JP2006226014A - Grouting construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a grouting construction method which maintains cut-off properties and strength over a long period of time even under underground seepage pressure, even if a grouting material is injected into the ground. <P>SOLUTION: In this grouting construction method, silica grout composed of silica colloid as an active ingredient, or a material, which simultaneously uses the silica colloid as the active ingredient and a suspension grouting material composed of particulate cement and/or particulate slug as active ingredients, is injected into the ground; and consequently, the silica grout or the material simultaneously using the silica grout and the suspension grouting material maintains the cut-off properties and the strength over a long period of time even under the underground seepage pressure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, a specific silica grout is injected into the ground, or a specific silica grout and a specific suspension type ground injection material are used in combination and injected into the ground. The present invention relates to a ground injection method that maintains water-stopping and strength over a long period of time.

  In tunnel excavation under high osmotic water pressure or deep underground development, ground injection with excellent strength and water stop effect is required for grouting. In particular, when excavation work under high water pressure or deep underground development takes a long time, long-term waterstop and long-term strength durability are required. If these problems are solved, not only will the safety of excavation work under pressure be suppressed, but the groundwater level drop and ground deformation in the surrounding ground will be suppressed, and repair costs such as leakage after construction will be reduced. .

  Conventionally, various solution-type silica grouts using water glass as a raw material are known as grouts used for ground improvement. For example, water glass alkaline grout, grout mainly composed of acidic silica sol, grout mainly composed of active silica obtained by treating water glass with cation exchange resin or ion exchange resin membrane, and concentrated granulation of active silica And a weakly alkaline and stable silica colloid having a pH of 9 to 10.

However, in the above-mentioned solution-type silica grout, the gel between the soil particles or the silica component constituting the gel is pushed out by water pressure, and the water-stopping property and long-term durability are reduced. For this reason, a cement-based suspension type injection material is used in place of the solution type silica grout, but the suspension type injection material has a large particle diameter and is unsuitable for the ground having low water permeability. Therefore, it is an object to develop an injection technique that is easy to permeate, can adjust the gelation time, has little silica leaching under high osmotic water pressure, and provides long-term water stopping and strength.
Japanese Patent No. 3205900 JP 2004-35584 A

  The object of the present invention is to inject a specific solution-type silica grout into the ground to be infused, firmly solidify with high strength even under high water pressure, and exhibit an excellent water-stopping effect. It is to provide an improved ground injection method.

  In order to solve the above-mentioned problems, according to the present invention, silica grout containing silica colloid as an active ingredient is injected into the ground, whereby even if the silica grout is under osmotic water pressure in the underground, it is long-term. It is characterized by maintaining water-stopping and strength.

  Furthermore, in order to solve the above-mentioned problems, according to the present invention, a silica grout having silica colloid as an active ingredient and a suspension type ground injection material having fine particle cement and / or fine particle slag as an active ingredient are used in combination. This is characterized by being injected into the ground, so that the combined product retains water-stopping and strength over a long period even under osmotic water pressure in the underground.

  In the present invention, silica grout containing silica colloid as an active ingredient is injected into the ground, or silica grout containing silica colloid as an active ingredient, and suspension-type ground injecting material containing fine particle cement and / or fine particle slag as an active ingredient, As a result, the silica grout or the concomitant material retains the water stoppage and strength for a long time even under osmotic water pressure in the underground.

  Hereinafter, the present invention will be described in detail.

  The silica colloid used in the present invention is a colloid obtained by concentrating and increasing the active silica to make it weakly alkaline. Furthermore, active silica colloid, which is a polymer of active silica obtained by treating water glass or acidic water glass formed by mixing water glass and acid with an ion exchange resin or ion exchange membrane, Silica colloid obtained by adding glass, acid or salt. These silica colloids contain silica having a particle size of 10 nm or more. Alternatively, these silica colloids are silica colloids having a particle size of 5 nm or more, particularly 10 nm or more, distributed on active silica having a particle size of 1 nm or less to 5 nm. Further, the silica colloid used in the present invention is mixed with water glass, acid, or salt.

  In the case of a silica colloid having a large particle size, the strength is low and the strength development is slow for a high silica concentration, but it has a long-term water pressure resistance effect even under high water pressure. On the other hand, in the case of a silica colloid with a small particle size, even if the silica concentration is low, strength development and consolidation are excellent. In addition, silica colloids composed of these mixtures reliably achieve excellent water-stopping properties and strong consolidation effects, particularly under high osmotic water pressure.

