JP2023133018A - Ground injection method and ground injection material - Google Patents

Abstract

To provide an environmentally friendly ground injection method and ground injection material by converting the conventional qualitative techniques into quantitative techniques in order to further develop the conventional invention and reduce the environmental load of the ground injection.SOLUTION: The present invention relates to a ground injection material that is made of non-alkali silica grout with a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10, and is injected into the ground to form a ground improvement area. The ground injection material contains water-soluble reaction products such that the concentration of the water-soluble reaction products derived from the ground injection material does not affect the environment within the ground improvement area, and consists of a silica concentration that meets the injection purpose for the ground conditions and a formulation that is compatible with the applied construction method.SELECTED DRAWING: None

Description

The present invention relates to a durable grout and a durable grout injection method using non-alkali silica grout, and relates to a highly durable ground injection material and a ground injection method that have little or reduced environmental impact. be.

In recent years, there has been an increase in the number of cases in which permanent grout is used as a permanent grout method for liquefaction prevention works such as seawalls, directly beneath buildings, and urban infrastructure. Furthermore, as the scope of its application expands as a durable grout for temporary injection, environmental protection such as impact on groundwater, underground structures, marine life, etc. is required.

For permanent injection, especially for liquefaction countermeasure works, in order to obtain economic efficiency, wide-area infiltration and consolidation is performed by continuous injection for several hours to more than ten hours at large injection hole intervals (1.0 to 3.0 m). Table 17), a solution type silica grout that has a long gelation time and maintains long-term durability must be used (Figures 1 and 2). In addition, during excavation work, it can be used to improve the surrounding area of existing concrete structures, directly under it, or the ground where concrete structures are planned to be constructed in the future. Application of silica grout is required. Years of research have demonstrated the suitability of dealkalized non-alkaline silica solutions. Dealalization includes a colloidal method using an ion exchange method or a metal silica method, and a neutralization method using an acidic neutralizing agent (silica sol method) (Figures 1 and 2).

Both activated composite silica (silica grout containing colloid and water glass) used as permanent grout and medium acidic water glass grout (silica sol grout containing water glass and acid as active ingredients) use acid as a neutralizing agent for water glass. . As the acid, sulfuric acid or phosphoric acid, an inorganic acid salt, an organic acid, or a salt of an organic acid is used, but sulfuric acid is often used in consideration of economic efficiency. In addition, organic reactants such as various inorganic salts, salts of organic acids, esters such as acetic esters and carbonic esters that act as acids against alkalis, and aldehydes such as glyoxal may be used as auxiliaries.

Non-alkali silica grout is a grout that uses water glass, silica colloid, or both as a main ingredient, and is a grout from which alkali, which causes deterioration of silica gel, has been removed. Figures 1 and 2 show the characteristics of non-alkali silica grout. Removal of alkali from water glass is carried out by neutralization with acid, or by silica colloid formation using ion exchange method or metal silica method, but in both cases, the alkali content is negligible, so neutralization of water glass with acid is performed. is the main thing. As the acid, sulfuric acid is mainly used because it is economical. For this reason, the applicant has developed an environmentally friendly, highly durable non-alkali silica grout and a ground injection method that takes into account the impact of sulfate ions on the environment.

The present applicant has already filed applications for construction methods and protection construction methods for reducing the influence of sulfate ions on concrete structures in non-alkali silica grout (Patent Documents 1 to 6).

However, in actual ground injection, non-alkaline silica grout containing sulfate ions must contain enough sulfate ions to have no effect on underground structures, and when injecting into the ground, it is necessary to Unless the ground injection material has a formulation that is compatible with the method, injection design, and gel time that enables penetration, it is not possible to simultaneously satisfy durability and environmental protection.

In this specification, the following names are registered trademarks of Reinforced Soil Engineering Co., Ltd. Permanent grout (Registration No. 4354870, Registration No. 4360797), Durable silica (Registration No. 5925766), Honsetsu (Registration No. 5153955), Colloidal (Registration No. 5274223, Registration No. 5255070), Silica sol (Registration No. 4044042) ), composite silica (registration no. 4334170), activated silica (registration no. 4263001), activated composite silica (registration no. 5490920, registration no. 5497092), composite injection (registration no. 3057154), non-alkali silica (registration No. 6322403), Masking Silica (Registration No. 4629139), Masking Separate (Registration No. 5381384), Activated Silica Colloid (Trademark Registration No. 4295262, Trademark Registration No. 4189116).

Patent No. 5277380 Patent No. 5309384 Patent No. 4948661 Patent No. 4766532 Patent No. 4827039 Patent No. 4780803

The present invention further develops the above-mentioned invention of the prior application, and in order to reduce the environmental load of the grouting ground, the conventional qualitative technique is changed to a quantitative technique to perform durable grouting into the ground, which is environmentally friendly and has excellent durability. The purpose is to provide materials and durable grouting methods.

Through many years of indoor and field experiments, the present inventors have found that durable non-alkali silica grout containing sulfuric acid contains sulfate ions at a level that does not affect concrete structures, and that it can be injected into the ground. In order to do so, the non-alkaline silica grout must have a silica concentration that satisfies the injection purpose, a silica concentration that meets the injection method and injection design applicable to various ground conditions, a silica concentration that meets the permeable gel time, and a sulfate ion concentration. The present invention was developed as a result of efforts to address this issue.

The present invention is a non-alkali silica grout made by neutralizing the alkali of water glass with an acid, which has strength that satisfies the purpose of injection in relation to ground conditions, is compatible with the applied injection method and injection design, and has a high penetration rate. This invention relates to a durable grout that has a formulation that is excellent in hardness, solidification, and durability, and is environmentally friendly, and a durable grout injection method into the ground.

An outline of the present invention will be described below.

The present inventors have demonstrated that the sulfate ion concentration of non-alkaline silica grout injected into the ground is reduced by being diluted with groundwater. (Fig. 4), and numerically demonstrated that the sulfate ion concentration of the injection solution elutes from the gel after being injected into the ground and decreases over time in a relatively short period of time (Fig. 4, Table 7).

Next, when the reduction factor of sulfate ions from gel is Y (Table 10) and Y is the residual rate △, the residual sulfate ion concentration when a ground injection material with sulfate ion concentration (a) is injected into the ground. (Δ) The sulfate ion concentration (X) of the injection ground was set from (Table 10), and the formulation of the injection solution was set so that the concentration was equal to or less than the concentration (W) that affected the mortar specimen.

The reduction factor of sulfate ions is affected by the ground conditions and groundwater conditions, so in order to understand this concretely, we decided to select a type of non-alkaline silica solution that is suitable for the ground conditions and groundwater conditions in the injected ground. (Table 4). Next, the reduction factors (Y) for sulfate ions are summarized as △ (Table 10), and for each △, sulfate ions (X) in the ground are calculated, and (X) is safe for concrete structures. If it is not safe, safety measures will be provided (Figures 20 to 29).

However, even if the X value is safe for concrete, in actual construction, the silica concentration must be determined so that the injection material with the sulfate ion concentration has the strength (Figure 3 (d)) that meets the injection purpose under various ground conditions. retention (Fig. 1(c), Fig. 3), injection method (Fig. 11, Fig. 12, Table 6), injection design (Table 17), and gel time that enables penetration (Fig. 1(b), (c), Fig. 6). It must be a non-alkali silica grout with a formulation that meets the conditions as shown in Figures 10, 32, and 33). For this reason, the present inventors clarified the relationship among water glass molar ratio, water glass concentration, pH, sulfate ion concentration, gel time, and consolidation strength (Figure 1 (b) and (c)), and furthermore, Test examples of water glass concentration, sulfate ion concentration, gel time (Figure 1, Figures 6 to 10, Table 11), injection method, injection design, penetration test method and penetration test results (Figures 13 to 17), durability test From the results (Figure 3(c)), it was possible to set a formulation for an injection solution containing sulfate ions that would not affect concrete.

From the above, conventional environmentally friendly injection materials or injection methods were qualitative techniques, but the present invention has turned them into quantitative techniques. In addition, in the present invention, any or more of the injection method, injection design (Table 16, Table 17, Figure 11, Figure 12, Figure 32), gel time setting to enable penetration (Figures 6 to 10), etc. , described as a ``construction method.''

Generally, chemicals have some effect on the durability of concrete. Chemicals are used in the injection materials used in the chemical injection method, but the influence of the injection materials on concrete cannot simply be discussed in the same way as the relationship between chemicals and concrete.

Reactants commonly used in chemical injection, such as sulfuric compounds, bicarbonates, and chlorides, all have more or less negative effects if they continue to act on concrete. Among these, sulfuric compounds are basic materials in the modern chemical industry, including fertilizers such as ammonium sulfate (ammonium sulfate) and food additives, and are also used as neutralizing treatment agents for industrial wastewater and wastewater from construction work. Widely used. Sulfate ions are widely present in the natural world, with concentrations of 2.649 (‰, g/kg) in seawater and 15.11 mg/L in rivers ("Industrial Water and Wastewater Treatment", Nippon Kogyo Shimbun) , P.4,5).

In addition, sulfate ions are widely distributed in hot spring soil, volcanic deposits, river bottom soil, trash piles, etc., and there are virtually no references in the literature that they have a negative effect on concrete. We are discussing the case where it continues to act on concrete semi-permanently at a constant concentration.

Concerning the causes of concrete embrittlement, it is known that the cause of concrete embrittlement, expansion, and destruction is due to deterioration due to sulfates. When ettringite is produced in this reaction, a large expansion pressure is generated. This expansion pressure destroys the concrete. Moreover, when drying and wetting are repeated, localized destruction and sulfate seepage into the concrete are repeated, and the destruction progresses.

On the other hand, when considering it as a drug solution injection material, it is necessary to consider the following points that differ from the above-mentioned conditions.
i) The chemical solution injected into the ground is extremely limited in quantity when viewed from the groundwater level of the entire injected ground, and is also limited in terms of injection period and location. It is not something that continues to work permanently.
ii) The injection liquid injected into the ground forms a gel after penetrating between the soil particles. Water-soluble reaction products, excluding the silica component that constituted the gel, rapidly dissolve into groundwater. The effect on concrete structures is not due to the pH of the injection solution but to the concentration of sulfate ions, which are water-soluble reaction products. The water-soluble reaction product and concentration of silica grout vary depending on the formulation, such as the composition of the silica component, the composition of the reactant, and the gel time.
iii) The sulfate ions eluted from the gel into the groundwater diffuse into the groundwater and the concentration decreases, and at the same time the concentration of sulfate ions remaining in the gel decreases and eventually dissipates (Figures 4 and 5 and natural sulfate ion concentrations).
iv) For the above reasons, the concentration of sulfate ions, excluding the silica component that forms gels, in the injection material injected into the ground rapidly decreases in concentration in a relatively short period of time due to dilution and diffusion by groundwater. It does not act on concrete forever at a constant concentration.
v) However, the elution rate of sulfate ions from silica gel into groundwater varies depending on ground conditions, groundwater conditions, etc. Therefore, a ground injection material that is environmentally friendly and has excellent durability and consolidation properties is one that has a pH in the non-alkaline range (pH 1 to 10) and that sulfate ions can be used in concrete under ground conditions or groundwater conditions in the implanted ground. The injection material must be at a concentration that does not affect the structure, and has a formulation that is compatible with the construction method, including the injection purpose, injection method, injection design (Figure 32), and gel time to enable penetration. required. As described above, in the present invention, any one or more of the injection method, injection design, and gel time setting that enables penetration is expressed as a "construction method."

From this point of view, the present inventors have arrived at the present invention.

The ground injection material of the present invention is composed of a non-alkali silica grout having a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10, and is a ground injection material that is injected into the ground to form a ground improvement area,
The ground injection material contains a water-soluble reaction product whose concentration is such that the concentration of water-soluble reaction products derived from the ground injection material does not affect the environment within the ground improvement area, and the concentration of water-soluble reaction products derived from the ground injection material is such that it does not affect the environment in the ground improvement area, and It is characterized by having a silica concentration that satisfies the purpose of injection and a formulation that is compatible with the applied construction method.

In the present invention, the ground injection material contains as active ingredients one or more silica components of water glass or silica colloid, and an acidic agent that neutralizes alkali in the silica component, and the ground injection material The concentration of sulfate ions, which are water-soluble reaction products from the origin, contains sulfate ions to an extent that does not affect the structures in the ground improvement area, and has a silica concentration that satisfies the purpose of injection in the ground condition. It is preferable that the formulation be comprised of a formulation that enables a gel time with permeability that is compatible with the applied construction method.

In the present invention, the concentration of sulfate ions as a water-soluble reaction product derived from the ground injection material in the ground improvement area contains sulfate ions in the ground to an extent that does not affect concrete, and the purpose of injection is achieved. It is preferable that the composition has a silica concentration that achieves the required strength and a formulation that provides permeability that is compatible with the applied construction method.

In the present invention, it is preferable that the acidic agent is one or more of a sulfuric acid compound and a non-sulfuric acid compound.

In the present invention, it is preferable that the non-sulfuric acid compound is one or more of an inorganic acid other than sulfuric acid, an organic acid, or an acidic salt thereof.

In the present invention, it is preferable that the ground injection material contains one or more of a phosphoric acid compound, a sequestering agent, and a chelating agent as an active ingredient.

In the present invention, the ground injection material is such that the concentration of sulfate ions as a water-soluble reaction product derived from the ground injection material in the ground improvement area does not affect the environment in the ground by the following method. The silica concentration is adjusted to a certain level, or the concentration is adjusted to a level that does not affect the environment and the structure, and has a silica concentration that satisfies the purpose of injection into the ground and a formulation that is compatible with the applied construction method. It is preferable that
1) Calcium contained in the ground improvement area and sulfate ions in the ground injection material become calcium sulfate and are fixed in the ground, thereby reducing the sulfate ion concentration in the ground.
2) After primary injection of cement bentonite, calcium silicate, or slag-based calcium-containing suspension-type injection material or calcium-containing solution-type injection material into the ground improvement area, the above-mentioned ground injection material is injected as a secondary injection material. By reducing the injection rate of the sulfate ion-containing ground injection material by the injection amount of the suspension type injection material or the calcium-containing solution type injection material, water-soluble reaction products derived from the ground injection material can be treated. reduce the concentration of sulfate ions.
3) A non-sulfuric acid injection part, a low sulfuric acid injection material injection part, or a non-injection part of the injection material is provided in the ground improvement area to reduce sulfate ions in the ground improvement area.
4) It is assumed that sulfate ions are eluted from the ground improvement area into groundwater and the sulfate ions in the ground improvement area are reduced.
5) Part or all of the silica component contained in the ground injection material is replaced with silica colloid to reduce sulfate ions in the ground improvement area.
6) As a reactive agent contained in the ground injection material, one or both of a non-sulfuric acid compound and a sulfuric acid compound is used.
7) Fixing sulfate ions in the ground improvement area or in the ground injection material to reduce sulfate ions in the ground improvement area. For example, by fixing sulfate ions in primary injection cement or secondary injection materials containing sulfate ions with calcium-containing injection materials, the concentration of sulfate ions in the implanted ground can be adjusted to a level that is assumed to have no impact on the environment. It can be reduced to
8) The ground improvement area is to be improved by injecting the alkaline water glass grout and the sulfuric acid-based ground injection material, and the injection rate of the alkaline water glass grout is set to The injection rate is set to reduce the concentration of water-soluble reaction products to a level that does not affect the environment.
9) Part or all of the sulfate ions in the ground injection material are replaced with non-sulfate ions.
10) For example, a calcium material is added to the ground injection material to trap some or all of the sulfate ions.
11) For the surrounding area of the concrete structure in the ground improvement area, by using one or more of the following (1) to (5) in combination, the sulfuric acid-based ground injection material in the ground improvement area The concentration of sulfate ions in the concrete structure is reduced to a concentration that is assumed not to affect the concrete structure.
(1) Water glass injection materials (2) Suspension injection materials (3) Low sulfate compound injection materials (4) Combination of sulfate compound injection materials and non-sulfate compound injection materials (5) Phosphoric acid compounds, metals An injection material containing one or more of an ion sequestering agent and a chelating agent 12) The surrounding area of the concrete structure in the ground improvement area is treated with one or more of a phosphoric acid compound, a metal ion sequestering agent, and a chelating agent. Consolidate with non-alkali silica grout containing multiple.

