Ground improvement method and injection device

Abstract

By adding infiltration injection to the conventional high-pressure grouting method, it becomes possible to form large-diameter solidified bodies using suspended grout. Furthermore, it is possible to add injection material to excavated soil and reinject it, enabling ground improvement that is environmentally friendly and reduces CO2 emissions, while also providing a ground improvement method and injection device that can form larger solidified bodies that are lighter than conventional methods. [Solution] A ground improvement method and injection apparatus comprising cutting the ground to form a cutting area by using a jet fluid from an injection pipe inserted into the ground, and injecting an injection material into the formed cutting area, wherein the injection material mainly consists of suspended particles, or further contains one or more of a hardening agent, an alkaline agent, and a solution-type silica, and the injection material is filled into the cutting area and penetrates between the soil particles of the surrounding ground from the cutting area, thereby solidifying the cutting area and the surrounding ground.

Description

[Technical Field]

[0001] This invention relates to a ground improvement method using a combined injection and infiltration injection method, which utilizes the kinetic energy of a jetted fluid to cut and solidify the ground. In this method, a suspension-type injection material or a mixture of the suspension-type injection material and the soil of the cutting area is filled into the cutting area, and the injection material is allowed to penetrate and solidify into the surrounding ground from the cutting area to form a large solidified body. In particular, this invention relates to a combined injection method consisting of jet injection and infiltration injection, with a suspension as the main component. Specifically, it relates to a combined injection method and injection apparatus that uses a jetted fluid to fill the cutting area with injection material using kinetic energy, followed by infiltration injection to penetrate the injection material into the surrounding ground for ground improvement. The injection material may be a suspension such as cement or slag, calcined silica or hydraulic alumina, or a mixture thereof, and the method may consist of jet injection and infiltration injection. Furthermore, the invention relates to a combined injection and infiltration injection method that uses a suspension containing a silica solution, and allows for the simultaneous formation of a high-strength region by suspended particles and a infiltration-solidified region by separated silica solution by gelation of the separated silica solution while the suspension-type injection material penetrates between soil particles. Furthermore, by reusing excavated soil from high-pressure injection and injecting it into the ground, the volume of industrial waste is reduced. Moreover, the invention relates to a low-carbon ground improvement method that reduces CO2 emissions by using non-cement-based injection materials or injection materials with reduced cement content. This method utilizes suspension-type injection materials mainly composed of silica powder such as on-site soil, waste sludge, and crushed concrete, as well as artificially calcined silica such as slag, fly ash, sewage incineration ash, and plant incineration ash, and also uses naturally occurring silica particles with pozzolanic properties, such as soils containing soluble silica such as rammed earth, rammed earth, loam, shirasu, and volcanic deposits. Furthermore, by using hardening agents, solution silica, and alkaline agents together with these materials, it is possible to form a solidified body over a wide range of temperatures near neutral, and furthermore, it enables immediate strength development after injection, ensuring safety for surrounding structures and reducing the weight of the solidified body, thereby solving the problems of conventional high-pressure injection mixing methods using cement-based injection materials. [Background technology]

[0002] Various ground improvement methods have been known for soft ground and ground susceptible to liquefaction. Among these, the chemical injection method, which involves injecting an injection material (chemical solution) into the gaps between soil particles to permeate and solidify the ground, is widely used in many construction projects due to its simplicity.

[0003] The chemical grouting method is a construction method in which the injected chemical solution penetrates into the gaps between soil particles and solidifies, acting as an adhesive to strengthen the ground and provide waterproofing (improvement of permeability). Because it can be easily implemented with compact equipment, it is mainly used for short-term temporary construction (a supplementary method in underground construction) and for liquefaction countermeasures using rapid penetration grouting methods with permanent grout.

[0004] Other known methods include high-pressure injection molding, which involves injecting cement at high pressure to cut and agitate the ground while simultaneously mixing the excavated soil with cement; and mechanical mixing, which involves injecting a slurry-like injection material into soft soil layers that have accumulated to deep depths, and then using mixing blades to agitate and mix the in-situ soil with the injection material to form cylindrical improved bodies underground, thereby creating a strong and stable improved ground. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-40950 [Patent Document 2] Japanese Patent Publication No. 3413398 (Japanese Unexamined Patent Publication No. 2002-88752) [Patent Document 3] Japanese Patent Publication No. 7193105 (Japanese Unexamined Patent Publication No. 2024-53139) [Patent Document 4] Japanese Patent Publication No. 2022-66686 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, today, in order to curb global warming caused by CO2, there is a strong demand for the elimination of cement in ground improvement methods. The applicant has previously made inventions related to high-pressure injection grouting using slag, as described in Patent Documents 1 to 3, but the present invention is a ground improvement method that further develops those inventions.

[0007] In other words, in conventional high-pressure injection mixing methods, cement is used as the main component of the injection material. However, while cement has a high specific gravity of 3.17, its specific surface area is 3,220 cm². 2 The particle size is small, around 1g, and therefore, for the purpose of strengthening soft ground targeted by high-pressure injection mixing, the heavy cement particles result in a short penetration distance, making it difficult to form large solidified bodies.

[0008] Furthermore, because the process involves removing soil and replacing it with cement to form a solidified body, the disposal of this excavated sludge has become a major environmental problem today. In addition, in improving soft ground, there is a problem that the improved cement-solidified body tends to settle easily because soft ground has low bearing capacity, and the displacement of the structure tends to be large.

[0009] As described above, while the high-pressure injection mixing method has the advantage of producing a strong solidified body, it also has problems such as generating industrial waste soil, having low bearing capacity until solidification, and being heavy and rigid after solidification, making it prone to settlement in soft ground where integration with the existing ground cannot be achieved. In addition, there is the problem that the cement injection material is mixed with the high-pressure injection water in the excavated ground and is easily discharged to the surface along with the excavated soil.

[0010] On the other hand, in liquefaction countermeasures, economic efficiency takes precedence over strength, so the unconfined compressive strength of the soil using chemical solutions is 100-200 kN / m². 2 A certain level is sufficient, and when replacing conventional soil and solidifying it with cement, a density of several to tens of MN / m 2 It does not require such high strength.

[0011] When the soil particles of the ground are discharged by high-pressure jetting and replaced with cement, as the improved strength of the ground increases, the weight of the ground increases, resulting in an increase in inertial force. Also, since it becomes easier to transmit shock, there was a risk of brittle failure under repeated loads such as earthquakes.

[0012] Also, for the area directly beneath friction pile foundation structures, direct foundations, or detached houses, when seismic reinforcement and liquefaction countermeasures are carried out by the above-mentioned conventional methods, in the mechanical cement mixing method and the high-pressure jet mixing method, it is possible to easily reinforce the structure foundation. However, due to the increase in the shear rigidity of the ground (for example, by 100 - 2000 MN / m 2 level), it becomes easier to transmit seismic motion to the superstructure. As a result, during an earthquake, even if damage to the foundation (lower part) can be prevented, seismic forces exceeding the design value may act on the structure (upper part), causing it to lose its function.

[0013] Furthermore, in the conventional high-pressure jet mixing method, the uniaxial compressive strength was about 3 MN / m 2 level, making it difficult to excavate easily.

[0014] Here, the high-pressure jet mixing method is roughly divided into two types. First, an injection material such as cement or a mixture of air and the injection material is jetted from an injection pipe inserted into the ground to form a consolidated body composed of the injection material or a mixture of the injection material and the soil cut by the injection material in the ground. Second, a hole is drilled to the target depth with a guide pipe, an inner pipe is inserted into it, and then the guide pipe is pulled up. Cutting is performed by jetting high-pressure jet water or a mixture of air and high-pressure jet water from the inner pipe. The cut soil generated by the cutting is discharged from the gap (cut soil discharge path) on the outer periphery of the injection pipe rod to the ground surface. Then, an injection material is injected from a discharge port located below the high-pressure water jetting port into the cutting area thus formed (Figure 1).

[0015] Conventional construction methods primarily utilize single pipes, as well as double pipes (Figure 2) and triple pipes (Figure 3). The key differences are that single pipes can inject only solidifying agent, Figure 2 can inject solidifying agent plus air, and Figure 3 can inject solidifying agent plus air plus cutting fluid. Because these methods involve sludge discharge, there is a need to reduce or effectively utilize the discharged sludge in order to improve economic efficiency and reduce environmental impact. In prior art, to increase the diameter of the improved section, a double- or triple-pipe rod is used, and a solidifying agent and air, or cutting fluid, air, and solidifying agent, are injected at high pressure from an injection nozzle provided on the rod. The primary purpose of this air is to create a large-diameter improved section by forming a gas-liquid interface around the injected fluid (solidifying agent or cutting fluid), thereby suppressing the attenuation of the jet stream with distance. Furthermore, immediately after construction, the improved ground is in an unsolidified state because sufficient hydration reactions have not yet occurred. Therefore, when construction is carried out near a structure, the reduced bearing capacity may impair the function of the structure. In addition, in conventional high-pressure injection methods that rely on the energy of the high-pressure injection fluid, the cutting area is limited by the distance of the injected fluid, thus restricting the size of the improved ground.

[0016] In all of the above methods, the excavated soil, mixed with the injection material, is discharged to the ground from the outer circumference of the injection pipe. In this process, the disposal of the cement-mixed excavated soil poses a significant environmental problem.

[0017] The applicant has already proposed in Patent Documents 1 and 2 a ground injection method using a suspension-type grout and a suspension-type injection material mainly composed of slag and silica, and has also developed a method for mixing excavated soil with the above injection material and reinjecting it (Patent Document 1), and a high-pressure jet injection method using an injection material mainly composed of slag and gypsum or magnesium oxide (Patent Document 3). Furthermore, the applicant has clarified that the bleeding liquid of slag and low molar specific water glass grout gels (Patent Document 4).

