Ground injection method and ground injection device

Abstract

To provide a ground injection method and a ground injection device which use non-alkali silica grout to instantaneously and continuously change gel time and can obtain the optimal gel time and solidification strength according to the ground conditions and injection conditions without using excessive acid.SOLUTION: In this ground injection method, silica grout is injected through an injection pipe inserted into the ground. A liquid A and a liquid B are passed through the injection pipe to join above ground or underground, and the mixed injection liquid is injected into the ground. The liquid A is a solution that contains water glass, and the liquid B is a solution that contains a reaction agent. Multiple drive devices that send these liquids with a liquid A pump and a liquid B pump, an inverter, and a control device that collectively manages multiple drive devices are used to control the inverter to continuously and variably control the flow rate and joining ratio of the liquid A and B according to the ground conditions and injection purposes, and the injection solution with a predetermined gel time and silica concentration, which is mixed in the pipeline from the aboveground or underground junction to the injection pipe outlet, is injected into the ground.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an environmentally friendly injection consolidation method for soft ground using silica grout, and more particularly to a ground injection method and device that homogeneously and firmly consolidates or stops water in soft or leaky ground by continuously varying the gel time and the concentration of environmentally impacting ions in accordance with the ground conditions, and that manages the concentration of environmentally impacting ions generated in the injected ground.

[0002] Soft ground is usually a weak ground formed by alternating layers of coarse and fine soil. It is necessary to inject a consolidating agent into the ground to consolidate it homogeneously and with low environmental impact. [Background technology]

[0003] In recent years, the frequency of earthquakes has increased, construction work has become longer due to the large-scale excavation work, and an increase in the number of construction works that require safe operation under complex ground conditions has led to a demand for ground improvement injection technologies that have excellent long-term durability, excellent penetration and solidification properties below the groundwater table, and are safe for ground structures and water quality.

[0004] In order to meet this demand, the applicant has already developed and put into practical use a non-alkaline silica grout (see FIG. 1). As shown in FIG. 2, non-alkaline silica grout includes medium to acidic silica grout (silica sol grout) with a pH of about 1 to 10, which is made by neutralizing the alkali of water glass with acid, colloids in which the alkali of water glass is removed by ion exchange and the grains are increased to stabilize it as a weak alkali, and silica grout (active composite silica grout) with a pH of 1 to 10, which is made of metal silicon, water glass, and acid. The applicant has also proposed a technology described in Patent Document 1 regarding the reduction of reaction products in the ground of non-alkaline silica grout. Since the gel time of any of the non-alkaline silica grouts can be set from several seconds to several tens of hours, not only is there no need to worry about gelling even if a large amount of injection solution is prepared and left, but also a large amount of injection solution can be pumped over a long period of time, and after being injected into the ground, it gels reliably, has low viscosity, and has good permeability (see FIG. 1).

[0005] As can be seen from Figures 1 and 2, non-alkali silica grout has a short gel time near neutral pH and a significantly longer gel time near pH 2, showing stable gel times in that range, but the gel time changes suddenly in the intermediate pH range, making it impossible to inject grout with a gel time corresponding to a specified pH. For this reason, in actual injection, the only options were to inject a flash-setting grout, or to inject an injection solution with a pH of 1 to 2 and an extremely long gel time, or to frequently use a combination of these in combination.

[0006] On the other hand, as a method for injection into soft ground, the following method has been conventionally known.

[0007] (1) Rod injection method This method uses an aqueous solution of a reactant or a suspension containing cement material (liquid A) and an aqueous solution of water glass (liquid B) as consolidation materials, which are injected into the ground while being joined together using a Y-shaped pipe. However, gaps are formed between the boring rod and the ground, and the consolidation material may gush out onto the ground surface from these gaps, or the injection liquid may escape through coarse layers, making it difficult to consolidate the fine-grained soil layer or to consolidate the specified area.

[0008] (2)Double pipe injection method This method uses water glass as liquid A and a gelling agent as liquid B, and these two are joined at the tip of a double pipe installed in the ground, and a grout mixture that will solidify even in a short gelling time is injected. With this method, the short gelling time prevents the grout from spurting out above ground along the periphery of the rod, but because the gelling time is short, the grout can only solidify in vein-like patterns in the coarse layer, and cannot penetrate between the soil particles. This makes it easy for the spring water and sand to collapse during excavation.

[0009] (3) Double pipe composite injection method In order to solve the above problems, a ground injection method has been developed in which a seal with a packing effect is first formed by filling the gap between the injection pipe and the ground with an injection material with a short gelling time, and a consolidated layer consisting mainly of veins that fill the rough layers and the boundary surfaces of the layers is formed, and then an injection material with a long gelling time is injected into the area where the injection material with a short gelling time has already been injected, breaking the seal. This method aims to ensure that the injection material with a long gelling time penetrates the target and solidifies, since it does not escape from the surroundings of the injection pipe or the rough layers (Patent Document 2).

[0010] The invention described in Patent Document 2 involves mixing a reactant with a main compound liquid to form a grout. A water glass compound liquid or a mixed liquid of water glass and a reactant is used as the main compound liquid A, and a water glass solution or a reactant solution containing a quick-setting agent is mixed with this as liquid B.

[0011] Specifically, a quick-setting grout made by mixing water glass and a reactant is injected, and then a penetrating grout made of an alkaline penetrating grout is injected. Alternatively, a reactant is mixed with an acidic water glass to inject a quick-setting grout, and then only the acidic water glass is injected. The quick-setting grout is injected primarily while the mixture of the reactant with the base material is turned on and off, and then the penetrating grout is switched to for the secondary injection.

[0012] Furthermore, when the pH of the water glass mixture becomes alkaline, the gelation becomes unstable, or the gel time becomes infinite and the mixture stops gelling (Fig. 1).To deal with this problem, a method is used in which water glass is mixed with acid water glass and the instant-setting grout is injected, and then acid water glass alone, or acid water glass with a slow-setting reactant added, is injected by switching the injection process on and off, but this is extremely complicated, and since the gelation of acid water glass progresses during the mixture, the gel time and pH of the injection solution actually injected are unclear.

[0013] In addition, the stable gelling region for solution-type silica grout is a region where the pH is around 2 and a region where the pH is around 7 to 8, and the gel time varies greatly with a slight difference in pH between these two regions, so it was difficult to use either the instant setting region where the pH is around 7 to 8 or the very long gel time region where the pH is around 2 to 3 depending on the ground conditions and injection conditions (see Figure 1). Therefore, an excess of acid was required to obtain a pH value in the stable region, and as a result, it was necessary to consider the impact on the ground of the reaction products generated in the ground.

[0014] Thus, as an injection material with excellent durability and permeability, there is silica grout in the non-alkaline region, but it is difficult to set and apply the optimal gel time of the non-alkaline silica grout as a slow-setting grout in the intermediate region between the instantaneous setting region (pH is around 8) and the long-setting region (pH is around 3). In addition, the combined use of instantaneous setting grout and slow-setting grout is complicated to apply, and since the pH and gel time change rapidly, it is difficult to continuously change the gel time according to the ground conditions and injection conditions. Of course, in the alkaline region, these are even more difficult. Furthermore, Patent Document 3 describes a ground hardening method that does not bring a large amount of sulfate ions into the ground, and the hardening agents used are sulfuric acid and aluminum sulfate. However, this method does not have the idea of ​​controlling the generation of sulfate ions in the ground within a predetermined range by instantly and continuously changing the gel time according to the ground conditions and the purpose of injection, and does not show a method of controlling the sulfate ion concentration within a range that does not affect the environment based on the relationship between the gel time and the concentration of sulfate ions, which are reaction products.

[0015] In Patent Document 1, the applicant has proposed a technology for reducing the concentration of sulfate ions, which are reaction products generated in the ground after injection. However, it has not yet been possible to grasp the behavior of the concentration of sulfate ions in the ground during injection or the ground conditions in real time, or to reduce the components that affect the environment generated in the ground to the specified concentration of water quality standards or environmental standards. In addition, the technology described in Patent Document 4 is a method in which liquid A and liquid B are mixed in batches and then injected, and it is not possible to instantly and continuously change the flow rate and the joining ratio of liquid A and liquid B to inject them. Furthermore, the technology described in Patent Document 5 is a system in which liquid A is an acidic silica solution containing water glass and an acidic reactant, and liquid B is an alkaline silica solution containing water glass, and in the method in which liquid A and liquid B are mixed and injected, the gel time is changed by changing the ratio of liquid A and liquid B. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Patent No. 7146202 [Patent Document 2] Special Publication No. 61-017970 [Patent Document 3] JP 2000-328056 A [Patent Document 4] Patent No. 5017488 [Patent Document 5] Patent No. 7212423 Summary of the Invention [Problem to be solved by the invention]

[0017] In the alkaline region, gelation is unstable due to slight differences in the pH of the water glass grout or the amount of reactant, and in the slow-setting region, gelation does not occur.Furthermore, if the amount of gelling agent is reduced and the gel time is extended, gelation is incomplete and strength cannot be obtained.

[0018] Therefore, the present invention provides an improved ground injection method and ground injection device that uses a non-alkaline silica grout as a permeable grout.

[0019] Non-alkaline silica grouts include silica grouts in which alkali, a factor in the deterioration of water glass grouts, has been removed with acid, and silica grouts containing silica colloids derived from the metal silicon method or geothermal water. These non-alkaline silica grouts are excellent in that they gel reliably from the instantaneous setting region to the slow setting region, and reliably harden from the high silica concentration region to the low silica concentration region, but in the acidic region, the gel time varies greatly with a slight difference in pH, so it is impossible to adjust the gel time, and they can only be used in the stable gel time region of around pH 1 to 3, which lasts several tens of hours, or in the instantaneous setting region of several seconds to several tens of seconds (see Figure 1).

[0020] The object of the present invention is to provide a ground grouting method and a ground grouting device which can instantaneously and continuously change the gel time by using a non-alkali silica grout, thereby obtaining optimal gel time and solidification strength according to the ground conditions and injection conditions without using excessive acid. [Means for solving the problem]

[0021] In Patent Document 5, the acidic silica solution of Liquid A itself undergoes gelation in the base mixture in the grout blending section of FIG. 4, so the pH and gel time of the combined liquid of Liquid A and Liquid B fluctuate during injection of the combined liquid. In contrast, in the present invention, Liquid A is a water glass solution and Liquid B is a reactant solution, so the gel time and pH of the combined liquid are always constant depending on the mixture ratio during injection, and the combined liquid having the exact pH and gel time mixed in the pipeline from the aboveground or underground junction to the outlet of the injection pipe can be injected. When the combined liquid of Liquid A and Liquid B is simply injected, it may happen that Liquid A and Liquid B are injected into the ground as laminar flows without being mixed. In this case, the grout injected into the ground is not mixed, and cannot be said to have the exact pH and gel time. Therefore, in the present invention, there is no need for a production section for producing an acidic silica solution, as in the grout blending section of Patent Document 5. Furthermore, if a grout solution delivery section in which the merging ratio of liquid A and liquid B is accurately and continuously controlled by the control section shown in Figures 4 and 5 is not used as in the present invention, the grout solution injected into the ground cannot be said to have an accurately specified pH and gel time even if liquid A and liquid B are simply merged and mixed. Thus, the present invention makes it possible to inject a mixed solution having an accurately specified pH and gel time into the ground only when the above-mentioned two elements are present. Furthermore, in the present invention, the merged solution having the specified gel time and pH is accurately produced by mixing by aboveground or underground merging of the injection pipe and injected into the ground, so there is an advantage that a simple structure is sufficient. In this way, in this invention, without using a batch system as in conventional methods, the turbulence generated by the confluence of liquids A and B in the pipeline mixes liquids A and B, and an injection solution with a specified pH and gel time can be instantly and continuously formulated, so that the pipeline from the confluence of liquids A and B to the tip of the injection pipe functions as an injection device with the ability to mix liquids A and B. As a result, a ground improvement method and injection device capable of injecting an injection solution with a specified pH and gel time into the ground has been successfully invented.

