JP3643303B2 - Rotary press-fit steel pipe pile - Google Patents

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である。
例えば孔の径を２．５倍（Ｄｏ＝０．５Ｄｐ）にすると（図３６（ｃ））

となる。
図３７において、羽根を曲げ加工により螺旋状にし、かつ始端ａｃと終端ａ’ｃ’を平行にした場合に、円盤中心部に設けた孔の周長が伸びる状態を、展開図によって示している。
Ｄｏ＝０．２Ｄｐ時の羽根の曲げ加工後の周長 ＝０．７Ｄｐ
Ｄｏ＝０．５Ｄｐ時の羽根の曲げ加工後の周長 ＝１．６Ｄｐ
となる。
曲げ加工によって周長が伸びることによる歪みは
Ｄｏ＝０．２Ｄｐの時は、
（０．７−０・６３）／０．６３ ＝０．１１
Ｄｏ＝０．５Ｄｐの時は、
（１．６−１．５７）／１．５７ ＝０．０１９
であり、それぞれの比を計算すると、０．１１／０．０１９＝５．８となる。即ち孔径が０．２Ｄｐの場合は、孔径が０．５Ｄｐの場合に比べて、羽根の曲げ加工による歪みが５．８倍にも達する。
以上により、円板中心部の孔が小さいと、羽根を螺旋状に曲げ加工する場合の孔内周縁の歪みが過大になり、亀裂が生じやすいことは明らかである。
【００３１】
円板に設けた半径方向の切り込み８２部分のａｃとａ'ｃ'の平行を保ったままで、螺旋状羽根を形成するためには、ピッチ＝０．３Ｄｐのときは、中心部の孔の径が鋼管杭の直径の２分の１以下の場合は亀裂が生じやすいことが、本発明者らの実験によって明らかになっている。
板の材質や加工時の温度などの条件によっては、孔径は鋼管内径の０．４倍程度まで可能であるが、前記理由により鋼管内径の０．５倍以上とする方がより望ましい。
羽根と鋼管のなす角度をほぼ直角とすることが望ましいが、従来技術では、羽根を鋼管外周に固定する場合においてしか、これは実現化されていなかった。つまり羽根が螺旋状に切り欠きされた鋼管の先端に固定された杭においては、鋼管と羽根のなす角度をほぼ直角にする方法は示されていなかった。
【００３２】
（２−８） 先端形状と先端鋼管板厚の問題
鋼管杭はいうまでもなく、地中の礫・砂・粘性土等からなる固い支持層に貫入して、主として上部構造物による上からの圧縮力に対して支持力を発揮するものであり、杭先端面によって支えられている。前述の従来タイプ１、２の場合は、鋼管の外側に羽根を固定するため、図３８(イ)、（ロ）に示すように、螺旋羽根は片持ち梁のような形状となり、羽根付け根及びその近傍の鋼管部分に大きな曲げモーメントが作用する。この曲げモーメントに抵抗するために、杭先端の羽根を固定している部分の鋼管を、支持力から必要となる板厚よりも厚くする必要があり、その厚さは支持力から必要な厚さと比べて、２〜３倍程度になることも多い。鋼管の必要厚さが極厚になると、鋼管作製のコストもアップするという問題を生じる。
【００３３】
図３９（イ）に示すように、従来タイプ３の羽根は鋼管の先端に固定されており、羽根は鋼管の内・外両側に張り出している。このことによって、内側・外側の羽根がそれぞれ地盤から受ける反力による曲げモーメントが、鋼管と羽根の接続位置で打ち消し合うため、鋼管に作用する曲げモーメントは上記従来タイプ１，２の形状と比べてかなり小さくなる。従って、鋼管杭先端部の板厚も、従来タイプ１，２と比べて相当に薄くすることができる。鋼管の厚さは、羽根の内・外面への張り出し量のバランスなどの条件にもよるが、支持力から決定される板厚と同厚程度とすることも可能である。
【００３４】
以上述べてきた課題を整理すると次のようになる。
（３−１）貫入性の面からは、羽根は螺旋状に切り欠いた鋼管の先端に固定されていることが望ましい。
（３−２）さらに施工中に管内に土砂が進入して貫入抵抗を低減できるような形状であることが望ましい。
（３−３）支持力の面からは、先端が閉端または、支持層への根入れが小さくても進入した土砂を閉塞できるものであることが望ましい。
（３−４）先端鋼管の板厚の面からは、羽根が鋼管の内側にも張り出していることが望ましい。
（３−５）特に大径杭の施工面からは、大トルクを発揮できる既存の施工機械を利用するために、羽根と鋼管がほぼ直角に固定されていることが望ましい。
また、貫入メカニズムの面からも、推進力をできるだけ有効に発揮させるために、羽根と鋼管がほぼ直角に固定されていることが望ましい。
従来の技術ではこれらの５点を全て満足するような形状は明らかにされておらず、その形状を実際に製作する手段も未知であった。本願発明はこれら５つの条件を全て満たす形状と、その実現手段を提供するものである。
【表１】

【００３５】
【課題を解決するための手段】
本発明者は回転圧入鋼管杭、特に大径杭の前記問題点を種々研究した結果、施工面、支持機能面、製作面等で従来の問題点を解決できる新規な構成を見出した。
本発明は、次のように構成されている。
本発明は開端杭に属し、それ故に、杭径が１０００mmを越えるような大径であっても施工性が閉端杭に比べ優れている。また本発明では、開端杭の難点である鋼管内での土砂の閉塞促進手段として、鋼管内に設ける閉塞促進リングの形状や位置、さらには閉塞促進リングと同等の効果を最大限に引き出すための形状を実験等によって研究確認し、具体化した。つまり、本発明では、閉塞促進効果はドーナツ状リングの閉塞促進リングと殆ど同等の効果を持ちながら、それよりも加工しやすく、材料も、鋼製ブロックや帯鋼板または型鋼をそのまま切断するだけでよい閉塞促進突起を創案している。この閉塞促進突起は閉塞促進リングよりもコスト的に優れている。さらに、閉塞促進リングを鋼管内に設ける場合にあっては、その内径を実験結果にもとづいて所定の寸法に設定し、更に多段に設けるなどの特別な改良がなされている。
【００３６】
さらに、鋼管の内側に羽根を張り出して固定したため、羽根付け根及びその近傍の鋼管部分に作用する、大きな曲げモーメントを軽減し、鋼管内側方向への変形を防止している。
また、羽根の外周部分と鋼管杭本体の軸とのなす角を直角とすることにより、効率よく圧入推進力を得ることができ、従来よりも小さな回転力及び推進力で、大径の杭を固い支持層にまで圧入することができるようにした。
また、上記の直角にすることにより、既存の杭施工用機械のチャック構造に適合するので、従来は掘削が困難であった杭が大径である場合でも、既存の杭施工用機械を用いて効率のよい施工が可能である。
【００３７】
第１の発明に係る回転圧入鋼管杭は、先端に螺旋状羽根を備え、地中に回転圧入される羽根付き鋼管杭において、鋼管外径の略１．５〜３倍の外径で、鋼管杭内径の略０．４〜０．９倍の内径としたドーナツ状鋼板を、一箇所又は複数箇所切断し、螺旋状に切断した鋼管杭端部に、同心円状に溶接固定し、鋼管杭先端部の内外に螺旋状羽根を張り出して、かつ、該螺旋状羽根が鋼管杭の外周より外側に突き出た部分と鋼管杭本体とのなす角度が略直角となる形状に構成することを特徴とする。
【００３８】
第１の発明を更に説明する。
（１）杭先端の螺旋状羽根の面積を大きくするほど、杭の先端支持力も大きくなる。
（２）しかし先端支持力を大きくするために、螺旋状羽根を杭の外側のみに大きくしていくと、施工時に杭が地盤に貫入する際の抵抗が増大する。また、螺旋状羽根が大きくなる分回転圧入時に羽根の推進力は大きくなるが、その分羽根に作用する反力も大きくなり、羽根部分と鋼管先端部分に大きな曲げモーメントが作用する。従って、螺旋状羽根を杭の外側のみに大きくすると、羽根の板厚だけでなく、鋼管先端部分の板厚も厚くする必要があり、また施工装置も大容量のものになる。
（３）先端が開端である本発明杭の場合、鋼管内に土砂が閉塞しない限り開端部分の支持力は有効とならない。杭が小径であれば、土砂を閉塞させることは比較的容易である。しかし杭が大径になると閉塞効果を得ることが困難になってくる。この点から、羽根を螺旋状のまま杭の内側にも張り出させることで、閉塞効果が小さな状態であっても、開端部についても支持力に有効な構造とすることができる。つまり、羽根を内側に張り出すことで、開口面積を小さくしているので、開口部に負担させる鉛直支持力も小さくなる。従って１００％の開端状態よりも必要となる閉塞効果が小さくて済むのである。
【００３９】
（４）一方、大径杭で閉端の場合は、先端の貫入抵抗が大きくなり施工不能になる。これを避けるために杭先端を開端としている。螺旋状羽根を内側に張り出させた場合は、やや土砂の進入が制限される面もあるが、羽根形状が螺旋であり、羽根の段差部分からも杭内に土砂の進入ができるため、先端の貫入抵抗は、閉端杭のように大きくならず、施工不能になることはない。
（５）なお、杭内に張り出す程度即ち、杭内径Ｄ₁に対する羽根の開口径（螺旋状羽根の内径Ｄ₃）の比は杭径や地盤条件によって決める。この比は一般的には０．５程度が望ましいが、杭が支持層に到達する前に中間層としてやや硬い地盤があり、そのため貫入抵抗が大きくなる場合はこの比を大きくする。また、杭径が大きく閉塞効果が得にくい時に先端部の面積をより有効に使いたい場合にはこの比を小さくする。
【００４０】
（６）図１２に示すように、羽根の外周部分と鋼管杭本体とのなす角を直角としたことにより、地盤の反力が鉛直方向に作用するので効率よく圧入推進力を得ることができ、従 来よりも小さな回転力及び推進力で、大径の杭を固い支持層にまで貫入することができる。また、直角であることにより、既存の杭施工用機械のチャック構造に適合するので、杭が大径になっても既存の杭施工用機械を用いて効率のよい施工が可能になる。
【００４１】
第２の発明は、前記ドーナツ状鋼板を、中心角０°〜９０°で中心が該ドーナツ状鋼板の中心と一致し、外周が該ドーナツ上鋼板の外周と一致するような扇形形状に切断し、切断後の中心角２７０°〜３６０°のドーナツ状鋼板を曲げ加工して、螺旋状に切断した鋼管杭端部に同心円状に溶接固定し、鋼管杭先端部の内外に螺旋状羽根を張り出して、かつ、該螺旋状羽根が鋼管杭の外周より外側に突き出た部分と鋼管杭本体とのなす角度が略直角となる形状に構成することを特徴とする。
前記第１の発明に対して、ドーナツ状鋼板を扇形形状に切断したものであり、掘削土砂の進入を容易にしたものである。
【００４２】
第３の発明は、先端に螺旋状羽根を備え、地中に回転圧入される羽根付き鋼管杭において、鋼管外径の略１．５〜３倍の外径で、鋼管杭内径の略０．４〜０．９倍の内径としたドーナツ状鋼板を一箇所又は複数箇所切断し、あるいは、中心角０°〜９０°で中心が該ドーナツ状鋼板の中心と一致し外周が該ドーナツ状鋼板の外周と一致するような扇形形状に１箇所切断し、切断後の中心角２７０°〜３６０°のドーナツ状鋼板を、中心角０°と３６０°の位置の切断面、あるいはドーナツ状扇形の中心角が３６０°未満の場合には中心角を３６０°まで延長した位置の仮想切断面と中心角０°の位置の切断面が、お互いに平行を保つように曲げ加工して螺旋形状の羽根に成形し、羽根の螺旋形状に対応するように、螺旋状に切断した鋼管杭端部に同心円状に溶接固定し、鋼管杭先端部の内外に螺旋状羽根を張り出して、かつ、該螺旋状羽根が鋼管杭の外周より外側に突き出た部分と鋼管杭本体とのなす角度が略直角となる形状に構成したことを特徴とする。
【００４３】
第３の発明を更に説明する。
（１）従来の技術で、羽根を鋼管の内側まで張り出した場合には、羽根の始と終端が平行とはならず、Ｖ字型をなしている。
（２）そのため羽根の間からは、土砂が管内に進入する効果が小さく、施工性の向上にはつながらない。
（３）羽根の始端と終端を平行に形成することで、羽根の段差部分の面積を最大とすることで、この部分からも土砂が管内に進入できるため、貫入抵抗を低減し、施工性の向上につながる。
（４）ドーナツ状鋼板の１個所に切りこみを入れて曲げ加工した場合は、図１５に示すように、羽根の始端と終端が同一平面上に平行に形成することができる。しかし、ドーナツ状鋼板の１個所を扇形形状に切り欠いて曲げ加工した場合は、図１６に示すように、羽根の始端と終端は同一平面上になく、平行に形成することができない。したがって、中心角を３６０°まで延長した位置の仮想切断面と中心角０°の位置の切断面が、お互いに平行を保つよう曲げ加工することが必要である。
（５）図１２に示すように、羽根の外周部分と鋼管杭本体とのなす角を直角としたことにより、地盤の反力が鉛直方向に作用するので効率よく圧入推進力を得ることができ、従来よりも小さな回転力及び推進力で、大径の杭を固い支持層にまで貫入することができる。また、直角であることにより、既存の杭施工用機械のチャック構造に適合するので、杭が大径になっても既存の杭施工用機械を用いて効率のよい施工が可能になる。
【００４４】
第４の発明は、前記鋼管杭先端より当該鋼管杭内径の略０．５〜３倍の高さ範囲の鋼管杭内部に、鋼管内に進入した土砂の閉塞促進用突起を具備したことを特徴とする。
【００４５】
第４の発明を更に説明する。
（１）螺旋状羽根を鋼管杭の内側まで張り出させた場合には、杭先端が支持層に確実に到達していれば、支持層への貫入が無くても、羽根の見付け面積分の先端支持力は発揮できる。
（２）しかし、鋼管杭の先端部分の全てを支持力に有効とするためには、一般の開端杭と同様に杭体内に進入した土砂を閉塞させる必要がある。
（３）土砂の閉塞を促進させ、支持層への貫入を小さくして支持力を発揮するためには、閉塞促進用の突起を具備することが有効である。
（４）一般に、開端の鋼管杭の先端を土砂によって十分に閉塞させるためには、鋼管内部に支持層の土砂を鋼管内径の５倍程度充填させることが必要とされている。従って、図９（Ｂ）に示すように、杭先端を支持層に鋼管径の５倍程度貫入させることが望ましいとされており、支持層２４への貫入量Ｈは、鋼管径Ｄの５倍以上必要である。ここで、支持層とは地盤の条件によって決めるが、一般的にはＮ値５０以上の良好な地盤を指すことが多い。
（５）本発明では、閉塞促進用突起を具備することで、鋼管杭内部に進入した土砂が閉塞しやすくなり、図９（Ａ）に示すように支持層への貫入量が小さくても（貫入量が杭径の１倍程度でも）土砂が閉塞するようにできる。
（６）本発明者が実験を行ったのでその結果を 図１０によって説明する。図１０（Ａ）、（Ｂ）は共に直径（Ｄ）が８００ｍｍの鋼管であり、（Ａ）は鋼管先端から内径（Ｄ ₁ ）の１．０倍の高さ位置に閉塞促進用突起（リング）を設けており、同図（Ｂ）は閉塞促進用突起がないものである。閉塞促進用突起（リング）２１は内径を、鋼管杭内径（Ｄ ₁ ）の０．８倍になるようにしている。図１０（Ａ）、（Ｂ）は、それぞれ鋼管の内側に砂を充填し、下から押し抜くような載荷をしている。その結果として、鉛直荷重と変位量の関係のグラフを同図（Ｃ）に示す。
同図から分かるとおり、本発明に係るリング有りの鋼管杭は、リング無しの従来鋼管杭に比べて、略７〜８倍の鉛直荷重支持力が有ることが確認される。また、（Ａ）に作用する荷重は、先端が閉塞しているとみなすに十分な大きさである。
