JP4461428B2 - Impermeable wall - Google Patents

Description

The present invention relates to a water-impervious wall that blocks a water channel generated in a rock around a shaft .

In the geological disposal of high-level radioactive waste generated from a nuclear power plant or the like, the high-level radioactive waste is enclosed in a metal overpack and buried in a plurality of disposal holes. This disposal hole is installed in a horizontal disposal tunnel below 300m underground, and the disposal tunnel is connected to the ground by a vertical shaft. After the radionuclide released from the waste is buried in the disposal hole, the performance of the artificial barrier deteriorates due to corrosion of the overpack or chemical alteration of bentonite. As a result, the radionuclide may be released into the rock, which is a natural barrier, and further transported to the ground by groundwater flowing through the rock. In particular, the rock around the tunnel after excavation is in a relaxed state, has higher permeability than before excavation, and becomes a waterway for groundwater. In order to prevent the groundwater from contaminated groundwater from flowing out, it is effective to block the water channel around the shaft that is the access tunnel connecting the disposal hole and the ground.
As a method for shutting off a waterway in a shaft, there is a method of constructing a water stop plug composed of a bentonite block or the like at a shut off point, and a method of injecting bentonite grout or the like is also common. The bentonite grout is formed from bentonite slurry in which bentonite is mixed with an organic solvent such as water or ethanol. The water stop plug is constructed by widening excavation larger than the cross section of the shaft and installing a highly swellable and low water-permeable bentonite block or the like at the widened portion. Thereby, the water flow which flows around a shaft is interrupted. In addition, there is a method of injecting bentonite grout into a place where an excavation damaged region caused by widening excavation can become a new water channel (for example, see Patent Documents 1 and 2).
Another method for blocking water channels is a method for preventing radionuclides from leaking into groundwater by constructing a water stop plug for each disposal hole in the geological disposal method for buried radioactive waste. 3 is disclosed.
JP-A-8-49242 JP 2001-323453 A JP-A-3-150500

  However, when the water stop plug is constructed in the shaft, the water channel around the shaft can be shut off, but a new excavation damage area may be generated outside the water stop plug due to the widening excavation, which may become a water channel. On the other hand, the geological disposal method shown in Patent Document 3 generally has disposal holes for every tens of thousands of waste bodies, and it is necessary to install a water stop plug in each of these disposal holes. The amount of construction is not realistic.

This invention is made | formed in view of the problem mentioned above, and it aims at providing the impermeable wall which can suppress the loosening of the bedrock accompanying construction and can interrupt the water channel which generate | occur | produces around a shaft .

To achieve the above object, impervious wall constructed in the vertical shaft of the present invention is a water-impervious wall to be built in vertical shaft, from inside the vertical shaft and away from the gradually shafts toward the lower outer shafts all A feature is that a continuous groove formed by excavation in a predetermined region over the circumference is filled with a water-stopping material.
In the present invention, it is possible to prevent water from entering the formed impermeable wall, and it is possible to block the water channel generated in the excavation damage area around the shaft and around the water stop plug in the prior art. That is, it is possible to prevent contaminated groundwater from being transported to the ground by blocking the water channel around the vertical shaft that provides access between the disposal hole and the ground. Moreover, since the cross section of the excavation groove associated with the construction of the impermeable wall is small compared to the excavation cross section when the water stop plug is widened, excavation of the rock mass can be suppressed.

Moreover, it is preferable that the water shielding wall which concerns on this invention is provided with the water stop plug in the inside of a vertical shaft, and is closely_contact | adhered and joined to the outer periphery.
In the present invention, can be blocked water flowing inside vertical shaft, it is possible to prevent ground water from entering into the pit from the joint between the impervious wall and vertical shaft.

ADVANTAGE OF THE INVENTION According to this invention, the water-blocking wall with a high water stop can be constructed | assembled, and the water flow which flows around a shaft can be interrupted | blocked.

Hereinafter, the impermeable wall by 1st embodiment of this invention is demonstrated based on drawing. FIG. 1 is an overall view showing a shaft provided with a water shielding wall according to the present embodiment. 2 is an enlarged view of the impermeable wall portion shown in FIG. 1, FIG. 3 is a schematic explanatory view of the impermeable wall shown in FIG. 2 as viewed from above, and FIG. 4 is a cross-sectional view taken along line AA of the impermeable wall shown in FIG. FIG. 5 is related to the water-impervious wall shown in FIG. 3, and is a cross-sectional view taken along the line AA of hard rock using a slot drill. FIG. 6 is an internal structure of the water stop plug and the water-impervious wall. FIG.
As shown in FIG. 1, the geological disposal site for high-level radioactive waste includes a plurality of disposal holes 2 in which the high-level radioactive waste 1 is buried, a horizontal disposal tunnel 3 in which these disposal holes 2 are installed, and a vertical shaft 4 for communicating the disposal tunnel 3 and the ground. The rock around the shaft 4 has an excavation damage area 5 in which loosening has occurred by excavation, and the excavation damage area 5 forms a water channel flowing in the direction of arrow D shown in FIG.
The water-blocking structure in the shaft according to the present embodiment is to block the water-stopping plug 6 constructed by filling a water-stopping material in the shaft 4 in order to stop the movement of water in the shaft 4 and the excavation damage area 5. The water blocking wall 7 is provided on the periphery of the water stop plug 6.

