JP7643289B2 - 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 bentonite and the base material in bentonite mixed soil differs significantly, various factors, such as transporting in a dry state or mechanical vibrations during transport using a screw feeder, can cause the base material and bentonite to separate, leading to a deterioration in quality. 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 assumed at the time of design.

The present invention has been developed 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 materials and small-diameter granular materials are supplied to a screw feeder having a conveying area and a mixing and stirring area, and the large-diameter granular materials and the small-diameter granular materials are mixed and stirred while being conveyed to produce backfill material.

The method for producing 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 granular materials and small-diameter granular materials are mixed and stirred while being transported by a screw feeder provided with a transport area and a mixing and stirring area. This makes it possible to continuously produce high-quality backfill material in which the large-diameter granular materials and small-diameter granular materials are kept uniformly mixed when discharged from 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 the backfilling material of the present invention, characterized in that the large-diameter granular material and the small-diameter granular material are mixed and stirred while being transported toward the cavity to produce the backfilling material, and the cavity is filled with the backfilling material.

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 backfilling material is produced by mixing and stirring the large-diameter granular material and the small-diameter granular material while transporting them toward the cavity, which makes it possible to significantly improve the work efficiency of the backfilling work. In addition, by immersing the discharge outlet of the screw feeder in the backfilling material that fills the cavity first, these can be compressed by the backfilling material that is produced later. As a result, the backfilling material that fills the cavity is compacted, making it possible to omit work such as 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 uniformly backfill the tunnel with backfill material over its entire length, even when the planned backfill range of the tunnel is long. On the other hand, if it is necessary to change the mix of backfill material to be produced in response to changes in the properties of the surrounding rock mass along the way within the planned backfill range of the tunnel, this can be done by appropriately adjusting the supply amount of large-diameter granular material and small-diameter granular material to the screw feeder. In this way, backfill material with a changed mix can be easily produced without interrupting the backfilling work. 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 apparatus of the present invention is a backfilling material manufacturing apparatus used in the backfilling material manufacturing method of the present invention, which is a backfilling material manufacturing apparatus that conveys and mixes and stirs large-diameter granular materials and small-diameter granular materials to manufacture backfilling material, and is characterized by having a screw feeder having a conveying area for conveying the large-diameter granular materials and the small-diameter granular materials, and a mixing and stirring area for conveying the large-diameter granular materials and the small-diameter granular materials while mixing and stirring them.

The backfilling material manufacturing device of the present invention is characterized in that the mixing and stirring area is arranged on the discharge side of the screw feeder.

The backfilling material manufacturing device of the present invention is characterized in that the mixing and stirring area is arranged on the supply port side of the screw feeder.

The backfilling material manufacturing device of the present invention is characterized in that a hopper having a large diameter storage section for storing the large diameter granular material and a small diameter storage section for storing the small diameter granular material is installed at the supply port of the screw feeder via an opening and closing gate.

According to the backfilling material manufacturing device of the present invention, when large-diameter granular materials and small-diameter granular materials are supplied to a hopper, they are transported while being mixed and stirred to produce backfilling material, and the backfilling material can be discharged at the destination. Therefore, there is no need to install a separate plant or other facility for producing backfilling material on-site. In addition, since the hopper is installed on a screw feeder via an opening and closing gate, it is possible to easily manufacture backfilling materials with different compositions by appropriately changing the supply amount of large-diameter granular materials and small-diameter granular materials via the opening and closing gate.

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 a 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 homogeneously 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. 3 is a diagram showing a backfilling material manufacturing apparatus according to an embodiment of the present invention (part 3). FIG. 4 is a diagram showing a backfilling material manufacturing apparatus according to an embodiment of the present invention (part 4). FIG. 5 is a diagram showing a backfilling material manufacturing apparatus according to an embodiment of the present invention (part 5). FIG. 2 is a diagram showing a backfilling device according to an embodiment of the present invention. FIG. 1 is a diagram showing a procedure for backfilling an access tunnel in an embodiment of the present invention. 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 and mix dry large-diameter and small-diameter granules, which are then continuously discharged from the screw conveyor as a homogeneously mixed, high-quality backfill material, to backfill cavities homogeneously and efficiently.

