JP4189550B2

JP4189550B2 - Construction method of ready-made pile with spiral blade, casing for propulsion

Info

Publication number: JP4189550B2
Application number: JP2003150363A
Authority: JP
Inventors: 洋一加藤
Original assignee: Mitani Sekisan Co Ltd
Current assignee: Mitani Sekisan Co Ltd
Priority date: 2002-05-30
Filing date: 2003-05-28
Publication date: 2008-12-03
Anticipated expiration: 2023-05-28
Also published as: JP2004052538A

Description

【０００１】
【発明の属する技術分野】
この発明は、建造物の下方に構築される基礎に関するものであり、特に螺旋羽根付き既製杭の施工方法、推進用ケーシングに関する。
【０００２】
【従来の技術】
既製杭の中空部に駆動軸を挿入し、該駆動軸を、既製杭の下端に固着された掘削用の先端金具に伝達して静荷重を加えながら既製杭を回転圧入する方法が提案されている（第一の従来例。特許文献１）。
【０００３】
また、他の従来例では、軟弱地盤の基礎として、鋼管の外面にスパイラルウイングを複数、不連続に取付け、先端に先端金具や掘削補助金具を取り付けた小口径鋼管杭も提案されている（第二の従来例。特許文献２）。
【０００４】
また、他の従来例では、鋼管に内角の総和が３６０°になるように形成された扇状平板を形成した翼付きねじ込み鋼管杭が提案されている（第三の従来例。特許文献３）。
【０００５】
【特許文献１】
特開平２−１３２２１５
【０００６】
【特許文献２】
特開平１−１４２１２２
【０００７】
【特許文献３】
特開平１０−１０２４８９
【０００８】
【発明が解決しようとする課題】
前記第一の従来例では、杭自身の回転により押し込みするので、掘削地盤の土質変動に対する杭の回転貫入時の押し圧、回転負荷などを調節・制御することが必要であり、先端からの注水等で掘削速度も工夫されているが、固有の制御装置が必要である上に、掘削土の排土処理及び抗基礎の各種耐力など課題も多く使用範囲が狭かった。また、得られる周面摩擦力、鉛直支持力は、既製杭の径に応じた値しか得られない問題点があった。
【０００９】
また、第二の従来例では、鋼管杭を直接に杭打ち機のオーガで回転して埋設するので、掘削時に鋼管杭の上端で与えられた回転力が、先端金具に伝えられて掘削する方法である。従って、鋼管軸部が一体で該肉厚が一定であり鋼管が回転駆動の捻りに破壊されないようにするために使用範囲が限定されている。また、構造的に鋼材自身の肉厚を調節して、曲げモーメントはある程度満足しても、鉛直方向耐力の点に関しては杭材の圧縮力が不足するため、通常、杭径はせいぜい５０〜６０ｃｍ程度しか使用されていなかった。従って、高強度地盤あるいは大径杭が必要な重量建造物等の施工では使用範囲が限られていた。
【００１０】
また、第三の従来例も、ねじ込み時の反力に対しては工夫されているとは言え、鋼管杭を直接に杭打ち機のオーガで回転して埋設するので、前記第二の従来例と同様の問題点があった。
【００１１】
従って、この発明では、先端部に螺旋羽根を有する既製杭を地盤中に回転しながらねじ込むことにより、掘削土の排出を軽減すると共に、以下の課題を目的とする。
【００１２】
(1) 既製杭の先端部に形成された螺旋羽根を使用して捻じ込む際に、杭打ち機の能力を増強することなく、既製杭を押し込む圧力を増強し、高強度地盤あるいは外径１ｍ程度の大径杭等であっても、高回転駆動力でも既製杭を破損することなく施工できるようにすること。
逆をいえば、既製杭自体の捻りの負荷を減らして、捻りに対向する為の材料選定ではなく、鉛直支持力及び水平耐力の側からの合理的な材料選定をできるようにすること。
(2) 既製杭の先端部に形成した大径の螺旋羽根による高支持力に見合った杭軸部の水平耐力、圧縮耐力を容易に提供できること。即ち、同材質の既製杭を使用して、既製杭の下端部の口径と、既製杭の上部及び中間部（軸部）の口径とを同等に形成できるようにすること。
また、少なくとも従来の鋼管杭より圧縮力を増強してコンクリート杭並とし、高先端支持力とバランスの取れた杭軸部の耐力を確保すること。
(3) 先端部に螺旋羽根が形成された既製杭において、既製杭周辺の地盤に関して、従来の螺旋羽根の捻じ込み後の地盤強度を更に強化し、杭基礎の鉛直支持力などの耐力を総合的に増強すること。
【００１３】
【課題を解決するための手段】
然るにこの発明では、螺旋羽根等の推進手段を有する推進用ケーシングを螺旋羽根を有する既製杭の外側に装着して、下端部で互いを係止して掘削するので、前記各問題点を解決した。
【００１４】
即ち、この施工法方法の発明は、以下の工程をとることを特徴とした螺旋羽根付き既製杭の施工方法である。
(1) 杭用螺旋羽根を形成した鋼管を、下端部に固着した中空の既製杭の外周に、推進用螺旋羽根を有する推進用ケーシングを装着する。前記推進用螺旋羽根は、前記推進用ケーシングの下端部に「１周の推進用螺旋羽根を１つ設け、あるいは前記１周の推進用螺旋羽根の上方に、正回転時に掘削土を連続して上方に排土しない距離の間隙を設けて、さらに他の推進用螺旋羽根を設けて」構成し、さらに、前記推進用ケーシングは、推進用螺旋羽根の上方には螺旋羽根を形成しない構成とする。
(2) 前記推進用ケーシングを正回転し、その正回転を既製杭の下端部に伝達して既製杭の杭用螺旋羽根により地盤を掘進すると共に、推進用螺旋羽根の直上で掘削土を保持して、推進用ケーシングの外側周辺に緩い掘削土層を形成する。
(3) 所定の深さに既製杭の先端が至った状態で、前記推進用ケーシングを逆回転しながら、前記推進用螺旋羽根で、既製杭の外周の緩い掘削土層を締め固めながら地上まで引き抜く。
(4) 続いて、前記既製杭の中空部内に水硬性セメント材料を充填して、該水硬性セメント材料が固化した状態で、基礎杭構造を形成する。
【００１５】
また、他の施工方法の発明は、以下の工程をとることを特徴とした螺旋羽根付き既製杭の施工方法である。
(1)大径の杭用螺旋羽根を形成した鋼管を、下端部に固着した中空の既製杭の外周に、小径推進用螺旋羽根を有する推進用ケーシングを装着する。前記推進用螺旋羽根は、前記推進用ケーシングの下端部に「１周の推進用螺旋羽根を１つ設け、あるいは前記１周の推進用螺旋羽根の上方に、正回転時に掘削土を連続して上方に排土しない距離の間隙を設けて、さらに他の推進用螺旋羽根を設けて」構成し、さらに、前記推進用ケーシングは、推進用螺旋羽根の上方には螺旋羽根を形成しない構成とする。
(2) 前記推進用螺旋羽根を前記杭用螺旋羽根の直上に位置させて、前記推進用ケーシング及び既製杭を正回転して地盤を掘進すると共に、前記掘進用螺旋羽根の直上で掘削土を保持して、推進用ケーシングの外側周辺に緩い掘削土層を形成する。
(3) 所定の深さに既製杭の先端が至った状態で、前記推進用ケーシングを逆回転しながら、既製杭の外周の緩い掘削土層を締め固めつつ、地上まで引き抜く。
(4) 続いて、前記既製杭の中空部内に水硬性セメント材料を充填して、該水硬性セメント材料が固化した状態で、基礎杭構造を形成する。
【００１６】
また、前記において、推進用ケーシングを正回転した際に、該推進用ケーシング下端の係脱手段と既製杭の螺旋羽根の上方の係脱手段とを係止して、前記推進用ケーシングと既製杭とを共に正回転させ、前記推進用ケーシングを逆回転した際に、前記既製杭との係脱手段を解除して、前記推進用ケーシングを前記既製杭から分離することを特徴とした螺旋羽根付き既製杭の施工方法である。
【００１７】
