Ground strengthening method

Abstract

To provide a ground strengthening method and a ground solidifying material used for the same, which can realize advantages of both by covering each disadvantage: the disadvantage of unstable strength development and the impossibility of designing to achieve a desired effect within a specified period of time in microorganism-containing grout; and the disadvantage of difficulty in penetrating fine-grained soil in a suspension-type grout which uses calcined silica such as slag or fly ash as a main ingredient and contains a hardener.SOLUTION: In a ground strengthening method, ground is solidified by using a ground solidifying material whose active ingredients are a suspension-type grout that has calcined silica as a main ingredient and contains a hardener, and a microorganism-containing grout that contains microorganisms.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a ground strengthening method and a ground consolidation material used therein, which uses a suspension grout containing calcined silica such as slag or fly ash and a hardener as active ingredients to solve the problems that it takes a long time for the effect of ground improvement using a grout using microbial metabolism (hereinafter referred to as "microorganism-containing grout") to appear, and that the improvement effect is unstable due to low strength. The present invention also makes it possible to obtain both a rapid and reliable consolidation effect of large gaps by the suspension grout and a ground consolidation effect of fine gaps by microorganisms by using a suspension grout containing calcined silica such as slag or fly ash and a hardener as active ingredients, and contributes to carbon neutrality. In addition, the present invention makes it possible to achieve a low-carbon ground improvement method by eliminating the use of cement in order to prevent global warming, which has become a national issue in recent years, and contributes to carbon neutrality.

[0002] Furthermore, the present invention solves the problem that the hardening by microorganism-containing grout has good permeability but weak strength and the period for developing strength is unclear, by the rapid high-strength hardening effect of the suspension grout mainly composed of calcined silica. Furthermore, the present invention relates to a method for preventing the hardening by microorganism-containing grout from being damaged by CO generated by the microorganism-containing grout, in which polyvalent metal compounds such as calcium and magnesium contained in the suspension grout not containing cement are reacted with CO 2 The present invention also provides a mutual effect between a suspension grout containing calcined silica such as slag or fly ash and a microorganism-containing grout, in order to prevent the problem of high alkalinity of cement inhibiting the activity of microorganisms. [Background technology]

[0003] Conventionally, there are many known injection methods for consolidating the ground using cement grout or water glass grout. However, in the case of suspension grout, these have poor permeability, and only solidify around the injection pipe, and if injected widely, the injection pressure is high, which has the disadvantage of causing ground displacement. In addition, injection materials that gel, such as water glass grout, have a narrow injection range, and are prone to ground uplift when attempting to solidify over a wide area. In addition, since there is a demand for ground improvement that does not contain cement in order to prevent global warming, which has become a national issue in recent years, the applicant has particularly used a low-alkaline consolidation material to enable a low-carbon ground improvement method that is less likely to limit microbial metabolism, thereby contributing to carbon neutrality.

[0004] In response to this, the applicant has developed a ground consolidation method in which silica compounds and microorganisms such as yeast are injected into the ground together with a nutrient source to consolidate the ground, as described in Patent Document 1, etc. However, there were problems with this method in that the consolidation strength was insufficient, strength development was slow, and strength development and improvement effects were unclear depending on the ground conditions.

[0005] The applicant has also proposed a method of culturing and using microorganisms collected on-site, as in Patent Document 3. Furthermore, the applicant has also proposed a method of collecting and culturing urease bacteria, which are calcifying bacteria present on-site, in order to obtain high strength, as in Patent Document 4. However, none of these methods solves the above-mentioned problems. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4240501 [Patent Document 2] Patent No. 4621634 [Patent Document 3] Patent No. 4709201 [Patent Document 4] Patent No. 5140879 Summary of the Invention [Problem to be solved by the invention]

[0007] As disclosed in Patent Documents 1 to 4, etc., soil consolidation methods using microorganisms have already been developed, and it is clear that the soil strength increases, but the mechanism of consolidation depends on the type of microorganism, soil conditions, and natural conditions, and the period until consolidation and the soil strength are unclear, and it is difficult to grasp the relationship between environmental conditions, soil conditions, and soil strength. Therefore, there is a problem that it is difficult to incorporate this method into liquefaction countermeasures and soil reinforcement designs.

[0008] Therefore, the object of the present invention is to provide a ground reinforcement method and a ground consolidation material used therein that can overcome the disadvantages of microorganism-containing grout, such as unstable strength development and the inability to design it to achieve the specified effect within a specified period of time, and the disadvantage of cement-free suspension-type grout, such as its difficulty in penetrating fine-grained soil, thereby enabling the realization of the advantages of both methods. [Means for solving the problem]

[0009] In order to solve the problems of unstable strength development in the microorganism-containing grout and the impossibility of designing to obtain a predetermined effect within a predetermined period, the inventors focused on the combined use of the microorganism-containing grout with a suspension-type grout that does not contain cement, which is a low-carbon grout. According to the present invention, while taking advantage of the property of obtaining a high-strength consolidation effect within a predetermined period of time in the suspension-type grout that does not contain cement, the suspension-type grout is made to play the role of a carrier of the consolidation material components of the microorganism-containing grout, and it is possible to permeate the microorganism-containing grout into fine fine-grained soil that the suspension-type grout cannot penetrate, and to gradually consolidate the ground, thereby rapidly consolidating the ground. In other words, the disadvantages of the microorganism-containing grout, which has good permeability but weak consolidation and slow and unclear strength development, and the disadvantage of the above-mentioned suspension-type grout, which can obtain high strength in a short period of time but is difficult to penetrate into fine-grained soil because of its suspension nature, are covered by each other, and a ground improvement method that can express both features has been developed.

[0010] In addition, calcium and magnesium components released from the above-mentioned suspension grout react with CO generated by the microorganism-containing grout. 2 reacts with insoluble CaCO 2 or MgCO 2 and it was found that it is possible to form a solidified body in which the two are integrated with each other.

