JP4706994B2

JP4706994B2 - Foundation pile structure using ready-made piles

Info

Publication number: JP4706994B2
Application number: JP2003121272A
Authority: JP
Inventors: 好伸木谷; 竜松田
Original assignee: Mitani Sekisan Co Ltd
Current assignee: Mitani Sekisan Co Ltd
Priority date: 2002-04-26
Filing date: 2003-04-25
Publication date: 2011-06-22
Anticipated expiration: 2023-04-25
Also published as: JP2004003324A

Description

【０００１】
【発明の属する技術分野】
杭下端部に、突起、例えば節、スパイラル翼、鋼棒、鋼板等の突起物を形成した既製杭を、所定の根固め部のソイルセメント層に設置し、その突起を利用して高支持力を発現している基礎杭構造に関する。尚、根固め部は拡径の有無の何れでも適用できる。
【０００２】
【従来の技術】
従来、杭基礎において、根固め部内に埋設する杭の下端部に突起類を形成して杭穴内に埋設した既製杭と一体で基礎杭全体で支持力を増強させた発明がなされていた。例えば、円筒状コンクリートパイルの下端部外周に複数組の拡開鉄筋を形成し、それら拡開鉄筋の鉄筋間に横筋としてチェーンを連結した構造（特許文献１。特開平１１−６１８１１、特許３０５４３８９号（以下、従来例Ａ））、また、既製杭の先端部に、フランジ外面に凸部を有するＨ型鋼を固定した構造（特許文献２。特開２００１−２７１３４７（以下、従来例Ｂ））、また、下端部外周に突起を有するコンクリート製の既製杭を使用した構造（特許文献３。特開平１１−２８００６７（以下、従来例Ｃ））等が知られている。
【０００３】
従来例Ａ公報に記載の実施例の図１〜５等によれば、下部外表面に形成した拡開鉄筋６を折畳んだ既製杭３を、杭穴１の軸部を通して貫入させ、孔底拡開部２に押し込み、その拡開鉄筋６を拡開し、図５のように埋設・固化させることにより高支持力が得られるとしている。杭穴掘削寸法は具体的に記載されていないが、図３、図５によれば、軸部の杭穴１の寸法は少なくとも、「杭径＋拡開鉄筋部厚」以上であり、杭外径の約３０％以上の大径寸法の杭穴が掘削されている。従って、通常の杭基礎の軸部杭穴の所要寸法の「杭経＋３０ｍｍ（杭径の１０％以下）」に比べ杭と杭穴の間隙が余分となっている。根固め部の掘削径も杭径の２倍以上と通常の支持力での（杭径×１．２５〜１．５程度）に比べ大径である。
【０００４】
また、従来例Ｂ公報の３頁の実施例によれば、外径Ｄ（５００ｍｍ）の外殻鋼管コンクリート杭１（通常ＳＣ杭と呼称する。）の下端部に鋼材のＨ鋼が形成されており、軸部の杭穴径Ｄ_１は６５０ｍｍで掘削されている。従来の基礎杭での所要軸部掘削径は「杭径＋３０ｍｍ（杭径の１０ｍ％以下）」程度であり従来に比べ杭穴内壁と杭外側面との間隔が余分である。また、高支持力を発現させるために拡底根固め部掘削径Ｄ_０は１０００ｍｍで杭径の約２倍と通常支持力での（杭径×１．２５〜１．５程度）に比べ大幅な大径掘削が行われている。
【０００５】
また、図２（ａ）によれば、杭１の下端部に形成したＨ鋼２および補強リブ４が、一見、上部の杭１の外径寸法以下で形成されているようであるが、図１、図３等と対比すると実施例と略同様な寸法で作図されており、実施例同様に、軸部掘削および拡底根固め部掘削共に大径掘削がおこなわれていると推察される。
【０００６】
さらに、特開２００１−２７３４７の図２等のように、突起が杭下端部を閉栓する構造の場合には、特に根固め部の高濃度のソイルセメントに関して、杭下端中央部および杭穴中空部などでの均一性に不安があり、更にその閉栓形状の各突起の上下の重なり等によりせん断力が充分に利用できない。また、突起により掘削ヘッドが杭穴中空部を貫入できない構造であるため中掘り工法による施工ができない等汎用性に問題があった。
【０００７】
また、従来例Ｃ公報の図１の実施例１による杭基礎１０によれば、杭下部の構造としては、拡底根固め部３に埋設した杭下端部に形成し、高持力発現に寄与させる突起部は環状リブ（節形状）とし３個の環状リブ５、６、７を形成している。この突起部のせん断力を充分発揮させるために、この突起の環状リブ外径Ｄ_１（７５ｃｍ）は杭４の軸部外径Ｄ_０（６０ｃｍ）より大径として突起表面積を大きくしている。従って、既製杭の上部の外径は軸部外径寸法Ｄ_０で杭材が限定されると共に、杭穴軸部２の掘削寸法はその環状リブが貫入し易い寸法Ｄ_００（８０ｃｍ）で掘削され杭穴内壁と杭外側面との間隙が広く、かつ、根固め部の拡底寸法Ｄ_１１も従来にない比率の大径掘削が必要とされており、軸部、拡底根固め部共に従来にない大径の掘削工事に対する新たな技術対応が必要であった。
【０００８】
その他、従来から既製杭の根固め部に埋設した部分に突起あるいは凹部を形成して支持力を増強した杭基礎が多数提案されているが、その突起部あるいは凹部に近接する突起によるせん断力が充分発現するように突起間隔あるいは凹間隔が充分に取られておらず、またソイルセメント層の所要固化強度なども含め総合的にせん断力が充分発現し支持力が得られるように配慮されておらず多数施工実績のあるものは従来例Ｃの発明を利用した基礎杭のみのようである。
【０００９】
また、総じて、根固め部で発現する高支持力に対し、細い径の軸部杭が使用されており、軸部杭自身の水平耐力などが不足し、杭基礎全体としてバランスを取るのに杭材の選択が限られ鉛直支持力を最大に生かす杭基礎の構築が難しかった。
【００１０】
【特許文献１】
特開平１１−６１８１１公報
【００１１】
【特許文献２】
特開２００１−２７１３４７公報
【００１２】
【特許文献３】
特開平１１−２８００６７公報
【００１３】
【発明が解決しようとする課題】
前記従来の技術では、以下のような問題点があった。
【００１４】
（１）杭下端部において、ソイルセメント層との付着及びそのせん断力を発現させる突起部の面積を大きくするために、簡便な方法として、その突起を杭の外側面に形成しているので、拡底根固め部掘削径および杭孔軸部径が従来の通常の支持力杭基礎に比べ杭径比で大きくなっている。杭穴軸部の杭径と杭穴軸部径との間隙も余分に広くせざるを得なくなっている。
