JP7643288B2 - Backfilling material manufacturing method, cavity backfilling method, backfilling material manufacturing device, and backfilling device - Google Patents

Description

The present invention relates to a method for manufacturing a backfilling material containing large-diameter granular materials and small-diameter granular materials, a method for backfilling a cavity by filling it with a backfilling material manufactured by the backfilling material manufacturing method, a backfilling material manufacturing device, and a backfilling device.

For example, a proposed deep underground repository for high-level radioactive waste will have all of the spaces, such as access tunnels, connecting tunnels, and main tunnels, excavated from above ground for construction and operation purposes, backfilled to their original state upon closure of the repository, in order to prevent leakage of leachate and ensure the mechanical safety of the repository. Bentonite mixed soil is being considered as a material to be used to backfill these tunnels.

Bentonite-mixed soil is widely used in sites where high water-proofing performance is required, such as in containment works for general waste and contaminated soil, and in foundation ground works for structures. For example, in Patent Document 1, bentonite-mixed soil is used as the material for the impermeable layer formed at the bottom and on the slopes of a facility where waste is disposed of.

Specifically, on the slopes of the facility, bentonite and water are mixed and stirred with excavated soil and other base materials to produce a bentonite mixture, which is then sprayed onto the ground as a spraying material to form an impermeable layer. On the other hand, on the bottom of the facility, the base material, bentonite and water are mixed and stirred, then granulated to produce a granulated material, which is then spread out and compacted to form an impermeable layer.

JP 2016-87579 A

As disclosed in Patent Document 1, spraying of bentonite-mixed soil and spreading and compacting of granulated material mainly made of bentonite are suitable for covering the slopes and bottom of a facility with an impermeable layer. However, neither of these construction methods is suitable for filling a long, large-capacity backfill space such as the tunnel described above with bentonite-mixed soil.

In this situation, a method that can be considered is to use a screw feeder (screw conveyor) that is used as an earth removal device for earth pressure shields to transport the bentonite mixed soil to the tunnel and backfill it. By using a screw feeder, not only can large amounts of bentonite mixed soil be transported continuously, but the bentonite mixed soil can also be handled without adding water.

However, because the particle size of the base material and the bentonite in bentonite-mixed soil differs greatly, the base material and the bentonite can easily separate and deteriorate in quality due to various factors, such as transportation in a dry state, mechanical vibrations during transport by a screw feeder, and even when the soil falls after being discharged from the screw feeder. If this type of degraded bentonite-mixed soil is filled into the backfill space, it may not be able to fully demonstrate the permeability performance expected at the time of design.

The present invention has been made in consideration of these problems, and its main objective is to produce a backfill material that is a uniform mixture of large-diameter granular material and small-diameter granular material in a dry state, and to use the produced backfill material to backfill cavities uniformly and efficiently.

To achieve this objective, the method for producing backfill material of the present invention is characterized in that large-diameter granular material and small-diameter granular material are transported separately by a screw feeder, and at the destination, the small-diameter granular material is filled into the gaps between the large-diameter granular material dropped from the screw feeder to produce backfill material.

The method for manufacturing backfill material of the present invention is characterized in that the backfill material is a bentonite mixed soil, the large-diameter granules contain gravel, and the small-diameter granules contain bentonite.

According to the method for producing backfill material of the present invention, large-diameter granules and small-diameter granules are transported separately by a screw feeder, and the small-diameter granules are dropped at the destination, filling the gaps between the large-diameter granules. This makes it possible to continuously produce high-quality backfill material in which large-diameter granules and small-diameter granules in a dry state are mixed uniformly without being affected by mechanical vibrations caused by the screw feeder. In addition, when using bentonite mixed soil as backfill material, it can be produced in a dry state, which eliminates the need for cumbersome work such as adjusting the amount of water added, and it is easier to handle during construction compared to bentonite mixed soil that has been adjusted by adding water.

The method for backfilling a cavity of the present invention is a method for backfilling a cavity in the ground with the backfilling material produced by the method for producing backfilling material of the present invention, characterized in that the large-diameter granular material and the small-diameter granular material are transported toward the cavity, and the cavity is filled while the backfilling material is produced in the cavity.

The method for backfilling a cavity of the present invention is characterized in that the backfilling material is continuously produced while the discharge port of the screw feeder is buried in the previously produced backfilling material.

