JP2023006556A - Silica grout and ground injection method using the same - Google Patents

Abstract

To provide a silica grout excellent in stability from manufacture of silica colloid to site work by reducing variation of quality as an injection material, with stable gelation for on-site injection and stable permeation solidification, and less environmental burden, and to provide a ground injection method using the silica grout.SOLUTION: A silica grout contains silica colloid obtained by collecting silica in geothermal water as an active ingredient, wherein a content of heavy metals contained in the silica colloid is below the environmental standard value that meet the purpose of ground injection.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a silica grout containing geothermal water-derived silica colloid as an active ingredient and a ground grouting method using the silica grout.

A grouting material using colloidal silica proposed by the present applicant is already known as a ground grouting material that consolidates the ground and has excellent durability (Patent Document 1). Colloidal silica itself is very stable and non-caking, so you can add salt and/or acid to destabilize and gel, or add water glass to speed up strength development. It is used in silica grout, adjusted to an acidic to slightly alkaline pH with long penetration.

These colloidal silicas are produced by granulating a weakly acidic silica sol obtained by removing alkali from water glass by an ion exchange method in a weakly alkaline pH range, or by dissolving metallic silica. These silica colloids require a lot of energy and cost to manufacture, so in response to the social demand for CO ₂ reduction to prevent global warming in recent years, low-energy ground improvement materials and ground injection methods are desired. there is

On the other hand, in recent years, geothermal power generation using geothermal energy in volcanic areas has attracted attention, and along with this, a method for collecting colloidal silica derived from geothermal water has been proposed (Patent Document 2). In geothermal power generation, geothermal fluids, such as steam and hot water, are taken out from underground and used for power generation. Underground is high temperature and high pressure, and silica, which is a component of rocks in the ground, is also dissolved.This silica colloid derived from geothermal water is a conventional colloid obtained by the ion exchange method that uses water glass and requires high energy. Compared to , silica colloid can reduce CO ₂ gas, which is a cause of global warming, and can be said to be excellent in terms of environmental conservation and production cost reduction.

Further, Patent Documents 3 and 4 disclose a consolidating material for ground injection using silica derived from geothermal water.

Japanese Patent Publication No. 6-62953 Japanese Patent Publication No. 2018-524256 JP 2019-11473 A Japanese Patent No. 6796305

As described above, silica grout using silica colloid obtained by the ion exchange method is used as a consolidating material for ground injection in the invention (Patent Document 1) and the like by the present inventors. In addition, a ground injection technique using colloidal silica derived from geothermal water is already known (Patent Documents 3 and 4). However, according to research by the present inventors, geothermal water-derived silica colloids have a large variation in composition depending on the conditions of the location in the geothermal water and the conditions of colloid formation. Compared to colloidal silica produced by the ion exchange method, which contains almost no impurities other than ₂ , the particle size distribution is wide (6 to 90 nm) or varies, and the stability from production to on-site use is insufficient. In addition, the gel time during construction is unstable, the viscosity is high, the infiltration and solidification properties for obtaining the predetermined design strength and permeability required for the injection purpose are unstable, and it is not suitable for fine-grained soil. was found to be unfavorable because the permeation of This is because, when used as a countermeasure against liquefaction, laboratory tests and infiltration caking tests are carried out using on-site soil, and the composition that achieves the specified strength is set and applied to the actual construction, so the quality of silica colloid is constant. Otherwise, when applied in the field, the prescribed permeation and caking properties obtained in the laboratory test cannot be ensured in the field, and injection design becomes difficult.

According to a ground injection material using colloidal silica derived from geothermal water (Patent Document 3), colloidal silica collected from geothermal water has a wide particle size width of 6 to 90 nm and a kurtosis of 0 to 6.0 nm. 0 (that is, the particle size distribution width is wide and the peak of the particle size distribution is low), and according to Patent Document 2, geothermal water contains Ca, K, Al, Na, S in addition to SiO ₂ , Cl, As, etc. are dissolved. The reason why geothermal water-derived silica colloid has such a wide particle size distribution and contains various concentrations of dissolved substances is that geothermal water contains many dissolved substances such as ions derived from rocks in the earth's crust. Therefore, when the geothermal water is cooled from the initial temperature of 85 to 200 ° C to 25 to 70 ° C, the solubility of these dissolved substances decreases, the dissolved substances precipitate and silica colloid growth starts, and this precipitates This is because the silica colloid can be obtained by forming a colloidal silica concentrate by using a material or by using ultrafiltration or diafiltration. Another reason is that the types and concentrations of dissolved substances in geothermal water differ depending on the location and density of geothermal water eruptions, the type of bedrock, and geothermal heat.

Also, in Patent Document 2, arsenic, antimony, mercury, boron, etc. contained in geothermal water are not bound within silica colloids, and therefore ultrafiltration and diafiltration are combined from the concentrate that produced silica colloids. It is described that heavy metals can be removed below the detection limit by chemical analysis by ICP and XRF when obtained by However, the environmental standard values include soil elution standards, groundwater standards, second elution standards, and uniform wastewater standards, each of which is a different value (Patent Document 4). Therefore, if the detection limit value below the environmental standard value corresponding to the purpose of ground injection is set as a uniform wastewater standard, if it is below the standard value, it can be used for ground injection as it is, and if it exceeds that, it will be further refined or an insolubilizing agent will be used. should be below the reference value.

The particle size, particle size distribution width, and concentration of colloids generated from geothermal water vary depending on the cooling temperature, heat treatment, and subsequent pH. Silica colloids having various particle size distributions can be produced under these conditions (Patent Document 2). However, although the physical properties of silica colloids from geothermal water have been described in the past, there has been no knowledge about the problems when applying them to ground injection and how to solve them. The inventors of the present invention conducted research on the practical application of ground injection of silica colloid derived from geothermal water, and as a result, found the following.

The following are the problems when using silica material contained in geothermal water for ground injection.
That is, the silica material contained in the geothermal water contains Ca, K, Al, Fe, As, etc. in addition to _SiO2 . Also, NaCl, CaCl ₂ , FeCl ₃ , MgCl, polyaluminum chloride, etc. are used as precipitating agents for producing colloidal silica concentrates from geothermal water. These dissolved substances are components that affect not only the stability of silica colloid but also the gelation of silica grout (see Patent Document 1). Geothermal water eruptions vary depending on location, depth, and rock composition. Accordingly, the types and concentrations of dissolved substances other than SiO ₂ also differ depending on the location and concentration of the geothermal water collected and the geothermal heat. In addition, since these dissolved substances are ions that affect the gelation and stability of the silica solution, when applying to ground injection, the storage period (pot life) after silica colloid production until use Stability as a material, mixing of injection materials, gelation at the time of strength design, or variation in gelation in the soil due to reaction with the composition in the ground when injected into various grounds. Also, temperature-dependent gelation during field storage may result in instability as an injection material.

In order to solve the above problems, the present inventors, when applying the silica material contained in the geothermal water to ground injection, prevent the above-mentioned difference in dissolved substances from affecting the ground injection, as described later. The quality is stabilized during storage or construction by keeping the quality constant as described above, and the gel time and pH of the injection material itself, that is, gel time in air (GT0), pH in air (pH 0), and it is applied to the ground. Confirm the soil pH (pHs) and soil gel time (GTs) when injected, confirm the relationship with the injection time (H) obtained from the injection method and injection design, and dissolve in the injection solution By suppressing the influence of variations in materials and making it possible to design a mixture that satisfies the purpose of injection, silica grout using silica material derived from geothermal water has been made practical.

In addition, in order to achieve the purpose of injection, it is necessary to prevent the injection material from deviating from the ground to be injected, and to homogenize the ground by first injecting a suspension or a quick-setting grout into the rough layer, and then the silica of the present invention. By injecting grout, the target ground can be firmly consolidated.