[0018] However, as mentioned above, conventional ground improvement methods have limitations in terms of the diameter of the work area and environmental issues, and further improvements are desired. Therefore, the objective of the present invention is to not only fill the cutting area with injection material in the conventional high-pressure injection method, but also to penetrate the outside of the cutting area with injection material to form a large solidified body. Furthermore, by reducing cementation, it is possible to perform ground improvement that is considerate of the global environment by reducing CO2, and the present invention aims to provide a ground improvement method and injection device that can form a larger solidified body that is lighter than conventional methods. [Means for solving the problem]

[0019] Here, generally speaking, bleeding liquid refers to the supernatant solution obtained when a suspension is allowed to stand still, after the suspended particles have settled. However, in actual ground injection, the liquid equivalent to bleeding liquid refers to the solution obtained when the suspended particles are filled between soil particles and separated while penetrating into the ground. Therefore, since the separated liquid of a suspension containing silica solution contains fine suspended particles and silica solution, it is referred to as "separated silica solution" in this invention. In this invention, "bleeding liquid" and "separated silica solution" mean substantially the same thing.

[0020] The applicant applied the phenomenon described in Patent Document 4 to the high-pressure injection method and advanced research on a ground improvement method using injection and seepage combined injection. The applicant, through continued research on the gelation of bleeding solutions, found that suspensions containing solution-type silica gel at both 50% and 50% bleeding rates (Figure 4). Furthermore, it was discovered that the gelation time and strength of the bleeding solution can be adjusted by adding a hardening agent. The applicant also identified the relationship between the silica concentration required for homogels (solidified injection material alone) and sand gels (solidified mixture of injection material and soil) of the bleeding solution to be self-supporting (Table 9, Figures 6, 8-10, 12, and 13). As a result, we have invented a new ground improvement method based on the concept of combined injection and seepage injection shown in Figure 15. Figures 15(a) to (e) show the form of seepage solidification in the ground improvement method of the present invention. Figure 15 shows that the injection material is injected into the cutting area of ​​the injection material by injection, filling with the injection material alone or a mixture of the injection material and the soil of the cutting area, and the injection material penetrates to a wider area than the cutting area, allowing suspended particles to penetrate between soil particles, and further, the separated silica solution separated from the suspension seeps and solidifies, forming an integrated seepage solidified area. Therefore, the high-strength injection material alone, or the improved body solidified in a mixed state with the ground, and the separated silica solution separated from the suspension around it, which was filled into the cutting area by high-pressure injection through multiple injection holes, permeate and solidify into the ground, enabling integrated ground improvement of the entire ground. Furthermore, this invention substantially expands the applicability range of suspended grout (from a soil-related perspective) to that of solution-type grout, and develops it from a simple high-pressure injection mixing method to a ground improvement method based on a new technological concept called high-pressure injection infiltration injection (Figures 11 and 14).

[0021] Specifically, the present invention solves the aforementioned problems of conventional high-pressure injection mixing methods that primarily use cement by using suspended particles made of artificially calcined silica such as slag and fly ash, or silica particles (natural pozzolanes) obtained through a natural calcination process, as the injection material, and by mixing the excavated soil containing the injection material with the excavated soil and reinjecting it into the ground.

[0022] Thus, the applicant has invented a ground improvement method using a combined injection and infiltration injection method that enables the formation of a large solidified body not only by solidifying the cutting area by high-pressure injection, but also by infiltration and solidification from the cutting area to the surrounding area (Figure 15). Furthermore, the present invention realizes a ground improvement method that reduces the weight of the solidified body, expands the infiltration and solidification range, and contributes to the global environment by reducing CO2 emissions, by using naturally or artificially produced silica particles, calcined silica, silica particles with natural pozzolanic properties, and fluidized soil made by slurrying on-site excavated soil as the main injection material. Moreover, by using fluidized soil made by slurrying excavated sludge (on-site excavated soil) as the injection material, it is possible to reduce the volume of industrial waste.

[0023] Furthermore, as described above, the present invention relates to a ground improvement method for improving soft ground and liquefiable ground to high strength and light weight, utilizing the kinetic energy of a high-pressure injection fluid to cut the ground, filling the cut area with an injection material such as the above-mentioned suspended particles or slag, or a mixture of the injection material and the soil of the cut area, and further allowing the injection material to penetrate from the cut area to the surrounding area to form a large solidified body. According to the present invention, by reusing the mixed soil, which is a mixture of the cut soil and the injection material discharged to the surface by high-pressure injection, and reinjecting it into the ground, low-carbon ground improvement becomes possible. Moreover, by using a suspension-type injection material mainly composed of calcined silica such as slag or fly ash, or silica particles with natural pozzolanic properties, it is possible to reduce CO2 from a material standpoint by using a non-cement-based injection material or an injection material with reduced cement content, providing an environmentally friendly ground improvement method. Furthermore, the present invention enables ground improvement that simultaneously obtains the advantages of both high-pressure injection injection method for solidification and chemical injection method, by including solution-type silica in the suspension-type injection material, allowing the separated silica solution separated from the suspension to permeate and gel, thereby expanding the permeation and solidification range beyond the cutting area.

[0024] In other words, the ground improvement method of the present invention is a ground improvement method that involves cutting the ground with a jetted fluid from an injection pipe inserted into the ground to form a cutting area, and injecting an injection material into the formed cutting area, wherein the injection material mainly consists of suspended particles, and the injection material is filled into the cutting area and permeates between the soil particles of the surrounding ground, thereby solidifying the cutting area and the surrounding ground.

[0025] Furthermore, another ground improvement method of the present invention is a ground improvement method that involves cutting the ground with a jetted fluid from an injection pipe inserted into the ground to form a cutting area, and injecting an injection material into the formed cutting area, wherein the injection material mainly consists of suspended particles and contains one or more of a hardening agent, an alkaline agent, and a solution-type silica, and the injection material is filled into the cutting area and penetrates between the soil particles of the surrounding ground from the cutting area, thereby solidifying the cutting area and the surrounding ground.

[0026] In the present invention, it is preferable that the solution-type silica contains silica colloid and / or water glass, and that the bleeding liquid of the injection material gels.

[0027] In the present invention, it is preferable that the suspended particles contain one or more of calcined silica, natural silica having pozzolanic activity, and curable silica particles as active ingredients.

[0028] In the present invention, it is preferable that the calcined silica is one or more of slag, fly ash, cement, sewage incineration ash, plant incineration ash, and calcined clay.

[0029] In the present invention, it is preferable that the natural silica having pozzolanic activity is one or more of loam, shirasu, volcanic ash, fuwado, and sanwado.

[0030] In the present invention, it is preferable that the curing agent, alkaline agent, and solution-type silica consist of one or more of the following: (1) A substance containing gypsum and / or MgO as active ingredients. (2) A product containing one or more of the following as active ingredients: Ca salt, Mg salt, Al salt, carbonate, and bicarbonate. (3) A substance having one or more of the following as active ingredients: lime, cement, caustic alkali, water glass, and silica colloid.

[0031] In the present invention, it is preferable that the injection material contains clay and / or soil as a bulking agent.

[0032] In the present invention, the particle size of the suspended particles is a Blaine value of 4000 to 20000 cm². 2 The range is in the g / g range, and it is preferable that the amount of suspended particles in the injection material is 40 to 200 kg / 400 L.

[0033] In the present invention, it is preferable that the injection material contains slag as the suspended particles, and the amount of slag in the injection material is 10 to 50 w / v%, or, if the injection material contains slag as the suspended particles and cement, the weight of the cement is 5 to 50% of the weight of the suspended particles.

[0034] In the present invention, it is preferable that the molar ratio of the water glass is 1.0 to 5.0, and the amount of the water glass in the injection material is 10 to 150 L / 400 L.

[0035] In the present invention, when using an injection material consisting of a suspension mainly composed of the suspended particles and the solution-type silica as an active ingredient, and injecting the injection material into the ground through a plurality of injection holes provided in the ground, it is preferable that the bleeding liquid of the injection material gels and the homogel has sufficient strength to stand on its own, that the sand gel formed by the penetration and solidification of the bleeding liquid has sufficient strength to stand on its own, that the bleeding liquid penetrates into parts of the ground that the suspension could not penetrate, thereby expanding the solidification area, or that it integrates with the parts of the ground that the suspension has penetrated to form a solidified body.

[0036] Here, in the above, "the bleeding solution gels and the homogel stands upright" means that the silica concentration of the bleeding solution is 0.5 w / v% or higher, and that the homogel does not collapse and stands upright even when tilted at an angle within the mold. "The sand gel stands upright" means that the silica concentration of the bleeding solution is 0.5 w / v% or higher, and when using No. 6 silica sand, the sand gel prepared by mixing with the bleeding solution to achieve a relative density of 60% in a diameter of 5 cm × height of 10 cm stands upright, and the strength measured in a uniaxial compression test using the sand gel is 2.0 kN / m². 2 This means that it is more than that.

[0037] In the present invention, it is preferable to set the injection material in a formulation that is lightweight, low in alkalinity, and low in carbon, resulting in a suitable ground improvement.

[0038] In the present invention, it is preferable that the injection material contains one or more of microbubbles, air, a dispersant, and a thickening agent as active ingredients.

[0039] In the present invention, the curing agent is preferably a polyvalent metal compound, which is one or more of the hydroxides, oxides, or salts of Ca, Mg, or Al, and / or gypsum.