[0022] As described above, the conventional invention described in Patent Document 1 describes a compounding composition of the grout solution that reduces the generation of sulfate ions, but it does not allow the concentration of sulfate ions in the injected ground to be controlled in real time, instantaneously, and continuously to a concentration that does not affect the environment during the injection work, based on the behavior of sulfate ions in the improved ground. In contrast, the present inventors have realized in the invention described in Patent Document 1 that, in response to the ground conditions, groundwater flow conditions, and injection design, the concentration of sulfate ions in the injected ground during the injection work is adjusted to a value that is considered to have no effect on the environment, by mixing liquid A containing water glass and liquid B containing sulfate ions, and instantaneously and continuously variably controlling the flow rates and mixing ratio of liquid A and liquid B, thereby making it possible to improve the ground without prescribing an excessive amount of a reactant containing sulfuric acid. In addition, since it can be formulated within a predetermined concentration required for setting the gel time, the pipeline for the combined liquid after the confluence of liquid A and liquid B itself becomes a mixing device for liquid A and B, and the sulfuric acid concentration of liquid B and / or the sulfuric acid concentration in the combined liquid of liquid A and B is within the range of 10% or less, which is not deleterious, that is, it is possible to perform ground improvement safely with little environmental impact as a manufacturing device for grouting liquid. Furthermore, the present inventors have further developed the invention described in Patent Document 1 by the present inventors using a similar principle, and have developed a ground improvement method that can control not only the sulfate ion concentration in the reaction product in the ground, but also components that affect the environment such as water quality and soil during ground injection, such as BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), and heavy metals, so that they can be controlled within the range of water quality standards and soil environmental standards.

[0023] 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, in which liquid A and liquid B are passed through the injection pipe to be mixed on the ground or underground, and the mixed liquid is injected into the ground, The method is characterized in that a solution containing water glass is used as the A liquid, a solution containing a reactant is used as the B liquid, and the A liquid and the B liquid are pumped by a plurality of drive devices, an inverter, and a control device which collectively controls the plurality of drive devices, and the inverter is controlled to continuously variably control the flow rates and the joining ratio of the A liquid and the B liquid according to the ground conditions and the injection purpose, thereby injecting the injection liquid having a predetermined gel time and silica concentration mixed in the pipeline from the aboveground junction or the underground junction to the discharge port of the injection pipe into the ground.

[0024] In the ground grouting method of the present invention, it is preferable that a solution containing sulfate ions is used as the liquid B, and the sulfuric acid concentration of the liquid B and / or the grouting solution is 10% or less.

[0025] Furthermore, in the ground injection method of the present invention, when injecting an injection solution having a predetermined gel time and silica concentration mixed in the pipeline from the aboveground junction or the underground junction to the discharge port of the injection pipe, the ion concentration of the reaction product is continuously changed to grasp the gel time and the ion concentration of the reaction product in real time, and the ground can be consolidated within the predetermined concentration required to set the gel time without prescribing an excessive amount of the reactant.

[0026] Furthermore, in the ground injection method of the present invention, the injection liquid is a non-alkaline silica grout having a silica concentration of 1 to 40 w / vol%, a pH of 1 to 10, and a gel time of 5 seconds to 7 days at 20°C, and an acid-containing solution is used as the B liquid, and the confluence ratio β of the A liquid and the B liquid is set to β=A / B=0.5 to 2.0. The flow rates and confluence ratio of the A liquid and the B liquid are variably controlled so that the pH and silica concentration correspond to the gel time continuously from the fast-setting mix to the slow-setting mix, and thereby the injection liquid having a predetermined gel time and silica concentration can be injected into the ground.

[0027] Furthermore, in the ground grouting method of the present invention, the flow rates and the confluence ratio of the A liquid and the B liquid are continuously variably controlled from a quick-setting mix to a slow-setting mix, and when the resulting grout is injected into the ground, the confluence ratio at the start of injection can be variably controlled so that the pH of the grout starts on the acidic side.

[0028] Furthermore, in the ground injection method of the present invention, the flow rates and confluence ratios of the A liquid and the B liquid can be set based on the ground conditions and groundwater conditions in the ground improvement area so that the residual ion concentration of the reaction product in the ground becomes a predetermined concentration, thereby making it possible to solidify the ground by bringing the concentration of the reaction product in the ground within a predetermined range.

[0029] Furthermore, in the ground injection method of the present invention, the injection liquid is a non-alkali silica grout containing sulfate ions, having a silica concentration of 1 to 40 w / vol% and a pH of 1 to 10, and the ground is an area adjacent to a concrete structure or an area adjacent to a concrete structure to be constructed after excavation, Based on the ground conditions and groundwater conditions in the ground improvement area, the injected ground is classified into one of the following types based on the behavior of the sulfate ions dissolved in the ground: (1) open system, (2) stagnant system, or (3) concentrated system. (1) Open system: Groundwater flows outward from the concrete structure, and the sulfate ion concentration decreases through dilution. (2) Stagnant system: Ground where groundwater flow is stagnant and sulfate ion concentration hardly changes (3) Concentration system: Sulfate ions penetrate the surface of the concrete structure and are concentrated in the ground, increasing the sulfate ion concentration. According to the type of the injection ground classified as above, one or more factors selected from the following △1 to △7 are set as a reduction factor (Y) of sulfate ions in the injection ground, △1: The residual rate of sulfate ions in the improved ground when a non-injected portion is provided within the ground improvement area and the ratio of the non-injected portion is the sulfate ion elution rate α1. △1=1-α1 △2: The residual rate of sulfate ions in the ground improvement area when the dissolution rate of sulfate ions in groundwater is α2. △2=1-α2 △3: The residual rate of sulfate ions in the ground improvement area when the fixed rate of sulfate ions in the ground improvement area is the elution rate α3. △3 = 1-α3 △4: When the replacement rate of sulfate ions of the sulfuric acid grout by the non-sulfuric acid grout or the low-sulfuric acid grout in the ground improvement area is the dissolution rate α4, the remaining rate of sulfate ions in the ground improvement area is △4=1-α4 △5: When the replacement rate of the silica component in the ground grouting material by colloid is the dissolution rate α5, the remaining 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 grouting material and the capture rate is the elution rate α6, the remaining rate of sulfate ions in the ground improvement area is △6=1-α6△7: When the injection rate of the ground grouting material in the ground improvement area is reduced and the reduction rate of the injection rate is the elution rate α7, the remaining rate of sulfate ions in the ground improvement area is △7=1-α7 Based on the reduction factor (Y) set according to the injection ground, the ground injection material can be selected from a reactant formulation in which the sulfate ions derived from the non-alkali silica grout have an average sulfate ion concentration (X) remaining in the ground improvement area of ​​8,000 ppm or less.

[0030] Furthermore, in the ground injection method of the present invention, the mixing ratio of the A liquid and the B liquid is continuously changed from a quick-setting mix to a slow-setting mix, so that the injection liquid can be injected into the ground so that the gel time and the concentration of the reaction product in the improved ground become predetermined values ​​according to the ground conditions, groundwater conditions, and injection purpose.

[0031] Furthermore, in the ground injection method of the present invention, the silica grout is injected into the ground in succession from a quick-setting mix to a slow-setting mix, and the grout with a short gelling time is injected into the ground as a primary injection material for rough setting, and the grout with a long gelling time is injected into the ground as a secondary injection material.

[0032] Furthermore, in the ground injection method of the present invention, the grout can be injected into the ground by any one 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 / slow setting composite injection method 7) Multi-stage simultaneous injection method 8) Multiple injection hole simultaneous injection method

[0033] The ground injection device of the present invention is a ground injection device used in the above-mentioned ground injection method, The liquid A pump, the liquid B pump, the multiple drive devices, the inverter, the control device, and the injection pipe are included, and a mixing device for the liquid A and the liquid B is provided at the confluence of the liquid A and the liquid B, or in a pipeline from the confluence to the discharge port of the injection pipe.

[0034] The ground injection device of the present invention is a ground injection device used in the above-mentioned ground injection method, The system includes the A liquid pump, the B liquid pump, the multiple drive devices, the inverter, the control device, and the injection pipe, and is characterized in that the A liquid and the B liquid are mixed in a static mixer.