According to the research of the present inventors, silica grout containing geothermal water-derived silica colloid as an active ingredient has a larger particle size distribution width of silica colloid due to the influence of the above-mentioned dissolved matter, and silica with a larger particle size It was found that the more colloid contained, the greater the above-mentioned problems due to the variation in quality. On the other hand, if the particle size is too small, the silica colloid becomes unstable due to the presence of metal ion inclusions. Furthermore, from the viewpoint of silica colloid intended for ground injection, the temperature at the construction site is low in winter, and the temperature in the storage tank and mixing tank is high due to direct sunlight in summer. Therefore, in summer, the silica colloid solution reacts at high temperatures, and in winter, a condensation phenomenon occurs. Therefore, as a ground injection method, it is desirable to stabilize the quality of silica colloid itself. In addition, it was found that if the amount of dissolved matter is large, the viscosity becomes high, the gelation time and the permeation caking property become unstable, and the injection pressure increases in order to lengthen the permeation distance. Furthermore, it has been found that if the colloidal silica containing dissolved matter contains silica having a large particle size, the filling ratio of the voids between the soil particles decreases, and the consolidation strength tends to vary, causing a problem. Furthermore, when injecting into heterogeneous ground, if the viscosity is high and the gel time is short, it will deviate from the injection target from the rough part and it will be difficult to penetrate the fine part, so it was found that it is difficult to apply to the ground injection purpose. .

In the prior art, neither the presence of dissolved substances other than SiO ₂ nor the problems thereof were known when applying colloids derived from geothermal water to ground injection. In addition, in Patent Document 3, silica colloid derived from geothermal water has a larger particle size distribution width (6 to 90 nm) than silica colloid obtained by an ion exchange method (particle size distribution width is 10 to 20 nm), and kurtosis is small (0 to 6.0) and has a solidification effect equivalent to or slightly lower than that of ion-exchange colloids. There is no description of the problem of instability of hardening and infiltration and solidification, the ground injection method to solve the problem, and the problem of heavy metals.

In addition, Patent Document 2 merely describes a geothermal water-derived silica colloid and a method for producing the same, and its use as an injection material and the problems in using it as an injection material are also discussed. There is no description of a ground grouting method that can solve the problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and to make it possible to apply geothermal water-derived silica colloid to the ground grouting method. In addition, Cited Document 4 is an invention by the present applicant, in which the content of heavy metals in the geothermal water itself containing silica is reduced to below the environmental standard value or uniformly below the wastewater standard value using an insolubilizing material. In contrast to the geothermal water to which the insolubilizing agent is added is directly injected as the injection material, the present invention uses silica collected from the geothermal water with a predetermined silica concentration and a particle size distribution width. is narrowly adjusted to reduce the influence of variations in dissolved matter, and the quality is stabilized. The silica grout of the present invention can be injected as it is if the silica colloid derived from geothermal water meets the environmental standard value or less corresponding to the injection purpose, or it can be adjusted to below the standard value by adding an insolubilizing agent to the silica colloid. It is an injection method, and only a small amount of insolubilizing material is required, and the geothermal water itself is not injected into the ground. Therefore, Patent Documents 2 and 4 are also injection materials different from the present invention.

Therefore, the object of the present invention is to reduce the variation in quality as an injection material, thereby achieving excellent stability from silica colloid production to on-site construction, and stable gelation of silica grout during on-site injection. To provide a silica grout which has a stable permeation and consolidation property and less environmental load, and a ground grouting method using the silica grout.

The geothermal water-derived silica colloid is described in Patent Document 3 as having a particle size distribution width of 6 to 90 nm, and in Patent Document 2, it is described that depending on the production method, colloids with various particle size ranges can be obtained. It is Thus, geothermal water-derived silica colloid has a wide _SiO2 concentration and a wide particle size distribution width, and the particle size distribution width varies depending on the manufacturing method, and it contains dissolved substances other than _SiO2 , and these dissolved substances are , Stability as an injection material until construction due to variations in quality when used for injection into the ground, gelation and solidification in the ground when injected, and formulation design to obtain a predetermined effect in on-site construction. Affect.

In order to solve the problems of silica grout using conventional silica colloids derived from geothermal water, as described above, the present inventors found that geothermal water-derived silica colloids originally have a large particle size distribution width. , Alternatively, there is a large variation in the particle size distribution width, and there is a large variation in the concentration and type of composition, and it contains dissolved substances other _than SiO that affect colloidal stability and gelation. As shown in 1, by reducing the particle size and narrowing the particle size distribution width between the maximum particle size and the minimum particle size (that is, reducing the standard deviation in the particle size distribution or increasing the kurtosis), the quality is kept constant. By using silica grout containing silica colloid as an active ingredient, it stabilizes the quality at the site during storage and construction described above, and solves the problems of colloidal gelation and penetration caking stability and formulation design. It was found that it was possible to solve the problem and obtain infiltration and caking properties into fine-grained soil and a long infiltration distance. In addition, by stabilizing the quality in this way, it is thought that the dissolved metal ions contribute to the strength increase, and compared to the silica colloid produced by the ion exchange method, the cemented sand strength is greatly increased, which is extremely excellent. It was found that the effect was obtained. As a result, it is possible to apply silica colloid derived from geothermal water to ground injection, and to suppress the influence on ground injection due to variations in quality during injection work, to obtain stable gelation and consolidation, and high strength. It is possible to achieve the design strength required for the injection purpose, ensure the infiltration consolidation property to obtain the predetermined permeability, and adapt to a wide range of ground improvement such as liquefaction countermeasure work. . In particular, as shown in FIG. 2, the silica colloid collected from geothermal water in Patent Document 3 has a large particle size distribution width of 6 to 90 nm and a low kurtosis of 3.29 (0 to 6). On the other hand, the silica colloid produced by the ion exchange method has a narrower particle size distribution width and a large kurtosis of 14.51. Here, the kurtosis is an index representing the form of distribution with respect to the normal distribution. In both strength tests, the strength of the cemented sand by silica grout using the silica colloid derived from the geothermal water is slightly lower than that by the ion exchange method. On the other hand, the present inventors narrowed the width of the particle size distribution in the direction of smaller particle size, and used geothermal water-derived silica colloid that does not contain large-sized silica particles and has a constant quality. It was found that the strength of silica grout was greatly increased by comparing with the strength using silica colloid by ion exchange method.

In addition, the particle size distribution width (powder, that is, the size of the particles as an aggregate is the distribution of the abundance ratio for each size (particle size) based on the measurement results of a large number of particles in the direction of decreasing the particle size according to FIG. This is referred to as a particle size distribution.) With respect to the silica colloid according to the present invention, the standard deviation was determined from FIGS. The standard deviation is one of the indices representing the degree of dispersion from the average value, and here, when this value is large, the distribution width of the particle size is large. The standard deviation in Table 2 is 11.7 for the silica colloid of Patent Document 3 and 4.24 for colloid 1. Among the silica colloids used in the present invention, colloid 2 was 1.44 and colloid 3 was 1.93. According to the present inventors, by narrowing the width of the particle size distribution in the direction of smaller particle size, the silica colloid derived from geothermal water used in the present invention does not contain large size silica particles and has a constant quality. In , the standard deviation was as small as 10 or less, and it was found that an excellent effect as a ground injection material was obtained.

The inventors of the present invention have found that silica colloids derived from geothermal water differ in silica concentration, particle size distribution, and dissolved matter types and concentrations depending on the location where the geothermal water springs out, the type of rock, the temperature, and the method of forming the colloid. , we investigated what kind of particle size distribution of silica colloid is suitable for the purpose of ground injection.

