JP2006219547A - Soil-solidifying material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil-solidifying material which can change the pH of treated soil to a weak alkaline to neutral region, does not elute a harmful substance, and can impart high solidification strengths to various soils. <P>SOLUTION: This soil-solidifying material containing magnesium oxide as a main component is characterized in that the magnesium oxide has an average particle diameter (D<SB>50</SB>) of 2.50 to 4.5μm and a standard deviation of 0.20 to 0.35 μm. The soil-solidifying material, wherein the magnesium oxide has preferably a particle size distribution comprising 5 to 1 μm particles in an amount of ≥60% and 15 to 5 μm particles in an amount of ≤35%. If necessary, the soil-solidifying material preferably further contains at least one of a solidifying agent, a pH-adjusting agent, an organic polymer coagulating agent and/or a water-absorbing agent, and a solidification accelerator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solidifying material for soil, in particular, to solidify soil such as volcanic ash soil, shield method, underground continuous wall method, dredging method, surface layer and deep ground improvement method, etc. The present invention relates to a solidifying material for soil for improving the ground by receiving work or chemical injection.

  Soil such as volcanic ash soil and generated soil contains a large amount of moisture and is fluid, and as such is difficult to transport and transport. Therefore, a method of transporting and transporting these soils after adding a solidifying material for soil has been adopted. Moreover, the solidification material for soil is also used for the purpose of modifying these soils.

  As these solidifying materials for soil, cement-based solidified materials, quicklime-based solidified materials, gypsum-based solidified materials, organic polymer-based flocculants and the like are used.

  The cement-based solidified material and quicklime-based solidified material are usually added in an amount of 10 to 15% by weight with respect to the volcanic ash soil or the generated soil. There is a problem that it takes a long time to solidify to such an extent that it can be conveyed.

  Furthermore, in the above-mentioned gypsum-based solidifying material, the treated soil solidifies in a short time, but when contacted with water, the solidified material dissolves and the treated soil dissolves, and in the case of soil containing a large amount of moisture, solidification failure occurs. Wake up.

  Even with the organic polymer flocculant, the solidification time is fast, but the treated soil is not water resistant, and the treated soil collapses when in contact with water. In particular, in the case of soil that contains a large amount of water, the amount of organic polymer flocculant added becomes large, and the treated soil becomes an elastic body, which makes it difficult to break down or carry it out with heavy machinery. Become.

  On the other hand, in the natural ground where the geological conditions are poor, a preparatory work is being carried out to improve the ground at the upper part of the site to be excavated at the back of the tunnel face, and the purpose is to strengthen the ground, stop water, shut off water, prevent liquefaction, etc. As an example, a chemical solution injection method for injecting a chemical solution into a gap in the ground has been implemented. For these purposes, soil solidification materials are also used.

  Conventionally, cement-based solidified material and urethane-based solidified material are mainly used in the above-mentioned prior construction, and water glass-based solidified material is mainly used in the above-mentioned chemical solution injecting work.

  In the case of a cement-based solidified material, there is a risk that high alkali content or hexavalent chromium may be eluted from the improved ground, and the injection pressure may rise abnormally and may be difficult to inject. In such a case, a urethane-based solidified material is used, but in the case of a urethane-based solidified material, strength is expressed early, but it is said that the urethane-based solidified agent is eluted from the improved ground and pollutes the environment. There is a problem, and there is also a problem with cost. Furthermore, it is difficult to inject even a urethane-based caking agent into dense sandy soil.

  Furthermore, in the water glass-based solidified material, the initial homogel strength and the long-term homogel strength are not sufficient, and the silica is leached from the water glass solidified material in the improved ground, or the strength deteriorates, or the cement There is a problem that high alkali content is eluted from the improved ground as well as the system solidified material.

  For this reason, it replaces with the conventionally used solidification material, and the solidification material which has magnesium oxide or magnesium hydroxide as a main component is proposed.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 51-20414) proposes a solidifying material in which magnesium hydroxide and a basic aluminum composite salt are combined, and Patent Document 2 (Japanese Patent Laid-Open No. 2000-239660) proposes an oxidation material. Solidification materials combining magnesium and polyvalent metal salts have been proposed.

