JP5531234B1 - Ground injection material and ground injection method - Google Patents

Abstract

The present invention provides a ground injection material having a high consolidation strength, particularly excellent in permeability, durability and environmental conservation, and suitable not only for ground reinforcement and water stoppage but also for liquefaction countermeasures. And provide ground injection method.
A silica solution, a reactant, and white carbon are produced as active ingredients. The silica solution is water glass and / or silica colloid, and the PH of the mixed solution of the silica solution and the reactant is in a non-alkali region. The white carbon is 10 to 200 g / 1000 ml, the silica solution is 0 to 400 liters, and the injection solution is PH1 to 10 per 1000 ml of the ground injection material.
[Selection] Figure 1

Description

  The present invention is a ground injection material using white carbon, which has a high consolidation strength, particularly excellent permeability, durability, and environmental preservation, and a ground injection material and a ground injection method. The present invention relates to an injection material and an injection method suitable not only for ground reinforcement and water stoppage but also for liquefaction countermeasures.

  The present invention relates to a ground injection material excellent in durability, environmental conservation and economy, and a ground improvement method, and particularly has a strong resistance to the flow of groundwater and is excellent in liquefaction strength and is less likely to cause ground displacement. Involved in technology to prevent damage caused by liquefaction.

  When loosely deposited saturated sand is subjected to repeated shearing forces due to earthquake motion, the structure between sand particles is disturbed, and the intergranular meshing gradually disengages, resulting in an increase in excess pore water pressure and a decrease in effective stress. As a result, the sand ground exhibits liquid properties (liquefaction phenomenon). As a result, sand sand, uneven settlement of structures, lateral flow, earthquake oscillation, fluid failure of slopes, reduced bearing capacity, revetments and retaining walls Damage due to liquefaction such as destruction of the pipes and floating of buried pipes occurs.

  In preparation for such a liquefaction phenomenon, ground improvement by chemical injection is widely implemented, but chemical injection is intended to prevent liquefaction by filling the gaps between sand particles with gel to suppress the increase in pore water pressure. To do.

Japanese Patent Publication No. 6-72222

  However, the problem of preventing liquefaction by injecting chemical solution is the problem of preventing liquefaction by injecting chemical solution. In order to obtain the uniaxial compressive strength corresponding to the liquefaction strength, There was a problem that the concentration had to be sufficiently high and the cost was high.

  In addition, in order to obtain durability with a long gelation time, silica grout in the acidic region must be used. Therefore, a large amount of acid is required, and there is an adverse effect due to underground buried objects due to the acid and the adverse effect of water quality on aquatic organisms. It becomes a problem.

  In addition, in order to obtain durability with a long gelation time, silica grout in the acidic region must be used. Therefore, a large amount of acid is required, and there is an adverse effect due to underground buried objects due to the acid and the adverse effect of water quality on aquatic organisms. It becomes a problem.

  The characteristics of silica grout pH and gelation time are shown in FIG. FIG. 2 (a) shows the relationship between pH and soluble silica, and FIG. 2 (b) shows the relationship between the specific surface area of silica particle size and soluble silica.

  FIG. 2 (a) shows that the thinner the silica concentration, the longer the gelation time the more acidic the pH, and the darker the silica concentration, the shorter the gelation time. 2 (a) and 2 (b), it can be seen that the soluble silica is reduced when the alkali content is small, the pH is neutral to acidic, and the specific surface area of the silica is reduced. That is, when the molar ratio is high and the silica particle size is large, the soluble silica is small. In the case of water glass, if the gelation time is lengthened, it must be made strongly acidic, and in order to increase the strength by increasing the silica concentration, it must be made more strongly acidic.

  White carbon has a fine particle size, but the particle size of silica is larger than water glass and is almost neutral. Adding white carbon to a thin silica solution makes the silica solution acidic and reduces the silica content. A long gelation time can be obtained even if the concentration of silica in the injection solution is increased and the amount of acid is reduced. In other words, it has a high molar ratio, low acid content, low specific surface area, long gelation time, and low silica elution, resulting in a silica grout with excellent durability and water quality and excellent strength. Thus, the present invention has been completed.

