JP4094285B2

JP4094285B2 - Silicate-based soil stabilization chemicals

Info

Publication number: JP4094285B2
Application number: JP2001383221A
Authority: JP
Inventors: 健司澤田; 雅則小堀; 雅中村
Original assignee: Mitsubishi Chemical Corp; Mitsubishi Rayon Co Ltd
Current assignee: Mitsubishi Chemical Corp; Mitsubishi Rayon Co Ltd
Priority date: 2001-12-17
Filing date: 2001-12-17
Publication date: 2008-06-04
Anticipated expiration: 2021-12-17
Also published as: JP2003183654A

Description

【０００１】
【発明の属する技術分野】
本発明は、地盤安定化工法用の珪酸塩系土質安定用薬液に関する。
【０００２】
【従来の技術】
従来、軟弱地盤を強化したり、漏水地盤を止水するために種々の薬液を地盤内に注入し、地盤内でゲル化させる安定化工法が知られているが、特に、アルカリ珪酸塩水溶液を主成分とする主剤液と、硬化剤とを組み合わせた薬液からなる、いわゆる珪酸塩系土質安定用薬液は、安価である、他の土質安定用薬液と比較して公害を起こすおそれが小さいなどの特徴から、現在広く実用化されている。この珪酸塩系土質安定用薬液は、施工の目的や地盤の状況に応じて硬化剤の使用量を調節することにより薬液のゲルタイムを調整して施工が行われている。例えば、土壌粒子の間隙に薬液を充分浸透させた後ゲル化させる、いわゆる浸透注入工法による施工では薬液のゲルタイムを数分〜数十分に調整して用いられている。
【０００３】
また、上記浸透注入工法においても、地盤の土質条件によって薬液が未だゲル化しないうちに施工箇所以外の地盤中に流出して施工を不確実なものにしたり、薬液が地下水や井戸水に流入して公害問題を起こしたりするおそれがある場合や、漏水地盤を止水するような場合には薬液のゲルタイムを十数秒以内に調整してゲル化させる施工法、いわゆる瞬結工法で施工が行われている。
【０００４】
珪酸塩系土質安定用薬液の硬化剤としては現在種々の物質が知られており、幅広く実用化されているが、この中でも特にスルファミン酸は吸湿性、腐食性の低い粉末状白色結晶であり、水に溶解すると硫酸に匹敵する強酸性を示すので取り扱いの容易な硬化剤として有用なことは周知の通りである。
【０００５】
特開昭５６−１５５２８７号公報にはスルファミン酸に水溶性無機塩を配合成分として併用する珪酸塩系土質安定用薬液に用いる硬化剤が開示されている。この公報に記載されている硬化剤はスルファミン酸と水溶性無機塩とを質量比２：１〜１：１程度とした混合物を主体としており、スルファミン酸と混合させられる水溶性無機塩としては、硫酸、塩酸、硝酸、燐酸、ピロ燐酸、硼酸、炭酸、アルミン酸、塩素酸、過塩素酸、珪フッ酸、重クロム酸、過マンガン酸、スルファミン酸などの無機酸のアルカリ金属塩、アルカリ土類金属塩、遷移金属塩などの金属塩または酸性金属塩もしくはアンモニウム塩のうち水溶性のものが挙げられている。特に有用な水溶性無機塩として、塩化アルミニウム、硫酸アルミニウム、塩化マグネシウム、硫酸マグネシウム、塩化カルシウムなどが挙げられ、これにより生成する珪酸ゲルの硬度が大きくなること、即ちスルファミン酸を硬化剤とした場合に比べ強度の発現が改良されることが記載されている。
【０００６】
さらにこの公報に開示された珪酸塩系土質安定用薬液に用いる硬化剤は、通常５〜１５質量％の水溶液とした硬化剤１００質量部程度と、通常３０〜７０％の水溶液とした珪酸塩系土壌安定剤１００質量部とを混合し硬化剤として使用している。
【０００７】
ここで、アルカリ珪酸塩として珪酸塩系土質安定用薬液用に通常使用されるＪＩＳ３号水ガラスを用い、水溶性無機塩として塩化カルシウムを用いた場合、薬液中のＳｉＯ_２成分に対する硬化剤中の水溶性無機塩のモル比（ＳｉＯ_２／水溶性無機塩）は２．１〜２２．５となるが、このような範囲では薬液中のＳｉＯ_２成分の析出を生じる場合があり、均一な硬化体が得難いものであった。
【０００８】
【発明が解決しようとする課題】
スルファミン酸を硬化剤とした珪酸塩系土質安定用薬液では以下のような問題点があった。
【０００９】
▲１▼強度の発現が充分なものとは言えず、例えばアルカリ珪酸塩に対する硬化剤の量比を少なく用い、薬液のゲルタイムを十〜十数分程度に調整し、地盤中への浸透注入により施工を行なった場合、処理された地盤を切削したときにこの地盤が崩壊してしまう。また、漏水地盤を止水するためにアルカリ珪酸塩に対する硬化剤の量比を多くして薬液のゲルタイムを十数秒以内とする瞬結工法で施工した場合でも漏水地盤を充分に止水できない。
【００１０】
▲２▼実施工現場では、硬化剤液を調製する際の硬化剤の溶解時間は短いほど作業効率が向上して好ましいものである。しかし、硬化剤であるスルファミン酸は水に対する溶解速度が遅いため、特に冬場の施工など水温が低い時期での施工では硬化剤を溶解して硬化材液を調製するのに長時間を要する。そのため、薬液の地盤への注入速度によっては硬化剤液調製が間に合わず、硬化剤液調製のために施工を一時中断せねばならないなど施工効率が悪い。