According to the method for backfilling a cavity of the present invention, the manufacturing process of the backfilling material can be omitted, and the cavity can be backfilled while the backfilling material is being manufactured in the cavity, which makes it possible to significantly improve the work efficiency of the backfilling work. In addition, by first burying the discharge outlet of the screw feeder in the backfilling material that fills the cavity, these can be compressed by the backfilling material that is manufactured later. This compacts the backfilling material that fills the cavity, making it possible to omit the work of rolling and compacting that is generally carried out separately.

The method for backfilling a cavity of the present invention is characterized in that the density of the backfilling material for the cavity is evaluated, and when a preset density is reached, the production of the backfilling material is stopped.

The method for backfilling a cavity of the present invention is also characterized in that the cavity is a tunnel in a waste disposal site.

The method for backfilling a cavity of the present invention allows the backfilling material in the cavity to be compacted to a preset density, and also makes it possible to prevent the screw feeder from being overloaded and breaking down. In addition, if the cavity is a tunnel, by repeating the process of stopping the production of backfilling material, then retracting the screw feeder and restarting the production of backfilling material, it is possible to continuously provide backfilling material compacted to a uniform density along the longitudinal direction of the tunnel.

This makes it possible to backfill the tunnel with backfill material uniformly over its entire length, even when the planned backfilling range of the tunnel is long. On the other hand, if it is necessary to produce backfill material with a different mix due to changes in the properties of the surrounding rock mass along the way within the planned backfilling range of the tunnel, backfill material with a changed mix can be easily produced without interrupting the backfilling work by appropriately adjusting the supply amount of large-diameter granular material and small-diameter granular material opened and closed to the screw feeder. In this way, it is also possible to continuously backfill the tunnel while appropriately adjusting the mix of the backfill material in response to changes in the surrounding rock mass.

The backfilling material manufacturing device of the present invention is a backfilling material manufacturing device used in the backfilling material manufacturing method of the present invention, and is characterized in that it is equipped with the screw feeder and hopper, and the storage sections for storing the large diameter granular material and the small diameter granular material are arranged in pairs on either side of a partition member provided inside the hopper, and opening and closing gates that are alternately opened are installed at the bottom of the pair of storage sections.

The backfilling material manufacturing device of the present invention is a backfilling material manufacturing device used in the backfilling material manufacturing method of the present invention, and is characterized in that it includes the screw feeder and a hopper, two screw feeders are arranged in parallel with a gap in the height direction, and each discharge outlet is arranged with a position offset in the axial direction, a small diameter storage section for storing the small diameter granular material is provided in the hopper provided on the screw feeder located above, and a large diameter storage section for storing the large diameter granular material is provided in the hopper provided on the screw feeder located below.

According to the backfilling material manufacturing device of the present invention, backfilling material can be manufactured at the destination by simply storing large-diameter and small-diameter granules in the hopper, so there is no need to install a separate facility such as a plant for manufacturing backfilling material on-site. In addition, by appropriately changing the amount of large-diameter and small-diameter granules supplied to the screw feeder, it is possible to easily manufacture backfilling material with different compositions.

The backfilling device of the present invention is a cavity backfilling device that fills cavities in the ground with backfilling material, and is characterized by comprising the backfilling material manufacturing device of the present invention and an evaluation means for evaluating the density of the backfilling material filled in the cavity.

The backfilling device of the present invention can handle a series of tasks related to backfilling construction, including manufacturing the backfilling material, transporting and filling the cavity, compacting the backfilling material filled in the cavity, and managing the finished shape. This makes it possible to improve the efficiency of backfilling construction, contributing to reducing construction costs and shortening construction time. Furthermore, by further installing equipment for supplying large-diameter granular material and small-diameter granular material, it is possible to automate the backfilling construction.

According to the present invention, it is possible to produce backfill material that is a uniform mixture of large-diameter and small-diameter granules in a dry state, and to use the produced backfill material to backfill cavities uniformly and efficiently.

1 is a diagram showing an outline of a high-level radioactive waste disposal site in an embodiment of the present invention. FIG. 1 is a diagram showing a backfilling material manufacturing apparatus according to an embodiment of the present invention (part 1). FIG. 2 is a diagram showing a backfilling material manufacturing apparatus according to an embodiment of the present invention (part 2). FIG. 2 is a diagram showing a backfilling device according to an embodiment of the present invention. FIG. 1 is a diagram showing the procedure for backfilling an access tunnel in an embodiment of the present invention (part 1). FIG. 2 is a diagram showing the procedure for backfilling an access tunnel in an embodiment of the present invention (part 2). FIG. 1 is a diagram showing a scattering-type RI densitometer according to an embodiment of the present invention. FIG. 13 is a diagram showing how to evaluate the density of a backfill material in an embodiment of the present invention.

