Ground improvement method and injection equipment

Abstract

By adding penetration injection to the conventional high-pressure jet mixing method, it is possible to form large-diameter solidified bodies using suspended grout. It also makes it possible to add injection material to the cut soil and re-inject it, which allows for environmentally friendly ground improvement with reduced CO2 emissions, and provides a ground improvement method and injection device that can form large solidified bodies that are lighter than conventional methods. [Solution] A ground improvement method and injection device in which a cutting area is formed by cutting the ground with a jet of fluid from an injection pipe inserted into the ground, and then an injection material is injected into the cut area. The injection material is made primarily of suspended particles, or further contains one or more of a hardener, an alkali agent, and solution-type silica. The injection material is filled into the cut area and allowed to penetrate from the cut area between the soil particles of the surrounding ground, thereby solidifying the cut area and the surrounding ground.

Description

[Technical field]

[0001] The present invention relates to a ground improvement method using a combined injection and permeation injection method, in which a suspension-type injection material or a mixture of the suspension-type injection material and the soil of the cut area is filled in the cut area and the injection material is permeated and solidified from the cut area into the surrounding ground to form a large solidified body, in cutting and solidifying the ground using the kinetic energy of a jet fluid. In particular, the present invention relates to a combined injection method consisting of injection injection and permeation injection, in which a jet fluid is used as the main component and a jet fluid is used to fill the cut area with injection material using kinetic energy, followed by permeation injection to permeate the injection material into the surrounding ground, thereby improving the ground. The present invention relates to a combined injection method consisting of injection injection and permeation injection, in which a suspension of calcined silica such as cement or slag, hydraulic alumina, or a mixture of these is used as the injection material, and a combined injection method consisting of injection injection and permeation injection is used. The present invention also relates to a combined injection and permeation injection method, in which a suspension containing a silica solution is used and the separated silica solution that is separated while the suspension-type injection material is permeating between the soil particles is gelled, thereby simultaneously forming a high-strength region by the suspended particles and a permeation and solidification region by the separated silica solution. Furthermore, by reusing the cut soil by high-pressure injection and injecting it into the ground, it is possible to reduce the volume of industrial waste.Furthermore, this invention relates to an invention that uses as injection materials silica powder from on-site soil, waste mud, crushed concrete materials, suspension-type injection materials mainly composed of artificially fired silica such as slag, fly ash, sewage incineration ash, plant incineration ash, etc., and natural silica particles with pozzolanic action such as soil containing soluble silica such as 2-layer soil, 3-layer soil, loam layer, shirasu, volcanic sedimentary soil, etc., together with hardeners, solution silica, and alkali agents, to reduce CO2 by using non-cement injection materials or injection materials with reduced cement, which can form a wide range of solidified bodies near neutral, and further enables strength to be developed immediately after injection, ensuring safety for surrounding structures, and reducing the weight of the solidified bodies, thereby solving the problems of the conventional high-pressure injection mixing method using injection materials mainly composed of cement. [Background technology]

[0002] Various methods have been known for improving ground for soft ground or ground that is at risk of liquefaction. Among them, the liquid grouting method, which injects a grouting material (chemical solution) into the gaps between soil particles to permeate and solidify the ground, is widely used due to its simplicity.

[0003] The chemical injection method involves injecting a chemical solution into the gaps between soil particles, where it hardens and acts as an adhesive to strengthen the ground and stop water leakage (improve permeability). Because it can be easily carried out with compact equipment, it is primarily used for short-term temporary construction work (as an auxiliary method for underground construction) and for liquefaction countermeasures using a rapid penetration injection method with permanent grout.

[0004] Other well-known methods include the high-pressure injection mixing method, in which cement is injected at high pressure to cut and mix the ground while stirring and mixing the cut soil and cement, and the mechanical mixing method, in which a slurry-like injection material is injected into a soft soil layer that has accumulated deep down, and the on-site soil and injection material are stirred and mixed with an impeller to form a cylindrical improvement body underground, creating strong, stable improved ground. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-40950 [Patent Document 2] Patent No. 3413398 (JP Patent Publication No. 2002-88752) [Patent Document 3] Patent No. 7193105 (Patent Publication No. 2024-53139) [Patent Document 4] Patent Publication No. 2022-66686 Summary of the Invention [Problem to be solved by the invention]

[0006] However, today, in order to prevent global warming caused by CO2, there is a strong demand for non-cement ground improvement methods. The applicant has previously made inventions relating to high-pressure injection methods using slag, as described in Patent Documents 1 to 3, and the present invention is a ground improvement method which is a further development of those inventions.

[0007] In other words, in conventional high-pressure injection mixing methods, cement is used as the main component of the injection material. Although cement has a high specific gravity of 3.17, it has a specific surface area of ​​3,220 cm 2 / g, and therefore, when it comes to strengthening the soft ground that is the target of high-pressure jet mixing methods, the heavy cement particles have a short reach and it is difficult to form large solidified bodies.

[0008] In addition, because the soil is removed and replaced with cement to form a solidified body, the disposal of the waste mud has become a major environmental problem today. Furthermore, when improving soft ground, there is a problem in that the improved cement-solidified body is prone to settling because soft ground has a low bearing capacity, and this can lead to large displacement of structures.

[0009] As mentioned above, the high-pressure jet mixing method has the advantage of high strength of the solidified body, but in addition to the problem of industrial waste soil, it has the problem that the bearing capacity until solidification is low, and the weight after solidification is large and the rigidity is high, so that in soft ground, it is not integrated with the existing ground and is prone to subsidence. In addition, there is a problem that the cement injection material is mixed with the high-pressure jet water in the excavated ground, so it is easily discharged to the aboveground together 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 treated with chemicals is 100-200kN / m 2 It is sufficient to have a strength of several to several tens of MN / m when replacing conventional soil and solidifying with cement itself. 2 It does not require such a large strength.

[0011] If soil particles are removed from the ground by high-pressure injection and replaced with cement, the improved strength of the ground will increase, and the weight of the ground will become heavier, which will increase the force of inertia.In addition, the ground will become more susceptible to shock transmission, which could lead to brittle failure under repeated loads such as earthquakes.

[0012] In addition, when carrying out earthquake-resistance reinforcement or liquefaction countermeasures using the above-mentioned conventional methods for structures with friction pile foundations, spread foundations, or directly beneath detached houses, the mechanical cement mixing method and high-pressure jet mixing method can easily reinforce the foundations of structures, but the shear stiffness of the ground increases due to ground improvement (for example, 100 to 2000 MN / m 2 By strengthening the foundation (to a certain degree), earthquake motion is more easily transmitted to the superstructure. As a result, even if damage to the foundation (lower part) is prevented during an earthquake, the structure (upper part) may be subjected to seismic forces greater than the design value, which may cause it to lose its functionality.

[0013] Furthermore, with the conventional high-pressure injection mixing method, the uniaxial compressive strength was 3MN / m 2 The damage was so severe that excavation was difficult.

[0014] There are two main types of high-pressure jet mixing methods. The first is a method in which an injection material such as cement or a mixture of injection material and air is injected from an injection pipe inserted into the ground to form a solidified body in the ground consisting of the injection material or a mixture of the injection material and the cut soil. The second is a method in which a hole is drilled to the target depth with a guide pipe, an inner pipe is inserted into the hole, the guide pipe is then raised, and cutting is performed by injecting 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 to the ground from the gap around the outer periphery of the injection pipe rod (cut soil discharge path), and the injection material is injected into the cutting area formed by this from a discharge port located below the high-pressure water nozzle (Fig. 1).

[0015] The pipe structures used in conventional methods are mainly single pipes, double pipes (Fig. 2) and triple pipes (Fig. 3), each characterized by the fact that the single pipe can inject only the solidification material, the solidification material + air in Fig. 2, and the solidification material + air + cutting water in Fig. 3. Since these methods involve the discharge of sludge, there is a demand for reducing this discharge and making effective use of it in order to improve economic efficiency and reduce the burden on the environment. In the prior art, in order to increase the diameter of the improved area, a double- or triple-tube rod is used, and the solidification material and air, or cutting water, air, and solidification material are sprayed at high pressure from a spray nozzle attached to the rod. The air is used primarily to form a gas-liquid interface around the sprayed fluid (solidification material or cutting water), suppressing the attenuation of the jet flow over the distance, and to create a large-diameter improved body. In addition, the improved body immediately after construction is in an unsolidified state because sufficient hydration reactions have not yet occurred. Therefore, if construction is carried out near a structure, the function of the structure may be hindered due to a decrease in bearing capacity. Furthermore, with conventional high-pressure jetting methods that rely on the energy of high-pressure jetting fluid, the cutting area is limited by the distance of the jetting fluid, so the size of the improved body is restricted.

[0016] In either of the above methods, the cut soil is mixed with the grout and discharged onto the ground from the outer periphery of the injection pipe. Disposal of the cut soil mixed with cement is a major environmental problem.

