JP5401664B2 - Injection material construction method - Google Patents

Description

  The present invention relates to a method for constructing an injection material used in a radioactive waste disposal site constructed in a bedrock in the deep underground.

  In general, there is spring water in underground mine excavation, so that excavation is performed after draining water, injecting an injection material, and stopping water so as not to hinder the excavation.

  In the radioactive waste disposal site constructed in the bedrock in the deep underground, it is highly possible that the amount of spring water is more severely restricted than normal underground structures in consideration of workability during operation. For this reason, the highly permeable injection material which can stop water reliably also to the slight spring water from a fine crack is calculated | required. Moreover, since high groundwater pressure is assumed to be applied, a high-strength injection material is required. Furthermore, the injection material is required to have durability to ensure water-stopping during the operation period.

Examples of the injection material include cement-based, water glass-based, colloidal silica-based, and organic resin-based materials.
The cement system has high strength and high durability, but its permeability is lower than that of other material systems, and higher permeability is required. Blast furnace slag-containing fine particles or ultrafine particle cement (see Patent Document 1) with improved permeability has been developed. For rock cracks with a maximum particle size of about 18 μm and a crack opening width of several tens of μm. Hardly penetrates. In addition, it is assumed that calcium hydroxide is generated by hydration of cement, and the influence of its high alkalinity causes the alteration of the rocks that serve as natural barriers and the artificial barrier materials that serve as engineering barriers. There is concern about the impact on the isolation performance.

  The water glass system (see Patent Document 2) has high permeability and good water stopping properties. However, since the gel strength is low, there is a problem that the gel body may be pushed out when high water pressure is applied, and durability is lowered due to elution of silica.

  Although colloidal silica type (refer patent document 3) is low alkalinity, the intensity | strength of a gel body is low and there exists a possibility that a gel body may be extruded when high water pressure is applied like a water glass type | system | group.

  The organic resin system (see Patent Document 4) has the advantage of strong adhesion, but organic substances and decomposition products of organic substances may form a carrier with the radionuclide to accelerate the transfer of the radionuclide. It was.

As a method for solving these problems, a low alkaline cement (see Patent Document 5) in which silica fume or the like is blended with ultrafine normal portland cement is known.
This low alkaline cement is based on ultrafine ordinary Portland cement and has a maximum particle size of about 15 μm, which is the same as that of ultrafine cement.

  On the other hand, it is known that spherical spherical silica powder (spherical silica fine powder) is obtained by melting a silicon material in a high-temperature air stream (see Patent Documents 6 and 7). Describes that spherical silica fine powder is used as a sealing material, but it is not suggested to use it as an injection material.

JP 2001-233645 A Japanese Patent Laid-Open No. 2004-27023 JP-A-5-70776 Japanese Patent Laid-Open No. 3-233075 JP 2000-65992 A JP 2001-335313 A Japanese Patent Laid-Open No. 2002-2011

In the radioactive waste disposal site constructed in the bedrock in the deep underground, in order to reduce the amount of spring water, it has higher permeability against fine cracks and high resistance to resist high groundwater pressure. There was a need for a strong injection material. Furthermore, the durability which ensures the water stop in the operation period was also calculated | required. In addition, rocks that serve as natural barriers for radioactive waste disposal sites and artificial barriers installed around radioactive wastes are required to have long-term stability and resistance to alteration. However, if the groundwater in contact with the rock mass or the artificial barrier becomes highly alkaline due to the cement-based material used as an injection material for the support work or water stoppage, there is a concern about the alteration of the rock mass or the artificial barrier. In order to reduce the impact on the long-term performance of such rocks and artificial barriers, in the development of cement-based materials including injecting materials used in the disposal environment, the pH value is set to 11 or less. Yes.
The present invention is intended to solve the above-described problems, and is an injection material construction method required for a radioactive waste disposal site, which has high permeability, high strength, high durability, and at least a pH value of 11. It aims at providing the construction method of the following injection | pouring materials.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that this can be achieved by selecting spherical silica fine powder as the base material of the permeable injecting material. The spherical silica is a spherical body of silica as described in Patent Documents 6 and 7 obtained by melting a siliceous material in a high-temperature air stream. The spherical body is cooled, classified and collected to obtain fine spherical silica powder used in the present invention. The spherical silica fine powder is finer than the cement-based material, and exhibits high permeability because of the spherical body. Even if spherical silica fine powder is put in water, hydraulic properties cannot be obtained by itself, but by adding a specific amount of slaked lime fine powder as a curing agent, a hydration reaction occurs to produce calcium silicate hydrate, which has high strength and high strength. Shows durability and low alkalinity.

