Liquid solidifying agent for soil and soil improvement method using the same

Abstract

The invention described in this application aims to provide a solidifying agent that is easy for contractors to use and has a lower environmental impact, as well as a soil improvement method using the solidifying agent. [Solution] In order to solve this problem, the invention of this application employs a liquid soil solidification material that is neutral and consists of two liquids: a main component comprising magnesium oxide and water, and an auxiliary component comprising one or more compounds selected from the group consisting of aluminum sulfate, polyaluminum chloride, magnesium chloride, and ferrous sulfate, and water as a solvent, wherein the ratio of magnesium oxide to water in the main component is 1:0.5 to 1:1.2 by weight, and the ratio of the main component to water in the auxiliary component is 1:0.5 to 1:1.5 by weight, and the ratio of the main component to the auxiliary component is 6:4 to 8:2 by weight.

Description

[Technical Field]

[0001] This application relates to a liquid solidifying agent for soil. More specifically, it relates to a neutral liquid solidifying agent for soil. Furthermore, the invention described in this application relates to a method of soil improvement using the said liquid solidifying agent. [Background technology]

[0002] Traditionally, solidifying agents have been used for ground improvement and subgrade stabilization. They are also used to solidify soil with a high water content (also simply referred to as "water content") so that it can be transported by dump trucks, and to improve construction waste soil (also referred to as "excavated soil" or simply "excavated soil") for reuse. However, if the solidifying agent is in powder form, it can be scattered by the wind when spread at the construction site, causing it to adhere to unintended locations. Furthermore, depending on the work environment, dust may be generated, potentially causing health problems for workers. Therefore, dust-proof powdered solidifying agents are now being developed.

[0003] Separately, a slurry has been developed in which a powdered solidifying agent is mixed with water. For example, Patent Document 1 discloses "a ground improvement material comprising a slurry containing cement-containing solidifying agent powder, a naphthalene sulfonic acid-based admixture, a setting retarder, and water, characterized in that the setting retarder consists of one or more selected from the group consisting of tartrate, hexametaphosphate, and citrate." Such liquid solidifying agents (ground improvement materials) have the advantage of being easy for contractors to use because they can be efficiently scattered to the target location by methods such as spraying, injecting, or jetting. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-109929 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] While cement-based solidifying agents (cement-containing solidifying agent powder), such as those used in Patent Document 1, are widely used for ground improvement and subgrade stabilization, soil improved with cement-based solidifying agents becomes alkaline, and alkaline components may leach from the soil, potentially affecting plant growth and groundwater quality. Therefore, there is a market demand for the development of solidifying agents that are easier for contractors to use and have a lower environmental impact, as well as soil improvement methods using such solidifying agents. [Means for solving the problem]

[0006] A. Liquid solidifying agent for soil The liquid soil solidification material relating to this application is neutral and consists of two liquids: a main component comprising magnesium oxide and water, and an auxiliary component comprising one or more compounds selected from the group consisting of aluminum sulfate, polyaluminum chloride, magnesium chloride, and ferrous sulfate, and water as a solvent. The ratio of magnesium oxide to water in the main component is 1:0.5 to 1:1.2 by weight, and the ratio of the main component to water in the auxiliary component is 1:0.5 to 1:1.5 by weight, with the ratio of the main component to the auxiliary component being 6:4 to 8:2 by weight.