[0011] Therefore, if the properties of the ground consolidation material developed by the inventors, which is a combination of a cement-free suspension-type grout and a microorganism-containing grout, are effectively utilized, the suspension-type grout can reliably solve the unstable strength development caused by microbial solidification, while the microorganism-containing grout can penetrate and solidify fine gaps that cannot be improved by the suspension-type grout alone.

[0012] In other words, the ground reinforcement method of the present invention is characterized by consolidating the ground using a ground consolidation material whose active ingredients are a suspension-type grout based on calcined silica such as slag and / or fly ash and containing a hardener, and a microorganism-containing grout containing microorganisms. In the present invention, the suspension grout is preferably low alkaline, and the hardener is preferably low alkaline.

[0013] In the ground reinforcement method of the present invention, the suspension grout and the microorganism-containing grout are mixed, the components of the microorganism-containing grout are retained in the suspension grout, and after the suspension grout has permeated into the ground, the microorganism-containing grout permeates into the fine-grained ground that the suspension grout was unable to permeate, and calcium carbonate and / or magnesium carbonate produced by the reaction between the suspension grout and the microorganism-containing grout can be precipitated in the ground.

[0014] Furthermore, in the ground reinforcement method of the present invention, the suspension grout is injected into the ground and allowed to penetrate, and then the microorganism-containing grout is injected into the ground, so that calcium carbonate and / or magnesium carbonate produced by a reaction between the suspension grout and the microorganism-containing grout can be precipitated in the ground.

[0015] Furthermore, in the ground reinforcement method of the present invention, the ground consolidation material can be penetrated into the ground by any one or more of the following techniques: spreading, injection, mixing, and high-pressure spraying, and calcium carbonate and / or magnesium carbonate produced by the reaction between the suspension grout and the microorganism-containing grout can be precipitated in the ground.

[0016] Furthermore, in the ground strengthening method of the present invention, it is preferable to repeatedly infiltrate the ground with the ground consolidation material by any one or more of the following techniques: scattering, injection, mixing, and high-pressure injection, thereby increasing the amount of calcium carbonate and / or magnesium carbonate precipitated in the ground.

[0017] Furthermore, in the ground strengthening method of the present invention, the injection of the suspension grout and the injection of the microorganism-containing grout into the ground are carried out simultaneously or alternately once or repeatedly a plurality of times, whereby calcium carbonate and / or magnesium carbonate produced by the reaction between the suspension grout and the microorganism-containing grout can be precipitated in the ground.

[0018] Furthermore, in the ground reinforcement method of the present invention, it is preferable that the ground consolidation material further contains a silica compound and / or a metal ion sequestering agent, and it is also preferable that it contains one or more of water glass, porozone, slag, cement and a carbonate compound.

[0019] Furthermore, in the ground strengthening method of the present invention, a mixed liquid containing a calcium compound and / or a magnesium compound as an active ingredient among the ground consolidation materials is designated as Liquid A, and other ingredients are designated as Liquid B, and calcium carbonate and / or magnesium carbonate produced by a reaction between the suspension-type grout and the microorganism-containing grout can be precipitated in the ground by any of the following procedures (1) to (3). (1) A mixture of liquid A and liquid B is allowed to permeate into the ground. (2) Either liquid A or liquid B is first infiltrated into the ground, and then the other is infiltrated. (3) Repeating either or both of the above steps (1) and (2) to allow the ground consolidation material to penetrate into the ground.

[0020] Furthermore, in the ground strengthening method of the present invention, the improvement effect due to the precipitation of calcium carbonate and / or magnesium carbonate produced by the reaction between the suspension-type grout and the microorganism-containing grout can be confirmed by a non-destructive test, and the non-destructive test can be an elastic wave velocity logging method, an acoustic tomography or a surface wave exploration.

[0021] The ground consolidation material of the present invention is used in the above-mentioned ground reinforcement method of the present invention, and is characterized in that it contains, in addition to the microorganisms, any one or more of the following (A) to (E) as active ingredients: (A) Biodegradable organic matter (B) Calcium Compound and / or Magnesium Compound (C) Soil bacteria or biodegradation bacteria (D) Nutrient source for soil bacteria or biodegradation bacteria (E) pH adjusters or pH buffers

[0022] In the ground consolidation material of the present invention, the calcium compound is preferably one or more of a salt or hydroxide of calcium, a calcium salt of an organic compound, slag, or gypsum. Effect of the Invention

[0023] According to the present invention, a ground strengthening method and a ground consolidation material used therein have been realized that can overcome the drawbacks of microorganism-containing grout and cement-free suspension-type grout and realize the advantages of both. In addition, while conventional chemical injection and cement injection have problems such as ground displacement and leakage of the injection liquid due to pressure, the present invention has the advantage that deformation of structures, ground displacement, and leakage are unlikely to occur because it can be injected at low pressure or solidified under natural flow. [Brief description of the drawings]

[0024] [Figure 1] This is a graph showing the relationship between unconfined compressive strength and S-wave velocity Vs in laboratory tests of consolidated specimens using field soil, and the relationship between calcium carbonate content and unconfined compressive strength. [Diagram 2] 1 is a graph showing an example of the relationship between the number of curing days and the shear wave velocity. [Diagram 3] This is an explanatory diagram for measuring S-wave velocity Vs and P-wave velocity Vp by installing receiving holes and transmitting holes in the consolidated zone or the zone expected to be consolidated. [Figure 4] This is an explanatory diagram for understanding the solidification range and solidification strength at the injection site. [Diagram 5] 1 is a graph showing an example of a typical growth curve for a bacterial culture. [Figure 6] 1 is a graph showing unconfined compressive strength versus permeation distance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of the present invention will be described in detail. The ground reinforcement method of the present invention involves consolidating the ground using a ground consolidation material whose active ingredients are a suspension-type grout containing calcined silica such as slag and / or fly ash as a base agent and a hardener, and a microorganism-containing grout containing microorganisms.

[0026] Here, the differences between ground consolidation using microorganism-containing grout and general injection are as follows.

