Backfilling material, its manufacturing method and backfilling method

Abstract

To provide a backfilling material capable of preventing infiltration by rainfall and water inflow during backfilling work, to provide a manufacturing method of the same, and to provide a backfilling method.SOLUTION: A backfilling material 10 which includes a clay-based material having a water-absorbing and swelling property, and a soil-based material includes: a massive material 12 formed by a mixed material in which the clay-based material and the soil-based material are mixed is molded into a massive shape; and a water-proof sheet 14 for covering the massive material 12. The sheet 14 can be a sheet which has biodegradability.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a backfilling material, a method for producing the same, and a backfilling method. [Background technology]

[0002] Conventionally, in underground facilities such as low-level radioactive waste disposal facilities, it has been required to backfill the area around the burial pit with a soil-based material mixed with bentonite (hereinafter referred to as "bentonite-mixed soil") to form a low-permeability layer there (see, for example, Patent Documents 1 and 2).

[0003] Low-level radioactive waste disposal facilities must maintain their functionality (closure function) for a long period of time after backfilling (closure), and it is considered undesirable to backfill the impermeable layer with any material other than bentonite mixed soil in order to maintain and exert its function (impermeability). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-17060 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-193796 Summary of the Invention [Problem to be solved by the invention]

[0005] However, bentonite-mixed soil swells when it comes into contact with water, so it is necessary to prevent infiltration by rainfall, groundwater springs, etc. during backfilling work. One waterproofing measure is to carry out construction while covering the soil with a waterproof sheet, but this makes it difficult to respond to sudden, unpredictable weather changes. Furthermore, while installing a large roof over the facility can prevent infiltration by rainfall, it is difficult to prevent infiltration by groundwater springs.

[0006] The present invention has been made in consideration of the above, and aims to provide a backfilling material that can prevent infiltration by rainfall or spring water during backfilling work, a manufacturing method thereof, and a backfilling method. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the objectives, the backfill material of the present invention is a backfill material containing a clay-based material that has water-absorbing and swelling properties, and is characterized by comprising a mass formed by molding the clay-based material into a mass, and a waterproof sheet covering the mass.

[0008] Another backfill material according to the present invention is characterized in that, in the above-mentioned invention, the lumps are lumps formed by mixing the clay-based material and the soil-based material and molding them into lumps.

[0009] Another backfilling material according to the present invention is characterized in that, in the above-mentioned invention, the sheet is a biodegradable sheet.

[0010] In addition, the method for manufacturing backfill material according to the present invention is a method for manufacturing backfill material containing a clay-based material having water absorption and swelling properties in the above-mentioned invention, and is characterized by having a step of forming the clay-based material into a mass to produce a mass, and a step of covering the mass with a waterproof sheet to produce backfill material.

[0011] In addition, another method for manufacturing backfill material according to the present invention is characterized in that, in the step of producing the lumps in the above-mentioned invention, a mixed material obtained by mixing the clay-based material and the soil-based material is formed into a lump to produce the lumps.

[0012] Another method for producing a backfilling material according to the present invention is characterized in that, in the above-mentioned invention, the sheet is a biodegradable sheet.

[0013] The backfilling method according to the present invention is characterized in that the above-mentioned backfilling material is transported to a backfilling space underground to perform backfilling. [Effects of the Invention]

[0014] According to the backfill material of the present invention, the backfill material contains a clay-based material that absorbs and swells, and includes lumps formed by molding the clay-based material into lumps and a waterproof sheet covering the lumps, so that the waterproof sheet can prevent water from seeping into the lumps inside. Therefore, it is possible to prevent the clay-based material in the lumps from being wetted by rainfall or spring water during transportation of the backfill material or backfilling work.

[0015] Furthermore, according to another backfill material of the present invention, the aggregates are formed by molding a mixture of clay-based material and soil-based material into aggregates, and the waterproof sheet can prevent water from seeping into the aggregates (e.g., bentonite-mixed soil) inside. This has the effect of preventing the clay-based material in the aggregates from being infiltrated by rainfall or spring water during transportation or backfilling work.

[0016] Furthermore, according to another backfill material of the present invention, the sheet is biodegradable, and therefore will eventually decompose and return to the soil due to the action of microorganisms in the surrounding soil and groundwater where it is backfilled. Therefore, waterproofing can be ensured during the backfilling work, and after the backfilling is completed, the sheet will eventually decompose, leaving only the mixed material of clay-based material and soil-based material, which can function as a low-permeability layer.

