JP7633952B2 - Drill hole backfilling device and drill hole backfilling method - Google Patents

Description

The present invention relates to a borehole backfilling device and a borehole backfilling method.

Traditionally, when selecting a disposal site for high-level radioactive waste, drilling surveys are carried out to confirm the geological structure, etc. Boreholes need to be sealed off because they could become a pathway for radiation to migrate when the disposal site is actually operational.

As one of the filler materials used to plug boreholes, the use of bentonite-based materials, which mainly contain bentonite that has the property of swelling when it comes into contact with water, is being considered. From the viewpoint of workability, the use of pellets of bentonite compacted into small particle sizes, or crushed material compacted into a plate and then finely crushed, etc. is also being considered. In the following description, bentonite and/or bentonite-based materials mainly containing bentonite, as well as pellets compacted into small particle sizes and crushed material compacted into a plate and then finely crushed, are collectively referred to as bentonite.

The plugging of a borehole is usually carried out using a device called a dump bailer. Specifically, the dump bailer transports bentonite contained in a container to the plugging point in the borehole, and then opens the discharge port of the container to discharge the bentonite.

The borehole is flooded with groundwater, and as soon as the discharge port of the dump bailer container is opened, the groundwater comes into contact with the bentonite. This causes the bentonite to rapidly swell and clog the discharge port, which may make it impossible to discharge the bentonite into the borehole. Experiments conducted by the inventors have confirmed that when bentonite comes into contact with water, it rapidly swells, causing a blockage in the container's discharge port.

It is also being considered to equip the dump bailer with a mechanism that would forcibly push out the bentonite with strong pressure in the event of such a blockage. However, because dump bailers are designed to fit through narrow boreholes, their internal volume is originally limited. If complex functional parts are placed inside them, the volume required to contain the bentonite will become even more limited. Conversely, if the size of the dump bailer is made larger within the allowable limits, the gap between the inner wall of the borehole and the outer surface of the dump bailer will be narrowed, resulting in problems with the dump bailer's raising and lowering within the borehole.

On the other hand, a method has been considered in which the bentonite is coated in advance with a water-insoluble natural resin to prevent clogging at the container's discharge port. However, this method leaves the coating material, which is an organic impurity, in the area to be blocked in the borehole. If the remaining coating material is decomposed by microorganisms, gas may be generated, which may hinder blocking.

Various fluid transport technologies using containers similar to dump bailers have been proposed. Chemical liquids are used to prevent lost circulation in boreholes drilled for oil and metal exploration. One proposal is to use a cylinder to transport the chemical liquid, lower the cylinder to a specified position, and activate the lifting valve to dissipate the enclosed chemical liquid (see, for example, Patent Document 1). Another method has been proposed in which a cylinder that serves as both a cement bailer and a container for storing measuring instruments is lowered to the bottom of a completed borehole, where the measuring instruments are buried in cement while the cement milk is dispersed (see, for example, Patent Document 2).

Special Publication No. 2-9158 JP 2006-112102 A

However, the above-mentioned conventional technology does not address the problem that when the bentonite comes into contact with groundwater during the plugging of the borehole, it swells rapidly and causes clogging of the container's discharge port. In addition, it is necessary to avoid leaving any coating material, which acts as an organic impurity, at the plugging point in the borehole. If the coating material remains in the ground, it will be decomposed by microorganisms and gas will be generated, which may hinder the plugging of the borehole.

The present invention has been made in consideration of the above, and aims to provide a backfilling device and a backfilling method for a borehole that can reliably discharge a filler material from a container into the borehole without using a coating material.

(1) The present invention, which achieves the above object, is a backfilling device for a borehole that uses bentonite and/or a bentonite-based material that mainly contains bentonite as a filler to backfill a borehole, and includes a cylindrical container made of a double tube of an outer tube and an inner tube, a bag material having a bag-shaped storage section whose end is fixed to the inner surface at the top of the outer tube and which is formed by folding back from the lower opening of the inner tube toward the inner surface of the top at the upper side, a lid that can be opened and closed and located at the lower end of the outer tube, and a filler discharge mechanism that allows the inner tube to be displaced downward relative to the outer tube when the lid is opened when the container is transported to a predetermined position in the borehole, and discharges the filler loaded in the bag-shaped storage section to the outside of the container.