[0027] (1) Since it does not involve gelation, it has excellent permeability and can solidify a wide area. (2) Since it does not involve gelation, natural infiltration is possible and ground displacement is unlikely to occur. (3) It is possible to increase ground strength over the long term. (4) The strength of the concrete can be increased by repeatedly infiltrating the grout or the components that form it, thereby increasing the amount of calcium carbonate that precipitates. (5) Calcium carbonate is extremely safe from an environmental standpoint, so it does not cause any environmental problems even in residential areas. (6) In the present invention, by using a silica compound such as water glass or silica colloid in combination, insoluble calcium silicate can be formed, which can improve the durability of calcium carbonate, the development of early strength, and the effect of increasing long-term strength. In addition, by using a phosphate compound in combination, calcium phosphate can be precipitated, which can improve durability. (7) If it were possible to use on-site microorganisms as the microorganisms in the microbial grout, rather than introducing new microorganisms into the ground from outside, this would be an extremely safe ground consolidation technology. (8) In addition to the components already described in the prior art patents, the components of the binder that forms calcium carbonate using the microorganism-containing grout can include biodegradable polymers and biodegradable grout.

[0028] On the other hand, when using a microbial ground consolidation agent to precipitate calcium carbonate in the ground and consolidate the ground, the following problems arise:

[0029] (1) Unlike ordinary injection materials, it does not gel, so it has the advantage of being less likely to cause ground displacement even if it penetrates a wide area into unstable ground. However, it takes several days to harden, so it can be easily diluted by groundwater or washed away before it can harden. (2) The ground is usually heterogeneous and often consists of large voids, rocks, fine soil and sand, and weathered bedrock, and there is a problem that the highly permeable microbial injection solution easily flows out through the large voids. (3) Permeability varies depending on the ground conditions. In the case of coarse ground, the soil is easy to permeate, but is also prone to deviation. Therefore, it is desirable to inject a primary grout into the ground in advance to homogenize it, and then permeate the solution grout. According to the applicant's research into the micro-gaps of rock mass permeability, the permeability limit of fine cement into rock mass with micro-cracks is up to 0.22 mm, and the permeability limit of silica colloid is up to 0.05 mm. Therefore, it can be considered that the permeability limit of suspension-type grout such as slag is 0.22 mm, and that microorganism-containing grout can permeate into micro-gaps of 0.05 mm or less. The permeability of suspended particles into soil particles can be determined by the already known groutability formula. (4) In the present invention, the cement-free suspension grout and the microorganism-containing grout are used in combination to obtain the required strength within a given period of time by one injection. Of course, the components can be pumped separately or repeatedly to easily and rapidly generate calcium carbonate in the ground.

[0030] In the present invention, the above-mentioned suspension grout plays a role as a carrier of the components of the microorganism-containing grout, seeps into the fine-grained soil over a long period of time, and solidifies, so that problems such as dilution by groundwater before solidification, runoff by groundwater flow, and runoff of injection liquid in heterogeneous ground can be solved. Also, the heterogeneous ground can be homogenized by roughly packing and injecting the above-mentioned suspension grout, and then the highly permeable microorganism-containing grout can be injected to achieve the injection purpose.

[0031] When conventional water glass grout is injected, once the injection material reaches its gelation time, it loses its fluidity and the pressure rises rapidly. If it is injected any further, the ground will be destroyed, weakened, or displaced. When water glass comes into contact with calcium chloride, the hardener, the calcium and silica in both liquids react instantly to produce a gel with no fluidity. This means that the injection range is narrow, and repeated injections will cause destruction or ground upheaval.

[0032] In contrast, microorganism-containing grout, which forms calcium carbonate using microorganisms, reacts very slowly and does not gel as a whole, so its fluidity is not lost. Therefore, even if it is injected as is, the entire amount does not react immediately, but permeates the ground as it is. However, if it is mixed with the above-mentioned suspension-type grout and injected, or if it is injected into ground into which the above-mentioned suspension-type grout has been injected beforehand, the reaction will proceed while the injection liquid is retained in the gaps between the soil particles in that area.

[0033] Therefore, in the present invention, the microorganism-containing grout attached to the components of the suspension grout reacts with calcium or magnesium of the suspension grout to generate CO 2 It forms calcium carbonate and / or magnesium carbonate and hardens over a long period of time, seeping into fine-grained soil, enabling integrated ground improvement for fine and coarse-grained soils. It can also harden a wide area without displacing the ground or allowing the grout to escape.

[0034] The cement-free suspension grout of the present invention is a grout containing calcined silica as a main component, together with hardeners such as hydroxides, oxides, carbonates, water glass, and alkali metal salts of calcium and magnesium as active ingredients. Calcined silica in the present invention refers to silica that has undergone a natural or artificial incineration process, such as slag, fly ash, pozzolan, paper sludge, sewage sludge incineration ash, natural aluminosilicate, minerals, volcanic ash, dip-type earth, dip-type earth, silt, white clay, tuff, diatomaceous earth, plants, and incineration ash. These are siliceous particles containing a large amount of soluble silica, and react with Ca and Mg compounds such as gypsum, slaked lime, quicklime, and magnesium oxide, suspension-type alkali agents such as cement, solution-type alkali agents such as water glass-soluble alkali, and silica colloids to form a strong solidified body through hydration bonds. In particular, it is preferable to use slag and / or fly ash as the calcined silica. Here, slag has a higher CO2 emission rate than cement during its formation. 2 The occurrence of CO2, which is a national issue today, is expected to decrease to about one-tenth of what it was before.2 The other components include cements such as Portland cement, low-alkali cement, and fly ash cement, paper sludge, clays such as bentonite, porous silica, silicas such as white carbon, clays, pozzolans, calcium aluminate, gypsum, inorganic sulfates such as sodium sulfate, mixed or melted, slag, lime, fibers, cellulose, polymeric compounds such as CMC (carboxymethyl cellulose), and polysaccharides, and these components react to form insoluble silica compounds such as calcium and magnesium. The suspension grout of the present invention may contain a calcium compound or a magnesium compound alone or in a mixture thereof as an active ingredient, or may be solidified by reaction of calcium or magnesium present in the ground with the silica compound of the suspension grout. In the present invention, it is preferable that the suspension grout is low alkaline, and it is also preferable that the hardener is low alkaline. Here, low alkaline means a pH of 12 or less.