[0040] In the present invention, it is preferable to confirm the improvement effect of injecting the injection material by non-destructive testing.

[0041] In the present invention, it is preferable that the non-destructive test is performed by elastic wave velocity logging, acoustic tomography, or surface wave exploration.

[0042] The present invention relates to an injection device used in a high-pressure jet agitation method, characterized by comprising: a guide pipe inserted into the ground; an injection pipe disposed within the guide pipe and used for injecting an injection material; and an opening / closing mechanism for opening or closing the space between the guide pipe and the injection pipe.

[0043] In the injection device of the present invention, the opening and closing mechanism comprises an annular rubber bag disposed between the guide tube and the injection inner tube and having a conduit through which fluid can flow, a ball bearing provided on the inner surface of the rubber bag on the injection inner tube side, and sealing members provided at the upper and lower ends of the rubber bag, and the opening or closing of the space by the opening and closing mechanism can be performed by whether or not there is pressurization inside the rubber bag due to the inflow and outflow of fluid into the rubber bag.

[0044] In the injection device of the present invention, the opening and closing mechanism comprises an annular rubber bag disposed between the guide tube and the injection inner tube and having a conduit through which fluid can flow, a fixing member for fixing the rubber bag to the guide tube, and ring-shaped fittings for closing the upper and lower ends of the rubber bag, and the opening or closing of the space by the opening and closing mechanism may be performed by the presence or absence of pressurization inside the rubber bag due to the inflow and outflow of fluid into the rubber bag.

[0045] Furthermore, yet another ground improvement method of the present invention is a ground improvement method using a high-pressure injection mixing method with the above-described injection device, characterized in that it includes the steps of: drilling a hole in the ground to a target depth using the guide pipe and inserting the injection inner pipe into the guide pipe; opening the space using the opening and closing mechanism and injecting the injection material from the injection inner pipe at high pressure together with high-pressure injection water or air, injecting and mixing the ground while cutting, and mixing the excavated soil generated by the cutting with the injection material on the surface to produce a mixed injection material; and injecting the mixed injection material from the injection inner pipe into the ground at high pressure together with high-pressure injection water or air.

[0046] Furthermore, yet another ground improvement method of the present invention is a ground improvement method using a high-pressure injection mixing method with the above-described injection device, characterized in that it includes the steps of: drilling a hole in the ground to a target depth using the guide pipe and inserting the injection inner pipe into the guide pipe; opening the space with the opening / closing mechanism and injecting the injection material from the injection inner pipe at high pressure together with high-pressure injection water or air, injecting and mixing the ground while cutting, and filling the area created by the cutting with the injection material; and closing the space with the opening / closing mechanism and pressurizing the injection material into the ground.

[0047] In the ground improvement method of the present invention, different injection materials are used for injection agitation and pressurized infiltration, and the injection material used for pressurized infiltration can be made to have higher permeability than the injection material used for injection agitation. Furthermore, the injection material used for injection agitation and the injection material used for pressurized infiltration can be switched by opening and closing the space using the opening and closing mechanism. [Effects of the Invention]

[0048] According to the present invention, it is possible to perform ground improvement that is environmentally friendly and reduces CO2 emissions by eliminating cement or reducing the cement content in conventional high-pressure injection methods, and it is also possible to provide a ground improvement method and injection device that can form a larger solidified body that is lighter than conventional methods. [Brief explanation of the drawing]

[0049] [Figure 1] This is a conceptual diagram comparing a conventional ground improvement method using high-pressure injection with the ground improvement method according to the present invention. (a) shows an example of using a triple-pipe rod in the conventional method, and (b) shows an example of using a double-pipe rod in the conventional method. [Figure 2] This is a cross-sectional view showing an example of a conventional construction method using a double-pipe rod (the JSG method (registered trademark) of the Japan Jet Grout Association ("JSG method" is a registered trademark of N.I.T. Corporation)). [Figure 3]This is a cross-sectional view showing an example of a conventional construction method using a triple-pipe rod (the column jet grout method of the Japan Jet Grout Association). [Figure 4] This is a photographic diagram showing the bleeding state of the sample from Example 36. [Figure 5] This is a photographic diagram showing the bleeding state of the sample in Comparative Example 1. [Figure 6] This is a photographic diagram showing the state of the sample from Example 36 several days after penetration. [Figure 7] This is a photograph showing the condition of the sample from Comparative Example 1 several days after penetration. [Figure 8] This graph shows the results of the long-length penetration test for Example 36 and Comparative Example 1. [Figure 9] This is a magnified graph of the portion of Figure 8 where the penetration distance is between 90 cm and 120 cm. [Figure 10] This photograph shows the bleeding fluid gelling, and the gel remains intact (self-supporting) even when tilted. [Figure 11] This graph shows the particle size accumulation curves of various on-site sands treated with solution-type grout for liquefaction countermeasures. [Figure 12] This is a photograph showing the strength measurement of test specimens on day 7 using a mixing method with bleeding fluid. [Figure 13] This is a photograph showing the condition of a test specimen after strength measurement using a mixing method with bleeding fluid. [Figure 14] This graph shows the physical properties of the sand used. [Figure 15(a)] This is an explanatory diagram showing one form of seepage solidification in the ground injection method of the present invention. [Figure 15(b)] This is an explanatory diagram showing another form of seepage solidification in the ground injection method of the present invention. [Figure 15(c)] This is an explanatory diagram showing yet another form of seepage solidification in the ground injection method of the present invention. [Figure 15(d)] This is an explanatory diagram showing yet another form of seepage solidification in the ground injection method of the present invention. [Figure 15(e)]This is an explanatory diagram showing yet another form of seepage solidification in the ground injection method of the present invention. [Figure 15(f)] This is an explanatory diagram showing yet another form of seepage solidification in the ground injection method of the present invention. [Figure 16(a)] This is an explanatory diagram relating to an injection device used in the injection / penetration composite injection method of the present invention. [Figure 16(b)] This is another explanatory diagram relating to the injection device used in the injection-penetration composite injection method of the present invention. [Figure 16(c)] This is yet another explanatory diagram relating to an injection device used in the injection-penetration composite injection method of the present invention. [Figure 16(d)] This is an explanatory diagram of the construction procedure using the injection device used in the injection-penetration composite injection method of the present invention. [Figure 17(a)] This is an explanatory diagram relating to another injection device used in the injection / penetration composite injection method of the present invention. [Figure 17(b)] This is another explanatory diagram relating to another injection device used in the injection / penetration composite injection method of the present invention. [Figure 17(c)] This is an explanatory diagram of the construction procedure using other injection devices for the injection / penetration composite injection method of the present invention. [Modes for carrying out the invention]

[0050] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The ground improvement method of the present invention involves cutting the ground with a fluid jet from an injection pipe inserted into the ground to form a cutting area, and then injecting an injection material into the formed cutting area to perform ground improvement.

[0051] In this invention, the injection material is made primarily of suspended particles, or primarily of suspended particles and further containing one or more of a hardening agent, an alkaline agent, and a solution-type silica. This injection material is filled into the cutting area and allowed to penetrate between the soil particles of the surrounding ground, thereby solidifying the cutting area and the surrounding ground.

[0052] The above-mentioned present invention cuts soft ground with the force of an injection fluid, particularly a high-pressure injection fluid (for example, pressure 40 to 70 MPa), discharges the soft soil to the ground surface, and fills the cutting area with an injection material or a mixture of the discharged cut soil and the injection material. The injection material is a low-carbon grout, and carbon reduction is carried out from the viewpoints of sludge transportation, waste treatment, and waste disposal sites, enabling the reduction of environmental problems. The mixing of the discharged cut soil and the injection material can be carried out by filling a recycled injection material production tank.

[0053] When the recycled injection material treated by the above method is used for filling the cutting area, protecting surrounding structures, or improving the bottom of a shaft, the uniaxial compressive strength is 2 to 6 MN / m 2 in the cohesive soil layer and 5 to 15 MN / m 2 in the sandy soil layer. -5 It is preferably improved to about 10 -9 to 10

[0054] In this way, the present invention uses artificial calcined silica such as the above-mentioned silica powder, slag, or fly ash as the main component, or silica particles having a natural pozzolanic action as the main component, or forms a solidified body with a small amount of cement used, and in the entire improved area, the improved body has the advantage of reduced weight and elimination of settlement caused by the improved body. This is because the specific gravity of cement is 3.15, while the specific gravity of slag is 2.9, the specific gravity of fly ash is 2.8, and the specific gravity of volcanic ash is generally 0.9 to 2.5, which is almost the same as that of ordinary soil.

[0055] Table 1 described later shows an example of a consolidation strength test of a mixture with an injection material when the ground is sandy soil or cohesive soil. Alternatively, it can be an example of a consolidation strength test of a mixing ratio example of recycled soil when the cut soil is sandy soil or cohesive soil. It can be seen that the mixing formula of the injection material can be adjusted according to the injection purpose, required strength, mixing time, and cut soil sand.

