Seabed landfill method

Abstract

To provide a sea surface landfill method enabling early stage stabilization of a sea surface waste disposal site and a landfill site.SOLUTION: The sea surface landfill method installs an alkaline solidification material in an inside of a shore protection 3, solidifies the alkaline solidification material to form a water shield layer 6 having a certain thickness, and then landfills an inside of the water shield layer 6 with a waste or a landfill material and performs outer drainage of water 8 in a landfill region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for landfilling the sea surface for landfilling a sea surface waste treatment site or a landfill site.

Background Art

[0002] Conventionally, alkaline wastes such as incineration ash and coal ash are often disposed of at sea surface waste disposal sites.

[0003] However, this type of alkaline waste contains a lot of calcium, and the retained water in the waste disposal site where this alkaline waste is introduced often becomes highly alkaline, and highly alkaline leachate is generated with the infiltration of rainwater. Therefore, not only during landfilling but also after the completion of landfilling, water treatment may be required for a long time.

[0004] In particular, from the latter half of the landfilling work, the residual water surface of the pond decreases, that is, the ratio of water to the disposal material decreases, and accordingly, the pH and the chemical oxygen demand (COD) increase rapidly. Therefore, there has been a problem that the load required for water treatment of the discharged water increases.

[0005] Conventionally, as a method for early stabilization, the installation of a collector pipe and covering the landfilled waste with a thick layer of soil have been proposed, but there has been a problem that the amount of disposal is reduced by that much due to the collector pipe and the soil cover.

[0006] On the other hand, in a land-based waste disposal site, a so-called solidification type disposal method has been developed as a method for stabilizing the disposal site at an early stage.

[0007] This solidification type disposal method uses a mixer to mix materials containing incineration ash and fly ash, and then vibrates the material to fluidize the powder, and fills and compresses it. By solidifying the incineration ash and fly ash, the permeability of the landfill ground is reduced and rainwater infiltration is suppressed. Therefore, the water quality of the leachate can meet the landfill closure standards at an early stage.

Prior Art Documents

Patent Document

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in the conventional technology as described above, it is difficult to perform vibration and compaction after dropping the mixed material into water. Therefore, it has been difficult to apply the solidification treatment method to the sea disposal site.

[0010] In addition, when a solidified body made of a material containing incineration ash or fly ash is directly disposed of at a disposal site or landfill site as it is or after being crushed, the voids between the solidified bodies become large, the disposal capacity decreases, and when the solidified body is crushed, problems such as an increase in pH occur.

[0011] Therefore, in view of such conventional problems, the present invention has been made for the purpose of providing a sea reclamation method capable of achieving early stabilization of a sea waste disposal site or landfill site.

Means for Solving the Problems

[0012] The feature of the invention according to claim 1 for solving the above - described conventional problems is a sea reclamation method for reclaiming a reclamation area surrounded by a seawall. In this method, an alkaline solidifying material having a certain fluidity inside the seawall and low water permeability after solidification is placed, and after forming a water - impermeable layer surrounding the inside of the reclamation area having a certain thickness and strength capable of withstanding the water pressure from outside the seawall by solidifying the alkaline solidifying material, the inside of the water - impermeable layer is filled with waste or landfill material, and at the same time, external drainage is performed while leaving internal water to cover all of the water in the reclamation area or the surface of the waste to a certain extent, and the reclamation is performed by lowering the water level inside the water - impermeable layer.

[0013] The feature of the invention according to claim 2 is that, in addition to the configuration of claim 1, the alkaline solidifying material is placed on the inner bottom surface of the revetment to form a bottom water barrier layer.

[0014] The feature of the invention according to claim 3 is that, in addition to the configuration of claim 1 or 2, inside the water barrier layer, a solidified body obtained by mixing cement with incineration ash, coal ash, or fly ash as the waste is filled.

[0015] The feature of the invention according to claim 4 is that, in addition to the configuration of claim 1 or 2, the surface of the waste introduced inside the water barrier layer is covered with a solidified body obtained by mixing cement with incineration ash, coal ash, or fly ash.

