Site improvement construction methods

Abstract

To provide a suspension / solution simultaneous composite injection excellent in permeability, strength, water cut-off properties, etc.SOLUTION: By using an injection material composed of a suspension containing suspended particles composed of one or more kinds of silica particles of sintered silica and natural sintered silica having pozzolanic action and a silica solution, the separated silica solution separated from the suspension permeates into a region into which the suspended particles cannot permeate with permeability into the fine-grained soil and is then gelled. In the ground improvement method, silica particles are set to a prescribed Blaine value and a prescribed blending amount, the silica sol is set to silica colloid and / or prescribed water glass, the separated silica sol is set to a prescribed silica concentration, the separated silica sol has a self-supporting strength of a homogel and a sand gel, and the separated silica sol connects the solidified bodies of the suspended particles to form a solidified body having a high-concentration solidified region and a low-concentration solidified region from the center toward the outside.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a ground improvement method using suspension grout, and more particularly to a ground improvement method for improving soft or leaky ground by simultaneous combined injection of suspension and solution, which simultaneously performs consolidation with suspended particles and infiltration and consolidation with a separated silica solution separated from the suspension grout (suspension). [Background technology]

[0002] The basics of the conventional composite grouting method are explained below. (1) The basic principle of the injection method is to allow grout to penetrate between soil particles, replacing the interstitial water with grout and solidifying it.

[0003] (2) However, the target ground for injection is usually complex, with coarse soil layers, fine soil layers, and different soil layers interspersed. Therefore, when a highly permeable solution grout is injected, the injected grout is likely to deviate from the target area. On the other hand, suspension grout cannot penetrate the fine soil layers with suspended particles. For this reason, suspension grout or instant-setting grout is injected in advance to fill the coarse layers, homogenize the ground, and then a highly permeable solution grout is injected.

[0004] (3) For these reasons, the specific injection methods used are the double-pipe composite injection method (Figure 1(a)) and the double-pipe double packer method (Figure 1(b)). In the double-pipe composite injection method, a quick-setting grout is injected as the primary injection, and a slow-setting grout is injected as the secondary injection (Fig. 1(a)). In the double-pipe double packer method, a suspension-type grout such as cement bentonite (CB) is injected as the primary grout, and a solution-type grout is injected as the secondary grout (Fig. 1(b)). In both cases, the primary and secondary injections are carried out in separate processes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-066686 [Patent Document 2] Japanese Patent Application Publication No. 2024-053139 [Non-patent literature]

[0006] [Non-Patent Document 1] Yurika Tsunoda, Shunsuke Shimada, Tadao Koyama, Takamitsu Sasaki, Ryozo Yonekura, "Demonstration Study on the Permanence and Penetration / Solidification of Ultrafine Composite Silica," 66th Annual Academic Conference of the Japan Society of Civil Engineers, 2011 [Non-patent document 2] Takamitsu Sasaki, Ryozo Yonekura, Shunsuke Shimada, "Field Demonstration Test of the Long-Term Consolidation of Consolidated Ground Using Activated Silica and Ultrafine Composite Silica," 54th Geotechnical Engineering Research Conference, 2019, 0241 Summary of the Invention [Problem to be solved by the invention]

[0007] Generally, to reinforce soft soil made of soil or leaky ground such as bedrock with high strength, injection of suspension grout is required, but suspension grout does not penetrate fine-grained soil or fine cracks, and therefore it is difficult to achieve watertightness. For this reason, conventionally, a two-step injection process has been carried out, in which suspension grout is injected in the first injection, and then solution grout is injected in the second injection.

[0008] In addition, in conventional injection materials, suspension grouts that are mainly composed of cement have a high specific gravity of 3.17, but a specific surface area of ​​3,220 cm 2 / g, and the cement particles are heavy. In addition, penetration between soil particles in fine-grained soil is difficult, resulting in a short penetration distance, making it difficult to form large solidified bodies.

[0009] In the high-pressure jet mixing method, which mainly uses cement, the solidified material immediately after construction is in an unsolidified state because sufficient hydration reactions have not yet occurred. Therefore, when construction is carried out near a structure, a temporary decrease in bearing capacity can impede the function of the structure. Furthermore, with the conventional high-pressure jet mixing method, which relies on the energy of the high-pressure jet fluid, the cutting area is limited by the distance of the jet fluid, which restricts the size of the solidified material made of cement.

[0010] Furthermore, in the high-pressure injection mixing method, the soil is removed and replaced with cement to form a solidified mass, so disposal of the removed mud has become a major environmental problem today.Furthermore, when improving soft ground, there is a problem that the bearing capacity of soft ground is low, so the cement solidified mass, which has a high specific gravity, is prone to settling, and the displacement of structures is likely to increase.

[0011] In view of the above, the present invention aims to realize simultaneous combined injection of suspension and solution by expanding the permeability limit of suspension grout to the permeability range of solution grout during construction, thereby realizing the permeability required to form a large solidified body, and simultaneously achieving high strength and excellent water-stopping properties as improved effects.The invention also aims to realize simultaneous combined injection of suspension and solution by enabling the permeation and solidification of solution grout while injecting suspension grout in a single process, thereby enabling the permeation and solidification of suspension and solution grout to be carried out simultaneously, without the problems associated with high-pressure injection and mixing methods. [Means for solving the problem]

[0012] Specific means for solving the problems of the present invention will be described below. (1) The present inventors have already developed a high-strength permanent grout using silica particles such as slag and fly ash as a low-carbon injection material and injection method (Patent Documents 1 and 2). These low-carbon grouts have been proven to have long-term durability and earthquake resistance (Patent Document 1). (2) In Patent Document 1, the present inventors conducted research focusing on the gelation of the bleeding liquid of ultrafine particle composite silica consisting of silica particles and silica solution, and as a result, discovered the conditions under which the gelation of the bleeding liquid, strength, and ground improvement effects can be obtained. (3) As a result, the inventors have realized ground improvement by simultaneous combined injection of suspension and solution, which is a new concept that integrates the entire target ground, has high permeability, high strength, and excellent water-stopping properties, by covering the injectable limit of suspended particles with the gelling function of solution-type silica (bleeding liquid) separated from the suspension-type injection material (Figure 13).

[0013] As described above, the present invention makes it possible to carry out a ground improvement construction method using simultaneous combined injection of suspension and solution that combines the strength, permeability, and water-stopping effect of the infiltration injection of a suspension by injecting a ground grout consisting of a suspension containing silica solution and suspended particles as active ingredients into the ground, solidifying the coarse-grained soil with the suspended particles, and solidifying the fine-grained soil, which the suspended particles cannot penetrate, by gelling the silica solution separated from the suspension, thereby forming a solidified body that is larger than the solidified body of suspended particles (Figure 13). Here, the "separated silica solution separated from the suspension" that is produced when the suspension is injected into the ground corresponds to the "bleeding liquid of the suspension" in the experiment, so in the actual test, the "bleeding liquid of the suspension" is used as the "separated silica solution separated from the suspension."