The present invention employs the following means in order to solve the above problems.
( 1 ) A radioactive waste characterized by injecting an injection material containing spherical silica fine powder and slaked lime fine powder, which has a pH value of 11 or less from leachate from the cured product, and pressurizing and dehydrating the injection material This is a construction method for the injection material used for the underground rock mass during the construction of the disposal site.
( 2 ) In the construction method of the injection material used for the underground rock mass at the time of construction of the radioactive waste disposal site according to ( 1 ), wherein the injection material is pressurized and dehydrated in the crack of the rock mass. is there.
(3) the spherical molar ratio of slaked lime pulverized to silica fine powder, radioactive waste of the to and less than 1.5 in a molar ratio in terms of CaO / SiO ₂ (1) or (2) Disposal This is the method of construction of the injection material used for the underground bedrock during the construction of the site.
( 4 ) Construction of injection material to be used for underground rocks when constructing the radioactive waste disposal site according to any one of (1) to ( 3), wherein a high-performance water reducing agent is used as a dispersant. Is the method.
( 5 ) The spherical silica fine powder has a maximum particle size of 1 μm or less, and the injection used for the underground bedrock during construction of the radioactive waste disposal site according to any one of (1) to ( 4) above It is a construction method of materials.
( 6 ) The injection material used for the underground bedrock when constructing the radioactive waste disposal site according to any one of (1) to ( 5) above, wherein the maximum particle size of the slaked lime fine powder is 1 μm or less This is the construction method.
In addition, as long as there is no description, the part and% described in this invention mean a mass part and mass%.

By the injection method of the present invention, spring water generated by underground mine excavation or the like can be stopped by prior injection. Even cracks that do not penetrate with cement material and are difficult to stop water can be solidified and stopped by using this method. The pH value of leachate from the cured product of the injection material is 11 or less.
In addition, the injection material has a small amount of bleeding and also has a pressure dehydration effect of the injection material due to the injection pressure, and the injection hardened body has a feature that voids due to bleeding cannot be formed even after filling with respect to small cracks.

Hereinafter, embodiments of the present invention will be specifically described.
Spherical silica is a spherical body of silica obtained by melting a siliceous material in a high-temperature air stream. The spherical body is cooled, classified and collected to obtain fine spherical silica powder used in the present invention. A smaller maximum particle size is preferred from the viewpoint of permeability. The maximum particle size is preferably 1 μm or less.
The particle diameter of the slaked lime fine powder of the present invention is preferably equal to or less than the spherical silica fine powder used for the maximum particle diameter. A maximum particle size of 1 μm or less is preferred.

In the present invention, the molar ratio of the slaked lime fine powder to the spherical silica fine powder is preferably less than 1.5 in terms of a molar ratio converted to CaO / SiO ₂ , more preferably 1.0 or less. It is particularly preferable to set it to 8 or less.
By setting the CaO / SiO ₂ molar ratio to less than 1.5, the pH value of leachate from the cured product of the injection material can be made 11 or less.
In the present invention, from the viewpoint of improving the compressive strength, the molar ratio of the slaked lime fine powder to the spherical silica fine powder is preferably 0.04 or more in terms of a molar ratio converted to CaO / SiO _2. More preferably.

  The concentration of the injection material is not particularly limited, but is preferably 70 to 500%, more preferably 90 to 300%, and most preferably 100 to 150% in terms of water / powder ratio. The powder means a mixture of spherical silica fine powder and slaked lime fine powder. When the concentration is high, the strength is high but the permeability is lowered. When the concentration is thin, the permeability is high but the strength tends to be lowered.

