JP3669288B2 - Liquefaction prevention method - Google Patents

Liquefaction prevention method Download PDF

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JP3669288B2
JP3669288B2 JP2001126649A JP2001126649A JP3669288B2 JP 3669288 B2 JP3669288 B2 JP 3669288B2 JP 2001126649 A JP2001126649 A JP 2001126649A JP 2001126649 A JP2001126649 A JP 2001126649A JP 3669288 B2 JP3669288 B2 JP 3669288B2
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JP2002322637A (en
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美好 忠平
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美好 忠平
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【０００１】
【発明が属する技術分野】
本発明は、地中の過剰間隙水を排水し地震時の地盤液状化を防止する液状化防止工法に関する。
【０００２】
【発明が解決しようとする課題】
地盤改良を必要とする地盤では、大地震により地盤柱の水圧が急上昇し、せん断抵抗が失われて砂が流動化する液状化現象が発生し易い。そして、このような液状化に対する対策として、特開平７−１５８０４４号公報の０００２段にあるように、砂地盤を締め固めて地盤の間隙率の低減およびせん断強さの向上を図る方法、地盤柱に砂杭あるいは砕石柱を形成して高圧地下水の排水促進を図る方法、地盤中に水ガラス系その他の薬剤を注入する等して地盤固化を図る方法あるいは地盤柱にディープウェルと止水壁を設けてポンプ排水によって地下水水位の低下を図る方法などがある。
【０００３】
そして、従来の砂杭あるいは砕石柱は、略全長に渡ってスクリューを周設した へーシングパイプを用い、回転駆動によって地盤中に嵌入させ、砕石を投入しながらケーシングパイプを引き抜き、地盤中に排水用の砕石柱を形成する（公報第０００３段）。
【０００４】
従来の砂杭あるいは砕石柱は、地下水の排水促進することができる。しかし、上述した従来の方法では、一定の支持力は得られるものの、周囲地層に対する締め固め作用が十分に得られず、全体として支持力を効果的に向上することができなかった。また、施工においては、その全長にケーシングパイプを挿入した後、そのケーシングパイプを引く抜く工程が必要であり、軟弱地盤の上部に礫質層などがあると、挿入効率が低下することが予想される。さらに、施工後の砕石柱に対して、周囲の地層から微細土粒子が侵入すると、排水機能が低下する問題も予想される。
【０００５】
そこで、本発明は、施工性に優れ、中詰め材を効率良く締め固めて高い支持力が得られ、地震時には、地層の水を排水して液状化現象の発生を防止できる液状化防止工法を提供することを目的とし、加えて、基礎柱の透水性を保持することができる液状化防止工法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
請求項１の液状化防止工法は、地震時に想定される地盤の液状化に伴って発生する地盤内の過剰間隙水を排水する液状化防止工法において、前記地盤は、難透水地層の下部に透水地層を有し、前記難透水地層は前記透水地層より透水性が低く、杭の下端に圧縮水を噴射する圧縮水用ノズルと圧縮空気を噴射する圧縮空気用ノズルとを設け、それらノズルから圧縮水と圧縮空気とを噴射して前記透水地層に達する深さまで打ち込んで掘削孔を形成し、前記圧縮水と圧縮空気との噴射により地中の微細粒子を前記杭に沿って上昇させると共に、地表に排出し、この微細粒子を排出した後、前記圧縮空気の噴射を停止又は噴射圧を下げ、前記杭を引き抜くと共に、この引き抜き時に掘削孔内に中詰め材を投入して周囲より透水性が高い基礎柱を形成し、この基礎柱にパイプを設け、このパイプの下部に前記基礎柱内の下部に開口する孔を設け、前記パイプの上部に、空気圧送手段と地下水吸引手段とを選択的又は切換可能に接続する工法である。
【０００７】
この請求項１の構成によれば、下方に向かって噴射した圧縮空気と圧縮水とにより、杭の下方の掘削孔において、土粒子（土塊）の攪拌が行われ、圧縮空気が泡となって上昇する際に土粒子を揺動して分解が行われ、これにより分解した微細粒子たる水溶性微細粒子が上昇水流と泡の上昇に伴うリフトアップ効果によりに地表に効率よく排土される。そして、掘削孔内に投入した中詰め材を圧縮水により圧密することにより、基礎柱に高い支持力が得られる。このようにして、ケーシングを使用しなくても、掘削孔に充填した中詰め材に微細土粒子が混合して透水性を損なうことがない。また、その基礎柱は高い透水性を有するため、地震時には、地盤内の水が基礎柱を通って地表側に排出され、該地盤における液状化現象を防止することができる。
【０００８】
また、パイプに接続した空気圧送手段により、孔から空気を噴出し、この空気は基礎柱内を上昇し、この際、中詰め材間の目詰まりの原因となる微細土粒子などを押し上げて、地表に排出し、これにより基礎柱の目詰まりを防止することができる。さらに、常時は、パイプに接続した地下水吸引手段により、孔から地下水を吸引し、井戸として使用することもできる。
【０００９】
また、請求項２の液状化防止工法は、前記杭を引く抜く際に該杭を上下動し、前記杭により前記掘削孔内の前記中詰め材を叩く工法である。
【００１０】
この請求項２の構成によれば、掘削孔に投入した中詰め材を叩くことにより、中詰め材が圧密されると共に、中詰め材の周囲の土質を締め固めることができる。
【００１１】
また、請求項３の液状化防止工法は、複数の前記基礎柱の前記パイプを接続パイプにより接続し、この接続パイプに前記空気圧送手段と前記地下水吸引手段とを選択的又は切換可能に接続する工法である。
【００１２】
この請求項３の構成によれば、複数の前記基礎柱の前記パイプを接続パイプにより接続し、この接続パイプに前記空気圧送手段と前記地下水吸引手段とを選択的又は切換可能に接続することにより、複数の基礎柱のパイプを空気圧送手段と地下水吸引手段に接続することができる。
【００１３】
【発明の実施形態】
以下、本発明の実施例を添付図面を参照して説明する。図１〜図１５は本発明の第１実施例を示し、図１に示すように、地盤201は、難透水地層202の下部に透水地層203を有し、この透水地層203は砂層である。尚、前記難透水地層202は、図面では一層に図示しているが、シルトや粘土層を有し、前記砂層より透水性が低い層である。
【００１４】
液状化防止構造として、前記地盤201には基礎柱211が設けられ、この基礎柱211の上に住宅などの構造物204が設けられている。この基礎柱201は、中詰め材154に透水地層203のサンプル材の２倍以上の粒度を有する砂利や砕石を用い、前記中詰め材154を掘削孔151に充填してなり、前記透水地層203より透水性が高いものである。また、掘削孔151の内面に沿ってパイプ212を設け、このパイプ212の下部が基礎柱211まで至り、該パイプ212の下部には基礎柱211内に開口する孔213が複数設けられている。また、前記パイプ212の上部は、空気圧送手段214と地下水吸引手段215とに選択的又は切換可能に接続される。尚、図１では複数の基礎柱211，211のパイプ212，212を接続パイプ216により接続し、この接続パイプ216の端部216Ａに前記空気圧送手段214と地下水吸引手段215とが接続可能となっている。このように接続パイプ212により複数の基礎柱211のパイプ212を空気圧送手段214と地下水吸引手段215に接続することができる。
【００１５】
また、基礎柱211の上部に導管217Ａにより沈砂枡217を接続し、この沈砂枡217に導管218Ａにより外部水路218が接続され、この外部水路218は側溝や河川などである。
【００１６】
図１の中央の基礎柱211´にもパイプ212を設けることができ、構造物204の支持のみと
して使用する場合は、パイプ212を用いる必要はなく、また、所定の透水性を備える必要はない。尚、この基礎柱211´も後述する施工方法により形成される。また、図１では中詰め材153を図示しているが、後述するように、地中砂利163を中詰め材とすることができる。
【００１７】
次に、前記構成につき、その作用を説明する。透水地層203が水分を多く含んでいると、この水分を多く含んだ砂質土粒子は、地震などによる衝撃を受けると下方向に落下しようとする。この際、土粒子間の水は瞬間的に排水できず土粒子間の水圧が上昇する。この現象が地盤全体で発生し、土粒子構成が破壊され液状化することが液状化現象である。図１で右側の基礎柱211に示すように、前記土粒子間の水圧が上昇すると、土粒子間の水が基礎柱211の中詰め材153の隙間に入り込み、該基礎柱211内を伝わって外部の沈砂枡217から外部水路218へと排出される。これにより透水地層203における前記水圧の上昇が防止され、液状化を防止することができる。
【００１８】
常時は、パイプ212に接続した地下水吸引手段215により、孔213から地下水を吸引し、井戸として使用することもできる。
【００１９】
また、パイプ212に接続した空気圧送手段214により、孔213から空気を噴出し、この空気は基礎柱211内を上昇し、この際、中詰め材153間の目詰まりの原因となる微細土粒子なども押し上げて、地上に排出し、これにより基礎柱211の目詰まりを防止できる。
【００２０】
一方、図１の左側の基礎柱211は、右側と同一構成であるが、地上水を透水地層203に排水する作用を示し、大量の降雨などの条件化では、地盤201上は舗装などにより自然浸透だけでは対応できず、水位が上昇し、道路の冠水や洪水などが発生する虞がある。これに対して、外部水路218の余水が基礎柱211を通って地下の透水地層203に排水され、これにより洪水が防止される。尚、図中211は雨樋であり、212は雨樋211に接続した排水管であって、前記沈砂枡217に雨水を導くものである。
【００２１】
次に、この液状化防止工法に用いる地盤改良装置は、図２〜図７に示すように、自走式車両１は、車体２の下部に走行手段たる無限軌道３を有し、この無限軌道３は車体２に搭載した原動機（図示せず）により駆動する。前記車体２の後部には、ショベルたるブレード４が設けられ、このブレード４は昇降駆動可能に設けられている。
【００２２】
また、車体２の前部にはリーダ５が起伏可能に設けられ、このリーダ５は前後方向の起伏装置６により、図２の鎖線に示す収納位置と地表に対してほぼ垂直な使用位置とに起伏可能になっている。尚、実際には、約５度程度だけリーダ５の上部が前側に倒れることが可能である。前記起伏装置６は、前記車体２に起伏ベース７の下部を枢着部８により前後方向起伏可能に設け、その枢着部８より後方で前記車体２に枢着部９により起伏シリンダ10の下部を枢着し、この起伏シリンダ10の伸縮杆10Ａを枢着部11により前記起伏ベース７の上部に枢着してなる。そして、前記起伏シリンダ10がリーダ５の前後方向角度調整手段である。前記起伏ベース７の前側には揺動ベース12が左右方向揺動可能に設けられ、前記起伏ベース７と揺動ベース12の上部を枢着部13により回動可能に設けると共に、前記起伏ベース７と揺動ベース12の下部を左右スライド駆動機構14により左右移動可能に設けている。そして、左右スライド駆動機構14がリーダ５の左右方向角度調整手段である。また、前記揺動ベース12の前部に前記リーダ５を上下方向移動可能に設け、リーダ昇降手段たるスライドシリンダ15により、前記揺動ベース12に対して、リーダ５を昇降可能に設けている。したがって、図２の鎖線に示す収納位置にリーダ５を収納した状態で作業場所まで移動し、起伏シリンダ10を延ばしてリーダ５を地面に対し前後方向ほぼ垂直に合わせ、さらに、左右スライド駆動機構14により、枢着部13を中心としてリーダ５の下部を左右に回転して左右方向ほぼ垂直に合わせ、この後、スライドシリンダ15によりリーダ５の高さ位置を調節できる。尚、前記シリンダ10，15及び左右スライド駆動機構14は油圧などにより駆動する。
【００２３】
前記リーダ５の前部には案内レール21が設けられ、この案内レール21に沿って杭挟持体22が昇降可能に設けられ、この杭挟持体22はチェーンを備えた昇降手段23によりリーダ５に沿って昇降する。前記杭挟持体22は内部に挿通した杭を挟持及び挟持解除可能なものであって、挟持した杭を回転する回転駆動手段24を内蔵する。また、前記リーダ５の下部には杭固定手段25が固定して設けられ、該杭固定手段25は、これに挿通した杭を挟持及び挟持解除可能なものである。
【００２４】
前記車体２上にはホッパ状の収納部31が設けられ、この収納部31に中詰め材が収納され、前記収納部31の底部には送り装置たるベルトコンベア32が設けられ、このベルトコンベア32は中詰め材を後から前に送るものである。このベルトコンベア32の終端側で前記収納部31には投入路33が設けられ、この投入路33は先端側の投入口34が低くなる傾斜をなし、その投入口34は、起立位置のリーダ５の下部まで延設されている。また、前記投入路33の両側には壁部33Ａが設けられている。そして、前記ベルトコンベア32と投入路33により、中詰め材を投入すると投入装置35を構成している。
【００２５】
41は、掘削孔の上部に設けるホッパであり、筒部42の上部に拡大筒部43を設けてなる。
【００２６】
この例では、図４及び図５などに示すように、前記杭はパイプから構成された二重管51であって、この二重管51は外管52と内管53とからなり、この内管53内により圧縮水路54を形成し、前記外管52内面と内管53外面との間により圧縮空気路55を形成し、前記圧縮水路54の下端に圧縮水用ノズル56を設け、前記圧縮空気路55の下端に圧縮空気用ノズル57を設けている。さらに、前記二重管51の上端には、前記圧縮水路54に連通する水ホースアダプタ58と、前記圧縮空気路55に連通する空気ホースアダプター59とが設けられている。そして、前記水ホースアダプター58に高圧ホース60を介して圧縮水供給装置たる高圧ポンプ61を接続し、この高圧ポンプ61が水槽62に接続され、この水槽62は複数の家庭用水道を接続して水を溜めておく。また、前記空気ホースアダプター59にホース63を介して圧縮空気供給装置たるエアーコンプレッサ64を接続している。尚、二重管51は、長さ方向中央部分を交換することにより長さ調節可能である。そして、二重管51はロッドである。
【００２７】