更に、推進用ケーシングの発明は、既製杭の上方から嵌装して、回動及び上下に摺動可能な内径を有する鋼管の下端に、既製杭との係脱手段を形成し、該鋼管の下端部外周に「１周の推進用螺旋羽根を形成し、あるいは前記１周の推進用螺旋羽根の上方に、正回転時に掘削土を連続して上方に排土しない距離の間隙を設けて、他の推進用螺旋羽根を設けて形成する」と共に、前記推進用ケーシングは、推進用螺旋羽根の上方には螺旋羽根を形成しない構成としたことを特徴とする推進用ケーシングである。
【００１８】
前記における水硬性セメント類とは、各種セメント材料に、必要ならば求める強度に応じた各種骨材を混ぜて、セメントミルク、セメントモルタル、コンクリート等を生成したものをいう。
【００１９】
【発明の実施の形態】
(1) 既製杭１２は、中空部２を有する既存のコンクリート製又は鋼管製等の杭基体１の下端部に、螺旋羽根７を形成した短鋼管６を嵌装固着して、構成する（図１）。螺旋羽根７は、通常は、１周分が形成されていれば、充分である。螺旋羽根７の直上部分、通常は短鋼管６の上縁に、推進用ケーシングとの係脱手段（凸ねじ）１０を設ける。
【００２０】
杭基体１として鋼管杭や、外側に鋼管を被覆したコンクリート杭を使用した場合には、直接に外側面に螺旋羽根７を形成することもできるが、短鋼管６を使用すれば、既製杭の下端部を短鋼管で補強でき、既存の杭基体に容易に大径の螺旋羽根７を構成でき、更に短鋼管６を使用して係脱手段１０の形成が容易である。
【００２１】
(2) 推進用ケーシング１８は、鋼管１４の下端部に、推進手段（地盤の締め固め手段及び補助掘削手段）としての螺旋羽根（推進手段）１６を形成して構成する（図２）。鋼管１４の下端に既製杭との係脱手段（凹ねじ）１５を形成する。また、螺旋羽根１６（外径Ｄ_１１）は、既製杭１２の螺旋羽根７（外径Ｄ_２）より小径に形成する（Ｄ_１１＜Ｄ_２）ことが望ましい（図３）。
【００２２】
鋼管１４は、既製杭１２の杭基体１の外側に装着して、既製杭１２と分離して回動及び上下移動できることが必要であり、かつ、既製杭１２の外径をできるだけ大きくとれるようにする必要がある。従って、鋼管１４の内径は、既製杭１２の杭基体１の外径と同等で、若干大きく形成する。
【００２３】
(3) 推進用ケーシング１８の下端側から既製杭１２の上端側を挿入して、既製杭１２に推進用ケーシング１８を装着する。推進用ケーシング１８を相対的に正回転することにより、両係脱手段１０、１５を係止状態とする（図３（ａ））。通常は互いに螺合するねじで係脱手段を形成するが、フックと突起の組合せなどとすることもできる。要は、推進用ケーシング１８を正回転することにより、容易に係止状態とすることができ、かつ地盤内で逆回転して、容易に係止状態を解除できる構成であればよい。
【００２４】
(4) 掘削機のオーガー２０に推進用ケーシング１８と既製杭１２を支持して、推進用ケーシング１８の上端部を正回転することにより、回転力を推進用ケーシング１８の下端部から係脱手段１０、１５を介して、既製杭１２の下端部に伝えて掘進する（図４（ａ）（ｂ））。従って、既製杭１２の杭基体１の軸部には捻りはほとんど生じない。
【００２５】
地盤中では、既製杭１２の螺旋羽根７のねじ込みにより地盤を掘削して掘進できるが、推進用ケーシング１８の螺旋羽根１６も補助的に掘削に作用する。即ち、既製杭１２の螺旋羽根７により掘削土は上方に上げられ、直上に位置する推進用ケーシング１８の螺旋羽根１６によりさらに上方に上げられるので、既製杭１２の螺旋羽根７による掘削効率を確保できる。従って、既製杭１２の螺旋羽根７により掘削除去された掘削土は、螺旋羽根７の直上に送られ、更に、推進用ケーシング１８の螺旋羽根１６に取らえられ、破砕されて上方に送られるが、螺旋羽根１６が１周しか設けられていないので、各深さで螺旋羽根１６の直上部に留まることになる。
【００２６】
(5) このようにして、所定深さまで既製杭１２を沈設したならば（図４（ｃ））、オーガ２０の回転を逆回転に切換える。逆回転により、係脱手段１０、１５の係止が解除され、既製杭１２から分離された推進用ケーシング１８を引き上げる（図３（ｂ）、図４（ｄ））。この際、逆転しながら引き上げれば、推進用ケーシング１８の引き上げにより既製杭１２の外側に推進用ケーシング１８の跡が空隙として生じ、この既製杭１２の外側の空隙である緩く残置された掘削土を、螺旋羽根１６の下面で締め固めることができる。また、螺旋羽根１６の径Ｄ_１１を既製杭１２の螺旋羽根７の径Ｄ_２より小さく形成することにより、掘削土の締め固めに併せて、引き抜き駆動用のオーガの負荷を螺旋羽根１６の面積比より以上に軽減できる。尚、この時、推進用ケーシング１８を引き上げるオーガ２０の回転数ｗ（r.p.m.）、引き上げ速度ｖ（cm／min.）、螺旋羽根１６の上下のずれｄ（cm）（図２（ａ））、とを適宜調節すれば、より効率的かつ確実な締め固めができる。
【００２７】
即ち、引き上げ速度ｖを（ｗ×ｄ）より遅くすれば、全地層が確実に締め固めされると共に、ｖ／（ｗ×ｄ）を、例えば、
ｖ／（ｗ×ｄ）＝１／２
等の一定の値に固定することにより、地盤の締め固め度を一定とすることができ、安定した周辺摩擦力が得られる。従って、全敷地に亘って、各基礎杭構造で、均一な支持力を得られる。
【００２８】
(6) 推進用ケーシング１８を地上に引き上げた後（図４（ｅ））、既製杭１２の中空部２にコンクリート２２を注入して、コンクリート２２が固化発現後、基礎杭構造２３を構築する（図４（ｆ））。また、引き上げた推進用ケーシング１８は、他の既製杭１２の埋設に使用できる。
【００２９】
また、既製杭１２に捻れ応力はほとんど生じないので、杭基体１の材質・形状・大きさ・肉厚等は、捻れに対する耐力を考慮することなく、基礎杭構造２３として求める所望の鉛直支持力、水平耐力等に応じて設定できる。
【００３０】
(7) 前記において、推進用ケーシング１８の螺旋羽根１６を既製杭１２の螺旋羽根７（外径Ｄ_２）より小径に形成した（Ｄ_１１＜Ｄ_２）とした理由は以下の内容である。推進用ケーシング１８の螺旋羽根１６は、既製杭１２をねじ込む際に、掘削を補助する効果も多少あるが、主目的は、推進用ケーシング１８を引き抜く際の土の埋め戻し等にあるからである。即ち、螺旋羽根１６付きの推進用ケーシング１８と共に螺旋羽根７付きの既製杭１２を所定深度までねじ込みした後に、推進用ケーシング１８を地上へ引き抜く際に、推進用ケーシング１８を逆回転させて、螺旋羽根１６により、推進用ケーシング１８を抜いた跡の空隙（緩く残置された掘削土）に土を戻し込み、かつ締め固めして、結果として既製杭１２の周辺地盤を補強することを主目的とする。
【００３１】
従って、推進用ケーシング１８の螺旋羽根１６は、支持力を高める為に使用する既製杭１２の螺旋羽根７と異なって、推進用ケーシング１８を上昇させて抜いた跡の空隙部分に土を戻し込み、地盤を締め固めるために使用するので、螺旋羽根１６は螺旋羽根７ほどに大径にする必要はなく、より小径で充分に機能を果たすことができる。また、螺旋羽根１６は螺旋羽根７より小径であるので、既製杭１２と共にねじ込む時及び引き抜く時に、地盤との抵抗が少なく回転の駆動負荷が少なく好都合である。つまり、締め固めの効果は、既製杭１２から離れた部分を締め固めるより、既製杭１２の外周に近い部分を締め固めることにより、既製杭１２と地盤との一体性が高まり、効率的な締め固めの効果が発揮できる。
【００３２】
また、ねじ込み時の既製杭１２への負担を更に軽減して、既製杭１２からより遠い部分の地盤をも締め固めて、引き抜き時の地盤の締め固めを更に強化する場合には、螺旋羽根１６を螺旋羽根７と同程度の外径（Ｄ_１１≒Ｄ_２）に形成することもできる（図示していない）。また、推進用ケーシング１８を推進させ、また地盤を締め固める機能を補強するために、推進用ケーシング１８に複数の螺旋羽根１６、１６を形成することもできる（図５）。
【００３３】
【実施例１】
図１〜３に基づきこの発明の実施例を説明する。