【００４６】
（７）開端杭であっても、杭径が大きい場合は杭先端を支持層に杭径の５倍程度貫入させることは困難であり、大型の施工機械が必要で、施工時間も長くなり、コストの増加につながる。しかるに、前述のように、本発明の閉塞促進用突起を具備することにより、支持層への貫入量が低減できるので施工時間を短くでき、コスト的にも有利になる。
（８）閉塞促進用の突起を具備する範囲は、杭の先端より鋼管杭内径の略０．５〜３倍の高さの範囲とする。
（９）閉塞促進用突起の取り付け範囲が鋼管の先端より鋼管の内径の０．５倍未満の場合は、鋼管先端から突起までの距離が小さすぎるため、閉塞効果を有効に発揮することができない。
【００４７】
ここで、閉塞促進リングの効果は、土砂の持つダイレタンシーという特性を利用したものであり、次のように説明できる。ダイレタンシーとは、せん断変形中に体積が変化する現象であり、金属等の材料では見られない、土砂のような粒状体の持つ大きな特性である。支持層の土砂のような密な地盤であれば、ダイレタンシーによって図１１に示すように、滑り面の両側の土粒子がずれを生じ、隣の粒子を乗り越える際に体積変化（膨張）する。
閉塞促進リングを杭体内部に取り付けた場合は、リング先端から杭先端に向かって滑り面が発生し、それによって杭先端内部の土砂の体積が膨張する。鋼管内部の土砂が膨張することによって、押し抜きに対する抵抗が増大するのである。
【００４８】
第５の発明は、第４の発明において、土砂の閉塞促進用突起が、１段または複数段の溶接固定された鋼製ドーナツ状リブであり、その外径が鋼管杭の内径と一致し、内径が鋼管杭内径（Ｄ₁）の略０．９〜０．７倍であることを特徴とする。
【００４９】
第５の発明を更に説明する。
（１）リブの内径が０．９×Ｄ₁より大きいと、閉塞効果を殆ど発生しない。このことは実験によっても確認している。
（２）リブの内径は一般的には０．７×Ｄ₁程度まで考えておけば十分で、これより内径を小さくするとリブの張り出し量が大きくなり、一枚のリブで負担する荷重が大きくなる。従って、リブ内径があまり小さくなると、リブの必要厚さが増大し、リブを鋼管内部に溶接する場合の溶接量が増えるなど、コストも増大する。そのため内径が、０．７×Ｄ₁のリブで不足する場合は、リブを複数段に設ける方がコスト的に有利になる。
【００５０】
第６の発明は、第４〜５の発明において、回転圧入鋼管杭の閉塞促進用突起が、鋼製ブロック、帯鋼板または型鋼であり、鋼管杭の周方向に間隔を隔てて複数溶接固定したことを特徴とする。
【００５１】
第６の発明を更に説明する。
（１）従来技術では開孔リブを鋼管杭内面にドーナツ状に配置したものだけであった。この形状は閉塞促進の目的では効果が大きいが、ドーナツ状のリングを杭の内面に溶接する加工が煩雑になる問題点を持っていた。本発明では、閉塞促進効果はドーナツ状リングとほぼ同等の効果を持ちながら、より加工しやすく、材料も鋼製ブロック、帯鋼板または型鋼をそのまま切断するだけでよいリブ型の閉塞促進突起を創案している。この発明は複数段のドーナツ状リングよりもコスト的に優れている場合がある。
（２）この形状の場合も、ドーナツ状リブと同様の張り出し量で十分であり、突起に内接する円の直径が０．９×Ｄ₁〜０．７×Ｄ₁となるようにすることが望ましい。
（３）突起は管内円周方向に複数設けるが、それぞれの突起の周方向長さの合計が、鋼管杭内周長さの５〜２０％とするのが望ましい。５％未満では閉塞効果を十分に発揮できない。２０％を越えても、効果はそれ以上にあまり向上しない。
【００５２】
第７の発明は、第１〜第６のいずれかの発明において、前記羽根の厚さを、羽根に生じる曲げモーメント分布に対応させて半径方向に変化させてなることを特徴とする。
【００５３】
第７の発明を更に説明する。
螺旋羽根の板厚は全体を同じ厚さにする必要はなく、羽根２に作用する力によって生じる曲げモーメントに応じて羽根の径方向に厚さを変化させるために、図１３に概念的に示すように、鋼管に近い部分を２枚重ねの羽根にする方法が考えられる。また図１４に示すように、鋳造等によって板厚を連続的に変化させることも可能である。
【００５４】
本発明は、第１〜第７のいずれかの発明の回転圧入鋼管杭において、螺旋状に切断した鋼管杭端部の始終端の段差部分を円弧状に形成してもよい。
【００５５】
上記段差部分について更に説明する。
（１）円弧状の段差部分は図１に示す段差部６のように構成されている。
（２）螺旋状に切断した鋼管杭端部の始終端の段差部分には、回転圧入時に大きな力が集中するため、この部分が鋭角に切断されたままでは、図３に示すように、角部分から杭本体の鋼管に亀裂が発生する場合がある。
（３）そこで、応力集中を緩和し、杭の破壊を防ぐためこの段差部分を円弧状に形成した。
【００５６】
本発明は、第１〜第７のいずれかの発明において、螺旋状羽根の先端の小口面に、羽根の回転進行方向に対して抵抗が少なくなるような傾斜を設け、その小口面又は傾斜面に掘削刃を溶接などの方法で接着し、羽根下面と掘削刃の下面のなす角度を、１３５°〜１７０°としてもよい。
【００５７】
上記角度について更に説明する。
（１）杭を回転圧入する際に、地盤のＮ値がほぼ均一な層であれば、先端に掘削刃を設けなくても貫入性は問題ない。
（２）地盤のＮ値が急激に増加する場合には、掘削刃が無いと硬い地盤の上面へ羽根が噛み込むことができずに滑り現象を発生する。
（３）滑り現象を発生させないためには、硬い地盤へ螺旋状羽根が噛み込むためのきっかけを作ることが重要であり、掘削刃が必要となる。
【００５８】
（４）さらに、掘削刃および螺旋状羽根の小口面は、羽根の回転方向に対しては抵抗が少なくなるような形状とすることが重要であり、抵抗が大きいと螺旋状羽根が回転するための必要トルクが増大し、施工性が悪くなる。
（５）従って、羽根先端の小口面は当該螺旋状羽根の回転方向に対して抵抗が少なくなるような傾斜面を設け、あるいはその小口面又は傾斜面に掘削刃を接着することが望ましい。
（６）掘削刃下面と螺旋状羽根の下面のなす角度は１３５°〜１７０°が効果的であり、１７０°を越えると噛み込みの効果がそれほど高くなく、１３５°未満では逆に先端の抵抗が大きくなり、施工性が悪くなる。
（７）地盤のＮ値が急激に変化しないような地盤であれば、掘削刃は必要のない場合もある。また、Ｎ値の変化が小さい場合は１７０°を越える角度でも十分な場合もある。
（８）掘削刃は連続的に設けても、断続的に設けてもよい。
【００５９】
本発明は、上記掘削刃を、羽根先端の小口面又は傾斜面と羽根下面の両面にまたがるような形状に形成して接着してもよい。
【００６０】
上記掘削刃について更に説明する。
杭を回転圧入する際には、羽根の先端に固定された掘削刃によって地盤を掘削することになる。従って掘削刃には地盤からの反力が作用するが、掘削刃が羽根の小口又は傾斜面、あるいは羽根下面のみに固定されていると、この反力によって掘削刃がもぎ取られないだけの十分な溶接が必要である。これに対して、掘削刃が羽根先端の小口面又は傾斜面と羽根下面の両面にまたがるように固定されていれば、掘削刃と羽根の接触面で地盤からの反力に抵抗できるため、溶接量を低減できる。
【００６１】
本発明は、螺旋状羽根の先端の小口面に、螺旋状羽根の回転進行方向に対して抵抗が少なくなるような傾斜面を設け、該小口面又は傾斜面に掘削刃を溶接などの方法で接接着し、羽根下面と掘削刃の下面のなす角度を、略１３５°〜１７０°としてもよい。
【００６２】
本発明は、上記掘削刃を、羽根先端の小口面又は傾斜面と羽根下面の両面にまたがるような形状に形成して接着してもよい。
【００６３】
本発明は、第１〜第７のいずれかの発明において、羽根の先端を、鋼管と羽根の接合部付近を頂点とする多角形形状又は円弧形状に形成し、前記接合部からの羽根の突出長さを、鋼管と羽根の溶接に必要な最小寸法程度としてもよい。
【００６４】
上記羽根について更に説明する。
羽根の先端の形状には、直線形状、三角形状、四角形状等の種々の多角形状や、円弧形状がある（掘削刃は、先端形状にそって製作される）。鋼管の先端と羽根の接合部において、羽根の先端は鋼管との接合部よりも突出させた方が、溶接や地盤の掘削という面から望ましいが、突出長さが大きくなると、施工中の地盤掘削に伴う地盤からの反力によって、羽根をもぎ取るような力が作用し、鋼管と羽根の溶接が切れてしまう場合がある。従って、該突出長さは羽根と鋼管の溶接に必要な最小限の長さ程度としておくことが望ましい。
【００６５】
第８の発明は、第１〜第７のいずれかに記載の、先端に螺旋状の羽根を固着した回転圧入鋼管杭を吊り上げ、該螺旋状羽根のピッチに対応する凹溝を設けたチャックカラー又はチャック部材を有するチュービング装置を地盤上の所定位置に設置し、吊り上げた前記回転圧入鋼管杭を回転させ、先端の螺旋羽根を前記チュービング装置の凹溝に挿入し、鋼管杭軸部を前記チャックカラー又はチャック部材によって締め付けて把持し、該チャックカラー又はチャック部材をチュービング装置中の回転装置により回転させ、鋼管杭を回転駆動して地盤中に埋設することを特徴とする鋼管杭の施工方法である。
【００６６】
第８の発明を更に説明する。
本施工方法は、鋼管の外径よりも外側に突出した羽根の外周部分が、鋼管の軸に対して放射状にほぼ直角に形成したことにより、直角に形成することが必要な施工機械を使用するものである。従来は、螺旋状に切り欠いた鋼管の先端に鋼管の内外両面に羽根が張り出すような形で固定し、かつ鋼管杭と羽根のなす角度をほぼ直角とする方法は見いだされていなかったため、本施工方法は実施できなかった。本発明により、既存の場所打ちコンクリート杭用の孔掘削などに使用していた施工機械と溝付チャックカラーを組み合わせることによって大径で、且つ前述の羽根形状を持った回転圧入鋼管杭の施工が可能となり、また羽根が受ける地盤反力方向が鋼管杭の推進方向と一致するので、大径の鋼管杭を効率良く施工することが可能である。
【００６７】
【発明の実施の形態】
［第１実施形態］
本発明の第１実施形態を図を参照して説明する。
図１（Ａ），（Ｂ）、図２（Ａ），（Ｂ），（Ｃ）は、先端が開端の回転圧入鋼管杭を示し、この鋼管杭１の先端には、内縁１０と外縁１１が鋼管杭１の内側と外側に所定寸法張り出した螺旋状羽根２を備えている。また、鋼管杭先端部３は螺旋状に切断されており、その始端５と終端４の段差部分６を円弧状に形成してある。
【００６８】
螺旋状羽根２の外径（Ｄ₂）は、鋼管杭外径（Ｄ）の略１．５〜３倍の外径で、螺旋状羽根２の内径（Ｄ₃）は、鋼管杭内径（Ｄ₁）の略０．４〜０．９倍の内径とし、ドーナツ状鋼板を用いて当該螺旋状羽根２が構成される。つまり、このドーナツ状鋼板を半径方向に１箇所切断し、一方を円周方向始端８、他方を円周方向終端７として、螺旋状に切断した鋼管杭先端部３に同心円状に溶接固定し、この螺旋状羽根２の内縁１０と外縁１１を鋼管杭先端部の内外に張り出して構成する。図示例において、鋼管杭１の肉厚を１２ｍｍ、外径（Ｄ）を１０００ｍｍ、内径（Ｄ₁）を９７６ｍｍとしたとき、螺旋状羽根２の外径（Ｄ₂）を１５００ｍｍ〜３０００ｍｍの範囲に設け、螺旋状羽根２の内径（Ｄ₃）を３９０ｍｍ〜８７８ｍｍの範囲に設けてある。
【００６９】
前記において、鋼管杭先端部３の螺旋の始端５と終端４の段差部分６には回転圧入時に大きな力が作用するが、この段差部分６を図２（Ａ）に示すように、円弧状部に形成してあることにより１ケ所に応力集中することがなく、ここに亀裂が発生することがない。比較例として図３に、鋼管杭先端部３の螺旋の始端５と終端４の段差部分６に隅角部９がある場合を示す。この場合、鋼管杭の回転圧入時隅角部９に応力集中を発生し、図のような亀裂２２を生じる可能性がある。
【００７０】
また、羽根の内縁１０と外縁１１を鋼管杭先端部３の内側と外側に張り出して構成する螺旋状羽根２によって、その中心部に開口部１２が形成されて、回転圧入鋼管杭は開端杭となる。螺旋状羽根２の外径（Ｄ₂）を、鋼管杭外径（Ｄ）の略１．５〜３倍の外径で、螺旋状羽根２の内径（Ｄ₃）を鋼管杭内径（Ｄ₁）の略０．４〜０．９倍の内径とした数値は、実験とシミュレーションの結果得られた数値であって、この数値の範囲内であると、大径杭の地中への円滑な貫入と、杭の支持機能確保の両条件を満たすことが可能であるが、この数値を外れると両条件を円滑に満すことがむずかしかった。
【００７１】
本発明の実施形態においては、図４（Ａ）〜（Ｆ）に示すように螺旋状羽根２の先端の小口面１３又は、小口面に設けた傾斜面１７に掘削刃１４,１８が設けられる。小口面に設けた傾斜面は、螺旋状羽根２の回転進行方向に対して抵抗が少なくなるように設けられて入る。掘削刃１４,１８は、小口面１３又は傾斜面１７に溶接などの方法で接合してある。図示例の場合、螺旋状羽根２に前記の傾斜を与えるため、羽根下面と掘削刃１４,１８の下面のなす角度θを、ほぼ１３５°〜１７０°に設けてある。
【００７２】
図４を順に説明すると、図（Ａ），（Ｂ）では掘削刃１４は、頂部１５が中間よりやや外寄りに位置する平面略山形状で、その基端面を羽根先端の垂直な小口面１３に溶接してあり、角度θを、略１３５°〜１７０°に設けてある。図（Ｃ），（Ｄ）は図（Ａ），（Ｂ）に示す掘削刃１４の変形例であり、いずれも、羽根先端の上部を傾斜させてあり、この傾斜先端の小口面１３に掘削刃１４の基端面が溶接してあり、羽根先端の傾斜面と掘削刃１４の上面の傾斜面とが接続するように設けられている。
【００７３】
図４（Ｅ），（Ｆ）は、掘削刃のさらに他の変形を示す。この例では、羽根先端を平面略山形状とし、この山形状先端１６に傾斜面１７を形成し、この平面山形の傾斜面１７に複数の掘削刃１８を櫛歯状に等間隔で、かつ角度θを、略１３５°〜１７０°に設けて溶接した例を示す。
【００７４】
図５（Ａ）〜（Ｃ）は、羽根先端の平面形状の他例を示す。同図（Ａ）には、羽根先端に掘削刃として内周側が尖ったナイフ状の傾斜面１９を一体形成した例を示し、図（Ｂ）には、図４（Ｃ），（Ｄ）と同じ構造の掘削刃１４を中間に頂部１５がある平面略山形状に構成した例を示し、図５（Ｃ）には、羽根先端に内周側が尖ったナイフ状の傾斜面１９を形成し、この傾斜面１９にナイフ状の掘削刃２０を溶接した例を示す。掘削刃の形状は図示以外のものであっても構わない。
【００７５】
図６（イ）は、羽根の先端に取り付けた掘削刃の平面図であり、（ロ）、（ハ）は、掘削刃を羽根の小口面と羽根下面の両面にまたがるように接着した本発明の実施例及び掘削刃の詳細図である。（ニ）は、掘削の際の掘削刃に作用する地盤からの反力（Ｒ１，Ｒ２）に対する抵抗機構を図示したものであり、（ニ）左図においてはＲ２に対してはＲ２'という力で抵抗するが、Ｒ１に対しては溶接部のみで抵抗することになる。これに対して（ニ）右図ではＲ１，Ｒ２に対してそれぞれＲ１'、Ｒ２'という力で抵抗できるため、溶接量を低減できる。