[0014] That is, the ground improvement method of the present invention is a ground improvement method in which a ground grouting material consisting of a suspension containing a silica solution and suspended particles as active ingredients is injected into the ground, 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 simultaneously solidifying the ground with the suspended particles and the separated silica solution.

[0015] In the present invention, it is preferred that the silica solution is silica colloid and / or water glass, the separated silica solution is gelled, and the silica concentration of the separated silica solution is 0.5 w / v % or more.

[0016] In the present invention, the suspended particles preferably contain, as an active ingredient, one or more of pyrogenic silica, natural pyrogenic silica having pozzolanic action, and hardenable silica particles.

[0017] In the present invention, the pyrogenic silica is preferably made of one or more of slag, fly ash, cement, sewage incineration ash, plant incineration ash, and calcined clay.Furthermore, in the present invention, the natural pyrogenic silica having pozzolanic activity is preferably made of one or more of loam, shirasu, volcanic ash, niwado, and sanwado.

[0018] In the present invention, the ground grouting material preferably contains an alkaline agent consisting of one or more of the following (1) to (3): (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) Alkaline agents containing one or more of lime, cement, caustic alkali, water glass, and silica colloid as active ingredients.

[0019] In the present invention, the suspended particles have a Blaine value of 4000 to 20000 cm 2 It is preferable to use particles having a particle size of 50 to 200 kg / 400 L and to blend the suspended particles in the ground grouting material in an amount of 50 to 200 kg / 400 L.

[0020] In the present invention, it is preferable that the suspended particles are slag, and that the amount of slag mixed in the ground grouting material is 10 to 25 w / v% when cement is not used, and 10 to 30 w / v% when cement is used.

[0021] In the present invention, it is preferable that the molar ratio of the water glass is 1.0 to 5.0, and the amount of the water glass mixed in the ground grouting material is 10 to 150 L / 400 L.

[0022] In the present invention, the ground grouting material preferably contains one or more of microbubbles, air, a dispersant, and a thickener as active ingredients.

[0023] In the present invention, it is preferable that the ground grouting material contains a hardening agent consisting of a polyvalent metal compound, and that the hardening agent is one or more of hydroxides, oxides, or salts of Ca, Mg, or Al, and / or gypsum.

[0024] In the present invention, since the ground injection material has excellent permeability, under conditions where the permeable grout is likely to deviate into the ground other than the specified one, is likely to be diluted by groundwater, or is extremely permeable, it is preferable to inject a suspension grout or a quick-setting grout as a primary injection material into the ground prior to injecting the ground injection material.

[0025] The ground improvement method of the present invention can strengthen an underground structure having an underground space by injecting the ground grouting material into the periphery of the underground structure.

[0026] The ground improvement method of the present invention is also suitable for strengthening and watertighting of excavation wall surfaces or bottom injection. Furthermore, the ground improvement method of the present invention is also suitable for reinforcing rock cracks in rock shafts, watertightness, or containment of harmful substances. Furthermore, the ground improvement method of the present invention is also suitable for reinforcing existing foundations or repairing damaged foundations. Furthermore, the ground improvement method of the present invention is also suitable for liquefaction countermeasures or repairing damaged ground.

[0027] In the present invention, the improvement effect of the injection of the grouting material can be confirmed by a non-destructive test, which is preferably performed by elastic wave velocity logging, acoustic tomography, or surface wave exploration.

[0028] In the ground improvement method of the present invention, a ground grouting material consisting of the suspension is injected into the ground through a plurality of injection holes provided in the ground, The separated silica solution separated from the suspension of the ground grouting material 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, The separated silica solution can penetrate into parts of the ground that the suspended particles could not penetrate, expanding the solidification range, or can integrate with the parts of the ground that the suspended particles have penetrated to form a solidified body.

[0029] In the present invention, the term "the separated silica solution gels and the resulting homogel is self-supporting" means that the silica concentration of the separated silica solution is 0.5 w / v% or more, and the homogel is self-supporting even when tilted obliquely in a mold without collapsing, and the term "sand gel is 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 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 in a uniaxial compression test measured using the sand gel is 2.0 kN / m 2 This means that it is more than or equal to this.

[0030] In the present invention, it is preferable to set a formulation for the ground grouting material that provides a lightweight, low-alkali, and low-carbon type ground improvement material. [Effects of the Invention]

[0031] According to the present invention, the permeability limit of suspension grout is expanded to the permeability range of solution grout, thereby realizing a large solidification range, and simultaneously achieving high strength and excellent water-stopping and permeability.It also makes it possible to infiltrate and solidify solution grout while injecting suspension grout in a single process, thereby enabling the permeation and solidification of suspension grout and solution grout to be carried out simultaneously, thereby realizing simultaneous combined injection of suspension and solution without the problems that occur with high-pressure injection mixing methods.

[0032] The present invention relates to a ground improvement method in which a ground grout consisting of a suspension containing a silica solution and suspended particles as active ingredients is injected into the ground, and the separated silica solution penetrates and solidifies into areas where the suspended particles cannot penetrate, thereby simultaneously solidifying the ground with the suspended particles and the separated silica solution. The present invention substantially expands the injectability limit of conventional suspension grouts to that of solution-type silica grouts, and also significantly expands the penetration and solidification range of conventional suspension-type grouts. This allows for a wide range of applications for the ground improvement method, including not only liquefaction countermeasures, increasing the bearing capacity of ground, and constructing water-stopping walls, but also injection into the periphery of underground structures with underground spaces to strengthen underground structures, water-stop and strengthen excavated ground, strengthen and water-stop injection into the base of rock, reinforcement and water-stopping of rock cracks in rock shafts, and containment of harmful substances. [Brief explanation of the drawings]