Japanese Patent Laid-Open No. 51-20414 JP 2000-239660 A

  In the solidified material containing magnesium oxide or magnesium hydroxide, the pH of the treated soil can be made to be lower than the upper limit 8.6 of the allowable value of the water quality standard indicated in Article 4 of the Water Supply Law, In addition, no harmful substances are eluted. Furthermore, the initial homogel strength and the long-term homogel strength are relatively high, leaching is small, the strength of the treated soil is durable, and there is no problem of deterioration over time.

  However, although the solidified material for soil mainly composed of magnesium oxide or magnesium hydroxide has the above-mentioned many advantages, there is a problem that the solidified strength is still not sufficient when added to the soil, and it has a higher level in various soils. There is a demand for a solidified material for soil that imparts a solidified strength.

  Therefore, the object of the present invention is to make the pH of the treated soil a weak alkaline to neutral region, and there is no elution of harmful substances, and a solidified material for soil that can impart high solidification strength to various soils. Is to provide.

  Thus, as a result of the study, the present inventors have found that a solidified material for soil using magnesium oxide having specific powder characteristics can achieve the above object, and have reached the present invention.

That is, the present invention is a soil solidifying material mainly composed of magnesium oxide, wherein the magnesium oxide has an average particle diameter (D ₅₀ ) of 2.50 μm to 4.50 μm and a standard deviation of 0.20 μm to 0.00. It has a powder characteristic of 35 μm.

  And the solidifying agent for soil according to the present invention is characterized in that the particle size distribution of the magnesium oxide powder is less than 5 μm to 1 μm particles of 60% or more and less than 15 μm to 5 μm particles of 35% or less. A solidifying material for soil is provided.

More preferably, the magnesium oxide used in the solidifying material for soil according to the present invention has an average particle diameter (D ₅₀ ) of 3.00 μm to 4.00 μm and a standard deviation of 0.25 μm to 0.30 μm. And it is preferable that the particle size distribution of the magnesium oxide powder in such a case is 65% to 75% for particles of less than 5 μm to 1 μm and 25% to 30% for particles of less than 15 μm to 5 μm.

  In addition, the solidifying material for soil according to the present invention desirably contains a solidifying agent, and a polyvalent metal salt is preferably used as such a solidifying agent.

  Furthermore, it is desirable that the solidifying material for soil according to the present invention contains various compounding agents depending on its use. Such a compounding agent is at least one of a pH adjuster, an organic polymer flocculant and / or a water absorbing agent, and a solidification accelerator.

  Since the solidifying material for soil of the present invention is mainly composed of magnesium oxide, the pH of the target soil can be maintained in a neutral range, no toxic substances are eluted, and the strength is durable and time-dependent. Since there is no problem of deterioration and magnesium oxide having specific powder characteristics is used, various soils can be rapidly solidified and high solidification strength can be imparted.

  Hereinafter, the best mode for carrying out the present invention will be described.

(Solidifying material for soil according to the present invention)
Magnesium oxide used for the solidifying material for soil according to the present invention has specific powder characteristics. That is, the soil solidifying material according to the present invention is a soil solidifying material mainly composed of magnesium oxide, and has an average particle size (D ₅₀ ) of 2.50 μm to 4.50 μm, preferably 3.00 μm to 4. Magnesium oxide powder having a powder property of 0.000 μm and a standard deviation of 0.20 μm to 0.35 μm, preferably 0.25 μm to 0.30 μm is used.

