Method for manufacturing stabilized tunnel surrounding rock structure

Abstract

To provide a rock bolting method which enables long-term stabilization without making any major changes to a conventional process when stabilizing the bedrock around a tunnel installed deep underground with rock bolts and can simultaneously improve a problem of spring water caused by a construction of rock bolts.SOLUTION: A method for manufacturing a stabilized tunnel rock structure includes a step (S110) of forming a hole from a surface of a tunnel located deep underground, a step (S120) of inserting a rock bolt into the hole, an injection step (S130) of injecting a mixture of a hardener and a concretion agent into the hole, and a fixation step (S140) of hardening the hardener and fixing a loosened area of the rock around the tunnel to the rock layer in a deep portion of the tunnel surrounding rock via the rock bolt, thereby stabilizing the rock around the tunnel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a stabilized rock structure around a tunnel, and more particularly to a method for manufacturing a stabilized rock structure around a tunnel by supporting a tunnel located deep underground with rock bolts. [Background technology]

[0002] Radioactive waste generated during the operation of nuclear power plants is ultimately buried in tunnels dug deep underground in order to isolate it from the human environment. Figure 12(a) is a schematic diagram of an intermediate depth disposal facility for radioactive waste, and Figure 12(b) is a vertical cross-sectional view of the buried cavity d shown in part (b) of Figure 12(a).

[0003] (Note that Figures 12(a) and (b) are based on Figure 4 in "The Background and Concept of Establishing Regulatory Standards for Intermediate Depth Disposal" by Hiroomi Aoki et al., Journal of the Atomic Energy Society of Japan, Vol. 65, No. 1, p. 21 (2023), with the symbols deleted and added.)

[0004] As shown in Figure 12(a), the intermediate depth disposal facility for radioactive waste comprises a surface facility a, an access tunnel b leading underground, a main tunnel c, a buried cavity d, and a connecting tunnel e.

[0005] As shown in Figure 12(b), if each tunnel is exemplified by a buried cavity d, a horseshoe-shaped tunnel f is covered with sprayed concrete g, and rock bolt holes (not shown) are drilled into the surface of the tunnel f covered with the sprayed concrete g until they reach the bedrock layer k deep inside the tunnel. Rock bolts h are inserted into these rock bolt holes, and mortar or the like is injected into the rock bolt holes and allowed to harden, so that together with the shotcrete g, the loosened area i of the bedrock layer around the tunnel is fixed to the deep bedrock layer k via the rock bolts h, providing support.

[0006] However, not only in tunnels storing radioactive waste, but in rock formations deep underground as well, (1) the distribution of poor geological quality such as fault fracture zones and porous layers is expected. (2) Furthermore, in the rock surrounding tunnels in formations deeper than 70 meters underground, in addition to primary cracks, there is a risk of loosening cracks occurring due to excavation. (3) Furthermore, rock bolts installed immediately after excavation often cause new springs of water.

[0007] Therefore, in the rock surrounding tunnels built in deep underground strata, it is necessary to appropriately block the highly permeable areas and water paths caused by these factors (1) to (3).

[0008] Conventionally, problems (1) and (2) above have been addressed in general tunnels by injecting grout. However, the durability of cement-based materials is said to be 50 to 100 years, and they cannot withstand use for more than 100 years. Therefore, there is a need for an alternative injection material to grout that has long-term durability.

[0009] Furthermore, no effective countermeasure has yet been found for the problem (3) above.

[0010] Patent Document 1 discloses that a mixed solution of an epoxy compound (hardening compound), an epoxy hardener (hardening agent), calcium chloride, and sodium bicarbonate is injected into holes in a sandstone block to obtain a repaired block (see Examples 1-2). As a result, calcium carbonate particles (calcite structure of calcium carbonate) are formed over the entire surface of the repaired block. It also discloses a method for repairing ground, etc., by drilling an injection port from the surface of the bedrock (ground) toward the crack or junk part instead of using a sandstone block, and then injecting the mixed solution through the injection port.