The present invention is because liquefaction is likely to occur in loose sand ground under the groundwater surface,
(1) Injecting fine particles into the ground in the particle size distribution shown in FIG. 9 and shifting the particle size distribution to the left side,
(2) By adding fine particles to loose ground, changing the relative density from loose to medium to dense ground, it can be made economically difficult to liquefy,
(3) White carbon, as described later,

(a) Since it has a fine and porous structure and is lightweight, it is cloudy and dispersed in a silica solution and is difficult to precipitate.
(b) Difficult to dissolve but disperse throughout. However, it precipitates within a few hours.
(c) However, in a silica solution, it becomes cloudy and disperses and does not easily precipitate for a long time.
(d) For this reason, when part of the silica solution dissolves in the silica solution but is injected into the ground, when the silica solution is diluted with groundwater and approaches water, white carbon deposits between the soil particles and bridges the soil particles. Causes solidification.
(e) When the silica solution is alkaline or warmed, the solubility of silica increases and the concentration of dissolved silica increases, but an acidic agent is added to bring PH to the acidic side or the temperature is increased. If it falls, the part which white carbon melt | dissolved will precipitate. For this reason, if injected into the ground, it has excellent permeability at the initial stage of injection, the penetration spreads and dilutes in the groundwater, and the silica content caused by white carbon whose pH of the injected liquid is close to neutral is that white carbon fine particles are between the soil particles. Precipitate and fill. Alternatively, when a heated injection solution is injected, the temperature is lowered in the ground, and the silica content of white carbon is deposited and deposited between the soil particles, thereby causing the effect of solidifying the ground.

(f) White carbon is almost neutral, and even if the silica concentration is increased by white carbon without directly affecting the gel time, acidic water glass (acidic silica sol) is used to increase the gelation time by making it acidic. Unlike the above, it is not necessary to increase the amount of acid, so it is excellent in water quality conservation.

(g) When silica fine particles due to white carbon adhere between soil particles in the ground, even if the silica concentration is low, the strength of the white carbon particles between the soil particles is increased and the liquefaction strength is excellent. In addition, the present invention has been completed by paying attention to the fact that there is little displacement with respect to earthquake motion, and there is little shrinkage of the gelled product, and resistance to the flow of groundwater is increased.
(h) The white carbon region is silica as well as the soil particles and has no environmental problems.

  Since the injection ground is formed from soil particles as shown in Table 1, it is difficult for the suspension to penetrate between the soil particles regardless of how fine the suspension is. That is, there is a problem that the particles are clogged by the filtration between the soil particles and the permeability is hindered.

  In the present invention, by using white carbon, the above problems have been solved by paying attention to the characteristics of dissolution and precipitation of white carbon.

  The white carbon in the present invention is fine powder or ultrafine anhydrous or hydrated silicate and silicate.

White carbon is generally classified into the following four types according to its composition.
1) Silicic anhydride (SiO ₂ )
SiO2 is about 98% or more, and there is very little adhering moisture and bound water. Although it contains a small amount of water, it is called anhydrous silicic acid as compared with the hydrous silicic acid of 2) below.
2) Hydrous silicic acid (SiO ₂ · nH ₂ O)
It is also called hydrated silicic acid with about 80 to 90% SiO2 and a large amount of water adhering and bonding water.
3) hydrated calcium silicate _{(xSiO 2 · CaO · nH 2} O)
It is also called hydrated calcium silicate with SiO2 of about 55-65%.
4) Hydrous aluminum silicate (xSiO ₂ · Al ₂ O ₃ · nH ₂ O)
It is also called hydrated aluminum silicate with SiO ₂ of about 60-70%.
Fine powdered aluminosilicate is also included in this.

White carbon is produced as follows.
(a) Dry method =
A. Decomposition of organosilicon compounds
B. Decomposition of silicon halide
C. Decomposition of silicohydrofluoric acid
D. Arc heating of silica sand and coke mixture

(b) Wet method =
A. Decomposition of sodium silicate with acid
B. Decomposition with sodium silicate ammonium salt
C. Decomposition of sodium silicate with ion exchange resin
D. Degradation of alkaline earth acid derived from sodium silicate by acid
E. There is an organogel method in which an airgel is made from an organogel of silicic acid by autoclaving.

  The PH of white carbon is anhydrous silica: 3-7, hydrous silicate: 5-11, hydrous calcium silicate: 9.5-10.5, hydrous aluminum silicate: 9.5-10.5.

  The single particle diameter of white carbon is usually 10 to 100 mμ, but these are gathered lightly to form aggregated particles of about 1 to 5 μm. Some have an average particle size of 1 to 100 μm.

The inventor of the present application paid attention to the fact that the following characteristics of white carbon are extremely useful as an injection material when white carbon is used as the injection material.
(a) The particle size is small and light.
(True specific gravity: about 2.0 apparent specific gravity: 0.15-0.35g / cc)
(b) Large specific surface area (BET surface area: 50-300 m2 / g), strong adsorption activity on the particle surface.
(c) The particles constitute a structure (network structure).
The measurement of the structure of white carbon is based on the measurement of oil absorption, but the oil absorption can be exemplified by values of approximately 120 to 280 cc / 100 g.

  That is, the water glass-reactant-white carbon system and the injection solution are dispersed throughout the liquid without precipitation of white carbon to form a structure, partially dissolved, and precipitated by the reaction of the water glass-reactant with time. The silica content adsorbed on the structure causes gelation to proceed. The structure imparts tensile stress to the gel and contributes to increased hardness.

