JP2005281407A - Method for improving ground - Google Patents

Method for improving ground Download PDF

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JP2005281407A
JP2005281407A JP2004095069A JP2004095069A JP2005281407A JP 2005281407 A JP2005281407 A JP 2005281407A JP 2004095069 A JP2004095069 A JP 2004095069A JP 2004095069 A JP2004095069 A JP 2004095069A JP 2005281407 A JP2005281407 A JP 2005281407A
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soil
gypsum
milk
cement
ground
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JP4462980B2 (en
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Kenji Miyawaki
賢司 宮脇
Masahiro Yoshihara
正博 吉原
Jun Shimizu
準 清水
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Sumitomo Osaka Cement Co Ltd
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Sumitomo Osaka Cement Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for improving ground at an inexpensive construction cost by which a soil containing a component for inhibiting the hardening of the soil such as allophane can be strengthened very effectively, and the solidification of the ground is carried out easily at the construction site. <P>SOLUTION: The method for improving the ground comprises kneading gypsum milk or a milk of mixed gypsum and slag, with a target soil, leaving the resultant mixture for a prescribed time, and kneading the resultant soil with a cement milk again to solidify the soil and to exhibit the strength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、地盤改良方法に関し、特に、火山灰や軽石を母材とする土壌に対して地盤の強度改善を簡便に図ることができる地盤改良方法に関する。   The present invention relates to a ground improvement method, and more particularly, to a ground improvement method capable of easily improving the strength of the ground with respect to soil using volcanic ash or pumice as a base material.

従来地盤改良方法として、地盤中にセメントなどの固化材の水性ミルクを注入し、これを水和硬化させて、土壌を固化して強度を発現させる方法が用いられている。
しかし、このような地盤改良方法を用いても、土壌の種類によってその固化程度はさまざまであり、土壌の種類に応じて、特定の組成を有する地盤改良材や特定の地盤改良方法が開発されてきている。
As a conventional ground improvement method, a method of injecting an aqueous milk of a solidifying material such as cement into the ground and hydrating and hardening it to solidify the soil and develop strength is used.
However, even if such a ground improvement method is used, the degree of solidification varies depending on the type of soil, and depending on the type of soil, a ground improvement material having a specific composition or a specific ground improvement method has been developed. ing.

例えば、関東ローム土壌のような火山灰や軽石を多く含む土壌の地盤では、従来の地盤改良を行っても、地盤の硬化が有効になされず、強度が上がらなかった。これは、関東ローム土壌には、アロフェン(Al・(1〜2)SiO・nHO)等の粘度鉱物が多量に含有されているからである。
このことは、セメント成分から供給されるカルシウムの一部が、アロフェンから溶出したAl成分に吸着してしまい、セメント成分の硬化反応を阻害することにより、水和物生成量が減少するため、改良対象である土壌の固化が有効に発現できなくなり、強度発現が低くなってしまうからである。
For example, in soils containing a large amount of volcanic ash and pumice, such as Kanto loam soil, even if conventional ground improvement is performed, the hardening of the ground is not effective and the strength does not increase. This is because Kanto loam soil contains a large amount of viscous minerals such as allophane (Al 2 O 3. (1 to 2) SiO 2 · nH 2 O).
This is because a part of calcium supplied from the cement component is adsorbed to the Al 2 O 3 component eluted from the allophane, and the amount of hydrate produced is reduced by inhibiting the hardening reaction of the cement component. For this reason, the solidification of the soil to be improved cannot be effectively expressed, and the strength expression becomes low.

従って、従来では、このような土壌における地盤改良には、多量のセメント成分を添加する必要があった。しかし、このように必要以上のセメント成分の添加は、セメント成分を多量に使用するため、施工コストの高騰を招き、また多量の添加にもかかわらず、所望する強度の向上が有効に図られていなかった。   Therefore, conventionally, in order to improve the ground in such soil, it has been necessary to add a large amount of cement components. However, the addition of an excessive amount of cement component as described above uses a large amount of the cement component, leading to an increase in construction cost. In spite of the large amount of addition, the desired strength is effectively improved. There wasn't.

また、対象土壌が関東ロームの場合には、関東ローム中に含まれるアロフェンが、エーライト(C3S)から溶出するカルシウムと容易に反応してC−S−H系やC−A−H系の水和物を生成することから、エーライト(C3S)や水酸化カルシウムの多いものが強度発現性の面で好ましく、これより、普通ポルトランドセメントよりは、早強ポルトランドセメントや消石灰が適したものとして用いられている。   In addition, when the target soil is Kanto loam, allophane contained in the Kanto loam easily reacts with calcium eluted from alite (C3S), so that the C-S-H or C-A-H system. Since it produces hydrates, it is preferable to use a high amount of alite (C3S) or calcium hydroxide in terms of strength development. From this, it is assumed that early strength Portland cement and slaked lime are more suitable than ordinary Portland cement. It is used.