【００３４】
［１］既製杭１２の構成
【００３５】
中空部２を有する杭基体１は、外径Ｄ_０、厚さｔ_０、長さＨ_０のコンクリート製とする。図中４は杭基体１の端板である。
【００３６】
高さＨ_１、外径Ｄ_１の短鋼管６の外側面に、外径Ｄ_２の鋼製の螺旋羽根７を固着する。螺旋羽根７は、厚さｔ_２の１周分のドーナツ状の基体を一半径８で、切断したものを捻って形成する。短鋼管６は、底板９で塞がれ、埋設時に杭基体１の中空部２に土砂が入らないようになっている。また、短鋼管６の上端部外周に凸ねじ部１０を形成する。
【００３７】
螺旋羽根７を設けた短鋼管６を杭基体１の下端３側から嵌装固着して、既製杭１２を構成する。また、既製杭１２の捻り込み性（掘削効率）を良くするために、螺旋羽根７の最下端の位置を、短鋼管６の底板９の下面より下方に突出させることも容易にできる（図示していない）。
【００３８】
既製杭１２の寸法は、求める捻り強度等により寸法は適宜設定されるが、例えば、以下の値を採用する。
【００３９】
杭基体１外径Ｄ_０１０００ｍｍ
厚さｔ_０１３０ｍｍ
長さＨ_０１０ｍ
短鋼管６外径Ｄ_１１０４０ｍｍ
厚さｔ_１４０ｍｍ
高さＨ_１１０００ｍｍ
螺旋羽根７の外径Ｄ_２２０００ｍｍ
厚さｔ_２≒ｔ_１
【００４０】
［２］推進用ケーシング１８
【００４１】
既製杭１２の杭基体１の外側に嵌装できる外径Ｄ_２２の鋼管１４の下端内側面に、既製杭１８の凸ねじ部１０に螺合できる凹ねじ部１５が形成されている。鋼管１４の外側面に、鋼製で外径Ｄ_１１の螺旋羽根１６を固着して、推進用ケーシング１８を構成する。凹ねじ部１５、凸ねじ部１０は、推進用ケーシング１８を正回転することにより締まり、逆回転により緩むように形成されている。また、螺旋羽根１６は、厚さｔ_４の１周分のドーナツ状の基体を一半径１７で、切断したものを捻って形成する。切断位置（一半径１７）での螺旋羽根１６は、上下端が距離ｄだけ離れて形成される。
【００４２】
推進用ケーシングは、求める捻り強度等により寸法は適宜設定されるが、例えば、以下の値を採用する。また、引き抜きを主とする推進抵抗を調整するために、螺旋羽根の形成数も適宜変更することができる。
【００４３】
鋼管１４の内径Ｄ_００１０００ｍｍ（Ｄ_０）＋α
肉厚ｔ_３４０ｍｍ
長さＨ_１１１０ｍ
螺旋羽根１６の外径Ｄ_１１１４００ｍｍ
厚さｔ_４≒ｔ_３
【００４４】
ここで、鋼管１４の内径Ｄ_００のαは、既製杭１２の杭基体１（外径Ｄ_０）に装着した状態で、鋼管１４が回転及び上下移動（螺旋状移動）が可能となる隙間αが形成されれば良い。
【００４５】
また、螺旋羽根１６の上下端での位置のずれ寸法ｄは、
ｄ＝０．１×Ｄ_２２〜０．３×Ｄ_２２
で、形成される（図２（ａ）（ｂ））。但し、Ｄ_２２は、鋼管１４の外径である（Ｄ_２２＝Ｄ_００＋２×ｔ_３）。
【００４６】
［３］施工方法
【００４７】
(1) 先ず、既製杭１２の上から推進用ケーシング１８を嵌装して、既製杭１２を覆い、推進用ケーシング１８の下端の凹ねじ部１５を、既製杭１２の凸ねじ部１０に螺合する。推進用ケーシング１８の上端部を杭打ち機のオーガー２０に装着し吊上げ、施工する地面２１の設置地点に設置する（図４（ａ）、図３（ａ））。
【００４８】
(2) オーガー２０を正回転して、推進用ケーシング１８を正回転させると、凹凸ねじ１０、１５で連結されて既製杭１２も同時に、正回転する。既製杭１２の螺旋羽根７と推進用ケーシング１８の螺旋羽根１６により、地盤を崩しながら、地盤に既製杭１２及び推進用ケーシング１８を押し込め貫入させていく（図４（ｂ））。
【００４９】
この際、螺旋羽根７により崩された掘削土は、上方へ上げられ、螺旋羽根１６で更に破砕され、上方に移動される。螺旋羽根７により既製杭１２の先端部から除去された掘削土は、螺旋羽根１６により更に上方に上げられるので、螺旋羽根７による掘削効率は維持される。従って、螺旋羽根１６は、螺旋羽根７の掘進補助として機能し、既製杭１２及び推進用ケーシング１８の貫入が容易となる。
【００５０】
螺旋羽根１６で破壊された掘削土は、更に上方には螺旋羽根が無いので、螺旋羽根１６の直上に留まり、揚上されない。従って、推進用ケーシング１８の周囲に崩された掘削土が溜まり、地上への排土がなされないあるいは排土が極めて少量となる。
【００５１】
(3) 既製杭１２及び推進用ケーシング１８を所定深度まで掘進し、貫入したならばオーガー２０の回転を止める（図４（ｃ））。
【００５２】
(4) 次に、オーガー２０を逆回転させると、既製杭１８は螺旋羽根７と地盤との抵抗により回転せずにあるいは若干の回転に留まり、推進用ケーシング１８のみ逆回転して、凹ねじ部１５と凸ねじ部１０の螺合が解かれ、既製杭１２から推進用ケーシング１８を切り離す。引き続き、オーガー２０を逆回転（回転数ｗ（r.p.m.））させながら推進用ケーシング１８を引き上げる（図４（ｄ）、図３（ｂ））。この逆回転により、推進用ケーシング１８の螺旋羽根１６により掘進時に緩んだ土砂を下方に押圧し、推進用ケーシング１８の抜き跡である既製杭１２の外周周辺の地盤を締め固めると共に排土を抑えることができる。
【００５３】
ここで、既製杭１２を埋設する周辺の地盤の所要強度等により、掘進ケーシング用１８の引き上げ速度ｖ（cm／min.）を、
ｖ＜ｗ×ｄ
として、引き上げ効率を考慮しつつ、引き上げ速度ｖをより遅くして、全地層を締め固める。この際、例えば、
ｖ／（ｗ×ｄ）≦１／２
として、確実かつ一定に締め固めた地盤とする。
【００５４】
(5) 推進用ケーシング１８を抜き去ると、杭穴に螺旋羽根７付きの既製杭１２が埋設されており、この状態で、既製杭１２の中空杭２の上端（杭口）３ａを地上に少し出た位置に保持される（図４（ｅ））。従って、短鋼管６の底板９で、既製杭１２の中空部２内に土砂が入ることが防止される。また、上端（杭口）３ａも汚さず、中空部２内に土泥等が入らないようにようにして、後で充填する生コンクリート等の強度を低下させないようにする。
【００５５】
(6) 埋設されている既製杭１２の中空部２に、所定固化強度の生コンクリート（固化強度２４Ｎ／ｍｍ^２程度）を注入し充填する。この際、トレミー管などの吐出口を中空部２の底（短鋼管６の底板９）付近まで入れて注入すれば容易に充填できる。この生コンクリート２２が固化すれば本発明の基礎杭構造２３が完成する（図４（ｆ））。
【００５６】
［４］他の実施例
【００５７】
(1) 前記実施例において、推進用ケーシング１８は、螺旋羽根１６を１つ形成したが、直上に、同一形状の螺旋羽根１６ａを嵌装固着することもできる（図５（ａ））。この場合、上下の螺旋羽根１６、１６ａは、正回転時に掘削土を連続して、上方に排土しないように、間隙２５（高さＨ_１２）を設けてある。また、間隙２５により、逆回転時に、掘削土を締め固める効率も高められる。
【００５８】
また、螺旋羽根１６と同一形状の螺旋羽根１６ｂ、１６ｂを、鋼管１４の中間部に、所定間隙２６（高さＨ_１３）を設けて、嵌装固着することもできる（図５（ｂ））。
【００５９】
(2) また、前記実施例において、推進用ケーシング１８と既製杭１２とは、凸ねじ１０、凹ねじ１５とで、係脱したが、推進用ケーシング１８の正回転で係止して、逆回転で係止が解除できる手段であれば、他の係止手段を使用することもできる（図示していない）。
【００６０】
(3) また、前記実施例において、既製杭は、コンクリート杭としたが、外側を鋼管で被覆したコンクリート杭や鋼管杭を適用することもできる（図示していない）。この場合には、推進用ケーシング１８との係脱手段を別途設ければ、短鋼管６を省略して、外側面に直接、螺旋羽根７を嵌装固着することもできる。
【００６１】
(4) また、前記実施例において、推進用ケーシング１８の推進手段として、螺旋羽根１６を使用したが、推進用ケーシング１８の押し込み時、引き上げ時等に同様の作用を発揮できれば、他の構造を採用することもできる（図示していない）。
【００６２】