[0017] The applicant has already proposed a ground injection method using a suspension grout-based suspension grout-based injection material mainly composed of slag and silica in Patent Documents 1 and 2, and has also developed a method of mixing the cut soil with the above-mentioned injection material and re-injecting it (Patent Document 1), and a high-pressure injection method using a slag grout-based injection material mainly composed of gypsum or magnesium oxide (Patent Document 3).The applicant has also revealed that a bleeding liquid of slag and low molar ratio water glass grout gels (Patent Document 4).

[0018] However, as mentioned above, conventional ground improvement methods have problems in terms of the diameter of the ground and environmental issues, and further improvements are desired. Therefore, the object of the present invention is to not only fill the cut area with the injection material in the conventional high-pressure injection method, but also to make the injection material penetrate outside the cut area to form a large solidified body. In addition, by promoting de-cementation, it is possible to perform ground improvement that is environmentally friendly by reducing CO2, and to provide a ground improvement method and injection device that can form a large solidified body that is lighter than conventional methods. [Means for solving the problem]

[0019] Here, the term "bleeding liquid" generally refers to the supernatant solution of suspended particles that have settled when the suspension is at rest. However, in actual ground injection, the liquid equivalent to the bleeding liquid refers to the solution in which suspended particles are filled between soil particles and separated while penetrating into the ground. Therefore, the separated liquid of a suspension containing a silica solution contains fine suspended particles and silica solution, and is therefore referred to as "separated silica solution" in the present invention. In the present invention, "bleeding liquid" and "separated silica solution" mean substantially the same thing.

[0020] The present applicant has applied the phenomenon described in Patent Document 4 to a high-pressure injection method and has conducted research into a ground improvement method using combined injection and infiltration grouting. The applicant continued to study the gelation of the bleeding liquid and found that the suspension containing solution-type silica gels whether the bleeding rate is 50% or less or 50% or more (Fig. 4). It was also found that the gelation time and strength of the bleeding liquid can be adjusted by adding a hardener. The applicant also found the relationship of silica concentration sufficient for the gelation of the bleeding liquid to be self-supporting for homogel (solidified injection material alone) and sandgel (solidified mixture of injection material and soil) (Table 9, Fig. 6, Fig. 8 to Fig. 10, Fig. 12, Fig. 13). As a result, we have invented a ground improvement method based on a new concept of combined injection and permeation injection, as shown in Figure 15. Figures 15(a) to (e) show the form of permeation and consolidation in the ground improvement method of the present invention. Figure 15 shows that the injection material is injected into the injection material cut area by injection, and the injection material alone or a mixture of the injection material and the soil in the cut area is filled, and the injection material permeates over a wider area than the cut area, causing the suspended particles to permeate between the soil particles, and further, the separated silica solution separated from the suspension is permeated and solidified, forming an integrated permeation and consolidation area. Therefore, the high-strength injection material alone is filled into the cut area by high-pressure injection from multiple injection holes, or the improvement body solidified while being mixed with the ground and the separated silica solution separated from the suspension in the surrounding area penetrate and solidify into the ground, making it possible to integrate the entire ground into an integrated ground improvement project. In addition, the present invention substantially expands the scope of application of suspension grout (from a soil quality perspective) to the scope of solution-type grout, and develops the method from a simple high-pressure jet mixing method into a ground improvement method based on a new technical concept called the high-pressure jet penetration injection method (Figs. 11 and 14).

[0021] Specifically, the present invention solves the above-mentioned problems associated with the conventional high-pressure injection mixing method that uses cement as the main component by using suspended particles made of artificially calcined silica such as slag or fly ash, or silica particles obtained through a natural calcination process (natural pozzolan) as an injection material, and by mixing cutting mud that has been removed above ground and that has been mixed with injection material, and then reinjecting the mixture into the ground.

[0022] In this way, 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 by infiltration and solidification from the cut area to the surrounding area in addition to solidification of the cut area by high-pressure injection (Fig. 15). In addition, the present invention uses as the main material for the injection material natural or artificially manufactured silica particles, calcined silica, natural silica particles with pozzolanic action, and fluidized soil made by slurrying soil generated on-site, thereby reducing the weight of the solidified body, expanding the range of infiltration and solidification, and contributing to the global environment by reducing CO2 emissions. Furthermore, the present invention is a ground improvement method that can reduce the volume of industrial waste by using fluidized soil made by slurrying waste mud (on-site soil) generated during cutting as an injection material.

[0023] Furthermore, the present invention relates to a ground improvement method for improving the soft ground or liquefied ground with high strength and light weight as described above, in which the ground is cut using the kinetic energy of a high-pressure jet fluid, the cut area is filled with the above-mentioned injection material such as suspended particles or slag, or a mixture of the injection material and the soil of the cut area, and the injection material is allowed to penetrate further from the cut area to the surrounding area to form a large solidified body. According to the present invention, low-carbon ground improvement is possible by re-injecting the mixed soil and sand, which is a mixture of the cut soil and injection material discharged to the ground by high-pressure jet, into the ground. Furthermore, by using a suspension-type injection material mainly composed of calcined silica such as slag or fly ash, or silica particles having natural pozzolanic action, a reduction in CO2 from the material side is realized by using a non-cement-based injection material or an injection material with reduced cement, and an environmentally friendly ground improvement is provided. Furthermore, in the present invention, since the above-mentioned suspension-type injection material contains solution-type silica, the separated silica solution separated from the suspension permeates and gels, making it possible to expand the range of permeation and solidification beyond the cut area, thereby making it possible to simultaneously obtain the advantages of both the formation of a solidified body by the high-pressure jet injection method and the permeation and solidification by the chemical injection method for ground improvement.

[0024] That is, the ground improvement method of the present invention involves cutting the ground with jet fluid from a plurality of injection pipes inserted into the ground to form a cut area, and injecting grout into the cut area, The following i) to iii) i) Silica particles comprising either or both of pyrogenic silica and natural silica having pozzolanic activity; ii) Silica particles, wherein the calcined silica is made of any one or more of slag, fly ash, cement, sewage incineration ash, plant incineration ash, and calcined clay; iii) Silica particles, in which the natural silica having pozzolanic activity is any one or more of loam soil, volcanic ash, diploid soil, and triploid soil; A ground improvement method for consolidating a cut area and the surrounding ground by injecting an injection material consisting of a suspension containing any one of the above-mentioned suspended particles of silica particles as a main material and containing solution-type silica as an active ingredient from a plurality of injection pipes into the ground, filling the cut area and allowing the injection material to permeate between soil particles in the surrounding ground from the cut area, The separated silica solution separated from the suspension penetrates into an area where the suspended particles cannot penetrate, and then the separated silica solution gels and solidifies the ground, thereby solidifying the ground by the suspended particles and the separated silica solution, The silica particles have a Blaine value of 4000 to 20000 cm 2 / g, the amount of the silica particles in the injection material is 40 to 200 kg / 400 L, and silica colloid and / or water glass are used as the solution-type silica, When the solution-type silica contains water glass, the injection material uses water glass at a molar ratio of 1.0 to 5.0, and the amount of the water glass in the injection material is 10 to 150 L / 400 L; The silica concentration of the separated silica solution is 0.5 w / v% or more, the homogel formed by gelling the separated silica solution has a strength to be self-supporting, and the sand gel formed by permeating the separated silica solution and solidifying has a strength to be self-supporting, The term "the separated silica solution gels and the homogel becomes self-supporting" means that the silica concentration of the separated silica solution is 0.5 w / v% or more, and the homogel does not collapse even when tilted in a mold and can stand on its own. The term "the sand gel becomes self-supporting" means that the silica concentration of the separated silica solution is 0.5 w / v% or more, and when No. 6 silica sand is used, the sand gel prepared by a mixing method using the separated silica solution to have a relative density of 60% and a size of 5 cm in diameter and 10 cm in height can stand on its own, and the strength of the sand gel measured in a uniaxial compression test is 2.0 kN / m 2 It means that it is more than or equal to The separated silica solution has permeability to fine-grained soil and penetrates into areas of the ground that the suspended particles could not penetrate, forming an area near the center where the concentration of suspended particles is high and therefore relatively strong, an area away from the center where the concentration of suspended particles decreases and therefore relatively weak, and an outside of this, a solidified body with a high silica content due to gelation of the separated silica solution, and the solidified bodies of suspended particles from adjacent injection pipes are connected to each other.

[0030] In the present invention, it is preferable that the injection material contains an alkaline agent consisting of one or more of the following: (1) An alkaline agent containing gypsum and / or MgO as active ingredients. (2) An alkaline agent containing one or more of Ca salts, Mg salts, Al salts, carbonates, and bicarbonates as active ingredients. (3) An alkaline agent containing one or more of the following active ingredients: lime, cement, caustic alkali, water glass, and silica colloid.

