JP7497116B2 - Soil solidification agent - Google Patents

Soil solidification agent Download PDF

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JP7497116B2
JP7497116B2 JP2020112353A JP2020112353A JP7497116B2 JP 7497116 B2 JP7497116 B2 JP 7497116B2 JP 2020112353 A JP2020112353 A JP 2020112353A JP 2020112353 A JP2020112353 A JP 2020112353A JP 7497116 B2 JP7497116 B2 JP 7497116B2
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JP2021014573A (en
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豊 松田
隆一 松田
幸一 漆原
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松田技研工業株式会社
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Description

本発明は、土壌用固化剤に関し、詳しくは土木工事等により発生する含水土壌(軟弱土壌や汚泥)の強度を向上させることのできる土壌用固化剤に関する。 The present invention relates to a soil solidification agent, and more specifically to a soil solidification agent that can improve the strength of water-containing soil (soft soil and sludge) generated by civil engineering works, etc.

従来より、含水土壌の強度向上を図るための固化剤として、セメント系材料や石灰系材料又はこれらの混合材料が主に用いられている。 Traditionally, cement-based materials, lime-based materials, or mixtures of these have been used primarily as solidification agents to improve the strength of wet soil.

例えば、特許文献1には、セメント成分と石膏又はこれに加えてスラグを一定量含むセメント系固化材が記載されている。また、特許文献2には、セメント成分に対して生石灰と石膏又はこれに加えてスラグを一定量含むセメント石灰系固化材が記載されている。これら特許文献1及び特許文献2に係る固化材は、含水土壌に対して改良処理を施した場合の強度発現性に優れるとされている。 For example, Patent Document 1 describes a cement-based solidification material that contains a certain amount of cement components and gypsum or slag in addition to these. Patent Document 2 describes a cement-lime-based solidification material that contains a certain amount of quicklime and gypsum or slag in addition to these, in addition to the cement components. The solidification materials described in Patent Documents 1 and 2 are said to have excellent strength development when water-containing soil is treated for improvement.

ところが、これら従来の土壌用固化剤では、含水土壌の土質(例えば、火山灰質粘性土)によっては、固化処理後の土壌(改良土壌)として十分な強度を安定的に得ることができなかった。これをふまえ、本発明者は、処理対象となる含水土壌の土質を問わずに、従来よりも高い固化強度を得ることの可能な土壌用固化剤を見出している(特許文献3を参照)。この土壌用固化剤は、700℃~1000℃で焼成し、粉末度4000cm/g以上となるように調整された酸化マグネシウムを用いたものである。 However, these conventional soil solidifying agents were unable to stably obtain sufficient strength for the soil (improved soil) after solidification treatment, depending on the soil quality of the moist soil (e.g., volcanic ash clayey soil). Based on this, the present inventor has discovered a soil solidifying agent that can obtain a higher solidification strength than conventional agents, regardless of the soil quality of the moist soil to be treated (see Patent Document 3). This soil solidifying agent uses magnesium oxide that has been calcined at 700°C to 1000°C and adjusted to a fineness of 4000 cm2 /g or more.

特開2002-137950号公報JP 2002-137950 A 特開2002-294232号公報JP 2002-294232 A 特開2006-176669号公報JP 2006-176669 A

しかし、特許文献3に開示の土壌用固化剤では、含水土壌の土質によってばらつきはあるものの、改良土壌として必要十分な強度を得るのに少なくとも数時間程度を要していた。また、特許文献3に開示の土壌用固化剤では、改良土壌のpH値を中性範囲(日本国環境省が定める排水基準値pH5.8~pH8.6を指標とする)に安定的に制御することが困難であった。改良土壌のpHが高い場合(pH値が8.6を超えてアルカリ性となる場合)、植物の生育に障害が生じる等して環境破壊を起こす恐れがある。 However, with the soil solidification agent disclosed in Patent Document 3, it took at least several hours to obtain sufficient strength for improved soil, although this varied depending on the quality of the wet soil. In addition, with the soil solidification agent disclosed in Patent Document 3, it was difficult to stably control the pH value of the improved soil to a neutral range (using the wastewater standard value of pH 5.8 to pH 8.6 set by the Ministry of the Environment of Japan as an indicator). If the pH of the improved soil is high (if the pH value exceeds 8.6 and becomes alkaline), there is a risk of environmental destruction, such as impeding plant growth.

そこで、本発明では、上述の問題に鑑み、含水土壌の土質を問わずに、改良土壌として必要十分な強度を従来よりも短時間で得ることができ、且つアルカリ公害の恐れがない土壌用固化剤を提供することを目的とする。 In view of the above problems, the present invention aims to provide a soil solidification agent that can provide sufficient strength for improved soil in a shorter time than conventional methods, regardless of the type of water-containing soil, and that does not pose a risk of alkali pollution.