Below, we will use the backfilling of an access tunnel to a high-level radioactive waste disposal site as an example, and with reference to Figures 1 to 10, we will explain the backfilling material manufacturing method, the backfilling method for a cavity, the backfilling material manufacturing device, and the backfilling device.

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 provided deep underground, a connecting tunnel 12 connected to the disposal tunnel 11, and an access tunnel 13 extending 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 is located in stable bedrock deep underground, excavated waste from this bedrock is used as the base material. In other words, the backfill material M for the access tunnel 13 is produced by mixing gravel M1 obtained by crushing the excavated waste and adjusting its grain size with fine-grained material 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 soil mixture, a backfilling material production device MD is used that is equipped with a screw feeder 20 having a mixing and stirring area 20A and a conveying area 20B, as shown in Figure 2. In this way, the gravel portion M1, which is a large-diameter granular material, and the fine-grain portion M2, which is a small-diameter granular material, can be mixed and stirred while being conveyed.

As a result, when discharged from the screw feeder 20, a high-quality bentonite mixed soil can be produced as backfill material M, in which the gravel fraction M1 and the fine-grained fraction M2 remain uniformly mixed. In addition, because the bentonite mixed soil can be produced in a dry state, cumbersome work such as adjusting the amount of water added can be omitted, and the bentonite mixed soil can be handled more easily during construction than when adjusting the amount of water added.

The backfilling material manufacturing device MD that manufactures the backfilling material M will be described in detail below. The backfilling device BD equipped with the backfilling material manufacturing device MD will also be described. In this embodiment, a bentonite mixed soil consisting of gravel M1 and fine grain M2 as shown in FIG. 1(b) will be described as an example of the backfilling material M, but the backfilling material M that can be manufactured by the backfilling material manufacturing device MD is not limited to the above-mentioned bentonite mixed soil. Any backfilling 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>>>>
As shown in the cross-sectional view of FIG. 2( a ) and the plan view of FIG. 2( b ), the backfilling material manufacturing device MD includes a screw feeder 20 and a hopper 30 provided on each of the screw feeders 20 .

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. The opening/closing gates 32a, 32b are provided at the connection between the hopper body 31 and the screw feeder 20.

The opening and closing gates 32a and 32b are both configured so that their opening degree can be adjusted when the connection with the screw feeder 20 is in an open state. This allows the supply amount of each of the gravel fraction M1 and the fine fraction M2 supplied from the hopper body 31 to the screw feeder 20 to be freely adjusted. In FIG. 2, the opening and closing gates 32a and 32b are shaped as a sliding type, but any shape is acceptable as long as the opening degree can be adjusted.

The screw feeder 20 is of the shafted type and includes a shaft 21 and a screw blade 22 attached around the shaft 21. A motor 23 for rotating the shaft 21 is provided on one end of the shaft 21, and the shaft 21 and the screw blade 22 are contained within a trough 24. The trough 24 includes a supply port 242 connected to a hopper 30 on one end of the motor 23 side, and a discharge port 241 for discharging the backfill material M at the other end.

<<When the mixing and stirring area 20A is located on the discharge port 241 side>>
2(a), the screw feeder 20 having such a configuration has a mixing and stirring region 20A set on the discharge port 241 side, and a conveying region 20B on the supply port 242 side. The conveying region 20B is a region that conveys the gravel fraction M1 and the fine grain fraction M2 supplied from the hopper 30 toward the mixing and stirring region 20A without mixing and stirring them. For this reason, the screw blades 22 are attached to the shaft portion 21 at a blade pitch generally adopted when conveying granular materials.

On the other hand, the mixing and stirring area 20A is an area where the gravel portion M1 and the fine grain portion M2 transported from the transport area 20B are mixed and stirred to produce backfill material M and transport it toward the discharge port 241. For this reason, the screw blade 22 is attached to the shaft portion 21 with a blade pitch wider than that of the transport area 20B. By forming the blade pitch wider in this way, it is possible to buy time for the gravel portion M1 and the fine grain portion M2 to remain between the rotating screw blades 22. During this period, the gravel portion M1 and the fine grain portion M2 are mixed and stirred while being transported by rotating together with the screw blade 22. In this way, the backfill material M is produced and discharged toward the discharge port 241.