【発明の効果】
(1) この発明は、先端に螺旋羽根を有する中空の既製杭の外周に、推進手段を有する推進用ケーシングを装着して、推進用ケーシングの正回転を既製杭の下端部に伝達して、既製杭の螺旋羽根で地盤を掘進するので、既製杭の軸部にねじり応力をほとんど発生させないので、掘進効率が良いと共に、既製杭の設計にあたり、捻り応力を考慮することなく、水平耐力、鉛直支持力等埋設状態で既製杭に求められる性能のみで、肉厚の小さい既製杭の選定ができるので、より経済的な基礎杭構造の設計ができる効果がある。また、既製杭に捻り応力をほとんど発生させないので、埋設状態で、捻りによる残留応力の悪影響を除去できる。
【００６３】
また、推進用ケーシングの推進手段と併用して掘進するので、螺旋羽根の厚さ等にもよるが、既製杭として従来の外径の２倍程度（外径１０００ｍｍ程度）の既製杭を使用でき、既製杭の下端部の螺旋羽根を、杭基体の外径の１．５〜２倍程度の外径を有する螺旋羽根を使用することがきる。よって、構築される基礎杭構造は、従来の汎用される大径の鋼管杭（外径５００〜６００ｍｍ）に比して、２倍以上の支持力が確保できる。
【００６４】
また、推進用ケーシングは、ねじり強度の大きい肉厚の鋼管を繰り返し使用するので、鋼管材料の有効利用を図ることができる効果がある。
【００６５】
(2) また、下端部に螺旋羽根を形成した推進用ケーシングを使用すれば、既製杭の螺旋羽根の直上に、推進用ケーシングの螺旋羽根（推進手段）を位置させることができ、推進手段として掘削効率を高めることがき、既製杭の埋設時間を短縮できると共に、推進用ケーシングを逆回転させて引き上げれば、引き上げた推進用ケーシングの引き抜き跡に生じる緩んだ掘削土（埋設した既製杭の外側の緩んだ掘削土）を締め固めることができ、形成される基礎杭構造の周面摩擦力を高めることができる効果がある。
【００６６】
また、推進用ケーシングの引き上げ速度と回転速度を適宜に組み合わせることにより、地盤強度を制御でき、安定かつ確実に所望の支持力とすることが可能である。
【００６７】
更に、掘進時には、掘削土を推進用ケーシングの外側に存置し、引き上げ時には、存置した掘削土を締め固めるので、産業廃棄物として処理する掘削土を大幅に削減して、環境に優しい工法を実現できる。
【００６８】
(3) また、推進用ケーシングの下端の係脱手段と短鋼管の上縁の係脱手段とを使って、推進用ケーシングから既製杭への正回転を伝達し、逆回転により係止を解除させてば、回転力の伝達が確実となり、地盤中での係止の解除も容易となる効果がある。
【００６９】
(4) また、鋼板製の螺旋羽根を形成した短鋼管を、外殻鋼管コンクリート製の既製杭等の杭基体に嵌装固定（例えば、溶接による固定）すれば、コンクリート製の既製杭に容易に鋼板製の螺旋羽根を形成でき、螺旋羽根による垂直支持力を発揮する性能に、軸部に有効な圧縮力を付加できる効果がある。また、杭基体として既存の杭を使用できるので、求める基礎杭構造の性能に応じて杭基体としての既存の杭を適宜選定して容易に耐力を増強できる効果がある。
【００７０】
(5) また、推進用ケーシングに小径螺旋羽根を、既製杭に大径螺旋羽根を夫々形成した場合には、押し込み時に既製杭に生じるねじれを軽減して、引き上げ時に、埋設した既製杭の少なくとも外周近辺の緩んだ掘削土を締め固めることができ、更に、推進用ケーシングの押し込み時及び引き上げ時に、駆動用のオーガの負荷をできるだけ少なくできる。従って、所望の支持力を発揮できる基礎杭構造を効率が良く構築できる効果がある。
【００７１】
(6) また、総じて、杭基体としての既存の既製杭を使用して、この発明の既製杭を構成できるので、軸部を下端部より小径にすることなく、杭の軸部を下端部と同等の性能を有する構成にでき、軸部を小径にする必要が無いので、他の増強手段を使用することなくなく杭の軸部の圧縮強度、水平耐力を確保して増強できる効果がある。従って、基礎杭構造の下端で大径の螺旋羽根により発揮されるせん断力の伝搬等により発揮される鉛直支持力及び引抜力、中空部に充填されるセメント類と相まって基礎杭構造の全体により発揮される圧縮耐力、水平耐力、既製杭の外側での周面摩擦力等、全体としてバランスの良い基礎杭構造とすることができる効果がある。
【図面の簡単な説明】
【図１】この発明の実施に使用する既製杭で、（ａ）は正面図、（ｂ）は平面図、（ｃ）は（ｂ）のＡ−Ａ線における断面図である。
【図２】この発明の実施に使用する推進用ケーシングで、（ａ）は正面図、（ｂ）は平面図である。
【図３】この発明の実施に使用する既製杭に推進用ケーシングを装着した状態の一部正面図で、（ａ）は掘進中、（ｂ）は既製杭の設置完了後を夫々表す。
【図４】（ａ）〜（ｆ）は、この発明の施工方法を説明する概略した正面図である。
【図５】（ａ）（ｂ）は、この発明の他の推進用ケーシングの正面図である。
【符号の説明】
１杭基体
２中空部
３杭基体の下端
３ａ杭基体の上端（杭口）
４杭基体の下端板
６短鋼管
７螺旋羽根
９底板
１０凹ねじ部
１２既製杭
１４鋼管
１５凹ねじ部
１６螺旋羽根（推進手段）
１８推進用ケーシング
２０オーガー
２１地面
２２コンクリート
２３基礎杭構造[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a foundation constructed under a building.ScrewedConstruction method of ready-made piles with swirl blades, GuessThe present invention relates to a progressive casing.
[0002]
[Prior art]
  A method has been proposed in which a drive shaft is inserted into the hollow portion of a ready-made pile, and the drive shaft is transmitted to a tip metal fitting for excavation fixed to the lower end of the ready-made pile to rotationally press-fit the ready-made pile while applying a static load. (First conventional example. Patent Document 1).
[0003]
  In another conventional example, as a foundation for soft ground, a small-diameter steel pipe pile in which a plurality of spiral wings are attached discontinuously on the outer surface of the steel pipe and a tip metal fitting or a drilling auxiliary metal fitting is attached to the tip is proposed (No. 1). Second conventional example, Patent Document 2).
[0004]
  In another conventional example, a winged screwed steel pipe pile in which a fan-like flat plate formed so that the total sum of inner angles is 360 ° is formed on a steel pipe is proposed (third conventional example, Patent Document 3).