[0056] Tables 1 to 8 show that even if the soil is not excavated, it can be mixed with the on-site soil and injected as an injection material. The strength of the injection-mixed soil of the injection material and the soil of the excavated area is also shown in the excavated area. In the present invention, as will be described later, by selecting a lightweight suspension mainly composed of small-particle suspensions with good fluidity according to the ground conditions, it is possible to penetrate and solidify the surrounding ground of the excavated area (Figures 7 to 9, 11, and 14). If the suspension contains solution-type silica, the separated silica solution separated from the suspension will gel and solidify, so the solidification range will extend to the surrounding soil of the excavated area even in ground that cannot be penetrated by the suspension alone, and a watertight effect and continuous solidification of solidified bodies are possible (Figures 4, 6, 8 to 13). Figure 11 shows the particle size distribution curve in which a penetration and solidification effect was obtained with a solution-type grout. Since the suspension-type injection material containing the above-mentioned suspended particles with solution-type silica can penetrate and solidify down to the ground with the particle size distribution shown in Figure 11, a new ground improvement method called the "injection-penetration composite injection method" is possible, which simultaneously combines the advantages of high-pressure injection injection and chemical injection methods. Furthermore, the silica solution gels immediately after injection, and if an increase in strength is obtained, or if a plastic gel is injected, it does not cause deformation or settlement of the structure in the ground near the structure as in the high-pressure injection mixing method. In addition, it has the advantages of requiring a lightweight injection device, producing less noise and vibration, and being environmentally friendly, thus solving the problems of the conventional high-pressure injection mixing method (Figure 15(e)).

[0057] The injection material used in the present invention will be described below. The injection material according to the present invention mainly consists of suspended particles, or mainly consists of suspended particles and further includes one or more of a curing agent, an alkaline agent, and a solution-type silica. As a suspension mainly consisting of suspended particles, calcined silica such as slag or fly ash is prepared as an aqueous suspension, and a curing agent such as water glass and / or an alkaline agent is mixed in to prepare and use the suspension. As suspended particles, calcined silica, natural silica with pozzolanic properties, and curable silica particles, or any or more of them, can be used as active ingredients.

[0058] Among these, calcined silica includes slag and fly ash, as well as cement, papermaking sludge, sludge incineration ash, sewage incineration ash, plant incineration ash, and calcined clay, and plant incineration ash containing a large amount of silica. One or more of these can be used. In addition, natural silica with pozzolanic properties includes natural calcined soils such as loam (Kanto loam), shirasu, volcanic ash, fuwado, and sanwado, and one or more of these can be used. These calcined silicas are silica particles with latent hydraulic properties, containing soluble silica, and, upon the action of alkalis such as slaked lime, gypsum, magnesium hydroxide, water glass, silica colloid, caustic alkali, carbonate, bicarbonate, aluminum salt, calcium salt, and magnesium salt, solidify firmly by forming a crystalline structure similar to that of cement through a pozzolanic reaction. Furthermore, by using aggregates such as clay and / or soil as thickeners or bulking agents, it becomes possible to perform ground improvement economically. Furthermore, the on-site soil can also be used after being formed into a slurry with the hardening agent mentioned above.

[0059] The above suspended particles have a Blaine value of 4000 to 20000 cm³. 2 By using particles with a particle size of / g, interparticle penetration between soil particles becomes possible. Furthermore, by using artificial or natural calcined silica as suspended particles and setting the amount of suspended particles in the injection material to 40 to 200 kg per 400 L, high strength can be obtained. The amount of calcined silica such as slag in the injection material according to the present invention is determined by the desired strength of the hardened product, but it is preferably 50 to 200 kg per 400 L, with 10 to 50 w / v% when cement is not used in combination, and when cement is used in combination, the weight of cement is preferably 5 to 50% of the weight of suspended particles.

[0060] The hardening agent used in the grout material in the present invention may be a polyvalent metal compound, which may be one or more of the hydroxides, oxides, or salts of Ca, Mg, or Al, and / or gypsum. Specifically, it may be a Ca molten product such as cement, slaked lime, or gypsum, or an alkaline agent. Slaked lime is particularly preferred for shortening the gelation time and improving initial strength. The grout material may also be used in combination with slag, bentonite, calcium carbonate, clay, silica powder such as soil, etc., as a filler material. As a plastic grout, fly ash, polymers, cement, plasticizers such as aluminum salts, thickeners, clay, etc., can be used as fillers.

[0061] The hardening agent, alkaline agent, and solution-type silica used in the injection material of the present invention can be any or more of the following (1) to (3). (1) A substance containing gypsum and / or MgO as active ingredients. (2) A product containing one or more of the following as active ingredients: Ca salt, Mg salt, Al salt, carbonate, and bicarbonate. (3) A substance having one or more of the following as active ingredients: lime, cement, caustic alkali, water glass, and silica colloid.

[0062] The solution-type silica used in the injection material of the present invention preferably contains silica colloid and / or water glass, which causes the bleeding liquid of the injection material to gel. In this case, the molar ratio of water glass is preferably 1.0 to 5.0, and the amount of water glass in the injection material is preferably 10 to 150 L / 400 L.

[0063] In the present invention, the slag used is finely ground blast furnace slag, and a finer particle size is preferable to enhance reactivity, for example, a specific surface area (Blaine value) of 4000 cm². 2 / g or more, preferably 6000cm² 2 / g~20000cm 2 Suitable for materials with a density of / g and an average particle size of 10 μm or less.

[0064] In the present invention, the water glass is preferably one with a high alkali concentration due to its reactivity with slag, and particularly preferably one with a molar ratio of SiO2 / Na2O of 2.5 or less. A low molar ratio allows for the acquisition of a high-strength solidified body and a long gelation time. In addition, as the water glass, a mixture of anhydrous orthosilicate and sodium hydroxide, crystalline sodium silicate containing sodium metasilicate, a mixture containing some crystalline sodium silicate, sodium silicate glass (cullet), hydrated glass, dehydrated sodium silicate, semi-solid sodium silicate, viscous sodium silicate, or a dilute solution of commercially available sodium silicate can be used, and the viscosity, molar ratio, and silica concentration may be changed, or it may be used in powder form. The alkalinity of the water glass stimulates the latent hydraulic properties of the slag. Furthermore, water glass with a low molar ratio may be a mixture of water glass and caustic alkali. However, when using molten calcium materials such as slaked lime or cement in combination, water glass with a high SiO2 / Na2O molar ratio, such as water glass No. 3 and No. 4, can be used.

[0065] The salts used in this invention may include aluminum compounds such as aluminum sulfate and polyaluminum chloride, as well as Ca, Mg chlorides and sulfates, or those obtained by reacting these with a caustic alkali. Furthermore, the molar ratio of Na2O / Al2O3 is not particularly limited, but due to its reactivity with the slag, it is preferable that the Na2O concentration in the grout be 1 wt% or more. The caustic alkali is effective in stimulating the hydraulic properties of the slag, and the aluminum reacts with the water glass and the silica in the slag to form aluminum silicate and calcium aluminosilicate. In addition, the gel time and strength of this suspension and the separated silica solution separated from the suspension can be adjusted by changing the amount of these additives added. Furthermore, seawater can also be used as the compounding liquid for the suspension.

[0066] The proportions of water glass and aluminum compound in the grout are such that the curing time of the grout is several hours, usually within one hour, preferably within 30 minutes. This also depends on the molar ratio of Na2O, Al2O3, and SiO2, but it is preferable that the amount of Na2O in the grout is 1 wt% or more. However, when solidifying a large area, a proportion that results in a curing time of several hours is necessary.

[0067] In this invention, the amount of injection material mixed with the excavated soil varies greatly depending on the properties of the excavated soil to be treated, but 1 m 3 Hit rate: 0.1-0.5m 3 It is preferable that it be within the range of [specify range].

[0068] Furthermore, the injection material of the present invention can be made lighter by adding foaming agents or foaming agents to improve its fluidity. By adding salt-free high-performance water-reducing agents, dispersants, clay, bentonite, and polymer-based thickeners, such as polyvinyl alcohol, carboxymethylcellulose (CMC), and methylcellulose, it is possible to suppress dispersibility in water, reduce precipitation, improve workability, or have it function as a water-retaining material or as a binder for suspended particles such as slag, which are the main material, thereby forming a pseudo-gel-like fluid that maintains fluidity while being difficult to disperse. As a result, diffusion and dilution in the ground can be reduced, and the expansion of the solidified body can be promoted.

[0069] In the present invention, microbubbles or microbubbles and air can be mixed into the above-mentioned suspensions such as slag and fly ash, or suspensions such as cement, and injected into the cutting area. This allows for the construction of a large-area solidified body by the bearing action of the microbubbles or microbubbles and air that surround the suspended particles, and also makes it possible to reduce the weight and strength of the solidified body by increasing the amount of gas in the solidified body. In the present invention, microbubbles, air, dispersants, and thickeners, or any or more of them, can be used as active ingredients in the injection material.

[0070] Furthermore, it has been found that air bubbles present in the solidified material improve the liquefaction prevention effect, even if the amount of suspended particles in the solidified material is small and the strength is low.

[0071] Furthermore, the use of excavated soil in this invention is effective as a low-carbon technology. That is, conventionally, excavated soil had to be disposed of in uneconomical and time-consuming ways, such as being dumped as industrial waste or being transported from the site to a treatment plant and mixed with lime. However, the problems of such conventional methods are resolved by applying this invention. According to this invention, economical and rapid construction becomes possible by backfilling with excavated soil on site or by mixing the excavated soil with injection material and then filling the mixture into the excavated area.

[0072] In this invention, a formulation can be set for the injection material that is lightweight, low-alkali, and low-carbon, resulting in a suitable ground improvement.

[0073] In the present invention, the injection material may be directly mixed and delivered to the injection rod as a single liquid, or the above-mentioned suspension (liquid A) and water glass and / or alkaline agent (liquid B) may be transported by pump, mixed, and then injected. In this case, it is preferable that liquids A and B be mixed in a ratio of approximately 1:1 (volume), but they are usually mixed in any ratio within the range of 10:1 to 1:10.