[0033] [Figure 1] (a) and (b) are explanatory diagrams relating to the composite injection method, where (a) shows an example of the double-pipe composite injection method, and (b) shows an example of the double-pipe double packer method. [Figure 2] FIG. 10 is a photograph showing the bleeding state of the sample of Example 36. [Figure 3] FIG. 1 is a photograph showing the bleeding state of the sample of Comparative Example 1. [Figure 4] FIG. 10 is a photograph showing the state of the sample of Example 36 several days after penetration. [Figure 5] FIG. 1 is a photograph showing the state of the sample of Comparative Example 1 several days after penetration. [Figure 6] 1 is a graph showing the results of a long-distance penetration test for Example 36 and Comparative Example 1. [Figure 7] 7 is a graph showing an enlarged portion of the permeation distance of 90 cm to 120 cm in FIG. 6. [Figure 8] 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 9]This is a graph showing particle size accumulation curves for various on-site sands that have been treated with liquefaction countermeasures using solution-type grout. [Figure 10] FIG. 10 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 11] FIG. 10 is a photograph showing the state of a test specimen after strength measurement using a mixing method using a bleeding liquid. [Figure 12] 1 is a graph showing the physical properties of the sand used. [Figure 13(a)] FIG. 1 is an explanatory diagram showing one form of permeation consolidation in the ground improvement method of the present invention. [Figure 13(b)] FIG. 10 is an explanatory diagram showing another form of permeation consolidation in the ground improvement method of the present invention. [Figure 13(c)] FIG. 10 is an explanatory diagram showing yet another form of permeation consolidation in the ground improvement method of the present invention. [Figure 13(d)] FIG. 10 is an explanatory diagram showing yet another form of permeation consolidation in the ground improvement method of the present invention. [Figure 14(a)] FIG. 1 is an explanatory diagram showing reinforcement injection into the periphery of a tunnel, as an example of application of the ground improvement method of the present invention. [Figure 14(b)] FIG. 1 is an explanatory diagram showing an example of application of the ground improvement method of the present invention, in which concrete is repaired from inside an underground structure in service and reinforced and injected into the surrounding ground. [Figure 14(c)] FIG. 1 is an explanatory diagram showing an example of strengthening an underground structure, among application examples of the ground improvement method of the present invention. [Figure 14(d)] FIG. 1 is an explanatory diagram showing the strengthening and waterproofing of the base plate by base plate injection, as an example of application of the ground improvement method of the present invention. [Figure 14(e)] FIG. 1 is an explanatory diagram showing reinforcement of a missing portion of a retaining sheet pile and water-stopping injection in an application example of the ground improvement method of the present invention. [Figure 14(f)] FIG. 1 is an explanatory diagram showing the prevention of subsidence of a tunnel foundation and water sealing in an application example of the ground improvement method of the present invention. [Figure 14(g)] FIG. 1 is an explanatory diagram showing an example of application of the ground improvement method of the present invention, in which a foundation is reinforced or a damaged foundation is repaired. [Figure 14(h)]FIG. 1 is an explanatory diagram showing reinforced filling of rock cracks and water sealing or waste containment in an application example of the ground improvement method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The ground improvement method of the present invention is a method of injecting into the ground a ground grouting material consisting of a suspension whose active ingredients are a silica solution and suspended particles, and is characterized in that the separated silica solution separated from the suspension penetrates into areas that the suspended particles cannot penetrate, and then gels and solidifies the ground, thereby simultaneously solidifying the ground with the suspended particles and the separated silica solution.

[0035] As a result of continuing research into the gelation of bleeding liquid, the inventors have found that in suspensions containing silica solutions, bleeding liquid gels whether the bleeding rate is 50% or less or 50% or more (Fig. 2, Fig. 4, Figs. 6-8, Table 8). They also found that the gelation time and strength of the bleeding liquid can be adjusted by adding a curing agent, and they also found the relationship between the gelation of the bleeding liquid and the silica concentration sufficient to form self-supporting homogels and sand gels (Table 9, Fig. 2, Fig. 4, Figs. 6-8, Fig. 10, Fig. 11).

[0036] Figures 13(a) to (d) show the form of permeation consolidation in the ground improvement method of the present invention. Figure 13 shows that by injecting the silica suspension, the suspended particles permeate between the soil particles, and further, the separated silica solution from the suspension permeates and solidifies, forming an integrated permeation consolidation area. Figure 13 corresponds to Figures 6, 7, and Table 8. Therefore, the suspended particles of the suspension and the separated silica solution from the suspension are injected into the ground through multiple injection holes and solidify, making it possible to improve the ground as a whole (Figure 13). Furthermore, the present invention has substantially expanded the injection limit of suspension grout (Fig. 12) to include solution grout (Fig. 9), making it possible to carry out ground improvement using suspension grout injection and solution grout in a single process, and has developed into a ground improvement method based on a new technological concept of simultaneous combined injection of suspension and solution.

[0037] As mentioned above, the grout used in this invention can be called a permeable suspension grout, which is a suspension grout that penetrates and solidifies not only coarse-grained soil but also fine-grained soil in a single step. Therefore, in cases where the permeable grout is prone to deviating into undesired soil due to its excellent permeability or is prone to being diluted by groundwater, as shown in Figure 1, a suspension grout or instant-setting grout such as cement bentonite (CB) can be injected first, followed by a secondary injection of the above-mentioned grout. This allows the specified amount to be injected at the specified injection stage without deviation, enabling ground improvement with high strength, excellent permeability, and water-stopping properties.

[0038] The suspension grout used for the primary injection can be a suspension grout consisting of silica particles and a binder, such as the above-mentioned slag or fly ash, which does not contain silica solution, in addition to CB. Also, if a quick-setting agent such as calcium chloride, gypsum, or water glass is added to a suspension containing silica solution, it will become an instant-setting grout that sets in a few to 10-odd seconds.

[0039] The present invention also relates to a ground improvement method for improving soft or liquefied ground around underground structures with high strength and light weight. This method involves infiltrating silica particles, slag-based consolidating materials, or other materials into the surrounding area to form large consolidations, enabling low-carbon ground improvement. By using particles primarily composed of calcined silica, such as slag or fly ash, or silica particles with natural pozzolanic properties, non-cement-based consolidating materials or consolidating materials with reduced cement content, it is possible to provide environmentally friendly ground improvement with reduced CO2 emissions from a material perspective. Furthermore, by incorporating silica solution into the suspended particles, the separated silica solution from the suspension penetrates and solidifies, expanding the penetration and solidification area, resulting in high-strength improvement effects, water-stopping effects, and the ability to repair deteriorated underground concrete structures.

[0040] Therefore, the present invention provides the advantage of reducing the weight of the entire improved area and eliminating settlement caused by the solidified body by forming a solidified body using artificial calcined silica such as slag or fly ash as the main component of suspended particles, or by using silica particles with natural pozzolanic action as the main component, or by using a formulation with a small amount of cement. This is because the specific gravity of cement is 3.15, while that of slag is 2.9, that of fly ash is 2.8, and that of volcanic ash generally ranges from 0.9 to 2.5, which is almost the same as that of sand or clay.

[0041] Table 1 below shows an example of a consolidated strength test of a mixture with a consolidating agent when the ground is sandy or clayey soil. Bleeding measurements were performed using bleeding bags (JSCE-F 522-2018, JSCE-F 532-2013) in accordance with the test method. The viscosity was measured using a tuning fork vibration viscometer (SV-10 manufactured by A&D). Tables 1 through 7 show examples of the consolidation strength of homogeneous gels or their mixtures with in-situ soil. Table 8 shows the uniaxial compressive strength of sand gels prepared using a blending method with a bleeding solution. In this invention, a lightweight suspension based on small, fluid particles is selected depending on the ground conditions. This allows penetration and solidification of the surrounding ground. If the suspension contains silica solution, the separated silica solution gels and solidifies. This extends the consolidation range to surrounding areas, even in areas where the suspension alone cannot penetrate. Furthermore, this provides a watertight effect and continuous solidification of the aggregates (Figures 2, 4, 6 through 11). Figure 9 shows the particle size distribution curves for solution-type grouts that achieve a permeation consolidation effect. The above-mentioned suspension-type consolidation materials containing silica solution are capable of permeating and solidifying ground with the particle size distribution shown in Figure 9. This enables a new ground grouting method based on the concept of "simultaneous combined suspension / solution injection," which combines the advantages of both suspension and solution injection methods. FIG. 12 shows the particle size distribution of the permeable limit of the suspension grout without silica solution.