また図７（イ）では、鋼管先端と羽根の接合部からの羽根の突出量を最小限にしている状態を示している。
図７（ロ）は、該突出量が大きかった場合に、施工中に作用する力によって羽根がもげている状態を示した図である。施工中の地盤掘削に伴う地盤からの反力によって、羽根に鋼管端面からをもぎ取るような力が作用し、鋼管と羽根の溶接が切れてしまう場合がある。従って、該突出長さは図７（イ）のように、羽根と鋼管の溶接に必要な最小限の長さ程度としておくことが望ましい。
【００７６】
次に、図８（Ａ），（Ｂ）は、鋼管杭１内に進入する土砂の閉塞促進用突起２１を鋼管内周に具備した例を示す。図示例では、閉塞促進用突起２１は溝形鋼で構成され、この所定長さの溝形鋼を縦にして、かつ鋼管内円周方向に所定間隔で複数（図示例では、９０°間隔で４個）配置し、各溝形鋼の両側縁を鋼管内周面に溶接してある。この閉塞促進用突起２１は、本実施例では開端状の鋼管杭１の杭先端３ａより鋼管の内径（Ｄ₁）の略０．５〜２倍の高さ範囲の鋼管杭内部に設けられている。図８の鋼管杭１の他の構成は図１、２の鋼管杭１の構成と同じである。
【００７７】
実験結果では、前記の溝形鋼からなる閉塞促進用突起２１は、鋼管内周面全周でなくて、図示のように間隔をあけて複数設けるだけで、土砂の閉塞促進効果が十分あることが確認された。このように、閉塞促進用突起２１による土砂の閉塞促進と圧密効果で鋼管杭１の支持層への貫入量が低減できるので施工時間を短くできる。この溝形鋼からなる閉塞促進用突起２１は、鋼管杭１の内周への溶接加工も比較的容易で製作コスト的にも有利になる。また、図示省略するが、前記の溝形鋼にかえて、鋼製ブロック、帯鋼板または型鋼を、鋼管の内径の略０．５〜３倍の高さ範囲の杭周方向に間隔を隔てて複数溶接固定して構成してもよい。すなわち、縦リブ型形状に限定する必要はなく、角リブ型形状、横長リブ型形状であっても、ほとんど同様の効果を奏する。
【００７８】
さらに図示省略するが、前記の鋼製ブロック、溝形鋼、帯鋼板または型鋼等に変えて、閉塞促進用突起２１を、鋼管杭１の内周へ溶接固定された１段または複数段の鋼製ドーナツ状リブで構成し、その外径が鋼管杭の内径と一致し、内径が鋼管杭内径（Ｄ₁）の略０．９〜０．７倍になるように設けるのがよい。１段で鋼製ドーナツ状リブを構成する必要がある場合は、板厚が厚くなるので、内径が鋼管杭の略０．９〜０．７倍の鋼製ドーナツ状リブを設ける方が、一枚のリブの厚みが増大せず、コスト的に優れている。例えば、リブの内径が、０．５Ｄ₁の場合の板厚は、リブの内径が、０．８Ｄ₁の場合の板厚の２倍程度必要となる。この場合は、内径が、０．８Ｄ₁のリブを杭軸方向に２段に設ける方が、溶接面、加工での作業性で優れている。
【００７９】
図１２は、螺旋羽根２における鋼管１の外周から外側に突出した部分と、鋼管杭本体１の軸とのなす角が直角となるように、杭本体１の先端部螺旋羽根２を取り付けた状態を示している。羽根２が受ける地盤の反力が鉛直方向に作用するので、鋼管杭の推進方向と一致し、効率よく圧入推進力を得ることができる。従来よりも小さな回転力及び推進力で、大径の杭を固い支持層にまで貫入することが可能となった。
【００８０】
また、直角であることにより、既存の施工機械を使用して、大径の鋼管杭１の施工が可能となった。図３１に示すように、従来工法においては、主として施工機械６０を使用していたが、図３２に示すような、鋼管杭本体を外側から把持して回転させる形式の施工機械７０すなわち図３２と図３３に示すチュービング装置７０を使用する施工方法が採用される。
このチュービング装置７０を用いるときは、羽根径の大きさと羽根の螺旋ピッチに対応する凹溝を形成した、溝付きチャックカラーを用いる必要がある。
【００８１】
ここで図３３に示す溝付チャックカラーについて説明すると、溝付のチャックカラーを用いない従来の工法では、回転圧入鋼管杭は杭鋼管径よりも先端羽根径がかなり大きいので、回転圧入杭のチュービング装置への装着は、カラーを取り付けていない状態で地面に設置したチュービング装置に回転圧入鋼管杭を挿入してから、クレーンで吊り上げたチャックカラー（溝無し）をチャック装置に取り付ける方法か、回転圧入鋼管杭を、まず施工機械６０を用いて地面上に設置しておいて、予めチャックカラー（溝無し）を取り付けたチュービング装置をクレーンで吊り上げ、回転圧入鋼管杭の上部から被せて設置する施工方法が採用されていた。前者の方法は、複数のチャックカラーを回転圧入鋼管杭とチャック装置の間に挿入して固定しなければならず、作業工程が非常に面倒であった。後者の方法では、重量のあるチュービング装置を高い位置まで吊り上げるので危険を伴い、能力の大きなクレーンを必要とすると共に、設置作業を慎重に行うため長時間の作業になってしまうという欠点があった。溝付きチャックカラーを使用すれば、チュービング装置に対する回転圧入鋼管杭の装着工程を簡略にして効率よく施工することができる。溝付チャックカラーを用いた場合は杭の装着を数分程度で完了できるのに対し、前記の２つの方法では３０分から１時間は必要であった。
なお図３３は、チュービング装置７０における、ケーシングチューブ回転装置７５、チャック装置７８、回転杭７３、掘削羽根７３ｂ、チャックカラー７４の主要な構成を示している。
【００８２】
図３３に示すように、チャックカラーの溝は回転圧入鋼管杭の羽根の螺旋形状に対応しており、杭を上部から吊り込んで人力により回転させると、溝の間を羽根が通過する構造になっており、螺旋羽根は鋼管軸部に対してほぼ直角に固定されていることが必要である。羽根が杭鋼管に対して直角でない場合には、チャックカラーの溝を広くする必要があるが、その分凸部が薄くなってしまう。この凸部は杭鋼管を把持すると共に、回転力を伝達し、必要に応じて押込み力や引き抜き力も伝達する必要があり、凸部の付け根が現状よりも薄くなるとこれらの力を伝達するための強度・剛性が不足してしまう。また、凸部先端の面積が小さいと、杭を把持する際に杭に作用する圧力が大きくなり、杭鋼管に損傷を生じるなどの問題がある。
該溝付きチャックカラーを用いることで大径杭の施工が非常に効率的になるが、そのためには、螺旋羽根は杭軸部に対してほぼ直角に取り付けられている必要があった。つまり、大径の回転圧入杭施工のためには、杭軸部と羽根がほぼ直角に固定されていることが必須であり、本願発明は、このチュービング装置を使用する施工方法により、大きな効果を奏している。
【００８３】
鋼管杭はいうまでもなく、地中の礫・砂・粘性土等からなる固い支持層に貫入して、主として上部構造物による上からの圧縮力に対して支持力を発揮するものであり、杭先端面によって支えられている。したがって、鋼管の外側に羽根を固定すると、図３８(イ)、（ロ）に示すように、螺旋羽根は片持ち梁のような形状となり、羽根付け根及びその近傍の鋼管部分に大きな曲げモーメントが作用し、鋼管内側方向に変形が生じる。
この曲げモーメントに抵抗して鋼管の変形を防止するために、杭先端の羽根を固定している部分の鋼管を、支持力から必要となる板厚よりも厚くする必要があり、その厚さは支持力から必要な厚さと比べて、２〜３倍程度になることも多い。鋼管の必要厚さが極厚になると、鋼管作製のコストもアップするという問題を生じる。
【００８４】
図３９（イ）に示すように、従来技術３の羽根は鋼管の先端に固定されており、羽根は鋼管の内・外両側に張り出している。このことによって、内側・外側の羽根がそれぞれ地盤から受ける反力による曲げモーメントが、鋼管と羽根の接続位置で打ち消し合うため、鋼管に作用する曲げモーメントはかなり小さくなる。従って、鋼管杭先端部の板厚も、相当に薄くすることができる。鋼管の厚さは、羽根の内・外面への張り出し量のバランスなどの条件にもよるが、支持力から決定される板厚と同厚程度とすることも可能である。本発明のように、鋼管杭先端に螺旋羽を取り付けた開端杭の鋼管の板厚については、羽根中央部の開口が比較的大きいことから、従来技術３ほどには板厚を低減することができないが、図３９（イ）、（ロ）に示すものよりは板厚を低減できる。
【００８５】
【発明の効果】
本発明によると、特に大径の羽根付き回転圧入鋼管杭の開端杭において、鋼管杭先端部の内外に螺旋状羽根を張り出して、かつ、該螺旋状羽根が鋼管杭の外周より外側に突き出た部分と鋼管杭本体とのなす角度が略直角となる構造であるので、従来の閉端杭または開端杭の何れによっても解決できなかった、円滑な施工と、十分な杭支持機能と、製作の容易性の問題点が解決されたものである。すなわち本発明に係る回転圧入鋼管杭により、大径の羽根付き回転圧入鋼管杭であっても、その施工、実用化が可能となったものである。本発明は、大径以外の中径等の回転圧入鋼管杭にも勿論適用できるものである。さらに、鋼管内に進入した土砂の閉塞促進用突起を設けたので、支持層への根入れが１Ｄ（Ｄ：杭径）程度でも鋼管杭の支持力を閉端杭と同程度にまで、大きく増加することを可能とした。この閉塞促進用突起は、鋼管への取り付け作業が極めて容易であり、コストも低減され、しかも閉塞効果においても、従来技術に比べて優れた効果を奏するものである。
【００８６】
また、掘削刃を羽根の小口面と羽根下面の両面にまたがるように接着したので、掘削の際の地盤からの反力を抑えて、掘削を推進することができる。さらに、鋼管先端と羽根の接合部からの羽根の突出量を最小限にしたので、施工中に作用する地盤の反力によって、羽根が鋼管端面からもぎ取られたり、鋼管と羽根の溶接が切れてしまう恐れが解消した。
【００８７】
また、羽根の外周部分が鋼管に対してほぼ直角に張り出しているので、大きな推進力が得られ、必要な回転トルクが縮減され、加えて、チュービング装置に適用可能としたので、大径の鋼管杭であっても既存の施工機を用いてを施工することができるようになった。こうして、施工時に資材、労力、施工時間等の面で、大幅なコストの削減を可能とした。
【図面の簡単な説明】
【図１】 （Ａ）は本発明に係る回転圧入鋼管杭の正面図、（Ｂ）は同縦断面図である。
【図２】 （Ａ）は回転圧入鋼管杭の上方斜視図、（Ｂ）は同じく下方斜視図、（Ｃ）は同じく平面図である。
【図３】 本発明の比較例として杭先端の螺旋状部の始端と終端の段差部に隅角部が形成された回転圧入鋼管杭の斜視図である。
【図４】 （Ａ）、（Ｂ）は掘削刃の第１例の斜視図と断面図、（Ｃ）、（Ｄ）は掘削刃の第２例と第３例の断面図、（Ｅ）、（Ｆ）は掘削刃の第４例の斜視図と断面図である。
【図５】 （Ａ）、（Ｂ）、（Ｃ）は掘削刃の更に他の３例を示す説明図である。
【図６】 （イ）、（ロ）、（ハ）は本発明の掘削刃の詳細図であり、（ニ）は説明図である。
【図７】 本発明の螺旋羽根先端の掘削刃と鋼管先端との接着位置を示す説明図である。
【図８】 （Ａ）は本発明の実施形態に係る回転圧入鋼管杭の正面図、（Ｂ）は同平面図である。
【図９】 （Ａ）、（Ｂ）は本発明と従来例の鋼管杭の作用説明断面図である。
【図１０】 閉塞促進用突起の効果を調べるために行った実験結果の一例を示す図で、（Ａ）は、閉塞促進用突起を設けた場合の試験体の説明図、図（Ｂ）は閉塞促進用突起を設けない場合の試験体の説明図で、図（Ｃ）は、図（Ａ）、（Ｂ）の試験結果として鉛直荷重と変位の関係をグラフで示した図である。
【図１１】 土砂の持つダイレタンシー特性の説明図である。
【図１２】 本発明の杭本体と掘削羽根とを直角に取り付けたことを示す断面図である。
【図１３】 本発明の螺旋羽根の板厚の説明図である。
【図１４】 本発明の螺旋羽根の板厚の他の例を示す説明図である。
【図１５】 本発明の螺旋羽根のドーナツ状鋼板の切断位置を示す説明図である。
【図１６】 本発明の螺旋羽根のドーナツ状鋼板を扇形に切断した説明図である。
【図１７】 従来技術１、２、３、４、の概念図である。
【図１８】 従来技術１の説明図である。
【図１９】 従来技術３の概略を示す斜視説明図である。
【図２０】 従来技術３の切り込みを示す説明図である。
【図２１】 従来技術３の閉じ板を示す説明図である。
【図２２】 従来技術３の底板に設けた掘削刃を示す説明図である。
【図２３】 従来技術３の底板に設けた掘削刃を示す説明図である。
【図２４】 従来技術３の開口部を示す説明図である。
【図２５】 従来技術３の螺旋羽根の説明図である。
【図２６】 従来技術３の螺旋羽根の説明図である。
【図２７】 従来技術３の羽根と杭軸との角度を示す説明図である。
【図２８】 同じく従来技術３の羽根と杭軸との角度を示す説明図である。
【図２９】 従来技術３の閉塞部材を示す説明図である。
【図３０】 従来技術４の説明図である。
【図３１】 従来の施工方法及び施工機械を示す説明図である。
【図３２】 本発明の施工方法及び施工機械を示す説明図である。
【図３３】 本発明の施工機械のチュービング装置を示す詳細説明図である。
【図３４】 貫入のメカニズムの説明図である。
【図３５】 従来技術３の説明図である。
【図３６】 本願発明と従来技術の塑性歪みと亀裂を対比した説明図である。
【図３７】 本願発明と従来技術の塑性歪みと亀裂の説明図である。
【図３８】 従来技術における曲げモーメントの作用を示す説明図である。
【図３９】 本発明における曲げモーメントの作用を示す説明図である。
【符号の説明】
１ 鋼管杭
２ 螺旋状羽根
３ 先端部
３ａ 杭先端
４ 終端
５ 始端
６ 段差部分
７ 円周方向終端
８ 円周方向始端
９ 隅角部
１０ 羽根の内縁
１１ 羽根の外縁
１２ 開口部
１３ 小口面
１４ 掘削刃
１５ 頂部
１６ 山形状先端
１７ 傾斜面
１８ 掘削刃
１９ ナイフ状の傾斜面
２０ 掘削刃
２１ 閉塞促進用突起
２２ 亀裂
２３ 従来鋼管杭
２４ 支持層
２５ 軟弱層
２６ 鋼管内に進入した支持層の土砂
２７ 鋼管内に進入した軟弱層の土砂
３０ 鋼管杭
３１ 螺旋状羽根
３２ 底板
４０ 鋼管杭
４１ 螺旋状羽根
４２ 切り込み
４３ 土砂進入孔
４４ 閉じ板
４５ 掘削刃
５０ 鋼管杭
５１ 螺旋状羽根
５２ 切り込み
５３ 土砂進入孔
５４ 閉塞部材
５５ 鋼管杭
５６ 螺旋状羽根
５７ 開口リブ
５８ 有孔筒状部
６０ 従来の施工機械
７０ 本発明に使用する施工機械：チュービング装置
７３ 回転杭
７３ｂ 掘削羽根
７４ チャックカラー
７５ ケーシングチューブ回転装置
７８ チャック装置
８０ 鋼管杭
８１ 螺旋状羽根[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a rotary press-fit steel pipe pile in which a spiral blade is attached to the tip of a steel pipe.