In the present invention, the ground injection material has a concentration of sulfate ions in the ground improvement area that is based on one or more of the concrete structure, ground condition, groundwater situation, and injection conditions in the ground improvement area. It is preferable that the amount is such that the influence on the concrete structure can be reduced in response to the behavior of the water-soluble reaction product derived from the ground injection material, and that the formulation is compatible with the construction method employed.

In the present invention, the ground injection material has a sulfate ion concentration (a) such that the sulfate ion concentration (X) in the ground improvement area is equal to or lower than a maximum value W, and the ground injection material to which it is applied It is preferable that the composition be made of a formulation that satisfies the purpose of injection in the construction method.

In the present invention, the ground injection material is applied to the ground improvement area or the injection solids according to the injection ground condition and groundwater condition by one or more of the following methods (1) to (6). The concentration of the water-soluble reaction product derived from the ground injection material is adjusted to a level that does not affect the concrete structure, and the silica concentration satisfies the above ground conditions and injection purpose, and the applied construction method It shall consist of a formulation that is compatible and allows for a gel time that is permeable.
(1) Setting the silica concentration based on the injection purpose and the ground conditions.
(2) Setting the elution rate (α) and residual rate (Δ) of the water-soluble reaction product in the factor (Y) that reduces the influence of the water-soluble reaction product on the concrete structure in the ground improvement area.
(3) Setting the maximum value (W) of sulfate ion concentration in the ground that is assumed not to affect the concrete structure.
(4) Setting the sulfate ion concentration (X) in the ground based on the ground conditions and the reduction factor (Y).
(5) Setting the concentration (a) of sulfate ions in the ground injection material that satisfies W≧X (=A×a×Y).
(6) Setting the formulation of the ground injection material corresponding to the silica concentration and sulfate ion concentration (a) that satisfies the injection purpose, which is compatible with the injection purpose, ground condition, and applied construction method.

In this way, the injection material of the present invention has a silica concentration that satisfies the injection purpose (Fig. 1 (c), Fig. 3), an applied construction method (injection method (Fig. 11, Fig. 12), and an injection design ( Table 16, Table 17), sulfate ion concentration (a) in the formulation of the injection solution that is compatible with the gel time that enables penetration (Figures 1 (b), (c), Figures 6 to 10)) is injected into the ground. Based on the residual rate of sulfate ions in the ground, it is possible to set a formulation that satisfies the safety of underground structures. In addition, it is possible to check whether the set formulation of the ground injection material is compatible with the injection purpose, ground condition, construction method (injection method, injection design, gel time), and is safe for concrete.

The ground injection material of the present invention changes the behavior of the water-soluble reaction product derived from the ground injection material based on any or more of the concrete structure, ground condition, groundwater condition, and injection conditions in the ground improvement area. Correspondingly, we quantitatively set the factors (Y) that reduce the environmental impact of the water-soluble reaction product, and in addition to reducing the environmental impact, we determined the purpose of injection that is compatible with the ground conditions and the applied construction method. It can be made of a formulation corresponding to the silica concentration and sulfate ion concentration (a) to be satisfied.

In the present invention, the elution rate of the water-soluble reaction product in the factor (Y) for reducing the influence of sulfate ions on the concrete structure in the ground improvement area is set as (α), and the residual rate is set as (△). Any or more of the following △1 to △7 can be set as the reduction factor (Y).
X ₁ =A×a W ₁ ≧X ₁
X ₂ =A×a×Y W ₂ ≧X ₂
A: Injection rate (%)/100
a: Sulfate ion concentration in the injection material (ppm)
_{X 1 ,} Residual rate of sulfate ion △1=1-α ₁
△2: Residual rate of sulfate ions in the ground improvement area, when the elution rate of sulfate ions into groundwater is α ₂ △ 2 = 1 - α ₂
△3: When the fixation rate of sulfate ions in the ground improvement area is α ₃ (=elution rate), the residual rate of sulfate ions in the ground improvement area △3=1−α ₃
△4: When the substitution rate of sulfate ions of sulfate-based injection material by non-sulfuric acid-based injection material or low-sulfuric acid-based injection material in the ground improvement area is α ₄ (=elution rate), within the ground improvement area Residual rate of sulfate ions in △4=1-α ₄
△5: When the substitution rate of the silica component in the ground injection material with the colloid is α ₅ (=elution rate), the residual rate of sulfate ions in the ground improvement area △ 5 = 1 - α ₅
△6: When some or all of the sulfate ions are captured in the ground injection material and the capture rate is α ₆ (=elution rate), the residual rate of sulfate ions in the ground improvement area △6=1 -α ₆
△7: When the injection rate of the ground injection material in the ground improvement area is reduced and the reduction rate of the injection rate is α ₇ (= elution rate), the residual rate of sulfate ions in the ground improvement area △ 7=1-α ₇

In the present invention, the expression "elution rate of sulfate ions from the gel" can be replaced with the expression "reduction rate of sulfate ions in the gel".

The ground injection material of the present invention contains sulfate ions such that the sulfate ion concentration (X) in the ground improvement area or the injected compact is below the maximum value W that is assumed not to affect the concrete structure. It is preferable to have the concentration (a) and a formulation that satisfies the purpose of injection in the applied ground condition and applied construction method.

The ground injection material of the present invention is a non-alkaline silica grout made of a sulfuric acid-based injection material with a silica concentration of 1 to 40 w/vol% and a sulfate ion concentration of 50,000 to 5,000 ppm, and is The sulfate ion concentration (X) in the body contains a sulfate ion concentration (a) that satisfies W≧X with respect to the maximum value W that is assumed not to affect the concrete structure, and the silica concentration that satisfies the purpose of injection. It is preferable to have a formulation that satisfies the injection purpose under the applied ground conditions and construction method.

The ground injection material of the present invention is a non-alkali silica grout with a sulfate ion concentration within the range of 50,000 to 5,000 ppm, and the sulfate ion concentration of the ground into which the non-alkali silica grout is injected does not affect the structure. It is preferable that the composition contains sulfate ions at a low level, and has a silica concentration that satisfies the purpose of injection, and a formulation that is compatible with the applied ground conditions and construction method.

The ground injection material of the present invention has a silica concentration that satisfies the purpose of injection, and a sulfate ion concentration that does not affect the environment in the injection ground, and contains sulfate ions in the soil in the injection ground. It is preferable that the gel time consists of a formulation that is compatible with the construction method.

The ground injection method of the present invention is characterized by injecting the above-mentioned ground injection material into the ground.

In the ground injection method of the present invention, the concentration of sulfate ions derived from the ground injection material is set as (a), and the sulfate ion concentration in the ground improvement area or the injection solids is set as (X), so as to have no effect on the concrete structure. The maximum value of the sulfate ion concentration Regarding the elution rate (α) of sulfate ions and the residual rate (△) of sulfate ions in the gel (△=1-α), (Y) is one of the following △1 to △7 or Multiple settings can be made.
X ₁ =A×a W ₁ ≧X ₁
X ₂ =A×a×Y W ₂ ≧X ₂
A: Injection rate (%)/100
a: Sulfate ion concentration in the injection solution (ppm)
X ₁ , _{X 2} : Sulfate ion concentration in _the implanted ground The sulfate ion concentration in the implanted ground where the sulfate ion concentration of the injection solution is reduced △1: improvement when a non-injected part is provided in the ground improvement area and the ratio of the non-injected part is α ₁ Residual rate of sulfate ions in the ground △1=1-α ₁ (Here, α ₁ corresponds to the elution rate of sulfate ions from the gel in the injected ground)
△2: The residual rate of sulfate ions in the ground improvement area _, where α ₂ is the elution rate of sulfate ions in _the groundwater. (corresponds to the elution rate of sulfate ions)
△3: When the fixation rate of sulfate ions in the ground improvement area is _α3 , the residual rate of sulfate ions in the ground improvement area △3=1− _α3 (here, _α3 is the gel of the injected ground) (corresponds to the elution rate of sulfate ions from
△4: When the replacement rate of sulfate ions in the sulfate-based injection material by the non-sulfuric acid-based injection material or the low-sulfuric acid-based injection material in the ground improvement area is α ₄ , the residual sulfate ions in the ground improvement area Rate △4=1- _α4 (here, _α4 corresponds to the elution rate of sulfate ions from the gel at the injection site)
△5: When the replacement rate of the silica component in the ground injection material by the colloid is _α5 , the residual rate of sulfate ions in the ground improvement area is △5=1− _α5 (here, _α5 is the ratio of the silica component in the ground injection material to the colloid). (corresponds to the elution rate of sulfate ions from the gel)
△6: When some or all of the sulfate ions are captured in the ground injection material and the capture rate is α ₆ , the residual rate of sulfate ions in the ground improvement area is △ 6 = 1 - α ₆ (here (α ₆ corresponds to the elution rate of sulfate ions from the gel at the injection site)
△7: When the injection rate of the ground injection material in the ground improvement area is reduced and the reduction rate of the injection rate is _α7 , the residual rate of sulfate ions in the ground improvement area △7=1−α ₇ (Here, α ₇ corresponds to the elution rate of sulfate ions from the gel at the injection site)

In the above, the expressions ``ratio of non-injected portion, reduction rate of sulfate ions in the gel, fixation rate, substitution rate, and capture rate'' are the same as the expression ``elution rate α of sulfate ions from the gel.'' This is because in either case, the concentration of sulfate ions from the gel in the entire implanted ground decreases, which is the same as sulfate ions being eluted from the entire implanted ground, which affects underground structures in the entire ground improvement area. This is because it means that the amount of sulfate ions has decreased.

Further, in the above, when sulfate ions increase in the concentration system, the sulfate ion reduction factor Y can be expressed as the fluctuation rate of sulfate ions. In that case, use a non-sulfate-based reactive agent or increase the amount of non-sulfated-based reactive agents used in combination, or use a calcium-containing suspension or calcium-containing solution type grout to reduce the concentration of sulfate ions in the concrete. An injection material with a formulation that reduces the sulfate ion concentration in the injection ground to a level that does not cause any adverse effects shall be used.

In the present invention, a non-sulfuric acid injection material is injected into the ground, and an alkaline water glass grout is injected into the injection area of the non-sulfuric acid injection material, and the amount of alkali contained in the alkaline water glass grout is However, it is preferable to use a material that is almost neutralized by the acid content contained in the acidic silica grout around the injection part. This neutralizes the alkali content of the alkaline water glass, thereby imparting durability and increasing strength.

In the present invention, as shown in FIG. 31, the ground improvement area is treated with a sulfuric acid-based injection material and one or more of alkaline grout, calcium-containing grout, or suspension grout. and the injection rate of the alkaline grout, calcium-containing grout, or suspension grout is _A1 , and the injection rate of the acidic silica grout is _A2 ,
When using the alkaline grout, the durability of the alkaline grout is obtained by neutralizing the alkali with the acid of the acidic silica grout, and at an injection rate _A2 of the acidic silica grout, sulfate ions shall be set so that the injection rate is assumed to have no effect on the structure,
When using the calcium-containing grout or suspension type grout as the non-sulfuric acid grout, the injection rate _A1 is changed to the acidic silica grout injection rate _A2 , which is assumed that sulfate ions will not affect the structure. By setting the injection rate to
The durability and environmental protection of the ground improvement area can be achieved.
In addition, in the above, the sulfate ion concentration in the ground improvement area is reduced not only by decreasing the injection rate of the sulfate ion-containing injection solution, but also by the sulfate ions being captured (fixed) as calcium sulfate by calcium. do.
Furthermore, similarly, when suspension type grout is used as the calcium-containing grout in primary injection, the sulfate ion concentration in the ground improvement area is calculated by subtracting the injection rate of the primary injection material from the total injection rate. In addition to the reduction in sulfate ions due to a reduction in the injection rate of the injection material, the sulfate ions in the secondary injection material are also reduced by being captured (fixed) by the calcium in the primary injection material (Table 1, △3 , 4, 6, 7).

According to the present invention, the silica component of water glass or silica colloid or a plurality of silica components and an acidic agent that neutralizes the alkali in the silica component are included as active ingredients (FIGS. 1 and 2), The sulfate ion concentration of the water-soluble reaction product derived from the injection material (Table 11, Figure 10, Table 13) is a concentration that is assumed not to affect the structure within the ground improvement area (Table 10), It also has a silica concentration (Fig. 1 (c), Fig. 3) that achieves the strength that satisfies the ground condition and injection purpose, as well as the applied construction method (injection method (Fig. 11, Fig. 12, Table 16), injection design (Table 1). 16, Table 17, Fig. 32) and gel time (Fig. 1, Fig. 6 to Fig. 10)), which enables penetration, allows for durable ground injection with excellent environmental protection. construction method became possible.

The ground injection material of the present invention has a silica concentration of 1 to 40 w/vol%, contains one or more of water glass and silica colloid as a main component, and uses one of sulfuric acid or phosphoric acid as a neutralizing agent to remove the main component alkali. or a non-alkaline silica grout containing multiple active ingredients (Figures 1 and 2), and it is assumed that the sulfate ion concentration (X) in the ground injection area or in the injection aggregate will not affect the concrete structure. It has a sulfate ion concentration (a) such that W≧X for the maximum value W, and has a silica concentration that satisfies the injection ground condition and injection purpose, and has a gel time and penetration that are compatible with the applied injection method and injection design. It can be made into a ground injection material consisting of a compounding prescription that has properties.

According to the present invention, it has become possible to provide an environmentally friendly ground injection method and ground injection material that reduce the environmental load on the ground.

