Method for confirming ground improvement effect, ground improvement method, and ground improvement construction method

Abstract

To provide a method for confirming the improvement effect of the improved ground formed by injecting a chemical that forms an organic polymer into the ground so that the improvement effect can be efficiently grasped without turbulence of the sample or the ground condition before the ground improvement when the chemical is injected into the ground to improve reinforcement, etc., and a ground improvement method and a ground improvement work method using this confirmation method.SOLUTION: A method of confirming the effect of improving the ground on which an organic polymer is formed after use by using a chemical containing at least one of a metal element and a carbon element comprises a step of quantitatively analyzing the content of at least one of metal and carbon in the soil collected from the ground before injecting the chemical and the improved ground after injecting the chemical into the ground.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for confirming the improvement effect of ground after injecting a chemical agent into the ground, and a ground improvement method and a ground improvement construction method using the method.

Background Art

[0002] Conventionally, injecting a chemical agent into the ground to improve it when the ground is soft or the like has been widely practiced. For example, in an area with relatively rich groundwater such as a landfill site, when an earthquake occurs, the ground may liquefy. Therefore, for the soil of soft ground, chemicals for various purposes are selected and used from temporary reinforcement to permanent reinforcement.

[0003] After injecting a chemical agent into the ground, it is common to confirm its effect. For example, there is a method of measuring the compressive strength of a sample taken by boring the improved ground. In addition, the following techniques are known as confirmation methods other than the above. Patent Document 1 discloses a method for evaluating the effect of chemical solution injection by comparing the reflection intensity data obtained by borehole television viewer (BHTV) logging performed before injecting the chemical solution and the reflection intensity data obtained by borehole television viewer (BHTV) logging performed after injecting the chemical solution in one drilled hole. Patent Document 2 measures the resistivity value of the ground before improvement by chemical solution injection by EM exploration or the like, measures the resistivity value of the improved ground after a predetermined number of days have passed after chemical solution injection by the same method, and collects a plurality of samples of the chemical solution injection ground to measure the liquefaction strength and resistivity value of the chemical solution injection ground indoors. Then, a correlation relationship between the liquefaction strength and the resistivity value is obtained, a resistivity value corresponding to the required liquefaction strength is set, and from the resistivity value of the ground after a predetermined number of days have passed after chemical solution injection, a range below the resistivity value corresponding to the required liquefaction strength is evaluated as the shape of the chemical solution injection ground, and a method for confirming the shape of the ground improved by chemical solution injection is disclosed. In addition, Patent Document 3 discloses a method for confirming the ground improvement effect by injecting a chemical solution of a solution-type silica grout. The measured value of the silica content per unit volume of a specimen prepared with an injection rate of 100% using sand collected from the ground before chemical solution injection is designated as (A), and the measured value of the silica content per unit volume of consolidated soil collected on-site from the improved ground after chemical solution injection is designated as (B). A method for confirming the ground improvement effect is characterized by obtaining the injection rate λ [percent] of the improved ground from B / A×100.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of the technologies of Patent Documents 1 and 2, data can be collected over a wide range without boring the improved ground formed by injecting a chemical agent into soft ground. However, due to the influence of non-uniformity and disturbance of the improved ground layer, variations in ground strength values may occur. In addition, the technology of Patent Document 3 is a method for confirming the ground improvement effect when using a solution-type silica grout as a chemical agent. However, a method for confirming the ground improvement effect when using a chemical agent containing an organic polymer is not known. When attempting to measure the compressive strength of a sample by boring into improved ground, the collected sample may be disturbed or cracked, and clay or silt contained in the ground before improvement may be partially mixed in, preventing the chemical agent from being successfully injected and making it impossible to measure the compressive strength, so the effect of ground improvement may not be fully confirmed. An object of the present invention is to efficiently grasp the improvement effect of improved ground formed by injecting a chemical agent that forms an organic polymer into the ground, without being affected by the disturbance of the sample or the ground conditions before ground improvement, and to provide a method for confirming the ground improvement effect, as well as a ground improvement method and a ground improvement construction method using this confirmation method.