[0035] Furthermore, the ground injection device of the present invention is a ground injection device used in the above-mentioned ground injection method, The system includes the A liquid pump, the B liquid pump, the multiple drive devices, the inverter, the control device, and the injection pipe, and is characterized in that the multiple drive devices are collectively managed by the control device. Effect of the Invention

[0036] According to the present invention, it is possible to provide a ground injection method and a ground injection device that can obtain optimal gel time and solidification strength without using excessive acid according to the ground conditions and injection conditions by instantly and continuously changing the gel time using a non-alkali silica grout. [Brief description of the drawings]

[0037] [Figure 1(a)] FIG. 1 is a graph showing the relationship between pH, gel time, and silica concentration of non-alkaline silica grout. [Figure 1(b)] FIG. 1 shows the relationship between [H+] / [SiO2]n and gel time. [Figure 1(c)] 1 is a table showing the relationship between pH, silica concentration, gel time, and strength when water glass (molar ratio=3) is used. [Diagram 2] 1 is a graph showing the relationship between pH and gel time of a silica solution of a durable silica grout. [Diagram 3] 1 is a block diagram showing an overview of an injection system of the present invention; [Figure 4] FIG. 2 is a block diagram illustrating details of an injection system in one embodiment of the present invention. [Diagram 5] FIG. 2 is a conceptual diagram illustrating details of an injection system in one embodiment of the present invention. [Figure 6]1 is a graph showing the relationship between the ratio of liquid A to liquid B and the gel time and silica concentration (Examples 1 and 2). [Figure 7] 1 is a graph showing the relationship between the ratio of liquid A to liquid B and the gel time and silica concentration (Examples 3 and 4). [Figure 8] 1 is a graph showing the relationship between the ratio of liquid A to liquid B and the gel time and silica concentration (Examples 5 and 6). [Figure 9] 1 is a graph showing the relationship between the ratio of liquid A to liquid B and the gel time and silica concentration (Examples 7 and 8). [Figure 10] 1 is a graph showing the relationship between the ratio of liquid A to liquid B and the gel time and silica concentration (Examples 9 and 10). [Figure 11] 1 is a graph showing the relationship between the ratio of liquid A to liquid B and the gel time and silica concentration (Examples 11 and 12). [Figure 12] 1 is a graph showing the elution rate of sulfate ions from a gel. [Figure 13] 1 is a graph showing the change in SO4 -- concentration in a gel over time. [Figure 14] FIG. 1 is a diagram showing a curing method in a test to confirm the effect of non-alkali silica grout on concrete in an injection ground. [Figure 15] FIG. 1 is a photograph showing the curing conditions in a test to confirm the effect of non-alkali silica grout on concrete in the injection ground. [Figure 16] FIG. 1 is a photograph showing the state after curing in a test to confirm the effect of non-alkali silica grout on concrete in the injection ground. [Figure 17] 1 is a graph showing the change over time in mortar strength and curing solution pH due to different curing conditions. [Figure 18] 1 is a graph showing the effect of the sulfuric acid mixing rate in the reactant on the pH of the curing medium. [Figure 19] FIG. 1 shows the state of the mortar surface on which an insoluble coating was formed after curing for three years in a silica sol containing a sequestering agent of the same volume as the mortar specimen. [Figure 20]This figure shows the condition of a mortar specimen containing a sequestering agent after 16.5 years of curing in a homogel of the same volume as the mortar specimen, and the formation of an insoluble coating (masking silica) by the sequestering agent. [Figure 21] This is an X-ray chart of the coating on the surface of mortar that was immersed in homogenized gel and cured. [Figure 22] FIG. 1 is a diagram illustrating the functions of sodium hexametaphosphate and a sequestering agent. [Diagram 23] FIG. 13 shows an experiment to confirm the effect of a sequestering agent when a mortar specimen is wrapped in a sand gel of the same volume as that of a sequestering agent-containing silica grout and cured in a sand gel of a sulfate-based silica grout. [Figure 24] FIG. 1 is a diagram showing the concrete protection effect of masking silica and the masking separation method. [Diagram 25] FIG. 13 shows the division of the infusion portions of different infusion fluids in the infusion area. [Figure 26] FIG. 1 shows an actual example of a non-alkaline silica grout injected in the field. [Figure 27] FIG. 1 is a diagram showing an example of the relationship between acid type and gel time for non-alkali silica grout. [Figure 28] 1 is a graph showing the relationship between the pH of the chemical solution and the gel time in the air and in the soil. [Figure 29] FIG. 1 is a diagram showing the permeation mechanism of an injection liquid. [Diagram 30] FIG. 13 is a diagram showing deviation and diffusion of injected fluid. [Diagram 31] (a) and (b) show the unconfined compressive strength of consolidated sand as a function of silica concentration, and (c) shows the unconfined compressive strength of different in-situ sands. [Diagram 32] FIG. 1 is a diagram showing an example of a conventional injection system for a quick-setting / slow-setting grouting method. [Diagram 33] FIG. 2 shows the static mixer device injection pipe. [Diagram 34] FIG. 13 is a diagram showing an example in which a mixing device is provided at the tip of an injection pipe in a double-pipe rod injection method. [Diagram 35]FIG. 1 is a diagram showing an injection pipe device that mixes liquid A and liquid B by injection at the outlet of a double-tube rod to prepare an injection liquid and injects it into the ground. [Diagram 36] This is a diagram showing an apparatus that generates a vortex at the tip of a double-pipe injection pipe to mix and inject liquid A and liquid B. [Figure 37] FIG. 1 shows an injection tube used in a double packer system. [Figure 38] This is a diagram showing an example of a double packer method in which the inside is composed of pipelines for liquid A and liquid B, and the mixture of liquid A and liquid B discharged into the packers above and below the inner pipe is injected into the ground from a discharge outlet covered by an outer pipe sleeve. [Figure 39] FIG. 13 is an explanatory diagram of a method of injecting through an outer tube rubber sleeve. [Diagram 40] FIG. 2 is a diagram showing particle size of silica. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0039] The ground injection method of the present invention involves injecting silica grout through an injection pipe inserted into the ground, in which liquid A and liquid B are passed through the injection pipe to join above ground or underground, and the mixed liquid is then injected into the ground.

[0040] In the present invention, a solution containing water glass is used as liquid A, and a solution containing a reactant is used as liquid B. A plurality of drive devices are used to pump liquid A and liquid B, respectively, an inverter, and a control device which collectively controls the plurality of drive devices. The inverter is controlled to continuously variably control the flow rates and mixture ratio of liquid A and liquid B from a quick-setting mix to a slow-setting mix according to the ground conditions and the purpose of injection, and the injection liquid having a predetermined gel time and silica concentration is mixed in the pipeline from the aboveground or underground junction to the discharge outlet of the injection pipe and injected into the ground.

[0041] Since the gel time of non-alkaline silica grout changes rapidly depending on pH, it is almost impossible to set the gel time in the acidic region. In order to solve this problem, the present invention uses an injection system as shown in Figures 3, 4, and 5, which makes it possible to change the pH instantly and continuously, and to inject the non-alkaline silica grout while controlling the gel time by changing it instantly and continuously according to the ground conditions and injection conditions, or to change it continuously to a specified strength.

[0042] In particular, in the case of soft soil layers, this method enables ground improvement in which the optimum gel time and strength can be set for each soil layer, and also in the case of the same soil layer, after the primary injection of a quick-setting mix in one stage, the method continuously changes to the secondary injection of a slow-setting mix with optimally controlled gel time, and further enables ground improvement in which the optimum strength can be maintained constant or continuously changed to the optimum strength. Here, the neutral pH region means a pH of approximately 10 or less (see FIG. 1).

[0043] The ground injection device of the present invention is used in the ground injection method of the present invention, and includes an A liquid pump and a B liquid pump, a plurality of drive devices, an inverter, a control device, and an injection pipe, and a mixing device for A liquid and B liquid is provided at the confluence of A liquid and B liquid, or in the pipeline from the confluence to the discharge port of the injection pipe.

[0044] In addition, the ground injection device of the present invention is used in the ground injection method of the present invention, and includes an A liquid pump and a B liquid pump, multiple drive devices, an inverter, a control device, and an injection pipe, and the multiple drive devices are collectively managed by the control device.

[0045] An example of the injection system of the present invention is shown below (see Figs. 3, 4, and 5). The liquid is injected from the material blending section to the injection production section, then from the injection liquid delivery section through a pressure gauge and flow meter, through the delivery pipe to the mixing device, and into the injection pipe section. Data is input in real time from the injection liquid delivery section, pressure gauge, flow meter, and delivery pipe to the injection control section, where it is recorded in the recording section, and the blending etc. are adjusted in the injection production section according to the ground conditions and injection conditions.

[0046] Next, in the injection system of Figures 4 and 5, the material to be used is adjusted in the material mixing section according to the ground conditions and injection conditions, and is separated into liquid A and liquid B in the injection mixing section. Liquid B, a mixed liquid consisting of an acidic liquid, and liquid A, a silica solution, are placed in the material mixing section. Additives may be added to either liquid A or liquid B, or to the acid.

[0047] In the grouting liquid delivery section, an inverter, a pump, and a PQ (flow rate / pressure detector) are respectively arranged and adjusted by a controller, and the grouting liquid is mixed above ground or underground using a mixer in the grouting liquid injection section. The controller in the control section controls the material blending section, the grouting liquid delivery section, and the inverter, and transmits data to the recording section.

[0048] The A and B liquids may be mixed and joined at the above-ground part of the injection pipe as shown in Figures 3, 4 and 5, or at the tip of the double pipe, or may be joined and injected from multiple pipes inside the outer injection pipe (Figures 33 to 39). Even with single-rod injection, various injection methods as shown in Table 11 can be applied.

[0049] FIG. 5 shows a schematic diagram of an example of an injection system for implementing the present invention, which 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) controls the inverters of the A liquid pump and the B liquid pump in conjunction with each other according to the ground conditions and injection conditions, and variably manages the discharge amount of the A liquid and B liquid merged liquid and the flow rate ratio of each pump, thereby making it possible to instantaneously and continuously change the discharge amount of the A and B liquid merged liquid and the ratio of the discharge amounts of the A and B liquids. The A and B liquids are mixed by generating turbulence due to a change in the pipe diameter at the merged part (FIGS. 36 and 37), are mixed by injection (FIGS. 34 and 35), or are mixed in the pipeline by a tubular mixer such as a static mixer (FIG. 33), so that it is possible to prevent the A and B liquids from being injected into the ground without being mixed. The mixing device is installed inside the injection pipe or above ground, and the mixture of liquid A and liquid B can be injected into the ground from the injection pipe.

[0050] Furthermore, according to the injection method and injection device of the present invention, it is possible to adjust the injection concentration according to the specified pH and gel time by the silica concentration and reactant of the A and B liquids in the material mixing section using a controller, without the need to adjust the pH and gel time in the mixing tank as in the conventional batch system. Moreover, in the conventional batch system, gelation progresses in the mixing tank during the injection work, making it difficult to inject at the specified pH and gel time.

[0051] In the present invention, the A liquid is an alkali silica solution containing water glass, and the B liquid is an acidic solution (acid or acid salt (FIG. 4)) (FIGS. 4 and 5). The controller issues an instruction to the material mixer to vary the amount of silica according to the ground conditions. By changing the ratio of the discharge amounts of the A liquid and the B liquid, the gel time of the A and B liquid merge can be varied instantaneously and continuously. At the same time, the concentration of the reaction product can be changed instantaneously and continuously. Alternatively, if the change in the concentration of the reaction product with respect to the change in the discharge amount of the A liquid and the B liquid merge and the ratio of the A liquid and the B liquid is grasped in advance by experiments (Tables 3 to 14, FIGS. 6 to 11), and the inverter is calibrated before injection at the site, the concentration of the reaction product can be grasped in real time in response to the control of the inverter during injection. That is, the injection can be substantially visualized and managed by using the system of FIG. 5.

[0052] By changing the ratio of liquid A and liquid B, it is possible to control the concentration of the reaction product by controlling the silica concentration to a specified concentration while varying the gel time. For example, by controlling the flow rate ratio of liquid A and B and the combined discharge volume with inverters for liquid A and B, it is possible to instantaneously and continuously vary the gel time, pH, and concentration of the reaction product.

[0053] In the present invention, when injecting an injection solution having a predetermined gel time and silica concentration mixed in a pipeline, the ion concentration of the reaction product is continuously changed and the gel time and the ion concentration of the reaction product are grasped in real time, so that the ground can be consolidated within the predetermined concentration required to set the gel time without prescribing an excessive amount of reactant.