【００１５】
（２）根固め部で発現する従来の２倍程度の高支持力に対し、杭穴軸部の杭もバランスの取れた大きい耐力（上載荷重伝達および曲げ耐力を共に満たす強度）が必要であるが、杭径が小さいため杭材の選択範囲が限られ、根固め部の高支持力をフルに生かすことに難があった。
【００１６】
（３）杭穴軸部の掘削経が、その杭穴軸部に埋設する杭径の摩擦力を発現するに必要な杭穴径（通常の杭孔内壁と杭の間隔が３０ｍｍで杭径の１０％以下）より大きく（例えば２０％以上）としてあり、掘削面積が無駄（約４０％）となっており、また、拡底根固め部の掘削径も従来にくらべ杭径比で相対的に大きくなっており、結果として、掘削時間が長く、掘削排土も多く経済的、環境的に問題である。さらに、掘削装置も従来にない大径の杭穴用の掘削装置の調達が必要など無駄な点が多い。
【００１７】
特に、中掘り施工については拡底杭穴が従来にない大径（杭中空部内径に比べ）であるため掘削の安定施工に関し、掘削装置技術上解決すべき課題が多い。
【００１８】
【課題を解決するための手段】
然るにこの発明では、接続する既製杭の最大外径と同等又はより小径の突起を形成した先端金具を形成し、あるいは、根固め部に位置する既製杭の下端部を、上部軸部より小径の下部軸部とし、下部軸部に上部軸部の最大外径と同等又はより小さな外径を有する突起等を形成したので、前記問題点を解決した。
【００１９】
即ち、この基礎杭構造の発明は、所定軸径の主軸部を有する既製杭の下端に先端金具又は「他の既製杭」を連結し、該先端金具又は「他の既製杭」は、前記既製杭に連結される前記主軸部と略同一径の大径部を有し、前記主軸部より小径の下部軸部を形成し、該下部軸部に突起部を形成し、該突起部の先端が前記主軸部の最大外径と同等又はそれ以下に形成して、かつ前記大径部の下面に段差部を形成して構成し、支持地盤に、根固め液を充填した根固め部を有する杭穴内に、前記既製杭を、前記先端金具又は「他の既製杭」及び前記既製杭の下端部が前記杭穴の根固め部内に位置し、かつ前記先端金具又は「他の既製杭」が一体となって前記支持地盤に支持するように、埋設したことを特徴とする既製杭を使用した基礎杭構造である。
【００２０】
また、前記において、突起部は、突起部の上面と、主軸部及び下部軸部との段差部下面とに所定間隙を設け、または隣接する前記突起部の上下面の間に所定間隙を設けるように配置すると共に、杭穴の所定形状の根固め部内に、固化強度が支持地盤の強度以上となるソイルセメントを充填したことを特徴とする既製杭を使用した基礎杭構造である。
【００２１】
また、他の基礎杭構造の発明は、所定軸径の主軸部を有する既製杭の下端に先端金具または「他の既製杭」を連結し、該先端金具又は「他の既製杭」は、前記既製杭に連結される前記主軸部と略同一径の大径部を有し、下端部に、側面から軸側に向けての横方向の凹部を形成して、かつ前記大径部の下面に段差部を形成して構成し、支持地盤に、根固め液を充填した根固め部を有する杭穴内に、前記既製杭を、前記先端金具又は「他の既製杭」及び前記既製杭の下端部が、前記杭穴の根固め部内に位置し、かつ前記先端金具又は「他の既製杭」が一体となって前記支持地盤に支持するように、埋設した既製杭を使用した基礎杭構造である。
【００２２】
また、前記において、既製杭の下端部及び先端金具又は「他の既製杭」を覆うカバーを取付けて既製杭を構成し、前記カバーは、該既製杭を埋設後に地上に引き上げ可能に構成したことを特徴とする基礎杭構造である。
【００２３】
前記における既製杭は、既製杭の下端に突起部又は凹部を有する先端金具を連結して構成するが、１本の既製杭の下端部を加工して突起部又は凹部を有する所定構造とした場合、あるいは、突起部又は凹部を有する所定構造を有する下杭に、１本又は複数の上杭を接合した構造とすることもできる。
【００２４】
また、前記における既製杭は、主にコンクリート系の既製杭の先端に鋼製の先端金具を連結して構成するが、既製杭を鋼管系あるいはこれらの複合構造の材質を採用して、更に、先端金具と既製杭とを一体で製造することもできる。
【００２５】
また、前記における外径範囲とは、既製杭の最大外径と同等で円筒状の範囲を形成し、その円筒状の側面から放射状に突出しない範囲をいう。
【００２６】
また、前記における既製杭の最大外径とは、通常は、ストレート状の既製杭を使用するので、その外径を指すが、外径が異なる既製杭を使用する場合には、大径部や突起部等が先端金具を接続する既製杭の下面より大径の場合には、これら大径部や突起部等の外径をいう。即ち、既製杭の最大外径に応じた口径で杭穴を掘削するので、その杭穴の掘削径の規定する既製杭の最大外径をいう。
【００２７】
また、前記における突起部の上面と、主軸部及び下部軸部との段差部下面とに形成する所定間隙、または隣接する前記突起部の上下面の間に形成する所定間隙とは、有効なせん断力の伝搬を図る為には、せん断力の伝搬角度を考慮して、各突起におけるせん断力の伝搬が上下で重ならないような突起間隔とすることが望ましい。例えば、上下に２個の突起が形成されている場合、基礎杭構造の全体に鉛直荷重が作用した場合、段差部下面、各突起部の下面、既製杭（先端金具）の下面から付着しているソイルセメント層（固化）へせん断力が伝搬する。この際、せん断力は、斜め下方に向けて、鉛直方向と成す角度は約３０度で伝搬することが、試験により、確認されている。従って、このせん断力がその下方に位置している突起部の上面に当たらないように、伝搬させれば、突起部等によりせん断力を充分に発現させることができるので、所定間隙は、突起部の高さの√３倍以上が好ましい。上記を前提として、実施に当たっては、所要の支持力に応じて、所定間隙に突起部を設定した設計をすれば良いが、通常では、所定間隙を考慮した根固め用の突起部付きの既製杭として予め製造しておくことが望ましい。
【００２８】
また、基礎杭構造全体に引抜力が作用した場合には、せん断力は同様に上方に向けて作用し、鉛直荷重が作用した場合と同様の所定間隙が必要になる。
【００２９】
また、前記における所定形状の根固め部とは、前記のようなせん断力が下方あるいは上方に伝搬する際に、必要とする固化ソイルセメント層の強度に見合う大きさ（層厚、外径、長さ等）を意味する。既製杭（先端金具）の下面と杭穴底との間のソイルセメント層の層厚としては、既製杭（先端金具）の杭径以上（例えば、５０ｃｍ程度）、また、根固め径としては、突起部の径の１．５倍弱程度とすることが望ましい。
