Injection device and ground improvement method

Abstract

By imparting infiltration injection to the conventional high-pressure jet mixing method, it becomes possible to form a large-diameter solidified body using suspension grout. In addition, it is possible to add an injection material to the cut soil and reinject it, enabling ground improvement that takes into account the global environment with reduced CO2, and providing a ground improvement method and an injection device that are lighter than conventional ones and can form large solidified bodies. 【Solution means】An injection device used in the high-pressure jet mixing method, comprising a guide pipe inserted into the ground, an injection inner pipe disposed inside the guide pipe and used for injecting an injection material, and an opening / closing mechanism for opening or closing the space between the guide pipe and the injection inner pipe.

Description

Technical Field

[0001] The present invention relates to a ground improvement method by an injection and penetration composite injection method in which, in cutting and solidifying the ground using the kinetic energy of the injection fluid, a suspension-type injection material or a mixture of the suspension-type injection material and the soil in the cutting area is filled into the cutting area, and the injection material is infiltrated and solidified into the surrounding ground from the cutting area to form a large consolidated body. In particular, the present invention relates to a composite injection comprising an injection of a suspension as a main component and an injection and penetration injection. Specifically, it relates to a composite injection method and an injection device comprising an injection injection and a penetration injection in which an injection fluid is used, and after filling the injection material into the cutting area using kinetic energy, the injection material is infiltrated into the surrounding ground by penetration injection to improve the ground. The injection material relates to a composite injection method comprising an injection injection and a penetration injection using a suspension of fired silica such as cement or slag, hydraulic alumina, or a mixture thereof. Further, a separation silica solution separated while a suspension containing a silica solution is used and the suspension-type injection material penetrates between soil particles is gelled, so that it is possible to simultaneously form a high-strength region by suspension particles and a penetration consolidation region by the separation silica solution. The present invention relates to an injection and penetration composite injection method. Furthermore, it enables volume reduction of industrial waste by reusing the cut soil by high-pressure jetting and injecting it into the ground. Moreover, a suspension-type injection material mainly composed of artificial fired silica such as silica powder, slag, fly ash, incinerated sewage ash, and plant incinerated ash, such as on-site soil, waste mud, and concrete crushed material, as well as soil containing soluble silica such as loess, sand-lime soil, pumice layer, shirasu, and volcanic sedimentary soil, having a natural pozzolanic action, such as silica particles, are used, and together with these, a curing agent, solution silica, and an alkaline agent are used, so that it is a low-carbon ground improvement method that reduces CO2 with a non-cement-based injection material or an injection material with reduced cement, can form a wide range of consolidated bodies near neutrality, and furthermore, enables strength development immediately after injection, ensures safety for surrounding structures, and reduces the weight of the consolidated body to solve the problems of the high-pressure jet mixing method using a conventional cement-based injection material.

Background Art

[0002] Conventionally, various ground improvement methods have been known as ground improvement methods for soft ground or ground with a risk of liquefaction. Among them, the chemical injection method, which injects an injection material (chemical solution) into the gaps between soil particles of the ground to penetrate and solidify the ground, has been adopted in many construction works because of its simplicity.

[0003] The chemical injection method is a method in which the injected chemical solution penetrates into the gaps between soil particles and solidifies, and this acts as an adhesive to exert effects such as strengthening the ground and stopping water (improving water permeability). Since it can be easily implemented with compact equipment, it is mainly used in temporary construction works in a short period (auxiliary method in underground construction) and liquefaction countermeasure works such as rapid penetration injection method using permanent grout.

[0004] In addition, the high-pressure jet mixing method, which injects cement by high-pressure jetting and stirs and mixes the cut soil and cement while cutting and stirring the ground, and the mechanical stirring method, which injects a slurry-like injection material into the soft soil layer deposited to the deep layer and stirs and mixes the in-situ soil and the injection material with a stirring blade to form a cylindrical improved body in the ground to create a strong and stable improved ground, are also known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, today, in order to suppress global warming caused by CO2, de-cementation is strongly desired even in ground improvement methods. The applicant has hitherto made the inventions described in Patent Documents 1 to 3 regarding the high-pressure jet grouting method using slag, but the present invention is a ground improvement method that further develops it.

[0007] That is, in the conventional high-pressure jet mixing method, cement is used as the main component of the injection material. However, although cement has a large specific gravity of 3.17, its specific surface area is as small as about 3,220 cm 2 / g. Therefore, for strengthening soft ground targeted by the high-pressure jet mixing method, since cement particles are heavy, the reach distance is short, and it is difficult to form a large solidified body.

[0008] In addition, since soil is excavated and replaced with cement to form a solidified body, the treatment of the dredged mud has become a major environmental problem today. Furthermore, in the improvement of soft ground, there has been a problem that since the soft ground has low bearing capacity, the improved body of the cement solidified body is likely to subside, and the displacement of the structure is also likely to increase.

[0009] As described above, although the high-pressure jet mixing method has the advantage of high strength of the solidified body, in addition to causing the problem of industrial waste soil, the bearing capacity until solidification is low, and after solidification, the weight is large and the rigidity is high. Therefore, there has been a problem that integration with the existing ground cannot be achieved in soft ground and it is likely to subside. In addition, there has also been a problem that since the cement injection material is mixed with high-pressure jet water in the cut ground, it is easily discharged to the ground surface together with the cut soil and sand.

[0010] On the other hand, in liquefaction countermeasure works, since economy is prioritized over strength, the uniaxial compressive strength of the soil by the chemical solution only needs to be about 100 to 200 kN / m 2 and does not require a large strength such as several to several tens of MN / m 2 when replacing the conventional soil and solidifying with cement itself.

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

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

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

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

[0015] In the conventional construction methods, the structures of the pipes used are mainly single pipes, double pipes (Fig. 2), and triple pipes (Fig. 3). Among them, the single pipe can only inject solidifying materials, Fig. 2 can inject solidifying materials + air, and Fig. 3 can inject solidifying materials + air + cutting water. These construction methods involve sludge discharge, so in order to improve economic efficiency and reduce the environmental load, reduction and effective utilization of sludge are required. In the prior art, in order to increase the size of the improved diameter, double or triple pipe rods are used, and solidifying materials and air, or cutting water, air, and solidifying materials are injected at high pressure from injection nozzles provided on the rods. This air is used mainly for the first purpose of forming a gas-liquid interface around the injection fluid (solidifying material or cutting water) to suppress the attenuation associated with the distance of the jet flow and create an improved body with a large diameter. Moreover, since sufficient hydration reaction etc. has not occurred in the improved body immediately after construction, it is in an uncured state. Therefore, when construction is carried out near a structure, the function of the structure may be inhibited due to a decrease in the supporting force. Furthermore, in the conventional high-pressure jet grouting method that relies on the energy of the high-pressure jet fluid, the size of the improved body is restricted because the cutting area is limited by the distance of the jet fluid.

[0016] In any of the above methods, the cut soil and sand are discharged to the ground from the outer periphery of the injection pipe with the injection material mixed. At this time, the disposal of the cut soil and sand mixed with cement has become a major environmental problem.