[0042] The grouting material used in the present invention will be described below. The grouting material used in the present invention is a suspension containing a silica solution and suspended particles as active ingredients. The grouting material used in the present invention may contain suspended particles made of silica particles as the main ingredient, and one or more of a hardener, an alkali agent, and a silica solution.

[0043] The grouting material used in the present invention is primarily composed of calcined silica such as slag or fly ash, which can be mixed with water glass and / or an alkali agent or a hardener to prepare a suitable grouting agent. The suspended particles preferably contain one or more of the following active ingredients: calcined silica, natural calcined silica with pozzolanic action, and hardenable silica particles.

[0044] Examples of calcined silica include slag and fly ash, as well as cement, paper sludge, sludge incineration ash, sewage incineration ash, plant incineration ash, and calcined clay, as well as plant incineration ash rich in silica. Any one or more of these can be used. Natural calcined silica with pozzolanic properties includes natural calcined soils such as loam (Kanto loam), shirasu, volcanic ash, and niwado (fine-ground soil) and sanwado (fine-ground soil). Any one or more of these can be used. These calcined silicas are silica particles with pozzolanic properties, contain soluble silica, and form a crystalline structure similar to that of cement through hydration reactions with alkalis such as slaked lime, gypsum, magnesium hydroxide, water glass, silica colloid, caustic alkali, carbonates, bicarbonates, aluminum salts, calcium salts, and magnesium salts, thereby solidifying firmly. Furthermore, the use of aggregates such as soil and clay as thickeners or bulking agents in these compounds enables economical ground improvement. Furthermore, the on-site soil can be used in the form of a slurry together with the hardening agent.

[0045] The suspended particles, i.e., silica particles, have a Blaine value of 4000 to 20000 cm 2 / g, penetration between soil particles becomes possible. Furthermore, high strength can be achieved by using artificial or natural calcined silica as the suspended particles and setting the amount of suspended particles in the ground grouting material to 50 to 200 kg per 400 L. The amount of calcined silica such as slag in the ground grouting material according to the present invention is determined depending on the desired strength of the hardened product, but is preferably 50 to 200 kg per 400 L, 10 to 25 w / v % when no cement is used, and 10 to 30 w / v % when cement is used.

[0046] The grouting material of the present invention preferably contains a hardening agent made of a polyvalent metal compound. The hardening agent can be one or more of hydroxides, oxides, or salts of Ca, Mg, or Al, and / or gypsum. Specifically, calcium molten materials such as cement, slaked lime, and gypsum, or alkaline agents, are used. Slaked lime is particularly preferred for shortening gelation time and improving early strength. The grouting material can also contain fillers such as slag, bentonite, calcium carbonate, clay, and silica powders such as earth and sand. Plastic grouts can also be made using fly ash, polymers, cement, plasticizers such as aluminum salts, thickeners, and clay.

[0047] The alkaline agent used in the ground grouting material according to the present invention may be any one or more of the following (1) to (3). (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) Alkaline agents containing one or more of lime, cement, caustic alkali, water glass, and silica colloid as active ingredients.

[0048] In the ground grouting material of the present invention, the silica solution is preferably silica colloid and / or water glass, the separated silica solution separated from the suspension of the ground grouting material is gelled, and the silica concentration of this separated silica solution is preferably 0.5 w / v% or more. 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 ground grouting material is 10 to 150 L / 400 L.

[0049] In the present invention, the slag used is finely pulverized blast furnace slag, and the finer the particle size, the better in order to enhance reactivity. For example, the finer the particle size, the better in terms of the specific surface area (Blaine value) of 4000 cm 2 / g or more, preferably 6000 cm 2 / g~20000cm 2 / g and an average particle size of 10 μm or less is suitable.

[0050] In the present invention, the water glass preferably has a high alkali concentration due to its reactivity with slag. In particular, a SiO2 / Na2O molar ratio of 1.0 to 2.5 is preferred. This allows for the production of high-strength solidified bodies and the adjustment of gelation time. Furthermore, water glass can be used in the form of a mixture of anhydrous sodium orthosilicate and sodium hydroxide, crystalline sodium silicate containing sodium metasilicate, a mixture containing a portion of crystalline sodium silicate, sodium silicate glass (cullet), hydrated glass, dehydrated sodium silicate, semi-solid sodium silicate, viscous sodium silicate, commercially available sodium silicate solutions, or a combination of the water glass with a molar ratio of 1.5 to 5.0. Water glass with a molar ratio of 2.5 to 5.5 or a silica solution obtained by mixing silica colloid with water glass to further increase the molar ratio may also be used with different viscosities, molar ratios, and silica concentrations, or it may be used as a powder. The alkali content of water glass stimulates the hydraulic properties of slag. Water glass with a low molar ratio may be a mixture of water glass and caustic alkali. However, when used in combination with calcium molten materials such as slaked lime or cement, water glass with a high SiO2 / Na2O molar ratio, such as water glass No. 3 and No. 4, can be used.

[0051] In addition to water glass, silica colloid can also be used as the silica solution, and a mixture of silica colloid, calcined silica such as slag, and cement can also be used. Any silica colloid can be used as the silica colloid, such as colloid obtained by reducing the alkalinity of water glass by ion exchange and removing and stabilizing it in a weakly alkaline range, silica colloid made of metallic silica, silica colloid originating from geothermal water, and silica colloid obtained by removing the alkalinity from water glass with acid.

[0052] The salts used in this invention include aluminum compounds such as aluminum sulfate and polyaluminum chloride, chlorides and sulfates of calcium and magnesium, and products obtained by reacting these with caustic alkali. Furthermore, the molar ratio of Na2O / Al2O3 is not particularly limited, but due to its reactivity with slag, a Na2O concentration of 1 wt% or higher in the grouting agent is preferred. Caustic alkali is effective in stimulating the hydraulic properties of slag, and the aluminum reacts with water glass and the 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 from the suspension can be adjusted by adjusting the amount of these additives. Furthermore, seawater can be used as a blending liquid for the suspension.

[0053] The amounts of water glass and aluminum compound in the grout are such that the grout hardens over several hours, usually within an hour, and preferably within 30 minutes. Although this varies depending on the molar ratio of Na2O, Al2O3, and SiO2, it is preferable that the grout contains 1 wt% or more of Na2O. However, when solidifying a wide area, amounts that will result in a hardening time of several hours are necessary.

[0054] Furthermore, the grouting material of the present invention can be made lighter by adding a foaming agent or foaming agent to improve its fluidity, and by adding clay, bentonite, or polymeric thickeners such as polyvinyl alcohol, carboxymethyl cellulose (CMC), or methyl cellulose, it can be made to suppress dispersibility in water, reduce precipitation, and improve workability. It can also function as a water-retaining material and as a binder for the silica particles of the main material, such as slag, to create a pseudo-gel-like fluid that maintains fluidity but is difficult to disperse. This reduces diffusion and dilution in the ground and promotes the expansion of the solidified body.

