JP7390081B1 - Ground injection method - Google Patents

Abstract

[Problem] To provide a ground injection method that forms a consolidated ground that is entirely integrated, homogeneous, watertight, and highly strong, in response to complex ground conditions such as soft ground. [Solution] When injecting silica grout into the ground, this is a ground injection method in which a combined liquid of liquids A and B is injected into the ground. The A liquid is a water glass solution, the B liquid is a reactant, and multiple drive devices, inverters, and multiple drive devices that pump A liquid and B liquid using A liquid pump and B liquid pump, respectively, are integrated. By controlling the inverter and continuously variable control of the flow rate and merging ratio of the combined liquids A and B according to the ground conditions, the merging of liquids A and B can be Continuously changing the concentration of the reaction product or component of the liquid to bring the concentration of the reaction product or component in the ground improvement region within a predetermined concentration to solidify the ground. [Selection diagram] None

Description

The present invention relates to an environmentally friendly injection consolidation method for soft ground using silica grout. Specifically, the gel time and the concentration of environmentally influential ions are continuously varied according to the ground conditions to make soft or leaky ground homogeneous and strong. The present invention relates to a ground injection method that not only solidifies or stops water, but also controls the concentration of environmentally harmful ions generated in the ground.

Soft ground is usually formed by a layer of coarse-grained soil and a layer of fine-grained soil, but this can be achieved by injecting a consolidation agent into the ground to make it homogeneous and with a low environmental impact. It is necessary to solidify with

In recent years, as the number of earthquakes has increased and the scale of excavation work has increased, construction work has become longer, and construction work that requires safe construction under complex ground conditions has increased. There is a growing demand for ground improvement injection technology that has excellent permeation and consolidation properties and is safe for ground structures and water quality.

In order to meet this demand, the present applicant has already developed and put into practical use a non-alkali silica grout (FIG. 1). As shown in Figure 2, non-alkali silica grout is produced by neutralizing the alkali of water glass with an acid and using medium-to-acidic silica grout (silica sol grout), which is made by neutralizing the alkali of water glass with an acid and using an ion exchange method. There is silica grout (active composite silica grout) that is made of weakly alkaline and stable colloid, water glass, and acid and has a pH of 1 to 10. Furthermore, regarding the reduction of reaction products of non-alkali silica grout underground, we have developed a technique described in Patent Document 1. With all non-alkaline silica grouts, the gel time can be set from a few seconds to several tens of hours, so there is no need to worry about gelation even if you make a large amount of injection solution, and you can also pump a large amount of injection solution over a long period of time. It has the advantage of being a liquid, reliably gelling after being injected into the ground, and having low viscosity and good permeability (see Figure 1).
In the present invention, as the acid used in the acidic solution, inorganic acids such as sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, and sulfamic acid, organic acids such as citric acid, mixed acids thereof, and salts thereof can be used. It is not limited as long as it is an acid that can adjust. Additionally, salts that act as acids (eg, aluminum chloride, polyaluminum chloride, etc.) can be used. Furthermore, the gel time and strength can be adjusted by using any salt, alkali, or pH adjuster as an additive.
As the silica solution, it is possible to use water glass, activated silica, colloidal silica, metal silica, silica derived from geothermal water, or one or more of these.
In the present invention, the type, concentration, and molar ratio of water glass used are not limited either.

However, as can be seen from Figures 1 and 2, non-alkaline silica grout has a short gel time when the pH is around neutral, and a significantly long gel time when the pH is around 2, and shows a stable gel time in that region. Since the gel time changes rapidly in the intermediate pH range, it has been impossible to inject grout having a gel time corresponding to a predetermined pH. For this reason, in actual injection, there is no choice but to inject instantaneous grout, inject an injection solution with an extremely long gel time, or frequently use a combination of these. In addition, the following conventional methods are known as injection methods for soft ground.

(1) Rod injection method This method uses an aqueous solution of a reactant or a suspension containing a cement substance (liquid A) and an aqueous water glass solution (liquid B) as consolidation materials, and these are poured into a Y-tube. This method involves press-fitting the material into the ground while merging it with the boring rod, but a gap is created between the boring rod and the ground, and the solidified material may spout onto the ground surface through this gap, or the injected liquid may escape through the rough layer. Therefore, it is difficult to consolidate into fine-grained soil layers or within a predetermined consolidation range.

(2) Double-pipe injection method This method uses water glass as liquid A and a gelling agent as liquid B, which are merged at the tip of a double-pipe installed in the ground, allowing for a short gel time. This is a method of injecting grout with a composition that hardens. According to this method, the gel time is short, so it is possible to prevent grout from spewing out above ground along the periphery of the rod. I can't let you. For this reason, during excavation, the spring water soil is likely to collapse.

(3) Double-pipe composite injection method In order to solve the above problem, conventionally, the gap between the injection pipe and the ground is first filled with the injection material with the shorter gel time, thereby forming a seal with a packer effect. , a consolidated layer consisting mainly of veins filling the rough layers and layer interfaces is formed, and then the injection material with a longer gel time breaks the seal and the injection material with a shorter gel time has already been injected. A ground injection method has been developed in which water is poured into certain areas. This method is aimed at ensuring that the injection material with a longer gel time penetrates and solidifies the injection target because it does not deviate from the surroundings of the injection pipe or the rough layer (Patent Document 2, Figure 3).

In the invention described in Patent Document 2, a reactant is combined with a base compound liquid to form an injection material, and a water glass compound liquid or a mixed compound liquid of water glass and a reactant is used as a base compound liquid as liquid A. A reactant solution containing a water glass solution and an accelerating agent is added thereto as a B solution.

Specifically, after a flash setting grout made by combining water glass and a reactant is injected, a permeable grout consisting of an alkaline permeable grout is injected. Alternatively, after combining the reactant with the acidic water glass and injecting the instant setting grout, only the acidic water glass is injected. While turning on and off the merging of the reactant with the main agent, the flash setting grout is first injected, and then the permeable grout is switched to the second injection (see Figure 3). In this case, the silica concentration between the primary injection and the secondary injection differs, making it impossible to obtain a constant strength.

In addition, when the pH of the water glass mixture becomes alkaline, gelation becomes unstable, or the gel time becomes infinite, resulting in no gelation (FIG. 1). Furthermore, instant setting grout obtained by combining acidic water glass with an aqueous alkaline reactant solution has a lower silica concentration and has lower strength than acidic water glass grout. Therefore, after combining the water glass with the acidic water glass and injecting the instant setting grout, it is possible to switch on and off the process of injecting only the acidic water glass or adding a slow setting reactant to the acidic water glass. , the instant-set grout has a higher silica concentration than the loose-set grout, and therefore has higher strength, making it impossible to obtain a constant strength (Figure 3).

In this way, even with alkaline grout, if you increase the amount of hardening agent, it will become instant setting grout, but if you reduce the amount of hardening agent to obtain slow setting grout, the strength of slow setting grout will be lower than that of instant setting grout. In addition, gelation is prolonged and unstable, resulting in variations in strength, making it difficult to improve homogeneous soil. Furthermore, if the gel time is prolonged, unreacted products will be produced, and there are problems in that it is not only impossible to confirm whether gelation will occur during injection, but also that the concentration of reaction products that have an impact on the environment is unknown.

In addition, for solution-type silica grout, the stable gelation region is around pH 2 and around pH 7 to 8, and in between, the gel time can vary significantly with a slight difference in pH, so the pH It was difficult to use either the instant setting region where pH is around 7 to 8 or the extremely long gel time where pH is around 2 to 3, and to use the gel time at an intermediate pH depending on the ground conditions and injection conditions ( (see Figure 1). Therefore, in order to obtain a pH value in a stable range, an excess amount of acid is required, and as a result, it is necessary to consider the influence of reaction products generated in the soil on the soil.
In this way, the injection material with excellent durability and permeability is silica grout in the non-alkaline range, but non-alkali silica grout has properties ranging from the instant setting range (pH around 8) to the ultra-long setting range (around pH 3). The problem is that it was difficult to set and apply the optimal gel time in the intermediate region as a slow-setting grout, and the silica concentration changes when converting the gel time between instant-setting grout and slow-setting grout, resulting in a significant change in strength. Therefore, it was difficult to continuously change gel time and strength according to ground conditions and injection conditions. Furthermore, it was difficult to continuously vary the gel time according to ground conditions and injection conditions without changing the silica concentration (without changing the strength). Of course, these were even more difficult in the alkaline region. Furthermore, Patent Document 3 describes a ground hardening method that does not introduce large amounts of sulfuric acid roots into the ground, but the hardening agents used are sulfuric acid and aluminum sulfate, and the idea is to adjust the chemical composition by adjusting the pH. be. However, the effect of grout containing sulfate radicals is not the pH but the concentration of sulfate radicals. However, Patent Document 3 describes how the injection material containing sulfate roots behaves in ground conditions and groundwater conditions, how the concentration of sulfate roots fluctuates in the ground improvement area, and how the concentration can be reduced to a range that does not affect the environment. There is no description of whether the sulfate ion concentration is controlled within a range that does not affect the environment.