[0033] In the present invention, when the suspended particles are slag and no cement is used, the amount of the slag in the injection material is preferably 10 to 50 w / v %, or when the injection material contains slag as the suspended particles and also contains cement, the weight of the cement is preferably 5 to 50% of the weight of the suspended particles.

[0037] In the present invention, the injection material is injected into the ground surrounding an underground structure having a space, thereby strengthening the underground structure. The present invention is also suitable for self-supporting and water-stopping of an excavation surface, and for ground improvement of liquefied ground. In the present invention, the separated silica solution can penetrate into the part of the ground into which the suspended particles could not penetrate, expanding the solidification range, or can be integrated with the part of the ground into which the suspended particles have penetrated to form a solidified body.

[0038] In the present invention, the injection material preferably contains, as an active ingredient, any one or a combination of microbubbles, air, a dispersant, and a thickener.

[0039] In the present invention, it is preferable that the injection material contains a hardener consisting of a polyvalent metal compound, and the hardener is one or more of hydroxides, oxides, or salts of Ca, Mg, or Al, and / or gypsum.

[0040] In the present invention, it is preferable to confirm the improving effect by injecting the injection material by a non-destructive test.

[0041] In the present invention, the non-destructive testing is preferably carried out by elastic wave velocity logging, acoustic tomography or surface wave exploration.

[0042] The injection device of the present invention is an injection device used in the high-pressure injection mixing method in the ground improvement method of the present invention, and is characterized in that it comprises a guide pipe to be inserted into the ground, an inner injection tube that is placed within the guide pipe and is used to inject injection material, and an opening and closing mechanism that opens or closes the space between the guide pipe and the inner injection tube.

[0043] In the injection device of the present invention, the opening and closing mechanism comprises a ring-shaped rubber bag arranged between the guide tube and the inner injection tube and having a pipeline through which a fluid can flow, a ball bearing provided on the inner surface of the rubber bag facing the inner injection tube, and sealing members provided at the upper and lower ends of the rubber bag, and the opening and closing mechanism can open or close the space depending on whether or not pressure is applied inside the rubber bag due to the flow of fluid in and out of the rubber bag.

[0044] In the injection device of the present invention, the opening and closing mechanism comprises a ring-shaped rubber bag arranged between the guide tube and the inner injection tube and having a pipeline through which a fluid can flow, a fixing member for fixing the rubber bag to the guide tube, and ring-shaped metal fittings for closing the upper and lower ends of the rubber bag, and the opening and closing mechanism can open or close the space depending on whether or not pressure is applied inside the rubber bag due to the flow of fluid in and out of the rubber bag.

[0045] Furthermore, still another ground improvement method of the present invention is the above-mentioned ground improvement method of the present invention using the high-pressure jet mixing method with the above-mentioned injection device, characterized in that it includes the steps of: drilling a hole to a target depth in the ground with the guide pipe and inserting the inner injection pipe into the inside of the guide pipe; opening the space with the opening / closing mechanism, high-pressure jetting the injection material from the inner injection pipe together with high-pressure jet water or air, cutting the ground while jetting and mixing, and mixing the cuttings produced by cutting with the injection material above ground, thereby producing a mixed injection material; and high-pressure jetting the mixed injection material from the inner injection pipe together with high-pressure jet water or air into the ground.

[0046] Furthermore, still another ground improvement method of the present invention is the above-mentioned ground improvement method of the present invention using a high-pressure injection mixing method with the above-mentioned injection device, characterized in that it includes the steps of drilling a hole to a target depth in the ground with the guide pipe and inserting the inner injection tube into the inside of the guide pipe, opening the space with the opening / closing mechanism, high-pressure spraying the injection material from the inner injection tube together with high-pressure jet water or air, cutting the ground while jetting and mixing, and filling the area created by cutting with the injection material, and closing the space with the opening / closing mechanism to pressurize and infiltrate the injection material into the ground.

[0047] In the ground improvement method of the present invention, different injection materials are used for injection mixing and pressure infiltration, and the injection material used for pressure infiltration can be made more permeable than the injection material used for injection mixing. Also, the opening and closing of the space by the opening and closing mechanism can switch between the injection material used for injection mixing and the injection material used for pressure infiltration. Effect of the Invention

[0048] According to the present invention, it is possible to provide a ground improvement method and injection device which can form a larger, lighter consolidated body than conventional methods, while enabling environmentally friendly ground improvement with reduced CO2 emissions by eliminating the need for cement or by reducing the cement content in the conventional high-pressure injection method. [Brief description of the drawings]

[0049] [Figure 1] FIG. 1 is a conceptual diagram comparing a conventional ground improvement method using high-pressure jetting with the ground improvement method of the present invention, where (a) shows an example of the conventional method using a triple tube rod, and (b) shows an example of the conventional method using a double tube rod. [Diagram 2] FIG. 1 is a cross-sectional view showing an example of a conventional method using a double-tube rod (the JSG method (registered trademark) of the Japan Jet Grouting Association ("JSG method" is a registered trademark of NIT Corporation)). [Diagram 3]FIG. 1 is a cross-sectional view showing an example of a conventional method using a triple tube rod (the column jet grouting method of the Japan Jet Grout Association). [Figure 4] FIG. 13 is a photograph showing the bleeding state of the sample of Example 36. [Diagram 5] FIG. 2 is a photograph showing a bleeding state of the sample of Comparative Example 1. [Figure 6] FIG. 13 is a photograph showing the state of the sample of Example 36 several days after permeation. [Figure 7] FIG. 1 is a photograph showing the state of the sample of Comparative Example 1 several days after infiltration. [Figure 8] 1 is a graph showing the results of a long-length penetration test for Example 36 and Comparative Example 1. [Figure 9] 9 is a graph showing an enlarged portion of the permeation distance of 90 cm to 120 cm in FIG. 8. [Figure 10] This is a photograph showing the state in which the bleeding liquid has gelled and the gel does not collapse (stands on its own) even when tilted. [Figure 11] 1 is a graph showing particle size accumulation curves of various field sands that have been treated with liquefaction countermeasures using solution-type grout. [Figure 12] FIG. 13 is a photograph showing the strength measurement status of a test specimen on the 7th day after the mixing method using a bleeding liquid. [Figure 13] FIG. 13 is a photograph showing the state of a test specimen after strength measurement using a mixing method with a bleeding liquid. [Figure 14] 1 is a graph showing the physical properties of the sand used. [Figure 15(a)] FIG. 2 is an explanatory diagram showing one embodiment of infiltration and solidification in the ground injection method of the present invention. [Figure 15(b)] FIG. 2 is an explanatory diagram showing another form of permeation and solidification in the ground injection method of the present invention. [Figure 15(c)] FIG. 10 is an explanatory diagram showing yet another form of infiltration and consolidation in the ground injection method of the present invention. [Figure 15(d)] FIG. 10 is an explanatory diagram showing yet another form of infiltration and consolidation in the ground injection method of the present invention. [Figure 15(e)]FIG. 10 is an explanatory diagram showing yet another form of infiltration and consolidation in the ground injection method of the present invention. [Figure 15(f)] FIG. 10 is an explanatory diagram showing yet another form of infiltration and consolidation in the ground injection method of the present invention. [Figure 16(a)] FIG. 2 is an explanatory diagram of an injection device used in the combined injection and penetration injection method of the present invention. [Figure 16(b)] FIG. 2 is another explanatory diagram of the injection device used in the combined injection and penetration injection method of the present invention. [Figure 16(c)] 10 is yet another explanatory diagram of the injection device used in the combined injection and penetration injection method of the present invention. FIG. [Figure 16(d)] FIG. 2 is an explanatory diagram of the construction procedure using the injection device used in the combined injection and penetration injection method of the present invention. [Figure 17(a)] FIG. 11 is an explanatory diagram of another injection device used in the combined injection and penetration injection method of the present invention. [Figure 17(b)] 13 is another explanatory diagram of another injection device used in the combined injection and penetration injection method of the present invention. FIG. [Figure 17(c)] FIG. 11 is an explanatory diagram of the construction procedure using another injection device used in the combined injection and penetration injection method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 jet of fluid from an injection pipe inserted into the ground to form a cut area, and then injecting grout into the cut area to improve the ground.

[0051] In the present invention, an injection material is used that is primarily composed of suspended particles, or that is primarily composed of suspended particles and further contains one or more of a hardener, an alkali agent and solution-type silica. This injection material is filled into the cut area and allowed to penetrate from the cut area into the spaces between the soil particles in the surrounding ground, thereby solidifying the cut area and the surrounding ground.

[0052] The present invention described above cuts the soft ground with the force of a jet fluid, particularly a high-pressure jet fluid (for example, pressure 40 to 70 MPa), discharges the soft soil to the ground surface, and fills the cut area with an injection material or a mixture of the discharged cutting soil and the injection material, making it possible to reduce environmental problems by using a low-carbon grout as the injection material and by achieving low carbon in terms of transport of the discharged sludge, waste treatment, and disposal sites. The discharged cutting soil can be mixed with the injection material by filling it into a recycled injection material manufacturing tank.