The present invention uses a screw conveyor to transport large and small dry granular materials separately, then drops them into the cavity to which they are transported, continuously producing a high-quality backfill material in which they are evenly mixed, backfilling the cavity homogeneously and efficiently.

Below, we will take the case of backfilling an access tunnel to a high-level radioactive waste disposal site with backfilling material as an example, and explain the backfilling material manufacturing method, the backfilling method for cavities, the backfilling material manufacturing device, and the backfilling device with reference to Figures 1 to 8.

In this embodiment, the threshold for large and small granular matter is a particle size of 2 mm, and granular matter exceeding the threshold is classified as large granular matter, while granular matter below the threshold is classified as small granular matter. However, the threshold is not limited to a particle size of 2 mm and can be changed as appropriate. In addition, when the large and small granular matter include soil material, the dry state includes not only the bone dry state, but also the air-dry state and the surface dry state.

<<<<High-level radioactive waste disposal site>>>>
As shown in Fig. 1(a), a disposal site 10 for high-level radioactive waste planned deep underground comprises a disposal tunnel 11, a connecting tunnel 12 that connects to the disposal tunnel 11, and an access tunnel 13 that extends from the connecting tunnel 12 to the ground. During operation, waste is transported to the disposal tunnel 11 using the access tunnel 13 and the connecting tunnel 12, and the waste is appropriately treated and disposed of in the disposal tunnel 11.

When closing the disposal site 10, the disposal tunnels 11 and the access tunnels 12 are filled with a filling material and closed with plugs or the like to prevent the filling material from moving or flowing out. The access tunnels 13 are closed evenly with backfill material M, returning them to their original state before excavation. The backfill material M is required to have low permeability similar to that of the surrounding rock mass, and to have self-sealing properties that allow it to close the access tunnels 13 evenly and blend in with the surrounding rock mass without creating gaps. For this reason, bentonite mixed soil is used as the backfill material M.

The bentonite-mixed soil is produced on-site, using on-site generated soil as the base material, and mixing this base material with a mixture amount of bentonite designed based on the results of laboratory tests, etc., to ensure the desired water-proofing performance. Since the high-level radioactive waste disposal site 10 will be located in stable bedrock deep underground, there are plans to select excavated waste from this bedrock as the base material. The backfill material M for the access tunnel 13 is produced by mixing gravel M1 obtained by crushing the excavated waste and adjusting the grain size as described above, with fine grained matter M2 containing bentonite, as shown in Figure 1(b).

Gravel fraction M1 is adjusted to a particle size of about 2-75 mm and classified as large-diameter granules. Fine fraction M2 contains bentonite and is adjusted to a particle size of 2 mm or less and classified as small-diameter granules. Fine fraction M2 may be bentonite only, or may contain other soil materials such as sand as long as the particle size is about 2 mm or less. Bentonite-mixed soil may contain not only gravel fraction M1 and fine fraction M2, but also bentonite granules with a particle size exceeding 2 mm. In this case, gravel fraction M1 and bentonite granules are classified as large-diameter granules, and fine fraction M2 is classified as small-diameter granules.

When producing the bentonite mixture, a backfilling material production device MD is used, which can transport the gravel portion M1, which is classified as large-diameter granules, and the fine-grained portion M2, which is classified as small-diameter granules, separately to a predetermined position in the access tunnel 13, as shown in Figure 2, and drop the fine-grained portion M2 at the destination to fill the gaps in the gravel portion M1.

In this way, it becomes possible to continuously produce high-quality bentonite in the access tunnel 13, in which the gravel fraction M1 and the fine-grained fraction M2 are uniformly mixed, without being affected by mechanical vibrations caused by the screw feeder. In addition, because the bentonite mixture can be produced in a dry state, it is possible to omit cumbersome work such as adjusting the amount of water added, and the bentonite mixture can be handled more easily during construction than when adjusting the amount of water added.

The backfill material manufacturing device MD for manufacturing the backfill material M will be described in detail below, taking as examples a case where two screw feeders 20 are used and a case where one screw feeder 20 is used. In this embodiment, a bentonite mixed soil consisting of gravel M1 and fine grain M2 as shown in FIG. 1(b) will be taken as an example of the backfill material M, but the backfill material M that can be manufactured by the backfill material manufacturing device MD is not limited to the above-mentioned bentonite mixed soil. Any backfill material M can be used as long as it can be manufactured by mixing and stirring large-diameter granular material and small-diameter granular material.