本件の発明者等は、鋭意研究の結果、以下の発明に想到した。 As a result of extensive research, the inventors of this case came up with the following invention.

すなわち、本発明は、土壌に混入させ固化させるための土壌用混合固化剤であって、700℃~1000℃で焼成して粉末度4000cm/g以上となるように調整された酸化マグネシウムと、固化強度推進剤とを含有し、当該酸化マグネシウムの含有量(X重量部)と当該固化強度推進剤の含有量(Y重量部)との比率X/Yが0.38~0.97であることを特徴とする。 That is, the present invention relates to a soil solidification agent mixture for mixing with soil to solidify it, which contains magnesium oxide adjusted by calcining at 700°C to 1000°C to have a fineness of 4000 cm2 /g or more, and a solidification strength propellant, and is characterized in that the ratio X/Y of the content of the magnesium oxide (X parts by weight) to the content of the solidification strength propellant (Y parts by weight) is 0.38 to 0.97.

また、本発明に係る土壌用固化剤において、前記固化強度推進剤は、硫酸アルミニウム、硫酸第一鉄、ポリ塩化アルミニウム、塩化第二鉄、及び塩化マグネシウムから選択される一種以上であることが好ましい。 In the soil solidification agent according to the present invention, the solidification strength accelerator is preferably one or more selected from the group consisting of aluminum sulfate, ferrous sulfate, polyaluminum chloride, ferric chloride, and magnesium chloride.

また、本発明に係る土壌用固化剤は、高分子凝集剤を、総量に対して0.1重量部~4.0重量部の割合で更に含有したことが好ましい。 Moreover, the soil solidifying agent according to the present invention preferably further contains a polymer flocculant in an amount of 0.1 to 4.0 parts by weight based on the total amount.

本発明に係る土壌用固化剤は、従来のセメント材料や石灰系材に代わる材料であり、これらセメント材料等では十分な固化強度が得られ難かった土質の含水土壌であっても、改良土壌として必要十分な強度にまで従来よりも短時間で向上させることができる。また、本発明に係る土壌用固化剤は、改良土壌の高強度化を図りながらも、改良土壌のpH値を従来よりも中性(pH7)に近いものとすることができる。 The soil solidification agent of the present invention is a material that replaces conventional cement materials and lime-based materials , and can improve the strength of water-containing soil that is difficult to obtain sufficient solidification strength with these cement materials, etc., to a necessary and sufficient strength for improved soil in a shorter time than conventional methods. Furthermore, the soil solidification agent of the present invention can increase the strength of the improved soil while making the pH value of the improved soil closer to neutral (pH 7) than conventional methods.

以下、本発明を実施するための最良の形態について説明する。 The best mode for implementing the present invention is described below.

本発明に係る土壌用固化剤は、700℃~1000℃で焼成し、粉末度4000cm/g以上となるように調整された酸化マグネシウムと固化強度推進剤とを含有する。そして、当該酸化マグネシウムの含有量(X重量部)と当該固化強度推進剤の含有量(Y重量部)との比率X/Yが0.38~0.97となるものである。酸化マグネシウムは土中の水と反応すると、水酸化マグネシウムを生じる。この水酸化マグネシウムは難溶性であるが、土に対して硬化物としての強度をもたらすものではなく、土壌中のシリカ成分等と反応して、その反応生成物が含水土壌の固化に寄与すると考えられる。その結果、改良土壌として必要十分な強度を得ることが可能となる。 The soil solidification agent according to the present invention contains magnesium oxide, which has been calcined at 700°C to 1000°C and adjusted to have a fineness of 4000 cm2 /g or more, and a solidification strength promoter. The ratio X/Y of the content of the magnesium oxide (X parts by weight) to the content of the solidification strength promoter (Y parts by weight) is 0.38 to 0.97. When magnesium oxide reacts with water in the soil, it produces magnesium hydroxide. This magnesium hydroxide is sparingly soluble, but does not provide soil with strength as a hardened material. It is believed that the reaction product reacts with silica components and the like in the soil and contributes to the solidification of the water-containing soil. As a result, it becomes possible to obtain sufficient strength as improved soil.