[0002]
[Prior art]
  Many methods have been proposed in the past for applying rotational force to a rotary press-fit steel pipe pile provided with a spiral blade at the tip of the steel pipe and penetrating it into the ground, some of which have already been put into practical use. If these construction methods are classified from the steel pipe pile tip shape, there are two types: an open-ended pile whose tip is open and a closed-end pile whose tip is closed. From the viewpoint of the position where the blade is attached to the tip of the pile, the blade is fixed to the outer periphery of the steel pipe, the tip of the steel pipe is notched in a spiral shape, and the spiral blade is fixed to the surface There are two types. Further, many combinations of these have been proposed or used, but typical types of conventional types are roughly classified into four types and described with reference to FIG. 17 (described later).
[0003]
  Needless to say, the piles must penetrate into a hard support layer made of underground gravel, sand, cohesive soil, etc. to ensure that the support capacity is exerted. Depending on the application, various rotary press-fit steel pipe piles are required, from small-diameter piles with a pile diameter of about 100 mm to large-diameter piles with a pile diameter exceeding 1000 mm. In this case, in order to construct a rotary press-fit steel pipe pile that is a large-diameter pile and requires a high bearing capacity compared to a small-diameter pile, there are various problems in terms of cost, construction method, support function, production aspect, etc. Exists.
[0004]
  FIG. 17 is a schematic diagram showing the performance characteristics of each type of conventional rotary press-fit steel pipe pile. Hereinafter, the problem of each type will be clarified with reference to the drawings.
[0005]
  (1-1) Conventional type 1
  The steel pipe pile of the conventional type 1 of FIG. 17 is a closed end pile as shown in a schematic diagram, and the blades are fixed to the outer periphery of the steel pipe, not the tip of the pile main body steel pipe.
  As an example of conventional type 1,Patent Document 1(Hereinafter referred to as a conventional type 1 embodiment). As shown in FIG. 18, this steel pipe pile 30 in which a spiral blade 31 is fixed to the outer peripheral surface of the pile tip portion is a closed-end pile, and a bottom plate provided with an excavating blade 34 at the lower part of the steel pipe pile main body 30. 32 is fixed, and a spiral blade 31 of about one turn having an outer diameter about twice as large as the outer diameter of the lower end of the steel pipe is provided.
  As for the excavating blade 34, those that do not require this have been proposed.
[0006]
  (Problems of conventional type 1)
  In Conventional Type 1, since the blades are fixed to the outer periphery of the closed end steel pipe, the ground at the tip of the steel pipe shaft cannot be excavated. Therefore, the penetration resistance at the tip of the steel pipe is very large, the penetration does not proceed during construction, and a slip phenomenon often occurs, and the workability is not good. The slip phenomenon is a state in which the pile hardly penetrates in the depth direction, and the pile penetrates little by little while idling at almost the same position, or cannot penetrate at all. When a slip phenomenon occurs, the surrounding earth and sand will be disturbed by the blades, and the bearing capacity will be affected. When a deeper position is penetrated while causing a slip phenomenon, the friction of the disturbed portion is reduced. When the penetration of the support layer is performed while causing a sliding phenomenon, the sediment on the lower surface of the blade is disturbed, or a gap is formed on the lower surface of the blade, and the vertical support force at the tip is reduced.
  In order to reduce the penetration resistance, a vertical excavation blade 34 may be provided on the tip bottom plate portion 32 of the steel pipe pile 30. However, the excavation blade 34 has an effect of reducing the penetration resistance by excavation of the tip earth and sand. In order to disturb the earth and sand, even if it is a closed-end pile, the bearing capacity will be adversely affected.
[0007]
(Penetration amount, rotational torque and construction machine)
  When construction is performed so that the depth of penetration of the pile per revolution (hereinafter referred to as the amount of penetration per revolution) is substantially the same as the height of the stepped portion of the blade (hereinafter referred to as the blade pitch), Therefore, it is considered that this is the most desirable construction condition. However, when the penetration of the conventional type 1 is performed so that the amount of penetration per rotation and the blade pitch are substantially matched (hereinafter referred to as ideal penetration), the torque required for construction is estimated to be approximately 1.6 of the present invention. It will be about double. The increased torque required for construction means that the necessary construction machinery will also be large, which will not only increase the construction cost, but also the existing construction machinery will lack capacity if the piles have a large diameter. Therefore, the construction with ideal penetration becomes impossible. As in the case of the slip phenomenon, if the amount of penetration per rotation is made considerably smaller than the blade pitch, the torque at the time of construction will be reduced, but such construction will adversely affect the supporting force as described above.
[0008]
  (1-2) Conventional type 2
  Conventional type 2 is an open end of conventional type 1. As an example of conventional type 2,Patent Document 2(Hereinafter referred to as a conventional type 2 embodiment).
  (Problems of conventional type 2)
  Although the penetration resistance is smaller than that of the closed-end pile due to the open-end pile, the blades are fixed to the outer periphery of the steel pipe, and the steel pipe portion projects to the bottom of the blade. Therefore, at the time of the penetration of the pile, the protruding steel pipe portion becomes the penetration resistance, and although the penetration is improved as compared with the conventional type 1, the penetration resistance is still considerably large.
  The torque required for ideal intrusion construction for this type is approximately 1.4 times that of the present invention, which is better than the conventional type 1, but it is still difficult to construct large-diameter piles. It is.
  In addition, since the tip is an open end, it is difficult to secure a supporting force. In order to improve this point, proposals have been made to make it easy for the open end part to be blocked with earth and sand. It is necessary to satisfy the condition of doing, and another means for that is required.
[0009]
(1-3) Conventional type 3
  In the conventional type 3, the tip of the steel pipe is cut out in a spiral shape, and a blade processed into a spiral shape corresponding to the cut-out surface is fixed to the tip of the steel tube, and the tip portion of the steel pipe is almost closed by the blade. It is classified as a closed-end pile. Since this type does not have a steel pipe protruding from the lower surface of the blade as in the conventional type 1, the penetration resistance during construction is reduced.
  With regard to the shape of the tip of the shaft portion, in some cases, only a small hole is provided in the vicinity of the center of the spiral blade, so that it can be regarded as a closed end. Regarding the step shape at the tip of the shaft part, there is a small V-shaped opening in the side view inside the steel pipe, but the opening area is small and the amount of soil entering is small. In particular, the V-shaped root portion hardly contributes to the ingress of earth and sand.
  As an example of conventional type 3,Patent Document 3Steel pipe piles (hereinafter referred to as Example-1 of conventional type 3). As shown in FIG. 19 to FIG. 23, the distal end portion of the pile main body 40 cut out in a spiral shape, with the distal end portion of the tubular pile main body 40 cut substantially spirally along the outer periphery of the distal end. A circular bottom plate 41 having a diameter about twice that of the pile main body 40, and a spiral bottom plate 41 serving as an excavating blade formed by cutting a radial cut 42 reaching the center along the tip end surface. Welded.
[0010]
  (Problems of conventional type 3)
  Although this type can reduce the penetration resistance as compared with the conventional type 1 as described above, since the tip shape is almost closed, the penetration resistance is not so reduced as compared with the conventional type 2 which is an open end shape. If earth and sand enter the pipe during construction from the hole near the center of the blade or the stepped portion of the spiral blade, the penetration resistance will be reduced by that amount, but according to the description of the above method, the hole diameter of the spiral blade is small, The step of the blade is V-shaped with the inner side being smaller than the outer side, and the opening area of the step portion is considerably small. Therefore, there is little entry of earth and sand into the pipe, and it hardly contributes to the reduction of penetration resistance.
  That is, since the conventional type 3 has a substantially closed end shape, the support force has high reliability, but the penetration resistance is comparable to that of the conventional type 2, and the construction becomes difficult when a large-diameter pile is used. Even in this type, the torque required for ideal penetration is approximately 1.4 times that of the present invention.
[0011]
  In addition, as shown in FIGS.Patent Document 3In the steel pipe pile 40 according to the second aspect of the present invention, a drilling blade 45 having a stepped blade is fixed to a spiral bottom plate 41. Since this excavating blade 45 disturbs the soil below the tip of the steel pipe pile 40 during construction, the workability is improved, but the tip ground that contributes to the tip support force of the steel pipe pile 40 is disturbed, so the support force is reduced. The problem arises.
  thisPatent Document 3According to the third aspect of the present invention, the steel pipe pile 40 is provided with the earth and sand entrance hole 43 for guiding the earth and sand softened by excavation and softening into the pile main body 40 at the center of the spiral bottom plate 41. And since the part becomes an open end, the possibility that a supporting force will fall arises. Further, as shown in FIGS. 19 to 21, if the diameter of the earth and sand entering hole 43 is reduced, it is judged that the improvement in workability cannot be expected so much though there is almost no influence on the supporting force.
[0012]
  Also,Patent Document 3According to the above, “because the spiral bottom plate 41 is fixed to the tip of the pile body 40, the bending moment of the spiral bottom plate 41 does not act on the pile body 40”. When a spiral bottom plate with a diameter about twice that of the pile body is fixed, it is impossible to generate a bending moment in the pile body itself, depending on the condition of the ground under construction. In order to make it as small as possible, at least the size of the sediment entry hole 43 must be made quite small.
  The purpose of allowing the earth and sand to enter the pile body 40 is to reduce the tip resistance when the steel pipe pile 40 penetrates and to improve the workability. Since the closing plate 44 that closes the gap between the start end ac and the end a′c ′ of the spiral bottom plate 41 is provided in FIG. 21, the effect of the soil and sand entering the pile body 40 is further reduced. It is judged that there is not much effect on the improvement of sex. Even in the absence of the closing plate 44, the cutting surface of the starting end ac and the terminal end a'c 'of the bottom plate 21 is V-shaped. The approach is not promoted, and the effective area for entering the earth and sand is only about half of the opening area.
[0013]
  (Other examples of conventional type 3)
  Patent Document 424 to FIG. 29 (hereinafter referred to as a conventional type 3 embodiment-2) is disclosed. 24-29 is explanatory drawing of a screwed-type steel pipe pile.
  the abovePatent Document 4The screw-type steel pipe pile 50 according to claim 1 is a closed-end pile, and a substantially circular steel plate having a diameter larger than the diameter of the steel pipe 50 is directed from the circumference to the center of the circle as shown in FIGS. A notch 52 is inserted and bent into a shape corresponding to the shape of the lower surface of the tip of the steel pipe to form a spiral plate 51, which is attached to the tip of the steel pipe 50 cut into a spiral shape.
[0014]
  As shown in FIGS.Patent Document 4The screwed steel pipe pile 50 according to claim 2 is a pile in which a spiral blade is attached to the tip of the pile and the tip of the pile is closed. In the case of closed-end piles, the blocking effect of piles due to the consolidation of earth and sand entering the steel pipe as in open-ended piles does not affect the bearing capacity. However, when the closed-end pile is rotationally press-fitted, the penetration resistance of the tip increases because the pile tip is closed. The penetration resistance increases in proportion to the area of the closed portion at the tip of the pile, and the torque (screwing force) required for construction is proportional to the second to third power of the pile diameter. This is not a big problem when the pile has a small diameter. However, in the case of a large-diameter pile (for example, a pile diameter of about 1000 mm or more), the construction machinery required for the pile diameter becomes excessive, and in reality the construction is Nearly impossible.
  In addition, the shape of the stepped portion at the beginning and end of the spiral blade is V-shaped inside the steel pipe as viewed from the side, and the blade mounting angle on the outer periphery of the steel pipe does not become a right angle, so the thrust force is lost. As a result, the workability decreases.
[0015]
  Further, as shown in FIG. 29, a portion surrounded by the steel pipe is closed by a closing member 54 in the opening formed by the difference between both ends of the spiral blade 51. Therefore, earth and sand do not enter the inside of the steel pipe 50, and it is difficult to improve workability. Further, even in the case where the closing member 54 is not provided, for the same reason as in Example 1 of the conventional type 3, the effective opening ratio with respect to the ingress of earth and sand is about ½, and the improvement in workability is not so great. . This meansPatent Document 4It is also clear from the statement that "Since the sand is hardly penetrated into the steel pipe because the opening of the staggered portion formed by bending the spiral plate is small".
  Also,Patent Document 4In the [Problems to be Solved by the Invention] column, there is a description that “a steel pipe pile having a widely used outer diameter of 500 to 600 mm is a big problem in design”, and the [Effects of the Invention] column. Describes that "the present invention can also be implemented in a screwed steel pipe pile made of a steel pipe having a large diameter (for example, 600 mm)."
  That is, in this invention, a large-diameter pile is at most about a pile diameter of about 600 mm (this is referred to as a medium diameter in the present invention), and a large-diameter pile having a pile diameter exceeding 1000 mm is not targeted. Is clear.
[0016]
  (1-4) Conventional type 4
  Patent Document 5Discloses an open-ended pile as shown in FIG. This is an open-ended steel pipe pile 55 provided with a spiral blade 56 at the tip, provided with an opening rib 57 that facilitates blockage of earth and sand when the steel pipe pile is buried inside the steel pipe pile above the steel pipe tip. This is a steel pipe pile in which a perforated cylindrical portion 58 is formed by the inner periphery of the steel pipe below the opening rib 57 and the opening rib 57.
[0017]
  (ConventionaltypeProblem 4)
  Conventional type 4 is a steel pipe pile with the open end of the pile, and an opening rib (hereinafter referred to as a closure promoting ring) for promoting blockage of earth and sand is attached to the inner surface of the steel pipe of conventional type 2 and attached to the support layer. The support force can be expressed even if the amount of the root is small. This is conventionaltypeIt has been proposed in order to develop a supporting force by making the penetration resistance smaller than that of the closed-end pile of 1 and by closing and compacting the earth and sand entering the steel pipe at the tip of the pile when the support layer is installed. This conventionaltypeIn No. 4, the opening rib is merely arranged in a donut shape on the inner surface of the steel pipe pile, and the inner diameter of the closing promotion ring and the desirable dimensions for the mounting position of the inner surface of the steel pipe are not disclosed. In addition, when it is necessary to reduce the inner diameter of the donut-shaped ring in order to close the earth and sand, there is a problem that the thickness of the ring increases and the cost increases.
  Also, since the spiral blade is attached to the outer periphery of the steel pipe,typeAlthough the press-fitting performance is improved as compared with 1, the tip end portion of the steel pipe has a press-fitting resistance during the press-fitting work.
  Further, since the blades are fixed to the outside of the steel pipe, the shape is like a cantilever, and a large bending moment acts on the blade root and the steel pipe portion in the vicinity thereof, which may cause deformation in the inner direction of the steel pipe.
[Patent Document 1]
          JP 59-85028 A
[Patent Document 2]
          JP-A-2-194212
[Patent Document 3]
          JP-A-8-326053
[Patent Document 4]
          JP-A-9-324420
[Patent Document 5]
          JP-A-8-226124
[0018]
[Problems to be solved by the invention]
  The alluvial plain where the main cities of Japan are developed is soft ground, and it is necessary to support the superstructure by penetrating the steel pipe piles to the strong support layer. Rotating press-fit steel pipe piles have a greater bearing capacity than conventional pile methods, and are superior in earthquake resistance to being steel pipe piles, and the tip of the pile penetrates into the support layer due to rotational torque. It has the performance that it can be confirmed with certainty.
  However, as is clear from the above conventional example, there are some unsolved problems in the rotary press-fit steel pipe pile. The problems are summarized below and the issues to be solved are clarified.
[0019]
  (2-1) Relationship between penetration properties and closed-end / open-end piles
  When constructing piles, the tip of the piles should generally reach the support layer (rubble / sand / viscous land). The support layer is a strong ground having sufficient strength to support the weight of the superstructure, and is often a layer having an N value (ground strength evaluation value in a standard penetration test) = 50 or more. The space between the ground surface and the support layer is a soft ground (hereinafter referred to as a soft layer). Even if it is called a soft layer, there is a variation of about 0 to 50 in terms of N value (even if N value = 50, if the layer thickness is thin, it may not be a support layer. A layer that is a hard layer but cannot be a support layer is called an intermediate layer.), And various layers are mixed.
