 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 part of the slope 3b, and a water shielding layer 2 is present between this outer wall 11a and the storage space 3a.

[0021] 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 penetrates the water impermeable layer 2 and the outer wall 11a and is inserted into the water storage structure 11, and the leachate discharge outlet 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 outlet 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 surface of the leachate in the water reservoir 21.

[0022] Furthermore, if the pressure inside the leachate collection pit 10 is increased by, for example, a predetermined device installed inside 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, thereby promoting the stabilization of the waste.

[0023] 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 inclined relative to the horizontal plane. Like the slope 3b, the passage 13 is inclined in a direction that increases as it approaches the outside of the storage tank 3, but the inclination of the passage 13 is smaller than that of the slope 3b. The connecting structure 15 is formed, for example, in the shape of a rectangular parallelepiped with a horizontal bottom, 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 top of the rectangular parallelepiped. The vertical shaft 17 is rectangular and extends vertically from the top 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.

[0024] This leachate collection pit 10 is provided with a transfer pipe 29 for transferring the leachate in the water reservoir section 21 to the outside. The transfer pipe 29 starts from the pump 23 and extends along the inner wall surfaces of the water storage structure section 11, the passage section 13, the connecting structure section 15 and the vertical shaft section 17. The leachate temporarily stored in the water reservoir section 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).

[0025] Furthermore, workers can access the leachate collection pit 10 from the outside through the building 19. They 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 facilitate the movement of workers. A vertically extending lifting space is provided in the connecting structure 15, parallel to the staircase 27, for raising and lowering equipment and the like. Furthermore, the passageway formed within the passageway 13 is not a stairway but a simple slope, making it easy to transport equipment through the passageway 13. The passageway formed within the passageway 13 may have both a staircase and a slope like the one described above provided in parallel.

[0026] 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 below, 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.

[0027] 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, in order to reduce construction costs, 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 contrast, the water storage structure 11 and the connecting structure 15, which have more complex shapes than the passageway 13 and the shaft 17, are constructed using cast-in-place concrete.

[0028] [Aisle section] 3 and 4, the passageway 13 has a plurality of arch culverts 31 that are continuously connected in the longitudinal direction of the passageway 13. That is, the passageway 13 is constructed such that a plurality of arch culverts 31 are continuously connected obliquely upward from the water storage structure 11 to the connecting structure 15.

[0029] When constructing the leachate collection pit 10, at least a portion of the ground 100A (see FIG. 2) above the leachate collection pit 10 is excavated, exposing a support surface 35 for supporting the passageway 13. When constructing the passageway 13, as shown in FIG. 4, arch culverts 31 are lowered one by one from above using a crane, placed on the support surface 35, and connected to adjacent arch culverts 31. Furthermore, the arch culverts 31 are connected to each other using a well-known, general-purpose method, such as sandwiching a water-stop material 33, such as water-stop rubber, between them and fastening them with PC steel rods inserted between them. The length of each arch culvert 31 may be set appropriately based on, for example, the installation location and lifting capacity of a crane that can be installed at the construction site.

[0030] Furthermore, among the multiple arch culverts 31 that make up the passageway 13, arch culverts 31 (hereinafter referred to as "arch culverts 31A") that have a different configuration from the others are mixed in at a predetermined interval. This arch culvert 31A has anchor bars 39 (anchor portions) that protrude in a direction perpendicular to the longitudinal direction of the passageway 13. Specifically, the arch culvert 31A has two square pillar portions 37 that protrude approximately horizontally on both sides from the lower end of the main body of the arch culvert 31A, and two anchor bars 39 are provided to extend downward from the underside of each square pillar portion 37.

[0031] The arch culvert 31A may be fabricated by attaching a rectangular column portion 37 and anchor bars 39 to a general-purpose arch culvert 31, for example, using a resin anchor. The arch culvert 31A may be prefabricated and then lowered onto the support surface 35, as illustrated in FIG. 4, or the rectangular column portion 37 and anchor bars 39 may be attached to the arch culvert 31 after it has been installed on the support surface 35. The anchor bars 39 of the arch culvert 31A are inserted into the ground 100 below the support surface 35 to generate shear force. Therefore, by including at least some of these arch culverts 31A, it is possible to prevent the passageway 13 from sliding on the support surface 35 during construction. Note that all of the arch culverts 31 constituting the passageway 13 may be arch culverts 31A having anchor bars 39.