Means for Solving the Problems

[0006] The present invention is as follows. 1. A method for confirming the improvement effect of ground in which a chemical agent containing at least one of a metal element and a carbon element is injected into the ground and an organic polymer is formed after injection, comprising a step of quantitatively analyzing the content of at least one of metal and carbon with respect to soil collected from the ground before injecting the chemical agent and improved ground after injecting the chemical agent into the ground. A method for confirming the improvement effect of ground, characterized by this. 2. The method for confirming the improvement effect of ground according to item 1 above, wherein the metal element is at least one selected from Al, Mg, Zr, Ca, Ag, Cu, and Fe. 3. The method for confirming the improvement effect of ground according to item 1 or 2 above, wherein the chemical agent contains Al, Mg, and C. 4. The method for confirming the improvement effect of ground according to any one of items 1 to 3 above, wherein in the quantitative analysis, a liquid obtained by treating the soil or the improved ground with an acidic aqueous solution is used. 5. The method for confirming the improvement effect of ground according to item 4 above, wherein the pH of the acidic aqueous solution is 2 or less. 6. The method for confirming the improvement effect of ground according to any one of items 1 to 5 above, wherein the organic polymer is at least one selected from an acrylic polymer, an acrylamide polymer, polyvinyl alcohol, and a urethane polymer. 7. A ground improvement method comprising a confirmation step based on the ground improvement effect confirmation method according to any one of the above items 1 to 6. 8. A ground improvement construction method comprising a confirmation step based on the ground improvement effect confirmation method according to any one of the above items 1 to 6.

Advantages of the Invention

[0007] According to the present invention, by taking measures for the soil collected from the ground that requires reinforcement or the like, the improvement effect of the chemical agent can be efficiently grasped without being affected by the disturbance of the sample and the ground conditions before ground improvement for the improved ground formed by injecting the chemical agent. Using the ground improvement effect confirmation method of the present invention, the ground improvement method and the ground improvement construction method can be smoothly advanced. In particular, it is suitable for mountain tunnel construction methods or their auxiliary construction methods (advance construction methods, various reinforcement construction methods), in-situ consolidation construction methods, water stop construction methods, permeation solidification treatment construction methods, jet grouting construction methods, etc.

Brief Description of the Drawings

[0008]

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MODE FOR CARRYING OUT THE INVENTION

[0009] In this specification, “(meth)acryl” means acrylic and / or methacrylic, “(meth)acrylate” means acrylate and / or methacrylate, and (meth)acrylamide means acrylamide and / or methacrylamide.

[0010] The method for confirming the ground improvement effect of the present invention is a method that can efficiently grasp the improvement effect of the improved ground formed by injecting a chemical agent that contains at least one of a metal element and a carbon element and forms an organic polymer into the ground for improvement such as reinforcement, without being affected by the disturbance of the sample and the ground conditions before the ground improvement. It includes a step of quantitatively analyzing the content of at least one of metal and carbon with respect to the soil collected from the ground before injecting the chemical agent and the improved ground after injecting the chemical agent into the ground (hereinafter referred to as the "quantitative analysis step").

[0011] In the present invention, the specific method for confirming the ground improvement effect will be described in detail later, but it is as follows. That is, after collecting the soil of the ground that requires injection of the chemical agent and performing elemental analysis on it, usually, a plurality of types of chemical agents composed of an aqueous composition and prepared so that the concentrations of specific components are different are mixed with the collected soil, and at least one of metal and carbon in the plurality of types of mixtures (corresponding to the improved ground) is quantitatively analyzed (quantitative analysis step). Next, a graph representing the relationship between the concentration of the above specific component and the quantitative analysis value is created, and on the other hand, a graph representing the relationship between the concentration of the above specific component and the theoretical value is created, and the region with correlation is grasped in each linear graph. Since chemical agents within the concentration range with correlation can be used, when measuring the physical properties such as strength for the plurality of types of mixtures obtained using these chemical agents and the above soil, a graph representing the relationship between the concentration of the specific component and the physical property value can be obtained. The chemical agent to be injected into the ground is usually a specific type of chemical agent, that is, a chemical agent with a known concentration selected from the concentration range with correlation of the above specific component. Therefore, the performance (physical property value) exhibited by the improved ground can be grasped from the above graph. That is, the effect of the improved ground formed by injecting the chemical agent can be grasped.

[0012] First, the chemical agent to be used will be described. The above chemical agent is used for purposes such as leakage prevention, water stoppage, liquefaction suppression, and ground strengthening (reinforcement). It may consist of a single component, but usually consists of a plurality of components.

[0013] The metal element contained in the above agent is not particularly limited, but a metal element having a polyvalent charge in water with an atomic number is preferred, and it is particularly preferred that it is at least one selected from Al, Mg, Zr, Ca, Ag, Cu, and Fe. The above agent preferably contains both a metal element and a carbon element, and particularly preferably contains Al, Mg, and C. In this case, the molar ratio of all metal elements and carbon elements (metal element / carbon element) is preferably 0.01 to 100, more preferably 0.1 to 10, since the object of the present invention is sufficiently achieved.