【００３０】
【発明の実施の形態】
（１）この発明の先端金具１２は、既製杭１４の下端部（端板部等）にボルトなどで装着可能な構造とし、鋼管本体１の上端部に連結用の大径部２とする。鋼管本体１の中間部及び下端部（大径部を除く部分）には、環状突起１０、１０が形成されている。環状突起１０の外径Ｄ_４は、大径部２即ち既製杭１４の最大外径Ｄ_５と同等又は、小さく形成されている。尚、ここでは環状突起１０の先端が、大径部２即ち既製杭１４の最大外径から外方に突出しないように形成されている（図１）が、同等の範囲で、かつ杭穴の軸部掘削径以下であれば、多少突出して形成することもできる。
【００３１】
先端金具１２を連結した既製杭１４を、ソイルセメント等の固化物が充填された杭穴３２内に下降して、杭穴下端部に形成した根固め部３４に先端金具１２が位置するように、既製杭１４を埋設して、基礎杭構造３７とする（図３）。ソイルセメントは、地盤強度以上の所定の固化強度を有することが望ましい。
【００３２】
基礎杭構造３７の上端に、基礎ベース及び建造物等の上部構造物を構築する。
【００３３】
（２）装着する先端金具１２の機能、構造等
【００３４】
既製杭１４から伝達されてくる建造物等の荷重を、先端金具１２の環状突起１０の表面等からのせん断力等として支持地盤等に伝搬させ、先端金具１２は杭穴３２内の固化ソイルセメント層と一体となって、支持地盤に支持する機能を有している。
【００３５】
先端金具１２の上端部の大径部２は、その上面が、既製杭１４の下端板１７の下面に密着して、既製杭１４に装着する連結部として機能する。大径部２は、鋼管本体１に溶接され、あるいは鋼管本体１と一体に成形して形成する。
【００３６】
また、鋼管本体１の外側面８は、杭穴３２内の固化ソイルセメントと付着して、一体に埋設されるように機能する。尚、環状突起１０は、環状突起１０の外径Ｄ_４を基準とすれば、環状突起１０、１０の間に深さＬ_７の凹部４０が形成されていることと同じになる。
【００３７】
（３）各構成部分の説明
【００３８】
(a) 先端金具１２の上端部に位置する大径部（連結部）２は、その上方に位置する既製杭１４から伝達されてくる建造物等の荷重を鋼管本体１および環状突起１０へ伝達する。更に、大径部２の外側縁下面（鋼管本体との段差部分）から杭穴内のソイルセメント層を通じて鉛直方向のせん断力を伝搬させて、環状突起１０と共に、支持力を増強する機能も有する。
【００３９】
大径部２と鋼管本体１とは溶接あるいは成形加工などにより接続・固着等され、応力の伝達が円滑に伝搬するように、一体化した構造の鋼材を使用する。また、大径部２には、環状の連結板が形成されており、強度上の必要性により、連結板の上に応力分分散を複数積層すること等により厚さを調節することも可能であり、連結板周縁下面と鋼管本体の外側面との間に斜め状の補強リブを複数形成することもできる。
【００４０】
(b) 環状突起１０は、杭穴３２内のソイルセメント層に一体に付着して埋設され、環状突起１０の上下表面は所望支持力に見合ったソイルセメント層との付着面積および強度（厚さ、材質）を有することが必要であり、通常、鋼材を使用する。従って、環状突起１０は、複数形成され、各環状突起１０の上下面４２、４１、段差部下面４３からの上下方向へのせん断力が斜め下方（約３０度）へ充分伝搬できるように所定の間隔Ｌ_１を設けることが望ましい。このような環状突起１０が、鋼管本体１の外側面８に溶接等で固着し鋼管本体１と一体的に構成されている。
【００４１】
環状突起１０の構造は、例えば、鋼板によるドーナツ形状で、鋼管本体１に３個取り付けた構造（図１）、鋼板によるドーナツ形状で２個取り付けた構造（図５（ａ））とすることができる。この場合、環状突起１０の上下面と鋼管本体１の外側面８との間に、補強リブ１１、１１を形成することもできる（図５（ａ））。またドーナッツ状の形成は、鋼板に代えて鋼棒を重ねて巻き付けて同様の構造とすることもできる（図示していない）。
【００４２】
また、環状突起１０は、ドーナッツ状の鋼板を捻って、スパイラル翼形状を２箇所に形成した構造とすることもできる（図５（ｂ））。この場合、ソイルセメント層内でのせん断力の伝搬を考慮して、スパイラル翼の傾斜角度は小さくすると共に、一周より少なく形成することが必要である。
【００４３】
また、環状突起１０は、肉厚が厚い断面台形状のドーナッツ状に形成することもできる（図５（ｃ））。この場合、環状突起１０は中空又は中実いずれでも可能である。
【００４４】
(c) 鋼管本体１は、大径部２及び環状突起１０と一体となり、更に、埋設した際に、杭穴３２内の固化ソイルセメント層と一体となって、上下方向の応力を伝達、支持する基体となる構造体である。従って、鋼管本体１は応力伝達、支持に見合った所要強度の厚さｔ_１、材質が必要である。また、鋼管本体１の内部は、接続する既製杭１４の中空部と同一内径で連通して、中空部内にソイルセメントが均一に充填できるように形成する。また、接続する既製杭１４の中空部と同一内径で形成することにより、中掘り工法に適用する場合、掘削ロッドを支障無く挿通できる。
【００４５】
（４）先端金具１２の寸法
【００４６】
鋼管本体１の内径寸法Ｄ_２は、上部に位置する既製杭１４の中空部内径寸法以上とすれば良いが、突起の有効面積を増すために、既製杭１４の中空部内径と略同一寸法の内径とが望ましい（図１）。
【００４７】
また、環状突起１０の外径Ｄ_４は、上部に位置する既製杭１４の外径Ｄ_５以下の寸法とすれば可能であるが、既製杭１４の外径Ｄ_５と略同一の場合が、強度設計、支持力等の面から望ましい（図１、図４）。また、既製杭１４の杭穴への沈設に際して、少なくとも杭穴の軸部への貫入時に支障無く貫入できる範囲の外径寸法以下に限定することが必要である。即ち、杭穴の軸部掘削径以下が望ましい。
【００４８】
また、環状突起１０の鋼管本体１の外側面からの長さＬ_７（＝「Ｄ_４−Ｄ_１」の２分の１）と、設置間隔Ｌ_１とは、下方へのせん断力の伝搬角度θ（≒３０度）とした場合、せん断力を充分発現できるように、
Ｌ_７＜Ｌ_１×ｔａｎθ
となるように形成し、かつ、ソイルセメント層へのせん断力の伝搬の面及びソイルセメントとの付着の面の両面から、環状突起１０の表面積を確保できるように、できるだけＬ_７を大きくすることが望ましい（図１（ａ））。
【００４９】
（５）また、前記のような技術的思想から、先端金具に代わり、既製杭の下端に螺旋翼付きの鋼管杭（取付ける既製杭より小径）を固定して、この発明の既製杭を構成することもできる。