【００１１】
▲３▼所定のゲルタイムを得るために必要なアルカリ珪酸塩に対する硬化剤の量比が多いため、実施工の場面では多量の硬化剤を施工現場へ搬入し貯蔵しておくためのスペースが必要となり、現場での作業性が悪いうえ不経済である。
【００１２】
一方、上記特開昭５６−１５５２８７号公報で開示された珪酸塩系土質安定用薬液に用いる硬化剤では、スルファミン酸を硬化剤とした場合の溶解速度が遅いこと、所定のゲルタイムを得るために必要なアルカリ珪酸塩に対する硬化剤の量比が多いことに関する問題点は未だ解決されていない。さらに上述のように、薬液を調製した際、ゲル体の主体をなす薬液中のＳｉＯ_２成分が析出し沈降して、均一な硬化体を形成されず、実質上地盤安定用薬液として使用できないという問題もあった。
【００１３】
本発明の目的は、従来の珪酸塩系土質安定用薬液に用いる硬化剤における上記問題点を改善し、低温時の施工においても硬化剤の水に対する溶解速度が速く、かつ、アルカリ珪酸塩に対する硬化剤の量比が従来よりも少量であっても所定のゲルタイムが得られ、さらに、調製された薬液がゲル体の主体をなす薬液中のＳｉＯ_２成分の析出・沈降により均一な硬化体が得られなくなるということがなく、アルカリ珪酸塩に対する硬化剤の量比の少ないゲルタイム十分〜十数分のいわゆる中結〜長結型とした場合においても、又、アルカリ珪酸塩に対する硬化剤の量比を多くしたゲルタイム十秒以内のいわゆる瞬結型の場合においても形成された硬化体の強度発現が良好であり、確実・効率よく地盤を安定化処理できる珪酸塩系土質安定用薬液に用いる硬化剤を提供することにある。
【００１４】
本発明の珪酸塩系土質安定用薬液に用いる硬化剤は下記（１）〜（４）のような性能を満たすことが目安となる。
【００１５】
（１）スルファミン酸としては、３２メッシュ篩残分が５０質量％程度の一般に市販されている工業用のスルファミン酸を用いて調製された硬化剤２０ｋｇを５℃の水に溶解して２００リットルの硬化剤液とする際の硬化剤の溶解時間が８分以内であること。
【００１６】
アルカリ珪酸塩としてＪＩＳ３号珪酸ソーダを用い、ＪＩＳ３号珪酸ソーダ８０リットルと水１２０リットルの割合で混合して調製した水溶液を主剤液とし、硬化剤を含む水溶液を硬化剤液として、主剤液と硬化剤液とを等容量ずつ混合して得られた薬液が温度２０℃において、
（２）ゲル体の主体をなす薬液中のＳｉＯ_２成分が析出し沈降して、均一な硬化体が得られること。
【００１７】
（３）１５秒未満のゲルタイムの薬液を得るのに必要な硬化材液２００リットル中の硬化剤の使用量が２０ｋｇ未満であること。
【００１８】
（４）硬化剤液の硬化剤量を調整して薬液のゲルタイムを十〜十数分程度に調製したときに形成された硬化体（ホモゲル体）の材令１日の一軸圧縮強度が０．０１Ｎ／ｍｍ^２以上であり、かつ、硬化剤液中の硬化剤量を調整して薬液のゲルタイムを１５秒未満に調製したときに形成された硬化体（ホモゲル体）の材令１日の一軸圧縮強度が０．０３Ｎ／ｍｍ^２以上であること。
【００１９】
【課題を解決するための手段】
本発明者らは上記課題を解決すべく鋭意検討した結果、酸性アンモニウム塩及び水溶性多価金属塩をスルファミン酸に対して特定の質量比の範囲内で組み合わせ硬化剤とすることで、意外にも、アルカリ珪酸塩に対する硬化剤の量比が少なくゲルタイム十分程度とした場合も、硬化剤の量比を多くしてゲルタイム十数秒以内とした場合でも形成された硬化体の強度の発現が良好であること。また、低温時においても硬化剤の水に対する溶解速度が速く、アルカリ珪酸塩に対する硬化剤の量比が少量であっても所定のゲルタイムが得られること、さらに薬液中のＳｉＯ_２成分に対する硬化剤中の多価金属塩のモル比を特定の範囲内とすることで、薬液中のＳｉＯ_２成分が析出し沈降することを回避できることを見出し、本発明に到達した。
【００２０】
すなわち、本発明の第一の発明は、アルカリ珪酸塩水溶液を含む主剤液と硬化剤の水溶液を組み合わせてなる珪酸塩系土質安定用薬液であって、硬化剤がスルファミン酸１００質量部に対して鉱酸のアンモニウム塩０．０１３〜１質量部、水溶性多価金属塩５〜３０質量部を含んでなり、主剤液のＳｉＯ_２成分に対する硬化剤中の水溶性多価金属塩のモル比（ＳｉＯ_２／水溶性多価金属塩）が１０〜１３５となるように配合されてなることを特徴とする珪酸塩系土質安定用薬液を要旨とする。
【００２１】
本発明の第二の発明は、珪酸塩系土質安定用薬液を地盤内に注入し、地盤内で硬化させて地盤を安定化させるにあたり、前記第一の発明の珪酸塩系土質安定用薬液を用いることを特徴とする地盤安定化工法を要旨とする。
【００２２】
【発明の実施の形態】
本発明の珪酸塩系土質安定用薬液の主剤として使用されるアルカリ珪酸塩は、従来から珪酸塩系土質安定用薬液に用いられているもの、例えば日本工業規格（ＪＩＳＫ−１４０８）に規定される１〜３号珪酸ソーダ、ＳｉＯ_２／Ｎａ_２Ｏ（モル比）が４〜１００の範囲にあるシリカゾルなどを用いることができる。又「ニトロック」（商品名、三菱レイヨン社製）を用いることもできる。これらの珪酸ソーダは一般に水溶液になっているが施工時に土質安定化に適した濃度とするために適宜水で希釈することもできる。例えば、珪酸ソーダ水溶液（以下、Ａ液ともいう。）と硬化剤液（以下、Ｂ液ともいう。）とを等容量ずつ混合しながら地盤内に注入する通常の施工方法において、珪酸ソーダとしてＪＩＳ３号を用いる場合は、通常、ＪＩＳ３号水ガラス７０〜１２０容量部を水で希釈して２００容量部にしたものをＡ液として使用する。Ａ液中の珪酸ソーダの濃度は高くするほど処理地盤の強度を大きくすることができる。