[0014] The above agent may already contain an organic polymer at the time of injection into the ground, or may be a substance that becomes an organic polymer after injection into the ground. Further, the above agent may be composed only of a compound containing at least one of a metal element and a carbon element, but preferably, it is a mixture containing both a metal element and a carbon element, and containing two or more compounds containing these elements separately, and is exemplified below. (1) A mixture containing a compound containing a metal element and not containing a carbon element and a compound containing a carbon element and not containing a metal element (2) A mixture containing a compound containing a metal element and not containing a carbon element and a compound containing a metal element and a carbon element (3) A mixture containing a compound containing a carbon element and not containing a metal element and a compound containing a metal element and a carbon element (4) A mixture containing two or more compounds containing a metal element and a carbon element that are different from each other

[0015] In the above aspects (1) and (2), the compound containing a carbon element preferably contains a polymerizable unsaturated compound, and particularly preferably contains a polymerizable unsaturated compound that forms an acrylic polymer, an acrylamide polymer, polyvinyl alcohol, or a urethane polymer. Further, the compound containing a metal element and a carbon element is preferably a polymerizable unsaturated compound containing a portion such as a metal carboxylate, a metal sulfonate, a metal phosphate, or a metal borate.

[0016] In the above aspect (3), it is preferable that at least one of the compound containing a carbon element and not containing a metal element and the compound containing a metal element and a carbon element contains a polymerizable unsaturated compound, and it is particularly preferable to contain a polymerizable unsaturated compound that forms an acrylic polymer, an acrylamide polymer, polyvinyl alcohol, or a urethane polymer. When any one of these compounds is not a polymerizable unsaturated compound, it can be a normal organic compound (which may be an organic polymer).

[0017] Furthermore, in the above aspect (4), at least one of the compounds containing a metal element and a carbon element is a polymerizable unsaturated compound containing a part such as a metal carboxylate, a metal sulfonate, a metal phosphate, or a metal borate, and it is particularly preferable that it is a polymerizable unsaturated compound that forms an acrylic polymer, an acrylamide polymer, polyvinyl alcohol, or a urethane polymer.

[0018] In the present invention, from the viewpoint of the durability of the improved ground, the organic polymer formed by the above agent is preferably a gel-like organic polymer, and when it is an acrylic polymer, an acrylamide polymer, polyvinyl alcohol, or a urethane polymer, the above effects can be surely obtained.

[0019] The above agent is preferably a composition further containing water, and from the viewpoint of its corrosion inhibitory property when there is a structure in the underground ground, the pH is preferably in the neutral range. Also, from the point of ensuring the permeability to the underground ground, the viscosity of the above agent is preferably low.

[0020] Hereinafter, in the present invention, a particularly preferable agent, that is, an agent (hereinafter referred to as "acrylic agent") that suitably forms a gel-like acrylic polymer excellent in permeability to soil and excellent in durability will be described. The above acrylic agent is preferably a composition containing a metal (meth)acrylate (hereinafter referred to as "component (P)") and a polymerization initiator (hereinafter referred to as "component (Q)").

[0021] Examples of the above component (P) include alkali metal salts such as lithium salts, sodium salts, and potassium salts of (meth)acrylic acid; alkaline earth metal salts such as calcium salts and barium salts; magnesium salts, aluminum salts, zirconium salts, etc. The component (P) contained in the above acrylic agent may be only one kind or two or more kinds. In the present invention, calcium salts and magnesium salts are preferred, and magnesium salts are particularly preferred because a gel-like organic polymer having good strength and deformation resistance can be obtained.

[0022] When the total amount of the acrylic agent is 100% by mass, the content ratio of the above component (P) is preferably 0.5 to 50% by mass, more preferably 2 to 30% by mass.

[0023] The above component (Q) is not particularly limited as long as it can polymerize component (P), and conventionally known compounds can be used. For example, azo compounds; organic peroxides such as percarboxylic acids, hydroperoxides, ketone peroxides, and diacyl peroxides; inorganic peroxides such as peroxides, percarbonates, perborates, and persulfates. The organic peroxide or inorganic peroxide may be used in combination with a reducing agent to form a redox initiator. Examples of this reducing agent include thiosulfate compounds such as sodium thiosulfate and potassium thiosulfate; bisulfite compounds such as sodium bisulfite and potassium bisulfite; hypophosphite compounds such as sodium hypophosphite and potassium hypophosphite; sulfite compounds such as sodium sulfite and potassium sulfite; hydroxymethanesulfinate salts such as sodium hydroxymethanesulfinate (rongalite); ascorbic acid or its salts such as sodium ascorbate; erythorbic acid or its salts such as sodium erythorbate; ferrous salts; amine compounds such as diethanolamine, triethanolamine, hydrazine, hydroxylamine, dimethylaminopropionitrile, dimethylaminopropanol, piperazine, and morpholine; thiourea disulfide, copper sulfate, etc. can be used.