[0053] The recycled grout processed by the above method has a uniaxial compressive strength of 2 to 6 MN / m for clayey soil layers when used for filling cutting areas, protecting surrounding structures, and improving shaft bottoms. 2 , 5~15MN / m in sandy soil layer 2 It is preferable that the permeability coefficient is 10 -5 ~10 -9 It is preferable that the speed be improved to about m / sec.

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

[0055] Table 1 below shows an example of a consolidated strength test of a mixture with an injection material when the ground is sandy or clayey. It can also be used as an example of a consolidated strength test of a mixture example of reclaimed soil when the cut soil is sandy or clayey. It can be seen that the injection material and the mix recipe of the reclaimed soil can be adjusted according to the purpose of injection, the required strength, the mixing time, and the cut soil.

[0056] Tables 1 to 8 indicate that even if the soil is not cut, it can be mixed with the on-site soil as an injection material and injected. Also, the strength of the injection material and the soil of the cutting area in the cutting area is shown. In the present invention, as described later, by selecting a lightweight suspension mainly made of small suspended particles with good fluidity according to the ground conditions, the suspension can be infiltrated into the surrounding ground of the cutting area and solidified (Figs. 7 to 9, 11, and 14). If the suspension contains solution-type silica, the separated silica solution separated from the suspension gels and solidifies, so that even in ground that cannot be infiltrated by the suspension alone, the solidification range extends to the surrounding soil of the cutting area, and furthermore, a water-stopping effect and continuous solidification of the solidified bodies are possible (Figs. 4, 6, 8 to 13). Figure 11 shows the particle size distribution curve where the penetration and solidification effect was obtained with solution-type grout, and the suspension-type grout made of the above-mentioned suspended particles containing solution-type silica can penetrate and solidify the ground with the particle size distribution shown in Figure 11, making it possible to realize a new concept of ground improvement method called "injection and penetration combined injection method" that has the advantages of both high-pressure injection injection method and chemical injection method. In addition, the silica solution gels immediately after injection, and if the strength is increased or 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, and it can be used with a lightweight injection device, and has the advantage of being environmentally friendly with little noise and vibration, 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 is mainly composed of suspended particles, or mainly composed of suspended particles and further containing one or more of a hardening agent, an alkali agent, and solution-type silica. As a suspension mainly composed of suspended particles, calcined silica such as slag or fly ash is made into a water suspension, which is mixed with a hardening agent such as water glass and / or an alkali agent, and then used after adjustment. As the suspended particles, any one or more of calcined silica, natural silica having a pozzolanic action, and hardenable silica particles can be used as an active ingredient.

[0058] Among these, examples of calcined silica include, in addition to slag and fly ash, cement, paper sludge, sludge incineration ash, sewage incineration ash, plant incineration ash, and calcined clay, as well as the incineration ash of plants that contain a lot of silica, and any one or more of these can be used. In addition, examples of natural silica that has a pozzolanic effect include natural calcined soil such as loam soil (Kanto loam), shirasu, volcanic ash, dip-soil soil, and trip-soil soil, and any one or more of these can be used. These calcined silicas are silica particles with latent hydraulic properties, contain soluble silica, and are firmly solidified by forming a crystal structure similar to that of part of cement through a pozzolanic reaction under the action of alkalis such as slaked lime, gypsum, magnesium hydroxide, water glass, silica colloid, caustic alkali, carbonates, bicarbonates, aluminum salts, calcium salts, and magnesium salts. In addition, by using aggregates such as clay and / or soil and sand as thickeners or bulking agents, it becomes possible to economically improve the ground. Furthermore, the on-site soil can be used in the form of a slurry together with the hardening agent.

[0059] The above suspended particles have a Blaine value of 4000 to 20000 cm 2 By using particles with a particle size of 1 / g, it becomes possible for the particles to penetrate between soil particles. Also, by using artificial or natural calcined silica as the suspended particles and setting the amount of suspended particles in the injection material to 40-200 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 depending on the strength of the hardened product to be aimed for, but it is preferably 50-200 kg per 400 L, 10-50 w / v% when no cement is used, and 5-50% by weight of cement when cement is used relative to the weight of the suspended particles.

[0060] The hardener used in the injection material of the present invention is a polyvalent metal compound, and may be one or more of hydroxides, oxides, or salts of Ca, Mg, or Al, and / or gypsum. Specifically, it is a Ca melt or an alkali agent such as cement, slaked lime, or gypsum, and in particular, slaked lime is preferable for shortening the gelation time and improving the initial strength. In addition, the above-mentioned injection material may be used in combination with slag, bentonite, calcium carbonate, clay, silica powder such as earth and sand, etc. as a filler. As a plastic grout, fly ash, polymers, cement, plasticizers such as aluminum salts, thickeners, clay, etc. may be used as a filler.

[0061] The hardener, alkali agent, and solution-type silica used in the injection material of the present invention may be any one or more of the following (1) to (3). (1) Those containing gypsum and / or MgO as active ingredients. (2) Those containing one or more of the following active ingredients: Ca salts, Mg salts, Al salts, carbonates, and bicarbonates. (3) Those containing one or more of the following 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, it is preferable that the molar ratio of water glass is 1.0 to 5.0, and the blending amount of water glass in the injection material is 10 to 150 L / 400 L.

[0063] In the present invention, the slag used is finely ground blast furnace slag. In order to increase reactivity, the finer the particle size, the more preferable. For example, the finer the specific surface area (Blaine value) is, the greater the slag is. 2 / g or more, preferably 6000 cm 2 / g~20000cm 2 / g and an average particle size of 10 μm or less is suitable.

[0064] In the present invention, the water glass is preferably one having a high alkali concentration in view of reactivity with slag, and in particular, one having a molar ratio of SiO2 / Na2O of 2.5 or less. A low molar ratio can provide a high-strength solidified body and a long gelation time. As the water glass, a mixture of anhydrous sodium orthosilicate and sodium hydroxide, crystalline sodium silicate containing sodium metasilicate, a mixture containing a part of crystalline sodium silicate, sodium silicate glass (cullet), hydrated glass, dehydrated sodium silicate, semisolid sodium silicate, viscous sodium silicate, a dilute solution of commercially available sodium silicate, etc. can be used, and the viscosity, molar ratio, and silica concentration may be changed, or the powder may be used as it is. The alkali content of the water glass stimulates the latent hydraulic properties of the slag. A low molar ratio water glass may be a mixture of water glass and caustic alkali. However, when using calcium molten materials such as slaked lime and 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 the present invention may be aluminum compounds such as aluminum sulfate and polyaluminum chloride, chlorides and sulfates of Ca and Mg, or may be those reacted with caustic alkali. Furthermore, the molar ratio of Na2O / Al2O3 is not particularly limited, but it is preferable that the Na2O concentration in the grouting material is 1 wt% or more because of its reactivity with slag. Caustic alkali is effective in stimulating the hydraulic properties of slag, and the aluminum reacts with water glass and silica in the slag to form aluminum silicate and calcium aluminosilicate. Furthermore, the gel time and strength of the suspension and the separated silica solution separated from the suspension can be adjusted by the amount of these additives added. Furthermore, seawater can be used as a blending liquid for the suspension.

[0066] The amount of water glass and aluminum compound in the grout is such that the grout hardens in a few hours, usually within an hour, and preferably within 30 minutes, and although it varies depending on the molar ratio of Na2O, Al2O3, and SiO2, it is preferable that the grout contains 1wt% or more of Na2O. However, when solidifying a wide area, the amount is necessary to harden in a few hours.

[0067] In the present invention, the amount of grout mixed with the cut soil varies greatly depending on the properties of the cut soil to be treated. 3 Per 0.1~0.5m 3 It is preferable that the range is 100%.

[0068] In addition, the injection material of the present invention can be made lighter by adding a foaming agent or a foaming agent to improve the fluidity, and can be made lighter by adding salt-free high-performance water reducing agents, dispersants, clay, bentonite, polymer thickeners, such as polyvinyl alcohol, carboxymethyl cellulose (CMC), and methyl cellulose, to suppress dispersibility in water, reduce precipitation, and improve workability, or to function as a water-retaining material and as a binder for suspended particles such as slag, which is the main material, to form a pseudo-gel-like fluid that retains fluidity but is 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 suspension of slag, fly ash, etc., or into a suspension of cement, etc., and then injected into the cutting area. This allows the suspension particles to be covered by the microbubbles or the bearing action of the microbubbles and air, making it possible to construct a wide-area consolidated body from the suspended particles, and also to reduce the weight and strength of the consolidated body due to the increase in the amount of gas in the consolidated body. The injection material in the present invention can use any one or more of microbubbles, air, dispersants, and thickeners as active ingredients.