ここで用いる酸化マグネシウムは、700℃~1000℃で焼成して粉末度4000cm/g以上となるように調整されたもの(所謂「軽焼マグネシア」)である。酸化マグネシウムを700℃~1000℃で焼成するのは、後に焼成後の酸化マグネシウムを解砕し粉砕することで、粉末度4000cm/g以上となるようにするために最も良好な焼成温度範囲だからである。ここで焼成温度が700℃未満の場合には、焼成不良を起こしやすく酸化マグネシウムの細粒化が困難となり、活性度に優れた良好な酸化マグネシウム粉末を得ることができない。一方、焼成温度が1000℃を超える場合には、焼成後の酸化マグネシウムが強固に凝集し易くなり、後の解砕作業が困難となり、低温焼成品に比べて固化速度が遅くなる傾向が強くなる。 The magnesium oxide used here is adjusted to have a fineness of 4000 cm 2 /g or more by firing at 700°C to 1000°C (so-called "light-burned magnesia"). Magnesium oxide is fired at 700°C to 1000°C because this is the most suitable firing temperature range for crushing and pulverizing the fired magnesium oxide to have a fineness of 4000 cm 2 /g or more. If the firing temperature is less than 700°C, firing failure is likely to occur, making it difficult to refine the magnesium oxide, and good magnesium oxide powder with excellent activity cannot be obtained. On the other hand, if the firing temperature exceeds 1000°C, the fired magnesium oxide is likely to aggregate strongly, making the subsequent crushing operation difficult, and the solidification rate tends to be slower than that of low-temperature fired products.

また、上述した温度範囲で焼成を行う場合の時間は、大気雰囲気中で4時間~5時間の範囲とすることが好ましい。ここで、焼成時間が4時間未満の場合には、焼成後のミル装置を用いての粉末化作業が困難となる。一方、焼成時間が5時間を超える場合には、得られた焼成後の酸化マグネシウムの活性度が低下し、固化反応を迅速に行わせることができなくなる。 When firing within the above-mentioned temperature range, the time is preferably in the range of 4 to 5 hours in an air atmosphere. If the firing time is less than 4 hours, it becomes difficult to powder the material using a mill after firing. On the other hand, if the firing time exceeds 5 hours, the activity of the resulting magnesium oxide after firing decreases, and the solidification reaction cannot be carried out quickly.

一般的に酸化マグネシウム(MgO)には、低温焼成品(1000℃以下での焼成)と高温焼成品(1000℃を超える温度での焼成)とがあるが、反応性の点からみて低温焼成品(軽焼マグネシア)の使用が望ましい。そして、酸化マグネシウムの粉末度は4000cm/g以上が好ましい。粉末度が、4000cm/g以下のものを用いると、低温焼成品を用いても、土壌の固化速度が遅くなり、土壌の固化に適さなくなるからである。なお、ここで言う粉末度とは、所謂粉体として捉えたときの比表面積であり、本発明では、実測した値であり、酸化マグネシウム粉2.00gを75℃で10分間の脱気処理を行った後、モノソーブ(カンタクロム社製)を用いてBET1点法で測定した結果として得られる比表面積のことである。 Generally, magnesium oxide (MgO) is available in low-temperature fired products (fired at 1000°C or less) and high-temperature fired products (fired at temperatures above 1000°C). From the viewpoint of reactivity, it is preferable to use low-temperature fired products (lightly burned magnesia). The fineness of magnesium oxide is preferably 4000 cm2 /g or more. If a fineness of magnesium oxide of 4000 cm2 /g or less is used, the soil solidification speed will be slow, even if a low-temperature fired product is used, and it will not be suitable for soil solidification. The fineness here means the specific surface area when considered as a so-called powder, and in the present invention, it is an actually measured value, and it means the specific surface area obtained as a result of degassing 2.00 g of magnesium oxide powder at 75°C for 10 minutes and then measuring it by the BET one-point method using Monosorb (manufactured by Quantachrome).

更に言えば、上述した温度範囲で酸化マグネシウムを焼成すると、粉体化するため現在の技術レベルのミル処理をしたときに、経験的に4000cm/g~8500cm/gの粉末度の酸化マグネシウム粉にできることが判明している。ちなみに、粉末度が大きくなる程、固化反応の速度は上昇する傾向となり好ましい。 Furthermore, it has been empirically proven that when magnesium oxide is sintered within the above-mentioned temperature range and then milled to powderize it using the current level of technology, it can be made into magnesium oxide powder with a fineness of 4000 cm2 /g to 8500 cm2 /g. Incidentally, the greater the fineness, the faster the solidification reaction tends to occur, which is preferable.

なお、上述した酸化マグネシウムは、固化処理対象となる含水土壌1mに対して10kg~300kgを添加することが望ましい。ここで、酸化マグネシウムの添加量が30kg未満の場合には、土質を問わず当該含水土壌を安定して速やかに固化させることは困難となる。一方、酸化マグネシウム添加量が300kgを超える場合には、当該含水土壌の固化が進行し過ぎて、得られる改良土壌に微小な亀裂や肌荒れを生じ美観が損なわれると共に脆くなる。 It is preferable to add 10 kg to 300 kg of the above-mentioned magnesium oxide per 1 m3 of the moist soil to be solidified. If the amount of magnesium oxide added is less than 30 kg, it is difficult to stably and quickly solidify the moist soil, regardless of the soil quality. On the other hand, if the amount of magnesium oxide added exceeds 300 kg, the moist soil will be solidified too much, causing microcracks and roughness in the improved soil obtained, impairing its aesthetic appearance and making it brittle.