  It is preferable to use a high-performance water reducing agent as the dispersant, and the components of the high-performance water reducing agent are not particularly limited. High-performance water reducing agents are polyalkylallyl sulfonate-based high-performance water reducing agents, aromatic amino sulfonate-based high-performance water reducing agents, melamine formalin resin sulfonate-based high-performance water reducing agents, and polycarboxylate-based water reducing agents. The main component is any one of a high-performance water reducing agent, and one or more of these are used. Polyalkylallyl sulfonate-based high-performance water reducing agents include methyl naphthalene sulfonic acid formalin condensate, naphthalene sulfonic acid formalin condensate, and anthracene sulfonic acid formalin condensate. Also, it has a feature that the setting delay is small. Typical examples of commercially available products are “FT-500” and its series, trade name of “Electrochemical Industry Co., Ltd.”, “Mighty 100 (powder)” and “Mighty 150” and its series of Kao Corporation. The amount of the high-performance water reducing agent added is not particularly limited, but is preferably 10% or less, more preferably 5% or less, in terms of solid content, based on the total amount of spherical silica and slaked lime. The amount of the high-performance water reducing agent added is not particularly limited, but is preferably 0.5% or more, and more preferably 1% or more. The gel time can be adjusted by the amount of the high-performance water reducing agent added, and the gel time can be lengthened as the added amount increases.

In injecting the injection material into a rock crack or the like, it is preferable to inject and pressure dehydrate. More preferably, the injection pressure is higher than the spring water pressure by 0.5 MPa or more and pressure dehydration is performed. When the injection material penetrates into cracks and gels by hydration, the spherical silica and slaked lime are combined to increase the particle size. For this reason, the injection material is stopped at the minimum part of the crack, and the subsequent injection material is pressure-dehydrated. Due to the pressure dehydration, the injection material becomes a high concentration, and exhibits higher strength properties than those initially set at the start of injection. A high-strength cured body makes it difficult for water to pass through and increases water-stopping and durability.
Further, pressure dehydration occurs even in the injection material before gelation. The pressure dehydration action similar to that described above occurs when the infiltrated material that has penetrated has a crack width that prevents the infused material from penetrating at the minimum crack portion. In the present invention, in principle, high-pressure injection is performed up to the final injection pressure set in order to actively utilize pressurized dehydration, and it is preferable that the injection end pressure is at least 0.5 MPa higher than the injection start pressure.

  The construction method is to drill the target ground and install a leak-proof packer in the ground such as rock. Spherical silica and slaked lime are preliminarily blended or mixed separately with water, and the respective slurries are pumped and merged with separate pumps and injected through a borehole. The injection rate is usually 10 to 50 liters / minute.

When the gel time is short, gelation occurs near the injection hole, and the injection range becomes small. When the gel time is long, the injection range becomes wide. Usually, the water stoppage range of underground structures such as tunnels is 1.5 to 2.0D (D: diameter) where the ground is good, and about 5D where it is bad. The gel time is as short as 10 to 30 minutes and as long as 15 hours. If the gel time is long, close the inlet valve and wait for curing. By conducting test injection in advance, the state of cracks in the natural ground, the penetration range, etc. are investigated and the gel time is set.
In the method of the present invention, the gel time can be set by adjusting the addition amount of the high-performance water reducing agent, the concentration of the injection material, the temperature of the injection material, and the like.

  As the injection method, an injection method such as a double pipe double packer method or a strainer method can be used, and a 1, 1.5, two-shot method or the like can be used as a slurry mixing method.

Hereinafter, the present invention will be described based on examples.
Examples and Comparative Examples were performed at 20 ° C. unless otherwise specified.

Example 1
Spherical silica fine powder having a SiO ₂ purity of 99% or more (Electrochemical Industry Co., Ltd., trade name “SFP20M”) was dispersed in water to prepare a slurry having a concentration of 50%. As a result of measurement by a particle size distribution meter, the maximum particle size was 1.0 μm.
An ultrafine slaked lime powder (purity 99% or more) was used as a 20% concentration slurry to prepare a curing material. As a result of measurement by a particle size distribution meter, the maximum particle size was 1.0 μm.
The spherical silica fine powder / slaked lime fine powder in a slurry state is 1/1 (CaO / SiO ₂ molar ratio 0.35) by volume, immediately mixed and put into a mold having a diameter of 5 × 10 cm in height and demolded after one day. The uniaxial compressive strength and the pH value of leachate from the cured body (hereinafter referred to as “the pH value of the cured body”) were measured according to the age of the material cured at 20 ° C. The pH value was measured with a glass electrode pH meter after mixing 100 g of the cured product of the injection material and 1 liter of water. The gel time was 20 seconds.
Table 1 shows the measurement results of uniaxial compressive strength and pH value.

