Moisture content adjustment method

Abstract

This invention provides a method for efficiently adjusting the moisture content of soil contained in a flexible container bag. [Solution] A moisture content adjustment method according to one embodiment comprises the steps of: forming pores H extending from the surface S1 of the soil S into the interior of the soil S contained inside a flexible container bag 1; filling the pores H with a water-absorbing modifier 10; and reducing the moisture content of the water W by allowing the modifier 10 to absorb the water W inside the soil S.

Description

Technical Field

[0001] The present disclosure relates to a water content adjustment method for adjusting the water content of soil contained in a flexible container bag.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2016-185539 describes a water removal device that removes water from water removal treatment targets such as earth and sand and sludge containing a large amount of water. The water removal device includes a first flexible container made of a mesh material and a second flexible container that houses the first flexible container. The second flexible container is a bag-shaped packaging material made of a flexible material having a moisture-proof and leak-proof function and airtightness, and is flexible. Further, the water removal device includes a pipe inserted into the second flexible container and a vacuum pump that sucks the water inside the second flexible container through the pipe. When the vacuum pump operates, the water inside the second flexible container and the first flexible container is sucked out.

[0003] Japanese Patent Application Laid-Open No. 2016-206003 describes a water content reduction method for reducing the water content of soil contained in a waterproof storage bag. The storage bag contains soil particles having a specific gravity higher than that of water, radioactive substances, and water. Inside the storage bag, supernatant water is generated on the surface of the soil by the sedimentation of the soil particles and radioactive substances. An absorbent material is arranged at the location where the supernatant water is generated. In this water content reduction method, the absorbent material absorbs and holds the supernatant water, and then the water content of the soil is reduced by removing the absorbent material from the storage bag.

[0004] Japanese Patent Application Laid-Open No. 2020-111384 describes a method for reducing the water content of earth and sand etc. contained in a flexible container bag. This flexible container bag includes a bag body having an opening formed on the side surface and a filter that closes the opening and has water permeability. The water content of earth and sand etc. is reduced by discharging the water inside the bag body through this filter.

[0005] Japanese Patent Publication No. 5887637 describes a method for reducing the volume of water-containing soil. This method uses a strainer pipe that is inserted into the water-containing soil filled in a bag. The strainer pipe has three strainer pipe bodies and a connecting pipe that connects the three strainer pipe bodies to each other. A vacuum pump is provided on the side of the connecting pipe opposite the three strainer pipes. When this vacuum pump is activated, the water contained in the water-containing soil is absorbed and discharged to the outside of the bag. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-185539 [Patent Document 2] Japanese Patent Publication No. 2016-206003 [Patent Document 3] Japanese Patent Publication No. 2020-111384 [Patent Document 4] Patent No. 5887637 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the aforementioned moisture removal device and moisture content reduction method, the moisture content of the soil inside the bag is reduced by sucking out the moisture inside the bag with a vacuum pump. In the aforementioned moisture content reduction method, the moisture content of the soil is reduced by absorbing the supernatant water. In the aforementioned method for reducing the moisture content of soil and other materials contained in flexible container bags, the moisture content is reduced by discharging water from a filter.

[0008] However, in methods such as those described above, where moisture is removed from the bag by suction or other means, post-treatment measures such as preventing water diffusion are necessary if the moisture contains harmful substances. Therefore, it is currently not possible to efficiently adjust the moisture content of the soil contained inside. Furthermore, a method is known in which the flexible container bag containing the soil is torn open, the soil is modified, and then the soil is put back into the flexible container bag. However, this method has the problem that it is not possible to efficiently adjust the moisture content of the soil because it is time-consuming to tear open and put back into the flexible container bag.

[0009] This disclosure aims to provide a method for adjusting the moisture content of soil contained in a flexible container bag, which can efficiently adjust the moisture content of the soil. [Means for solving the problem]

[0010] (1) The moisture content adjustment method according to the present disclosure comprises the steps of forming holes in soil contained inside a flexible container bag that extend from the surface of the soil to a predetermined depth into the soil, filling the holes with a water-absorbing modifier, and reducing the moisture content of the soil by allowing the modifier to absorb moisture from inside the soil, wherein in the step of forming holes, three or more holes are formed, and in the step of reducing the moisture content, the moisture content of the soil contained in the flexible container bag is reduced and the soil hardens.