そして、上述した固化強度推進剤は、硫酸アルミニウム、硫酸第一鉄、ポリ塩化アルミニウム、塩化第二鉄、及び塩化マグネシウムから選択される一種以上であることが好ましい。本発明の固化強度推進剤は、pH調整剤としても作用する。当該固化強度推進剤は、酸化マグネシウムよりも弱酸性であり、得ようとする改良土壌のpHの上昇を抑制することができる。 The solidification strength accelerator is preferably one or more selected from aluminum sulfate, ferrous sulfate, polyaluminum chloride, ferric chloride, and magnesium chloride. The solidification strength accelerator of the present invention also acts as a pH adjuster. The solidification strength accelerator is weaker acidic than magnesium oxide, and can suppress an increase in the pH of the improved soil to be obtained.

本発明に係る土壌用固化剤は、酸化マグネシウムの含有量(X重量部)と固化強度推進剤の含有量(Y重量部)との比率X/Yを0.38~0.97としたものである。本発明に係る土壌用固化剤は、上述した酸化マグネシウム及び固化強度推進剤をこの比率で共に含むことで、従来困難であった、改良土壌の高強度化を図りつつpHを中性に近いものとすることが可能となる。ここで、当該比率X/Yが0.38未満の場合には、従来よりも短時間で固化処理対象となる含水土壌を、改良土壌として必要十分な強度にまで向上させることが困難となる。一方、当該比率X/Yが0.97を超える場合には、得られる改良土壌のpHが高くなる傾向がある。その結果、改良土壌のpH値を中性範囲(pH5.8~pH8.6)に安定的に制御することが困難となる。さらに、この場合、上述した酸化マグネシウムの添加量とのバランスを欠き、弾力性のない脆い固化状態の改良土壌となりやすい。なお、本発明に係る土壌用固化剤において、当該比率X/Yは、改良土壌の高強度化を図ると共に、改良土壌のpHを中性範囲に制御する上で0.43~0.67とすることがより好ましい。 The soil solidification agent according to the present invention has a ratio X/Y of the magnesium oxide content (X parts by weight) to the solidification strength promoter content (Y parts by weight) of 0.38 to 0.97. The soil solidification agent according to the present invention contains both the above-mentioned magnesium oxide and the solidification strength promoter in this ratio, which makes it possible to increase the strength of the improved soil while keeping the pH close to neutral, which was previously difficult. Here, if the ratio X/Y is less than 0.38, it becomes difficult to improve the water-containing soil to be solidified in a shorter time than before to a strength necessary and sufficient for improved soil. On the other hand, if the ratio X/Y exceeds 0.97, the pH of the improved soil obtained tends to be high. As a result, it becomes difficult to stably control the pH value of the improved soil in the neutral range (pH 5.8 to pH 8.6). Furthermore, in this case, the balance with the amount of magnesium oxide added as described above is lacking, and the improved soil is likely to be in a brittle solidified state without elasticity. In addition, in the soil solidification agent according to the present invention, the ratio X/Y is preferably set to 0.43 to 0.67 in order to increase the strength of the improved soil and control the pH of the improved soil to a neutral range.

ちなみに、改良土壌について必要十分とされる強度は、コーン指数200kN/m以上であり、より好ましくはコーン指数400kN/m以上である。日本国国土交通省が定める土質区分基準によれば、コーン指数が200kN/m以上であれば第4種改良土の区分に分類され、コーン指数が400kN/m以上であれば第3種改良土の区分に分類され、コーン指数が800kN/m以上であれば第2種改良土の区分に分類される。第1種改良土には、コーン指数の規定は存在しない。第1種~第4種改良土は、十分な強度を有することから、工作物の埋戻し、建築物の埋戻し、土木構造物の裏込め、道路用盛土、河川築堤、土地造成、鉄道盛土、空港盛土等としても好適に使用することが可能となる。なお、ここで言うコーン指数は、「JGS T 716(締固めた土のコーン指数試験方法)」に準拠して測定した値である。 Incidentally, the necessary and sufficient strength of improved soil is a cone index of 200 kN/ m2 or more, more preferably 400 kN/ m2 or more. According to the soil classification standards established by the Ministry of Land, Infrastructure, Transport and Tourism of Japan, soil with a cone index of 200 kN/m2 or more is classified as improved soil of the fourth type, soil with a cone index of 400 kN/m2 or more is classified as improved soil of the third type, and soil with a cone index of 800 kN/ m2 or more is classified as improved soil of the second type. There is no regulation of the cone index for improved soil of the first type. Since improved soils of the first to fourth types have sufficient strength, they can be suitably used for backfilling of structures, backfilling of buildings, backfilling of civil engineering structures, embankments for roads, river embankments, land development, railway embankments, airport embankments, etc. The cone index referred to here is a value measured in accordance with "JGS T 716 (Cone Index Test Method for Compacted Soils)".