[0016] The feature of the invention according to claim 5 is that, in addition to the configuration of claim 1 or 2, cement solidified treated soil or calcia modified soil as the landfill material is filled inside the water barrier layer.

[0017] The feature of the invention according to claim 6 is that, in addition to the configuration of any one of claims 1 to 5, as the alkaline solidifying material, cement solidified treated soil, calcia modified soil, or a solidified body obtained by mixing cement with incineration ash, coal ash, or fly ash is used.

[0018] The feature of the invention according to claim 7 is that, in addition to the configuration of any one of claims 1 to 6, the fluidity is adjusted by adjusting the water addition amount to the alkaline solidifying material.

[0019] The feature of the invention according to claim 8 is that, in addition to the configuration of any one of claims 1 to 7, when filling the inside of the water barrier layer with the external drainage Solidified body no internal water is left, and when filling with ordinary waste, internal water is left to the extent of covering the surface of the ordinary waste.

Advantages of the Invention

[0020] The method for reclaiming the sea surface according to the present invention includes the configuration of claim 1, thereby constructing an impervious layer and enabling stable external drainage of water within the reclamation area, so that it is possible to achieve early stabilization of a sea surface waste disposal site or a landfill site.

[0021] Moreover, in the present invention, by including the configuration of claim 2, it is possible to cope with the case where the bottom is not a water-blocking ground or the case where it is desired to ensure high water-blocking property at the bottom.

[0022] Furthermore, in the present invention, by including the configuration of claim 3, it is possible to suitably landfill waste such as incineration ash, and at the same time, the water permeability is reduced to suppress the penetration of rainwater, and the leachate satisfies the standards of a disposal site, etc. at an early stage, so that it is possible to achieve early stabilization of a sea surface waste disposal site or a landfill site.

[0023] Moreover, in the present invention, by including the configuration of claim 4, even when landfilling general waste, the water permeability is reduced to suppress the penetration of rainwater, and the leachate satisfies the standards of a disposal site, etc. at an early stage, so that it is possible to achieve early stabilization of a sea surface waste disposal site or a landfill site. Also, by using a solidified body, which is waste, as the soil cover for general waste, it is possible to reduce the disposal amount.

[0024] Furthermore, in the present invention, by including the configuration of claim 5, the ground of the landfill site is strengthened and the seepage of water into the ground can be prevented.

[0025] Moreover, in the present invention, by including the configuration of claim 6, the water permeability becomes low after solidification, and a firm water-blocking layer can be formed.

[0026] Moreover, in the present invention, by including the configuration of claim 7, the fluidity can be adjusted according to the input situation, so that the input of the alkaline solidified body becomes easy.

[0027] In addition, in the present invention, by providing the configuration of claim 8, it is possible to reduce the water in the landfill area where water quality management is required during drainage, and reduce the load of water treatment.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0029] Next, embodiments of the sea landfill method according to the present invention will be described based on the examples shown in FIGS. 1 to 6.

[0030] In this embodiment, the case of landfilling the sea waste disposal site 1 will be described as an example. In the figure, reference numeral 1 is the sea waste disposal site, and reference numeral 2 is the impervious ground.

[0031] This sea waste disposal site 1 is formed with a landfill area 4 partitioned by a seawall 3, and waste is put into and landfilled in this landfill area 4.

[0032] The landfill of this marine waste disposal site 1 is first carried out as shown in Fig. 1(a) and Fig. 2. A revetment 3 is formed on the outer edge of the marine waste disposal site 1, a landfill area 4 surrounded by the revetment 3 is formed, backfill stones are put inside the revetment 3, and a backfill layer 5 is constructed.