In the mixing and stirring area 20A, the configuration for mixing and stirring the gravel portion M1 and the fine grain portion M2 to produce backfill material M is not limited to adjusting the blade pitch of the screw blade 22.

Figure 3(a) illustrates a configuration in which multiple stirring rods 25 extending parallel to the shaft portion 21 are provided on the screw blade 22 located within the mixing and stirring region 20A. Also, Figure 3(b) illustrates a configuration in which multiple stirring rods 25 are attached to the shaft portion 21 located within the mixing and stirring region 20A so that they extend in a direction perpendicular to the shaft portion 21. As a result, the gravel portion M1 and the fine grain portion M2 transported from the transport region 20B are mixed and stirred by the stirring rods 25 while being transported by the screw blade 22 within the mixing and stirring region 20A. As a result, backfill material M is produced and discharged toward the discharge port 241.

Furthermore, FIG. 4 illustrates a configuration in which the stirring blades 26 are provided within the range of the mixing and stirring region 20A. Specifically, the shaft portion 21 of the screw feeder 20 is composed of an outer shaft 21a and an inner shaft 21b that penetrates the outer shaft 21a, and the outer shaft 21a is formed to be shorter than the trough 24. In addition, since the inner shaft 21b has a length that reaches the discharge port 241, the inner shaft 21b is exposed from the outer shaft 21a near the discharge port 241.

Utilizing this, the area from the supply port 242 of the screw feeder 20 to the tip of the outer shaft 21a is the conveying area 20B, and the screw blade 22 is attached to the outer shaft 21a. On the other hand, the area from the tip of the outer shaft 21a to the discharge port 241 of the screw feeder 20 is the mixing and stirring area 20A, and the stirring blade 26 is installed on the exposed inner shaft 21b.

The outer shaft 21a and the inner shaft 21b are each rotatable about their own axis, and motors 23a and 23b are provided on the supply port 242 side. As a result, when the outer shaft 21a and the inner shaft 21b rotate, the gravel fraction M1 and the fine grain fraction M2 transported from the transport area 20B are mixed and stirred by the stirring blades 26 rotating in the mixing and stirring area 20A to produce backfill material M, which is then discharged toward the discharge port 241. The inner shaft 21b to which the stirring blades 26 are attached is set to rotate at a higher speed than the outer shaft 21a.

<<When the mixing and stirring area 20A is located on the supply port 242 side>>>
On the other hand, the screw feeder 20 may have a mixing and stirring region 20A on the supply port 242 side and a conveying region 20B on the discharge port 241 side. In this case, the mixing and stirring region 20A mixes and stirs the gravel portion M1 and the fine grain portion M2 supplied from the hopper 30 to produce backfill material M, which is then conveyed to the conveying region 20B. In the conveying region 20B, the backfill material M produced in the mixing and stirring region 20A is conveyed toward the discharge port 241 and discharged.

For example, in FIG. 5(a), in the conveying area 20B located on the discharge port 241 side, a screw blade 22 is installed on the shaft 21, and in the mixing and stirring area 20A located on the supply port 242 side, a number of paddle blades 27 are installed on the shaft 21 and the inner circumferential surface of the trough 24. The paddle blades 27 are provided in paddle mixers that are widely and generally used when mixing powder and granular materials, and they mix and stir the powder and granular materials by lifting them up as the shaft 21 rotates. Therefore, in the mixing and stirring area 20A, the gravel portion M1 and the fine grain portion M2 supplied from the hopper 30 are mixed and stirred by the paddle blades 27 attached to the rotating shaft 21 and the paddle blades 27 of the trough 24, producing the backfill material M, and can be conveyed to the conveying area 20B.

The configuration of using the paddle blade 27 in the mixing and stirring area 20A is not limited to the above. As shown in FIG. 5(b), the screw feeder 20 may be configured as a two-shaft type by arranging the additional shaft part 21' in parallel with a gap between them and the shaft part 21, and the paddle blade 27 may be installed on both shaft parts. The additional shaft part 21' is also rotatable around its axis, and a motor 23c is provided on the supply port 242 side. Therefore, in the mixing and stirring area 20A, the gravel part M1 and the fine grain part M2 supplied from the hopper 30 are mixed and stirred by the paddle blade 27 attached to both the rotating shaft part 21 and the additional shaft part 21', and the backfill material M is produced and transported to the transport area 20B.