(Example 2)
The volume of the spherical silica fine powder / slaked lime fine powder in the slurry state of Example 1 is 1/1, and a high-performance water reducing agent (trade name “Kao Co., Ltd.” having a solid content conversion of 2% with respect to the total of the spherical silica fine powder and slaked lime fine powder. The gel time of the injection material mixed and mixed with “Mighty 150” and naphthalenesulfonic acid formalin condensate) was 9 hours, the specimen compressive strength after 7 days was 0.6 N / mm ² , and the pH value of the cured product was 10.4. there were. No. 7 cinnabar sand was packed in an acrylic tube having a diameter of 5 cm and a height of 1 m, and water penetration was performed, and then a permeability test was performed. The injection pressure was 0.5 MPa using air pressure. A 1.5 liter mixture was allowed to pass through in 10 minutes. The pH value at the age of 28 days was 10.2.

(Comparative Example 1)
For comparison, a permeability test into No. 7 sand was conducted in the same manner as in Example 2 using a 30% concentration slurry of ultrafine cement (Electrochemical Industry Co., Ltd., trade name “DENKA Ultrafine Cement Colloidal Super”). . It penetrated up to 10 cm, but did not penetrate any further. The pH value of the cured product was 12.3.

(Example 3)
Liquid A and liquid B were prepared according to the formulation shown in Table 2, and both liquids were mixed and placed in a cylindrical frame having a diameter of 5 cm and a height of 10 cm to prepare a cured body, and the uniaxial compressive strength was measured according to material age. Table 3 shows the test results at a curing temperature of 20 ° C. The same high performance water reducing agent as in Example 2 was used as a dispersant. The pH value of the cured product with a material age of 28 days was measured.

Example 4
In the blend of 30% slaked lime of Example 3, the gel time was measured by changing the blending amount of the high-performance water reducing agent. The measurement temperature was 20 ° C. Table 4 shows the measurement results.
In the case where the high-performance water reducing agent was not blended, the viscosity increased 10 seconds after mixing and the fluidity was lost and gelled. Increasing the blending amount increased the gel time.
The gel time was defined as the point at which the fluidity disappeared even when the injection material was placed in a 200 ml plastic container and tilted.

(Example 5)
The compounding material of Example 1 was used to adjust the injecting material to gel. Moreover, the specimen for compressive strength was sampled before gelatinization. The gelled material was pressurized with a pressure dehydration tester, and the pressure dehydration rate and the subsequent compressive strength were measured. Table 5 shows the measurement results.
It was confirmed that the compressive strength was increased by dehydrating under pressure after gelation.
The pressure dehydration rate was expressed as (dehydrated amount dehydrated by pressurization / total water amount before pressurization) × 100 (%).

  INDUSTRIAL APPLICABILITY The present invention is an injection material construction method that exhibits high permeability and low alkalinity, and can be used for construction of a radioactive waste disposal site.

Claims (6)

  An injecting material containing spherical silica fine powder and slaked lime fine powder, and injecting an injecting material having a pH value of 11 or less from leachate of the cured product, and dehydrating under pressure. Construction method of injection material used for underground rock mass during construction. The method for constructing an injection material used for an underground rock mass when constructing a radioactive waste disposal site according to claim 1 , wherein the injection material is pressurized and dehydrated in a crack of the rock mass. The molar ratio of the hydrated lime fines with respect to the spherical silica fine powder, when the construction of radioactive waste disposal site according to claim 1 or 2, characterized in that less than 1.5 in a molar ratio in terms of CaO / SiO ₂ The method of construction of the injection material used for underground bedrock. The high performance water reducing agent is used as a dispersing agent, The construction method of the injection material used with respect to an underground bedrock at the time of construction of the radioactive waste disposal site as described in any one of Claims 1-3 characterized by the above-mentioned. The grout maximum particle size of the spherical silica fine powder to be used for radioactive waste disposal site during construction underground rock according to any one of claims 1 to 4, characterized in that at 1μm or less Construction method. Construction of grout maximum particle size of the hydrated lime fines be used for claims 1 to 5 or underground rock during construction of radioactive waste disposal sites according to one of, characterized in that at 1μm or less Method.