  Furthermore, the above-described silica colloid according to the present invention has high reactivity, and even when it is injected into the ground into which a suspension of fine particles exhibiting alkalinity is injected, it is not easily affected by alkalinity and is greatly affected under high water pressure. Consolidation and water-stopping properties are expressed simultaneously In particular, the silica colloid according to the present invention achieves a water-stopping property and a strong caking property excellent in long-term durability under a high osmotic water pressure, and firmly solidifies the ground to be injected.

  In the present invention, the silica grout containing the above-described silica colloid as an active ingredient and the suspension-type ground injection material are used in combination and injected into the ground. This suspension type ground injection material is an injection material containing fine particle cement as an active ingredient, or an injection material containing fine particle slag and an alkali material as active ingredients. By injecting this combination into the ground, even under osmotic water pressure in the underground, the waterproofness and strength are maintained for a long time, and the ground is improved.

  In the above, a suspension type ground injection material containing fine particle cement and / or fine particle slag as an active ingredient is injected into the ground beforehand, and then silica grout containing silica colloid as an active ingredient is injected into the injected ground, Can be used together in the ground. Moreover, after inject | pouring this silica grout, this suspension type injection material grout is inject | poured. Both the suspension-type injection material and the silica grout can be used in the ground by alternately injecting the suspension-type injection material and the silica grout multiple times.

  In general, deep underground development does not require land acquisition costs, and furthermore, because it has great economic and planning advantages that it can be developed without being affected by existing structures, various structures utilizing shield technology Development is expected. Especially for long-distance and multi-directional lifelines, a deep underground underground of 40m to 100m is considered optimal, and for the time being, construction of lifelines for electric power and gas is expected to take precedence. .

  In addition, tunnel excavation in submarine tunnels and volcanic deposits may involve excavation under pressurized water corresponding to a water pressure of 100 to 200 m. These do not only take a long time for excavation work, but are also under high water pressure after completion of construction, and high osmotic pressure water may leak into the tunnel. Therefore, tunnel excavation under high pressure water and permanent ground improvement for the purpose of deep underground development are subject to great earth pressure and water pressure on the excavated ground, and the excavation work takes a long time. It is necessary to increase the strength uniformly and to obtain a water stop effect and a consolidation effect over a long period of time. In addition, having excellent durability is also necessary to withstand the prolonged period from injection to excavation work, maintenance after the work is completed, and prevention of groundwater from filling.

  The colloidal solution (silica colloid) in the present invention is obtained by removing most of the alkali metal ions from a liquid alkali metal silica salt aqueous solution (water glass). What is obtained by passing water glass through an ion exchange resin of an ion exchanger, adding the generated silica colloid to the water glass at a temperature of 80 ° C. to 90 ° C., and passing the ion exchange resin again to perform ion exchange A relatively pure (dilute) silica colloid (active silica colloid) is obtained.

  Furthermore, in order to obtain a pure silica colloid, the above-mentioned dilute silica colloid is prepared to be slightly alkaline, and the above silica colloid is further added to the mixture to evaporate to simultaneously stabilize and concentrate, or after ion exchange. A method is used in which the active silica colloid is heated under an appropriate alkali, and further, the active silica colloid is added thereto for stabilization.

  Thus, the colloidal solution in the present invention has a larger particle size (particle size) than mere water glass grout or active silica-based grout (particle size is 5 nm or less) mainly composed of active silica obtained by ion exchange of water glass. The diameter is larger than 5 nm, usually 10 nm or more).

Since the silica colloid solution in the present invention has almost separated and removed Na ions, it usually shows weak alkalinity with a pH of 10 or less, and Na ₂ O is in the range of 4% to 0.2%. When Na ₂ O becomes 4% or more, the silica colloid dissolves and becomes an aqueous solution of silicate. On the other hand, when Na ₂ O is 1% or less, the silica colloid cannot be present stably and aggregates.

That is, when Na ₂ O is in the range of 4% to 0.2%, Na ions are distributed on the surface of the silica colloid and can be kept in a stable colloidal state. In this case, the particle size of the silica colloid is mainly about 6 to 50 nm. If the particle size of the silica colloid is 50 nm or more, it will precipitate. Moreover, this shows about 40-80 grade by molar ratio.