[0011] Furthermore, Non-Patent Documents 1 to 3 disclose that in a test tunnel 350 m underground, the tunnel wall and bottom were excavated, multiple holes were made, and a concretion agent was injected into the holes. According to Patent Document 2 (Japanese Patent No. 6889508) cited in Non-Patent Documents 1 to 3, the concretion agent is, for example, Ca 2+Ion exchange resin with adsorbed ions, Ca 2+ Examples of such a combination include a liquid or sheet containing capsules that encapsulate and release ions, and an ion source that supplies bicarbonate ions. According to the concretion agents of Non-Patent Documents 1 to 3, Ca released from the concretion agent 2+ The ions react with bicarbonate ions from the ion source to form sparingly soluble calcium carbonate, which densifies the underground rock around the hole and reduces the permeability of the underground rock. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2022-48720 [Patent Document 2] Patent No. 6889508 [Non-patent literature]

[0013] [Non-Patent Document 1] Eiichi Yoshida, Koji Yamamoto et al., "Underground Demonstration Test Study on Self-Sealing of Water Pathway Cracks by Concretion," Abstracts of the 129th Annual Meeting of the Geological Society of Japan, pp. 441-442, Geological Society of Japan, 2022 [Non-patent document 2] Eiichi Yoshida, Koji Yamamoto et al., "Study on Self-Sealing of EDZ and Water Pathway Cracks by Concretion," Proceedings of the 2021 Japan Society of Engineering Geology Research Presentation Meeting, Japan Society of Engineering Geology, 2021 [Non-patent document 3] Eiichi Yoshida, Koji Yamamoto, Yoshihiro Asahara et al., "Demonstration Test Study on Self-Sealing of EDZ and Water Pathway Cracks by Concretion," Proceedings of the 2022 Japan Society of Engineering Geology Research Presentation Meeting, Japan Society of Engineering Geology, 2022 Summary of the Invention [Problem to be solved by the invention]

[0014] However, while the method for repairing rock masses and the like described in Patent Document 1 can pinpoint and repair cracked or junk rock masses, it is difficult to fix the rock mass around the tunnel, which becomes weakened by tunnel excavation and the subsequent external forces and external environments (temperature, dryness, construction quality, etc.), to the deeper rock mass layer for a long period of time. In particular, as shown in (2) above, loosening cracks are thought to occur in the tunnel surface layer due to tunnel excavation, and the technology described in Patent Document 1 cannot fix the tunnel surface layer containing such loosening cracks to the deeper rock mass layer for a long period of time.

[0015] The same applies to the methods disclosed in Non-Patent Documents 1 to 3, in which a concretion agent is injected into the tunnel wall or bottom to form concretions in the surrounding area of ​​the tunnel. That is, although the area around the hole is reinforced, the weakened rock around the tunnel is not fixed to the deep rock layer radially outward of the tunnel.

[0016] Furthermore, neither Non-Patent Documents 1 to 3 nor Patent Document 1 discloses any measures to prevent new spring water from being generated by rock bolts installed immediately after excavation.

[0017] The object of the present invention, made in view of the above problems, is to provide a rock bolting method that, when using rock bolts to stabilize the bedrock surrounding a tunnel located deep underground, enables long-term stabilization without making any major changes to the conventional process, and also alleviates the problem of water seepage caused by the installation of rock bolts. [Means for solving the problem]

[0018] The present inventors have conducted extensive research to achieve the above object, and as a result have discovered that when using rock bolts to fix and stabilize loosened portions of rock around a tunnel located deep underground to the deeper rock, adding not only a liquid hardener but also a concretion agent to the holes in which the rock bolts are fixed makes it possible to fix the loosened portions of rock around the tunnel to the deeper rock layer for a longer period of time than conventional methods, prevents water seepage caused by the rock bolts, and does not require any major changes to the conventional process, thereby completing the present invention.