[0017] Furthermore, according to the method for producing backfill material of the present invention, a method for producing a backfill material containing a clay-based material having water absorption and swelling properties includes the steps of forming the clay-based material into lumps to produce lumps, and covering the produced lumps with a waterproof sheet to produce the backfill material, so that it is possible to provide a backfill material in which the waterproof sheet prevents water from seeping into the lumps inside. Therefore, it is possible to provide a backfill material that prevents the clay-based material in the lumps from being seeped in by rainfall or spring water during transportation or backfilling work.

[0018] Furthermore, according to another method for producing backfill material of the present invention, in the step of producing the lumps, a mixed material obtained by mixing a clay-based material and a soil-based material is formed into lumps to produce the lumps, so that a backfill material can be provided in which a waterproof sheet prevents water from seeping into the internal lumps (e.g., bentonite-mixed soil).This has the effect of providing a backfill material that prevents the clay-based material in the lumps from being seeped in by rainfall or spring water during transportation or backfilling work.

[0019] Furthermore, according to another method for manufacturing backfill material of the present invention, the sheet is biodegradable, and therefore it is decomposed by microorganisms in the surrounding soil and groundwater and returns to the soil. Therefore, waterproofing can be ensured during the backfilling work, and after the backfilling is completed, the sheet will eventually decompose, leaving only the mixed material of clay-based material and soil-based material, which can function as a low-permeability layer.

[0020] Furthermore, according to the backfilling method of the present invention, the above-mentioned backfilling material is transported to the backfilling space underground and backfilled, which has the effect of preventing the clay-based material in the aggregate from becoming infiltrated by rainfall or spring water during the transportation of the backfilling material or the backfilling work. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view showing an embodiment of a backfill material according to the present invention. [Figure 2] FIG. 2 is a flow chart showing an embodiment of the method for producing a backfilling material according to the present invention. [Figure 3] Figure 3 is a conceptual diagram of backfilling work using a crane. [Figure 4] Figure 4 is a conceptual diagram of backfilling work using a forklift. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the backfilling material, the manufacturing method thereof, and the backfilling method according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments.

[0023] (backfill material) First, an embodiment of the backfill material according to the present invention will be described. As shown in FIG. 1, a backfill material 10 according to this embodiment includes a block 12 (lump) and a waterproof sheet 14 that covers the six peripheral surfaces of the block 12.

[0024] The block 12 is a bentonite-mixed soil formed into a rectangular parallelepiped (lump). This bentonite-mixed soil is a mixed material obtained by mixing bentonite (clay-based material) that absorbs and swells with soil-based materials such as gravel. The bentonite-mixed soil has the function of absorbing water and swelling, thereby exhibiting low water impermeability. Note that in this embodiment, a case in which the block 12 is formed into a rectangular parallelepiped shape will be described as an example, but the mass of the present invention is not limited to this and may have any other shape as long as it is lumpy. Also, in this embodiment, a case in which the block 12 is formed of a bentonite-mixed soil will be described as an example, but the mass of the present invention is not limited to this and the mass (block 12) may be formed only of bentonite.

[0025] It is desirable that the sheet 14 be made of a biodegradable sheet. In this way, the sheet 14 covering the block 12 will eventually decompose and return to the soil due to the action of microorganisms in the soil and groundwater surrounding the area where the backfill material 10 is backfilled. The sheet 14 ensures waterproofing during the backfilling work of the backfill material 10. Furthermore, after the backfilling is completed, the sheet 14 will eventually decompose, so the backfill material 10 will consist only of bentonite mixed soil, which is a mixture of bentonite and soil-based materials, and will be able to function as a low-permeability layer in the backfilled area.

[0026] The sheet 14 can be fixed by bonding the sheets together by heat fusion, by attaching it to the surface of the block 12 with an adhesive, or by using a fastener such as a clip. The sheet 14 may also be made up of multiple sheets, and each sheet may be folded and placed on the surface of the block 12. For the same reasons as the sheet 14, it is desirable that the adhesive and fasteners such as clips used be made from a biodegradable material.

[0027] According to the backfill material 10 of this embodiment, a waterproof sheet 14 is placed on the outside of the blocks 12, and the sheet 14 can prevent water from seeping into the internal blocks 12. Therefore, even if rain or spring water occurs during the transportation of the backfill material 10 or during the backfilling work, the resulting water will not seep inside the sheet 14. This can prevent the bentonite-mixed soil of the blocks 12 inside the sheet 14 from becoming wet.

[0028] (Manufacturing method of backfill material) Next, an embodiment of a method for manufacturing a backfill material according to the present invention will be described. As shown in FIG. 2(1), first, two long strip-shaped sheets 14 are prepared and placed on the work floor surface, with each sheet 14 extending in the front-to-back and left-to-right directions and crossing each other in a cross shape. It is preferable to use a sheet 14 that is slightly wider than the width W of the block 12. Alternatively, a rolled sheet may be used. Each sheet 14 is cut from the roll body 14A to the length required to cover the block 12.