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

[0071] The use of cutting soil in the present invention is effective as a low-carbon technology. Conventionally, cutting soil was either dumped as it is as industrial waste or transported from the site to a processing plant where it was mixed with lime, which was uneconomical and time-consuming. However, the problems of such conventional methods can be solved by applying the present invention. According to the present invention, economical and rapid construction is possible by backfilling the soil on site or by mixing the cutting soil with grout and then filling the mixture in the cutting area.

[0072] In the present invention, a mix recipe can be set for the injection material, which is a lightweight, low-alkaline, and low-carbon type ground improvement material.

[0073] In the present invention, the grouting materials may be directly mixed and fed to the injection rod as one liquid, or the above-mentioned suspension (liquid A) and water glass and / or alkaline agent (liquid B) may be pumped and mixed before injection. In this case, it is preferable to mix liquid A and liquid B at a ratio of approximately 1:1 (by volume), but they are usually mixed at any ratio within the range of 10:1 to 1:10.

[0074] The hardening time of the regenerated grout when the grout is re-injected into the cutting area may be a time that allows sufficient mixing with the cutting soil, and is therefore determined by the mixing method or mixing device, and is, for example, about 10 to 30 minutes. In addition, it may be determined to be several hours to several tens of hours in consideration of workability.

[0075] In the present invention, the improvement effect of the injection of the grouting material can be confirmed by a non-destructive test, which can be performed using an elastic wave velocity logging method, an acoustic tomography, or a surface wave exploration method.

[0076] (test) Clay soil and sandy soil were used as the cutting soil, and these were mixed with the injection material and consolidated with the above-mentioned injection material according to the present invention. The test results of the embodiment in which the strength of the consolidated body was measured are shown in Table 1.

[0077] As can be seen below, injection materials that use calcined silica or natural silica with pozzolanic action as their 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 their main material, and therefore solidify the ground with a material that has almost the same specific gravity as the original ground, or even a lighter material, thereby achieving the effect of reducing the weight of the solidified body.

[0078] [Materials used] Slag: specific gravity 2.9, Blaine value 8000cm 2 / g, a silica-based non-hardening powder. Fly ash (FA): Coal ash discharged from thermal power plants. It is a silica-based non-hardening powder. Specific gravity: 1.9-2.3g / cm 3 The particle size distribution is 0.1 mm or less for more than 90%. 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 material, specific gravity 2.6. Bentonite: Water retention and thickening material, 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 and foam materials can also be used.

[0079] [Test method and test results] For the unconfined compressive strength tests in Tables 1 to 7, cylindrical specimens with a height of 100 mm and a diameter of 50 mm were used and were in accordance with the Japanese Industrial Standards (JIS A 1216:2020 Unconfined Compression Test Method for Soil). The results of measuring the strength on the 1st day, 7th day, and 28th day, or on the 28th day, are shown, respectively. In addition, in Tables 1 to 8, the gel time is the time it takes for the suspension to thicken while continuing to stir with a stirring rod.

[0080] From this example, it can be seen that in the present invention, not only can a solidified body formed by mixing cuttings soil and this injection material in the ground be formed by mixing the cuttings soil with this injection material and injecting it into the cutting area to form a sufficiently consolidated ground, but also that it is possible to economically improve the ground by mixing obtained soil or clay other than cuttings soil with this injection material and injecting the resulting 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] Below, test examples (Figs. 4 to 13) showing the effect of gelling the bleeding liquid in the above suspension containing a silica solution, or the separated silica solution separated from the suspension, will be described. Fig. 10 shows the tilted state of Fig. 4 using Example 36 in Table 4. Figs. 12 and 13 show the state of a strength test of a sand specimen solidified with the bleeding liquid in Table 8.

[0090] (Permeability test) (Test equipment and test method) A one-dimensional infiltration apparatus (length 2m) was used to carry out infiltration tests on No. 6 silica sand, and the infiltration length and strength distribution were investigated.

[0091] Test conditions: acrylic mold h=2m, mixed liquid 3L. After the sample was saturated with water, the suspension was poured into the bottom until no more liquid was discharged.

[0092] The uniaxial compression test was conducted in accordance with the Japanese Industrial Standard (draft) (JIS A 1216:2020) for the uniaxial compression test method for soil, and cylindrical specimens measuring 100 mm in height and 50 mm in diameter were used.

[0093] The experiments were carried out using the compositions of Example 36 and Comparative Example 1 (FIGS. 6 to 9, 12, and 13).

[0094] The solid lines in Figures 8 and 9 show the results for the formulation of Example 36. Strength measurements were possible even with a penetration distance of 120 cm. There was no discoloration of the sand gel after 90 cm, but the strength measurements were possible because the silica solution separated from the suspension solidified after 90 cm. The portion after 90 cm is thought to contain 0.5% or more silica.

[0095] The dotted lines in Figures 8 and 9 show the results obtained with the formulation of Comparative Example 1. The strength could be measured up to 90 cm, but there was no discoloration beyond 90 cm, making it impossible to measure the strength, and it was found that the silica solution separated from the suspension had not gelled.

[0096] In the penetration test shown in Figure 7, the areas where there was no discoloration of the sand are thought to be areas where the slag did not penetrate. Because the bleeding liquid was not self-supporting, the areas where the solution separated from the suspension penetrated were also not self-supporting and did not solidify. In contrast, in Figure 6, the bleeding liquid has gelled and is self-supporting, so the suspended particles do not penetrate and the sand gel does not discolor, but the separated silica solution separated from the suspension penetrates and solidifies, allowing it to stand on its own and develop strength.

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

[0098] From Figures 8 and 9, even if the penetration distance of the suspended particles in the suspension is 90 cm, the separated silica solution from the suspension penetrates up to 120 cm, and the solution has the strength to stand on its own, and the sand gel has the strength to stand on its own. In that case, it can be predicted that the silica concentration is 0.5 to 2% or more (Table 9). Therefore, even if the injection hole interval is long, the solidified bodies penetrated by the suspended particles, which can obtain high strength, will be connected by the homogel of the silica solution.

[0099] In this way, an integrated solidified body can be formed even under ground conditions in which suspended particles cannot penetrate, and even if the injection hole spacing is wide, the solidified bodies between the holes can be connected by the self-supporting gelled product of the silica solution, forming an integrated solidified ground.

[0100] Suspension-type grout can achieve higher strength than solution-type grout, but its large particle size makes it less permeable to fine-grained soil. However, by including solution-type silica, a solidification effect can be achieved even in ground that cannot be penetrated by suspended particles, making it possible to achieve integrated ground improvement and water-stopping properties (Figure 15).

[0101] As described above, the inventors have focused on the gelation of the bleeding liquid of the suspension grout, and have studied the gelation of the bleeding liquid, the self-supporting property of the homogel of the bleeding liquid, and the self-supporting property and strength of the sand gel of the bleeding liquid, and by making them the conditions, they have improved the penetration and consolidation property of the suspension grout for fine-grained soil or ground containing fine-grained soil, which was previously thought to be inapplicable, and completed the present invention. In addition, according to the present invention, an improvement effect is obtained that allows the excavated surface to be self-supporting and watertight even in excavated ground. Therefore, the present invention can be applied not only to the reinforcement of the ground as shown in FIG. 15, but also to the reinforcement and watertightness of excavated ground.

[0102] In particular, when a suspension grout containing a silica solution is applied, the present invention exerts the following effect due to the gelation of the separated silica solution from the suspension grout. By exerting such an effect that could not be obtained with the conventional high-pressure jet mixing method, the present invention has realized a ground improvement method based on a new concept of jetting and penetration injection that simultaneously obtains the advantages of the high-pressure jet mixing method and the penetration injection method. (1) Permeation and consolidation of suspended particles into fine-grained soil layers, where permeation and consolidation was previously impossible. (2) Self-supporting and water-tight properties of the cutting surface. (3) Expansion of the area improved by infiltration and solidification. (4) Ground improvement in which adjacent consolidated bodies are connected and integrated. (5) Reduction in construction costs by increasing the spacing between holes in the injection pipe. (6) The separated silica solution from the suspended grout has a short-term solidification effect, which improves resistance to earth pressure from adjacent structures and the back of retaining walls, improving the safety of construction, the safety of buried objects through infiltration injection, strengthening the ground surrounding underground structures with spaces, and waterproofing and repairing deterioration.

[0103] An example is given below. (Strength test) (Preparation of sand gel specimen) Using No. 6 silica sand (Figure 14) and bleeding liquid, specimens 5cm in diameter and 10cm in height were prepared using a mixing method to achieve a relative density of 60%, and the unconfined compressive strength was measured after 28 days. The bleeding rate was higher when the amount of water glass was greater, and higher when the amount of slag was reduced. In the case of sand gels using bleeding liquid, the strength development rate was higher when the amounts of water glass and slag were greater. In cases where gypsum was also used, the bleeding rate decreased and the strength increased when gypsum was added.