[0007] B. Soil improvement method The soil improvement method relating to this application uses the liquid soil solidification material relating to this application described above, and is characterized by comprising the following steps 1 to 5. Step 1: Weigh out the main ingredients, magnesium oxide and water, in a weight ratio of 1:0.5 to 1:1.2. Step 2: The main component, which is one or more compounds selected from the group consisting of aluminum sulfate, polyaluminum chloride, magnesium chloride, and ferrous sulfate, and the solvent, water, are weighed in a weight ratio of 1:0.5 to 1:1.5. Step 3: The main agent and the auxiliary agent are prepared by putting the raw materials of the main agent and the raw materials of the auxiliary agent into the raw material inlets of separate mixers and stirring them. Step 4: Weigh the main agent and the auxiliary agent so that the ratio between them is 6:4 - 8:2 by weight, and inject the main agent and the auxiliary agent into the injection ports of a Y-shaped tube or a double tube designed such that the chemical liquids converge and contact near the tip inside the tube, and make them contact inside the tube to prepare the liquid solidifying material for soil. Step 5: Add the liquid solidifying material for soil to the soil so that it is 10 kg / m 3 ~140 kg / m 3 in terms of the weight of the main agent, and mix the liquid solidifying material for soil and the soil.

Advantages of the Invention

[0008] According to the invention related to this application, it is possible to provide a solidifying material in a liquid form that is easy for constructors to use and has less environmental impact. Also, according to the invention related to this application, it is possible to provide a soil improvement method by which constructors can perform ground improvement work, solidification treatment work for making soil with a high weight moisture content transportable by a dump truck, etc. more efficiently and safely at the construction site.

Embodiments for Carrying out the Invention

[0009] A. Liquid solidifying material for soil The liquid solidifying material for soil related to this application is used for ground improvement, roadbed stability treatment, solidification treatment for making soil with a high weight moisture content transportable by a dump truck, etc., and improvement for reusing construction-generated soil. There is no particular limitation on the type (soil quality) of the soil to be treated (in the case of ground improvement, the soil constituting the ground; in the case of roadbed stability treatment, the roadbed soil), but especially, the weight moisture content is 20% or more and the cone index is 200 KN / m 2It can be suitably used for the muddy soil below. Therefore, for example, it can be suitably used to improve the strength of a soft ground composed of such muddy soil with an N value indicating the ground strength in the vicinity of 0 to 4 to a predetermined value. Here, there is no limit to the upper limit of the weight moisture content, but for muddy soil with a weight moisture content exceeding 50%, the working efficiency can be improved by dehydrating it in advance by methods such as consolidation (pressing) or drainage. Therefore, the weight moisture content of the muddy soil for ground improvement, etc. using the liquid solidifying material for soil according to the present application is preferably 50% or less.

[0010] In addition, the liquid solidifying material for soil according to the present application consists of two liquids, a main agent and an auxiliary agent, and by mixing these two liquids, it exhibits a neutrality with a pH of 5.8 to pH 8.6. When the pH of the liquid solidifying material for soil is within this numerical range, even immediately after adding the liquid solidifying material for soil to the soil to be treated, the pH does not greatly tend to be acidic or alkaline. Therefore, for example, when the liquid solidifying material for soil is used for ground improvement or roadbed stability treatment, compared with conventional solidifying materials, there is less possibility of causing unexpected effects on the surrounding environment. Furthermore, different from powder solidifying materials, the liquid solidifying material for soil does not have the problem of scattering by wind during spraying, and can be efficiently sprayed to the target location by methods such as spraying, spraying, injection, etc. or by pumping and discharging from the tip of a pipe.

[0011] The main component of the liquid soil solidification material related to this application consists of magnesium oxide, which is the main component, and water. This main component functions to improve the strength of soils with low bearing capacity or traffic load support capacity, such as mud, and to improve the soil quality of mud and other soils. The preferred ratio of magnesium oxide to water is 1:0.5 to 1:1.2 by weight. Since magnesium oxide is almost insoluble in water, the main component takes the form of a slurry. Furthermore, when stirred, this main component can maintain its slurry form for more than 3 hours from preparation. Here, if the ratio of water to magnesium oxide is less than 0.5 by weight, the viscosity of the slurry obtained by mixing them becomes too high, making stirring difficult, and it tends not to mix uniformly when in contact with auxiliary agents, which is undesirable. On the other hand, even if the ratio of water to magnesium oxide exceeds 1.2 by weight, no particularly new functions are expressed, and it only increases the amount of main component necessary to produce the function of a liquid soil solidification material, so it is simply a waste of resources and undesirable. Furthermore, it is more preferable that the ratio of magnesium oxide to water is 1:0.6 to 1:1 by weight. This is because when the ratio of magnesium oxide to water is within this range by weight, the magnesium oxide content in the main component is high, and the stirring process is also easier.