[0032] As shown in Figure 3, among the arch culverts 31, the arch culverts 31B arranged at both ends of the passage section 13 have one end face 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, respectively. In addition, some of the arch culverts 31 may have a different longitudinal length of the passage section 13 than others in order to fine-tune the length of the finally completed passage section 13. Furthermore, each arch culvert 31 has small parts such as steps for joints between arch culverts 31, holes and anchor boxes for PC steel rods, grooves for installing water-stopping materials 33, and anchors for hanging bolts, as needed, but these will not be shown in the drawings or described in detail.

[0033] [Shaft section] As shown in Figure 5, the shaft section 17 has a plurality of square box culverts 41 connected continuously in the longitudinal direction (vertical direction) of the shaft section 17. In other words, the shaft section 17 is constructed by connecting a plurality of box culverts 41 continuously in a vertically upward direction from the connecting structure section 15 to the ground surface 101. Note that the box culverts 41 are general-purpose products and are primarily connected horizontally in their original usage, but in this embodiment they are connected vertically.

[0034] Construction of the shaft section 17 is carried out after the completion of the connecting structure section 15. Specifically, as shown in Figure 4, the box culverts 41 are lowered one by one from above using a crane, connected in order, and stacked on top of the connecting structure section 15. The box culverts 41 are connected to each other using a well-known, general-purpose method in which water-stopping material 43 is sandwiched between them and the box culverts 41 are fastened together with PC steel rods inserted through them.

[0035] [Water storage structure and connecting structure] The construction of the water storage structure 11 and the connecting structure 15 shown in Figure 2 is carried out while the ground 100A (see Figure 2) above the leachate collection pit 10 has been excavated. As described above, the water storage structure 11 is constructed using cast-in-place concrete. Specifically, the water storage structure 11 is constructed using a known cast-in-place concrete pouring method, in which rebar is installed at the construction position of the water storage structure 11, concrete formwork is assembled, and concrete is poured into the formwork. The connecting structure 15 is constructed in the same manner. Furthermore, water-stopping material and lining concrete are installed at the joint 12j between the water storage structure 11 and the passageway 13, the joint 14j between the passageway 13 and the connecting structure 15, and the joint 16j between the connecting structure 15 and the shaft 17, respectively, to ensure watertightness at each of the joints 12j, 14j, and 16j. Furthermore, 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.

[0036] An example of the watertight structure of joints 12j, 14j, and 16j will be described. FIG. 6 is a partially cutaway, enlarged perspective cross-sectional view of the watertight structure of joint 16j between connecting structure 15 and shaft 17. As shown in the figure, inside the lining concrete 45 of joint 16j, the lower end face of the lowest box culvert 41 constituting shaft 17 abuts against the upper end face of connecting structure 15. Around corner 47 where the outer wall surface of box culvert 41 intersects with the upper end face of connecting structure 15, a primer application area 49 of a predetermined width is set, as indicated by a dashed line in the figure. The primer application area 49 is then surface cleaned and then coated with a primer.

[0037] Furthermore, three layers of butyl-based waterproof seals 51, 52, and 53 are stacked on top of the applied primer and installed along the corner 47. The waterproof seals 51 to 53 are strip-shaped sealing materials of the same width and are stacked and installed with their positions offset from each other in the width direction. The waterproof seal 51 is attached on top of 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 be offset from the waterproof seal 51 toward the connecting structure 15 and partially overlap the waterproof seal 51, and the waterproof seal 53 is attached so as to be offset from the waterproof seal 51 toward the box culvert 41 and partially overlap the waterproof seals 51 and 52. Although the waterproof seals 51 to 53 are shown partially cut away in the longitudinal direction in FIG. 6, 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.

[0038] These three layers of waterproof seals 51 to 53 waterproof the gap between the box culvert 41 and the connecting structure 15 at the corner 47. Furthermore, a waterproof structure for the joint 16j is constructed by applying lining concrete 45 around the corner 47 so as to cover the primer application area 49 and the waterproof seals 51 to 53. Note that although 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.

[0039] After the water storage structure 11, passageway 13, connecting structure 15, and shaft 17 are completed as described above, the ground 100A is formed by backfilling and filling with earth, thereby completing the structure of the leachate collection pit 10 in the ground 100.

[0040] Next, we will explain the effects of the above-mentioned leachate collection pit 10, its construction method, and the waste disposal facility 1. Generally, structures constructed using secondary concrete products have higher water-tightness reliability than structures constructed with cast-in-place concrete. That is, separators remain inside the cast-in-place concrete, and these separators can become a passageway for water. In addition, with cast-in-place concrete, the water-tightness of the concrete joints can be affected by the quality of concrete filling and compaction.

[0041] In contrast, secondary concrete products avoid the possibility of a decrease in 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.