[0005]
[Patent Document 1]
JP-A-2-132215
[0006]
[Patent Document 2]
JP-A-1-142122
[0007]
[Patent Document 3]
JP-A-10-102489
[0008]
[Problems to be solved by the invention]
  In the first conventional example, since the pile is pushed in by the rotation of the pile itself, it is necessary to adjust and control the pressing pressure, the rotation load, etc. at the time of the pile intrusion against the soil fluctuation of the excavated ground, and water injection from the tip Although the excavation speed has been devised, etc., a unique control device is required, and there are many problems such as excavating soil excavation and various anti-foundation strengths, so the range of use has been narrow. Further, the obtained peripheral friction force and vertical support force have a problem that only a value corresponding to the diameter of the ready-made pile can be obtained.
[0009]
  Further, in the second conventional example, the steel pipe pile is directly rotated by the auger of the pile driving machine and buried, so that the rotational force applied at the upper end of the steel pipe pile at the time of excavation is transmitted to the tip fitting and excavated. It is. Therefore, the range of use is limited in order to prevent the steel pipe shaft part from being integrated and the wall thickness being constant, and the steel pipe from being broken by the twist of the rotational drive. Moreover, even if the thickness of the steel material itself is structurally adjusted and the bending moment is satisfied to some extent, the compression force of the pile material is insufficient in terms of the vertical strength, and the pile diameter is usually 50 to 60 cm at most. Only used to the extent. Therefore, the range of use has been limited in the construction of heavy buildings that require high-strength ground or large-diameter piles.
[0010]
  In addition, the third conventional example is also devised with respect to the reaction force at the time of screwing, but the steel pipe pile is directly rotated and buried by the auger of the pile driving machine. There were similar problems.
[0011]
  Therefore, in this invention, while discharging the ready-made pile which has a spiral blade | wing in a front-end | tip part while rotating in the ground, while reducing discharge | emission of excavated soil, it aims at the following subjects.
[0012]
  (1) When using a spiral blade formed on the tip of a ready-made pile, the pressure to push the ready-made pile is increased without increasing the capacity of the pile driving machine, and high-strength ground or an outer diameter of 1 m Even if it is a large-diameter pile, etc., it should be possible to construct it without damaging the ready-made pile even with high rotational driving force.
  To put it the other way, reduce the torsional load of the ready-made piles themselves, and make it possible to select a rational material from the viewpoint of vertical bearing force and horizontal strength, rather than selecting a material to face the twist.
  (2) It is possible to easily provide the horizontal and compression proof stresses of the pile shaft commensurate with the high bearing capacity of the large-diameter spiral blade formed at the tip of the ready-made pile. That is, using a ready-made pile made of the same material, the diameter of the lower end of the ready-made pile and the diameter of the upper part and the intermediate part (shaft part) of the ready-made pile can be formed equally.
  Also, at least compressive force more than that of conventional steel pipe piles to make it equal to that of concrete piles, and to ensure the strength of pile shafts that are well balanced with high tip support.
  (3) For prefabricated piles with spiral blades at the tip, with regard to the ground around the prefabricated piles, the ground strength after twisting of conventional spiral blades is further strengthened, and the strength such as the vertical support force of the pile foundation is integrated. Strengthening.
[0013]
[Means for Solving the Problems]
  However, in the present invention, the casing for propulsion having propulsion means such as spiral blades is attached to the outside of the ready-made pile having spiral blades, and the lower ends are engaged with each other for excavation. .
[0014]
  That is,thisThe invention of the construction method method is a construction method of a ready-made pile with spiral blades characterized by taking the following steps.
(1)The steel pipe that formed the spiral blade for the pile was fixed to the lower end.On the outer periphery of the hollow ready-made pile,Propulsion spiral bladeA propulsion casing havingThe propulsion spiral blade is provided with “one round propulsion spiral blade provided at the lower end portion of the propulsion casing, or continuously excavating soil above the one round propulsion spiral blade during forward rotation. The above-described propulsion casing is configured not to form a spiral blade above the propulsion spiral blade. .
(2) Rotate the propulsion casing forward and transmit the forward rotation to the lower end of the ready-made pile.For pileWhile excavating the ground with spiral blades,For promotionThe excavated soil is held immediately above the spiral blade, and a loose excavated soil layer is formed around the outer periphery of the propulsion casing.
(3) While the tip of the ready-made pile reaches a predetermined depth, while rotating the propulsion casing in the reverse direction,Propulsion spiral bladeThen, pull out to the ground while compacting the loose excavated soil layer on the outer periphery of the ready-made pile.
(4) Subsequently, a hydraulic cement material is filled in the hollow portion of the ready-made pile, and a foundation pile structure is formed in a state where the hydraulic cement material is solidified.
[0015]
  Moreover, invention of another construction method is a construction method of the ready-made pile with a spiral blade characterized by taking the following processes.
(1)A steel pipe formed with a large-diameter pile spiral blade was fixed to the lower end.Outside the hollow ready-made pileZhouIn addition,Small-diameter propulsion spiral bladeA propulsion casing havingThe propulsion spiral blade is provided with “one round propulsion spiral blade provided at the lower end portion of the propulsion casing, or continuously excavating soil above the one round propulsion spiral blade during forward rotation. The above-described propulsion casing is configured not to form a spiral blade above the propulsion spiral blade. .
(2) saidFor promotionThe spiral bladeFor pileLocated directly above the spiral blade, the propulsion casing and the ready-made pile are rotated forward to excavate the ground.At the same time, the excavated soil is held just above the spiral blade for excavation, and a loose excavated soil layer is formed around the outer periphery of the propulsion casing.
(3) With the tip of the ready-made pile reaching a predetermined depth, the propulsion casing is reversely rotated, and the loose excavated soil layer on the outer periphery of the ready-made pile is compacted and pulled out to the ground.
(4) Subsequently, a hydraulic cement material is filled in the hollow portion of the ready-made pile, and a foundation pile structure is formed in a state where the hydraulic cement material is solidified.
[0016]
  Further, in the above, when the propulsion casing is rotated forward, the engagement / disengagement means at the lower end of the propulsion casing and the engagement / disengagement means above the spiral blades of the ready-made pile are locked, so that the propulsion casing and the ready-made pile are And the propulsion casing is separated from the ready-made pile by releasing the engagement / disengagement means with the ready-made pile when the propulsion casing is rotated in the reverse direction. It is a construction method for ready-made piles.
[0017]
  Further, the invention of the casing for propulsion is formed by engaging and disengaging means with the ready-made pile at the lower end of the steel pipe having an inner diameter that is fitted from above the ready-made pile and can be rotated and slid vertically. “For one round of propulsionForming a spiral blade,Alternatively, a gap of a distance that does not continuously excavate excavated soil during forward rotation is provided above the one-round propulsion spiral blade, and another propulsion spiral blade is provided. " The casing for use shall not be formed with a spiral blade above the propulsion spiral blade.This is a propulsion casing characterized by that.
[0018]
  The hydraulic cements mentioned above are those in which cement milk, cement mortar, concrete or the like is produced by mixing various cement materials with various aggregates according to the required strength if necessary.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
(1) The ready-made pile 12 is configured by fitting and fixing a short steel pipe 6 having a spiral blade 7 to a lower end portion of an existing concrete or steel pipe pile body 1 having a hollow portion 2 (see FIG. 1). Usually, it is sufficient for the spiral blade 7 to have one round. Engagement / disengagement means (convex screw) 10 with the propulsion casing is provided immediately above the spiral blade 7, usually at the upper edge of the short steel pipe 6.
[0020]
  When a steel pipe pile or a concrete pile coated with a steel pipe on the outside is used as the pile base 1, the spiral blade 7 can be directly formed on the outer surface, but if the short steel pipe 6 is used, The lower end portion can be reinforced with a short steel pipe, the large-diameter spiral blade 7 can be easily formed on an existing pile base, and the engagement / disengagement means 10 can be easily formed using the short steel pipe 6.
[0021]
(2) The propulsion casing 18 is formed by forming a spiral blade (propulsion means) 16 as propulsion means (ground compaction means and auxiliary excavation means) at the lower end of the steel pipe 14 (FIG. 2). An engagement / disengagement means (concave screw) 15 with the ready-made pile is formed at the lower end of the steel pipe 14. Further, the spiral blade 16 (outer diameter D₁₁) Is the spiral blade 7 (outer diameter D) of the ready-made pile 12₂) Smaller diameter (D₁₁<D₂Is desirable (FIG. 3).
[0022]
  The steel pipe 14 is attached to the outside of the pile base 1 of the ready-made pile 12 and needs to be able to rotate and move up and down separately from the ready-made pile 12, and so that the outer diameter of the ready-made pile 12 can be taken as large as possible. There is a need to. Therefore, the inner diameter of the steel pipe 14 is equivalent to the outer diameter of the pile base 1 of the ready-made pile 12, and is formed slightly larger.