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

[0018] However, as described above, the conventional ground improvement methods have problems in terms of the formation diameter and environmental issues, and further improvement is desired. Therefore, an object of the present invention is, in the conventional high-pressure jet grouting method, not only to fill the cutting area with the injection material, but also to further infiltrate the injection material outside the cutting area to form a large consolidated body. Further, by aiming for decarbonation, it is possible to perform ground improvement in consideration of the global environment with reduced CO2, and to provide a ground improvement method and an injection device that are lighter than conventional ones and can form a large consolidated body.

Means for Solving the Problems

[0019] Here, generally, bleeding liquid refers to the supernatant solution in which suspended particles settle when the suspension is left stationary. However, in actual ground injection, the liquid corresponding to the bleeding liquid refers to the solution in which the suspended particles are filled between the soil particles and separated while infiltrating into the ground. Therefore, since the separated liquid of the suspension containing the silica solution contains fine suspended particles and the silica solution, it is referred to as "separated silica solution" in the present invention. In the present invention, "bleeding liquid" and "separated silica solution" substantially mean the same thing.

[0020] The applicant of the present application applied the phenomenon described in Patent Document 4 to the high-pressure jet grouting method and advanced the research on the ground improvement method by jetting and infiltration composite injection. As a result of continuous research on the gelation of the bleeding liquid, the applicant of the present application found that in the suspension containing solution-type silica, gelation occurs regardless of whether the bleeding rate is 50% or less or 50% or more (Figure 4). It was also found that by adding a hardening agent, the gelation time and strength of the bleeding liquid can be adjusted. And the relationship of the silica concentration sufficient for the homogel (the one in which the injection material alone is solidified) and the sand gel (the one in which the injection material and soil are mixed and solidified) related to the gelation of the bleeding liquid was also found (Table 9, Figures 6, 8 to 10, 12, 13). As a result, the inventors have arrived at an invention of a ground improvement method based on a new concept of injection and penetration composite injection shown in Fig. 15. Figs. 15(a) to (e) show the form of osmotic consolidation of the ground improvement method of the present invention. Fig. 15 shows that the injection material is injected into the injection material cutting area by injection, and the injection material alone or a mixture of the injection material and the soil in the cutting area is filled, and the injection material penetrates into a wider area than the cutting area and the suspended particles penetrate between the soil particles. Further, the separated silica solution separated from the suspension solidifies by osmosis, indicating that an integrated osmotic consolidation region is formed. Therefore, from a plurality of injection holes, a high-strength injection material alone filled in the cutting area by high-pressure jet injection or a modified body solidified in a stirred state with the ground and the separated silica solution separated from the suspension in the peripheral part penetrate and solidify in the ground, enabling ground improvement that integrates the entire ground. In addition, the present invention substantially expands the application range (from the perspective of soil quality) of suspension grout to the range of solution grout, and develops from a simple high-pressure jet mixing method to a ground improvement method consisting of a new technical concept of high-pressure jet penetration injection method (Figs. 11 and 14).

[0021] Specifically, the present invention solves the above-mentioned problems of the conventional high-pressure jet mixing method mainly composed of cement by using suspended particles composed of artificial calcined silica such as slag and fly ash or silica particles (natural pozzolan) obtained by a natural calcination process as the injection material, and by mixing the cutting mud mixed with the injection material discharged to the ground surface with the injection material and reinjecting it into the ground.

[0022] In this way, the applicant of the present invention has invented a ground improvement method by an injection and penetration composite injection method that enables the formation of a large consolidated body by penetration consolidation from the cutting area to the peripheral part in addition to the consolidation of the cutting area by high-pressure injection (Fig. 15). Further, in the present invention, as the above injection material, by using natural or artificially manufactured silica particles, fired silica, silica particles having a natural pozzolanic action, and fluidized soil obtained by slurrying on-site generated soil as the main material, the weight of the consolidated body is reduced, the penetration consolidation range is expanded, and a ground improvement method that can contribute to the global environment by reducing CO2 is realized. Furthermore, it is a ground improvement method capable of reducing the volume of industrial waste by using fluidized soil obtained by slurrying sludge (on-site generated soil) accompanying cutting as an injection material.

[0023] Furthermore, the present invention relates to a ground improvement method for improving soft ground and liquefiable ground to be high-strength and lightweight as described above. The ground is cut using the kinetic energy of high-pressure jet fluid, and the cutting area is filled with an injection material such as the above-mentioned suspended particles or slag-based material, or a mixture of the injection material and the soil in the cutting area. In addition, the injection material is infiltrated from the cutting area to its peripheral part to form a large consolidated body. According to the present invention, low-carbon ground improvement becomes possible by reusing the mixed soil and sand obtained by mixing the cutting soil discharged to the ground surface by high-pressure injection and the injection material and reinjecting it into the ground. Furthermore, by using a suspension-type injection material mainly composed of fired silica such as slag or fly ash and silica particles having a natural pozzolanic action, reduction of CO2 from the material aspect by using a non-cement-based injection material or an injection material with reduced cement content is realized, and ground improvement friendly to the global environment is provided. Furthermore, in the present invention, since the above suspension-type injection material contains solution-type silica, the separated silica solution separated from the suspension liquid is infiltrated and gelled, and the penetration consolidation range can be expanded beyond the cutting area, enabling ground improvement that can simultaneously obtain the advantages of both the formation of a consolidated body by the high-pressure jet injection method and the penetration consolidation by the chemical solution injection method.

[0024] That is, the ground improvement method of the present invention is a ground improvement method in which the ground is cut by an injection fluid from an injection pipe inserted into the ground to form a cutting area, and an injection material is injected into the formed cutting area. As the injection material, a material mainly composed of suspended particles is used, and the injection material is filled into the cutting area and infiltrated between the soil particles of the surrounding ground from the cutting area, thereby consolidating the cutting area and the surrounding ground.

[0025] Further, another ground improvement method of the present invention is a ground improvement method in which the ground is cut by an injection fluid from an injection pipe inserted into the ground to form a cutting area, and an injection material is injected into the formed cutting area. As the injection material, a material mainly composed of suspended particles and containing any one or a plurality of a curing agent, an alkaline agent, and solution-type silica is used, and the injection material is filled into the cutting area and infiltrated between the soil particles of the surrounding ground from the cutting area, thereby consolidating the cutting area and the surrounding ground.

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

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

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

[0029] In the present invention, it is preferable that the natural silica having a pozzolanic action is any one or a plurality of loam soil, shirasu, volcanic ash, niwato soil, and sanwato soil.

[0030] In the present invention, it is preferable that the curing agent, the alkaline agent, and the solution-type silica are composed of any one or a plurality of the following. (1) Those containing any one or more of gypsum and MgO as active ingredients. (2) Those containing any one or more of Ca salts, Mg salts, Al salts, carbonates and bicarbonates as active ingredients. (3) Those containing any one or more of lime, cement, caustic alkali, water glass and silica colloid as active ingredients.

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

[0032] In the present invention, the particle size of the suspended particles is in the range of 4000 to 20000 cm 2 / g, and the blending amount of the suspended particles in the injection material is preferably 40 to 200 kg / 400 L.

[0033] In the present invention, the injection material contains slag as the suspended particles, and the blending amount of the 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 preferably 5 to 50% with respect to the weight of the suspended particles.