そして、本発明に係る土壌用固化剤は、高分子凝集剤を当該土壌用固化剤の総量に対して0.1重量部~4.0重量部の割合で更に含有したことが好ましい。固化処理対象となる含水土壌が水分を多く含んだものである場合に、高分子凝集剤を加えることで、土壌が凝縮し、当該水分が吸収されて固化強度に優れた土壌固化物を得ることができる。ここで、高分子凝集剤の含有量が土壌用固化剤の総量に対して0.1重量部未満の場合には、当該含水土壌に含まれる水分を十分に排除することができず、含有効果を得ることができない。一方、高分子凝集剤の含有量が土壌用固化剤の総量に対して4.0重量部を超える場合には、固化強度の点で好ましくない。 The soil solidification agent according to the present invention preferably further contains a polymer flocculant in a ratio of 0.1 to 4.0 parts by weight relative to the total amount of the soil solidification agent . When the water-containing soil to be solidified contains a lot of water, the addition of the polymer flocculant causes the soil to condense, and the water is absorbed, resulting in a soil solidification product with excellent solidification strength. Here, if the content of the polymer flocculant is less than 0.1 parts by weight relative to the total amount of the soil solidification agent , the water contained in the water-containing soil cannot be sufficiently removed, and the effect of inclusion cannot be obtained. On the other hand, if the content of the polymer flocculant exceeds 4.0 parts by weight relative to the total amount of the soil solidification agent , it is not preferable in terms of solidification strength.

上述した高分子凝集剤としては、例えば、ポリアクリル酸ソーダ、ポリアクリルアミド、アクリル酸ソーダアクリルアミド共重合体、ポリエチレンオキサイド等の合成高分子凝集剤やグアガム、キサンタンガム、アルギン酸等の天然高分子凝集剤が挙げられる。このうち、吸剤としての機能を得ようとする場合には、ポリアクリル酸ソーダを好適に用いることができる。 Examples of the above -mentioned polymer flocculants include synthetic polymer flocculants such as sodium polyacrylate, polyacrylamide, sodium acrylate, acrylamide copolymer , polyethylene oxide, etc., and natural polymer flocculants such as guar gum, xanthan gum, alginic acid, etc. Among these, sodium polyacrylate can be suitably used when it is desired to obtain a function as a water absorbent .

ところで、本発明に係る土壌用固化剤は、固化処理対象となる含水土壌に添加する前に全成分を混合し、その後、当該含水土壌に添加してもよく、また各成分を個々に当該含水土壌に添加してもよい。さらに、成分のうちの2種以上を予め混合しておいて当該含水土壌に添加してもよい。また、本発明に係る土壌用固化剤は、粉末状で当該含水土壌に添加してもよく、また水等の溶媒に溶解してスラリー状にして当該含水土壌に添加してもよい。 The soil solidification agent according to the present invention may be added to the moist soil by mixing all of the components before adding to the moist soil to be solidified, or each component may be added to the moist soil individually. Furthermore, two or more of the components may be mixed in advance and added to the moist soil. The soil solidification agent according to the present invention may be added to the moist soil in powder form, or may be dissolved in a solvent such as water to form a slurry and then added to the moist soil.

本発明に係る土壌用固化剤の含水土壌に対する添加量は、土質、含水量等によって適宜調節される。一般に有機質を多く含む土質の場合には、添加量は多くする必要があり、有機質の少ない土質の場合には、添加量は少なくてよい。また、含水量の多い土壌の場合には、添加量を多くする必要があり、含水量の少ない土壌の場合には、添加量は少なくてよい。一般的に言えば、含水比100%未満の土壌の場合には、本発明に係る土壌用固化剤は、土壌1m当たり、30kg~100kg程度添加され、含水比100%~400%の土壌の場合には、本発明に係る土壌用固化剤は、土壌1m当たり、50kg~300kg程度添加される。 The amount of the soil solidifying agent according to the present invention added to the water-containing soil is appropriately adjusted depending on the soil quality, water content, etc. In general, in the case of soil with a high organic content, a large amount needs to be added, and in the case of soil with a low organic content, a small amount may be added. In addition, in the case of soil with a high water content, a large amount needs to be added, and in the case of soil with a low water content, a small amount may be added. Generally speaking, in the case of soil with a water content of less than 100%, about 30 kg to 100 kg of the soil solidifying agent according to the present invention is added per 1 m3 of soil, and in the case of soil with a water content of 100% to 400%, about 50 kg to 300 kg of the soil solidifying agent according to the present invention is added per 1 m3 of soil.