In addition, white carbon does not react rapidly with the reactant like the silica colloidal solution, and hardly affects the gelation time.
That is, gelation does not occur even when a reactant is added to a colloidal solution in which white carbon is dispersed.

Therefore, even if the concentration of white carbon in the water glass-reactant-white carbon system increases or decreases, the gelling time is hardly affected, but the strength increases, and the strength increases as the concentration of white carbon increases. In addition, the shrinkage of the gel is extremely reduced by the action of the structure, and the leaching of SiO ₂ is also greatly reduced, so that the permanentness is greatly improved without lowering the water stopping property and the caking property.

  Note that hydrous calcium silicate or hydrous aluminum silicate as white carbon is different from calcium silicate usually used in the grout method. That is, calcium silicate used in grout is a powdered slag produced as a by-product in the production of pig iron, etc., and contains soluble silicic acid, lime, and bitter earth, and is curable with lime. It precipitates immediately and does not form a structure by dispersing in water like white carbon, and has a small specific surface area and no adsorption activity.

This is because white carbon has many OH groups inside and on the surface of hydrous silicic acid (hydrous calcium silicate, hydrous aluminum silicate) particles and adsorbs water by hydrogen bonding.
Therefore, in the present invention, white carbon is distinguished from ordinary calcium silicate and aluminum silicate.

Similarly, there are posolans such as fly ash, diatomaceous earth, and silica fumed sinter as SiO ₂ particles, but these precipitate as they are mixed with water and left to stand.

  That is, unlike white carbon, the characteristics such as surface activity, surface adsorption, and apparent specific gravity cannot be dispersed and formed in the entire water like white carbon. Therefore, it shall be distinguished from white carbon in the present invention.

  Also, white carbon has a porous structure that is different from silica colloid that is stable to weak alkali by increasing the silica monomer by removing alkali of water glass usually used for ground injection by ion exchange method etc. Not done.

  Table 2 shows typical examples of white carbon.

Hereinafter, the present invention will be shown by experiments.
In this experiment, white carbon shown in Table 3 was used (Shionogi Pharmaceutical Co., Ltd., Carplex).

  The present invention is intended to prevent liquefaction by injecting fine particles such as white carbon into the ground to increase the fine soil or density of the ground. is there. In addition, it is intended to improve the ground economically.

  By making the ground fine or dense, it provides viscoelastic connection and restraint function between soil particles, increases shear strength against shearing force due to earthquake motion, and suppresses increase in pore water pressure. This makes it possible to prevent liquefaction economically.

  In the prediction of liquefaction, the ground having a particle size distribution as shown in FIG. 9 is considered to be easily liquefied, and chemical injection is extremely effective as a countermeasure against such liquefaction, There is an economic problem.

  Therefore, the applicant has come up with the idea of increasing the fine particle content of loose sandy ground and increasing its density, using a silica solution in which white carbon-containing PH is acidic to neutral.

  In particular, when white carbon is mixed in water in a container, it precipitates without being dissolved, but in the silica solution, the fine particles are dispersed for a long time and partly dissolved, and the remaining fine particles are dispersed in the liquid. It was found that after a certain period of time, the solution and the silica particles were separated and a precipitate of silica particles was formed at the bottom. The reason why white carbon disperses in silica solution without settling for a long time seems to be that white carbon is porous and light, while silica solution is more viscous and denser than water.

  When this phenomenon is injected into the ground, it is thought that as it penetrates, the silica solution is diluted and becomes close to water, so that the dissolved white carbon breaks out. In order to increase the dissolution of white carbon, if the silica solution is alkaline, the dissolution of white carbon is further increased.

  Further, when the silica solution has a high temperature or is heated, the white carbon is further dissolved. Therefore, it was found that when a silica solution exhibiting acidic to neutral pH in such a state is injected into the ground, a phenomenon occurs in which the silica content in which white carbon is dissolved is broken out with time (FIG. 3). .

  It was found that if the above solution is poured into the ground and the silica particles are deposited between the soil particles after a certain time, the particle size distribution of the soil also shifts to the left side, and the density and increase of the soil (Fig. ) Was found.

  Since these silica solutions containing white carbon contain fine particles (white carbon) smaller than the particles of the particle size distribution ground as shown in FIG. 9 (see Table 4), liquefaction as shown in FIG. For the ground consisting of a possible particle size distribution, by increasing the fine particle content of the particle size distribution curve by moving the particle size distribution in the direction of the fine ground where liquefaction does not occur easily, or We focused on the fact that liquefaction can be prevented very economically by increasing the density.

  White carbon has no curability and is easy to penetrate with no resistance between soil particles. White carbon is not curable like cement and ultrafine particle cement, but shifts the particle size distribution of the soil in the direction of fine soil. Of course, curable particles may be mixed in white carbon. However, the aqueous solution of white carbon alone can be injected into the sand of the ground that may be liquefied due to its particle size, but in the case of fine-grained ground, it may not be able to penetrate.