上記問題点に鑑み、特開2000−34483号公報には、関東ローム土壌のような土壌中の硬化阻害成分であるAlを迅速に捕捉するために、スラグ、アルカリ金属水酸化物、水酸化カルシウム、水酸化カルシウム形成性カルシウム化合物及びトリエタノールアミンの中から選ばれる少なくとも1種の添加剤を含有する混合物からなる、特定組成を有する土壌改良剤が開示されており、かかる土壌改良剤を、水の存在下で混合する土壌改良方法が提案されている。 In view of the above problems, Japanese Patent Application Laid-Open No. 2000-34483 discloses slag, alkali metal hydroxide, in order to quickly capture Al 2 O 3 which is a hardening inhibiting component in soil such as Kanto loam soil. A soil conditioner having a specific composition, comprising a mixture containing at least one additive selected from calcium hydroxide, a calcium hydroxide-forming calcium compound and triethanolamine is disclosed, and such a soil conditioner A soil improvement method is proposed in which water is mixed in the presence of water.

また、特開2003−301451号公報には、排土をすることなく地盤を掘削し、その掘削土に、土砂及び水硬性硬化剤を添加し、その掘削土と、添加した土砂及び水硬性硬化剤とを混合攪拌して掘削した地盤を改良する地盤改良方法が開示されており、地盤を改良する現場で、掘削土に水硬性硬化剤だけでなく、土砂をも添加して混合攪拌することとして、関東ローム土壌に対する固化不良の改善を図る方法が提案されている。   JP-A-2003-301451 excavates the ground without discharging soil, adds earth and sand and a hydraulic hardening agent to the excavated earth, the excavated earth, and the added earth and sand and hydraulic hardening. A ground improvement method for improving the ground excavated by mixing and agitating the agent is disclosed. At the site where the ground is improved, not only hydraulic hardening agent but also earth and sand are added to the excavated soil and mixed and stirred. A method for improving the solidification failure of Kanto loam soil has been proposed.

しかし、上記のような地盤改良方法では、所望する強度の改善を図ることは不十分であり、関東ローム土壌のような土質の有効な地盤改良固化技術の開発が望まれている。   However, in the ground improvement method as described above, it is insufficient to improve the desired strength, and development of an effective ground improvement solidification technique for soil such as Kanto loam soil is desired.

本発明の目的は、アロフェン等の土壌硬化阻害成分を含む土壌にも、極めて有効に強度を発現させることができる、現場で簡便に地盤の固化を図ることができる、地盤改良方法を提供する。
また、本発明の目的は、特定の組成を有する地盤改良材を多量に添加する必要がなく、施工性にも優れ、施工コストが安価な、地盤改良方法を提供する。
An object of the present invention is to provide a ground improvement method capable of very effectively expressing strength even in soil containing a soil hardening inhibiting component such as allophane and capable of easily solidifying the ground on site.
The object of the present invention is to provide a ground improvement method that does not require the addition of a large amount of ground improvement material having a specific composition, is excellent in workability, and is low in construction cost.

本発明者らは、上記課題を解決するため研究した結果、セメントの水和反応を円滑に行わしめるには、地盤改良材を二材型にして、予めセメントを除いた材料と土壌を混練し、土壌の硬化阻害成分であるアロフェン等の硬化阻害成分を選択的にブロックした後、該土壌とセメントを混練することにより、地盤の強度を向上させることができることを見出し、本発明に到達した。   As a result of researches to solve the above-mentioned problems, the inventors of the present invention have made the ground improvement material into a two-material type and kneaded the material excluding the cement and the soil beforehand in order to smoothly perform the cement hydration reaction. The present inventors have found that the strength of the ground can be improved by selectively blocking a hardening inhibiting component such as allophane, which is a soil hardening inhibiting component, and then kneading the soil and cement.

すなわち、本発明の地盤改良方法は、石膏ミルクを土壌と混練し、所定時間放置した後、該土壌にセメントミルクを再混練することを特徴とするものである。
好適には、前記地盤改良方法において、セメントミルク中のセメント300〜400重量部に対して、石膏ミルク中の石膏が100〜200重量部を含有することを特徴とする。
That is, the ground improvement method of the present invention is characterized in that gypsum milk is kneaded with soil, left for a predetermined time, and then cement milk is re-kneaded in the soil.
Preferably, in the ground improvement method, the gypsum in the gypsum milk contains 100 to 200 parts by weight with respect to 300 to 400 parts by weight of the cement in the cement milk.