[0054] As an injection system used in the practice of the present invention, other than a diaphragm pump, a plunger pump or a piston pump can be used, which is a multiple injection system that delivers at least liquid A and liquid B and has a control system that instantaneously and continuously varies the total flow rate of liquid A and liquid B and the delivery ratio of liquid A and liquid B.

[0055] In this way, the present invention can switch between a quick-setting blend and a slow-setting blend by controlling the total amount of liquid A and liquid B and the ratio of liquid A to liquid B. Moreover, the ratio can be made instantaneous and continuously variable by inverter control, and the gel time of the slow-setting blend can be controlled, so that the gel time corresponding to the set ratio can be set.

[0056] FIG. 30(c) shows an example in which instant-setting grout is injected into a coarse layer of the grout ground, and then continuously injected into a fine layer.

[0057] In the present invention, the B liquid is an acid solution and the A liquid is a water glass solution, and the inverters of the A liquid pump and the B liquid pump for the A liquid and the B liquid are controlled to manage the ratio of the total flow rate of the A liquid and the B liquid and the flow rate of the A liquid and the B liquid, thereby obtaining the following features.

[0058] In the present invention, the acid used in the acidic solution may be an inorganic acid such as sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, or sulfamic acid, an organic acid such as citric acid, or a mixed acid or a salt thereof, for example, an aluminum salt such as aluminum sulfate, aluminum chloride, or polyaluminum chloride, or iron chloride, iron sulfate, magnesium chloride, or magnesium sulfate, and is not limited as long as it can adjust the pH. In addition, a salt that acts as an acid (for example, aluminum chloride, polyaluminum chloride, etc.) or an alkali agent that shifts the pH from acidic to neutral, for example, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, aluminum hydroxide, sodium aluminate, or other alkali, may be used. Furthermore, any salt, alkali, or pH adjuster may be used as an additive to adjust the gel time or strength.

[0059] Examples of silica solutions include water glass, activated silica (silica obtained by removing alkali from water glass, or silica obtained by removing alkali from water glass and colloid), colloidal silica, metallic silicon, and silica derived from geothermal water, and one or more of these can be used. In the present invention, the type, concentration, and molar ratio of the water glass used are not limited.

[0060] In the present invention, a solution containing sulfate ions is used as Liquid B, and the sulfuric acid concentration of Liquid B and / or the injection solution is set to 10% or less, making it possible to carry out ground improvement work with reduced environmental impact.

[0061] For example, the injection liquid is a non-alkaline silica grout having a silica concentration of 1 to 40 w / vol%, a pH of 1 to 10, and a gel time of 5 seconds to 7 days at 20°C. An acid-containing solution is used as liquid B, and the confluence ratio β of liquid A and liquid B is set to β=A / B=0.5 to 2.0. By variably controlling the flow rates and confluence ratio of liquid A and liquid B so that the pH and silica concentration correspond to the gel time continuously from the fast-setting mix to the slow-setting mix, an injection liquid having a predetermined gel time and silica concentration can be injected into the ground.

[0062] In addition, it is preferable to continuously variably control the flow rates and the confluence ratio of liquid A and liquid B from a quick-setting mix to a slow-setting mix, and when injecting the resulting grout into the ground, to variably control the confluence ratio at the start of injection so that the pH of the grout starts on the acidic side.

[0063] In the present invention, the flow rates and confluence ratios of liquids A and B are set based on the ground conditions and groundwater conditions in the ground improvement area so that the residual ion concentration of the reaction products in the ground is a predetermined concentration, thereby making it possible to solidify the ground by bringing the concentration of the reaction products in the ground within a predetermined range.

[0064] In addition, in the present invention, by continuously changing the mixing ratio of liquid A and liquid B from a quick-setting mix to a slow-setting mix, the injection liquid can be injected into the ground so that the gel time and the concentration of the reaction products in the improved ground reach predetermined values ​​according to the ground conditions, groundwater conditions, and injection purpose.

[0065] Furthermore, in the present invention, as silica grout, a grout with a relatively short gel time and a grout with a relatively long gel time are injected into the ground successively from a quick-setting mix to a slow-setting mix, and the grout with a short gel time is injected into the ground as a primary injection material for rough setting, and the grout with a long gel time can be injected by penetration as a secondary injection material.

[0066] A specific example will be described below. (Examples 1 to 12) Tables 3(a) to 14(b) show the formulations of liquids A and B, the sulfate ion concentration and phosphate ion concentration which are the reaction products of the joint liquid of liquids A and B, and the gel time, pH, and silica concentration corresponding to β=A / B.

[0067] The sulfate ion concentration at that time is also indicated in ppm, with 10,000 ppm being 1%.

[0068] 6 to 11 show the relationship between the gel time corresponding to β=A / B and the silica concentration (that is, the joining ratio of liquid A and liquid B).

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072]

Table 4

[0073]

Table 5

[0074]

Table 6

[0075]

Table 7

[0076]

Table 8

[0077]

Table 9

[0078]

Table 10

[0079]

Table 11

[0080]

Table 12

[0081]

Table 13

[0082]

Table 14

[0083] From the above, it can be seen that by continuously changing β=A / B, it is possible to instantaneously and continuously change the gel time, silica concentration (strength), and concentration of reaction products (sulfate ions, phosphate ions).

[0084] On the other hand, the applicant has clarified that the concentration (X) of the reaction product in the ground improvement area by injection of the grout is greatly affected by the ground conditions of the injection ground, the groundwater conditions, and the injection design conditions (Patent Document 1).

[0085] Regarding the sulfate ion concentration, if the sulfate ion concentration in the improved ground is X and the elution rate of sulfate ions from the gel in the improved ground is α, the residual rate of sulfate ions in the ground is △=1-α. The concentration of reaction products in the ground can be kept within a specified value (W) by injecting a prescription (reactant concentration = a) of the injection solution that makes the sulfate ion residual rate △ below the concentration X that does not affect concrete, and controlling the discharge amount of A and B solutions by inverters of A and B solutions to obtain β=A / B that makes X below W. On the other hand, the elution rate of sulfate ions from the gel of the silica mixture solution in the laboratory experiment is α, and the effect of the sodium sulfate concentration shown in Figures 12 and 13 on the concrete specimen is shown in Table 16. From Table 16, the minimum concentration that does not affect concrete is W. From the above, it can be seen that the inverters for solutions A and B should be controlled by setting a formulation for the injection solution so that the sulfate ion concentration corresponding to β=A / B in Figures 6 to 11 is 8000 ppm (=W) or less from Table 16, which is the residual rate of sulfate ions corresponding to the ground conditions, groundwater conditions, and injection design conditions.

[0086] When forming a ground improvement region using the above-mentioned ground grouting material, the present inventors conducted the following study on the relationship between the components contained in the ground grouting material and the injected ground.

[0087] [Effect of sulfate ions on concrete] [experiment] Assuming that the groundwater remains stagnant (or retained) with almost no groundwater flow, and assuming that the concentration of the aqueous sodium sulfate solution, which is a water-soluble reaction product, acts on the concrete (mortar) without changing for one year, mortar specimens in Table 17(a) were cured for one year in aqueous sodium sulfate solutions with sulfate ion concentrations of 10,000 ppm, 8,000 ppm, 5,000 ppm, 3,000 ppm and 0 ppm, and then uniaxial compressive strength tests were conducted to examine the effects on the concrete.

[0088] In the absence of dilution by groundwater, the experiment showed that SO4 -- At 10,000 ppm, visible changes to concrete occur within six months, while at 8,000 ppm, slight changes occur within one year.

[0089] Table 16 shows the results of immersing concrete specimens in a sodium sulfate solution and observing the effect of sulfate ion concentration on concrete. ○ indicates a state where there is no abnormality in the external shape, △ indicates a state where the surface is partially peeled off, and × indicates a state where the surface is severely peeled off. From these results, in the absence of dilution by groundwater, sulfate ion concentrations of 10,000 ppm or more will affect concrete structures within one year, while concentrations of 5,000 ppm or less will have almost no effect even after more than one year. In Table 16, a sodium sulfate concentration of 8,000 ppm is a concentration that will have a slight effect within one year, but since sulfate ions are actually diluted by groundwater, it is considered safe to assume that there will be no problems with mortar specimens if the sulfate ion concentration of the injection ground is 8,000 ppm or less.

[0090] [Effect of non-alkaline silica grout on concrete in injection ground] For non-alkali silica grout, in which alkali that causes deterioration of water glass grout is removed with an acid neutralizer, (1) sulfuric acid, (2) phosphoric acid, (3) mixed acid of sulfuric acid and phosphoric acid, (4) non-sulfuric acid, (5) non-sulfuric acid salt, or (6) a combination of any of the above (1) to (5) is used as the acid neutralizer (Tables 21 to 23).

[0091] As mentioned above, it is expected that sulfate ions will dissolve into the curing water within a few months and reach a nearly constant value (Fig. 12, Fig. 13). In an actual site, there is an extremely large amount of groundwater relative to the solidified material, and if the groundwater flows and dilutes the material, the dissolution and diffusion rates are expected to be fast. However, the dilution rate and the concentration of SO4 -- It is necessary to consider that the residual rate of in the gel is affected by the ground conditions, groundwater conditions, the size of the injection area, etc. Therefore, it is effective to consider a silica grout that has almost no effect on the mortar specimen even without dilution. This is the application of a non-alkali silica grout that contains a sequestering agent.

[0092] The mortar specimens in Table 17(a) were cured in a non-alkaline silica gel containing the same volume of sequestering agent (Fig. 14), and the appearance of the coating deposited on the concrete surface was observed. As a result, it was confirmed that a white coating was formed on the mortar surface for all injection materials (Figs. 15 and 16). For comparison, the coatings of mortar specimens cured in non-alkaline silica II (non-sulfate / phosphate, Table 21, No. 2), IIα (sulfate / phosphate, Table 21, No. 3), and IIδ (sulfate, Table 21, No. 1) under similar conditions were collected, and their components were evaluated by X-ray fluorescence and their crystal structures by X-ray diffraction (Fig. 21, Table 24).

[0093] The coating components are shown in Table 24, and the X-ray diffraction chart is shown in Figure 21. From these measurement results, it is believed that the coating on the mortar surface is hydroxyapatite in II, hydroxyapatite or calcium phosphate in IIα, and calcite or vaterite in IIδ.

[0094] The coating of II and IIα is achieved by the formation of a film using a sequestering agent, and phosphoric acid, sodium phosphate, sodium hexametaphosphate, and phosphate salts are particularly effective. Organic acids and organic acid salts such as citric acid and succinic acid are also effective. Figure 22 shows the function of a sequestering agent, using sodium hexametaphosphate as an example. Non-alkali silica grout containing a sequestering agent passivates calcium and magnesium ions present on the mortar surface by chelating them, and also reacts with the silica contained in the injection material to form a sparingly soluble film that suppresses the elution of Ca ions from within the mortar and the penetration of sulfate ions from the outside (Figure 23).