Patent Document 1 describes a technique developed by the present applicant to reduce the concentration of sulfate ions, which are reaction products generated in the implanted ground. However, during injection, it is possible to grasp the behavior of the concentration of sulfate ions in the ground in real time according to the ground conditions, and to reduce the components that are generated in the ground that affect the environment to a predetermined concentration according to water quality standards or environmental standards. It has not yet been invented.

In this way, conventional Patent Document 1 describes the composition of an injection solution that reduces the generation of sulfate ions, but it is difficult to determine the concentration of sulfate ions in the implanted ground during the injection work based on the behavior of sulfate ions in the improved ground. It was not possible to control the concentration in real time to a level that did not affect the environment. In contrast, in the invention of Patent Document 1, the present inventors have determined that the concentration of sulfate ions in the injection ground during injection work does not affect the environment, depending on the ground conditions, groundwater flow conditions, and injection design. We have developed a ground injection method that can be performed in real time to keep the amount below the expected value. Furthermore, the present inventors have further developed the technology of Patent Document 1 by the present inventors based on the same principle, and have determined that the concentration of reaction products in the ground is not limited to the sulfate ion concentration, but also the water quality and soil We have developed a ground injection method that can manage the components that affect the environment, such as soil, to ensure that they fall within the range of water quality standards and soil environmental standards.

Patent No. 7146202 Special Publication No. 61-017970 Japanese Patent Application Publication No. 2000-328056 Patent No. 7072818

With water glass grout, gelation is unstable due to slight differences in pH and the amount of reactant, and gelation may not occur in loosely set areas, and gelation may be incomplete if the amount of gelling agent is reduced and the gel time is lengthened. There was a problem that strength could not be obtained. Similarly, it has been impossible to control and inject the concentration and composition of reaction products that affect the environment during construction.

Therefore, the present applicant has solved the above problem and has developed an injection system and injection method that can manage the concentration of the following reaction products and components in the injection ground on-site in real time for silica grout. .

Conventionally, a method of injecting an injection solution having a formulation that is in a neutral region in an injection region is already known. However, no technology existed to control the concentration of reaction products of the injection solution, which changes depending on the ground conditions, groundwater conditions, and injection design, within a range that does not affect the environment in ground improvement areas. It has been impossible to control the injection solution within a predetermined range during injection, that is, it has been virtually impossible to visualize and control the concentration of the reaction product during injection.

The present invention further develops the invention of Patent Document 1 of the present applicant, and takes the case of silica grout as an example, by continuously varying the gel time and the concentration of the reaction product on site, depending on the ground conditions and injection conditions. This has enabled an injection system and ground injection method with excellent environmental protection that allows the concentration of reaction products generated in the ground to be controlled within a predetermined range.

Injected ground generally consists of soft ground with different soil layers deposited on it, so injection rates are applied depending on soil type, purpose, and construction method (see Table 1). The present invention thoroughly consolidates such complex coarse-grained soil layers and fine-grained soil layers, has excellent environmental protection, is integrated as a whole, and has water-stopping and consolidation properties that affect the environment. The purpose of the present invention is to provide an injection management system with reduced environmental impact, which can control the concentration of reaction products or compositions in improved ground within a predetermined range in real time during injection work, and a ground injection method using the system. This method solves the problems of the conventionally used methods.

That is, the ground injection method of the present invention is a ground injection method in which silica grout is injected through an injection pipe inserted into the ground, and liquid A and B are combined above the ground or underground through the injection pipe, and the combined liquid is poured into the ground. A ground injection method that injects into
The A liquid is a water glass solution, the B liquid is a solution consisting of a reactant and water, and a plurality of drive devices for feeding the A liquid and the B liquid with an A liquid pump and a B liquid pump, respectively. and an inverter and a control device that collectively manages the plurality of drive devices, and controls the inverter to change the flow rate and merging ratio of the A liquid and the B liquid from an instant mixture to a slow mixture according to the ground condition. By continuously variable control of the formulation, the gel time and the concentration of the reaction product of the combined liquid of the A liquid and the B liquid can be continuously changed, without formulating an excessive amount of the reactant. The method is characterized in that the concentration of the reaction product in the ground improvement area is within a predetermined concentration necessary for setting the gel time and the ground is consolidated by injecting the reaction product at a confluence ratio that is the amount necessary for setting the gel time. It is something.
In the present invention, the gel time and the ion concentration of the reaction product of the combined liquid of the liquid A and the liquid B are continuously changed, the gel time and the ion concentration of the reaction product are visualized in real time, and the reaction agent is visualized in real time. It is preferable to consolidate the ground by keeping the ion concentration of the reaction product within a predetermined concentration necessary for setting the gel time without prescribing in an excessive amount.
In addition, in the present invention, a ground injection method is used in which non-alkaline silica grout, which is a combined liquid of liquid A and liquid B and has a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10, is injected into the ground. The B solution is a solution containing an acid, and the flow rate and merging ratio of the A and B solutions are continuously changed from an instant setting formulation to a slow setting formulation to a pH and silica concentration corresponding to the gel time. and continuously changing the ion concentration of the reaction product of the combined solution of the liquid A and the liquid B, visualizing the gel time and the ion concentration of the reaction product in real time, and prescribing the reactant in an excessive amount. It is preferable to consolidate the ground by injecting at a confluence ratio that is within a predetermined limit necessary for setting the gel time, without having to do so.

In the present invention, by understanding in advance the relationship between the gel time and the change in the ion concentration of the reaction product with respect to the continuous change in the confluence ratio of the liquid A and the liquid B, the reaction product in the ground improvement area is The ground can be consolidated by controlling the ion concentration within a predetermined concentration required for setting the gel time.

In addition, in the present invention, the flow rate and confluence ratio of the A liquid and the B liquid are controlled in advance by an inverter, and the gel time and the reaction product are By knowing the concentration of the reaction product in the improved ground, it is possible to know in real time whether or not the concentration of the reaction product in the improved ground is within a predetermined concentration before injecting it into the ground.

Furthermore, in the present invention, the concentration of the reaction product in the ground is such that the residual ion concentration of the reaction product in the ground becomes a predetermined concentration based on the ground condition and groundwater condition of the soil improvement area. By setting the flow rate and merging ratio of the liquid and the B liquid, the concentration of the reaction product in the improved ground can be set within a predetermined concentration and the ground can be consolidated.

Furthermore, in the present invention, when forming a ground improvement area by injecting non-alkali silica grout having a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10 as a ground injection material,
Based on the ground conditions and groundwater conditions of the ground improvement area, and based on the behavior of sulfate ions eluted into the ground, the injection ground is classified into the following (1) open system, (2) stagnation system, or (3) concentrated system. Classify as one of
(1) Open system: Groundwater flows outward from the concrete structure, and the sulfate ion concentration decreases. (2) Stagnant system: Groundwater flow stagnates, and the sulfate ion concentration hardly changes. (3) Concentration system: Ground where sulfate ions permeate from the surface of the concrete structure and become concentrated, increasing the concentration of sulfate ions Depending on the type of the classified injection ground, the concentration of sulfate ions in the injection ground increases. As the reduction factor (Y), set one or more selected from △1 to △7 below,
△1: Residual rate of sulfate ions in the improved ground when a non-injected part is provided in the ground improvement area and the ratio of the non-injected part is the elution rate of sulfate ions α ₁ △1 = 1 - α ₁
△2: Residual rate of sulfate ions in the ground improvement area, when the elution rate of sulfate ions into groundwater is α ₂ △ 2 = 1 - α ₂
△3: When the fixation rate of sulfate ions in the ground improvement area is set as the elution rate α ₃ , the residual rate of sulfate ions in the ground improvement area △3=1−α ₃
△4: When the substitution rate of sulfate ions of the sulfuric acid injection material by the non-sulfuric acid injection material or the low sulfuric acid injection material in the ground improvement area is the elution rate α ₄ , the sulfate ions in the ground improvement area Survival rate △4=1-α ₄
△5: When the substitution rate of the silica component in the ground injection material with colloid is the elution rate _α5 , the residual rate of sulfate ions in the ground improvement area △5=1− _α5
△6: When some or all of the sulfate ions are captured in the ground injection material, and the capture rate is set as the elution rate _α6 , the residual rate of sulfate ions in the ground improvement area is △6=1− _α6
△7: When the injection rate of the ground injection material in the ground improvement area is reduced and the reduction rate of the injection rate is set as the elution rate _α7 , the residual rate of sulfate ions in the ground improvement area is △7=1 -α ₇
Based on the reduction factor (Y) set according to the injection ground,
The ground injection material is made of a reactant formulation such that the sulfate ions derived from the non-alkali silica grout are 8,000 ppm or less as the average value (X) of the sulfate ion concentration remaining in the ground improvement area. You can choose something.