[0011] (2) In the above (1), the modifier may include an absorbent material which is either a superabsorbent resin or cellulose fiber, and a base material which is either sand, sandy soil, gravelly soil or silty soil.

[0012] (3) In (1) or (2) above, the method for adjusting the moisture content may include a step of determining the hardness of the soil contained in the flexible container bag after the step of reducing the moisture content of the soil.

[0013] (4) In any one of (1) to (3) above, the water content adjustment method may include a step of stirring the soil by collapsing the soil located around the hole in plan view after the step of filling the modifier.

[0014] (5) In any one of (1) to (4) above, in the step of reducing the water content, the hardness of the soil may be increased to make the flexible container bag stand on its own.

[0015] (6) In any one of (1) to (5) above, the modifier may be sprayed on the soil to further increase the hardness of the soil.

Advantages of the Invention

[0016] According to the present disclosure, the water content of the soil contained in the flexible container bag can be efficiently adjusted.

Brief Description of the Drawings

[0017] [Figure 1] It is a perspective view schematically showing a flexible container bag according to an embodiment. [Figure 2] It is a view showing the state in which the flexible container bag of FIG. 1 is lifted. [Figure 3] It is a longitudinal sectional view showing the state in which a perforator is inserted into the soil of the flexible container bag of FIG. 2. [Figure 4] (a) is a longitudinal sectional view showing the state in which holes are formed in the soil of FIG. 3. (b) is a plan view of the soil of FIG. 4(a). [Figure 5] (a) is a longitudinal sectional view showing the state in which the modifier filled in the hole of FIG. 4(a) absorbs the moisture of the soil. (b) is a plan view of the soil and the modifier of FIG. 5(a). [Figure 6] (a), (b) and (c) are longitudinal sectional views showing the steps of the water content adjustment method according to a modification. [Figure 7] It is a longitudinal sectional view showing an example of the steps of the water content adjustment method according to a further modification.

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments of the moisture content adjustment method according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. Also, the drawings may be drawn with some parts simplified or exaggerated for ease of understanding, and dimensional ratios and the like are not limited to those shown in the drawings.

[0019] For example, at a decontamination site, the topsoil of soil containing radioactive substances is removed, and this soil (also referred to as contaminated soil) is stored in impermeable flexible container bags in certain quantities. The flexible container bags for storing the soil may be stored stacked, for example, in a construction yard provided at the decontamination site. The flexible container bags may contain a large amount of water-containing soil. In this case, it is required to increase the hardness of the soil by reducing the moisture content of the soil and make the flexible container bags stand on their own.

[0020] FIG. 1 is a perspective view schematically showing a flexible container bag 1 according to the present embodiment. The flexible container bag 1 is a bag body for storing and transporting soil S. The soil S is, for example, contaminated soil containing radioactive substances. In the present embodiment, the flexible container bag 1 has a bottomed cylindrical shape. However, the shape of the flexible container bag may be, for example, a bottomed rectangular cylindrical shape and is not particularly limited. As an example, the height and diameter of the flexible container bag 1 are 1 m.

[0021] For example, the flexible container bag 1 has impermeability and flexibility. As an example, the flexible container bag 1 is made of polypropylene. For example, the flexible container bag 1 may have a double structure including an inner bag and an outer bag. In this case, the inner bag has flexibility and water permeability and is, for example, made of vinyl. The outer bag, for example, has flexibility and impermeability. The outer bag is composed of chemical fibers such as polyethylene or polypropylene, for example.

[0022] As an example, the flexible container bag 1 has a lower part 2 of the bag body that contains soil S, and an upper part 3 of the bag body located above the lower part 2 and having an opening 3b through which the soil S is exposed. The flexible container bag 1 may also have a lifting belt 4 for lifting the flexible container bag 1.