【００５０】
【実施例１】
図面に基づきこの発明の先端金具の実施例を説明する。
【００５１】
（１）外径Ｄ_１（＝４５０ｍｍ）、内径Ｄ_２（＝４２０）の鋼管本体（厚さｔ_１＝１５ｍｍ）１の上端部に、外径Ｄ_３（＝６００ｍｍ）の大径部２を形成し、既製杭１４との連結部とする。大径部２の上端側の外周に、連結用のバンド２３を嵌装するための環状溝部３を形成する。連結部の外径、即ち、大径部２の外径Ｄ_３は、接続すべき既製杭１４の外径（下端板の外径）と略同一としてある。環状溝部３には、連結用のボルト穴４、４が形成されている。
【００５２】
大径部２の外周には、環状溝部３を有する筒状表面材５と、筒状表面材５の上端内側に連続して、既製杭１４の下面と当接するドーナッツ状の当接材６とが埋め込まれている。ボルト穴４、４は、筒状表面材３に形成されている。
【００５３】
鋼管本体１の中間部及び下端部の外周に、鋼管の外側面８から距離Ｌ_７（＝７５〜９０ｍｍ）（即ち外径Ｄ_４＝６００〜６３０ｍｍ）、厚さｔ_２（＝１０〜４０ｍｍ）の環状突起１０を突設する。環状突起１０は、薄い円盤状に形成され、鋼管本体１の下端から、大径部２の下部までの距離を等分するように、間隔Ｌ_１（＝５００ｍｍ）で、３枚形成されている。尚、環状突起１０を別な表現すれば、基準径Ｄ_４から深さＬ_７の凹部４０が形成されていることになる。
【００５４】
以上のようにして、先端金具１２を構成する（図１（ａ）（ｂ）（ｃ））。
【００５５】
前記における間隔Ｌ_１は、環状突起１０の下面４１、上面４２、大径部２の段差部下面４３からのせん断力の有効な伝搬を考慮して、
Ｌ_１＞√３×Ｌ_７
となるように形成されている。
【００５６】
（２）次に、前記実施例に基づくこの発明の先端金具１２の使用、即ち既製杭１４の構成について説明する（図２（ａ）（ｂ））。
【００５７】
コンクリート製の既製杭１４の下端部に、鋼製の接続金具１６が一体に取り付けられている。接続金具１６は、円盤状の下端板１７と、下端板１７に連結し、既製杭１４の側面に周設した筒状の側板１８とからなり、側板１８は、下端板１７に連続した部分に、材厚を厚くした肉厚部１９を有する。側板１８に、先端金具１２の環状溝部３と略同一形状の環状溝部２０を形成する。環状溝部２０には、先端金具１２のボルト穴４に対応したボルト穴２１、２１が形成されている。環状溝部２０、ボルト穴２１は、肉厚部１９に形成されている。
【００５８】
接合用のバンド２３は、先端金具１２の大径部２と既製杭１４の下端板１７に嵌装できる内径を有する鋼製で構成される。バンド２３には、上側の内面に、環状溝部２０に嵌挿できるように内方に向けて突出する環状凸部２５が形成され、下側に、環状溝部３に対応した同様の環状凸部２６が形成されている。また、バンド２３の環状凸部２５、２６には、ボルト穴４、２１に対応した貫通孔２７、２７が形成され、バンド２３の外面で、貫通孔２７、２７を拡径した収容部２８が形成され、接合用のボルト３０の頭部を収容できるようになっている。また、バンド２３は、連結作業がし易いように、３つのバンド片２４、２４に等分割されている。
【００５９】
既製杭１４を縦に吊り上げて、あるいは既製杭１４を地面に寝かせた状態で、既製杭１４の下端板１７に先端金具１２の上面（大径部２の上面）を当接して合わせ、両当接部分にバンド片２４、２４を環状に並べて当接してバンド２３とし、バンド２３の環状凸部２５、２６を既製杭１４の環状溝部２０、先端金具１２の環状溝部３に夫々嵌挿する。貫通孔２７、２７からボルト３０を挿通して、ボルト穴２１、４にボルト３０の先端部を螺合緊結して、バンド２３を既製杭１４及び先端金具１２に固定し、既製杭１４に先端金具１２を一体に固定する。
【００６０】
この状態で既製杭１４の内径と、先端金具１２の内径は略同径に形成されている。即ち、既製杭１４の内側面１５と先端金具１２の内側面９とは略面一に形成される（図２（ｂ））。
【００６１】
（３）他の実施例
【００６２】
また、前記実施例において、既製杭１４は、下端に先端金具１２を固定して、形成したが、先端金具１２を既製杭と一体に形成して、既製杭１４とすることもできる（図６）。この場合でも、突起部１０の間隔Ｌ_１は、環状突起１０の下面４１、上面４２、段差部下面４３からのせん断力の有効な伝搬を考慮して、
Ｌ_１＞√３×Ｌ_７
となるように形成されている。また、環状突起１０を別な表現すれば、基準径Ｄ_４から深さＬ_７の凹部４０が形成されていることになる。
【００６３】
【実施例２】
次に、この発明の基礎杭構造について説明する。
【００６４】
（１）所定口径Ｄ_１１（Ｄ_１１＝Ｄ_５＋３０ｍｍ程度）の杭穴３２の軸部３３を所定深さＬ_２まで掘削し、杭穴３２の軸部３３に連続して深さＬ_３に亘り口径Ｄ_１２に拡底掘削して、杭穴３２の根固め部３４を形成する。杭穴２３内には、根固め部３４内に根固め液を、軸部３３に杭周固定液を夫々充填する。根固め液、杭周固定液は、セメントミルク等の固化性材料、又は固化性材料を掘削土と撹拌混合して形成したソイルセメントから構成する。根固め液は、支持地盤の地盤強度と同等の固化強度を有するように調整する（図３）。尚、根固め部３４の径Ｄ_１２は、設計上で必要とされる支持力により既製杭１４の軸部外径Ｄ_５の１．５倍程度までで調節することが望ましい。
【００６５】
（２）杭穴３２内に、下端に先端金具１２を取り付けた既製杭（下杭。ストレート形状）１４を埋設し、所定深さまで埋設した所で、杭穴３２の開口部で、既製杭１４を保持して、既製杭１４の上端に、他の既製杭（上杭。ストレート形状）１４Ａを連結する。
【００６６】
続いて、既製杭１４、１４Ａを杭穴３２内に下降して、先端金具１２が完全に根固め部３４内に収容され、かつ既製杭１４の下端２２が所定長さＬ_５だけ、根固め部３４内に入り、かつ先端金具１２の下面１３が根固め部３４の底３５から所定長さＬ_４だけ上方に位置するような位置で、既製杭１４の下降を停止して、その状態で既製杭１４、１４Ａを保持する（図４）。
【００６７】
（３）根固め液及び杭周固定液が固化発現した状態で、この発明の基礎杭構造３７を構成する（図３）。
【００６８】
（４）他の実施例
【００６９】
前記実例において、杭穴の掘削完了後に既製杭を埋設するいわゆる先掘工法について説明したが、杭穴を掘削しながら既製杭を埋設するいわゆる中掘工法に適用して、従来と同様に基礎杭を構築することもできる。
【００７０】