また、本発明の他の地盤改良方法は、石膏及びスラグの混合ミルクを土壌と混練し、所定時間放置した後、該土壌にセメントミルクを再混練することを特徴とするものである。
好適には、前記地盤改良方法において、セメントミルク中のセメント300〜400重量部に対して、石膏及びスラグの混合ミルク中の石膏が75〜100重量部とスラグが50〜75重量部含有されることを特徴とする。
Another ground improvement method of the present invention is characterized in that a mixed milk of gypsum and slag is kneaded with soil, left for a predetermined time, and then cement milk is re-kneaded in the soil.
Preferably, in the ground improvement method, 75 to 100 parts by weight of gypsum in the mixed milk of gypsum and slag and 50 to 75 parts by weight of slag are contained with respect to 300 to 400 parts by weight of cement in cement milk. It is characterized by that.

本発明の地盤改良方法は、石膏とスラグと水とを混合して調製した混合ミルクまたは石膏ミルクを、地盤中に注入して該地盤と混練し、所定時間経過させることにより、この地盤中に含有されるアロフェン等の固化阻害物質が後に添加されるセメントの水和反応を阻害させないように、予めアロフェン中に石膏から溶出するカルシウムを吸着させる。その後、セメントミルクを、土壌に注入して該土壌と混練させることにより、水和硬化が正常に進行し、その結果前記地盤が硬化し、地盤が改良されて、高強度を発現することができるものである。   According to the ground improvement method of the present invention, mixed milk or gypsum milk prepared by mixing gypsum, slag and water is poured into the ground, kneaded with the ground, and a predetermined time elapses. Calcium eluted from gypsum is adsorbed in advance in allophane so that the solidification inhibitor such as allophane contained does not inhibit the hydration reaction of cement added later. Thereafter, cement milk is poured into the soil and kneaded with the soil, so that hydration hardening proceeds normally. As a result, the ground is hardened, the ground is improved, and high strength can be expressed. Is.

本発明を以下の好適な地盤改良方法に基づき説明するが、これらに限定されるものではない。
本発明の地盤改良工法は、石膏ミルクを土壌と混練し、所定時間放置した後、該土壌にセメントミルクを再混練する方法である。
または、本発明の他の地盤改良工法は、石膏及びスラグの混合ミルクを土壌と混練し、所定時間放置した後、該土壌にセメントミルクを再混練する方法である。
Although this invention is demonstrated based on the following suitable ground improvement methods, it is not limited to these.
The ground improvement method of the present invention is a method in which gypsum milk is kneaded with soil, left for a predetermined time, and then cement milk is re-kneaded in the soil.
Alternatively, another ground improvement method of the present invention is a method in which a mixed milk of gypsum and slag is kneaded with soil and left for a predetermined time, and then cement milk is re-kneaded in the soil.

このように、本発明の地盤改良方法では、予め石膏とスラグの混合ミルク、または石膏ミルクを対象土壌と混練し、所定時間放置する。かかる所定放置時間は、この間に石膏から溶出したカルシウムの一部が、対象土壌中に含まれるアロフェン等の固化阻害物質に吸着するのに十分な時間である。当該所定放置時間中においては、土壌の固化作用は発現されず、強度の向上はなされない。   Thus, in the ground improvement method of this invention, the mixed milk of gypsum and slag, or gypsum milk is knead | mixed with object soil previously, and is left for predetermined time. The predetermined standing time is a time sufficient for a part of calcium eluted from the gypsum during this time to be adsorbed to a solidification inhibitor such as allophane contained in the target soil. During the predetermined standing time, the solidifying action of the soil is not expressed and the strength is not improved.

次いで、所定の放置時間を経て、対象土壌中に含まれるアロフェン等の固化阻害物質に石膏からのカルシウムが捕獲された状態の対象土壌に、セメントミルクを添加して、再混練する。
これにより、セメントから溶出するカルシウムがアロフェン等に捕獲されることがなく、セメントの水和硬化反応が正常に進行して、従来の一材型固化材を用いた地盤改良方法よりも、効果的に土壌を固化することができる。
Subsequently, cement milk is added to the target soil in a state where calcium from gypsum is captured in a solidification inhibitor such as allophane contained in the target soil after a predetermined standing time, and re-kneaded.
As a result, calcium eluting from the cement is not captured by allophane, etc., and the hydration hardening reaction of the cement proceeds normally, which is more effective than the conventional ground improvement method using a one-material solidifying material. The soil can be solidified.