[0023] Figure 2 is a schematic perspective view showing the state in which the lifting belt 4 of the flexible container bag 1 is being lifted. As shown in Figure 2, the flexible container bag 1 has a belt holding part 5 which is fixed to the upper part 3 of the bag body and has an opening 5b through which the lifting belt 4, which extends in the vertical direction, is inserted. For example, the flexible container bag 1 has a plurality of lifting belts 4 and a plurality of belt holding parts 5.

[0024] For example, the lower end of the lifting belt 4 is fixed to the lower part 2 of the bag, and the lifting belt 4 extending upward from the lower part 2 of the bag is passed through the opening 5b of the belt holding part 5. The portion of the lifting belt 4 that extends upward from the belt holding part 5 is hooked onto the hook F of the lifting device. The flexible container bag 1 can be made upright by being lifted by the lifting device using multiple lifting belts 4. "Upright" refers to the state in which the flexible container bag 1 is standing upright so that the portion of the flexible container bag 1 in which the soil S is exposed (opening 3b) faces upward. The above is an example of the configuration of the flexible container bag 1. However, the configuration of the flexible container bag is not limited to the example described above and can be changed as appropriate.

[0025] In the moisture content adjustment method according to this embodiment, a water-absorbing modifier is used. "Water-absorbing" refers to the property of absorbing moisture. "Having water absorption properties" refers to having the property of absorbing moisture, for example, that the modifier absorbs moisture greater than or equal to the weight (or volume) of the modifier. "Modification" refers to improving the composition (or properties) of the soil. "Modifier" refers to a material that modifies the soil. For example, the modifier includes a water-absorbing material that absorbs moisture from the soil S and a base material that is mixed with the water-absorbing material. "Water-absorbing material" refers to a substance that absorbs moisture from the soil. "Base material" refers to, for example, a material that forms the backbone of the modifier.

[0026] In this embodiment, for example, the water-absorbing material is a superabsorbent polymer. A superabsorbent polymer is a resin that absorbs moisture by osmosis. Since the ion concentration inside the superabsorbent polymer is higher than the ion concentration of moisture contained in the soil, when the superabsorbent polymer comes into contact with the soil, moisture from the soil moves into the inside of the superabsorbent polymer. The superabsorbent polymer is a water-absorbing polymer that retains the absorbed moisture.

[0027] Superabsorbent polymers are used, for example, as sanitary materials in disposable diapers. For example, superabsorbent polymers absorb water up to 80 times their own weight and up to 1000 times their own weight (for example, 200 times). Superabsorbent polymers absorb water (free water) from soil S, reducing the fluidity of soil S and thus improving soil S. For example, superabsorbent polymers are in granular form, or they may swell into a spherical shape when they absorb water. For example, superabsorbent polymers are neutral.

[0028] The superabsorbent polymer includes, for example, one or more superabsorbent polymers selected from polyacrylic acid, polyacrylate salts, partially crosslinked polymer compounds having carboxyl groups or salts thereof, or partially crosslinked polysaccharides. Partial crosslinked polymer compounds having carboxyl groups or salts thereof include polyacrylate crosslinked polymers, poly(vinyl alcohol / acrylate) copolymers (crosslinked polymers), starch-acrylate graft copolymers (crosslinked polymers), and polyvinyl alcohol-polymaleate anhydride graft copolymers (crosslinked polymers). Partial crosslinked polysaccharides include carboxymethylcellulose salt crosslinked polymers, etc.

[0029] Furthermore, the "salt" constituting the superabsorbent resin may include, for example, one or more salts selected from alkali metal salts (sodium salt, potassium salt, lithium salt, etc.), alkaline earth metal salts (calcium salt, magnesium salt, barium salt, etc.), or ammonium salts (quaternary ammonium salt, quaternary alkylammonium salt, etc.). For example, the superabsorbent resin may include one or more superabsorbent resins selected from polyacrylic acid, sodium polyacrylate, or crosslinked sodium polyacrylate. The superabsorbent resin described above can be used in this embodiment.

[0030] The absorbent material may contain cellulose fibers. The cellulose fibers may be fine particles that absorb moisture from the soil. Peat moss, bark, or okara (soy pulp) can be used as cellulose fibers. The main raw material for cellulose fibers is, for example, recycled paper (for example, shredded paper).