[0019] In other words, it has been found that the above-mentioned object can be achieved by a method for manufacturing a stabilized rock structure around a tunnel, which comprises the steps of: a hole forming step of forming a hole from the surface of a tunnel located deep underground to reach the bedrock layer deep inside the tunnel; a rock bolt inserting step of inserting a rock bolt into the hole; an injection step of injecting a mixture of a hardener and a concretion agent into the hole before or after the rock bolt inserting step; and a fixation step of hardening the hardener and fixing the loosened area of ​​the bedrock around the tunnel to the bedrock layer deep inside the tunnel via the rock bolt, thereby stabilizing the bedrock around the tunnel.

[0020] It is also preferable that the hardener contains cement.

[0021] Furthermore, it is preferred that the concretion agent comprises sodium bicarbonate and a calcium ion source.

[0022] Furthermore, it is preferable that the tunnel is a tunnel for storing radioactive waste. [Effects of the Invention]

[0023] According to the manufacturing method of the present invention for a stabilized tunnel surface structure, when loosened sections of bedrock around a tunnel located deep underground are stabilized by fixing them to the deeper bedrock with rock bolts, a hardener and a concretion agent are used in combination as fillers for the holes, which densifies the voids and cracks in the rock section (loose area) around the holes, and this densification effect is maintained for a long period of time.Therefore, without making any major changes to the conventional process, it is possible to fix the loosened sections of bedrock around the tunnel to the deeper bedrock layer for a longer period of time than before, and to prevent water springing due to rock bolt holes. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a flow chart showing a method for manufacturing a stabilized tunnel surrounding rock structure according to the present invention. [Figure 2]1 is a schematic cross-sectional view showing a stabilized tunnel surrounding structure according to the manufacturing method of the stabilized tunnel surrounding rock structure of the present invention. FIG. [Figure 3] 1A is a photograph in place of a drawing showing specimens 1 and 2 of the embodiment, and FIG. 1B is a photograph in place of a drawing showing a sample of specimens 1 and 2 bonded with silicone for concretion treatment. [Figure 4] In the working example, (a) is a photograph in place of a drawing showing the state in which a mixture of hardener and concretion agent is poured into the sample of Figure 3(b), and (b) is a photograph in place of a drawing showing a laminate of specimens 1 and 2 and a hardened layer of hardener and concretion agent. [Figure 5] 5A is a photograph showing the bottom view of the laminate of FIG. 4B (the state of water path formation) of the embodiment, and FIG. 5B is a photograph showing the concretion treatment of the laminate of FIG. 5A. [Figure 6] 1 is a graph showing the results of an indoor water permeability test for evaluating the influence of the presence or absence of concretion treatment on porous concrete in an example. [Figure 7] FIG. 1 is a schematic perspective view of a cylindrical specimen 3 used in an X-ray microscope observation test to evaluate the influence of the presence or absence of a concretion treatment on ordinary concrete in an embodiment. [Figure 8] 8 is an element map obtained by an X-ray microscope observation test, showing a cross section of the cylindrical specimen 3 of the example taken along line VII-VII in FIG. The vertical axis represents calcium concentration. [Figure 9] This shows the Ca profile of the area surrounded by the white line in Figure 8 of the Example. The vertical axis represents the X-ray intensity, and the horizontal axis represents the length. [Figure 10] FIG. 3 is a plan view of specimen 3-1 of the example. [Figure 11] In the working examples, (a) is a photograph in lieu of a drawing showing the results of elemental mapping of the cut surface of specimen 3-1, and (b) is a photograph in lieu of a drawing showing the results of elemental mapping of the cut surface of a disk-shaped pumice tuff (hereinafter referred to as specimen 3-0) to which the mixture of hardener and concretion agent has not been applied. [Figure 12](a) is a schematic diagram of a conventional intermediate depth disposal facility for radioactive waste, and (b) is a vertical cross-sectional view of the buried cavity d shown in part (b) of the same figure (a). DETAILED DESCRIPTION OF THE INVENTION

[0025] <Method for manufacturing stabilized tunnel surface structure> The manufacturing method of the stabilized tunnel surface structure of the present invention will be described with reference to Fig. 1. Fig. 1 is a flow diagram showing the manufacturing method of the stabilized tunnel surface structure of the present invention. As shown in the figure, the manufacturing method of the stabilized tunnel surface structure of the present invention includes a hole forming step (S110), a rock bolt inserting step (S120), an injection step (S130), and a fixing step (S140).