The gelling properties of non-alkali silica grout are shown. The relationship between [H ⁺ ]/[SiO ₂ ] ⁿ and gel time is shown. The relationship between molar concentration, pH, gel time, and strength of water glass (n=3) is shown. The relationship between gel time, pH, and durability of silica grout is shown. The consolidated strength of activated composite silica, changes in strength over time, and strength test results of various consolidated soils are shown. The elution rate and residual rate of SO ₄ ^-- from homogel and sand gel are shown. Figure 3 shows changes over time in SO ₄ ^-- of a homogel cured in water. The relationship between the amount of reactant added, pH, and gel time of non-alkali silica grout is shown. The soil Ca content, soil gel time GT _S , and soil pH _S are shown. The gel time of silica sol grout homogel and sand gel is shown. The pH and soil gel time of active composite silica grout in various on-site soils are shown. An example of the relationship between the type of acid and gel time in non-alkali silica grout is shown. Examples of various penetration injection methods are shown. An example of simultaneous penetration injection method from multiple injection holes is shown. The specimen preparation device is shown. This figure shows the preparation of a solidified specimen using the infiltration method. This figure shows an injection liquid penetration test device using the penetration method. The one-dimensional injection test situation is shown. Penetration distance and unconfined compressive strength are shown. The curing test method is shown. The curing status in the curing test is shown. The condition of mortar specimens after long-term curing in non-alkali silica grout containing sequestering agents is shown. The graph shows changes over time in mortar strength and curing solution pH due to differences in curing conditions. The influence of the type of neutralizing agent on the pH of the curing solution is shown. The condition of a mortar specimen cured in silica sol containing a sequestering agent after three years is shown. The condition of the mortar specimen after curing for 16 and a half years in silica sol containing a sequestering agent is shown. An X-ray chart of the coating on the surface of a mortar specimen cured by immersion in homogel is shown. The effects of sodium hexametaphosphate and sequestering agents are shown. This figure shows the protective effect against sulfate ions of a sand gel of silica grout containing a sequestering agent that coated a mortar specimen. The concrete protection effect of masking silica and the masking separate method are shown. A curing test method is shown in which a mortar specimen is semi-immersed in non-alkali activated composite silica containing a sequestering agent. The situation after 3 years of immersion is shown. The division of the injection part of the injection liquid in the injection area is shown. The critical injection speed and injection pressure for interparticle penetration are shown. This shows the penetrating and setting properties of non-alkaline silica grout. Figure 3 shows the change in conductivity due to dilution of the injection solution with silica solution.

Embodiments of the present invention will be described in detail below with reference to the drawings.
The present invention relates to a ground injection method in which a ground injection material is injected into the ground to form a soil improvement area, and to improvements in the ground injection material that is injected into the ground to form a ground improvement area.

In the present invention, a ground injection material made of non-alkali silica grout having a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10 can be used.

As for the ground injection material of the present invention, it is assumed that the concentration of the water-soluble reaction product derived from the ground injection material in the ground improvement area or the injection compact does not affect the environment or the structures in the ground improvement area. Use a compounding formula that enables a gel time that is reduced to a concentration that meets the injection purpose for the ground conditions and has a permeability that is compatible with the applied ground conditions and construction method. The above-mentioned ground injection material preferably contains as active ingredients one or more silica components of water glass or silica colloid, and an acidic agent that neutralizes the alkali in these silica components. Here, in the present invention, the silica concentration that satisfies the purpose of injection is set within the range of 1 to 40 w/vol%. In addition, the results of curing concrete in sodium sulfate solutions with various sulfate ion concentrations show that the concentration of sulfate ions that is assumed to have no effect on concrete is 8000 ppm or less in the ground where it is poured, preferably 5000 ppm or less. It is. This value corresponds to the condition that the concentration of sulfate ions is not diluted with groundwater by curing in a sodium sulfate solution. Since it is actually diluted with groundwater, it is considered that there is no problem if 8,000 ppm is considered as the standard ([Table 9], Figures 4 and 5).

The above-mentioned non-alkali silica grout refers to silica grout having a pH of 1 to 10 and containing silica colloid and/or water glass as an active ingredient.

In the present invention, acidic to neutral means a pH range of 1 to 10. The silica concentration is 1 to 40 w/vol% and the pH is 1 to 10. In order to stabilize the colloid, silica colloid contains only a small amount of alkali and is supplied at a pH around 10, so a pH up to around 10 is called neutral. Water glass exhibits a pH of 11 to 12 when the silica concentration is 1 to 50 w/wt%, but when an acid is added to remove the alkali from water glass, the pH becomes around 1 to 8.5 (Figure 1(a)). Therefore, non-alkali silica grout containing water glass and/or silica colloid as an active ingredient has a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10 (Figure 2). Therefore, even if a non-alkali silica grout containing silica colloid and water glass as active ingredients has a high silica concentration, the alkali content of the silica colloid is negligibly small, so the alkali content is actually determined by the water glass concentration. Silica colloids also gel with neutral salts. Therefore, non-alkali silica grout containing one or more of silica colloid and water glass as an active ingredient has a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10, and the formulation should be set within that range. I can do it.

Furthermore, the relationship between the silica concentration, pH, gel time, and strength of non-alkali silica grout using sulfuric acid is shown in FIG. 1(b) and FIG. 1(c). Further, blending examples are also shown in FIG. 10 and Tables 13(a) and (b). From these, in non-alkali silica grout using water glass and sulfuric acid, it is possible to know the relationship between the concentration of sulfate ions, pH, and gel time corresponding to the concentration of water glass.

Non-alkaline silica grout is available in two types: (1) a type that uses an acidic to neutral silica solution obtained by removing the alkali from water glass with an acid, and (2) a type that uses an acidic to neutral silica solution obtained by removing the alkali from water glass with an acid, and (2) a type that uses a pH-neutral silica solution obtained by dealkalizing water glass using an ion exchange method. Use materials such as weakly acidic to neutral silica colloids of 2 to 5 or neutral to weakly alkaline silica colloids that are further concentrated and stabilized with a trace amount of alkali, metallic silica, silica derived from geothermal water, etc. (These are expressed as "silica colloid" in the present invention), and (3) a type that uses a composite silica containing silica colloid and water glass silica as active ingredients as a material. Non-alkali silica grout uses not only silica colloid which itself contains almost no alkali as the silica component, but also especially the alkali of water glass that has been removed with acid to achieve excellent durability and solidification properties in water. , it exhibits very unique injection effects such as keeping groundwater in a neutral region (Figures 1 and 2). For this reason, the method of injecting durable silica grout is called the durable silica grout injection method.

The alkali of water glass in non-alkali silica grout is produced on-site by mixing water glass and a sulfuric acid neutralizer to remove the alkali in water glass. For this reason, non-alkali silica grouts produce the following properties not found in normal alkaline water glass grouts.
(1) Since the alkali in the water glass has been removed, the entire amount of silica contained in the water glass precipitates and participates in gelation, and since it is diluted with water and gels even at low concentrations, it can be used even under the groundwater table. Solidifies securely. Therefore, even if the silica concentration is low, silica will precipitate and solidify even in the ground below the groundwater table (Figure 1).
(2) Even if the injected grout is acidic and gelation takes a long time, the pH in the ground shifts to neutral, promoting gelation and solidifying solidly (Figures 1, 8, and 9).
(3) Since the alkali in the water glass has been removed, the gel once formed will not be dissolved again by the alkali in the gel, resulting in excellent long-term durability (Figure 3 (c) (a) ,(B)).
(4) Keep the pH of groundwater almost in the neutral range (Figures 1 and 2).
(5) Since the gelation time can range from instant setting to long setting, it can be applied to all construction methods such as double pipe instant setting method, double pipe instant setting/loose setting composite injection method, and double pipe double packer method ( Figure 11, Figure 12, Table 16).
(6) Extremely safe for fish, animals, and plants.

The silica concentration at which the injection effect can be obtained in non-alkali silica grout is 1 to 40 w/vol%, but usually 2 to 30 w/vol%. The concentration of water glass, or the concentration of sulfate ions in the injection material that neutralizes the alkaline content of the mixed solution of water glass and silica colloid to make it acidic to neutral (pH 1 to 10), is usually about 50 ,000 to 5,000 ppm, but the required silica concentration and sulfate ion concentration can be determined from the relationship between the applied silica concentration, pH, gel time, and strength from Figures 1(b) to (c). Figures 1(b)-(c)).

Tables 1 to 3 show non-alkali silica grouts applicable to the ground conditions described above.

As the acidic agent, one or more of a sulfuric acid compound or a non-sulfuric acid compound can be used. Among these, the non-sulfuric acid compound can be an inorganic acid other than sulfuric acid, an organic acid, or an acidic salt thereof. Or more than one can be used. Specifically, sulfuric acid compounds include sulfuric acid and sulfuric acid salts; non-sulfuric compounds include non-sulfuric acid inorganic acids such as phosphoric acid; organic acids and organic acid salts such as citric acid, succinic acid, and fumaric acid; Inorganic non-sulfuric acid acid salts such as AlCl ₃ and FeCl ₃ can be used. Moreover, the above-mentioned ground injection material can also contain one or more of a phosphoric acid compound, a metal ion sequestering agent, and a chelating agent as an active ingredient. Phosphoric acid compounds, sequestrants, and chelating agents react with Ca in concrete to form an insoluble coating on the surface of concrete, preventing sulfate ions from entering the concrete and preventing Ca from leaching out from inside the concrete. It has the function of protecting concrete from sulfate ions (Fig. 23, Fig. 24, Fig. 25, Fig. 26).

As sequestering agents, phosphoric acid compounds, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, propylenediaminetetraacetic acid, bis(2-hydroxyphenylacetic acid)ethylenediamine, succinic acid, salts thereof, Examples include aliphatic oxycarboxylic acids and their salts, condensed phosphates, and the like.

Examples of aliphatic oxycarboxylic acids include tartaric acid, citric acid, succinic acid, gluconic acid, dihydroxyethylglycinate, etc., and their salts; examples of condensed phosphates include pyrophosphoric acid, triphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid, etc. There are salts of polyphosphoric acid, and specific examples include sodium pyrophosphate, acidic sodium pyrophosphate, sodium tripolyphosphate, sodium tetrapolyphosphate, sodium hexametaphosphate, acidic sodium hexametaphosphate, and potassium salts thereof.

The phosphoric acid compound and/or chelating agent used in the present invention has a chelating effect, and includes, for example, phosphoric acid, various acidic phosphates, neutral phosphates, and basic phosphates, Examples include condensed phosphates such as tetrapolyphosphate, hexametaphosphate, tripolyphosphate, pyrophosphate, acidic hexametaphosphate, and acidic pyrophosphate, and the condensed phosphates are sodium salts. preferable. As the phosphoric acid compound forming the non-alkaline silica solution, sodium hexametaphosphate is preferred because it forms a particularly strong masking silica. In addition to the above-mentioned phosphoric acid compounds, examples of chelating agents include ethylenediaminetetraacetic acid, nitrilotriacetic acid, gluconic acid, tartaric acid, and salts thereof. form the most effective coating on the concrete surface. In this way, a durable foundation can be formed in the vicinity of a concrete structure by selecting a composition according to environmental conditions. Note that the above is just an example, and it goes without saying that the present invention is not limited to these examples.

The functions of sodium hexametaphosphate and sequestering agent in non-alkali silica grout will be explained with reference to FIG. 26. In the present invention, the chelating agent is described as a sequestering agent (FIG. 26(b)). Figures 23 and 24 show the situation in which mortar specimens cured for 3 and 16 years in the same volume of homogel as mortar specimens of sulfuric acid-containing silica grout containing a sequestering agent (phosphoric acid) do not deteriorate. The analysis results of the mortar surface coating are shown in Table 14 and FIG. 25. In the non-alkali silica grout of the present invention, in addition to the above-mentioned acids and salts, any of the following gelling modifiers can be used. In addition to various inorganic acids and organic acids, various salts such as alkali metals, alkaline earth metals, and other salts such as carbonates, bicarbonates, aluminum salts, polyaluminum chloride salts, chlorides, and aluminic acids can be used as gelling modifiers. Any salt can be used.

Among these, a sparingly soluble alkaline material such as magnesium hydroxide can be added to the silica grout to make the curve in FIG. 10 gentler and make it easier to adjust the gel time.

In addition, as pH adjusting agents or gelling time adjusting agents, salts (inorganic salts, organic salts, basic salts, neutral salts, acid salts, etc.), alcohols, caustic soda, etc. are used as shown in the examples below. Alkalies, etc. can be used to form a silicic acid gel by reacting with silicic acid, changing the pH, or other chemical or electrochemical actions, changing the gelation time, and changing the fluidity. It refers to something that changes the temperature or increases the caking property.

The following example shows an example, and is not limited to these.
Inorganic salt:
Acidic salts, neutral salts, basic salts, etc.
Chlorides such as calcium chloride, sodium chloride, magnesium chloride, potassium chloride, aluminum chloride, sulfates such as calcium sulfate, sodium sulfate, aluminum sulfate, aluminates such as sodium aluminate, potassium aluminate, ammonium chloride, zinc chloride , hydrochlorides such as aluminum chloride, chlorates such as sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, bicarbonate. Carbonates such as ammonium, bisulfates such as sodium bisulfate, potassium bisulfate, and ammonium bisulfate, bisulfites such as sodium bisulfite, potassium bisulfite, and ammonium bisulfite, and fluorosilicic acids such as sodium silicofluoride and potassium silicofluoride. Salts, silicates such as alkali metal salts of silicic acid, alkaline earth metal salts, aluminum salts, borates such as sodium borate, potassium borate, ammonium borate, sodium hydrogen phosphate, potassium hydrogen phosphate, phosphoric acid Hydrogen phosphates such as ammonium hydrogen, pyrosulfates such as sodium pyrosulfate, potassium pyrosulfate, and ammonium pyrosulfate, pyrophosphates such as sodium pyrophosphate, potassium pyrophosphate, and ammonium pyrophosphate, sodium dichromate, and dichromic acid. Potassium, dichromates such as ammonium dichromate, permanganates such as potassium permanganate, sodium permanganate, etc.

Organic salt:
Sodium acetate, sodium succinate, potassium formate, sodium formate, etc.

In addition to acting as a pH adjuster or gelling time adjuster, these also have the effect of a strength enhancer.

In forming a ground improvement area using the ground injection material as described above, the present inventors conducted the following study on the relationship between the components contained in the ground injection material and the ground.

[Experiment 1]
Elution test of SO ₄ ^-- from gel of silica sol grout (water glass + sulfuric acid-based non-alkali silica grout) (1) Elution method Table 5 shows the silica sol formulation used in the test. Table 6 shows Toyoura sand consolidated by the silica sol in Table 5. A homogel or sand gel according to Tables 5 and 6 of approximately 5 mm in diameter and 10 cm in height is placed in a polypropylene container of 6.8 cm in diameter and 12.7 cm in length (volume 430 cm ³ ), and 200 mL of water is poured into it to diffuse the sulfate ions in the gel into groundwater. Alternatively, assuming that groundwater is flowing, the water was exchanged periodically and SO ₄ ^-- of the water was measured after 1, 3, 7, 28, and 60 days had elapsed. Water exchange was performed on the 1st, 3rd, 7th, and 28th day after measuring the SO ₄ ^-- concentration.