[0055] In the present invention, microbubbles or microbubbles and air can be mixed and injected into the above-mentioned suspensions of slag, fly ash, etc., or into suspensions of cement, etc. In this way, the bearing action of the microbubbles or microbubbles and air covering the suspended particles enables the construction of a wide-area solidified body of suspended particles, and the increased amount of gas in the solidified body can reduce the weight and strength of the solidified body. It has also been found that the presence of air bubbles in the solidified body improves the liquefaction prevention effect even when the amount of suspended particles in the solidified body is small and the strength is low. Furthermore, in addition to microbubbles and air, the injection material of the present invention can also contain dispersants and thickeners, and one or more of these can be used as active ingredients.

[0056] In the present invention, a formulation can be set for a ground grouting material that is lightweight, low in alkali, and low in carbon, and that provides ground improvement.

[0057] In the present invention, the grouting material may be directly mixed and sent to the injection rod as a single liquid, or the above-mentioned suspension (Liquid B) and water glass and / or alkaline agent (Liquid A) may be pumped, mixed, and then injected. In this case, Liquid A and Liquid B are preferably mixed in a ratio of approximately 1:1 (by volume), but are usually mixed in any ratio within the range of 10:1 to 1:10.

[0058] In the present invention, in ground with extremely high water permeability, it is preferable to inject a suspension grout or a quick-setting grout as a primary grout prior to injecting the above-mentioned ground grouting material.

[0059] In the present invention, the improvement effect of the injection of the grouting material can be confirmed by non-destructive testing, which can be performed using elastic wave velocity logging, acoustic tomography, or surface wave exploration.

[0060] The ground improvement method of the present invention can be applied to strengthening underground structures by injecting a ground grouting material into the periphery of an underground structure having an underground space. The ground improvement method of the present invention can also be suitably applied to strengthening and watertighting of excavation wall or bottom injection, reinforcing and watertighting of rock cracks in rock shafts or containing harmful substances, reinforcing existing foundations or repairing damaged foundations, liquefaction countermeasures or repairing damaged ground.

[0061] (test) Clayey soil and sandy soil were used, and these were mixed and consolidated with the above-mentioned grouting material according to the present invention. The test results of the example in which the strength of the consolidated body was measured are shown in Table 1.

[0062] As can be seen from the following, cement-free injection materials, or injection materials that use reduced amounts of cement, that are primarily made of calcined silica or natural silica with pozzolanic properties, have a lower specific gravity than cement-based injection materials, 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 a lightweight solidified body.

[0063] [Materials used] Slag: specific gravity 2.9, Blaine value 8000 cm 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. Its specific gravity is 1.9-2.3g / cm. 3 The particle size distribution is 0.1 mm or less, with 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 hardener. Gypsum or gypsum hemihydrate: hardening material, specific gravity 2.6. Bentonite: Water-retaining and thickening agent, specific gravity 2.6. Magnesium oxide (gelling agent): specific gravity 3.65. Calcium chloride (gelling agent): specific gravity 1.85. Baking soda: specific gravity 2.2. Dispersant: Specific gravity 1.04. Sulfuric acid: specific gravity 1.67, 75w / w%. No. 5 water glass: specific gravity 1.32, silica concentration 25.5%, Na2O 7.03, molar ratio 3.75. No. 1 water glass: specific gravity 1.35, silica concentration 21.59%, Na2O 10.80%, molar ratio 2.06. No. 3 water glass: specific gravity 1.41, silica concentration 29.16%, Na2O 9.36, molar ratio 3.22. Polyaluminum chloride and foam materials can also be used.

[0064] [Test method and test results] The specimens for the unconfined compressive strength tests shown in Tables 1 to 7 were prepared in accordance with the Japanese Industrial Standard (draft) (JIS A 1216:2020) for unconfined compression testing of soil, using cylindrical specimens with a height of 100 mm and a diameter of 50 mm. The results of measuring the strength on the 1st, 7th, and 28th days, or on the 28th day, are shown, respectively. In Tables 1 to 8, the gel time is the time it takes for the suspension to aggregate while continuing to stir with a stirring rod.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] [Table 4]

[0069] [Table 5]

[0070] [Table 6]

[0071] [Table 7]

[0072] [Table 8]

[0073] The grouting material according to the present invention can penetrate and solidify sandy ground. In particular, when the grouting material according to the present invention contains solution-type silica, it penetrates and solidifies fine-grained soil, connects the solidified bodies together, and provides a water-stopping effect.

[0074] Below, we will explain test examples (Figs. 2 to 11) that demonstrate the effect of gelling the bleeding liquid in the above suspension containing silica solution, or the separated silica solution separated from the suspension. Fig. 8 shows the tilted state of Fig. 2 using Example 36 in Table 4. Figs. 10 and 11 show the state of a strength test of a sand specimen solidified with the bleeding liquid in Table 8.

[0075] (Permeability test) (Test equipment and test method) A one-dimensional infiltration test was carried out on No. 6 silica sand using a one-dimensional infiltration apparatus (length 2m), and the infiltration length and strength distribution were investigated.

[0076] 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.

[0077] The specimens were prepared in accordance with the Japanese Industrial Standard (draft) (JIS A 1216:2020) for the unconfined compression test of soil, and cylindrical specimens with a height of 100 mm and a diameter of 50 mm were used for the unconfined compression test.

[0078] The tests were carried out using the formulations of Example 36 and Comparative Example 1 (Figs. 4 to 7, 10, and 11).

[0079] The solid lines in Figures 6 and 7 show the results for the formulation of Example 36. Strength measurements were possible even with a penetration distance of 120 cm. Although there was no discoloration of the sand gel after 90 cm, the strength measurements were possible because the silica solution separated from the suspension solidified after 90 cm. The portion after 90 cm is believed to contain 0.5% or more silica.

[0080] The dotted lines in Figures 6 and 7 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 after 90 cm, making it impossible to measure the strength, and it was found that the separated silica solution that separated from the suspension had not gelled.

[0081] In the penetration test shown in Figure 5, 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-sustaining, the areas where the solution that separated from the suspension penetrated were also not self-sustaining and did not solidify. In contrast, in Figure 4, the bleeding liquid had gelled and was self-sustaining, so the suspended particles did not penetrate and the sand gel did not discolor, but the separated silica solution that separated from the suspension penetrated and solidified, allowing it to stand on its own and develop strength.

[0082] From the above, under conditions where penetration between soil particles is not possible depending on the particle size and density of the soil and the particle size distribution of the suspended particles, the separated silica solution will penetrate from the suspension (Figures 9 and 12).

[0083] Figures 6 and 7 show that even if the penetration distance of the suspended particles in the suspension is 90 cm, the separated silica solution from the suspension will penetrate up to 120 cm, and the solution will be strong enough to stand on its own, and the sand gel will be strong enough to stand on its own. In this case, it can be predicted that the silica concentration will be 0.5 to 2% or more (Table 9). Therefore, even if the injection hole spacing is long, the homogel of the silica solution will connect the solidified bodies into which the suspended particles have penetrated, resulting in high strength.

[0084] In this way, an integrated solidified body can be formed even under ground conditions where suspended particles cannot penetrate, and even if the injection hole spacing is wide, the solidified bodies between the holes can be connected by a self-supporting gel of silica solution, thereby forming an integrated solidified ground.