例えば、一般に、石膏及びスラグの混合ミルクまたは石膏ミルク、セメントミルクの土壌への注入は、5〜30℃の温度、0〜200kgf/cmの圧力下において行われ、この注入のときに、注入装置としてミルクを製造する為のグラウトミキサー又はアジテーター、ミルクを圧送する為のグラウトポンプ又はスクイズポンプ、注入圧力、注入量の制御測定装置などが用いられる。
前記石膏及びスラグの混合ミルク、または石膏ミルクを土壌へ注入するとともに、当該土壌と注入された石膏及びスラグの混合ミルク、または石膏ミルクとを撹拌混合して、石膏から溶出されるカルシウムが、アロフェン等に容易に吸着されるように当該ミルクの分布を土壌中均一にしておくことが好ましい。さらに、所定時間放置後、セメントミルクを、当該領域に注入して、当該土壌と、セメントミルクとを再混合するが、その際には例えば、機械オーガー撹拌装置又は高圧噴射装置などを用いることができる。
For example, in general, mixing of gypsum and slag mixed milk or gypsum milk and cement milk into soil is performed at a temperature of 5 to 30 ° C. and a pressure of 0 to 200 kgf / cm 2. As a device, a grout mixer or agitator for producing milk, a grout pump or squeeze pump for pumping milk, an injection pressure, an injection amount control measurement device, or the like is used.
The mixed milk of gypsum and slag, or gypsum milk is poured into the soil, and the mixed gypsum and slag mixed milk or gypsum milk is stirred and mixed, so that calcium eluted from the gypsum is allophane. It is preferable to make the distribution of the milk uniform in the soil so that it is easily adsorbed to the soil. Further, after being allowed to stand for a predetermined time, cement milk is poured into the region, and the soil and cement milk are remixed. In this case, for example, a mechanical auger stirring device or a high-pressure spray device may be used. it can.

本発明の地盤改良工法に用いるスラグは、ポゾラン反応による強度増進に寄与する機能を有し、例えば製鉄所の高炉から副成する高炉スラグが例示され、従来の前記地盤改良方法に用いられているスラグを使用することができる。
かかるスラグの粉末の粉末度ブレーン比表面積は3000〜5000cm/g、特に3500〜4500cm/gであることが好ましく、ブレーン比表面積が3000cm/g未満であると、改良対象土壌の強度発現性が劣り、また、5000cm/gを超えると、強度発現性は良いが経費がかかり経済的ではない。
The slag used in the ground improvement method of the present invention has a function that contributes to strength enhancement by pozzolanic reaction. For example, blast furnace slag by-produced from a blast furnace at a steelworks is exemplified, and is used in the conventional ground improvement method. Slag can be used.
Fineness Blaine specific surface area of the powder of such slag 3000~5000cm 2 / g, particularly preferably from 3500~4500cm 2 / g, the Blaine specific surface area is less than 3000 cm 2 / g, strength development improvement target soil When the strength is inferior and exceeds 5000 cm 2 / g, the strength development is good, but the cost is high and it is not economical.

また本発明に用いられる石膏の種類には、特に限定はなく、市場で入手できる種々の二水石膏、半水石膏、または無水石膏などから選ぶことができるが、特に二水石膏が好適に使用することができ、かかる二水石膏としては、天然石膏、排脱石膏、リン酸石膏、チタン酸石膏、フッ酸石膏等のいずれの石膏も利用することができる。
また石膏の粉末度は、特に限定されず、ブレーン比表面積1000〜4000cm/g程度の粉末度のものを用いることが好ましい。
ブレーン比表面積が1000cm/g未満であると、石膏から溶出されるカルシウムの溶出速度が遅くなり、対象土壌中に含有されるアロフェン等の固化阻害物質へのカルシウムの吸着に長時間を要し、土壌改良の工期が長くなり、経済的ではない。また、ブレーン比表面積が4000cm/gを超えると、工期短縮は図れるが、粉砕コストが上昇して経済的ではない。
The type of gypsum used in the present invention is not particularly limited, and can be selected from various dihydrate gypsum, hemihydrate gypsum, anhydrous gypsum, and the like that are commercially available. As such dihydrate gypsum, any gypsum such as natural gypsum, drainage gypsum, phosphate gypsum, titanate gypsum, hydrofluoric gypsum, and the like can be used.
Moreover, the fineness of gypsum is not particularly limited, and it is preferable to use a fine powder having a brane specific surface area of about 1000 to 4000 cm 2 / g.
When the Blaine specific surface area is less than 1000 cm 2 / g, the elution rate of calcium eluted from gypsum is slow, and it takes a long time for calcium to be adsorbed on solidification inhibitors such as allophane contained in the target soil. The soil improvement period is long and not economical. On the other hand, if the Blaine specific surface area exceeds 4000 cm 2 / g, the work period can be shortened, but the pulverization cost increases, which is not economical.