(2) Test results When silica sol grout is injected into the ground, the Na ⁺ ions and SO ₄ ^-- in the gel dissolve into the groundwater in a short period of time, leaving only the insoluble silica as a gel. .
It can be assumed that the SO ₄ ^-- eluted into the groundwater is diffused into the groundwater and disappears within a short period of time (FIG. 4, Table 7).
According to experiments, 40% of SO ₄ ^-- is eluted in about 1 day (residual rate in gel is about 60%), 85% is eluted in 1 month (residual rate in gel is about 15%), and in 2 months. Almost 100% is eluted (residual rate in gel is almost 0%). In the above, if (Y) is the factor that causes the sulfate ion concentration in the injected ground to be lower than the sulfate ion concentration contained in the injection solution, then (Y) is the elution rate of sulfate ions from the gel (α ) is related to the residual rate (=△) of sulfate ions in the gel (△=1−α).

[Experiment 2]
Furthermore, the present inventors cured a homogel specimen of sulfuric acid-based silica sol grout (sulfate ion concentration 50,000 ppm) in water, measuring 5 cm in diameter x 10 cm in height, and measured the sulfate ion concentration in the specimen after 1 day, 7 days, and 28 days. It was measured later (Fig. 5).

FIG. 5 is a curve showing the change in SO ₄ ^-- in the gel over time, assuming that there is an infinite amount of curing water without replacing the curing water. This result shows that sulfate ions in the gel diffuse in a relatively short period of time under such conditions.

According to the above results, sulfate ions are eluted from the solids (sand gel) into the groundwater, and finally the sulfate ion concentration (X) in the entire ground improvement area is determined from the sulfate ion concentration (a) contained in the injection solution. It turned out to be lower. In an actual field, it can be seen that the concentration of sulfate ions in the implanted ground will eventually diffuse and become uniform throughout the ground improvement area, depending on the sulfate ion concentration gradient. On the other hand, although it depends on the size of the compact, the permeability of the soil, and the groundwater situation, the higher the leaching rate of sulfate ions from the gel in the ground (reduction rate α of sulfate ions in the gel), the more the sulfate ions in the gel. The survival rate (△) of decreases (△=1−α). The sulfate ion concentration remaining in the gel will eventually diffuse out of the solidified region due to the concentration gradient and disappear. Therefore, it is only necessary to consider the sulfate ion concentration in the entire ground to be poured and the influence of concrete.

[Experiment 3]
When it is assumed that the sulfate ions eluted from the gel are rapidly diluted with groundwater and finally dissipated. To understand the situation when concrete is poured by excavating the injection ground solidified with non-alkaline silica grout. After a concrete specimen (mortar specimen) was embedded in sand and solidified with silica sol grout, the solidified body was cured in water for a long period of time, the solidified sand outside the mortar was broken, and the concrete specimen inside was cured. The external appearance of the specimen (mortar specimen) was observed, and a uniaxial compressive strength test was conducted (FIGS. 18 to 24).

A mortar specimen with a diameter of 5 ^cm and a length of 10 cm ( ^approx . )), and were cured in 2 pieces each in 2,500 cc of water (Figure 18(c)).

This is equivalent to cutting a large concrete structure into small concrete pieces and applying a chemical solution to the surface of each piece, which means setting extremely severe conditions.

Furthermore, in this case, assuming that all of the sulfate ions in the silica sol grout were eluted into the curing water, the concentration of sulfate ions would be approximately 3,700 ppm. This means that it was cured in water containing sulfate ions, which changed to . After 1 month, 3 months, 6 months, and 1 year, we destroyed the consolidated sand on the outside of the mortar specimen, observed the external appearance of the mortar specimen inside, and conducted a uniaxial compressive strength test. No deterioration or change in appearance was observed.

That is, it is shown that even in 50,000 ppm of sulfate ions, there is no adverse effect on the mortar specimen when the sulfate ions are diluted to a concentration of 3,700 ppm.

After 1 year and 8 months, the outer compacted sand of the mortar test specimen was destroyed and the external shape of the test specimen inside was observed, and then the specimen was left to cure with the broken compacted sand over time. We continued to observe the external appearance of the mortar specimens, but even after 5 years and 6 months, no particular change in the external appearance had occurred. At this site, since the groundwater is large compared to the solids and is flowing, it is assumed that if the sulfate ions diffuse and dissipate, there will be almost no impact on the concrete (Y = △ in Table 10). 2, Figure 4, Figure 5).

[Effect of sulfate ions on concrete]
[Experiment 4]
Assuming a case where groundwater remains stagnant (or stagnates) and there is almost no groundwater flow, it is assumed that the concentration of sodium sulfate aqueous solution, which is a water-soluble reaction product, acts on concrete (mortar) without changing for one year. The mortar specimens shown in Table 8(a) were cured for one year in a sodium sulfate aqueous solution with a sulfate ion concentration of 10,000 ppm, 8,000 ppm, 5,000 ppm, 3,000 ppm, and 0 ppm, and a uniaxial compressive strength test was conducted. The effect on concrete was investigated.

In the absence of dilution by groundwater, experiments have shown that SO ₄ ^-- causes visible changes in concrete within 6 months at 10,000 ppm, and slight changes in 1 year at 8,000 ppm. .

Table 9 shows the results of immersing a concrete specimen in an aqueous sodium sulfate solution and observing the effect of the concentration of sulfate ions on the concrete. From this, when there is no dilution by groundwater, the sulfate ion concentration that affects concrete structures within one year is 10,000 ppm or more, and 5,000 ppm or less has almost no effect even after one year. In Table 9, when the concentration of sodium sulfate is 8,000 ppm, it is a concentration that causes a slight effect in one year, but in reality, sulfate ions are diluted by groundwater, so the sulfate ion concentration in the injection ground is 8,000 ppm. ,000 ppm or less, it can be considered that no problem will occur in the mortar specimen (FIGS. 4 and 5).

○：外観形状に異常なし
△：一部表面が剥離している
×：表面の剥離が著しい

○: No abnormality in appearance △: Partial surface peeling ×: Significant surface peeling

[Effect of non-alkali silica grout on concrete in poured ground]
For non-alkaline silica grout, the alkali that causes the deterioration of water glass grout has been removed using an acidic neutralizing agent. , (4) non-sulfuric acids, (5) non-sulfuric acid salts, and (6) any of the above (1) to (5) are used in combination (Tables 1 to 3).

Among these neutralizing agents, sulfuric acid-based neutralizers are often used in consideration of economic efficiency. It is generally believed that sulfate ions have a negative effect on concrete structures, but when injected into the ground, the sulfate ions in the gel are rapidly diluted into groundwater, reaching a concentration that does not affect concrete, and eventually Dissipate. However, the rate of dissipation of sulfate ions in groundwater depends on the soil quality (ground condition), groundwater condition, etc., and the applied injection material, so the effect of the injection material on concrete is limited to the sulfate ions of the injection material itself. It is also necessary to consider the sulfate ion concentration in the entire implanted ground area, taking into account changes over time.Environmental conservation can be achieved by using an implantation material with a formulation that satisfies the purpose of the implantation and exhibits gelling behavior that is compatible with the applied implantation method. Type non-alkali silica injection method is required.

[Non-alkali silica grout containing sequestering agent]
As mentioned above, sulfate ions are expected to be eluted into the curing water within a few months and become approximately constant. In experiments, there was almost no difference in the elution rate of SO ₄ ^-- between sand gel and homogel (FIGS. 4 and 5). In actual sites, the amount of groundwater is extremely large compared to the solidified matter, and if the groundwater flows ^and is diluted, the rate of elution and diffusion will be faster, but the rate of dilution and the amount of SO ₄ in the gel will increase. It is necessary to take into account that the survival rate is affected by ground conditions, groundwater conditions, the size of the injection area, etc. Therefore, it is effective to consider silica grout, which has almost no effect on mortar specimens even without dilution. That is the application of non-alkaline silica grouts containing sequestering agents.

In Experiment 5, the mortar specimens shown in Table 8(a) were cured in non-alkaline silica gel containing the same volume of sequestering agent (Fig. 18(a)), and the appearance of the film deposited on the concrete surface was determined. As a result of observation, it was confirmed that a white film was formed on the mortar surface in all injection materials (FIGS. 23 and 24). Therefore, for comparison, II (non-sulfuric acid/phosphoric acid type, Table 1, No. 2), IIα (sulfuric acid/phosphoric acid type, Table 1, No. 3) and IIδ (sulfuric acid type, The coating of the mortar specimen cured on non-alkali silica (Table 1, No. 1) was collected, and its components were measured by fluorescent X-ray method, and the crystal structure was measured by X-ray diffraction method (Fig. 25, Table 14).

Table 14 shows the coating components, and FIG. 25 shows the X-ray diffraction chart. From these measurement results, it seems that the coating on the mortar surface is hydroxyapatite in II, hydroxyapatite or calcium phosphate in IIα, and calcite or vaterite in IIδ.

The coatings of II and IIα are formed using metal ion sequestering agents, and phosphoric acid, sodium phosphate, sodium hexametaphosphate, and phosphates are particularly notable. Organic acids and organic acid salts such as citric acid and succinic acid are also effective. FIG. 26 shows the function of a sequestering agent using sodium hexametaphosphate as an example. Non-alkaline silica grout containing a metal ion sequestering agent becomes passivated by chelate bonding with calcium and magnesium ions present on the mortar surface, and also reacts with the silica contained in the injection material to remove Ca ions from within the mortar. This is thought to form a poorly soluble film that suppresses the elution of sulfuric acid ions and the intrusion of sulfate ions from the outside.

[Experiment 5]
It was confirmed that a silica solution containing a sequestering agent forms an insoluble coating of masking silica (non-alkali silica grout containing a sequestering agent) on the concrete surface and has the effect of protecting concrete.

1) Test overview After curing the mortar specimens shown in Table 8(a) in water for one month, three specimens were combined into a set, and 600 mL of homogel of the silica grout solution shown in Tables 12(a) and 13(a) was added. (curing medium) and cured for one year. Neutralizing agent A is phosphoric acid, which is expected to have the effect of a metal ion sequestering agent, but neutralizing agent B is sulfuric acid, which is not expected to have this effect. Using the specimens under the above conditions, appearance observation and pH measurement of the curing medium were performed. The curing medium in Case 1 is ion exchange water. This test was conducted with the silica grout homogel (curing medium) in which the mortar specimen was immersed sealed in a closed state so that sulfate ions were not diluted.

2) Test Results 2-1) Appearance Observation The condition of the specimen after one year of immersion is shown in Table 13(c). No deformation was observed in Cases 1, 2, 3, and 4, but cracks were observed in the upper part of Case 5. Furthermore, in Cases 2, 3, 4, and 5, adhesion of white crystalline substances was observed on the surface of the specimen.
2-2) pH of curing medium
The pH measurement results of the curing medium are shown in Table 13(b). While the pH of the ion-exchanged water used to cure the mortar specimen was 13 or higher, Case 2, in which a masking effect is expected, showed a neutral value. On the other hand, in Cases 3 and 4 using a mixture of Neutralizing Agents A and B, the higher the mixing ratio of Neutralizing Agent B, the higher the pH of the curing medium, and the curing water of Case 5 containing only Neutralizing Agent B had the highest pH. It showed a high pH value (Figure 22).

The masking effect is achieved by forming an insoluble film of masking silica on the surface of the mortar specimen, which blocks the elution of alkali from the mortar and suppresses neutralization, as well as prevents the intrusion of sulfate ions, a neutralizing agent, and improves the mortar. It turned out that it was protected.

Moreover, Table 13(c) shows the appearance observation of the mortar specimen cured in the acidic silica grout of Table 13(a). Table 13(c) shows the effect of the sequestering agent when the mixing rate (%) of sulfate ions in the acidic reactant (neutralizing agent) is 0, 50, 66, and 100. The results show that even in the presence of 15,000 ppm of sulfate ions, which have an adverse effect on mortar, the mortar is protected by the effect of the sequestering agent.
From this result, if the phosphate ions are 50% of the sulfate ions (Case 4), the same amount as the sulfate ions (Case 3), and of course the entire amount (Case 2), no problem will occur in the concrete.

[Experiment 6]
Strength test of mortar specimen in gel of non-alkali silica grout containing sequestering agent The mortar shown in Table 13(d) and the non-alkali silica grout containing the sequestering agent shown in Table 15 were prepared using the curing method shown in FIG. The conditions of the curing test after 16 years of curing are shown in FIGS. 19 and 20, and the pH and strength ratio of the curing water during that period are shown in FIG. 21, respectively. The pH of the distilled water used to cure the mortar specimen is around 12, but when it disintegrates in the sulfate aqueous solution, the pH becomes 13 or more, indicating that the alkali in the mortar is eluted. In contrast, when coated with non-alkaline silica containing a sequestering agent, the pH remains approximately neutral. From this result, it is considered that the silica blocks the elution of alkali in the mortar (suppresses neutralization) and also prevents sulfate ions from entering the mortar. From the above, the same function of the sequestering agent as in Experiment 5 was confirmed (Table 15, FIGS. 18 to 21, and 23 to 26).

[Experiment 7]
Effect of sequestering agent when a mortar specimen was wrapped in the same volume of sand gel of silica grout containing a sequestering agent and cured in a sand gel of sulfuric acid-based silica grout. The mortar in a) was wrapped in a sand gel of silica grout in Table 12 containing a sequestering agent marked with △ in Table 11, and it was cured in a homogel of sulfuric acid-based silica grout marked with ○ in Table 11 (Fig. 27 (b) )). After 6 months, the homogel and sand gel were disassembled (Fig. 27(c)) and the mortar was observed. There was no change, and a white coating of silica (masking silica) containing the metal ion sequestering agent was formed on the surface. (Fig. 27(d)), no deformation was observed in the mortar. Even when phenolphthalein was sprayed on the mortar surface, no red reaction occurred, and when the mortar was scratched (Figure 27(d)) and phenolphthalein was sprayed, only the scratches turned red, indicating the alkali inside the concrete. showed a reaction. Further, when the taken-out mortar specimen was immersed in water, the pH of the curing water was around neutral. This indicates that the masking silica layer prevents sulfate ions from entering the mortar and also prevents alkali from leaching out from inside the mortar specimen. This experiment corresponds to FIG. 28 in its implementation.

[Experiment 8]
An experimental example is shown in which a mortar specimen is half-immersed in a gel containing a sequestering agent (FIGS. 29 and 30).

a) Homogel immersion curing (Figure 29(a))
A 5 cmφ x 10 cm mortar specimen (Table 8 (a)) was placed in the center of a 600 mL airtight container, and No. 1 in Table 1 was placed. Add 400 mL of the metal ion sequestrant-based silica grout from step 2 and cure for a predetermined period of time.
After one year, the homogel was destroyed, the concrete specimen inside was taken out, and the condition of the concrete specimen was observed.

b) Curing in the same volume of homogel (Figure 29(b))
1) Place a 3 cmφ x 6 cm mortar specimen (mortar for immersion test in Table 8 (a)) in the center of a 300 mL airtight container, and Add 50 mL of the metal ion sequestrant-based silica grout from step 2 and cure for a predetermined period of time. Make sure that the grout reaches about half the height of the specimen.
2) The upper part of the grout of the specimen is sealed using paraffin to prevent evaporation.

In both a) and b) above, a protective film was formed on the mortar surface even after 3 years of curing, and no deterioration occurred in the mortar (FIG. 30).