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

[0035] In the present invention, when injecting the injection material into the ground from a plurality of injection holes provided in the ground using a suspension composed of the suspended particles as the main material and the solution-type silica as the active ingredient, the bleeding liquid of the injection material gels, and the homogel has self-supporting strength, the sand gel formed by the penetration and consolidation of the bleeding liquid has self-supporting strength, and the bleeding liquid penetrates into the portion of the ground where the suspension could not penetrate to expand the consolidation range, or preferably integrates with the portion of the ground where the suspension has penetrated to form a solid.

[0036] Here, in the above, the fact that the bleeding liquid gels and the resulting homogeneous gel stands on its own means that the silica concentration of the bleeding liquid is 0.5 w / v% or more, and in the mold, even when the homogeneous gel is tilted diagonally, the gel does not collapse and stands on its own. The fact that the sand gel stands on its own means that the silica concentration of the bleeding liquid is 0.5 w / v% or more. When No. 6 silica sand is used, the sand gel prepared by the mixing method with a diameter of 5 cm × height of 10 cm so as to have a relative density of 60% using the bleeding liquid stands on its own, and the strength in the uniaxial compression test measured using the sand gel is 2.0 kN / m 2 This means that it is as described above.

[0037] In the present invention, it is preferable to set the injection material with a formulation for lightweight, low-alkali, and low-carbon ground improvement.

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

[0039] In the present invention, it is preferable that the curing agent is a polyvalent metal compound, any one or a plurality of hydroxides, oxides, or salts of Ca, Mg, or Al, and / or gypsum.

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

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

[0042] The injection device of the present invention is an injection device used in the high-pressure jet mixing method, and is characterized by including a guide pipe inserted into the ground, an injection inner pipe disposed 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 injection inner pipe.

[0043] In the injection device of the present invention, the opening and closing mechanism is disposed between the guide tube and the injection inner tube, and includes an annular rubber bag having a fluid-permeable pipeline, a ball bearing provided on the inner surface of the rubber bag on the injection inner tube side, and seal members provided at the upper and lower ends of the rubber bag. The opening or closing of the space by the opening and closing mechanism can be performed depending on the presence or absence of pressurization inside the rubber bag due to the inflow and outflow of fluid into the rubber bag.

[0044] In the injection device of the present invention, the opening and closing mechanism is disposed between the guide tube and the injection inner tube, and includes an annular rubber bag having a fluid-permeable pipeline, a fixing member for fixing the rubber bag to the guide tube, and a ring-shaped fitting for closing the upper and lower ends of the rubber bag. The opening or closing of the space by the opening and closing mechanism can be performed depending on the presence or absence of pressurization inside the rubber bag due to the inflow and outflow of fluid into the rubber bag.

[0045] Furthermore, still another ground improvement method of the present invention is a ground improvement method by a high-pressure jet mixing method using the above injection device, including a step of drilling a hole to a target depth of the ground with the guide tube and inserting the injection inner tube into the guide tube; a step of opening the space by the opening and closing mechanism and jetting the injection material from the injection inner tube at a high pressure together with high-pressure jet water or air, cutting and stirring the ground while jetting, and mixing the cut soil generated by cutting with the injection material at the ground surface to produce a mixed injection material; and a step of jetting the mixed injection material from the injection inner tube into the ground at a high pressure together with high-pressure jet water or air.

[0046] Furthermore, still another ground improvement method of the present invention is a ground improvement method by a high-pressure jet mixing method using the above injection device, including a step of drilling a hole to a target depth of the ground with the guide pipe and inserting the injection inner pipe into the guide pipe; a step of opening the space by the opening / closing mechanism and jetting the injection material from the injection inner pipe at high pressure together with high-pressure jet water or air, cutting the ground while jet mixing, and filling the injection material into the region generated by the cutting; and a step of closing the space by the opening / closing mechanism and pressurizing and permeating the injection material into the ground.

[0047] In the ground improvement method of the present invention, different injection materials can be used for jet mixing and pressure permeation, and the injection material used for pressure permeation can be made more permeable than the injection material used for jet mixing. Further, by opening and closing the space by the opening / closing mechanism, the injection material used for jet mixing and the injection material used for pressure permeation can be switched.

Advantages of the Invention

[0048] According to the present invention, it is possible to perform ground improvement in consideration of the global environment with reduced CO2 by demetallizing or reducing the cement content in the conventional high-pressure jet method, and to provide a ground improvement method and an injection device that are lighter than conventional ones and can form a large consolidated body.

Brief Description of the Drawings

[0049]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15(a)

Figure 15(b)

Figure 15(c)

Figure 15(d)

Figure 15(e)

Figure 15(f)

Figure 16(a)

Figure 16(b)

Figure 16(c)

Figure 16(d)

Figure 17(a)

Figure 17(b)

Figure 17(c)

Embodiments for Carrying Out the Invention

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

[0051] In the present invention, as the injection material, one using suspended particles as the main material, or one using suspended particles as the main material and further containing any one or a plurality of a curing agent, an alkaline agent, and solution-type silica is used. By filling this injection material into the cutting area and infiltrating it between the soil particles of the surrounding ground from the cutting area, the cutting area and the surrounding ground are consolidated.

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

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

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

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

[0056] Tables 1 to 8 mean that even if it is not cut soil, it can be mixed with on-site soil as an injection material and injected. Also, it shows the strength of the jet-mixed soil of the injection material and the soil in the cutting area in the cutting area. In the present invention, as will be described later, by selecting a lightweight suspension liquid mainly composed of suspension particles with good fluidity and small particle size according to the ground conditions, it can penetrate and solidify the surrounding ground of the cutting area (Figs. 7 to 9, Fig. 11, Fig. 14). If the suspension liquid contains solution-type silica, the separated silica solution separated from the suspension liquid gels and solidifies. Therefore, even in a ground where the suspension liquid alone cannot penetrate, the consolidation range extends to the surrounding soil of the cutting area, and moreover, a water stop effect and continuous solidification of the solidified bodies are possible (Figs. 4, 6, 8 to 13). Fig. 11 shows a particle size distribution curve in which a penetration consolidation effect is obtained with a solution-type grout. Since the suspension-type injection material using the above suspension particles containing solution-type silica can penetrate and consolidate up to the ground with the particle size distribution shown in Fig. 11, a ground improvement method based on a new concept called "jetting and penetration composite injection method" that simultaneously has the advantages of the high-pressure jet injection method and the chemical solution injection method becomes possible. Also, the silica solution gels immediately after injection. If strength increase is obtained or a plastic gel is injected, it does not cause deformation or settlement of the structure to the ground near the structure like the high-pressure jet mixing method, and the injection device can also be a lightweight device, with less noise and vibration, which is good for the environment, and can solve the problems of the conventional high-pressure jet mixing method (Fig. 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 suspension particles, or mainly composed of suspension particles and further contains any one or more of a curing agent, an alkaline agent, and solution-type silica. As a suspension liquid mainly composed of suspension particles, calcined silica such as slag or fly ash is used as an aqueous suspension, and a curing agent such as water glass and / or an alkaline agent is mixed and adjusted for use. As the suspension particles, any one or more of calcined silica, natural silica having a pozzolanic action, and curable silica particles can be used as active ingredients.