  The silica colloid prepared in this way is almost neutral and semi-permanently stable. When this is used as an infusion solution, there is a risk of gelation during delivery from the factory to the site and during the infusion operation. Absent. Even if this colloidal solution of silica is poured into the ground as it is, it does not gel within a practical time itself, so a practical consolidation effect cannot be obtained.

  However, by adding a monovalent alkali metal salt such as acid, NaCl or KCl to the silica colloid solution in advance, or a gelling material of an alkaline earth metal hydroxide or salt and injecting the mixture into the ground, In the colloidal solution of silica, colloidal particles destabilized by the gelling material are bonded to each other in the ground to form a strong solidified body and solidify the ground. Further, active silica or water glass may be added to the silica colloid, or an acid or salt may be further added.

  The present inventor solidified the soil using the silica colloid having a large particle size and conducted a long-term water permeability test under high water pressure. As a result, the inventors found that the water pressure resistance lasted for a long time, and completed the present invention. . In addition, when this silica colloid is used as a secondary injection material and a fine particle type suspension grout exhibiting alkalinity is used as the primary injection material, mutual reaction with the primary injection material is unlikely to occur, so that the water stoppage is not lowered. And, in order to fill the large voids, it was found that the long-term water stoppage is greatly improved. At this time, the reason why the secondary injection material and the alkali of the primary injection material are less reactive and difficult to deteriorate is that the colloidal particle size is large and the specific surface area is small.

The suspension-type ground injecting material containing fine particle cement as an active ingredient in the present invention is fine particle cement, or a mixture of fine particle cement and powder such as bentonite, fine particle slag, fly ash, or water glass, colloidal silica, Mixtures obtained by adding solution-type silica such as active colloidal silica, and alkali metals such as KCl, NaCl, NHCO ₃ and KHCO ₃ , polyvalent metal compounds such as lime, slag and aluminum salts, or acids and This refers to a mixture of reaction materials such as salt.

  Suspension-type ground injection material containing fine particle slag as an active ingredient is mixed with alkaline compound such as water glass, aluminate, slaked lime, caustic soda, or colloidal silica, active colloidal silica, etc. Say things.

  Conventionally, as a ground injection method that uses both suspension-type ground injection material (suspension type grout) and water glass-based ground injection material (water glass grout), the ground into which suspension type grout mainly composed of slag and cement has been injected. In addition, an alkaline solution-type water glass grout using water glass as a main component and using acids, alkali metal salts, organic aldehydes and esters as a gelling material for water glass, and alkali in water glass with an acid. A so-called compound injection method is known in which acid water glass grouts that have been combined are superposed and injected into the ground.

  In this compound injection method, the suspension type grout penetrates into the rough part of the ground, and the solution-type water glass grout penetrates into the thin part of the ground, and the former firmly fills and solidifies the rough part, while the latter Solidifies in a thin part, and as a result, the entire ground is consolidated uniformly and with high strength.

  However, when the fine particle type suspension grout is brought into contact with an alkaline solution type grout using these sodium bicarbonate and other inorganic or organic reactants, the alkali of the fine particle type suspension grout from the contact surface, It was found that the solution type silica grout gel in the alkaline region dissolves in a short time.

  This is because the solution type water glass grout in the alkaline region is gelled with a lot of unreacted water glass in the gel together with the alkali of the water glass, so the alkali in the fine particle suspension is further added to the water in the ground. This is probably because the silica in the glass gel is dissolved. In addition, water glass grout (acidic silica sol) in the acidic region made by mixing water glass and acid is stable in silica even when used in combination with cement grout, but emits a strong odor when used in combination with a fine particle suspension. As a result, the gel of the acidic water glass melts, and on the other hand, the fine particle suspension is insufficiently consolidated, so that both of them cannot obtain sufficient consolidated properties.

  This is presumably because the acid of the acidic silica sol and the alkali of the fine particle suspension react strongly with each other because the specific surface area of the fine particle suspension is large and the reactivity is excellent, thereby degrading the cohesiveness of both. Therefore, when these are used for deep underground excavation, the water stoppage tends to further decrease due to water pressure.

  As described above, the present inventors' research has revealed that the particle size of silica has a great influence on the reactivity and durability when used in combination with a fine particle suspension, particularly under high water pressure.