[0042] Furthermore, if the passageway 13 and shaft 17 were constructed using cast-in-place concrete, the repeated pouring of rebar, formwork, and concrete would be required on an unstable sloping surface, potentially increasing the workload. Furthermore, the structure and construction sequence of the waterstops would become more complex depending on the concrete pouring lot allocation, and curing would be necessary after the concrete was poured, potentially lengthening the construction period. Furthermore, the need for lifting work on narrow sloping ground and working at heights would place a strain on the measures required to ensure work safety.

[0043] In contrast, by using a secondary concrete product for the leachate collection pit 10, the construction period is shortened and the quality (homogeneity, strength, and beautiful appearance) is improved compared to constructing the entire leachate collection pit 10 with cast-in-place concrete. Furthermore, construction using secondary concrete products reduces the labor load compared to casting concrete in place, and allows the work to be done by a smaller number of people, shortening the work time and resulting in improved safety.

[0044] Furthermore, in general, pre-cast concrete products have relatively high strength due to the manufacturing process, such as steam curing, that is not used in cast-in-place concrete. Therefore, the passage 13 and shaft 17 constructed with pre-cast concrete products have higher strength than those constructed with cast-in-place concrete.

[0045] On the other hand, the water storage structure 11 and the connecting structure 15 have more complex shapes than the cylindrical passage 13 and the shaft 17. Therefore, it would be difficult and costly to construct the water storage structure 11 and the connecting structure 15 using precast concrete products, so 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 when they are constructed using cast-in-place concrete.

[0046] Furthermore, as shown in Figure 4, by using an arch culvert 31 as the secondary concrete product for the passageway 13, the passageway 13 is more resistant to earth pressure from the ground 100A and waste layer S than 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 body is borne by the strength of the embankment body itself, so the pressure that the precast culvert receives from the embankment body is relatively small.

[0047] In contrast, in the leachate collection pit 10, a relatively large earth pressure from the ground 100A and the like acts on the passageway 13, so there is a greater need to strengthen the passageway 13 than in the inspection gallery of the dam, etc. described above. Therefore, for example, it is preferable to adopt a thick-walled arch culvert, among general-purpose arch culverts, as the arch culvert 31. The wall thickness, etc. of the arch culvert 31 may be selected appropriately depending on the earth pressure from the ground 100A and the waste layer S, etc.

[0048] Furthermore, the arch culverts 31 that make up the passageway 13 include some arch culverts 31A with anchor reinforcement 39. As mentioned above, the passageway 13 is installed at an angle, so that the passageway 13 undergoes a force due to its own weight that causes it to slide obliquely downward in the longitudinal direction on the support surface 35 during construction. In contrast, the anchor reinforcement 39 of the arch culvert 31A is embedded in the ground 100 below the support surface 35, thereby generating a shear force against the ground 100. Therefore, as mentioned above, it is possible to suppress the passageway 13 from sliding on the support surface 35 during construction.

[0049] Furthermore, because the passage 13 is inclined, an axial force due to its own weight acts on the passage 13 itself during construction. Such axial forces are not originally anticipated in the general-purpose arch culvert 31, and there is a risk that they could cause a deterioration in quality. However, the presence of the anchor reinforcement 39 reduces such axial forces. Furthermore, even after the leachate collection pit 10 is completed, the presence of the anchor reinforcement 39 suppresses axial displacement of the passage 13 in the ground 100.

[0050] 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 makes it possible to place the connecting structure 15 at a shallow position and shorten the shaft 17, and also reduces the amount of soil excavated from the ground 100A, thereby reducing the construction period and costs.

[0051] On the other hand, the greater the gradient of the passageway 13, the greater the force that tends to cause the passageway 13 to slide, as described above. Furthermore, if the inclination of the support surface 35 is large, the arch culvert 31 installed on the support surface 35 becomes less stable during construction, making construction difficult. Furthermore, a large gradient of the passageway 13 is undesirable because it increases the axial force acting on the passageway 13 itself due to its own weight, as described above. From this perspective, it is necessary to keep the gradient of the passageway 13 to a minimum, and it is preferable to keep the gradient of the passageway 13 to 20% or less. In other words, ultimately, it is preferable to keep the gradient of the passageway 13 between 0 and 20%.

[0052] In addition, because the passageway 13 is linear, general-purpose arch culverts 31 can be connected together using a general-purpose method, eliminating the need for special materials or methods. Furthermore, the structure of simply connecting the arch culverts 31 in a straight line is simple, reducing the possibility of a decrease in watertightness.