本発明の地盤改良方法に石膏及びスラグの混合ミルクを用いる場合には、好適には、セメントミルク中のセメント含有量300〜400重量部に対し、石膏及びスラグの混合ミルクは、石膏を75〜100重量部とスラグを50〜75重量部を含有することが、土壌の強度発現性の点から好ましい。
スラグの含有量が50重量部未満であると、早期に強度発現を生じるという不都合を生じ、またそれが75重量部を超えると、固化材の土壌固化作用が不良という不都合を生ずることがあるので好ましくない。
また石膏の含有量は、75〜100重量部であることが好ましく、石膏の含有量が75重量部未満であると、石膏から溶出されるカルシウムの溶出速度が遅くなり、対象土壌中に含有されるアロフェン等の固化阻害物質へのカルシウムの吸着量が不足するため、改良土壌の強度が低くなってしまうことがあり、また100重量部を超えると、固化材に占める石膏の含有量が増加し、その結果、本来土壌の固化作用に寄与するセメントやスラグの含有量が減少し、土壌の固化作用が低下するという不都合を生ずることがあるので好ましくない。
When using the mixed milk of gypsum and slag in the ground improvement method of the present invention, preferably the mixed milk of gypsum and slag is 75 to 100 parts by weight and 50 to 75 parts by weight of slag are preferable from the standpoint of soil strength.
If the slag content is less than 50 parts by weight, there will be an inconvenience that strength develops early, and if it exceeds 75 parts by weight, the solidification action of the solidifying material may be inferior. It is not preferable.
The gypsum content is preferably 75 to 100 parts by weight, and if the gypsum content is less than 75 parts by weight, the elution rate of calcium eluted from the gypsum becomes slow and is contained in the target soil. Since the amount of calcium adsorbed on solidification inhibitors such as allophane is insufficient, the strength of the improved soil may be lowered, and if it exceeds 100 parts by weight, the content of gypsum in the solidified material will increase. As a result, the contents of cement and slag, which originally contribute to the solidification action of the soil, are reduced, which may cause a disadvantage that the solidification action of the soil is lowered.

本発明の地盤改良方法に石膏ミルクを用いる場合には、好適には、セメントミルク中のセメント含有量300〜400重量部に対し、石膏ミルク中の石膏が100〜200重量部含有される石膏ミルクを用いることが、土壌の強度発現性の点から好ましく、その理由は、上述した石膏とスラグとの混合ミルクで記載した石膏の含有量の理由と同様である。   When gypsum milk is used in the ground improvement method of the present invention, gypsum milk preferably contains 100 to 200 parts by weight of gypsum in gypsum milk with respect to 300 to 400 parts by weight of cement content in cement milk. Is preferable from the viewpoint of soil strength development, and the reason is the same as the reason for the content of gypsum described in the above-described mixed milk of gypsum and slag.

本発明方法において、石膏及びスラグの混合ミルクまたは石膏ミルクの調製は、格別の制限はないが、一般に、混合ミルク中または石膏ミルク中の水(W)混合粉体または石膏粉体(C)の比(重量比)が50〜200となるように調製される。   In the method of the present invention, preparation of gypsum and slag mixed milk or gypsum milk is not particularly limited, but in general, water (W) mixed powder or gypsum powder (C) in mixed milk or gypsum milk. The ratio (weight ratio) is adjusted to 50 to 200.