  If the soft layers of the ground on which the piles are constructed are all layers having a small N value, construction is relatively easy even for closed-type piles such as conventional types 1 and 3. However, for example, when a layer having an N value = 30 forms an intermediate layer of several meters and it is necessary to construct a pile by penetrating the layer, it is very difficult to construct a closed-end pile. Even if construction is possible, it is a case where the pile diameter is about 600 mm or less, and construction of a large-diameter closed-end pile exceeding 1000 mm is almost impossible.
[0020]
  On the other hand, in the case of an open-ended pile, if the steel pipe protrudes to the lower surface of the blade as in the conventional type 2, it has the same problems as the closed-ended pile. If the penetration resistance is reduced by fixing the spiral blade to the steel pipe tip with the steel pipe tip open, and letting earth and sand enter the pipe, the workability is improved, even if it is a large-diameter pile, the intermediate layer as described above Can be penetrated. However, the open-end pile must satisfy the condition that the open-end pile is closed with earth and sand when it penetrates into the support layer, and sufficient support force is generated.
[0021]
  (2-2) Relationship between bearing capacity and closed-end pile / open-end pile
  Needless to say, the main problem in the pile construction method is securing the bearing capacity of the pile.
  From the point of view of the tip shape, the closed-end pile is most advantageous for the bearing capacity and has high reliability. In order to sufficiently exert the supporting force in the open-end pile, it is necessary to close the opening at the tip of the pile with earth and sand. It is generally pointed out that it is necessary to penetrate the pile tip to the support layer about 5 times the diameter of the pile in order to block the pile tip and exert sufficient support force, and it is also described in "Road Bridge Specification". Yes.
[0022]
  The closed-end pile is the most advantageous shape for the supporting force, but in order to exert the supporting force surely, generally, the pile tip is penetrated into the supporting layer by about 1D (D: pile diameter). Has been done. As described above, the closed-end pile has a problem in workability, and it is very difficult to penetrate the support layer, which requires labor and time. In addition, a large-diameter pile requires a super-large construction machine, and the construction itself becomes impossible in terms of construction site conditions and cost. Therefore, many inventions have been provided to attach a downward excavation blade to a closed bottom plate, but although the workability is improved, all of them are disturbing the support layer below the pile tip and are important for securing the support force. It has the disadvantage that it results in weakening the support of the part. For these reasons, all the closed-end rotary press-fit piles that have been put to practical use so far have a diameter of about φ600 mm or less.
  For open-ended piles, workability is improved, but how to make sure that the bearing capacity is demonstrated is a challenge. Although it is said that the workability is excellent compared to the closed-end pile, in order to penetrate the support layer by about 5D, considerable labor and time are required, resulting in a cost problem. Therefore, various improvements are required.
[0023]
  (2-3) Large-diameter rotary press-fit pile and construction machine
  A rotary press-in pile is a pile in which a spiral blade is fixed to the tip of the pile, and existing construction machines used for construction are roughly classified into the following two types. The construction machine 60 shown in FIG. 31 applies a rotational force from the pile head to the pile body.And figureA construction machine 70 shown in FIG. 33 grips the pile steel pipe body and applies a rotational force to the pile body. The construction machine 60 has a relatively small torque that is generally about 30 tm or less, and is mainly used for construction of piles having a medium diameter (about φ600 mm) or less. Since the construction machine 70 has a machine having a large torque that can be exerted generally at about 400 tm, it can cope with construction of a large-diameter pile. In particular, when the intermediate layer is penetrated with a large-diameter pile or when the intermediate layer is embedded in the support layer, the required torque is very large, and the construction machine 70 is required. This construction machine 70 is an existing construction machine that has been conventionally used for hole excavation for cast-in-place concrete piles, rock excavation, and the like, and is also used for the construction of rotary penetrating piles.
[0024]
  Since the construction machine 60 has a structure in which a rotational force is applied to the pile head, joining of the pile and the construction machine is easy. However, since the construction machine 70 has a structure in which the body portion of the pile is gripped from the periphery, the rotary press-fitted pile with a blade at the tip is efficiently set on the construction machine 70 (hereinafter referred to as the tubing device 70). Requires a special jig. The present inventors have already developed this special jig (hereinafter referred to as a grooved chuck collar). As shown in FIG. 33, the grooved chuck collar is a grooved collar in which concave grooves corresponding to the spiral pitch of the blades are formed. The present inventors have proposed Japanese Patent Application No. 11-054133.(See JP 2000-248549 A)The proposal has been put into practical use.
  By using this grooved chuck collar, a rotary press-fit steel pipe pile with a blade at the tip can be inserted from the upper side of the tubing device. In contrast, when the grooved chuck collar is not used, since the blades cannot pass through the tubing device 70, the pile is first placed on the ground and the tubing device 70 is put on the pile. Will be very bad. This point will be described in detail in an embodiment described later.
[0025]
  (2-4) Relationship between the angle between the pile shaft and the blade
  Here, the angle between the pile shaft portion and the blade will be described with reference to the drawings, as shown in FIG. 12, from one point on the outer periphery of the blade projecting outward from the outer periphery of the pile steel pipe body, toward the pile shaft center, It means the angle between the straight line drawn along the blade surface and the pile steel pipe axis.
  In order to use the above-mentioned grooved chuck collar, the angle needs to be almost right angle. If the right angle is not secured, the rotary press-fit steel pipe pile can be inserted from above even if the grooved chuck collar is used. As in the case where the grooved chuck collar described above is not used, the workability is very poor.
  Therefore, considering the angle between the blade and the steel pipe in the prior art, it is as follows. Since there is nothing in the prior art that mentions and specifies the mounting angle between the blade and the steel pipe, it is judged from the description in the drawings and the specification. It is clear that the conventional type 1 embodiment has a mounting angle which is not a right angle as judged from the drawing. In the figure of the conventional type 2 embodiment, the mounting angle is almost a right angle. In the case of the conventional type 4, the mounting angle is almost a right angle. In other words, in the type in which the blades are fixed to the outer periphery of the steel pipe, those having an attachment angle of right angle are disclosed in the prior art.
  On the other hand, regarding the conventional type 3 which is a closed-end pile in which a spiral blade is fixed to the tip of the steel pipe, it is determined from the above-described embodiment that the attachment angle is not a right angle. This point will be described later.
[0026]
  (2-5) Penetration mechanism of rotary press-fit steel pipe pile with spiral blades
  Here, the point which the inventors of this application clarified so far about the penetration mechanism of the rotary press-fit steel pipe pile by the spiral blade is briefly described. As shown in Fig. 34 (a), the rotary press-fit steel pipe pile rotates the pile body from the ground, excavates the earth and sand at the tip of the spiral blade (spiral bottom plate), and rotates the blade by excavating the earth and sand excavated at the upper surface of the blade. It pushes upward along with it and penetrates into the ground by the propulsive force generated by the reaction force of the ground. In this case, if the ground is uniform, the pile penetrates into the ground with only the rotational torque without applying a vertical pushing force. This is the same principle that a wood screw is screwed into a tree only by rotational force. Therefore, it is important to generate the propulsive force efficiently by the blades. As shown in FIG. 34 (b), the traveling direction of the rotary press-fit steel pipe pile and the reaction force direction of the ground are matched to bring the earth and sand directly above Pushing is the most efficient. In other words, it is most desirable to attach the blades at a substantially right angle to the pile body. On the other hand, as shown in FIG. 34 (a) in the shape of the prior art, when the spiral blade (or the spiral bottom plate) is not perpendicular to the pile body, the propulsive force is lost and the workability is increased. Cause a drop in From the viewpoint of penetration mechanism and workability, it is desirable that the angle between the pile shaft and the blades is almost a right angle.
[0027]
  (2-6) Problem of tip clogging in open-ended piles
  In the case of an open-ended pile, the penetration resistance can be reduced more than in a closed-ended pile, but in order to exert a supporting force, it is necessary to close the opening at the tip of the pile with earth and sand when the support layer penetrates. For this reason, it is generally pointed out that it is necessary to penetrate the pile tip into the support layer about 5 times the diameter of the pile as described above, and it is also described in the “Road Bridge Specification”. However, even with an open-ended pile having good penetrability, penetrating the tip of the pile into the support layer about 5 times the diameter of the pile requires considerable labor and time, which is problematic in terms of workability and cost. This problem becomes more serious as the diameter of the pile increases. Therefore, as shown in FIG. 30, a proposal has been made that ribs are arranged in a donut shape on the inner surface of a steel pipe pile, and at the time of rooting the support layer, the earth and sand entering the steel pipe at the tip of the pile is closed and consolidated to develop a support force. ing. This shape has a large effect for the purpose of promoting the blockage of earth and sand, and a sufficient blockage effect can be obtained even when the rooting of the support layer is about 1D (D: pile diameter), and the supporting force can be secured. However, the appropriate diameter of the blockage promoting ring and the desired mounting position in the pipe are not disclosed, and what can be further reduced in cost is desired.
[0028]
  (2-7) Problems of plastic strain and cracks
  As in Example-1 of the conventional type 3 described above, the tip portion of the steel pipe pile is cut out in a spiral shape, and a disk having a diameter larger than the diameter of the steel pipe is bent along the spiral cut-out tip surface. When welding a processed spiral blade that is also used as a drilling blade, it is essential to make a cut in the radial direction to the center of the disk. It has also been proposed to provide a small hole in the center of the disc.
  According to the description in the publication of the above embodiment, the steel pipe pile 40 shown in FIGS. 19 to 23 is formed by bending an annular disk serving as the spiral bottom plate 41.
  In this case, when the diameter of the earth and sand entrance hole 43 provided in the center part of the disk is small, in order to attach the spiral blade and the pile shaft part at a right angle, the surfaces ac and a′c ′ of the radial cuts 42 are parallel to each other. If it is to be formed in a spiral shape as it is, the distortion caused by the bending process inside the disk becomes excessive, and a crack occurs from the inner periphery. The level difference between the start end ac and the end a′c ′ of the spiral bottom plate 41 formed by bending within a range in which no crack occurs is smaller on the inside than on the outside, and the surface of the radial cut 42 is an elevation projection. It will be V-shaped. This is clear also from FIG. 19, FIG. 20, and when this shape considers the vertical cross section of the pile which passes a steel pipe pile axial part, the angle which the pile main body 40 and the spiral bottom plate 41 make does not become a right angle. It is shown that.
[0029]
  Patent Document 4 (Example 2 of Conventional Type 3)According to the description of FIG.FigureSince the manufacturing method of the spiral blade 51 shown in FIG. 29 is a bending process, the spiral blade 51 and the steel pipe 50 are not at right angles. This is shown in FIG.and,It is clear also from FIG.
[0030]
  The above relationship is shown in FIG.And figureThis will be described with reference to FIG.
  In FIG. 36, (a) shows only the blades of the pile shown in FIG. (B) When the crack is generated because the start end ac and the end a′c ′ of the blade are made parallel, (c) When the hole is enlarged, the start end ac and the end a′c ′ are made parallel. It shows that no cracks occur. From FIG. 35, it can be read that in the blade of FIG. 36 (a), Dw = 2Dp, Do = 0.2Dp, and the pitch at the steel pipe position is about 0.3Dp. Here, Dw is the blade diameter, Do is the hole diameter in the center of the disk, and Dp is the steel pipe pile diameter.

    It is.
    For example, when the hole diameter is 2.5 times (Do = 0.5 Dp) (FIG. 36 (c))

    It becomes.
  In FIG. 37, when the blade is spirally formed by bending, and the start end ac and the end a′c ′ are parallel, a state in which the peripheral length of the hole provided in the center of the disk extends is shown by a development view. .
      Peripheral length after bending of blades when Do = 0.2 Dp = 0.7 Dp
      Peripheral length after bending of blades when Do = 0.5 Dp = 1.6 Dp
    It becomes.
  Distortion caused by extending the circumference due to bending
      When Do = 0.2Dp,
          (0.7-0.63) /0.63 = 0.11
      When Do = 0.5Dp,
          (1.6-1.57) /1.57 = 0.019
  When the respective ratios are calculated, 0.11 / 0.019 = 5.8. That is, when the hole diameter is 0.2 Dp, the distortion due to the bending of the blade reaches 5.8 times as compared with the case where the hole diameter is 0.5 Dp.
  From the above, it is clear that if the hole at the center of the disk is small, the distortion of the inner periphery of the hole when the blade is bent in a spiral shape becomes excessive, and cracks are likely to occur.
[0031]
  In order to form a spiral blade while keeping ac and a'c 'parallel to the radial notch 82 portion provided in the disk, when the pitch is 0.3 Dp, the diameter of the hole in the center portion It has been clarified by experiments by the present inventors that cracks are likely to occur when the diameter is less than half the diameter of the steel pipe pile.
  Depending on the conditions such as the material of the plate and the processing temperature, the hole diameter can be up to about 0.4 times the inner diameter of the steel pipe.
  Although it is desirable that the angle formed between the blade and the steel pipe is substantially a right angle, in the prior art, this has been realized only when the blade is fixed to the outer periphery of the steel pipe. That is, in the pile fixed to the tip of the steel pipe in which the blade is cut out in a spiral shape, a method for making the angle formed by the steel pipe and the blade almost perpendicular is not shown.
[0032]
  (2-8) Problems of tip shape and tip tube thickness
  Needless to say, the steel pipe pile penetrates into a hard support layer consisting of underground gravel, sand, cohesive soil, etc., and exerts a support force mainly against the compressive force from above by the upper structure, Supported by the pile tip. In the case of the above-described conventional types 1 and 2, the blades are fixed to the outside of the steel pipe, so that the spiral blades are shaped like a cantilever as shown in FIGS. A large bending moment acts on the nearby steel pipe. In order to resist this bending moment, it is necessary to make the steel pipe of the part that fixes the blade at the tip of the pile thicker than the plate thickness required from the support force. In comparison, it is often about 2 to 3 times. When the necessary thickness of the steel pipe becomes extremely thick, there arises a problem that the cost for producing the steel pipe increases.
[0033]
  As shown in FIG. 39 (a), the conventional type 3 blade is fixed to the tip of the steel pipe, and the blade projects over both the inside and the outside of the steel pipe. Because of this, the bending moment due to the reaction force that the inner and outer blades receive from the ground cancels each other at the connecting position of the steel pipe and blade, so the bending moment acting on the steel pipe is compared with the shapes of the conventional types 1 and 2 above. It becomes quite small. Therefore, the plate thickness of the steel pipe pile tip can also be made considerably thinner than the conventional types 1 and 2. Although the thickness of the steel pipe depends on conditions such as the balance of the amount of protrusion on the inner and outer surfaces of the blade, it can also be set to the same thickness as the plate thickness determined from the supporting force.
[0034]
  The issues described above can be summarized as follows.
  (3-1) From the viewpoint of penetrability, it is desirable that the blade is fixed to the tip of a steel pipe cut out in a spiral shape.
  (3-2) Further, it is desirable that the earth and sand enter the pipe during construction to reduce the penetration resistance.
  (3-3) From the standpoint of supporting force, it is desirable that the tip can be closed or the soil that has entered can be closed even if the penetration into the support layer is small.
  (3-4) From the surface of the thickness of the tip steel pipe, it is desirable that the blades also protrude from the inside of the steel pipe.
  (3-5) In particular, from the construction surface of a large-diameter pile, it is desirable that the blade and the steel pipe are fixed substantially at right angles in order to use an existing construction machine that can exhibit a large torque.
  Also, from the viewpoint of the penetration mechanism, it is desirable that the blades and the steel pipe are fixed substantially at right angles in order to exert the driving force as effectively as possible.
  In the prior art, a shape that satisfies all these five points has not been clarified, and the means for actually manufacturing the shape has not been known. The present invention provides a shape that satisfies all these five conditions and means for realizing the shape.
[Table 1]

[0035]
[Means for Solving the Problems]
  As a result of various studies on the above-mentioned problems of rotary press-fit steel pipe piles, particularly large-diameter piles, the present inventor has found a novel configuration that can solve the conventional problems in terms of construction, support functions, production, and the like.