It is clear that the cement system is superior to the solution system in increasing the strength of the ground. However, normal Portland cement only penetrates the coarse layer and cannot penetrate the fine layer. Therefore, in recent years, fine particle cement having a specific surface area of 5000 cm ² / g or more, more preferably 8000 cm ² / g or more and 20000 cm ² / g has been used. It cannot penetrate and the water stop effect is insufficient. In particular, no waterstop is obtained under high osmotic water pressure.

  In order to solve the above problems, the inventor of the present invention has an effect of the particle size of the colloid under the high osmotic water pressure of the solution type silica grout, and further, the reaction between these solution type silica grout and the fine particle suspension. By continuing long-term research on long-term water stoppage and cohesiveness under high water pressure of the consolidated soil poured and consolidated separately, as well as mutual durability between the properties and consolidated The large-sized silica colloid consolidated soil maintains its water-stopping property even under high osmotic water pressure, and the silica colloid does not react with the fine particle suspension and the ground normally, and normally solidifies, and the fine particle suspension for a long time. It was found that durable ground improvement in the presence of alkali in the suspension was possible.

  It is considered that the silica colloid contains a silica colloid having a large particle size of 6 to 50 nm, usually 10 to 20 nm, thereby forming a stable gel that is not extruded even against water pressure. For this reason, the fine particle suspension is firmly consolidated to a fine part, and the finer part is infiltrated and solidified with silica colloid, and its boundary surface is also chemically stable in the part that has penetrated and overlapped. Thus, the present invention has been completed, which simultaneously satisfies the consolidation effect and the water stop effect that can withstand long-term excavation work and tunnel injection under high pressure water.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Experiment 1
In order for the present invention to confirm the effect of long-term durability of consolidation strength under osmotic water pressure, as an example, silica colloid was cured under osmotic water pressure, and this strength change was observed.

Materials used 1. Sand Toyoura standard sand is used. The density of sand (ρs) is 2.667 g / cm ^2.
2. The injection material is shown in Table 1 below.
3. Injection specimen Internal diameter 5cm x Height 10cm Use transparent acrylic mold.

Experimental Method The active silica colloid obtained by dealkalizing water glass ions with an ion exchange resin is reacted with potassium chloride, and the sand is placed in a transparent acrylic cylindrical mold so that the sand density is 1.5 g / cm ^3. And made by injection method.

  Thereafter, room curing at 20 ° C. was performed for 2 days. After curing, the specimen was removed from the acrylic mold and placed in the center of the mold capable of osmotic water curing, and bentonite was packed around it so that there were no gaps or cavities. As a result, the permeated water from other than the specimen was completely blocked. After assembling the mold, it was installed in the curing water tank 1a shown in FIG. This water tank 1a was adapted to be applied with osmotic water pressure 2a, and the osmotic water pressure 2a was applied from below the injection specimen 3a. The water pressure was adjusted so that the dynamic water gradient was 10. In addition, specimens prepared in the same manner were cured and compared under hydrostatic pressure. 4a is a heater and 5a is a water surface.

  Further, it was known from another experiment that the acceleration rate of the curing strength at 55 ° C. and 65 ° C. was about 30 times and about 50 times that of the standard curing temperature of 20 ° C., and thus the accelerated curing was performed. There were three curing temperatures of 20 ° C, 55 ° C, and 65 ° C.

  Changes in strength were measured for specimens cured under hydrostatic pressure and those subjected to hydrostatic gradient 10 in water for a long term. The results are shown in FIG.

  From this, it was found that the silica colloid-based injection material was not affected by the osmotic water pressure for a long time, and could obtain the same increase in strength as in the hydrostatic pressure state. From this measured value, when the injection improvement range is 10 m, with the head of 100 m (H) acting, at least about 2900 days (about 8 years), it is not affected by the osmotic pressure and increases the same strength as the hydrostatic pressure state. I was able to guess.

  Similarly, the solidified standard sand obtained by ion exchange treatment of acidic silica sol, alkaline solution type water glass grout, and water glass shown in Experiment 2 is not consolidated within one month. It became almost the same as standard sand, and it was found that neither water-stopping nor caking property could be obtained for long-term durability under high osmotic water pressure.

Experiment 2
In order to show the effectiveness of the present invention, a compatibility test between a suspension type grout and a solution type grout was conducted. As the suspension grout, a grout mainly composed of fine particle cement, fine particle slag, a composite of fine particle cement and fine particle slag was used, and a grout mainly composed of Portland cement was used as a comparison. As the solution type grout, silica colloid was used, and for comparison, acidic silica colloid, water glass added with sodium bicarbonate was used.