[0058] Among these, as the calcined silica, in addition to slag and fly ash, cement, paper sludge, sludge incineration ash, sewage incineration ash, plant incineration ash, calcined clay, etc., and incineration ash of plants containing a large amount of silica can be mentioned, and any one or a plurality of these can be used. Further, as the natural silica having a pozzolanic action, natural calcined soil such as loam soil (Kanto loam), shirasu, volcanic ash, niwa soil, and sanwa soil can be mentioned, and any one or a plurality of these can be used. These calcined silicas are silica particles having latent hydraulicity, contain soluble silica, and form a crystal structure similar to a part of cement by the pozzolan reaction by the action of alkalis such as slaked lime, gypsum, magnesium hydroxide, water glass, silica colloid, caustic alkali, carbonate, bicarbonate, aluminum salt, calcium salt, magnesium salt, etc., and solidify firmly. Further, by using aggregates such as clay and / or earth and sand as thickeners or extenders, it becomes possible to economically improve the ground. Furthermore, the in-situ soil can also be used in a slurried state together with the above hardener.

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

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

[0061] As the hardening agent, alkaline agent and solution-type silica used in the injection material of the present invention, any one or more of the following (1) to (3) can be used. (1) Those containing any one or more of gypsum and MgO as active ingredients. (2) Those containing any one or more of Ca salts, Mg salts, Al salts, carbonates and bicarbonates as active ingredients. (3) Those containing any one or more of lime, cement, caustic alkali, water glass and silica colloid as active ingredients.

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

[0063] In the present invention, as the above slag, finely pulverized blast furnace slag is used. In order to enhance the reactivity, it is preferable that the particle size is finer. For example, the specific surface area (Blaine value) is 4000 cm 2 / g or more, preferably 6000 cm 2 / g to 20000 cm 2 / g, and those with an average particle size of 10 μm or less are suitable.

[0064] In the present invention, as the water glass, those having a high alkali concentration are preferred in terms of reactivity with slag. In particular, those having a molar ratio of SiO2 / Na2O of 2.5 or less are preferred. When the molar ratio is low, a high-strength solidified body and a long gelation time can be obtained. Further, as the water glass, a mixture of sodium orthosilicate anhydride and sodium hydroxide, crystalline sodium silicate containing sodium metasilicate, a mixture containing partially crystalline sodium silicate, sodium silicate glass (cullet), hydrated glass, dehydrated sodium silicate, semi-solid sodium silicate, viscous sodium silicate, a dilute solution of commercially available sodium silicate, etc. can be used, and they may be used by changing the viscosity, molar ratio, and silica concentration, or they may be used as powders. The alkali content of the water glass exhibits an action of stimulating the latent hydraulicity of the slag. Further, the water glass having a low molar ratio may be a mixture of water glass and caustic alkali. However, when a Ca melt such as slaked lime or cement is used in combination, a water glass having a high molar ratio of SiO2 / Na2O such as water glass No. 3 and No. 4 can be used.

[0065] As the salts used in the present invention, aluminum compounds such as aluminum sulfate and polyaluminum chloride, chlorides and sulfates of Ca and Mg, and those obtained by reacting these with caustic alkali may be used. Further, the molar ratio of Na2O / Al2O3 is not particularly limited, but from the reactivity with slag, it is preferable that the Na2O concentration in the injection material is 1 wt% or more. Caustic alkali is effective for stimulating the hydraulicity of slag, and the aluminum content reacts with the silica content of water glass or slag to form aluminum silicate or calcium aluminosilicate. Further, the gel time and strength of the present suspension or the separated silica solution separated from the suspension can be adjusted by the addition amount of these additives. Furthermore, seawater can also be used as the blending liquid of the suspension.

[0066] The blending amounts of water glass and aluminum compound in the injection material are such that the hardening time of the injection material is several hours, usually within 1 hour, preferably within 30 minutes, and vary depending on the molar ratio of Na2O, Al2O3, and SiO2. However, the amount of Na2O in the injection material is preferably 1 wt% or more. However, when consolidating a wide range, a blending amount that allows the hardening time to be several hours is required.

[0067] In the present invention, the mixing amount of the injection material with respect to the cut soil varies greatly depending on the properties of the cut soil to be treated. However, for every 1 m 3 of the cut soil, it is preferably in the range of 0.1 to 0.5 m 3 .

[0068] Further, the injection material of the present invention can be improved in fluidity and reduced in weight by adding a foaming agent or a foaming agent, and can be made into a salt-free type high-performance water reducing agent, a dispersant, clay, bentonite, a polymer thickener, that is, polyvinyl alcohol, carboxymethyl cellulose (CMC), methyl cellulose, etc. By adding these, the dispersibility in water can be suppressed, sedimentation can be reduced, the workability can be improved, or as a water retention material, and also as a binder for suspended particles such as slag as the main material, it can function to form a pseudo-gel state and form a fluid having a structure that is difficult to disperse while maintaining fluidity. 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 suspension such as slag or fly ash or the suspension such as cement and injected into the cutting area. Thereby, due to the bearing action of microbubbles or microbubbles and air covering the suspended particles, it becomes possible to construct a wide solidified body by the suspended particles, and it becomes possible to reduce the weight and strength of the solidified body due to an increase in the gas volume in the solidified body. In the injection material of the present invention, any one or a plurality of microbubbles, air, a dispersant, and a thickener can be used as active ingredients.

[0070] In addition, it has been found that air bubbles present in the solidified body can improve the anti-liquefaction effect even when the amount of suspended particles in the solidified body is small and the strength is low.

[0071] In addition, the use of cut soil in the present invention is effective as a low-carbon technology. That is, conventionally, cut surplus soil has had to be disposed of as industrial waste as it is, or transported from the site to a treatment plant and mixed with lime for treatment, etc., which is uneconomical and time-consuming. However, the problems of such conventional methods are solved by applying the present invention. According to the present invention, it is possible to backfill the surplus soil on-site, or to mix the cut surplus soil and the injection material and then fill the mixture into the cutting area, enabling economical and rapid construction.

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

[0073] In the present invention, the injection material may be directly mixed into a single liquid and fed to the injection rod, or the above-mentioned suspension (liquid A) and water glass and / or alkali agent (liquid B) may be transferred by a pump, mixed, and then injected. In this case, it is preferable that these liquid A and liquid B are mixed at a ratio of approximately 1:1 (by volume), but usually, they are mixed at an arbitrary ratio within the range of 10:1 to 1:10.

[0074] In addition, the curing time of the recycled injection material when the above injection material is re-injected into the cutting area may be any time as long as sufficient mixing with the cut soil can be achieved. Therefore, it is determined by the mixing method or mixing device. For example, about 10 minutes to 30 minutes is appropriate. Also, considering workability, it can be determined to be several hours to a dozen or so hours.

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

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

[0077] From the following, injection materials mainly composed of calcined silica or natural silica having pozzolanic action and not using cement, or injection materials with reduced cement usage, have a smaller specific gravity than injection materials mainly composed of cement. Therefore, it can be seen that a weight reduction effect of the solidified body can be obtained because the material hardly changes in specific gravity from the original ground or further lightens the ground with a lighter material.