<<<<<Backfilling material manufacturing equipment MD>>>>
<<When two screw feeders 20 are used>>
As shown in Figures 2(a) and (b), the backfilling material manufacturing device MD is equipped with two screw feeders 20 (an upper screw feeder 20a and a lower screw feeder 20b) and a hopper 30 installed on each of the screw feeders 20.

The screw feeder 20 is of the shafted type and includes a shaft 21 and a screw blade 22 attached around the shaft 21. As shown in the plan view of FIG. 2(b), a motor 23 for rotating the shaft 21 is provided at one end of the shaft 21, and the shaft 21 and the screw blade 22 are contained within a trough 24. A hopper 30 is installed on the side of one end of the trough 24 adjacent to the motor 23, and a discharge port 241 is provided at the other end for discharging the material conveyed by the rotation of the shaft 21 and the screw blade 22.

As shown in FIG. 2(a), the hopper 30 comprises a hopper body 31 and an opening/closing gate 32 provided at the connection with the screw feeder 20. By adjusting the opening of the connection with the opening/closing gate 32, the amount of material supplied from the hopper body 31 to the screw feeder 20 can be freely adjusted. The opening/closing gate 32 does not necessarily have to be a sliding type, as long as the opening can be adjusted.

Two screw feeders 20 equipped with hoppers 30 of this configuration are arranged in parallel in the height direction with a gap between them, and each discharge outlet 241 is arranged with a position offset in the axial direction. In addition, a small diameter storage section 312 is formed in the hopper body 31 of the hopper 30 installed in the upper screw feeder 20a, and a large diameter storage section 311 is formed in the hopper body 31 of the hopper 30 installed in the lower screw feeder 20b.

As a result, when the motors 23 provided on each of the two screw feeders 20 are operated to operate the backfilling material manufacturing device MD, the fine grain fraction M2 transported to the upper screw feeder 20a and dropped from the discharge port 241 can be dropped toward the gravel fraction M1 transported to the lower screw feeder 20b and discharged from the discharge port 241. Then, the fine grain fraction M2 enters and fills the gaps in the gravel fraction M1, and backfilling material M in which the gravel fraction M1 and the fine grain fraction M2 are mixed uniformly can be produced without mixing and stirring.

<<When one screw feeder 20 is used>>
The backfilling material manufacturing device MD may include only one screw feeder 20 having a hopper 30 installed therein, as shown in Fig. 3. In this case, the configuration of the hopper 30 is different from that in the case where the above-mentioned two screw feeders 20 are used.

The hopper 30 comprises a hopper body 31 and opening/closing gates 32a, 32b, and a partition member 313 is erected inside the hopper body 31. This divides the inner space of the hopper body 31 into two, with a large diameter storage section 311 formed on one side and a small diameter storage section 312 formed on the other side. In addition, the opening/closing gates 32a, 32b provided at the connection between the hopper body 31 and the screw feeder 20 are linked together so that when one is opened, the other is closed.

Therefore, when the backfilling material manufacturing device MD is operated and the opening/closing gate 32a on the large diameter storage section 311 side and the opening/closing gate 32b on the small diameter storage section 312 side are alternately opened and closed, the gravel portion M1 and the fine grain portion M2 are alternately transported to the screw feeder 20 and dropped from the discharge outlet 241. This allows the operation of dropping the fine grain portion M2, which has been transported to the screw feeder 20 and dropped from the discharge outlet 241, toward the gravel portion M1, which has been transported to the screw feeder 20 and dropped from the discharge outlet 241, can be continuously performed.

Then, the fine grains M2 penetrate and fill the gaps in the gravel portion M1, and backfill material M can be produced in which the gravel portion M1 and the fine grains M2 are evenly mixed without mixing and stirring. In addition, the opening degree of each of the opening and closing gates 32a, 32b is adjustable when the connection is opened, and the supply amount of each of the gravel portion M1 and the fine grains M2 supplied to the screw feeder 20 can be freely adjusted.

As described above, each backfilling material manufacturing device MD can manufacture backfilling material M in the access tunnel 13 to which it is transported simply by supplying gravel M1 and fine-grained material M2 to the hopper 30. This makes it possible to omit the process of manufacturing backfilling material M in a separate plant or the like installed on-site, as is commonly done in backfilling construction.

In addition, by appropriately adjusting the opening of the opening/closing gates 32, 32a, and 32b, the supply amount of gravel portion M1 and fine grain portion M2 to the screw feeder 20 can be appropriately changed. This makes it possible to easily manufacture backfill material M with different compositions continuously without stopping the backfill material manufacturing device MD.