[0035] As a specific example of the cement-free suspension grout of the present invention, Geopolymer Grout (registered trademark) (trademark registration number 6650587 by the applicant) can be used.

[0036] Furthermore, the microorganisms to be used in the microorganism-containing grout of the present invention may be any microorganism that is unlikely to have an adverse effect on the human body or the environment. For example, fermentation bacteria such as lactic acid bacteria and yeast bacteria that have traditionally been used in food, soil bacteria that are abundant in general ground, and calcifying bacteria may be used.

[0037] The applicant has aimed to develop a ground strengthening method that "consolidates the ground by forming calcium carbonate using soil bacteria present in any ground, particularly calcifying bacteria that can provide high strength." Furthermore, solidified bodies formed by calcifying bacteria have the characteristic of being stronger than solidified bodies formed by other bacteria. The calcifying bacteria in the present invention can be obtained by collecting urease bacteria present in the ground and culturing them.

[0038] Calcifying bacteria are defined in a broad sense as "bacteria that grow or cause the growth of carbonates" and are called carbonate-producing bacteria, but in a narrow sense they are also called "urease-producing microorganisms, which decompose urea to generate carbonate ions through the catalytic action of the urease enzyme produced by calcifying bacteria." Calcium carbonate is formed in the presence of a calcium source (calcium ions).

[0039] Examples of calcifying bacteria include bacteria selected from the list of genera including Bacillus, Sporosarcina, Sporolactobacillus, Clostridium, and Desulfotomaculum, among which Sporosarcina pasteurii, which is calcium tolerant and has a fast culturing rate, is preferred. Note that calcium tolerance refers to urease activity in the presence of calcium, and can be determined by, for example, examining whether the calcifying bacteria can survive in lime water or calcium chloride solution and have urease activity.

[0040] FIG. 5 shows a typical growth curve of bacterial culture. When culturing bacteria or microorganisms, a growth curve as shown in FIG. 5 is generally drawn. When cells in a stationary phase culture are transferred to fresh medium of the same composition, a change occurs in the chemical composition of the cells before they can start to grow. This period of adaptation is the lag phase. The cells then grow logarithmically, which is the period of logarithmic growth. However, the growth of a bacterial population is usually limited by the exhaustion of available nutrient sources or the accumulation of toxic metabolites, and it cannot continue to grow. The growth rate decreases and eventually stops. This period is the stationary phase. Bacterial cells placed in a non-growing state eventually begin to die due to a lack of intracellular energy stores, etc., and the number of viable cells in the bacterial population decreases. This period is the death phase.

[0041] When using calcifying bacteria as a ground grouting material, it goes without saying that it is preferable to use as many live and active bacteria as possible. Specifically, the calcifying bacteria are those in the range from the latter half of the logarithmic growth phase to the stationary phase in the growth curve of Figure 5. Therefore, in the present invention, it is preferable to grow the calcifying bacteria by culturing at the construction site until they reach this range. If the ground consolidation material is manufactured using those within the range indicated by the thick line in this figure, a high-quality ground consolidation material can be obtained.

[0042] In order to cultivate and grow calcifying bacteria, it is preferable to do so in an indoor incubator where temperature and humidity are controlled. Since the construction site is outdoors, it is directly affected by the weather and climate. Since the cultivation temperature is particularly important when culturing calcifying bacteria, it is preferable to keep the temperature of the culture solution at 20 to 37°C, even when culturing at the construction site. Therefore, it is preferable that the culture tank is equipped with a heating means that can heat the culture solution so that the temperature can be maintained within the above range even in winter, when the outside air temperature is below 20°C.

[0043] The nutrient source for the microorganisms in the microorganism-containing grout can be used to provide nutrients to microorganisms such as calcifying bacteria to survive and even grow. The nutrient source is preferably a sugar that is metabolically decomposed by microorganisms in the soil, such as monosaccharides such as glucose and fructose, disaccharides such as sucrose, maltose or galactose, other oligosaccharides, polysaccharides such as starch and maltodextrin, other sugars, organic matter, salts, and phosphate compounds for pH adjustment. Among them, it is preferable to use glucose or sucrose, which are easily metabolized by a wide range of microorganisms. Since the metabolic rate varies depending on the microorganism or the nutrient source, it is necessary to select appropriately depending on the ground to be constructed.

[0044] Urea is (NH 2 ) 2 It is made of CO and produces carbonate ions when hydrolyzed, so it is used as a carbonate ion source. Commercially available urea media is one example.

[0045] The hydrolysis of urea by calcifying bacteria and the calcification (formation of calcium carbonate) caused by the reaction of the carbonate ions produced by this hydrolysis with calcium ions from a calcium source (calcium chloride) can be expressed by the following equation.

[0046] JPEG2025085128000001.jpg60164

[0047] The alkaline earth metal compound that forms an insoluble salt with the microorganism-containing grout is one or more selected from the group consisting of chlorides of alkaline earth metals, fine lime, and fine cement, and is preferably a water-soluble compound, specifically, a calcium compound and a magnesium compound. Examples of calcium and magnesium compounds include salts, oxides, hydroxides, chlorides, cement, and gypsum of calcium and magnesium, and among these, calcium chloride, calcium hydroxide, and magnesium carbonate compounds that form calcium carbonate and magnesium carbonate are particularly preferred.

[0048] Calcium carbonate has three different crystal forms (calcite, aragonite, and vaterite). Calcite usually precipitates from calcium carbonate solutions at room temperature and pressure. 2+ When a small amount of calcium carbonate or a certain type of organic component is added to the solution, aragonite and vaterite are precipitated. Since aragonite and vaterite have a significant directional property when the crystals grow, if the crystal morphology of calcium carbonate can be controlled, it may be possible to relatively freely control the anisotropy of the mechanical and hydraulic properties of the ground.