[0095] [Strength test of mortar specimens in gel of non-alkaline silica grout containing sequestering agent] The mortar specimens in Table 26 were cured for 16 years using the non-alkaline silica grout containing the sequestering agent shown in Table 23, and the curing method shown in Figure 14. The status of the curing test is shown in Figures 15 and 16, and the pH and strength ratio of the curing water during that time are shown in Figure 17. The pH of the distilled water in which the mortar specimens were cured is around 12, but the pH when it disintegrates in a sulfate aqueous solution is 13 or more, and it is found that the alkali in the mortar is eluted. On the other hand, when it is covered with non-alkaline silica containing a sequestering agent, the pH is kept almost neutral. From this result, it is considered that the above silica blocks the elution of the alkali in the mortar (suppresses neutralization) and prevents the penetration of sulfate ions into the inside of the mortar. From the above, the function of the sequestering agent was confirmed (Figures 14 to 24).

[0096] [Effect of sequestering agent on mortar specimens when they are wrapped in sand gel of the same volume as silica grout containing sequestering agent and cured in sand gel of sulfate-based silica grout] As shown in Figure 23(a), the mortar in Table 17(a) was wrapped in a sand gel of silica grout in Table 22(a) containing a sequestering agent marked with a △ in Table 27, and then cured in a homogel of sulfuric acid-based silica grout marked with a ◯ in Table 27 (Figure 23(b)). After six months, the homogel and sand gel were dismantled (Figure 23(c)) and the mortar was observed. No change was observed, and a white coating of silica (masking silica) containing the sequestering agent was formed on the surface (Figure 23(d)), and no abnormality was observed in the mortar. When phenolphthalein was sprayed on the mortar surface, no red reaction occurred. Furthermore, when the mortar was scratched (Figure 23(d)) and phenolphthalein was sprayed, only the scratched area showed a red reaction indicating the alkali inside the concrete. When the removed mortar specimen was immersed in water, the pH of the curing water was near neutral (Figure 17). This indicates that the masking silica layer prevents sulfate ions from penetrating into the mortar and also prevents alkali from leaching out from inside the mortar specimens.

[0097] Below is an explanation of the behavior of sulfate ions depending on the ground conditions, groundwater conditions, and injection design when the injection solution contains sulfate ions and the ground is adjacent to a concrete structure or an adjacent area where a concrete structure is planned to be constructed after excavation (Table 15).

[0098] [Table 15]

[0099] [Table 16]

[0100] [Table 17]

[0101] [Experiment 1] SO4 from gel of silica sol grout (water glass + sulfate based non-alkaline silica grout) -- Dissolution test

[0102] (1) Elution method The silica sol mixture used in the test is shown in Table 18. The Toyoura sand consolidated with the silica sol in Table 18 is shown in Table 19. 3 ) polypropylene container, place homogel or sand gel according to Table 18 or Table 19, measuring approximately φ5 × h10 cm, pour 200 mL of water into it, and assuming that sulfate ions in the gel are diffusing into the groundwater or that groundwater is flowing, change the water periodically and measure the SO4 -- The water was exchanged on the 1st, 3rd, 7th, and 28th days, and the SO4 -- This was done after measuring the concentration.

[0103] (2) Test results When silica sol grout is injected into the ground, the Na in the gel + Ions and SO4 -- Dissolves in groundwater in a short period of time, leaving only the insoluble silica as a gel. SO4 dissolved in groundwater -- It can be assumed that SO4 diffuses into the groundwater and disappears in a short time (Table 20). Experiments have shown that 40% of SO4 -- of the sulfate ions in the injected ground will dissolve (residual rate in the gel is approximately 60%), 85% will dissolve in one month (residual rate in the gel is approximately 15%), and almost 100% will dissolve in two months (residual rate in the gel is approximately 0%). From the above, if the factor that causes the sulfate ions in the injected ground to be reduced compared to the sulfate ion concentration contained in the injection solution is (Y), it can be seen that (Y) changes into the elution rate of sulfate ions from the gel (α) and the residual rate of sulfate ions in the gel (=△) (△=1-α).

[0104] [Table 18]

[0105] [Table 19]

[0106]

Table 20

[0107]

Table 21

[0108]

Table 22(a)

[0109]

Table 22(b)

[0110]

Table 23

[0111]

Table 24

[0112]

Table 25

[0113]

Table 26

[0114]

Table 27

[0115] (A) Open system: When the gel in the injected ground easily dissolves out of the injection range, and when groundwater flows outward from the concrete structure. For example, when the coast or river is nearby and flows in that direction, when the groundwater level fluctuates with the tides, when the hydraulic gradient is outward, or when the ground is highly permeable such as sand and gravel, sulfate ions are diluted and reduced within a relatively short period of time, within 1 to 2 months. According to the inventors' laboratory experiments, almost all of the sulfate ions diffuse within 1 to 2 months (Figure 12, Table 21 1, Figure 13, Table 15). It can be considered that the sulfate ion concentration will eventually converge to that in nature. Therefore, even if the sulfate system in Figure 1 is used, the SO4 ions in the injected ground are easily reduced in a short period of time. However, in an actual field, the dissolution rate of sulfate ions is thought to be affected by the ground conditions, groundwater requirements, and the size of the solidified range, so when these conditions are unclear, it is preferable to use 2 and 3 in Table 21, or a combination of 1, 2, 3 and 4 and 5. In addition, by increasing the injection rate of the suspended calcium-containing primary injection material, the secondary injection rate of the sulfate ion-containing silica grout can be reduced, and at the same time, the sulfate ions can be fixed by calcium. In addition, since the water quality change in the inspection hole located 10 m away from the injection area in the chemical injection ground usually becomes almost constant in 1 to 2 months, the concentration of the reaction product from the gel in the injection ground can be considered to become almost constant by diffusion in 1 to 2 months. Therefore, it can be considered to be 1 / 10 or less according to Figures 12 and 13.

[0116] (B) Stagnant system (retention system): When there is almost no groundwater flow and the groundwater is stagnant. The SO4 ions in this area will sooner or later move in the direction of the lower ion concentration gradient, i.e., toward the outside of the injection range, and will be diluted and eventually reduced to a concentration that will have no effect, but the dissolution 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 25. This makes it possible to protect the concrete until it is diluted to a concentration that will have no effect on the concrete, or even after that. Or, even if the sulfate ions are not diluted, the concrete can be protected as it is.

[0117] (C) Concentration system: If there is a high possibility that sulfate ions will not be reduced and will instead be concentrated, this is the case when sulfate ions that have penetrated through 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 a combination of E, F, or G in Table 25. Also, if the concrete is of high quality, sulfate ions will not penetrate and will not cause any problems (Table 17(b)).

[0118] (D) A non-injected area is provided within the injection range, leaving an unconsolidated area so that sulfate ions diffuse into that area, reducing the overall sulfate ion concentration (Figure 25).

[0119] (E) 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 beforehand, the sulfate ions in the injection material are passivated as calcium sulfate. A calcium-containing alkali injection area is provided within the injection range to passivate the sulfate ions in the injection material as calcium sulfate. Alternatively, the calcium contained in the ground and the sulfate ions in the injection material become calcium sulfate and passivate, thereby reducing the sulfate ion concentration. When the injection material is injected into the ground, the pH of the soil shifts to a neutral direction, and the soil gel time GTs is shortened (Figures 1 and 2), but other soil components, especially the Ca content of the ground to be injected, have a large effect. Figure 26 shows an actual example at a site where a non-alkali silica grout was injected. From this data, the sulfate ions in the ground are finally reduced after construction is completed, and the reduction rate of the sulfate ions is, for example, the SO4 -- When using a formulation with 20,000 ppm ions, it can be considered that the amount of Ca ions in silica grout with 10,000 ppm is reduced by almost half or to one-third.

[0120] (F) Inject compounds 2, 3, 4, and 5 in Table 21 around the concrete structure to prevent sulfate ions from penetrating the concrete and to passivate them (Figure 25). In addition, among the sequestering agents, non-alkali silica containing sodium hexametaphosphate in particular causes very little sulfate ion elution from the gel at the beginning, at 30% of the sulfate ion concentration used. This provides excellent protection for concrete. The reason for this is that the strong structure of hydroxyapatite bound to calcium formed on the concrete surface traps SO4 -- It is presumed that ions were taken in (Figures 21 and 22).

[0121] The above groundwater condition can be understood as follows. The injection liquid or detection liquid is collected from an injection hole in the injection ground and from an observation well in the injection area or at a position distant from the injection area, and the components and pH of the injection liquid in the groundwater are analyzed to estimate the presence or absence of elution, the elution rate, and the degree of dilution. For example, a detection liquid such as a dye or electrolyte is injected from the injection hole, groundwater is collected from an observation well distant from the injection area, and the conductivity and concentration are measured to detect the elution. It can also be determined by the fluctuation of the groundwater level in the ground due to the tides. It can also be determined by analyzing the leaked water that has leaked into the inside of the concrete structure. In this way, electrical conductivity measurement and pH measurement can be used as sensors to know the diffusion rate, dilution rate, and dilution rate.

[0122] In addition, in the above, the sulfate ion concentration in the ground improvement region is reduced not only by a decrease in the injection rate of the sulfate ion-containing grout solution, but also by the sulfate ions being captured (fixed) as calcium sulfate by calcium.

[0123] Similarly, when a suspension type grout is used as a calcium-containing grout in the primary injection, the sulfate ion concentration in the ground improvement area is reduced not only by the reduction in sulfate ions due to the reduction in the injection rate of the secondary injection material by the sulfate ion-containing injection material, which is calculated by subtracting the injection rate of the primary injection material from the total injection rate, but also by the capture (fixation) of the sulfate ions of the secondary injection material by the calcium of the primary injection material (Table 15, △3, 4, 6, 7).

[0124] That is, in the present invention, when the ground is adjacent to a concrete structure or adjacent to a planned area where a concrete structure will be constructed after excavation, a non-alkali silica grout containing sulfate ions and having a silica concentration of 1 to 40 w / vol% and a pH of 1 to 10 is injected as a ground injection material to form a ground improvement area, the ground is classified into the following (1) open system, (2) stagnant system, or (3) concentrated system based on the behavior of sulfate ions dissolved in the ground from the ground conditions and groundwater conditions of the ground improvement area, and one or more of the following △1 to △7 are set as the reduction factor (Y) of sulfate ions in the injection ground according to the classified type of injection ground, and based on the reduction factor (Y) set according to the injection ground, it is preferable to select a ground injection material consisting of a reactant formulation such that the sulfate ions derived from the non-alkali silica grout are 8,000 ppm or less in terms of the average value (X) of the sulfate ion concentration remaining in the ground improvement area (Table 15).