以上に、本発明に係る土壌用固化剤について説明したが、以下に本発明の実施例を示し、本発明をより詳細に説明する。なお、本発明はこれらの例により何ら限定されるものではない。 The soil solidification agent according to the present invention has been described above. The following examples of the present invention will be used to explain the present invention in more detail. Note that the present invention is not limited to these examples.

実施例1は、本発明に係る土壌用固化剤について、含水土壌の強度を短時間でどれだけ向上させることができるか、また、pH値をどれだけ中性に近いものとすることができるかを実証するための実施例であり、以下に述べる比較例1~3と対比するためのものである。 Example 1 is an example intended to demonstrate how much the soil solidification agent of the present invention can improve the strength of wet soil in a short period of time and how close the pH value can be to neutral, and is intended to be compared with Comparative Examples 1 to 3 described below.

この実施例1では、土壌用固化剤として、酸化マグネシウムの含有量(X重量部)と固化強度推進剤の含有量(Y重量部)との比率X/Yが、本発明で規定する条件を満たす「0.45」となるものを用い、所定時間経過後に得られる改良土壌の強度及びpH値の確認を行った。具体的には、災害発生した粘土質の試料土壌(含水率:32.7重量%、コーン指数:57kN/m、pH:7.3)1000ccに対して、軽焼マグネシア9、硫酸アルミニウム20、ポリアクリル酸ソーダ1からなる土壌用固化剤30gを添加し、混練機で混練し、モールドに充填して1時間後に湿潤養生して、「直後、1日後、2日後、3日後」のそれぞれについて「コーン指数」及び「pH値」を測定した。その結果を、後述する比較例1~3との対比が可能なように以下の表1に示す。
In this Example 1, the soil solidification agent was used in which the ratio X/Y of the content of magnesium oxide (X parts by weight) to the content of solidification strength promoter (Y parts by weight) was 0.45 , which satisfies the condition specified in the present invention, and the strength and pH value of the improved soil obtained after a certain time had passed were confirmed. Specifically, 30 g of soil solidification agent consisting of 9 g of light burnt magnesia, 20 g of aluminum sulfate, and 1 g of sodium polyacrylate was added to 1000 cc of a clayey sample soil (moisture content: 32.7% by weight, cone index: 57 kN/ m2 , pH: 7.3) that had been damaged by a disaster, and the soil was mixed with a mixer, filled into a mold, and wet-cured one hour later. The cone index and pH value were measured immediately after, one day after, two days after, and three days after. The results are shown in Table 1 below so that they can be compared with Comparative Examples 1 to 3 described later.

実施例2では、実施例1と同様の実証確認を行った。この実施例2では、土壌用固化剤として、酸化マグネシウムの含有量(X重量部)と固化強度推進剤の含有量(Y重量部)との比率X/Yが、本発明で規定する条件を満たす「0.38」となるものを用い、所定時間経過後に得られる改良土壌の「コーン指数」及び「pH値」を実施例1と同じ条件で測定した。その結果を、後述する比較例1~3との対比が可能なように以下の表1に示す。 In Example 2, a verification test was conducted similarly to Example 1. In Example 2, a soil solidification agent was used in which the ratio X/Y of the magnesium oxide content (X parts by weight) to the solidification strength promoter content (Y parts by weight) was 0.38, which satisfies the conditions stipulated in the present invention, and the "cone index" and "pH value" of the improved soil obtained after a specified time had elapsed were measured under the same conditions as in Example 1. The results are shown in Table 1 below so that they can be compared with Comparative Examples 1 to 3 described later.

実施例3では、実施例1と同様の実証確認を行った。この実施例3では、土壌用固化剤として、酸化マグネシウムの含有量(X重量部)と固化強度推進剤の含有量(Y重量部)との比率X/Yが、本発明で規定する条件を満たす「0.97」となるものを用い、所定時間経過後に得られる改良土壌の「コーン指数」及び「pH値」を実施例1と同じ条件で測定した。その結果を、後述する比較例1~3との対比が可能なように以下の表1に示す。 In Example 3, a verification test was conducted similarly to Example 1. In Example 3, a soil solidification agent was used in which the ratio X/Y of the magnesium oxide content (X parts by weight) to the solidification strength promoter content (Y parts by weight) was 0.97, which satisfies the conditions stipulated in the present invention, and the cone index and pH value of the improved soil obtained after a specified time had elapsed were measured under the same conditions as in Example 1. The results are shown in Table 1 below so that they can be compared with Comparative Examples 1 to 3 described later.