【００２３】
一方、珪酸ソーダ濃度が高くなりすぎると薬液の粘度が高くなり、ポンプによる圧送の際機器負荷が増大したり、薬液の地盤内での浸透性が低下する傾向にある。
【００２４】
本発明の珪酸塩系土質安定用薬液の硬化剤は、スルファミン酸に後述する鉱酸のアンモニウム塩と水溶性多価金属塩を後述の量比で配合することで得られる。スルファミン酸は上記Ａ液を地盤内でゲル化させるために用いられるものであって、一般に市販されているものを用いることができる。
【００２５】
本発明の珪酸塩系土質安定用薬液に用いる硬化剤の配合成分の鉱酸のアンモニウム塩とは、スルファミン酸、硫酸、塩酸、硝酸、燐酸、ピロ燐酸、硼酸、炭酸、アルミン酸、塩素酸、過塩素酸、珪フッ酸、重クロム酸、過マンガン酸などの鉱酸のアンモニウム塩であり、安全性・取り扱い性から、スルファミン酸アンモニウムが好ましい。
【００２６】
本発明の珪酸塩系土質安定用薬液に用いる硬化剤の配合成分である鉱酸のアンモニウム塩の配合量はスルファミン酸１００質量部当たりの下限値として０．０１３質量部、好ましくは０．２質量部以上である。上限値としては１質量部、好ましくは０．５質量部以下である。
【００２７】
酸性アンモニウム塩の配合量が本発明で規定する量比よりも少ない場合は硬化剤の溶解時間が長くなり、一方、多い場合は硬化剤の使用量が多くなり、本発明が目的とする性能が得られない。
【００２８】
本発明の珪酸塩系土質安定用薬液に用いる硬化剤の配合成分の水溶性多価金属塩とは、スルファミン酸、硫酸、塩酸、硝酸、燐酸、ピロ燐酸、硼酸、炭酸、アルミン酸、塩素酸、過塩素酸、珪フッ酸、重クロム酸、過マンガン酸などの鉱酸の２価または３価金属の塩のうち水溶性のものである。この中で、水溶性のカルシウム塩、マグネシウム塩、アルミニウム塩が好ましい。なかんずく有用な水溶性多価金属塩としては、塩化カルシウム、塩化マグネシウム、硫酸アルミニウムを例示することができる。なお、カルシウム塩、マグネシウム塩、アルミニウム塩であっても、例えば硫酸カルシウム、燐酸カルシウム、硫酸マグネシウム、炭酸マグネシウムなど水に対し難溶性の塩もあるが、これら難溶性の塩は土質安定用薬液としてのＢ液を調製できず、実質上使用できない。また、金属塩として、塩化ナトリウム、塩化カリウムなどの１価の金属塩などの本発明で規定する配合成分以外のもののみを配合しても、本発明が目的とする硬化体（ホモゲル体）の一軸圧縮強度が得られない。
【００２９】
本発明の珪酸塩系土質安定用薬液に用いる硬化剤の配合成分である水溶性多価金属塩の配合量は、スルファミン酸１００質量部当たりの下限値としては５質量部、好ましくは２０質量部であり、上限値としては３０質量部である。水溶性多価金属塩の配合量が本発明で規定する量比の範囲を外れた場合は、本発明が目的とする硬化体（ホモゲル体）の一軸圧縮強度が得られない。
【００３０】
本発明の珪酸塩系土質安定用薬液に用いる硬化剤の配合成分である酸性アンモニウム塩及び水溶性多価金属塩は一般に市販されているものを用いることができる。本発明の珪酸塩系土質安定用薬液に用いる硬化剤は水に溶解してＢ液として用いる。
【００３１】
水溶性多価金属塩の使用量は、Ａ液とＢ液とを混合した薬液において、薬液中のＳｉＯ_２成分に対する硬化剤中の水溶性多価金属塩のモル比ＳｉＯ_２／多価金属塩が、下限値１０、上限値１３５の範囲内において、所望のゲルタイムに応じて薬液のゲルタイムを短くする場合は多く、薬液のゲルタイムを長くする場合は少なく調節して用いる。
【００３２】
薬液中のＳｉＯ_２成分に対する硬化剤中の水溶性多価金属塩のモル比（ＳｉＯ_２／水溶性多価金属塩）が１０より小さい場合は、ゲル体の主体をなす薬液中のＳｉＯ_２成分が析出し沈降して均一な硬化体が得られなくなる。
【００３３】
一方、薬液中のＳｉＯ_２成分に対する硬化剤中の多価金属塩のモル比（ＳｉＯ_２／水溶性多価金属塩）が１３５よりも大きい場合は、本発明が目的とする硬化体（ホモゲル体）の一軸圧縮強度が得られない。
【００３４】
本発明の珪酸塩系土質安定用薬液に用いる硬化剤を地盤安定化工法に用いる場合、主剤としてアルカリ珪酸塩を主成分とするものと必要に応じて水とを混合したＡ液を調製する。また、本発明で規定した硬化剤と水とを混合したＢ液を調製する。さらに、Ａ液とＢ液の混合液中におけるＳｉＯ_２／水溶性多価金属塩のモル比が本発明で規定したモル比となるように混合して得られた薬液を地盤内に注入して硬化させて、地盤を安定化させる。
【００３５】
薬液の注入に際しては、短管式、二重管式、多重管式等の各種注入管を用いることができ、又、Ａ液とＢ液とを予め混合して注入管に導く方法、Ａ液とＢ液とを注入管の基部に設けた混合部、例えばＹ字管形状の混合部で混合、注入する方法、Ａ液とＢ液とをそれぞれ独立に注入管に導いて注入管から地盤内に注入しながら地盤内において合流、混合させるなど、適宜の方法を薬液のゲルタイムや施工性に応じて採用することができる。
【００３６】
以上述べたように、本発明の珪酸塩系土質安定用薬液を用いると、低温時の施工においても硬化剤の水に対する溶解速度が速く、硬化剤の量比が従来よりも少量であっても所定のゲルタイムが得られ、薬液のゲルタイム十数秒以内であっても十分程度であっても得られる硬化体に高い強度を付与でき、薬液中のＳｉＯ₂成分の析出し沈降して均一な硬化体が得られなくなって、地盤の安定化処理ができなくなるといった不測の事態も回避できる。
【００３７】
【実施例】
以下に本発明を実施例を用いて更に説明するが、本発明はこれら実施例に限定されるものではない。