Furthermore, in the present invention, by continuously changing the confluence ratio of the A liquid and the B liquid, the gel time and the concentration of the reaction product in the improved ground can be adjusted depending on the ground condition, groundwater condition, and injection design. The injection liquid can be injected to a predetermined value accordingly.

Furthermore, in the present invention, as the silica grout, a grout with a relatively short gel time and a grout with a relatively long gel time are successively injected into the ground, and the grout with a short gel time is coarsely injected into the ground. The grout with a long gel time can be infiltrated as a secondary injection material.

Furthermore, in the present invention, the silica grout having the same silica concentration can be used while continuously changing the gel time.

Furthermore, in the present invention, the silica grout can be injected so as to obtain a gel time and silica concentration corresponding to the ground conditions while continuously changing the gel time.

Furthermore, in the present invention, the combined liquid of the liquid A and the liquid B can be injected into the ground by any of the injection methods 1) to 8) below.
1) Rod injection method 2) Double packer method 3) Point injection method 4) Multi-point simultaneous injection method 5) Column injection method 6) Instant setting/loose setting combined injection method 7) Multi-stage simultaneous injection method 8) Multi-hole simultaneous injection construction method

The present invention is a ground improvement method in which a combined liquid of liquids A and B is injected into the ground in a ground injection method in which silica grout is injected into the ground, and the concentration or composition of reaction products in the combined liquid A and B is It is assumed that the concentration of reaction products remaining in the ground improvement area varies or decreases depending on the ground conditions in the ground improvement area, ground water conditions, and injection design.As a result, the concentration of reaction products remaining in the injection ground or By controlling the inverters of liquids A and B within the range β = A / B, where the concentration of the components is below the concentration considered to have no effect on the environment, the gel time and the concentration of the reaction product or the concentration of the components can be reduced. This enables a ground injection method that reduces environmental impact by managing the water in real time during the injection process.

It is a figure showing the relationship between pH, gel time, silica concentration, and strength of non-alkaline silica grout. It is a figure showing the relationship between pH, gel time, silica concentration, and strength of non-alkaline silica grout. It is a figure showing the relationship between pH, gel time, silica concentration, and strength of non-alkaline silica grout. It is a graph showing the relationship between pH and gel time of a silica solution of non-alkaline silica grout. FIG. 1 is a diagram showing an overview of a conventional injection system. FIG. 2 is a block diagram showing details of an injection system in an embodiment of the invention. 1 is a diagram conceptually showing details of an injection system in an embodiment of the present invention. 1 is a diagram conceptually showing details of an injection system in an embodiment of the present invention. 1 is a diagram conceptually showing details of an injection system in an embodiment of the present invention. This is an injection model in which permeable grout was secondly injected after primary injection. It is an example of a graph showing the relationship between the ratio of A liquid and B liquid, gel time, and silica concentration. This is another example of a graph showing the relationship between the ratio of A liquid and B liquid, gel time, and silica concentration. This is yet another example of a graph showing the relationship between the ratio of liquids A and B, gel time, and silica concentration. This is yet another example of a graph showing the relationship between the ratio of liquids A and B, gel time, and silica concentration. This is yet another example of a graph showing the relationship between the ratio of liquids A and B, gel time, and silica concentration. This is yet another example of a graph showing the relationship between the ratio of liquids A and B, gel time, and silica concentration. It is a graph showing the elution rate and residual rate of sulfate ions from gel. It is a graph showing a change in sulfate ion concentration in a gel over time. It is a figure which shows the curing method of homogel and sand gel. It is a photograph diagram showing the curing status of a mortar specimen. FIG. 2 is a photographic diagram showing the condition of a mortar specimen after long-term curing of metal ion-containing non-alkali silica grout. It is a graph showing changes over time in mortar strength and pH after curing due to differences in curing conditions. It is a graph showing the influence of the mixing rate of sulfuric acid in the reactant on the pH of the curing medium. FIG. 2 is a diagram showing the state of a mortar surface on which an insoluble coating was formed after curing for 3 years in a silica sol containing the same volume of a sequestering agent as the mortar specimen. FIG. 3 is a photographic diagram showing the condition of a mortar specimen after curing for 16 and a half years in the same volume of homogel as the mortar specimen containing a sequestering agent, and the formation of an insoluble coating (masking silica) by the sequestering agent. It is an X-ray chart of a coating on the surface of mortar cured by immersion in homogel. FIG. 3 is a diagram showing the functions of sodium hexametaphosphate and a sequestering agent. It is a figure which shows the test situation which shows the effect of metal silica grout. It is a figure showing the concrete protection effect by masking silica and a masking separate method. It is a figure which shows the division of the injection part of different injection liquid in an injection area. FIG. 3 is a diagram showing changes in electrical conductivity due to dilution of an injection solution using a silica solution. FIG. 3 is a diagram showing the influence of primary injection of soil Ca or CB. FIG. 3 is a diagram showing an example of the relationship between the type of acid and gel time in non-alkali silica grout.

Embodiments of the present invention will be described in detail below with reference to the drawings.
In the ground injection method of the present invention, an injection pipe is inserted into the ground, and when silica grout is injected, liquids A and B are combined and injected into the ground through the injection pipe.

In the present invention, liquid A can be a water glass solution, and liquid B can be a reactant. In the present invention, an inverter is controlled using a plurality of drive devices that pump liquid A and a liquid B using a liquid A pump and a liquid B pump, respectively, and a control device that collectively manages an inverter and a plurality of drive devices. By continuously variable control of the flow rate and merging ratio of the combined liquid of liquids A and B according to the ground conditions, the concentration of reaction products or components of the combined liquid of liquids A and B can be continuously controlled. The soil is consolidated by varying the concentration of the reaction product or component in the soil improvement area to within a predetermined concentration.

In the present invention, by understanding in advance the relationship between the change in the concentration of reaction products or components with respect to continuous changes in the flow rate and confluence ratio of the combined liquid of liquids A and B, reaction generation in the ground improvement area can be achieved. At the time of injection, the flow rate of liquid A, the flow rate of liquid B, the flow rate of combined liquid, and the combined ratio can be set and injected into the ground using inverter control so that the concentration of the substance or component is within a predetermined concentration. The flow rates and merging ratios of the combined liquids of liquids A and B are controlled by an inverter, and changes in the concentration of reaction products or components in response to continuous changes in the flow rates of liquids A and B, the flow rates of combined liquids, and the merging ratios are controlled by an inverter. By knowing this, it is also possible to know in real time whether the concentration of reaction products or components in the improved soil is within a predetermined concentration range, and then inject it into the soil.

In the present invention, the combined liquid and the combined ratio are set so that the residual concentration of the reaction products or components eluted into the ground becomes a predetermined concentration based on the ground conditions and groundwater conditions of the ground improvement area, and the injection is carried out. You can also do this. In addition, by continuously changing the confluence ratio of liquids A and B, the concentration of reaction products or components in the improved ground can be adjusted to a value that reduces the environmental load depending on the ground conditions, groundwater conditions, and injection design. An injection solution can also be injected so that

In the present invention, as silica grout, when grout with a relatively short gel time and grout with a relatively long gel time are successively injected into the ground, the grout with a short gel time is injected as the primary injection material for coarsely injecting into the ground. However, grout with a long gel time can also be infiltrated as a secondary injection material. Furthermore, the silica grout having the same silica concentration can be used while continuously changing the gel time, or the silica grout can be injected to provide a gel time and silica concentration that correspond to the ground conditions.

In the present invention, by continuously changing the flow rates of liquids A and B through inverter control, the concentration of reaction products or components that are generated in the improved soil and have an impact on the environment can be reduced to reduce the environmental load. An injection solution can also be injected to achieve the desired value.

The invention will now be described using an example of a non-alkali silica grout. Since the gel time of non-alkali silica grout changes rapidly depending on the pH, it is almost impossible to set the gel time in an acidic region. In order to solve this problem, we used an injection system as shown in Figures 4 to 7, which makes it possible to continuously vary the pH and gel time as well as the concentration of the reaction product. It is possible to inject while controlling the pH and these according to the ground conditions and injection conditions.