[0078] [Materials Used] Slag: Specific gravity 2.9, Blaine value 8000 cm 2 / g, a silica-based non-curable powder. Fly ash (FA): Coal ash discharged from a thermal power plant: A silica-based non-curable powder. Specific gravity 1.9 - 2.3 g / cm 3 , with 90% or more having a particle size distribution of 0.1 mm or less. Cement: Ordinary Portland cement: PC, specific gravity 3.15, a hardening material. Sulfate band: Aluminum sulfate, Al2O3 = 17.2%, a gelling agent, specific gravity 1.32. Slaked lime: Industrial calcium hydroxide, a gelling accelerator and a hardening material. Gypsum or hemihydrate gypsum: A hardening appearance material, specific gravity 2.6. Bentonite: A water retention material and a 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, 75 w / w%. No. 5 water glass: Specific gravity 1.32, silica concentration 25.5%, Na2O 7.03, molar ratio 3.75. No. 1 water glass: Specific gravity 1.35, silica concentration 21.59%, Na2O 10.80%, molar ratio 2.06. No. 3 water glass: specific gravity 1.41, silica concentration 29.16%, Na2O 9.36, molar ratio 3.22. Polyaluminum chloride or foam materials can also be used.

[0079] [Test methods and test results] For the uniaxial compression strength tests in Tables 1 to 7, cylindrical specimens with a height of 100 mm and a diameter of 50 mm were used and complied with the Japanese Industrial Standard (JIS A 1216:2020 Method for Uniaxial Compression Test of Soils). The results of measuring the strength on the 1st day, 7th day, and 28th day, or the strength on the 28th day, are shown respectively. Also, in Tables 1 to 8, the gel time is the time until the suspension thickens while continuing to stir with a stir bar.

[0080] From this example, in the present invention, not only can a solidified body formed by mixing the cut soil and the present injection material in the ground be formed by mixing the cut soil and the present injection material and injecting it into the cutting area to form a sufficient solidified ground, but it can also be seen that the ground can be economically improved by injecting the injection material obtained by mixing the obtained earth and sand or clay, instead of the cut soil, with the present injection material.

[0081] [Table 1]

[0082] [Table 2]

[0083] [Table 3]

[0084] [Table 4]

[0085] [Table 5]

[0086]

Table 6

[0087]

Table 7

[0088]

Table 8

[0089] The following describes test examples (Figs. 4 to 13) showing the effect of gelation of the bleeding liquid in the above suspension containing the silica solution or the separated silica solution separated from the suspension. Fig. 10 shows the state where Fig. 4 using Example 36 of Table 4 is tilted. Figs. 12 and 13 show the state of the strength test of the specimen of sand solidified with the bleeding liquid of Table 8.

[0090] (Permeability test) (Test apparatus and test method) Using a one-dimensional permeation device (length 2 m), a permeation test was conducted on No. 6 silica sand to examine the permeation length and strength distribution.

[0091] Test conditions: Acrylic mold h = 2 m, compound solution 3 L. After saturating the sample with water, the suspension was injected from the bottom until the drainage liquid stopped draining.

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

[0093] It was carried out with the formulations of Example 36 and Comparative Example 1 (Figs. 6 to 9, 12, 13).

[0094] The solid lines in Figs. 8 and 9 show the results obtained with the formulation of Example 36. Strength measurement was possible even at a penetration distance of 120 cm. Although there was no discoloration of the sand gel after 90 cm, it is considered that strength measurement was possible because the separated silica solution separated from the suspension solidified after 90 cm. It is considered that the portion after 90 cm contains 0.5% or more of silica.

[0095] The dotted lines in Figs. 8 and 9 show the results obtained with the formulation of Comparative Example 1. Strength measurement was possible up to 90 cm, but there was no discoloration after 90 cm and strength measurement was not possible. It was found that the separated silica solution separated from the suspension did not gel.

[0096] In the penetration test of Fig. 7, the portion where there was no discoloration reaction of the sand is considered to be the portion where the slag did not penetrate. Since the bleeding liquid did not have self-supporting properties, the portion where the solution separated from the suspension penetrated also did not have self-supporting properties and did not solidify. On the other hand, in Fig. 6, since the bleeding liquid gelled and had self-supporting properties, although the suspension particles did not penetrate and the sand gel did not discolor, the separated silica solution separated from the suspension penetrated and solidified, thereby exhibiting self-supporting strength.

[0097] From the above, depending on the particle size and density of the soil and the particle size distribution of the suspended particles, under conditions where they cannot penetrate between the soil particles, only the separated silica solution separated from the suspension will penetrate (Figs. 11 and 14).

[0098] From Figs. 8 and 9, even when the penetration distance of the suspended particles in the suspension is 90 cm, the separated silica solution separated from the suspension penetrates up to 120 cm, and the solution has self-supporting strength and the sand gel has self-supporting strength. 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 increased, the homogeneous gel of the silica solution will connect the consolidated bodies in which the suspended particles that can obtain high strength penetrate.

[0099] In this way, even in ground conditions where suspended particles cannot penetrate, a consolidated body can be formed integrally. Also, even when the injection hole interval is widened, the consolidated bodies between them can be connected by a gelled product of a silica solution that can stand on its own, forming an integrated consolidated ground.

[0100] Although suspension grout can achieve higher strength compared to solution grout, due to its large particle size, its permeability to fine-grained soil is poor. However, by containing solution-type silica, a consolidation effect can be obtained even in ground where suspended particles cannot penetrate, enabling the realization of integrated ground improvement and water stoppage (Fig. 15).

[0101] As described above, the inventors of the present invention focused on the gelation of the bleeding liquid of suspension grout, studied the gelation of the bleeding liquid, the self-supporting property of the homogeneous gel of the bleeding liquid, the self-supporting property and strength of the sand gel of the bleeding liquid, and by making this a condition, improved the permeation consolidation property of suspension grout for fine-grained soil and ground containing fine-grained soil, which was conventionally considered inapplicable, and completed the present invention. Further, according to the present invention, an improvement effect capable of self-supporting and water stoppage of the excavation surface can also be obtained even in the 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 water stoppage of the excavated ground.

[0102] In particular, when the present invention applies suspension grout containing a silica solution, the following effects due to the gelation of the separated silica solution separated from the suspension grout are exhibited. By exhibiting such effects that cannot be obtained by the conventional high-pressure jet mixing method, the present invention has realized a ground improvement method consisting of a new concept of jetting and permeation injection that can simultaneously obtain the advantages of the high-pressure jet mixing method and the permeation injection method. (1) Permeation consolidation of fine-grained soil ground where permeation consolidation of suspended particles was impossible. (2) Self-supporting effect and water stoppage of the cutting surface. (3) Expansion of the improvement range by permeation consolidation. (4) Ground improvement in which adjacent consolidated bodies are connected and integrated. (5) Reduction of construction cost by expanding the boring interval of the injection pipe. (6) Improvement in construction safety by enhancing the resistance against earth pressure from adjacent structures and earth pressure from the back of soil retaining walls due to the manifestation of the short-term consolidation effect of the separated silica solution separated from the suspension grout, safety for underground buried structures by permeation injection, strengthening of the surrounding ground of underground structures with space, water stoppage, and repair of deterioration.

[0103] Examples are shown below. (Strength test) (Preparation of sand gel specimens) Using No. 6 silica sand (Figure 14), specimens with a diameter of 5 cm and a height of 10 cm were prepared by the mixing method to a relative density of 60% using a bleeding solution, and the uniaxial compressive strength on the 28th day was measured. The bleeding rate increases with a larger amount of water glass and decreases with a smaller amount of slag. In the sand gel using the bleeding solution, a higher strength development ratio is obtained with a larger amount of water glass and slag. Also, when gypsum was used in combination, the bleeding rate decreased and the strength increased when gypsum was added.