[0029] Thereafter, the blocks 12 are placed on the upper surface of the sheet 14 in the cross-intersection area, and the front and rear sides of the blocks 12 are oriented in the front-to-rear direction, and the left and right sides are oriented in the left-to-right direction. Note that the blocks 12 in this embodiment are made by molding bentonite mixed soil into a cubic shape (lump). The shape of the blocks 12 is not limited to a cubic shape, and other shapes are also possible.

[0030] Next, as shown in Figure 2(2), the sheet 14 extending in the front-to-rear direction is folded along the surface of the block 12 and placed so as to cover the front, rear, side and top and bottom surfaces of the block 12. The sheet 14 is preferably attached to the surface of the block 12 with an adhesive.

[0031] Next, as shown in Figure 2 (3), the sheet 14 extending in the left-right direction is folded along the surface of the block 12 and placed so as to cover the left and right side surfaces and the top and bottom surfaces of the block 12. It is desirable to attach the sheet 14 to the surface of the block 12 and the surface of the existing sheet 14 with an adhesive.

[0032] Finally, as shown in Figure 2(4), the sheet 14 is folded one last time onto the front and rear sides of the block 12 and secured with adhesive and fasteners such as clips 16. In this way, the backfill material 10 is obtained, with the six peripheral sides of the block 12 covered with the waterproof sheet 14.

[0033] In the backfill material 10 manufactured according to this embodiment, the waterproof sheet 14 is disposed on the outside of the block 12, and the sheet 14 can prevent water from seeping into the internal block 12. Therefore, even if rain or spring water occurs during transportation of the backfill material 10 or during backfilling work, the resulting water will not seep into the sheet 14. Therefore, it is possible to prevent the bentonite-mixed soil of the block 12 inside the sheet 14 from becoming infiltrated.

[0034] (Backfilling method) Next, embodiments of the backfilling method according to the present invention will be described, taking as examples a method of lowering the material by using a crane and a method of using a forklift.

[0035] [How to lower the product using a crane] As shown in Fig. 3, an underground facility 18 such as a low-level radioactive waste burial facility is disposed in an underground space S. In this embodiment, backfill material 10 is transported by a crane 20 on the ground to a backfill space T around the underground facility 18, and this backfill space T is then backfilled.

[0036] According to this embodiment, the outside of the blocks 12 of the backfill material 10 is covered with a waterproof sheet 14, so that the bentonite-mixed soil of the blocks 12 can be prevented from becoming infiltrated by rainfall or spring water during the transport of the backfill material 10 by the crane 20 or during the backfilling work.

[0037] [Forklift method] As shown in Fig. 4, the backfill material 10 is transported to the backfill space T by a forklift 22. More specifically, as shown in Fig. 4(1), the push-pull plate 24 of the forklift 22 carrying the backfill material 10 is positioned above and in front of the existing backfill material 10. Next, as shown in Fig. 4(2), the push-pull attachment 26 is extended to push out the backfill material 10 on the push-pull plate 24 and place it on top of the existing backfill material 10. By repeating this process, the forklift 22 transports the backfill material 10 to the backfill space T and performs backfilling.

[0038] According to this embodiment, the outside of the blocks 12 of the backfill material 10 is covered with a waterproof sheet 14, so that the bentonite-mixed soil of the blocks 12 can be prevented from becoming infiltrated by rainfall or spring water during the transport of the backfill material 10 by the forklift 22 or during the backfilling work.

[0039] As described above, the backfill material of the present invention is a backfill material containing a clay-based material that absorbs and swells, and includes lumps formed by molding the clay-based material into lumps and a waterproof sheet covering the lumps, so that the waterproof sheet can prevent water from seeping into the lumps inside. Therefore, it is possible to prevent the clay-based material in the lumps from being wetted by rainfall or spring water during transportation of the backfill material or backfilling work.

[0040] Furthermore, according to another backfill material of the present invention, the aggregates are formed by molding a mixture of clay-based material and soil-based material into aggregates, and the waterproof sheet can prevent water from seeping into the aggregates (e.g., bentonite-mixed soil) inside. Therefore, it is possible to prevent the clay-based material in the aggregates from being infiltrated by rainfall or spring water during transportation of the backfill material or backfilling work.