  Here, it is preferable that the average particle diameter of the magnesium oxide contained in the soil solidifying agent according to the present invention is in the range of 2.50 μm to 4.50 μm. The smaller the average particle size of the magnesium oxide, the larger the contact interface area with the soil, the higher the reactivity, and the solidification can be completed early. However, if the solidification reaction becomes too fast, fine cracks will occur in the soil after solidification and the appearance will deteriorate, the hardness after solidification will become too high, and it will feel comfortable when people step on it. Does not occur. That is, when the average particle diameter of the magnesium oxide powder constituting the soil solidifying agent is less than 2.50 μm, the solidification reaction time is too short, the appearance is poor and brittle as described above, and the walking feeling is deteriorated. On the other hand, when the average particle diameter of the magnesium oxide powder constituting the soil solidifying agent exceeds 4.50 μm, the solidification time becomes long, and the working efficiency becomes remarkably inferior. Therefore, it is possible to homogenize and control the solidification time, which has been conventionally dispersed, by using a soil solidifying agent composed of particles having an average particle diameter in the above range. Furthermore, it is more preferable that the average particle size of the particles of the soil solidifying agent is in the range of 3.00 μm to 4.00 μm. When the average particle diameter of the magnesium oxide powder of the soil solidifying agent is within this range, the time required for the solidification reaction hardly varies and the most stable one is obtained.

  And on the premise that the magnesium oxide powder particles of the soil solidifying agent have an average particle size in the above range, particles of less than 5 μm to 1 μm are 60% or more, and particles of less than 15 μm to 5 μm are 35% or less of magnesium oxide. It is preferable to use it. The average particle diameter of the magnesium oxide described above serves as a constant index representing the fineness of the powder particles, but cannot be an index of how much coarse particles are contained. On the other hand, what is meant by the particle size distribution as described herein is an index of how much coarse particles in a range not shown here are present. That is, from the above particle size distribution, particles of less than 5 μm to 1 μm are 60% or more and particles of less than 15 μm to 5 μm are 35% or less, so the total of coarse particles of 15 μm or more and ultrafine particles of less than 1 μm is about 5%. There is a possibility that it exists. And even if all of these are considered as coarse particles of 15 μm or more, the coarse particles do not exceed 5%. By using a soil solidifying agent having such a good particle size distribution, the solidification time and the like can be further controlled.

  When the particle size distribution is specified more clearly with respect to this particle size distribution, particles of less than 5 μm to 1 μm become 5% to 75%, and particles of less than 15 μm to 5 μm become 25% to 30% magnesium oxide powder. The range described here is a range as a result of the results of the present inventors' research and diligent efforts to keep the particle size distribution within a certain range.

Even when using magnesium oxide whose average particle size (D ₅₀ ), standard deviation, particle size of less than 5 μm to 1 μm and particle size of less than 5 μm to 5 μm is out of the above range, the solidification time is long, and it can be quickly applied to various soils. Appropriate solidification strength cannot be imparted.

The average particle diameter (D ₅₀ ), standard deviation, the amount of particles of less than 5 μm to 1 μm, and the amount of particles of less than 5 μm to 5 μm are measured by the following methods. The average particle size in the present invention is measured by mixing 0.1 g of magnesium oxide powder with a 0.1% aqueous solution of SN Dispersant 5468 (manufactured by San Nopco) and using an ultrasonic homogenizer (US-300T, manufactured by Nippon Seiki Seisakusho). After dispersing for 5 minutes, the measurement was performed using a laser diffraction / scattering particle size distribution analyzer, Micro Trac HRA 9320-X100 (Leeds + Northrup).

  The solidifying material for soil according to the present invention preferably contains a solidifying agent. As such a solidifying agent, a polyvalent metal salt is mainly used. Examples of the polyvalent metal salt include aluminum sulfate, ferrous sulfate, polyferric sulfate, polyaluminum chloride, alum, calcined alunite, zinc sulfate and the like. May be used.

  Among the above-mentioned polyvalent metal salts, aluminum sulfate, polyaluminum chloride, ferrous sulfate, and polyferric sulfate have the effect of lowering the pH of the target soil as the solidifying agent, and are desirably used from this point. The solidifying agent described above is desirably contained in an amount of 10 to 100 parts by weight with respect to 100 parts by weight of magnesium oxide.

  It is desirable that the soil solidifying material according to the present invention contains various compounding agents depending on its use. Examples of such a compounding agent include one or more of a pH adjuster, an organic polymer flocculant and / or a water absorbing agent, and a solidification accelerator.