[0026] [Hole formation process (S110)] In this process, a hole is formed from the surface of a tunnel provided deep underground to reach the bedrock layer deep within the tunnel.

[0027] "Deep underground" refers to the area 70 meters or more below the surface. Examples of tunnels include access tunnels, connecting tunnels, main tunnels, and buried cavities of intermediate depth disposal facilities for radioactive waste, but this does not limit the scope to these tunnels; it also includes all tunnels located deep underground.

[0028] The cross-sectional shape of the tunnel is not limited to a horseshoe shape, but can take various shapes such as a circle, an oval, a square (including a rectangle), and a hexagon.

[0029] In the case of a buried cavity with a horseshoe-shaped cross section, the size of the tunnel is, for example, approximately 10 to 20 m wide and 15 to 20 m high, but this is not limited to this and any size can be used depending on the purpose of the tunnel.

[0030] The rock around the tunnel, which forms the surface of the tunnel, is at risk of loosening due to cracks that occur during excavation, in addition to primary cracks. Therefore, support work is generally carried out by applying shotcrete to the surface of the tunnel and / or installing rock bolts that are inserted and fixed radially outward from the tunnel surface.

[0031] In the present invention, in order to install rock bolts to stabilize the rock around the tunnel, holes m (see Figure 2) are formed from the surface of the tunnel to reach the rock layer deep inside the tunnel, which will serve as rock bolt holes. Note that, before the holes are formed, shotcrete g (see Figure 2) is usually applied to the tunnel surface as described above.

[0032] Since the hole portion is a rock bolt hole for inserting a rock bolt, the diameter of the hole portion is larger than the diameter of the rock bolt, for example, in the range of 45 mm to 50 mm, and the length of the hole portion is, for example, in the range of 4 m to 5 m (this is the hole portion forming process (S110)).

[0033] [Rock bolt insertion process (S120)] In this step, a rock bolt is inserted into the hole. Examples of rock bolts 12 (see FIG. 2) include deformed steel bars, fully threaded steel bars, and twisted steel bars. The rock bolts may be inserted in accordance with a conventionally known rock bolting method, and detailed explanations thereof will be omitted here (this concludes the rock bolt insertion step (S120)).

[0034] [Injection process (S130)] In this step, a mixture of a hardener and a concretion agent is injected into the hole before or after the rock bolt inserting step (S120).

[0035] Examples of the hardener include cement-based hardeners and resin-based hardeners. Examples of cement-based hardeners include cement milk, which is made by adding water to cement, and mortar, which is made by adding fine aggregate (sand) to cement.

[0036] Examples of resin-based hardeners include silica resin, polyester, and urethane.

[0037] In particular, from the viewpoint of strength after hardening and service life, it is preferable that the hardener contains cement, i.e., is a cement-based hardener. Also, as will be described later, cement-based hardeners serve as a source of calcium ions in concretion, so it is preferable that the hardener contains cement.

[0038] Before explaining the concretion agent, the mechanism of concretion will be explained.

[0039] Concretions are spherical rock masses that are formed when the gaps between the detrital particles (sand or mud) in sedimentary rock are filled with minerals, making them extremely dense and hard. The mechanism of concretions formation is that, for example, in the case of a horn shell, after its death, organic matter is decomposed as it decays, and bicarbonate ions (HCO3 - ) or carbonate ions (CO3 2- ) combines with calcium ions in seawater to form calcium carbonate, which then grows round like a balloon expanding.

[0040] This can be expressed as the formula below.

[0041] R·CH2COOH (organic matter) → R·H + HCO3 - + H + HCO3 - → CO3 2- + H + CO3 2- + Ca 2+ (seawater derived) →CaCO3 Concretions include those whose main component is calcium carbonate as described above, as well as carbonates containing iron, silica, and some magnesium. The concretion agent of the present invention is a concretion agent that produces concretions whose main component is calcium carbonate.