The particle size distribution of silica colloid 2 and silica colloid 3 in Tables 4 and 5 used in the present invention was measured by the dynamic light scattering method or the Sears method. In addition, when diluting this silica colloid and using it with salt, acid, or water glass, a 10-fold diluted solution was used, and the particle size distribution at a silica concentration of 3 w/v% was shown in FIGS. . For reference, the particle size distribution of silica colloid 1 in Table 3 is shown in FIG. 2, and the particle size distribution width of 3 w/v %, which is a 10-fold diluted solution thereof, is shown in FIG. Also, the particle size distribution of each colloid is summarized in FIG. Table 2 shows the volume average diameter (nm) obtained by measuring the particle diameter distribution in FIGS.
Furthermore, Table 2 summarizes the physical properties, particle size, kurtosis, standard deviation, and volume average diameter (value of volume average diameter).

Figure 1 summarizes the pattern of the particle size distribution. As shown in FIG. 1, the silica colloid in the present invention is characterized by a small particle diameter and a uniform grain size. In addition, it was found that by using a silica colloid derived from geothermal water with such a pattern, it is possible to obtain a ground grouting material with little variation.

As a result of research, silica colloid derived from geothermal water has a wide range of silica concentration and particle size distribution, or a large variation (standard deviation is larger than 11, kurtosis is 0 to 6). had the problem of lacking quality stability. Therefore, the present inventors reduced the particle size of silica colloid in the silica concentration range of 2 to 50 w / v% and narrowed the particle size distribution width to make the quality constant, thereby reducing the variation as a ground injection material. Silica grout using silica colloid was developed. Preferably, when the concentration of silica colloid is in the range of 2 to 50 w/v%, the particle size distribution width is narrowed so that the volume average diameter of the particle size distribution shifts in the direction of smaller particle size. A silica grout that uses silica colloid with reduced variation in the particle size distribution, and more preferably, by narrowing the particle size distribution width to make the quality constant in the range of 2 to 20 nm, the above effect is obtained. It was found that The silica colloid used in the present invention is silica colloid 2 in FIG. 2 and Table 4 and silica colloid 3 in FIGS. FIG. 7 shows silica colloid obtained by diluting the silica colloid of FIG. 4 by 10 times. This is because, in actual silica grout, the silica colloid in Table 4 and FIG. 3 is diluted by using it together with water glass and a reactant, and the silica concentration of the silica colloid may be reduced to 3%. From silica colloids 2, 3, and 4 in FIG. 2, FIGS. 20 nm, kurtosis greater than 6. That is, the silica grout using a silica colloid with a large particle size distribution width and a small kurtosis in Patent Document 3 has a higher cohesion strength than the cohesion strength obtained by the ion exchange method (colloid 1 in FIG. 2, FIG. 5, Table 3). While it is lower or almost the same, the silica grout using geothermal water-derived silica colloid by the present inventors has a higher consolidation strength than the silica grout by the ion exchange method (silica colloid 1). It was found (Table 2, Table 6, Table 7). As can be seen from FIG. 2, the geothermal water-derived silica colloids (silica colloids 2, 3, and 4) by the present inventors have a smaller particle size distribution width than the ion-exchange colloid (silica colloid 1), and , the slope of the particle size distribution curve is steep. That is, as shown in FIG. 1, the particle size is small in the particle size distribution, and naturally the particle size distribution width is smaller than that of the colloid of Patent Document 3, and the kurtosis is greater than 6, preferably 7-50. As described above, the present invention stabilizes gelation and permeation caking when used for ground injection, and improves durability by narrowing the particle size distribution width of the silica colloid and making the particle size small and uniform in quality. We have realized a silica grout and an injection method that are excellent, have high strength and excellent permeability, provide a stable predetermined design strength, and are environmentally friendly. A specific description will be given below.

That is, the silica grout of the present invention is a silica grout containing as an active ingredient a silica colloid obtained by collecting silica in geothermal water, and as the silica colloid, the number of particles for each particle diameter generated in the generation of the colloid A raw silica colloid with a wide range of particle size distribution with large variations, or a raw silica colloid with a large variation in the number of particles for each particle size, is reduced in particle size and particles in a silica concentration range of 2 to 50 w / v%. It is characterized by the use of materials with uniform diameters, a narrowed particle size distribution, and reduced variation as a ground injection material.

Another silica grout of the present invention is a silica grout containing silica colloid obtained by collecting silica in geothermal water as an active ingredient, and the silica colloid has a silica concentration of 2 to 50 w / v%. In the range, by narrowing the standard deviation of the particle size distribution width of the raw silica colloid, which has a wide particle size distribution width with a large variation in the number of particles for each particle size that occurs in colloid generation, to 10 or less, it can be used as a ground injection material. It is characterized by using a material with reduced variation.

In the silica grout of the present invention, it is preferable to use, as the silica colloid, one whose particle size distribution width is narrowed to a range of 2 to 20 nm to reduce variations as a ground injection material.

Furthermore, still another silica grout of the present invention is a silica grout containing as an active ingredient a silica colloid obtained by collecting silica in geothermal water, wherein the silica colloid has a silica concentration of 2 to 50 w / v% In the range, the raw material silica colloid having a wide particle size distribution width with a large variation in the number of particles for each particle size that occurs in the generation of colloids, the particle size distribution width is in the range of 2 to 20 nm, and the standard deviation of the particle size distribution width is 10 In the following, the kurtosis is set to 7 to 50 to reduce variations as a ground injection material.

In the silica grout of the present invention, preferably, the silica colloid has a silica concentration in the range of 2 to 50 w/v% and a particle size distribution width in the range of 2 to 20 nm, preferably 2.0 to 14.5 nm. and preferably the volume average diameter of the silica colloid is in the range of 2 to 15 nm. Moreover, the pH of the silica colloid is preferably 8.5 to 10.5. Further, the particle size distribution has a kurtosis of 7 or more, preferably 7-50. Furthermore, the standard deviation of the particle size distribution width is 10 or less.

Furthermore, still another silica grout of the present invention is a silica grout containing as an active ingredient a silica colloid obtained by collecting silica in geothermal water, and containing harmful heavy metals contained in the silica colloid The amount is characterized by being below the environmental standard value corresponding to the purpose of ground injection.

In the silica grout of the present invention, the content of heavy metals contained in the silica colloid and / or silica grout is an analysis value of heavy metals eluted by immersing the gelled material in distilled water, corresponding to the purpose of ground injection. It is preferably below the environmental standard value.

The silica grout of the present invention preferably contains acid and/or salt and blended water as active ingredients together with the silica colloid, and has a pH in the range of 1.0 to 10.5. In addition, the silica grout of the present invention contains water glass, an acidic reactant and / or salt and mixed water as active ingredients together with the silica colloid, and has a silica concentration of 0.4 to 50.0 w / v%, It is also preferred that the pH is in the range of 1.0 to 10.0. In the above, the mixed water is usually tap water, river water, seawater, or the like used for ground injection.

The ground grouting method of the present invention is characterized by injecting the silica grout of the present invention into the ground to improve the ground.

In the ground injection method of the present invention, the pH (pH 0) of the silica grout is set to a range of 1 to 4, which is more acidic than the pH value (pHs0) of the ground, and the silica grout is injected into the ground. Therefore, it is preferable to shift the soil pH (pHs) of the silica grout toward neutrality, shorten the soil gel time (GTs), and consolidate the ground.

Further, in the ground grouting method of the present invention, it is also preferable to inject the primary grouting material to perform rough packing of the ground, and then inject the silica grout as the secondary grouting material into the ground.

According to the present invention, using silica colloid derived from geothermal water, which has a large variation, it has excellent stability from the production of silica colloid to on-site construction, and the gelation of silica grout during on-site injection is stable. Therefore, it has become possible to provide silica grout with stable permeation and consolidation and low environmental impact, and a ground grouting method using the silica grout.