即ち、先端金具１２を取り付けた既製杭１４の中空部に、中掘用掘削ロッドを挿通し、先端金具の下端から掘削ヘッドを突出して杭穴を掘削しながら、既製杭１４を下降させる（図示していない）。掘削した土砂は、圧縮空気を利用しながら、掘削ロッドに周設したスパイラルにより、先端金具１２及び既製杭１４の中空部を通って、地上に排出される。続いて、既製杭１４Ａを連結して、掘削ロッドを継ぎ足して、注水しながら掘削し、既製杭１４、１４Ａを下降し、所定位置まで下降したならば、根固め部を形成し、セメントミルクを注入撹拌し、セメントミルク類を吐出しながら掘削ロッドを、既製杭１４、１４Ａ、先端金具１２の中空部内を通って、地上に引き上げる。
【００７１】
以下、既製杭１４を下降しながら、前記先掘工法と同様に、先端金具１２が完全に根固め部３４内に収容され、かつ既製杭１４の下端２２が所定長さＬ_５だけ、根固め部３４内に入り、かつ先端金具１２の下面１３が根固め部３４の底３５から所定長さＬ_４だけ上方に位置するような位置で、既製杭１４の下降を停止して、その状態で既製杭１４、１４Ａを保持する。以上で、根固め液等が固化発現して、基礎杭構造を構築する。
【００７２】
【実施例３】
本願発明の基礎杭構造と、従来例Ｃの基礎杭構造とを、同じ地盤に適用した場合の比較を説明する（図８）。
【００７３】
（１）本願発明
前記実施例１のように、既製杭１４の下端に先端金具１２を取付け、根固め部３４を有する杭穴３２内に埋設する（図１、図３）。各部の寸法は、以下の通りとする。
【００７４】
既製杭１４
ＳＣ杭（鋼管被覆コンクリート杭）
杭長１３．５ｍ
外径Ｄ_５＝６００ｍｍ
中空部内径Ｄ_２＝４２０ｍｍ
先端金具１２
鋼管本体１ｔ_１＝１５ｍｍ
Ｄ_１＝４５０ｍｍ
Ｄ_２＝４２０ｍｍ
大径部２Ｄ_３＝６００ｍｍ
環状突起１０Ｌ_７＝７５〜９０ｍｍ
Ｄ_４＝６００〜６３０ｍｍ
ｔ_２＝１０〜４０ｍｍ
Ｌ_１＝５００ｍｍで３枚
【００７５】
尚、Ｄ_４＝６３０ｍｍとした場合であっても、杭穴軸部の掘削径Ｄ_１１以下であり、Ｄ_３（＝６００ｍｍ）と同等の範囲である。
【００７６】
杭穴３２
軸部３３長さＬ_２＝１３５００ｍｍ
口径Ｄ_１１＝Ｄ_５＋３０ｍｍ
＝６３０ｍｍ
（尚、少なくともＤ_１１≧Ｄ_４となるよう多少調節する）
根固め部３４長さＬ_３＝３０００〜３５００ｍｍ
口径Ｄ_１２＝９００ｍｍ
【００７７】
（２）比較例（従来例Ｃ）
同じ既製杭１４を上杭１４Ａとし、先端金具１２に代えて、節３９付きの下杭１４Ｂを連結した、従来例Ｃに相当する比較例で、基礎杭構造を構築する（図７）。
【００７８】
(a) 上杭１４Ａ
ＳＣ杭（鋼管被覆コンクリート杭）
杭長＝１２ｍ
杭の肉厚＝８０ｍｍ
鋼管厚さ＝９ｍｍ
外径Ｄ_５＝５００ｍｍ
中空部内径＝３４０ｍｍ
(b) 下杭１４Ｂ
節付きコンクリート杭
杭長＝４ｍ
杭の肉厚＝８０ｍｍ
杭の軸部外径Ｄ_６＝Ｄ_５＝５００ｍｍ
杭の節部外径Ｄ_７＝６５０ｍｍ
杭の中空部内径＝３４０ｍｍ
(c) 杭穴３２
軸部３３長さＬ_２＝１３５００ｍｍ
口径Ｄ_１１＝６５０ｍｍ＋３０ｍｍ
＝６８０ｍｍ
根固め部３４長さＬ_３＝２５００ｍｍ
口径Ｄ_１２＝９５０ｍｍ
【００７９】
（３）効果等
【００８０】
(a) 載荷試験では、共に最大荷重として、６．５ＭＮ以上が得られている。本実施例３においては、環状突起の形成枚数を３枚としたが、この枚数を増減することにより、根固め部内のソイルセメントとの付着面積の増減及びせん断力の伝搬面積の増減が可能であり、更に、加えて根固め部のソイルセメントの固化強度を増加させると共に支持地盤の土質を適切に選定することにより、更に高い耐荷重が可能となる。
【００８１】
(b) 同じ支持力を発揮する基礎杭構造とする場合、杭穴の軸部径を従来の１０％弱の小径化できる。これに伴い、掘削土の排出量を同様に削減でき、また、施工時間も同様に短縮される。従って、排土量と掘削時間の軽減に比例して、現場から産業廃棄物として排出される排土の軽減、掘削機の排気ガスの軽減を図ることができ、より環境に優しい基礎杭造成となる。
【００８２】
また、既製杭と杭穴軸部との間隙が約６分の１に削減され、使用するセメントミルクも４０％節減される。
【００８３】
(c) 根固め部の高支持力に対し、杭軸部の外径が約２０％大径化できるので、既製杭材の曲げモーメント強度として、ＳＣ杭で約２倍強い値へと選択範囲が広がる。
【００８４】
(d) 既製杭の中空部内径寸法としては、同様な支持力で対比した時、従来高支持力を発揮させる為の既製杭の内径を３４０ｍｍとした場合、同じ外径の既製杭を使用した場合、本願発明では既製杭の内径は４２０ｍｍで済む。
【００８５】
即ち、通常規格の既製杭を使用する場合、１ランク外径が大きな既製杭を使用した場合と同一な内径となり、内径が２０％以上拡大できる。
【００８６】
従って、中掘工法においては、中空部に挿入する掘削ロッドの最大外径を大きくできるので、各種構造の掘削ヘッドを有する掘削ロッドを選択できる。また、根固め部の掘削寸法をより拡大できる。従って、その根固め部径を拡大できることにより、更に高支持力の発現が可能である。従来の掘削ロッドを用いて掘削でき高支持力が得られる等設備技術面からも有効である。
【００８７】
従来、中掘り工法では拡底掘削が困難であり、また可能であっても、せいぜい既製杭の外径の１．３〜１．４倍程度の拡底部の掘削しかできず、中掘工法では高支持力を発揮する基礎杭構造の構築が困難であったが、本願発明により、従来の施工技術で１ランク上となる既製杭の外径の１．５〜１．６倍迄の拡底部の掘削を可能とし、中掘工法の適用範囲を拡大できる。
【００８８】
【実施例４】
前記各実施例において、先端金具１２は、鋼管本体１の中間部及び下端部に環状突起１０、１０を形成したが、他の構造の先端金具１２とした実施例である。
【００８９】
（１）外径Ｄ_１の鋼管本体１の上端に、既製杭との連結部を有する外径Ｄ_３の大径部を形成し、下端に外径Ｄ_４の環状突起を連設して構成する（図９）。
【００９０】
外径Ｄ_１、内径Ｄ_２の鋼管本体１の上端部に、外径Ｄ_３の大径部２を形成し、大径部２を既製杭１４との連結部とする。大径部２は、上面を水平平面状とし、下面側を徐々に小径とした部分円錐状の傾斜斜面を有する段差部下面４３を形成してある。連結部の外径、即ち、大径部２の外径Ｄ_３は、接続するべき既製杭１４の外径（下端部の外径）と略同一としてある。
【００９１】
鋼管本体１の下端部外側面に、外径Ｄ_４の円盤状（ドーナツ状）の環状突起１０を突設する。環状突起１０の上面４４は、水平面状に形成し、下面４５は部分円錐状の傾斜斜面を形成し、傾斜斜面の下端は鋼管本体１の下端に至っている。