[0042] Therefore, in the present invention, the concretion agent contains at least a bicarbonate ion source and / or a carbonate ion source as an anion source. Examples of bicarbonate ion sources include sodium hydrogen carbonate (baking soda), and examples of carbonate ion sources include sodium carbonate (sodium carbonate). Among these, from the viewpoints of availability and cost, it is preferable that the concretion agent contains sodium hydrogen carbonate as the bicarbonate ion source.

[0043] In addition, when the concretion agent employs a bicarbonate ion source and / or carbonate ion source as an anion source but does not contain a calcium ion source as a cation source, the calcium ions required to form concretions are supplied from the bedrock around the tunnel, deep bedrock layers, calcium ions dissolved in water in these bedrock layers, etc., and further, when the hardener is a cement-based hardener, calcium ions are also supplied from the cement-based hardener.

[0044] However, in order to increase the density of the concretions, it is preferred that the concretion agent further contains a calcium ion source in addition to the anion source.

[0045] Examples of calcium ion sources include calcium chloride, calcium hydroxide (slaked lime), calcium formate, calcium acetate, calcium citrate, etc. Among them, calcium formate also acts as a cement hardening accelerator, so when the hardener is a cement-based hardener, it is preferable to use calcium formate as the calcium ion source.

[0046] It is particularly preferred that the concretion agent comprises sodium bicarbonate and a source of calcium ions.

[0047] Prior to this step, a mixture of hardener and concretion agent is prepared. As described above, the mixture of hardener and concretion agent is injected into the hole either before or after the rock bolt insertion step (S120). If it is done before the rock bolt insertion step (S120), it is called a pre-filling method, and if it is done after the rock bolt insertion step (S120), it is called a post-injection method.

[0048] The injection of the mixture of hardener and concretion agent into the hole can be done using a tip-fixation method, in which a packer or the like is used to separate an area of ​​the rock layer deep in the tunnel in the hole, and the mixture of hardener and concretion agent is injected only into this area to fix only the tip of the rock bolt, or a full-surface fixation method, in which the mixture of hardener and concretion agent is injected along the entire length of the hole to fix the entire length of the rock bolt.

[0049] However, from the viewpoint of stabilizing the rock around the tunnel, which may become a loose area, it is preferable to adopt the full-surface anchorage method.

[0050] After or before the mixture of hardener and concretion agent is injected into the hole, a nut 16 (see Figure 2), a bearing plate 18 (see Figure 2), etc. are attached to the head of the rock bolt (this is the injection process (S130)).

[0051] [Fixing process (S140)] In this process, the hardener is hardened, and the loosened areas of the rock around the tunnel are fixed to the rock layer deep inside the tunnel via rock bolts, thereby stabilizing the rock around the tunnel.

[0052] The curing conditions for the curing agent vary depending on the type of curing agent. For example, a resin-based curing agent will harden within a few hours depending on the curing agent, curing accelerator, temperature conditions, ultraviolet irradiation, etc.

[0053] If the hardener is a cement-based one, it will harden slowly over a period of several weeks, just like mortar or concrete.

[0054] Furthermore, since concretion using a concretion agent involves sealing by the diffusion of elements, the loosened areas of the rock around the tunnel are densified over a long period of time, such as several months, and this densified rock around the tunnel is fixed to the deeper rock layer via rock bolts, thereby stabilizing the rock around the tunnel (this is the fixing process (S140)).

[0055] 2 is a schematic cross-sectional view showing a stabilized tunnel-surrounding rock structure manufactured by the method of the present invention. Note that some of the reference numerals are the same as those in FIG. 12, and their explanations will be omitted.

[0056] Therefore, according to the manufacturing method of the present invention for stabilizing the rock structure around a tunnel, as shown in Figure 2, when loosened portion i of the rock around a tunnel located deep underground is fixed to the deep rock k using rock bolts 12 to stabilize it, a mixture of a hardener and a concretion agent is used as filler 14 for hole m, and as shown by the arrows in Figure 2, bicarbonate ions and / or carbonate ions penetrate into the rock portion around the hole (loosened portion i) due to a concentration gradient, and react with calcium ions in the rock and groundwater of loosened portion i (if a cement-based hardener is used as the hardener, they also react with calcium ions that have penetrated from the cement-based hardener), precipitating calcium carbonate, which fills the voids and cracks in loosened portion i, and as a result, loosened portion i is improved into a dense rock structure.