FIG. 2 is an explanatory diagram showing a particle size distribution pattern and a silica colloid used in the present invention; 4 is a graph showing the cumulative frequency distribution of each colloid; 2 is a graph showing particle size distribution measurement results of silica colloid 2 (by Chori Co., Ltd.). 4 is a graph showing the results of particle size distribution measurement of Silica Colloid 3 (by Chori Co., Ltd.). 4 is a graph showing the particle size distribution measurement results of silica colloid 1 (diluted by 10%). 4 is a graph showing the particle size distribution measurement results of silica colloid 2 (diluted by 10%). 4 is a graph showing the particle size distribution measurement results of silica colloid 3 (diluted by 10%). FIG. 2 is an explanatory diagram showing a test piece manufacturing apparatus; FIG. 11 is a photograph showing the state of preparation of a solidified test piece by the permeation method. It is a photograph figure which shows the test apparatus of a permeation test (one-dimensional injection|pouring test, mold length 1m). It is a graph which shows the uniaxial compressive strength by a penetration method. Fig. 3 is a graph showing penetration distance and unconfined compressive strength; 4 is a graph showing the relationship between the strength of sand gels (6% and 10%) using each silica colloid and the number of days elapsed.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The silica grout of the present invention contains silica colloid obtained by collecting silica in geothermal water as an active ingredient. In the present invention, as the silica colloid, a raw silica colloid having a wide particle size distribution width due to a large variation in the number of particles for each particle size generated in colloid production, or a raw silica colloid having a large variation in the number of particles for each particle size. Colloids with a silica concentration range of 2 to 50 w / v%, the particle size is reduced and the particle size is made uniform to narrow the particle size distribution width, and the variation as a ground injection material is reduced, or the silica concentration is In the range of 2 to 50 w/v%, the standard deviation of the particle size distribution width of the raw silica colloid, which has a wide particle size distribution width with a large variation in the number of particles for each particle size that occurs during colloid production, is narrowed to 10 or less. A material with reduced variation as a ground injection material, or a raw material with a wide particle size distribution width with a large variation in the number of particles for each particle size that occurs in the generation of colloids in the silica concentration range of 2 to 50 w / v% Silica colloid has a particle size distribution width of 2 to 20 nm, a standard deviation of the particle size distribution width of 10 or less, and a kurtosis of 7 to 50, so that the variation as a ground injection material is reduced. . Alternatively, colloidal silica containing heavy metals in which the content is equal to or less than the environmental standard value corresponding to the purpose of ground injection is used.

As a result, the quality of the ground injection material is made uniform, the problem caused by the variation in the dissolved substances contained in the geothermal water is resolved, the stability is secured from manufacturing to construction on site, and the It is possible to provide a silica grout and a ground grouting method using the silica grout that stabilizes the gelation and penetration and consolidation properties of the silica grout and enables predetermined ground improvement while causing no ground pollution and less environmental load.

Examples of effluent standards and environmental standards are shown in Table 1 below. Standards for Class II Specified Hazardous Substances include soil elution standards, groundwater standards, second elution standards, guidelines for upper limits for natural factors, and uniform wastewater standards. Environmental standards for groundwater pollution and soil environmental standards are listed.

Heavy metals in geothermal water-derived silica colloids are not bound within the silica colloids, as described in US Pat. A combination of rations can be removed below the detection limits of chemical analysis by ICP and XRF. In addition, depending on the purpose, the standard value can be satisfied by adding an insolubilizing agent.

Examples of insolubilization of contaminant heavy metals are described below.
An example of insolubilization using "Green Lime MP-S", a magnesium-based insolubilizer manufactured by Ube Materials Co., Ltd., is shown as an example of insolubilization for composite contaminated soil. In a test using a formulation amount of 30 kg/m ³ , the arsenic and selenium contents were about 0.03 mg/L, but after 6 hours of curing, the soil elution amount was reduced to 0.01 mg/L or less. ing. This is a case in which a magnesium-based chemical made arsenic insoluble. Therefore, it can be seen that it is possible to insolubilize heavy metals such as arsenic and selenium contained in geothermal water to levels below environmental standard values.

For the purpose of ground injection, a uniform effluent standard is usually used. Therefore, silica grout should satisfy the reference value or less corresponding to the purpose of ground injection by chemical analysis such as ICP and XRF (Patent Document 4). In addition, whether or not the content of heavy metals contained in silica colloid and/or silica grout is below a value corresponding to the purpose of ground injection is determined by immersing the gelled product in distilled water and extracting heavy metals. Judgment should be made based on the analytical value.

(Physical properties of silica colloid)
FIG. 2 shows the particle size accumulation curve of each silica colloid. Table 2 shows physical properties of each silica colloid. 3 and 4 show the particle size distribution measurement results (particle size distribution width of 9.0 to 14.5 nm) when the silica concentration in Tables 4 and 5 is approximately 30 wt %, respectively. 6 and 7 are 10% dilutions of the silica colloids in Tables 4 and 5, respectively, and show the results of particle size distribution measurement with a silica concentration of 3 wt%. In carrying out the present invention, the concentration of silica colloid used is in the range of 2 wt % to 50 wt %, so FIGS. be able to. The particle size distribution in that case is approximately in the range from 2 to 7 nm. As described above, the silica colloid in the present invention can be used with a silica concentration of 2 to 50 wt % and a narrow particle size distribution width. Since the maximum concentration of silica colloid is 50 wt %, the silica concentration of the silica colloid according to the present invention was set to 2 to 50 wt %. In Table 2, the particle size and kurtosis of the geothermal water-derived colloid of Patent Document 3 are described in Patent Document 3. 3 to 7 show the particle size distribution measurement results of silica colloid. 3 is silica colloid 2, FIG. 4 is silica colloid 3, FIG. 5 is a 10% dilution of silica colloid 1, FIG. 6 is a 10% dilution of silica colloid 2, and FIG. , particle size distribution measurement results. Silica colloid 1 is a conventional silica colloid produced by the ion exchange method shown in Table 3, and its kurtosis is that of conventional colloidal silica shown in Patent Document 3. Also, the kurtosis of colloids 2, 3, and 4 are estimates by the inventors. The physical properties of colloids 2 and 3 in Table 2 are from Chori Co., Ltd. (Tables 4 and 5). Colloid 4 is a colloid obtained by mixing colloid 2 and colloid 3 at a ratio of 1:1. The physical properties of the silica colloid obtained by the ion exchange method are according to Kanto Silicate Glass Co., Ltd. (Table 3).

Silica colloid of Document 3: Silica colloid derived from geothermal water of Patent Document 3, having a wide particle size distribution width (6 to 90 nm) and a kurtosis of 3.29 in the range of 0 to 6.0 silica colloid. Silica colloid has a wide particle size distribution width and a low peak in the particle size distribution map.

Silica colloid 1: A silica colloid produced from water glass by an ion exchange method, having a particle size distribution width of 10 to 20 nm and a kurtosis of 14.51, which is 10 or more (see Patent Document 3). In any case, the silica colloid in the ion exchange method has a smaller particle size distribution width than the geothermal water-derived silica colloid, a high peak in the particle size distribution, and a kurtosis of 7 or more (Patent Document 3, 14, 51).