[0074] Furthermore, when the above-mentioned injection material is re-injected into the cutting area, the hardening time of the regenerated injection material should be sufficient to achieve adequate mixing with the cut soil. Therefore, it is determined by the mixing method or mixing device, and for example, 10 to 30 minutes is appropriate. Alternatively, considering workability, it can be set to several hours to more than ten hours.

[0075] In this invention, the improvement effect of injecting the injection material can be confirmed by non-destructive testing. Non-destructive testing methods that can be used include elastic wave velocity logging, acoustic tomography, or surface wave exploration.

[0076] (test) Clayey soil and sandy soil were used as excavated soil, and these were mixed with the injection material, respectively, and solidified using the injection material according to the present invention. The test results of the example in which the strength of this solidified body was measured are shown in Table 1.

[0077] From the following, it can be seen that injection materials that use calcined silica or natural silica with pozzolanic properties as the main material, and do not use cement, or injection materials that use a reduced amount of cement, have a lower specific gravity than injection materials that use cement as the main material. Therefore, because the ground is consolidated with a material that has almost the same specific gravity as the original ground, or even lighter, a weight reduction effect on the consolidated body can be obtained.

[0078] [Materials used] Slag: Specific gravity 2.9, Blaine value 8000 cm³ 2 It is a silica-based, non-curable powder. Fly ash (FA): Coal ash discharged from thermal power plants; a silica-based, non-hardening powder. Specific gravity: 1.9-2.3 g / cm³ 3 , with a particle size distribution of 90% or less being 0.1 mm or smaller. Cement: Ordinary Portland cement: PC, specific gravity 3.15, hardening agent. Aluminum sulfate: Aluminum sulfate, Al2O3 = 17.2%, gelling agent, specific gravity 1.32. Slaked lime: Industrial calcium hydroxide, gelling accelerator, and hardening agent. Gypsum or hemihydrate gypsum: hardening agent, specific gravity 2.6. Bentonite: Water-retaining and thickening agent, specific gravity 2.6. Magnesium oxide (gelling agent): Specific gravity 3.65. Calcium chloride (gelling agent): Specific gravity 1.85. Baking soda: Specific gravity 2.2. Dispersant: Specific gravity 1.04. Sulfuric acid: specific gravity 1.67, 75w / w%. No. 5 water glass: Specific gravity 1.32, silica concentration 25.5%, Na2O 7.03, molar ratio 3.75. No. 1 water glass: Specific gravity 1.35, silica concentration 21.59%, Na2O 10.80%, molar ratio 2.06. No. 3 water glass: Specific gravity 1.41, silica concentration 29.16%, Na2O 9.36%, molar ratio 3.22. Polyaluminum chloride or foaming agents can also be used.

[0079] [Test Methods and Test Results] Tables 1 to 7 show the results of the uniaxial compressive strength tests, using cylindrical specimens with a height of 100 mm and a diameter of 50 mm, in accordance with the Japanese Industrial Standard (JIS A 1216:2020 Method for uniaxial compressive strength testing of soil). The results of the strength measurements taken on day 1, day 7, and day 28, or on day 28, are shown separately. Furthermore, in Tables 1 to 8, gel time is the time it takes for the suspension to thicken while continuously stirring with a stirring rod.

[0080] From this embodiment, it can be seen that in the present invention, a solidified body obtained by mixing excavated soil and this injection material in the ground can be used to form a sufficiently solidified ground by mixing excavated soil and this injection material and injecting it into the excavated area. Furthermore, it can be seen that even if excavated soil is not used, ground improvement can be economically achieved by injecting an injection material obtained by mixing soil or clay obtained from other sources with this injection material.

[0081] [Table 1]

[0082] [Table 2]

[0083] [Table 3]

[0084] [Table 4]

[0085] [Table 5]

[0086] [Table 6]

[0087] [Table 7]

[0088] [Table 8]

[0089] The following describes test examples (Figures 4 to 13) demonstrating the effects of gelation by the bleeding solution in the above suspension containing silica solution, or by the separated silica solution separated from the suspension. Figure 10 shows Figure 4 tilted, using Example 36 from Table 4. Figures 12 and 13 show the state of strength tests on sand specimens solidified with the bleeding solution from Table 8.

[0090] (Penetration test) (Test equipment and test method) A one-dimensional infiltration device (2m in length) was used to conduct infiltration tests on silica sand No. 6, and the infiltration length and intensity distribution were investigated.

[0091] Test conditions: Acrylic mold h=2m, mixing solution 3L. After saturating the sample with water, the suspension was injected from the bottom and continued until no more drainage fluid was discharged.

[0092] The unconfined compression test was conducted in accordance with the Japanese Industrial Standard (Draft) (JIS A 1216:2020) for the unconfined compression test of soil, using cylindrical specimens with a height of 100 mm and a diameter of 50 mm.

[0093] The formulations of Example 36 and Comparative Example 1 were used (Figures 6-9, 12, 13).

[0094] The solid lines in Figures 8 and 9 show the results obtained using the formulation of Example 36. Strength measurement was possible even at a penetration distance of 120 cm. Although there was no discoloration of the sand gel beyond 90 cm, the strength measurement was possible because the separated silica solution separated from the suspension solidified beyond 90 cm. The portion beyond 90 cm is thought to contain 0.5% or more silica.

[0095] The dotted lines in Figures 8 and 9 show the results obtained using the formulation of Comparative Example 1. Strength measurements were possible up to 90 cm, but beyond 90 cm, there was no discoloration, and strength measurements could not be taken, indicating that the separated silica solution separated from the suspension had not gelled.

[0096] In the penetration test shown in Figure 7, areas where the sand did not show a discoloration reaction are thought to have not been penetrated by the slag. Due to the lack of self-supporting properties of the bleeding liquid, the areas where the solution separated from the suspension penetrated also lacked self-supporting properties and did not solidify. In contrast, in Figure 6, the bleeding liquid gelled and became self-supporting, so although the suspended particles did not penetrate and the sand gel did not discolor, the separated silica solution separated from the suspension penetrated and solidified, resulting in self-supporting properties and strength.

[0097] Based on the above, under conditions where penetration between soil particles is not possible depending on the soil particle size and density, and the particle size distribution of suspended particles, only the separated silica solution separated from the suspension will penetrate (Figures 11, 14).

[0098] Figures 8 and 9 show that even if the penetration distance of the suspended particles in the suspension is 90 cm, the separated silica solution penetrates up to 120 cm, and the solution has enough strength to stand on its own, as does the strength of the sand gel. In this case, the silica concentration can be predicted to be 0.5-2% or higher (Table 9). Therefore, even if the injection hole spacing is long, the homogel of the silica solution will connect the solidified bodies in which the suspended particles have penetrated, resulting in high strength.

[0099] In this way, even in ground conditions where suspended particles cannot penetrate, a unified solidified body can be formed, and even if the injection holes are spaced far apart, the solidified bodies between them can be connected by a self-supporting silica solution gel, thereby forming a unified solidified ground.

[0100] Although suspension-type grout can achieve higher strength compared to solution-type grout, its large particle size results in poor permeability into fine-grained soil. However, by including solution-type silica, a solidification effect can be obtained even in ground where suspension particles cannot penetrate, enabling integrated ground improvement and watertightness (Figure 15).

[0101] As described above, the inventors focused on the gelation of the bleeding liquid in suspension-type grout and studied the gelation of the bleeding liquid, the self-supporting properties of the homogel of the bleeding liquid, and the self-supporting properties and strength of the sand gel of the bleeding liquid. By using these conditions, they improved the penetration and solidification properties of suspension-type grout in fine-grained soil and ground containing fine-grained soil, which were previously considered unsuitable, and completed the present invention. Furthermore, according to the present invention, an improvement effect that enables self-supporting and watertightness of the excavated surface can be obtained even in excavated ground. Therefore, the present invention can be applied not only to ground strengthening as shown in Figure 15, but also to strengthening and watertightness of excavated ground.

[0102] In particular, when a suspension-type grout containing a silica solution is applied, the present invention exhibits the following effects due to the gelation of the separated silica solution separated from the suspension-type grout. By exhibiting such effects that cannot be obtained with conventional high-pressure injection mixing methods, the present invention realizes a new ground improvement method consisting of injection and infiltration injection, which simultaneously obtains the advantages of both high-pressure injection mixing and infiltration injection methods. (1) Penetration and consolidation of suspended particles into fine-grained soil where penetration and consolidation were previously impossible. (2) Self-supporting effect and watertightness of the cut surface. (3) Expansion of the improvement range through penetration and solidification. (4) Ground improvement in which adjacent solidified bodies are connected and integrated. (5) Reduction of construction costs by increasing the drilling interval of the injection pipes. (6) Construction safety is improved by the short-term solidification effect of the separated silica solution separated from the suspension grout, thereby increasing resistance to earth pressure from adjacent buildings and from the back of retaining walls; safety for underground structures through seepage injection; strengthening of the surrounding ground of underground structures with spaces; waterproofing and repair of deterioration.

[0103] Examples are shown below. (Strength test) (Preparation of sand gel specimens) Using silica sand No. 6 (Figure 14), specimens measuring 5 cm in diameter and 10 cm in height were prepared by mixing with a bleeding solution to achieve a relative density of 60%, and the uniaxial compressive strength was measured after 28 days. The bleeding rate increased with a higher water glass content and decreased slag content. In sand gels using the bleeding solution, a higher proportion of strength development was observed with higher water glass and slag content. Furthermore, in samples using gypsum, the addition of gypsum reduced the bleeding rate and increased the strength.