  A pH adjuster is contained in order to keep the treated soil weakly alkaline to neutral. As the pH adjuster, an acid agent is used in order to adjust the pH to a neutral range of 5.8 to 8.6. Examples of such an acid agent include powdered organic acids such as oxalic acid, citric acid, malic acid, benzenesulfonic acid, and sulfamic acid, and powdered salts of strong acid and weak base such as ammonium sulfate and ammonium benzenesulfonate, Powdered acidic salts such as ferric chloride, magnesium chloride, magnesium sulfate, and ammonium chloride are used. Two or more of the above pH adjusters may be used in combination. The pH adjuster is contained in the solidified material for soil in an amount of 5% by weight to 50% by weight. Needless to say, the content should be adjusted according to the pH of the soil.

  When the moisture of the treated soil is contained in a large amount of, for example, 50% by weight or more, an organic polymer flocculant and / or a water absorbing agent may be contained. Examples of the organic polymer flocculants include synthetic polymer flocculants such as sodium polyacrylate, polyacrylamide, sodium acrylate-acrylamide copolymer, polyethylene oxide, natural polymer flocculants such as guar gum, xanthan gum, and alginic acid. Examples of the water absorbing agent include sewage incineration ash, charcoal, activated carbon, and silica gel. The organic polymer flocculant and / or water-absorbing agent is contained in the solidified material for soil in an amount of 0.1% to 2.0% by weight, but the content should be adjusted according to the moisture content of the soil. Needless to say.

In order to promote the solidification of the treated soil, a solidification accelerator is further contained. As the solidification accelerator, a compound capable of generating carbon dioxide gas by reacting with water, such as sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ethylene carbonate, isocyanate compound, or the like is used. When the solidification accelerator is used in combination with the above pH adjuster, the pH can be easily lowered even when the pH of the treated soil is high, so that it can also be used as an acidic auxiliary agent.
It is desirable that the solidification promoting material is contained in the solidification material for soil in an amount of 0.3% by weight to 10.0% by weight.

  In the above components, the magnesium oxide and the solidifying agent solidify the soil by the solidification reaction of the soil, but the pH is adjusted to a weak alkali to neutral region, preferably pH 5 to pH 9, more preferably pH 5.8 to pH 8 by the pH adjusting agent. The solidification reaction of magnesium oxide, a solidifying agent, and soil is promoted by adjusting to .6, and solidification is further promoted by adding a solidification accelerator. In addition, in the case of soil containing a large amount of water, adding an organic polymer flocculant and / or a water absorbing agent in addition to the above components will condense the soil and eliminate the water, or It is absorbed and the desired soil solidification is obtained.

  Further, if desired, a filler such as calcium carbonate, anhydrous gypsum, hemihydrate gypsum, talc, unbaked dolomite, quartzite powder, slag may be contained. And these fillers are contained in 25% by weight to 500% by weight in the solidified material for soil.

  The solidifying material for soil according to the present invention is used for solidifying soil such as volcanic ash soil or generated soil, or for improving the ground by receiving soil or chemical injection.

  The solidifying material for soil according to the present invention mixes all the components before adding to the soil, and then may be added to the soil, or each component may be added individually to the soil, and further the components Two or more of them may be mixed in advance and added to the soil.

The amount of the solidified material for soil according to the present invention added to the soil is appropriately determined depending on the soil quality and water content. In general, the amount of addition is reduced in the case of soil with a high viscosity (clay), and the amount of addition is increased in the case of soil with a low viscosity (sand). Further, the amount of addition is increased in the case of soil with a high water content, and the amount of addition is decreased in the case of soil with a low water content. In general, in the case of soil having a water content of 80% by weight to 100% by weight, the solidified material for soil according to the present invention is added in an amount of about 30 kg to 100 kg per 1 m ³ of soil, and the water content is 100% by weight to 200% by weight. In the case of soil, about 50 kg to 200 kg of soil solidifying material according to the present invention is added per 1 m ³ of soil.