Silica colloid of the present invention: The particle size distribution width is narrower than the particle size distribution width of the ion-exchange colloid (silica colloid 1) from FIG. 1 higher than silica colloid. Note that the kurtosis of silica colloids 2, 3, and 4 in Table 2 are values estimated by the present inventors. The silica colloid of the present invention is a geothermal water-derived silica colloid used for silica grout for ground injection purposes. When the average value of the particle size is taken as the median value, the median value is narrowed so that the median value is small, and by making the particle size small, the quality of the colloid is kept constant, and the stability of the colloid of the metal ions contained. Suppresses the effect on gelation to improve applicability to construction sites, stabilizes gelation in compounding, improves permeability, increases the strength of solidified sand and stabilizes solidification, and is designed on site. It is designed to provide strength. The geothermal water-derived silica colloid used for the silica grout of the present invention has a standard deviation of 10 or less, is narrower than the particle size distribution width of the silica colloid of Patent Document 3, and has a large kurtosis. The kurtosis is 7-100, preferably 7-50.

Silica colloids 2 and 3 (Tables 4 and 5) are geothermal water-derived silica colloids used in the present invention, silica colloid 2 has a particle size distribution width of 9 to 11 nm, and silica colloid 3 has a particle size distribution width. is adjusted to 12.5 to 14.5 nm by narrowing the particle size distribution width, and silica colloid 4 is a mixture of silica colloids 2 and 3 at a ratio of 1:1. Silica colloids 2, 3, and 4 are silica colloids used in the silica grout of the present invention, and the silica concentration of the silica colloids is in the range of 2 to 50 wt% (Figs. 3, 4, 6, 7), more preferably At a silica concentration of 30 wt %, the particle size distribution width is adjusted to be narrow within the range of 9 to 14.5 nm. Furthermore, the standard deviation is 10 or less, resulting in a silica colloid with a kurtosis of 7 or more.

As described above, the geothermal water-derived silica colloid according to the present invention has a wide silica particle size distribution of the geothermal water-derived silica colloid of Patent Document 3, and the particle size distribution width is narrowed in the direction of narrow particle size. It has a narrow size distribution width and uniform quality within a range of particle sizes suitable for injection. As a result, when applied to ground injection, it does not contain silica particles with a large particle size and does not contain silica particles with a too small particle size, and as a ground injection material, the permeability and gelation are stable and the quality is constant. This improves the instability of gelation due to variations in SiO ₂ and dissolved ions. As a result, gelation is stabilized, permeability is improved, and the specific surface area of the colloid is increased by reducing the particle size of the colloid, which increases the reactivity between silica particles or between the colloid and soil particles. , it was found that the strength of the consolidated sand increases. The reason for this is that the smaller the particle size of the colloid, the larger the specific surface area, so the number of silanol groups (Si—OH) on the surface of the colloid increases, resulting in an increase in siloxane bonds (—Si—O—Si—). It is believed that this increases the number of bonds between colloids and increases the strength of the gel. If the particle size is smaller than this, gelation will be accelerated and colloidal aggregation will easily occur, and the stability during storage and the injection solution during injection will become unstable, which is not preferable. On the other hand, if the particle size is larger than this, the specific surface area becomes small, the number of silanol groups on the surface of the colloid becomes small, and therefore the strength of the gel becomes small. In addition, if the silica solution contains reactive components such as Ca and Al, the reaction progresses during storage, and the silica tends to precipitate and become unstable. penetration is likely to be insufficient.

Silica colloids 2 and 3 have a smaller silica particle size distribution width than silica colloid 1, as shown in FIGS. Moreover, the peak of the particle size distribution is higher than that of colloidal silica 1, and the kurtosis is also higher than that of colloidal silica 1. Silica colloid 4 is also the same. Since silica colloid 4 is a 1:1 mixture of silica colloids 2 and 3, silica colloid 4 has the average characteristics of silica colloids 2 and 3.

The silica colloid used for the silica grout of the present invention has a narrowed particle size distribution width of the raw material silica colloid, preferably by narrowing the particle size distribution width to a range of 2 to 20 nm to reduce variations as a ground injection material. More preferably, the particle size distribution width is 9 to 14.5 nm, and both are in a narrower particle size range than silica colloid 1. 36.0 to 42.9 with a kurtosis in the range of 7 to 100, preferably in the range of 7 to 50.

Therefore, the silica grout containing silica colloid according to the present invention is silica grout different from the silica colloid of Patent Document 3. The silica colloid of Patent Document 3 is described as having a slightly lower strength than silica colloid 1. Therefore, silica colloids 2 and 3 were used as the silica colloids used in the present invention and compared with silica colloid 1. As a result, it was found that the silica colloid according to the present invention has a higher cohesive strength than silica colloid 1, demonstrating the effect of the present invention by reducing the particle size and narrowing the particle size distribution width to keep the quality constant. We were able to.

Table 3 shows physical properties of the silica colloid obtained by the ion exchange method.

(Particle size characteristics of each silica colloid)
FIG. 2 shows the cumulative frequency distribution of silica colloids 1, 2 and 3 and the silica colloid of Patent Document 3. In addition, it is generally known that the injectable limit of the grouting material is that the large grain size region of the grain size distribution curve inhibits the permeability to fine-grained soil. From Table 2, it can be seen that silica colloids 2, 3, and 4, which do not contain silica colloids having a particle size larger than approximately 20 nm, have excellent infiltration and caking properties for fine-grained soil. Therefore, in the present invention, focusing on the particle size and particle size distribution width of the silica grout containing the present silica colloid as an active ingredient, the quality is constant, and the ground grouting material is excellent in solidification and permeability. Therefore, an example of the experiment is shown below.

Regarding the performance as a casting material of silica grout using silica colloid derived from geothermal water in the present invention, silica colloid 2 does not contain silica with a large particle size compared to the silica colloid of Patent Document 3, and Small diameter and particle size distribution width. As a result, the uniaxial compressive strength of homogel and solidified sand (sand gel) increases due to the large specific surface area and the large number of silanol groups on the silica surface. Also, with regard to permeability, from FIG. , 3 are the most excellent in permeability, and the results show that the permeability is superior to that of silica colloid 1. The geothermal water-derived silica colloid used in the present invention has a silica concentration of 2 to 50 wt % and a narrow particle size distribution width, so that silica colloid suitable for ground injection can be obtained.

As a result of the research by the present inventors, the range of the particle size distribution width of silica colloid derived from geothermal water varies depending on the silica concentration, and in the silica concentration range of 2 to 50 wt%, the higher the silica concentration, the larger the particle size. It was found that the particle size distribution has a region, and when the silica concentration is lowered, the particle size distribution shifts to the region of smaller particle size (Figs. 3-6). 6 and 7 are particle size distribution curves of a colloidal solution with a silica concentration of 30 wt %, and are the results obtained by measuring this with a 10-fold diluted solution (silica concentration of 3 wt %). Similar results are obtained with silica concentrations of 2-50 wt %. Such a phenomenon has not been known in the prior art, and was discovered by the inventors for the first time. As a result, it is possible to obtain a reliable design and a stable improvement work effect that can obtain the required improvement effect even if the silica concentration corresponding to the ground conditions and injection purpose is used.

According to the research of the present inventors, silica colloid with a particle size distribution of 9.0 to 14.5 nm with a silica concentration of 2 to 50 wt% and a silica concentration of 30 wt% is diluted by 10 times to a silica concentration of 3 wt%. Then, the particle size distribution is around 2 to 7 nm. In other words, it was found that the particle size distribution width of the silica colloid is distributed by moving toward smaller particle sizes as the silica concentration becomes lower.

Further, the silica colloid of the present invention has a silica concentration of 2 to 50 w/v%, a particle size distribution width of 2.0 to 14.5 nm, and a volume average diameter of 2 to 15 nm. A range is preferred.