[0041] Furthermore, according to another backfill material of the present invention, the sheet is biodegradable, so that it will eventually decompose and return to the soil due to the action of microorganisms in the surrounding soil and groundwater where it is backfilled. Therefore, waterproofing can be ensured during the backfilling work, and after the backfilling is completed, the sheet will eventually decompose, leaving only the mixed material of clay-based material and soil-based material, which can function as a low-permeability layer.

[0042] Furthermore, according to the method for producing a backfill material of the present invention, a method for producing a backfill material containing a clay-based material having water absorption and swelling properties includes the steps of forming the clay-based material into lumps to produce lumps, and covering the produced lumps with a waterproof sheet to produce the backfill material, so that a backfill material can be provided in which the waterproof sheet prevents water from seeping into the lumps inside.Therefore, a backfill material can be provided that prevents the clay-based material in the lumps from being seeped in by rainfall or spring water during transportation or backfilling work.

[0043] Furthermore, according to another method for producing backfill material of the present invention, in the step of producing the lumps, a mixed material obtained by mixing a clay-based material and a soil-based material is formed into lumps to produce the lumps, so that a backfill material can be provided in which a waterproof sheet prevents water from seeping into the internal lumps (e.g., bentonite-mixed soil).Therefore, a backfill material can be provided that prevents the clay-based material in the lumps from being infiltrated by rainfall or spring water during transportation or backfilling work.

[0044] Furthermore, according to another method for manufacturing backfill material of the present invention, the sheet is biodegradable, and therefore it will eventually decompose and return to the soil due to the action of microorganisms in the surrounding soil and groundwater where it is backfilled. Therefore, waterproofing can be ensured during the backfilling work, and after the backfilling is completed, the sheet will eventually decompose, leaving only the mixed material of clay-based material and soil-based material, which can function as a low-permeability layer.

[0045] Furthermore, according to the backfilling method of the present invention, the above-mentioned backfilling material is transported to the backfilling space underground and backfilled, so that it is possible to prevent the clay-based material in the aggregate from becoming infiltrated by rainfall or spring water during the transportation of the backfilling material or the backfilling work. [Industrial Applicability]

[0046] As described above, the backfill material, its manufacturing method, and backfilling method of the present invention are useful for backfilling the area around a burial pit in underground facilities such as low-level radioactive waste burial facilities to form a low-permeability layer, and are particularly suitable for preventing infiltration by rainfall or spring water during backfilling work. [Explanation of symbols]

[0047] 10 Backfill material 12 Blocks 14 sheets

Claims

1. A backfill material containing a clay-based material having water absorption and swelling properties, The clay material is formed into a lump, and a waterproof sheet is provided to cover the lump. The backfill material is characterized in that the sheet is a biodegradable sheet and is fixed to the surface of the mass using a biodegradable adhesive or fixing device.

2. 2. The backfill material according to claim 1, wherein the lumps are formed by mixing the clay-based material and the soil-based material and molding the mixture into lumps.

3. A method for producing a backfill material containing a clay-based material having water absorption and swelling properties, comprising: The method includes a manufacturing step of forming the clay-based material into a mass to manufacture a mass, and a manufacturing step of covering the mass with a waterproof sheet to manufacture a backfill material, The sheet is a biodegradable sheet, The mass is cubic, The manufacturing steps include: preparing two long strip-shaped sheets wider than the width of the lump, and arranging the two sheets on the work floor surface so that they extend in the front-to-back direction and the left-to-right direction, respectively, in a cross shape; Thereafter, the block is placed on the upper surface of the sheet in the cross-intersecting region, and the front and rear sides of the block are oriented in the front-rear direction and the left and right sides are oriented in the left-right direction; a step of folding the sheet extending in the front-rear direction along the surface of the block, arranging the sheet so as to cover the front, rear, side and top and bottom surfaces of the block, and attaching the sheet to the surface of the block with a biodegradable adhesive; A method for manufacturing backfill material, characterized by the steps of: folding the sheet extending in the left-right direction along the surface of the lump, placing it so as to cover the left and right sides and top and bottom surfaces of the lump, attaching it to the surface of the lump and the surface of the existing sheet with a biodegradable adhesive, and then fixing it to the surface of the existing sheet on the front and back sides of the lump with a biodegradable adhesive and biodegradable fixing devices.

4. 4. The method for producing a backfill material according to claim 3, wherein in the producing step, the clay-based material and the soil-based material are mixed and formed into a mass to produce the mass.

5. A backfilling method comprising transporting the backfilling material according to claim 1 or 2 to a backfilling space underground to perform backfilling.

6. A backfilling method characterized by transporting backfilling material manufactured by the backfilling material manufacturing method described in claim 3 or 4 to a backfilling space underground and backfilling it.

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