[0024] When the content ratio of the above component (Q) is based on 100% by mass of the entire acrylic agent, it is preferably 0.01 to 2% by mass, more preferably 0.02 to 1% by mass.

[0025] The above acrylic agent can further contain other components. Examples of other components include other monomers (hereinafter referred to as "component (R)"), cross-linking agents (hereinafter referred to as "component (S)"), rust inhibitors, defoaming agents, emulsifiers, metal sequestering agents, fillers, and the like.

[0026] The above component (R) can be either an ionic monomer (an anionic monomer or a cationic monomer) or a non-ionic monomer, or a combination thereof can be used. Examples of anionic monomers include (meth)acrylic acid; carboxy group-containing monomers such as itaconic acid, monoalkyl itaconate, maleic acid, monoalkyl maleate, fumaric acid, monoalkyl fumarate, citraconic acid, monoalkyl citraconate, cinnamic acid, itaconic anhydride, maleic anhydride, and salts or anhydrides thereof; 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, polyoxyalkylene mono(meth)acrylate sulfate, 2-hydroxyethyl (meth)acryloyl phosphate, phenyl-2-acryloyloxyethyl phosphate, 2-acryloyloxyalkylphosphonic acid and their salts (alkali metal salts, alkaline earth metal salts or ammonium salts), etc. The above component (R) can contain a reducing agent which may be included in the above component (Q).

[0027] When the above acrylic agent contains component (R), the upper limit of the content ratio of this component (R) is preferably 40% by mass, more preferably 30% by mass, based on 100% by mass of the entire acrylic agent.

[0028] The above component (S) is a component that forms an organic polymer having a crosslinked structure together with the above component (P) in the ground. The above component (S) may be either an organic compound component (S1) or an inorganic compound component (S2), and the above acrylic agent may contain both of them.

[0029] When the above component (S) is an organic compound component (S1), water-soluble divinyl compounds such as polyethylene glycol di(meth)acrylate, methylene bisacrylamide, and hydroxyethylene bisacrylamide, and N-methylol acrylamide, etc. can be mentioned.

[0030] When the above acrylic agent contains the organic compound component (S1), the upper limit of the content ratio of this organic compound component (S1) is preferably 25% by mass, more preferably 15% by mass, when the total acrylic agent is 100% by mass.

[0031] When the above component (S) is an inorganic compound component (S2), a polyvalent metal salt which is a compound other than the component (P) is preferable. This polyvalent metal salt may be either a divalent metal salt or a trivalent or higher-valent metal salt, and the above acrylic agent may contain both of them. Examples of the divalent metal salt include magnesium salts, calcium salts, barium salts, etc. Examples of the trivalent or higher-valent metal salt include aluminum salts, zirconium salts, titanium salts, cerium salts, etc. In the present invention, from the viewpoint of easily controlling the strength of the gel-like organic polymer formed by the polymerizable unsaturated compound containing the component (P), it is preferable to contain a trivalent or higher-valent metal salt.

[0032] Examples of metal salts with a valence of 3 or higher include aluminum salts such as aluminum chloride, aluminum nitrate, aluminum sulfate, alum, sodium alum, aluminum acetate, aluminum lactate, polyaluminum chloride (basic aluminum chloride), and polyaluminum sulfate chloride (basic aluminum sulfate chloride); zirconium salts such as zirconium acetate, zirconium nitrate, zirconium chloride, zirconium lactate, zirconium carbonate, zirconium oxynitrate, zirconium oxyacetate, zirconium sulfate, and zirconiumoxysulfate; and titanium chloride and cerium nitrate. Among these, aluminum salts and zirconium salts are preferred, and aluminum salts are particularly preferred. Also, when the above component (S) is a basic salt, it acts as a crosslinking agent and can effectively improve the corrosion inhibition ability.

[0033] When the above acrylic agent contains an inorganic compound component (S2), the upper limit of the content ratio of this inorganic compound is preferably 25% by mass, more preferably 15% by mass, when the total acrylic agent is 100% by mass.