[0031] The water-absorbing material may be cement, lime, or a ground improvement material. As cement, for example, water-absorbing cement that absorbs moisture from soil S may be used. As lime, quicklime with high water absorption or paper sludge incineration ash (PS ash) may be used. As a ground improvement material, for example, a water-absorbing soil modifier may be used.

[0032] As described above, in the method for adjusting the moisture content of soil S according to this embodiment, a modifier is used, and various water-absorbing materials can be used as the modifier. For example, when the aforementioned superabsorbent resin is sprinkled onto soil S with the opening 3b of the flexible container bag 1 open, the superabsorbent resin can modify the soil S by absorbing moisture from the soil S.

[0033] However, when superabsorbent resin is applied to soil S from above, a problem may arise where the surface (top) of soil S is modified, but the lower part of soil S is not. On the other hand, a method can be considered in which the flexible container bag 1 containing the soil S is broken open, the soil S is removed into a vessel, and the soil S and superabsorbent resin are mixed inside the vessel. However, this method requires the work of breaking open the flexible container bag 1 and putting the modified soil S back into the flexible container bag 1, and a new flexible container bag 1 is required. Furthermore, a construction yard for storing the soil S is required, and problems may arise in which work is difficult in rainy weather.

[0034] In contrast, the moisture content adjustment method according to this embodiment allows for the overall modification of the soil S and enables efficient work associated with the modification of the soil S. Below, a specific example of the moisture content adjustment method according to this embodiment will be described. First, as shown in Figure 2, the soil S is placed in a flexible container bag 1, and the flexible container bag 1 is lifted upright using a lifting device (step of making the flexible container bag upright).

[0035] The flexible container bag 1 may also be placed upright on a flexible container stand. The flexible container stand is formed in a frame shape by multiple (for example, four) columnar members and multiple beam members that support the columnar members in an upright position. The flexible container bag 1 can be placed upright by placing it inside this frame-shaped flexible container stand.

[0036] Then, as shown in Figure 3, holes H are formed extending from the surface S1 of the soil S into the interior of the soil S (hole formation step). At this time, holes H are formed by pushing a drilling tool T from the surface S1 of the soil S contained inside the flexible container bag 1 into the interior of the soil S.

[0037] The drilling tool T is, for example, rod-shaped. The drilling tool T has an insertion portion T1 at one end in its longitudinal direction, which is inserted into the soil S. The insertion portion T1 tapers towards the end of the drilling tool T in its longitudinal direction; that is, the insertion portion T1 is pointed. The insertion portion T1 is inserted into the surface S1 of the soil S, and the drilling tool T is pushed downwards.

[0038] Figure 4(a) is a longitudinal cross-sectional view showing a hole H formed in the soil S. Figure 4(b) is a plan view showing the soil S in which the hole H is formed. As shown in Figures 3, 4(a), and 4(b), the drilling tool T is inserted into the soil S with the insertion part T1 facing downwards, and the drilling tool T is pushed downwards. The drilling tool T is inserted to a depth of, for example, more than half but no more than 90% of the height A of the flexible container bag 1. Then, the hole H is formed by pulling up the drilling tool T that has been pushed downwards.

[0039] Various types of drilling tools T can be used. In the example above, a drilling tool T having an insertion part T1 was described. However, a drilling tool without an insertion part T1 may also be used. The drilling tool T may be cylindrical (for example, cylindrical or rectangular). For example, the drilling tool T may be a steel pipe (for example, a bottomed cylindrical pipe). The drilling tool T may be made of metal. The drilling tool T may also be made of wood. The drilling tool T may be a wooden stake. The drilling tool T may also be a red and white pole. Furthermore, the drilling tool T may be a drill. As a drill, for example, a hand drill for excavating soil S can be used.

[0040] For example, the diameter Z of hole H is 1.5 cm or more and 5 cm or less (3 cm as an example). The height of hole H is, for example, more than half and 90% or less of the height A of flexible container bag 1. For example, if height A is 1 m, then the height of hole H is 50 cm or more and 90 cm or less.