[0033] The revetment 3 is composed of a sheet pile whose lower end reaches an impervious ground 2, a revetment structure body caisson such as a plurality of caissons and cells with a water-stop structure at the connection part, and a water-stop revetment 3 where the spaces between the structures such as caissons and cells are water-stopped by a water-stop work. The landfill area 4 and the open sea are separated by this water-stop revetment 3. A plurality of revetment structure bodies such as caissons and cells with a water-stop structure at the connection part are arranged in the direction normal to the revetment on the seabed ground and installed. A plurality of revetment structure bodies such as caissons and cells with a water-stop structure at the connection part are arranged in the direction normal to the revetment on the seabed ground and installed. A plurality of revetment structure bodies such as caissons and cells with a water-stop structure at the connection part are arranged in the direction normal to the revetment on the seabed ground and installed.

[0034] The backfill layer 5 is formed in a dike shape having a slope 5a inclined inward by putting backfill stones inside the revetment 3.

[0035] Next, as shown in Fig. 1(b) and Fig. 3, an alkaline solidifying material for the water-stop layer 6 is placed along the backfill layer 5, and this alkaline solidifying material is solidified to form a water-stop layer 6 having a certain thickness.

[0036] The water-stop layer 6 has a thickness of 50 cm or more, and the alkaline solidifying material is placed so that the water permeability coefficient k after solidification is 10 -5 cm / s (10 -7 m / s) or less to exhibit a water-stop performance equivalent to that. Here, the equivalent water-stop performance means that the penetration time is equivalent.

[0037] The alkaline solidifying material is a material having alkaline solidifying characteristics, having a certain fluidity before solidification, and is composed of a material with low water permeability after solidification.

[0038] For this alkaline solidifying material, a solidified body obtained by mixing cement with cement solidified soil, calcia-modified soil, or incineration ash, coal ash, or fly ash is used.

[0039] The solidified body is appropriately formulated by mixing 70 - 80 wt% of incineration ash, 20 - 30 wt% of fly ash or coal ash, and 5 - 10 wt% of cement, adding water thereto and mixing, and ensuring fluidity so that no gaps are generated when it is put into water. Note that the water addition amount is adjusted according to the properties of the material so that fluidity is ensured.

[0040] Furthermore, to this solidified body, if necessary, admixtures such as water reducing agents may be mixed in addition to the above materials.

[0041] The method of mixing the materials constituting the alkaline solidifying material is not particularly limited, and for example, it can be mixed by mixing with a mixer, mixing with a belt conveyor or a vibrating belt conveyor, dropping and mixing, etc.

[0042] Furthermore, this alkaline solidifying material increases fluidity by increasing the water addition amount, facilitating placement in water, and solidifying in a state having a desired permeability coefficient without compaction.

[0043] Before solidifying, the alkaline solidifying material may be placed by a general waste input method such as a one-way pressing method, a slope flow-down method, or direct input from a dump truck, or it may be placed by a tremie pipe, input by a grab bucket, or placed using a pump or the like.

[0044] After the placement of the alkaline solidifying material is completed and the alkaline solidifying material is cured for a certain period to be solidified, a water barrier layer 6 (water barrier wall) having a certain thickness in the shape of a wall surrounding the inside of the landfill area is formed.

[0045] After the water barrier layer 6 is formed, as shown in FIGS. 1(c) to (e) and FIGS. 4 to 6, the water 8 in the landfill area 4 is drained (hereinafter referred to as external drainage), and a solidified body is placed inside the water barrier layer 6 to form alkaline solidifying material landfill layers 7, 7...

[0046] For external drainage, it is desirable to drain while leaving the minimum necessary amount of internal water 8 according to the waste to be put in after the formation of the water barrier layer 6. For example, if solidified bodies are landfilled as waste, there is no need to leave internal water because there is no scattering or odor generation. On the other hand, if ordinary waste is landfilled, it is desirable to leave internal water to the extent that it covers the surface of the discarded ordinary waste for odor and scattering countermeasures.

[0047] Also, external drainage may be carried out after a certain amount of solidified bodies are put in, may be carried out simultaneously with external drainage according to the amount of solidified bodies put in, or drainage of the entire landfill area 4 may be carried out before the solidified bodies are put in. In the figure, reference numeral 9 is a pump for external drainage and reference numeral 8 is a drain pipe.