[0104] The gelation of the bleeding liquid, its self - standing property, and the strength and self - standing property of the sand (sand gel) consolidated by the bleeding liquid vary depending on the blending amount of slag and water glass in the suspension, the ratio of calcium oxide (CaO) in the water glass to silica (SiO2) in the slag (CaO / SiO2), the gel time, the particle size and density of the sand solidified by the bleeding liquid. Therefore, as conditions that comprehensively affect these several factors, tests were conducted to confirm the gelation, self - standing property, and the minimum value of the strength of the bleeding liquid (Table 9). The gel time in Table 8 is the stirring gel time, which cannot be obtained for the bleeding liquid, so the standing gel time was used here. The standing gel time was measured as follows. First, when 100 mL of the bleeding liquid is put into a standard bag No. 8 (thickness 0.03 × width 130 × height 250 mm), it is divided into a lower part with many suspended particles and an upper part with few suspended particles (bleeding liquid). Among them, the time when the upper part of the lower suspended part no longer tilts by 2 / 3 of the solid content when slowly tilted horizontally was defined as the standing gel time. The standing gel time was shorter than the stirring gel time, and most of them were about half of the stirring gel time. When preparing the sand gel in Table 8, the mixture of 2L or 3L was put into a 3L poly bucket, and the sand gel was prepared using the liquid taken out of the bleeding liquid at half of the standing gel time.

[0105] As a result, on the condition that the gelation and self - standing of the bleeding liquid and the self - standing of the sand gel penetrated by the bleeding liquid are satisfied, ground improvement by suspension - solution composite injection became possible, in which the fine - grained soil part where penetration consolidation of suspended particles was difficult or the part that did not reach penetration was consolidated by the separated silica solution separated from the suspension and the whole was integrated.

[0106] It was found that whether the bleeding rate is 50% or more or 50% or less, the property that the separated silica solution separated from the suspension during injection penetrates and consolidates can be obtained due to gelation. The minimum strength for the sand gel to be self - standing was 2.0 kN / m 2 It was. The strength of the self - standing sand gel with a blend of only 75 g of slag and 100 mL of No. 1 water glass per 400 mL was 15 kN / m on the 28th day2 It was found that it is. Also, the strengths on the 1st day and the 7th day were measured. The strength on the 1st day was 2.0 kN / m 2 of strength was obtained. On the 7th day, it was 10 kN / m 2 (Figs. 12 and 13). Also, a similar tendency was obtained with Toyoura sand. Also, if salts such as Ca, Mg, and Al are contained in the bleeding liquid, it can be considered that the strength of the sand gel further increases.

[0107] In the present invention, the specimen is adjusted according to the specimen size of the uniaxial compression test of soil. The diameter D0 (mm) is usually 35 mm or 50 mm, and the height H0 (mm) is 1.8 times to 2.5 times the diameter D0 (mm). Any age can be judged as long as it is a self-standing sand gel. Fig. 12 shows the test situation. From this, it was found that even with on-site sand, if the strength of 2.0 kN / m 2 is obtained at an injection rate of 40%, it can stand on its own. Also, the injection rate is the ratio of the injection liquid to the volume of the ground to be improved. When the injection rate for 1 m 3 of the improved ground is 40%, the injection amount is 0.4 m 3 .

[0108] When the addition amount of slaked lime increased, the gel time was shortened. Also, when the amount of slag was large, the strength increased. In Comparative Example 1, the portion containing suspended particles solidified, but the portion of the bleeding liquid did not gel. The bleeding liquid of Example 36 gelled. It was also found that the bleeding liquid gels even when either or both of silica colloid and water glass are used in combination.

[0109] (Relationship between silica concentration and strength) A chemical solution in the neutral to alkaline region was put into an acrylic mold whose bottom surface comes off and solidified, and the presence or absence of gelation according to the silica concentration of the homogeneous gel and the self-standing property of the gel were confirmed. Also, the same was done with the sand gel, and the self-standing property of the solidified and consolidated sand was confirmed. The results are shown in Table 9.

[0110] When the silica concentration was less than 0.5%, the self-standing properties of the homogeneous gel and the sand gel were not obtained. Furthermore, additional tests were carried out, and it was found that gelation also occurred at a silica concentration of 0.25%, but the self - standing property of the gel, the consolidation and self - standing properties of the sand - gel were not obtained (Table 9).

[0111]

Table 9

[0112] That is, even if the bleeding liquid simply gels, if neither the homogel nor the sand - gel can obtain self - standing property, or even if the homogel does not self - stand but the sand - gel may self - stand, it was found that conditions for obtaining the self - standing properties of the homogel and the sand - gel are necessary (Tables 8, 9).

[0113] Also, from the infiltration test using a one - dimensional infiltration device (length 2 m), in the water glass - slag system, the bleeding liquid gels and the gel has a strength that can self - stand. However, when water glass is not included, the bleeding liquid does not gel. Also, since the bleeding liquid gels whether the bleeding rate is 50% or more or 50% or less, it was found that the separated silica solution separated from the suspension has the property of infiltrating and consolidating. In that case, the silica concentration of the separated silica solution was predicted to be 0.5 w / v% or more (Table 9).

[0114] Also, from the infiltration test, in the water glass - slag system and the suspension without water glass, it has been confirmed that the above - mentioned separated silica solution infiltrates and solidifies in sand where the suspended particles by the separated silica solution separated from the suspension cannot infiltrate in the suspension containing water glass. Therefore, since this separated silica solution can infiltrate even in the ground of the particle size accumulation curve of the infiltration consolidation of the solution - type grout, it was found that the infiltration possibility of the solution - type silica grout can be obtained (Figure 11).

[0115] In this way, in the case of the suspension-type grout, by using fine particle silica such as slag or fly ash and solution-type silica, since the bleeding liquid penetrates and solidifies even in a portion where the suspension cannot penetrate, paying attention to the gelation of the bleeding liquid, the following conditions under which the bleeding liquid and the sand gel can stand on their own were found.

[0116] From the above, other preferred embodiments of the present invention are as follows. An injection method in which an injection material is injected into the ground from a plurality of injection holes provided in the ground, filled into the cutting area, and infiltrated and solidified between soil particles around the cutting area. As the injection material, a suspension comprising suspension particles such as slag or fly ash as the main material and solution-type silica such as water glass or silica colloid as an active ingredient is used, and it infiltrates and solidifies up to a region where the suspension cannot penetrate.

[0117] The present inventors paid attention to the gelation of the bleeding liquid, found conditions under which the separated silica solution and the sand gel can stand on their own, and by using suspension particles such as slag or fly ash and solution-type silica, it became possible for the separated silica solution separated from the suspension to penetrate and solidify even in a portion where the suspension particles cannot penetrate.

[0118] When the above suspension contains solution-type silica, the separated silica solution gels, and the homogel has a strength to stand on its own. The sand gel infiltrated and solidified by the separated silica solution has a strength to stand on its own. The separated silica solution penetrates into a portion of the ground where the suspension could not penetrate, expands the solidification range, or forms a solid by integrating with a portion of the ground where the suspension particles penetrated, thereby connecting the solids formed by the suspension particles from adjacent injection holes. Also, if CMC, MC, polyacrylamide, clay, etc. are added to the injection liquid, an effect can be obtained in which it is difficult to disperse in the ground and it is difficult to be diluted even in a gravel ground. Furthermore, even if it is injected into the ground to be excavated, an injection method combining injection and infiltration that can make the cut surface of the excavated ground stand on its own and stop groundwater becomes possible.