[0023]
(3) Insert the upper end side of the ready-made pile 12 from the lower end side of the propulsion casing 18, and attach the propulsion casing 18 to the ready-made pile 12. By relatively positively rotating the propulsion casing 18, the engaging / disengaging means 10 and 15 are brought into a locked state (FIG. 3A). Usually, the engaging / disengaging means is formed by screws that are screwed together, but a combination of a hook and a protrusion may be used. In short, any configuration may be used as long as the propulsion casing 18 can be rotated forward so that it can be easily locked and can be reversely rotated in the ground to easily release the locked state.
[0024]
(4) The propulsion casing 18 and the ready-made pile 12 are supported on the auger 20 of the excavator, and the upper end of the propulsion casing 18 is rotated in the forward direction so that the rotational force is engaged and disengaged from the lower end of the propulsion casing 18. 10 and 15 are transmitted to the lower end portion of the ready-made pile 12 to dig (FIGS. 4A and 4B). Therefore, the twist of the shaft portion of the pile base 1 of the ready-made pile 12 hardly occurs.
[0025]
  In the ground, the ground can be excavated by screwing the spiral blade 7 of the ready-made pile 12, but the spiral blade 16 of the propulsion casing 18 also acts on the excavation as an auxiliary. That is, since the excavated soil is raised upward by the spiral blade 7 of the ready-made pile 12 and further upward by the spiral blade 16 of the propulsion casing 18 positioned immediately above, the excavation efficiency by the spiral blade 7 of the ready-made pile 12 is ensured. it can. Therefore, the excavated soil excavated and removed by the spiral blades 7 of the ready-made pile 12 is sent directly above the spiral blades 7 and further taken up by the spiral blades 16 of the propulsion casing 18 and crushed and sent upward. Since only one spiral blade 16 is provided, the spiral blade 16 stays directly above the spiral blade 16 at each depth.
[0026]
(5) In this way, when the ready-made pile 12 is laid down to a predetermined depth (FIG. 4C), the rotation of the auger 20 is switched to the reverse rotation. Due to the reverse rotation, the engagement / disengagement means 10 and 15 are unlocked, and the propulsion casing 18 separated from the ready-made pile 12 is pulled up (FIGS. 3B and 4D). At this time, if it is pulled up while being reversed, the lifting of the propulsion casing 18 causes a mark of the propulsion casing 18 to be formed as a void on the outside of the ready-made pile 12, and loosely left excavated soil that is a void on the outer side of the ready-made pile 12 Can be compacted by the lower surface of the spiral blade 16. Further, the diameter D of the spiral blade 16₁₁The diameter D of the spiral blade 7 of the ready-made pile 12₂By making it smaller, the load of the auger for pulling out driving can be reduced more than the area ratio of the spiral blades 16 together with the compacting of the excavated soil. At this time, the rotational speed w (rpm) of the auger 20 for lifting the propulsion casing 18, the lifting speed v (cm / min.), The vertical displacement d (cm) of the spiral blade 16 (FIG. 2A), Can be adjusted more efficiently and reliably.
[0027]
  That is, if the lifting speed v is made slower than (w × d), the entire formation is surely compacted, and v / (w × d) is, for example,
v / (w × d) = 1/2
By fixing to a constant value such as, the degree of compaction of the ground can be made constant, and a stable peripheral frictional force can be obtained. Therefore, a uniform supporting force can be obtained in each foundation pile structure over the entire site.
[0028]
(6) After raising the propulsion casing 18 to the ground (FIG. 4 (e)), the concrete 22 is poured into the hollow portion 2 of the ready-made pile 12, and after the concrete 22 is solidified, the foundation pile structure 23 is constructed. (FIG. 4 (f)). Further, the pulled-up propulsion casing 18 can be used for burying other ready-made piles 12.
[0029]
  Further, since almost no torsional stress is generated in the ready-made pile 12, the desired vertical bearing force required for the foundation pile structure 23 can be determined without considering the strength to torsion of the pile base 1 in terms of material, shape, size, thickness, etc. It can be set according to the horizontal strength.
[0030]
(7) In the above, the spiral blade 16 of the propulsion casing 18 is replaced with the spiral blade 7 of the ready-made pile 12 (outer diameter D₂) With a smaller diameter (D₁₁<D₂The reason for this is as follows. The spiral blade 16 of the propulsion casing 18 also has an effect of assisting excavation when screwing the ready-made pile 12, but the main purpose is to backfill the soil when the propulsion casing 18 is pulled out. . That is, after the ready-made pile 12 with the spiral blades 7 is screwed to a predetermined depth together with the propulsion casing 18 with the spiral blades 16, when the propulsion casing 18 is pulled out to the ground, the propulsion casing 18 is reversely rotated to The main purpose is to return the soil to the space (the loosely left excavated soil) from which the propulsion casing 18 has been pulled out by the blades 16 and to compact, and as a result, to reinforce the surrounding ground of the ready-made pile 12 To do.
[0031]
  Accordingly, the spiral blade 16 of the propulsion casing 18 is different from the spiral blade 7 of the ready-made pile 12 used to increase the supporting force, and the soil is returned to the void portion of the trace that has been pulled out by raising the propulsion casing 18. Since it is used for compacting the ground, the spiral blade 16 does not need to be as large as the spiral blade 7 and can function sufficiently with a smaller diameter. Further, since the spiral blade 16 has a smaller diameter than the spiral blade 7, when screwing and pulling out with the ready-made pile 12, resistance to the ground is small and the rotational driving load is small and convenient. In other words, the effect of compaction is that, by tightening the portion near the outer periphery of the ready-made pile 12 rather than compacting the portion away from the ready-made pile 12, the integrity of the ready-made pile 12 and the ground is increased, and efficient tightening is achieved. The effect of hardening can be demonstrated.
[0032]
  Further, when the load on the ready-made pile 12 at the time of screwing is further reduced, the ground farther from the ready-made pile 12 is also compacted, and the ground compaction at the time of pulling out is further strengthened, the spiral blade 16 The outer diameter (D₁₁≒ D₂) (Not shown). Further, in order to reinforce the function of propelling the propulsion casing 18 and compacting the ground, a plurality of spiral blades 16 and 16 can be formed in the propulsion casing 18 (FIG. 5).
[0033]
[Example 1]
  An embodiment of the present invention will be described with reference to FIGS.
[0034]
[1] Configuration of ready-made pile 12
[0035]
  The pile base 1 having the hollow portion 2 has an outer diameter D.₀, Thickness t₀, Length H₀Made of concrete. In the figure, 4 is an end plate of the pile base 1.
[0036]
  Height H₁, Outer diameter D₁On the outer surface of the short steel pipe 6₂Fasten the steel spiral blade 7Ru. The spiral blade 7 has a thickness t₂The doughnut-shaped substrate for one round is cut with one radius 8 and the cut one is twisted. The short steel pipe 6 is closed by a bottom plate 9 so that earth and sand do not enter the hollow portion 2 of the pile base 1 when buried. A convex thread portion 10 is formed on the outer periphery of the upper end portion of the short steel pipe 6.
[0037]
  The short steel pipe 6 provided with the spiral blade 7 is fitted and fixed from the lower end 3 side of the pile base 1 to constitute the ready-made pile 12. In addition, in order to improve the twistability (excavation efficiency) of the ready-made pile 12, the position of the lowermost end of the spiral blade 7 can be easily protruded downward from the lower surface of the bottom plate 9 of the short steel pipe 6 (illustration). Not)
[0038]
  Although the dimension of the ready-made pile 12 is appropriately set depending on the torsional strength and the like to be obtained, for example, the following values are adopted.