[Environmentally friendly non-alkali silica injection method]
In the immediate vicinity of the contact area of the concrete structure, the sulfate ions in the gel are restrained by the impermeable solidification caused by injection between the concrete structure and the surrounding area, so the degree of dilution of the sulfate ions in the gel is small and it remains in the gel for a long period of time. However, sulfate ions are gradually eluted from the outer periphery of the soil improvement area into the surrounding groundwater due to the concentration gradient, and the sulfate ion concentration in the entire soil improvement area decreases, and as a result, the concentration of sulfate ions in the area immediately adjacent to the concrete structure decreases. The amount of sulfate ions in the solids decreases. However, the rate of reduction of the sulfate ion concentration in the immediate vicinity of concrete is unclear because it depends on the above-mentioned requirements. For this reason, in the area immediately adjacent to or in contact with concrete, the area between the concrete structure and the solidified portion of the sulfuric acid-based non-alkaline silica grout contains phosphoric acid-based, sequestering agent-based, non-sulfuric acid-based, and calcium-based (cement-based) It is preferable to interpose a solidified portion of non-alkaline silica grout such as (including). In this case, before the sulfate ions attack the concrete, the phosphate ions reach the concrete and react with the calcium content of the concrete, forming a protective film on the concrete surface with a chelating effect along with the silica content, blocking the sulfate ions. It turned out that.

In the past, the environmentally friendly injection method has been discussed qualitatively, including its safety for concrete, but it has not yet been developed into a quantitative technology. This is because the ground conditions and groundwater conditions are too complex, the long-term relationship with the ground, the chemical and physical changes in silica gel that change after gelation, and the gelation reaction with the ground are complex, and the purpose of injection This is because it has been difficult to set a compounding prescription that is compatible with the injection method and injection method. The present inventors completed the present invention with the aim of clarifying these factors and quantitatively establishing an injection technique that is excellent in environmental conservation.

The present invention will be explained in detail below.

The present invention is a further development of the technology described in Japanese Patent No. 5277380, which is an earlier invention by the present inventors.

Traditionally, silica grouts have been targeted solely to gelation through a combination of injection materials. On the other hand, the above-mentioned prior application is a ground injection method that uses non-alkali silica grout, which makes it possible to reduce sulfate ions in the entire injection ground in order to prevent concrete deterioration.

The present invention aims to facilitate the prevention of concrete deterioration in the poured ground by finding quantitative conditions for the poured ground and the poured material, from the conventional idea of reducing concrete deterioration, which was qualitative. This paper focuses on the elution and persistence of sulfate ions from gel, and relates to a ground injection method and ground injection material that quantitatively determines the formulation of the injection material to reduce the impact on the environment in the ground where it is injected.

The gelatinable silica concentration of silica grout in a non-alkaline area where the injection liquid is sufficient is 0.5 to 40 w/vol%, but in order to obtain an injection effect with sufficient penetration, the silica concentration is 1 to 40 w/vol%. is preferred. To obtain sufficient permeable gel time at this silica concentration, the sulfate ion concentration would be 5,000 to 50,000 ppm, sufficient to remove the alkali from the water glass with sulfuric acid alone.

To meet the purpose of injection, it is necessary to have a gel time that exhibits permeability that is compatible with the injection method employed, and a silica concentration that provides the required consolidation strength. By the way, the higher the silica concentration is required for the purpose of injection, the higher the silica concentration must be, and the longer the gel time is to obtain high permeability, the more acidic the silica must be in order to obtain durability. It is necessary to neutralize the alkali (Figure 1(b)). Therefore, from the viewpoint of environmental protection, it is preferable that the acid concentration of the injection liquid be as low as possible, but from the viewpoint of the purpose of injection, it is not necessarily better. In particular, in terms of strength, the concentration of water glass has a greater influence than that of silica colloid, so sulfuric acid is used to economically neutralize the alkali of water glass. As described above, if the sulfate ion concentration (a) of the implantation material is too low, the purpose of implantation cannot be met, and if the concentration (a) is too high, it is not preferable in terms of environmental protection. Therefore, if a non-alkali silica grout containing as an active ingredient an acidic agent that neutralizes the alkali of water glass and/or silica colloid is used as a ground injection material, the concentration of water-soluble reaction products derived from the ground injection material may be It is assumed that a formulation is used that has a silica concentration that is reduced to a concentration that is assumed to have no effect on the environment, especially structures, within the improvement area and that satisfies the purpose of injection. In particular, a formulation is used that has a silica concentration that satisfies the purpose of injection obtained from the soil and the applied injection method, as well as a gel time that ensures permeability.

As mentioned above, under conditions where it is assumed that the groundwater is stagnant at the injection site and the concentration of water-soluble reaction products is not diluted, it is thought that this will have an effect on concrete (Table 9, Table 13 (c) Case (5)). Therefore, it can be seen that in such a case, a non-sulfuric acid or metal ion sequestering agent system (Table 13(c) Case 2, Case 3, Case 4) may be used.

On the other hand, the present inventors found that the sulfate ions of the silica solution injected into the ground were diluted by groundwater in a relatively short period of time, and the _SO4 ions eventually diffused and had a negative impact on concrete. It was found that there was no effect (Fig. 4, Fig. 5, Experiments 1 to 3).

However, the reduction of SO ₄ ions in the consolidated area by groundwater depends on (1) the concentration of SO ₄ in the gel, the concentration of SO ₄ in the ground, the ground condition, the injection range, the ground water conditions, the concrete conditions, and the relationship with concrete. Depends on location. Furthermore, it varies depending on the purpose of injection and the formulation suitable for the injection method. Therefore, the present inventors have made it possible to reduce the environmental load by quantitatively understanding and reducing the factors that affect concrete structures as described below.

From the prior invention by the present inventors, factors that affect concrete have been known. It was also known to reduce sulfate ions based on these factors. However, based on these factors, it has not yet been possible to establish an injection solution with a quantitative formulation that satisfies the injection purpose and safety for concrete. The reason is as described above. On the other hand, the present inventors elucidated the behavior of _SO4 ions eluted from the gelled material of the injection material over time, and the behavior of the eluted sulfate ions in the ground, as shown below from Experiment 2 and Figure 4. The soil improvement area is classified into open, stagnant, and concentrated based on the ground conditions and groundwater conditions, and the quantitative reduction factor (Y) of sulfate ions in the implanted ground and the elution rate and residual rate of sulfate ions in the gel are determined. Furthermore, the gel time, consolidation strength, and permeability into the ground of the injection solution due to the sulfate ion concentration and silica concentration are determined according to the purpose of injection and the injection method to be applied. By injecting into the ground an injection material containing a sulfate ion concentration that is below the sulfate ion concentration that does not affect This is what I did.

The factors (Y) that affect underground concrete over time are groundwater conditions and ground conditions that have the greatest influence, so the following five ground conditions (A, B, C, D, E) should be assumed. I can do it. That is, water-soluble reaction products derived from the ground injection material are determined based on one or more of the concrete structure, ground condition, groundwater condition, and injection conditions (△8 to △10 in Table 10, etc.) in the ground improvement area. We quantitatively established the factors that reduce the environmental impact of water-soluble reaction products in the injected ground in response to the behavior of the ground, and determined that the formulation of the injection material injected into the ground will reduce the impact on the environment, especially on concrete structures. It is preferable to use a compounding recipe that corresponds to the silica concentration and sulfate ion concentration (a) that satisfies the purpose of injection that is compatible with the ground conditions and the applied construction method.

(A) Open system: When gelled material in the ground is easily leached out of the injection area, or when groundwater is flowing outward from the concrete structure. For example, if the coast or river is close and flowing in that direction, if the groundwater level fluctuates with the tide, if the hydraulic gradient is outward, or if the ground is highly permeable such as sand and gravel. In some cases, sulfate ions decrease within a relatively short period of time, within 1-2 months. According to laboratory experiments conducted by the present inventors, almost all of the sulfate ions diffuse within 1 to 2 months (FIGS. 4, 5, and Table 7). It is likely that the concentration of sulfate ions will eventually converge to that found in nature. Therefore, even if the sulfuric acid system shown in Table 1 is used, SO ₄ ions in the implanted ground are likely to be reduced in a short period of time. However, in actual sites, the elution rate of sulfate ions is thought to be affected by ground conditions, groundwater requirements, and the size of the consolidation area, so if these conditions are unclear, 2, 3, or It is desirable to use a combination of 1, 2, 3 and 4, 5. In addition, as described later, the injection rate of the suspended calcium-containing primary injection material in Table 12 was increased, and the secondary injection rate of the sulfate ion-containing silica grout was reduced, and at the same time, sulfate ions were fixed by calcium. can be achieved. In addition, in the chemical injection ground, the water quality change in the inspection hole located 10 m away from the injection area usually becomes almost constant in 1 to 2 months, so the concentration of the reaction product from the gel in the injection ground is usually 1 to 2 months. It can be assumed that it becomes almost constant due to diffusion in two months. Therefore, it can be considered that it is 1/10 or less from FIGS. 4 and 5.

(B) Stagnant system (stagnation system): If there is little groundwater flow and it is stagnant, _SO4 ions in this area will sooner or later move in the direction where the gradient of ion concentration is lower, that is, in the direction outside the injection range. Although it is diluted and eventually reduced to a concentration that has no effect, its elution rate is unknown. In this case, it is preferable to use 2 and 3 in Table 1 or a combination system of 1, 2, and 3 in Table 1 and E and F in Table 4. This allows the concrete to be protected until it is diluted to a concentration that does not affect the concrete, or even afterwards. Alternatively, sulfate ions can be used to protect concrete without being diluted.

(C) Concentration system: A case in which sulfate ions are not reduced and is more likely to be concentrated is a case in which sulfate ions that permeate from the surface of the concrete are concentrated by repeated drying and concentration. In this case, it is preferable to use 2 or 3 in Table 1 or E, F, or G in Table 4 in combination.
Furthermore, if the concrete is of high quality, sulfate ions will not enter and cause no problems (Table 8(b)).

(D) A non-implanted portion is provided within the implantation range, leaving an unconsolidated portion, and sulfate ions diffuse into that portion to reduce the overall sulfate ion concentration.

(E) Sulfate ions in the injection material are passivated as calcium sulfate depending on the calcium content of the ground within the injection range or the calcium content of the calcium-containing injection material injected into the ground in advance. A calcium-containing alkaline implant region is provided within the implant range to passivate the sulfate ions in the implant as calcium sulfate. Alternatively, calcium contained in the ground and sulfate ions in the injection material become calcium sulfate and become passivated, thereby reducing the sulfate ion concentration. When the air pH of the injection material is ₀ , when it is injected into the ground, the pH shifts to neutral depending on the soil pH, and the soil gel time _GTS is shortened (Figures 7, 8, and 9). In addition, the soil components, especially the Ca content of the ground to be injected, have a large influence. Figure 7 shows a practical example in the field of injecting non-alkaline silica grout. From this data, the sulfate ions in _the ground will eventually decrease after construction is completed, and the reduction rate of ^sulfate ions will be as follows: When Ca ion is 10,000 ppm in No. 10 silica grout, the sulfate ion concentration can be considered to be reduced by approximately half or one-third.

(F) Inject 2, 3, 4, and 5 of Table 1 around the concrete structure to prevent intrusion into the concrete and passivate sulfate ions.
Furthermore, among the metal ion sequestering agents, particularly in non-alkaline silica containing sodium hexametaphosphate, the amount of sulfate ions eluted from the gelled product is extremely small at the initial stage, being 30% of the sulfate ion concentration used. Therefore, the protective function of concrete is extremely high. The reason for this is presumed to be that SO ₄ ^-- ions were incorporated into the strong structure of hydroxyapatite bonded to calcium formed on the concrete surface.

The groundwater situation mentioned above can be understood as follows. The injection liquid or detection liquid is collected from the injection hole established in the injection ground and the injection area, or from an observation well established at a location away from the injection area, and the components and pH of the injection liquid in the groundwater are analyzed to determine the presence or absence of elution. , the elution rate and degree of dilution can be estimated. For example, a detection liquid such as a dye or an electrolyte may be injected through an injection hole, groundwater may be sampled from an observation well located far from the injection area, and conductivity and concentration may be measured and detected. This can be determined by changes in the groundwater level in the ground. It can also be determined by analyzing leakage water that has leaked into the concrete structure. In this way, electrical conductivity measurement and pH measurement can be used as sensors to determine the diffusion rate, dilution rate, and degree of dilution. FIG. 34 shows the relationship between silica solution concentration and conductivity. By injecting silica solution through the injection hole and measuring the conductivity of the liquid sampled from the observation well, it is possible to understand groundwater conditions and dilution conditions. Of course, this can also be determined based on past performance.
In addition, in the above, the sulfate ion concentration in the ground improvement area is reduced not only by decreasing the injection rate of the sulfate ion-containing injection solution, but also by the sulfate ions being captured (fixed) as calcium sulfate by calcium. do.
Furthermore, similarly, when suspension type grout is used as the calcium-containing grout in primary injection, the sulfate ion concentration in the ground improvement area is calculated by subtracting the injection rate of the primary injection material from the total injection rate. In addition to the reduction in sulfate ions due to a reduction in the injection rate of the injection material, the sulfate ions in the secondary injection material are also reduced by being captured (fixed) by the calcium in the primary injection material (Table 1, △3 , 4, 6, 7).

Since the elution of SO ₄ ^-- from the injection area occurs from the peripheral area where the concentration is low due to the concentration gradient of SO ₄ ^-- , the greater the water permeability of the ground (the area outside the injection area) before injection, the higher the It can be thought of as a rapidly leaching ground. Note that the permeability of the ground for injection is usually reduced (k = 10 ^-7 to 10 ^-8 m/sec), and generally speaking, the higher the permeability of the ground to be injected (k = 10 ^-4 to 10 ^{- 5} m/sec or more), if the injection ground is close to the coast or a river, groundwater flows due to the ebb and flow of the tide, and sulfate ions are rapidly reduced to the level in the natural state described above.

In addition, if it is difficult to judge the groundwater dilution conditions due to complex ground conditions, the dilution rate may be reduced, for example, 1/10 or 1/2 from Figures 4 and 5, or as shown in Table 4. In Table 1, classification No. 2.No. 3 or No. It is safer to use 5 in combination. In addition, if the injection area is in contact with a concrete structure and the water permeability of the injection area is low, so the period during which sulfate ions will flow out of the injection area is unclear, apply injection materials 2 or 3 in Table 1, or It is preferable to use E and F of 4 together.

Based on this knowledge, the present inventors conducted further intensive studies and found that the above-mentioned problems could be solved by configuring the formulation of non-alkali silica grout as shown below, and thus completed the present invention. reached.

That is, a further ground injection method of the present invention improves the ground by injecting a non-alkaline silica-based injection material containing sulfate ions into the vicinity of a concrete structure or the vicinity where a concrete structure is planned to be constructed after excavation. In the ground injection method, the non-alkaline silica injection material with a pH of 1 to 10 is used so that the average value (X) of the sulfate ion concentration in the entire ground improvement area is W or less, and the value of (X) is 8,000 ppm or less. , More preferably, the value of (X) is 5000 ppm or less, and the injection material is composed of a formulation having a sulfate ion content that satisfies the purpose of injection and is compatible with the injection method, as well as a method for setting the injection material and its use. This is the injection method used. Here, W is the water-soluble reaction product derived from the ground injection material in the ground improvement area assuming environmental safety, taking into account the durability period required for durable ground and the importance of concrete structures, especially is the maximum concentration of sulfate ions, and is set to a value such that X≦W. Moreover, non-alkaline means a pH of 10 or less.