[0049] Further, examples of the preferable water-soluble compounds include fine lime, fine cement, gypsum, and aluminum compounds, each of which contains a calcium salt or a hydroxide of calcium. The fine lime, fine cement, and alkaline earth metals are those having an average particle size of 10 μm or less and a specific surface area of ​​4000 cm 2 / g or more is preferable. These alkaline earth metal compounds are used alone or in combination of two or more. The concentration of the alkaline earth metal compound is not particularly limited, but is preferably 1 to 30 wt %.

[0050] In particular, calcium compounds such as slaked lime, slag, cement hydrate, calcium chloride, calcium hydroxide, calcium acetate, and calcium saccharose are preferably used as calcium sources. For example, a culture solution containing proliferated calcifying bacteria can be mixed with a calcium source and used as a microorganism-containing grout.

[0051] The precipitation of calcium carbonate and / or magnesium carbonate in the ground in the present invention can be achieved by infiltrating the ground with a ground consolidation material by any one or more of the following methods: scattering, injection, mixing, and high-pressure injection. Natural infiltration or pumping may be used. It is also possible to increase the amount of calcium carbonate and / or magnesium carbonate precipitated in the ground and strengthen the ground by repeating the infiltration of the ground with any one or more of the following methods: scattering, injection, mixing, and high-pressure injection. Furthermore, calcium carbonate and / or magnesium carbonate can be precipitated by mixing any one or a mixture of the components of the ground consolidation material with the on-site ground or by injecting it into the ground from the foundation of a structure or an earth retaining structure.

[0052] The microorganism-containing grout of the present invention may be a liquid mixture containing powders such as white carbon, silica fume, clay, etc., which allows the powders to remain in the gaps in the ground, allowing the microorganism-containing grout to gradually penetrate into the fine-grained soil and solidify.

[0053] The hardened material containing calcium carbonate and / or magnesium carbonate as the main component obtained as described above is a completely non-polluting hardened material that does not elute alkali or acids. It is almost neutral, but over the long term artificially forms the crystal structure seen in limestone caves. Therefore, by devising the mixture and construction method, it is possible to promote the strength and the rate of formation of the crystal structure. In the present invention, the formation of the crystal structure is further promoted by heating the aqueous solution of the above-mentioned binder, and the strength increase can be accelerated.

[0054] Specifically, for example, Biogrout (registered trademark) (trademark registration number 4979671 by the applicant) can be used as the microorganism-containing grout in the present invention.

[0055] In the ground reinforcing method of the present invention, the durability and consolidation strength can be improved by using a silica compound and / or a sequestering material in addition to the ground consolidation material.

[0056] Examples of silica compounds include water glass, active silica obtained by removing alkali from water glass using ion exchange resin or ion exchange membrane, active silica obtained by removing acid radicals and alkali metals from acidic water glass obtained by removing alkali from water glass using ion exchange resin or ion exchange membrane, colloidal silica obtained by concentrating and granulating active silica, and silica colloids made of metal silicon. There are also silica colloids derived from geothermal water. Alternatively, silica solutions obtained by mixing water glass with these may be used. By using these, gelation can be ensured. Furthermore, the time required for gelation can be shortened by adding a small amount of acid to water glass to form a colloid. Furthermore, grouts in which fine particles of air bubbles are mixed in water or a silica solution, such as microbubble grout, can also be used. Furthermore, active silica can be stabilized with water glass or caustic soda, left for one week, aged, and formed into a colloid. Since colloids are less alkaline than water glass, when the colloids, slag, and cement amount are less than half the amount of the slag, the mixture becomes less alkaline and can be used in the present invention.

[0057] Calcium carbonate is easily dissolved by acidic liquids, but produces insoluble calcium phosphate such as phosphate compounds. If an organic sequestering material is used as the sequestering material, it reacts with soil bacteria to produce carbon dioxide gas to form calcium carbonate, and the calcium reacts with the sequestering material to form an insoluble salt of the organic compound. This insoluble salt is insoluble in acid, and therefore has excellent durability. In addition, by using an inorganic sequestering material in combination, an insoluble salt is formed in which the carbonate is less soluble in acids such as acid rain. Inorganic sequestering materials such as phosphate compounds have the same effect.

[0058] Examples of sequestering agents include condensed phosphates such as tetrapolyphosphate, hexametaphosphate (particularly sodium salt is preferred), tripolyphosphate, pyrophosphate, acid hexametaphosphate, acid pyrophosphate, ethylenediaminetetraacetic acid, nitrilotriacetic acid, gluconic acid, tartaric acid, citric acid, and salts thereof, and from a practical standpoint, condensed phosphates are preferred.

[0059] Examples of the phosphoric acid compound include phosphoric acid, various acidic phosphates, neutral phosphates, and basic phosphates.

[0060] The above-mentioned sequestering agent and phosphate compound can be used either alone or together. They may be injected into the ground together with a calcium source or separately to react with calcium carbonate in the ground. They may also be used in combination with water glass. In this case, when the sequestering agent is a condensed phosphate, the total amount or the amount of each of them is the same as the Na content of the water glass. 2 The content of phosphorus (P) is preferably in the range of about 1 to 30% relative to the amount of O. When the sequestering agent is a compound that does not contain phosphorus, such as the above-mentioned ethylenediaminetetraacetic acid, the content of this compound is preferably in the range of about 1 to 30% relative to the amount of Na in the water glass. 2 It is preferably in the range of about 3 to 50% with respect to the amount of O. If these contents exceed the above-mentioned upper limits, partial gelation of the water glass occurs or the water glass becomes cloudy and unstable, making it difficult to completely dissolve the sequestering agent and phosphate compound and maintain a stable state.

[0061] Furthermore, in the ground reinforcing method of the present invention, the ground consolidation material may further include any one or more of water glass, porazon, slag, cement and a carbonate compound.

[0062] Furthermore, in the ground strengthening method of the present invention, carbonate, carbonated water, carbon dioxide gas or oxygen can be further used as the ground consolidation material. The metabolic action of the microorganisms and the gelation time of the silica compound can be adjusted.