[0104] The gelation and self-supporting property of the bleeding liquid, as well as the strength and self-supporting property of the sand solidified by the bleeding liquid (sand gel), vary depending on the amount 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 liquid. Therefore, tests were conducted to confirm the gelation and self-supporting property of the bleeding liquid, as well as the minimum value of its strength, as conditions that comprehensively affect these several factors (Table 9). The gel time in Table 8 is the stirring gel time, which cannot be obtained with the bleeding liquid, so here we used the static gel time. The static gel time was measured as follows. First, 100 mL of the bleeding liquid was placed in a standard bag No. 8 (thickness 0.03 × width 130 × height 250 mm), and it was separated into a lower part with many suspended particles and an upper part with few suspended particles (bleeding liquid). The time when the upper part of the lower suspension part was slowly tilted to the side and the solid content no longer tilted by 2 / 3 was defined as the static gel time. The static gel time was shorter than the stirring gel time, and in most cases it was half the stirring gel time. When making the sand gel in Table 8, 2L or 3L of the composition was put into a 3L plastic mug, and the bleeding liquid was taken out when it was half the static gel time, and the liquid was used to make the sand gel.

[0105] As a result, it became possible to improve the ground by a combined suspension-solution injection method in which the fine-grained soil parts where the penetration and solidification of suspended particles was difficult, or the parts where the penetration did not occur, were solidified by the separated silica solution separated from the suspension, and the whole was integrated, provided that the bleeding liquid gelled and became self-supporting, and the sand gel into which the bleeding liquid had permeated became self-supporting.

[0106] It was found that the gelation occurs whether the bleeding rate is 50% or more or 50% or less, and that the silica solution separated from the suspension during injection penetrates and hardens. The minimum strength for the sand gel to stand on its own is 2.0kN / m 2 The strength of the self-supporting sand gel, which was made with 75 g of slag and 100 mL of No. 1 water glass per 400 mL, was 15 kN / m on the 28th day.2 The strength was also measured on the first and seventh days. The strength on the first day was 2.0 kN / m 2 On the 7th day, the strength was 10 kN / m 2 (Figures 12 and 13). A similar trend was also observed with Toyoura sand. If the bleeding solution contains salts such as Ca, Mg, and Al, the strength of the sand gel will be further increased.

[0107] In the present invention, the test specimen is adjusted to the size of the specimen for the uniaxial compression test of soil, and the diameter D0 (mm) is usually 35mm or 50mm, and the height H0 (mm) is 1.8 to 2.5 times the diameter D0 (mm). If it is a self-supporting sand gel, it can be judged at any age. Figure 12 shows the test conditions. From this, it can be judged that even in-situ sand can achieve a strength of 2.0kN / m at an injection rate of 40%. 2 It was found that the soil would be self-supporting if it had a strength of 1 m. The injection rate is the ratio of the injection liquid to the volume of the ground to be improved. 3 When the injection rate is 40%, the injection volume is 0.4 m 3 It becomes.

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

[0109] (Relationship between silica concentration and strength) A neutral to alkaline solution was poured into an acrylic mold with a removable bottom and allowed to solidify, and the presence or absence of gelation of the homogel at each silica concentration and the self-supporting ability of the gel were confirmed. The same procedure was also carried out with the sand gel, and the solidification and the self-supporting ability of the consolidated sand were confirmed. The results are shown in Table 9.

[0110] At silica concentrations below 0.5%, the homogel and sand gel did not become self-supporting. Further testing revealed that gelation occurred even at a silica concentration of 0.25%, but the gel did not remain self-supporting, and the sand gel did not solidify or remain self-supporting (Table 9).

[0111] [Table 9]

[0112] In other words, simply because the bleeding solution gels, there are cases in which neither the homogel nor the sand gel can become self-supporting, and cases in which the sand gel can become self-supporting even though the homogel cannot. This shows that certain conditions are necessary for the homogel and sand gel to become self-supporting (Tables 8 and 9).

[0113] In addition, a penetration test using a one-dimensional penetration device (length 2m) showed that in the water glass-slag system, the bleeding liquid gels and has the strength to stand on its own, but when water glass is not included, the bleeding liquid does not gel, and because the bleeding liquid gels whether the bleeding rate is above or below 50%, the separated silica solution separated from the suspension penetrates and solidifies. In this case, the silica concentration of the separated silica solution was predicted to be 0.5w / v% or more (Table 9).

[0114] In addition, penetration tests have confirmed that in the case of a water glass-slag system and a suspension not containing water glass, the separated silica solution penetrates and solidifies into sand, which cannot be penetrated by suspended particles from the separated silica solution in a suspension containing water glass. Therefore, since this separated silica solution is capable of penetrating even in ground that follows the particle size accumulation curve for the penetration and solidification of solution-type grout, it was found that the penetration potential of solution-type silica grout was achieved (Figure 11).

[0115] In this way, suspension-type grout uses fine silica particles such as slag or fly ash and solution-type silica, and the bleeding liquid penetrates and solidifies even in areas where suspensions cannot penetrate. Therefore, by focusing on the gelation of the bleeding liquid, the following conditions were found under which the bleeding liquid and sand gel can be self-supporting.

[0116] In view of the above, other preferred embodiments of the present invention are as follows. This is an injection method in which injection material is injected into the ground from multiple injection holes installed in the ground, filling the cut area and causing interparticle penetration and solidification of the surrounding soil. The injection material used is a suspension made mainly of suspended particles such as slag or fly ash, with solution-type silica such as water glass or silica colloid as the active ingredient, and is capable of penetrating and solidifying even areas that the suspension cannot penetrate.

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

[0118] When the suspension contains solution-type silica, the separated silica solution gels and the homogel has a strength to stand on its own, and the sand gel solidified by the penetration of the separated silica solution has a strength to stand on its own, and the separated silica solution penetrates into the part of the ground where the suspension could not penetrate, expanding the solidification range, or integrating with the part of the ground where the suspended particles penetrated to form a solidified body, thereby connecting the solidified bodies of the suspended particles from the adjacent injection holes. In addition, by adding CMC, MC, polyacrylamide, clay, etc. to the injection solution, it is difficult to disperse in the ground and difficult to dilute even in gravel ground. Furthermore, even if it is injected into the ground to be excavated, it becomes possible to use a combined injection and infiltration injection method that can make the cut surface of the excavated ground self-supporting and stop groundwater.

[0119] Here, the above-mentioned gelation of the separated silica solution separated from the suspension and the homogel becoming self-supporting means that the silica concentration of the separated silica solution is 0.5 w / v% or more, and the homogel does not collapse and remains self-supporting even when tilted diagonally in the mold.

[0120] The sand gel is self-supporting if the silica concentration of the separated silica solution is 0.5 w / v% or more, and if No. 6 silica sand is used, a sand gel made by a mixing method using the separated silica solution with a diameter of 5 cm and a height of 10 cm so as to have a relative density of 60% is self-supporting, and the strength of the sand gel measured in a uniaxial compression test is 2.0 kN / m 2 This means that it is more than or equal to this.

[0121] In the above, the sand gel made from the bleeding liquid of silica grout, which is made of water glass and silica particles containing Ca, increases in strength over time (Table 8). This is thought to be because the Ca ions in the silica particles continue to dissolve in the gel of the bleeding liquid over a long period of time even after gelation and react with the silica, forming calcium silicate, which contributes to the increase in strength. Alternatively, it is thought that the added hardener containing Ca or Mg reacts with the soluble silica in 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 and consolidation range can be set by the size of the solidified bodies in the cut area by injection, the suspended particles, and the gelation of the separated silica solution separated from the suspension, depending on the ground conditions and the purpose of ground improvement (strength, range of the consolidated area, etc.). In addition, the penetration and consolidation range of the suspended particles and the penetration and consolidation range of the separated silica solution separated from the suspension can be set by the type and particle size of the suspended particles of the suspension grout, the mixing amount, the hardener and alkali agent, the type and amount of solution-type silica, the bleeding rate, the strength of the bleeding liquid, and the gelation time. As a result, as shown in Figure 15, a new concept of injection and penetration combined injection was created, and ground improvement by injection and penetration injection using suspension grout became possible.

[0123] The injection material used according to the invention has, in particular, the following characteristics: (1) By setting the composition of the suspension injection material, which is mainly composed of small, lightweight, and highly fluid suspended particles, it is possible to make the material penetrate over a wide area from the cut area into the surrounding ground (Figures 7 to 9). (2) By including silica solution, the separated silica solution from the suspension gels while penetrating into the ground, and the silica solution penetrates into the fine-particle parts of the ground where suspended particles cannot penetrate (Fig. 6, Fig. 8-10), causing the fine-particle parts of the ground to solidify and become self-supporting. Since the separated silica solution from the suspension has the same permeability as solution-type silica grout, the fine-grained soil permeability range shown in Fig. 11 can be expected. Fig. 4 shows the state in which the suspended matter solidifies and the bleeding liquid gels when a silica suspension containing silica is left to stand. Fig. 5 shows the state in which only the suspended matter solidifies and the bleeding liquid does not gel when a silica suspension not containing silica is left to stand. (3) Table 9 shows the self-supporting properties of homogel, the solidification of sand gel, and the self-supporting properties of consolidated sand at low silica concentrations of 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 into the sandy ground.