Suspended grout (1) Portland cement (2) Fine particle suspension 1) Grout based on fine particle cement 2) Grout based on fine particle slag 3) Grout based on fine particle cement and fine particle slag

Solution type grout (1) Colloidal silica (2) Acidic silica sol (3) Water glass + baking soda

1. Materials used (1) Fine particle slag / fine particle cement Blane specific surface area of 6000 cm ² / g and average particle size of 10 μm or less are used.

(2) Cement A Portland cement (specific gravity: 3.17) having a specific surface area of 3300 cm ² / g of brane is used.

(3) Water glass Low molar ratio water glass having a molar ratio of 2.0 and silica concentration of 25% by weight JIS No. 3 water glass and JIS No. 5 water glass are used.

(4) Colloidal silica The colloidal silica according to the present invention is obtained by passing water glass through an ion exchange resin, condensing and stabilizing the resulting active silica aqueous solution to a molecular weight of several tens of thousands or more by heating or the like, and 20 to 30% SiO _2. Concentrate to a concentration and use an average particle size of 10 to 20 nm. Gelation occurs when a monovalent alkali metal salt is added to the colloidal silica.

(5) Active colloidal silica Colloidal silica and water glass are passed through an ion-exchange resin, and a small amount of water glass or alkali is added to the obtained active silicic acid to polymerize it. The silica concentration is 25%, among which the silica content due to the active silica is 5%, and the others are due to the silica content of the colloidal silica. Gelation is performed by adding an acid or salt to this silica colloid aqueous solution.

(6) Curing agent 75% phosphoric acid is used.

2. Formulation (1) Suspension type injection material

(2) Solution type injection material

3. Compatibility test (1) A suspension-type injection material is prepared for each formulation.
(2) Place 200 ml of the suspension-type injection material in a 500 ml sealed container and cure.
(3) Suspension-type injection material measures the eluted water after curing for one week and removes it once.
(4) A solution-type injection material is prepared for each formulation, and 200 ml each is poured on top of each cured suspension-type injection material.
(5) When the solution type injection material has hardened, add water from which the suspension type injection material has been removed.
(6) Observe the amount of elution water, pH, grout condition, etc.
Table 9 shows the observation results.

  As a result of observing the compatibility between the silica colloid and the suspension type from Table 9, Portland cement, grout based on fine particle slag, grout based on fine particle cement, grout based on fine particle cement and fine particle slag as main components All were compatible, and both the solution-type and suspension-type grout were able to maintain the same state of curing as homogel alone even after one year.

  The acidic silica sol was able to maintain consolidation with Portland cement, but volume shrinkage was observed. Both the acidic silica sol and the alkaline water glass grout are incompatible with the fine particle suspension grout, and dissolution started near the boundary and almost dissolved after one month to one year.

Experiment 3
The injection material according to the present invention was found to show an increase in consolidation strength by the following test under high osmotic water pressure. Using the laboratory injection apparatus shown in FIG. 3, the primary injection material described above was injected into No. 6 silica sand in Table 10, and then the secondary injection material was injected. Specimens in which both of the injection materials were permeated were prepared, and changes in strength were observed between those which were cured in a room and those which were cured under osmotic pressure.

  FIG. 3 is a schematic diagram of an injection device in a laboratory. In FIG. 3, 1 is a compressor, and 2 and 3 are pressure gauges. A water tank 5 equipped with a stirrer 4 connected to the compressor 1 is filled with a grout mainly composed of silica colloid, acidic silica sol, water glass and baking soda as secondary injection. 7 is an acrylic mold, filled with No. 6 silica sand, and injected with a primary injection material. The secondary injection material 6 filled in the water tank 5 is injected into No. 6 silica sand 8 after the primary injection material in the acrylic mold 7 is injected by the operation of the compressor 1. The temperature was about 20 ° C.

  The injection material 6 is permeated into the sand 8, and the permeation material 6 that has permeated is collected by the female cylinder 11 and the permeation state is observed. Reference numerals 9 and 10 are wire meshes. Then, indoor curing at 20 ° C. was performed for 2 days. After curing, the specimen was removed from the acrylic mold and placed in the center of the mold that can be cured under high osmotic water pressure, and bentonite was packed around it so that there were no gaps or cavities. As a result, it was possible to completely block the permeated water from other than the specimen. After assembling the mold, it was placed in the same curing water tank as in FIG. The water tank was adapted to be subjected to high osmotic water pressure, and the high osmotic water pressure was applied from below the injection specimen. The water pressure was adjusted so that the dynamic water gradient was 10.