【００３８】
実施例及び比較例
Ａ液：ＪＩＳ３号珪酸ソーダ８０リットルに水１２０リットルを加えて調製した。
【００３９】
Ｂ液：スルファミン酸と各種配合成分を表１に記載の量を容量が２００リットルとなるように水に溶解して調製した。
【００４０】
スルファミン酸は工業用品を、各種配合成分は試薬１級を用いた。
【００４１】
各試験におけるスルファミン酸の量、配合成分の種類、量、Ｂ液２００リットルにおける硬化剤組成物の配合量、Ａ液とＢ液との混合液(Ａ＋Ｂ液)中におけるＳｉＯ_２／水溶性多価金属塩ないし、比較例として１価の金属塩のモル比、及び硬化剤及び薬液の性能評価項目として、硬化剤組成物２０ｋｇを含むＢ液２００リットルを調製時での５℃における硬化剤組成物の溶解時間、Ａ液とＢ液混合時の状況（表中では混合状況と表示）、Ａ液とＢ液との混合液のゲルタイム、形成された硬化体（ホモゲル体）の材令１日の一軸圧縮強度のそれぞれについての測定結果と総合評価を表１に示した。
【００４２】
表の配合成分としての鉱酸のアンモニウム塩や水溶性多価金属塩の種類の欄において、Ｃ：スルファミン酸アンモニウム、Ｄ：硫酸アンモニウム、Ｅ：塩化カルシウム、Ｆ：塩化マグネシウム、Ｇ：硫酸アルミニウム、Ｈ：塩化カリウムを示す。
【００４３】
また、硬化剤及び薬液性能の各評価項目の試験法と評価の基準は以下の通りである。
【００４４】
硬化剤溶解時間：５℃の環境下、ドラム缶内に硬化剤組成物２０ｋｇと硬化剤溶解後のＢ液が２００リットルとなるように５℃の水を加え、ミキサー（パワーミックスＰＭ２２０Ｂ東芝（株）製）を用いて攪拌し、硬化剤が完全に溶解し均一な水溶液となるまでに要した時間を測定した。なお、同欄では硬化剤組成物２０ｋｇの場合の測定結果を示し、表記：＊は測定しなかったことを示す。
【００４５】
Ａ液とＢ液混合時の状況：液温２０℃において、等容量のＡ液とＢ液をよく混合して容器内に静置し、混合液の状況を目視観察した。同欄における表記：○は珪酸成分の析出し沈降することが無く、均一なゲル体が形成されたことを示し、表記：×は珪酸成分が析出し沈降して、均一なゲル体が形成されなかったことを示す。
【００４６】
薬液のゲルタイム：液温２０℃において、当容量のＡ液とＢ液をよく混合して容器内に静置し、混合液の流動性がなくなるまでの所要時間をゲルタイムとした。
【００４７】
硬化体の一軸圧縮強度：液温２０℃において、Ａ液とＢ液の当容量混合液を円柱型の型枠（径５ｃｍ×高さ１０ｃｍ）内に流し込み、形成された硬化体（ホモゲル体）の材令１日の一軸圧縮強度を測定した。
【００４８】
なお、表１中、表記：−は、硬化剤溶解時間、Ａ液とＢ液混合時の状況、１５秒未満のゲルタイムの薬液を得るに必要な硬化剤の使用量、の何れかの性能が本発明の目的に達していなかったため、測定しなかったことを示す。
【００４９】
総合評価：硬化剤２０ｋｇの５℃での溶解時間が８分以内、混合状況が○、１０秒未満のゲルタイムの薬液を得るに必要な硬化材液２００リットル中の硬化剤の使用量が２０ｋｇ未満、ゲルタイムが十〜十数分程度の場合は、測定した一軸圧縮強度が０．０１Ｎ／ｍｍ^２以上であり、ゲルタイムが１５秒未満の場合は一軸圧縮強度が０．０３Ｎ／ｍｍ^２以上であるものを○とし、何れかの性能が上記基準に達しないものを×とした。
【００５０】
【表１】

表１から明らかなように、本発明の要件を満たした場合には、硬化剤２０ｋｇの５℃での溶解時間が８分以内であり、Ａ液とＢ液の混合時にも珪酸成分の析出・沈降が無く均一なゲル体が形成され、硬化剤液２００リットル中の硬化剤の使用量が２０ｋｇ未満で１５秒未満のゲルタイムの薬液が得られ、ゲルタイムが十〜十数分程度とした場合に形成された硬化体（ホモゲル体）の材令１日の一軸圧縮強度が０．０１Ｎ／ｍｍ^２以上であり、ゲルタイムが１５秒未満とした場合は硬化体の材令１日の一軸圧縮強度が０．０３Ｎ／ｍｍ^２以上となり、本発明の目的を達成することができたのに対し、本発明で規定する配合成分を用いても、スルファミン酸に対する鉱酸のアンモニウム塩や水溶性多価金属塩の量比が本発明の規定から外れた場合や、水溶性多価金属塩の珪酸成分に対するモル比が本発明の規定から外れた場合は、硬化剤２０ｋｇの５℃での溶解時間が長かったり、珪酸成分が析出し沈降したり、硬化剤の使用量が２０ｋｇ未満で１５秒未満のゲルタイムの薬液が得られなかったり、得られた硬化体の強度が低くなるなど、本発明の目的を達成できなかった。
【００５１】
【発明の効果】
本発明の珪酸塩系土質安定用薬液に用いる硬化剤は、従来のスルファミン酸に水溶性無機塩を配合成分として併用する珪酸塩系土質安定用薬液に用いる硬化剤に比較し、下記の特徴を有する。
▲１▼低温時の施工においても硬化剤の水に対する溶解速度が速い。
▲２▼アルカリ珪酸塩に対する硬化剤の量比が従来よりも少量であっても所定のゲルタイムが得られる。
▲３▼本発明の硬化剤を用いて調製される珪酸塩系土質安定用薬液は、薬液中の珪酸成分が析出し沈降することがないため、得られる硬化体が不均一となるようなことがない。
▲４▼薬液のゲルタイムを十分〜十数分とした場合であっても十数秒以内とした場合であっても得られる硬化体の強度発現が良好である。
従って、より安全・確実・効率的に地盤を安定化できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silicate-based soil stabilization chemical for ground stabilization.