[0124] The particle size distribution of the sand used in the infiltration test (Figs. 6-9) is the No. 6 silica sand shown in Fig. 14. With this particle size distribution, in the suspension not containing silica solution, the suspended particles can infiltrate between the soil particles for 80 cm (Figs. 8 and 9). In Toyoura sand, which is finer than that, the infiltration distance was almost half or less. Furthermore, if the above suspension containing silica solution (Example 36) is used, the infiltration range shown in Fig. 11, which is the same as the particle size range of the infiltration possible range of the solution type, is obtained, and although the infiltration distance varies depending on the soil condition, it is possible to form a solidified body as shown in Fig. 15. Figs. 15(c) and (d) are plan views of the infiltration solidified body. The type and size of the suspended particles of the suspension type grouting material may be selected depending on the soil condition. In addition, since infiltration injection is possible as shown in Fig. 15(e), it is possible to stabilize the surrounding structures without causing damage to the underground buried objects. Fig. 15(f) shows that there is a risk of damage to the underground buried objects in the high-pressure jet mixing method.

[0125] As described above, the inventors have found that when a suspension containing the above-mentioned suspended particles as a main component is injected, the area close to the center becomes a high-strength area with a large number of suspended particles, and the concentration of suspended particles decreases with distance from the center, resulting in a low-strength area. Furthermore, they have found that outside of the area, a solidified body with a large silica content is formed by gelation of the separated silica solution separated from the suspension, which connects adjacent solidified bodies. Conventionally, a large amount of bleeding in a suspension has been considered a disadvantage, but in the present invention, focusing on the fact that the separated silica solution separated from the suspension can penetrate between soil particles that cannot be penetrated by suspended particles, research has been conducted 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 the sand, and the strength of the sand gel have a significant effect on the improvement of the penetration and consolidation properties of the suspension-type grout. Based on these findings, the conditions were examined that not only can the suspension penetrate into the ground surrounding the injection area, but also that the separated silica solution separated from the suspension can penetrate and gel into the fine-grained soil area where suspended particles cannot penetrate, allowing the formation of a large improved body. As a result of this research, the inventors were able to cover the injectability limit of suspended particles by using the gelling function of solution-type silica (bleeding liquid) separated from the suspension injection material, thereby making it possible to achieve integrated ground improvement work for the entire target ground, which has high permeability, high strength and excellent water-stopping properties.

[0126] According to the present invention, the coarse-grained soil is solidified, and the gelation of the separated silica solution separated from the suspension allows the fine-grained soil, which the suspended particles cannot penetrate, to be solidified, and a larger solidified body than the solidified body of the suspended particles can be formed. However, sufficient strength cannot be obtained by only gelling the separated silica solution separated from the suspension. From this point of view, it was found that the strength condition for the self-supporting homogel and sandgel of the bleeding liquid is that the silica concentration of the bleeding liquid is 0.5 w / v% or more (Table 9). By applying this as the above-mentioned suspension type grout to the high-pressure injection mixing method, the problems of the high-pressure injection mixing method mainly using cement as described above are solved, and a new ground improvement method is realized.

[0127] Furthermore, the present invention provides a ground improvement method that can obtain a solidified body with excellent durability and is expected to reduce CO2 emissions by using a non-cement-based injection material whose main component is silica particles with natural pozzolanic action, including artificially calcined silica such as slag or fly ash, or soluble silica such as loam soil.

[0128] (Injection equipment and procedure) As described above, the present invention is a combined injection and penetration injection method. Therefore, the injection device must be capable of injection mixing and pressure penetration injection. In order to inject and mix high-pressure water to fill the suspension according to the present invention into the cut space and to infiltrate it under pressure, it is necessary to prevent the injected suspension from being discharged to the ground together with the drained mud. Figure 16 shows an injection device with this function (Figure 16(a)) and the construction procedure using this device (Figures 16(b) to (d)).

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

[0130] In the ground improvement method using the high-pressure injection mixing method with the injection device, specifically, first, a hole is drilled to the target depth of the ground with a guide pipe, and the inner injection pipe is inserted into the hole. Next, the space between the guide pipe and the inner injection pipe is opened by the opening and closing mechanism, the guide pipe is raised, and the injection material is high-pressure injected from the inner injection pipe together with high-pressure jet water or air, cutting the ground while injecting and mixing it. Next, the cut soil produced by cutting is mixed with the injection material above ground to produce a mixed injection material, and this mixed injection material is high-pressure injected from the inner injection pipe together with high-pressure jet water or air into the ground. Alternatively, after filling the area produced by cutting with the injection material, the opening and closing mechanism closes the space, and the injection material is pressurized and infiltrated into the ground. When the injection material is to be infiltrated into the surrounding ground, it is necessary to apply an infiltration pressure.

[0131] Fig. 16(a) shows an opening and closing mechanism using a rubber bag that allows for the removal of cut soil and the application of seepage pressure. In the example shown, the opening and closing mechanism is arranged between the guide tube and the inner injection tube, and is made up of an annular rubber bag with a duct through which fluid can flow, a ball bearing provided on the inner surface of the inner injection tube side, and seal members provided on the upper and lower ends of the rubber bag. The opening and closing mechanism opens or closes the space depending on whether or not the inside of the rubber bag is pressurized by the flow of fluid in and out of the rubber bag.

[0132] The rubber bag has ball bearings on its inner surface and sealing members such as O-rings on both the top and bottom ends to maintain airtightness when fluids such as air are injected inside. During cutting, the space between the inner injection tube and the guide tube is open, and the cut soil is discharged to the ground. On the other hand, when injecting the grout material, fluid is sent into the rubber bag, which expands and closes the space between the inner injection tube and the guide tube, so that the grout material permeates the ground under pressure. When moving through the cutting area, the ball bearings of the opening and closing mechanism allow mutual movement between the guide tube and the inner injection tube.

[0133] 17(a)-(c) show the structure and construction procedure of an example using another opening / closing mechanism. In this case, the opening / closing mechanism is arranged between the guide tube and the inner injection tube, and is composed of an annular rubber bag having a duct through which a fluid can flow, a fixing member for fixing the rubber bag to the guide tube, and ring-shaped metal fittings for closing the upper and lower ends of the rubber bag. The opening / closing mechanism opens or closes the space depending on whether or not the inside of the rubber bag is pressurized by the flow of fluid in and out of the rubber bag.

[0134] First, the injection material is injected at high pressure together with high pressure water or air from the inner injection tube inserted into the guide tube equipped with an opening and closing mechanism, cutting the ground and stirring it, and discharging the cut soil produced by cutting to aboveground level. Next, the rubber bag is inflated by pressurizing it with air or other fluid and brought into close contact with the guide tube, blocking the space between the guide tube and the inner injection tube, injecting the injection material without discharging the mud, and injecting it into the outer periphery of the cut area with the injection pressure. After that, the pressure on the rubber bag is stopped, the rubber bag is no longer attached to the inner injection tube, the inner injection tube is pulled up, and the same process is repeated.

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

[0136] By using the injection device of Figures 16 and 17, the injection material (injection material X) during pressure penetration injection can be switched to an injection material with higher permeability than the injection material (injection material Y) during injection and stirring injection, and a blend of different gelation times can be used. That is, in the present invention, different injection materials are used for injection and stirring and the injection material used for pressure penetration can be made to have higher permeability than the injection material used for injection and stirring. Also, in the present invention, the injection material used for injection and stirring and the injection material used for pressure penetration can be switched by opening and closing the above-mentioned space with the opening and closing mechanism.