本発明の地盤改良方法に用いられるセメントは、早強ポルトランドセメント、超早強ポルトランドセメント、普通ポルトランドセメント、中庸熱ポルトランドセメント、低熱ポルトランドセメント、耐硫酸塩ポルトランドセメント、フライアッシュセメント、高炉セメント、シリカセメント等から選ばれる少なくとも1種類を用いることができる。
その粉末度などの物理的性質は、規格値に拘束されるものではないが、好適には、2000〜6000cm/gの粉末度ブレーン値を有するものが使用できる。かかる値が、2000cm/g未満では土壌固化作用が不良という不都合を生じ、またそれが、6000cm/gをこえると、ミルクの粘性が増大し、ミルクを土壌と混合するためにポンプなどで圧送する場合、ポンプ圧力が大きくなり圧送が困難になるという不都合を生ずる場合があり望ましくない。
Cement used in the ground improvement method of the present invention is early-strength Portland cement, super-early-strength Portland cement, ordinary Portland cement, medium heat Portland cement, low heat Portland cement, sulfate-resistant Portland cement, fly ash cement, blast furnace cement, silica At least one selected from cement and the like can be used.
The physical properties such as fineness are not restricted by the standard value, but preferably those having a fineness brain value of 2000 to 6000 cm 2 / g can be used. In such a value, 2000 cm inconvenience that poor soil solidification effect is less than 2 / g, also is it exceeds 6000 cm 2 / g, increases the viscosity of the milk, the milk such as a pump for mixing with the soil In the case of pumping, there is a case where the pump pressure becomes large and it becomes difficult to pump, which is not desirable.

また、セメントミルクの調製にも格別の制限はないが、一般に、セメントミルク中の水セメント比(重量比)が50〜200となるようにセメントミルクを調製することが望ましい。   Moreover, although there is no special restriction | limiting also in preparation of cement milk, Generally, it is desirable to prepare cement milk so that the water cement ratio (weight ratio) in cement milk may be 50-200.

本発明方法において、前記配合の石膏及びスラグの混合ミルクまたは前記配合の石膏ミルクの土壌への注入量は、格別の制限はないが、一般に、混合ミルク中または石膏ミルク中の水(W)混合粉体または石膏粉体(C)の比(重量比)が、50〜200に調製された当該ミルクを、改良対象土壌m3 当り100〜800kgの割合で注入することが好ましく、また、セメントミルクの注入量にも格別の制限はないが、一般に、前記セメントミルク中の水セメント比(重量比)が50〜200に調製されたセメントミルクを注入することが、関東ローム土の地盤改良を有効に進行させることができるので好ましい。 In the method of the present invention, the amount of the mixed milk of gypsum and slag having the above composition or the amount of the gypsum milk having the above composition to be injected into the soil is not particularly limited, but in general, water (W) mixing in the mixed milk or gypsum milk It is preferable to inject the milk having a ratio (weight ratio) of powder or gypsum powder (C) of 50 to 200 at a rate of 100 to 800 kg per m 3 of the soil to be improved. Although there is no particular limitation on the amount of injection of water, in general, injecting cement milk prepared with a water-cement ratio (weight ratio) of 50 to 200 in the cement milk is effective for improving the ground of Kanto loam soil. It is preferable because it can be made to proceed.

本発明の方法において、石膏及びスラグの混合ミルクまたは前記配合の石膏ミルクの土壌への注入から、セメントミルクの注入までの時間には特に制限がなく、改良対象土壌中に含有されるアロフェン等の固化阻害物質に石膏からのカルシウムが吸着できる時間であれば、適宜に設定することができ、一般に2時間程度である。
本発明の方法においては、第2段階のセメントミルクの注入により、水和硬化が有効に進行し、これにより地盤に所望設定強度、例えば28日材齢一軸圧縮強さで40kgf/cm以上の強さを付与することが可能となる。
In the method of the present invention, there is no particular limitation on the time from the injection of the mixed milk of gypsum and slag or the gypsum milk of the above composition into the soil until the injection of the cement milk, and allophane and the like contained in the soil to be improved The time can be appropriately set as long as the calcium from the gypsum can be adsorbed to the solidification inhibiting substance, and is generally about 2 hours.
In the method of the present invention, the hydration and hardening effectively proceeds by the injection of the cement milk in the second stage, whereby the desired set strength in the ground, for example, the 28-day age uniaxial compressive strength is 40 kgf / cm 2 or more. It becomes possible to give strength.