In the present invention, the non-alkaline silica-based implantation material containing sulfate ions contains water glass and/or silica colloid as an active ingredient, and the silica content resulting from water glass or water glass and colloid is 1 to 40 w/vol%. , preferably 2 to 30 w/vol%. Furthermore, in the present invention, by partially injecting the non-alkaline silica-based implantation material containing sulfate ions into the ground improvement region, it is possible to reduce the sulfate ion concentration in the entire implantation region (Fig. 31(a)). ~(d), corresponding to △1 in [Table 10]). In this case, if the injection part of the non-sulfuric acid-based injection material is an alkaline water glass grout (for example, water glass-baking soda system), the excess sulfate ions in the shaded area of the injection part in Figure 31 are the excess sulfate ions in the water glass grout. It has the effect of neutralizing alkali and helping to increase strength and durability. Furthermore, if we consider the elution of sulfate ions from the injection ground into groundwater (α2 in (Table 10)), it can be assumed that the sulfate ions in the injection ground decrease over time (corresponding to △2 in [Table 10]). It can be assumed. Furthermore, in the present invention, a silica-based implantation material that does not contain sulfate ions or a silica-based implantation material that has a lower sulfate ion concentration than the above-mentioned implantation material that contains sulfate ions is replaced with a non-alkaline silica-based implantation material that contains sulfate ions. It can be implanted in place of a part of the implanted region (corresponding to Δ4 in FIG. 31 and [Table 10]). Furthermore, in the present invention, an injection material containing calcium (including cement type) as an active ingredient can be injected as a fixing material for sulfate ions (corresponding to △3 in [Table 10]). In this case, in addition to reducing sulfate ions as a fixing material for sulfate ions, there is an effect that the injection amount of the calcium-containing injection solution is replaced by the sulfate ion-containing injection solution (corresponding to △4). In addition, by injecting an injection material containing sulfate ions into calcium-containing ground, it is possible to passivate the calcium ions in the ground and the sulfate ions in the injection material as calcium sulfate, thereby reducing sulfate ions (△3 ). Furthermore, in the present invention, the non-alkaline silica-based implantation material containing sulfate ions can reduce the content of sulfate ions by including silica colloid. This is because although the colloid is stabilized by a trace amount of alkali, the amount of alkali can be almost ignored (corresponding to △5 in [Table 10]). In addition, in the present invention, it is preferable that the non-alkaline silica injection material that does not contain sulfate ions or has a low concentration of sulfate ions contains phosphoric acid or a phosphoric acid compound as an active ingredient (△4 in [Table 10]). equivalent). Furthermore, in the present invention, phosphoric acid or a phosphoric acid compound, or a metal ion sequestering agent is used as an active ingredient in the area between the concrete structure and the area where the non-alkali silica-based injection material containing sulfate ions is injected. It is preferable to inject an injection material (corresponding to △4 in FIG. 31(b) and [Table 10]).

In addition, the non-alkali silica-based implantation material containing sulfate ions with a low sulfate ion concentration is defined as a sulfate ion concentration lower than the sulfate ion concentration required to neutralize the silica colloid in the implantation material and/or the alkali in the water glass. A non-alkali silica injection material with a low

Based on the above research results, the present inventors conducted intensive studies to solve the above problems, and as a result, the present inventors determined that a non-alkaline silica-based injection material containing sulfate ions should be mixed in the vicinity of the area where a concrete structure is to be constructed. The following injection design is used to reduce the environmental impact, provide excellent long-term durability, and provide a ground improvement effect that meets the purpose of injection.Group material and ground injection that quantitatively form a solidified area of the ground. Invented a construction method. This has made it possible to protect concrete structures by reducing sulfate ions that come into contact with concrete. Of course, the present invention can be applied to the environmentally superior ground injection method even under ground conditions unrelated to concrete structures.

The present inventors have discovered that the influence of water-soluble reaction products such as sulfate ions on concrete depends on the compacted soil in the ground to be injected or the sulfate ion concentration (not the pH) of the entire ground improvement area. Assuming that ). By quantifying _this Y, the sulfate ion concentrations X ₁ , A non-alkali silica grout with a formulation containing a sulfate ion concentration (a) that is less than the maximum value W of the sulfate ion concentration expected, and that satisfies the purpose of injection and is compatible with the applicable ground and injection method, and It has become possible to put into practical use a ground improvement design method and a non-alkaline silica injection method using the same. As a result, the present invention enables quantitative design and ground improvement, as opposed to environment-friendly silica grouting and injection methods that have conventionally been done qualitatively. In addition, in the present invention, the meaning of "it is assumed that there is no effect on the concrete structure" means that it is assumed that there will be no effect on the concrete structure, which may cause substantial damage such as external damage or decrease in strength of the concrete structure. It means no.

[Mixture setting method]
The concentration (a) of water-soluble reaction products such as sulfate ions derived from the ground injection material is used as the concentration (X) of water-soluble reaction products such as sulfate ions in the ground injection area or injected solids to affect the concrete structure. The maximum value of the sulfate ion concentration (α), the residual rate of the reaction product is △, and the reduction factor (Y) is the elution rate (α) of sulfate ions as the water-soluble reaction product from the gel and the residual rate of sulfate ions in the gel ( As a factor related to Δ) (Δ=1−α), one or more of the following Δ1 to Δ7 is set as a reduction factor (Y). Injection rate A refers to the injection rate per 1 ^m3 of soil to be injected, but it may be difficult to find ground that is uneven and easily deviates, ground that is easily deviated due to groundwater, ground that is difficult to penetrate, or the importance of the purpose of injection. Table 12b can be varied as a standard.
X ₁ =A×a...Formula (1)
X ₁ : Sulfate ion concentration (ppm) in the ground injection area or injected solidity
A: Injection rate (%)/100 (For example, if the injection volume per ^1m3 of injection ground is 400L, the injection rate A=0.4.)
a: Sulfate ion concentration in injection material (ppm)
X ₁ ≦W ₁ ...Formula (2)

If the factor that reduces sulfate ions in the implanted ground is (Y), the elution rate of sulfate ions is α, and the residual rate of sulfate ions in the gel is △, then
X ₂ =A×a×Y...Formula (3)
X ₂ : Sulfate ion concentration (ppm) in the entire ground improvement area or in the implanted compact
A: Injection rate (%)/100
a: Sulfate ion concentration in the injection material (ppm)
If Y is △, △ is the residual rate of the water-soluble reaction product (sulfate ion) in the improved ground below.
X ₂ ≦W ₂ ...Formula (4)

W ₁ and W ₂ are determined by taking into account the importance of the structure, ground conditions, groundwater conditions, positional relationship of underground structures, structure of underground structures, and △8, △9, and △10 in Table 10. The concentration of water-soluble reaction products shall be determined as the maximum value (tolerable value) that is assumed to have no adverse effect on concrete structures.

_W2 may be 8,000 ppm based on Table 9 and the above description, or 5000 ppm in consideration of ground conditions and groundwater conditions. In any case, appropriate values can be set by also considering △8 to △10 in Table 10. If the water glass concentration of non-alkali silica grout is high and the gelation time is long, more sulfuric acid is required, so the amount of acidic agent required to set the pH to a neutral or acidic range is: The alkali content of the silica and the set gel time are related.

Note that, as mentioned above, since the alkali of the silica solution containing silica colloid and/or water glass as the active ingredient is substantially the alkali of water glass, the silica concentration of 1 to 40 w/w to achieve the purpose of injection into the improved soil is used. When solidifying with silica grout containing only sulfate ions in vol% (silica sol grout), the basics of silica concentration, pH, sulfuric acid concentration, gel time, and solidification strength can be found from Figure 1 (b) and (c). Normally, a sulfate ion concentration of 50,000 to 5,000 ppm is used.As a factor (Y) for reducing sulfate ions in improved ground, Table 10 shows the elution rate as α, the residual rate as △, and (Y) as △ It was summarized on a scale of 1 to △10. In the above, standard values for the injection rate A are shown in Table 12(b). Among these, the injection rate for the solution type is a value that also includes the injection rate of the primary injection material. Therefore, if the injection rate (α ₇ = equivalent to elution rate (reduction rate of injection rate)) of suspension-type injection material or calcium-based injection material is increased as the primary injection material, injection of sulfate ion-containing silica grout will be possible. rate is reduced. Therefore, the residual rate of sulfate ions in the ground is Δ7=1− _α7 .

For non-alkaline silica grout to have a practical sand gel strength, the silica concentration is 1 to 40 w/vol%. In order to bring the pH of silica grout with this concentration into a non-alkaline range, when using sulfuric acid alone, the sulfate ion concentration is usually a = 50,000 ppm to 5,000 ppm (Figure 1 (b), Figure 1 ( c)).
In this case, the concentration _X1 due to sulfate ions in the injection ground is, when the injection rate A=0.4,
X ₁ = A x a = 0.4 x (50,000 to 5,000)
=20,000~2,000ppm
Therefore, when W ₂ = 5,000 ppm, if the ground condition and groundwater condition are B or C in Table 4, use 2 or 3 in Table 1 to determine if the sulfate ion concentration in the injection ground is 8,000 ppm or less or 5, 000 ppm or less, and the sulfate ion concentration (a) of the injection solution that is compatible with the injection purpose and injection method (Table 17, Table 16, Figure 11, Figure 12) is set. must be injected.

When the groundwater condition is A or B in Table 4, the maximum sulfate ion value in the injection ground that does not affect the concrete structure is W, the sulfate ion concentration of the injection solution is a, and the sulfate ion concentration in the injection ground is Assuming that the concentration is X ₂ and the factor that reduces the impact on the environment is Y (Table 10), an example of setting a formulation for an injection material having a sulfate ion concentration such that W ₂ ≧X ₂ in the injection ground is as follows. Shown below.

[Concrete example]
Factor Y that reduces the environmental impact of sulfate ions in the ground is set, and an injection material containing sulfate ions with X ₂ of 5,000 ppm or less satisfies the purpose of injection and enables the injection method. The formulation is set so that the sulfate ion concentration is a.
When the sulfate ion concentration of the injection material is a = 50,000,
X ₂ = 50,000 x 0.4 = 20,000
If α ₂ = 0.9, then Y = △2 = 0.1
Therefore, X ₂ =2,000≦W ₂ .
Therefore, when a = 50,000 ppm injection liquid is injected into the ground, if it is assumed that it will be diluted 10 times within one year (△2 = 0.1), then X = within 5,000 ppm. It turns out that there is no problem. However, if it is assumed that the ground condition or groundwater condition is difficult to make such an assumption, △4, △5, or △7 may be applied as Y.

Below, methods for setting the mix of injection materials so that non-alkali silica grout does not have an adverse effect on concrete structures are shown (Table 10). Depending on the injection ground conditions and groundwater conditions, use one or more of the following methods (1) to (6) to remove the water-soluble material derived from the ground injection material in the ground improvement area or the injection solids. A formulation can be set in which the reaction product is reduced to a concentration that is assumed to have no effect on the concrete structure.
(1) Setting the silica concentration to obtain the strength required based on the purpose of injection and the ground conditions for injection.
(2) Elution rate (α) of water-soluble reaction products such as sulfate ions from the gel in the factor (Y) that reduces the influence of water-soluble reaction products such as sulfate ions on concrete structures in the ground improvement area Setting the type and value of the residual rate (△) in the gel.
(3) Setting the maximum value (W ₂ ) of sulfate ion concentration in the injection ground that is assumed to have no effect on the concrete structure or the environment.
(4) Setting the sulfate ion concentration (X) in the ground based on the ground conditions and reduction factor (Y). However, W ₂ ≧X ₂ =A×a×Y
(5) Setting the concentration (a) of sulfate ions derived from the ground injection material that satisfies _W2 ≧ _X2 .
(6) Supports silica and sulfate ion concentrations (a) that meet the injection purpose, enabling injection methods and injection designs that are safe for concrete and compatible with the injection purpose, ground conditions, and applicable construction method. Setting the formulation of the ground injection material.

<Specific example>
The sulfate ion concentration X (ppm) in the improved ground after injection of the sulfate-based non-alkaline silica injection material is assumed to be based on equation (1) if there is no reduction in the sulfate ion concentration. If so, it shall be obtained from equation (2).
X ₁ =A×a...Formula (1)
Here, A is the injection rate (%)/100 of the injection material, and a is the sulfate ion concentration (ppm) of the injection material.
For example, if A=0.4,
X ₁ =A×a=0.4a, a=X ₁ /A=5,000/0.4=12,500,
Therefore, if X ₁ ≦5,000 ppm, the sulfate ion concentration of the implant must be a≦12,500 ppm. For example, it is possible to incorporate a silica concentration of 1 to 2 w/vol% (FIG. 3(a)).
Assume that a formulation with a SiO ₂ concentration of 6 w/vol% is used as a silica grout that can be used for injection purposes. It is assumed that W ₂ ≧X ₂ =A×a×Y (=△), and in consideration of the ground conditions and groundwater conditions, the blending design of the injection material will be performed so that W=5,000 ppm.
Assuming that the sulfate ion reduction factor is Y (=△), and assuming that the sulfate ion concentration will be diluted 10 times within one year from Figures 4 and 5, 90% of the sulfate ions will be eluted (elution rate =α2=0.9), and the residual rate of sulfate ions Δ2=1−0.9=0.1. In the curve 1 of Figure 10, using the mixture marked with ○ in Table 11 and the sulfate ion concentration of 21,000 to 28,000 ppm, the sulfate ion in the ground is X ₂ = a x 0.4 x 0.1 = 872 ~1,120 ppm, W ₂ ≧X ₂ =872 ~ 1,120 ppm, and there is no problem. Also, if we set △2=0.3 for safety in a ground with cohesive soil,
X ₂ =A×a×Y(=Δ2(=0.3))=0.4×(21,000 to 28,000 ppm)×0.3=2,520 to 3,360 ppm.
Therefore, it can be seen that the range of curve 1 in FIG. 10 and the combinations marked with ○ in Table 11 may be used. In addition, if the applicable conditions are B or C in Table 4, that is, if the injection ground is in a stagnant or concentrated state, use the combination of curve 3 in Figure 10 (x mark in Table 11) or take safety into account. Therefore, it can be seen that the combination of curve 4 (marked with △ in Table 11) may be used.

As mentioned above, Equation (2) makes it possible to design a mixture recipe that is safe for concrete based on the purpose of injection, construction method, and ground conditions, and reduces the environmental burden by quantitative injection design. Reduced ground injection becomes possible.