比較例Comparative Example

(比較例1)
比較例1は、実施例1~3と対比するための比較例であり、土壌用固化剤を添加しない原土の「コーン指数」及び「pH値」を実施例1と同じ条件で測定した。原土に関しては、実施例1と同じ試料土壌を用い、且つ実施例1と同様に混練を施した。その結果を以下の表1に示す。
(Comparative Example 1)
Comparative Example 1 is a comparative example for comparison with Examples 1 to 3, and the "Cone Index" and "pH value" of raw soil to which no soil solidifying agent was added were measured under the same conditions as in Example 1. The raw soil used was the same sample soil as in Example 1, and was kneaded in the same manner as in Example 1. The results are shown in Table 1 below.

(比較例2)
比較例2は、実施例1~3と対比するための比較例であり、土壌用固化剤として、酸化マグネシウムの含有量(X重量部)と固化強度推進剤の含有量(Y重量部)との比率X/Yが「0.3」となるものを用い、所定時間経過後に得られる改良土壌の「コーン指数」及び「pH値」を実施例1と同じ条件で測定した。その結果を以下の表1に示す。
(Comparative Example 2)
Comparative Example 2 is a comparative example for comparison with Examples 1 to 3, in which a ratio X/Y of the magnesium oxide content (X parts by weight) to the solidification strength promoter content (Y parts by weight) of "0.3" was used as the soil solidification agent, and the "Cone Index" and "pH value" of the improved soil obtained after a predetermined time had elapsed were measured under the same conditions as in Example 1. The results are shown in Table 1 below.

(比較例3)
比較例3は、実施例1~3と対比するための比較例であり、土壌用固化剤として、酸化マグネシウムの含有量(X重量部)と固化強度推進剤の含有量(Y重量部)との比率X/Yが「1.1」となるものを用い、所定時間経過後に得られる改良土壌の「コーン指数」及び「pH値」を実施例1と同じ条件で測定した。その結果を以下の表1に示す。
(Comparative Example 3)
Comparative Example 3 is a comparative example for comparison with Examples 1 to 3, in which a ratio X/Y of the magnesium oxide content (X parts by weight) to the solidification strength promoter content (Y parts by weight) of "1.1" was used as the soil solidification agent, and the "Cone Index" and "pH value" of the improved soil obtained after a predetermined time had elapsed were measured under the same conditions as in Example 1. The results are shown in Table 1 below.

Figure 0007497116000001
Figure 0007497116000001

(実施例と比較例との対比)
表1に示す結果から、実施例1~3では、試料土壌に固化処理を施した直後からコーン指数が全て200kN/m以上となり、改良土壌として適切な強度にまで極めて短時間で到達することが分かる。また、固化処理を施して3日経過後の改良土壌のコーン指数が全て800kN/m以上となり、改良土壌の強度が大きく向上していることが分かる。そして、pH値に関しては、僅かな上昇が見受けられるものの全て中性範囲(pH5.8~pH8.6)に制御され、問題のないレベルである。
(Comparison between Examples and Comparative Examples)
From the results shown in Table 1, it can be seen that in Examples 1 to 3, the cone index of the sample soil was 200 kN/ m2 or more immediately after the solidification treatment, and the soil reached an appropriate strength for improved soil in an extremely short time. In addition, the cone index of the improved soil was 800 kN/ m2 or more three days after the solidification treatment, and the strength of the improved soil was greatly improved. As for the pH value, although a slight increase was observed, it was all controlled to a neutral range (pH 5.8 to pH 8.6), which is at a level that does not cause problems.

一方、表1に示す結果から、比較例1~3では、改良土壌について必要十分とされる強度(コーン指数200kN/m以上)を得ることと、改良土壌のpH値を中性範囲(pH5.8~pH8.6)に制御することとの両立を図ることが困難であることが分かる。具体的に、比較例1では、原土を混練機で混練した直後から3日経過後にかけてコーン指数が57kN/mであり、土壌の強度が適切な強度(200kN/m以上)を満足していない。また、比較例2では、固化処理を施して3日経過後の改良土壌のコーン指数が198kN/m以下であり、改良土壌について必要十分とされる強度(200kN/m以上)を満足していない。そして、比較例3では、固化処理を施して1日経過後から3日経過後にかけて改良土壌のpH値が8.9となり、中性範囲(pH5.8~pH8.6)に制御されていない。 On the other hand, from the results shown in Table 1, it can be seen that in Comparative Examples 1 to 3, it is difficult to obtain a necessary and sufficient strength (cone index 200 kN/m 2 or more) for the improved soil and to control the pH value of the improved soil to a neutral range (pH 5.8 to pH 8.6). Specifically, in Comparative Example 1, the cone index was 57 kN/m 2 from immediately after the raw soil was mixed with the mixer until 3 days later, and the strength of the soil did not satisfy the appropriate strength (200 kN/m 2 or more). In Comparative Example 2, the cone index of the improved soil 3 days after the solidification treatment was 198 kN/m 2 or less, and the strength of the improved soil did not satisfy the necessary and sufficient strength (200 kN/m 2 or more). And in Comparative Example 3, the pH value of the improved soil became 8.9 from 1 day to 3 days after the solidification treatment, and was not controlled to the neutral range (pH 5.8 to pH 8.6).