[0041] For example, multiple pores H are formed in the soil S. These multiple pores H are formed, for example, so as to be aligned along the inner circumference of the flexible container bag 1 in a plan view. For example, the number of pores H formed is between 3 and 10. In this case, three or more pores H are formed at positions that do not lie on a single straight line in a plan view. That is, in a plan view, three or more pores H are formed to form a polygon.

[0042] In the example shown in Figure 4(b), the four holes H are formed to form a quadrilateral shape in plan view. The quadrilateral X formed by the four holes H in plan view is, for example, rectangular (or square). The distance Y between two holes H in plan view is, for example, 20 cm or more and 60 cm or less (for example, 40 cm or 50 cm).

[0043] After forming the pores H, the modifier 10 is filled as shown in Figures 5(a) and 5(b) (process of filling with modifier). The modifier 10 includes the water-absorbing material and base material described above. For example, the water-absorbing material is either a superabsorbent resin or cellulose fiber, and the base material is either sand, sandy soil, gravelly soil, or silty soil. For example, the particle size (average particle size) of the sand is 0.075 mm or more and 2 mm or less. Sandy soil is soil that contains a lot of sand, and as an example, soil that contains 50% or more coarse particles and has a particle size of 2 mm or less. Gravelly soil is soil that contains more than 50% coarse particles and has more gravel than sand. Silty soil is soil that contains detritus that is finer than sand and coarser than clay.

[0044] The water-absorbing material of the modifier 10 is, for example, the superabsorbent polymer mentioned above. The superabsorbent polymer is, for example, in granular form. The particle size of the superabsorbent polymer is, for example, 2 mm or less (or 1 mm or less). For example, the particle size of the superabsorbent polymer is about the same as the particle size of the base material. In this case, the stirring of the superabsorbent polymer and the base material, as described later, can be performed more effectively. The permeability coefficient of the superabsorbent polymer and the permeability coefficient of the base material of the modifier 10 are, for example, both 1.0 × 10⁻⁶. -5 It is (m / s) or greater.

[0045] First, the amount of modifier 10 to be filled is determined (step for determining the amount to be filled). At this time, the water content of the soil S and the liquid limit of the soil S are measured, and the required amount of water absorption is calculated from the measured water content and liquid limit. The liquid limit is the water content that is the boundary value when the soil transitions from a plastic state to a liquid state. As an example, the liquid limit is 46% or more and 50% or less, and the water content of the soil S is adjusted so that the water content is 46% or less.

[0046] For example, 1m 3 If we want to reduce the moisture content of the soil S in the flexible container bag 1 by 5%, the required amount of water to be absorbed is 50 L (liters). Then, the amount of modifier 10 to be filled is determined from the amount of water absorbed. For example, if 1 g of superabsorbent resin absorbs 200 g of water W (the absorption ratio is 200 times), then 250 g of superabsorbent resin will be able to absorb 50 L of water W.

[0047] As described above, for example, the amount of water-absorbing material in the modifier 10 is determined. If the water-absorbing material is a superabsorbent polymer, the amounts of superabsorbent polymer and the base material are adjusted so that the weight ratio of the base material to the superabsorbent polymer is 0.01 or more and 10000 or less (100 as an example) (step of adjusting the amounts of superabsorbent polymer and base material). In the example above, the amount of superabsorbent polymer is determined to be 250g.

[0048] Next, the amount of base material for the modifier 10 is determined. For example, if the weight ratio of the superabsorbent resin to the base material is 1:X (where X is a positive real number, for example 100), then X times the weight of the superabsorbent resin is prepared as base material. Then, the superabsorbent resin and the base material are stirred to produce the modifier 10. As described above, the modifier 10 is produced by mixing the water-absorbing material and the base material. The mixing of the water-absorbing material and the base material is carried out, for example, at the site where the flexible container bag 1 is managed. For example, the mixing of the water-absorbing material and the base material is carried out by stirring with a shovel.

[0049] After preparing the modified material 10 as described above, the prepared modified material 10 is filled into the holes H. For example, the modified material 10 is injected into each of the multiple holes H. Then, the modified material 10 is allowed to absorb the moisture inside the soil S. The modified material 10 filled into the holes H absorbs, for example, the moisture W within a certain range R in a plan view.