[0085] Suspension grout can achieve higher strength than solution grout, but its large particle size makes it less permeable to fine-grained soil. However, by including solution 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 watertightness (Figure 13).

[0086] As described above, the inventors focused on the gelation of the bleeding liquid of suspension grout and studied the gelation of the bleeding liquid, the self-sustaining properties of the homogel of the bleeding liquid, and the self-sustaining properties and strength of the sand gel of the bleeding liquid. By using these results as conditions, they were able to improve the penetration and consolidation properties of suspension grout for fine-grained soil or ground containing fine-grained soil, which was previously thought to be inapplicable, and completed the present invention. Furthermore, according to the present invention, even in excavated ground, improvement effects can be achieved, enabling the excavated surface to become self-sustaining and waterproof. Therefore, the present invention can be applied not only to the reinforcement of ground as shown in Figure 14, but also to the reinforcement and waterproofing of excavated ground.

[0087] In particular, when a suspension grout containing a silica solution is used, the present invention exhibits the following effects due to the gelation of the separated silica solution from the suspension grout. These effects cannot be obtained by conventional high-pressure injection mixing methods. (1) Permeation consolidation of suspended particles into fine-grained soil where permeation consolidation was previously impossible. (2) Self-supporting effect and water-stopping effect of the cutting surface. (3) Expansion of the improvement area through permeation and solidification. (4) Ground improvement in which adjacent solidified bodies are connected and integrated. (5) Reduction of construction costs by increasing the intervals between holes drilled in the injection pipe. (6) The short-term solidification effect of the separated silica solution separated from the suspension grout improves resistance to earth pressure from adjacent structures and the back of the retaining wall, improving construction safety, safety for buried objects through infiltration injection, strengthening the ground around underground structures with spaces, waterproofing, and repairing deterioration.

[0088] An example is shown below. (Strength test) (Preparation of sand gel specimen) Using No. 6 silica sand (Figure 12) and a 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 increased when the amount of slag was reduced. In sand gels using bleeding liquid, the strength development rate was higher when the amounts of water glass and slag were greater. In addition, in cases where gypsum was used in combination, the bleeding rate decreased and the strength increased when gypsum was added.

[0089] The gelation and self-sustaining properties of the bleeding solution, as well as the strength and self-sustaining properties of the sand gel solidified by the bleeding solution, depend 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), gel time, and the particle size and density of the sand solidified by the bleeding solution. Therefore, tests were conducted to determine the minimum gelation and self-sustaining properties of the bleeding solution, as conditions that comprehensively affect these factors (Table 9). The gel time in Table 8 is the stirred gel time; since no bleeding solution was obtained, the static gel time was used. The static gel time was measured by placing 100 mL of the solution in a standard No. 8 bag (0.03 mm thick x 130 mm wide x 250 mm high). The solution was separated into a lower portion with a high concentration of suspended particles and an upper portion with a low concentration of suspended particles (the bleeding solution). The static gel time was determined when the upper portion of the lower suspended portion no longer tilted by two-thirds when slowly tilted sideways. The static gel time was shorter than the stirring gel time, and in most cases it was half the stirring gel time. When preparing the sand gels shown in Table 8, 2 or 3 L of the formulation was placed in a 3 L plastic mug, and the bleeding liquid was removed when the static gel time was half the time, and the resulting liquid was used to prepare the sand gels. As a result, it became possible to improve the ground by injection of a combined suspension and solution, solidifying the fine-grained soil parts where it was difficult for suspended particles to penetrate and solidify, or the parts that did not penetrate, using a separated silica solution separated from the suspension, and integrating the whole, provided that the bleeding solution gelled and became self-sustaining, and the sand gel into which the bleeding solution had penetrated became self-sustaining.

[0090] Whether the bleeding rate is 50% or more or less, gelation occurs, and the silica solution that separates from the suspension during injection penetrates and solidifies. The minimum strength at which the sand gel can stand on its own is 2.0 kN / m. 2 The strength of the self-standing sand gel, which was made with only 75g of slag and 100mL of No. 1 water glass per 400mL, was 15kN / 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 / m2 On the 7th day, the strength was 10 kN / m 2 (Figures 10 and 11). A similar trend was also observed with Toyoura sand. Furthermore, if salts such as Ca, Mg, and Al are included in the bleeding solution, the strength of the sand gel can be expected to increase further.

[0091] In this invention, the test specimen is adjusted to the size of the specimen used in the uniaxial compression test of soil, and the diameter D0 (mm) is usually 35 mm or 50 mm, and the height H0 (mm) is 1.8 to 2.5 times the diameter D0 (mm). As long as it is a self-standing sand gel, it can be judged at any age. Figure 10 shows the test conditions. From this, it can be seen that even in-situ sand can achieve a strength of 2.0 kN / m at an injection rate of 40%. 2 In addition, the injection rate is the ratio of the injection liquid to the volume of the ground to be improved, and 3 When the injection rate is 40%, the injection volume is 0.4 m 3 This becomes:

[0092] The gel time was shortened by increasing the amount of slaked lime added, and the strength increased with increasing the amount of slag. 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 silica colloid or water glass or both were used in combination.

[0093] (Relationship between silica concentration and strength) A neutral to alkaline solution was placed in an acrylic mold with a removable bottom and allowed to solidify. The homogel was checked for gelation and the self-supporting ability of the gel at different silica concentrations. The same procedure was also performed on the sand gel, and the solidification and self-supporting ability of the consolidated sand were checked. The results are shown in Table 9.

[0094] At silica concentrations below 0.5%, the homogel and sand gel did not become self-supporting. Further tests showed that gelation occurred even at a silica concentration of 0.25%, but the gel did not become self-supporting, and the sand gel did not solidify or become self-supporting (Table 9).

[0095] [Table 9]

[0096] In other words, simply gelling the bleeding liquid may result in neither homogels nor sand gels being self-supporting, and there are also cases where the sand gels are self-supporting even though the homogels are not. This shows that certain conditions are necessary for the homogels and sand gels to be self-supporting (Tables 8 and 9).

[0097] Furthermore, penetration tests using a one-dimensional penetration device (2m long) showed that in water glass-slag systems, the bleeding liquid gels and has the strength to stand on its own, but that when water glass is not included, the bleeding liquid does not gel. Furthermore, whether the bleeding rate is above or below 50%, the bleeding liquid gels, and the separated silica solution from the suspension penetrates and solidifies. In this case, the silica concentration of the silica solution is predicted to be 0.5w / v% or higher (Table 9).

[0098] Furthermore, penetration tests confirmed that in the case of a water glass-slag system and a suspension that does not contain water glass, the separated silica solution separated from the suspension in the case of a suspension that contains water glass penetrates and solidifies into sand that suspended particles cannot penetrate. Therefore, this separated silica solution is capable of penetrating even in ground that follows the particle size accumulation curve of the penetration and solidification of solution-type grout, and it was found that the penetration potential of solution-type silica grout can be achieved (Figure 9).