【００９２】
以上のようにして、先端金具１２を構成する（図９（ａ））。先端金具１２の内径Ｄ_２は、上端（大径部２の上端）から下端まで、既製杭１４の内径と略同一で、形成されている。即ち、既製杭１４の内側面１５と先端金具１２の内側面９とは略面一に形成される（図１０（ｂ））。
【００９３】
また、大径部２と環状突起１０との間隔は、前記各実施例と同様に形成され、環状突起１０の間に、更に、本実施例又は前記実施例１の環状突起１０を連設することもでき、この場合にも前記実施例１と同様に上下方向の間隔が形成される。
【００９４】
尚、ここでは、例えば、
Ｄ_１＝６２０ｍｍ
Ｄ_２＝５８０ｍｍ
Ｄ_３＝８００ｍｍ
Ｄ_４＝８５６ｍｍ
として、Ｄ_３に比して、Ｄ_４を多少大径に形成したので、より大きな支持力が期待できる。また、大径に形成した分、既製杭の埋設作業において、作業性に劣る場合もあるが、所要の支持力が得られれば、Ｄ_４≦Ｄ_３、とすることもできる。尚、上記において、Ｄ_４（＝８５６ｍｍ）は、杭穴軸部の掘削径（８３０ｍｍ）以下とし、Ｄ_３（＝８００ｍｍ）と同等の範囲である。
【００９５】
（２）前記先端金具１２の大径部２の上面を、前記実施例１と同じ外径Ｄ_３の既製杭１４の下端板１７の下面に当て、大径部２と下端板１７とをボルトや溶接等で一体に固定して、杭穴に埋設して、基礎杭構造を構成する（図示していない）。
【００９６】
既製杭１４を埋設する際に、大径部２を含む鋼管本体１の全体及び既製杭１の下端部を覆い、該部に泥土が固着することを防止できる筒状のカバー４７を使用することが望ましい。この場合、カバー４７の下端を環状突起１０の外周部４６に、ストッパー５を介して係止仮止めし、カバー４７の上端のカプラー４８、４８にＰＣ鋼棒４９の下端をねじ止めし、ＰＣ鋼棒４９の上端を既製杭１４の上端に連設した円盤状治具５２にナット５１、カプラー５０でねじ止めする（図１０（ａ））。この状態で、既製杭１４を埋設すれば、後に述べるように、カバー４７により保護される環状突起１０の上面４４及び下面４５には、泥土が固着あるいは滞留し難く、先端金具１２及び既製杭１４の下端部に泥土が固着することなく、該部を杭穴の根固め部内に設置できる。
【００９７】
既製杭１４を所定の位置に設置したならば、ＰＣ鋼棒の上端を引き上げ、カバー４７と環状突起１０のストッパー５３による仮止めを解除して、カバー４７及びＰＣ鋼棒４９を地上に引き上げる。
【００９８】
従って、カバー４７を使用した場合、先端金具１２及び既製杭１４の下端部が根固め部内に形成されるセメントミルク層内に確実に密着して定着でき、高品質の基礎杭構造を構築できる。また、カバー４７として、ここでは円筒状の肉厚の薄い鋼管を使用するが、該部をカバーして埋設してその後に引き上げできれば、材質、構造は任意である。また、実施例１の先端金具１２にも同様にカバー４７を適用できる（図示していない）。
【００９９】
保護カバー４７を利用することにより、既製杭１４の下端部とソイルセメントとの密着性を低下させる粘着性の土泥の固着を防止できるので、既製杭１４（下端部）の外径と杭穴軸部の外径と間隙を小さくいても、既製杭１４の下端部とソイルセメント層との密着性が土質に関係なく維持でき、基礎杭構造で安定した先端支持力が得られる。
【０１００】
（３）この実施例の先端金具１２では、前記保護カバー４７を使用して安定した支持力が得られるので、同一外径の場合には、前記実施例１の先端金具１２（図１、５）に比して、全表面積及びせん断力が伝達する面が少ない分、支持力が多少小さな設計となっているが、施工上取扱い易いと共に、杭穴の根固め部の掘削径を小さく形成できる等の利点がある。
【０１０１】
即ち、具体的には、前記構造の先端金具１２を使用し、更には前記保護カバー４７を使用することにより、以下のような利点が安定して得られる。
【０１０２】
(a) 鋼管本体１（筒状基部）の長さを短くし（長さ１．０ｍ程度。実施例１では、長さ２．５ｍ程度）、先端金具１２における支持力の発揮に寄与が少ない、鋼管本体１の側面の面積を減らした。これにより、杭穴の根固め部の拡底掘削する長さを短くし、結果、施工時間の短縮、セメントミルクの使用量を削減する等を実現できる。
(b) また、環状突起１０の根付け部分（鋼管本体１に近い側）を厚くし、機械的強度を高めた。
(c) また、環状突起１０の下面４５を部分円錐状の傾斜斜面としたので、根固め部内のソイルセメント層及び地盤への応力が効率的に伝搬される。
(d) 鉛直支持力の発生に最も寄与すると考えられる先端部に広い表面積の環状突起１０を形成したので、外径の小さい突起部で、また少ない数で、より大きな鉛直支持力を発揮できる。
(e) 鉛直支持力の発生に寄与する環状突起１０の下面４５を傾斜させて形成したので、先端金具を杭穴へ埋設する際に環状突起１０の下面４５に泥土が固着し難い。従って、ソイルセメント層と下面４５との付着を高め、せん断力のソイルセメント層への伝搬を確実になし得る。
(f) 既製杭１４の最先端に最も大径な部分が形成してあるので、既製杭１４を埋設する際に、既製杭１４のセンタリング（杭穴の芯との芯合わせ）が容易となる。
【０１０３】
【発明の効果】
既製杭の下端部に、突起部を有する先端金具を固定して、あるいは、下端部に突起部又は凹部を形成した既製杭に関し、ソイルセメントとの付着面積を広くして、先端金具の大径部下面、先端金具の突起部上下面、既製杭の主軸部と下部軸部の段差部、突起部の上下壁、凹部の上下壁より、せん断力が障害なく充分に伝搬できるように配置して、支持地盤強度以上の固化強度のソイルセメントを充填した根固め部内に埋設するので、根固め部内で、せん断力を有効に伝搬させ、高い支持力を有する基礎杭構造を形成できる効果がある。
【０１０４】
また、先端金具の突起部の外径を既製杭の最大外径と同等又はより小径に形成したので、より小さな杭穴軸部の掘削径で、より大きな支持力を発揮できる効果がある。また、杭穴軸部の掘削径に比してより大きな支持力を発揮できるので、同じ支持力で、掘削径を小さくできるので、排土量を削減し、杭穴の掘削時間を削減できる効果が有る。従って、現場から排出される産業廃棄物としての排土を減らし、掘削時間の軽減により掘削機の排気ガスの軽減を図り、より環境に優しく、基礎杭を構築できる。
【０１０５】
また、杭穴の軸部径、既製杭の外径を同じにして、従来と同等の支持力を発揮させる場合に、既製杭の内径を大きくできるので、既製杭の中空部を有効活用して、中掘工法でより高支持力を有する基礎杭を従来設備で容易に構築できる効果がある。