Especially in soft soil layers, it enables ground improvement by setting the optimum gel time and strength for each soil layer, and even in the same soil layer or after primary injection of flash setting grout or suspension grout in one stage. By continuously changing the secondary injection of a slow setting mixture with optimally controlled gel time, it is possible to improve the ground by keeping the optimal strength constant or changing the optimal strength continuously, and improving the soil at the same time. It is possible to substantially "visualize" and control the concentration of reaction products or components produced within a predetermined range during the injection operation.
Note that the neutral pH region herein refers to a pH of approximately 10 or less (see FIG. 1).

Examples of the injection system of the present invention are shown below (see FIGS. 4 to 7). The material is injected from the material mixing section to the injection liquid mixing section, and from the injection liquid feeding section to the injection tube section through the pressure gauge and flow meter. Data is input in real time from the injection liquid sending section, pressure gauge/flow meter, and liquid sending pipe to the control section, is recorded in the recording section, and the mixture is adjusted in the material mixing section according to the ground conditions and injection conditions. Ru.

Next, in the injection systems shown in FIGS. 4 to 7, the materials used are adjusted in accordance with the ground conditions and injection conditions in the material mixing section, and are divided into liquid A and liquid B at the injection mixing section. In the material blending section, liquid A of the main compounding section, which is made of an acidic silica liquid containing a reactant, and liquid B, which is a silica solution, are arranged. The additive may be added to either the A liquid or the B liquid or the acid.

In the injection liquid sending section, an inverter, a pump, and a PQ (flow rate/pressure detector) are arranged respectively, and the injected liquid is adjusted by a controller, and the injection liquid is combined above ground or underground at the injection liquid injection section. The controller of the control section controls the material blending section, injection/liquid feeding section, and inverter, and transmits data to the recording section.

As shown in Figures 5 and 6, the A liquid and the B liquid may merge at the above-ground part of the injection tube, or may merge at the tip of the double tube, or they may merge at the tip of the double tube as shown in Figures 5 and 6. It may also be injected by merging from the tract (Fig. 7, Fig. 8). In addition, for single tube rod injection, the following injection methods 1) to 8) and various injection methods shown in Table 2 can also be applied. Incidentally, for the above-ground merging, the combined liquids A and B may be adjusted in a mixing tank in the injection liquid sending section shown in FIGS. 5 and 6 and sent to the injection pipe.
1) Rod injection method 2) Double packer method 3) Point injection method 4) Multi-point simultaneous injection method 5) Column injection method 6) Instant setting/loose setting combined injection method 7) Multi-stage simultaneous injection method 8) Multi-hole simultaneous injection construction method

FIG. 7 shows an example of a schematic diagram of an injection system implementing the present invention, and shows an example of an injection system using a diaphragm type dual grout pump (manufactured by Toyo Shoji Co., Ltd.). By using this injection system, the control unit (controller) can control the inverters of the A liquid pump and B liquid pump in conjunction with each other, depending on the ground conditions and injection conditions, to control the combined liquid of A liquid and B liquid. By variably managing the discharge amount and the flow rate ratio of each pump, it is possible to continuously change the discharge amount of the AB combined liquid and the ratio of the discharge amounts of the A liquid and the B liquid.
In addition, the silica concentration and the reactant concentration of liquid A and liquid B in the material blending section can be adjusted. At the same time, the concentration of reaction products can be controlled.

That is, in FIG. 6 (liquid A is an alkali silica solution (water glass + or silica solution + reactant) and liquid B is an acidic solution (acid or pH adjuster), as explained in FIG. 7), the material is transferred from the controller. By instructing the blending department to vary the amount of silica depending on the ground conditions and changing the ratio of the discharge amounts of liquids A and B, it is possible to continuously vary the gel time of the combined liquid A and B. Moreover, at the same time, the concentration of the reaction product can be varied continuously. Alternatively, the change in the concentration of the reaction product with respect to the discharge amount of the combined liquid of liquids A and B and the ratio of liquids A and B can be ascertained in advance through experiments (Tables 3 to 14, Figures 9 to 14). ), if the inverter is calibrated in advance before injection at the site, the concentration of the reaction product can be grasped in real time by controlling the inverter during injection. That is, visualization management can be performed substantially during injection work using the systems shown in FIGS. 5 to 7.

By changing the ratio of liquids A and B, it is possible to control the silica concentration to a predetermined concentration while varying the gel time, thereby controlling the concentration of the reaction product. For example, by controlling the flow rate ratio and combined discharge amount of liquids A and B using inverters for each of liquids A and B, it is possible to continuously vary the gel time and the concentration of the reaction product.

In addition, the injection system used to carry out the present invention may use a plunger pump, piston pump, or monopump in addition to the diaphragm pump, and is a multiple injection system that delivers at least liquid A and liquid B, An injection system having a control system that continuously varies the total flow rate of liquids A and B and the feeding ratio of liquids A and B using an inverter can be used.

In this way, by controlling the inverters of pump A and pump B to continuously vary the ratio of β=A/B, it is possible to continuously control the gel time and the concentration of the reaction product. can. In this way, the gel time of non-alkaline silica grout fluctuates due to slight differences in pH, which makes it difficult to prepare a formulation with a predetermined gel time, and at the same time, the concentration of reaction products can be measured on-site in real time. It can be easily solved.

As described above, the present invention allows the total amount of liquids A and B and the ratio (β=A/B) of liquids A and B to be continuously varied between instant setting and slow setting by inverter control. Since it is possible to control the gel time and the concentration of the reaction product of the slow-setting formulation, it is possible to set the gel time and the concentration of the reaction product corresponding to the set ratio.

In FIG. 5, by using liquid B as a preparation liquid for liquid A, the number of mixing tanks for raw materials in the material mixing section can be reduced.

Using the above method, the applicant has determined that the concentration α of the reaction product in the combined liquid A and B changes or decreases (reduces) depending on the ground conditions in the soil improvement area, ground conditions in the soil improvement area, groundwater conditions, and injection design. rate = residual rate = △) (Table 15), and as a result, the concentration (X) of the reaction product remaining in the injection ground is below the concentration (W) that is considered to have no effect on the environment, β = A. The present invention was completed by discovering that by controlling the inverters of liquids A and B within the range of /B, the gel time and the concentration of the reaction product can be controlled in real time during the injection operation.

A specific example will be explained below.
Examples 1 to 12 (Tables 3 to 14, Figures 9 to 14)
Tables 3 (a) to 14 (b) correspond to the combination of liquids A and B, the sulfate ion concentration and phosphate ion concentration which are the reaction products of the combined liquid of liquid A and liquid B, and β = A/B. The gel time, pH, and silica concentration are shown.
Further, FIGS. 9 to 14 show the relationship between gel time and silica concentration (ie, A-liquid B confluence ratio) corresponding to β=A/B.

From the above, it can be seen that by continuously varying β=A/B, the gel time can also be continuously varied in the silica concentration (strength) and the concentration of reaction products (sulfate ion, phosphate ion).
On the other hand, the applicant has clarified that the concentration (X) in the ground improvement area by injection of the reaction product of this injection liquid is greatly influenced by the ground conditions of the injection ground, groundwater conditions, and injection design conditions ( Patent Document 1).
Regarding the sulfate ion concentration, if the concentration of sulfate ions in the improved ground is X, and the elution rate of sulfate ions from the gel in the improved ground is α, then the residual rate of sulfate ions in the ground is △ = 1 - α. Formulate the injection liquid so that the concentration of sulfate ion residual rate △ is below the concentration X that does not affect the concrete (reactant concentration = a) so that β = A / B so that X is within W By injecting the discharge amounts of liquid A and liquid B by controlling the inverters for liquid A and liquid B, the concentration of reaction products in the ground can be kept within a predetermined value (W). On the other hand, the elution rate of sulfate ions from the gelled product of the silica mixture in laboratory experiments is shown in FIGS. 15 and 16 as α, and the concentration of sodium sulfate on the concrete specimen is shown in Table 16. From Table 16, W is the minimum concentration that does not affect concrete. From the above, the sulfate ion concentration corresponding to β=A/B in Figures 10 to 15 is an injection in which the residual rate of sulfate ions corresponding to ground conditions, groundwater conditions, and injection design conditions is 8000 ppm (=W) or less as shown in Table 16. It turns out that all you need to do is set the liquid formulation and control the inverters for liquids A and B.