  The solidified material for soil according to the present invention may be mixed with volcanic ash soil containing a silica component and used as a mixed solidified material for soil. In this case, 5 parts by weight to 300 parts by weight of volcanic ash soil is blended with 100 parts by weight of the solidified material for soil.

  Such mixed solidification material for soil replenishes silica components such as allophane, which is an amorphous component required for solidification, and thereby appropriate solidification of volcanic ash soil, alluvial soil, sandy soil with less silica component Is possible. Hereinafter, the present invention will be specifically described based on examples.

The thing with the following property was used as magnesium oxide used for the solidification material for soil.
・ Average particle diameter (D ₅₀ ): 3.52 μm
Standard deviation: 0.266 μm
・ Less than 1 μm: 2.32%
-Particles of less than 5 μm to 1 μm: 69.33%
-Particles of less than 15 μm to 5 μm: 28.35%
・ 15μm or more: 0.00%

100 kg of solidified material for soil consisting of 100 parts by weight of magnesium oxide and 20 parts by weight of aluminum sulfate (solidifying agent) was added to 1 m ³ of volcanic ash soil (Kanto loam), and mixed and stirred. Table 1 shows the solidification status when this treated soil is cured in the atmosphere.

(Comparative Example 1)
The thing with the following property was used as magnesium oxide used for the solidification material for soil.
・ Average particle diameter (D ₅₀ ): 13.73 μm
Standard deviation: 0.473 μm
・ Less than 1 μm: 4.04%
-Particles of less than 5 μm to 1 μm: 11.36%
-Particles of less than 15 μm to 5 μm: 24.15%
・ 15μm or more: 60.45%

100 kg of solidified material for soil consisting of 100 parts by weight of magnesium oxide and 20 parts by weight of aluminum sulfate (solidifying agent) was added to 1 m ³ of volcanic ash soil (Kanto loam), and mixed and stirred. Table 1 shows the solidification status when this treated soil is cured in the atmosphere.

  As can be seen from Table 1, compared to Comparative Example 1, Example 1 can quickly solidify volcanic ash soil and can quickly impart high solidification strength. From the contents listed in Table 1, the uniaxial compression strength after 7 to 20 days is higher in the examples. And about the solidification intensity | strength after 60 days, although it seems that there is no big difference in an Example and a comparative example, the Example becomes a slightly higher intensity | strength. From these facts, it can be understood that when the particle size of magnesium oxide contained in the soil solidifying agent is reduced, the reactivity is increased and the solidification rate is increased, and at the same time, good solidification strength can be obtained.

  Since the solidified material for soil of the present invention uses magnesium oxide having specific powder characteristics, it can quickly solidify various soils and impart high solidification strength. For this reason, the construction period can be shortened as a solidifying material for various soils, and it is suitably used for a wide range of applications.

Claims (7)

A solidifying material for soil mainly composed of magnesium oxide,
The magnesium oxide is a magnesium oxide powder having an average particle size (D ₅₀ ) of 2.50 μm to 4.50 μm and a standard deviation of 0.20 μm to 0.35 μm. The solidification for soil according to claim 1, wherein the particle size distribution of the magnesium oxide powder is 60% or more of particles of less than 5 µm to 35% of particles of less than 15 µm to 5 µm. Wood. The solidified material for soil according to claim 1 or 2, wherein the magnesium oxide powder has an average particle size (D ₅₀ ) of 3.00 µm to 4.00 µm and a standard deviation of 0.25 µm to 0.30 µm. 4. The solidified material for soil according to claim 3, wherein the particle size distribution of the magnesium oxide powder particles is 65% to 75% of particles of less than 5 μm to 1 μm and 25% to 30% of particles of less than 15 μm to 5 μm. . The solidifying material for soil according to any one of claims 1 to 4, comprising a solidifying agent. The solidifying material for soil according to claim 5, wherein the solidifying agent is a polyvalent metal salt. The solidifying material for soil according to any one of claims 1 to 6, comprising any one or more of a pH adjuster, an organic polymer flocculant and / or a water absorbing agent, and a solidification accelerator.