In addition, when the screw feeder 20 provided in the mixing and stirring area 20A is a two-shaft type having a shaft portion 21 and an additional shaft portion 21' parallel to the shaft portion 21, the screw blade 22 and stirring rod 25 may be provided instead of the paddle blade 27, as shown in Figures 6(a) and 6(b).

For example, in FIG. 6(a), multiple stirring rods 25 are installed on the shaft 21 and the additional shaft 21' together with the screw blade 22. At this time, the multiple stirring rods 25 are installed perpendicular to the shaft 21 and the additional shaft 21'. Also, in FIG. 6(b), the screw blade 22 is installed on the shaft 21 and the additional shaft 21', and the stirring rods 25 are installed on the screw blade 22. The stirring rods 25 installed on the screw blade 22 are installed parallel to the shaft 21 and the additional shaft 21'. As a result, in the mixing and stirring area 20A, the gravel fraction M1 and the fine grain fraction M2 supplied from the hopper 30 are mixed and stirred by the stirring rods 25 attached to the shaft 21 or the screw blade 22 to produce the backfill material M, and the produced backfill material M can be transported to the transport area 20B by the screw blade 22.

<<Backfilling device BD>>
As shown in FIG. 7, the backfilling device BD includes a traveling body 40 having the backfilling material manufacturing device MD mounted thereon, a material supply vehicle 50, a density evaluation means 60, and a dustproof plate 70.

The running body 40 supports the backfilling device BD, and comprises 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 the screw feeder 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 when it exhibits a behavior of retreating on the vehicle body 42 via the slide base 43.

The slide base 43 and the reaction force receiving member 45 assist in the compaction of 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 increases in the access tunnel 13, and as the backfill material M continues to be discharged, 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 these, 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 large diameter storage section 311 of the hopper 30 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 small diameter storage section 312 of the hopper 30 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 7 shows an example in which an RI density meter 62 is installed near the discharge outlet 241 of the screw feeder 20. Figure 8, which will be described later, 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. 7, in this type of backfilling device BD, a dustproof plate 70 that blocks the cross section of the access tunnel 13 is provided on the running body 40, preventing the backfilling material M filling the access tunnel 13 from collapsing and the fine particles M2 from scattering. Note that the dustproof 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 can be covered, including the production of the backfilling material M, 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>>>>
First, as shown in Figure 8 (a), a backfilling device BD is installed at a predetermined position in the access tunnel 13, and then gravel M1 and fine grain M2 are continuously or intermittently supplied from the material supply vehicle 50 to the large diameter storage section 311 and small diameter storage section 312 of the hopper 30. In addition, the screw feeder 20 is operated and the opening and closing gates 32a and 32b are opened.

The opening degree of the gates 32a and 32b is set in advance so that the gravel portion M1 and the fine grain portion M2 are supplied to the screw feeder 20 in the designed mixture amount. The screw feeder 20 then conveys and mixes the gravel portion M1 and the fine grain portion M2 through the conveying area 20B and the mixing and stirring area 20A, continuously producing backfill material M and discharging it toward the discharge port 241.

When backfill material M is continuously discharged from the access tunnel 13, the discharge port 241 of the screw feeder 20 is buried in the backfill material M, as shown in FIG. 8(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, that is, 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. 8(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 provided 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 necessary 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 opening degree of the opening and closing 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.

<<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. 8, an insertion type scattering type RI densitometer 62 provided near the discharge port 241 of the screw feeder 20 is used in Fig. 7, and a data logger 65 provided on the screw feeder 20 for recording the motor current or rotation torque is used in Fig. 2. The density evaluation method using the compression type load cell 61, the RI densitometer 62, and the data logger 65 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. 8(b) , in the backfilling device BD, when the density of the backfilling material M increases in the access tunnel 13, the screw feeder 20 moves backward on the vehicle body 42 via the slide base 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 7.

As shown in FIG. 9, 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 backfill 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 backfill 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.