(2) In addition, the bag material in the present invention that achieves the above object may be made of a foldable polyethylene material.

(3) In addition, the inner tube in the present invention that achieves the above object may be made of polyvinyl chloride and the lower opening edge may be deburred.

(4) In addition, the filler discharge mechanism of the present invention that achieves the above object may include a stopper that is disposed in the drilled hole at the predetermined position and that restricts downward movement of only the outer tube.

(5) In addition, the filler discharge mechanism of the present invention that achieves the above object may include a power source that causes the inner tube to move downward relative to the outer tube.

(6) In the present invention that achieves the above object, the borehole may be a borehole provided in a radioactive waste disposal site.

(7) The present invention, which achieves the above object, is a method for backfilling a borehole by using bentonite and/or a bentonite-based material mainly containing bentonite as a filler, the method comprising the steps of: fixing an end of a predetermined bag material to the upper inner surface of the outer tube of a cylindrical container having a double tube with a lid that can be opened and closed at the lower end and an inner tube that is disposed inside the outer tube and has an open lower end; and folding back the bag material from the lower opening of the inner tube toward the inner surface of the top of the inner tube to form a bag-shaped storage section; and forming the bag-shaped storage section by folding back the bag material formed in the bag-shaped storage section forming step. This method of backfilling a borehole includes a loading step of loading the filler into the storage section, a transport step of transporting the container, which is a double tube consisting of the outer tube with the lower end closed by the lid and the inner tube with the filler loaded into the bag-like storage section inside the outer tube, to a predetermined position in the borehole, and a filler discharge step of discharging the filler loaded into the bag-like storage section into groundwater by allowing the inner tube to move downward relative to the outer tube as the lid is opened when the container reaches the predetermined position in the borehole during the transport step.

The present invention provides a borehole backfilling device and a borehole backfilling method that can reliably discharge a filler material from a container into a borehole without using a coating material.

2 is a schematic diagram showing a state in which the cover of the outer pipe in the backfilling device for a borehole according to an embodiment of the present invention is closed; FIG. 2 is a diagram illustrating a state in which the lower end of the outer pipe in the borehole backfilling device of FIG. 1 abuts against a stopper member in a borehole side casing. FIG. 2 is a schematic diagram showing a state in which the borehole backfilling device of FIG. 1 is lowered to a predetermined position in the borehole and the lid of the outer pipe begins to open. FIG. 2 is a schematic diagram showing a state in which the borehole backfilling device of FIG. 1 is lowered to a predetermined position in the borehole, the lid of the outer pipe is opened, the inner pipe is displaced relative to the outer pipe, and the filler material is discharged. FIG. 2 is an enlarged view illustrating a lower end portion of an inner pipe in the borehole backfilling device of FIG. 1 . FIG.

The following describes in detail an embodiment of the present invention with reference to the drawings.

Figure 1 is a schematic diagram showing a state in which the lid of the outer pipe of the backfilling device 1 of the embodiment of the present invention is closed. Hereinafter, the backfilling device 1 of the borehole is abbreviated as the backfilling device 1 as appropriate. Figure 2 is a diagram explaining the state in which the lower end of the outer pipe of the backfilling device 1 abuts against the stopper member in the borehole side casing. Figure 3 is a schematic diagram showing the state in which the backfilling device 1 descends to a predetermined position in the borehole and the lid of the outer pipe begins to open. Figure 4 is a schematic diagram showing the state in which the backfilling device 1 descends to a predetermined position in the borehole, the lid of the outer pipe opens, the inner pipe is displaced relative to the outer pipe, and the filler is discharged. Figure 5 is a diagram explaining an enlarged lower end portion of the inner pipe in the backfilling device 1.