The silica grout of the present invention contains silica colloid obtained by collecting silica contained in the geothermal water and an acid and / or salt as active ingredients, and has a pH in the range of 1.0 to 10.5. Alternatively, it contains silica colloid obtained by collecting silica contained in the geothermal water, water glass and an acidic reactant and / or salt as active ingredients, and the silica concentration is 0.4 to 50.0 w / v% and a pH in the range of 1.0 to 10.0. In addition, the silica grout of the present invention is a non- It can also be an alkaline silica grout. Other compositions of the silica grout of the present invention are not limited, and water glass, acid components, salts, and the like can be widely used as long as they are usually used in ground grouting materials.

Specifically, as the acid, inorganic acids such as sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, sulfamic acid, and mixed acids thereof can be used. Other mineral acids such as citric acid, glycolic acid, malic acid, tartaric acid, and other organic acids can be widely used, but among them, at least one of sulfuric acid, phosphoric acid and organic acids is preferred. Salts include, for example, inorganic salts of polyvalent metals such as sodium chloride, calcium chloride, magnesium chloride, iron chloride, aluminum chloride, sodium bicarbonate, aluminum sulfate, magnesium sulfate, aluminum nitrate, and aluminum phosphate. . Examples of alkali include slaked lime and caustic alkali. The injection material of the present invention may further contain polyvalent metal compounds and inorganic or organic sequestering agents. Also, the pH of the silica colloid according to the present invention is preferably in the range of 8.5 to 10.5.

The silica grout of the present invention can be widely applied to ground improvement (reinforcement), liquefaction prevention, seismic reinforcement, house lifting, and the like.

The geothermal water containing silica used in the present invention may be of a flash type, a binary type, or geothermal water using other geothermal power generation methods. In the present invention, ultrafiltration, diafiltration, concentration, or the like can be used as a method for recovering silica from geothermal water.

In addition, the silica concentration derived from the silica material obtained by collecting silica in the geothermal water is 30%, and the average particle size as colloidal silica is 1 to 100 nm. It is preferable from the viewpoint of formation of durable ground in ground injection and stability as an injection material.

In the compounding of silica colloid and salt or acid+acid of the present invention, the silica content may be 2 to 50 wt % of silica concentration. In the case of the silica colloid, water glass and acid or acid+salt of the present invention, a silica concentration of 0.4% to 50% can be used.

The ground grouting method of the present invention is characterized by pouring the silica grout of the present invention into the ground to improve the ground.

In the ground injection method of the present invention, the pH (pH 0) of the silica grout is set to a range of 1 to 4, which is more acidic than the pH value (pHs0) of the ground, and the silica grout is injected into the ground. , the soil pH (pHs) of silica grout can be shifted toward neutrality, the soil gel time (GTs) can be shortened, and the ground can be consolidated. As a result, in addition to narrowing the particle size distribution and making the quality uniform, the problem of infiltration caking due to variations in the quality of silica grout using silica derived from geothermal water can be fixed. Even with the improvement, it becomes possible to perform ground injection with a predetermined effect even in various types of ground.

Further, since the silica colloid according to the present invention contains reactive ions in the geothermal water, the viscosity is high, so the silica grout also has a high viscosity. In the present invention, the particle size distribution of silica colloid is made narrow and small to keep the quality constant, thereby improving the permeation and caking properties. The grout tends to deviate from the highly permeable layer, and it is difficult to penetrate into fine-grained soil, resulting in insufficient ground improvement. In order to prevent this, the ground is roughly packed by injecting a primary grouting material consisting of quick setting grout or suspension grout into the target ground, and then the silica grout of the present invention is applied twice. By injecting it into the ground as the next injection material, even if the viscosity of the injection liquid is high, it can penetrate into fine soil layers without deviating.

Experimental examples of silica grout using silica colloid 1, silica colloid 2, and silica colloid 3 are shown below as examples. As a result of the experiment, it was found that the silica grout of the present invention using a silica colloid with a small particle size and a narrow particle size distribution width has better permeability and strength than a silica colloid with a large particle size distribution width. . The geothermal water-derived silica colloid has a higher initial viscosity than the silica colloid obtained by the ion exchange method. This is because the geothermal water _- derived silica colloid contains Cl, K, Ca, Fe, This is considered to be due to the inclusion of As and the like. In the present invention, by reducing the particle size and narrowing the particle size distribution width to increase the kurtosis, it maintains more stable permeability and strength than silica colloid with a large particle size distribution width derived from geothermal water. It retains stable permeability and strength higher than silica colloid 1 by ion exchange method, and has improved penetration caking property. Silica colloid 1 is stable in quality because it does not contain dissolved substances other than SiO ₂ , and has excellent workability as a civil engineering product because of its low viscosity. On the other hand, in the present invention, the above-mentioned problem of geothermal water-derived silica colloid as a ground injection product is solved by reducing the particle size and narrowing the particle size distribution width to keep the quality constant. is. Furthermore, it is believed that the use of a constant quality stabilizes the gelation, and the presence of K, Ca, Fe, and Al contained in the geothermal water contributes to the increase in strength.

(Silica colloid used)
1) Silica colloid 1: Silica colloid produced by the ion exchange method, see Table 3.
2) Silica colloid 2: Silica colloid derived from geothermal water, see Table 4.
3) Silica colloid 3: Silica colloid derived from geothermal water, see Table 5.
4) Silica Colloid 4: Silica Colloid 2 + Silica Colloid 3 (mixed 1:1).

(Physical properties of materials used)
No. 5 water glass: molar ratio 3.75, SiO ₂ = 25.5 w/w%,
Sulfuric acid: 75% concentration, specific gravity 1.675,
Phosphoric acid: 75% concentration, specific gravity 1.58,
Mixed acid: specific gravity 1.63 (a mixture of the above phosphoric acid and sulfuric acid at a volume ratio of 1:1),
Potassium chloride: specific gravity 2.0,
Silica colloid by ion exchange method (silica colloid 1): specific gravity (25° C.) 1.212, silica concentration 30.6 wt %, Na ₂ O concentration 0.39%, pH 10.0, average particle size 10 to 20 nm,
No. 3 water glass: specific gravity (20° C.) 1.412, SiO2: 28.29 wt %, Na ₂ O: 2.94, n molar ratio: 2.94

Test examples of silica grout containing each silica colloid as an active ingredient are shown below.
1. Silica colloid + salt (+ acidic reactant)
1) Characteristics of compounded liquid Table 6 shows the viscosity, pH, and gel time (20°C) of a compounded example (silica concentration: 29 w/v%). From Table 6, silica grout with (silica colloid + (salt + acid)) as an active ingredient has the same silica concentration and almost the same pH, and when the concentrations are the same, silica colloid 1 has a longer gel time than others. become longer. This is because the silica colloid produced by the ion exchange method contains almost no ions other than SiO ₂ , whereas the geothermal water-derived silica colloid contains the above-mentioned other ions, so it is thought that the gelation is faster. be done.

In the above tests, 14g KCL or 14g KCL and 1g _NaHSO4 dissolved in 100ml water were mixed at 20°C. The pH of this mixture is 8.4 with a gel time of 2 minutes and 45 seconds for 14 g of KCL and approximately 6.9 for 14 g of KCL and ₁ g of NaHSO4. , and a homogeneous gelled product was obtained after 30 minutes. From this, it was found that the presence of the acidic reactant NaHSO ₄ increases the gel time when it becomes acidic. Therefore, it was found that the pH should be shifted to the acidic side in order to lengthen the gelation time. The acid here may be phosphoric acid instead of sulfuric acid, or an acidic reactant such as _NaHSO4 . Alternatively, only a salt may be used without using an acid.

2) Strength of consolidated sand Table 6 also shows the strength characteristics of sand gel produced by No. 7 silica sand, a relative density of 60%, and a mixing method. From Table 6, it was found that silica colloids 2, 3 and 4 had higher strength than silica colloid 1, and silica colloid 2 in particular had significantly higher strength. The reason is as described above.