図４及ぶ図５に示すように、前記二重管51の下端には、該二重管51を中心とする筒体71が設けられ、この筒体71は、長さ方向両端が開口し、先端側を二重管51の周囲放射方向で一直線に設けた先端側連結部72，72Ａにより二重管51に固定されると共に、基端側を二重管51の周囲放射方向で一直線に設けた基端側連結部73，73Ａにより二重管51に固定され、先端側連結部72，72Ａと基端側連結部73，73Ａとは交差方向をなし、この例では図５に示すように、ほぼ９０度の角度をなしている。尚、連結部72，72Ａ，73，73Ａは、二重管51より細い棒状の部材である。また、筒体71は掘削孔151の設計寸法より若干大径に形成され、また、その直径より長さは短く形成されている。一方の前記先端側連結部72にビット体74，74Ａが間隔をおいて設けられ、他方の前記先端側連結72Ａにビット体74Ｂ，74Ｃが間隔をおいて設けられ、それぞれ外側のビット体74，74Ｃは二重管51から等しい位置にあり、内側のビット体74Ａは内側のビット体74Ｂより二重管51に近い位置にある。したがって、ボーリングロッドである二重管51の回転すると、ビット体74Ａとビット体74Ｂとは同心円上で、異なる直径で掘削を行い、さらに、それらの外側をビット体74，74Ｃが掘削するから、効率よい掘削が行われる。また、図５などに示すように、各ビット体74，74Ａ，74Ｂ，74Ｃは、その先端がそれぞれ二重管51の回転方向に対して同一方向に向くよう斜めに取付けられている。そして、前記先端側連結部72，72Ａ及びビット体74，74Ａ，74Ｂ，74Ｃによりビット装置75を構成している。また、前記二重管の外管51には、前記筒体71内に位置して複数の空気噴射口76を設け、これら空気噴射口76は、外管51にほぼ直交方向で穿設されており、前記圧縮空気路55に連通する。
【００２８】
図８及び図９に示すように、前記圧縮水用ノズル56は、前記内管53に螺合されており、下端（先端）には噴射口81が形成されている。また、前記圧縮水用ノズル56には下方に向って縮小するテーパ状外周面82が形成され、さらに、圧縮水用ノズル56の下端には平面十字型をなすスリット83が形成されている。また、前記外管52の下端内面に雌螺子部52Ａを形成し、この雌螺子部52Ａに螺合する雄螺子部57Ａが、前記圧縮水用ノズル57の上端外面に形成されている。さらに、前記圧縮空気用ノズル57の上端（基端）には、テーパ状内周面84が形成され、前記外管52に圧縮空気用ノズル57を螺合した状態で、前記テーパ状外周面82とテーパ状内周面84との間に、前記圧縮空気路55と連通するテーパ状の案内空気路85が形成され、この案内空気路85により圧縮空気が圧縮空気用ノズル57の中央側に案内される。さらに、前記案内空気路85から前記圧縮空気用ノズル57の下端の噴射口86に至る通路87が、該圧縮空気用ノズル57の内部に形成されている。そして、前記案内空気路85と前記圧縮空気用ノズル57の噴射口86との間の長さは、前記噴射口46の直径Ｄより長く形成されている。また、前記圧縮空気用ノズル27の下端には平面一側方向のスリット88が形成されている。また、前記圧縮水用ノズル26の噴射口41の直径ｄは、前記圧縮空気用ノズル27の噴射口46の直径Ｄより小さく形成されている。また、前記案内空気路85の断面積を、前記圧縮空気路55の断面積以上としている。
【００２９】
実験例１
この実験例１は、複数土質互層に本発明を適用した場合を検討する例であり、透明水槽91内に下層から粘土92、細砂93、中砂94、粗砂95、小砂利96を順に敷き詰めて層97を形成する。
【００３０】
図１０及び図１１に示すように、内管101と外管102とからなる二重管103を形成し、内管101の先端から圧縮水、内管101と外管102の間から圧縮空気を噴射可能とする。圧縮空気と圧縮水とを噴射しながら、前記二重管103の先端を前記層97内にほぼ垂直に挿入すると、二重管103の下方にフラスコ状の掘削孔が形成され、二重管103の挿入を停止し、圧縮空気と圧縮水とを噴射を継続すると、フラスコ状掘削孔98内において、土粒子の攪拌が行われ、この攪拌により土粒子成分が分解する。すなわち砂の層であれば、砂本体とそれに含まれていた水溶性微細土粒子に分解する。比重の軽い水溶性微細土粒子は、二重管103の外周に沿う上昇水流と、圧縮空気の上昇に伴うリフトアップ効果により水と共に地上に排土される。この排土状況を地上で確認し、実際には地上に排出される水の濁り具合により確認し、水溶性微細土粒子の排土がほぼ終了したら、圧縮空気の噴射を停止し、圧縮水のみ噴射を継続する。このように圧縮空気の供給を停止すると、フラスコ状掘削孔内での攪拌力が低下し、土粒子は圧縮空気により攪拌されない比重の大きな土粒子から順次掘削孔の底部に体積し、かつ体積した土粒子は、下方に向かって噴射される圧縮水により水締めされ、隙間なく堆積し、圧縮水の噴射を続けながら徐々に二重管103を上方に引き抜くと、順次圧密された土粒子柱が形成された。
【００３１】
そして、二重管103を引く抜くと、排土された水溶性微細粒子と、土粒子が圧密された分の体積だけ、掘削孔98の上部が空洞となり、この部分に充填する中詰め材が必要となる。
【００３２】
この実験により、複数土質体積地層に高圧噴射水を噴射し、土粒子を分解でき、さらに、分解した土粒子に圧縮水と圧縮空気を供給することにより、攪拌できることが分かった。また、比重の軽い水溶性微細粒子は、空気を含む圧縮水の上昇力により良好に地表に排出される。さらに、圧縮空気の噴射を停止して圧縮水のみの噴射とすると、攪拌力が低下し、圧縮水のみの力では攪拌力の影響を受けない重たい土粒子から順次堆積していく。そして、出来上がった土粒子柱は、下から、小砂利96、粗砂95、中砂94、細砂93、粘土92となった。
【００３３】
実験例２
透明水槽91内に、粘土92、細砂93、中砂94、粗砂95、小砂利96を混合して敷き詰め、実験例１と同様に、二重管103を用いて実験を行ったところ、実験例１と同様に、出来上がった土粒子柱は、下から、小砂利96、粗砂95、中砂94、細砂93、粘土92となった。
【００３４】
このように土質、土層堆積条件を変えても、出来上がる土粒子柱は、比重の重たいものから圧密堆積することが分かった。
【００３５】
さらに、上記実験例１，２に対して圧縮水と圧縮空気の噴射圧を変えた他の実験から、以下のことが分かった。
【００３６】
まず、土質条件の異なる実験においても、掘削孔98には下から比重の重たいものが堆積する。また、圧縮水の噴射圧を上げるように調整すれば砂類も排土できる。特に、加重支持土質として不適当な水溶性微細土粒子のみを圧縮水と圧縮空気の噴射圧の調整により任意に排土することができ、現状地盤に含まれる加重支持土質として有効な土粒子を利用し、土粒子を圧密することにより、強固な土粒子柱を作ることができる。
【００３７】
実験例３
透明水槽91内に、下層から粘土92、細砂93、中砂94、粗砂95、小砂利96を順に敷き詰める。実験例１と同様にして、所定深さまで二重管103を挿入し、水溶性微細土粒子の排土を確認した後、すなわち水と共に水溶性微細土粒子が排土されなくなったら、圧縮空気の噴射を停止し、圧縮水の噴射のみを継続する。この状態では、比重の重たい土粒子から堆積し、かつ圧縮水の噴射圧により水締めされる。この後、地表の掘削孔98から、小砂利を投入して供給し、この小砂利は二重管103の外周に沿って沈下し、掘削孔98の底部に堆積し、さらに、圧縮水の噴射圧により締め固められ、また、小砂利の供給を続けると共に、二重管103を上下運動させながら序々に引き抜いていく。この場合、二重管103の下端により、堆積した小砂利を叩くようにして点圧締め固めを行い、また、供給する小砂利の堆積分だけ地中の土粒子が上昇水流によって地表に排土され、二重管103の上下運動を繰り返して該二重管103を引き抜き、地表側に形成された前記排土分の体積だけ掘削孔98に小砂利を充填し、加圧支持砂利杭を形成することができた。また、この実験例３と同様にして行った他の実験例で、圧縮空気の噴射を停止した後、あるいは圧縮空気の噴射停止と同時に圧縮水の噴射のみ下げて行った実験では、地中に含まれる水溶性微細土粒子以外に排土される土粒子の量を削減でき、地中に含まれる加重支持土質を加圧支持砂利杭の形成に利用できることが分かった。
【００３８】
次に、本発明の施工例について、図７，図１２〜図１５を参照して説明する。まず、地震時に液状化が予想される透水地層203までボーリングを行い、該透水地層203のサンプル材を採取する。このサンプル材の粒度を測定し、後述する中詰め材には前記サンプル材の２倍以上の粒度を有する砂利や砕石を用いる。現場での基礎柱の施工においては、自走式車両１により施工位置まで移動し、起伏シリンダ10を延ばしてリーダ５を前後方向ほぼ垂直に合わせ、さらに、左右スライド駆動機構14により、枢着部13を中心としてリーダ５の下部を左右に回転して左右方向ほぼ垂直に合わせ、この後、スライドシリンダ15によりリーダ５の高さ位置を調節できる。したがって、自走式車両１位置が傾斜となっていても、リーダ５を所定の向きに調整して掘削孔151を掘削できる。また、掘削位置にはホッパ41をセットしておく。そして、まず、ホッパ41を通して、ビット装置75を地表152に接地し、杭固定手段25は固定解除状態で、昇降駆動手段23により杭挟持体22を降下させて二重管51を圧入すると共に、回転駆動手段22により二重管51を回転する。このようにして、ビット装置75による掘削により二重管51を効率よく押し込むことができる。このようにしてビット装置75の回転による掘削で二重管51を所定深さまで地中に圧入したら、今度は、ノズル56，57から圧縮水Ｗと圧縮空気Ａを噴射し、図１２に示すように、これら圧縮水Ｗと圧縮空気Ａを主体とした掘削を行う。尚、掘削開始から圧縮水Ｗと圧縮空気Ａを噴射しておいてもよい。図１２に示すように、前記圧縮水Ｗと圧縮空気Ａの噴射により、二重管51の下方には底部が広いフラスコ状の掘削孔151が形成され（上記水槽91を用いた実験例により確認）、下端を深さ略７ｍまで挿入した。この位置で、二重管51のフラスコ状の掘削孔151内においては、圧縮水Ｗと圧縮空気Ａとにより土粒子攪拌作用が発生し、その攪拌作用により既設土粒子構成（土の塊）を分解し、分解された比重の軽い水溶性微細土粒子が、二重管51の外面に沿って、上昇水流と空気のリフトアップ作用により、水と共に地表面152に排土される。また、下端から圧縮空気Ａを噴射すると、同時に筒体71内に位置する複数の空気噴射口76からも圧縮空気Ａが噴射され、筒体71内においても、圧縮空気Ａによる攪拌作用が発生し、筒体71内においても土の分解作用が発生する。また、掘削において、二重管51の下端には、上下に開口した筒体71を設けたから、その筒体71が掘削孔151の内面に当り、該掘削孔151を筒体の外形形状に合わせて形成することができ、さらに、空気噴射孔76からは周囲に向って圧縮空気Ａを噴射するが、この横方向の圧縮空気Ａが筒体71の内面に当るため、掘削孔151に当ることがなく、横方向の圧縮空気Ａの力を土の分解に有効に作用させることができる。このような掘削により、地盤により異なるが、例えば、軽い方から、腐植土、シルト、高濃度茶褐色水、細砂などの順に排土される。細砂の排土を目視により確認した後、圧縮空気Ａの供給を停止し、圧縮水Ｗのみの噴射を継続した。尚、二重管51の押込み作業において、杭挟持体22を最下部まで降下したら、杭挟持体22による挟持を解除し、杭固定手段25により二重管51を挟持固定し、杭挟持体22をリーダ５の最上部まで昇降した後、杭挟持体22により二重管51を挟持し、杭固定手段25による二重管51の挟持を解除して、再び杭挟持手段22を降下することにより二重管51を押込むことができる。さらに、リーダ昇降手段たるスライドシリンダ15により、リーダ15を昇降して二重管51を圧入・引き抜きすることができる。また、ノズル56，57から圧縮水Ｗと圧縮空気Ａを噴射をすれば、これらの噴射により二重管51の下方が掘削されるため、二重管51を回転せずに圧入することができるが、回転駆動手段24により二重管51の回転を掘削孔151の設計深さまで継続するようにしてもよく、ビット装置75の回転駆動により補助的に掘削効率を高めることができ、また、ビット装置75が回転すると、連結部72，72Ａ，73，73Ａとビット体74，74Ａ，74Ｂ，74Ｃにより掘削孔151内の水と泡等を攪拌して土の分解作用が得られる。
【００３９】
次に、二重管51の引き上げ時における中詰め材の投入作業について説明すると、図１３に示すように、設計深さ（最深部）まで二重管51を押込んだら、二重管51の回転駆動を停止する。尚、その設計深さは、少なくとも掘削孔98の下部が透水地層203に達した位置である。そして、図７に示すように、車体２の収納部31に、砂利や砕石などの中詰め材153を収納しておき、投入時には、ベルトコンベア32を駆動により投入口34から掘削孔151の開口部151Ａに、中詰め材153を該中詰め材153の沈下速度に合わせて供給する。この場合、ベルトコンベア32の駆動速度を調整することにより中詰め材153の供給量を調整できる。そして、図１２及び図１３に示すように、掘削孔151内に供給された中詰め材153は、上昇水流に係わらず、二重管151の外周に沿って沈下し、掘削孔151の底部に堆積し、圧縮水Ｗにより水締めされる。尚、この場合、高圧水Ｗの影響を受けない比重の重たい既設地中の土粒子も掘削孔151の底部に堆積する。さらに、中詰め材153の投入に合わせて、すなわち掘削孔151内の中詰め材153の上面153Ａの高さに合わせるようにして二重管51を上下運動しながら引上げる。この場合、二重管51の上下運動により上面53Ａの高さを確認し、昇降手段23を駆動して二重管51及びビット装置75により、上面153Ａに、１０トン程度の加圧を掛けて点圧締め固めを行うことが好ましい。点圧締め固めを行う際には、二重管51の下端が上面153Ａに当たれば、杭挟持体22の下方への加圧力が変わるから、当たった位置を自走式車両１の装置により確認できる。例えば、杭挟持体22を昇降する昇降手段23に二重管51から加わる反力を測定する手段を設けることができる。そして、一例として、中詰め材153を投入しつつ、二重管51を所定の長さだけ、例えば６０ｃｍ程度引き上げたら、この位置で下方に向かって、所定のストロークＳ、例えば１ｍのストロークＳで複数回上下動させ、上面153Ａを叩く、あるいは上面153Ａからその下方に二重管51とビット装置75の下端を圧入するようにして締め固めを行う。この場合、中詰め材153中に、二重管51とビット装置75を圧入することにより、この圧入力が周囲の土質の締め固め力（図１４に矢印Ｙ´で示す。）として働く。尚、後述する第２実施例により、地下水位の高い箇所における二重管51の圧入においては、圧縮水Ｗと圧縮空気Ａの噴射により、ノズル26，27の下端部周囲に圧縮水Ｗの噴射により負圧が発生し、この負圧により掘削孔151の内壁部から土粒子の間隙水が吸引され、同時に吸引された土粒子に対して上方から土圧荷重が加わり、掘削孔151の周囲が圧密される。
【００４０】
そして、上述した工程を繰り返し、二重管51を序々に引上げ、圧縮水Ｗの噴射を弱めることなく、ベルトコンベア32により中詰め材153を供給し続け、地中に含まれる土粒子を上昇水流と共に地表面152に排土することにより、図１５に示すように、掘削孔151のほぼ全てが供給した砂利・中詰め材153からなる基礎柱201とすることができる。
【００４１】
あるいは、上述した工程を繰り返し、二重管51を序々に引上げ、掘削孔151の開口部151Ａから、固結可能で中詰め材153以上の粒度の砂利163が排出され始めたら、圧縮水Ｗの噴射圧又は噴射量を弱め、さらに、二重管51の引上げと上下運度を繰り返して投入した中詰め材153を叩きながら二重管51を引く抜き、二重管51を所定位置まで引き抜いたら、中詰め材153の供給を停止し、地中の固結可能な砂利 を締め固める。これにより、図１５に示すように、掘削孔151の上部を地中から出た地中砂利163により形成することができる。この場合、引き抜きの途中で、圧縮水Ｗの噴射圧または噴射量を弱めることにより、地中の固結可能な地中砂利163を地表面152に排土することなく利用できる。