  The present invention is configured as follows.
  The present invention belongs to an open-ended pile, and therefore, workability is superior to a closed-ended pile even if the pile diameter is a large diameter exceeding 1000 mm. Further, in the present invention, as means for promoting the blockage of earth and sand in the steel pipe, which is a difficult point of the open-ended pile, the shape and position of the blockage promoting ring provided in the steel pipe, and further, to obtain the same effect as the blockage promoting ring to the maximum The shape was studied and confirmed by experiments. In other words, in the present invention, the blockage promoting effect is almost the same as the blockage promoting ring of the donut-shaped ring, but it is easier to process than that, and the material can be cut just as it is by cutting a steel block, a strip or a steel plate. A good occlusion-promoting projection is devised. This closing promotion protrusion is superior in cost to the closing promotion ring. Further, when the blockage promoting ring is provided in the steel pipe, special improvements are made such that the inner diameter thereof is set to a predetermined dimension based on the experimental results and further provided in multiple stages.
[0036]
  Further, since the blades are projected and fixed inside the steel pipe, a large bending moment acting on the blade root and the steel pipe portion in the vicinity thereof is reduced, and deformation in the steel pipe inner direction is prevented.
  In addition, by making the angle between the outer peripheral part of the blade and the axis of the steel pipe pile main body a right angle, it is possible to obtain a press-fitting propulsion efficiently, and a large-diameter pile with a smaller rotational force and propulsion than before. It was possible to press into a hard support layer.
  Also, by making the right angle above, it matches the chuck structure of existing pile construction machines, so even if the piles that were previously difficult to excavate have a large diameter, use the existing pile construction machines Efficient construction is possible.
[0037]
  The rotary press-fit steel pipe pile according to the first invention is a steel pipe pile with blades that is provided with a spiral blade at the tip and is press-fitted into the ground, and has an outer diameter that is approximately 1.5 to 3 times the outer diameter of the steel pipe. A donut-shaped steel plate with an inner diameter approximately 0.4 to 0.9 times the inner diameter of the pile,Cut one or more places and spirally cut the steel pipe pile end,Concentrically welded and fixed, projecting spiral blades inside and outside the steel pipe pile tip,And the angle formed by the portion where the spiral blade protrudes outside the outer periphery of the steel pipe pile and the steel pipe pile body is substantially a right angle.It forms in the shape which becomes.
[0038]
  The first invention will be further described.
  (1) The larger the area of the spiral blade at the tip of the pile, the greater the support force at the tip of the pile.
  (2) However, if the spiral blade is enlarged only on the outside of the pile in order to increase the tip support force, the resistance when the pile penetrates into the ground during construction increases. In addition, the propulsive force of the blade increases at the time of rotational press-fitting as the spiral blade increases, but the reaction force acting on the blade also increases accordingly, and a large bending moment acts on the blade portion and the steel pipe tip portion. Therefore, if the spiral blade is enlarged only on the outside of the pile, not only the blade thickness but also the plate at the tip of the steel pipeThicknessNeed to be thicker, and the construction equipment has a large capacity.
  (3) In the case of the present invention pile having an open end, the open end portion is supported unless the earth and sand are blocked in the steel pipe.PowerIs not valid. If the pile has a small diameter, it is relatively easy to close the earth and sand. However, it becomes difficult to obtain a blocking effect when the pile has a large diameter. From this point, even if the closing effect is small, by extending the blades to the inside of the pile while keeping the spiral shape, it is possible to make the structure effective for the supporting force even for the open end portion. That is, since the opening area is reduced by projecting the blades inward, the vertical supporting force imposed on the opening is also reduced. Therefore, the required blocking effect is smaller than in the 100% open end state.
[0039]
  (4) On the other hand, in the case of a closed end with a large-diameter pile, the penetration resistance at the tip becomes large and the construction becomes impossible. In order to avoid this, the tip of the pile is open. When the spiral blade is extended inward, there are some restrictions on the entry of earth and sand, but the shape of the blade is spiral and the earth and sand can enter the pile from the stepped part of the blade. The penetration resistance is not as large as a closed-end pile, and it will not be impossible to construct.
  (5) It should be noted that the extent of overhanging the pile, that is, the pile inner diameter D₁Diameter of the blade against the inner diameter (inner diameter D of the spiral blade)_Three) Ratio depends on pile diameter and ground conditions. In general, this ratio is preferably about 0.5, but there is a slightly hard ground as an intermediate layer before the pile reaches the support layer, and therefore this ratio is increased when the penetration resistance increases. In addition, when the pile diameter is large and it is difficult to obtain the closing effect, the ratio is reduced when the tip end area is more effectively used.
[0040]
  (6) As shown in FIG. 12, by making the angle formed between the outer peripheral portion of the blade and the steel pipe pile main body a right angle, the reaction force of the ground acts in the vertical direction, so that the press-fitting propulsive force can be obtained efficiently. , Obedience It is possible to penetrate a large-diameter pile into a hard support layer with smaller rotational force and propulsive force than before. Moreover, since it is suitable for the chuck structure of the existing pile construction machine by having a right angle, even if a pile becomes a large diameter, efficient construction is attained using the existing pile construction machine.
[0041]
  According to a second aspect of the present invention, the doughnut-shaped steel sheet is cut into a fan shape having a central angle of 0 ° to 90 °, the center of which coincides with the center of the donut-shaped steel sheet, and the outer periphery of the donut-shaped steel sheet matches the outer periphery of the donut-shaped steel sheet. Bending doughnut-shaped steel plate with a central angle of 270 ° to 360 ° after cutting, concentrically welding and fixing to the end of the steel pipe pile that was cut into a spiral shape, and extending the spiral blades inside and outside the tip of the steel pipe pile TheAnd the angle formed by the portion of the spiral blade projecting outward from the outer periphery of the steel pipe pile and the steel pipe pile body is substantially a right angle.It forms in the shape which becomes.
  In contrast to the first aspect of the invention, the donut-shaped steel plate is cut into a fan shape to facilitate the entry of excavated soil.
[0042]
  First3In the steel pipe pile with a blade having a spiral blade at the tip and rotationally press-fitted into the ground, the outer diameter is approximately 1.5 to 3 times the outer diameter of the steel pipe and the inner diameter of the steel pipe pile is approximately 0.4 to Cut one or more donut-shaped steel plates with an inner diameter of 0.9 times, or,The center angle is 0 ° to 90 °, the center coincides with the center of the donut-shaped steel plate, and the outer periphery is the donutConditionCut into a fan shape that matches the outer periphery of the steel plate, and cut the doughnut-shaped steel plate with the central angle of 270 ° to 360 ° after cutting into the cut surfaces at the central angles of 0 ° and 360 °, or the donut-shaped fan shape. When the central angle is less than 360 °, the virtual cutting surface at the position where the central angle is extended to 360 ° and the cutting surface at the position at the central angle of 0 ° are bent so as to be parallel to each other to form a spiral blade In order to correspond to the spiral shape of the blade, it is welded and fixed concentrically to the end of the steel pipe pile that has been cut in a spiral shape, and the spiral blade extends over the inside and outside of the tip of the steel pipe pile.And the angle formed by the portion of the spiral blade projecting outward from the outer periphery of the steel pipe pile and the steel pipe pile body is substantially a right angle.It is characterized by having formed into the shape which becomes.
[0043]
  First3The invention will be further described.
  (1) When the blade is extended to the inside of the steel pipe by the conventional technique, the beginning and the end of the blade are not parallel and are V-shaped.
  (2) Therefore, from the space between the blades, the effect of the earth and sand entering the pipe is small, and the workability is not improved.
  (3) By forming the start and end of the blades in parallel, the area of the stepped portion of the blades is maximized, so that earth and sand can enter the pipe from this portion as well, reducing penetration resistance and improving workability. It leads to improvement.
  (4) When a cut is made in one place of the donut-shaped steel plate and bending is performed, as shown in FIG. 15, the start and end of the blade can be formed in parallel on the same plane. However, when one portion of the donut-shaped steel plate is cut into a fan shape and bent, as shown in FIG. 16, the start and end of the blades are not on the same plane and cannot be formed in parallel. Therefore, it is necessary to perform bending so that the virtual cut surface with the central angle extended to 360 ° and the cut surface with the central angle of 0 ° are kept parallel to each other.
  (5) As shown in FIG. 12, by making the angle between the outer peripheral portion of the blade and the steel pipe pile main body a right angle, the reaction force of the ground acts in the vertical direction, so that the press-fitting propulsive force can be obtained efficiently. A large-diameter pile can be penetrated into a hard support layer with a smaller rotational force and propulsive force than in the past. Moreover, since it is suitable for the chuck structure of the existing pile construction machine by having a right angle, even if a pile becomes a large diameter, efficient construction is attained using the existing pile construction machine.
[0044]
  First4The invention of the present invention is characterized in that a protrusion for promoting blockage of earth and sand entering the steel pipe is provided inside the steel pipe pile having a height range of about 0.5 to 3 times the inner diameter of the steel pipe pile from the tip of the steel pipe pile. .
[0045]
  First4The invention will be further described.
  (1) When the spiral blade is extended to the inside of the steel pipe pile, if the pile tip reaches the support layer reliably, even if there is no penetration into the support layer, the amount of the vane found area The tip support force can be demonstrated.
  (2) However, in order to make all the tip portions of the steel pipe pile effective for supporting force, it is necessary to block the earth and sand that has entered the pile body like a general open-ended pile.
  (3) In order to promote blockage of earth and sand, to reduce penetration into the support layer and to exert a support force, it is effective to have a blockage for promoting blockage.
  (4) Generally, in order to sufficiently close the tip of the open-ended steel pipe pile with earth and sand, it is necessary to fill the steel pipe with earth and sand of the support layer about 5 times the inner diameter of the steel pipe. Therefore, as shown in FIG. 9 (B), it is desirable that the pile tip penetrates the support layer about 5 times the diameter of the steel pipe, and the penetration amount H into the support layer 24 is 5 times the steel pipe diameter D. This is necessary. Here, the support layer is determined according to the ground conditions, but in general, it often refers to a good ground having an N value of 50 or more.
  (5) In the present invention, by providing the projection for promoting the closure, the earth and sand that has entered the steel pipe pile can be easily blocked, and even if the amount of penetration into the support layer is small as shown in FIG. (Even if the penetration amount is about 1 times the pile diameter), the soil can be blocked.
  (6) Since the inventor conducted experiments, the results will be described with reference to FIG. FIGS. 10A and 10B are both steel pipes having a diameter (D) of 800 mm, and FIG. ₁ ) Is provided with a closure-promoting protrusion (ring) at a position 1.0 times as high as (), and FIG. Protrusion (ring) 21 for clogging promotion has an inner diameter, steel pipe pile inner diameter (D ₁ ) 0.8 times. 10 (A) and 10 (B), the steel pipe is filled with sand and loaded so as to be pushed out from below. As a result, a graph of the relationship between the vertical load and the displacement is shown in FIG.
  As can be seen from the figure, it is confirmed that the steel pipe pile with a ring according to the present invention has a vertical load supporting force approximately 7 to 8 times that of a conventional steel pipe pile without a ring. Moreover, the load which acts on (A) is large enough to consider that the front-end | tip is obstruct | occluded.
[0046]
  (7) Even with open-ended piles, if the pile diameter is large, it is difficult to penetrate the pile tip into the support layer about 5 times the pile diameter, a large construction machine is required, and the construction time becomes longer. This leads to an increase in cost. However, as described above, since the amount of penetration into the support layer can be reduced by providing the closure promoting protrusion of the present invention, the construction time can be shortened, which is advantageous in terms of cost.
  (8) The range including the projections for promoting the closing is set to a range of about 0.5 to 3 times the inner diameter of the steel pipe pile from the tip of the pile.
  (9) When the attachment range of the closure promoting protrusion is less than 0.5 times the inner diameter of the steel pipe from the tip of the steel pipe, the distance from the tip of the steel pipe to the protrusion is too small to effectively exert the closing effect. .
[0047]
  Here, the effect of the clogging promoting ring is based on the property of dilatancy possessed by earth and sand, and can be explained as follows. Dilatancy is a phenomenon in which the volume changes during shear deformation, and is a significant characteristic of granular materials such as earth and sand that are not found in materials such as metals. In the case of a dense ground such as earth and sand of the support layer, as shown in FIG. 11, due to the dilatancy, the soil particles on both sides of the sliding surface are displaced, and the volume changes (expands) when overcoming the adjacent particles.
  When the blockage promoting ring is attached to the inside of the pile body, a sliding surface is generated from the ring tip to the pile tip, thereby expanding the volume of earth and sand inside the pile tip. The expansion of the earth and sand inside the steel pipe increases the resistance to punching.
[0048]
  First5The invention of the4In the invention of the invention, the blockage promoting protrusion of earth and sand is a steel donut-shaped rib welded and fixed in one or more stages, the outer diameter of which coincides with the inner diameter of the steel pipe pile, and the inner diameter is the inner diameter of the steel pipe pile (D₁) Approximately 0.9 to 0.7 times.
[0049]
  First5The invention will be further described.
  (1) The inner diameter of the rib is 0.9 x D₁If it is larger, almost no occlusion effect occurs. This has been confirmed by experiments.
  (2) The inner diameter of the rib is generally 0.7 x D₁It is sufficient to consider to the extent, and if the inner diameter is made smaller than this, the protruding amount of the rib increases, and the load borne by one rib increases. Therefore, if the rib inner diameter becomes too small, the required thickness of the rib increases, and the cost increases, such as the amount of welding when the rib is welded to the inside of the steel pipe. Therefore, the inner diameter is 0.7 x D₁If the ribs are insufficient, it is advantageous in cost to provide the ribs in a plurality of stages.
[0050]
  First6The invention of the4~5In the invention, the protrusions for accelerating the closure of the rotary press-fit steel pipe pile are steel blocks, strip steel plates or mold steel, and a plurality of them are fixed by welding at intervals in the circumferential direction of the steel pipe pile.
[0051]
  First6The invention will be further described.
  (1) In the prior art, only the open ribs are arranged in a donut shape on the inner surface of the steel pipe pile. Although this shape is very effective for the purpose of promoting blockage, there is a problem that the process of welding the donut-shaped ring to the inner surface of the pile becomes complicated. According to the present invention, a rib-type blockage-promoting protrusion is created, which has the same effect as a donut-shaped ring, is easier to process, and can be simply cut a steel block, strip or steel plate as it is. doing. The present invention may be more cost effective than a multi-stage donut ring.
  (2) In the case of this shape, the amount of protrusion similar to that of the donut-shaped rib is sufficient, and the diameter of the circle inscribed in the protrusion is 0.9 × D.₁~ 0.7 × D₁It is desirable that
  (3) A plurality of protrusions are provided in the pipe circumferential direction, and the total circumferential length of each protrusion is preferably 5 to 20% of the steel pipe pile inner circumferential length. If it is less than 5%, the occlusion effect cannot be exhibited sufficiently. Even if it exceeds 20%, the effect does not improve much more.
[0052]
  First7The invention of the first to first6In any one of the inventions, the thickness of the blade is changed in the radial direction in accordance with a bending moment distribution generated in the blade.
[0053]
  First7The invention will be further described.
  The plate thickness of the spiral blade does not need to be the same as the whole, and is conceptually shown in FIG. 13 in order to change the thickness in the radial direction of the blade according to the bending moment generated by the force acting on the blade 2. Thus, the method of making the part close | similar to a steel pipe into a double-layered blade | wing is considered. Further, as shown in FIG. 14, it is possible to continuously change the plate thickness by casting or the like.
[0054]
  BookThe invention provides a rotary press-fit steel pipe pile according to any one of the first to seventh inventions, wherein a step portion at the start and end of a steel pipe pile end portion cut in a spiral shape is formed in an arc shape.May.
[0055]
  About the above stepFurther explanation will be given.
  (1) The arc-shaped step portion is configured as a step portion 6 shown in FIG.
  (2) Since a large force concentrates on the step portion at the start and end of the steel pipe pile end portion cut in a spiral shape, when this portion is cut at an acute angle, as shown in FIG. Cracks may occur from the part to the steel pipe of the pile body.