3) Homogel strength and volume change rate As shown in Table 6, silica colloids 2, 3 and 4 have higher strength than silica colloid 1, and silica colloid 2 in particular has higher strength. From the above, it was found that silica colloid with a narrow particle size distribution width and small particle size has high strength. This is thought to be because silica colloids with smaller particle sizes have a larger specific surface area, and because silica colloids with smaller particle sizes and larger particle sizes are less in number, they have better permeability into the interstices of soil grains. . In addition, it was found that the silica colloid 1 and the silica colloids 2, 3, and 4 had similarly small volume change rates.

2. silica colloid + water glass + acid (or acid + salt)
1) Formulation and strength Table 7 shows the viscosity, pH, gel time (20 ° C.) and each silica grout (silica colloid + water glass + acid ) shows the relationship between the strength of the sand gel produced using No. 7 silica sand and the elapsed days.

Specimen preparation method: A mold having a diameter of φ5 cm and a height of 10 cm was filled with the compounded solution after putting No. 7 silica sand so that the relative density was 60%.

From Table 7, the gel time of silica grout using silica colloid (silica colloid + water glass + acid or (acid + salt)) as an active ingredient is the same silica concentration and adjusting the amount of reactant, pH It was found that the gel time can be controlled by As for the strength of the sand gel, it was found that the strength of the silica colloid of the present invention was higher than that of silica colloid 1, or almost the same.

From the above, silica grout containing silica colloid derived from geothermal water containing silica colloid with a narrow particle size distribution width and a narrow particle size distribution width is more likely to produce solidified sand than silica grout containing silica colloid obtained by the ion exchange method. It was found to be stronger. The reason for this is thought to be the inclusion of metal ions, which are reactive dissolved substances.

13(a) and (b) show the relationship between the strength of sand gels (6% and 10%) using each silica colloid and the elapsed days.

A comparison was made in the uniaxial compression test of solidified Toyoura sand of each silica colloid with the formulation of Table 8, which is the same formulation as described in Table 1 of Patent Document 3. The relative density was 50%, and the one-week strength results are shown in Table 9. As a result, it was found that the silica grout of the present invention (silica colloids 2, 3, and 4) having a narrow particle size distribution width and a small particle size has a higher strength than Example 1 of Patent Document 3. In addition, it was found that the strength was higher than that of the silica grout of the ion exchange method (Comparative Example 1 of Patent Document 3).

From the above, the silica grout using the geothermal water-derived silica colloid of the present invention, which has a narrow particle size distribution width and a small particle size, is the geothermal water-derived silica grout with a large particle size distribution width of Patent Document 3. It was found that the cemented sand strength was higher than

In addition, it was found that the silica grout derived from geothermal water of the present invention has higher strength than the silica grout using silica colloid obtained by the ion exchange method of Patent Document 3.

The following are examples of formulation designs using field-collected soil for the silica grout of the present invention.

3. Concrete Sand Strength by Field Collected Soil Using Silica Colloid 2 1) Chemicals Used Table 10 shows the physical properties of the materials used.

2) Formulation Table 11 shows a list of formulations.

3) Strength test Fig. 8 shows the apparatus for preparing the specimen, and Fig. 9 shows the method for preparing the consolidated body.

The mold 1 is a mold for shaping a sample such as sand into a cylindrical specimen, and is made of acrylic material as shown in the figure and formed into a cylindrical shape. It is fixed to the lower flange 6b.

At the same time, residual air and water in the sample are discharged out of the mold 1 through the hollow rod 9 and discharged into the waste water tank 11 .

A valve 12 for injecting chemical solution, carbon dioxide gas and degassed water respectively sent from the chemical injection device 3, the carbon dioxide gas injection device 4 and the deaerated water injection device 5 is connected to the lower part of the mold 1. Porous water-permeable layers 13 are provided on the bottom and ceiling of the mold 1 so that the sample in the mold 1 is evenly permeated with the chemical solution and the degassed water.

The pressure control device is a device that applies a necessary confining pressure to the specimen in the mold 1 through a loading plate by air pressure. It is configured so that various confining pressures can be applied at once.

Moreover, the pressure control device 2 is configured so that the test piece can be produced and cured at once even under several kinds of test conditions.

The chemical injection device 3 is a device for feeding a chemical solution into the mold 1 and permeating and injecting the chemical solution into the specimen in the mold 1. The regulator 15 is driven by a screw jack 16 and attached to the tip of the regulator 15. The load plate 17 pushes the injection material in the chemical liquid tank 18 to feed the injection material into the mold 1, and the chemical liquid is permeated and injected into the specimen in the mold 1 at a constant speed.

The speed of the screw jack 16 can be controlled by the action of an inverter, thereby adjusting the injection speed, injection amount and injection pressure of the injection material.

The carbon dioxide gas injection device 4 is a device for injecting carbon dioxide gas into the mold 1 for fabricating a specimen. In this case, by injecting carbon dioxide gas into the mold 1, degassed water can be injected from the degassed water injection device 5 to bring the sample in the mold 1 into a completely saturated state. 1 can be evenly permeated with the chemical solution.

In addition, the inside of the water tank of the degassed water injection device 5 and the inside of the chemical tank 18 of the chemical injection device 3 are subjected to degassing treatment of the water and the chemical in advance by a vacuum pump, so that a high-quality chemical injection specimen can be produced. can be done.

Next, a method of manufacturing a chemical-injected specimen using the apparatus and method of the present invention will be described.

First, grease is applied to the inner periphery of the mold 1 to facilitate demolding of the test piece after fabrication, and a porous water-permeable layer is provided on the bottom of the mold 1 . Also, a sample is placed in the mold 1, compacted to a predetermined density, and a permeable layer is placed thereon. Then, the upper end of the mold 1 is fixed to the upper flange.

For the density of the sample, the wet density and water content ratio of undisturbed samples collected from the original ground are used. Make predictions from tests.

Next, after compacting the sample in the mold 1 to a predetermined density to prepare a test piece, the mold 1 is assembled with a pressure control device 2, a chemical injection device 3, a carbon dioxide gas injection device 4, and a degassing device as shown in FIG. They are connected to the water injection device 5 respectively.

4) Determining the setting composition of silica grout Relative density 38.0%, site collected soil, site soil pH 4.44, design strength qu = 145 kN / m ² , indoor target strength qu = 145 × 2 = 290 kN / m ² bottom.
Under the above conditions, a strength test was conducted with the formulations shown in Table 11. The results are shown in FIG. From this, it was found that the silica concentration should be 9% in order to satisfy the indoor target strength of 290 kN/m ² with the design strength of qu=145 kN/m ² and the safety factor of 2. Based on this result, Table 12 was used as the setting composition of silica grout. Moreover, from Table 13, it was found that sufficient permeation and caking properties can be obtained by setting the composition of the composition solution to be more acidic than the pH of the soil at the site (pH 4.44). In addition, from the above, we conducted laboratory tests with multiple mixtures using field-collected soil, and based on the data, we found that the target design strength can be obtained in the actual field, and the mixture can be designed.

5) Gel time in soil, gel time in air, and pH in air of compounded liquid
Table 13 shows.

4. Silica Grout Penetration Test Using Silica Colloid 2 1) Chemical Solution Used The composition set in the above "3. Solidified sand strength by site-collected soil using silica colloid 2" was used.

2) Test conditions Test equipment: In-situ sand is filled in an acrylic mold with a length of 1.0 m and a diameter of 0.05 m in Fig. 10 so that the relative density is 38.0%, and the hydraulic conductivity is determined after saturation with water. Water was injected at a water pressure of 50 kPa for the purpose. As a result, a permeability coefficient of k=3.23 ⁻⁵ m/sec was obtained. After that, the result of injecting the silica grout at 50 kPa is shown in FIG. Based on the above, a permeation test was performed using the formulation (Table 12) set by the same laboratory test using on-site soil as in "3. Strength of consolidated sand by on-site soil collection using silica colloid 2". It was found that a design strength of 134 kN/m ² and an indoor target strength of 290 kN/m ² can be obtained at a penetration length of 1 m.