【００４２】
上記の実験例３，４の結果から以下のことが分かった。この工法はほぼ全ての土質、土層の軟弱地盤に施工可能である。また、点圧加重の調整により、必要加重支持力柱の支持力を調整することができる。さらに、支持杭の深さを任意に設定でき、すなわち、支持杭の深さが支持層まで達しない深さである場合は、砕石を供給して支持杭を形成できる。さらに、中詰め材は、砕石、砂利、コンクリートを粉砕したコンクリート砕等で、透水地層より透水性の高い基礎柱を形成できるものを用いることができるから、コンクリート砕等を用いれば建設廃材の再利用が可能となる。このように使用する材料が安価であり、特別な装置を用いる必要もないから、施工コストも安価となる。しかも、水と空気を用いるから薬剤等が不要である。
【００４３】
また、二重管51を引き抜く際に該二重管51を上下動し、二重管51により掘削孔151内の中詰め材153を叩くから、中詰め材153を叩くことにより、より一層中詰め材153が圧密されると共に、中詰め材153の周囲の土質を締め固めることができる。また、このように圧縮水Ｗと圧縮空気Ａとを同時に噴射する方法において、圧縮水用ノズル56を圧縮空気用ノズル57の上方に設けているから、圧縮水Ｗより低圧な圧縮空気Ａを良好に噴射することができる。そして、圧縮水用ノズル56から噴射された圧縮水Ｗは、その噴射口81が圧縮空気用ノズル57より細いため、圧縮空気用ノズル57内の通路87の中央側を通って外部に噴射され、同時に圧縮空気路55から案内空気路45を通って通路87内に圧縮空気Ａが流れ込み、この圧縮空気Ａはテーパ状の圧縮空気路85により通路87の中央側に案内され、この中央側を流れる圧縮水Ａと一部が効率良く混合すると共に、前記圧縮水Ｗの流れにより周囲の圧縮空気Ａが引っ張られるようにして圧縮空気用ノズル57の噴射口86から噴射され、掘削孔151の底部まで効率良く供給される。
【００４４】
したがって、このような工法によって形成された基礎柱211は、所定の透水性を有すると共に、高い支持力を得ることができる。
【００４５】
このように本実施例では、請求項１に対応して、地震時に想定される地盤201の液状化に伴って発生する地盤201内の過剰間隙水を排水する液状化防止工法において、地盤 201 は、難透水地層 202 の下部に透水地層 203 を有し、難透水地層 202 は透水地層 203 より透水性が低く、杭たる二重管51の下端に圧縮水Ｗを噴射する圧縮水用ノズル56と圧縮空気Ａを噴射する圧縮空気用ノズル57とを設け、それらノズル56，57から圧縮水Ｗと圧縮空気Ａとを噴射して透水地層 203 に達する深さまで打ち込んで掘削孔151を形成し、圧縮水Ｗと圧縮空気Ａとの噴射により地中の微細粒子を二重管51に沿って上昇させると共に、地表面152に排出し、この微細粒子を排出した後、圧縮空気Ａの噴射を停止又は噴射圧を下げ、二重管51を引き抜くと共に、この引き抜き時に掘削孔151内に中詰め材153を投入して周囲より透水性を有する基礎柱211を形成し、この基礎柱 211 にパイプ 212 を設け、このパイプ 212 の下部に基礎柱 211 内の下部に開口する孔 213 を設け、パイプ 212 の上部に、空気圧送手段 214 と地下水吸引手段 215 とを選択的又は切換可能に接続する工法であるから、下方に向かって噴射した圧縮空気Ａと圧縮水Ｗとにより、二重管51の下方の掘削孔151において、土粒子（土塊）の攪拌が行われ、圧縮空気Ａが泡ａとなって上昇する際に土粒子を揺動して分解が行われ、これにより分解した微細粒子たる水溶性微細粒子が上昇水流と泡ａの上昇に伴うリフトアップ効果によりに地表に効率よく排土される。そして、掘削孔151内に投入した中詰め材153を圧縮水Ａにより圧密することにより、基礎柱211に高い支持力が得られる。また、その基礎柱211は透水性を有するため、地震時には、地盤201内の水が基礎柱211を通って地表側に排出され、該地盤201における液状化現象を防止することができる。
【００４６】
また、パイプ212に接続した空気圧送手段214により、孔212から空気を噴出し、この空気は基礎柱211内を上昇し、この際、中詰め材153間の目詰まりの原因となる微細土粒子などを押し上げて、地表に排出し、これにより基礎柱211の目詰まりを防止することができる。さらに、パイプ 212 に接続した地下水吸引手段 215 により、孔 213 から地下水を吸引し、井戸として使用することもできる。
【００４７】
また、このように本実施例では、請求項２に対応して、二重管51を引く抜く際に該二重管51を上下動し、二重管51により掘削孔151内の中詰め材153を叩く工法であるから、掘削孔151に投入した中詰め材153を叩くことにより、中詰め材153が圧密されると共に、中詰め材153の周囲の土質を締め固めることができる。
【００４８】
また、実施例上の効果として、基礎柱211を設ける周囲の層である透水地層203からサンプル材を採取し、中詰め材153にはサンプル材の２倍以上の粒度を有するものを用いる工法であるから、透水地層203のものの２倍以上の粒度を有する中詰め材153を用いることにより、基礎柱211の透水性を確保することができる。
【００４９】
また、このように本実施例では、請求項３に対応して、複数の基礎柱 211 のパイプ 212 を接続パイプ 216 により接続し、この接続パイプ 216 に空気圧送手段 214 と地下水吸引手段 215 とを選択的又は切換可能に接続する工法であるから、複数の基礎柱 211 のパイプ 212 を空気圧送手段 214 と地下水吸引手段 215 に接続することができる。
【００５０】
そして、この液状化防止構造では、液状化防止以外にも、降雨等の余水を地下に放流する設備も兼用でき、住宅基礎などでは、砂利パイプとして載荷支持力を得ることができ、道路等では、現状地盤の載荷強度を高めて沈下防止を図ることができる。また、基礎柱211と集水場所とを導水管で接続すれば、基礎柱211の施工場所位置等を任意に設定できる。また、基礎柱211によって地下の透水地層203に地上水を排水するから、大量排水を効率よく行うことができる。さらに、基礎柱211に圧縮空気を噴射することにより目詰まりを防止し、その維持管理を簡便に行うことができる。
【００５１】
また、実施例上の効果として、空気圧送手段214は複数の基礎柱211のパイプ212に空気を送るものであるから、複数の基礎柱211の目詰まり防止を同時に行い管理することができる、また、パイプ212に地下水吸引手段215を接続すれば、透水地層203の地下水を吸引して利用することができる。さらに、本発明の基礎柱211は、液状化防止以外にも、大量の降雨などの条件化では、雨水を基礎柱211を通って地下の透水地層203に排水し、これにより洪水を防止することができる。
【００５２】
さらに、実施例上の効果として、自走式車両１に、リーダ５と、このリーダ５に沿って昇降可能に設けられた杭挟持体22と、中詰め材たる中詰め材153を収納する収納部31と、この収納部31の中詰め材153を掘削孔151に投入する投入装置35とを設けたから、自走式車両１により施工位置まで移動し、二重管51を杭挟持体22により挟持し、該杭挟持体22をリーダ５に沿って下降して二重管51を圧入し、この圧入時に、下方に向かって噴射した圧縮空気Ａと圧縮水Ｗとにより、下方の掘削孔151において、土粒子（土塊）の攪拌が行われ、圧縮空気Ｗが泡ａとなって上昇する際に土粒子を揺動して分解が行われ、これにより分解した微細粒子たる水溶性微細粒子が上昇水流と泡の上昇に伴うリフトアップ効果によりに地表面52に効率よく排土される。そして、杭挟持体22をリーダ５に沿って上昇することにより、二重管51を引き抜き、この引き抜き時に、自走式車両１の収納部31に収納した中詰め材153を、ベルトコンベア32より掘削孔151内に投入し、この掘削孔151内に投入した中詰め材153を圧縮水Ｗにより水締めして圧密柱を形成することができる。そして、中詰め材153を投入後は、中詰め材153が攪拌されない程度なら圧縮空気Ａの噴射を継続できるから、圧縮空気Ａの噴射圧を下げるようにしても同様に圧密柱を形成することができ、特に、掘削孔151の全てを中詰め材153による基礎柱211にする場合に有効である。
【００５３】
また、投入装置35は、投入口34側を低くして傾斜した投入路33と、この投入路33に中詰め材たる中詰め材153を送る送り装置たるベルトコンベア32とを備えるから、投入路33に中詰め材153を送ってやれば、傾斜した投入路33により、中詰め材153が投入口34から掘削孔151内に投入され、リーダ５が邪魔にならず直接掘削孔151に、車体２から中詰め材153を投入できる。
【００５４】
また、杭たる二重管51の先端側に、該二重管51を中心として掘削孔151に対応すると共に先端と基端とが開口した筒体71を設けたから、筒体71が掘削孔151の内面に当り、掘削孔151を筒体71の外形形状に合わせて仕上げることができる。尚、掘削孔151内の中詰め材を打撃する場合、該筒体71によりその打撃効率をも向上することができる。
【００５５】
さらに、筒体71内に空気を噴射する空気噴射口76を、二重管51に設けたから、筒体71内に空気を噴射することにより、筒体71内に位置する複数の空気噴射口76から圧縮空気Ａが噴射され、筒体71内においても、圧縮空気Ａによる攪拌作用が発生する。
【００５６】
さらに、前記杭がロッドたる二重管51であり、先端側で筒体71と杭たる二重管51とを連結する先端側連結部72，72Ａに掘削用のビット体74，74Ａ，74Ｂ，74Ｃを設け、杭挟持体22に二重管51を回転する回転駆動手段24を備える杭を回転して先端側のビット体74，74Ａ，74Ｂ，74Ｃにより掘削を行うことにより、掘削効率を向上することができる。
【００５７】
また、リーダ５が起伏可能で且つ長さ方向に移動可能に自走式車両１に設けられているから、リーダ５を使用時には立て、収納時には倒すことにより、自走式車両１の移動が容易となる。また、リーダ５自体を長さ方向に移動することにより、二重管51を圧入・引き抜きできるから、その移動分だけリーダ５の長さを短くできる。
【００５８】
そして、自動式車両１は無限軌道３を備えるから、従来の固定式の装置に比べて、現場内を機械移動で自走でき、起動力を大幅にアップできる。また、自走式車両１は中詰め材を収納部31に搭載可能であるから、施工時にバックホーなどの投入装置を必要とせず、狭い場所でも効率よく、中詰め材を投入でき、且つ、リーダ５の下部まで伸びる投入路33により掘削孔151に確実に供給でき、中詰め材における材料の無駄もない。また、リーダ昇降手段たるスライドシリンダ15を備えるから、該スライドシリンダ15によりリーダ５を昇降することによっても杭を圧入・引き抜きできるから、その昇降分だけリーダ５の長さを短くでき、また、リーダ５の収納、すなわち図１の鎖線に示す位置では、スライドシリンダ15によりリーダ５を前後させることにより、収納状態のリーダ５を含めた車体２の長さを押えることができ、自走式車両１の移動が容易になる。さらに、ビット装置75には外周同一位置にビット体74，74Ｃを設け、これらと異なる位置にビット装置74Ａ，74Ｂを設けたから、均一な掘削を行うことができる。
【００５９】
他の実験例
また、他の現地実験を行い、水位の低い砂質層への打ち込みを行ったが、この場合は、圧縮水Ｗの噴射圧は、比較的低圧な７０kg／cm2前後で、大水量がよく、施工の際には、掘削孔151の開口部151Ａからでる水及び空気の状態を確認しながら、自走式車両１による二重管51の地中への圧入を行う。この場合、所定深さまで二重管51を回転して圧入し、この後、二重管51を回転せずに、圧縮水Ｗと圧縮空気Ａの噴射だけで圧入を試みたが、圧縮水の噴射圧を上記より高圧にすると、二重管51の圧入が不可能となり、これは、圧縮水の噴射が高いため、二重管51の下方の掘削孔151の深さが極端に深くなり圧縮水が砂層に吸収されるためであると思われる。さらに、他の実験で、水位の高い砂質層への打ち込みを行ったが、この場合は、圧縮水Ｗの噴射圧は、１１０kg／cm2前後で、大水量がよいことが分かった。いずれも、二重管51の回転によりビット装置75により掘削を行うことにより、圧縮水Ｗと圧縮空気Ａの噴射だけで行う場合より、圧入作業を短時間で行うことができた。
【００６０】
図１６〜図１８は本発明の第２実施例を示し、上記各実施例と同一部分に同一符号を付し、その詳細な説明を省略して詳述する。
【００６１】
図１６に示すように、前記水槽91における前記二重管103の実験において、あらかじめ水槽91に水を供給しておき、水位Ｈとする。前記図１１と同様に圧縮空気と圧縮水とを噴射しながら、実験を行った。この場合、圧縮空気の噴射量を圧縮水の噴射量より多く設定すると共に、圧縮水の噴射速度を大きく設定した。そして、前記二重管103の先端を前記層97内にほぼ垂直に挿入し、二重管103を除々に押し込んでいくと、それぞれの位置において二重管103の下方に形成されたフラスコ状掘削孔98には、噴射した圧縮空気が溜り、この空気が溜まったフラスコ状掘削孔98に圧縮水を下方に向って比較的高速で噴射することにより、二重杆103の下端部周囲に負圧が発生し、この負圧により掘削孔98内壁面の土粒子成分の間隙水が掘削孔98の内部に吸引され、同時に上方からの土圧荷重により間隙水のなくなった上方の土粒子が下方の土粒子に結合し、図１６に示すように、粘土92、細砂93、中砂94、粗砂95、小砂利96の上部にすり鉢状の窪み93Ａ，94Ａ，95Ａ，96Ａが形成された。
【００６２】
このようにフラスコ状の掘削孔98に、圧縮水Ｗと圧縮空気Ａとを連続噴射すると、フラスコ状掘削孔98内の土粒子を攪拌した空気が、上方に浮上することにより泡が溜まった空気溜まりが発生し、ここに圧縮空気が高速で噴射されることにより二重管103の下端部周辺に負圧域181が発生し、この負圧により一点鎖線の矢印Ｙに示すように、掘削孔98内壁部の土粒子の間隙水が吸引される。
【００６３】
上記の水槽実験を現場で確認するため、現場での実験を行った。実験を行った現場は、腐植土を含む軟弱地盤であり、地下水位がＧＬ（地表面）から１．２ｍ、ＧＬから２ｍまでが埋め立て表土、２〜４ｍまでがＮ値5以下の腐植土、４〜７ｍまでがＮ値２０以下のシルト混じり細砂、７〜１３ｍまでがＮ値２０の細砂、１３〜１４ｍがＮ値３５の中砂、１４ｍ以下がＮ値５０の中砂であった。
【００６４】
まず、上記図２〜図７に示した装置を用いて二重管51を地中に圧入し、この実験では、所定深さまで二重管51を回転し、ビット装置75により掘削を行った後、ビット装置75を回転させながら、圧縮空気を噴射することなく、圧縮水Ｗのみを噴射しながら掘削を行い、深さ１４ｍまで二重管51を打ち込んだ。二重管51が１４ｍまで達したら、二重管51の回転と圧縮水Ｗの噴射を中止し、二重管51の地表面152周囲を観察したところ、掘削孔151から水と共に排出された腐食土、シルト、細砂などが掘削孔151の地表面152の周囲に堆積していた。この実験では二重管51の地表面152周囲の陥没は僅かであった。
【００６５】
実験例５