[0104] The gelation and self-supporting properties of the bleeding solution, as well as the strength and self-supporting properties of the sand solidified by the bleeding solution (sand gel), vary depending on the proportions of slag and water glass in the suspension, the ratio of silica (SiO2) in the water glass to calcium (CaO) in the slag (CaO / SiO2), the gel time, and the particle size and density of the sand solidified by the bleeding solution. Therefore, as a condition that comprehensively affects several of these factors, we conducted tests to confirm the minimum values ​​of gelation, self-supporting properties, and strength of the bleeding solution (Table 9). The gel time in Table 8 is the agitated gel time, which cannot be obtained for the bleeding solution, so we used the static gel time here. The static gel time was measured as follows. First, 100 mL of the bleeding solution was placed in a standard bag No. 8 (thickness 0.03 × width 130 × height 250 mm), and it separated into a lower part with many suspended particles and an upper part with few suspended particles (bleeding solution). Of the components, the standing gel time was defined as the point at which the upper part of the lower suspension portion no longer tilted by 2 / 3 when slowly tilted sideways. The standing gel time was shorter than the agitated gel time, and in most cases it was half the agitated gel time. When preparing the sand gels shown in Table 8, 2L or 3L of the mixture was placed in a 3L poly jug, and the bleeding liquid was removed at half the standing gel time and used to prepare the sand gel.

[0105] As a result, provided that the bleeding liquid gels and becomes self-supporting, and the sand gel permeated with the bleeding liquid becomes self-supporting, it has become possible to improve the ground by suspension-solution composite injection, which solidifies areas of fine-grained soil where penetration and solidification of suspended particles was difficult, or areas where penetration did not occur, using a separated silica solution separated from the suspension, and integrates the entire structure.

[0106] It was found that gelation occurs even with a bleeding rate of 50% or more, or even below 50%, indicating that the separated silica solution, which was separated from the suspension during injection, permeates and solidifies, thus providing the desired property. The minimum strength at which this sand gel can stand on its own is 2.0 kN / m 2 The strength of a self-supporting sand gel, composed of only 75g of slag and 100mL of No. 1 water glass per 400mL, was 15kN / m² after 28 days.2 It was found that... The intensity was also measured on day 1 and day 7. The day 1 intensity was 2.0 kN / m 2 An intensity of 10 kN / m was obtained. On the 7th day, it was 10 kN / m 2 This was the case (Figures 12 and 13). A similar trend was also observed with Toyoura sand. Furthermore, it can be assumed that the strength of the sand gel will increase even further if salts such as Ca, Mg, and Al are included in the bleeding solution.

[0107] In this invention, the test specimen is a self-supporting sand gel, with a diameter D0 (mm) of 35 mm or 50 mm and a height H0 (mm) of 1.8 to 2.5 times the diameter D0 (mm), matching the specimen size for uniaxial compression tests of soil. This allows for determination of any material age. Figure 12 shows the test setup. Therefore, even with field sand, a 40% injection rate yields 2.0 kN / m³. 2 It was found that the structure would be self-supporting if sufficient strength was achieved. Furthermore, the injection rate is the ratio of the injection liquid to the volume of the ground to be improved, and the improved ground is 1 m². 3 If the injection rate is 40%, the injection volume is 0.4 m 3 This is the result.

[0108] Increasing the amount of slaked lime added shortened the gel time. Furthermore, increasing the amount of slag increased the strength. In Comparative Example 1, the portion containing suspended particles solidified, but the bleeding liquid portion did not gel. The bleeding solution in Example 36 gelled. It was also found that the bleeding solution gelled when either silica colloid, water glass, or both were used in combination.

[0109] (Relationship between silica concentration and strength) We poured a neutral to alkaline chemical solution into an acrylic mold with a removable bottom and allowed it to solidify. We then checked whether the homogel formed at different silica concentrations and whether the gel was self-supporting. The same procedure was performed on sand gels to check their solidification and the self-supporting properties of the solidified sand. The results are shown in Table 9.

[0110] At silica concentrations below 0.5%, the homogel and sand gel did not exhibit self-support. Further tests revealed that gelation occurred even at a silica concentration of 0.25%, but the gel's self-supporting ability, the sand gel's solidification, and its self-supporting ability were not achieved (Table 9).

[0111] [Table 9]

[0112] In other words, even if the bleeding solution simply gels, neither the homogel nor the sand gel may achieve self-support, and conversely, the sand gel may achieve self-support even if the homogel does not. This indicates that conditions are necessary for the homogel and sand gel to achieve self-support (Tables 8 and 9).

[0113] Furthermore, penetration tests using a one-dimensional penetration apparatus (2m in length) revealed that in the water glass-slag system, the bleeding solution gelled and the gel had sufficient strength to stand on its own. However, when water glass was not included, the bleeding solution did not gel. Also, since the bleeding solution gelled whether the bleeding rate was above or below 50%, it was found that the separated silica solution, separated from the suspension, penetrated and solidified. In that case, the silica concentration of the separated silica solution was predicted to be 0.5 w / v% or higher (Table 9).

[0114] Furthermore, penetration tests have confirmed that in suspensions containing water glass, the separated silica solution penetrates and solidifies into sand, whereas in suspensions containing water glass, the suspended particles separated from the suspension cannot penetrate the sand. Therefore, it was found that this separated silica solution can penetrate even in ground with a particle size accumulation curve for the penetration and solidification of solution-type grout, thus demonstrating the potential for penetration of solution-type silica grout (Figure 11).

[0115] Thus, in suspension-type grout, by using fine silica particles such as slag or fly ash and solution-type silica, the bleeding liquid penetrates and solidifies even in areas where the suspension cannot penetrate. Focusing on the gelation of the bleeding liquid, we found the following conditions under which the bleeding liquid and sand gel can stand independently.

[0116] Based on the above, other preferred embodiments of the present invention are as follows. This injection method involves injecting an injection material into the ground through multiple injection holes, filling the cutting area and causing inter-particle penetration and solidification of the surrounding soil particles. The injection material consists of a suspension mainly composed of suspended particles such as slag or fly ash, with solution-type silica such as water glass or silica colloid as the active ingredient, allowing for penetration and solidification even in areas where the suspension cannot penetrate.

[0117] The inventors focused on the gelation of the bleeding liquid and discovered the conditions under which the separated silica solution and sand gel can stand independently. By using suspended particles such as slag or fly ash and solution-type silica, they made it possible for the separated silica solution, separated from the suspension, to penetrate and solidify even in areas where the suspended particles cannot penetrate.

[0118] When the above suspension contains solution-type silica, the separated silica solution gels, and its homogel has the strength to stand on its own. The sand gel formed by the penetration and solidification of the separated silica solution also has the strength to stand on its own. The separated silica solution penetrates into parts of the ground that the suspension could not penetrate, expanding the solidification area, or integrates with parts of the ground where the suspended particles have penetrated to form a solidified body, thereby connecting the solidified bodies formed by suspended particles from adjacent injection holes. Furthermore, by adding CMC, MC, polyacrylamide, clay, etc., to the injection solution, it becomes difficult to disperse in the ground and less likely to be diluted even in sandy or gravelly ground. Moreover, even when injected into the ground to be excavated, it becomes possible to use a jet-infiltration composite injection method that allows the excavated surface to stand on its own and stop groundwater flow.

[0119] Here, in the above, when we say that the separated silica solution separated from the suspension has gelled and that its homogel is self-supporting, it means that the silica concentration of the separated silica solution is 0.5 w / v% or higher, and that the homogel does not collapse and remains self-supporting even when tilted at an angle within the mold.

[0120] Furthermore, the sand gel being self-supporting means that the silica concentration of the separated silica solution is 0.5 w / v% or higher, and when No. 6 silica sand is used, a sand gel prepared by mixing using the separated silica solution to achieve a relative density of 60% with a diameter of 5 cm and a height of 10 cm is self-supporting, and the strength measured in a uniaxial compression test using the sand gel is 2.0 kN / m². 2 This means that it is more than that.

[0121] In the above, the sand gel formed by bleeding a silica grout consisting of water glass and Ca-containing silica particles increases in strength over time (Table 8). This is thought to be because the Ca ions from the silica particles dissolve into the gel of the bleeding solution over a long period even after gelation and react with the silica to form calcium silicate, contributing to the increase in strength. Alternatively, it is thought that the curing agent containing added Ca and Mg reacts with the soluble silica of the silica particles over a long period of time through pozzolanic action, resulting in an increase in strength due to the pozzolanic reaction.

[0122] As described above, according to the present invention, the penetration solidification range can be set according to the ground conditions and the purpose of ground improvement (strength, range of solidified area, etc.) by the size of the solidified body in the cutting area by injection, the suspended particles, and the gelation of the separated silica solution separated from the suspension. Furthermore, the penetration solidification range of the suspended particles and the penetration solidification range by the separated silica solution separated from the suspension can be set by the type and particle size of the suspended particles of the suspension-type injection material, the amount of hardener and alkaline agent, the type and amount of solution-type silica added, the bleeding rate, and the strength and gelation time of the bleeding liquid. As a result, as shown in Figure 15, a new concept of injection-penetration composite injection has been created, making it possible to improve the ground by injection-penetration injection using suspension-type grout.