このように、本発明の地盤改良方法においては、石膏とスラグと水とを混合して調製した混合ミルクまたは石膏ミルクを、地盤中に注入して地盤と混練し、所定時間経過させることにより、この地盤中に含有されるアロフェン等の固化阻害物質が後に添加されるセメントの水和反応を阻害させないように、予めアロフェン中に石膏から溶出するカルシウムを吸着させる状態を形成させ、当該土壌は、まだ未硬化状態にあり、時間とともに水和硬化が進行することはない。次に、所望時間の経過後、セメントミルクを、前記所定時間が経過した土壌に注入し、該土壌と混練することでセメントの水和硬化が正常に進行し、その結果前記地盤が硬化し、高強度を発現することができるものである。   Thus, in the ground improvement method of the present invention, mixed milk or gypsum milk prepared by mixing gypsum, slag and water is poured into the ground and kneaded with the ground, and by allowing a predetermined time to elapse, In order that the solidification inhibitor such as allophane contained in the ground does not inhibit the hydration reaction of cement added later, a state in which calcium eluting from gypsum is adsorbed in allophane in advance is formed, and the soil is It is still in an uncured state, and hydration curing does not proceed with time. Next, after the lapse of the desired time, cement milk is poured into the soil after the predetermined time, and the hydration and hardening of the cement proceeds normally by kneading with the soil, with the result that the ground is cured, High strength can be expressed.

本発明を次の実施例、比較例及び試験例により説明する。
試験材料
実施例及び比較例には、以下の材料を用いた。
関東ローム土壌;東京都世田谷区産
セメント;早強セメント(住友大阪セメント株式会社製)
ブレーン比表面積;4800cm/g
スラグ;高炉スラグ(住友金属工業株式会社製)
ブレーン比表面積;4000cm/g
石膏;排脱二水石膏 ブレーン比表面積;2000cm/g
The invention is illustrated by the following examples, comparative examples and test examples.
The following materials were used in the test material examples and comparative examples.
Kanto loam soil; cement from Setagaya-ku, Tokyo; early strength cement (manufactured by Sumitomo Osaka Cement Co., Ltd.)
Blaine specific surface area: 4800 cm 2 / g
Slag: Blast furnace slag (manufactured by Sumitomo Metal Industries, Ltd.)
Blaine specific surface area: 4000 cm 2 / g
Gypsum; Excreted dihydrate gypsum Blaine specific surface area: 2000 cm 2 / g

実施例1〜2
下記表1に示す配合割合で、石膏及びスラグと水とを混練して石膏及びスラグの混合ミルクを調製し、別に早強セメントと水とを混練してセメントミルクを調製した。かかる石膏及びスラグの混合ミルクを、関東ローム土壌1350kg(1m相当)に対して添加してソイルミキサで10分間混練し、2時間放置した。当該2時間放置後の関東ローム土壌に、更に前記セメントミルクを添加して、ソイルミキサにて更に10分間混練した。
混練後の関東ローム土壌を直径50mm×高さ100mmの共試体として得た。その一軸圧縮強さを1日後、7日後、28日後の材齢で測定し、その結果を表1に示す。
実施例3
下記表1に示す配合割合で、石膏と水とを混練して石膏ミルクを調製した以外は、実施例1と同様にして、所定の材齢の圧縮強さを測定し、その結果を表1に示す。
Examples 1-2
Gypsum and slag and water were kneaded at a blending ratio shown in Table 1 below to prepare a mixed milk of gypsum and slag, and cemented milk was prepared by kneading early strong cement and water separately. The mixed milk of gypsum and slag was added to 1350 kg (equivalent to 1 m 3 ) of Kanto loam soil, kneaded with a soil mixer for 10 minutes, and allowed to stand for 2 hours. The cement milk was further added to the Kanto loam soil after being left for 2 hours and kneaded for 10 minutes in a soil mixer.
The Kanto loam soil after kneading was obtained as a co-test body having a diameter of 50 mm and a height of 100 mm. The uniaxial compressive strength was measured after 1 day, 7 days, and 28 days later, and the results are shown in Table 1.
Example 3
Except that the gypsum milk was prepared by kneading gypsum and water at the blending ratio shown in Table 1 below, the compressive strength at a predetermined age was measured in the same manner as in Example 1, and the results are shown in Table 1. Shown in

実施例4〜5
石膏及びスラグの混合ミルクを関東ローム土壌に添加して混練した後の放置時間を96時間とした以外は、実施例1と同様にして、所定の材齢の圧縮強さを測定し、その結果を表1に示す。
実施例6
石膏ミルクを関東ローム土壌に添加して混練した後の放置時間を96時間とした以外は、実施例3と同様にして、所定の材齢の圧縮強さを測定し、その結果を表1に示す。
Examples 4-5
The compressive strength of a predetermined age was measured in the same manner as in Example 1 except that the leaving time after adding the mixed milk of gypsum and slag to the Kanto loam soil and kneading was 96 hours, and the result Is shown in Table 1.
Example 6
The compressive strength of a predetermined age was measured in the same manner as in Example 3 except that the standing time after adding gypsum milk to Kanto loam soil and kneading was 96 hours, and the results are shown in Table 1. Show.