[0002]
[Prior art]
Conventionally, a stabilization method is known in which various chemicals are injected into the ground to strengthen the soft ground or to stop the leaked ground and gel in the ground. The so-called silicate-based soil stabilization chemical solution, which consists of a chemical solution that combines the main agent solution as the main component and a curing agent, is inexpensive and less likely to cause pollution compared to other soil stabilization chemical solutions. Due to its features, it is currently in wide use. This silicate-based soil stabilization chemical solution is applied by adjusting the gel time of the chemical solution by adjusting the amount of the curing agent used according to the purpose of the construction and the ground conditions. For example, in a construction by a so-called osmotic injection method in which a chemical solution is sufficiently permeated into a gap between soil particles and then gelled, the gel time of the chemical solution is adjusted from several minutes to several tens of minutes.
[0003]
Also, in the above osmotic injection method, the chemical solution still flows into the ground other than the construction site before it gels due to the soil condition of the ground, making the construction uncertain, or the chemical solution flows into the groundwater or well water When there is a possibility of causing pollution problems or when the water leakage ground is stopped, the construction is performed by the so-called instantaneous setting method, in which the gel time of the chemical solution is adjusted within 10 seconds to make it gel. Yes.
[0004]
Various substances are currently known and widely used as curing agents for silicate-based soil stabilization chemicals. Among them, sulfamic acid is a powdery white crystal with low hygroscopicity and low corrosivity. As is well known, it is useful as a curing agent that is easy to handle because it exhibits strong acidity comparable to sulfuric acid when dissolved in water.
[0005]
Japanese Patent Application Laid-Open No. 56-155287 discloses a curing agent used in a silicate-based soil stabilization chemical solution in which a water-soluble inorganic salt is used in combination with sulfamic acid. The curing agent described in this publication is mainly composed of a mixture of sulfamic acid and a water-soluble inorganic salt in a mass ratio of about 2: 1 to 1: 1. As a water-soluble inorganic salt mixed with sulfamic acid, Alkali metal salts of inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, pyrophosphoric acid, boric acid, carbonic acid, aluminate, chloric acid, perchloric acid, silicic acid, dichromic acid, permanganic acid, sulfamic acid, alkaline earth Water-soluble metal salts such as metal salts such as metal salts and transition metal salts, or acidic metal salts or ammonium salts are mentioned. Particularly useful water-soluble inorganic salts include aluminum chloride, aluminum sulfate, magnesium chloride, magnesium sulfate, calcium chloride, etc., and the resulting silicic acid gel increases in hardness, that is, when sulfamic acid is used as a curing agent. It is described that the expression of strength is improved as compared with the above.
[0006]
Further, the curing agent used in the silicate-based soil stabilization chemical solution disclosed in this publication is usually about 100 parts by mass of a curing agent in an aqueous solution of 5 to 15% by mass and a silicate type in an aqueous solution of usually 30 to 70%. 100 parts by mass of a soil stabilizer is mixed and used as a curing agent.
[0007]
Here, when JIS No. 3 water glass usually used for a silicate-based soil stabilization chemical solution is used as an alkali silicate, and calcium chloride is used as a water-soluble inorganic salt, in the curing agent for the SiO ₂ component in the chemical solution The molar ratio of the water-soluble inorganic salt (SiO ₂ / water-soluble inorganic salt) is 2.1 to 22.5, but in such a range, precipitation of the SiO ₂ component in the chemical solution may occur, and uniform curing The body was difficult to obtain.
[0008]
[Problems to be solved by the invention]
The silicate-based soil stabilization chemical solution using sulfamic acid as a curing agent has the following problems.
[0009]
(1) It cannot be said that the strength is sufficiently developed. For example, by using a small amount ratio of the curing agent to the alkali silicate, the gel time of the chemical solution is adjusted to about ten to ten and several minutes, and osmotic injection into the ground When construction is performed, this ground collapses when the treated ground is cut. Moreover, even if it constructs by the instantaneous setting method which makes the gel time of a chemical | medical solution less than ten seconds by increasing the quantity ratio of the hardening | curing agent with respect to alkali silicate in order to stop a water leak ground, a water leak ground cannot fully stop.
[0010]
(2) On the construction site, the shorter the dissolution time of the curing agent when preparing the curing agent solution, the better the working efficiency and the better. However, since sulfamic acid, which is a curing agent, has a slow dissolution rate in water, it takes a long time to prepare a curing material liquid by dissolving the curing agent, especially in construction at a low water temperature such as construction in winter. Therefore, depending on the injection speed of the chemical liquid to the ground, the preparation of the curing agent solution may not be in time, and the construction efficiency is poor, such as the construction must be temporarily suspended for the preparation of the curing agent solution.
[0011]
(3) Since there is a large amount ratio of the curing agent to the alkali silicate required to obtain a predetermined gel time, a space for carrying a large amount of the curing agent to the construction site and storing it is required in the construction work. The workability on site is poor and uneconomical.
[0012]
On the other hand, in the curing agent used in the silicate-based soil stabilization chemical disclosed in JP-A-56-155287, the dissolution rate is slow when sulfamic acid is used as the curing agent, in order to obtain a predetermined gel time. The problem with the large amount of curing agent to the required alkali silicate has not yet been solved. Furthermore, as described above, when a chemical solution is prepared, the SiO ₂ component in the chemical solution that forms the main body of the gel body precipitates and settles, so that a uniform cured body is not formed, and it cannot be used substantially as a ground stabilization chemical solution. There was also a problem.