[0063] Specifically, in the ground strengthening method of the present invention, the suspension grout and the microorganism-containing grout are mixed and injected into the ground, or the suspension grout is injected into the ground first, and then the microorganism-containing grout is injected into the area that could not be penetrated by the suspension grout, thereby solidifying the ground. Both methods are characterized by the fact that they solidify by themselves. The solidification of both methods is caused by the calcium and magnesium eluted from the suspension grout and the CO generated by the microorganism-containing grout. 2 The microorganism-containing grout reacts with the ground and solidifies as a carbonate of calcium or magnesium. Alternatively, the microorganism-containing grout may contain calcium or magnesium, or may solidify due to calcium or magnesium contained in the ground. Furthermore, the microorganism-containing grout may be injected prior to the injection of the suspension-type grout. When a suspension grout is mixed with a microorganism-containing grout, the suspension grout itself is low alkaline (pH 12 or less), and it is possible to adjust the pH of the suspension grout and the microorganism-containing grout to be low alkaline or less, that is, closer to neutral. When the microorganism-containing grout is injected after the suspension grout, a mixture can be selected that shifts the suspension grout's low alkaline to a neutral state, making it an injection material with better environmental performance. Also, low alkaline has a favorable effect on the metabolic activity of microorganisms.

[0064] Furthermore, the injection of the ground consolidation material or a plurality of components of the ground consolidation material into the ground can be performed simultaneously, alternately, or repeatedly to precipitate calcium carbonate and / or magnesium carbonate in the ground, but high-strength ground improvement can be achieved by a single injection by mixing the microorganism-containing grout with the suspension-type grout or by simultaneously injecting them. Also, when the composition contains a magnesium compound in addition to the calcium compound, calcium carbonate or dolomite can be precipitated.

[0065] For example, a suspension grout and a microorganism-containing grout can be mixed, the components of the microorganism-containing grout can be retained in the suspension grout, and after the suspension grout has permeated into the ground, the microorganism-containing grout can permeate into fine-grained ground that the suspension grout has not been able to permeate, and calcium carbonate and / or magnesium carbonate produced by the reaction between the suspension grout and the microorganism-containing grout can be precipitated in the ground.

[0066] In addition, after injecting a suspension grout into the ground and allowing it to penetrate, a microorganism-containing grout can be injected into the ground, and calcium carbonate and / or magnesium carbonate produced by a reaction between the suspension grout and the microorganism-containing grout can be precipitated in the ground.

[0067] Furthermore, by simultaneously or alternately injecting the suspension grout and the microorganism-containing grout into the ground once or repeatedly a plurality of times, calcium carbonate and / or magnesium carbonate produced by the reaction between the suspension grout and the microorganism-containing grout can be precipitated in the ground.

[0068] Furthermore, calcium carbonate and / or magnesium carbonate produced by the reaction between the suspension grout and the microorganism-containing grout can be precipitated in the ground by any of the procedures (1) to (3) below, with the suspension grout as the A liquid and a component of the microorganism-containing grout as the B liquid, or with a mixed liquid of the ground consolidation material containing a calcium compound and / or a magnesium compound as an active ingredient as the A liquid and the other component as the B liquid, or with any of the components of the suspension grout and the microorganism-containing grout as the A liquid and the other component as the B liquid. (1) A mixture of liquid A and liquid B is allowed to seep into the ground. (2) Either liquid A or liquid B is first allowed to seep into the ground, and then the other is allowed to seep into the ground. (3) Repeat either or both of (1) and (2) above to allow the ground consolidation material to penetrate into the ground.

[0069] Furthermore, by simultaneously injecting the microorganism-containing grout and organic matter, or by injecting organic matter into the ground when construction is performed in a ground where many microorganisms exist, it is possible to adjust the respiration and metabolism of the microorganisms, i.e., the amount of carbon dioxide generated, and promote or regulate the gelation of the silica compound. Also, by simultaneously injecting gases such as carbon dioxide and oxygen, it is possible to adjust the metabolic rate of the microorganisms and promote or regulate the gelation.

[0070] The gelation time can be adjusted by adding a gelation accelerator or regulator for the silica compound that has little effect on microorganisms. Examples include inorganic salts such as potassium chloride and sodium chloride, and trace amounts of acids and organic salts. In addition, by adding polyvalent metal compounds such as calcium compounds and magnesium compounds, the carbon dioxide gas released by the metabolism of the microorganisms reacts with the polyvalent metal compound to form an insoluble polyvalent metal carbonate, which not only adjusts the gelation time of the silica compound but also increases the strength of the solidified product. As the polyvalent metal compound, one or more types selected from the group consisting of calcium salts such as calcium chloride, polyvalent metal salts such as magnesium chloride, calcium hydroxide, fine lime, fine cement, fine slag, gypsum, and calcium carbonate can be used. Calcium and lime from shells and the like contained in the ground also affect the reaction. In addition, since it is necessary to adjust the pH to a level at which the microorganisms are activated, a small amount of a pH regulator may be used. Furthermore, as gelation regulators, for example, alkali metal bicarbonates, carbonates, phosphates, acid phosphates, pyrophosphates, citric acid, tartaric acid, sodium ligninsulfonate, sodium polysulfonate, etc., are effective as retarders. Carboxylate salts (oxycarboxylic acid, polyhydroxycarboxylic acid, etc.), gluconates (sodium gluconate, etc.), chelating agents (polyol compounds, etc.), other acids, salts, alkalis, etc. can also be used to regulate gelation.

[0071] When microorganisms, organic matter as a nutrient source for the microorganisms, and alkaline earth metal compounds are introduced into calcium-containing soil, the alkaline earth metals in the soil react and consolidate the soil. As shown in the following formula, the microorganisms produce carbon dioxide from organic nutrient sources during their metabolic activity.

[0072] JPEG2025085128000002.jpg24165

[0073] At this time, the calcium dissolved in the soil or the calcium injected into the ground reacts with the carbon dioxide produced by the microorganisms, precipitating and depositing calcium carbonate between the soil particles as shown in the following formula, hardening the ground.