[0012] The auxiliary agent in the liquid soil solidification material related to this application is aluminum sulfate (also called "aluminum sulfate"), which is the main component, and polyaluminum chloride (also called "PAC"). Its chemical formula is [Al2(OH) n Cl 6-n ] mThe additive consists of one or more compounds selected from the group consisting of (and 1 ≤ n ≤ 5, m ≤ 10), magnesium chloride, and ferrous sulfate, and water as a solvent. The additive mainly functions as a pH adjuster. The preferred ratio of the main component to water (if the main component consists of two or more compounds, the preferred ratio of the total amount of the main component to the amount of water) is 1:0.5 to 1:1.5 by weight. The main component of the additive is readily soluble in water, and the resulting additive is in the form of an aqueous solution. Furthermore, when polyaluminum chloride is used as the main component, using it in combination with aluminum sulfate is undesirable because precipitates form in the aqueous solution of the additive, preventing it from functioning properly. Here, if the ratio of water to the main component is less than 0.5 by weight, the content of the main component in the additive becomes too high, making it difficult to adjust the pH of the liquid soil solidification material, which is undesirable. On the other hand, if the ratio of water to the main component exceeds 1.5 by weight, the amount of auxiliary agents needed to neutralize the pH of the liquid soil solidification agent increases, which is undesirable because it increases manufacturing costs.

[0013] The preferred ratio of the main agent to the auxiliary agent in the liquid soil solidification material relating to this application is 6:4 to 8:2 by weight. If the weight of the main agent is less than 60% of the total weight of the main agent and auxiliary agent (i.e., if the weight of the main agent is less than 60% of the total weight of the main agent and auxiliary agent), it is undesirable because it tends not to improve the strength of soils with low bearing capacity or traffic load support capacity, such as mud, or to improve the soil quality of soils such as mud. On the other hand, if the weight of the main agent is more than 80% of the total weight of the main agent and auxiliary agent (i.e., if the weight of the main agent is more than 80% of the total weight of the main agent and auxiliary agent), the amount of auxiliary agent becomes relatively small, requiring an extremely high concentration of the auxiliary agent, which tends to make it difficult to adjust the pH of the liquid soil solidification material to neutral, and is therefore undesirable.

[0014] The appropriate amount of liquid soil solidification agent to be added to soil when improving the soil quality of the soil to be treated is 10 kg / m³, based on the weight of the main agent per unit volume of soil. 3 ~140kg / m 3This is the case. When the addition amount of the liquid solidifying material for soil is less than 10 kg / m as the weight of the main agent, it is not preferable because the effect of improving the strength of soil with low bearing capacity such as mud or the supporting force of traffic load or improving the soil quality of soil such as mud is not sufficiently obtained. On the other hand, even if the addition amount of the liquid solidifying material for soil exceeds 140 kg / m as the weight of the main agent, no effect such as more rapid improvement of the soil strength occurs, which results in a mere waste of resources and is not preferable. The suitable amount of the liquid solidifying material for soil as the main agent and the auxiliary agent added to the soil to be treated is within the numerical range calculated from the above-mentioned "suitable ratio of the main agent and the auxiliary agent in the liquid solidifying material for soil". Specifically, the suitable amount of the liquid solidifying material for soil as the main agent and the auxiliary agent added to the soil when improving the soil quality of the soil to be treated is 12.5 kg / m 3 to 233.3 kg / m 3 is as follows. The cone index of the soil after soil improvement is preferably 400 KN / m 3 or more, more preferably 800 KN / m 3 or more, and still more preferably 1100 KN / m