A silica grout having a sulfate ion concentration a where X ₂ =5,000 ppm is calculated using equation (2). Normally, when the silica concentration of water glass is 1 to 50 w/wt%, the sulfate ion concentration needs to be 50,000 to 5,000 ppm when using sulfuric acid alone to make it a non-alkaline region. Therefore, the sulfate ion concentration X of the injection ground is 50,000 to 5,000 ppm, and when the groundwater is stagnant, the injection rate is t=0.4, the sulfate ion concentration X is 20,000 to 2,000 ppm. In order to reduce this value to 5,000 ppm or less, if half of the silica concentration in water glass is replaced with colloid, the sulfate ion concentration in the injection solution will be halved (△5 = 0.5), and the sulfate ion concentration in the injection ground (X ₂ ) is 10,000 to 1,000 ppm. In addition, if half of the sulfate ion concentration in the injection solution is replaced with non-sulfuric acid such as phosphoric acid, citric acid, succinic acid, AlCl ₃ , FeCl ₃ (Δ4 = 0.5), the sulfate ion concentration in the injection ground will be 10, 000 to 1,000 ppm. If the above is used in combination (△4=0.5, △5=0.5), the sulfate ion in the implantation ground will be 5,000 to 500 ppm≦W ₂ . Furthermore, if the above is diluted to 1/10 with groundwater, and the injection rate A=0.4, the sulfate ion concentration will be 2,000 to 200 ppm<W ₂ .

As described above, it is understood that a part of sulfuric acid may be replaced with an inorganic acid such as phosphoric acid, an organic acid, an inorganic salt such as AlCl ₃ or FeCl ₃ , or a salt exhibiting acidity of an organic substance. Furthermore, if a sequestering agent is used, concrete can be protected without reducing sulfate ions, as described above.

As an example, if the ground condition is open, the injection rate is 45%, 10% of which is suspended cement bentonite (CB) as the primary injection rate, and sulfuric acid-based silica grout as the secondary injection. reduced the rate. At the same site, CB was found to have solidified normally in the form of veins. In this case, of the injection rate A (=0.45), 0.1 was the primary injection material (CB) and 0.35 was the secondary injection material (silica sol grout). The reactant for the silica sol grout used was sulfate ion alone (No. 1 in Table 1).The formulation of the injection solution was as follows. injection of 25,000 ppm silica grout. The injection rate A was 45%, and the injection rates of CB:silica sol grout were 10% and 35%, respectively. If the injection rate of primary injection (CB) is 0.1 and the injection rate of secondary injection (silica sol grout) is 0.35, the sulfate ion concentration in the ground is X ₂ = 25,000 x 0.35 = 8,750 ppm. becomes. When diluted ten times with groundwater, the elution rate of sulfate ions becomes α ₂ =0.9, and therefore the residual rate of sulfate ions in the ground becomes Δ2=1−0.9=0.1. Therefore, the sulfate ion concentration of the implanted ground X ₂ =8,750×0.1=875<W ₂ . Alternatively, the water permeability decreases due to the injection of the primary injection material, and the elution rate of sulfate ions becomes α ₂ = 0.5. Therefore, the residual rate of sulfate ions in the injection ground is set to △2 = 1 - 0.5 = 0.5. Then, X ₂ =8,750×0.5=4,375<W ₂ . Based on the above, we assumed the elution rate in accordance with the ground conditions so that the concentration of sulfate ions in the ground would be within W ₂ = 5,000 ppm by injecting the primary injection material and injecting sulfuric acid-based silica grout into the ground. It turns out that it is only necessary to set the injection rate of the primary injection material. The same thing can be done using a suspension type grout, such as a calcium silicate type or slag type grout, or a calcium-containing solution type grout as the primary grout. In addition, if cement grout, lime, slag, or other calcium-containing material is injected in the primary injection, if 0.1 (α4 = 0.1) of the injection rate of 0.4 is injected as the primary injection material, The injection rate of silica grout is 0.3. Furthermore, assuming that the Ca content of cement, lime, and slag reacts with sulfate ions, and 0.1 of the sulfate ions out of the injection rate of 0.4 are fixed as CaSO ₄ (α3=0.1), The residual rate of sulfate ion concentration in the ground is Δ3=0.2. Therefore, X ₂ =25,000×0.2=5,000 ppm. Therefore, when 25,000 ppm of silica grout is injected, the sulfate ions in the ground will be X ₂ =5,000≦W ₂ . The fixation rate of sulfate ions by Ca ions when injected into Ca-containing ground can be predicted by mixing a sulfate-based injection solution with Ca-ion-containing soil.

Specifically, as shown in FIG. 31, by dividing the ground improvement area 2 so that, for example, the unimproved area 3 and the improved area 4 are equal, the sulfate ions are diffused into the unimproved area and the concentration is 5000 ppm or less. (Δ1=0.5). Alternatively, a non-sulfuric acid-based silica solution may be injected into the unimproved portion 3 in FIG. 31 (Δ4). For example, water glass-heavy sodium alkaline water glass grout, other water glass-inorganic salts, inorganic acids, organic reactants, etc. may be injected into the unimproved area (Figures 31(a) and 31(b)). (c)(d)). In this case, alkaline water glass grout is not durable because unreacted water glass and alkali remain in the alkaline region, but excess acid in the surrounding area penetrates into the gel and neutralizes the alkali. , durability can be improved. In this case, it is preferable that the amount of alkaline content of the alkaline water glass grout injected into the injection area of the non-sulfuric acid injection material is the same as or smaller than the amount of acid content of the acidic silica grout around the injection area. This is because if the alkali content is large, the acidic silica gel may deteriorate. To confirm this, as shown in Figure 18(b), after wrapping the gel of alkaline water glass grout with the same volume of sand gel of acidic silica grout, the strength of the sand gel of alkaline water glass grout increases. Just make sure that.

That is, for example, the ground improvement area is injected together with a sulfate-based grout and one or more non-sulfate-based grouts, such as alkaline grout, calcium-containing grout, or suspension grout; Let the injection rate of calcium-containing grout or suspension grout be A ₁ , and the injection rate of acidic silica grout be A ₂ . When using an alkaline grout, the durability of the alkaline grout is obtained by neutralizing the alkali with the acid of the acidic silica grout _. Set the injection rate so that it is assumed that there will be no impact. In addition, when using calcium-containing grout or suspension type grout as a non-sulfuric acid-based injection material, the injection rate _A1 is changed from the injection rate _A2 of acidic silica grout, assuming that sulfate ions do not affect the structure. Set the injection rate to be the same. Thereby, durability of the ground improvement area can be obtained.
In addition, in the above, the sulfate ion concentration in the ground improvement area is reduced not only by decreasing the injection rate of the sulfate ion-containing injection solution, but also by the sulfate ions being captured (fixed) as calcium sulfate by calcium. do.
Furthermore, similarly, when suspension type grout is used as the calcium-containing grout in primary injection, the sulfate ion concentration in the ground improvement area is calculated by subtracting the injection rate of the primary injection material from the total injection rate. In addition to the reduction in sulfate ions due to a reduction in the injection rate of the injection material, the sulfate ions in the secondary injection material are also reduced by being captured (fixed) by the calcium in the primary injection material (Table 1, △3 , 4, 6, 7).

From the above, in the present invention, assuming that the value of the average X of the sulfate ion concentration in the entire ground improvement area that does not affect concrete is W or less, W is 8,000 ppm or less or 5,000 ppm or less, or, The value of W can be determined based on ground conditions, groundwater conditions, structure and positional relationship of concrete structures, water quality conditions, soil conditions, actual results, etc. In addition, in areas where sulfuric acid-based non-alkali silica injection materials are not injected in the ground improvement area, injection materials containing metal ion sequestrants such as alkaline silica injection materials or phosphoric acid-based injection materials, calcium, cement, and slag may be added. Alkaline suspensions can also be injected; furthermore, the sulfate-based non-alkaline silica filler may include a phosphate compound or a sequestering agent; furthermore, the silica compound used in the sulfate-based non-alkaline silica filler may include: It consists of silica grout with a pH of 1 to 10 containing water glass and/or silica colloid as an active ingredient. In addition, for the surrounding area of concrete structures in the ground improvement area, by using one or more of the following (1) to (5) in combination, sulfate ions of sulfuric acid-based ground injection materials in the ground improvement area The concentration can also be reduced to a concentration that is assumed to have no effect on concrete structures.
(1) Water glass injection materials (2) Suspension injection materials (3) Low sulfate compound injection materials (4) Combination of sulfate compound injection materials and non-sulfate compound injection materials (5) Phosphoric acid compounds, metals Injection materials containing one or more of sequestrants and chelating agents

[Example of injection design for non-alkali silica grout with excellent environmental protection]
[Environmental integrity]
(1) Silica concentration: 6w/vol% (silica colloid: water glass = 1:1)
(2) Ground conditions: Stagnant to open system (3) Injection rate 1 = A/100 = 0.4
(4)X ₂ =a×A×Y
a: Sulfate ion concentration in the implanted material, _X2 : Sulfate ion concentration in the improved ground, Y: Sulfate ion concentration reduction factor in the implanted ground, α: Elution rate of sulfate ions in the ground, △: Sulfuric acid in the ground Ion residual rate (5) Y = △4 = 0.5 Sulfuric acid: Phosphoric acid = 1:1
(6) W ₂ =5000ppm
W ₂ : Sulfate ion concentration that is assumed not to affect concrete structures in the poured ground (7) X ₂ ≦W ₂
(8) Setting an injection material that satisfies X ₂ ≦ W ₂ and has a compounding recipe that satisfies injection purpose, construction conditions, ground conditions, injection design, injection method, penetration solidification, and long-term durability.
(9) Gel time: Air gel time GT ₀ 1000 minutes (Figure 1, Figure 9, Figure 10), soil gel time GT _S 10 to 1,000 minutes (Figure 9), injection method: double packer method (Figure 11 (a) , Table 16, Table 17), Injection rate: 10 L/min (within the limit injection pressure in Figure 32)
(10) [Formulation of injection material] Composition of silica components of non-alkali silica Silica of silica colloid:
Silica concentration: 6w/vol% (Table 12a, Figure 10)
Silica concentration ratio of water glass and silica colloid = 1:1 (Figure 10, Table 11)
Reactant blending amount and gel time 16L/400L (Symbol × in Figure 10 and Table 11)
Sulfuric acid: phosphoric acid = 1:1 (Figure 10) (Y: △4 = 0.5)

[Soil improvement effect]
Design strength qu = 0.1 MN/m ² (relative density 60%)
The indoor test target strength qu = 0.2 MN/m ² is set as a safety factor of 2.

[Setting a compounding recipe for the injection material that provides durability with excellent environmental protection that matches the injection purpose, ground conditions, and injection conditions]
The composition of the injection liquid is set based on the relationship between the air gel time GT ₀ and the amount of reactant blended (FIG. 10, No. 3 line, Table 11, symbol X). In this case, if Y is △4=0.5,
X ₂ =A×a×Y(=△4)=0.4×a×0.5=0.2×a≦W=5,000
Therefore, a≦25,000
From the above, if a=25,000 (symbol x in Table 11, No. 3 line in Figure 10), the sulfate ion concentration in the improved ground will be 5,000 ppm or less.
From the above, per 400 L of injection solution, the formulation is as follows: silica concentration 6 w/vol%, colloid: water glass = 1:1, sulfuric acid content 20000 ppm, phosphoric acid content 20000 ppm, and air gel time GT ₀ = 1000 minutes (20°C). (Table 11, Table 12a, Figure 10).

Based on the results of conventional penetration consolidation effects obtained with this formulation (Figure 9), the gel time in air (GT ₀ = 1,000 minutes) falls within the range of gel time in soil GT _S = 300 minutes to 10 minutes. 16. Using the double packer injection method (point injection) shown in Figure 11(a), the injection rate was 10 minutes per minute, the injection rate was within the permeability limit between soil particles (Figure 32), the injection hole interval was 2m, and the injection rate was 10L. /min, injection time per stage is 80 minutes (Table 17), even if the soil gel time is reduced from the air gel time (GT0) of 1,000 minutes to 300 to 10 minutes (Figure 9). , Due to the Norikoshi penetrating consolidation effect shown in Figure 33, a consolidated body corresponding to the injection amount is formed, and a durable consolidation effect with excellent permeability that achieves the injection purpose is achieved (Figure 3 (c), Figure 14, Figure 16). Note that Table 16, FIG. 11, and FIG. 12 show examples of injection methods, and the present invention is not limited thereto.

(11) Penetration test Test conditions Test equipment: Fill an acrylic mold with a length of 1.0 m and a diameter of 0.05 m in Figures 15 and 16 to a relative density of 60%, and after saturating it with water. Water was injected at a water pressure of 50 kPa for the purpose of determining the hydraulic conductivity (Figure 16). As a result, a hydraulic conductivity k=3.23 ⁻⁵ m/sec was obtained. Thereafter, the silica grout was injected at 50 kPa, and the results are shown in FIG. From the above, it was found that a strength satisfying the design strength of 100 kN/m ² and the indoor target strength of 200 kN/m ² could be obtained with a penetration length of 1 m.

(12) Determining the setting composition of silica grout Relative density 60.0%, soil collected on site, pH of site soil 4.44, design strength qu = 100 kN/m ² , indoor target strength qu = 100 x 2 = 200 kN/m ² And so.
Under the above conditions, gel time and strength tests were conducted with the combination of symbol X in Table 11 and curve 3 in FIG. The results are shown in FIG. 3(c)A. As a result, it was found that the silica concentration should be 6 w/vol% in order to satisfy the indoor target strength of 200 kN/m ^{2 when the design strength is qu=100 kN/m 2 and} the safety factor is 2. Based on this result, the set formulation of silica grout was designated as symbol X in Table 11. In this case, the sulfate ion concentration is 7.0 to 7.6 L/400L, and the sulfate ion concentration is 20,000 ppm, which falls within the range of 18,000 to 25,000. Moreover, the gel time is as shown in FIG. Furthermore, it was found from the penetration tests (FIGS. 15, 16, and 17) that sufficient penetration and consolidation properties were obtained. Furthermore, from the above, it was found that laboratory tests were conducted using soil sampled from the field with multiple mixtures, and based on the data, it was possible to obtain the target design strength and design the mixture in actual on-site conditions. In addition, FIGS. 3(a) and 3(b) use activated composite silica (active composite silica refers to non-alkaline silica grout with a pH of 1 to 10 containing silica colloid and/or water glass as an active ingredient). The relationship between the relative density, silica concentration, and unconfined compressive strength of consolidated Toyoura sand is shown, and FIG. 3(c) shows the durability regarding long-term maintenance of strength. Furthermore, Fig. 3(d) shows the silica concentration and unconfined compressive strength of the soil collected at the site of consolidation. In addition, Figure 6 shows the relationship between the amount of reactant added, pH, and gel time for non-alkaline silica grout, and Figure 7 shows the relationship between silica concentration and aerial gel time (active silica colloid refers to the relationship between silica colloid and silica colloid as an active ingredient). non-alkali silica grout). These include the strength data and penetration test data obtained for each soil sampled on site using Figures 14, 15, and 16, and the actual data showing the injection effect shown in Figures 3(d), 8, and 9. This invention makes it possible to set an injection material with a formulation that is compatible with the purpose of injection, ground conditions, and injection method, as well as environmental protection in the improved ground.