As shown in FIGS. 1 and 2, a plug installation region 8 is provided inside the shaft 4, and a water stop plug 6 formed from a bentonite block is constructed in the plug installation region 8. And the water stop plug 6 is formed so that the upper and lower sides may be pinched | interposed by the backfill material 9. FIG.
The impermeable wall 7 is joined to the water blocking plug 6 and is composed of upper and lower two stages of a first impermeable wall 7a and a second impermeable wall 7b. The impermeable wall 7 is bentonite slurry 11 (waterstop) in a continuous groove 10 formed in a predetermined region over the entire outer periphery of the shaft so as to gradually move away from the shaft as it goes downward from the plug installation region 8 in the shaft 4 . Material). Here, as shown in FIG. 3, the predetermined region where the impermeable wall 7 is formed specifically means that the outer peripheral edge of the impermeable wall 7 is larger than the inner diameter of the shaft 4 and the excavation damaged region 5 is defined. In this way, the water channel in the excavation damage area 5 is blocked in a range that extends beyond the outside. In addition, the reason that the impermeable wall 7 is formed so as to gradually move away from the shaft as it goes down the shaft is because there is a water channel from the bottom to the top of the shaft. What is necessary is just to form a water-impervious wall in the direction which leaves | separates from a vertical shaft gradually toward a direction.

The continuous groove 10 may be excavated with a constant width as shown in FIG. 4 or may be excavated with circular holes partially overlapped as shown in FIG. 5, but the width of the continuous groove is about 100 mm to 300 mm. As a guide.
And the continuous groove | channel 10 is located in the area | region which joins the water stop plug 6, and the joining area | region 10a filled with the insertion member 12 of the bentonite block is excavated and formed outside the joining area | region 10a, and the bentonite slurry 11 is filled. Filling region 10b (see FIG. 6).

Next, the construction method of the water stop plug and the water shielding wall according to the present embodiment will be described based on the drawings.
The continuous groove 10 is excavated outwardly away from the shaft as it goes downward from the plug installation region 8 of the shaft 4 already formed, and is provided over the entire circumference in the circumferential direction of the shaft 4. This continuous groove 10 is excavated by a mechanical excavation method that has little influence on the surrounding rock mass. For example, in the case of soft rock, a small horizontal multi-axis rotary continuous excavator is used, and a plurality of continuous grooves 10 extend from soft rock to hard rock. A machine that can excavate the continuous groove 10 at the same time is used (see FIG. 5).

Then, bentonite slurry 11 is injected into the filled region 10b of the excavated continuous groove 10. Here, the bentonite slurry 11 used in the first embodiment will be described. The material to be filled in the filling region 10b of the continuous groove 10 is required to have a high water-stopping property and have a low viscosity that easily flows into the deep part of the continuous groove 10, and is prepared by kneading bentonite slurry and an organic solvent such as ethanol. A highly concentrated bentonite slurry 11 is employed. Since the continuous groove 10 becomes an excavation groove inclined downward, the bentonite slurry 11 can flow into the deep part outside the continuous groove 10 and can be sufficiently filled, and the impermeable wall 7 with high water blocking ability can be constructed.
After injection into the filling region 10b, the insertion member 12 made of bentonite block is packed into the joining region 10a.

By the construction procedure so far, the first impermeable wall 7a to be a bentonite wall is constructed, and then the second impermeable wall 7b is constructed under the same construction procedure.
Subsequently, the backfill material 9 is buried below the plug installation area 8 in the shaft 4, and then a bentonite block is stacked in the plug installation area 8 to construct the water stop plug 6. And the water stop plug 6 is compacted in the arrow E direction of FIG. 6, and the backfill material 9 is installed in the upper part. As the water stop plug 6 is compacted, the gap between the insertion member 12 and the water stop plug 6 comes into close contact with each other. And the bentonite slurry 11 with which the filling area | region 10b is filled absorbs groundwater, reacts with water, swells, and water-stops the joint surface with the insertion member 12. FIG.

  As described above, according to the first embodiment, the water impermeable wall 7 can exhibit a high water blocking effect because the water absorbed in the bentonite slurry 11 hardly moves. Therefore, the water path of the excavation damage area | region 5 around the shaft 4 can be interrupted | blocked, and groundwater containing a high level radionuclide can be prevented from being carried to the ground. The continuous groove 10 is excavated by a machine, and since the cross-sectional width is small as described above compared to the excavated cross section in the case of widening like a water stop plug in the prior art, the loosening of the rock mass accompanying excavation is suppressed. be able to. Further, when the continuous groove 10 is excavated while being inclined obliquely downward of the shaft 4, the bentonite slurry 11 flows into the deep part of the continuous groove 10 and can be sufficiently filled. Furthermore, by providing the two impermeable walls 7, the first impermeable wall 7 a and the second impermeable wall 7 b, the water path around the shaft 4 bypasses the periphery of the impermeable wall 7. The distance of the water path connected to the ground becomes longer, and the groundwater can be prevented from being carried to the ground.