[0137] For example, when a cement suspension is used as the injection material, injection material Y may be high concentration and injection material X may be low concentration, and the injection device having the above-mentioned opening and closing mechanism may be used for injection stirring injection and pressure penetration injection, or injection material Y may be a suspension and injection material X may be a solution type grout. Furthermore, after injection material Y is injected, injection material Y may be used as injection material X by adding an accelerator to injection material Y to adjust the gelation time. Whether or not the suspension can penetrate is related to the grain size of the injection ground. In that case, the judgment can be made by using the numerical value calculated for the existing injection limit of the injection ground as a guide. For example, experimental statistical results on the injection limit of suspension grout by JC Cing (Proc. ASCE 1961) are used (from "Chemical Injection Method of Cutting-Edge Technology" Riko Tosho, Shimada Shunsuke, Sato Takeshi, Takumi, pp. 154-158). The D of soil particles 15 , D 10 and D of the suspension 85 , D 95 The amount of N that satisfies this condition is called the Groutability Ratio (usually N1). N1=D 15 / D 85 ≧15 N2=D 10 / D 95 ≧8 If this relationship is not satisfied, the grout (suspension) will not be able to penetrate smoothly. Therefore, in ground where the groutability ratio N is satisfied, the suspension can be injected through penetration. Even in ground where the suspension is difficult to inject through penetration, if a suspension containing silica solution is used, the gelation of the separated silica solution can form a ground where the suspended particles are integrated with fine-grained soil, even in ground where the suspension does not penetrate sufficiently, or the penetration of the separated silica solution over an even wider area can form a large consolidated body. In such cases, 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 changing the contents and mix of the injection material in this way, it is possible to adjust the solidification strength, permeability, and gel time, expand the solidification range and injectable limits, and realize a ground improvement method based on the new concept of injection, stirring, penetration, and combined injection. [Industrial Applicability]

[0139] The present invention relates to a ground improvement method capable of performing high-strength and uniform ground improvement on soft ground or liquefied ground, and in the destruction and solidification of the ground using the kinetic energy of a high-pressure jet fluid, not only does it form a solidified body in the cut area, but also allows the injection material to penetrate between the soil particles from the cut area to form a larger solidified body, and by reusing the soil cut by high-pressure jetting and filling it into the ground, it enables low-carbon ground improvement. 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 action, it is possible to perform wide-area ground improvement that is environmentally friendly and reduces CO2 emissions using a non-cement injection material or an injection material with reduced cement, and has the effect of expanding the penetration solidification range and reducing the weight of the solidified body, and thus it is possible to efficiently and economically perform ground improvement on soft ground or liquefied ground.

Claims

1. A method for forming a cut area by cutting the ground with jet fluid from a plurality of injection pipes inserted into the ground, and injecting an injection material into the cut area, The following i) to iii) i) Silica particles comprising either or both of pyrogenic silica and natural silica having pozzolanic activity; ii) Silica particles comprising any one or more of slag, fly ash, cement, sewage incineration ash, plant incineration ash, and calcined clay; iii) Silica particles in which the natural silica having pozzolanic activity is any one or more of loam soil, volcanic ash, diploid soil, and triploid soil; A ground improvement method for consolidating a cut area and the surrounding ground by injecting an injection material consisting of a suspension containing any one of the above-mentioned suspended particles of silica particles as a main material and containing solution-type silica as an active ingredient from a plurality of injection pipes into the ground, filling the cut area and allowing the injection material to permeate between soil particles in the surrounding ground from the cut area, The separated silica solution separated from the suspension penetrates into an area where the suspended particles cannot penetrate, and then the separated silica solution gels and solidifies the ground, thereby solidifying the ground by the suspended particles and the separated silica solution, The silica particles have a Blaine value of 4,000 to 20,000 cm 2 / g, the amount of the silica particles in the injection material is 40 to 200 kg / 400 L, and silica colloid and / or water glass are used as the solution-type silica, When the solution-type silica contains water glass, the injection material uses water glass having a molar ratio of 1.0 to 5.0, and the amount of the water glass in the injection material is 10 to 150 L / 400 L; The silica concentration of the separated silica solution is 0.5 w / v% or more, the homogel formed by gelling the separated silica solution has a strength to be self-supporting, and the sand gel formed by permeating the separated silica solution and solidifying has a strength to be self-supporting, The term "the separated silica solution gels and the homogel becomes self-supporting" means that the silica concentration of the separated silica solution is 0.5 w / v% or more, and the homogel does not collapse even when tilted obliquely in a mold and can self-support; the term "the sand gel becomes self-supporting" means that the silica concentration of the separated silica solution is 0.5 w / v% or more, and when No. 6 silica sand is used, the sand gel prepared by a mixing method using the separated silica solution to have a relative density of 60% and a size of 5 cm in diameter and 10 cm in height can self-support, and the strength of the sand gel measured in a uniaxial compression test is 2.0 kN / m2 or more; The separated silica solution has permeability to fine-grained soil and penetrates into areas of the ground that the suspended particles could not penetrate, forming an area near the center where the concentration of suspended particles is high and the strength is relatively high, an area away from the center where the concentration of suspended particles decreases and the strength is relatively low, and an outside of this, a solidified body with a high silica content due to gelation of the separated silica solution, and the solidified bodies made of the suspended particles from adjacent injection pipes are connected to each other.

2. A ground improvement method as described in claim 1, wherein the injection material contains an alkaline agent consisting of one or more of the following: (1) An alkaline agent containing either or both of gypsum and MgO as active ingredients. (2) An alkaline agent containing, as an active ingredient, one or more of Ca salts, Mg salts, Al salts, carbonates and bicarbonates. (3) An alkaline agent having as its active ingredient one or more of lime, cement, caustic alkali, water glass, and silica colloid.

3. A ground improvement method as described in claim 1, wherein, when the suspended particles are slag and no cement is used, the amount of slag in the injection material is 10 to 50 w / v %, or, when 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.

4. 2. The ground improvement method according to claim 1, wherein the injection material contains one or more of microbubbles, air, a dispersant, and a thickener as active ingredients.

5. A ground improvement method as described in claim 1, wherein the injection material contains a hardener consisting of a polyvalent metal compound, and the hardener is one or more of hydroxides, oxides or salts of Ca, Mg or Al, and / or gypsum.

6. A ground improvement method as described in claim 1, in which the injection material is injected into the ground surrounding an underground structure having a space, thereby strengthening the underground structure.

7. A ground improvement method as described in claim 1, which is applied to the self-supporting and watertightness of an excavation surface.

8. A ground improvement method as described in claim 1, which is applied to ground improvement of liquefied ground.

9. 2. The method according to claim 1, wherein the improvement effect of the injection of the grouting material is confirmed by a non-destructive test.

10. 10. The ground improvement method according to claim 9, wherein the non-destructive testing is carried out by elastic wave velocity logging, acoustic tomography or surface wave exploration.

11. A ground improvement method as described in claim 1, wherein the separated silica solution penetrates into parts of the ground into which the suspended particles could not penetrate, thereby expanding the solidification range, or integrates with the parts of the ground into which the suspended particles have penetrated to form a solidified body.

12. An injection device used in the high-pressure injection mixing method in the ground improvement method described in claim 1, comprising: a guide tube to be inserted into the ground, an inner injection tube disposed within the guide tube and used to inject injection material, and an opening / closing mechanism for opening or closing the space between the guide tube and the inner injection tube.

13. 13. The injection device according to claim 12, wherein the opening and closing mechanism comprises an annular rubber bag disposed between the guide tube and the inner injection tube and having a duct through which a fluid can flow, a ball bearing provided on the inner surface of the rubber bag facing the inner injection tube, and sealing members provided on the upper and lower ends of the rubber bag, and the opening and closing mechanism opens or closes the space depending on whether or not pressure is applied inside the rubber bag due to the flow of fluid in and out of the rubber bag.

14. 13. The injection device according to claim 12, wherein the opening and closing mechanism comprises an annular rubber bag disposed between the guide tube and the inner injection tube and having a duct through which a fluid can flow, a fixing member for fixing the rubber bag to the guide tube, and ring-shaped metal fittings for closing the upper and lower ends of the rubber bag, and the opening and closing of the space by the opening and closing mechanism is performed depending on whether or not pressure is applied inside the rubber bag due to the flow of fluid in and out of the rubber bag.

15. 13. The ground improvement method according to claim 1, which is a high-pressure jet mixing method using the injection device according to claim 12, comprising the steps of: drilling a hole to a target depth in the ground with the guide pipe and inserting the inner injection pipe into the inside of the guide pipe; opening the space with the opening / closing mechanism, jetting the injection material from the inner injection pipe at high pressure together with high-pressure jet water or air, cutting the ground while jetting and mixing, and mixing the cuttings produced by cutting with the injection material above ground, thereby producing a mixed injection material; and jetting the mixed injection material from the inner injection pipe at high pressure together with high-pressure jet water or air into the ground.

16. 13. The ground improvement method according to claim 1, which is a high-pressure injection mixing method using the injection device according to claim 12, comprising the steps of: drilling a hole to a target depth in the ground with the guide pipe and inserting the inner injection pipe into the inside of the guide pipe; opening the space with the opening / closing mechanism and high-pressure jetting the injection material from the inner injection pipe together with high-pressure jet water or air, cutting the ground while jetting and mixing, and filling the area created by cutting with the injection material; and closing the space with the opening / closing mechanism and pressurizing and penetrating the injection material into the ground.

17. 17. The method for improving ground according to claim 16, wherein different injection materials are used for the injection mixing and the pressure infiltration, and the injection material used for the pressure infiltration has higher permeability than the injection material used for the injection mixing.

18. The ground improvement method according to claim 16, wherein the injection material used for the injection mixing and the injection material used for the pressure infiltration are switched by opening and closing the space with the opening and closing mechanism.

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