<<Backfilling device BD>>
As shown in Fig. 4, the backfilling device BD includes a traveling body 40 on which the backfilling material manufacturing device MD is mounted, a material supply vehicle 50, a density evaluation means 60, and a protective plate 70. Fig. 4 shows an example in which the backfilling material manufacturing device MD equipped with two screw feeders 20 is mounted on the traveling body 40.

The running body 40 is equipped with a backfilling device BD, and is equipped with a vehicle body 42 equipped with crawlers 41, a slide base 43 slidably mounted on the upper surface of the vehicle body 42, and a support base 44 installed on the slide base 43. The support base 44 supports two screw feeders 20. In addition, a reaction force receiving member 45 is interposed between the rear side of the slide base 43 and the rising portion of the vehicle body 42. The reaction force receiving member 45 suppresses the screw feeder 20 from moving backward on the vehicle body 42 via the slide base 43.

The slide base 43 and the reaction force receiving member 45 function effectively when compacting the backfill material M in the access tunnel 13. In other words, when the backfill material M is continuously produced and discharged while the discharge port 241 of the screw feeder 20 is submerged in the previously produced backfill material M, the density of the backfill material M in the access tunnel 13 increases. Furthermore, as the screw feeder 20 continues to discharge the backfill material M, the screw feeder 20 exhibits a behavior of retreating via the slide base 43, but this is resisted by the vehicle body 42 equipped with the crawler 41 via the reaction force receiving member 45. As a result, the backfill material M in the access tunnel 13 is pressed by the newly produced backfill material M, making it possible to compact the backfill material M.

The material supply vehicle 50 is positioned behind the screw feeder 20 and the running body 40, and is equipped with a soil bin 51, a bucket 52, and a fine-grain separation bin 53, all of which, together with the running body 40, are configured to be freely movable within the access tunnel 13.

The soil tank 51 contains gravel M1, and as it moves above the bucket 52, it drops the gravel M1 from its bottom into the bucket 52. The bucket 52 is provided with a transport device 521 such as a screw conveyor, and the gravel M1 is dropped into the hopper 30 of the lower screw feeder 20b via the transport device 521. The fine particle separation tank 53 contains fine particle M2 and is provided with a transport device 531 such as a screw conveyor. As a result, the fine particle M2 is dropped into the hopper 30 of the upper screw feeder 20a via this transport device 531.

The density evaluation means 60 is equipment provided to evaluate the density of the backfill material M filling the access tunnel 13 and to prevent the screw feeder 20 from being overloaded and breaking down. Figure 4 shows an example in which an RI density meter 62 is installed near the discharge outlet 241 of the lower screw feeder 20b. Figure 3 shows an example in which a compression load cell 61 is installed on the reaction force receiving member 45 of the traveling body 40 as the density evaluation means 60. The density evaluation means 60 will be described in detail later.

As shown in FIG. 4, in this type of backfilling device BD, a protective plate 70 that blocks the cross section of the access tunnel 13 is provided on the traveling body 40 to prevent the backfilling material M filling the access tunnel 13 from collapsing and the fine particles M2 dropped from the upper screw feeder 20a from scattering. Note that the protective plate 70 does not necessarily have to be installed.

When backfilling work is carried out using a backfilling device BD equipped with the above-mentioned backfilling material manufacturing device MD, a series of tasks related to backfilling work using backfilling material can be covered, including the production of backfilling material, transporting and filling it into the access tunnel 13, compaction, and even as-built management. The procedure for backfilling the access tunnel 13 using the above-mentioned backfilling device BD is described below.

<<<<How to backfill the cavity>>>>
<<When one screw feeder 20 is used>>
First, as shown in Fig. 5(a), a backfilling device BD is installed at a predetermined position in the access tunnel 13, and then the gravel portion M1 and the fine grain portion M2 are supplied from the material supply vehicle 50 to the large diameter storage section 311 and the small diameter storage section 312 of the hopper 30, and the screw feeder 20 is operated and the opening/closing gates 32a, 32b are alternately opened and closed. The time interval and opening degree of the opening/closing gates 32a, 32b are preset so that the gravel portion M1 and the fine grain portion M2 are alternately supplied to the screw feeder 20 in the designed blending amount.

Then, the gravel portion M1 and the fine grain portion M2 dropped into the large diameter storage section 311 and the small diameter storage section 312 of the hopper 30 are alternately supplied to the screw feeder 20 and continuously transported toward the discharge outlet 241. Then, when the gravel portion M1 and the fine grain portion M2 are alternately dropped from the discharge outlet 241 into the access tunnel 13, backfill material M is continuously produced.