The backfilling device 1 according to an embodiment of the present invention is a device that uses a filler material 3 to backfill a borehole 2 that is drilled vertically from the ground surface. The borehole 2 is, for example, a borehole drilled in a radioactive waste treatment facility, and can reach a depth of approximately 300 m. Its diameter is usually 20 cm or less. The borehole 2 is prevented from collapsing by a casing 4 that is extended to the depth by successively adding metal pipes of a specified length, and the shape of the borehole at the time of drilling is maintained.

The backfilling device 1 has a cylindrical container 7 consisting of a double tube made of an outer tube 5 and an inner tube 6. The outer tube 5 is a metal tube made of stainless steel, for example, with an opening 8 at the lower end and a closed upper bottom 9 at the upper end. A hinge 10 is provided on the edge of the opening 8 at the lower end of the outer tube 5. A lid 11 that can be opened and closed is provided on the opening 8 of the outer tube 5, and rotates around the hinge 10 between a position that closes the opening 8 and a position that opens it.

An end 13 of a flexible bag material 12 is fixed to the inner surface near the upper bottom 9 above the outer tube 5. Meanwhile, the inner tube 6 has an opening 14 that is open at the bottom, and the upper end side of the inner tube 6 is closed at the top, forming a top portion 15. The inner tube 6 is, for example, a so-called PVC pipe made of polyvinyl chloride. The bag material 12 hanging down from the inner surface near the upper bottom 9 of the outer tube 5 is folded back toward the underside of the top portion 15 above the inner tube 6 to form a bag-shaped storage section 16.

The filler 3 is loaded into the bag-shaped storage section 16. The filler 3 is bentonite and/or a bentonite-based material that mainly contains bentonite. The filler 3 is, for example, in the form of roughly almond-shaped pellets, and may be a mixture of different sizes.

The outer tube 5, inner tube 6, bag material 12, and stopper member 19 described later constitute a filler discharge mechanism 17 that allows the inner tube 6 to move downward relative to the outer tube 5 when the lid 11 is opened when the container 7 is transported to a predetermined position within the casing 4 of the borehole 2, thereby discharging the filler 3 loaded in the bag-shaped storage section 16 into the groundwater.

The container 7 is suspended by wires 18 from a lifting device (not shown) installed on the ground at the upper bottom 9 of the outer pipe 5, and moves up and down inside the casing 4 of the borehole 2. A stopper member 19, which is a protruding piece, is provided on the inner circumference near the bottom end of the casing 4. Note that the manner in which the stopper member 19 is provided is merely one example, and as will be described later, the function of the stopper member 19 can be achieved by controlling the wires 18 and the lifting device on the ground, without providing the stopper member 19.

The stopper member 19 protrudes radially from the inner peripheral wall of the casing 4 toward the center, and abuts against the edge of the opening 8 of the outer tube 5 as it descends, restricting the downward movement of the outer tube 5. The lid 11, which was closed as shown in Figure 1, is opened as shown in Figure 3 by an opening/closing mechanism (not shown) that operates in response to the outer tube 5 abutting against the stopper member 19.

The position of the inner tube 6 is not restricted by the outer tube 5. Therefore, when the lid 11 is opened, the inner tube 6 is displaced downward relative to the outer tube 5 due to its own weight as shown in FIG. 4. At this time, the filler 3 is discharged downward due to its own weight from the opening 14 of the released inner tube 6. If the wire 18 is used to move the outer tube 5 upward abruptly for a short distance at the same time that the lower end of the outer tube 5 abuts against the stopper member 19, the discharge of the filler 3 can be promoted. On the other hand, the depth of the outer tube 5 can be controlled by a lifting device on the ground, and the wire 18 can be stopped at the timing when it extends to a depth where the lower end of the outer tube 5 abuts against the stopper member 19, thereby stopping the descent of the outer tube 5. In this case, there is no need to provide a stopper member 19. In this case, the discharge of the filler 3 can be promoted by using the wire 18 to move the outer tube 5 upward abruptly for a short distance after the outer tube 5 stops.