5. Summary of strength test results 1) In the case of compounding "silica colloid + (salt and/or acid)", the strength of consolidated sand was investigated with a constant silica concentration.
From this, it was found that colloid 2, which was adjusted to have a narrower particle size distribution width and a smaller particle size, had a higher strength of consolidated sand than colloid 1, which had a wider particle size distribution width. In addition, silica colloid 3 was equivalent to silica colloid 2. Silica colloid 4 was intermediate between silica colloid 2 and silica colloid 3. The reason why the strength of the silica grout of the present invention is higher than that of silica colloid 1 is that silica colloid with a narrow particle size distribution has a large specific surface area of the colloidal particles, so that the strength of the gel is high, and therefore the strength of the consolidated sand is high. and metal ions contained in the geothermal water contribute to the strength increase.

2) In the case where the composition is "colloid + water glass + (acid and/or salt)", the strength was investigated with a constant silica concentration. The particle size of water glass is 0.1 nm, and the particle size of acidic water glass, which is a mixture of water glass and acid, that is, acidic silica sol, is thought to be 1 nm. However, since the specific surface area of all silica is increased, the strength of the gel is increased and the strength of the solidified sand is increased. In the homogel according to the present invention, silica colloids 2, 3 and 4 all had higher strength than silica colloid 1. The strength of the sand gel was higher than or almost the same as silica colloid 1. Therefore, it was found that the smaller the particle size distribution width of the silica colloid contained, and the smaller the particle size, the greater the strength. From the above, the dissolved substances such as ions other than SiO ₂ contained in the geothermal water were originally unfavorable for the gelation stability of the infusion solution. As a result, a new effect as an injection construction method, which rather increases the strength, is realized.

6. Summary of penetration test results In the penetration test of Fig. 10 using field soil with the composition of Table 11 using silica colloid 2, there was little decrease in strength in the penetration distance of 1m section, and sufficient penetration consolidation strength was obtained over the entire length. It was found that It was also found that the indoor target strength corresponding to the required design strength can be obtained. From this, it was found that the silica grout of the present invention can obtain a predetermined design strength in actual construction.

7. Effect of the Invention As a result of studying the properties of silica colloid derived from geothermal water, the present inventors found that the silica colloid derived from geothermal water has a wide particle size distribution width and contains many dissolved substances other than _SiO2 . The drawback of unstable quality due to this can be eliminated by removing the silica colloid on the side with the larger particle size distribution width, adjusting the particle size distribution width to be small, and using silica colloid with constant quality. We have found that a silica grout with excellent permeability, strength and environmental friendliness and a ground grouting method using the same can be obtained.

1 Mold (mold for fabricating specimen)
2 pressure control device 3 chemical injection device 4 carbon dioxide gas injection device 5 degassed water injection device 6a support upper flange 6b support lower flange 8 valve 9 hollow rod 11 waste water tank 12 valve 13 porous water-permeable layer 14 compressor 15 regulator 16 screw jack 17 loading plate 18 chemical tank 19 displacement gauge

That is, the silica grout of the present invention is a silica grout containing silica colloid obtained by collecting silica in geothermal water as an active ingredient, and the content of heavy metals contained in the silica colloid is suitable for the purpose of ground injection. It is below the corresponding environmental standard value,
The silica colloid has a silica concentration in the range of 2 to 50 w/v%, has a wide particle size distribution width with a large variation in the number of particles for each particle size that occurs during colloid generation, and a type of dissolved matter other than SiO ₂ And the raw silica colloid with a large concentration variation is adjusted so that the standard deviation of the particle size distribution width is 10 or less and the kurtosis is 7 to 50 in the range of 2 to 20 nm, and the particle size is uniform. By narrowing the particle size distribution width, it is characterized by using a material with reduced variation as a ground injection material.

In the silica grout of the present invention, the silica colloid particle size distribution width region is in the range of 2 to 50 wt% of silica concentration, and the higher the silica concentration, the larger the particle size. It is preferable to move to the smaller particle size region.

Claims (13)

A silica grout containing silica colloid obtained by collecting silica in geothermal water as an active ingredient, wherein the content of heavy metals contained in the silica colloid is below the environmental standard value corresponding to the purpose of ground injection. A silica grout characterized by: The content of heavy metals contained in the silica colloid and/or silica grout is an analysis value of heavy metals eluted by immersing the gelled material in distilled water, and is below the environmental standard value corresponding to the purpose of ground injection. 1. Silica grout according to claim 1. A silica grout containing silica colloid obtained by collecting silica in geothermal water as an active ingredient, wherein the silica colloid has a wide particle size distribution width with a large variation in the number of particles for each particle size that occurs in the generation of the colloid. A raw material silica colloid having a raw material colloid, or a raw material silica colloid with a large variation in the number of particles for each particle size, is reduced in particle size and uniform in particle size in a silica concentration range of 2 to 50 w / v% to increase the particle size distribution width. A silica grout characterized by using a narrowed material with reduced variation as a ground grouting material. A silica grout containing as an active ingredient a silica colloid obtained by collecting silica in geothermal water, wherein the silica colloid has a silica concentration in the range of 2 to 50 w / v%, and each particle size generated in the generation of the colloid By narrowing the standard deviation of the particle size distribution width to 10 or less, the raw material silica colloid having a wide particle size distribution width with a large variation in the number of particles is used to reduce the variation as a ground injection material. silica grout. The silica grout according to claim 3 or 4, wherein the silica colloid is narrowed to a range of 2 to 20 nm in particle size distribution to reduce variation as a ground grouting material. A silica grout containing as an active ingredient a silica colloid obtained by collecting silica in geothermal water, wherein the silica colloid has a silica concentration in the range of 2 to 50 w / v%, and each particle size generated in the generation of the colloid A raw material silica colloid having a wide particle size distribution width with a large variation in the number of particles is adjusted so that the standard deviation of the particle size distribution width is 10 or less and the kurtosis is 7 to 50 within the range of 2 to 20 nm. A silica grout characterized by using a material with reduced variation as a ground injection material. Claims 1 to 4, wherein the silica colloid has a silica concentration of 2 to 50 w/v%, a particle size distribution width of 2.0 to 14.5 nm, and a volume average diameter of 2 to 15 nm. Silica grout according to any one of The silica grout according to any one of claims 1 to 7, wherein the silica colloid has a pH of 8.5 to 10.5. The silica grout according to any one of claims 1 to 8, which contains an acid and/or a salt as an active ingredient together with the silica colloid, and has a pH in the range of 1.0 to 10.5. Water glass and an acidic reactant and/or salt are included as active ingredients together with the silica colloid, and the silica concentration is 0.4 to 50.0 w/v% and the pH is in the range of 1.0 to 10.0. Silica grout according to any one of claims 1-5. A ground grouting method, characterized in that the silica grout according to any one of claims 1 to 10 is poured into the ground to improve the ground. By setting the pH (pH 0) of the silica grout to a range of 1 to 4, which is more acidic than the pH value (pHs0) of the ground, and injecting the silica grout into the ground, the soil pH of the silica grout 12. The ground grouting method according to claim 11, wherein the soil gel time (GTs) is shortened to consolidate the ground by shifting (pHs) toward neutrality. 13. The ground grouting method according to claim 11 or 12, wherein the ground is rough packed by injecting the primary grouting material, and then the silica grout is injected into the ground as a secondary grouting material.

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