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

[Effect of sulfate ions on concrete]
[experiment]
Assuming a case where groundwater remains stagnant (or stagnates) and there is almost no groundwater flow, it is assumed that the concentration of sodium sulfate aqueous solution, which is a water-soluble reaction product, acts on concrete (mortar) without changing for one year. The mortar specimens shown in Table 17(a) were cured for one year in a sodium sulfate aqueous solution with a sulfate ion concentration of 10,000 ppm, 8,000 ppm, 5,000 ppm, 3,000 ppm, and 0 ppm, and a uniaxial compressive strength test was conducted. The effect on concrete was investigated.

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

The results of immersing a concrete specimen in the sodium sulfate aqueous solution shown in Table 16 and observing the effect of the concentration of sulfate ions on the concrete are shown. From this, when there is no dilution by groundwater, the sulfate ion concentration that affects concrete structures within one year is 10,000 ppm or more, and 5,000 ppm or less has almost no effect even after one year. In Table 16, when the concentration of sodium sulfate is 8,000 ppm, it is a concentration that causes a slight effect in one year, but in reality, sulfate ions are diluted by groundwater, so the sulfate ion concentration in the injection ground is 8,000 ppm. ,000 ppm or less, it can be considered that no problem will occur in the mortar specimen.

[Experiment 1]
Elution test of SO ₄ ^-- from the gel of silica sol grout (water glass + sulfuric acid-based non-alkali silica grout) (1) Elution method Table 18 shows the silica sol formulation used in the test. Further, Table 19 shows the Toyoura sand consolidated by the silica sol in Table 18. A homogel or sand gel according to Tables 18 and 19 of approximately 5 mm in diameter and 10 cm in height is placed in a polypropylene container of 6.8 cm in diameter and 12.7 cm in length (volume 430 cm ³ ), and 200 mL of water is poured into it to diffuse the sulfate ions in the gel into groundwater. Alternatively, assuming that groundwater is flowing, the water was exchanged periodically and SO ₄ ^-- of the water was measured after 1, 3, 7, 28, and 60 days had elapsed. Water exchange was performed on the 1st, 3rd, 7th, and 28th day after measuring the SO ₄ ^-- concentration.

(2) Test results When silica sol grout is injected into the ground, the Na ⁺ ions and SO ₄ ^-- in the gel dissolve into the groundwater in a short period of time, leaving only the insoluble silica as a gel. .
It can be assumed that the SO ₄ ^-- eluted into the groundwater is diffused into the groundwater and disappears within a short period of time (FIG. 15, Table 20).
According to experiments, 40% of SO ₄ ^-- is eluted in about 1 day (residual rate in gel is about 60%), 85% is eluted in 1 month (residual rate in gel is about 15%), and in 2 months. Almost 100% is eluted (residual rate in gel is almost 0%). In the above, if (Y) is the factor that causes the sulfate ion concentration in the injected ground to be lower than the sulfate ion concentration contained in the injection solution, then (Y) is the elution rate of sulfate ions from the gel (α ) is related to the residual rate (=△) of sulfate ions in the gel (△=1−α).

[Effect of non-alkali silica grout on concrete in poured ground]
For non-alkali silica grout, the alkali that causes the deterioration of water glass grout has been removed using an acidic neutralizing agent. , (4) a non-sulfuric acid, (5) a non-sulfuric acid salt, and (6) a combination of any of the above (1) to (5) are used (Tables 21 to 23).
As mentioned above, sulfate ions are expected to be eluted into the curing water within a few months and become approximately constant (FIG. 16). In actual sites, there is an extremely large amount of groundwater relative to the solidified matter, and if the groundwater is diluted by flowing, the rate ^of elution and diffusion will be faster, but the rate of dilution and the amount of SO ₄ in the gel will increase. It is necessary to take into account that the survival rate is affected by ground conditions, groundwater conditions, the size of the injection area, etc. Therefore, it is effective to consider silica grout, which has almost no effect on the mortar specimen even without dilution. That is the application of non-alkaline silica grouts containing sequestering agents.

The mortar specimens in Table 17(a) were cured in a non-alkali silica gel containing the same volume of sequestering agent (Fig. 17), and the external appearance of the film deposited on the concrete surface was observed. It was confirmed that a white film was formed on the surface of the mortar in any of the injection materials (FIGS. 18 and 19). Therefore, for comparison, II (non-sulfuric acid-based/phosphoric acid-based, Table 21, No. 2), IIα (sulfuric acid-based/phosphoric acid-based, Table 21, No. 3) and IIδ (sulfuric acid-based, A coating of a mortar specimen cured on non-alkali silica (Table 21, No. 1) was taken, and its components were measured by fluorescent X-ray method, and its crystal structure was measured by X-ray diffraction method (Fig. 24, Table 24).

Table 24 shows the coating components, and FIG. 24 shows the X-ray diffraction chart. From these measurement results, it seems that the coating on the mortar surface is hydroxyapatite in II, hydroxyapatite or calcium phosphate in IIα, and calcite or vaterite in IIδ.

The coatings of II and IIα are formed using metal ion sequestering agents, and phosphoric acid, sodium phosphate, sodium hexametaphosphate, and phosphates are particularly notable. Organic acids and organic acid salts such as citric acid and succinic acid are also effective. FIG. 26 shows the function of a sequestering agent using sodium hexametaphosphate as an example. Non-alkaline silica grout containing a metal ion sequestering agent becomes passivated by chelate bonding with calcium and magnesium ions present on the mortar surface, and also reacts with the silica contained in the injection material to remove Ca ions from within the mortar. This is thought to form a poorly soluble film that suppresses the elution of sulfuric acid ions and the intrusion of sulfate ions from the outside (Figure 27).

(Strength test of mortar specimen in gel of non-alkaline silica grout containing sequestering agent)
Figures 18 and 19 show the conditions of a curing test in which the mortar in Table 26 was cured for 16 years with the non-alkali silica grout containing the sequestering agent shown in Table 23 using the curing method shown in Figure 18. The intensity ratios are shown in FIG. 20. The pH of the distilled water used to cure the mortar specimen is around 12, but when it disintegrates in the sulfate aqueous solution, the pH becomes 13 or more, indicating that the alkali in the mortar is eluted. On the other hand, when coated with non-alkaline silica containing a sequestering agent, the pH remains approximately at a neutral value. From this result, it is considered that the silica blocks the elution of alkali in the mortar (suppresses neutralization) and also prevents sulfate ions from entering the mortar. From the above, the function of the metal ion sequestering agent was confirmed (FIGS. 17 to 20, FIGS. 21 to 25).

(Effect of sequestering agent when a mortar specimen is wrapped in the same volume of sand gel of silica grout containing sequestering agent and cured in sand gel of sulfuric acid-based silica grout)
As shown in FIG. 26(a), the mortar in Table 17(a) is wrapped in the silica grout sand gel in Table 25(a) containing the sequestering agent marked △ in Table 27, and then It was cured in a homogel of sulfuric acid-based silica grout (FIG. 26(b)). After 6 months, the homogel and sand gel were disassembled (Fig. 26(c)) and the mortar was observed. There was no change, and a white coating of silica (masking silica) containing the metal ion sequestering agent was formed on the surface. (Fig. 26(d)), no deformation was observed in the mortar. Even when phenolphthalein was sprayed on the mortar surface, no red reaction occurred, and when the mortar was scratched (Figure 26(d)) and phenolphthalein was sprayed, only the scratches turned red, indicating the alkali inside the concrete. showed a reaction. Further, when the taken-out mortar specimen was immersed in water, the pH of the curing water was around neutral. This indicates that the masking silica layer prevents sulfate ions from entering the mortar and also prevents alkali from leaching out from inside the mortar specimen.

Below, we will explain the behavior of sulfate ions depending on ground conditions, groundwater conditions, and injection design.

(A) Open system: When gelled material in the ground is easily leached out of the injection area, or when groundwater is flowing outward from the concrete structure. For example, if the coast or river is close and flowing in that direction, if the groundwater level fluctuates with the tide, if the hydraulic gradient is outward, or if the ground is highly permeable such as sand and gravel. In some cases, sulfate ions decrease within a relatively short period of time, within 1-2 months. According to laboratory experiments conducted by the present inventors, almost all of the sulfate ions diffuse within 1 to 2 months (FIG. 15, 1 in Table 21, FIG. 16, Table 15). It is likely that the concentration of sulfate ions will eventually converge to that found in nature. Therefore, even if the sulfuric acid system shown in Table 1 is used, SO ₄ ions in the implanted ground are likely to be reduced in a short period of time. However, in actual sites, the elution rate of sulfate ions is thought to be affected by ground conditions, groundwater requirements, and the size of the consolidation area, so if these conditions are unclear, 2, 3, or It is desirable to use a combination of 1, 2, 3 and 4, 5. In addition, as described later, the injection rate of the suspended calcium-containing primary injection material in Table 1 was increased, and the secondary injection rate of the sulfate ion-containing silica grout was reduced, and at the same time, sulfate ions were fixed by calcium. can be achieved. In addition, in the chemical injection ground, the water quality change in the inspection hole located 10 m away from the injection area usually becomes almost constant in 1 to 2 months, so the concentration of the reaction product from the gel in the injection ground is usually 1 to 2 months. It can be assumed that it becomes almost constant due to diffusion in two months. Therefore, it can be considered that it is 1/10 or less compared to FIGS. 15 and 16.