[0015] or more. When the cone index of the soil after soil improvement is 400 KN / m 2 or more, it becomes easy to transport the soil, which was mud or the like before improvement, by a dump truck or the like, and the soil corresponds to the third type of construction-generated soil, so it can be said that the soil has been improved to a soil quality that can be used for land reclamation, river embankment construction, etc. Also, when the cone index of the soil after soil improvement is 800 KN / m 2 or more, it can be said that the soil has been improved to a better soil quality that can be used for applications such as road embankments and has been improved to a soil with a strength that allows a bulldozer to travel. And when the cone index of the soil after soil improvement is 800 KN / m 2 or more, it can be said that the soil has been improved to a better soil quality that can be used for applications such as road embankments and has been improved to a soil with a strength that allows a bulldozer to travel. And when the cone index of the soil after soil improvement is 800 KN / m 2 or more, it becomes easy to transport the soil, which was mud or the like before improvement, by a dump truck or the like, and the soil corresponds to the third type of construction-generated soil, so it can be said that the soil has been improved to a soil quality that can be used for land reclamation, river embankment construction, etc. Also, when the cone index of the soil after soil improvement is 800 KN / m 2 or more, it can be said that the soil has been improved to a better soil quality that can be used for applications such as road embankments and has been improved to a soil with a strength that allows a bulldozer to travel. And when the cone index of the soil after soil improvement is 1100 KN / m 2In this case, the N-value, which indicates the strength of the ground, is generally 12.8 or higher, meaning that the ground has been improved to a foundation suitable for constructing structures. Furthermore, the cone index of the soil after soil improvement is 1100 kN / m 2 As a result, it can be said that the soil has been improved to have sufficient strength for heavier self-propelled scrapers to operate on, and the N-value, which indicates the strength of the ground, is generally 17.6 or higher, indicating that the foundation ground has been improved to be more robust.

[0016] The liquid soil solidifying agent related to this application can be prepared by conventionally known methods. Specifically, for example, the main component is prepared by "measuring magnesium oxide and water in a predetermined weight ratio," and the auxiliary component is prepared by "measuring one or more compounds selected from the group consisting of aluminum sulfate, polyaluminum chloride, magnesium chloride, and ferrous sulfate, and water as a solvent, in a predetermined weight ratio." These are then added to the raw material inlets of separate mixers (also called "agitators," "blenders," etc.) and stirred to prepare the main component and the auxiliary component. Next, the main component is poured into one of the two inlets of a Y-shaped pipe in a predetermined amount, and the auxiliary component into the other, and the liquid soil solidifying agent can be prepared by bringing them into contact within the pipe. Alternatively, a liquid soil solidifying agent can be prepared by using a double-walled pipe designed so that the two chemical solutions merge and come into contact at the tip. A predetermined amount of the main agent is poured into the inlet of the inner pipe, and a predetermined amount of the auxiliary agent is poured into the inlet of the outer pipe, allowing them to come into contact within the pipe near the tip of the double-walled pipe. The double-walled pipe can be designed, for example, so that the length of the inner pipe is about 10% to 20% shorter than the length of the outer pipe, and configured so that the two liquids merge and come into contact within the pipe on the outlet side of the double-walled pipe (i.e., within the pipe near the tip of the double-walled pipe). Furthermore, the outer and inner pipes of the double-walled pipe can be fixed inside the pipe so that they form a single integrated double-walled pipe by providing a spacer or the like between the inner wall of the outer pipe and the outer wall of the inner pipe. In addition, a valve may be provided near the outlet end of these Y-shaped pipes or double-walled pipes, etc., as needed, to keep the prepared soil solidifying agent inside the Y-shaped pipe or double-walled pipe until just before it is released towards the soil to be treated. Furthermore, it is preferable that the outlet end of the Y-shaped pipe or the double pipe is fitted with a nozzle that determines the direction in which the adjusted liquid soil solidifying agent is discharged and also promotes the mixing of the main agent and the auxiliary agent.