  In this case, it was found that if a low-concentration silica solution containing white carbon is used, the low-concentration silica solution can be filtered and penetrated even in fine-grained ground where white carbon cannot permeate.

  In this way, even if the white carbon cannot be completely filled between the soil particles of the liquefied layer, the white soil is included in the silica solution to form a chain between the soil particles of the ground that are liable to liquefy. And they are connected with viscoelasticity. And liquefaction can be prevented economically.

  As described above, the injection solution of the present invention can prevent the pore water pressure from being increased by the earthquake motion using the low concentration silica solution. The silica solution containing white carbon forms a stable viscoelastic gel at a lower silica concentration than the silica solution not containing white carbon. Prevent complete destruction of the soil.

  With the above functions, it has been found that silica grouting using white carbon can economically prevent liquefaction, and the present invention has been completed. For reference, it is considered that the limit of suspension grout injection can be obtained from the porosity and diameter of soil, D10 and D15 of soil particles, and D85 and D95 of suspension.

  The “gap size” of the sphere of diameter D, that is, the gap diameter α is a porosity of 26% (most tight) and 15% of the sphere diameter D, and a porosity of 48% (loose) ) Is considered to be 41% of the diameter D of the sphere.

It is known that the porosity n of the gravel and the “gap diameter” α are most often shown to be 35 to 38% in the actual riverbed debris according to the results of many experiments. Further, in the laboratory experiment, when the result of actually measuring the “gap diameter” of the single-grain aggregate is statistically investigated, α / D≈20%, that is, α = D × (1/5) is the most “ "Frequency" is considered large. Here, d = gap diameter, and D particle diameter that can smoothly pass through the soil particle gap.

Based on this idea, it is thought that the 10% and 15% diameters of the particle size accumulation curve of soil particles that can be infiltrated by suspended particles can be obtained. When the 10% diameter of the particle size accumulation curve of the suspension is D10 and the 95% diameter of the ground particle size accumulation curve is D95, more experimental results than the experimental statistical results of the relationship between D10 and D95 are obtained. In summary,
N = D10 / D95 ≧ 8
It is known that the grout (suspension) cannot smoothly penetrate unless the above relationship is satisfied.
N is referred to as “Groutability Ratio”.
Assuming the following example as the value of white carbon 95% diameter: 5 nm to 5 μm, 95% diameter, the particle size of the soil particles into which the suspension can permeate is as follows.

D10 = D95 × 8 = 5 nm × 8 = 40 nm
D10 = D95 × 8 = 5μm × 8 = 40μm
That is, the permeation limit can be calculated by D10 = 40 nm to 40 μm.

When D95 = 0.03 μm, D10 = 0.03 μ × 8 = 0.24 μm Even if white carbon is injected into the ground of a particle size distribution that is easy to liquefy as shown in FIG. 9, a part of the gap is filled with white carbon. Therefore, the particle size distribution of the ground itself does not move to the left side, but even if the whole particle size distribution is not moved to the left side, the fine particle content of 20% or less of the 100% passing rate of the particle size distribution curve is increased. As a result, it was found that liquefaction would be difficult even if only moving to the left side.

  For example, in the case of a simulated ground in which 300 g of Toyoura sand (about 196 ml, Dr 60%) is packed in a mold with a diameter of 5 cm and a height of 10 cm, the particle size accumulation curve comes within the range where there is a possibility of liquefaction. The white carbon shown in Table 4 per ground is shown in FIG.

  When white carbon of 5 μm or less shown in Table 4 is injected into Toyoura sand having the particle size curve of FIG. 9 with an injection device, the particle size curve shifts to the left. Further, when 40 g of white carbon is injected into the ground, the particle size accumulation curve shifts to the left from the range where liquefaction is possible.

  If white carbon alone is not enough to fill the gap in the ground, or if the ground motion is large, there is a risk that the pore water pressure will increase and liquefaction will occur if repeated shearing force is applied by the earthquake. If used, it can be prevented. In general, the optimum application object of water glass grout is fine sand or coarse sand. That is, it is applied to sand having a specific surface area of 100 to 1000 cm @ -1 (Table 1).

  Although it is mainly applied to sand with k = 10-1 to 10-3 cm / sec in terms of hydraulic conductivity (Table 1), silica solution with extremely low silica concentration, especially silica concentration in non-alkaline PH region, is the silica concentration. Can penetrate even 1 to 3%, and it is possible even on 10-4 order ground of silty sand. When the silica concentration is 2% or less, the solidification of silica, especially the gelation ability of silica under the groundwater surface is extremely small, and the improvement in liquefaction strength is low. However, in the presence of white carbon, sufficient liquefaction strength can be obtained even if the silica concentration is 2% or less and 0.5%.