[0050] In a plan view, a certain range R exhibits a circular shape. The radius of this range R is, for example, approximately 20 cm. After filling the pores H with the modifier 10 and a certain period of time has elapsed, the moisture content of the soil S decreases due to the absorption of water W by the modifier 10 (the process of reducing moisture content). The aforementioned period of time is, for example, one day.

[0051] For example, after filling with the modifier 10 and waiting for one day, the water content of the soil S contained in the flexible container bag 1 decreases and the soil S hardens. This makes it possible to reliably make the flexible container bag 1 stand upright. After the water content of the soil S has decreased, the hardness of the soil S contained in the flexible container bag 1 is determined (step for determining soil hardness).

[0052] The hardness of soil S is determined, for example, by a soil hardness test (the Yamanaka soil hardness test being one example). In a soil hardness test, the hardness of soil S is measured using a penetration-type soil hardness tester. The soil hardness test may also be performed according to the "Soil Hardness Test Method" of JGS1441, a standard of the Japanese Geotechnical Society.

[0053] Alternatively, the hardness of soil S may be determined by a cone index test. In this case, a cone penetrator is pressed into the soil S, and the cone penetrator measures the penetration resistance of the soil S. The hardness of soil S is determined by measuring its hardness or penetration resistance as described above. The process is terminated when it is determined to be at or above a predetermined hardness. On the other hand, if it is determined that the hardness is not at or above a predetermined hardness, the process is terminated by further reducing the water content of soil S, for example, by increasing the number of holes H and filling more holes H with the modifier 10, or by spraying the modifier 10 onto soil S, thereby further increasing the hardness of soil S.

[0054] Next, the effects and benefits obtained from the moisture content adjustment method according to this embodiment will be described in detail. In this moisture content adjustment method, pores H extending from the surface S1 into the interior of the soil S are formed on the surface S1 of the soil S contained in the flexible container bag 1. A water-absorbing modifier 10 is filled into the pores H. The moisture content of the soil S is then reduced by allowing the modifier 10 filled into the pores H to absorb the moisture W inside the soil S. Therefore, the moisture content of the soil S can be reduced without using a vacuum pump or filter to suck and discharge moisture, and post-treatment is unnecessary, so the moisture content of the soil S contained in the flexible container bag 1 can be reduced efficiently.

[0055] Furthermore, by forming pores H on the surface S1 of the soil S that extend from the surface S1 into the interior of the soil S, and filling the pores H with a water-absorbing modifier 10, moisture W can be absorbed from a wide area of ​​soil S inside the flexible container bag 1. Therefore, moisture W from the soil S can be absorbed more reliably and comprehensively, reducing the moisture content of the soil S, thereby more reliably increasing the hardness of the soil S and enabling the flexible container bag 1 to stand upright. In other words, the high moisture W of the soil S inside the flexible container bag 1 can more reliably prevent the flexible container bag 1 from tipping over, making it easier to transport and manage the flexible container bag 1 containing the soil S.

[0056] In this embodiment, the modifier 10 may include a water-absorbing material which is either a superabsorbent resin or cellulose fibers, and a base material which is either sand, sandy soil, gravelly soil, or silty soil. In this case, by using a superabsorbent resin or cellulose fibers as the water-absorbing material, the absorption of moisture W from the soil S can be made more reliable. Furthermore, by using sand, sandy soil, gravelly soil, or silty soil as the base material, the base material can function as a skeleton, thereby making it possible to more reliably increase the hardness of the soil S.

[0057] In this embodiment, the modifier 10 may be a superabsorbent resin. The moisture content adjustment method according to this embodiment may include a step of adjusting the amounts of superabsorbent resin and base material before the step of filling with the modifier 10, such that the weight ratio of base material to superabsorbent resin is 0.01 or more and 10,000 or less. When the weight ratio of base material to superabsorbent resin is 0.01 or more, the base material can be made to function more reliably as a skeleton. Also, by keeping the weight ratio of base material to superabsorbent resin at 10,000 or less, it is possible to prevent the amount of base material from becoming too large.