[0123] The injection material used in this invention has, in particular, the following characteristics. (1) By setting the composition of the suspension-type injection material to mainly consist of small-particle-sized, lightweight, and highly fluid suspended particles, it is possible to penetrate a wide area from the cutting area into the surrounding ground (Figures 7-9). (2) By including a silica solution, the separated silica solution, which is separated from the suspension during infiltration into the ground, gels, allowing the silica solution to penetrate into the fine-grained parts of the ground that the suspended particles cannot penetrate (Figures 6, 8-10), causing the fine-grained parts of the ground to solidify and become self-supporting. Since the separated silica solution obtained from the suspension has the same permeability as a solution-type silica grout, the permeable range of fine-grained soil shown in Figure 11 can be expected. Figure 4 shows the situation when a silica suspension containing silica is left standing, where the suspended matter solidifies and the bleeding liquid gels. Figure 5 shows the situation when a silica suspension without silica is left standing, where only the suspended matter solidifies and the bleeding liquid does not gel. (3) Table 9 shows the self-supporting properties of homogels, solidification of sandgels, and self-supporting properties of solidified sand at low silica concentrations in solution-type grout. (4) From the particle size distribution of the sand used in the infiltration test (Figure 14), it can be seen that the suspended particles used in the present invention infiltrate and solidify in the sandy ground.

[0124] The particle size distribution of the sand used in the infiltration test (Figures 6-9) is that of silica sand No. 6, shown in Figure 14. With this particle size distribution, in a suspension without silica solution, suspended particles can penetrate between soil particles to a depth of 80 cm (Figures 8 and 9). In Toyoura sand, which is a finer-grained soil, the penetration distance was less than half of that. Furthermore, using the above suspension containing silica solution (Example 36), the same penetration range as the particle size range of the solution type, as shown in Figure 11, can be obtained, and although the penetration distance differs depending on the soil conditions, it can be seen that a solidified body like the one shown in Figure 15 can be formed. Figures 15(c) and (d) are plan views of the infiltration solidified body. The type and size of suspended particles in the suspension-type injection material should be selected according to the soil conditions. Also, because infiltration injection is possible as shown in Figure 15(e), it is possible to stabilize surrounding structures without damaging underground buried objects. Figure 15(f) shows that there is a risk of damaging underground buried objects with the high-pressure jet mixing method.

[0125] As described above, the inventors found that when a suspension mainly composed of the above-mentioned suspended particles containing a silica solution is injected, the area near the center becomes a high-strength region with a high concentration of suspended particles, and as the distance from the center increases, the concentration of suspended particles decreases, resulting in a low-strength region. Furthermore, they found that outside of this, a silica-rich solidified body is formed by the gelation of the separated silica solution separated from the suspension, and that this solidified body connects adjacent solidified bodies. Conventionally, a large amount of bleeding in suspensions has been considered a disadvantage, but in this invention, we focused on the fact that the separated silica solution separated from the suspension can penetrate between soil particles that the suspended particles cannot penetrate, and conducted research on the gelation of the bleeding liquid. As a result, it was found that the gelation and strength of the bleeding liquid itself, the permeability of the separated silica solution separated from the suspension into sand, and the strength of the sand gel greatly affect the improvement of the penetration and solidification properties of suspension-type grout. Based on these findings, we investigated the conditions under which the suspension can not only penetrate into the surrounding ground of the injection area, but also for the separated silica solution separated from the suspension to penetrate and gel even into fine-grained soil areas where the suspended particles cannot penetrate, enabling the formation of a large improved body. As a result of this research, the inventors have overcome the injection limit of suspended particles by using the gelling function of solution-type silica (bleeding liquid) separated from the suspension-type injection material. This has enabled a ground improvement method that integrates the entire target ground, possessing high permeability, high strength, and excellent watertightness.

[0126] According to the present invention, coarse-grained soil is solidified, and the gelation of the separated silica solution separated from the suspension allows penetration and solidification of fine-grained soil that the suspended particles cannot penetrate, making it possible to form a solidified body larger than the solidified body of the suspended particles. However, sufficient strength cannot be obtained by the gelation of the separated silica solution separated from the suspension alone. From this point of view, we found that the strength condition for the self-supporting homogel and sand gel of the bleeding liquid is that the silica concentration of the bleeding liquid is 0.5 w / v% or higher (Table 9), and by applying this as the above-mentioned suspension-type grout to the high-pressure injection mixing method, we have solved the problems of the aforementioned cement-based high-pressure injection mixing method and realized a new ground improvement method.

[0127] Furthermore, the present invention provides a ground improvement method that can obtain a highly durable solidified body and is expected to have a CO2 reduction effect by using a non-cement-based injection material mainly composed of silica particles having natural pozzolanic properties, including artificially calcined silica such as slag and fly ash, and soluble silica such as loam soil.

[0128] (Injection device and construction procedure) As described above, the present invention is a combined injection and permeation injection method. Therefore, the injection device must be capable of injection agitation and pressurized permeation injection. In order to fill the cutting space with the suspension according to the present invention by injection agitation of high-pressure water and to permeate it under pressure, it is necessary to prevent the injected suspension from being discharged to the surface along with the mud. Figure 16 shows an injection device with this function (Figure 16(a)) and the procedure for construction using it (Figures 16(b) to (d)).

[0129] The injection device of the present invention is used in a high-pressure injection mixing method and, as shown in the figure, comprises a guide pipe inserted into the ground, an injection inner pipe placed inside the guide pipe and used for injecting the injection material, and an opening / closing mechanism for opening or closing the space between the guide pipe and the injection inner pipe. When the injection material is injected into the ground at high pressure, the opening / closing mechanism opens the space, allowing mud to be discharged to the surface through the space. Conversely, when the opening / closing mechanism closes the space, the injection material is pressurized and permeates into the ground.

[0130] In this ground improvement method using a high-pressure injection mixing injection device, specifically, a guide pipe is first used to drill a hole in the ground to the target depth, and an injection pipe is inserted into the hole. Next, the space between the guide pipe and the injection pipe is opened using an opening / closing mechanism, the guide pipe is pulled up, and the injection material is injected from the injection pipe at high pressure along with high-pressure water or air, cutting and mixing the ground at the same time. Next, the excavated soil generated by the cutting is mixed with the injection material on the surface to produce a mixed injection material, and this mixed injection material is injected at high pressure into the ground from the injection pipe along with high-pressure water or air. Alternatively, after filling the area created by the cutting with the injection material, the opening / closing mechanism is used to close the space and pressurize the injection material into the ground. When attempting to inject the injection material into the surrounding ground, it is necessary to apply seepage pressure.

[0131] Figure 16(a) shows an opening and closing mechanism using a rubber bag that enables excavation and soil removal and can apply osmotic pressure. In the illustrated example, the opening and closing mechanism consists of an annular rubber bag positioned between a guide pipe and an injection inner pipe, having a conduit through which fluid can flow, a ball bearing provided on the inner surface on the injection inner pipe side, and sealing members provided at the upper and lower ends of the rubber bag. The opening or closing of the space by the opening and closing mechanism is performed by the presence or absence of pressurization inside the rubber bag due to the inflow and outflow of fluid into the rubber bag.

[0132] The rubber bag maintains airtightness when a fluid such as air is injected into it by providing ball bearings on its inner surface and sealing members such as O-rings at both the top and bottom ends. During cutting, the space between the injection inner tube and the guide tube is open, and the cut soil is discharged to the ground. On the other hand, when the injection material is injected, fluid is sent into the rubber bag, causing the rubber bag to expand and close the space between the injection inner tube and the guide tube, so that the injection material penetrates into the ground under pressure. When moving across the cutting area, the ball bearings of the opening and closing mechanism allow mutual movement between the guide tube and the injection inner tube.

[0133] Figures 17(a) to (c) show the structure and construction procedure of an example using a different opening / closing mechanism. In this case, the opening / closing mechanism consists of an annular rubber bag positioned between the guide pipe and the injection inner pipe and having a conduit through which fluid can flow, a fixing member that secures the rubber bag to the guide pipe, and ring-shaped fittings that close the upper and lower ends of the rubber bag. The opening or closing of the space by the opening / closing mechanism is performed by the presence or absence of pressurization inside the rubber bag due to the inflow and outflow of fluid into the rubber bag.

[0134] First, the injection material is injected at high pressure along with high-pressure water or air from an injection inner tube inserted into a guide tube equipped with an opening and closing mechanism. This cuts and agitates the ground, and the resulting excavated soil is discharged to the surface. Next, a rubber bag is inflated with the pressurization of a fluid such as air, and by making it tightly adhere to the guide tube, the space between the guide tube and the injection inner tube is closed, allowing the injection material to be injected without mud discharge, and the injection pressure is used to penetrate the outer perimeter of the cutting area. After that, the pressurization of the rubber bag is stopped, the contact of the rubber bag with the injection inner tube is interrupted, the injection inner tube is pulled up, and the same process is repeated.

[0135] This device can be used not only for the above-mentioned injection material, but also for all injection materials, including cement suspensions.

[0136] By using the injection apparatus shown in Figures 16 and 17, it is possible to switch the injection material used during pressurized poroscopy injection (injection material X) to an injection material with higher permeability than the injection material used during injection agitation injection (injection material Y), and to use formulations with different gelation times. In other words, in the present invention, different injection materials can be used for injection agitation and pressurized poroscopy, and the injection material used for pressurized poroscopy can be made to have higher permeability than the injection material used for injection agitation. Furthermore, in the present invention, the injection material used for injection agitation and the injection material used for pressurized poroscopy can be switched by opening and closing the above space using an opening and closing mechanism.