[0017] B. Soil improvement method The soil improvement method relating to this application uses the liquid soil solidification material relating to this application described above, and is characterized by comprising the following steps 1 to 5. Step 1: Weigh out the main ingredients, magnesium oxide and water, in a weight ratio of 1:0.5 to 1:1.2. Step 2: The main component, which is one or more compounds selected from the group consisting of aluminum sulfate, polyaluminum chloride, magnesium chloride, and ferrous sulfate, and the solvent, water, are weighed in a weight ratio of 1:0.5 to 1:1.5. Step 3: The main ingredient and the auxiliary ingredient are prepared by adding the main ingredient and the auxiliary ingredient to the ingredient inlets of separate mixers and stirring them. Step 4: The main agent and auxiliary agent are weighed out so that the weight ratio of the main agent to the auxiliary agent is 6:4 to 8:2, and the main agent and auxiliary agent are injected into the inlet of a Y-shaped pipe or a double pipe designed so that the two chemical solutions merge and come into contact near the end of the pipe, thereby preparing a liquid soil solidifying agent by bringing them into contact inside the pipe. Step 5: Add the liquid soil solidifying agent, with a main component weight of 10 kg / m². 3 ~140kg / m 3 The liquid soil solidifying agent is added to the soil and mixed with the soil.

[0018] The soil improvement method described in this application is more efficient and safer, achieving a cone index of 200 kN / m 2 Soil such as mud with a high water content and a weight of less than 400 kN / m³ can be transported by dump trucks, etc., and is equivalent to Type 3 construction excavated soil (cone index of 400 kN / m³). 2 (The above), or equivalent to Type 1 or Type 2 construction excavated soil (cone index of 800 kN / m³). 2 The soil improvement method described in this application can be improved to the above-mentioned soil conditions. Furthermore, the soil improvement method described in this application can be improved more efficiently and safely to soft ground with low bearing capacity and soft roadbeds with low bearing capacity for traffic loads (for example, a cone index of 200 kN / m²). 2 (A ground or subgrade consisting of mud or similar material with a cone index of less than 800 kN / m²) is replaced with a firm ground or subgrade with high bearing capacity and load-bearing capacity for traffic (specifically, a cone index of 800 kN / m²). 2 More preferably, the cone index is 1100 kN / m 2 The above-mentioned ground or subgrade can be improved.

[0019] There are no particular restrictions on the specific conditions for carrying out steps 1 to 5 described above; conventionally known conditions may be used. For example, when mixing the liquid soil solidification material with the soil to be treated in step 5 (the soil constituting the ground in the case of ground improvement, and the subgrade soil in the case of subgrade stabilization treatment), a mixer (also called a "mixer" or "blender") such as a self-propelled stabilizer or a vertical mixing and stirring device may be used. Furthermore, the double-walled pipe used in step 5 may be designed such that the length of the inner pipe is about 10% to 20% shorter than the length of the outer pipe, and the two liquids may be configured to merge and come into contact inside the pipe on the outlet side of the double-walled pipe (i.e., inside the pipe near the tip of the double-walled pipe). The outer and inner pipes of the double-walled pipe may be fixed inside the double-walled pipe by providing a spacer or the like between the inner wall of the outer pipe and the outer wall of the inner pipe to form a single integrated double-walled pipe. Furthermore, a valve such as a stop valve or gate valve may be provided near the outlet end of the Y-shaped pipe or double pipe used in step 5, if necessary, to keep the adjusted soil solidifying agent inside the Y-shaped pipe or double pipe until just before it is released toward the soil to be treated.