[0013]
The object of the present invention is to improve the above-mentioned problems in the curing agent used in the conventional silicate-based soil stabilization chemical solution, the dissolution rate of the curing agent in water is high even in the construction at low temperature, and the curing to the alkali silicate. Predetermined gel time can be obtained even if the amount ratio of the agent is smaller than before, and a uniform cured body can be obtained by precipitation and sedimentation of the SiO ₂ component in the chemical solution in which the prepared chemical solution is the main body of the gel body. Even in the case of a so-called medium to long tie type gel time with a small amount ratio of the curing agent to the alkali silicate without being lost, the amount ratio of the curing agent to the alkali silicate Even in the case of the so-called instantaneous setting type with a gel time of less than 10 seconds, the strength of the formed cured body is good, and it is a silicate-based soil stabilization chemical solution that can stably and efficiently stabilize the ground. It is to provide a curing agent to be used.
[0014]
It becomes a standard that the curing agent used in the silicate-based soil stabilization chemical solution of the present invention satisfies the following performances (1) to (4).
[0015]
(1) As the sulfamic acid, 20 kg of a curing agent prepared by using commercially available sulfamic acid for industrial use having a 32 mesh sieve residue of about 50% by mass in water at 5 ° C. The dissolution time of the curing agent when making the curing agent liquid is within 8 minutes.
[0016]
An aqueous solution prepared by mixing JIS No. 3 sodium silicate with 80 liters of JIS No. 3 sodium silicate at a ratio of 120 liters of water as a main liquid and using an aqueous solution containing a hardener as a hardener liquid and curing. The chemical solution obtained by mixing equal volumes of the chemical solution at a temperature of 20 ° C.
(2) A uniform cured body can be obtained by precipitating and precipitating the SiO ₂ component in the chemical that forms the main body of the gel body.
[0017]
(3) The amount of the curing agent used in 200 liters of the curing material liquid necessary for obtaining a chemical solution having a gel time of less than 15 seconds is less than 20 kg.
[0018]
(4) The uniaxial compressive strength of the cured material (homogel) formed when the amount of the curing agent in the curing agent solution is adjusted to adjust the gel time of the chemical solution to about ten to ten and several minutes is 0.1. 1 N / mm ^{2 of} the hardened body (homogel body) formed by adjusting the amount of the curing agent in the curing agent liquid and adjusting the gel time of the chemical liquid to less than 15 seconds. The compressive strength is 0.03 N / mm ² or more.
[0019]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have surprisingly realized that a combination curing agent of an acidic ammonium salt and a water-soluble polyvalent metal salt within a specific mass ratio with respect to sulfamic acid is used. In addition, even when the amount ratio of the curing agent to the alkali silicate is small and the gel time is sufficient, even when the amount ratio of the curing agent is increased and the gel time is within 10 seconds or less, the strength of the formed cured body is well expressed. There is. In addition, the dissolution rate of the curing agent in water is high even at low temperatures, and a predetermined gel time can be obtained even if the amount ratio of the curing agent to the alkali silicate is small. Further, in the curing agent for the SiO ₂ component in the chemical solution It was found that by setting the molar ratio of the polyvalent metal salt within a specific range, it is possible to avoid precipitation and precipitation of the SiO ₂ component in the chemical solution, and the present invention has been achieved.
[0020]
That is, the first invention of the present invention is a silicate-based soil stabilization chemical solution comprising a combination of a main agent solution containing an alkali silicate aqueous solution and an aqueous solution of a curing agent, and the curing agent is based on 100 parts by mass of sulfamic acid. It comprises 0.013 to 1 part by weight of an ammonium salt of a mineral acid, 5 to 30 parts by weight of a water-soluble polyvalent metal salt, and the molar ratio of the water-soluble polyvalent metal salt in the curing agent to the SiO ₂ component of the main agent liquid ( A gist is a chemical solution for stabilizing a silicate-based soil, characterized by being formulated so that (SiO ₂ / water-soluble polyvalent metal salt) is 10 to 135.
[0021]
The second invention of the present invention is a method for injecting a silicate-based soil stabilization chemical solution into the ground and curing the silicate-based soil stabilization chemical solution of the first invention to stabilize the ground. The gist is a ground stabilization method characterized by the use.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The alkali silicate used as the main agent of the chemical solution for stabilizing silicate soils of the present invention is stipulated in, for example, Japanese Industrial Standard (JIS K-1408), which is conventionally used for chemical solutions for stabilizing silicate soils. 1 to 3 sodium silicate, silica sol having SiO ₂ / Na ₂ O (molar ratio) in the range of 4 to 100, and the like can be used. “Nitroc” (trade name, manufactured by Mitsubishi Rayon Co., Ltd.) can also be used. These sodium silicates are generally in an aqueous solution, but can be appropriately diluted with water in order to obtain a concentration suitable for soil stabilization during construction. For example, in a normal construction method in which a sodium silicate aqueous solution (hereinafter also referred to as A liquid) and a curing agent liquid (hereinafter also referred to as B liquid) are injected into the ground while mixing equal volumes, JIS3 as sodium silicate is used. In the case of using No., normally, 70 to 120 parts by volume of JIS No. 3 water glass is diluted with water to 200 parts by volume, and the A liquid is used. The strength of the treated ground can be increased as the concentration of sodium silicate in the liquid A is increased.
[0023]
On the other hand, when the sodium silicate concentration becomes too high, the viscosity of the chemical solution becomes high, and the equipment load increases when pumping by the pump, or the permeability of the chemical solution in the ground tends to decrease.
[0024]
The hardening | curing agent of the chemical | medical solution for the silicate type | system | group soil stabilization of this invention is obtained by mix | blending the ammonium salt of the mineral acid mentioned later and water-soluble polyvalent metal salt with the below-mentioned quantitative ratio with sulfamic acid. The sulfamic acid is used for gelling the solution A in the ground, and a commercially available product can be used.
[0025]
The ammonium salt of the mineral acid as a compounding component of the curing agent used in the silicate-based soil stabilization chemical solution of the present invention is sulfamic acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, pyrophosphoric acid, boric acid, carbonic acid, aluminate, chloric acid, Ammonium salts of mineral acids such as perchloric acid, silicohydrofluoric acid, dichromic acid and permanganic acid, and ammonium sulfamate is preferred from the viewpoint of safety and handleability.
[0026]
The compounding amount of the ammonium salt of mineral acid, which is a compounding component of the curing agent used in the silicate-based soil stabilization chemical solution of the present invention, is 0.013 parts by mass, preferably 0.2 parts by mass, as the lower limit per 100 parts by mass of sulfamic acid. More than a part. As an upper limit, it is 1 mass part, Preferably it is 0.5 mass part or less.