[0034] The above acrylic agent is preferably a composition containing water. In such a composition, the total content ratio of the above components (P) and (S) (the content ratio of the injection material) is preferably 0.5 to 75% by mass, more preferably 2 to 45% by mass, from the viewpoint of the penetration rate into the underground ground.

[0035] In the above acrylic agent, depending on the type of polymerization initiator, the polymerization reaction of the polymerizable unsaturated compound containing component (P) may proceed immediately at the time when all the above components coexist (before use). Therefore, when injecting the above acrylic agent into the underground ground for ground improvement, depending on the type of the contained components, it is preferable to select whether to prepare the acrylic agent by mixing separately stored ones immediately before use or to use it so that all the components are mixed during the injection into the ground.

[0036] Next, as a specific method for confirming the ground improvement effect in the present invention, the method using the above acrylic-based agent will be described.

[0037] First, in order to grasp the soil composition of the ground that requires injection of the agent, the soil is sampled and qualitative and quantitative analysis of elements is performed. In this elemental analysis, known analysis means can be applied, and at least quantitative analysis of metals and carbon is performed. The metal elements to be measured in the quantitative analysis step can be determined based on the analysis results of the soil. However, with respect to the total of all elements constituting the soil, metal elements with a content ratio of preferably 15% by mass or less, more preferably 10% by mass or less, are selected. Thereafter, in order to determine a suitable acrylic-based agent or the metal element to be measured based on the types of constituent elements of the soil, the composition of the acrylic-based agent planned to be used, etc., the sampled soil and a plurality of types of acrylic-based agents prepared so that the concentrations of specific components are different are mixed to prepare a mixture. As the specific component, it is preferable to select either a component (P) containing a metal element or both a component (P) and a component (S) that may contain the above component (P) and a metal element. Among the components (R), there are compounds containing metal elements, and although components composed of such compounds may be included, they are in trace amounts and do not affect the quantitative analysis results. Therefore, usually, component (P) or component (S) is selected. Incidentally, when the prepared mixture is subjected to the quantitative analysis step, it usually becomes a consolidated material mainly composed of an acrylic polymer and soil components.

[0038] For the above-mentioned plurality of types of mixtures, specific means in the case of performing quantitative analysis of at least one of metals and carbon (quantitative analysis step) are preferably selected as appropriate according to the type of the metal to be analyzed selected according to the constituent elements of the soil. As the quantitative analysis method, for example, a liquid prepared by dissolving a mixture sample in a solvent (hereinafter referred to as a "sample solution") is subjected to inductively coupled plasma atomic emission spectrometry (ICP-AES) or total organic carbon analysis, whereby metals or carbon can be quantified respectively.

[0039] The above sample solution is preferably a solution obtained by treating a mixture sample with an acidic aqueous solution as a solvent (extraction solvent). This acidic aqueous solution is preferably an aqueous solution of an inorganic acid such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, etc., and an aqueous nitric acid solution, an aqueous sulfuric acid solution, and an aqueous hydrochloric acid solution are particularly preferred. The pH of the above acidic aqueous solution is not particularly limited, but is preferably 3 or less, more preferably 2 or less, and particularly preferably 1 or less. For example, when an acrylic agent containing a component (P) containing an alkaline earth metal salt of (meth)acrylic acid is used, the formed organic polymer will contain at least an alkaline earth metal such as Mg and C. Further, when this acrylic agent further contains a metal salt of trivalent or higher as the component (R), an organic polymer containing an alkaline earth metal, C, and a metal element of trivalent or higher and firmly networked will be formed. Therefore, in order to ensure that the element to be analyzed is contained in the above sample solution, it is preferable to extract using a strong acid aqueous solution.

[0040] The method for preparing the sample solution using the above acidic aqueous solution is not particularly limited. For example, 1 g of the mixture sample can be placed in 40 ml of the acidic aqueous solution and stirred under the conditions of 20°C to 80°C to obtain the sample solution.