【０１０６】
また、先端金具を使用する場合には、同じ口径の既製杭を使用する場合でも、求める先端支持力が異なる場合に、その先端支持力に応じて、先端金具の突起部の形成枚数等を変えて有効面積を増減、あるいはソイルセメントの固化強度を増減すること等により、より効率的な基礎杭構造を簡便に構築できる効果がある。
【０１０７】
また、先端支持力に関わる既製杭の下端部や先端支持具を保護カバーで覆う場合には、該部に泥土が固着又は滞留せずに、該部とソイルセメント層との密着性が改善される。従って、粘着性の高い地盤でも安定した支持力が得られるので、杭穴の軸部径と、既製杭及び先端金具の外径との間隙を小さくしても、築造される基礎杭構造において安定した高支持力が得られる。
【図面の簡単な説明】
【図１】この発明の先端金具の実施例で、（ａ）は正面図、（ｂ）は底面図、（ｃ）は縦断面図である。
【図２】この発明の先端金具と既製杭との連結を表す一部拡大縦断面図で、（ａ）は連結前、（ｂ）は連結後を夫々表す。
【図３】この発明の実施例の基礎杭構造の縦断面図である。
【図４】同じく根固め部の拡大縦断面図である。
【図５】この発明の他の先端金具の正面図である。
【図６】この発明の他の既製杭の正面図である。
【図７】この発明の従来例Ｃを説明する図で、（ａ）は上杭及び下杭の縦断面図、（ｂ）既製杭（上下杭）を埋設した基礎杭構造の縦断面図である。
【図８】実施例３を適用する地盤と既製杭設置状況を説明する図である。
【図９】実施例４の既製杭で、（ａ）は縦断面図、（ｂ）は杭打ち機に装着した状態の正面図である。
【図１０】同じく既製杭の一部拡大縦断面図で、（ａ）は上端部、（ｂ）は下端部を、夫々表す。
【符号の説明】
１鋼管本体
２大径部
３環状溝部
４ボルト穴
５筒状表面材
６当接材
８外側面
９内側面
１０環状突起
１１環状突起のリブ
１２先端金具
１３先端金具の下面
１４、１４Ａ既製杭
１５既製杭の内側面
１６既製杭の接続金具
１７既製杭の下端板
１８既製杭の側板
１９既製杭の側板の肉厚部
２０既製杭の環状溝部
２１既製杭のボルト穴
２２既製杭の下端
２３連結用のバンド
２４バンド片
２５、２６バンドの環状凸部
２７バンドの貫通孔
２８バンドの収容部
３０ボルト
３２杭穴
３３杭穴の軸部
３４杭穴の根固め部
３５杭穴の根固め部の底
３７基礎杭構造
４０凹部
４１突起部下面（凹部の上側側面）
４２突起部上面（凹部の下側側面）
４３段差部下面
４４環状突起１１の上面
４５環状突起１１の下面
４７カバー
４９ＰＣ鋼棒
５２円盤状治具[0001]
BACKGROUND OF THE INVENTION
  A pre-made pile with protrusions such as nodes, spiral wings, steel rods, steel plates, etc. formed on the bottom end of the pile is installed on the soil cement layer of the predetermined root-clamping part, and the high bearing capacity is utilized using the protrusions. Foundation pile structure expressingTo makeRelated. In addition, any of the presence or absence of a diameter expansion can be applied to a root hardening part.
[0002]
[Prior art]
  Conventionally, in a pile foundation, an invention was made in which protrusions were formed at the lower end portion of a pile embedded in a root-solidified portion, and the supporting force was enhanced with the entire foundation pile integrally with a ready-made pile embedded in a pile hole. For example, a structure in which a plurality of sets of expanded reinforcing bars are formed on the outer periphery of the lower end portion of a cylindrical concrete pile, and a chain is connected as a horizontal reinforcing bar between the reinforcing bars of the expanded reinforcing bars (Patent Document 1, Japanese Patent Laid-Open No. 11-61811, Japanese Patent No. 3054389). (Hereinafter, Conventional Example A)), and a structure in which an H-shaped steel having a convex portion on the outer surface of the flange is fixed to the tip of the ready-made pile (Patent Document 2. JP 2001-271347 A (hereinafter, Conventional Example B)), Further, a structure using a ready-made pile made of concrete having a protrusion on the outer periphery of the lower end (Patent Document 3, Japanese Patent Laid-Open No. 11-280067 (hereinafter, Conventional Example C)) is known.