[0020] On the other hand, it is preferable that the mixer used in step 3 and the Y-pipe or double pipe used in step 4 are connected via a pipe fitting. Specifically, for example, each of the two mixers used in step 3 is provided with a pipe serving as an outlet (discharge port) to which a flow meter and valve are attached, and these pipes are connected to the inlets of the Y-pipe or double pipe (the inlets of the two pipes that are branched to inject the two liquids separately in the Y-pipe, and the inlets of the inner and outer pipes in the double pipe) via a pipe fitting. It is also preferable to place a pump for pumping the prepared chemical solution between the outlet of the mixer and the inlet of the Y-pipe or double pipe. With such a configuration, the slurry-like main agent can be continuously stirred until just before it is injected into the inlet of the Y-pipe or double pipe used in step 4, and there is no risk that the magnesium oxide in the main agent will precipitate in the liquid before it is injected into the inlet. Furthermore, with such a configuration, ground improvement work and solidification work to make soil with a high weight and water content transportable by dump trucks, etc., can be carried out more smoothly at the construction site.

[0021] Furthermore, it is preferable that the Y-shaped pipe or double pipe used in step 4 is equipped with a pump for pressurization at the inlet side (more specifically, between the outlet of the mixer and the inlet of the Y-shaped pipe or double pipe), and that a nozzle is attached to the tip of the outlet side to determine the direction in which the adjusted liquid soil solidifying material is discharged and to promote the mixing of the main agent and auxiliary agent. The nozzle may be a single-hole cylindrical nozzle, or it may be a discharge nozzle such as a spray nozzle, injection nozzle, or spray nozzle. When the Y-shaped pipe or double pipe used in step 4 has such a configuration, a liquid soil solidifying material with more stable performance can be obtained, and the liquid soil solidifying material can be sprayed more accurately and efficiently towards the target location by methods such as spraying, spraying, or injection.

[0022] The present invention will be explained in more detail below, with examples of the present invention provided for this application. However, the technical concept of the present invention is not limited to the descriptions of the examples provided below. [Examples]

[0023] In Example 1, first, 55 kg of magnesium oxide and 44 kg of tap water (the ratio of magnesium oxide to water by weight was 1:0.8) were prepared as the main ingredient, and 22 kg of aluminum sulfate (the main component) and 22 kg of tap water (the solvent) were prepared as the auxiliary ingredient (the ratio of aluminum sulfate to water by weight was 1:1). These were then added to the raw material inlets of separate mixers and mixed to prepare the main ingredient and auxiliary ingredient. Next, using a double-walled pipe with a gate valve near the outlet end, designed so that the two chemical solutions would merge and come into contact near the end of the pipe, the main ingredient was poured into the inlet of the inner pipe and the auxiliary ingredient into the inlet of the outer pipe with the gate valve closed, and these were brought into contact near the end of the double-walled pipe to obtain a liquid soil solidifying material. In this case, the ratio of the main ingredient to the auxiliary ingredient poured into the inlets of the inner and outer pipes of the double-walled pipe was 6.9:3.1 by weight. Furthermore, the double-walled pipe is designed so that the length of the inner pipe is about 20% shorter than the length of the outer pipe, and the main agent and auxiliary agent are configured to merge and come into contact inside the pipe at the outlet end of the double-walled pipe (i.e., inside the pipe near the tip of the double-walled pipe). The outer and inner pipes of the double-walled pipe are fixed inside the double-walled pipe by providing a spacer between the inner wall of the outer pipe and the outer wall of the inner pipe to form a single integrated double-walled pipe.