[0119] Here, in the above, when the separated silica solution separated from the suspension gels and its homogeneous gel stands on its own, it means that the silica concentration of the above separated silica solution is 0.5 w / v% or more, and in the mold, even when the homogeneous gel is tilted diagonally, the gel does not collapse and stands on its own.

[0120] Also, when the above sand gel stands on its own, it means that the silica concentration of the above separated silica solution is 0.5 w / v% or more. When No. 6 silica sand is used, the sand gel prepared by the mixing method with a diameter of 5 cm × height of 10 cm so that the relative density becomes 60% using the above separated silica solution stands on its own, and the strength in the uniaxial compression test measured using the sand gel is 2.0 kN / m 2 or more.

[0121] In the above, the sand gel formed by the bleeding liquid of the silica grout composed of silica particles containing water glass and Ca increases in strength over time (Table 8). This is presumably because the Ca ions of the silica particles elute into the gel of the bleeding liquid over a long period even after gelation and react with silica to form calcium silicate, contributing to the increase in strength. Alternatively, it is presumably because the added hardening agent containing Ca or Mg reacts with the soluble silica of the silica particles over a long period by the pozzolanic action, resulting in an increase in strength due to the pozzolanic reaction.

[0122] From the above, according to the present invention, according to the ground conditions and the purpose of ground improvement (such as strength and the range of the consolidation region, etc.), the size of the solidified body in the cutting region by injection, the suspended particles, and the gelation of the separated silica solution separated from the suspension can set the penetration consolidation range. Further, depending on the type and particle size of the suspended particles of the suspension-type injection material, the blending amount, the hardening agent and the alkali agent, the type and addition amount of the solution-type silica, the bleeding rate, the strength and gelation time of the bleeding liquid, the penetration consolidation range of the suspended particles and the penetration consolidation range by the separated silica solution separated from the suspension can be set. As a result, as shown in Fig. 15, a new concept of injection-penetration composite injection was created, and ground improvement by injection penetration injection using a suspension-type grout became possible.

[0123] The injection material used in the present invention particularly has the following characteristics. (1) By setting the formulation of a suspension-type injection material mainly composed of lightweight and highly fluid suspension particles with a small particle size, it can penetrate widely from the cutting area into the surrounding ground (Figs. 7 to 9). (2) By containing a silica solution, the separated silica solution separated from the suspension during penetration into the ground gels, and the silica solution penetrates into the fine particle portion of the ground where the suspension particles cannot penetrate (Figs. 6, 8 to 10). The fine particle portion of the ground consolidates and becomes self-supporting. Since the separated silica solution separated from the suspension obtains the same permeability as the solution-type silica grout, the penetrable range of fine-grained soil in Fig. 11 can be expected. Fig. 4 shows the situation where when a silica suspension containing silica is left standing, the suspension solidifies and the bleeding liquid gels. Fig. 5 shows the situation where when a silica suspension not containing silica is left standing, only the suspension solidifies and the bleeding liquid does not gel. (3) Table 9 shows the self-supporting property of the homogel at a low silica concentration of the solution-type grout, the solidification of the sand gel, and the self-supporting property of the consolidated sand. (4) From the particle size distribution of the sand used in the penetration test (Fig. 14), it can be seen that the suspension particles used in the present invention penetrate and consolidate in the sandy ground.

[0124] The particle size distribution of the sand used in the penetration test (Figs. 6 to 9) is No. 6 silica sand in Fig. 14. In this particle size distribution, in a suspension not containing a silica solution, the suspension particles can penetrate between the soil particles up to 80 cm (Figs. 8, 9). In Toyoura sand, which is finer-grained soil, the penetration distance was approximately half or less of that. Furthermore, when the above suspension containing a silica solution (Example 36) is used, the same penetration range as shown in Fig. 11, which is the particle size of the penetrable range of the solution type, can be obtained. Although there are differences in the penetration distance depending on the soil conditions, it can be seen that a solidified body as shown in Fig. 15 can be formed. Figs. 15(c) and (d) are plan views of the penetration and consolidation body. The type and size of the suspension particles of the suspension-type injection material may be selected according to the soil conditions. Also, since penetration injection is possible as shown in Fig. 15(e), it enables the stabilization of the surrounding structures without damaging 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 mainly composed of the above-mentioned suspended particles containing a silica solution is injected, the portion near the center becomes a high-strength region with a large number of suspended particles, and as the distance from the center increases, the concentration of the suspended particles decreases, resulting in a low-strength region. Further, it has been found that on the outside thereof, a solidified body rich in silica is formed by the gelation of the separated silica solution separated from the suspension, and adjacent solidified bodies are connected to each other. Conventionally, a large amount of bleeding in a suspension has been regarded as a drawback. However, in the present invention, attention is paid to the fact that the separated silica solution separated from the suspension can penetrate between soil particles that cannot be penetrated by the suspended particles, and research on the gelation of the bleeding solution has been conducted. As a result, it has been found that the gelation and strength of the bleeding solution itself, the permeability of the separated silica solution separated from the suspension into sand, and the strength of the sand gel greatly affect the improvement of the penetration consolidation property of the suspension-type grout. Based on these findings, conditions were examined under which the suspension can penetrate not only into the surrounding ground of the injection area but also into the fine-grained soil area where the suspended particles cannot penetrate, and the separated silica solution separated from the suspension penetrates and gels to enable the formation of a large improved body. As a result of that research, the inventors have enabled ground improvement that integrates the entire target ground, which has high permeability, high strength, and excellent water stoppage properties, by covering the injection limit of the suspended particles with the gelation function of the solution-type silica (bleeding solution) separated from the suspension-type injection material.

[0126] According to the present invention, while consolidating coarse-grained soil, it is also possible to penetrate and solidify fine-grained soil into which suspended particles cannot penetrate due to the gelation of the separated silica solution separated from the suspension, enabling the formation of a consolidated body larger than the consolidated body of the suspended particles. However, simply gelating the separated silica solution separated from the suspension does not provide sufficient strength. From this perspective, it was found that the self-standing strength conditions for the homogel and sand gel of the bleeding liquid are 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 jet mixing method, the problems of the high-pressure jet mixing method mainly using cement described above are solved, and a new ground improvement method has been realized.

[0127] Further, the present invention provides a ground improvement method that can obtain a consolidated body with excellent durability and is expected to have a CO2 reduction effect by using a non-cement-based injection material mainly composed of silica particles having a natural pozzolanic action, including artificial calcined silica such as slag and fly ash, and soluble silica such as loam soil.

[0128] (Injection device and construction procedure) As described above, the present invention is an injection and penetration composite injection method. Therefore, the injection device needs to be able to perform jet mixing and pressure penetration injection. In order to fill the cutting space with the suspension according to the present invention by jet mixing high-pressure water and perform pressure penetration, it is necessary to prevent the injected suspension from being discharged to the ground together with the sludge. FIG. 16 shows an injection device having such a function (FIG. 16(a)) and the construction procedure using the same (FIGS. 16(b) to (d)).