  The specimen was subjected to a hydrodynamic gradient 10 in water and the strength change was measured for a long-term curing. The results are shown in FIG. It was found that the specimens into which Examples 1, 2, 3, 4, 5, and 6 were injected were not affected by osmotic water pressure for a long period of time and increased in strength. In the specimens injected with comparisons 1 and 2, dissolution started and the strength was weakened.

  Moreover, the change of the osmotic coefficient under high osmotic water pressure is shown in FIG. The specimens of Examples 1, 2, 3, 4, 5, and 6 of the present invention can maintain long-term water stoppage because the permeability coefficient does not change even after 100 days. On the other hand, in comparisons 1 and 2, it was found that when the osmotic pressure was applied, the permeation coefficient increased, and the test specimen collapsed after 10 days or more, and the water stoppage could not be maintained.

It should be noted that the penetration coefficient of the test piece of No. 6 silica sand alone was 5 × 10 ⁻² cm / sec. Further, when the primary injection material was only fine particle cement, the hydraulic conductivity of the consolidated sand was 7 × 10 ⁻³ cm / sec. Moreover, the water permeability coefficient of the consolidated sand using only the fine particle suspension type injection material containing the silica solution was 8.5 × 10 ⁻⁴ cm / sec.

  As described above, the ground injection method according to the present invention can achieve the following effects by injecting a silica grout containing silica colloid as an active ingredient.

1. Silica grout containing silica colloid as an active ingredient has long-term durability and water-stopping effect similar to those of hydrostatic pressure by obtaining long-term strength increase even under high water pressure.

2. Silica colloid or a mixture of silica colloid and active silica, or an active silica colloid mixture obtained by adding water glass and acid or salt to silica colloid has a long-term hydrostatic pressure effect because it contains a silica colloid having a large particle size of 6 to 50 nm. Since it contains silica having a small particle diameter of 1 nm or less to 5 nm, it is excellent in strength development and consolidation.

3. With only a suspension type ground injection material containing fine particle cement and / or fine particle slag as an active ingredient, the hydraulic conductivity does not become smaller than k = 10 ⁻⁴ cm / sec under high water pressure.

4). When silica grout containing silica colloid as an active ingredient is injected into sand into which fine particle suspension has been injected, it will consolidate into a thin part and solidify the entire ground uniformly and with high strength. Becomes possible.

5. The solidified body containing fine particle cement and / or fine particle slag as an active ingredient has a good compatibility with the silica colloid, and can remain solidified as it is when cured alone.

6). Silica grout containing silica colloid as an active ingredient has long-term durability and water-stopping effect by obtaining long-term strength increase even under osmotic pressure.

7). A long-term strength increase can be obtained even under high osmotic water pressure by injecting a suspension type ground injection material containing fine particle cement and / or fine particle slag as an active ingredient and silica grout containing silica colloid as an active ingredient. Can have long-term durability and water stop effect.

  As described above, the ground injection method using the silica grout of the present invention is highly applicable in the field of ground injection.

1 is a schematic view of a curing water tank to which osmotic water pressure is applied. It is a graph showing the intensity | strength change of a test body. 1 is a schematic diagram of an injection device in a laboratory. It is a graph showing the intensity | strength change of a test body. It is a graph showing the change of the penetration coefficient.

Explanation of symbols

1a Curing tank 2a Osmotic water pressure 3a Injection specimen 4a Heater 5a Water surface

Claims (3)

  A ground injecting method for injecting silica grout containing silica colloid as an active ingredient into the ground, wherein the silica grout contains silica colloid having a particle diameter of 6 to 50 nm as an active ingredient, whereby the silica grout A ground-injection method characterized by maintaining water-stopping and strength over a long period of time even if the consolidated ground is under osmotic pressure.   The ground injection construction method according to claim 1, wherein the silica grout is a silica grout containing silica smaller than the silica colloid. In injecting the silica grout in the ground injection method according to claim 1 or 2, a suspension type ground injection material containing fine particle cement and / or fine particle slag as an active ingredient is injected into the ground in advance. A ground-injection method characterized by maintaining water-stopping and strength even when the ground is under osmotic pressure.

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