[0099] In this way, suspension grout uses fine particle silica such as slag or fly ash and solution type silica, and the separated silica solution separated from the suspension penetrates and solidifies in areas where suspended particles cannot penetrate. Therefore, we focused on the gelation of the bleeding liquid and found the following conditions under which the separated silica solution and sand gel become self-sustaining.

[0100] From the above, other preferred embodiments of the ground improvement method used in the present invention are as follows. This is a ground improvement method in which a ground injection material consisting of the above-mentioned suspension is injected into the ground through a plurality of injection holes provided in the ground, and the separated silica solution separated from the suspension of the ground injection material gels, and the resulting homogel has the strength to be self-supporting, and the sand gel formed by the penetration of the separated silica solution and solidification has the strength to be self-supporting, and the separated silica solution penetrates into parts of the ground that the suspended particles could not penetrate, expanding the solidification range, or integrating with the parts of the ground into which the suspended particles have penetrated to form a solidified body.

[0101] When the grouting material contains solution-type silica, the separated silica solution gels, and the homogel has the strength to stand on its own, and the sand gel solidified by the penetration of the separated silica solution has the strength to stand on its own, and the separated silica solution penetrates into parts of the ground that suspended particles could not penetrate, and integrates with the parts of the ground that suspended particles penetrated, forming a solidified body, and the solidified bodies of suspended particles from adjacent injection holes are connected to each other to form a large, integrated solidified body (Figure 13).In addition, adding CMC, MC, polyacrylamide, clay, etc. to this grouting solution makes it less likely to disperse in the ground and less likely to be diluted even in gravel ground.

[0102] Here, the above statement that the separated silica solution separated from the suspension 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 that the homogel does not collapse and remains self-supporting even when tilted diagonally in the mold. The sand gel is self-supporting when 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 is self-supporting and has a diameter of 5 cm and a height of 10 cm, and is prepared by a mixing method using the separated silica solution so that the relative density becomes 60%. 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.

[0103] As mentioned above, the sand gel made from the bleeding liquid of silica grout, which is made from water glass and silica particles containing calcium, increases in strength over time (Table 8). This is thought to be because the calcium ions in the silica particles continue to dissolve into the gel of the bleeding liquid over a long period of time after gelation and react with the silica, forming calcium silicate, which contributes to the increase in strength. Alternatively, the added hardener containing calcium and magnesium may react 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 hydration reaction.

[0104] Based on the above, this invention allows the penetration and consolidation range to be set by adjusting the size of the consolidation bodies, 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 consolidation, etc.). Furthermore, the penetration and consolidation range of the suspended particles and the separated silica solution can be set by adjusting the type and particle size of the silica particles in the suspension, the blending 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 13, a new concept of simultaneous combined injection of suspension and solution was created, making ground improvement using suspension grout possible.

[0105] Furthermore, according to the present invention, by using as the main ingredients of the injection materials natural or artificial silica particles, calcined silica, silica particles with natural pozzolanic properties, or fluidized soil made by turning on-site soil into a slurry, it has become possible to provide a ground improvement method that reduces the weight of the solidified body, expands the range of penetration and solidification, and contributes to the global environment by reducing CO2 emissions.

[0106] As described above, the inventors have focused on the fact that a silica-rich suspension solidified body forms around the periphery of a suspension containing solution-type silica and primarily composed of silica particles, connecting adjacent solidified bodies. While the high level of bleeding in suspensions has traditionally been considered a drawback, in this study, we focused on the fact that the separated silica solution from the suspension can penetrate between soil particles that cannot be penetrated by suspended particles, and conducted research into the gelation of the bleeding solution. As a result, we found that the gelation and strength of the bleeding solution itself, the permeability of the bleeding solution into the sand, and the strength of the sand gel significantly affect the improvement of the penetration and consolidation properties of suspension-type grout. Based on these findings, we have identified the conditions for the penetration and gelation of the separated silica solution into areas where suspended particles could not penetrate, the homogelation of the separated silica solution, and the strength of the sand gel, and have invented a new ground improvement method based on the concept of simultaneous combined injection of suspension and solution.

[0107] Furthermore, the present invention provides a ground consolidation method that uses a non-cement-based ground grouting material containing slag as its main component, thereby making it possible to obtain a solidified body with excellent durability and that is expected to have a CO2 reduction effect.

[0108] The grouting material according to the present invention has the following characteristics in particular: (1) By setting the formulation of a suspension mainly made of silica particles, which are small in particle size, lightweight, and have good fluidity, it is possible to achieve widespread penetration (Figures 5 to 7). (2) The inclusion of silica solution causes the bleeding liquid to gel, allowing the separated silica solution from the suspension to penetrate into the fine particle areas where suspended particles cannot penetrate (Figure 4, Figures 6-8), solidifying and becoming self-supporting. Since the bleeding liquid or the separated silica solution from the suspension has the same permeability as solution-type silica grout, the fine soil permeability range shown in Figure 9 can be expected. Figure 2 shows the situation in which the suspended matter solidifies and the bleeding liquid gels when a silica suspension containing silica is left standing. Figures 3 and 5 show the situation in which only the suspended matter solidifies and the bleeding liquid does not gel when a suspension containing no silica is left standing. (3) The self-sustaining properties of homogel, solidification of sand gel, and self-sustaining properties of consolidated sand at low silica concentrations of solution-type grout are shown (Table 9). (4) From the particle size distribution of the sand used in the infiltration test (Fig. 12), it can be seen that the suspended particles used in the present invention infiltrate and solidify into the sandy ground.

[0109] The particle size distribution of the sand used in the infiltration tests (Figures 4–7) was No. 6 silica sand, as shown in Figure 12. With this particle size distribution, suspended particles can penetrate between soil particles at a depth of 80 cm (Figures 6 and 7). With Toyoura sand, a finer soil, the penetration distance was approximately half that distance. Furthermore, when using the above suspension containing silica solution, the penetration range (Figure 9) was achieved, which is the same as the particle size range for the solution-type infiltration. Although the penetration distance varies depending on the soil conditions, a solidified body like that shown in Figure 13 can be formed. Figures 13(c) and (d) are plan views of the infiltration solidified body. The type and size of silica particles in the suspension can be selected depending on the soil conditions. Furthermore, the ability to infiltrate, as shown in Figure 13(d), allows for the stabilization of surrounding structures without damaging buried underground structures. Furthermore, by strengthening and waterproofing the surrounding ground, underground structures with open spaces can be strengthened.

[0110] As described above, the inventors discovered that when a suspension containing the above-mentioned suspended particles as its main component is injected, the area near the center becomes a high-strength region due to the high concentration of suspended particles, while the strength of the suspended particles decreases with distance from the center, resulting in a low-strength region (Figures 6, 7, and 13). However, outside of this, silica-rich solidified bodies form due to gelation of the separated silica solution separated from the suspension, connecting adjacent solidified bodies. While the high level of bleeding in suspensions has traditionally been considered a drawback, in this study, we focused on the fact that the separated silica solution can penetrate between soil particles that suspended particles cannot penetrate, and conducted research on the gelation of the bleeding liquid. As a result, we found that the gelation and strength of the bleeding liquid itself, the permeability of the separated silica solution into the sand, and the strength of the sand gel significantly affect the improvement of the penetration and consolidation properties of suspension grout. Based on these findings, we investigated the conditions under which the suspension not only penetrates into the surrounding ground, but also penetrates and gels into fine-grained soil areas where suspended particles cannot penetrate, enabling the formation of large solidified bodies.