自走式車両１により、二重管51を地中に圧入し、同時にノズル56，57から圧縮水Ｗと圧縮空気Ａを噴射し、図１７に示すように、掘削を行う。この実験例では、圧縮水Ｗを１００〜１５０ｋｇｆ/ｍ2の圧力で、３５０ｌ/分（毎分３５０リッター）で噴射し、圧縮空気Ａを７〜８ｋｇｆ/ｍ2の圧力で、圧縮空気用ノズル56から１５００〜２０００ｌ/分で噴射した。この圧縮水Ｗと圧縮空気Ａの噴射により、二重管51の下方には底部が広いフラスコ状の掘削孔151が形成され（上記水槽91を用いた実験例により確認）、二重管51下方のフラスコ状の掘削孔151内においては、圧縮水Ｗと圧縮空気Ａとにより土粒子攪拌作用が発生し、その攪拌作用により既設土粒子構成（土の塊）を分解し、分解された比重の軽い水溶性微細土粒子が、二重管51の外面に沿って、上昇水流と空気のリフトアップ作用により、水と共に地表面152に排土される。同時に、図１７に示すように、空気噴射口76から筒体71内に噴射した圧縮空気Ａにより、前記分解作用とリフトアップ作用が得られる。また、掘削孔51下方のフラスコ状の掘削孔151に圧縮水Ｗと圧縮空気Ａとを同時に連続噴射するため、フラスコ状の掘削孔151において、掘削孔151の底部まで達した空気は上述したように土粒子を攪拌し、上方に浮上してノズル56，57の下端部周囲に負圧域161が発生し、この負圧により負圧域161に近接する掘削孔151の内壁部151Ｎの土粒子から、矢印Ｙに示すように間隙水が吸引され、同時に上方からの土圧荷重により該内壁部151Ｎが圧密され、二重管51が打ち込まれるに連れてノズル56，57の下端部周囲に対応した内壁部151Ｎが圧密される。そして、二重管51を打ち込むに連れて掘削孔151の内壁部151Ｎが圧密され、図１７で、仮想圧密境界線Ｋの上方では、細かいハッチングに示すように、内壁面151Ｎの土粒子の圧密がなされ、仮想圧密境界線Ｋの下方の粗いハッチングは圧密前の状態を示す。また、矢印Ｙに示すようにフラスコ状の掘削孔151の上部で間隙水の吸引が行われても、仮想圧密境界線Ｋの上部の掘削孔151に内面には筒部71があるため、この部分から掘削孔151の内壁部151Ｎが崩れることを防止できる。そして、内壁部151Ｎから掘削孔151の内部に吸引された間隙水は、噴射推力の減衰した圧縮水Ｗと共に、二重管51の周囲を伝わって地表面152に排出される。そして、二重管51を所定深さである１４ｍまで打ち込んだら、圧縮空気Ａの供給を停止し、圧縮水Ｗのみの噴射を継続するが、この圧縮水Ｗの圧力を掘削孔151が崩壊しない程度に下げる。このようにして二重管51の圧入が完了すると、図１８に示すように、地表面152には二重管51の周囲直径略２ｍに渡りすり鉢状に陥没部162が形成された。
【００６６】
そして、第１実施例と同様に、図１８に示すように、掘削孔151全体を中詰め材153による基礎柱211を形成したり、上部が地中の固結可能な地中砂利163からなる基礎柱211を形成したりできる。
【００６７】
上記のことから以下のことが分かった。圧縮水供給装置たる高圧ポンプ61や圧縮空気供給装置たるエアーコンプレッサ64の能力や、これらによる圧力及び流量を調節することにより、掘削孔直径の選定と深さとを任意に設定し、地盤改良を行うことができ、一般に、圧縮空気Ａを圧力と流量を大きくすれば、掘削孔の直径を大きくすることができる。また、施工工程が単純であるから、施工スピードが速い。さらに、現状地層の締め固め土質として有効な地中砂利163を圧密して再利用できるため、搬入土などの充填材料を節約でき、排土が少なく済む。
【００６８】
そして、この例では、杭たる二重管51の打ち込み中に、圧縮水Ｗと圧縮空気Ａとの噴射により二重管51の回りの掘削孔151の内壁部151Ｎから間隙水を負圧吸引するから、圧縮空気Ａの噴射により二重管51の下方には空気が溜まっており、ここに向って圧縮水Ａを噴射すると、圧縮水Ｗの噴射位置下方に負圧が発生し、この負圧により掘削孔151の内壁面151Ｎを構成する土粒子の間隙水が吸引され、同時に上方からの土圧荷重により掘削孔151の内壁部151Ｎを圧密化することができる。また、圧縮水Ｗを１００〜１５０ｋｇｆ/ｍ2の比較的高圧で噴射し、かつ圧縮空気Ａを圧縮水Ｗの略４〜６倍の噴射量で噴射することにより、圧縮水用ノズル56の下方に空気溜まり雰囲気を形成し、この空気溜まり雰囲気に高圧な圧縮水Ｗを噴射することにより、内壁部から間隙水を吸引する負圧が効果的に得られる。
【００６９】
図１９は本発明の第３実施例と示し、上記各実施例と同一部分に同一符号を付し、その詳細な説明を省略して詳述すると、この例では、基礎柱211の使用例を示し、同図の右側から、住宅・工場・店舗など構造物204の地盤201に基礎柱211を設け、道路や飛行場の舗装231の側溝232の地盤201に基礎柱211を設け、グラウンド・駐車場・公園など敷地233の地盤201に基礎柱211を設け、堤防・埠頭などの盛土234の地盤201に基礎柱211を設け、河川235などの地盤201に基礎柱211を設けている。
【００７０】
このようにすることにより、地震時には地盤201の透水地層203の水を基礎柱211により地表又は河川235に排水して液状化現象の発生を防止し、一方、大量降雨や水位の異常上昇時には、基礎柱211を通して雨水又は河川235の水を透水地層203に排水することができる。
【００７１】
図２０は本発明の第４実施例と示し、上記各実施例と同一部分に同一符号を付し、その詳細な説明を省略して詳述すると、この例では、前記基礎柱211´により、構造物である貯水槽241を支持し、この貯水槽241の上部と基礎柱211の上部とを水路242により接続する。尚、貯水槽241は調整池として使用することができる。
【００７２】
したがって、地震時には地盤201の透水地層203の水を基礎柱211により透水地層203に排出して液状化現象の発生を防止し、一方、大量降雨や水が多量に流れ込んで貯水槽241の水位が水路242位置より上昇時には、基礎柱211を通して貯水槽241内の水を透水地層203に排水することができる。
【００７３】
尚、本発明は上記実施例に限定されるものではなく本発明の要旨の範囲内において種々の変形実施が可能である。例えば、杭を打ち込む装置は実施例のものに限らず、バイブロハンマーなどの振動式杭打込引抜装置など各種の装置を用いることができる。また、走行手段は無限軌道に限らず車輪などでもよい。また、昇降手段も杭挟持体をリーダに沿って移動するものであれば各種のものを用いることができる。さらに、送り手段は、ベルトコンベアに限らず、スクリューコンベヤやプッシャなどもよい。また、実施例では、二重管を用いたが、圧縮水と圧縮空気とをそれぞれ別の管により供給するようにしてもよい。さらに、パイプを図示していない基礎柱にもパイプを設けることができることは言うまでもない。
【００７４】
【発明の効果】
請求項１の液状化防止工法は、周囲より透水性を有する基礎柱を形成形成し、この基礎柱にパイプを設け、このパイプの下部に前記基礎柱内の下部に開口する孔を設け、前記パイプの上部に、空気圧送手段と地下水吸引手段とを選択的又は切換可能に接続する工法であり、施工性に優れ、中詰め材を効率良く締め固めて高い支持力が得られ、地震時には、地層の水を排水して液状化現象の発生を防止できる液状化防止工法を提供することができる。
【００７５】
また、請求項２の液状化防止工法は、前記杭を引く抜く際に該杭を上下動し、前記杭により前記掘削孔内の前記中詰め材を叩く工法であり、施工性に優れ、中詰め材を効率良く締め固めて高い支持力が得られ、地震時には、地層の水を排水して液状化現象の発生を防止できる液状化防止工法を提供することができる。
【００７６】
また、請求項３の液状化防止工法は、複数の前記基礎柱の前記パイプを接続パイプにより接続し、この接続パイプに前記空気圧送手段と前記地下水吸引手段とを選択的又は切換可能に接続する工法であり、施工性に優れ、中詰め材を効率良く締め固めて高い支持力が得られ、地震時には、地層の水を排水して液状化現象の発生を防止でき、加えて、基礎柱の透水性を保持することができる液状化防止工法を提供することができる。
【図面の簡単な説明】
【図１】本発明の第１実施例を示す液状化防止構造の断面図である。
【図２】本発明の第１実施例を示す一部を切り欠いた装置の側面図である。
【図３】本発明の第１実施例を示す装置の正面図である。
【図４】本発明の第１実施例を示すビット装置を設けた杭の先端の断面図である。
【図５】本発明の第１実施例を示す図３のＡ−Ａ線断面図である。
【図６】本発明の第１実施例を示す図３のＢ−Ｂ線断面図である。
【図７】本発明の第１実施例を示す装置の使用状態の断面図である。
【図８】本発明の第１実施例を示す両ノズルの断面図である。
【図９】本発明の第１実施例を示す両ノズルの分解斜視図である。
【図１０】本発明の第１実施例を説明する水槽における実験例の断面図であり、二重管の挿入前の状態を示す。
【図１１】本発明の第１実施例を説明する水槽における実験例の断面図であり、二重管の挿入後の状態を示す。
【図１２】本発明の第１実施例を示す杭を圧入中の断面図である。
【図１３】本発明の第１実施例を示し、圧縮空気の噴射を停止し、中詰め材を叩く工程を説明する断面図である。
【図１４】本発明の第１実施例を示し、杭の引き抜き工程を説明する断面図である。
【図１５】本発明の第１実施例を示す基礎柱の断面図である。
【図１６】本発明の第２実施例を示す水槽における実験例の断面図であり、二重管の挿入後の状態を示す。
【図１７】本発明の第２実施例を示す杭を圧入中の断面図である。
【図１８】本発明の第２実施例を示す基礎柱の断面図である。
【図１９】本発明の第３実施例を示す液状化防止構造の他の例を示す断面図である。
【図２０】本発明の第４実施例を示す液状化防止構造のさらに他の例を示す断面図である。
【符号の説明】
51 二重管（杭・ロッド）
56 圧縮水用ノズル
57 圧縮空気用ノズル
151 掘削孔
152 地表面
153 砕石（中詰め材）
166 表土材（中詰め材）
201 地盤
202 難透水地層
203 透水地層
211 基礎柱
212 パイプ
213 孔
214 空気圧送手段
215 地下水吸引手段
216 接続パイプ
Ｗ 圧縮水
Ａ 圧縮空気[0001]
[Technical field to which the invention belongs]
  The present invention relates to a liquefaction prevention method for draining excess pore water in the ground to prevent ground liquefaction during an earthquake.
[0002]
[Problems to be solved by the invention]
  In the ground that requires ground improvement, the water pressure of the ground column rises rapidly due to a large earthquake, and the liquefaction phenomenon that the sand is fluidized due to the loss of shear resistance is likely to occur. As a countermeasure against such liquefaction, as disclosed in Japanese Patent Laid-Open No. 7-158044, 0002, a method of reducing the porosity of the ground and improving the shear strength by compacting the sand ground, A method to promote drainage of high-pressure groundwater by forming sand piles or crushed stone columns on the ground, a method to solidify the ground by injecting water glass or other chemicals into the ground, or a deep well and water blocking wall on the ground column There is a method to reduce the groundwater level by installing pump drainage.
[0003]
  The conventional sand pile or crushed stone pillar uses a housing pipe with a screw around its entire length and is fitted into the ground by rotational drive. A crushed stone pillar is formed (publication No. 0003).
[0004]
  Conventional sand piles or crushed stone pillars can promote groundwater drainage. However, in the conventional method described above, although a constant supporting force can be obtained, a sufficient compacting action on the surrounding formation cannot be obtained, and the supporting force cannot be effectively improved as a whole. In addition, in the construction, after inserting the casing pipe over its entire length, a process of pulling out the casing pipe is necessary, and if there is a gravel layer on the soft ground, the insertion efficiency is expected to decrease. The Furthermore, when fine soil particles enter the surrounding crushed stone pillars from the surrounding strata, a problem that the drainage function deteriorates is also expected.
[0005]
  Therefore, the present invention provides a liquefaction prevention method that is excellent in workability, can efficiently pack the filling material, and has a high bearing capacity, and can prevent the occurrence of liquefaction phenomenon by draining the formation water during an earthquake. It aims at providing, and also aims at providing the liquefaction prevention construction method which can hold | maintain the water permeability of a foundation pillar.