[0129] The injection device of the present invention is used in the high-pressure jet mixing method. As shown in the figure, it includes a guide pipe inserted into the ground, an injection inner pipe arranged inside the guide pipe and used for injecting the injection material, and an opening and closing mechanism for opening or closing the space between the guide pipe and the injection inner pipe. When injecting the injection material into the ground by high-pressure jet, the opening and closing mechanism opens the above space, and sludge is discharged to the ground through the above space. Also, by closing the space with the opening and closing mechanism, the injection material is pressure-penetrated into the ground.

[0130] In the ground improvement method by the high-pressure jet mixing method using this injection device, specifically, first, a hole is drilled to the target depth of the ground by a guide pipe, and an injection inner pipe is inserted into it. Next, the space between the guide pipe and the injection inner pipe is opened by an opening / closing mechanism, the guide pipe is pulled up, and the injection material is jet-injected from the injection inner pipe together with high-pressure jet water or air, while cutting the ground and jet-mixing. Next, a mixed injection material is produced by mixing the cut soil generated by cutting with the injection material on the ground surface, and this mixed injection material is jet-injected into the ground from the injection inner pipe together with high-pressure jet water or air. Or, after filling the area generated by cutting with the injection material, the above space is closed by an opening / closing mechanism, and the injection material is pressure-infiltrated into the ground. When trying to infiltrate and inject the injection material to the surrounding ground, it is necessary to apply an osmotic pressure.

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

[0132] The rubber bag is provided with a ball bearing on its inner surface and seal members such as O-rings at both the upper and lower ends, thereby maintaining airtightness when injecting a fluid such as air inside. During cutting, the space between the injection inner pipe and the guide pipe is in an open state, and the cut soil is discharged to the ground. On the other hand, when injecting the injection material, fluid is sent into the rubber bag, the rubber bag expands and closes the space between the injection inner pipe and the guide pipe, so that the injection material penetrates into the ground by pressure. When moving the cutting area, the ball bearing of the opening / closing mechanism enables relative movement between the guide pipe and the injection inner pipe.

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

[0134] First, from the injection inner pipe inserted into the guide pipe with the opening / closing mechanism attached, the injection material is jet-injected at high pressure together with high-pressure jet water or air, the ground is cut and jet-agitated, and the cut soil generated by the cutting is discharged to the ground surface. Next, the rubber bag is inflated by pressurization with a fluid such as air and brought into close contact with the guide pipe, thereby closing the space between the guide pipe and the injection inner pipe, injecting the injection material without discharging sludge, and performing infiltration injection into the outer peripheral portion of the cutting region by the injection pressure. After that, the pressurization of the rubber bag is stopped, the close contact of the rubber bag with the injection inner pipe is interrupted, the injection inner pipe is pulled up, and the same operation is repeated.

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

[0136] By using the injection devices of Figs. 16 and 17, the injection material (injection material X) during pressure infiltration injection can be switched to an injection material with higher permeability than the injection material (injection material Y) during jet agitation injection, and formulations with different gelation times can also be used. That is, in the present invention, different injection materials can be used as the injection materials for jet agitation and pressure infiltration, and the injection material for pressure infiltration can be made to have higher permeability than the injection material for jet agitation. Further, in the present invention, the injection material for jet agitation and the injection material for pressure infiltration can be switched by opening and closing the above space by the opening / closing mechanism.

[0137] For example, when using a cement suspension as the injection material, the injection material Y can be set at a high concentration and the injection material X at a low concentration, and the injection device having the above opening and closing mechanism can be used for pressure infiltration injection instead of jet stirring injection. Also, the injection material Y can be a suspension and the injection material X can be a solution-type grout. Furthermore, after injecting the injection material Y, an injection material obtained by adding an accelerator to the injection material Y as the injection material X to adjust the gelation time can also be used. Whether the suspension can penetrate is related to the particle size of the injection ground. In that case, the numerical value calculated for the existing injection limit of the injection ground can be used as a reference. For example, the experimental statistical results regarding the injection limit of suspension grout by J.C. King (Proc. ASCE 1961) can be used (from "Cutting-edge Chemical Solution Injection Construction Method", Riko Shoten, Shunsuke Shimada, Takeshi Sato, Minoru Taku, P.154 - P.158). The D 15 and D 10 of the soil particles and the D 85 and D 95 of the suspension are used to define N as the [Groutability Ratio] (usually N1 is taken). N1 = D 15 / D 85 ≥ 15 N2 = D 10 / D 95 ≥ 8 If the relationship is not satisfied, the grout (suspension) cannot penetrate smoothly. Therefore, in the ground where the groutability ratio N is satisfied, the infiltration injection of the suspension becomes possible. Also, even in the ground where the infiltration injection of the suspension is difficult, if a suspension containing a silica solution is used, in the ground where the infiltration of the suspension is insufficient, a ground integrated with the suspension particles even in fine-grained soil is formed by the gelation of the separated silica solution, or a large solidified body is formed by the infiltration of the separated silica solution over a wider range. In that case, the permeable particle size of the separated silica solution can be considered the same as that of the solution-type grout in Fig. 11.

[0138] By switching the content and composition of the injection material in this way, it becomes possible to adjust the consolidation strength, permeability, and gel time, expand the consolidation range and injection limit, and realize a ground improvement method based on a new concept of jet stirring infiltration composite injection.

Industrial Applicability

[0139] The present invention relates to a ground improvement method capable of improving soft ground and liquefied ground into high-strength and uniform ground. In the destruction and solidification of the ground using the kinetic energy of high-pressure jet fluid, not only a solidified body is formed in the cutting area, but also by infiltrating the injection material between the soil particles from the cutting area, a larger solidified body is formed, and by reusing the cut soil by high-pressure jet and filling it into the ground, low-carbon ground improvement is made possible. Further, by using a suspension-type injection material mainly composed of artificial calcined silica such as slag and fly ash or silica particles having a natural pozzolanic action, a non-cement-based injection material or an injection material with reduced cement content is used to widely perform ground improvement excellent for the global environment with reduced CO2, and has the effect of expanding the infiltration consolidation range and reducing the weight of the solidified body, and can efficiently and economically perform ground improvement of soft ground and liquefied ground.

Claims

1. An injection device for use in a high-pressure injection mixing method, comprising: a guide pipe that is drilled into the ground and inserted therein; an inner injection pipe that is disposed within the guide pipe and used to inject an injection material; and an opening / closing mechanism that opens or closes the space between the guide pipe and the inner injection pipe; an injection device characterized in that the opening and closing mechanism is disposed between the guide tube and the inner injection tube and comprises an annular rubber bag having a pipeline through which a fluid can flow, the opening and closing mechanism opens or closes the space by the presence or absence of pressure inside the rubber bag due to the flow of fluid in and out of the rubber bag, and the rubber bag is formed so as to be movable relative to the inner injection tube.

2. 2. The injection device according to claim 1, wherein the opening and closing mechanism comprises the rubber bag, 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.

3. 2. The injection device according to claim 1, wherein the opening and closing mechanism comprises the rubber bag, 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.

4. 2. A ground improvement method using a high-pressure jet mixing method with the injection device according to claim 1, 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 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.

5. 2. A ground improvement method using a high-pressure jet mixing method with the injection device according to claim 1, comprising the steps of: drilling a hole in the ground to a target depth 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 to pressurize and infiltrate the injection material into the ground.

6. 6. The method for improving ground according to claim 5, 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.

7. The ground improvement method according to claim 5, 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.

Images