  In addition, in a silica solution having a low silica concentration, if there is a flow of groundwater, the gel is finely broken for a long time and the durability becomes insufficient. However, if the voids are filled with white carbon and the influence of groundwater is blocked, the silica gel is stabilized.

  Therefore, if white carbon and dilute silica are used corresponding to the grain size of the ground in this way, the ground that may be liquefied can be transferred to a fine-grained ground where the density increases and most of the ground is difficult to liquefy. .

  Therefore, if white carbon + low-concentration silica solution is injected into the ground within the injectable limit, it can be regarded as a ground where the amount of viscous soil equivalent to the amount of the injected liquid has increased, so that it becomes a viscous ground where liquefaction does not occur. It can be seen that the ground can be similar.

  The present invention is to inject fine particles such as white carbon into ultrafine particles such as white carbon into a ground having a particle size distribution that may be liquefied, or to increase the relative density of the ground. Therefore, ground improvement can be performed extremely economically.

  In particular, since it has a high consolidation strength and is excellent in permeability, durability, environmental conservation, etc., it is suitable not only for ground reinforcement and water stoppage but also for liquefaction countermeasures.

It is a graph which shows the characteristic of pH and gelation time of a silica grout. (a) is a graph showing the relationship between soluble silica and PH, and (b) is a graph showing the relationship between the amount of silica dissolved and the surface area of particles. It is a schematic diagram which shows the example of the manufacturing method of this silica grout by the apparatus which manufactures this invention grout equipped with the heater. Although the heater does not have to be attached in the figure, an example in which the heater is attached is shown here. It is a model diagram of the ground showing the image of the present invention and increasing the density of the ground by replacing the interstitial water between the soil particles with solution-type silica and white carbon. It is a perspective view which shows the shaping outline of a test body. It is a schematic diagram of a consolidation constant pressure single surface shear tester. It is a graph which shows the relationship of a shear stress-shear displacement. It is a graph which shows the relationship of vertical displacement-shear displacement. (a), (b) is a graph which shows the particle size distribution of the ground which may be liquefied especially. Changes in the particle size distribution of white carbon and the particle size distribution of Toyoura sand when 10% white carbon liquid is injected into Toyoura sand as ultrafine particles are shown. It is a graph which shows the particle size distribution of the sand used for the test. It is a schematic diagram of an osmotic injection test apparatus.

  Hereinafter, the present invention will be specifically described.

  The silica solution used in the present invention is an alkaline water glass solution, a non-alkaline water glass (silica sol) removed with an acid of water glass, colloidal silica, or a mixture containing these as active ingredients. In particular, the silica solution used in the present invention is preferably a solution type chemical solution obtained by removing alkali from a silica solution made of water glass, such as a water glass grout, preferably a colloidal silica type or silica sol type water glass having excellent durability. .

  As the alkaline water glass, a water glass having a molar ratio of 1 to 5 can be used, but a low molar ratio water glass preferably has a molar ratio of 3 to 5 which requires a lot of acids to be acidic. .

  In the above, the alkaline water glass solution, the non-alkaline water glass (silica sol) removed with the acid of the water glass is a mixture of a diluted water glass and a reactant for adjusting the gelation time.

  As the above-mentioned reactants, as acid regulators, sulfuric acid, phosphoric acid, sodium bisulfate, aluminum chloride, aluminum sulfate, and other acidic salts, aluminum salts, carbonates, bicarbonates, carbon dioxide, carbonated water, chlorides, Examples include aluminate, glyoxal, carbonates such as ethylene carbonate, polyvalent acetates, etc. In addition, cement, lime, slag, etc. may be used alone or in combination with the above reactants. Can do.

  The silica colloid in the above is a colloid which is stabilized in weak alkalinity with a particle size of 5 to 100 nm. Moreover, the active silica obtained by processing water glass or acidic water glass formed by mixing water glass and acid with an ion exchange resin or an ion exchange membrane may be used. A silica colloid obtained by adding water glass, an acid, or a salt to the active silica colloid. In addition, the silica colloid may be made of metal silica.

  The 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). For example, a zeolite colloid exchanger, an ammonium ion exchanger It is obtained by passing water glass through an ion exchange resin, 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. Pure silica (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 silica colloid is further added to the above-mentioned silica colloid to evaporate to stabilize and concentrate simultaneously, or after ion exchange. A method is used in which the active silica colloid is heated under an appropriate alkali, and the active silica colloid is further added thereto for stabilization. Moreover, the silica solution which consists of metal silica may be sufficient.

Since the silica colloid solution in the present invention is almost separated and removed by Na ions, it usually shows weak alkalinity with a pH of 10 or less, and Na ₂ O is in the range of 0.2 mass% to 4.0 mass%. When Na ₂ O is 4% by mass or more, the silica colloid dissolves and becomes an aqueous solution of silicate.