(B) Stagnant system (stagnation system): If there is little groundwater flow and it is stagnant, _SO4 ions in this area will sooner or later move in the direction where the gradient of ion concentration is lower, that is, in the direction outside the injection range. Although it is diluted and eventually reduced to a concentration that has no effect, its elution rate is unknown. In this case, it is preferable to use 2 and 3 in Table 21 or a combination system of 1, 2, and 3 in Table 21 and E and F in Table 24. This allows the concrete to be protected until it is diluted to a concentration that does not affect the concrete, or even afterwards. Alternatively, sulfate ions can be used to protect concrete without being diluted.

(C) Concentration system: A case in which sulfate ions are not reduced and is more likely to be concentrated is a case in which sulfate ions that permeate from the surface of the concrete are concentrated by repeated drying and concentration. In this case, it is preferable to use 2 or 3 in Table 21 or E, F, or G in Table 24 in combination.
Furthermore, if the concrete is of high quality, sulfate ions will not enter and cause no problems (Table 17(b)).

(D) A non-implanted portion is provided within the implantation range, leaving an unconsolidated portion, and sulfate ions diffuse into that portion to reduce the overall sulfate ion concentration (FIG. 28).

(E) Sulfate ions in the injection material are passivated as calcium sulfate depending on the calcium content of the ground within the injection range or the calcium content of the calcium-containing injection material injected into the ground in advance. A calcium-containing alkaline implant region is provided within the implant range to passivate the sulfate ions in the implant as calcium sulfate. Alternatively, calcium contained in the ground and sulfate ions in the injection material become calcium sulfate and become passivated, thereby reducing the sulfate ion concentration. When the injected material is injected into the ground, the pH shifts to neutral depending on the soil pH and the soil gel time GTS is shortened (Figures 1 and 2). In particular, the Ca content of the ground to be injected has a large influence. Figure 30 shows an actual example in the field of injecting non-alkaline silica grout. From this data, sulfate ions in the ground will eventually be reduced after construction is completed, and the reduction rate of sulfate ions is, for example, the combination of 20,000 ppm of SO ₄ ^-- ions in Table 27 and Figure 31. When using a prescription, if Ca ion is 10,000 ppm in silica grout, the sulfate ion concentration can be considered to be reduced by approximately half or one-third.

(F) Inject 2, 3, 4, and 5 of Table 21 around the concrete structure to prevent intrusion into the concrete and passivate sulfate ions (Figure 28).
Furthermore, among the metal ion sequestering agents, in particular, with non-alkaline silica containing sodium hexametaphosphate, the amount of sulfate ions eluted from the gelled product is extremely small at the initial stage, being 30% of the sulfate ion concentration used. Therefore, the protective function of concrete is extremely high. The reason for this is presumed to be that SO ₄ ^-- ions were incorporated into the strong structure of hydroxyapatite bonded to calcium formed on the concrete surface.

The groundwater situation mentioned above can be understood as follows. The injection liquid or detection liquid is collected from the injection hole established in the injection ground and the injection area, or from an observation well established at a location away from the injection area, and the components and pH of the injection liquid in the groundwater are analyzed to determine the presence or absence of elution. , the elution rate and degree of dilution can be estimated. For example, a detection liquid such as a dye or an electrolyte may be injected through an injection hole, groundwater may be sampled from an observation well located far from the injection area, and conductivity and concentration may be measured and detected. This can be determined by changes in the groundwater level in the ground. It can also be determined by analyzing leakage water that has leaked into the concrete structure. In this way, electrical conductivity measurement and pH measurement can be used as sensors to determine the diffusion rate, dilution rate, and degree of dilution. FIG. 29 shows the relationship between silica solution concentration and conductivity. By injecting silica solution through the injection hole and measuring the conductivity of the liquid sampled from the observation well, it is possible to understand groundwater conditions and dilution conditions. Of course, this can also be determined based on past performance.
In addition, in the above, the sulfate ion concentration in the ground improvement area is reduced not only by decreasing the injection rate of the sulfate ion-containing injection solution, but also by the sulfate ions being captured (fixed) as calcium sulfate by calcium. do.
Furthermore, similarly, when suspension type grout is used as the calcium-containing grout in primary injection, the sulfate ion concentration in the ground improvement area is calculated by subtracting the injection rate of the primary injection material from the total injection rate. In addition to the reduction in sulfate ions due to a reduction in the injection rate of the injection material, the sulfate ions in the secondary injection material are also reduced by being captured (fixed) by the calcium in the primary injection material (Table 15, △3 , 4, 6, 7).
A specific example is shown below.

Assume that a formulation with a SiO ₂ concentration of 6 w/vol% is used as a silica grout that can be used for injection purposes. In Examples 1 to 10, after setting W ≧ From Tables 3 to 14 and Figures 9 to 14, it is clear that liquid A was prepared before injection by controlling the inverter for liquid A and liquid B so that the concentration of sulfate ions in the ground was within a concentration range that did not affect the concrete. Continuously vary the ratio (=β) of liquid B and check the gel time, sulfate ion concentration, changes in the value of β=A/B due to the inverter, and the corresponding sulfate ion concentration generated in the ground. By doing this, it is possible to grasp the gel time and the concentration of sulfate ions in the ground in real time during the actual injection, and therefore to ensure that the concentration of sulfate ions (X) generated in the ground is within W which causes problems for concrete. Injection can be managed to fit.

Assuming that the sulfate ion reduction factor is Y (=△), and assuming that the sulfate ion concentration will be diluted 10 times within one year from Figures 15 and 16, 90% of the sulfate ions will be eluted (elution rate =α ₂ =0.9), and the residual rate of sulfate ions Δ2=1−0.9=0.1. In the curve 1 in Figure 31, using the mixture marked with a circle in Table 27 and a sulfate ion concentration of 21,000 to 28,000 ppm, the sulfate ion in the ground is X = a × 0.4 × 0.1 = 872 ~ It becomes 1,120 ppm, and W≧X=872 to 1,120 ppm, so there is no problem. Also, if we set △2=0.3 for safety in a ground with cohesive soil,
X=A×a×Y(=Δ2(=0.3))=0.4×(21,000 to 28,000 ppm)×0.3=2,520 to 3,360 ppm. (a is the sulfate ion concentration in the injection solution)

Therefore, it can be seen that the range of curve 1 in FIG. 31 and the combinations marked with ○ in Table 27 can be used. In addition, if the applicable conditions are B or C in Table 24, that is, if the injection ground is in a stagnant or concentrated state, use the mixture of curve 3 in Figure 31 (x mark in Table 27) or take safety into consideration. By using the formulation of curve 4 (triangle mark in Table 27), the inverter control of β=A/B can be performed to control the predetermined gel time and reaction product (sulfate ion) concentration.

As mentioned above, it is now possible to design a mixture recipe that is safe for concrete based on the purpose of injection, construction method, and ground conditions, and quantitative injection design allows ground injection with reduced environmental impact. It becomes possible.