以上より、本発明に係る土壌用固化剤を用いた場合には、コーン指数が著しく大きくなり、含水土壌の強度を向上させる上で極めて有効であることが分かった。特に、本発明に係る土壌用固化剤によれば、含水土壌を改良土壌として求められる適切な強度にまで従来よりも短時間で向上させられることができる。そして、本発明に係る土壌用固化剤を用いた場合には、得られる改良土壌についてpH値の上昇が十分に抑制されて、改良土壌の高強度化を図りつつも、改良土壌のpH値を中性範囲(pH5.8~pH8.6)に安定的に制御可能であることが分かった。 From the above, it was found that when the soil solidification agent of the present invention is used, the cone index is significantly increased, and it is extremely effective in improving the strength of moist soil. In particular, the soil solidification agent of the present invention can improve moist soil to the appropriate strength required for improved soil in a shorter time than before. It was also found that when the soil solidification agent of the present invention is used, the increase in pH value of the obtained improved soil is sufficiently suppressed, and while the strength of the improved soil is increased, the pH value of the improved soil can be stably controlled in the neutral range (pH 5.8 to pH 8.6).

以上の通り、本発明に係る土壌用固化剤によれば、含水土壌の土質を問わず、改良土壌として必要十分な強度を従来よりも短時間で得ることができる。また、pH値に関しても、中性範囲(pH5.8~pH8.6)に安定的に制御可能である。従って、本発明に係る土壌用固化剤は、強度とpH値とのトータルバランスの点から地盤改良等の種々の用途に好適に用いられる。さらに、本発明に係る土壌用固化剤は、含水土壌の土質を問わずコーン指数200kN/m以上とすることができるため、従来産業廃棄物として埋め立て処分されていた建設汚泥等を盛土用材料や埋立用材料等として再利用することが可能となる。 As described above, the soil solidification agent according to the present invention can provide sufficient strength for improved soil in a shorter time than conventional methods, regardless of the type of water-containing soil. In addition, the pH value can be stably controlled to a neutral range (pH 5.8 to pH 8.6). Therefore, the soil solidification agent according to the present invention is suitable for various applications such as ground improvement in terms of the total balance between strength and pH value. Furthermore, the soil solidification agent according to the present invention can provide a cone index of 200 kN/ m2 or more regardless of the type of water-containing soil, so that construction sludge, which has been landfilled as industrial waste, can be reused as embankment material or landfill material.

Claims (2)

土壌に混入させモールドに充填してから1時間後のコーン指数を200kN/m 以上且つpHを5.8~7.7とするために用いる、土壌を固化させるための土壌用固化剤であって、
700℃~1000℃で焼成して粉末度4000cm/g~8500cm /gとなるように調整された酸化マグネシウムと、固化強度推進剤とを含有し、
当該酸化マグネシウムの含有量(X重量部)と当該固化強度推進剤の含有量(Y重量部)との比率X/Yが0.38~0.67であり、
ポリアクリル酸ソーダ、アクリル酸ソーダ、ポリエチレンオキサイド、グアガム、キサンタンガム及びアルギン酸の何れかからなる高分子凝集剤を、当該土壌用固化剤の総量に対して0.1重量部~4.0重量部の割合で更に含有することを特徴とする土壌用固化剤。
A soil solidification agent for solidifying soil, which is used to achieve a cone index of 200 kN/m2 or more and a pH of 5.8 to 7.7 one hour after being mixed into soil and filled into a mold,
The present invention comprises magnesium oxide that has been adjusted by calcining at 700° C. to 1000° C. to have a fineness of 4000 cm 2 /g to 8500 cm 2 /g , and a solidification strength promoter;
the ratio X/Y of the content of the magnesium oxide (X parts by weight) to the content of the solidification strength propellant (Y parts by weight) is 0.38 to 0.67 ;
A soil solidification agent characterized by further containing a polymer flocculant consisting of any one of sodium polyacrylate, sodium acrylate, polyethylene oxide, guar gum, xanthan gum and alginic acid in an amount of 0.1 to 4.0 parts by weight based on the total amount of the soil solidification agent .
前記固化強度推進剤は、硫酸アルミニウム、硫酸第一鉄、ポリ塩化アルミニウム、塩化第二鉄、及び塩化マグネシウムから選択される一種以上である請求項1に記載の土壌用固化剤。 2. The soil solidification agent according to claim 1, wherein the solidification strength promoter is one or more selected from the group consisting of aluminum sulfate, ferrous sulfate, polyaluminum chloride, ferric chloride, and magnesium chloride.
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