[0039]
  Pile base 1 Outer diameter D₀    1000mm
              Thickness t₀      130mm
              Length H₀  10m
  Short steel pipe 6 Outer diameter D₁    1040mm
              Thickness t₁        40mm
              Height H₁    1000mm
  Outside diameter D of spiral blade 7₂    2000mm
              Thickness t₂≒ t₁
[0040]
[2] Propulsion casing 18
[0041]
  Outer diameter D that can be fitted to the outside of the pile base 1 of the ready-made pile 12₂₂A concave screw portion 15 that can be screwed into the convex screw portion 10 of the ready-made pile 18 is formed on the inner surface of the lower end of the steel pipe 14. The outer surface of the steel pipe 14 is made of steel and has an outer diameter D.₁₁The propulsion casing 18 is configured by fixing the spiral blade 16. The concave screw portion 15 and the convex screw portion 10 are formed so as to be tightened by rotating the propulsion casing 18 forward and loosened by reverse rotation. The spiral blade 16 has a thickness t₄The doughnut-shaped substrate for one round is cut with a radius of 17 and the cut one is twisted. The spiral blade 16 at the cutting position (one radius 17) is formed such that the upper and lower ends are separated by a distance d.
[0042]
  The dimensions of the casing for propulsion are appropriately set depending on the required torsional strength and the like. For example, the following values are adopted. Further, in order to adjust the propulsion resistance mainly for pulling out, the number of spiral blades can be changed as appropriate.
[0043]
    Inner diameter D of steel pipe 14₀₀      1000mm (D₀) + Α
              Thickness t₃          40mm
              Length H₁₁        10m
    The outer diameter D of the spiral blade 16₁₁  1400mm
                  Thickness t₄≒ t₃
[0044]
  Here, the inner diameter D of the steel pipe 14₀₀Α of the pile base 1 of the ready-made pile 12 (outer diameter D₀), The gap α may be formed so that the steel pipe 14 can rotate and move up and down (spiral movement).
[0045]
  Also, the positional displacement dimension d at the upper and lower ends of the spiral blade 16 is:
    d = 0.1 × D₂₂~ 0.3 × D₂₂
(FIGS. 2A and 2B). However, D₂₂Is the outer diameter of the steel pipe 14 (D₂₂= D₀₀+2 x t₃).
[0046]
[3] Construction method
[0047]
(1) First, the propulsion casing 18 is fitted over the ready-made pile 12 to cover the ready-made pile 12, and the concave screw portion 15 at the lower end of the propulsion casing 18 is screwed to the convex screw portion 10 of the ready-made pile 12. Match. The upper end portion of the propulsion casing 18 is mounted on the auger 20 of the pile driving machine, lifted, and installed at the installation point of the ground 21 to be constructed (FIGS. 4A and 3A).
[0048]
(2) When the auger 20 is rotated in the forward direction and the propulsion casing 18 is rotated in the forward direction, the ready-made piles 12 connected with the concave and convex screws 10 and 15 are also rotated in the forward direction at the same time. The spiral blade 7 of the ready-made pile 12 and the spiral blade 16 of the propulsion casing 18 push the ready-made pile 12 and the propulsion casing 18 into the ground while breaking down the ground (FIG. 4B).
[0049]
  At this time, the excavated soil broken by the spiral blade 7 is raised upward, further crushed by the spiral blade 16, and moved upward. The excavated soil removed from the tip of the ready-made pile 12 by the spiral blade 7 is raised further upward by the spiral blade 16, so that the excavation efficiency by the spiral blade 7 is maintained. Accordingly, the spiral blade 16 functions as an aid for excavation of the spiral blade 7 and the ready-made pile 12 and the propulsion casing 18 can be easily penetrated.
[0050]
  The excavated soil destroyed by the spiral blade 16 does not have a spiral blade in the upper part, so that it remains just above the spiral blade 16 and is not lifted. Accordingly, the excavated soil collapsed around the propulsion casing 18 is accumulated, and the ground is not discharged or the amount of discharged soil is extremely small.
[0051]
(3) When the ready-made pile 12 and the propulsion casing 18 are dug to a predetermined depth and penetrated, the rotation of the auger 20 is stopped (FIG. 4C).
[0052]
(4) Next, when the auger 20 is rotated in the reverse direction, the ready-made pile 18 does not rotate due to the resistance between the spiral blade 7 and the ground or stays at a slight rotation, and only the propulsion casing 18 rotates in the reverse direction, and the concave screw The part 15 and the convex thread part 10 are unscrewed, and the propulsion casing 18 is separated from the ready-made pile 12. Subsequently, the propulsion casing 18 is pulled up while the auger 20 is rotated in the reverse direction (rotation speed w (r.p.m.)) (FIGS. 4D and 3B). By this reverse rotation, the earth and sand loosened at the time of excavation are pressed downward by the spiral blades 16 of the propulsion casing 18, and the ground around the outer periphery of the ready-made pile 12, which is the trace of the propulsion casing 18, is solidified and soil discharge is suppressed. be able to.
[0053]
  Here, the pulling speed v (cm / min.) Of the excavating casing 18 is determined according to the required strength of the surrounding ground where the ready-made pile 12 is buried,
    v <w × d
In consideration of the lifting efficiency, the lifting speed v is made slower and the entire formation is consolidated. At this time, for example,
    v / (w × d) ≦ 1/2
As such, the ground should be firmly and firmly compacted.
[0054]
(5) When the propulsion casing 18 is removed, the ready-made pile 12 with the spiral blade 7 is buried in the pile hole. In this state, the upper end (pile mouth) 3a of the hollow pile 2 of the ready-made pile 12 is placed on the ground. It is held at a slightly protruding position (FIG. 4 (e)). Therefore, the bottom plate 9 of the short steel pipe 6 prevents earth and sand from entering the hollow portion 2 of the ready-made pile 12. Further, the upper end (stake opening) 3a is not soiled, so that dirt and the like do not enter the hollow portion 2, so that the strength of ready-mixed concrete or the like to be filled later is not lowered.
[0055]
(6) In the hollow portion 2 of the ready-made pile 12 buried, ready-mixed concrete (solidification strength 24 N / mm)²Filling) and filling. At this time, if a discharge port such as a tremy tube is inserted up to the vicinity of the bottom of the hollow portion 2 (the bottom plate 9 of the short steel tube 6), it can be filled easily. If this ready concrete 22 solidifies, the foundation pile structure 23 of this invention will be completed (FIG.4 (f)).
[0056]
[4] Other embodiments
[0057]
(1) Although the propulsion casing 18 has one spiral blade 16 in the above embodiment, the spiral blade 16a having the same shape can be fitted and fixed immediately above (FIG. 5A). In this case, the upper and lower spiral blades 16, 16 a have gaps 25 (height H so that the excavated soil is continuously discharged during forward rotation and is not discharged upward.₁₂) Is provided. In addition, the clearance 25 increases the efficiency of compacting the excavated soil during reverse rotation.
[0058]
  Further, the spiral blades 16b and 16b having the same shape as the spiral blade 16 are provided in the intermediate portion of the steel pipe 14 with a predetermined gap 26 (height H₁₃) Can be provided and fixed (FIG. 5B).
[0059]
(2) Further, in the above embodiment, the propulsion casing 18 and the ready-made pile 12 are engaged and disengaged with the convex screw 10 and the concave screw 15, but are locked by the forward rotation of the propulsion casing 18 and reversed. Any other locking means can be used as long as it can be unlocked by rotation (not shown).
[0060]
(3) Moreover, in the said Example, although the ready-made pile was made into the concrete pile, the concrete pile and steel pipe pile which coat | covered the outer side with the steel pipe can also be applied (not shown). In this case, if the engagement / disengagement means for the propulsion casing 18 is provided separately, the short steel pipe 6 can be omitted and the spiral blade 7 can be directly fitted and fixed to the outer surface.
[0061]
(4) In the above embodiment, the spiral blade 16 is used as the propulsion means for the propulsion casing 18, but other structures can be used as long as the same effect can be exhibited when the propulsion casing 18 is pushed in or pulled up. It can also be employed (not shown).
[0062]
【The invention's effect】
(1) In this invention, a propulsion casing having propulsion means is attached to the outer periphery of a hollow ready-made pile having a spiral blade at the tip, and forward rotation of the propulsion casing is transmitted to the lower end of the ready-made pile, Since the ground is dug with the spiral blades of the ready-made piles, almost no torsional stress is generated in the shaft part of the ready-made piles, so the excavation efficiency is good and the horizontal strength, vertical without considering the torsional stress when designing the ready-made piles Since it is possible to select a ready-made pile with a small wall thickness only by the performance required for the ready-made pile in a buried state such as bearing capacity, there is an effect that a more economical foundation pile structure can be designed. Moreover, since almost no twisting stress is generated in the ready-made pile, the adverse effect of the residual stress due to twisting can be removed in the embedded state.