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

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

As an example, if the ground condition is open, the injection rate is 45%, 10% of which is suspended cement bentonite (CB) as the primary injection rate, and sulfuric acid-based silica grout as the secondary injection. reduced the rate. At the same site, CB was found to have solidified normally in the form of veins. In this case, of the injection rate A (=0.45), 0.1 was the primary injection material (CB) and 0.35 was the secondary injection material (silica sol grout). The reactant for the silica sol grout used was sulfate ion alone (No. 1 in Table 1).The formulation of the injection solution was as follows: ○ mark in Table 27, line 1 in Figure 31, gel time approximately 1,000 minutes, sulfate ion content injection of 25,000 ppm silica grout. The injection rate A was 45%, and the injection rates of CB:silica sol grout were 10% and 35%, respectively. If the injection rate of primary injection (CB) is 0.1 and the injection rate of secondary injection (silica sol grout) is 0.35, the sulfate ion concentration in the ground is X = 25,000 x 0.35 = 8,750 ppm. Become. When diluted ten times with groundwater, the elution rate of sulfate ions becomes α=0.9, and therefore the residual rate of sulfate ions in the ground becomes Δ=1−0.9=0.1. Therefore, the sulfate ion concentration of the implanted ground is X=8,750×0.1=875<W. Alternatively, the water permeability decreases due to the injection of the primary injection material and the elution rate of sulfate ions becomes α = 0.5. Therefore, the residual rate of sulfate ions in the injection ground is set as △ = 1 - 0.5 = 0.5. For example, X=8,750×0.5=4,375<W. Based on the above, we assumed the elution rate according to the ground conditions so that the primary injection material was injected and sulfuric acid-based silica grout was injected into the ground so that the concentration of sulfate ions in the ground was within W = 5,000 ppm. , it can be seen that it is sufficient to set the injection rate of the primary injection material. The same thing can be done using a suspension type grout, such as a calcium silicate type or slag type grout, or a calcium-containing solution type grout as the primary grout. In addition, if calcium-containing materials such as cement grout, lime, and slag are injected in the primary injection, 0.1 (α ₄ = 0.1, Table 15) of the injection rate of 0.4 will be added to the primary injection material. When injected as silica grout, the injection rate of silica grout is 0.3. Furthermore, the Ca content of cement, lime, and slag reacts with sulfate ions, and 0.1 of the sulfate ions out of the injection rate of 0.4 are fixed as CaSO ₄ (α ₃ =0.1, Table 15). Assuming that, the residual rate of sulfate ion concentration in the ground becomes Δ3=0.2. Therefore, X=25,000×0.2=5,000 ppm. Therefore, when 25,000 ppm of silica grout is injected, the sulfate ions in the ground will be X=5,000≦W. The fixation rate of sulfate ions by Ca ions when injected into Ca-containing ground can be predicted by mixing a sulfate-based injection solution with Ca-ion-containing soil. From the above values, if the inverter of A and B is controlled so that β = A / B is within the range of W and the gel time and sulfate ion production concentration are controlled, it is possible to achieve a ground injection method that meets the purpose of injection and has less environmental impact. becomes possible.

Furthermore, as shown in FIG. 28, by dividing the ground improvement area 2 so that, for example, the unimproved area 3 and the improved area 4 are equal, the sulfate ions can be diffused into the unimproved area and be reduced to 5000 ppm or less. (Δ1=0.5). Alternatively, a non-sulfuric acid-based silica solution may be injected into the unimproved portion 3 in FIG. 28 (Δ4). For example, water glass-heavy sodium alkaline water glass grout, other water glass-inorganic salts, inorganic acids, organic reactants, etc. may be injected into the unimproved area (Figures 28(a) and 28(b)). (c)(d)). In this case, alkaline water glass grout is not durable because unreacted water glass and alkali remain in the alkaline region, but excess acid in the surrounding area penetrates into the gel and neutralizes the alkali. , durability can be improved. In this case, it is preferable that the amount of alkaline content of the alkaline water glass grout injected into the injection area of the non-sulfuric acid injection material is the same as or smaller than the amount of acid content of the acidic silica grout around the injection area. This is because if the alkali content is large, the acidic silica gel may deteriorate. To confirm this, it is sufficient to wrap the gel of alkaline water glass grout with the same volume of sand gel of acidic silica grout, and then confirm that the strength of the sand gel of alkaline water glass grout increases.

That is, for example, the ground improvement area is injected together with a sulfate-based grout and one or more non-sulfate-based grouts, such as alkaline grout, calcium-containing grout, or suspension grout; The injection rate of calcium-containing grout or suspension grout is A1, and the injection rate of acidic silica grout is A2. When using alkaline grout, the durability of alkaline grout is obtained by neutralizing the alkali with the acid of acidic silica grout, and sulfate ions affect the structure at injection rate A2 of acidic silica grout. Set the injection rate so that it is assumed that this will not occur. In addition, when using calcium-containing grout or suspension grout as a non-sulfuric acid-based injection material, the injection rate A1 should be changed to the injection rate A2 of acidic silica grout, which is assumed to have no effect on the structure due to sulfate ions. Set it so that the rate is the same. Thereby, durability of the ground improvement area can be obtained.
In addition, in the above, the sulfate ion concentration in the ground improvement area is reduced not only by decreasing the injection rate of the sulfate ion-containing injection solution, but also by the sulfate ions being captured (fixed) as calcium sulfate by calcium. do.
Furthermore, similarly, when suspension type grout is used as the calcium-containing grout in primary injection, the sulfate ion concentration in the ground improvement area is calculated by subtracting the injection rate of the primary injection material from the total injection rate. In addition to the reduction in sulfate ions due to a reduction in the injection rate of the injection material, the sulfate ions in the secondary injection material are also reduced by being captured (fixed) by the calcium in the primary injection material (Table 15, △3 , 4, 6, 7).

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

In the present invention, the following procedure is used to form a ground improvement area by injecting non-alkali silica grout with a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10 as a ground injection material. Can be done. That is, first, based on the ground conditions and groundwater conditions of the ground improvement area, and based on the behavior of sulfate ions eluted into the ground, the injection ground is classified into the following (1) open system, (2) stagnation system, or (3) Classified as one of the concentrated systems.
(1) Open system: Groundwater flows outward from the concrete structure, and the sulfate ion concentration decreases. (2) Stagnant system: Groundwater flow stagnates, and the sulfate ion concentration hardly changes. (3) Concentration system: Ground where sulfate ions permeate from the surface of the concrete structure and become concentrated, increasing the sulfate ion concentration.

Next, one or more of the following Δ1 to Δ7 are set as the reduction factor (Y) for sulfate ions in the implanted soil according to the classified type of the implanted soil.
△1: Residual rate of sulfate ions in the improved ground when a non-injected part is provided in the ground improvement area and the ratio of the non-injected part is the elution rate of sulfate ions α ₁ △1 = 1 - α ₁
△2: Residual rate of sulfate ions in the ground improvement area, when the elution rate of sulfate ions into groundwater is α ₂ △ 2 = 1 - α ₂
△3: Residual rate of sulfate ions in the ground improvement area when the fixation rate of sulfate ions in the ground improvement area is set as the elution rate α ₃ △3 = 1 - α ₃
△4: When the substitution rate of sulfate ions of sulfuric acid injection material by non-sulfuric acid injection material or low sulfuric acid injection material in the ground improvement area is the elution rate α ₄ , the residual sulfate ions in the ground improvement area Rate △4=1-α ₄
△5: When the substitution rate of the silica component in the ground injection material by the colloid is the elution rate _α5 , the residual rate of sulfate ions in the ground improvement area is △5=1− _α5
△6: When some or all of the sulfate ions are captured in the ground injection material and the capture rate is set as the elution rate α ₆ , the residual rate of sulfate ions in the ground improvement area is △ 6 = 1 - α ₆
△7: When the injection rate of the ground injection material in the ground improvement area is reduced and the reduction rate of the injection rate is set as the elution rate α ₇ , the residual rate of sulfate ions in the ground improvement area is △ 7 = 1 - α ₇

Next, based on the above-mentioned reduction factor (Y) set according to the injection ground, sulfuric acid is used as a ground injection material such that the concentration of sulfate ions derived from the ground injection material does not affect the environment within the ground improvement area. The silica concentration is such that the average value (X) of the sulfate ion concentration remaining in the ground improvement area is 8,000 ppm or less, and the silica concentration satisfies the purpose of injection for the ground condition. Select a formulation that is compatible with the applicable construction method.

Above, an example of sulfate ion was shown as a reaction product. The same applies when setting the permissible range of phosphate ion concentration from the viewpoint of environmental integrity. Further, in the above, the sulfate ion concentration W=8000 ppm, but it goes without saying that β=A/B can be similarly managed even if the concentration is made more severe depending on the situation. In addition, in the present invention, if the amount of water glass in liquid A and the amount of water glass in liquid B are made the same using the system shown in FIG. Since the amount of water glass in the combined liquid does not change, the strength can be kept constant while changing the gel time. Furthermore, by setting the amount of water glass in liquid B to be different from the amount of water glass in liquid A, the gel time can be made variable and the strength can also be varied in accordance with the ground conditions and the purpose of injection. In this way, the present invention can continuously vary the gel time and strength through inverter control, and manage the concentration of reaction products or components in the improved soil to have a low environmental impact. It is an invention.

Further, it is also possible to apply other water quality standards or component concentrations based on soil environmental standards. For example, if the concentration of components such as heavy metals, reaction products, or organic substances that produce excessive amounts of BOD and COD in liquid A is higher than the environmental standard value, the problem is the ion concentration and component concentration that affect water quality standards. In this case, water or an insolubilizing agent may be used as the B liquid. When water is used as liquid B, by diluting liquid A, the concentration of problematic ions in the combined liquid A and B can be controlled within an acceptable range. In addition, in the patented invention by the present applicant (Patent Document 4), when the A liquid contains components such as heavy metals such as silica derived from geothermal water, the A liquid B can be By controlling the ratio of liquids, it is possible to stay within environmental standards. Additionally, when water glass is gelled using the following organic reactants, each organic reactant produces glycolic acid, acetic acid, and carbonic acid in the presence of an alkali, which react with the alkali in the water glass. Produces silicic acid gel.