[0048] In addition, the water barrier layer 6 made of an alkaline solidifying material adds a backup function, that is, a secondary water barrier function, to the water barrier revetment 3, and has a thickness and strength sufficient to withstand the water pressure outside the landfill site so that the revetment 3 does not displace due to the water pressure difference with the outside even when the water level in the landfill area 4 drops due to external drainage.

[0049] Also, in this external drainage, at the initial stage of landfill, the only factor that can cause alkalization is the water barrier layer 6, and since the high alkalization of the internal water does not progress, it can be drained to the outside without passing through surplus water treatment or with slight surplus water treatment.

[0050] On the other hand, when discarding or putting in solidified bodies into the air after external drainage, since there is almost no internal water 8, it can be sequentially put inside the water barrier layer 6 by the same method as the method of putting in waste at a general land disposal site such as a one-way pressing method, a slope flow-down method, or direct input from a dump truck before solidifying.

[0051] In addition, when the water depth at the installation site of the sea waste disposal site is deep, the water pressure during external drainage becomes large, so it is necessary to increase the thickness and strength of the water barrier layer 6 in order to drain the entire amount of internal water 8.

[0052] Therefore, at the initial stage of landfill, not all of the internal water 8 is drained externally, but drainage is carried out within the range where the water barrier layer 6 can withstand the water pressure. As the depth of the internal water becomes shallower due to the input of the solidified body or the like, and the water pressure on the water barrier layer 6 becomes smaller, after draining all of the remaining internal water 8 in the middle or late stage of landfill, the solidified body may be input into the air.

[0053] In addition, since it is drained externally and input into the air, the amount of added water can be reduced, and high-frequency vibration can be applied to the solidified body before solidification by a vibrator or the like held by a heavy machine after placement, and volume reduction can be achieved by vibration and compaction.

[0054] And by sequentially repeating the input of the solidified body inside the water barrier layer 6, a plurality of solidified body landfill layers 7, 7... are sequentially laminated.

[0055] At this time, even when the input of the solidified body on that day is completed, since incineration ash or the like does not scatter, immediate covering soil is not required. Also, accordingly, the volume of waste increases by the amount of covering soil that is not required.

[0056] In addition, each solidified body landfill layer 7, 7... is strengthened by integration to reinforce the landfill ground.

[0057] And when a certain amount is landfilled by the solidified body landfill layers 7, 7..., the remaining part may be landfilled with the solidified body, or other waste may be landfilled.

[0058] In addition, when a certain amount of internal water is retained, as the landfill work progresses, the remaining water surface in the pond 12 decreases, that is, the ratio of water to the disposal material decreases. However, since the solidified body becomes solidified and its water permeability decreases, infiltration of rainwater or the like into the solidified body landfill layers 7, 7... can be suppressed, a rapid increase in the pH or chemical oxygen demand (COD) of the internal water 8 in the pond can be suppressed, and the load on the water treatment of the external drainage is reduced.

[0059] In the method for land reclamation on the sea surface configured as described above, since the solidified body landfill layers 7, 7... with low water permeability are formed inside the water barrier layer 6, it is difficult for rainwater and the like to penetrate into the landfill site, and the leachate can meet the landfill site closure criteria, thereby enabling early stabilization.

[0060] In addition, in the above-described embodiment, an example using a solidified body obtained by mixing cement with incineration ash, incineration ash, coal ash, and fly ash as waste was described with a sea surface landfill site as an example. However, the inside of the water barrier layer 6 may be filled with ordinary waste.

[0061] At that time, when discharging the internal water 8 to the outside, a certain depth of the internal water 8 is retained to cover the surface of the ordinary waste put inside the water barrier layer 6 to prevent odors generated from the waste and the scattering of the waste.

[0062] Also, when ordinary waste is put inside the water barrier layer 6, instead of the covering soil covering the surface, the upper surface of the ordinary waste may be covered with a solidified body obtained by mixing cement with incineration ash, incineration ash, coal ash, and fly ash. In that case, by using the solidified body, which is waste, instead of the covering soil, the amount of waste to be disposed of increases.

