Leachate collection pit and method for constructing the 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 is a leachate collection pit. T, and and a method for constructing a leachate collection pit. [Background technology]

[0002] Conventionally, a known technology in this field is a 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 provided with a waterproofing work, 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-126638 A Summary of the Invention [Problem to be solved by the invention]

[0004] When constructing this type of water collection pit, the ground is excavated and the footing is relatively unstable, so it is often labor-intensive to repeatedly place reinforcing bars, forms, 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 provides a leachate collection pit that improves quality and shortens construction time. T, and The object of the present invention is to provide a method for constructing a leachate collection pit. [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 section where leachate from the storage tank flows in and is temporarily stored, a passage section that extends diagonally upward or horizontally from the water storage structure toward the outside of the storage tank, and a vertical shaft section that is connected to the passage section via a connecting structure section and extends upward from the connecting structure section to the ground surface, and at least a portion of the water storage structure, the passage section, the connecting structure section and the vertical shaft section are constructed using secondary concrete products.

[0006] The passage 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 passage may have a plurality of arch culverts connected in series, and the shaft may have a plurality of box culverts connected in series.

[0007] In addition, the passageway portion may be constructed by continuously connecting a plurality of precast culvert members diagonally upward from the water storage structure portion to the connecting structure portion, and at least a portion of the precast culvert members may be formed with anchor portions extending in a direction intersecting the longitudinal direction of the passageway portion.

[0008] The waste disposal facility of the present invention comprises a bowl-shaped storage tank excavated below the ground surface for storing 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 mortar-shaped storage tank in a waste disposal facility having a mortar-shaped storage tank dug from the ground surface and storing waste to be disposed of in landfill, the leachate collection pit includes a water storage structure provided adjacent to the storage tank at the intersection of the bottom surface and the slope of the storage tank and having a water reservoir portion in which leachate from the storage tank flows in and is temporarily stored, a passage portion extending from the water storage structure toward the outside of the storage tank, obliquely upward or horizontally, and 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, and at least a part of the water storage structure portion, the passage portion, the connecting structure portion, and the vertical shaft portion are constructed using a concrete secondary product. Also, the passage portion and the vertical shaft portion may be constructed using a concrete secondary product, and the water storage structure portion and the connecting structure portion may be constructed using cast-in-place concrete. Effect of the Invention

[0010] According to the present invention, a leachate collection pit that improves quality and shortens construction time is provided. T, and and a method for constructing a leachate collection pit. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a waste disposal facility of the present embodiment. [Diagram 2] This is an enlarged cross-sectional view showing the vicinity of the leachate collection pit at a waste disposal facility. [Diagram 3] FIG. [Figure 4] FIG. 4 is an exploded perspective view showing a construction method for the passage portion. [Diagram 5] FIG. 13 is an exploded perspective view showing a construction method for the shaft section. [Figure 6] 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 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 called 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, heavy metals), are dumped and disposed of in landfills. 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 landfills, valuable materials are extracted from the waste and the waste is mixed.

[0014] In the waste disposal facility 1, which is a closed, controlled 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, which will be described later, and is ultimately sent to a separate leachate treatment facility (not shown) for purification treatment. The waste disposal facility 1 is decommissioned after the landfill is completed and the waste is stabilized.

[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 to 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 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.

[0016] The water impermeable layer 2 is a layer that blocks water, and may be formed by laying a water impermeable sheet, may be a bentonite layer, may be a layer in which a water impermeable 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. In addition, since waste is piled up in layers in the storage space 3a and disposed of by landfill, the waste layer S is composed 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 water impermeability of the water impermeable layer 2 and is not leaked into the ground 100.

[0017] A plurality 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 a 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.

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

[0019] 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 separating 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 surrounding the gravel layer.

[0020] Next, the leachate collection pit 10 will be described in more detail with reference to Figs. 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 relative to the slope 3b. The framework 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 the 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 is inserted into the water storage structure 11, penetrating the water impermeable 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 is submerged below the liquid level of the leachate in the water reservoir 21 for pumping up the leachate.

[0022] If the pressure in the leachate collection pit 10 is increased by 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 or the like. The air supplied to the waste promotes aerobic reactions by aerobic bacteria in the waste, promoting the stabilization of the waste.

[0023] The passage 13 is cylindrical and extends in a straight line from the water storage structure 11 obliquely 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 goes outward from the storage tank 3, like 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 having a horizontal bottom surface, and one end of the passage 13 is connected to one side of the rectangular parallelepiped, and the lower end of the vertical shaft 17 is 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 so as to cover the 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 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 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).

[0025] In addition, workers can enter and exit the leachate collection pit 10 from the outside through the building 19, and the workers can access the water reservoir 21 by moving through the vertical shaft 17, the connecting structure 15, the passage 13, and the water storage structure 11. The workers can inspect the water reservoir 21, the pump 23, the transfer piping 29, and the like. In addition, a staircase 27 is provided connecting the building 19 to the connecting structure 15 for the movement of the workers. In addition, in the connecting structure 15, a vertically extending space for raising and lowering equipment and the like is secured in 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, the staircase and the above-mentioned slope may be provided in parallel.