When backfill material M is continuously produced in the access tunnel 13, the discharge port 241 of the screw feeder 20 is buried in the backfill material M, as shown in FIG. 5(b). In this state, the transport of the gravel portion M1 and the fine-grained portion M2 continues, filling the access tunnel 13 with backfill material M while increasing the density of the filled backfill material M. As described above, when the density increases, the newly produced backfill material M presses against the backfill material M filling the access tunnel 13, gradually compacting it.

In this way, the work of producing and filling the backfill material M in the access tunnel 13 is carried out while evaluating the density of the backfill material M by comparing the output value acquired by the density evaluation means 60 with a preset evaluation criterion. The evaluation criterion is set for each density evaluation means 60 used in accordance with the desired density, and when the evaluation criterion is reached, the backfilling device BD is stopped, i.e., the production of the backfill material M is stopped. This makes it possible to compact the backfill material M in the access tunnel 13 at the desired density, and also makes it possible to prevent the screw feeder 20 from becoming overloaded and breaking down.

After this, as shown in FIG. 5(c), the backfilling device BD is retreated a predetermined distance using the traveling body 40, and the screw feeder 20 is pulled out from the backfilling material M. The above operations are repeated until the backfilling area planned for the access tunnel 13 is backfilled. This allows the backfilling material M, compacted at a uniform density, to be continuously laid in the longitudinal direction of the access tunnel 13, and a uniform finished shape can be achieved over the entire length of the backfilling area planned for the access tunnel 13.

On the other hand, if it is desired to produce backfill material M by changing the mix of gravel M1 and fine-grained M2 due to changes in the properties of the surrounding rock mass midway through the planned backfilling range of the access tunnel 13, the time interval and opening degree for alternately opening the opening gates 32a and 32b can be appropriately changed. This makes it possible to easily produce and fill backfill material M with a changed mix without interrupting the backfilling work.

<<When two screw feeders 20 are used>>
First, as shown in Fig. 6(a), the backfilling device BD is installed at a predetermined position in the access tunnel 13, and then the screw feeder 20 is operated. Fine particles M2 are supplied from the material supply vehicle 50 to the hopper 30 of the upper screw feeder 20a, and gravel M1 is supplied to the hopper 30 of the lower screw feeder 20b, and the gates 32a and 32b are opened. The opening of the gates 32a and 32b is appropriately adjusted so that the gravel M1 and the fine particles M2 are supplied in a previously designed mixture.

Then, as described with reference to FIG. 2(a), the fine particles M2 transported to the upper screw feeder 20a and dropped from the discharge port 241 enter the gaps in the gravel particles M1 transported to the lower screw feeder 20b and discharged from the discharge port 241, and backfill material M is continuously produced. After that, the access tunnel 13 is backfilled in the same procedure as when two screw feeders 20 are used.

In other words, when the backfilling material M is continuously produced in the access tunnel 13, the discharge ports 241 of the two screw feeders 20 are buried in the backfilling material M as shown in FIG. 6(b). In this state, the work of producing and filling the backfilling material M in the access tunnel 13 is continued while evaluating the density of the backfilling material M. When the desired density is reached, the backfilling device BD is stopped, and as shown in FIG. 6(c), the backfilling device BD is moved back a predetermined distance to pull out the screw feeder 20 from the backfilling material M. The above work is repeated until the planned backfilling range in the access tunnel 13 is backfilled. In addition, if it is desired to produce the backfilling material M by changing the mixture of the gravel portion M1 and the fine grain portion M2 in the middle of the planned backfilling range in the access tunnel 13, the opening degree of the opening/closing gate 32 in the hopper 30 having the large diameter storage section 311 or the small diameter storage section 312 is appropriately changed.

<<Evaluation means for evaluating density of backfill material M>>
In the above-mentioned method for backfilling a cavity, a compression type load cell 61 provided on the reaction force receiving member 45 of the traveling body 40 is used as density evaluation means 60 for evaluating the density of the backfilling material M in Fig. 5. Also, in Fig. 6, an insertion type scattering type RI density meter 62 provided near the discharge port 241 of the screw feeder 20 is used. The compression type load cell 61 and the RI density meter 62 will be described below.