In this case, if there are standard values for COD and BOD in the water quality standards and environmental standards, if water glass is used as the A liquid and an organic reactant is used as the B liquid, the BOD and COD of the combined liquid A and B will be The flow rates of liquids A and B can be managed by inverter control so that they fall within standards within the improved ground.

1, 1', 1" Liquid blending device 2, 2', 2" Infusion pump 3 Multiple tube outer tube 3' Multiple tube inner tube 4, 4', 4'' Liquid feed tube 5, 5', 5'' Pressure measuring device 6, 6', 6" Flow rate measuring device 7 Elevator 7' Injection tube depth gauge 8 Controller 9 Inflow section from the inner tube to the injection tube tip 9' Injection tube tip 10, 10', 10" From the pressure gauge to the controller Information notification circuit 11, 11', 11'' Information notification circuit from the flow meter to the controller 12 Information notification circuit from the injection depth meter to the controller 13, 13', 13'' Instruction circuit from the controller to the injection pump 14 Injection material combination Adjustment device 15 Instruction circuit 16 from the controller to the injection material combination adjustment device Instruction circuit 17, 17', 17'' from the controller to the elevator Indication circuit A from the controller to the compounding liquid mixing device Rapid setting reaction compounding liquid B Main material compounding Solution C Reactant mixture solution

Claims (12)

In a ground injection method in which silica grout is injected through an injection pipe inserted into the ground, a ground injection method in which liquid A and B are combined above ground or underground through the injection pipe and a combined liquid is injected into the ground,
The A liquid is a water glass solution, the B liquid is a solution consisting of a reactant and water , and a plurality of drive devices for feeding the A liquid and the B liquid with an A liquid pump and a B liquid pump, respectively. and an inverter and a control device that collectively manages the plurality of drive devices, and controls the inverter to change the flow rate and merging ratio of the A liquid and the B liquid from an instant mixture to a slow mixture according to the ground condition. By continuously variable control of the formulation , the gel time and the concentration of the reaction product of the combined liquid of the A liquid and the B liquid can be continuously changed, without formulating an excessive amount of the reactant. The method is characterized in that the concentration of the reaction product in the ground improvement area is within a predetermined concentration necessary for setting the gel time and the ground is consolidated by injecting the reaction product at a confluence ratio that is the amount necessary for setting the gel time. Ground injection method. By continuously changing the gel time and the ion concentration of the reaction product of the combined liquid of the A liquid and the B liquid, the gel time and the ion concentration of the reaction product are visualized in real time, and the reactant is prescribed in an excessive amount. 2. The ground injection method according to claim 1, wherein the ion concentration of the reaction product is set within a predetermined concentration necessary for setting the gel time to solidify the ground. A ground injection method in which non-alkaline silica grout , which is a combined liquid of liquid A and liquid B and has a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10, is injected into the ground,
The B solution is a solution containing an acid, and the flow rate and merging ratio of the A and B solutions are continuously changed from an instant setting formulation to a slow setting formulation to a pH and silica concentration corresponding to the gel time,
By continuously changing the gel time and the ion concentration of the reaction product of the combined liquid of the A liquid and the B liquid, the gel time and the ion concentration of the reaction product are visualized in real time, and the reactant is prescribed in an excessive amount. 2. The ground injection method according to claim 1, wherein the ground is consolidated by injecting at a confluence ratio that falls within a predetermined limit necessary for setting a gel time, without having to do so. By understanding in advance the relationship between the gel time and the change in the ion concentration of the reaction product with respect to continuous changes in the confluence ratio of the liquid A and the liquid B, the ion concentration of the reaction product in the ground improvement area can be adjusted to the gel time. 2. The ground injection method according to claim 1, wherein the ground is consolidated by controlling the concentration within a predetermined concentration required for setting. The flow rate and merging ratio of the A liquid and the B liquid are controlled in advance by an inverter, and the gel time and the concentration of the reaction product are known for continuous changes in the flow rate and merging ratio of the A liquid and the B liquid. 2. The ground injection method according to claim 1, wherein the reaction product is injected into the ground after determining in real time whether the concentration of the reaction product in the improved ground is within a predetermined concentration range. As the concentration of the reaction products in the ground, the flow rates of the A liquid and the B liquid are determined so that the residual ion concentration of the reaction products in the ground becomes a predetermined concentration based on the ground condition and groundwater condition of the soil improvement area. 2. The ground injection method according to claim 1, wherein the concentration of the reaction product in the improved ground is set within a predetermined concentration by setting a confluence ratio. When forming a ground improvement area by injecting non-alkali silica grout with a silica concentration of 1 to 40 w/vol% and a pH of 1 to 10 as a ground injection material,
Based on the ground conditions and groundwater conditions of the ground improvement area, and based on the behavior of sulfate ions eluted into the ground, the injection ground is classified into the following (1) open system, (2) stagnation system, or (3) concentrated system. Classify as one of
(1) Open system: Groundwater flows outward from the concrete structure, and the sulfate ion concentration decreases. (2) Stagnant system: Groundwater flow stagnates, and the sulfate ion concentration hardly changes. (3) Concentration system: Ground where sulfate ions permeate from the surface of the concrete structure and become concentrated, increasing the concentration of sulfate ions Depending on the type of the classified injection ground, the concentration of sulfate ions in the injection ground increases. As the reduction factor (Y), set one or more selected from △1 to △7 below,
△1: Residual rate of sulfate ions in the improved ground when a non-injected part is provided in the ground improvement area and the ratio of the non-injected part is the elution rate of sulfate ions α ₁ △1 = 1 - α ₁
△2: Residual rate of sulfate ions in the ground improvement area, when the elution rate of sulfate ions into groundwater is α ₂ △ 2 = 1 - α ₂
△3: When the fixation rate of sulfate ions in the ground improvement area is set as the elution rate α ₃ , the residual rate of sulfate ions in the ground improvement area △3=1−α ₃
△4: When the substitution rate of sulfate ions of the sulfuric acid injection material by the non-sulfuric acid injection material or the low sulfuric acid injection material in the ground improvement area is the elution rate α ₄ , the sulfate ions in the ground improvement area Survival rate △4=1-α ₄
△5: When the substitution rate of the silica component in the ground injection material with colloid is the elution rate _α5 , the residual rate of sulfate ions in the ground improvement area △5=1− _α5
△6: When some or all of the sulfate ions are captured in the ground injection material, and the capture rate is set as the elution rate _α6 , the residual rate of sulfate ions in the ground improvement area is △6=1− _α6
△7: When the injection rate of the ground injection material in the ground improvement area is reduced and the reduction rate of the injection rate is set as the elution rate _α7 , the residual rate of sulfate ions in the ground improvement area is △7=1 -α ₇
Based on the reduction factor (Y) set according to the injection ground,
The ground injection material is made of a reactant formulation such that the sulfate ions derived from the non-alkali silica grout are 8,000 ppm or less as the average value (X) of the sulfate ion concentration remaining in the ground improvement area. The ground injection method according to claim 1, wherein the ground injection method is selected from the following. By continuously changing the confluence ratio of the A liquid and the B liquid, the gel time and the concentration of the reaction product in the improved ground can be made to a predetermined value depending on the ground condition, groundwater condition, and injection design. The ground injection method according to claim 1, wherein the injection liquid is injected into the ground. As the silica grout, a grout with a relatively short gel time and a grout with a relatively long gel time are successively injected into the ground, and the grout with a short gel time is injected as a primary injection material to be coarsely injected into the ground, 2. The ground injection method according to claim 1, wherein the grout having a long gel time is injected as a secondary injection material. 2. The ground injection method according to claim 1, wherein the silica grout having the same silica concentration is used while continuously changing the gel time. 2. The ground injection method according to claim 1, wherein the silica grout is injected to obtain a gel time and silica concentration corresponding to ground conditions while continuously changing the gel time. The ground injection method according to claim 1, wherein the combined liquid of the liquid A and the liquid B is injected into the ground by any of the following injection methods 1) to 8).
1) Rod injection method 2) Double packer method 3) Point injection method 4) Multi-point simultaneous injection method 5) Column injection method 6) Instant setting/loose setting combined injection method 7) Multi-stage simultaneous injection method 8) Multi-hole simultaneous injection construction method