  (3) Therefore, in order to alleviate the stress concentration and prevent the pile from breaking, this step portion was formed in an arc shape.
[0056]
  BookThe invention is first to first7In any of the inventions, an inclination is provided on the small edge surface of the tip of the spiral blade so as to reduce resistance with respect to the rotational traveling direction of the blade, and a drilling blade is welded to the small edge surface or the inclined surface by a method such as welding. The angle between the lower surface of the blade and the lower surface of the excavating blade is set to 135 ° to 170 °.May.
[0057]
  About the above angleFurther explanation will be given.
  (1) When the pile is rotationally press-fitted, if the ground N value is a substantially uniform layer, there is no problem even if the excavating blade is not provided at the tip.
  (2) When the N value of the ground increases rapidly, if there is no excavation blade, the blade cannot bite into the upper surface of the hard ground and a slip phenomenon occurs.
  (3) In order not to cause a slip phenomenon, it is important to create a trigger for the spiral blade to bite into hard ground, and an excavating blade is required.
[0058]
  (4) Furthermore, it is important that the excavation blade and the small blade surface of the spiral blade have a shape that reduces resistance in the rotation direction of the blade, and if the resistance is large, the spiral blade rotates. The required torque increases and the workability deteriorates.
  (5) Therefore, it is desirable to provide an inclined surface that reduces resistance with respect to the rotational direction of the spiral blade, or to bond a drilling blade to the small surface or the inclined surface.
  (6) The angle formed by the lower surface of the excavating blade and the lower surface of the spiral blade is effective from 135 ° to 170 °. When the angle exceeds 170 °, the effect of biting is not so high. Becomes larger and workability becomes worse.
  (7) If the ground is such that the N value of the ground does not change rapidly, the excavating blade may not be necessary. Further, when the change of the N value is small, an angle exceeding 170 ° may be sufficient.
  (8) Whether the excavating blade is provided continuously or intermittentlyYoYes.
[0059]
  BookThe inventionthe aboveDrilling blade,Form and adhere to a shape that spans the small edge or inclined surface of the blade tip and both surfaces of the blade lower surface.May.
[0060]
  About the above drilling bladeFurther explanation will be given.
  When the pile is rotationally press-fitted, the ground is excavated by the excavating blade fixed to the tip of the blade. Therefore, the reaction force from the ground acts on the excavation blade, but when the excavation blade is fixed only to the blade edge or inclined surface of the blade, or the lower surface of the blade, this reaction force is sufficient to prevent the excavation blade from being scraped off. Welding is necessary. On the other hand, if the excavation blade is fixed so as to straddle the small edge surface or inclined surface of the blade tip and both surfaces of the blade lower surface, the contact surface between the excavation blade and the blade can resist the reaction force from the ground. The amount can be reduced.
[0061]
  BookIn the invention, an inclined surface is provided on the small edge surface at the tip of the spiral blade to reduce resistance with respect to the rotational traveling direction of the helical blade, and a drilling blade is welded to the small edge surface or the inclined surface by a method such as welding. The angle between the lower surface of the blade and the lower surface of the drilling blade is approximately 135 ° to 170 °.May.
[0062]
  BookThe inventionUpThe drilling blade is formed in a shape that spans the small edge or inclined surface of the blade tip and both surfaces of the blade lower surface, and is bonded.May.
[0063]
  BookThe invention is first to first7In any of the inventions, the tip of the blade is formed in a polygonal shape or an arc shape with the vicinity of the joint between the steel pipe and the blade as an apex, and the protruding length of the blade from the joint is determined by welding the steel pipe and the blade. The minimum dimension required forMay.
[0064]
  About the above feathersFurther explanation will be given.
  The tip shape of the blade includes various polygonal shapes such as a linear shape, a triangular shape, and a quadrangular shape, and an arc shape (the excavation blade is manufactured along the tip shape). At the joint between the tip of the steel pipe and the blade, it is desirable to make the tip of the blade project beyond the joint with the steel pipe from the viewpoint of welding and ground excavation. In some cases, the reaction force from the ground accompanying the action of a force that tears off the blades may break the welding between the steel pipe and the blades. Therefore, it is desirable that the protruding length be about the minimum length necessary for welding the blade and the steel pipe.
[0065]
  First8The invention of the first to first7A rotating press-fit steel pipe pile with a spiral blade fixed to the tip is lifted, and a tubing device having a chuck collar or a chuck member provided with a concave groove corresponding to the pitch of the spiral blade is placed on the ground. The rotary press-fit steel pipe pile installed at a predetermined position is rotated, the spiral blade at the tip is inserted into the concave groove of the tubing device, and the steel pipe pile shaft portion is clamped and gripped by the chuck collar or chuck member, The steel pipe pile construction method is characterized in that a chuck collar or a chuck member is rotated by a rotating device in a tubing device, and the steel pipe pile is rotationally driven to be embedded in the ground.
[0066]
  First8The invention will be further described.
  This construction method uses a construction machine that needs to be formed at a right angle because the outer peripheral part of the blade protruding outward from the outer diameter of the steel pipe is formed at a substantially right angle to the axis of the steel pipe. Is. Conventionally, no method has been found to fix the blades on the inner and outer surfaces of the steel pipe in such a manner that the blades project to the tip of the steel pipe cut into a spiral shape, and to make the angle between the steel pipe pile and the blades substantially perpendicular, This construction method could not be implemented. According to the present invention, the construction of a rotary press-fit steel pipe pile having a large diameter and the aforementioned blade shape can be performed by combining a construction machine used for drilling holes for an existing cast-in-place concrete pile and a grooved chuck collar. In addition, since the ground reaction force direction received by the blades coincides with the propulsion direction of the steel pipe pile, it is possible to efficiently construct a large-diameter steel pipe pile.
[0067]
DETAILED DESCRIPTION OF THE INVENTION
  [First Embodiment]
  A first embodiment of the present invention will be described with reference to the drawings.
  1 (A), (B), FIGS. 2 (A), (B), (C) show a rotary press-fit steel pipe pile with an open end, and an inner edge 10 and an outer edge 11 at the tip of the steel pipe pile 1. Is provided with a spiral blade 2 projecting a predetermined dimension on the inside and outside of the steel pipe pile 1. Moreover, the steel pipe pile front-end | tip part 3 is cut | disconnected spirally, and the level | step-difference part 6 of the start end 5 and the termination | terminus 4 is formed in circular arc shape.
[0068]
  The outer diameter of the spiral blade 2 (D₂) Is an outer diameter approximately 1.5 to 3 times the outer diameter (D) of the steel pipe pile, and the inner diameter (D_Three) Is the steel pipe pile inner diameter (D₁The spiral blade 2 is formed using a donut-shaped steel plate. That is, this donut-shaped steel sheet is cut at one place in the radial direction, one is a circumferential direction start end 8 and the other is a circumferential end 7 and is welded and fixed concentrically to the steel pipe pile tip 3 cut in a spiral shape, The inner edge 10 and the outer edge 11 of the spiral blade 2 are configured to project from the inside and outside of the steel pipe pile tip. In the illustrated example, the thickness of the steel pipe pile 1 is 12 mm, the outer diameter (D) is 1000 mm, and the inner diameter (D₁) Is 976 mm, the outer diameter (D₂) In the range of 1500 mm to 3000 mm, and the inner diameter (D_Three) In the range of 390 mm to 878 mm.
[0069]
  In the above, a large force acts on the step portion 6 of the spiral start end 5 and the end end 4 of the steel pipe pile tip portion 3 at the time of rotational press-fitting. As shown in FIG. As a result, the stress is not concentrated in one place, and no crack is generated here. As a comparative example, FIG. 3 shows a case where there is a corner portion 9 at the step portion 6 of the spiral end portion 5 and the end portion 4 of the steel pipe pile tip portion 3. In this case, stress concentration occurs in the corner portion 9 at the time of rotational press-fitting of the steel pipe pile, and there is a possibility that a crack 22 as shown in the figure is generated.
[0070]
  Moreover, the opening 12 is formed in the center part by the helical blade | wing 2 which protrudes and comprises the inner edge 10 and the outer edge 11 of a blade | wing on the inner side and the outer side of the steel pipe pile front-end | tip part 3, A rotary press-fit steel pipe pile is an open end pile. Become. The outer diameter of the spiral blade 2 (D₂) Is approximately 1.5 to 3 times the outer diameter of the steel pipe pile (D), and the inner diameter (D_Three) Steel pipe pile inner diameter (D₁) Is a numerical value obtained as a result of experiments and simulations, and if it is within this numerical value range, the large-diameter pile will be smooth into the ground. It is possible to satisfy both the conditions of penetration and ensuring the support function of the pile, but it was difficult to satisfy both conditions smoothly if this value was deviated.
[0071]
  In the embodiment of the present invention, as shown in FIGS. 4A to 4F, the excavating blades 14 and 18 are provided on the small edge surface 13 at the tip of the spiral blade 2 or the inclined surface 17 provided on the small edge surface. . The inclined surface provided on the facet is provided so as to reduce the resistance with respect to the rotational traveling direction of the spiral blade 2. The excavation blades 14 and 18 are joined to the fore edge surface 13 or the inclined surface 17 by a method such as welding. In the case of the illustrated example, in order to give the above-described inclination to the spiral blade 2, the angle θ formed by the lower surface of the blade and the lower surfaces of the excavating blades 14 and 18 is set to approximately 135 ° to 170 °.
[0072]
  4 will be described in order. In FIGS. 4A and 4B, the excavation blade 14 has a substantially mountain-like shape in which the top portion 15 is located slightly outward from the middle, and the base end surface of the excavation blade 13 is a small edge surface 13 perpendicular to the blade tip. The angle θ is set to approximately 135 ° to 170 °. FIGS. (C) and (D) are modified examples of the excavating blade 14 shown in FIGS. (A) and (B). In each case, the upper part of the blade tip is inclined, and excavation is performed on the small edge surface 13 at the inclined tip. The base end surface of the blade 14 is welded, and is provided so that the inclined surface of the blade tip and the inclined surface of the upper surface of the excavating blade 14 are connected.
[0073]
  4E and 4F show still another modification of the excavating blade. In this example, the blade tip is formed into a substantially mountain-shaped tip, an inclined surface 17 is formed on the mountain-shaped tip 16, and a plurality of excavating blades 18 are comb-toothed at equal intervals and angled on the inclined surface 17 of the flat mountain shape. An example in which θ is set to approximately 135 ° to 170 ° and welding is shown.
[0074]
  5A to 5C show other examples of the planar shape of the blade tip. The same figure (A) shows the example which formed integrally the knife-shaped inclined surface 19 with which the inner peripheral side was sharpened as a digging blade at the blade | wing tip, FIG.4 (B) shows FIG.4 (C), (D) An example in which the excavating blade 14 having the same structure is configured in a substantially mountain shape with a top portion 15 in the middle is shown. In FIG. 5C, a knife-like inclined surface 19 with a sharp inner peripheral side is formed at the blade tip, The example which welded the knife-shaped excavation blade 20 to this inclined surface 19 is shown. The shape of the digging blade may be other than that illustrated.
[0075]
  FIG. 6 (a) is a plan view of the excavating blade attached to the tip of the blade, and (b) and (c) show the present invention in which the excavating blade is bonded so as to straddle both the small edge surface of the blade and the lower surface of the blade. It is detail drawing of the Example of and an excavation blade. (D) illustrates a resistance mechanism against the reaction force (R1, R2) from the ground acting on the digging blade during excavation. (D) In the left figure, R2 'is a force against R2. However, resistance to R1 is resisted only by the weld. On the other hand, (d) in the right figure, it is possible to resist R1 and R2 with the forces R1 ′ and R2 ′, respectively, so that the welding amount can be reduced.
  FIG. 7A shows a state in which the amount of protrusion of the blade from the joint between the steel pipe tip and the blade is minimized.
  FIG. 7 (b) is a diagram showing a state where the blades are bald by the force acting during construction when the amount of protrusion is large. A reaction force from the ground accompanying ground excavation during construction may cause a force to tear off the end face of the steel pipe to the blade, and the welding of the steel pipe and the blade may be cut off. Therefore, it is desirable that the protruding length be about the minimum length necessary for welding the blade and the steel pipe as shown in FIG.
[0076]
  Next, FIG. 8 (A), (B) shows the example which equipped the protrusion 21 for the obstruction | occlusion promotion of the earth and sand which approachs in the steel pipe pile 1 in the steel pipe inner periphery. In the illustrated example, the closing promotion protrusions 21 are made of grooved steel, and a plurality of grooved steels having a predetermined length are vertically arranged at predetermined intervals in the circumferential direction of the steel pipe (in the illustrated example, at intervals of 90 °). 4), and both side edges of each channel steel are welded to the inner peripheral surface of the steel pipe. In this embodiment, the closing promotion protrusion 21 has an inner diameter (D) of the steel pipe from the pile tip 3a of the open-end steel pipe pile 1.₁) In a steel pipe pile having a height range of approximately 0.5 to 2 times. The other structure of the steel pipe pile 1 of FIG. 8 is the same as the structure of the steel pipe pile 1 of FIGS.
[0077]
  As a result of the experiment, the clogging promotion protrusions 21 made of channel steel are not the entire circumference of the inner peripheral surface of the steel pipe, but a plurality of the projections 21 are provided at intervals as shown in the figure. Was confirmed. Thus, since the amount of penetration of the steel pipe pile 1 into the support layer can be reduced by the promotion of the blockage of the earth and sand and the consolidation effect by the blocking promotion protrusions 21, the construction time can be shortened. The closing promotion protrusion 21 made of channel steel is relatively easy to weld to the inner periphery of the steel pipe pile 1 and is advantageous in terms of production cost. In addition, although not shown in the drawing, instead of the above-mentioned grooved steel, a steel block, a strip steel plate or a steel plate is spaced apart in the circumferential direction of the pile having a height range of about 0.5 to 3 times the inner diameter of the steel pipe. A plurality of welds may be fixed. That is, it is not necessary to limit to the vertical rib type shape, and the same effect can be obtained even with a square rib type shape or a horizontally long rib type shape.
[0078]
  Further, although not shown in the drawing, instead of the steel block, channel steel, strip steel plate, or die steel, the one or more steels in which the closing promotion protrusions 21 are welded and fixed to the inner periphery of the steel pipe pile 1 are used. It consists of a donut-shaped rib made of steel, its outer diameter matches the inner diameter of the steel pipe pile, and the inner diameter is the inner diameter of the steel pipe pile (D₁) To be approximately 0.9 to 0.7 times larger. When it is necessary to construct a steel donut-shaped rib in one stage, the plate thickness becomes thick. Therefore, it is better to provide a steel donut-shaped rib whose inner diameter is approximately 0.9 to 0.7 times that of a steel pipe pile. The thickness of the rib of the sheet does not increase, and the cost is excellent. For example, the inner diameter of the rib is 0.5D₁In this case, the rib thickness is 0.8D.₁In this case, about twice the plate thickness is required. In this case, the inner diameter is 0.8D₁If the ribs are provided in two stages in the pile axis direction, the weld surface and workability in processing are excellent.
[0079]
  FIG. 12 shows a state in which the spiral blade 2 at the tip of the pile body 1 is attached so that the angle formed between the portion of the spiral blade 2 that protrudes outward from the outer periphery of the steel pipe 1 and the axis of the steel pipe pile body 1 is a right angle. Is shown. Since the ground reaction force received by the blades 2 acts in the vertical direction, it coincides with the propulsion direction of the steel pipe pile, and the press-fitting propulsion force can be obtained efficiently. It has become possible to penetrate a large-diameter pile into a hard support layer with a smaller rotational force and propulsive force than before.
[0080]
  Moreover, the construction of the large-diameter steel pipe pile 1 became possible using the existing construction machine due to the right angle. As shown in FIG. 31, in the conventional construction method, the construction machine 60 is mainly used. However, as shown in FIG. 32, the construction machine 70 of the type in which the steel pipe pile main body is gripped and rotated from the outside, that is, FIG.And figureA construction method using the tubing device 70 shown in FIG. 33 is employed.
  When this tubing device 70 is used, it is necessary to use a grooved chuck collar in which a concave groove corresponding to the blade diameter and the spiral pitch of the blade is formed.