The bag material 12 is a material that is not stretchable, has a predetermined breaking strength, and is flexible enough to be bent easily at the opening 14, which is the outlet of the inner tube 6. For example, polyethylene is suitable for this material. Meanwhile, the periphery of the opening 14 of the inner tube 6 is deburred and the corners are rounded, as shown in Figure 5. Therefore, the bag material 12 can slide smoothly against the periphery of the opening 14 of the inner tube 6 without getting caught, and can deform without resistance.

At the same time that the lid 11 of the outer pipe 5 is opened, groundwater begins to soak the filler 3 from the opening 14 side of the inner pipe 6, and the filler 3 begins to swell. At this point, most of the upper part of the filler 3 is covered by the bag material 12 that constitutes the bag-shaped storage section 16, so it has not yet come into contact with the groundwater (Figure 3). Therefore, as the inner pipe 6 moves downward and the bag-shaped storage section 16 gradually rolls down near the opening 14, the upper part of the filler 3 that is at the rear from the opening 14 side is still free from swelling (Figure 4). Therefore, swelling of the filler 3 does not begin in the part of the bag-shaped storage section 16 located inside the inner pipe 6, and clogging of the filler 3 through the bag material 12 does not occur inside the inner pipe 6.

From this state, the filler 3 descends under its own weight, and as the bag-shaped storage section 16 gradually rolls down and out, the filler 3 swells from the part that has left the bag-shaped storage section 16. At this point, the filler 3 is outside the inner pipe 6, and its swelling does not cause clogging within the inner pipe 6. Therefore, with the backfilling device 1, the entire amount of filler 3 loaded in the bag-shaped storage section 16 can be reliably discharged into the borehole 2 without causing clogging within the inner pipe 6. The discharged filler 3 descends through the groundwater, and backfilling of the area to be blocked within the borehole 2 proceeds.

The filler material 3 itself does not use a coating material that inhibits swelling, so there is no risk of gas generation due to microbial decomposition, which is a concern when this type of coating material remains underground, or of this gas preventing the borehole from being blocked.

As mentioned above, the borehole 2 is, for example, a borehole provided in a radioactive waste treatment facility. Applying the backfilling device 1 of the present invention to such a case will provide a promising solution to an important environmental problem.

The following describes a method for backfilling a borehole, which involves constructing the borehole backfilling device 1 as described above and backfilling the borehole with bentonite as a filler. This method for backfilling a borehole includes a bag-shaped storage section formation process, a loading process, a transport process, and a filler discharge process.

In the bag-shaped storage section formation process, an end 13 of a flexible bag material 12 is fixed to the inner surface above the outer tube 5 of a cylindrical container 7 consisting of a double tube consisting of an outer tube 5 having a lid 11 at the lower end that can be opened and closed, and an inner tube 6 that is placed inside the outer tube 5 and has an opening 14 at the lower end. The bottom side of the bag material 12 with the end 13 fixed in this manner is rolled up and folded back from the opening 14 of the inner tube 6 toward the inner surface of the top part 15 on the upper side to form a bag-shaped storage section 16.

Next, in the loading process, the filler 3 is loaded into the bag-shaped storage section 16 formed in the bag-shaped storage section formation process.

Next, in the transportation process, the container 7, which is made up of a double tube consisting of an outer tube 5 with its lower opening 8 closed by a lid 11 and an inner tube 6 with the filler material 3 loaded into its internal bag-shaped storage section 16, is transported to a predetermined position within the borehole 2.

Next, in the filler discharge process, when the container 7 reaches a predetermined position in the borehole 2 in the above-mentioned transport process, the inner tube 6 is allowed to move downward relative to the outer tube 5 as the lid 11 is opened, and the filler 3 loaded in the bag-shaped storage section 16 is discharged into the groundwater.

According to this method of backfilling a borehole, the entire amount of filler material 3 loaded in the bag-shaped storage section 16 can be reliably discharged into the borehole 2 without causing clogging in the inner pipe 6. The reason why clogging of the inner pipe 6 with the filler material 3 does not occur is as described above with respect to the backfilling device 1. This allows backfilling of the area to be blocked in the borehole 2 to proceed. In addition, since the filler material 3 itself does not use a coating material that inhibits swelling, there is no risk of gas generation due to microbial decomposition, which is a concern when this type of coating material remains in the ground, or of this gas impeding the blocking of the borehole.