[0058] In this embodiment, the water permeability coefficient of the base material is 1.0 × 10 -5 (m / s) or more is also acceptable. In this case, a material with high water permeability can be used as the base material, which further enhances the water absorption of the modifier 10. Furthermore, if the water permeability coefficient of the modifier 10 is 1.0 × 10 -5 The ratio may be (m / s) or higher. In this case, the absorption of moisture W by the modifier 10 can be carried out more quickly. Furthermore, water that has accumulated at the bottom of the flexible container bag 1 may pass through the modifier 10 (base material) and rise to the upper surface. In this case, the amount of water in the flexible container bag 1 can be reduced by absorbing the rising water with an absorbent bag or the like.

[0059] The moisture content adjustment method according to this embodiment may include a step of determining the hardness of the soil S contained in the flexible container bag 1 after the step of reducing the moisture content of the soil S. In this case, since the hardness of the soil S can be determined after the moisture content of the soil S has decreased, the flexible container bag 1 can be made to stand upright more reliably.

[0060] The moisture content adjustment method according to this embodiment may include a step of lifting the flexible container bag 1 with a lifting device to make it upright before the step of forming the holes H. In this case, the holes H are formed with the flexible container bag 1 upright after being lifted by the lifting device. Therefore, the formation of the holes H can be made even easier.

[0061] The moisture content adjustment method according to this embodiment may include a step of measuring the moisture content ratio and the liquid limit of the soil S before filling with the modifier 10, calculating the required amount of water absorbed by the soil S from the moisture content ratio and liquid limit, and determining the amount of modifier 10 to be filled from the amount of water absorbed. In this case, since the amount of modifier 10 to be filled is determined before filling the holes H with the modifier 10, the filling of the modifier 10 and the reduction of moisture content can be carried out more efficiently. In particular, when adjusting the moisture content of the soil S for a large number of flexible container bags 1, the filling of the soil S with the modifier 10 in the flexible container bags 1 can be carried out more efficiently.

[0062] In this embodiment, in the step of forming pores H, three or more pores H may be formed, and these three or more pores H may be formed at positions that do not lie on a single straight line in a plan view. In this case, since the modifier 10 is filled into the three or more pores H formed to form a polygon in a plan view, the hardened soil S can be stabilized more reliably by the absorption of moisture W by each modifier 10 into the soil S. Therefore, the flexible container bag 1 can be made self-supporting more reliably. The base material may include, for example, a water-absorbing material. In this case, the moisture content of the soil S can be reduced even more efficiently. As a specific example, the base material may be a mineral or rock with pores, such as zeolite or perlite. In this case, since the base material adsorbs water and combines the functions of both the modifier and the base material, the moisture content can be reduced more effectively.

[0063] Next, the method for adjusting the moisture content according to the modified example will be described with reference to Figures 6(a), 6(b), and 6(c). Some steps of the method for adjusting the moisture content according to the modified example are the same as some steps of the method for adjusting the moisture content according to the embodiment described above. Therefore, in the following, explanations that overlap with the steps of the method for adjusting the moisture content according to the embodiment described above will be omitted as appropriate.

[0064] First, as shown in Figure 6(a), holes H are formed in the soil S. Next, a portion of the modifier 10 is filled into the holes H. At this time, for example, the modifier 10 is filled into the holes H to a height of 25% or more and 40% or less of the height of the holes H (process of filling with modifier). Then, as shown in Figure 6(b), the soil S located around the holes H in a plan view is broken up and the soil S is stirred (process of breaking up and stirring the soil).

[0065] At this time, for example, the aforementioned drilling tool T is thrust into the surface S1 of the soil S, and the area around the hole H in a plan view is poked with the drilling tool T to break down a part of the wall surface of the hole H. This widens the diameter of the hole H and agitates a part of the soil S. Then, the modifier 10 is injected into the hole H. After the injection of the modifier 10, as shown in Figure 6(c), the wall surface of the hole H is further broken down to expand the hole H and fill the hole H with the modifier 10. After that, as in the embodiment described above, the moisture content of the soil S is reduced by the modifier 10, and the series of steps is completed.