[0057] Naturally, this concretion also occurs in the hole m, and if the concretion agent also contains calcium ions, the calcium ions will penetrate further into the hole m and the rock mass around the hole m, improving the loosened part i to an even denser rock mass structure.

[0058] Furthermore, the densification effect of concretion is maintained for a longer period than with hardened cement, so loosened portions of the rock around the tunnel can be fixed to the deeper rock layer for a longer period than conventional methods.

[0059] Furthermore, since the present invention can be implemented by simply mixing a concretion agent into a hardener in a conventional rock bolting method, no major changes are required to the conventional process.

[0060] Furthermore, as mentioned above, concretion using a concretion agent is not a filling process due to a pressure gradient, but rather a sealing process due to the diffusion of elements, so it can be carried out even in the presence of spring water, and as mentioned above, the voids and cracks in the rock mass around the hole (loosened portion i) are also filled, so the present invention can also prevent spring water from being generated by the formation of a rock bolt hole. This improves the function of the rock mass as a natural barrier, and has a beneficial effect on the safety assessment of radioactive waste disposal projects.

[0061] Furthermore, by installing multiple rock bolts at predetermined intervals on the surface of the tunnel, as in the case of reinforcing a tunnel using conventional rock bolting methods, the rock mass portion (loose portion i) around the tunnel sandwiched between the rock bolts 12, 12 can be effectively densified, as shown in Figure 2.

[0062] Furthermore, since the loosened rock mass around the tunnel can be fixed to the deeper rock layer for a longer period of time than before, the tunnel's lifespan will be extended and the environmental impact of cement production, which accounts for 8% of greenhouse gas emissions, will be reduced. [Example]

[0063] EXAMPLES The present invention will be specifically explained below by showing examples, but the present invention is not limited to these examples.

[0064] (1) Indoor permeability test To confirm the effect of concretion on the loosened area of ​​the rock mass around the tunnel, a laboratory permeability test was carried out using the following procedure.

[0065] 1-1. Creation of test specimen Specimen 1 was prepared by mixing and kneading fine aggregate (land sand), cement (ordinary Portland cement), and water (tap water) in the standard mortar mix for sprayed concrete shown in Table 1 (hereinafter referred to as Mix 1), and Specimen 2 was prepared using the mix used for pit concrete in Table 2, excluding coarse aggregate (hereinafter referred to as Mix 2).

[0066] Specimens 1 and 2 were obtained by mixing and kneading the above mixtures, injecting the mixtures into a mold with a diameter of 100 mm, and curing them underwater for 28 days at room temperature and pressure. -5 ~10 -6 The permeability coefficient of the loosened rock mass around the tunnel is generally smaller than this, but this is to make it easier to confirm the sealing effect on the voids that exist in the rock mass. Specimens 1 and 2 were cut to a thickness of 10 mm, as shown in Figure 3(a).

[0067] [Table 1]

[0068] [Table 2]

[0069] 1-2. Formation of a hardened layer of a mixture of hardener and concretion agent on the test specimen Specimens 1 and 2, each 100 mm in diameter and 10 mm thick, shown in Figure 3(a) were embedded in a plastic cup filled with silicone (silicon resin) (product name: G-30M, manufacturer: Shin-Etsu Chemical Co., Ltd.) so that their surfaces were flush with the surface of the silicone, as shown in Figure 3(b), and left to cure until the silicone solidified.

[0070] Next, 100 parts by mass of epoxy resin (product name: Infraguard (registered trademark) CRJ (main agent / curing agent), manufacturer: Sekisui Chemical Co., Ltd.) as a curing agent, 100 parts by mass of calcium formate (manufactured by Sekisui Chemical Co., Ltd.) and 100 parts by mass of sodium bicarbonate (manufactured by Sekisui Chemical Co., Ltd.) as concretion agents were added to a 5 L polypropylene beaker, and the mixture was stirred to obtain a mixture of curing agent and concretion agent. The actual amounts used are shown in Table 3 below.