[0053] Furthermore, 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, there is greater freedom in the design of the equipment (e.g., pumps, passages, piping) installed inside the leachate collection pit 10, making it easier to use such equipment. Note that the leachate collection pit 10 also has, as its internal equipment as described above, an inspection path for inspecting the water reservoir 21, etc., transport equipment for transporting heavy objects (e.g., the submersible pump 23, etc.), a transfer pipe 29 for transporting leachate to the outside, and ducts for ventilation and for sending atmospheric air to the waste layer S in the storage space 3a via the collection pipe 6, etc.

[0054] 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 configure modified examples by utilizing the technical matters described in the above-described embodiment. The configurations of the respective embodiments may be used in appropriate combination.

[0055] 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. Furthermore, it is not essential that the passage section 13 be provided at an incline, and the passage section 13 may extend horizontally. Furthermore, the precast culvert that constitutes the passage section 13 may be a box culvert instead of the arch culvert 31. Furthermore, the water storage structure section 11, the passage section 13, the connecting structure section 15, and the vertical shaft section 17 may all be constructed using secondary concrete products. [Explanation of symbols]

[0056] 1...waste disposal facility, 3...storage tank, 3c...bottom, 3b...slope, 100...ground, 101...surface, 11...water storage structure, 13...passage section, 15...connecting structure section, 17...shaft section, 21...water reservoir section, 31...arch culvert (secondary concrete product), 41...box culvert (secondary concrete product), 39...anchor reinforcement (anchor section).

Claims

1. A waste disposal facility includes a storage tank formed by a bowl-shaped recess dug below the ground surface and a water-impermeable layer applied to the inner surface of the recess, and a storage space that is a concave space inside the water-impermeable layer and stores waste, and a leachate collection pit that collects leachate generated in the storage space, a water storage structure provided adjacent to the storage tank and outside the water impermeable layer, in which the leachate flowing in from the storage space is temporarily stored; A leachate collection pit comprising: a passage portion provided outside the water impermeable layer and extending obliquely upward from the water storage structure portion.

2. A waste disposal facility includes a storage tank formed by a bowl-shaped recess dug below the ground surface and a water-impermeable layer applied to the inner surface of the recess, and a storage space that is a concave space inside the water-impermeable layer and stores waste, and a leachate collection pit that collects leachate generated in the storage space, a water storage structure provided adjacent to the storage tank and outside the water impermeable layer, in which the leachate flowing in from the storage space is temporarily stored; a passage portion provided outside the water impermeable layer and extending horizontally from the water storage structure portion;

3. A leachate collection pit as described in claim 1 or 2, wherein the water storage structure is located at the intersection of the bottom of the storage tank and the slope.

4. A leachate collection pit for collecting leachate generated in a waste disposal facility comprising a mortar-shaped recess dug below the ground surface, a water-impermeable layer applied to the inner surface of the recess, and a storage space that is a concave space inside the water-impermeable layer and in which waste is stored, a water storage structure provided adjacent to the storage space and outside the water impermeable layer, in which the leachate flowing in from the storage space is temporarily stored; a passage portion provided outside the water impermeable layer and extending obliquely upward from the water storage structure portion, The water storage structure has an outer wall that forms part of the slope of the recess, and the water impermeable layer is located between the outer wall and the storage space.

5. A leachate collection pit for collecting leachate generated in a waste disposal facility comprising a mortar-shaped recess dug below the ground surface, a water-impermeable layer applied to the inner surface of the recess, and a storage space that is a concave space inside the water-impermeable layer and in which waste is stored, a water storage structure provided adjacent to the storage space and outside the water impermeable layer, in which the leachate flowing in from the storage space is temporarily stored; a passage portion provided outside the water impermeable layer and extending horizontally from the water storage structure portion, The water storage structure has an outer wall that forms part of the slope of the recess, and the water impermeable layer is located between the outer wall and the storage space.

6. a water collection pipe for sending the leachate in the storage space to the water storage structure; The leachate collection pit according to any one of claims 1 to 5, wherein the water collection pipe penetrates the water impermeable layer and extends from within the storage space to within the water storage structure.

7. A leachate collection pit as described in any one of claims 1 to 6, comprising a transfer pipe that passes through the inside of the passage portion, extends from the water storage structure portion to the ground surface, and transfers the leachate from the water storage structure portion to the ground surface.

8. a vertical shaft portion provided outside the water impermeable layer and a connecting structure portion provided outside the water impermeable layer, A leachate collection pit as described in any one of claims 1 to 7, wherein the vertical shaft portion is connected to the passage portion via the connecting structure portion and extends upward from the connecting structure portion to the ground surface.

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