[0024] The liquid soil solidifying agent prepared in this manner can be immediately opened by opening the gate valve attached near the tip of the double-walled pipe, thereby reducing the volume of the container to 1 m³. 3 130 kg was applied to the muddy soil. In this case, the amount of main agent added to the muddy soil was 90 kg / m². 3 The amount of additive used is 40 kg / m². 3 The amount to be added as a liquid solidifying agent for soil is 130 kg / m². 3This mixture was then mixed with a hand mixer, filled into a mold with a diameter of 100 mm and a height of 200 mm, and left to stand in a dark, indoor location at 25°C. Subsequently, the pH and cone index of the test specimen were measured using a pH meter and a cone penetrometer, respectively, and the results shown in Table 1 were obtained. The soil used in the test was collected from a construction site, and before the addition of the liquid soil solidifying agent, the pH was 8.08, the weight water content was 38.5%, the weight water content ratio was 62.6%, and the cone index measured with a cone penetrometer was 50 kN / m 2 (This translates to an N-value of approximately 0.8, which indicates the strength of the soil.) Furthermore, when approximately 0.2 kg of the liquid soil solidification agent was collected in a glass container and measured with a pH meter, the pH was found to be 7.6. [Examples]

[0025] In Example 2, first, 77 kg of magnesium oxide and 61.6 kg of tap water (the ratio of magnesium oxide to water by weight was 1:0.8) were prepared as the main ingredient, and 33 kg of aluminum sulfate (the main component) and 33 kg of tap water (the solvent) were prepared as the auxiliary ingredient (the ratio of aluminum sulfate to water by weight was 1:1). These were then added to the raw material inlets of separate mixers and mixed to prepare the main ingredient and auxiliary ingredient. Next, using a double-walled pipe with a gate valve near the outlet end, designed so that the two chemical solutions would merge and come into contact near the end of the pipe, the main ingredient was poured into the inlet of the inner pipe and the auxiliary ingredient into the inlet of the outer pipe with the gate valve closed, and these were brought into contact near the end of the double-walled pipe to obtain a liquid soil solidifying material. In this case, the ratio of the main ingredient to the auxiliary ingredient poured into the inlets of the inner and outer pipes of the double-walled pipe was 6.8:3.2 by weight. Furthermore, the double-walled pipe is designed so that the length of the inner pipe is about 20% shorter than the length of the outer pipe, and the main agent and auxiliary agent are configured to merge and come into contact inside the pipe at the outlet end of the double-walled pipe (i.e., inside the pipe near the tip of the double-walled pipe). The outer and inner pipes of the double-walled pipe are fixed inside the double-walled pipe by providing a spacer between the inner wall of the outer pipe and the outer wall of the inner pipe to form a single integrated double-walled pipe.

[0026] The liquid soil solidifying agent prepared in this manner can be immediately opened by opening the gate valve attached near the tip of the double-walled pipe, thereby reducing the volume of the container to 1 m³. 3 186 kg was applied to the muddy soil. In this case, the amount of main agent added to the muddy soil was 126 kg / m². 3 The amount of additive used is 60 kg / m². 3 The amount to be added as a liquid solidifying agent for soil is 186 kg / m². 3 This mixture was then mixed with a hand mixer, filled into a mold with a diameter of 100 mm and a height of 200 mm, and left to stand in a dark, indoor location at 25°C. Subsequently, the pH and cone index of the test specimen were measured using a pH meter and a cone penetrometer, respectively, and the results shown in Table 1 were obtained. The soil used in the test was collected from a construction site, and before the addition of the liquid soil solidifying agent, the pH was 8.08, the weight water content was 38.5%, the weight water content ratio was 62.6%, and the cone index measured with a cone penetrometer was 50 kN / m 2 (This translates to an N-value of approximately 0.8, which indicates the strength of the ground.) Furthermore, when approximately 0.2 kg of the liquid soil solidification agent was collected in a glass container and measured with a pH meter, the pH was found to be 7.5.