[0006]
[Means for Solving the Problems]
  The liquefaction prevention construction method according to claim 1 is a liquefaction prevention construction method for draining excess pore water in the ground that occurs with the liquefaction of the ground assumed at the time of an earthquake.The ground has a permeable stratum below the hardly permeable stratum, and the hardly permeable stratum is less permeable than the permeable stratum,A nozzle for compressed water that injects compressed water and a nozzle for compressed air that injects compressed air are provided at the lower end of the pile, and compressed water and compressed air are injected from these nozzles.Reach the permeable formationIt is driven to a depth to form a drilling hole, and fine particles in the ground are raised along the pile by injection of the compressed water and compressed air, and discharged to the ground surface. After discharging the fine particles, the compression Stop the air injection or lower the injection pressure, pull out the pile, and insert the filling material into the excavation hole at the time of pulling out the water permeability from the surroundingsIs expensiveForm the foundation pillarA pipe is provided in the foundation pillar, a hole is formed in the lower part of the foundation pillar in the lower part of the pipe, and a pneumatic feeding means and a groundwater suction means are selectively or switchably connected to the upper part of the pipe. DoIt is a construction method.
[0007]
  According to the configuration of the first aspect, the compressed air and the compressed water jetted downward are used to agitate the soil particles (clumps) in the excavation hole below the pile, and the compressed air becomes bubbles. When rising, the soil particles are rocked and decomposed, so that the water-soluble fine particles, which are the decomposed fine particles, are efficiently discharged to the ground surface due to the lift-up effect accompanying the rising water flow and bubbles. And the high support force is obtained for a foundation pillar by compacting the filling material thrown into the excavation hole with compressed water. In this way, even if the casing is not used, the fine soil particles are not mixed with the filling material filled in the excavation hole and the water permeability is not impaired. Moreover, since the foundation pillar has high water permeability, water in the ground is discharged to the surface side through the foundation pillar at the time of an earthquake, and the liquefaction phenomenon in the ground can be prevented.
[0008]
  Also,Air is blown out from the hole by the pneumatic feeding means connected to the pipe, and this air rises in the foundation pillar. At this time, it pushes up fine soil particles etc. that cause clogging between filling materials, and on the ground surface Discharge, which can prevent clogging of the foundation pillars. Furthermore, normally, groundwater can be sucked from the hole by the groundwater suction means connected to the pipe and used as a well.
[0009]
  Further, the liquefaction prevention method of claim 2 is a method of moving the pile up and down when pulling out the pile, and hitting the filling material in the excavation hole by the pile.
[0010]
  According to the configuration of the second aspect, by hitting the filling material put into the excavation hole, the filling material is consolidated and the soil around the filling material can be compacted.
[0011]
  Moreover, the liquefaction prevention construction method of claim 3 is:The pipes of the plurality of foundation pillars are connected by connection pipes, and the pneumatic feeding means and the groundwater suction means are connected to the connection pipes selectively or switchably.It is a construction method.
[0012]
  According to the configuration of claim 3,The pipes of the plurality of foundation pillars are connected by connection pipes, and the pneumatic feeding means and the groundwater suction means are connected to the connection pipes selectively or switchably.ByA plurality of foundation pillar pipes can be connected to the pneumatic feeding means and the groundwater suction means.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 15 show a first embodiment of the present invention. As shown in FIG. 1, the ground 201 has a permeable formation 203 at a lower portion of a hardly permeable formation 202, and the permeable formation 203 is a sand layer. The hardly permeable formation layer 202 is a layer having a silt or clay layer and having a lower water permeability than the sand layer, although it is shown in a single layer in the drawing.
[0014]
  As a liquefaction prevention structure, a foundation pillar 211 is provided on the ground 201, and a structure 204 such as a house is provided on the foundation pillar 211. The foundation column 201 is formed by using gravel or crushed stone having a particle size more than twice as large as the sample material of the permeable formation 203 for the filling material 154, and filling the stuffing material 154 into the excavation hole 151. It has higher water permeability. In addition, a pipe 212 is provided along the inner surface of the excavation hole 151, a lower portion of the pipe 212 reaches the foundation pillar 211, and a plurality of holes 213 opened in the foundation pillar 211 are provided in the lower portion of the pipe 212. The upper part of the pipe 212 is connected to the pneumatic feeding means 214 and the groundwater suction means 215 so as to be selectively or switchable. In FIG. 1, pipes 212 and 212 of a plurality of foundation pillars 211 and 211 are connected by a connection pipe 216, and the pneumatic feeding means 214 and the groundwater suction means 215 can be connected to an end 216A of the connection pipe 216. ing. In this way, the pipes 212 of the plurality of foundation pillars 211 can be connected to the pneumatic feeding means 214 and the groundwater suction means 215 by the connection pipe 212.
[0015]
  Further, a sand basin 217 is connected to the upper part of the foundation pillar 211 by a conduit 217A, and an external water channel 218 is connected to the sand basin 217 by a conduit 218A. The external water channel 218 is a gutter or a river.
[0016]
  1 can also be provided with a pipe 212, supporting only the structure 204.
Therefore, it is not necessary to use the pipe 212, and it is not necessary to provide a predetermined water permeability. The foundation pillar 211 ′ is also formed by a construction method described later. Moreover, although the filling material 153 is illustrated in FIG. 1, the underground gravel 163 can be used as the filling material, as will be described later.
[0017]
  Next, the effect | action is demonstrated about the said structure. When the permeable formation 203 contains a lot of moisture, the sandy soil particles containing a lot of moisture tend to fall downward when shocked by an earthquake or the like. At this time, the water between the soil particles cannot be drained instantaneously, and the water pressure between the soil particles increases. It is a liquefaction phenomenon that this phenomenon occurs in the entire ground and the soil particle structure is destroyed and liquefied. As shown in the right foundation pillar 211 in FIG. 1, when the water pressure between the soil particles rises, the water between the soil particles enters the gap between the filling materials 153 of the foundation pillar 211 and travels through the foundation pillar 211. It is discharged from the external sand sink 217 to the external water channel 218. As a result, the increase in the water pressure in the permeable formation 203 is prevented, and liquefaction can be prevented.
[0018]
  Normally, groundwater can be sucked from the hole 213 by the groundwater suction means 215 connected to the pipe 212 and used as a well.
[0019]
  Further, air is blown out from the hole 213 by the pneumatic feeding means 214 connected to the pipe 212, and this air rises in the foundation pillar 211, and at this time, fine soil particles that cause clogging between the filling materials 153 Can also be pushed up and discharged to the ground, thereby preventing clogging of the foundation pillar 211.
[0020]
  On the other hand, the left-side foundation pillar 211 in FIG. 1 has the same configuration as the right side, but shows the effect of draining ground water to the permeable formation 203. Under conditions such as heavy rainfall, the ground 201 is naturally pavemented. Infiltration alone cannot cope with it, and the water level rises and there is a risk of flooding or flooding of the road. In contrast, the remaining water in the external water channel 218 is drained to the underground permeable formation 203 through the foundation pillar 211, thereby preventing flooding. In the figure, 211 is a rain gutter, 212 is a drain pipe connected to the gutter 211, and guides rain water to the sand sink 217.
[0021]
  Next, in the ground improvement device used for this liquefaction prevention method, as shown in FIGS. 2 to 7, the self-propelled vehicle 1 has an endless track 3 as a traveling means at the lower part of the vehicle body 2, and this endless track. 3 is driven by a prime mover (not shown) mounted on the vehicle body 2. A blade 4 as an excavator is provided at the rear portion of the vehicle body 2, and the blade 4 is provided so as to be driven up and down.
[0022]
  Further, a leader 5 is provided at the front portion of the vehicle body 2 so that it can be raised and lowered, and this leader 5 is moved to a storage position indicated by a chain line in FIG. It can be undulated. Actually, the upper portion of the reader 5 can be tilted forward by about 5 degrees. The hoisting device 6 is provided with a lower portion of the hoisting base 7 on the vehicle body 2 so as to be able to hoist in the front-rear direction by means of a pivoting portion 8. The telescopic rod 10A of the hoisting cylinder 10 is pivotally attached to the upper part of the hoisting base 7 by the pivoting portion 11. The hoisting cylinder 10 is a longitudinal angle adjusting means for the reader 5. A swing base 12 is provided on the front side of the undulation base 7 so as to be swingable in the left-right direction, and the undulation base 7 and the upper part of the swing base 12 are rotatably provided by a pivoting portion 13. The lower portion of the swing base 12 is provided so as to be movable left and right by the left and right slide drive mechanism 14. The left / right slide drive mechanism 14 is the left / right direction angle adjusting means of the reader 5. Further, the reader 5 is provided at the front portion of the swing base 12 so as to be movable in the vertical direction, and the reader 5 is provided so as to be lifted and lowered with respect to the swing base 12 by a slide cylinder 15 serving as a reader lifting / lowering means. Accordingly, the leader 5 is moved to the working position with the leader 5 being housed in the housing position indicated by the chain line in FIG. 2, the hoisting cylinder 10 is extended to align the leader 5 substantially vertically with respect to the ground, and the left and right slide drive mechanism 14 Thus, the lower part of the reader 5 is rotated left and right around the pivotal attachment part 13 so as to be substantially vertical in the left-right direction. Thereafter, the height position of the reader 5 can be adjusted by the slide cylinder 15. The cylinders 10 and 15 and the left / right slide drive mechanism 14 are driven by hydraulic pressure or the like.
[0023]
  A guide rail 21 is provided at the front portion of the leader 5, and a pile holding body 22 is provided along the guide rail 21 so as to be movable up and down. The pile holding body 22 is attached to the leader 5 by lifting means 23 having a chain. Go up and down along. The pile sandwiching body 22 can sandwich and release the pile inserted therein, and incorporates a rotation driving means 24 for rotating the sandwiched pile. Further, a pile fixing means 25 is fixedly provided at the lower part of the leader 5, and the pile fixing means 25 can clamp and release the pile inserted therethrough.
[0024]
  A hopper-like storage portion 31 is provided on the vehicle body 2, and filling material is stored in the storage portion 31, and a belt conveyor 32 serving as a feeding device is provided at the bottom of the storage portion 31. Is to send the filling material from the back to the front. On the end side of the belt conveyor 32, the storage section 31 is provided with a loading path 33. The loading path 33 is inclined so that the loading opening 34 on the front end side is lowered. It extends to the bottom of the. In addition, wall portions 33A are provided on both sides of the charging path 33. The belt conveyor 32 and the charging path 33 constitute a charging device 35 when the intermediate filling material is charged.
[0025]
  41 is a hopper provided in the upper part of the excavation hole, and is provided with an enlarged cylinder part 43 in the upper part of the cylinder part.
[0026]
  In this example, as shown in FIGS. 4 and 5, etc., the pile is a double pipe 51 composed of pipes, and the double pipe 51 is composed of an outer pipe 52 and an inner pipe 53. A compressed water channel 54 is formed in the tube 53, a compressed air channel 55 is formed between the inner surface of the outer tube 52 and the outer surface of the inner tube 53, and a compressed water nozzle 56 is provided at the lower end of the compressed water channel 54, A compressed air nozzle 57 is provided at the lower end of the air passage 55. Further, a water hose adapter 58 that communicates with the compressed water passage 54 and an air hose adapter 59 that communicates with the compressed air passage 55 are provided at the upper end of the double pipe 51. A high pressure pump 61 as a compressed water supply device is connected to the water hose adapter 58 via a high pressure hose 60. The high pressure pump 61 is connected to a water tank 62. The water tank 62 is connected to a plurality of domestic waterworks. Store the water. Further, an air compressor 64 as a compressed air supply device is connected to the air hose adapter 59 via a hose 63. The double tube 51 can be adjusted in length by exchanging the central portion in the length direction. The double tube 51 is a rod.
[0027]
  As shown in FIG. 4 and FIG. 5, a cylindrical body 71 centering on the double pipe 51 is provided at the lower end of the double pipe 51. The cylindrical body 71 is open at both ends in the length direction. The distal end side is fixed to the double tube 51 by the distal end side connecting portions 72 and 72A provided in a straight line in the radial direction around the double tube 51, and the proximal end side is provided in a straight line in the radial direction around the double tube 51. The base end side connecting portions 73 and 73A are fixed to the double pipe 51, and the front end side connecting portions 72 and 72A and the base end side connecting portions 73 and 73A are crossed. In this example, as shown in FIG. The angle is almost 90 degrees. The connecting portions 72, 72A, 73, 73A are bar-like members that are thinner than the double pipe 51. The cylindrical body 71 is formed to have a slightly larger diameter than the design dimension of the excavation hole 151, and the length is shorter than the diameter. Bit bodies 74 and 74A are provided at an interval at one of the distal end side connecting portions 72, and bit bodies 74B and 74C are provided at an interval at the other distal end side connection 72A. 74C is at an equal position from the double tube 51, and the inner bit body 74A is closer to the double tube 51 than the inner bit body 74B. Therefore, when the double pipe 51, which is a boring rod, rotates, the bit body 74A and the bit body 74B perform excavation with different diameters on the concentric circles, and further, the bit bodies 74 and 74C excavate the outside thereof. Efficient drilling is performed. Further, as shown in FIG. 5 and the like, each of the bit bodies 74, 74A, 74B, 74C is attached obliquely so that the tips thereof are directed in the same direction with respect to the rotation direction of the double tube 51, respectively. The front end side connecting portions 72 and 72A and the bit bodies 74, 74A, 74B, and 74C constitute a bit device 75. The outer pipe 51 of the double pipe is provided with a plurality of air injection ports 76 located in the cylindrical body 71, and these air injection holes 76 are formed in the outer pipe 51 in a substantially orthogonal direction. And communicates with the compressed air passage 55.
[0028]
  As shown in FIGS. 8 and 9, the compressed water nozzle 56 is screwed into the inner pipe 53, and an injection port 81 is formed at the lower end (tip). Further, the compressed water nozzle 56 is formed with a tapered outer peripheral surface 82 that is reduced downward, and a slit 83 having a flat cross shape is formed at the lower end of the compressed water nozzle 56. Further, a female screw portion 52A is formed on the inner surface of the lower end of the outer tube 52, and a male screw portion 57A that is screwed into the female screw portion 52A is formed on the outer surface of the upper end of the compressed water nozzle 57. Further, a tapered inner peripheral surface 84 is formed at the upper end (base end) of the compressed air nozzle 57, and the tapered outer peripheral surface 82 is engaged with the compressed air nozzle 57 in the outer tube 52. And a tapered guide air passage 85 communicating with the compressed air passage 55 is formed between the inner peripheral surface 84 and the tapered inner peripheral surface 84, and the guide air passage 85 guides the compressed air to the center side of the compressed air nozzle 57. Is done. Further, a passage 87 extending from the guide air passage 85 to the injection port 86 at the lower end of the compressed air nozzle 57 is formed inside the compressed air nozzle 57. The length between the guide air passage 85 and the jet port 86 of the compressed air nozzle 57 is longer than the diameter D of the jet port 46. In addition, a slit 88 in one plane direction is formed at the lower end of the compressed air nozzle 27. The diameter d of the injection port 41 of the compressed water nozzle 26 is smaller than the diameter D of the injection port 46 of the compressed air nozzle 27. Further, the sectional area of the guide air passage 85 is set to be equal to or larger than the sectional area of the compressed air passage 55.