[0063] Furthermore, in the above-described embodiment, the case where the seawall 3 is a water barrier seawall 3 was described. However, after forming a non-water barrier seawall 3, a water barrier layer 6 may be formed with an alkaline solidifying material so as to be able to cope with land reclamation.

[0064] Furthermore, in addition to the above-described embodiment, in the construction of the landfill site, cement-solidified treated soil or calcia-modified soil may be filled as landfill materials inside the water barrier layer 6.

[0065] In that case, by sequentially filling the cement-solidified treated soil and calcia-modified soil in the same manner as the landfill layers 7, 7... formed by the solidified body, the cement-solidified treated soil and calcia-modified soil are integrated to strengthen the landfill ground. Also, regarding water permeability, the water permeability is low in the same manner as the landfill layer formed by the solidified body, so it is difficult for rainwater and the like to penetrate into the landfill site.

[0066] When draining after introducing a certain amount of cement-solidified soil or calcia-modified soil, and when performing external drainage simultaneously in accordance with the amount of cement-solidified soil or calcia-modified soil introduced, similar to when forming the water barrier layer 6, the water addition amount is increased to enhance fluidity, facilitate placement in water, and solidify in a state having a desired permeability coefficient without compaction.

[0067] Also, when the bottom is not a water-impermeable ground or when it is desired to ensure high water barrier performance at the bottom, as shown in Fig. 7, a bottom water barrier layer 20 continuous with the water barrier layer 6 may be formed at the bottom of the landfill area 4.

Explanation of Signs

[0068] 1 Sea waste disposal site 2 Impermeable ground 3 Seawall 4 Landfill area 5 Backfill layer 6 Water barrier layer 7 Solidified body landfill layer 8 Water (internal water) 9 Pump 10 Drain pipe 12 Pond

Claims

1. In a method for landfilling a landfill area surrounded by a revetment, an alkaline solidifying material having a certain fluidity and low water permeability after solidification is placed inside the revetment, and the alkaline solidifying material is solidified to form a water barrier layer surrounding the inside of the landfill area having a certain thickness and strength capable of withstanding the water pressure from outside the revetment. After that, the inside of the water barrier layer is filled with waste or landfill material, and external drainage is performed while leaving internal water to cover all of the water in the landfill area or the surface of the waste, and the landfill is performed by lowering the water level inside the water barrier layer. A method for landfilling the sea surface, characterized in that.

2. The method for landfilling the sea surface according to claim 1, wherein the alkaline solidifying material is placed on the inner bottom surface of the revetment to form a bottom water barrier layer.

3. The method for landfilling the sea surface according to claim 1 or 2, wherein a solidified body obtained by mixing cement with incineration ash, coal ash, or fly ash is landfilled as the waste inside the water barrier layer.

4. The method for landfilling the sea surface according to claim 1 or 2, wherein the surface of the waste introduced inside the water barrier layer is covered with a solidified body obtained by mixing cement with incineration ash, coal ash, or fly ash.

5. The method for landfilling the sea surface according to claim 1 or 2, wherein cement-solidified treated soil or calcia-modified soil is landfilled as the landfill material inside the water barrier layer.

6. The method for landfilling the sea surface according to any one of claims 1 to 5, wherein the alkaline solidifying material uses cement-solidified treated soil, calcia-modified soil, or a solidified body obtained by mixing cement with incineration ash, coal ash, or fly ash.

7. The method for landfilling the sea surface according to any one of claims 1 to 6, wherein the fluidity is adjusted by adjusting the amount of water added to the alkaline solidifying material.

8. The method for landfilling the sea surface according to any one of claims 1 to 7, wherein in the case of landfilling the inside of the water barrier layer with a solidified body, no internal water is left, and in the case of landfilling with ordinary waste, internal water is left to cover the surface of the ordinary waste.

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