The present invention is not limited to the above embodiment, and modifications and improvements within the scope of the present invention are included in the present invention. For example, in the above-mentioned backfilling device 1, when the container 7 reaches a predetermined position in the borehole 2, the inner tube 6 is displaced downward relative to the outer tube 5 by its own weight as the lid 11 is opened. However, a power source that causes the inner tube 6 to be displaced downward relative to the outer tube 5 may be provided. As this power source, for example, a power source that utilizes the space between the lower surface of the upper base 9 of the outer tube 5 and the upper surface of the top part 15 of the inner tube 6 being airtight due to the bag material 12 may be used. That is, it is also possible to provide a small high-pressure nitrogen container in this airtight space, and to use the nitrogen pressure generated when the sealing of the high-pressure nitrogen container is released as the lower end of the outer tube 5 abuts against the stopper member 19 to push down the upper surface of the top part 15 of the inner tube 6 like a piston.

REFERENCE SIGNS LIST 1 Backfilling device 2 Borehole 3 Filling material 4 Casing 5 Outer pipe 6 Inner pipe 7 Container 8 Opening 9 Upper bottom 10 Hinge 11 Lid 12 Bag material 13 End 14 Opening 15 Top portion 16 Bag-shaped storage section 17 Filling material discharge mechanism 18 Wire 19 Stopper member

Claims (7)

A backfilling device for a borehole, which backfills a borehole using bentonite and/or a bentonite-based material mainly containing bentonite as a filler,
A cylindrical container having a double tube including an outer tube and an inner tube;
a bag material having an end portion fixed to an upper inner surface of the outer tube and a bag-shaped storage portion formed by folding back from an opening on a lower side of the inner tube toward an upper inner surface of a top portion of the inner tube;
A freely opening and closing lid disposed at a lower end of the outer tube;
a filler discharge mechanism that allows the inner tube to displace downward relative to the outer tube when the container is transported to a predetermined position within the borehole and discharges the filler loaded in the bag-shaped storage section to the outside of the container when the lid is opened. The backfilling device for a borehole according to claim 1, wherein the bag material is a foldable polyethylene material. The backfilling device for a borehole according to claim 1 or claim 2, wherein the inner pipe is made of polyvinyl chloride and the lower opening periphery is deburred. The backfilling device for a borehole according to any one of claims 1 to 3, wherein the filler discharge mechanism is disposed in the borehole at the predetermined position and includes a stopper that restricts downward movement of only the outer pipe. The backfilling device for a borehole according to any one of claims 1 to 4, wherein the filler discharge mechanism is provided with a power source that causes the inner pipe to move downward relative to the outer pipe. The backfilling device for a borehole according to any one of claims 1 to 5, wherein the borehole is a borehole provided in a radioactive waste disposal site. A method for backfilling a borehole, comprising backfilling the borehole with bentonite and/or a bentonite-based material mainly containing bentonite as a filler, comprising:
a bag-shaped storage section forming step of fixing an end of a predetermined bag material to an upper inner surface of the outer tube of a cylindrical container having a double tube with a lid that can be opened and closed at a lower end and an inner tube that is disposed inside the outer tube and has an open lower end, and folding back the bag material from a lower opening of the inner tube toward an upper top inner surface of the inner tube to form a bag-shaped storage section;
a loading step of loading the filler into the bag-shaped storage portion formed in the bag-shaped storage portion forming step;
a transport process for transporting the container, which is a double-pipe container consisting of the outer pipe whose lower end is closed with the lid and the inner pipe whose bag-shaped storage section is filled with the filler, to a predetermined position in the borehole;
a filler discharge step of discharging the filler loaded in the bag-shaped storage section into groundwater by allowing the inner tube to be displaced downward relative to the outer tube when the container reaches a predetermined position in the borehole in the transport step and opening the lid;
A method for backfilling a borehole, comprising:

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