[0137] For example, when using a cement suspension as the grout, the grout Y can be made highly concentrated and the grout X low, and the grouting device with the above-mentioned opening and closing mechanism can be used for pressurized infiltration grouting instead of injection agitation grouting. Alternatively, the grout Y can be a suspension and the grout X can be a solution-type grout. Furthermore, after injecting the grout Y, the grout X can be a grout in which an accelerator has been added to the grout Y to adjust the gelation time. Whether or not the suspension is permeable depends on the particle size of the ground being grouted. In that case, the judgment can be made using a value calculated from the existing injectable limit of the ground being grouted as a guideline. For example, experimental statistical results on the injectable limit of suspension grout by JCKing (Proc. ASCE 1961) can be used (from "Cutting-Edge Chemical Grouting Methods," Rikogaku Shoten, by Shunsuke Shimada, Takeshi Sato, and Minoru Taku, pp. 154-158). 15 , D 10 and suspension D 85 , D 95 The value of N that represents this is called the Groutability Ratio (usually N1 is taken). N1=D 15 / D 85 ≥15 N2=D 10 / D 95 ≥8 If the relationship is not satisfied, the grout (suspension) cannot penetrate smoothly. Therefore, in ground where the groutability ratio N is satisfied, infiltration injection of the suspension becomes possible. Furthermore, even in ground where infiltration injection of the suspension is difficult, if a suspension containing a silica solution is used, even in ground where the penetration of the suspension is insufficient, the gelation of the separated silica solution will form a ground that integrates with the suspended particles even in fine-grained soil, or, even more broadly, a large solidified body will be formed by the penetration of the separated silica solution. In that case, the permeable particle size of the separated silica solution can be considered to be the same as that of the solution-type grout in Figure 11.

[0138] By switching the contents and composition of the injection material in this way, it has become possible to adjust the solidification strength, permeability, and gel time, thereby expanding the solidification range and injection limits, and realizing a new ground improvement method based on the concept of injection-mixed permeation composite injection. [Industrial applicability]

[0139] This invention relates to a ground improvement method that enables high-strength and uniform ground improvement of soft ground and liquefiable ground. By utilizing the kinetic energy of a high-pressure injection fluid to destroy and solidify the ground, it not only forms a solidified body in the cutting area but also forms a larger solidified body by allowing the injection material to penetrate between soil particles from the cutting area. Furthermore, by reusing the soil cut by high-pressure injection and filling it into the ground, low-carbon ground improvement is made possible. In addition, by using a suspension-type injection material mainly composed of artificial calcined silica such as slag or fly ash, or silica particles with natural pozzolanic properties, it is possible to widely perform ground improvement that is environmentally friendly and reduces CO2 with non-cement-based injection materials or injection materials with reduced cement content. Furthermore, it has the effect of expanding the penetration and solidification range and reducing the weight of the solidified body, enabling efficient and economical ground improvement of soft ground and liquefiable ground.

Claims

1. A ground improvement method comprising cutting the ground with a jetted fluid from an injection pipe inserted into the ground to form a cutting area, and injecting an injection material into the formed cutting area, wherein the injection material mainly consists of suspended particles, and the injection material is filled into the cutting area and permeates between the soil particles of the surrounding ground, thereby solidifying the cutting area and the surrounding ground.

2. A ground improvement method comprising cutting the ground with a fluid jet from an injection pipe inserted into the ground to form a cutting area, and injecting an injection material into the formed cutting area, wherein the injection material mainly consists of suspended particles and contains one or more of a hardening agent, an alkaline agent, and a solution-type silica, and the injection material is filled into the cutting area and penetrates between the soil particles of the surrounding ground, thereby solidifying the cutting area and the surrounding ground.

3. The ground improvement method according to claim 2, wherein the solution-type silica contains silica colloid and / or water glass, and the bleeding liquid of the injection material gels.

4. The ground improvement method according to claim 1 or 2, wherein the suspended particles are any or more of calcined silica, natural silica having pozzolanic properties, and hardenable silica particles as active ingredients.

5. The ground improvement method according to claim 4, wherein the calcined silica is one or more of slag, fly ash, cement, sewage incineration ash, plant incineration ash, and calcined clay.

6. The ground improvement method according to claim 4, wherein the natural silica having pozzolanic properties is one or more of loam soil, shirasu (volcanic ash), volcanic ash, fuwa soil, and sanwa soil.

7. The ground improvement method according to claim 2, wherein the hardening agent, alkaline agent, and solution-type silica consist of any or more of the following: (1) A product containing gypsum and / or MgO as active ingredients. (2) A product containing one or more of the following as active ingredients: Ca salt, Mg salt, Al salt, carbonate, and bicarbonate. (3) A product containing one or more of the following as active ingredients: lime, cement, caustic alkali, water glass, and silica colloid.

8. The ground improvement method according to claim 1, wherein the injected material includes clay and / or soil as a bulking agent.

9. The particle size of the suspended particles is 4000 to 20000 cm² in Blaine values. ２ The ground improvement method according to claim 1, wherein the amount of suspended particles in the injection material is in the range of / g, and the amount of suspended particles in the injection material is 40 to 200 kg / 400 L.

10. The ground improvement method according to claim 1, wherein the injection material contains slag as the suspended particles, and the amount of slag in the injection material is 10 to 50 w / v%, or, if the injection material contains slag as the suspended particles and also contains cement, the weight of the cement is 5 to 50% of the weight of the suspended particles.

11. The ground improvement method according to claim 3, wherein the molar ratio of the water glass is 1.0 to 5.0, and the amount of water glass in the injection material is 10 to 150 L / 400 L.

12. The ground improvement method according to claim 3, wherein the injection material is made of a suspension mainly composed of the suspended particles and the solution-type silica as an active ingredient, and when the injection material is injected into the ground through a plurality of injection holes provided in the ground, the bleeding liquid of the injection material gels and the homogel has strength to stand on its own, the sand gel that has solidified after the bleeding liquid has permeated has strength to stand on its own, and the bleeding liquid penetrates into parts of the ground that the suspension could not penetrate, thereby expanding the solidification area, or integrates with the parts of the ground that the suspension has penetrated to form a solidified body.

13. The statement that the bleeding solution gels and its homogel stands upright means that the silica concentration of the bleeding solution is 0.5 w / v% or higher, and that the homogel does not collapse and stands upright even when tilted at an angle within the mold. The statement that the sand gel stands upright means that the silica concentration of the bleeding solution is 0.5 w / v% or higher, and when using No. 6 silica sand, the sand gel prepared by mixing with the bleeding solution to achieve a relative density of 60% in a 5 cm diameter x 10 cm height stands upright, and the strength measured in a uniaxial compression test using the sand gel is 2.0 kN / m². ２ The ground improvement method according to claim 12, which means the above.

14. The ground improvement method according to claim 1, wherein the injection material comprises one or more of microbubbles, air, a dispersant, and a thickening agent as active ingredients.

15. The ground improvement method according to claim 2, wherein the hardening agent is a polyvalent metal compound, and is one or more of the hydroxides, oxides, or salts of Ca, Mg, or Al, and / or gypsum.

16. The ground improvement method according to claim 1, wherein the improvement effect of injecting the aforementioned injection material is confirmed by non-destructive testing.

17. The ground improvement method according to claim 16, wherein the non-destructive test is performed by elastic wave velocity logging, acoustic tomography, or surface wave exploration.

18. An injection device for use in a high-pressure jet agitation method, characterized by comprising: a guide pipe inserted into the ground; an injection pipe placed inside the guide pipe and used for injecting an injection material; and an opening / closing mechanism for opening or closing the space between the guide pipe and the injection pipe.

19. The injection device according to claim 18, wherein the opening and closing mechanism comprises an annular rubber bag disposed between the guide tube and the injection inner tube and having a conduit through which fluid can flow, a ball bearing provided on the inner surface of the rubber bag on the injection inner tube side, and sealing members provided at the upper and lower ends of the rubber bag, and the opening or closing of the space by the opening and closing mechanism is performed by the presence or absence of pressurization inside the rubber bag due to the inflow and outflow of fluid into the rubber bag.

20. The injection device according to claim 18, wherein the opening and closing mechanism comprises an annular rubber bag disposed between the guide tube and the injection tube and having a conduit through which fluid can flow, a fixing member for fixing the rubber bag to the guide tube, and ring-shaped fittings for closing the upper and lower ends of the rubber bag, and the opening or closing of the space by the opening and closing mechanism is performed by whether or not there is pressurization inside the rubber bag due to the inflow and outflow of fluid into the rubber bag.

21. A ground improvement method using a high-pressure injection mixing method with an injection device according to claim 18, comprising the steps of: drilling a hole in the ground to a target depth using the guide pipe and inserting the injection inner pipe into the guide pipe; opening the space with the opening / closing mechanism and injecting the injection material from the injection inner pipe at high pressure together with high-pressure injection water or air, injecting and mixing the ground while cutting, and mixing the excavated soil generated by the cutting with the injection material on the surface to produce a mixed injection material; and injecting the mixed injection material from the injection inner pipe into the ground at high pressure together with high-pressure injection water or air.

22. A ground improvement method using a high-pressure injection mixing method with an injection device according to claim 18, comprising the steps of: drilling a hole in the ground to a target depth using the guide pipe and inserting the injection inner pipe into the guide pipe; opening the space with the opening / closing mechanism and injecting the injection material from the injection inner pipe at high pressure together with high-pressure injection water or air, injecting and mixing the ground while cutting, and filling the area created by the cutting with the injection material; and closing the space with the opening / closing mechanism to pressurize and permeate the injection material into the ground.

23. The ground improvement method according to claim 22, wherein different injection materials are used for injection agitation and pressurized infiltration, and the injection material used for pressurized infiltration has higher permeability than the injection material used for injection agitation.

24. The ground improvement method according to claim 22, wherein the injection material used for injection agitation and the injection material used for pressurized infiltration are switched by opening and closing the space by the opening and closing mechanism.

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