[Example of procedure for environmentally friendly injection design]
(1) Setting the silica concentration to obtain the strength that meets the injection purpose:
Set the silica concentration for the required design strength using soil sampled on site in the target ground improvement area.
(2) Setting the permissible concentration (W) of sulfate ions in the ground after injection, assuming that water-soluble reaction products have no effect on the environment.
(3) Setting injection rate for improved ground:
Set the injection rate for non-alkaline silica grout.
(4) Setting the Ca content in the ground:
Measurement of the amount of calcium in the ground and/or calcium-based suspended injection material before injection.
(5) Setting the reduction factor (Y) for sulfate ions in the implanted ground. (Elution rate = reduction rate (α) and residual rate (△))
(6) Reduction rate (α3) and residual rate (Δ3) of sulfate ion concentration in the implanted ground due to the formation of calcium sulfate by the sulfate-based non-alkali silica grout and calcium in the ground.
(7) Reduction rate (α2) and residual rate (△2) of sulfate ion concentration in the implanted ground due to dilution of sulfate ion concentration by groundwater.
(8) Reduction rate (α5) and residual rate (Δ5) of sulfate ion concentration in the implanted ground by replacing part or all of the silica content of silica grout with silica colloid.
(9) Reduction of sulfate ion concentration in the implanted ground (α4) and residual rate (△4) by replacing part or all of sulfate-based silica grout with non-alkali silica grout containing a sequestering agent or non-sulfate-based injection material ).
(10) Concentration of silica that meets the purpose of injection, type and concentration of reactant, gel time (air gel time, soil gel time), injection method, and formulation that is compatible with the construction method that enables permeability corresponding to the injection design. setting. In addition, in the above, the elution rate (α) corresponds to the reduction rate.
(11) Establishing environmentally friendly injection materials and injection methods.
Here, if (2) is satisfied in any or more of (6), (7), (8), and (9), it is possible to proceed to (10) and (11).
Furthermore, if (2) is not satisfied in (6), (7), and (8), it is possible to proceed to (9).
Furthermore, the order of steps (6), (7), (8), and (9) does not matter.
Furthermore, the above is a specific example of the procedure, and the order does not matter. Also, see Table 10 for (Y) (α) (△).

(Effect of the invention)
Traditionally, silica grout has been targeted solely at the gelation and effects created by the combination of injection materials. In contrast, the present inventors have discovered the factors that cause sulfate ions in the ground to affect concrete based on a prior invention, and based on this, developed a ground injection method to evaluate the safety of concrete when pouring material is injected into the ground. Proposed. However, the above-mentioned invention is an invention of a quantitative injection solution and injection method that satisfies the purpose of injection based on these factors, and has a formulation that satisfies safety for concrete with a sulfate ion concentration that is compatible with the injection ground and the injection method to be adopted. It had not reached that point. The reason for this was that there were too many and complex factors to equally satisfy the injection purpose, durability, and environmental protection under various ground conditions. In response to this, the present inventors have elucidated the behavior of SO ₄ ions eluted from the gelled material of the injection material, and have determined the quantitative reduction factor of sulfate ions in the injection ground in response to the behavior of sulfate ions in the ground. Set the elution rate or reduction rate (α) and residual rate (△) as (Y), and further set the value (W ), and the sulfate ion concentration (a) of the injection solution that satisfies this is set, and furthermore, the injection solution has the gel time, consolidation strength, and permeability into the ground of the sulfate ion concentration and silica concentration for the purpose of injection. By injecting into the ground an injection material with excellent long-term durability that has a formulation containing a sulfate ion concentration that is below the sulfate ion concentration that does not affect the concrete in the improved ground, it is compatible with the applied injection method. This enables a ground injection method based on a quantitative injection design with less load.

Claims (20)

A ground injection material consisting of a non-alkali silica grout with a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10, which is injected into the ground to form a ground improvement area,
The ground injection material contains a water-soluble reaction product whose concentration is such that the concentration of water-soluble reaction products derived from the ground injection material does not affect the environment within the ground improvement area, and the concentration of water-soluble reaction products derived from the ground injection material is such that it does not affect the environment in the ground improvement area, and A ground injection material characterized by having a silica concentration that satisfies the purpose of injection and a formulation that is compatible with the applied construction method. The ground injection material contains as active ingredients one or more silica components of water glass or silica colloid, and an acidic agent that neutralizes the alkali in the silica component, and the water-soluble reaction derived from the ground injection material The concentration of sulfate ions as a product is such that the concentration of sulfate ions does not affect structures in the ground improvement area, and the silica concentration satisfies the purpose of injection for the ground condition, and the method is applied. 2. The ground injection material according to claim 1, comprising a formulation that enables gel time with permeability that is compatible with the construction method. The concentration of sulfate ions as a water-soluble reaction product derived from the ground injection material in the ground improvement area is such that the concentration of sulfate ions in the ground is such that it does not affect the concrete, and the silica has a strength that satisfies the purpose of injection. 3. The ground injection material according to claim 1 or 2, comprising a compounding formulation that provides a concentration and permeability that is compatible with the applied construction method. The ground injection material according to claim 2, wherein the acidic agent is one or more of a sulfuric acid compound and a non-sulfuric acid compound. The ground injection material according to claim 4, wherein the non-sulfuric acid compound is one or more of an inorganic acid other than sulfuric acid, an organic acid, or an acid salt thereof. The ground injection material according to any one of claims 1 to 5, wherein the ground injection material contains one or more of a phosphoric acid compound, a metal ion sequestering agent, and a chelating agent as an active ingredient. The ground injection material is prepared such that the concentration of sulfate ions as a water-soluble reaction product derived from the ground injection material in the ground improvement area is adjusted in the ground to a level that does not affect the environment by the following method, Alternatively, the silica concentration is adjusted to a level that does not affect the environment and the structure, and the silica concentration satisfies the purpose of injection into the ground and the formulation is compatible with the applied construction method. The ground injection material described in any one of items 1 to 6.
1) Calcium contained in the ground improvement area and sulfate ions in the ground injection material become calcium sulfate and are fixed in the ground, thereby reducing the sulfate ion concentration in the ground.
2) After primary injection of cement bentonite, calcium silicate, or slag-based calcium-containing suspension-type injection material or calcium-containing solution-type injection material into the ground improvement area, the above-mentioned ground injection material is injected as a secondary injection material. By reducing the injection rate of the sulfate ion-containing ground injection material by the injection amount of the suspension type injection material or the calcium-containing solution type injection material, water-soluble reaction products derived from the ground injection material can be treated. reduce the concentration of sulfate ions.
3) A non-sulfuric acid injection part, a low sulfuric acid injection material injection part, or a non-injection part of the injection material is provided in the ground improvement area to reduce sulfate ions in the ground improvement area.
4) It is assumed that sulfate ions are eluted from the ground improvement area into groundwater and the sulfate ions in the ground improvement area are reduced.
5) Part or all of the silica component contained in the ground injection material is replaced with silica colloid to reduce sulfate ions in the ground improvement area.
6) As a reactive agent contained in the ground injection material, one or both of a non-sulfuric acid compound and a sulfuric acid compound is used.
7) Fixing sulfate ions in the ground improvement area or in the ground injection material to reduce sulfate ions in the ground improvement area.
8) The ground improvement area is to be improved by injecting the alkaline water glass grout and the sulfuric acid-based ground injection material, and the injection rate of the alkaline water glass grout is set to The concentration of water-soluble reaction products is set to be reduced to a level that does not affect the environment.
9) Part or all of the sulfate ions in the ground injection material are replaced with non-sulfate ions.
10) Part or all of the sulfate ions in the ground injection material are captured.
11) For the surrounding area of the concrete structure in the ground improvement area, by using one or more of the following (1) to (5) in combination, the sulfuric acid-based ground injection material in the ground improvement area The concentration of sulfate ions in the concrete structure is reduced to a concentration that is assumed not to affect the concrete structure.
(1) Water glass injection materials (2) Suspension injection materials (3) Low sulfate compound injection materials (4) Combination of sulfate compound injection materials and non-sulfate compound injection materials (5) Phosphoric acid compounds, metals An injection material containing one or more of an ion sequestering agent and a chelating agent 12) The surrounding area of the concrete structure in the ground improvement area is treated with one or more of a phosphoric acid compound, a metal ion sequestering agent, and a chelating agent. Consolidate with non-alkali silica grout containing multiple. The ground injection material is such that the concentration of sulfate ions in the ground improvement area is derived from the ground injection material based on any one or more of the concrete structure, ground condition, groundwater condition, and injection conditions in the ground improvement area. Any one of claims 1 to 7, wherein the amount is such that the influence on the concrete structure can be reduced in accordance with the behavior of the water-soluble reaction product, and the formulation is compatible with the construction method employed. Ground injection material as described in paragraph 1. A water-soluble reaction product derived from the ground injection material in the ground improvement area or the injection solidification body is produced by one or more of the following methods (1) to (6), depending on the injection ground conditions and groundwater conditions. Gel time is adjusted to a concentration that does not affect the concrete structure, has a silica concentration that satisfies the ground conditions and injection purpose, is compatible with the applied construction method, and has permeability. The ground injection material according to any one of claims 1 to 8, which has a compounding formulation that enables.
(1) Setting the silica concentration based on the injection purpose and the ground conditions.
(2) Setting the elution rate (α) and residual rate (Δ) of the water-soluble reaction product in the factor (Y) that reduces the influence of the water-soluble reaction product on the concrete structure in the ground improvement area.
(3) Setting the maximum value (W) of sulfate ion concentration in the ground that is assumed not to affect the concrete structure.
(4) Setting the sulfate ion concentration (X) in the ground based on the ground conditions and the reduction factor (Y).
(5) Setting the concentration (a) of sulfate ions in the ground injection material that satisfies W≧X.
(6) Setting the formulation of the ground injection material corresponding to the silica concentration and sulfate ion concentration (a) that satisfies the injection purpose, which is compatible with the injection purpose, ground condition, and applied construction method. The water-soluble reaction product is generated in response to the behavior of the water-soluble reaction product derived from the ground injection material based on any or more of the concrete structure, ground condition, groundwater condition, and injection conditions in the ground improvement area. Quantitatively set the factors (Y) that reduce the environmental impact of objects, and determine the silica and sulfate ion concentrations that reduce the environmental impact and meet the injection purpose that is compatible with the ground conditions and the applied construction method. The ground injection material according to any one of claims 1 to 9, comprising a formulation corresponding to (a). The elution rate of water-soluble reaction products in the factor (Y) that reduces the influence of sulfate ions on concrete structures in the ground improvement area is (α) and the residual rate is (△), and the reduction factor (Y) The ground injection material according to any one of claims 1 to 10, wherein one or more of the following △1 to △7 is set as.
X ₁ =A×a W ₁ ≧X ₁
X ₂ =A×a×Y W ₂ ≧X ₂
A: Injection rate (%)/100
a: Sulfate ion concentration in the injection material (ppm)
X ₁ , X ₂ : Sulfate ion concentration in the implanted ground △ 1: The concentration of sulfate ions in the improved ground when a non-injected part is provided in the ground improvement area and the ratio of the non-injected part is α ₁ (= elution rate) Residual rate of sulfate ion △1=1-α ₁
△2: Residual rate of sulfate ions in the ground improvement area, when the elution rate of sulfate ions into groundwater is α ₂ △ 2 = 1 - α ₂
△3: When the fixation rate of sulfate ions in the ground improvement area is α ₃ (=elution rate), the residual rate of sulfate ions in the ground improvement area △3=1−α ₃
△4: When the substitution rate of sulfate ions of sulfate-based injection material by non-sulfuric acid-based injection material or low-sulfuric acid-based injection material in the ground improvement area is α ₄ (=elution rate), Residual rate of sulfate ions in △4=1-α ₄
△5: When the substitution rate of the silica component in the ground injection material by the colloid is α ₅ (=elution rate), the residual rate of sulfate ions in the ground improvement area △ 5 = 1 - α ₅
△6: When some or all of the sulfate ions are captured in the ground injection material and the capture rate is α ₆ (=elution rate), the residual rate of sulfate ions in the ground improvement area △6=1 -α ₆
△7: When the injection rate of the ground injection material in the ground improvement area is reduced and the reduction rate of the injection rate is α ₇ (= elution rate), the residual rate of sulfate ions in the ground improvement area △ 7=1-α ₇ Having a sulfate ion concentration (a) such that the sulfate ion concentration (X) in the ground improvement area or the injected compact is below the maximum value W that is assumed not to affect the concrete structure, The ground injection material according to any one of claims 1 to 11, further having a formulation that satisfies the injection purpose in the ground condition to be applied and the construction method to be applied. A non-alkaline silica grout made of a sulfuric acid-based injection material with a silica concentration of 1 to 40 w/vol% and a sulfate ion concentration of 50,000 to 5,000 ppm, the sulfate ion concentration (X) in the ground improvement area or the implanted solid. Contains a sulfate ion concentration (a) that satisfies W ≧ The ground injection material according to any one of claims 1 to 12, which has a formulation that satisfies the purpose of injection. A non-alkali silica grout with a sulfate ion concentration within the range of 50,000 to 5,000 ppm, which contains sulfate ions to the extent that the sulfate ion concentration of the ground into which the non-alkali silica grout is injected does not affect the structure; The ground injection material according to any one of claims 1 to 13, further comprising a silica concentration that satisfies the purpose of injection and a formulation that is compatible with the applied ground conditions and construction method. A formulation with a silica concentration that satisfies the purpose of injection, a sulfate ion concentration that does not affect the environment in the injection ground, and a gel time in the soil in the injection ground that is compatible with the construction method. The ground injection material according to any one of claims 1 to 14, comprising a formulation. A ground injection method characterized by injecting the ground injection material according to any one of claims 1 to 15 into the ground. A non-sulfuric acid-based injection material is injected into the ground, and an alkaline water glass grout is injected into the injection area of the non-sulfuric acid injection material. 17. The ground injection method according to claim 16, wherein silica grout is neutralized by the acid contained in the grout. The ground improvement area shall be injected together with a sulfuric acid-based grout and any one or more of non-sulfuric acid-based grout, such as alkaline grout, calcium-containing grout, or suspended grout, and the alkaline grout, calcium-containing The injection rate of grout or suspension grout is _A1 , the injection rate of the acidic silica grout is _A2 ,
When using the alkaline grout, the durability of the alkaline grout is obtained by neutralizing the alkali with the acid of the acidic silica grout, and at an injection rate _A2 of the acidic silica grout, sulfate ions shall be set so that the injection rate is assumed to have no effect on the structure,
When using the calcium-containing grout or suspension type grout as the non-sulfuric acid grout, the injection rate _A1 is changed to the acidic silica grout injection rate _A2 , which is assumed that sulfate ions will not affect the structure. By setting the injection rate to
The ground injection method according to claim 17, wherein durability of the ground improvement area is obtained. 16. The sulfate ion concentration in the ground improvement area is reduced not only by decreasing the injection rate of the ground injection material containing sulfate ions, but also by the sulfate ions being captured by calcium as calcium sulfate. The ground injection method described in any one of ~18. By first injecting a suspended grout containing calcium into the ground improvement area and secondarily injecting the ground injection material containing sulfate ions into the ground improvement area, the sulfate ion concentration in the ground improvement area is lower than that of the secondary injection. 19. In addition to reducing sulfate ions by reducing the injection rate, the sulfate ions in the ground injection material are also reduced by being captured by calcium in the suspended grout. The ground injection method described.