[0029]
Experimental example 1
  This experimental example 1 is an example of examining the case where the present invention is applied to a plurality of soil layers, and in the transparent water tank 91, clay 92, fine sand 93, medium sand 94, coarse sand 95, and small gravel 96 are sequentially arranged from the lower layer. Spread layer 97 to form.
[0030]
  As shown in FIGS. 10 and 11, a double pipe 103 composed of an inner pipe 101 and an outer pipe 102 is formed, and compressed water is supplied from the tip of the inner pipe 101, and compressed air is supplied from between the inner pipe 101 and the outer pipe 102. Allow injection. When the tip of the double pipe 103 is inserted almost vertically into the layer 97 while jetting compressed air and compressed water, a flask-shaped excavation hole is formed below the double pipe 103, and the double pipe 103 Is stopped, and the injection of compressed air and compressed water is continued, the earth particles are stirred in the flask-shaped excavation hole 98, and the earth particle components are decomposed by the stirring. That is, if it is a layer of sand, it decomposes into a sand body and water-soluble fine soil particles contained therein. The water-soluble fine soil particles having a low specific gravity are discharged to the ground together with water by the rising water flow along the outer periphery of the double pipe 103 and the lift-up effect accompanying the rising of the compressed air. Check the soil discharge status on the ground, actually check the turbidity of the water discharged to the ground, and when the water-soluble fine soil particles are almost completely discharged, stop the jet of compressed air and use only compressed water. Continue jetting. When the supply of compressed air is stopped in this way, the stirring force in the flask-shaped excavation hole is reduced, and the soil particles are sequentially volumed to the bottom of the excavation hole from the soil particles having a large specific gravity that is not stirred by the compressed air. The soil particles are tightened by compressed water jetted downward, accumulated without gaps, and gradually pulled out of the double pipe 103 while continuing the jet of compressed water. Been formed.
[0031]
  Then, when the double pipe 103 is pulled out, the upper part of the excavation hole 98 becomes hollow by the volume of the water-soluble fine particles discharged and the compacted soil particles, and the filling material to be filled in this portion is Necessary.
[0032]
  From this experiment, it was found that high-pressure jet water was sprayed onto a plurality of soil volume formations to decompose soil particles, and further, stirring was possible by supplying compressed water and compressed air to the decomposed soil particles. In addition, water-soluble fine particles having a low specific gravity are well discharged to the ground due to the ascending force of compressed water containing air. Further, when the jet of compressed air is stopped and only the compressed water is jetted, the stirring force decreases, and the heavy soil particles that are not affected by the stirring force are sequentially deposited by the force of only the compressed water. The completed soil particle pillars became small gravel 96, coarse sand 95, medium sand 94, fine sand 93, and clay 92 from the bottom.
[0033]
Experimental example 2
  In the transparent water tank 91, clay 92, fine sand 93, medium sand 94, coarse sand 95, and small gravel 96 were mixed and spread, and the experiment was conducted using the double pipe 103 as in Experiment Example 1. As in Experimental Example 1, the completed soil particle columns became small gravel 96, coarse sand 95, medium sand 94, fine sand 93, and clay 92 from the bottom.
[0034]
  In this way, it was found that even if the soil conditions and soil layer deposition conditions were changed, the resulting soil particle pillars were consolidated from the ones with heavy specific gravity.
[0035]
  Furthermore, the following was found from other experiments in which the injection pressures of compressed water and compressed air were changed with respect to Experimental Examples 1 and 2 above.
[0036]
  First, even in experiments with different soil conditions, those having heavy specific gravity accumulate from the bottom in the excavation hole 98. Moreover, sand can also be discharged if it adjusts so that the injection pressure of compressed water may be raised. In particular, only water-soluble fine soil particles that are inappropriate as load-bearing soil can be discharged arbitrarily by adjusting the injection pressure of compressed water and compressed air, and soil particles that are effective as load-bearing soil contained in the current ground By using and compacting the soil particles, a solid soil particle column can be made.
[0037]
Experimental example 3
  In the transparent water tank 91, clay 92, fine sand 93, medium sand 94, coarse sand 95, and small gravel 96 are spread in order from the lower layer. In the same manner as in Experimental Example 1, after inserting the double pipe 103 to a predetermined depth and confirming the discharge of the water-soluble fine soil particles, that is, when the water-soluble fine soil particles are no longer discharged with water, Stop injection and continue only compressed water injection. In this state, it accumulates from heavy soil particles with a specific gravity and is water-tightened by the jet pressure of compressed water. After that, small gravel is supplied by supplying from the excavation hole 98 on the surface, and the small gravel sinks along the outer periphery of the double pipe 103, accumulates at the bottom of the excavation hole 98, and further injects compressed water. It is compacted by pressure, and while continuing to supply small gravel, it gradually pulls out while moving the double pipe 103 up and down. In this case, the bottom end of the double pipe 103 is used to perform point pressure compaction by hitting the accumulated small gravel, and the soil particles in the ground are discharged to the ground surface by the rising water flow by the amount of small gravel that is supplied. The double pipe 103 is repeatedly moved up and down to pull out the double pipe 103, and the excavation hole 98 is filled with small gravel by the volume of the soil formed on the ground surface side to form a pressure-supporting gravel pile. We were able to. Further, in another experimental example performed in the same manner as in Experimental Example 3, after the injection of compressed air was stopped, or in an experiment performed by reducing only the injection of compressed water at the same time as stopping the injection of compressed air, It was found that the amount of soil particles discharged in addition to the water-soluble fine soil particles contained can be reduced, and the load-bearing soil quality contained in the ground can be used for the formation of pressure-supported gravel piles.
[0038]
  Next, a construction example of the present invention will be described with reference to FIGS. 7 and 12 to 15. First, boring is performed to the permeable formation 203 expected to be liquefied during an earthquake, and a sample material of the permeable formation 203 is collected. The particle size of the sample material is measured, and gravel or crushed stone having a particle size twice or more that of the sample material is used as the filling material described later. In the construction of the foundation pillar at the site, it is moved to the construction position by the self-propelled vehicle 1, the undulating cylinder 10 is extended to align the leader 5 substantially vertically, and the left and right slide drive mechanism 14 The lower part of the reader 5 is rotated to the left and right around the center 13 so as to be substantially perpendicular to the left and right direction. Therefore, even if the position of the self-propelled vehicle 1 is inclined, the excavation hole 151 can be excavated by adjusting the leader 5 in a predetermined direction. A hopper 41 is set at the excavation position. And first, through the hopper 41, the bit device 75 is grounded to the ground surface 152, the pile fixing means 25 is in the unlocked state, and the pile holding body 22 is lowered by the elevating drive means 23 to press-fit the double pipe 51, The double pipe 51 is rotated by the rotation driving means 22. In this way, the double pipe 51 can be efficiently pushed by excavation by the bit device 75. When the double pipe 51 is press-fitted into the ground to a predetermined depth by excavation by the rotation of the bit device 75 in this way, compressed water W and compressed air A are jetted from the nozzles 56 and 57, as shown in FIG. In addition, excavation mainly using the compressed water W and the compressed air A is performed. In addition, you may inject the compressed water W and the compressed air A from the excavation start. As shown in FIG. 12, by the injection of the compressed water W and the compressed air A, a flask-shaped excavation hole 151 having a wide bottom is formed below the double pipe 51 (confirmed by an experimental example using the water tank 91). ), And the lower end was inserted to a depth of about 7 m. At this position, in the flask-shaped excavation hole 151 of the double pipe 51, the stirring action of the soil particles is generated by the compressed water W and the compressed air A, and the existing soil particle structure (soil lump) is generated by the stirring action. The decomposed and decomposed light water-soluble fine soil particles having a low specific gravity are discharged along the outer surface of the double pipe 51 to the ground surface 152 along with the water by the rising water flow and the air lift-up action. Further, when the compressed air A is injected from the lower end, the compressed air A is also injected from the plurality of air injection ports 76 located in the cylinder 71 at the same time, and the stirring action by the compressed air A is generated in the cylinder 71 as well. The soil decomposition action also occurs in the cylinder 71. In addition, in the excavation, a cylindrical body 71 opened up and down is provided at the lower end of the double pipe 51, so that the cylindrical body 71 hits the inner surface of the excavation hole 151, and the excavation hole 151 is matched to the outer shape of the cylinder. Further, the compressed air A is injected from the air injection hole 76 toward the periphery, but since the compressed air A in the lateral direction hits the inner surface of the cylinder 71, it hits the excavation hole 151. Therefore, the force of the lateral compressed air A can be effectively applied to the soil decomposition. By such excavation, for example, humus soil, silt, high-concentration brown water, fine sand, etc. are discharged in order from the lighter one, depending on the ground. After visually confirming the discharge of fine sand, the supply of the compressed air A was stopped and the injection of only the compressed water W was continued. In the pressing operation of the double pipe 51, when the pile holding body 22 is lowered to the lowest position, the holding by the pile holding body 22 is released, the double pipe 51 is held and fixed by the pile fixing means 25, and the pile holding body 22 Is lifted up and down to the top of the leader 5, the double pipe 51 is held by the pile holding body 22, the holding of the double pipe 51 by the pile fixing means 25 is released, and the pile holding means 22 is lowered again The double pipe 51 can be pushed in. Further, the double cylinder 51 can be press-fitted and pulled out by raising and lowering the leader 15 by the slide cylinder 15 as the leader raising and lowering means. Further, if the compressed water W and the compressed air A are jetted from the nozzles 56 and 57, the lower part of the double pipe 51 is excavated by these jets, so that the double pipe 51 can be press-fitted without rotating. However, the rotation of the double pipe 51 may be continued to the design depth of the excavation hole 151 by the rotation drive means 24, and the excavation efficiency can be supplementarily increased by the rotation drive of the bit device 75. When the device 75 rotates, the water and bubbles in the excavation hole 151 are agitated by the connecting portions 72, 72A, 73, 73A and the bit bodies 74, 74A, 74B, 74C, and the soil decomposition action is obtained.
[0039]
  Next, the filling operation of the filling material when pulling up the double pipe 51 will be described. As shown in FIG. 13, when the double pipe 51 is pushed down to the design depth (the deepest part), the double pipe 51 Stop rotation drive. The design depth is a position where at least the lower part of the excavation hole 98 reaches the permeable formation 203. Then, as shown in FIG. 7, a filling material 153 such as gravel or crushed stone is stored in the storage portion 31 of the vehicle body 2, and when being loaded, the belt conveyor 32 is driven to open the excavation hole 151 from the loading port 34. The filling material 153 is supplied to the section 151A in accordance with the settlement speed of the filling material 153. In this case, the supply amount of the filling material 153 can be adjusted by adjusting the driving speed of the belt conveyor 32. Then, as shown in FIGS. 12 and 13, the filling material 153 supplied into the excavation hole 151 sinks along the outer periphery of the double pipe 151 regardless of the rising water flow, and reaches the bottom of the excavation hole 151. It accumulates and is closed with compressed water W. In this case, soil particles in the existing ground having a high specific gravity that are not affected by the high-pressure water W are also accumulated at the bottom of the excavation hole 151. Further, the double pipe 51 is pulled up while moving up and down in accordance with the charging of the filling material 153, that is, according to the height of the upper surface 153A of the filling material 153 in the excavation hole 151. In this case, the height of the upper surface 53A is confirmed by the vertical movement of the double tube 51, the lifting means 23 is driven, and the upper surface 153A is pressurized by about 10 tons by the double tube 51 and the bit device 75. It is preferable to perform point pressure compaction. When performing point pressure compaction, if the lower end of the double pipe 51 hits the upper surface 153A, the pressure applied to the lower part of the pile sandwiching body 22 will change, so the hit position is confirmed by the device of the self-propelled vehicle 1 it can. For example, it is possible to provide means for measuring the reaction force applied from the double pipe 51 to the lifting means 23 that lifts and lowers the pile sandwiching body 22. As an example, if the double pipe 51 is pulled up by a predetermined length, for example, about 60 cm, while inserting the filling material 153, at this position, the predetermined stroke S, for example, a stroke S of 1 m, is applied downward. It is moved up and down a plurality of times, and the upper surface 153A is beaten, or the double pipe 51 and the lower end of the bit device 75 are press-fitted downward from the upper surface 153A. In this case, by press-fitting the double pipe 51 and the bit device 75 into the filling material 153, the pressure input acts as a compacting force (indicated by an arrow Y ′ in FIG. 14) of the surrounding soil. In the second embodiment to be described later, in the press-fitting of the double pipe 51 at a place where the groundwater level is high, the compressed water W is injected around the lower ends of the nozzles 26 and 27 by the injection of the compressed water W and the compressed air A. A negative pressure is generated by the negative pressure, and the pore water of the soil particles is sucked from the inner wall portion of the excavation hole 151 by this negative pressure, and simultaneously, an earth pressure load is applied to the sucked soil particles from above, and the periphery of the excavation hole 151 is Consolidated.
[0040]
  Then, the above-described steps are repeated, the double pipe 51 is gradually pulled up, and the filling material 153 is continuously supplied by the belt conveyor 32 without weakening the jet of the compressed water W, and the soil particles contained in the ground are At the same time, by discharging to the ground surface 152, as shown in FIG. 15, it is possible to form a foundation column 201 made of gravel / filling material 153 supplied by almost all of the excavation holes 151.
[0041]
  Alternatively, the above-described steps are repeated, and the double pipe 51 is gradually pulled up, and when gravel 163 having a particle size equal to or larger than the filling material 153 begins to be discharged from the opening 151A of the excavation hole 151, the compressed water W When the double pipe 51 is pulled out while pulling the double pipe 51 to a predetermined position by weakening the injection pressure or the injection amount, and further pulling out the double pipe 51 while hitting the filling material 153 that has been repeatedly pulled up and moved up and down. Then, the supply of the filling material 153 is stopped, and the solidified gravel in the ground is compacted. Thereby, as shown in FIG. 15, the upper part of the excavation hole 151 can be formed by the underground gravel 163 that has come out of the ground. In this case, by reducing the injection pressure or the injection amount of the compressed water W during the extraction, the underground gravel 163 that can be consolidated in the ground can be used without being discharged to the ground surface 152.
[0042]
  The following was found from the results of the above experimental examples 3 and 4. This method can be applied to almost all soils and soft ground. In addition, the support force of the required load support force column can be adjusted by adjusting the point pressure load. Furthermore, the depth of the support pile can be arbitrarily set, that is, when the depth of the support pile does not reach the support layer, crushed stone can be supplied to form the support pile. Furthermore, as the filling material, crushed stone, gravel, concrete crushed concrete, etc., which can form foundation columns with higher permeability than the permeable formation, can be used. It can be used. Since the material to be used in this way is inexpensive and it is not necessary to use a special device, the construction cost is also low. In addition, since water and air are used, no medicine or the like is required.