比較例1
下記表1に示す配合割合で混合して得られたミルクを関東ローム土壌に一度に投入(一材型)して混練した以外は、実施例1と同様にして、所定の材齢の圧縮強さを測定し、その結果を表1に示す。
Comparative Example 1
Compressive strength of a predetermined age in the same manner as in Example 1 except that the milk obtained by mixing at the blending ratio shown in Table 1 below was added to the Kanto loam soil at one time (one material type) and kneaded. The results are shown in Table 1.

上記表より、一材型である比較例1の地盤改良方法による関東ローム土壌よりも、2段階に分かれて土壌改良材を添加する二材型の実施例1〜6の地盤改良方法による関東ローム改良土の圧縮強さが全ての材齢に渡って高いことがわかる。
上記表では、放置時間との関係で2時間放置に比べて、96時間放置の方が圧縮強さが高くなっているのは、使用した石膏のブレーン比表面積が2000cm/gと低めであったために短時間では石膏から土壌中へのカルシウム溶出量がすくなかったためであり、ブレーン比表面積が4000cm/gの石膏を用いて実施例1〜6と同様の実験をおこなったところ、初期強度の発現性がよく、また長期にわたって、高強度が維持できることが確認された。
From the above table, Kanto Loam by the soil improvement method of Examples 1-6 of the two-material type, which is divided into two stages rather than Kanto loam soil by the ground improvement method of Comparative Example 1 which is a single material type It can be seen that the compressive strength of the improved soil is high over all ages.
In the above table, the compressive strength is higher for 96 hours than for 2 hours in relation to the standing time because the brane specific surface area of the gypsum used is 2000 cm 2 / g, which is lower. For this reason, the amount of calcium eluted from the gypsum into the soil was not so short in a short time, and when the same experiment as in Examples 1 to 6 was performed using gypsum having a brain surface area of 4000 cm 2 / g, It was confirmed that expression was good and that high strength could be maintained over a long period of time.

本発明の地盤改良方法は、アロフェン、水和ハロサイト、モンモリロナイト等の固化阻害物質が存在する土壌であっても、優れた強度の発現が良好で、特に、関東ローム土壌の地盤改良に有効に使用することができる。
The ground improvement method of the present invention is excellent in the expression of excellent strength even in soils containing solidification inhibitors such as allophane, hydrated halosite, montmorillonite, and is particularly effective for ground improvement in Kanto loam soil. Can be used.

Claims (4)

石膏ミルクを土壌と混練し、所定時間放置した後、該土壌にセメントミルクを再混練することを特徴とする、地盤改良方法。 A ground improvement method comprising kneading gypsum milk with soil, leaving it for a predetermined time, and then re-kneading cement milk into the soil. 石膏及びスラグの混合ミルクを土壌と混練し、所定時間放置した後、該土壌にセメントミルクを再混練することを特徴とする、地盤改良方法。 A ground improvement method characterized in that mixed milk of gypsum and slag is kneaded with soil, left for a predetermined time, and then cement milk is re-kneaded in the soil. 請求項1記載の土壌改良方法において、セメントミルク中のセメント300〜400重量部に対して、石膏ミルク中の石膏が100〜200重量部含有されることを特徴とする、地盤改良方法。 The soil improvement method according to claim 1, wherein 100 to 200 parts by weight of gypsum in gypsum milk is contained with respect to 300 to 400 parts by weight of cement in cement milk. 請求項2記載の土壌改良方法において、セメントミルク中のセメント300〜400重量部に対して、石膏及びスラグの混合ミルク中の石膏が75〜100重量部とスラグが50〜75重量部含有されることを特徴とする、地盤改良方法。
The soil improvement method of Claim 2 WHEREIN: 75-100 weight part of gypsum in the mixed milk of gypsum and slag and 50-75 weight part of slag are contained with respect to 300-400 weight part of cement in cement milk. The ground improvement method characterized by the above-mentioned.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007138102A (en) * 2005-11-22 2007-06-07 Mitsubishi Materials Corp Solidification agent for soil remediation
JP2012207400A (en) * 2011-03-29 2012-10-25 Sumitomo Osaka Cement Co Ltd Foundation improvement method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007138102A (en) * 2005-11-22 2007-06-07 Mitsubishi Materials Corp Solidification agent for soil remediation
JP2012207400A (en) * 2011-03-29 2012-10-25 Sumitomo Osaka Cement Co Ltd Foundation improvement method

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