Next, the construction method of the water shielding wall and the water stop plug according to the second embodiment will be described based on the drawings. Drawing 7 (a) thru / or (c) is a figure showing other examples of a impermeable wall concerning this embodiment, and is a construction procedure figure of a water stop plug and a impermeable wall.
In the second embodiment, the impermeable wall 7 constructed in the shaft 4 is only the first impermeable wall 7a, and the continuous groove 10 and the water stop in the first embodiment shown in FIGS. The structure is the same except for the joint portion of the plug 6. Specifically, as shown in FIG. 7 (c), the continuous groove 10 excavated below and below the peripheral part of the shaft 4, and the impermeable wall 7 in which the entire interior of the continuous groove 10 is filled with bentonite slurry 11. And the water stop plug 13 constructed | assembled from the bentonite block in the shaft 4 is comprised.
The water stop plug 13 is provided with a joint region 14 that forms a notch shape shown in FIG. 7A at a joint position with the water shielding wall 7. The joining region 14 is arranged in a substantially ring shape on the outer peripheral portion of the vertical shaft 4 in the longitudinal sectional view, and is filled with the bentonite slurry 11 like the continuous groove 10. Here, the water stop plug 13 is constructed so as to surround the joining region 14 as shown in FIG. 7C, and the first stop plug 13 a located below the joining region 14 and the position joining the joining region 14. The third water stop plug 13b and the third water stop plug 13c located above the second water stop plug 13b are formed.

In the second embodiment, the construction procedure up to excavation of the continuous groove 10 is the same as that in the first embodiment.
After excavation of the continuous groove 10, first, bentonite blocks are stacked with the joining region 14 left, and the first water stop plug 13a and the second water stop plug 13b are sequentially constructed. Next, bentonite slurry 11 is injected into the continuous groove 10 and the joining region 14. The injection position of the bentonite slurry 11 is up to a position substantially horizontal with the upper surface of the second water stop plug 13b. Furthermore, a bentonite block is piled up on the 2nd water stop plug 13b and the filling area | region 14, and the 3rd water stop plug 13c is constructed | assembled.
And the bentonite slurry 11 with which the continuous groove | channel 10 was filled is swollen with ground water like 1st embodiment, closely_contact | adhered to the water stop plug 13, and has a water stop effect.

  In the water-impervious wall according to the second embodiment, the bentonite slurry 11 and the water stop plug 13 are not the joint structure in which the insertion member 12 is provided between the circular hole 10 and the water stop plug 6 according to the first embodiment. Is a structure for direct joining. In the second embodiment, the impermeable wall 7 capable of obtaining the same water blocking effect as that in the first embodiment is constructed.

As mentioned above, although 1st and 2nd embodiment of the construction method of the impermeable wall concerning this invention was described, this invention is not limited to said embodiment, In the range which does not deviate from the meaning. It can be changed as appropriate. For example, as configured in the first and second embodiments described above, the water shielding wall 7 may be one or two places, and three or more water shielding walls 7 may be used to increase the water blocking effect. May be provided.
Moreover, the continuous groove | channel 10 will not be limited to a groove | channel cross section and a circular cross section, if it is a cross section of an equivalent magnitude | size.
In the above embodiment, the water blocking wall 7 is provided in the peripheral portion of the water blocking plug 6, but the water blocking plug 6 is not provided, and the water blocking wall 7 is constructed up to the inside of the shaft 4 and integrated. It is good also as the impermeable wall 7 which forms a shape.

It is a general view which shows the shaft provided with the impermeable wall which concerns on 1st embodiment of this invention. It is an enlarged view of the impermeable wall part shown in FIG. It is the schematic explanatory drawing which looked at the impermeable wall shown in FIG. 2 from the top. It is the sectional view on the AA line of the impermeable wall shown in FIG. FIG. 4 is a cross-sectional view taken along line AA, which is related to the water-impervious wall shown in FIG. 3 and is formed of hard rock using a slot drill. It is a sectional side view which shows the internal structure of the water stop plug and water-impervious wall which concern on 1st embodiment. It is a construction procedure figure of a water stop plug and a impermeable wall concerning a 2nd embodiment.

Explanation of symbols

4 shafts 5 excavation damage area 6 water stop plug 7 water blocking wall 8 plug installation area 9 backfill material 10 continuous groove 10a joint area 10b filling area 11 bentonite slurry (water stop material)
12 Insertion member 13 Water stop plug 14 Joining region

Claims (2)

In water-impervious wall built on the vertical shaft, said water stopping material progressively into a continuous groove that is drilled formed in a predetermined region over the entire outer periphery of said vertical shaft and away from the pit in accordance with the vertical shaft from the inside downward is filled A water shielding wall characterized by The water blocking wall according to claim 1, wherein a water blocking plug is provided inside the shaft, and the water blocking wall is provided in close contact with an outer periphery thereof .

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