[0066] As described above, the moisture content adjustment method according to the modified form includes a step of breaking up and agitating the soil S located around the holes H in a plan view, after the step of filling with the modifier 10. Therefore, since the soil S is agitated after filling with the modifier 10, the modifier 10 can be distributed more evenly throughout the soil S. Thus, the moisture content of the soil S can be reduced more efficiently, and the flexible container bag 1 can be made to stand upright more reliably.

[0067] The embodiments and modified examples of the moisture content adjustment method according to this disclosure have been described above. However, this disclosure is not limited to the embodiments or modified examples described above, and can be further modified within the scope of the gist described in the claims. That is, the content and order of the steps of the moisture content adjustment method according to this disclosure can be changed as appropriate within the scope of the gist described above. Furthermore, the moisture content adjustment method according to this disclosure may be a method that combines a part of the moisture content adjustment method according to the embodiment with a part of the moisture content adjustment method according to the modified example.

[0068] For example, as shown in Figure 7, the steps of forming the holes H and filling them with the modifier 10 may be performed simultaneously. In this case, for example, instead of the aforementioned drilling tool T, a drilling tool V having an opening V2 formed in the insertion part V1 is used to form the holes H. Specifically, the drilling tool V is inserted into the soil S with the insertion part V1 having the opening V2 facing downwards, and the drilling tool V is pushed downwards.

[0069] For example, the internal space of the drilling tool V is filled with the modifying material 10, and after a hole H of a predetermined depth is formed by the drilling tool V, the drilling tool V is pulled up while the modifying material 10 is discharged from the opening V2 into the hole H. In this way, the drilling tool V may be withdrawn from the hole H and the modifying material 10 may be discharged at the same time as the drilling tool V is discharged into the hole H, thereby filling the hole H with the modifying material 10. Thus, the timing of hole H formation and the timing of filling with the modifying material 10 can be changed as appropriate.

[0070] For example, the above-described embodiment described an example in which the moisture content adjustment method is performed at a decontamination site where the topsoil of soil S containing radioactive material is removed. However, the decontamination site to which the moisture content adjustment method according to this disclosure is applied may be, for example, a wetland or a paddy field, and can be changed as appropriate. Furthermore, the moisture content adjustment method according to this disclosure may be applied to soil other than contaminated soil, and may be applied to sites other than decontamination sites (for example, dredging sites). [Explanation of symbols]

[0071] 1...Flexible container bag, 2...Bottom of the bag, 3...Top of the bag, 3b...Opening, 4...Hanging belt, 5...Belt holder, 5b...Opening, 10...Modifier, F...Hook, H...Hole, R...Certain range, S...Soil, S1...Surface, T...Drilling tool, T1...Insertion part, V...Drilling tool, V1...Insertion part, V2...Opening, W...Moisture, X...Rectangle, Y...Spacing, Z...Diameter.

Claims

1. A step of forming holes in soil contained inside a flexible container bag, the holes extending from the surface of the soil to a predetermined depth into the interior of the soil, A step of filling the aforementioned holes with a water-absorbing modifying material, A step of reducing the water content of the soil by allowing the modifier to absorb moisture from within the soil, Equipped with, In the step of forming the holes, three or more of the holes are formed. In the step of reducing the moisture content, the moisture content of the soil contained in the flexible container bag decreases and the soil hardens. Moisture content adjustment method.

2. The aforementioned modifier includes a water-absorbing material which is either a superabsorbent resin or cellulose fiber, and a base material which is either sand, sandy soil, gravelly soil, or silty soil. The method for adjusting the moisture content according to claim 1.

3. The process includes, after the step of reducing the moisture content of the soil, a step of determining the hardness of the soil contained in the flexible container bag. A method for adjusting the moisture content according to claim 1 or 2.

4. The process includes, after the step of filling with the aforementioned modifying material, a step of breaking up the soil located around the hole in a plan view and stirring the soil. A method for adjusting the moisture content according to claim 1 or 2.

5. In the step of reducing the moisture content, the hardness of the soil is increased to make the flexible container bag self-supporting. A method for adjusting the moisture content according to claim 1 or 2.

6. The soil is further hardened by scattering the soil modifier onto it. A method for adjusting the moisture content according to claim 1 or 2.

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