[0125] (1) Open system: Ground where groundwater flows outward from the concrete structure, and the sulfate ion concentration decreases through dilution. (2) Stagnant system: Ground where groundwater flow is stagnant and sulfate ion concentration hardly changes (3) Concentration system: Sulfate ions penetrate the surface of the concrete structure and are concentrated in the ground, increasing the sulfate ion concentration.

[0126] △1: The residual rate of sulfate ions in the improved ground when a non-injected area is provided within the ground improvement area and the ratio of the non-injected area is the sulfate ion elution rate α1. △1=1-α1 △2: The remaining rate of sulfate ions in the ground improvement area when the dissolution rate of sulfate ions in groundwater is α2. △2=1-α2 △3: The residual rate of sulfate ions in the ground improvement area when the fixed rate of sulfate ions in the ground improvement area is the elution rate α3. △3=1-α3 △4: When the replacement rate of sulfate ions in the sulfuric acid grout by non-sulfuric acid grout or low-sulfuric acid grout in the ground improvement area is the dissolution rate α4, the remaining rate of sulfate ions in the ground improvement area is △4=1-α4 △5: When the replacement rate of the silica component in the ground grouting material by colloids is the dissolution rate α5, the remaining 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 grouting material and the capture rate is the dissolution rate α6, the remaining rate of sulfate ions in the ground improvement area is △6=1-α6 △7: When the injection rate of the ground grouting material in the ground improvement area is reduced and the reduction rate of the injection rate is set as the dissolution rate α7, the remaining rate of sulfate ions in the ground improvement area is △7=1-α7

[0127] Specific examples are given below.

[0128] As a silica grout suitable for injection purposes, a SiO2 concentration of 6 w / vol% is used. Here, t: injection rate (for example, 1 m of improved ground) 3 The injection volume per unit is 0.4 m 3If we assume that the injection rate is t = 0.4, a is the concentration of sulfate ions in the injection solution, and Y is the factor that reduces sulfate ions, then Y = △. △ is the remaining rate of sulfate ions, X is the concentration of sulfate ions generated in the ground, and W is the concentration of sulfate ions that cause problems for concrete. The value of W is set depending on the situation, but we will use W = 5000 ppm. Assuming that W≧X=t×a×Y (=△), and taking into consideration the ground conditions and groundwater conditions, a mix design of the injection material is performed so that W=5,000 ppm. In Examples 1 to 10, as shown in Tables 3 to 14 and Figures 6 to 11, the inverters of the A and B liquids are controlled so that the sulfate ion concentration in the ground is within a range of concentrations that do not affect concrete, and the ratio (=β) of the A and B liquids prepared before injection is continuously changed. The gel time, sulfate ion concentration, and the change in the value of β=A / B by the inverter and the corresponding sulfate ion concentration generated in the ground are confirmed, and the gel time and sulfate ion concentration in the ground can be grasped in real time during actual injection. Therefore, injection can be controlled so that the sulfate ion concentration (X) generated in the ground is within W, which causes problems for concrete.

[0129] If we take the reduction factor of sulfate ions as Y (=△), and assume from Figures 12 and 13 that the sulfate ion concentration will be diluted 10 times within a year, then 90% of the sulfate ions will be eluted (elution rate = α2 = 0.9), and the remaining rate of sulfate ions will be △2 = 1-0.9 = 0.1. For curve 1 in Figure 27, using the mix marked with an ◯ in Table 27 and a sulfate ion concentration of 21,000 to 28,000 ppm, the sulfate ions in the ground will be X = a x 0.4 x 0.1 = 872 to 1,120 ppm, and W ≧ X = 872 to 1,120 ppm, so there is no problem. Also, if we take △2 = 0.3 to be on the safe side in a ground with clayey soil, X=t×a×Y(=△2(=0.3))=0.4×(21,000~28,000ppm)×0.3=2,520~3,360ppm. (a is the sulfate ion concentration in the injection solution.) Therefore, it can be seen that it is sufficient to use the range of curve 1 in Figure 27 and the mix ratio marked with a circle in Table 27. Furthermore, when the application conditions are B or C in Table 24, that is, when the injection ground is in a stagnant or concentrated state, the mix ratio of curve 3 in Figure 27 (marked with an X in Table 27) can be used, or, for safety reasons, the mix ratio of curve 4 (marked with a triangle in Table 27) can be used and inverter control of β=A / B can be used to control the specified gel time and reaction product (sulfate ion) concentration.

[0130] As described above, the mix recipe to be used in the injection design can be designed to be safe for concrete based on the injection purpose, construction method, and ground conditions, and quantitative injection design enables ground injection with reduced environmental impact.

[0131] Next, calculate the silica grout with sulfate ion concentration a for X = 5,000 ppm. Normally, when the silica concentration of water glass is 1-50 w / wt%, a sulfate ion concentration of 50,000-5,000 ppm is required to make it non-alkaline using sulfuric acid alone. Therefore, the sulfate ion concentration X of the injected ground at 50,000-5,000 ppm will be 20,000-2,000 ppm under groundwater stagnation if the injection rate t = 0.4. To make this value 5,000 ppm or less, if half of the silica concentration of the water glass is replaced with colloid, the sulfate ion concentration of the injection solution will be half (△5 = 0.5), and the sulfate ion concentration (X) of the injected ground will be 10,000-1,000 ppm. Furthermore, if half of the sulfate ion concentration in the injection solution is replaced with non-sulfate such as phosphoric acid, citric acid, succinic acid, AlCl3, or FeCl3 (△4=0.5), the sulfate ion concentration in the injection ground will be 10,000-1,000 ppm. If the above is used in combination (△4=0.5, △5=0.5), the sulfate ion concentration in the injection ground will be 5,000-500 ppm≦W. Furthermore, if the solution is further diluted to 1 / 10 with groundwater, the injection rate t=0.4 will result in a sulfate ion concentration of 2,000-200 ppm. <Wとなる。

[0132] Thus, it is clear that it is sufficient to replace part of the sulfuric acid with inorganic acids such as phosphoric acid, organic acids, inorganic salts such as AlCl3, FeCl3, polyaluminum chloride, or organic salts that exhibit acidity. Also, as mentioned above, if a sequestering agent is used, concrete can be protected without reducing sulfate ions.

[0133] Also, as an example, assuming the ground conditions are an open system with an injection rate of 45%, and among them, 10% is the injection rate of the primary injection using suspension-type cement bentonite (CB), the injection rate of the sulfuric acid-based silica grout as the secondary injection was reduced. At the same site, the CB had solidified normally in a vein-like pattern. In this case, out of the injection rate t (=0.45), 0.1 was the primary injection material (CB) and 0.35 was the secondary injection material (silica sol grout). The reactant of the silica sol grout used was sulfuric acid ions alone (No. 1 in Table 1). The formulation of the injection fluid was the one marked with a circle in Table 27, the first line in Figure 27, with a gel time of approximately 1,000 minutes and a sulfuric acid ion content of 25,000 ppm for the injection of silica grout. With an injection rate t = 45%, the injection rates of CB:silica sol grout were 10% and 35% respectively. If the injection rate of the primary injection (CB) is 0.1 and the injection rate of the secondary injection (silica sol grout) is 0.35, then the sulfuric acid ion concentration X in the ground becomes X = 25,000×0.35 = 8,750 ppm. Diluted 10 times by groundwater, the elution rate α of sulfuric acid ions becomes 0.9. Therefore, the residual rate of sulfuric acid ions in the ground is △ = 1 - 0.9 = 0.1. Thus, the sulfuric acid ion concentration X in the injection ground becomes X = 8,750×0.1 = 875 <W. Or, if the water permeability decreases due to the injection of the primary injection material and the elution rate α of sulfuric acid ions becomes 0.5, then if the residual rate of sulfuric acid ions in the injection ground is △ = 1 - 0.5 = 0.5, X = 8,750×0.5 = 4,375 <W. From the above, it can be seen that by injecting the primary injection material and then injecting the sulfuric acid-based silica grout into the ground, and assuming the elution rate according to the ground conditions so that the concentration of sulfuric acid ions in the ground is within W = 5,000 ppm, the injection rate of the primary injection material can be set. The same can be done using suspension-type grouts such as calcium silicate-based or slag-based grouts, calcium-based grouts, or calcium-containing solution-type injection materials as the primary injection material. Also, if a calcium-containing material such as cement grout, lime, or slag is injected in the primary injection, out of the injection rate of 0.4 of the injection fluid, when 0.1 (α4 = 0.1, Table 15) is injected as the primary injection material, the injection rate of the silica grout becomes 0.3.Furthermore, assuming that the Ca content of cement, lime, and slag reacts with sulfate ions, and 0.1 of the 0.4 injection rate is fixed as CaSO4 (α3=0.1, Table 15), the residual rate of sulfate ion concentration in the ground is △3=0.2. Therefore, X=25,000×0.2=5,000ppm. Therefore, when 25,000ppm of silica grout is injected, the sulfate ions in the ground are X=5,000≦W. The fixation rate of sulfate ions by Ca ions when injecting into ground containing Ca can be predicted by mixing a sulfuric acid grout with soil containing Ca ions. From the above values, if the inverters of A and B liquids are controlled so that the gel time and the generated concentration of sulfate ions are such that β=A / B is within the range of W, a ground injection method that is both for the purpose of injection and has a low environmental impact will be possible.

[0134] Also, as shown in FIG. 25, by dividing the ground improvement area 2 so that the unimproved area 3 and the improved area 4 are equal, sulfate ions can be diffused into the unimproved area and the concentration can be reduced to 5000 ppm or less (△1=0.5). Furthermore, a non-sulfate silica solution can be injected into the unimproved area 3 in FIG. 25 (△4). For example, an alkali water glass grout of water glass-bicarbonate system or other water glass-inorganic salt, inorganic acid, organic reactant, etc. can be injected into the unimproved area (FIG. 25(a), (b), (c)). In this case, the alkali water glass grout is not durable because unreacted water glass and alkali remain in the alkali area, but the excess acid in the surrounding area can penetrate into the gel and neutralize the alkali, improving durability. In this case, it is preferable that the amount of alkali content of the alkali water glass grout injected into the injection area of ​​the non-sulfate grout is the same as or less than the amount of acid content of the acid silica grout around the injection area. This is because if there is a lot of alkali content, it may deteriorate the acid silica gel. This can be confirmed by encasing an alkaline water glass grout gel in an equal volume of an acidic silica grout sand gel, and then confirming that the strength of the alkaline water glass grout sand gel increases.

[0135] That is, for example, the ground improvement area is injected with either an alkaline grout, a calcium-containing grout, or a suspension grout together with a sulfate-based grout, or with a combination of a plurality of non-sulfuric acid grouts, and the injection rate of the alkaline grout, calcium-containing grout, or suspension grout is t1, and the injection rate of the acidic silica grout is t2. When an alkaline grout is used, the durability of the alkaline grout is obtained by neutralizing the alkali with the acid of the acidic silica grout, and the injection rate t2 of the acidic silica grout is set to be an injection rate at which sulfate ions are assumed not to affect the structure. Also, when a calcium-containing grout or a suspension grout is used as a non-sulfuric acid grout, the injection rate t1 is set to be an injection rate at which sulfate ions are assumed not to affect the structure at the injection rate t2 of the acidic silica grout. This provides durability to the ground improvement area.