[0071] [Table 3]

[0072] As shown in FIG. 4(a), this mixture was poured into a plastic cup so as to be flush with the silicone and each specimen surface, to a thickness of 15 mm (see FIG. 4(b)).

[0073] After the mixture of hardener and concretion agent had hardened, the plastic cup was removed, and the silicone on the back side of each specimen was removed, as shown in Figure 5(a), and two portions of the bottom edge of the silicone were hollowed out to form water channels.

[0074] 1-3.Concrete treatment of specimens The laminates of each specimen manufactured in this way and the hardened layer of hardener and concretion agent were placed in an enamel vat with the hardened layer of hardener and concretion agent facing up, and water (distilled water) was poured into the enamel vat until the hardened layer of hardener and concretion agent was completely submerged (see Figure 5(b)). Each laminate was left in this state and cured underwater at room temperature and pressure for three months, thereby carrying out the concretion treatment of each specimen. Water was periodically poured into the enamel vat during the underwater curing period to maintain a state in which the hardened layer of hardener and concretion agent was completely covered by water.

[0075] 1-4.Evaluation of the hydraulic conductivity of the specimen From the laminate of each test specimen and the hardened layer of hardener and concretion agent, only the hardened layer of hardener and concretion agent was scraped off to obtain test specimens 1-1 and 2-1 that had been subjected to concretion treatment, respectively.

[0076] As controls, specimens 1 and 2 that were not subjected to concretion treatment will be called specimens 1-0 and 2-0.

[0077] Laboratory permeability tests were conducted on specimens 1-1 and 2-1, which had been treated with concretion, and specimens 1-0 and 2-0, which had not been treated with concretion, as follows. Specifically, the tests were conducted in accordance with the Geotechnical Society standard JGS 0312-2018.

[0078] The results are shown in Figure 6. Figure 6 is a bar graph showing the hydraulic conductivity (vertical axis: m / s) of specimens 1-1, 2-1, 1-0, and 2-0. As shown in the figure, specimens 1-1 and 2-1, which were densified by concretion treatment, had a significantly lower hydraulic conductivity than specimens 1-0 and 2-0, which were not subjected to concretion treatment.

[0079] (2) X-ray microscope observation test Next, tests were conducted to confirm the effect of the concretion treatment on non-porous, denser general concrete (mortar).

[0080] 2-1. Creation of test specimen A cylindrical hardened mortar body with a diameter of 100 mm and a height of 100 mm was produced using the cement composition (mortar) of Mixture 1 shown in Table 1. The water permeability coefficient of the obtained hardened mortar body was 10 -12 ~10 -11 in the range of m / sec.

[0081] An injection hole 6 (see Figure 7) with a diameter of 36 mm and a depth of 80 mm was drilled in the center of the top surface of this hardened mortar body, downward in the height direction of the hardened mortar body. A mixed liquid of hardener and concretion agent was injected into this injection hole until it was completely filled. The mixed liquid of hardener and concretion agent had the same composition as that used in the above (1) indoor permeability test. The hardened mortar body into which the mixed liquid of hardener and concretion agent had been injected was left to cure in air at room temperature and pressure for three months, and a cylindrical specimen 3 shown in Figure 7 was obtained.

[0082] 2-2. X-ray microscope observation Figure 8 is an elemental map of the cross section taken along line VII-VII in Figure 7, created for the cylindrical specimen 3 using an X-ray analytical microscope (product name: XGT-5200S, manufacturer: Horiba, Ltd.). The vertical axis indicates calcium concentration, with red indicating areas with high calcium concentration and blue indicating areas with low calcium concentration.

[0083] Furthermore, Figure 9 shows the Ca profile of the area enclosed by the white line in Figure 8. The vertical axis represents X-ray intensity and the horizontal axis represents length, with higher X-ray intensity indicating a greater amount of the element.