[0043]
  Further, when pulling out the double pipe 51, the double pipe 51 is moved up and down, and the double packing 51 hits the filling material 153 in the excavation hole 151. As the filling material 153 is consolidated, the soil around the filling material 153 can be compacted. In the method of injecting the compressed water W and the compressed air A at the same time, since the compressed water nozzle 56 is provided above the compressed air nozzle 57, the compressed air A having a lower pressure than the compressed water W is good. Can be injected. The compressed water W injected from the compressed water nozzle 56 is injected outside through the central side of the passage 87 in the compressed air nozzle 57 because the injection port 81 is thinner than the compressed air nozzle 57. At the same time, compressed air A flows into the passage 87 from the compressed air passage 55 through the guide air passage 45, and this compressed air A is guided to the central side of the passage 87 by the tapered compressed air passage 85 and flows through this central side. A part of the compressed water A is mixed efficiently, and the surrounding compressed air A is pulled by the flow of the compressed water W and is injected from the injection port 86 of the compressed air nozzle 57 to the bottom of the excavation hole 151. It is supplied efficiently.
[0044]
  Therefore, the foundation pillar 211 formed by such a construction method has a predetermined water permeability and can obtain a high supporting force.
[0045]
  As described above, in this embodiment, in response to claim 1, in the liquefaction prevention method of draining excess pore water in the ground 201 that is generated along with the liquefaction of the ground 201 assumed at the time of an earthquake,ground 201 Is a poorly permeable stratum 202 Permeable formation at the bottom of 203 Has a poorly permeable stratum 202 Is a permeable formation 203 Less permeable,A compressed water nozzle 56 for injecting compressed water W and a compressed air nozzle 57 for injecting compressed air A are provided at the lower end of the double pipe 51 serving as a stake, and the compressed water W and compressed air A are supplied from the nozzles 56, 57. SprayPermeable formation 203 ReachThe drilling hole 151 is formed by driving to the depth, and the fine particles in the ground are raised along the double pipe 51 by the injection of the compressed water W and the compressed air A, and discharged to the ground surface 152. After discharging, the injection of the compressed air A is stopped or the injection pressure is lowered, and the double pipe 51 is pulled out, and at the time of this drawing, the filling material 153 is introduced into the excavation hole 151 and the foundation column 211 having permeability from the surroundings. FormingThis basic pillar 211 To pipe 212 Provide this pipe 212 Foundation pillar at the bottom of 211 Hole opening in the lower part of the inside 213 Provide the pipe 212 Pneumatic feeding means on top of 214 And groundwater suction means 215 To be selectively or switchableSince the construction method is used, the compressed air A and the compressed water W jetted downward are used to agitate the soil particles (clumps) in the excavation hole 151 below the double pipe 51, and the compressed air A is bubbled a. As it rises, the soil particles are rocked and decomposed, so that the water-soluble fine particles, which are decomposed fine particles, are efficiently discharged to the ground surface by the lift-up effect accompanying the rising water flow and the rising of the bubbles a. Earthed. Then, by filling the filling material 153 put into the excavation hole 151 with the compressed water A, a high support force can be obtained for the foundation column 211. Further, since the foundation pillar 211 has water permeability, water in the ground 201 is discharged to the surface side through the foundation pillar 211 in the event of an earthquake, and a liquefaction phenomenon in the ground 201 can be prevented.
[0046]
  Also,Air is blown out from the hole 212 by the pneumatic feeding means 214 connected to the pipe 212, and this air rises in the foundation pillar 211, and at this time, fine soil particles and the like that cause clogging between the filling materials 153 are removed. Push up and discharge to the ground surface, which can prevent clogging of the foundation pillar 211. In addition, pipe 212 Groundwater suction means connected to 215 By hole 213 It can also be used as a well by sucking groundwater from the ground.
[0047]
  Thus, in this embodiment, corresponding to claim 2, when pulling out the double pipe 51, the double pipe 51 is moved up and down, and the filling material in the drilling hole 151 is moved by the double pipe 51. Since it is a construction method of hitting 153, by hitting the filling material 153 introduced into the excavation hole 151, the filling material 153 can be consolidated and the soil around the filling material 153 can be compacted.
[0048]
  Also,As an effect on the embodimentThe sample material is taken from the permeable layer 203 which is the surrounding layer where the foundation pillar 211 is provided, and the filling material 153 is a construction method using a material having a particle size more than twice that of the sample material. By using the filling material 153 having a particle size twice or more, the water permeability of the foundation pillar 211 can be ensured.
[0049]
  In this way, in this embodiment, corresponding to claim 3,Multiple foundation pillars 211 Pipe 212 Connect pipe 216 Connect by this connection pipe 216 Pneumatic feeding means 214 And groundwater suction means 215 To be selectively or switchableBecause it is a construction method,Multiple foundation pillars 211 Pipe 212 The pneumatic feeding means 214 And groundwater suction means 215 Can be connected to.
[0050]
  And in this liquefaction prevention structure, in addition to liquefaction prevention, it can also be used for facilities that discharge surplus water such as rainfall to the underground, and in residential foundations etc., loading support can be obtained as gravel pipes, roads etc. Then, the load strength of the current ground can be increased to prevent settlement. Further, if the foundation pillar 211 and the water collection place are connected by a water conduit, the construction place position of the foundation pillar 211 can be arbitrarily set. Further, since the ground water is drained to the underground permeable formation 203 by the foundation pillar 211, a large amount of drainage can be performed efficiently. Further, the compressed air is injected into the foundation pillar 211 to prevent clogging, and its maintenance can be easily performed.
[0051]
  Further, as an effect on the embodiment, since the pneumatic feeding means 214 is for sending air to the pipes 212 of the plurality of foundation pillars 211, it is possible to simultaneously prevent and manage clogging of the plurality of foundation pillars 211. If the groundwater suction means 215 is connected to the pipe 212, the groundwater in the permeable formation 203 can be sucked and used. Furthermore, the foundation pillar 211 of the present invention, in addition to preventing liquefaction, drains rainwater through the foundation pillar 211 to the underground permeable formation 203 in conditions such as heavy rainfall, thereby preventing flooding. Can do.
[0052]
  Further, as an effect of the embodiment, the self-propelled vehicle 1 accommodates a leader 5, a pile sandwiching body 22 provided so as to be movable up and down along the leader 5, and a filling material 153 that is a filling material. Part 31 and a loading device 35 for feeding the filling material 153 of the storage part 31 into the excavation hole 151, the self-propelled vehicle 1 moves to the construction position, and the double pipe 51 is moved by the pile sandwiching body 22. The pile holding body 22 is lowered along the leader 5 to press-fit the double pipe 51, and the compressed air A and the compressed water W jetted downward at the time of the press-fitting are used to form a lower excavation hole 151. In this case, the soil particles (soil lump) are stirred, and when the compressed air W rises as bubbles a, the soil particles are rocked and decomposed, whereby the water-soluble fine particles as the decomposed fine particles are obtained. It is efficiently discharged to the ground surface 52 by the lift-up effect accompanying the rising water flow and the rising of the bubbles. Then, by lifting the pile sandwiching body 22 along the leader 5, the double pipe 51 is pulled out, and at this time, the filling material 153 stored in the storage unit 31 of the self-propelled vehicle 1 is removed from the belt conveyor 32. It is possible to form a consolidated column by putting it into the digging hole 151 and water-tightening the filling material 153 put into the digging hole 151 with the compressed water W. Then, after the filling material 153 is introduced, the compressed air A can be continuously injected as long as the filling material 153 is not agitated. Therefore, even if the injection pressure of the compressed air A is lowered, a compacted column is formed in the same manner. In particular, this is effective when the entire excavation hole 151 is the base column 211 made of the filling material 153.
[0053]
  In addition, the charging device 35 includes a charging path 33 that is inclined with the charging port 34 side lowered, and a belt conveyor 32 that is a feeding device that feeds the filling material 153 that is an intermediate packing material to the charging path 33. If the filling material 153 is sent to 33, the filling material 153 is thrown into the drilling hole 151 from the charging port 34 by the inclined charging path 33, and the leader 5 directly enters the drilling hole 151 without being obstructed. 2 can be filled with filling material 153.
[0054]
  Further, since the cylindrical body 71 corresponding to the excavation hole 151 centered on the double pipe 51 and having an opening at the distal end and the proximal end is provided on the distal end side of the double pipe 51 serving as a pile, the cylindrical body 71 is provided with the excavation hole 151. It is possible to finish the excavation hole 151 in accordance with the outer shape of the cylindrical body 71. When hitting the filling material in the excavation hole 151, the hitting efficiency can also be improved by the cylindrical body 71.
[0055]
  Furthermore, since the air injection port 76 for injecting air into the cylinder 71 is provided in the double pipe 51, a plurality of air injection ports 76 located in the cylinder 71 are injected by injecting air into the cylinder 71. Compressed air A is injected from the inside, and the stirring action by the compressed air A also occurs in the cylinder 71.
[0056]
  Further, the pile is a double pipe 51 that is a rod, and bit bodies 74, 74A, 74B for excavation are connected to tip side connecting portions 72, 72A that connect the cylindrical body 71 and the double pipe 51 that is a pile on the tip side. Drilling efficiency is improved by providing 74C and rotating the pile provided with the rotation drive means 24 for rotating the double pipe 51 to the pile sandwiching body 22 and excavating with the bit bodies 74, 74A, 74B, 74C on the tip side. can do.
[0057]
  Further, since the leader 5 is provided in the self-propelled vehicle 1 so as to be able to undulate and move in the length direction, the self-propelled vehicle 1 can be easily moved by standing the leader 5 when it is in use and tilting it when it is stored. It becomes. Further, since the double pipe 51 can be press-fitted and pulled out by moving the reader 5 itself in the length direction, the length of the reader 5 can be shortened by the amount of the movement.
[0058]
  And since the automatic vehicle 1 is equipped with the endless track 3, compared with the conventional fixed-type apparatus, it can carry out self-propelled by the machine movement in the spot, and can improve starting force significantly. Moreover, since the self-propelled vehicle 1 can mount the filling material in the storage portion 31, it does not require a charging device such as a backhoe at the time of construction, and can efficiently insert the filling material even in a narrow place. 5 can be reliably supplied to the excavation hole 151 by the input path 33 extending to the lower part of the No. 5, and there is no waste of material in the filling material. In addition, since the slide cylinder 15 serving as the leader lifting / lowering means is provided, the pile can be press-fitted / pulled out by raising / lowering the leader 5 by the slide cylinder 15, so that the length of the leader 5 can be shortened by the raising / lowering amount. 5, that is, in the position indicated by the chain line in FIG. 1, the length of the vehicle body 2 including the leader 5 in the stored state can be suppressed by moving the leader 5 back and forth by the slide cylinder 15. Is easy to move. Further, since the bit body 74 is provided with the bit bodies 74 and 74C at the same position on the outer periphery and the bit devices 74A and 74B are provided at positions different from these, uniform excavation can be performed.
[0059]
  Other experimental examples
  In addition, other field experiments were conducted, and a sandy layer with a low water level was driven. In this case, the injection pressure of the compressed water W was a relatively low pressure of 70 kg / cm.2Before and after the large amount of water is good, and during construction, the self-propelled vehicle 1 press-fits the double pipe 51 into the ground while checking the state of water and air coming from the opening 151A of the excavation hole 151. Do. In this case, the double pipe 51 is rotated and press-fitted to a predetermined depth, and after that, the double pipe 51 is not rotated and press-fitting is attempted only by the injection of the compressed water W and the compressed air A. When the injection pressure is higher than the above, it is impossible to press-fit the double pipe 51. This is because the injection of compressed water is high, and the depth of the drilling hole 151 below the double pipe 51 becomes extremely deep and compressed. This is probably because water is absorbed by the sand layer. Further, in another experiment, a sandy layer having a high water level was driven. In this case, the injection pressure of the compressed water W was 110 kg / cm.2Before and after, it was found that a large amount of water was good. In either case, excavation was performed by the bit device 75 by the rotation of the double pipe 51, so that the press-fitting operation could be performed in a shorter time than when only the injection of the compressed water W and the compressed air A was performed.
[0060]
  16 to 18 show a second embodiment of the present invention. The same reference numerals are given to the same parts as those of the above-mentioned embodiments, and detailed description thereof will be omitted.
[0061]
  As shown in FIG. 16, in the experiment of the double pipe 103 in the water tank 91, water is supplied to the water tank 91 in advance to obtain a water level H. The experiment was conducted while injecting compressed air and compressed water as in FIG. In this case, the injection amount of the compressed air was set to be larger than the injection amount of the compressed water, and the injection speed of the compressed water was set to be large. Then, when the tip of the double tube 103 is inserted almost vertically into the layer 97 and the double tube 103 is pushed in gradually, a flask-shaped excavation formed below the double tube 103 at each position. Injected compressed air accumulates in the hole 98, and negative pressure is generated around the lower end of the double rod 103 by injecting compressed water downward at a relatively high speed into the flask-shaped excavation hole 98 where the air has accumulated. Due to this negative pressure, the pore water of the soil particle component on the inner wall surface of the excavation hole 98 is sucked into the excavation hole 98, and at the same time, the upper soil particles from which pore water disappeared due to the earth pressure load from above As shown in FIG. 16, mortar-shaped depressions 93A, 94A, 95A, and 96A were formed on top of clay 92, fine sand 93, medium sand 94, coarse sand 95, and small gravel 96.
[0062]
  When the compressed water W and the compressed air A are continuously jetted into the flask-shaped excavation hole 98 in this way, the air in which the soil particles in the flask-shaped excavation hole 98 are agitated and floats upward, and thus bubbles are accumulated. When the compressed air is jetted at a high speed, a negative pressure region 181 is generated around the lower end portion of the double pipe 103, and this negative pressure causes the excavation hole as indicated by an arrow Y in a one-dot chain line. 98 The pore water of the soil particles on the inner wall is sucked.
[0063]
  In order to confirm the above water tank experiment in the field, the field experiment was conducted. The site where the experiment was conducted was a soft ground containing humus soil, the groundwater level was 1.2m from GL (ground surface), GL to 2m from landfill topsoil, 2 to 4m from humus soil with N value of 5 or less, Fine sand with silt with N value of 20 to 4-7m, fine sand with N value of 20 to 13m, medium sand with N value of 35 to 14m, medium sand of N value of 50 with 14m or less. .
[0064]
  First, the double pipe 51 is press-fitted into the ground using the apparatus shown in FIGS. 2 to 7. In this experiment, the double pipe 51 is rotated to a predetermined depth and excavated by the bit device 75. While rotating the bit device 75, excavation was performed while injecting only the compressed water W without injecting compressed air, and the double pipe 51 was driven to a depth of 14 m. When the double pipe 51 reaches 14 m, the rotation of the double pipe 51 and the injection of the compressed water W are stopped, and the periphery of the ground surface 152 of the double pipe 51 is observed. Soil, silt, fine sand and the like were deposited around the ground surface 152 of the excavation hole 151. In this experiment, the depression around the ground surface 152 of the double pipe 51 was slight.