[0074] JPEG2025085128000003.jpg12164

[0075] Therefore, in ground containing calcium, by injecting microorganisms into the ground, the carbon dioxide emitted by the microorganisms causes calcium in the ground to precipitate, thereby solidifying the ground. Furthermore, by injecting organic nutrient sources, the metabolic rate of the microorganisms changes depending on the type and amount of the organic nutrient sources, and the amount of calcium salts precipitated changes with the change in the amount of carbon dioxide emitted, so the hardening time and strength of the ground can be adjusted. When the amount of calcium dissolved in the ground is small or when improving the ground to a high strength, an alkaline earth metal compound can also be injected into the ground to increase the amount of calcium salts precipitated.

[0076] In addition, in soil containing many microorganisms, the metabolism of the microorganisms in the soil can be adjusted with organic nutrient sources, which react with the calcium in the soil or the calcium injected to precipitate calcium salts. In this case, soil containing calcium refers to seashells, limestone, etc., present in the soil, or dissolved calcium ions present in the soil.

[0077] (Test Example) Examples of materials used in each mix shown in the following Tables 1 to 5 are shown below. Examples 1, 2, and 4 show the composition of suspension-type grout, and Examples 3 and 5 show the composition of microorganism-containing grout. Magnesium oxide: specific gravity 3.65, No. 3 water glass: specific gravity 1.41, silica concentration 29 w / w%, molar ratio 2.9, No. 1 water glass: specific gravity 1.35, silica concentration 21 w / w%, molar ratio 2.0, Colloidal silica: specific gravity 1.21, silica concentration 30w / w%, Slaked lime: specific gravity 2.5, Slag: specific gravity 2.9, Blaine value 8000, Gypsum: specific gravity 2.16, Yeast: Nisshin Foods Co., Ltd., Nisshin Super Camellia, Glucose: A source of nutrition

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] [Table 4]

[0082] [Table 5]

[0083] In addition, when a silica solution is used in the microorganism-containing grout, water glass may be used instead of colloidal silica, or a silica compound may be used. It may be appropriately diluted with water. The ratio of the materials used may also be appropriately changed.

[0084] Example 1 is a formulation that solidified after a gel time of 200 minutes. Example 2 is a formulation that solidified after a gel time of 50 minutes. Example 3 is a mixture using a microorganism-containing grout. Since this is not an injection material that hardens entirely like an injection material containing silica, it was not possible to measure the gel time, but precipitation occurred within a few minutes. Example 4 is a formulation that solidified after a gel time of 75 minutes. Example 5 is a mix that solidified in a gel time of 1000 minutes. Example 5 can also be used instead of Example 3. In this case, a mix that shifts the low alkalinity of the suspension grout to the neutral side can be selected, resulting in a more environmentally friendly injection material.

[0085] (Test 1) 1. Test Method For the soil infiltration test, a 100 cm plastic mold was filled with 90 cm of No. 6 silica sand (relative density 60%, permeability coefficient = 1.5 × 10 -2 The injection device was then saturated with water.

[0086] Next, the mixture of Example 1 was infiltrated from the bottom of the mold. In addition, the mixture of Example 1 was infiltrated into the other mold, and then the mixture of Example 3 was infiltrated. On the 28th day, each mold was cut into 10 cm pieces, and the unconfined compressive strength was measured. The results are shown in Table 6 and FIG. 6.

[0087] [Table 6]

[0088] (Example of manufacturing microorganism-containing grout) First, the calcifying bacteria were cultured and grown in a culture medium. Cultivation and growth was carried out by adding 100 liters of sterile water containing 1 g heptone, 1 g glucose, 5 g sodium chloride, 1.2 g disodium hydrogen phosphate, and 0.8 g potassium dihydrogen phosphate per liter as nutrient sources to a culture tank, stirring with a stirring blade, and then adding 5 ml / liter of 40% urea solution and 1 g / liter of S. pasteuri as the calcifying bacteria, and stirring for 48 hours. The temperature was adjusted to a range of 25 to 35°C during the cultivation and growth. In this way, a culture medium was obtained.

[0089] Then, 2000 g of calcium acetate was added as a calcium source and stirred to obtain a microorganism-containing grout.

[0090] The obtained microorganism-containing grout was injected into the ground repeatedly 10 times, and the test results shown in Figures 1, 2, and 4 were obtained.

[0091] The improvement effect of the precipitation of calcium carbonate and / or magnesium carbonate in the ground strengthening method of the present invention can be confirmed by non-destructive testing, such as elastic wave velocity logging, acoustic tomography, or surface wave exploration.

[0092] Since the ground strengthening method of the present invention has the following characteristics related to strength and permeability, elastic wave velocity logging is extremely effective in understanding the effects of the ground improvement method according to the present invention.

[0093] (Relationship between uniaxial compressive strength and elastic wave velocity using bender elements) The specific explanation is as follows. Figure 1 shows the relationship between the unconfined compressive strength (28-day strength) and the S-wave velocity measured by the bender element method for Toyoura sand specimens consolidated by the ground reinforcement method of the present invention. Figure 2 shows an example of the relationship between the number of curing days and the shear wave velocity.

[0094] 3 is an explanatory diagram showing how to measure the S-wave velocity Vs and the P-wave velocity Vp by installing a receiving hole and a transmitting hole in the consolidated zone or the zone to be consolidated. The S-wave velocity Vs and the P-wave velocity Vp may be measured by using the injection hole as the receiving hole and the transmitting hole.

[0095] In laboratory tests, the S-wave velocity Vs and P-wave velocity Vp are measured using the bender element method, with transmitter and receiver elements installed at both ends of a solidified specimen, but in-situ, the S-wave velocity Vs and P-wave velocity Vp are measured using surface wave exploration and velocity logging.

[0096] The ground strengthening method of the present invention has the advantage that the improvement effect can be estimated by knowing the amount of calcium carbonate and the S-wave velocity Vs and P-wave velocity Vp, since the strength is determined almost uniquely by the amount of calcium carbonate and / or magnesium carbonate formed.

[0097] Figure 4 shows the relationship between unconfined compressive strength and S-wave velocity Vs in laboratory tests on consolidated specimens using field soil, and the relationship between calcium carbonate content and unconfined compressive strength. The measured values ​​of S-wave velocity at points A and B in the injected ground were plotted. From these results, the unconfined compressive strength at points A and B can be estimated. The amount of calcium carbonate at those points can also be estimated.