On the other hand, when Na ₂ O is less than 0.2% by mass, the silica colloid cannot be present stably and aggregates. That is, when Na ₂ O is in the range of 0.2% by mass to 4.0% by mass, Na ions can be distributed on the surface of the silica colloid and kept in a stable colloidal state.

  The silica colloid prepared in this way is almost neutral and semi-permanently stable, and when it is used as an infusion solution, it is gelled during delivery from the factory to the site and during the infusion operation. There is no worry. 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.

  Moreover, the ground injection material in this invention can be easily manufactured with an apparatus as shown in FIG. 3, for example. In FIG. 2, an alkaline silica solution and white carbon are injected into a chemical solution reaction material tank 1 at a fixed ratio and mixed, and the mixed solution is heated at a constant temperature through a heater 2 when being sent from the chemical reaction tank 1 to the outside. By doing so, it can be easily manufactured.

  In addition, a silica solution and white carbon may be added to dissolve a part of white carbon, and an acid agent may be added to produce the present grout and inject it. Alternatively, white carbon may be added after the silica solution and the acidic agent are mixed to form an acidic silica solution. Or you may perform these simultaneously. Also, the heater may be positioned at the infusion solution feeding tube, in the reaction agent tank, or in the material input tube, or the heater is attached to the white carbon / silica solution mixing tube. You may send it to the tank.

  In FIG. 3, the reference numeral 3 on the left and right is a pump for feeding the alkaline silica solution and white carbon to the chemical reaction tank liquid 1, 4 is an adjustment valve for adjusting these amounts, and 5 is a heater 2 and a pump 3. And a controller for adjusting the adjusting valve 4.

  Moreover, the ground injection material of this invention can also use these injection materials together. Water glass contains many silanol groups and has high reactivity, so that the initial strength development is fast. However, it contains more Na than silica colloid, and the gelled product shrinks after gelation.

As mentioned above, white carbon is a general term for synthesized fine powders of anhydrous silicic acid, hydrous silicate, hydrous calcium silicate, hydrous aluminum silicate, etc., and when added to rubber, white carbon has an excellent reinforcing effect after carbon black. Because it shows, it is called white carbon. There are various types of silica (silicon dioxide) SiO ₂ in products ranging from 98% or more to 50 to 70%. Although the particle diameter varies depending on the production method, it is 5 nm to 5 μm.

  By changing the particle diameter (particle size), structure (particle connection), and surface properties (functional group) in various ways, the characteristics change greatly, and these can be controlled to some extent by the production method.

  One or more of these can be mixed and injected into a medium / acidic silica solution to improve the improvement effect. Alternatively, a silica solution in which water glass and white carbon are mixed in advance can be prepared, and an acid can be added thereto to produce a white carbon-mixed non-alkaline silica solution.

  Table 5 shows the liquefaction strength after 28 days when the silica compound and white carbon of Table 4 were mixed in Tests 1 to 4 and injected into FIG. When PH was acidic, a value higher in liquefaction strength was obtained after one year than in the case of silica sand alone. However, when PH was alkaline, the strength decreased after one year.

  The improvement effect when using white carbon as fine particles and the improvement effect of dredged sand solidified with a mixture of white carbon and silica were confirmed. Thereby, it was found that the liquefaction strength increased in the acidic region.

  White carbon suspension or white carbon suspension + silica was prepared (Table 6) and injected into the in-situ sand using the apparatus shown in FIG. 12, and the improvement effect of in-situ sand was confirmed (Table 6). From Table 6, Nos. 6, 7, it was found that the liquefaction strength increased with time when the pH was acidic and the molar ratio was high.

  In the preparation procedure of the specimen using the apparatus shown in FIG. 12, first, sand is packed in a mold so as to have a density of 60%, the loading plate is attached to the specimen, and the loading plate is pushed down by air pressure to apply restraining pressure. In this state, the sample was saturated with degassed water, and then the chemical solution shown in Table 6 was injected.

  Further, the injected specimen was cured under a restraining pressure for a predetermined period, and the liquefaction strength ratio R after 4 weeks and 1 year was obtained. The results are shown in Table 3.

  The sand was molded using No. 7 silica sand that assumed fine sandy ground and No. 5 silica sand that assumed rough sand ground. The particle size curve of the sand used is shown in FIG. It was also found that finer sand has higher liquefaction strength.

Verification in sandy ground Specimens injecting 30 g of white carbon / 400 liters of injection solution (water + white carbon) into the silica sand shown in Table 7 showed a significant increase in liquefaction strength compared to before improvement (Table 7). .

  When a small amount of silica compound was mixed with silica sand (Table 7) and an injection material (Table 6, Tests 5 and 6) that gelled as a whole was injected, high liquefaction strength was obtained. In the case of grout, the liquefaction strength increased even after one year, but decreased in the alkaline region.