[0136] In addition, in the above, the sulfate ion concentration in the ground improvement region is reduced not only by a decrease in the injection rate of the sulfate ion-containing grout solution, but also by the sulfate ions being captured (fixed) as calcium sulfate by calcium.

[0137] Similarly, when a suspension type grout is used as a calcium-containing grout in the primary injection, the sulfate ion concentration in the ground improvement area is reduced not only by the reduction in sulfate ions due to the reduction in the injection rate of the secondary injection material by the sulfate ion-containing injection material, which is calculated by subtracting the injection rate of the primary injection material from the total injection rate, but also by the capture (fixation) of the sulfate ions of the secondary injection material by the calcium of the primary injection material (Table 15, △3, 4, 6, 7).

[0138] From the above, in the present invention, if the value of the average sulfate ion concentration X of the entire ground improvement area that does not affect the concrete is W or less, W is 8,000 ppm or less or 5,000 ppm or less, or this value of W can be determined based on the ground conditions, groundwater conditions, the structure and positional relationship of the concrete structure, water quality conditions, soil conditions, or past results. In addition, an injection material containing a metal ion sequestering agent such as an alkaline silica injection material or a phosphoric acid injection material, or an alkaline suspension containing calcium, cement, and slag can be injected into the area of ​​the ground improvement area where the sulfate-based non-alkaline silica injection material is not injected, and further, the sulfate-based non-alkaline silica injection material may contain a phosphoric acid compound or a metal sequestering agent, and further, the silica compound used in the sulfate-based non-alkaline silica injection material is made of silica grout with a pH of 1 to 10, which contains water glass and / or silica colloid as an active ingredient. In addition, by using one or more of the above-mentioned (1) sulfuric acid, (2) phosphoric acid, (3) mixed acid of sulfuric acid and phosphoric acid, (4) non-sulfuric acid acid, and (5) non-sulfuric acid salt as acid neutralizers in the surrounding area of ​​concrete structures in the ground improvement area, the sulfate ion concentration of the sulfate-based ground grouting material in the ground improvement area can be reduced to a concentration that is not expected to affect the concrete structure. For this, it is understood that the ratio β=A / B can be controlled by inverter as mentioned above.

[0139] The above shows an example of sulfate ions as a reaction product. The same applies when setting the allowable range of phosphate ion concentration from the viewpoint of environmental conservation. Also, in the above, the sulfate ion concentration W=8000 ppm, but even if it is more severe depending on the situation, β=A / B can be similarly controlled. In this way, according to the present invention, the gel time and strength can be continuously changed by inverter control, and the concentration of the reaction product or composition in the improved ground can be controlled so as to have a low environmental load.

[0140] The same is also possible when other water quality standards or component concentrations are soil environmental standards. For example, when a solution containing water glass as liquid A contains heavy metals in amounts greater than the water quality regulations or environmental standards, or organic matter whose reaction products produce BOD or COD values ​​greater than the water quality standards, the ion concentration of the A·B combined liquid can be controlled within an acceptable range by using water or an insolubilizing agent as liquid B. In addition, in a patent invention by the present applicant (Patent Document 4), when liquid A, such as silica derived from geothermal water, contains components such as heavy metals, an insolubilizing agent can be used as liquid B to control the ratio of liquid A to liquid B, thereby keeping the concentration within the environmental standards. 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 reacts with the alkali of the water glass to produce a silicic acid gel.

[0141] TIFF2025073317000030.tif88170

[0142] In this case, if there are standard values ​​for COD and BOD in the water quality standards or environmental standards, and liquid A is water glass and liquid B is an organic reactive agent, the flow rates of liquids A and B can be managed by inverter control so that the BOD and COD of the combined liquid A and B are within the standards in the improved ground.

[0143] As a result of the above, the present invention can achieve the following effects. (1) Instantaneous and slow-binding conversions can be performed continuously without any time lag. (2) The first instantaneous injection and the second penetrating injection can be performed consecutively. (3) If the penetrating secondary injection escapes to the aboveground area, the escape can be immediately prevented by the instantaneous setting primary injection. (4) The gel time and silica concentration of the injection solution can be continuously adjusted according to the ground conditions and injection conditions. (5) When injecting into ground consisting of multiple different soil layers, it is possible to improve the ground with the same strength for each soil layer. (6) It is possible to inject injection fluid with gel time and strength appropriate to the ground conditions at each injection stage. (7) By making liquid A alkaline and liquid B acidic, the mixture of liquids A and B can be instantly set; the conversion from neutral to alkaline and slow-setting to instantaneous setting can be achieved instantly and continuously without any time lag. (8) Based on the data on the soil gel time and / or soil pH when the sampled soil from the injection site is mixed with the injection solution, the mixture of air gel time GT0 and air PH0 that can penetrate to the expected injection range can be adjusted based on the infiltration conditions during the injection process. (9) By merging the A and B liquids above ground or underground, the present invention can be applied to all 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 / slow setting composite injection method 7) Multi-stage simultaneous injection method 8) Multiple injection hole simultaneous injection method

[0144] Specific application examples are shown below. In order to make liquefaction countermeasures and other works economical, non-alkaline grout is used for wide-area penetration and solidification by continuous injection over a period of several to several dozen hours with large injection hole intervals (1.0 to 4.0 m) (Table 2), so it is necessary to use a solution-type silica grout that has a long gel time that allows this and also maintains long-term durability (see Figures 1 and 2).

[0145] Also, in excavation work, the application of silica grout, which has excellent permeability, long-term durability and underwater hardening properties due to its long gelation period, is required for ground improvement work around or directly beneath existing concrete structures, or for ground where concrete structures are planned to be constructed in the future. As a result of many years of research, it has been demonstrated that dealkalized non-alkali silica solutions are suitable. There are two methods for dealkalization: colloidal methods using ion exchange and metallic silicon methods, and neutralization methods (silica sol method) that neutralize and remove the alkali from water glass using an acidic neutralizing agent (Figures 1 and 2).

[0146] Non-alkaline silica grout has the property that when injected into the ground, the soil pH (pHs) shifts toward neutral and the soil gel time (GTs) is shortened (Figure 1). Although it is difficult to measure changes in the ground when it comes to soil gel time (GTs) and soil pH (pHs), it is possible to measure the soil gel time (GTs0) and soil pH (pHs0) when the injection solution is mixed with the on-site soil, so the pH (pH0) and gel time (GT0) of the mixed solution should be considered as the standard (Figures 28 and 29).

[0147] The applicant's laboratory experiments and field tests using various injection methods have revealed the following about the gel time and fluidity behavior of non-alkaline silica injection solution injected into the ground.

[0148] The gel time of the acidic silica solution changes drastically with changes in pH. Moreover, when it enters the ground, it reacts with the pH of the ground and reactive components, causing the pH to change during injection, and the gel time underground to change (Figure 28). For this reason, it was found that it is practically impossible to adjust the solidification range of the acidic silica solution by adjusting the gel time in the air.

[0149] Furthermore, it is even more impossible to infiltrate and solidify a wide area such as 1.5 to 4 m with a preset pH and gel time of the mixed solution. Therefore, the inventors have made it possible to form a solidified body equivalent to the amount of the injected grout by the following method based on the concept of setting the mixed solution based on the injection time (H) and the soil gel time (GTs0) (Table 2, Figures 28, 29, and 30).

[0150] (1) In the case of relatively homogeneous ground: Research into the gelling properties of silica grout in such acidic regions has shown that in homogeneous ground, if a given amount is injected, even if the grout has not gelled at the time of injection, the grout will move in a neutral direction in the ground and will gel sooner or later at that location. This is due to the fact that the gelling of an acidic silica solution is accelerated in a ground with a higher pH, and the silica content in the acidic silica solution is reliably precipitated in its entirety even if it is diluted with groundwater.

[0151] (2) In the case of heterogeneous ground: While gelation in the ground is progressing, the material penetrates through the ground in a semi-gel state, preventing escape.

[0152] The prevention of deviations through compounding composition is explained below. Even if a specified amount of highly durable grouting material is injected into the ground, if the grout breaks into veins and escapes from the injection area (Figure 30(a)), or if it flows downward, a durable ground will not be formed (Figure 30(b)). To enable injection into a specified area, the ground must first be permeable to the injection of the chemical.

[0153] If the grout solution escapes through a coarse soil layer and goes outside the injection range, or if the injection speed is greatly divided and continues to escape outside the injection range, a phenomenon like that shown in Figure 30(a) occurs. In addition, if gelation does not occur even after injection of the specified injection amount, and the ground has high permeability, the solution flows downward and the specified area does not solidify (Figure 30(b)). In such cases, it is necessary to inject the following compounded solution developed by the inventors, which shows gelation behavior corresponding to the flow characteristics of the grout solution and the injection method in order to reduce the escape to the specified area and achieve infiltration and solidification (Table 2).

[0154] Figure 28 shows the relationship between the pH of the chemical solution and the gel time when the silica concentration is 6%, and the gel time in soil for each field soil. The ● in the figure shows the relationship between the pH of the chemical solution and the gel time in air (GT0). The rest show the relationship between the pH of the chemical solution and the gel time in soil (GTs) for the field sand.

[0155] In the present invention, by continuously varying the ratio of liquid A and liquid B, the pH of the chemical solution and the gel time in the air can be confirmed along the line ●. Also, the relationship between the pH of the chemical solution in the air, the pH of the on-site soil, and the gel time in the soil can be known in advance as shown in Figure 28.

[0156] If the flow characteristics during injection are within the range shown in Figure 28, the injection liquid will form a solidified mass corresponding to the specified injection amount while expanding the solidification range through the infiltration mechanism shown in Figure 29. Therefore, if the ratio of liquids A and B that will obtain the air gel time corresponding to the pH (pHs) and gel time (GTs) that allows infiltration and solidification according to the ground conditions is set by the inverter values ​​of the pumps for liquids A and B in on-site tests, it will be possible to inject a mixture with a specified gel time that is most suitable for the ground conditions, or a mixture with different gel times (instant setting or slow setting).

[0157] Figure 31(a) and (b) show the unconfined compressive strength of consolidated sand as a function of silica concentration, and Figure 31(c) shows the unconfined compressive strength of different in-situ sands.

[0158] Table 1 shows examples of injection rates for injection materials by injection method, injection purpose, and soil type, as shown in Table 2. As shown above, primary injection of suspension type is performed according to the ground conditions and injection purpose, and the injection rate of solution type injection liquid also differs.