[0111] In suspensions that do not contain silica solution, the bleeding liquid does not gel, and the sand that has been permeated with the solution that separates from the suspension does not stand up, nor does it obtain sufficient strength (Figures 3 and 5). However, sufficient strength cannot be obtained simply by gelling the bleeding liquid (Table 9). After examining these points, we found that the condition for the self-standing strength of the homogel and sand gel of the separated silica solution that has separated from the suspension is a silica concentration of 0.5 w / v% or more (Table 8). Based on this, we considered this to be permeation solidification using solution-type silica grout, and have invented the ground improvement method of the present invention.

[0112] Furthermore, the present invention provides a ground improvement method that can obtain a solidified body with excellent durability and is expected to have a CO2 reduction effect by using a non-cementitious ground 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.

[0113] FIG. 14 shows an example of application of the ground improvement method of the present invention. Figures 14(a)-(c) and (f) show examples of reinforcing underground structures by ground injection, with Figures 14(a), (b) and (f) showing examples of ground injection from underground space, and (c) showing injection from the ground surface. Due to their high strength and water-stopping effect, they can protect underground spaces from the impact of air raids and prevent water leakage into the underground space (Figure 13(d)). Both methods not only strengthen underground structures, but can also stop water leakage and repair cracks in deteriorated underground structures. In the examples shown in Figures 14(d) and (e), conventional suspension grouts could strengthen the soil, but they did not penetrate fine-grained soil sufficiently, making them difficult to apply because they did not provide water-stopping properties.However, the suspension of the present invention has a water-stopping effect, making such applications possible. Figure 14(f) enables strengthening of the tunnel foundation and waterproofing. Figure 14(g) shows an example of strengthening the earthquake resistance of an existing foundation by reinforcing it, or repairing a damaged foundation. Even in ground that is impermeable to suspended particles when reinforced with conventional suspension alone, the silica solution gels and integrates the solidified parts of the suspended particles, and the solidified area is expanded by the silica solution, thereby increasing the bearing capacity of the foundation. Figure 14(h) shows an example of reinforced filling of rock cracks and watertight or waste containment. Large rock cracks usually have a series of fine cracks deep inside, which are subject to water pressure. Therefore, suspension grout alone cannot penetrate the fine cracks, and solution grout alone will cause the gel to be pushed out by water pressure. Therefore, injecting either suspension grout or solution grout first will hinder the penetration of the subsequent injection. The present invention automatically enables the infiltration and consolidation process shown in Figure 9 in a single step. Therefore, the application of this invention is expected to expand beyond rock masses storing nuclear waste and other materials in shafts dug into the rock mass to include the containment of hazardous materials in ordinary soil and sand. Furthermore, Figure 13(c) can be applied to liquefaction countermeasures and the strengthening and repair of ground damaged by liquefaction. According to the ground improvement method of the present invention, the infiltration and solidification of suspended particles and silica solution can be carried out automatically while suppressing ground displacement, without causing ground uplift or ground displacement as occurs in ground strengthening methods in which a low-fluidity suspension is forcibly injected into the ground.

Claims

1. The following i) to iii) i) silica particles consisting of one or more of pyrogenic silica and natural pyrogenic silica having pozzolanic activity; ii) silica particles, wherein the pyrogenic silica is made of any one or more of slag, fly ash, cement, sewage incineration ash, plant incineration ash, and pyrogenic clay; iii) Silica particles in which the natural pyrogenic silica is composed of any one or more of loam soil, shirasu, volcanic ash, niwado and sanwado; a ground grouting material comprising a suspension containing suspended particles of any one of the silica particles as a main material and a silica solution as an active ingredient, injected into the ground through a plurality of injection holes provided in the ground, 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 to solidify the ground, thereby solidifying the ground with the suspended particles and the separated silica solution in a single step, The silica particles have a Blaine value of 4,000 to 20,000 cm ２ / g, the amount of the silica particles in the ground grouting material is 50 to 200 kg / 400 L, and silica colloid and / or water glass is used as the silica solution, When the silica solution contains water glass, the water glass has a molar ratio of 1.0 to 5.0, and the amount of water glass in the ground grouting 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 and solidifying the separated silica solution has a strength to be self-supporting, The phrase "the separated silica solution gels and the resulting homogel is self-supporting" means that the silica concentration of the separated silica solution is 0.5 w / v% or more, and the homogel is self-supporting even when tilted obliquely in a mold without collapsing; the phrase "the sand gel is 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 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 / 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, connecting the solidified bodies of the suspended particles from adjacent injection holes, and forming a solidified body in one step that consists of, from the center toward the outside, an area solidified with a high concentration suspension, an area solidified with a low concentration suspension, and an area solidified by the gelation of the separated silica solution and having water-stopping properties.

2. The ground improvement method according to claim 1, wherein the ground grouting material contains an alkaline agent consisting of one or more of the following (1) to (3): (1) An alkaline agent containing one or more of gypsum and 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 lime, cement, caustic alkali, water glass, and silica colloid as active ingredients.

3. The ground improvement method according to claim 1, wherein the suspended particles are slag, and the amount of slag mixed in the ground grouting material is 10 to 25 w / v% when cement is not used, and 10 to 30 w / v% when cement is used.

4. The ground grouting material is any one or more of microbubbles, air, a dispersant, and a thickener.

2. The ground improvement method according to claim 1, wherein the active ingredient is

5. The ground improvement method according to claim 1, wherein the ground grouting material contains a hardening agent consisting of a polyvalent metal compound, and the hardening agent is one or more of hydroxides, oxides or salts of Ca, Mg or Al, and / or gypsum.

6. 2. The ground improvement method according to claim 1, wherein a suspension grout or a quick-setting grout is injected into the ground as a primary grout prior to the injection of the ground grout material.

7. 2. The ground improvement method according to claim 1, wherein the underground structure is reinforced by injecting the ground grouting material into the periphery of the underground structure having an underground space.

8. The ground improvement method according to claim 1, which is applied to reinforcement and watertightness of excavation wall or bottom grouting.

9. 2. The ground improvement method according to claim 1, which is applied to reinforcement of rock cracks in a rock shaft, water sealing, or containment of harmful substances.

10. 2. The ground improvement method according to claim 1, which is applied to reinforcement of an existing foundation or repair of a damaged foundation.

11. 2. The ground improvement method according to claim 1, which is applied to liquefaction countermeasure works or repair of disaster-stricken ground.

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

13. 13. The ground improvement method according to claim 12, wherein the non-destructive testing is performed by elastic wave velocity logging, acoustic tomography, or surface wave exploration.

14. 2. The ground improvement method according to claim 1, wherein the separated silica solution penetrates into parts of the ground that the suspended particles could not penetrate, expanding the solidification range, or integrating with the parts of the ground into which the suspended particles have penetrated to form a solidified body.

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