  As shown in FIG. 3, the present invention is an improvement of the ground that suppresses liquefaction by increasing the density of the ground by replacing the interstitial water between the soil particles with solution-type silica and white carbon. When solution-type silica and white carbon are injected into the gap in the ground, the gap ratio decreases and the relative density increases.

  Moreover, it can be said that it is a liquefaction countermeasure work that has the effect of solidifying the ground by using solution-type silica together and the effect of increasing the density of density by injecting white carbon.

  A specimen for conducting a consolidation and constant pressure single surface shear test was prepared by a mixing method. The sample used was Toyoura sand, and a specimen having a diameter of 6.0 cm and a height of 9.5 cm was prepared. Table 8 shows the composition of the solution-type silica and white carbon (hereinafter “SW”) used for the specimen.

  The relative density after the injection was calculated from the amount of WC added to the injection material used for specimen preparation and the gap ratio before improvement. As a result, the relative density increased by about 10% from the initial relative density when WC was used at 30 g / 400 ml, and by about 20% when WC was used at 100 g / 500 ml.

  In addition, as shown in the outline of test specimen shaping in FIG. 4, the test specimens were shaped into a diameter of 6.0 cm and a height of 2.0 cm for testing, and (1), (2), and (3) were formed from the top of the shaped specimen. In the single-sided shear test of saturated sand, a specimen was prepared so that D = 70% in the shear box by the underwater dropping method.

  This test was conducted for the purpose of comparing the dilatancy characteristics of specimens prepared by the mixing method. Table 9 shows the test conditions. The outline of the test is shown in FIG. In the test, the compaction pressure was set to 50 KPa, the compaction was performed for about 10 minutes, and then sheared to a final shear displacement of about 10 mm at a shear rate of 0.2 mm / min. The specimen was shaped to a diameter of 6.0 cm and a height of 2.0 cm, and the lower part of the specimen was used.

Water glass: No. 5 water glass, specific gravity 1.32, SiO2 = 26%, Na2O = 7.16%
PH adjuster: Phosphoric acid non-alkali silica sol: Colloidal silica, specific gravity 1.21, SiO2 = 30%, Na2O = 0.3%
WC: White carbon, SiO2 = 100%.

より表８の配合のモル比は以下の通りになる。

Further, the molar ratios of the formulations in Table 8 are as follows.

Example Colloidal silica, specific gravity 1.21, SiO2 = 30%, Na2O = 0.3%
WC: White carbon, SiO ₂ = 100%.
No. 2 water glass, SiO ₂ = 35%, Na ₂ O = 14.5%

Preferably 3 to 5000 is preferable.
FIG. 7 shows the relationship between the test results and the consideration shear force-severance displacement. The maximum shear stress τ is τ = 11.9kPa for casel, τ = 18.6kPa for case2, τ = 23.6kPa for case3, and τ = 32.4kPa for case4, and the shear stress τ increases from case2 to case4. Increase in shear stress due to type silica and SW was confirmed. Further, when comparing Cases 2 to 4, the shear stress of SW tended to be stronger than that of solution-type silica, and the shear stress tended to increase as the amount of WC added increased. The relationship between the vertical displacement and the shear displacement is shown in FIG.

  When saturated sand starts cutting, the specimen sinks and the volume decreases. However, in case 2 to case 4, it can be seen that the specimen sinks in the early stage of cutting, but then the positive dilatancy works and the volume increases. In case 2 and case 3, the volume expansion converges at a constant value. In case 4, the volume expansion continues even when the shear displacement is 8 mm, which is considered to be due to the effect of increasing the density by the fine particles. However, when WC was used, if too much was added, it could not be mixed well with Toyoura sand, and in the SW (2) specimen, WC was biased in the specimen.

(1) Verification on fine sandy ground (No. 7 silica sand) The specimens injected with the injection materials of Test No. 1 and 2 increased in liquefaction strength to 0.26 compared to before improvement.

Furthermore, it was found that in the injection material test Nos. 3, 4, and 5 in which a small amount of a silica compound was mixed and the whole gelled, high liquefaction strength was obtained even without bubbles.
(2) Verification on coarse sand ground (No. 5 silica sand) The liquefaction strength of the material injected into the rough sand ground (No. 5 silica sand) was higher than that using fine silica sand.

  From this, it was found that in rough sand ground, white carbon easily penetrates into the gap, and a higher effect can be obtained.

  Experiments were carried out on changes in particle size distribution and relative density when white carbon was added to Toyoura sand as a countermeasure for liquefaction. The results are shown in Table 10. It was found that this increased the relative density and increased the fine grain content.

  After preparing specimens of Toyoura sand having a diameter of 5 cm × 10 cm and a relative density Dr of 40% and 60%, an injection solution having a silica concentration of 6% was prepared, and 100 g of white carbon was dissolved in the injection solution.