[0027]
When the blending amount of the acidic ammonium salt is less than the amount ratio specified in the present invention, the dissolution time of the curing agent becomes long, whereas when it is large, the amount of the curing agent used increases and the performance intended by the present invention is achieved. I can't get it.
[0028]
The water-soluble polyvalent metal salt as a component of the curing agent used in the silicate-based soil stabilization chemical solution of the present invention is sulfamic acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, pyrophosphoric acid, boric acid, carbonic acid, aluminate, chloric acid , Water-soluble salts of divalent or trivalent metal salts of mineral acids such as perchloric acid, silicic acid, dichromic acid and permanganic acid. Among these, water-soluble calcium salts, magnesium salts, and aluminum salts are preferable. Among others, useful water-soluble polyvalent metal salts include calcium chloride, magnesium chloride, and aluminum sulfate. In addition, even calcium salts, magnesium salts, and aluminum salts include, for example, calcium sulfate, calcium phosphate, magnesium sulfate, and magnesium carbonate, which are hardly soluble in water. However, these poorly soluble salts are used as a chemical solution for soil stabilization. Cannot be prepared and cannot be used substantially. Moreover, even if only a component other than the blending components specified in the present invention, such as a monovalent metal salt such as sodium chloride or potassium chloride, is blended as the metal salt, the cured product (homogel) targeted by the present invention Uniaxial compressive strength cannot be obtained.
[0029]
The blending amount of the water-soluble polyvalent metal salt that is a blending component of the curing agent used in the silicate-based soil stabilization chemical solution of the present invention is 5 parts by mass, preferably 20 parts by mass as the lower limit per 100 parts by mass of sulfamic acid. The upper limit is 30 parts by mass. When the blending amount of the water-soluble polyvalent metal salt is out of the range of the quantitative ratio defined in the present invention, the uniaxial compressive strength intended for the cured product (homogel body) of the present invention cannot be obtained.
[0030]
What is generally marketed can be used for the acidic ammonium salt and water-soluble polyvalent metal salt which are the components of the curing agent used in the silicate-based soil stabilization chemical solution of the present invention. The hardening | curing agent used for the chemical | medical solution for silicate type | system | group soil stabilization of this invention melt | dissolves in water, and uses it as B liquid.
[0031]
The amount of the water-soluble polyvalent metal salt used is the molar ratio of water-soluble polyvalent metal salt in the curing agent to the SiO ₂ component in the chemical solution in the chemical solution in which the liquid A and the liquid B are mixed. SiO ₂ / polyvalent metal salt However, within the range of the lower limit value 10 and the upper limit value 135, the drug solution gel time is often shortened according to the desired gel time, and the drug solution gel time is adjusted to be small.
[0032]
When the molar ratio of the water-soluble polyvalent metal salt in the curing agent to the SiO ₂ component in the chemical solution (SiO ₂ / water-soluble polyvalent metal salt) is less than 10, the SiO ₂ component in the chemical solution that forms the main body of the gel body Precipitates and settles, and a uniform cured body cannot be obtained.
[0033]
On the other hand, when the molar ratio of the polyvalent metal salt in the curing agent to the SiO ₂ component in the chemical solution (SiO ₂ / water-soluble polyvalent metal salt) is greater than 135, the cured product (homogeneous body) targeted by the present invention ) Uniaxial compressive strength cannot be obtained.
[0034]
When using the hardening | curing agent used for the chemical | medical solution for silicate type | system | group soil stabilization of this invention for a ground stabilization construction method, the A liquid which mixed the thing which has an alkali silicate as a main component and water as needed is prepared. Moreover, the B liquid which mixed the hardening | curing agent prescribed | regulated by this invention and water is prepared. Furthermore, a chemical obtained by mixing so that the molar ratio of SiO ₂ / water-soluble polyvalent metal salt in the liquid mixture of the liquid A and liquid B is the molar ratio specified in the present invention is injected into the ground. Harden to stabilize the ground.
[0035]
When injecting a chemical solution, various types of injection tubes such as a short tube type, a double tube type, a multi-tube type, etc. can be used. And B liquid are mixed and injected in a mixing part provided at the base of the injection pipe, for example, a Y-shaped mixing part, and A liquid and B liquid are guided to the injection pipe independently from the injection pipe to the ground. An appropriate method such as merging and mixing in the ground while being poured into the ground can be employed according to the gel time and workability of the chemical solution.
[0036]
As described above, when using the silicate-based soil stabilization chemical solution of the present invention, the dissolution rate of the curing agent in water is high even during low-temperature construction, and even if the amount ratio of the curing agent is smaller than that of the conventional one. Predetermined gel time is obtained, and even if the gel time of the chemical solution is within a few tens of seconds, it can impart high strength to the obtained cured product, and the SiO ₂ component in the chemical solution is precipitated and settled to be a uniform cured product. It is possible to avoid the unexpected situation that the soil cannot be stabilized and the ground stabilization process becomes impossible.
[0037]
【Example】
The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.
[0038]
Examples and Comparative Example A Solution: Prepared by adding 120 liters of water to 80 liters of JIS No. 3 sodium silicate.
[0039]
Liquid B: Sulfamic acid and various blending components were prepared by dissolving the amounts shown in Table 1 in water so that the volume was 200 liters.
[0040]
For sulfamic acid, industrial products were used, and for the various components, reagent grade 1 was used.
[0041]
Amount of sulfamic acid in each test, type and amount of blending component, blending amount of curing agent composition in 200 liters of B liquid, SiO ₂ / water-soluble polyvalent in liquid mixture of A liquid and B liquid (A + B liquid) Metal salt or molar ratio of monovalent metal salt as a comparative example, and curing agent composition at 5 ° C. at the time of preparation of 200 liters of B liquid containing 20 kg of curing agent composition as performance evaluation items of curing agent and chemical solution Dissolution time, situation when liquid A and liquid B are mixed (indicated in the table as mixing conditions), gel time of the liquid mixture of liquid A and liquid B, material age of the formed cured body (homogel body) 1 day Table 1 shows the measurement results and overall evaluation for each uniaxial compressive strength.