[0081]
  Here, the grooved chuck collar shown in FIG. 33 will be described. In the conventional method that does not use the grooved chuck collar, the rotary press-fit steel pipe pile has a considerably larger tip blade diameter than the pile steel pipe diameter. For mounting on the device, either by inserting the rotary press-fit steel pipe pile into the tubing device installed on the ground without attaching the collar and then attaching the chuck collar (no groove) lifted by the crane to the chuck device, or by rotary press-fitting A steel pipe pile is first installed on the ground using the construction machine 60, a tubing device with a chuck collar (no groove) attached in advance is lifted with a crane, and the steel pipe pile is placed over the rotary press-fit steel pipe pile. Was adopted. In the former method, a plurality of chuck collars must be inserted and fixed between the rotary press-fit steel pipe pile and the chuck device, and the work process is very troublesome. In the latter method, a heavy tubing device is lifted to a high position, which is dangerous and requires a crane with a large capacity. In addition, there is a drawback that it takes a long time to install carefully. . If a chuck collar with a groove is used, it is possible to simplify the installation process of the rotary press-fit steel pipe pile to the tubing device and to perform the construction efficiently. When a grooved chuck collar is used, the mounting of the pile can be completed in a few minutes, whereas the above two methods require 30 minutes to 1 hour.
  FIG. 33 shows the main configuration of the casing tube rotating device 75, the chuck device 78, the rotating pile 73, the excavation blade 73 b, and the chuck collar 74 in the tubing device 70.
[0082]
  As shown in FIG. 33, the groove of the chuck collar corresponds to the spiral shape of the blade of the rotary press-fit steel pipe pile, and when the pile is suspended from the top and rotated manually, the blade passes through the groove. Therefore, the spiral blade needs to be fixed substantially at right angles to the steel pipe shaft portion. If the blades are not perpendicular to the pile steel pipe, it is necessary to widen the groove of the chuck collar, but the convex portion becomes thin accordingly. This convex part grips the pile steel pipe and transmits the rotational force, and it is necessary to transmit the pushing force and the pulling force as necessary.When the root of the convex part becomes thinner than the current state, it is necessary to transmit these forces. Strength and rigidity will be insufficient. Moreover, when the area of the front-end | tip part of a convex part is small, there exists a problem that the pressure which acts on a pile when grasping a pile becomes large and a pile steel pipe is damaged.
  The use of the grooved chuck collar makes the construction of a large-diameter pile very efficient. For this purpose, the spiral blades must be attached substantially at right angles to the pile shaft. In other words, for the construction of large-diameter rotary press-fit piles, it is essential that the pile shaft and the blades are fixed substantially at right angles, and the present invention has a great effect by the construction method using this tubing device. I play.
[0083]
  Needless to say, the steel pipe pile penetrates into a hard support layer consisting of underground gravel, sand, cohesive soil, etc., and exerts a support force mainly against the compressive force from above by the upper structure, Supported by the pile tip. Therefore, when the blade is fixed to the outside of the steel pipe, as shown in FIGS. 38 (a) and (b), the spiral blade has a cantilever shape, and a large bending moment is applied to the root of the blade and the steel pipe portion in the vicinity thereof. Acts and deformation occurs in the steel pipe inner direction.
  In order to resist this bending moment and prevent deformation of the steel pipe, it is necessary to make the steel pipe of the part where the blade at the tip of the pile is fixed thicker than the plate thickness required from the support force, the thickness is It is often about 2 to 3 times the required thickness due to the supporting force. When the necessary thickness of the steel pipe becomes extremely thick, there arises a problem that the cost for producing the steel pipe increases.
[0084]
  As shown in FIG. 39 (a), the blade of the prior art 3 is fixed to the tip of the steel pipe, and the blade projects over both the inside and the outside of the steel pipe. As a result, the bending moment due to the reaction force received by the inner and outer blades from the ground cancels each other at the connection position of the steel pipe and the blade, so that the bending moment acting on the steel pipe is considerably reduced. Therefore, the plate thickness of the steel pipe pile tip can also be considerably reduced. Although the thickness of the steel pipe depends on conditions such as the balance of the amount of protrusion on the inner and outer surfaces of the blade, it can also be set to the same thickness as the plate thickness determined from the supporting force. About the plate thickness of the steel pipe of the open end pile which attached the spiral feather to the steel pipe pile tip like this invention, since the opening of a blade | wing center part is comparatively large, plate thickness can be reduced as much as the prior art 3. Although not possible, the plate thickness can be reduced as compared with those shown in FIGS.
[0085]
【The invention's effect】
  According to the present invention, in particular, in an open-ended pile of a rotary press-fit steel pipe pile with a large-diameter blade, a spiral blade is projected on the inside and outside of the tip portion of the steel pipe pile.In addition, the angle formed by the portion of the spiral blade projecting outward from the outer periphery of the steel pipe pile and the steel pipe pile body is substantially perpendicular.Since it is a structure, the problems of smooth construction, sufficient pile support function, and ease of manufacture, which could not be solved by any of the conventional closed-end pile and open-end pile, have been solved. That is, with the rotary press-fit steel pipe pile according to the present invention, even a rotary press-fit steel pipe pile with a large diameter blade can be constructed and put into practical use. Of course, the present invention can also be applied to a rotary press-fit steel pipe pile having a medium diameter other than a large diameter. In addition, because the projections for promoting the blockage of the earth and sand that entered the steel pipe were provided, the support capacity of the steel pipe pile was increased to the same level as that of the closed-end pile even if the penetration into the support layer was about 1D (D: pile diameter). It was possible to increase. The closing promotion protrusion is very easy to attach to the steel pipe, reduces the cost, and has an excellent closing effect as compared with the prior art.
[0086]
  In addition, since the excavating blade is bonded so as to straddle both the small face of the blade and the lower surface of the blade, excavation can be promoted while suppressing the reaction force from the ground during excavation. In addition, since the amount of protrusion of the blade from the joint between the tip of the steel pipe and the blade is minimized, the reaction force of the ground acting during construction causes the blade to be scraped from the end surface of the steel pipe or the welding between the steel pipe and the blade is cut. The fear of end was solved.
[0087]
  In addition, since the outer peripheral part of the blade protrudes at a substantially right angle to the steel pipe, a large driving force can be obtained, the necessary rotational torque is reduced, and in addition, it can be applied to a tubing device. Even piles can be constructed using existing construction machines. In this way, it was possible to significantly reduce costs in terms of materials, labor, construction time, etc. during construction.
[Brief description of the drawings]
FIG. 1A is a front view of a rotary press-fit steel pipe pile according to the present invention, and FIG. 1B is a longitudinal sectional view thereof.
2A is an upper perspective view of a rotary press-fit steel pipe pile, FIG. 2B is a lower perspective view, and FIG. 2C is a plan view.
FIG. 3 is a perspective view of a rotary press-fit steel pipe pile in which corner portions are formed at the step portion at the start and end of the spiral portion at the tip of the pile as a comparative example of the present invention.
4A and 4B are a perspective view and a cross-sectional view of a first example of a digging blade, FIGS. 4C and 4D are cross-sectional views of a second example and a third example of a digging blade, and FIG. (F) is the perspective view and sectional view of the 4th example of a digging blade.
FIGS. 5A, 5B, and 5C are explanatory views showing still another example of the excavating blade. FIG.
6A and 6B are detailed views of the excavating blade of the present invention, and FIG. 6D is an explanatory view.
FIG. 7 is an explanatory view showing a bonding position between the excavation blade at the tip of the spiral blade and the tip of the steel pipe according to the present invention.
8A is a front view of a rotary press-fit steel pipe pile according to an embodiment of the present invention, and FIG. 8B is a plan view of the same.
9A and 9B are sectional views for explaining the operation of the steel pipe pile of the present invention and the conventional example.
FIGS. 10A and 10B are diagrams showing an example of the results of an experiment conducted for examining the effect of a closure promoting protrusion, wherein FIG. 10A is an explanatory diagram of a specimen when a closure promoting protrusion is provided, and FIG. FIG. 5C is an explanatory diagram of the test body when the occlusion promotion protrusion is not provided, and FIG. 5C is a graph showing the relationship between the vertical load and the displacement as the test results of FIGS.
FIG. 11 is an explanatory diagram of dilatancy characteristics of earth and sand.
FIG. 12 is a cross-sectional view showing that the pile main body and excavation blades of the present invention are attached at right angles.
FIG. 13 is an explanatory diagram of the plate thickness of the spiral blade of the present invention.
FIG. 14 is an explanatory view showing another example of the plate thickness of the spiral blade of the present invention.
FIG. 15 is an explanatory view showing a cutting position of a doughnut-shaped steel plate of a spiral blade of the present invention.
FIG. 16 is an explanatory view of the spiral blade donut-shaped steel sheet of the present invention cut into a fan shape.
FIG. 17 is a conceptual diagram of prior art 1, 2, 3, 4;
FIG. 18 is an explanatory diagram of the prior art 1;
FIG. 19 is a perspective explanatory view showing an outline of the prior art 3;
FIG. 20 is an explanatory diagram showing the incision in the conventional technique 3;
FIG. 21 is an explanatory view showing a closing plate of prior art 3;
FIG. 22 is an explanatory view showing a digging blade provided on the bottom plate of the prior art 3;
FIG. 23 is an explanatory view showing a digging blade provided on the bottom plate of the prior art 3;
FIG. 24 is an explanatory view showing an opening of prior art 3;
FIG. 25 is an explanatory diagram of a spiral blade according to the prior art 3;
FIG. 26 is an explanatory diagram of a spiral blade according to the prior art 3;
FIG. 27 is an explanatory view showing an angle between a blade and a pile shaft according to prior art 3;
FIG. 28 is an explanatory view showing an angle between a blade and a pile shaft of the related art 3 in the same manner.
FIG. 29 is an explanatory view showing a closing member according to Prior Art 3.
FIG. 30 is an explanatory diagram of the prior art 4;
FIG. 31 is an explanatory view showing a conventional construction method and construction machine.
FIG. 32 is an explanatory view showing a construction method and a construction machine according to the present invention.
FIG. 33 is a detailed explanatory view showing a tubing device for a construction machine according to the present invention.
FIG. 34 is an explanatory diagram of a penetration mechanism.
FIG. 35 is an explanatory diagram of the prior art 3;
FIG. 36 is an explanatory diagram comparing plastic strain and cracks of the present invention and the prior art.
FIG. 37 is an explanatory diagram of plastic strain and cracks of the present invention and the prior art.
FIG. 38 is an explanatory diagram showing the action of a bending moment in the prior art.
FIG. 39 is an explanatory diagram showing the action of a bending moment in the present invention.
[Explanation of symbols]
  1 Steel pipe pile
  2 Spiral feather
  3 Tip
  3a Pile tip
  4 Termination
  5 Start
  6 steps
  7 Circumferential end
  8 Circumferential start
  9 Corner
  10 Inner edge of the feather
  11 The outer edge of the feather
  12 opening
  13 Small facet
  14 Drilling blade
  15 Top
  16 Tip of mountain shape
  17 Inclined surface
  18 Drilling blade
  19 Knife-shaped inclined surface
  20 Drilling blade
  21 Protrusion for closure promotion
  22 Crack
  23 Conventional steel pipe piles
  24 Support layer
  25 Soft layer
  26 Sediment of the support layer that entered the steel pipe
  27 Soft layer of earth and sand that entered the steel pipe
  30 Steel pipe pile
  31 Spiral feather
  32 Bottom plate
  40 Steel pipe pile
  41 Spiral feather
  42 notches
  43 sediment access hole
  44 Closing plate
  45 Drilling blade
  50 Steel pipe pile
  51 Spiral feather
  52 notches
  53 Earth and sand entrance hole
  54 Occlusion member
  55 Steel pipe pile
  56 Spiral feather
  57 Opening rib
  58 Perforated cylindrical part
  60 Conventional construction machines
  70 Construction Machine Used in the Present Invention: Tubing Device
  73 Rotating pile
  73b Excavation blade
  74 Chuck collar
  75 Casing tube rotating device
  78 Chuck device
  80 steel pipe pile
  81 Spiral feather

Claims (8)

In a steel pipe pile with blades that has a spiral blade at the tip and is rotationally press-fitted into the ground, the outer diameter is approximately 1.5 to 3 times the outer diameter of the steel pipe, and is approximately 0.4 to 0.9 times the inner diameter of the steel pipe pile. The donut-shaped steel plate with an inner diameter of one or more is cut at one or a plurality of locations, welded and fixed concentrically to the end of the steel pipe pile that has been cut in a spiral shape, and spiral blades extending over the inside and outside of the steel pipe pile tip, and A rotary press-fit steel pipe pile characterized in that the spiral blade is configured in a shape in which the angle formed by the portion of the steel pipe pile protruding outward from the outer periphery of the steel pipe pile and the steel pipe pile body is substantially perpendicular . The donut-shaped steel sheet is cut into a sector shape with a center angle of 0 ° to 90 °, the center of which coincides with the center of the donut-shaped steel sheet, and the outer periphery of the donut- shaped steel sheet. Bending a 270 ° to 360 ° donut-shaped steel plate, concentrically welding and fixing it to the end of the steel pipe pile that was cut in a spiral shape, and extending the spiral blades inside and outside the tip of the steel pipe pile; 2. The rotary press-fit steel pipe pile according to claim 1, wherein the angle between the portion of the steel blade pile projecting outward from the outer periphery of the steel pipe pile and the steel pipe pile main body is substantially perpendicular . In a steel pipe pile with blades that has a spiral blade at the tip and is rotationally press-fitted into the ground, the outer diameter is approximately 1.5 to 3 times the outer diameter of the steel pipe, and is approximately 0.4 to 0.9 times the inner diameter of the steel pipe pile. The donut-shaped steel plate having an inner diameter of 1 is cut at one or a plurality of locations, or the center angle is 0 ° to 90 °, the center coincides with the center of the donut-shaped steel plate, and the outer periphery coincides with the outer periphery of the donut- shaped steel plate When a doughnut-shaped steel sheet having a central angle of 270 ° to 360 ° after cutting is cut into a sector shape and the center angle of the donut-shaped sector is less than 360 ° Has a virtual cutting surface with a central angle extended to 360 ° and a cutting surface with a central angle of 0 ° are bent so as to be parallel to each other and formed into a spiral blade. To the end of the steel pipe pile that was cut in a spiral shape And, it projects a spiral blade in and out of the steel pipe pile tip, and was constructed in a shape which forms an angle between the portion and the steel pipe pile body to which the helical blade is protruding outward from the outer periphery of the steel pipe pile is substantially perpendicular Rotating press-fit steel pipe pile characterized by that.   A protrusion for promoting clogging of earth and sand entering the steel pipe is provided inside the steel pipe pile having a height range of about 0.5 to 3 times the inner diameter of the steel pipe pile from the tip of the steel pipe pile. The rotary press-fit steel pipe pile according to any one of the above.   The projection for promoting closure is a steel donut-shaped rib fixed by welding in one or more stages, the outer diameter of which corresponds to the inner diameter of the steel pipe pile, and the inner diameter is approximately 0.9-0. The rotary press-fit steel pipe pile according to claim 4, wherein the pile is 7 times.   6. The rotary press-fit steel pipe pile according to claim 4, wherein the projection for promoting closure is a steel block, a die steel, a strip steel plate, and the like, and a plurality of the welded protrusions are fixed by welding in the circumferential direction of the steel pipe pile.   The rotary press-fit steel pipe pile according to any one of claims 1 to 6, wherein a thickness of the blade is changed in a radial direction corresponding to a bending moment distribution generated in the blade. A tubing device having a chuck collar or chuck member provided with concave grooves corresponding to the pitch of the spiral blades is installed at a predetermined position on the ground, and the rotary press-fit steel pipe pile according to claim 1 is lifted and lifted. the helical blade of the press-fit the steel pipe pile tip passed by inserting and rotating the groove of the chuck collar or chuck member, a steel pipe pile shank gripped by clamping by the chuck collar or chuck member, the chuck collar or chuck A method for constructing a rotary press-fit steel pipe pile, wherein a member is rotated by a rotating device in a tubing device, and the steel pipe pile is driven to rotate and buried in the ground.

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