<When using a compression load cell (compression load)>
The compression load cell 61 measures the load in the compression direction acting on the reaction force receiving member 45. As shown in Fig. 5(b) , in the backfilling device BD, as the density of the backfilling material M increases in the access tunnel 13 and the screw feeder 20 continues to discharge the backfilling material M, the screw feeder 20 moves backward on the vehicle body 42 via the slide stand 43. This is resisted by the vehicle body 42 equipped with the crawlers 41 via the reaction force receiving member 45.

Therefore, a compression load cell 61 is provided on the reaction force receiving member 45, and the load in the compression direction (retraction force) is measured to evaluate the density of the backfilling material M that fills the access tunnel 13. The evaluation method involves determining in advance the load when the backfilling material M reaches the desired density, and setting this as the evaluation standard. Then, when the measurement value of the compression load cell 61 during backfilling work reaches the evaluation standard, the backfilling work is stopped.

<When using an RI density meter (number of scattered gamma rays)>
The insertion type scattering type RI density meter 62 is used as a means for measuring soil density, and is mounted at a position where it can be embedded in the backfill material M filled in the access tunnel 13, such as near the discharge outlet 241 of the screw feeder 20, as shown in Figure 6 (a).

As shown in FIG. 7, the RI density meter 62 is equipped with a gamma ray source unit 621 equipped with cesium 137 (Cs137) that emits gamma rays, and a detector 622, and is a device that detects the number of scattered gamma rays that are emitted from the gamma ray source unit 621, scattered in the backfilling material M, and then enter the detector 622. It is known that gamma rays are absorbed when the density of the passage is high. Therefore, as an evaluation method, a test is performed in advance and the output value of the RI density meter 62 corresponding to the density when the backfilling material M reaches the desired filling level is set as the evaluation standard. Then, when the measurement value of the RI density meter 62 reaches the evaluation standard during backfilling work, the backfilling work is stopped.

The evaluation methods using the compression load cell 61 and the RI density meter 62 described above are methods for directly evaluating the density of the backfill material M. However, the present invention is not limited to these methods, and an indirect evaluation method may also be used.

<<Estimation using load sensors>>
8(a) shows an example in which a load sensor 63 such as a load cell is provided near the discharge port 241 of the screw feeder 20. The load sensor 63 is provided on the upper surface of the trough 24 within a range that is buried in the backfilling material M during backfilling work. There is no limitation on the number of sensors, but by providing a plurality of sensors in the axial direction of the screw feeder 20 and using the average or median of the output values output from each sensor, a highly reliable output value can be obtained.

The density evaluation method involves conducting a test in advance to confirm the relationship between the density of the backfilling material M and the output value of the load sensor 63, and setting the output value of the load sensor 63 when the backfilling material M reaches the desired density as the evaluation standard. Then, when the output value of the load sensor 63 reaches the evaluation standard during the backfilling work, the backfilling work is stopped.

<<Estimation using a laser displacement meter>>
8(b) shows an example in which a laser displacement meter 64 is provided on the screw feeder 20. The laser displacement meter 64 is provided on the upper surface of the trough 24, at a position separated from the area that will be buried in the backfilling material M during backfilling work. The laser displacement meter 64 irradiates a laser beam toward the surface of the backfilling material M and receives the reflected light, thereby making it possible to measure the distance from the laser displacement meter 64 to the surface of the backfilling material M in a non-contact manner.

Therefore, the method for evaluating density involves conducting tests in advance to determine the distance from the laser displacement meter 64 to the surface of the backfilling material M when the backfilling material M reaches the desired density, and setting this as the evaluation standard. Then, when the output value of the laser displacement meter 64 reaches the evaluation standard during backfilling work, the backfilling work is stopped.

Note that neither the output values of the load sensor 63 nor the laser displacement meter 64 can directly evaluate the density of the backfill material M. Therefore, by using the compression load cell 61 and RI density meter 62 in combination and evaluating the density together with their output values, it becomes possible to perform as-built management with higher accuracy.

As described above, the method for backfilling the cavity makes it easy to manufacture backfill material M made of bentonite mixed soil in which dry gravel M1 and fine-grained material M2 are uniformly mixed, and the manufactured backfill material M can be used to backfill the access tunnel 13 homogeneously and efficiently.

The backfilling material manufacturing method, cavity backfilling method, backfilling material manufacturing device, and backfilling device of the present invention are not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.

For example, in this embodiment, as shown in FIG. 2, in the backfilling material manufacturing device MD in which the gravel portion M1 and the fine grain portion M2 are transported separately by two screw feeders 20, only one combination of an upper screw feeder 20a and a lower screw feeder 20b is provided. However, this is not limited to this, and a configuration having multiple of these combinations may be provided.