[0063]
  In addition, since the excavation is carried out in combination with the propulsion means of the propulsion casing, depending on the thickness of the spiral blade, a ready-made pile that is about twice as large as the existing outer diameter (outer diameter of about 1000 mm) can be used. The spiral blade having the outer diameter of about 1.5 to 2 times the outer diameter of the pile base can be used as the spiral blade at the lower end of the ready-made pile. Therefore, the built-up foundation pile structure can secure a supporting force that is twice or more that of a conventional large-diameter steel pipe pile (outer diameter: 500 to 600 mm).
[0064]
  Moreover, since the casing for propulsion repeatedly uses a thick steel pipe having a high torsional strength, there is an effect that the steel pipe material can be effectively used.
[0065]
(2) In addition, if a propulsion casing having a spiral blade formed at the lower end is used, the propulsion casing spiral blade (propulsion means) can be positioned directly above the spiral blade of the ready-made pile, The excavation efficiency can be improved, and the time required for burying the ready-made piles can be shortened, and if the propulsion casing is reversely rotated and pulled up, the loose excavated soil (outside the buried pre-made piles) The loosened excavated soil) can be compacted, and the peripheral frictional force of the formed foundation pile structure can be increased.
[0066]
  In addition, by appropriately combining the lifting speed and the rotation speed of the propulsion casing, the ground strength can be controlled, and a desired supporting force can be obtained stably and reliably.
[0067]
  In addition, when excavating, the excavated soil is placed outside the propulsion casing, and when it is lifted, the excavated soil that has been excavated is compacted, greatly reducing the excavated soil to be treated as industrial waste and realizing an environmentally friendly construction method. it can.
[0068]
(3) In addition, using the engagement / disengagement means at the lower end of the propulsion casing and the engagement / disengagement means at the upper edge of the short steel pipe, the forward rotation from the propulsion casing to the ready-made pile is transmitted, and the lock is released by reverse rotation. By doing so, there is an effect that the transmission of the rotational force is ensured and the release of the locking in the ground is facilitated.
[0069]
(4) Also, short steel pipes with spiral blades made of steel plates can be easily fixed to pre-made concrete piles by fitting and fixing (for example, welding) to pile bases such as pre-made piles made of outer shell steel pipe concrete. In addition, a steel plate spiral blade can be formed, and an effect of exerting an effective compressive force on the shaft portion has an effect of exerting a vertical supporting force by the spiral blade. Moreover, since the existing pile can be used as the pile base, there is an effect that the existing pile as the pile base can be appropriately selected according to the performance of the desired foundation pile structure and the proof stress can be easily increased.
[0070]
(5) In addition, when a small-diameter spiral blade is formed on the propulsion casing and a large-diameter spiral blade is formed on the ready-made pile, respectively, the twist generated in the ready-made pile is reduced at the time of pushing, and at least the embedded ready-made pile is The loose excavated soil near the outer periphery can be compacted, and the load on the driving auger can be reduced as much as possible when the propulsion casing is pushed in and pulled up. Therefore, there exists an effect which can construct | assemble the foundation pile structure which can exhibit desired supporting force efficiently.
[0071]
(6) Moreover, since the ready-made pile of this invention can be comprised using the existing ready-made pile as a pile base generally, the axial part of a pile is made into a lower end part, without making an axial part smaller than a lower end part. Since it can be set as the structure which has equivalent performance, and it is not necessary to make a shaft part small diameter, there is an effect which can secure and strengthen the compressive strength and horizontal proof stress of the shaft part of a pile, without using other reinforcement means. Therefore, combined with the vertical support force and pull-out force exhibited by the propagation of the shearing force exhibited by the large-diameter spiral blade at the lower end of the foundation pile structure, and the entire foundation pile structure combined with the cement filled in the hollow part There is an effect that it is possible to make a foundation pile structure with a good balance as a whole, such as compression strength, horizontal strength, and peripheral frictional force on the outside of the ready-made pile.
[Brief description of the drawings]
1A and 1B are ready-made piles used in the practice of the present invention, in which FIG. 1A is a front view, FIG. 1B is a plan view, and FIG. 1C is a cross-sectional view taken along line AA in FIG.
FIG. 2 is a propulsion casing used in the practice of the present invention, in which (a) is a front view and (b) is a plan view.
FIGS. 3A and 3B are partial front views showing a state where a propulsion casing is attached to a ready-made pile used in the practice of the present invention, wherein FIG. 3A shows a state during excavation, and FIG.
FIGS. 4A to 4F are schematic front views illustrating a construction method according to the present invention.
5A and 5B are front views of another propulsion casing according to the present invention. FIG.
[Explanation of symbols]
1 Pile base
2 Hollow part
3 Lower end of pile base
3a Upper end of pile base (pile mouth)
4 Lower end plate of pile base
6 Short steel pipe
7 Spiral feather
9 Bottom plate
10 Concave thread
12 Ready-made piles
14 Steel pipe
15 Concave thread
16 Spiral blade (propulsion means)
18 Propulsion casing
20 Auger
21 Ground
22 Concrete
23 Foundation pile structure

Claims

The construction method of the ready-made pile with a spiral blade characterized by taking the following processes.
(1) A steel casing on which pile spiral blades are formed is fitted with a propulsion casing having propulsion spiral blades on the outer periphery of a hollow ready-made pile fixed to the lower end . The propulsion spiral blade is provided with “one round propulsion spiral blade provided at the lower end portion of the propulsion casing, or continuously excavating soil above the one round propulsion spiral blade during forward rotation. The above-described propulsion casing is configured not to form a spiral blade above the propulsion spiral blade. .
(2) said propulsion casing rotates forward, the forward rotation while excavating the ground by pile spiral blade of prefabricated pile is transmitted to the lower end of the prefabricated pile, hold the excavated soil just above the propulsion spiral blade Thus, a loose excavated soil layer is formed around the outer periphery of the propulsion casing.
(3) With the tip of the ready-made pile reaching the predetermined depth, while rotating the propulsion casing in the reverse direction, with the propulsion spiral blade , the loose excavated soil layer on the outer periphery of the pre-made pile is compacted to the ground Pull out.
(4) Subsequently, a hydraulic cement material is filled in the hollow portion of the ready-made pile, and a foundation pile structure is formed in a state where the hydraulic cement material is solidified.

The construction method of the ready-made pile with a spiral blade characterized by taking the following processes.
(1) The steel pipe to form a pile spiral vane of large diameter, the outer circumference of the hollow prefabricated pile fixed to the lower end, mounting a propulsion casing having a small diameter propellant spiral blade. The propulsion spiral blade is provided with “one round propulsion spiral blade provided at the lower end portion of the propulsion casing, or continuously excavating soil above the one round propulsion spiral blade during forward rotation. The above-described propulsion casing is configured not to form a spiral blade above the propulsion spiral blade. .
(2) The propulsion spiral blade is positioned immediately above the pile spiral blade, the propulsion casing and the ready-made pile are rotated forward to excavate the ground, and excavated soil is directly above the excavation spiral blade. Hold and form a loose excavated soil layer around the outside of the propulsion casing.
(3) With the tip of the ready-made pile reaching a predetermined depth, the propulsion casing is reversely rotated, and the loose excavated soil layer on the outer periphery of the ready-made pile is compacted and pulled out to the ground.
(4) Subsequently, a hydraulic cement material is filled in the hollow portion of the ready-made pile, and a foundation pile structure is formed in a state where the hydraulic cement material is solidified.

When the propulsion casing is rotated forward, the engagement / disengagement means at the lower end of the propulsion casing and the engagement / disengagement means above the spiral blade of the ready-made pile are locked, and the propulsion casing and the ready-made pile are both rotated forward. 3. The spiral according to claim 1, wherein when the propulsion casing is reversely rotated, the engaging / disengaging means with the ready-made pile is released to separate the propulsion casing from the ready-made pile. Construction method for prefabricated piles with feathers.

And fitted from above the ready-made pile, the lower end of a steel pipe having a slidable inner diameter turning and vertically, forming disengagement means with the ready-made pile, promotion of "one round in the outer periphery of the lower end portion of the steel tube use spiral blade is formed, or over the propulsion helical blade of the one round, the distance gap without earth removal upwardly excavated soil continuously during forward rotation is provided, made of another propulsion spiral blade The propulsion casing is configured so that the spiral blade is not formed above the propulsion spiral blade .