[0026] In the leachate collection pit 10 as described above, the passage section 13 and the vertical shaft section 17 have a relatively simple structure, being cylindrical and extending linearly. 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 detail later, an arch culvert 31 (see FIG. 4) is used for the passage section 13, and a box culvert 41 (see FIG. 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 adopted as the arch culvert 31, and a general-purpose box culvert is adopted as the box culvert 41. In contrast, the water storage structure 11 and the connecting structure 15, which have shapes more complicated than those of the passage section 13 and the shaft section 17, are constructed of cast-in-place concrete.

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

[0029] 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. The connection between the arch culverts 31 is performed by a known general-purpose method, such as sandwiching a water-stopping material 33 such as water-stopping rubber between the arch culverts 31 and fastening them with a PC steel rod inserted between the arch culverts 31. The length of each arch culvert 31 may be appropriately set based on, for example, the installation position and lifting capacity of a crane that can be installed at the construction site.

[0030] Among the multiple arch culverts 31 constituting the passageway 13, arch culverts 31 having a different configuration from the others (hereinafter referred to as "arch culverts 31A") are mixed in at a predetermined interval. This arch culvert 31A has anchor bars 39 (anchor parts) protruding in a direction perpendicular to the longitudinal direction of the passageway 13. Specifically, the arch culvert 31A has two rectangular column parts 37 protruding 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 as to extend downward from the lower surface of each rectangular column part 37, two by two.

[0031] 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 using, for example, a resin anchor. The arch culvert 31A may be hung down 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 making it possible to suppress the passage portion 13 during construction from sliding on the support surface 35. All of the arch culverts 31 constituting the passage portion 13 may be arch culverts 31A having the anchor bar 39.

[0032] As shown in Fig. 3, among the arch culverts 31, the arch culverts 31B arranged at both ends of the passage section 13 have one end surface 31t inclined with respect to the extending 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 length in the longitudinal direction of the passage section 13 in order to finely adjust 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.

[0033] [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.

[0034] 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 with PC steel bars inserted between them while a water-stopping material 43 is sandwiched between them.

[0035] [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 lining 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.

[0036] 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 lining concrete 45 of the joint 16j, the lower end face of the lowest box culvert 41 constituting the shaft 17 abuts against the upper end face of the connecting structure 15. Around the corner 47 where the outer wall surface of the box culvert 41 and the upper end face of the connecting structure 15 intersect, a primer application area 49 of a predetermined width is set as shown by a dashed line in the figure. Then, the primer application area 49 is 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 seal materials of the same width, and are stacked 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 cut 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.

[0038] The 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 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 51-53. 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, passage section 13, connecting structure section 15, and shaft section 17 are completed in the manner described above, the ground 100A is formed by backfilling and banking, and the structure of the leachate collection pit 10 is completed in the ground 100.

[0040] Next, the above-mentioned leachate collection pit 10, its construction method, and the effects of the waste disposal facility 1 will be described. Generally, structures constructed using secondary concrete products have higher water-stopping reliability than structures constructed with cast-in-place concrete. That is, since separators remain inside cast-in-place concrete, these separators can become a passage 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.

[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 obtain relatively reliable watertightness. At least a portion (here, the passage 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 passage 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] In addition, if the passageway 13 and the shaft 17 were to be constructed with cast-in-place concrete, the work load would be high because the reinforcing bars, formwork, and concrete pouring would have to be repeated on an unstable sloping ground. Furthermore, the structure and construction sequence of the waterstop would be complicated depending on the concrete pouring lot allocation, and curing would be necessary after pouring the concrete, which could result in a longer construction period. Furthermore, if lifting work or working at heights were required on a narrow sloping ground, this would also place a strain on measures to ensure the safety of the work.

[0043] In contrast, by using a secondary concrete product in 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 can reduce 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 improving safety as a result.

[0044] In addition, in general, a secondary concrete product has a relatively large strength due to a manufacturing process that is not used in cast-in-place concrete, such as steam curing. Therefore, the passage 13 and the shaft 17 constructed with the secondary concrete product have a 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 a complicated shape compared to the cylindrical passage 13 and the shaft 17. Therefore, it would be difficult to construct the water storage structure 11 and the connecting structure 15 with secondary concrete products, and would likely result in higher costs, so they are constructed using cast-in-place concrete. The water storage structure 11 and the connecting structure 15 are constructed on a flat supporting surface, so the labor load is relatively small even if they are constructed using cast-in-place concrete.

[0046] As shown in Fig. 4, by adopting an arch culvert 31 as the secondary concrete product of the passage 13, the passage 13 is more resistant to earth pressure from the ground 100A and waste layer S than when a box culvert is adopted. For comparison, consider an inspection gallery of a dam constructed in 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.

[0047] In contrast, in the leachate collection pit 10, a relatively large earth pressure due to the ground 100A etc. acts on the passage 13, so there is a high need to strengthen the passage 13 compared to the above-mentioned inspection gallery of the dam. 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 appropriately selected according to the earth pressure due to the ground 100A and the waste layer S etc.