[0065]
Experimental Example 5
  The self-propelled vehicle 1 presses the double pipe 51 into the ground, and at the same time, the compressed water W and the compressed air A are injected from the nozzles 56 and 57, and excavation is performed as shown in FIG. In this experimental example, the compressed water W is 100 to 150 kgf / m.2At a pressure of 350 l / min (350 liters per minute) and compressed air A is 7-8 kgf / m2The air was sprayed from the compressed air nozzle 56 at 1500 to 2000 l / min. By the injection of the compressed water W and the compressed air A, a flask-shaped excavation hole 151 having a wide bottom is formed below the double pipe 51 (confirmed by an experimental example using the water tank 91). In the flask-shaped excavation hole 151, the soil water stirring action is generated by the compressed water W and the compressed air A, and the existing soil particle structure (soil lump) is decomposed by the stirring action. Light water-soluble fine soil particles are discharged along the outer surface of the double pipe 51 to the ground surface 152 together with water by the rising water flow and air lift-up action. At the same time, as shown in FIG. 17, the decomposition action and the lift-up action are obtained by the compressed air A injected from the air injection port 76 into the cylinder 71. Further, since the compressed water W and the compressed air A are simultaneously and continuously injected into the flask-shaped excavation hole 151 below the excavation hole 51, the air reaching the bottom of the excavation hole 151 in the flask-shaped excavation hole 151 is as described above. The soil particles are agitated and floated upward to generate a negative pressure region 161 around the lower ends of the nozzles 56 and 57. This negative pressure causes the soil particles in the inner wall portion 151N of the excavation hole 151 to be close to the negative pressure region 161. As shown by the arrow Y, pore water is sucked, and at the same time, the inner wall 151N is consolidated by the earth pressure load from above, and as the double pipe 51 is driven, it corresponds to the periphery of the lower ends of the nozzles 56 and 57. The inner wall 151N thus formed is consolidated. Then, as the double pipe 51 is driven, the inner wall portion 151N of the excavation hole 151 is consolidated, and in FIG. The rough hatching below the virtual consolidation boundary line K indicates a state before consolidation. In addition, even when suction of pore water is performed at the upper portion of the flask-shaped excavation hole 151 as indicated by the arrow Y, the inner surface of the excavation hole 151 at the upper portion of the virtual consolidation boundary line K has the cylindrical portion 71. It is possible to prevent the inner wall portion 151N of the excavation hole 151 from collapsing from the portion. Then, the interstitial water sucked into the excavation hole 151 from the inner wall portion 151N is discharged to the ground surface 152 along the periphery of the double pipe 51 together with the compressed water W in which the jet thrust is attenuated. When the double pipe 51 is driven to a predetermined depth of 14 m, the supply of the compressed air A is stopped and the injection of only the compressed water W is continued, but the pressure of the compressed water W does not collapse the excavation hole 151. Lower to the extent. When the press-fitting of the double pipe 51 was completed in this way, as shown in FIG. 18, a depression 162 was formed on the ground surface 152 in a mortar shape over a diameter of about 2 m around the double pipe 51.
[0066]
  Then, as in the first embodiment, as shown in FIG. 18, the entire excavation hole 151 is formed with a foundation pillar 211 made of filling material 153, or the upper part is made of underground gravel 163 that can be consolidated in the ground. The foundation pillar 211 can be formed.
[0067]
  From the above, the following was found. By adjusting the capacity of the high-pressure pump 61, which is a compressed water supply device, and the air compressor 64, which is a compressed air supply device, and by adjusting the pressure and flow rate thereof, the diameter and depth of the borehole can be set arbitrarily to improve the ground. Generally, if the pressure and flow rate of the compressed air A are increased, the diameter of the excavation hole can be increased. Moreover, since the construction process is simple, the construction speed is fast. Furthermore, since the underground gravel 163, which is effective as compaction soil for the current formation, can be compacted and reused, filling materials such as carry-in soil can be saved and soil removal can be reduced.
[0068]
  In this example, during the driving of the double pipe 51 as a pile, the pore water is sucked from the inner wall portion 151N of the excavation hole 151 around the double pipe 51 by negative pressure suction by the injection of the compressed water W and the compressed air A. Thus, air is accumulated below the double pipe 51 by the injection of the compressed air A, and when the compressed water A is injected toward this, a negative pressure is generated below the injection position of the compressed water W, and this negative pressure is generated. As a result, the pore water of the soil particles constituting the inner wall surface 151N of the excavation hole 151 is sucked, and at the same time, the inner wall portion 151N of the excavation hole 151 can be consolidated by the earth pressure load from above. Moreover, the compressed water W is 100 to 150 kgf / m.2The compressed air A is injected at an injection amount approximately 4 to 6 times that of the compressed water W, thereby forming an air pool atmosphere below the compressed water nozzle 56, and this air pool atmosphere. By jetting the high-pressure compressed water W, a negative pressure for sucking pore water from the inner wall portion is effectively obtained.
[0069]
  FIG. 19 shows a third embodiment of the present invention. The same reference numerals are given to the same parts as those of the above-described embodiments, and detailed description thereof will be omitted. In this example, the usage example of the base pillar 211 is used. From the right side of the figure, the foundation pillar 211 is provided on the ground 201 of the structure 204 such as a house, factory, store, etc., and the foundation pillar 211 is provided on the ground 201 of the side groove 232 of the pavement 231 of the road or airfield. The foundation pillar 211 is provided on the ground 201 of the site 233 such as a park, the foundation pillar 211 is provided on the ground 201 of the embankment 234 such as a dike / pier, and the foundation pillar 211 is provided on the ground 201 such as the river 235.
[0070]
  By doing in this way, the water of the permeable formation 203 of the ground 201 is drained to the ground surface or the river 235 by the foundation pillar 211 at the time of the earthquake to prevent the occurrence of liquefaction phenomenon, while at the time of heavy rainfall or abnormal rise of the water level, Rainwater or river 235 water can be drained to the permeable formation 203 through the foundation pillar 211.
[0071]
  FIG. 20 shows a fourth embodiment of the present invention. The same reference numerals are given to the same parts as the above-described embodiments, and detailed description thereof will be omitted. In this example, the base pillar 211 ′ A water tank 241 that is a structure is supported, and the upper part of the water tank 241 and the upper part of the foundation pillar 211 are connected by a water channel 242. The water tank 241 can be used as a regulating pond.
[0072]
  Therefore, in the event of an earthquake, water in the permeable formation 203 of the ground 201 is discharged to the permeable formation 203 through the foundation pillar 211 to prevent the occurrence of liquefaction, while a large amount of rainfall and water flow into the reservoir 241 When rising from the position of the water channel 242, the water in the water storage tank 241 can be drained to the permeable formation 203 through the foundation pillar 211.
[0073]
  Note that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, the device for driving the pile is not limited to that of the embodiment, and various devices such as a vibration type pile driving and drawing device such as a vibro hammer can be used. The traveling means is not limited to an endless track, and may be a wheel. Various lifting / lowering means may be used as long as they move the pile holding body along the leader. Further, the feeding means is not limited to a belt conveyor, and may be a screw conveyor or a pusher. Moreover, although the double pipe was used in the Example, you may make it supply compressed water and compressed air with a respectively separate pipe | tube. Furthermore, it goes without saying that a pipe can also be provided on a foundation pillar not shown.
[0074]
【The invention's effect】
  The liquefaction prevention method according to claim 1 forms and forms a foundation column having water permeability from the surroundings.A pipe is provided in the foundation pillar, a hole is formed in the lower part of the foundation pillar in the lower part of the pipe, and a pneumatic feeding means and a groundwater suction means are selectively or switchably connected to the upper part of the pipe. DoProviding a liquefaction prevention method that is excellent in workability, can provide high bearing capacity by efficiently compacting the filling material, and can prevent the occurrence of liquefaction by draining water from the formation during an earthquake. be able to.
[0075]
  Further, the liquefaction prevention method of claim 2 is a method of moving the pile up and down when pulling out the pile, and hitting the filling material in the excavation hole by the pile, and has excellent workability, It is possible to provide a liquefaction prevention method capable of efficiently compacting the stuffing material and obtaining a high supporting force and draining water from the formation to prevent the occurrence of a liquefaction phenomenon during an earthquake.
[0076]
  Moreover, the liquefaction prevention construction method of claim 3 is:The pipes of the plurality of foundation pillars are connected by connection pipes, and the pneumatic feeding means and the groundwater suction means are connected to the connection pipes selectively or switchably.It is a construction method, has excellent workability, and can efficiently pack the filling material to obtain a high bearing capacity.In the event of an earthquake, it can prevent the occurrence of liquefaction by draining the formation water, and in addition, A liquefaction prevention method that can retain water permeability can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a liquefaction prevention structure showing a first embodiment of the present invention.
FIG. 2 is a side view of the apparatus with a part cut away, showing a first embodiment of the present invention.
FIG. 3 is a front view of the apparatus showing the first embodiment of the present invention.
FIG. 4 is a cross-sectional view of the tip of a pile provided with a bit device according to the first embodiment of the present invention.
5 is a cross-sectional view taken along line AA of FIG. 3 showing a first embodiment of the present invention.
6 is a cross-sectional view taken along the line BB of FIG. 3 showing the first embodiment of the present invention.
FIG. 7 is a sectional view of the apparatus in use according to the first embodiment of the present invention.
FIG. 8 is a sectional view of both nozzles showing the first embodiment of the present invention.
FIG. 9 is an exploded perspective view of both nozzles according to the first embodiment of the present invention.
FIG. 10 is a cross-sectional view of an experimental example in a water tank explaining the first embodiment of the present invention, showing a state before insertion of a double pipe.
FIG. 11 is a cross-sectional view of an experimental example in a water tank for explaining the first embodiment of the present invention, showing a state after the double tube is inserted.
FIG. 12 is a cross-sectional view during press-fitting of a pile showing the first embodiment of the present invention.
FIG. 13 is a cross-sectional view illustrating a first embodiment of the present invention and illustrating a process of stopping the injection of compressed air and hitting the filling material.
FIG. 14 is a cross-sectional view illustrating a first embodiment of the present invention and illustrating a pile drawing process.
FIG. 15 is a cross-sectional view of a foundation pillar showing a first embodiment of the present invention.
FIG. 16 is a cross-sectional view of an experimental example in a water tank showing a second embodiment of the present invention, showing a state after insertion of a double pipe.
FIG. 17 is a cross-sectional view during press-fitting of a pile showing a second embodiment of the present invention.
FIG. 18 is a cross-sectional view of a foundation pillar showing a second embodiment of the present invention.
FIG. 19 is a cross-sectional view showing another example of the liquefaction prevention structure according to the third embodiment of the present invention.
FIG. 20 is a cross-sectional view showing still another example of the liquefaction prevention structure showing the fourth embodiment of the present invention.
[Explanation of symbols]
51 Double pipe (pile / rod)
56 Nozzle for compressed water
57 Compressed air nozzle
151 drilling holes
152 Ground surface
153 Crushed stone (filled material)
166 Topsoil material (filling material)
201 ground
202 Hardly permeable formation
203 Permeable formation
211 Foundation pillar
212 pipe
213 holes
214 Pneumatic feeding means
215 Groundwater suction means
216 Connection pipe
W Compressed water
A Compressed air

Claims (3)

地震時に想定される地盤の液状化に伴って発生する地盤内の過剰間隙水を排水する液状化防止工法において、前記地盤は、難透水地層の下部に透水地層を有し、前記難透水地層は前記透水地層より透水性が低く、杭の下端に圧縮水を噴射する圧縮水用ノズルと圧縮空気を噴射する圧縮空気用ノズルとを設け、それらノズルから圧縮水と圧縮空気とを噴射して前記透水地層に達する深さまで打ち込んで掘削孔を形成し、前記圧縮水と圧縮空気との噴射により地中の微細粒子を前記杭に沿って上昇させると共に、地表に排出し、この微細粒子を排出した後、前記圧縮空気の噴射を停止又は噴射圧を下げ、前記杭を引き抜くと共に、この引き抜き時に掘削孔内に中詰め材を投入して周囲より透水性が高い基礎柱を形成し、この基礎柱にパイプを設け、このパイプの下部に前記基礎柱内の下部に開口する孔を設け、前記パイプの上部に、空気圧送手段と地下水吸引手段とを選択的又は切換可能に接続することを特徴とする液状化防止工法。In the liquefaction prevention method of draining excess pore water in the ground that occurs with the liquefaction of the ground assumed at the time of an earthquake, the ground has a permeable formation below the hardly permeable formation, and the hardly permeable formation is the water permeability is lower permeability than the formation, and a nozzle for compressed air that injects compressed air nozzle for compressed water that injects compressed water to the lower end of the pile is provided, wherein by injecting compressed water and compressed air from their nozzle A drilling hole is formed by driving to a depth that reaches the permeable formation, and fine particles in the ground are raised along the piles by jetting the compressed water and compressed air, and discharged to the ground surface. Thereafter, the injection of the compressed air is stopped or the injection pressure is lowered, and the pile is pulled out, and at the time of the pulling, a filling material is introduced into the excavation hole to form a foundation column having higher permeability than the surroundings. A pipe is installed in The hole opened at the bottom of the base in the column at the bottom of the pipe is provided, at the top of the pipe, liquefaction prevention method, characterized by selectively or switchably connects the air feeding means and groundwater suction means . 前記杭を引く抜く際に該杭を上下動し、前記杭により前記掘削孔内の前記中詰め材を叩くことを特徴とする請求項１記載の液状化防止工法。  2. The liquefaction prevention method according to claim 1, wherein when the pile is pulled out, the pile is moved up and down and the filling material in the excavation hole is hit by the pile. 複数の前記基礎柱の前記パイプを接続パイプにより接続し、この接続パイプに前記空気圧送手段と前記地下水吸引手段とを選択的又は切換可能に接続することを特徴とする請求項１又は２記載の液状化防止工法。3. The pipes of a plurality of the foundation pillars are connected by connecting pipes, and the pneumatic feeding means and the groundwater suction means are connected to the connecting pipes selectively or switchably. Liquefaction prevention method.
JP2001126649A 2001-04-24 2001-04-24 Liquefaction prevention method Expired - Fee Related JP3669288B2 (en)

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CN100516375C (en) * 2006-03-07 2009-07-22 张志铁 Combined method for fastening soft soil ground by dual vacuum prepressing and dynamic extruding method
CN102116019A (en) * 2009-12-31 2011-07-06 上海港湾软地基处理工程(集团)有限公司 Method for rapidly treating soft foundation through high vacuum densification
JP6164949B2 (en) * 2013-06-26 2017-07-19 株式会社技研製作所 Filling reinforcement structure
CN105970899A (en) * 2016-06-14 2016-09-28 苏州杰姆斯特机械有限公司 Foundation reinforcement method for building construction
CN106436685B (en) * 2016-11-25 2019-02-15 天津大学 Jet thrust for vacuum preloading air pressure splitting system
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