[0084] As shown in Figures 8 and 9, it was found that the calcium ions in the concretion agent filled in the injection hole also penetrated into the hardened mortar.

[0085] 2-3.Evaluation As mentioned above, the permeability coefficient of standard mortar is 10 -12 ~10 -11 As the permeability of the concrete is at the level of m / sec, and it is difficult to confirm its effect in an indoor water permeability test, as with porous mortar, the effect of concretions in standard mortar was visually verified by the X-ray microscope observation test described above (2). As a result, it was confirmed that calcium ions penetrated the standard mortar as well, just like porous mortar.

[0086] Therefore, it can be evaluated that it is possible to form concretions in the hardener in the hole m (see Figure 2) for inserting a rock bolt formed on the surface of a tunnel located deep underground and in the loosened part i (see Figure 2) of the rock around the tunnel around the hole m.

[0087] In addition, the inventors have also confirmed that when a cement-based hardener (mortar) is used instead of a resin-based hardener, the concretion agent migrates to the rock mass (loose area) around the tunnel, and the effect of forming concretions in the rock mass (loose area) around the tunnel.

[0088] (3) Elemental analysis by EPMA Next, in order to confirm whether the concretion effect can be obtained on porous rock, following the porous mortar and standard mortar, a test was conducted to confirm the effect of concretion on rock (tuff).

[0089] A disk-shaped pumice tuff with a diameter of 50 mm and a height of 10 mm (collected by a backhoe at an excavation site within the Rokkasho Mura site of Japan Nuclear Fuel Co., Ltd., wet density 1.26 mg / m 3 As with the mortar specimens, a mixture of the hardener and concretion agent shown in Table 3 was applied to the surface of the mortar specimen to a thickness of 15 mm, and the mixture was then cured in water for three months. From the resulting laminate of the disk-shaped pumice tuff and the hardened layer of hardener and concretion agent, only the hardened layer of hardener and concretion agent was scraped off to obtain specimen 3-1.

[0090] Figure 10 is a plan view of specimen 3-1. As shown in the figure, specimen 3-1 was cut in its height direction at the location of line AA, and elemental mapping of the cut surface of specimen 3-1 was performed using an electron probe microanalyzer or electron probe microanalyzer (EPMA). In this test, a JXA-8230 electron probe microanalyzer (manufactured by JEOL Ltd.) was used as the EPMA.

[0091] Figure 11(a) is a photograph in lieu of a drawing showing the results of elemental mapping of the cut surface of specimen 3-1, and Figure 11(b) is a photograph in lieu of a drawing showing the results of elemental mapping of the cut surface of a disk-shaped pumice tuff (hereinafter referred to as specimen 3-0) to which the mixture of hardener and concretion agent had not been applied.

[0092] As shown in the figure, Ca (the red part that appears white) is only distributed locally in specimen 3-0, whereas in specimen 3-1, Ca is distributed across the entire cross section from the front to the back, indicating that concretions have occurred even inside the pumice tuff.

Claims

1. a hole forming step of forming a hole from a surface of a tunnel provided deep underground to a bedrock layer deep in the tunnel; a lock bolt insertion step of inserting a lock bolt into the hole; an injection step of injecting a mixture of a hardener and a concretion agent into the hole before or after the rock bolt insertion step; a fixing process in which the hardener is hardened and the loosened area of ​​the rock mass around the tunnel is fixed to the rock layer deep in the tunnel via rock bolts, thereby stabilizing the rock mass around the tunnel; A method for manufacturing a stabilized tunnel surrounding rock structure, comprising:

2. The method for manufacturing a tunnel surrounding rock structure according to claim 1, characterized in that the hardening agent contains cement.

3. The method for manufacturing a tunnel surrounding rock structure according to claim 1, characterized in that the concretion agent contains sodium bicarbonate and a calcium ion source.

4. The method for manufacturing a tunnel-periphery rock structure according to any one of claims 1 to 3, characterized in that the tunnel is a tunnel for storing radioactive waste.

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