Similarly, for the backfilling material manufacturing device MD shown in FIG. 3, in which a single screw feeder 20 transports the gravel portion M1 and the fine grain portion M2 separately, it is also possible to prepare not just one but multiple screw feeders 20 and arrange them in parallel with a gap between them.

In addition, in this embodiment, the method of filling the backfilling material M using the backfilling device BD is carried out directly on the access tunnel 13, but this is not necessarily limited to this. For example, the access tunnel 13 may be backfilled using other construction methods, such as spraying bentonite mixed soil produced by adding water and adjusting it onto the wall surface of the access tunnel 13, or spreading it out on the bottom surface and compacting it, and then filling the voids surrounded by these with the backfilling material M.

In addition, the cavity that is backfilled using the backfilling device BD is not limited to the access tunnel 13 in the high-level radioactive waste disposal site 10, but can be applied to any space.

In addition, in this embodiment, a shaft-type screw feeder 2 is used for the backfill material manufacturing device MD, but this is not limited to this, and a shaftless type may also be used.

10 Disposal site 11 Disposal tunnel 12 Connecting tunnel 13 Access tunnel 20 Screw feeder 20a Upper screw feeder 20b Lower screw feeder 21 Shaft 22 Screw blade 23 Motor 24 Trough 241 Discharge port 30 Hopper 31 Hopper body 311 Large diameter storage section 312 Small diameter storage section 313 Partition member 32 Opening and closing gate 32a Opening and closing gate 32b Opening and closing gate 40 Traveling body 41 Crawler 42 Vehicle body 43 Slide frame 44 Support frame 45 Reaction force receiving member 50 Material supply vehicle 51 Soil tank 52 Bucket 521 Conveying device 53 Fine grain separation tank 531 Conveying device 60 Density evaluation means 61 Compression type load cell 62 RI density meter 621 Gamma ray source section 622 Detector 63 Load sensor 64 Laser displacement meter 70 Protective plate M Backfill material M1 Gravel (large diameter granular material)
M2 Fine particles (small diameter particles)

Claims (9)

The large-diameter granules and the small-diameter granules are conveyed separately by a screw feeder.
A method for producing backfilling material, comprising the steps of: filling gaps between the large-diameter granules dropped from the screw feeder with the small-diameter granules at the destination to produce backfilling material. The method for producing a backfill material according to claim 1,
The backfill material is a bentonite backfill material,
A method for producing backfill material, characterized in that the large-diameter granules contain gravel and the small-diameter granules contain bentonite. A method for filling a cavity in ground with the backfilling material manufactured by the method for manufacturing a backfilling material according to claim 1 or 2, comprising the steps of:
conveying the large diameter granular material and the small diameter granular material toward the cavity;
A method for backfilling a cavity, comprising the steps of producing the backfilling material in the cavity while filling the cavity. The backfilling method according to claim 3,
A backfilling method, comprising the steps of: continuously producing the backfilling material while immersing the discharge port of the screw feeder in the backfilling material previously produced. The backfilling method according to claim 3 or 4,
Evaluating the density of the backfill material for the cavity;
A backfilling method, characterized in that production of the backfilling material is stopped when a preset density is reached. The backfilling method according to any one of claims 3 to 5,
A backfilling method characterized in that the cavity is a tunnel at a waste disposal site. A backfilling material manufacturing apparatus used in the method for manufacturing a backfilling material according to claim 1 or 2,
The screw feeder and a hopper are provided,
A pair of storage sections for storing the large diameter granular material and the small diameter granular material are arranged on either side of a partition member provided inside the hopper,
A backfilling material manufacturing apparatus characterized in that opening and closing gates which are alternately opened are provided at the bottoms of the pair of storage sections. A backfilling material manufacturing apparatus used in the method for manufacturing a backfilling material according to claim 1 or 2,
The screw feeder and a hopper are provided,
The screw feeders are arranged in parallel with a gap in the height direction, and each discharge port is arranged to be shifted in the axial direction,
A small diameter storage section for storing the small diameter granular material is provided in the hopper provided on the screw feeder located above,
A backfilling material manufacturing apparatus, characterized in that a large diameter storage section for storing the large diameter granular material is provided in the hopper equipped on the screw feeder located below. A backfilling device for a cavity in the ground that fills the cavity with a backfilling material,
The backfilling material manufacturing apparatus according to claim 7 or 8,
An evaluation means for evaluating the density of the backfilling material filled in the cavity;
A backfilling device comprising:

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