<When using a data logger (motor current or rotational torque)>
As shown in Fig. 2(a), the data logger 65 provided in the screw feeder 20 reads and records information such as the motor current of the motor 23 and the rotational torque of the shaft portion 21. As an evaluation method, the current value and rotational torque when the backfilling material M reaches a desired density are obtained in advance and set as the evaluation standard. Then, when the current value or rotational torque recorded in the data logger 65 during the backfilling work reaches the evaluation standard, the backfilling work is stopped. Both the motor current of the motor 23 and the rotational torque of the shaft portion 21 may be evaluated, or either one of them may be evaluated.

The above-mentioned evaluation methods using the compression load cell 61, RI density meter 62, and data logger 65 are each 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>>
10(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>>
10(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 the output values of the load sensor 63 and the laser displacement meter 64 cannot directly evaluate the density of the backfill material M. Therefore, by using the compression load cell 61, RI density meter 62, and data logger 65 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 produce backfill material M, which is a bentonite mixed soil in which dry gravel M1 and fine grain M2 are uniformly mixed. In addition, 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. 7, only one screw feeder 20 is provided in the backfill material manufacturing device MD, but multiple similar screw feeders 20 may be prepared and arranged in parallel with intervals 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.

10 disposal site 11 disposal tunnel 12 connection tunnel 13 access tunnel (cavity)
20 Screw feeder 21 Shaft portion 21a Outer shaft 21b Inner shaft 22 Screw blade 23 Motor 23a Motor 23b Motor 23c Motor 24 Trough 241 Discharge port 242 Supply port 25 Stirring rod 26 Stirring blade 27 Paddle blade 30 Hopper 31 Hopper body 311 Large diameter storage section 312 Small diameter storage section 313 Partition member 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 63 Load sensor 64 Laser displacement meter 65 Data logger 70 Dustproof plate M Backfill material M1 Gravel (large granular material)
M2 Fine particles (small diameter particles)
MD Backfilling material manufacturing equipment BD Backfilling equipment

Claims (11)

A method for producing backfill material, comprising: feeding large-diameter granular materials and small-diameter granular materials to a screw feeder having a conveying region and a mixing and stirring region; and producing backfill material by mixing and stirring the large-diameter granular materials and the small-diameter granular materials while conveying them. The method for producing a backfill material according to claim 1,
The backfill material is bentonite mixed soil,
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:
A method for backfilling a cavity, comprising the steps of: transporting and mixing the large-diameter granules and the small-diameter granules toward the cavity to produce the backfilling material, and filling the cavity with the backfilling material. The method for backfilling a cavity according to claim 3,
A method for backfilling a cavity, comprising the steps of: submerging a discharge port of the screw feeder in the backfilling material previously produced while continuously producing the backfilling material. The method for backfilling a cavity according to claim 3 or 4,
Evaluating the density of the backfill material for the cavity;
A method for backfilling a cavity, comprising the steps of: stopping production of the backfilling material when a preset density is reached. The method for backfilling a cavity according to any one of claims 3 to 5,
13. A method for backfilling a cavity, wherein the cavity is a tunnel at a waste disposal site. A backfilling material manufacturing apparatus for manufacturing backfilling material by conveying and mixing large-diameter granular materials and small-diameter granular materials, comprising:
a conveying region for conveying the large-diameter granular material and the small-diameter granular material;
a mixing and stirring region for mixing and stirring the large-diameter granules and the small-diameter granules while transporting them, The backfilling material manufacturing apparatus according to claim 7,
The backfilling material manufacturing apparatus is characterized in that the mixing and stirring area is disposed on the discharge outlet side of the screw feeder. The backfilling material manufacturing apparatus according to claim 7,
The backfilling material manufacturing apparatus is characterized in that the mixing and stirring area is disposed on the supply port side of the screw feeder. The backfilling material manufacturing apparatus according to any one of claims 7 to 9,
A backfill material manufacturing apparatus characterized in that a hopper having a storage section for storing the large-diameter granular material and a storage section for storing the small-diameter granular material is installed at the supply port of the screw feeder via an opening and closing gate. A backfilling device for a cavity in the ground that fills the cavity with a backfilling material,
The backfilling material manufacturing apparatus according to any one of claims 7 to 10,
An evaluation means for evaluating the density of the backfilling material filled in the cavity;
A backfilling device comprising:

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