[0041] When the metal is the element to be measured, a metal that is contained in the acrylic-based agent, constitutes the soil, and has a low content ratio is selected. Therefore, if the metal element to be measured is sufficiently extracted from the mixture (consolidated material) of the acrylic-based agent and the soil by the above acidic aqueous solution, not only when the element to be measured is a metal but also when it is carbon, theoretically, the concentration of the specific component contained in the acrylic-based agent and the analytical value of the element to be measured (metal or carbon) are in a proportional relationship (see (1) in FIG. 1). However, depending on the type of the element to be measured, when the concentration of the specific component increases, the quantitative value of the mixture (consolidated material) tends to be lower than the calculated value (theoretical value) calculated from the composition of the mixture. When graphed, it deviates below the theoretical straight line like the curve shown by the dotted line in (1) of FIG. 1. In order to surely obtain the effect of the present invention, it is preferable to use an agent in a region where the straight line obtained by connecting each quantitative value after extraction from a plurality of types of mixtures has little deviation from the theoretical straight line and has a correlation. In (1) of FIG. 1, in the region where the concentration of the specific component is up to C2, the correlation with the theoretical value calculated from the composition of the mixture is high, which means that the quantitative analysis of the element to be measured can be accurately performed in this region. By graphing in this way, it is possible to easily grasp a suitable acrylic-based agent according to the type of soil.

[0042] For the consolidated material composed of the above plurality of types of mixtures, for example, physical properties such as uniaxial compressive strength are measured and graphed, and the curve shown in (2) of FIG. 1 is obtained. Therefore, it is possible to grasp the physical properties in the agent consolidation part formed by injecting the agent into the ground, that is, when using the agent according to the concentration of the specific component.

[0043] Hereinafter, an example in which after preparing a plurality of types of mixtures using an acrylic-based agent, the quantitative analysis values obtained for metal or carbon are compared with the theoretical values is shown. In the following, parts and % are based on mass unless otherwise specified.

[0044] 1. Agent (Meta) magnesium acrylate, which is a metal acrylate salt (hereinafter referred to as "P"), was used as a base, and polyethylene glycol diacrylate (PEGDA, hereinafter referred to as "S1") or polyaluminum chloride (PAC, hereinafter referred to as "S2"), which is a crosslinking agent, was contained and not contained to prepare the drugs (X), (Y) and (Z) in Tables 1 to 3. The polymerization initiator is t-amyl hydroperoxide (hereinafter referred to as "Q"), and the additive is sodium thiosulfate. In Tables 1 to 3, the "concentration of the injection material" means the total concentration of magnesium acrylate and the crosslinking agent.

[0045]

Table 1

[0046]

Table 2

[0047]

Table 3

[0048] 2. Soil to which the drug was applied The soil used in combination for the effect confirmation using the above drugs is shown below. (1) Toyoura sand (2) Nagoya Port sand (collected from the coastal area of Minato Ward, Nagoya City, Aichi Prefecture) In addition, Table 4 shows the results of elemental analysis of the soil by inductively coupled plasma optical emission spectrometry (ICP-AES). However, since the content ratios of Al and Mg are both 10% in both Toyoura sand and Nagoya Port sand, it was determined that they can be used as the analysis targets for metal elements, and these Al and Mg, and C were used as the analysis targets.

[0049]

Table 4

[0050] 3. Experiment for confirming the effect of the drug The soil and the chemical agent were used at a mass ratio of 298:92, and they were mixed in a mold (φ5 cm × H10 cm) by the water-drop method in water to produce a cylindrical consolidated material. However, in the cases of chemical agents X1, Y1, and Z1, no consolidated material was obtained, and all were slurries. Thereafter, 40 g of the acidic aqueous solutions (A1) to (A4) or water (A5) shown in Table 5, which were used as extraction solvents, was added to 1 g of the consolidated material or slurry, and they were shaken (for 24 hours), and then the extract was centrifuged, and the supernatant was collected. Thereafter, elemental analysis (target: Mg and Al) of this supernatant was performed by inductively coupled plasma atomic emission spectrometry (ICP-AES), or total organic carbon (TOC) analysis was performed. In the case of chemical agents (X), (Y), and (Z), since chemical agents with different injection material concentrations were used, it was examined whether the results of the elemental analysis were in a proportional relationship with the injection material concentration. Also, a blank test was conducted when using the extraction solvents and soil shown in Table 5 without using the chemical solution, and correction was made to the above measurement values.

[0051]

Table 5

[0052] Experimental Example 1 Using the chemical agent (X) described in Table 1, Toyoura sand, and the extraction solvent (A1) described in Table 5, the above operations were performed. The elements to be measured were Mg and C. The corrected values of the elemental analysis data, together with the theoretical values calculated from the amounts of the chemical agent (X) and Toyoura sand used, are shown in Table 6.