  The sample was saturated with water, and a solution in which white carbon was dissolved was infiltrated into the sample, and then the infiltrated sample was dried and the dry weight was measured. A weight increase of 38 g at a relative density of 40% and 35.2 g at a relative density of 60% was confirmed. This amount applies to the white carbon contained in the specimen.

  Therefore, the maximum and minimum density tests were performed on the sample mixed with Toyoura sand and white carbon. When the relative density is 40%, Toyoura sand: white carbon = 283.1: 38.0, and when the relative density is 60%, Toyoura sand: white carbon = 295.3: 35.2. As a result, when the relative density was 40%, the maximum dry density was 1.742 and the minimum dry density was 1.388, and when the relative density was 60%, the maximum dry density was 1.737 and the minimum dry density was 1.381. As a result of calculating the relative density of the specimen containing white carbon, it showed 74% and 87%, respectively, and it was found that a dense ground can be formed.

  The particle size distribution when white carbon is contained in Toyoura sand with a relative density of 40% is shown (see Fig. 10). It is clear from the graph “Possibility of liquefaction” and it becomes difficult to liquefy. Also, according to Hazen's empirical formula, the permeability coefficient k of the ground has the following relationship with the 10% particle size D10.

K = CD102
Although C is about 100, D10 is said to be an effective diameter, and it has been found that a 10% particle diameter has a great influence on the hydraulic conductivity.

  By dissolving white carbon in water glass, the solubility is large and the 10% particle size is small, so that the water permeability is lowered and stable against liquefaction.

  From the above, it was found that the fine grain content of Toyoura sand increased by about 10% and the relative density increased by about 20 to 35%.

  Also, the solubility of white carbon differs depending on the pH of the mixed solution, and it hardly dissolves in water, but partly dissolves in silica solution, and others precipitate after a long time. Depending on the pH, alkalis are more soluble and less acidic. In the rest, white carbon is deposited between the soil particles, increasing the fine particle size distribution.

  Therefore, it is preferable to dissolve the white carbon in alkaline water glass in advance and add an acid when injecting it into the ground to form an acidic silica grout. Moreover, it turns out that the change of a particle size distribution and a relative density can be controlled with pH other than addition amount. In addition, it can be seen that when the reactant is contained in the silica solution, the silica in the supernatant liquid is gelled, so that the liquefaction strength is increased.

  The present invention has a high consolidation strength, is particularly excellent in permeability, durability, environmental conservation, and the like, and can be applied not only to ground reinforcement and water stopping purposes but also to liquefaction countermeasures.

1 Chemical reaction tank 2 Heater 3 Pump 4 Adjustment valve 5 Controller

Claims (7)

A ground injection material to be injected into a ground that is expected to be liquefied at the time of an earthquake, and the ground injection material contains 10 to 200 g of white carbon as an active ingredient per 1000 ml of a silica solution, an acidic reactant, and a ground injection material. the ground particle size distribution by increasing or Succoth particulate content of less than 20% passing 100 parts per particle size distribution curve of the ground is moved in the direction of the fine land board by, by causing increased soil density A ground injection material, which is a non-alkaline fine particle silica suspension that forms a ground that is difficult to liquefy.   2. The ground injection material according to claim 1, wherein the silica solution is water glass and / or silica colloid, and the pH of the mixed solution of the silica solution and the reactant is in a non-alkali region. In ground injection material according to claim 1 or 2, white carbon per ground grout 1000 ml is 10 to 200 g, SiO ₂ 0.5 to 30% silica solution, it is PH of the ground grout from 1 to 10 A ground injection material characterized by   The ground injection material according to any one of claims 1 to 3, wherein when the silica content of the silica solution per 1000 ml of the ground injection material is only water glass, the silica content is 15g to 800g, and the silica content of the silica solution is colloidal. In the case of silica, the ground content is 15g to 1030g, and when the silica content of the silica solution is composed of water glass and colloidal silica, the silica content is 15g to 1030g. The ground injection material according to any one of claims 1 to 4, wherein the molar ratio of the non-alkaline silica solution is increased by white carbon and heated . In ground grout according to any one of claims 1 to 5, the molar ratio of S _i O ₂ / Na ₂ O of the silica solution of the ground injection material in a non-alkaline fine silica suspension is 3-5000 ground injection material, characterized in that. In a molar ratio of S _i O ₂ / Na ₂ O to ground the silica solution and an acidic reactant and ground grout 1000 ml per 10~200g active ingredient white carbon which is expected to liquefy during earthquakes 3-5000 direction of a non-alkaline fine silica suspension is injected into the ground soil particle size distribution curve passing 100 min of 20% or less of particulate matter to increase and fine land Release the particle size distribution of the ground by Succoth of ground grouting method which is moved, by causing increased soil density, characterized by forming a liquefied hard ground to.

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