[0159] The following describes the pipeline leading to the junction of liquid A and liquid B or the grout outlet after junction, and the grout control device in the mixer. In the present invention, the pH and gel time of liquid A and liquid B can be changed instantaneously and continuously to produce a grout with a desired pH and gel time, and since the diameters of the pipelines for liquid A and liquid B at the junction of liquid A and liquid B are different from the diameter of the pipeline after junction, the junction liquid becomes turbulent and is mixed after junction. Therefore, the pipeline after junction itself serves as a mixer, and a mixing tank as in batch grouting is not required. In addition, the grout produced by the grout production equipment consisting of this confluence mixing system can be stored in a storage tank and injected into multiple injection holes using multiple injection pumps. The grout with a specified pH and gel time, mixed by the confluence system of liquids A and B, is instantly and continuously prepared and introduced into the storage tank, so there is no need to adjust the pH and gel time in the storage tank and it can be injected directly into the ground.

[0160] The silica in the injection solution obtained in this way has a particle size of approximately 1 nm compared to the 0.1 nm of water glass, and grows to a larger diameter before gelling, forming a gel with excellent durability.

[0161] Figure 33(a) shows a static mixer installed in a double pipe, and Figure 33(b) shows the shape of the static mixer element. A static mixer is a stationary mixer (line mixer) with no driving parts, in which liquid A and liquid B that enter the mixer are stirred and mixed sequentially by elements. A static mixer effectively mixes fluids by dividing, converting, and inverting the fluid. The fluid is divided into two each time it passes through an element. Number of divisions N=2 n ,n: Number of elements

[0162] The fluid is rearranged along the twisted surface in the element from the center of the pipe to the wall, and from the wall to the center. The direction of rotation of the fluid changes for each element, and the fluid is turbulently mixed due to the sudden reversal of inertial force. The static mixer may be installed inside the injection pipe, or at any aboveground location from the junction of liquids A and B in the hose leading to the injection pipe to the tip of the injection pipe. This static mixer may be connected to a single pipe rod or the inner pipe in the double packer method, not necessarily a double pipe rod, and may be used for injection from the injection pipe of any of the injection methods mentioned above.

[0163] Figure 34 shows an example of a double-tube rod injection method with a mixer attached to the tip of the injection tube. Figure 34(a) shows the situation in which the injection tube is drilled into the ground using water to insert the injection tube rod, and then the injection liquid obtained by mixing liquid A and liquid B is injected into the ground.

[0164] Figure 35 shows an injection pipe device that mixes and injects liquid A and B at the outlet of a double-tube rod to create a grout and injects it into the ground. Figure 35(a) shows the drilling state, and Figure 35(b) shows the injection state. Figure 36 shows an example of mixing and injecting liquid A and B by generating a vortex at the tip of the double-tube injection pipe. Figure 37 shows an example of the double-tube double packer method, in which liquid A and B join above ground and are injected from the inner injection pipe into the outer pipe, and the joined grout is injected from the sleeve of the outer pipe. Figure 38 shows an example of the double packer method, in which the inside is composed of pipes for liquid A and liquid B, and the mixed liquid A and B discharged into the packers above and below the inner pipe is injected into the ground from the outlet covered by the outer pipe sleeve. Figure 39 shows an example of injecting grout formed by mixing liquid A and liquid B inside the sleeve of the outer pipe into the ground. [Explanation of symbols]

[0165] 1,1',1” Compounding liquid blending device 2,2',2” Infusion Pump 3 Multiple outer tubes 3' Multiple inner tube 4,4',4" Liquid delivery tube 5,5',5” Pressure Gauge 6,6',6” flow meter 7. Lift 7' injection tube depth gauge 8 Controller 9 Inlet section from inner pipe to tip of injection pipe 9' Injection tube tip 10,10',10” Information notification circuit from pressure gauge to controller 11,11',11” Information notification circuit from flowmeter to controller 12 Information notification circuit from injection depth meter to controller 13,13',13" Command circuit from controller to injection pump 14. Injection material combination adjustment device 15 Command circuit from controller to grout combination adjustment device 16 Command circuit from controller to elevator 17,17',17" Command circuit from controller to blending device A Rapid-setting reaction mixture B Main material mixture liquid C. Reactant mixture

Claims

1. A ground injection method for injecting silica grout through an injection pipe inserted into the ground, comprising: passing liquid A and liquid B through the injection pipe to join above ground or underground, and injecting the mixed grout into the ground, A ground injection method using a solution containing water glass as the A liquid and a solution containing a reactant as the B liquid, using a plurality of drive devices for pumping the A liquid and the B liquid by an A liquid pump and a B liquid pump, respectively, an inverter, and a control device for collectively managing the plurality of drive devices, the inverter is controlled to continuously variably control the flow rates and the joining ratio of the A liquid and the B liquid according to the ground conditions and the injection purpose, thereby injecting the injection liquid having a predetermined gel time and silica concentration mixed in a pipeline from an aboveground junction or an underground junction to the discharge port of the injection pipe into the ground.

2. 2. The ground grouting method according to claim 1, wherein a solution containing sulfate ions is used as said liquid B, and the sulfuric acid concentration of said liquid B and / or said grouting solution is set to 10% or less.

3. 2. The ground injection method according to claim 1, wherein, in the injection of the injection solution having a predetermined gel time and silica concentration mixed in the pipeline from the aboveground junction or the underground junction to the discharge port of the injection pipe, the ion concentration of the reaction product is continuously changed to grasp the gel time and the ion concentration of the reaction product in real time, and the ground is consolidated within the predetermined concentration required to set the gel time without prescribing an excessive amount of the reactant.

4. The method according to claim 1, wherein the injection liquid is a non-alkali silica grout having a silica concentration of 1 to 40 w / vol%, a pH of 1 to 10, and a gel time of 5 seconds to 7 days at 20°C, and wherein an acid-containing solution is used as the B liquid, and the joining ratio β of the A liquid and the B liquid is set to β=A / B=0.5 to 2.0, and the flow rates and joining ratio of the A liquid and the B liquid are variably controlled so that the pH and silica concentration correspond to the gel time continuously from the instantaneous setting mix to the slow setting mix, thereby injecting the injection liquid having a predetermined gel time and silica concentration into the ground.

5. 2. The ground injection method according to claim 1, wherein the flow rate and the mixing ratio of the A liquid and the B liquid are continuously controlled from a fast-setting mix to a slow-setting mix, and the mixing ratio at the start of injection is controlled so that the pH of the injection liquid starts on the acidic side when the injection liquid is injected into the ground.

6. 2. The ground injection method according to claim 1, wherein the flow rates and confluence ratios of the A liquid and the B liquid are set based on the ground conditions and groundwater conditions in the ground improvement area so that the residual ion concentration of the reaction product in the ground is a predetermined concentration, thereby solidifying the ground by keeping the concentration of the reaction product in the ground within the predetermined concentration.

7. The injection liquid is a non-alkali silica grout containing sulfate ions, having a silica concentration of 1 to 40 w / vol% and a pH of 1 to 10, and the ground is in the vicinity of a concrete structure or in the vicinity of a concrete structure to be constructed after excavation, Based on the ground conditions and groundwater conditions in the ground improvement area, the injected ground is classified into one of the following types based on the behavior of the sulfate ions dissolved in the ground: (1) open system, (2) stagnant system, or (3) concentrated system. (1) Open system: Groundwater flows outward from the concrete structure, and the sulfate ion concentration decreases through dilution. (2) Stagnant system: Ground where groundwater flow is stagnant and sulfate ion concentration hardly changes (3) Concentration system: Sulfate ions penetrate through the surface of the concrete structure and are concentrated in the ground, increasing the sulfate ion concentration. According to the type of the injection ground classified as above, one or more factors (Y) for reducing sulfate ions in the injection ground are selected from the following △1 to △7, △1: A non-injected portion is provided within the ground improvement area, and the ratio of the non-injected portion is set to the elution rate α of sulfate ions. １ The remaining rate of sulfate ions in the improved ground when １ △2: The dissolution rate of sulfate ions in groundwater is α ２ The residual rate of sulfate ions in the ground improvement area when ２ △3: The fixation rate of sulfate ions in the ground improvement area is the elution rate α ３ The remaining rate of sulfate ions in the ground improvement area when ３ △4: The replacement rate of sulfate ions of the sulfuric acid grout by the non-sulfuric acid grout or the low-sulfuric acid grout in the ground improvement area is the elution rate α ４ When this is done, the remaining rate of sulfate ions in the ground improvement area is △4 = 1 - α ４ △5: The replacement rate of the silica component in the ground grouting material by colloid is the elution rate α ５ When this is done, the remaining rate of sulfate ions in the ground improvement area is △5 = 1 - α ５ △6: A part or all of the sulfate ions are captured in the ground grouting material, and the capture rate is expressed as the elution rate α ６ When this is done, the remaining rate of sulfate ions in the ground improvement area is △6 = 1 - α ６ △7: The injection rate of the ground grouting material in the ground improvement area is reduced, and the reduction rate of the injection rate is the elution rate α ７ When this is done, the remaining rate of sulfate ions in the ground improvement area is △7 = 1 - α ７ The ground injection method according to claim 1, wherein the ground injection material is selected from a reactant formulation that makes the sulfate ion concentration of the non-alkali silica grout-derived sulfate ion remaining in the ground improvement area 8,000 ppm or less as the average value (X) of the sulfate ion concentration based on the reduction factor (Y) set according to the injection ground.

8. 2. The ground injection method according to claim 1, wherein the mixing ratio of the A liquid and the B liquid is continuously changed from a quick-setting mix to a slow-setting mix, so that the gel time and the concentration of the reaction product in the improved ground are predetermined values ​​according to the ground conditions, groundwater conditions and injection purpose.

9. The silica grout is a grout having a relatively short gel time and a grout having a relatively long gel time, which are successively injected into the ground in a quick-setting mix followed by a slow-setting mix, and the grout having a short gel time is injected into the ground as a primary injection material for roughly setting the ground, and the grout having a long gel time is injected into the ground as a secondary injection material for penetrating the ground.

10. 2. The ground injection method according to claim 1, wherein the injection solution is injected into the ground by any one 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 / slow setting composite injection method 7) Multi-stage simultaneous injection method 8) Multiple injection hole simultaneous injection method

11. A ground injection device used in the ground injection method according to claim 1, A ground injection device comprising the A liquid pump, the B liquid pump, the multiple drive devices, the inverter, the control device, and the injection pipe, and characterized in that a mixing device for the A liquid and the B liquid is provided at the confluence of the A liquid and the B liquid, or in a pipeline from the confluence to the discharge port of the injection pipe.

12. A ground injection device used in the ground injection method according to claim 1, A ground injection device comprising the A liquid pump, the B liquid pump, the multiple drive units, the inverter, the control unit, and the injection pipe, and characterized in that the A liquid and the B liquid are mixed in a static mixer.

13. A ground injection device used in the ground injection method according to claim 1, A ground injection device comprising the A liquid pump, the B liquid pump, the multiple drive devices, the inverter, the control device, and the injection pipe, wherein the control device collectively controls the multiple drive devices.

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