Table 6

[0053] Based on the data in Table 6 regarding Toyoura sand, with the concentration of the injection material in chemical agent (X) on the X-axis and the Mg content and C content on the Y-axis, the corrected values and theoretical values were plotted and graphed. As a result, it was found that there is a concentration range with a high correlation between the corrected values and the theoretical values (see Figures 3 and 4). From Figure 3, when using chemical agent (X), it can be seen that by setting the concentration of the injection material to about 12% or less, it is possible to suitably confirm the improved ground with Mg as the analysis target. Also, from Figure 4, when using chemical agent (X), it can be seen that by setting the concentration of the injection material to about 12% or less, it is possible to suitably confirm the improved ground with C as the analysis target. Furthermore, it was found that the extraction solvent (A1), which is a strong acid aqueous solution, is also suitable.

[0054] Experimental Example 2 Using the chemical agent (Y) described in Table 2, Toyoura sand, and the extraction solvent (A1) or (A2) described in Table 5, the above operations were performed. The elements to be measured are Mg and C. The corrected values of the elemental analysis data are shown in Table 7 together with the theoretical values calculated from the usage amounts of the chemical agent (Y) and Toyoura sand.

Table 7

[0055] Based on the data in Table 7 regarding Toyoura sand, with the concentration of the injection material in chemical agent (Y) on the X-axis and the Mg content and C content on the Y-axis, the corrected values and theoretical values were plotted and graphed. As a result, it was found that there is a concentration range with a high correlation between the corrected values and the theoretical values (see Figures 5 and 6). From Figures 5 and 6, when using chemical agent (Y) with the concentration of the injection material up to about 12%, then using the extraction solvent (A1), it can be seen that it is possible to suitably confirm the improved ground with either Mg or C as the analysis target. Also, when using chemical agent (Y) with the concentration of the injection material up to about 6%, then using the extraction solvent (A2), it can be seen that it is possible to suitably confirm the improved ground with either Mg or C as the analysis target.

[0056] Experimental Example 3 Using the agent (Z) described in Table 3, the Nagoya Port sand, and the extraction solvent (A1) or (A2) described in Table 5, the above operations were performed. The elements to be measured are Mg, Al, and C. The corrected values of the elemental analysis data are shown in Table 8 together with the theoretical values calculated from the amounts of the agent (Z) and the Nagoya Port sand used.

Table 8

[0057] Based on the data in Table 8 regarding the Nagoya Port sand, with the concentration of the injection material in the agent (Z) on the X-axis and the amounts of Mg, Al, and C on the Y-axis, the corrected values and the theoretical values were plotted and graphed. It was found that there is a concentration region with a high correlation between the corrected values and the theoretical values (see Figures 7, 8, and 9). From Figures 7, 8, and 9, when using the agent (Z) with the concentration of the injection material up to about 12%, it can be seen that then, using the extraction solvent (A1) or (A2), the improved ground can be suitably confirmed with Mg as the analysis target. Also, when using the agent (Z) with the concentration of the injection material up to about 12%, it can be seen that then, using the extraction solvent (A1), the improved ground can be suitably confirmed with either Al or C as the analysis target.

[0058] Experimental Example 4 Using the agent (Z) described in Table 3, the Toyoura sand, and the extraction solvents (A1), (A2), (A3), (A4), or (A5) described in Table 5, the above operations were performed. The elements to be measured are Mg, Al, and C. The corrected values of the elemental analysis data are shown in Table 9 together with the theoretical values calculated from the amounts of the agent (Z) and the Toyoura sand used.

Table 9

[0059] Based on the data in Table 8 regarding Toyoura sand, with the concentration of the injection material in chemical agent (Z) on the X-axis and the amounts of Mg, Al, and C on the Y-axis, the corrected values and theoretical values were plotted and graphed. As a result, it was found that there is a concentration range with a high correlation between the corrected values and the theoretical values (see Figures 10, 11, and 12). From Figures 10, 11, and 12, when using chemical agent (Z) with an injection material concentration of up to about 12%, it can be seen that subsequently, using extraction solvents (A1), (A2), (A3), or (A4) and setting the analysis target as Mg, the improved ground can be suitably confirmed. Also, when using chemical agent (Z) with an injection material concentration of up to about 12%, it can be seen that subsequently, using extraction solvents (A1), (A3), or (A4), the improved ground can be suitably confirmed regardless of whether the analysis target is Al or C. Furthermore, when using chemical agent (Z) with an injection material concentration of up to about 6%, it can be seen that subsequently, using extraction solvent (A2), the improved ground can be suitably confirmed regardless of whether the analysis target is Al or C.