[0048] In addition, the arch culverts 31 constituting the passageway 13 are partially mixed with arch culverts 31A having anchor bars 39. As described above, the passageway 13 is provided at an incline, so that the passageway 13 under construction on the support surface 35 generates a force that tries to slide obliquely downward in the longitudinal direction on the support surface 35 due to its own weight. 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 under construction from sliding on the support surface 35.

[0049] In addition, since the passage 13 is inclined, an axial force caused by its own weight acts on the passage 13 itself during construction. Such an axial force is not originally anticipated in the general-purpose arch culvert 31, and may cause a deterioration in quality. However, the presence of the anchor reinforcement 39 reduces such an axial force. Furthermore, even after the leachate collection pit 10 is completed, the presence of the anchor reinforcement 39 suppresses the 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 passage 13, the greater the force that causes the passage 13 to slide as described above. Also, if the inclination of the support surface 35 is large, the arch culvert 31 installed on the support surface 35 during construction is less stable, and construction becomes less easy. Also, if the gradient of the passage 13 is large, the axial force acting on the passage 13 itself due to the weight of the passage 13 as described above also becomes large, which is not preferable. From this point of view, it is necessary to suppress the gradient of the passage 13, and it is preferable to set the gradient of the passage 13 to 20% or less. That is, ultimately, it is preferable to set the gradient of the passage 13 to 0 to 20%.

[0052] In addition, since the passage 13 is linear, general-purpose arch culverts 31 can be connected to each other using a general-purpose method, 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, so the possibility of a decrease in water-stopping performance can be reduced.

[0053] In addition, 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 degree of freedom in designing the equipment (e.g., pumps, passages, piping) provided 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, as the equipment provided inside as described above, an inspection path for inspecting the water reservoir 21, etc., a transport equipment for transporting heavy objects (e.g., the submersible pump 23, etc.), a transport pipe 29 for transporting leachate to the outside, a duct for ventilation and for sending air from the atmosphere to the waste layer S in the storage space 3a through the water collection pipe 6, etc.

[0054] The present invention can be implemented in various forms including the above-described embodiment and 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 each embodiment 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, and may be a waste disposal facility in which the roof 4 is omitted. Moreover, it is not essential that the passage section 13 is provided at an incline, and the passage section 13 may extend horizontally. Moreover, the precast culvert constituting the passage section 13 may be a box culvert instead of the arch culvert 31. Moreover, 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. [Explanation of symbols]

[0056] 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...shaft section, 21...water reservoir section, 31...arch culvert (secondary concrete product), 41...box culvert (secondary concrete product), 39...anchor bars (anchor sections).

Claims

1. A leachate collection pit for collecting leachate generated in a waste disposal facility having a storage tank formed of a bowl-shaped recess dug below the ground surface for storing waste to be disposed of in a landfill and a water impermeable layer applied to the inside of the recess, 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 is located outside the water impermeable layer of the storage tank, and into which the leachate from the storage tank flows and is temporarily stored; a cylindrical passage portion extending linearly obliquely upward from the water storage structure portion toward the outside of the storage tank; A cylindrical shaft portion connected to the passage portion via a connecting structure portion and extending linearly upward from the connecting structure portion to the ground surface, The passage portion, the connecting structure portion, and the vertical shaft portion are constructed underground at a position outside the storage tank relative to the slope, The passage formed in the passage portion is a slope. Leachate collection pit.

2. The leachate collection pit according to claim 1 , wherein the slope of the passage portion is 20% or less.

3. The leachate collection pit according to claim 1 or 2, wherein the shaft portion is constructed using a plurality of concrete preforms connected in series.

4. A leachate collection pit as described in any one of claims 1 to 3, wherein the passage portion is constructed using a plurality of continuously connected concrete prefabricated products, and the water storage structure portion is constructed using cast-in-place concrete.

5. 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 4, 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.

6. A method for constructing a leachate collection pit for collecting leachate generated in a waste disposal facility having a storage tank formed of a bowl-shaped recess dug below the ground surface for storing waste to be disposed of in landfill and a water impermeable layer constructed inside the recess, comprising: 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 is located outside the water impermeable layer of the storage tank, and into which the leachate from the storage tank flows and is temporarily stored; a cylindrical passage portion extending linearly obliquely upward from the water storage structure portion toward the outside of the storage tank; A cylindrical shaft portion is connected to the passage portion via a connecting structure portion and extends linearly upward from the connecting structure portion to the ground surface, The passage portion, the connecting structure portion, and the vertical shaft portion are constructed underground at a position outside the storage tank relative to the slope; The passage formed in the passage portion is a slope. How to construct a leachate collection pit.

7. The method for constructing a leachate collection pit according to claim 6, wherein the slope of the passage portion is 20% or less.

8. The shaft is constructed using a plurality of concrete prefabricated products connected in series; The method for constructing a leachate collection pit according to claim 6 or 7, wherein the vertical shaft portion is constructed after the connecting structure portion is completed.

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