[0098] In this way, the extent and strength of solidification at the injection site can be grasped. In the example of Figure 4, it can be seen that the target S-wave velocity Vs is met at points A and B, and therefore the design Vs is met.

[0099] Furthermore, in laboratory tests, if the relationship between the calcium carbonate filling rate and content and the S-wave and P-wave velocities is determined, the amount of filling and the composition of the ground can be determined from the measured values ​​of S-wave and P-wave velocities at the site. Using this device, a calcium hydroxide solution (50g / liter) was injected once, followed by three repeated injections of the microorganism-containing grout. Figure 6 shows the unconfined compressive strength as a function of the permeation distance. From the results of this unconfined compression test, as shown in Figure 1, the shear wave velocity of the solidified material at each permeation distance can be determined. Also, the amount of calcium carbonate filled in the ground can be determined.

[0100] Furthermore, the results of non-destructive testing can be useful in analyzing the results of non-destructive testing by comparing the penetration test values ​​of the injected ground before and after injection, and the strength test values ​​of the specimen obtained by core sampling with the estimated shear wave velocity and strength at that point (Figure 4).

[0101] Furthermore, if the receiver and transmitter are installed before injection (Fig. 3), the seepage situation in the ground can be grasped in real time during injection, and the injection amount and the amount of calcium source and microorganism-containing grout can be corrected in real time. By non-destructively measuring the S-wave velocity and P-wave velocity that change with curing, it is possible to determine whether the desired improvement effect has been achieved.

[0102] As described above, the flow characteristics, injection design, and injection effects of the ground consolidation material of the present invention can be understood and used for design purposes.

[0103] The construction sites to which the present invention is suitable include ground that requires liquefaction countermeasures, ground that requires water stoppage, and soft ground that requires increased strength, and by using the ground strengthening method of the present invention, it is possible to obtain the effect that less equipment is required and ground improvement can be easily performed compared to conventional injection methods. The injection of the ground consolidation material can be performed using conventional ground injection technology and is not particularly limited.

Claims

1. A ground reinforcement method characterized by consolidating the ground using a ground consolidation material whose active ingredients are a suspension-type grout based on calcined silica and containing a hardener, and a microorganism-containing grout containing microorganisms.

2. 2. The method for reinforcing ground according to claim 1, wherein the calcined silica is slag and / or fly ash.

3. 2. The ground reinforcement method according to claim 1, wherein the suspension grout and the microorganism-containing grout are mixed, the components of the microorganism-containing grout are retained in the suspension grout, and after the suspension grout has permeated into the ground, the microorganism-containing grout permeates into fine-grained ground that has not been completely permeated by the suspension grout, and calcium carbonate and / or magnesium carbonate produced by a reaction between the suspension grout and the microorganism-containing grout are precipitated in the ground.

4. 2. The ground reinforcement method according to claim 1, wherein the suspension grout is injected into the ground and allowed to penetrate, and then the microorganism-containing grout is injected into the ground, and calcium carbonate and / or magnesium carbonate produced by a reaction between the suspension grout and the microorganism-containing grout is precipitated in the ground.

5. 2. The method for reinforcing ground according to claim 1, wherein the suspension grout has a low alkaline property.

6. 2. The method for reinforcing ground according to claim 1, wherein the hardening agent has low alkaline properties.

7. 2. The ground reinforcement method according to claim 1, wherein the ground consolidation material is infiltrated into the ground by any one or more of the following methods: scattering, injection, mixing, and high-pressure injection, and calcium carbonate and / or magnesium carbonate produced by a reaction between the suspension grout and the microorganism-containing grout is precipitated in the ground.

8. 8. The ground reinforcement method according to claim 7, further comprising repeatedly penetrating the ground with the ground consolidation material by any one or more of the following techniques: scattering, injection, mixing, and high-pressure injection, thereby increasing the amount of calcium carbonate and / or magnesium carbonate precipitated in the ground.

9. 2. The ground reinforcement method according to claim 1, wherein the injection of the suspension grout and the injection of the microorganism-containing grout into the ground are carried out simultaneously or alternately once or multiple times, thereby causing calcium carbonate and / or magnesium carbonate produced by a reaction between the suspension grout and the microorganism-containing grout to precipitate in the ground.

10. 2. The ground reinforcement method according to claim 1, wherein the ground consolidation material further contains a silica compound and / or a sequestering agent.

11. 2. The method according to claim 1, wherein the ground consolidation material further comprises one or more of water glass, porazon, slag, cement and a carbonate compound.

12. The ground strengthening method according to claim 1, wherein the ground consolidation material is a mixture liquid containing a calcium compound and / or a magnesium compound as an active ingredient as liquid A, and other ingredients as liquid B, and calcium carbonate and / or magnesium carbonate produced by a reaction between the suspension grout and the microorganism-containing grout is precipitated in the ground by any of the following procedures (1) to (3). (1) A mixture of liquid A and liquid B is allowed to permeate into the ground. (2) Either liquid A or liquid B is first infiltrated into the ground, and then the other is infiltrated. (3) Repeating either or both of the above steps (1) and (2) to allow the ground consolidation material to permeate into the ground.

13. 2. The method of claim 1, wherein the improvement effect due to precipitation of calcium carbonate and / or magnesium carbonate produced by the reaction between the suspension-type grout and the microorganism-containing grout is confirmed by a non-destructive test.

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

15. A ground consolidation material used in the ground reinforcement method according to any one of claims 1 to 11, characterized in that in addition to the microorganism, any one or more of the following (A) to (E) are contained as active ingredients. (A) Biodegradable organic matter (B) Calcium Compound and / or Magnesium Compound (C) Soil bacteria or biodegradation bacteria (D) Nutrient source for soil bacteria or biodegradation bacteria (E) pH adjuster or pH buffer

16. 16. The ground consolidation material according to claim 15, wherein the calcium compound is any one or more of a salt or hydroxide of calcium, a calcium salt of an organic compound, slag, or gypsum.

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