[0042]
In the column of the types of ammonium salts of mineral acids and water-soluble polyvalent metal salts as blending components in the table, C: ammonium sulfamate, D: ammonium sulfate, E: calcium chloride, F: magnesium chloride, G: aluminum sulfate, H : Indicates potassium chloride.
[0043]
Moreover, the test method and evaluation criteria of each evaluation item of the curing agent and chemical solution performance are as follows.
[0044]
Curing agent dissolution time: In an environment of 5 ° C., add 20 kg of the curing agent composition and water at 5 ° C. so that the B liquid after dissolution of the curing agent is 200 liters in a drum, and add a mixer (Powermix PM220B Toshiba Corporation). The time required for the curing agent to completely dissolve and become a uniform aqueous solution was measured. In addition, the measurement result in the case of 20 kg of hardening | curing agent compositions is shown in the same column, and description: * shows not having measured.
[0045]
Situation when liquid A and liquid B were mixed: At a liquid temperature of 20 ° C., equal volumes of liquid A and liquid B were mixed well and placed in a container, and the condition of the liquid mixture was visually observed. The notation in the same column: ○ indicates that the silicic acid component did not precipitate and settled, and a uniform gel body was formed, and the notation: × indicates that the silicic acid component precipitated and settled, and a uniform gel body was formed. Indicates no.
[0046]
Gel time of the chemical solution: At a liquid temperature of 20 ° C., the A volume and B volume of this volume were mixed well and left in the container, and the time required until the fluidity of the mixed liquid disappeared was defined as the gel time.
[0047]
Uniaxial compressive strength of the cured body: At a liquid temperature of 20 ° C., a liquid mixture of the same volume of liquid A and liquid B was poured into a cylindrical mold (diameter 5 cm × height 10 cm), and a cured body (homogen body) formed The uniaxial compressive strength of the material age 1 day was measured.
[0048]
In Table 1, the notation:-indicates the performance of any one of the curing agent dissolution time, the situation at the time of mixing liquid A and liquid B, and the amount of curing agent used to obtain a chemical solution having a gel time of less than 15 seconds. This indicates that the measurement was not performed because the object of the present invention was not achieved.
[0049]
Comprehensive evaluation: Dissolving time of 20 kg of curing agent at 5 ° C. within 8 minutes, mixing condition ○ Less than 20 kg of curing agent used in 200 liters of curing material solution required to obtain a chemical solution with gel time of less than 10 seconds When the gel time is about 10 to 10 minutes, the measured uniaxial compressive strength is 0.01 N / mm ² or more. When the gel time is less than 15 seconds, the uniaxial compressive strength is 0.03 N / mm ² or more. A sample was evaluated as ◯, and a sample whose performance did not reach the above standard was evaluated as ×.
[0050]
[Table 1]

As is clear from Table 1, when the requirements of the present invention are satisfied, the dissolution time of 20 kg of the curing agent at 5 ° C. is within 8 minutes. When a uniform gel body without sedimentation is formed, a chemical solution having a gel time of less than 15 seconds is obtained with less than 20 kg of the curing agent used in 200 liters of the curing agent solution, and the gel time is about 10 to 10 minutes or more When the formed uniaxial compressive strength of the cured body (homogel) is 0.01 N / mm ² or more and the gel time is less than 15 seconds, the uniaxial compressive strength of the cured body is 1 day. 0.03 N / mm ² or more, and the object of the present invention could be achieved. On the other hand, even when the blending component specified in the present invention was used, ammonium salt of mineral acid against sulfamic acid and water-soluble polyvalent metal If the salt ratio is outside the scope of the present invention If the molar ratio of the water-soluble polyvalent metal salt to the silicic acid component is not within the scope of the present invention, the curing time of 20 kg of the curing agent at 5 ° C. is long, the silicic acid component is precipitated and settles, The object of the present invention could not be achieved, for example, a chemical solution having a gel time of less than 15 seconds and a gel time of less than 15 seconds could not be obtained, and the strength of the obtained cured product was reduced.
[0051]
【The invention's effect】
The curing agent used in the silicate-based soil stabilization chemical solution of the present invention has the following characteristics compared to the curing agent used in a silicate-based soil stabilization chemical solution that uses a water-soluble inorganic salt in combination with a conventional sulfamic acid. Have.
(1) The dissolution rate of the curing agent in water is fast even during construction at low temperatures.
(2) A predetermined gel time can be obtained even if the amount ratio of the curing agent to the alkali silicate is smaller than that of the conventional one.
(3) The silicate-based soil stabilization chemical solution prepared using the curing agent of the present invention does not precipitate and settle out the silicic acid component in the chemical solution, so that the resulting cured product is not uniform. There is no.
(4) The strength of the obtained cured product is good even when the gel time of the chemical solution is sufficiently to tens of minutes or within ten seconds.
Therefore, the ground can be stabilized more safely, reliably and efficiently.

Claims

A silicate-based soil stabilization chemical solution comprising a combination of a main agent solution containing an aqueous alkali silicate solution and an aqueous solution of a curing agent, wherein the curing agent is an ammonium salt of 0.013 to 1 mass of mineral acid with respect to 100 parts by mass of sulfamic acid. The water-soluble polyvalent metal salt 5 to 30 parts by mass, the molar ratio of the water-soluble polyvalent metal salt in the curing agent to the SiO ₂ component of the main agent liquid (SiO ₂ / water-soluble polyvalent metal salt) A silicate-based soil stabilization chemical solution, which is formulated so as to be 10 to 135.

The chemical solution for stabilizing silicate soil according to claim 1, wherein the ammonium salt of mineral acid is ammonium sulfamate.

The silicate-based soil stabilization chemical solution according to claim 1 or 2, wherein the water-soluble polyvalent metal salt is at least one selected from the group consisting of calcium salts, magnesium salts, and aluminum salts.

Injecting the silicate-based soil stabilization chemical into the ground and curing it in the ground to stabilize the ground, the use of the silicate-based soil stabilization chemical according to any one of claims 1 to 3. A feature of ground stabilization method.