[0027] [Table 1]

[0028] As can be seen from the test results of Examples 1 and 2, the liquid soil solidification material for this application exhibited a neutral pH of 5.8 to 8.6. Furthermore, a test specimen obtained by adding the liquid soil solidification material to mud (corresponding to soil constituting soft ground) with a pH of 8.08 collected at a construction site had a pH of around 8.5 one hour after being filled into a mold and left to stand (i.e., one hour after adding and stirring the liquid soil solidification material to the mud). In other words, adding the liquid soil solidification material for this application to the mud did not cause the pH to shift significantly towards acidity or alkalinity. Here, this pH value is within the range of pH 5.8 to pH 8.6, which is the water quality standard set by the Ministry of Health, Labour and Welfare. Therefore, it can be judged that the risk of unexpected impacts on the surrounding environment is extremely low, even immediately after improvement, when rainfall or groundwater inflow occurs on the ground or subgrade improved with the liquid soil solidification material.

[0029] Furthermore, the test specimens of Example 1 and Example 2 had a cone index of 400 KN / m³ three days after being filled into the mold and left to stand (i.e., three days after adding and stirring the liquid soil solidifying agent to the mud). 2 The above conclusions were reached. Therefore, it can be concluded that by adding the liquid soil solidification agent for soils according to this application to mud and other soils with a high weight water content, the soil can be improved to a state that can be easily transported by dump trucks, etc., and the soil can be improved to a state that can be used for purposes such as land development and river embankment construction. Furthermore, the cone index of the test specimens in Example 1 and Example 2 was 1100 KN / m after 7 days of being filled into molds and left to stand (i.e., 7 days after adding the liquid soil solidification agent for soil to the mud and stirring). 2 The result was above (approximately 17.6 or higher when converted to an N-value indicating ground strength). Therefore, it can be determined that by adding the soil liquid solidification material for soil according to this application to the soil such as mud that constitutes soft ground or soft subgrade, the soft ground or soft subgrade can be improved into strong ground or subgrade with high bearing capacity or support capacity for traffic loads. [Industrial applicability]

[0030] The invention described in this application can be used for stabilizing soft ground and roadbeds, solidifying soil with a high water content (watery soil) to make it transportable by dump trucks, and improving construction waste soil for reuse. Furthermore, the invention described in this application can be used as a soil improvement method that allows contractors to perform ground improvement work and solidification work to make soil with a high water content (watery soil) transportable by dump trucks, etc., more efficiently and safely at construction sites.

Claims

1. A neutral liquid solidifying agent for soil, The main component consists of magnesium oxide and water, It consists of two liquids: a main component which is one or more compounds selected from the group consisting of aluminum sulfate, polyaluminum chloride, magnesium chloride, and ferrous sulfate, and an auxiliary agent which is water as a solvent. The main component has a ratio of magnesium oxide to water of 1:0.5 to 1:1.2 by weight. The auxiliary agent has a ratio of 1:0.5 to 1:1.5 by weight of the main component and water. A liquid soil solidifying agent characterized in that the ratio of the main agent to the auxiliary agent is 6:4 to 8:2 by weight.

2. A soil improvement method using the liquid solidifying agent for soil described in claim 1, characterized by comprising the following steps 1 to 5. Step 1: Weigh out the magnesium oxide and water, which are the main ingredients, in a weight ratio of 1:0.5 to 1:1.

2. Step 2: The main component, which is one or more compounds selected from the group consisting of aluminum sulfate, polyaluminum chloride, magnesium chloride, and ferrous sulfate, and the solvent, water, are weighed in a weight ratio of 1:0.5 to 1:1.

5. Step 3: The main ingredient and the auxiliary ingredient are prepared by adding them to the ingredient inlets of separate mixers and stirring them. Step 4: The main agent and auxiliary agent are weighed to a weight ratio of 6:4 to 8:2, and the main agent and auxiliary agent are injected into the inlet of a Y-shaped pipe or a double pipe designed so that the two chemical solutions merge and come into contact near the end of the pipe, thereby preparing a liquid soil solidifying agent by bringing them into contact inside the pipe. Step 5: Add the liquid soil solidifying agent at a rate of 10 kg / m³ as the main component. ３ ~140 kg / m ３ The liquid soil solidifying agent is added to the soil and mixed with the soil.

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