[0060] From these experimental examples, it was found that depending on the type of soil, a suitable extraction solvent and the upper limit concentration (C2 in (1) of Figure 1) of specific components (in the above case, only magnesium acrylate or both magnesium acrylate and the crosslinking agent) in the alkaline chemical agent can be determined. Therefore, when injecting a chemical agent into the ground that requires reinforcement, etc., the soil and the chemical agent will mix in the injection part. Thus, by using the collected soil and performing operations including the quantitative analysis process shown in the above experimental examples to conduct metal analysis or carbon analysis, graphs such as those in Figures 2 to 11 can be created, and a suitable chemical agent can be grasped according to the soil composition. Subsequently, as described above, by combining a chemical agent in which the specific component is within a suitable concentration range with the soil to produce a consolidated material and measuring its physical properties, the performance of the improved ground can be grasped (see (2) of Figure 1).

[0061] In the above experimental examples, examples of using chemical agents that form acrylic polymers were shown. However, the present invention can efficiently grasp the improvement effect by the chemical agent by performing similar operations using chemical agents that form acrylamide polymers, polyvinyl alcohol, or urethane polymers.

[0062] The ground improvement method and ground improvement construction method of the present invention are characterized by including a confirmation step based on the above-described method for confirming the improvement effect of the ground of the present invention. The ground improvement construction method and ground improvement construction method of the present invention preferably proceed sequentially with a confirmation step and an injection step of injecting a chemical agent into the ground. Examples of construction methods suitable for ground improvement include a permeation solidification treatment method, a jet grouting method, etc. Among these, the permeation solidification treatment method is particularly preferable.

[0063] For example, in the permeation solidification treatment method using an acrylic-based chemical agent, when the chemical agent penetrates into the ground by chemical agent injection and replaces the water existing in the gaps of the ground with the chemical agent, the polymerization reaction of the polymerizable unsaturated compound containing the component (P) contained in the chemical agent proceeds, and while gelling, an organic polymer is formed, and it is a ground improvement method for preventing liquefaction as a improved ground composed of consolidated soil formed together with the soil around the gaps of the in-situ ground. Further, this permeation solidification treatment method is a method of injecting a chemical agent from an injection pipe to a required location using a relatively small-scale device and causing permeation solidification, and is effective for liquefaction countermeasures for the ground directly under existing structures such as tanks and bridge piers that are difficult to move. Since the above acrylic-based chemical agent has excellent permeability to soil and has an appropriate gelation time, particularly, the ground can be efficiently improved by the permeation solidification treatment method.

Industrial Applicability

[0064] According to the present invention, since a chemical agent containing at least one of a metal element and a carbon element and in which an organic polymer is formed later is used, by performing metal analysis or carbon analysis on the soil collected from a desired position of the in-situ ground when the ground is soft, etc., and the soil collected from the improved ground after chemical agent injection, the improvement effect by the chemical agent can be efficiently grasped. Therefore, it has high applicability in the technical field related to the injection of chemical agents for improving the ground.

Claims

1. A method for confirming the improvement effect of ground in which a chemical containing at least one of a metal element and a carbon element is injected into the ground and an organic polymer is formed after the injection, comprising: a step of quantitatively analyzing the content of at least one of metal and carbon with respect to the soil collected from the ground before injecting the chemical and the improved ground after injecting the chemical into the ground; the metal element to be measured is a metal element having a content ratio of 15% by mass or less with respect to the total of all elements constituting the soil; the chemical contains a metal (meth)acrylate, a polymerization initiator, and water, the content ratio of the metal (meth)acrylate is 2 to 30% by mass with respect to the whole chemical, and the content ratio of the polymerization initiator is 0.02 to 1% by mass with respect to the whole chemical, and a method for confirming the improvement effect of ground is characterized by this.

2. The method for confirming the improvement effect of ground according to Claim 1, wherein the metal element is at least one selected from Al, Mg, Zr, Ca, Ag, Cu, and Fe.

3. The method for confirming the improvement effect of ground according to Claim 1 or 2, wherein the chemical contains Al, Mg, and C.

4. The method for confirming the improvement effect of ground according to any one of Claims 1 to 3, wherein in the quantitative analysis, a liquid obtained by treating the soil or the improved ground with an acidic aqueous solution is used.

5. The method for confirming the improvement effect of ground according to Claim 4, wherein the pH of the acidic aqueous solution is 2 or less.

6. A ground improvement method characterized by comprising a confirmation step based on the method for confirming the improvement effect of ground according to any one of Claims 1 to 5.

7. A ground improvement construction method characterized by comprising a confirmation step based on the method for confirming the improvement effect of ground according to any one of Claims 1 to 5.

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