[0003]
  According to FIGS. 1 to 5 etc. of the embodiment described in the prior art A publication, the ready-made pile 3 in which the expanded reinforcing bar 6 formed on the lower outer surface is folded is penetrated through the shaft portion of the pile hole 1, and the hole bottom It is said that a high supporting force can be obtained by pushing into the expanded portion 2 and expanding the expanded rebar 6 so as to be embedded and solidified as shown in FIG. Pile hole excavation dimensions are not specifically described, but according to FIGS. 3 and 5, the dimension of the shaft hole 1 is at least “pile diameter + expanded rebar thickness” or more, Pile holes with a large diameter of about 30% or more of the diameter are drilled. Accordingly, the gap between the pile and the pile hole is extra as compared with “pile length + 30 mm (10% or less of the pile diameter)” of the required dimension of the shaft pile hole of the normal pile foundation. The excavation diameter of the root-solidified part is twice or more the pile diameter and larger than the normal support force (pile diameter x about 1.25 to 1.5).
[0004]
  Further, according to the example on page 3 of the conventional example B publication, the steel H steel is formed at the lower end of the outer shell steel pipe concrete pile 1 (usually called SC pile) having an outer diameter D (500 mm). And shaft hole diameter D₁Is excavated at 650mm. The required shaft excavation diameter in the conventional foundation pile is about “pile diameter + 30 mm (10 m% or less of the pile diameter)”, and the distance between the inner wall of the pile hole and the outer surface of the pile is excessive as compared with the conventional one. Also, in order to develop a high bearing capacity, the bottomed root consolidation part excavation diameter D₀Has a large-diameter excavation of 1000 mm, which is approximately twice the diameter of the pile, compared to the normal bearing force (pile diameter x 1.25 to 1.5).
[0005]
  Moreover, according to Fig.2 (a), although H steel 2 and the reinforcement rib 4 which were formed in the lower end part of the pile 1 seem to be formed below the outer diameter dimension of the pile 1 of the upper part at first glance, Compared with FIG. 1, FIG. 3, etc., it is drawn by the dimension substantially the same as an Example, and it is guessed that large-diameter excavation is performed for both axial part excavation and deepening root solidification part excavation like an Example.
[0006]
  Further, as shown in FIG. 2 of JP-A-2001-27347, in the case of a structure in which the projection closes the lower end portion of the pile, the pile lower end central portion and the pile hole hollow portion particularly with respect to the high-concentration soil cement of the root consolidation portion The shearing force cannot be fully utilized due to the upper and lower overlapping of each plug-shaped projection. In addition, there is a problem in versatility such that the excavation head cannot penetrate the hollow part of the pile hole due to the protrusion, so that the construction by the medium excavation method cannot be performed.
[0007]
  Moreover, according to the pile foundation 10 by Example 1 of FIG. 1 of a prior art example C gazette, as a structure of a pile lower part, it forms in the pile lower end part embed | buried under the bottom expansion root-solidifying part 3, and the protrusion part which contributes to high strength expression Is an annular rib (node-shaped), and three annular ribs 5, 6, 7 are formed. In order to sufficiently exhibit the shearing force of the protrusion, the annular rib outer diameter D of the protrusion₁(75cm) is the shaft outer diameter D of the pile 4₀The surface area of the protrusions is larger than (60 cm). Therefore, the outer diameter of the upper part of the ready-made pile is the shaft outer diameter dimension D.₀And the pile material is limited, and the excavation dimension of the pile hole shaft part 2 is the dimension D in which the annular rib is easy to penetrate.₀₀(80cm) is excavated and the gap between the inner wall of the pile hole and the outer surface of the pile is wide, and the bottom expansion dimension D of the root consolidation part₁₁However, a large-diameter excavation at an unprecedented ratio is required, and a new technical response to an unprecedented large-diameter excavation work is required for both the shaft portion and the bottomed root solidified portion.
[0008]
  In addition, a number of pile foundations have been proposed in the past, where protrusions or recesses have been formed in the embedded part of the pre-solidified piles to enhance the support force. There is not enough spacing between the protrusions or the recesses so that it can be fully expressed, and it is considered that the shear strength is fully developed and the bearing strength is obtained, including the required solidification strength of the soil cement layer. It seems that only the foundation pile using the invention of Conventional Example C seems to have a lot of construction results.
[0009]
  In general, the shaft piles with a small diameter are used for the high bearing capacity that develops at the root consolidation part, and the horizontal bearing strength of the shaft piles themselves is insufficient. It was difficult to construct a pile foundation that limited the choice of materials and maximized the vertical bearing capacity.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-61811
[0011]
[Patent Document 2]
JP 2001-271347 A
[0012]
[Patent Document 3]
JP-A-11-280067
[0013]
[Problems to be solved by the invention]
  The prior art has the following problems.
[0014]
(1) At the lower end of the pile, because the protrusion is formed on the outer surface of the pile as a simple method in order to increase the area of the protrusion that causes the adhesion with the soil cement layer and the shearing force, The excavation diameter of the deepening root consolidation part and the shaft diameter of the pile hole are larger in the pile diameter ratio than the conventional normal bearing capacity pile foundation. The gap between the pile hole shaft diameter and the pile hole shaft diameter must also be increased.
[0015]
(2) Pile at the pile hole shaft must have a well-balanced and high yield strength (strength that satisfies both the load bearing capacity and bending strength) against the high bearing capacity that is twice as high as the conventional level. However, since the pile diameter is small, the selection range of pile materials is limited, and it is difficult to make full use of the high bearing capacity of the root-solidified part.
[0016]
(3) Pile hole diameter required to develop the frictional force of the pile diameter embedded in the pile hole shaft (when the distance between the normal pile hole inner wall and the pile is 30 mm, 10% or less) (for example, 20% or more), the excavation area is wasted (about 40%), and the excavation diameter of the deepened root consolidation part is relatively large compared to the conventional pile diameter ratio. As a result, the excavation time is long and the excavation and soiling is also a problem economically and environmentally. Furthermore, there are many wasteful points, such as the need to procure a drilling device for a large-diameter pile hole, which is unprecedented.
[0017]
  In particular, for medium digging, large diameters that do not have an expanded bottom pile hole (compared to the inner diameter of the hollow part of the pile)InTherefore, there are many problems to be solved in the excavator technology regarding the stable construction of excavation.
[0018]
[Means for Solving the Problems]
  However, in the present invention, a tip metal fitting having a projection having a diameter equal to or smaller than the maximum outer diameter of the ready-made pile to be connected is formed, or the lower end portion of the ready-made pile located in the root consolidation portion is smaller in diameter than the upper shaft portion. Since the lower shaft portion is formed with a protrusion or the like having an outer diameter equal to or smaller than the maximum outer diameter of the upper shaft portion, the above-described problems have been solved.
[0019]
  That is, the invention of this foundation pile structure is to connect the tip fitting or "other ready-made pile" to the lower end of the ready-made pile having a main shaft portion of a predetermined shaft diameter, the tip fitting or "other ready-made pile"Having a large diameter portion of substantially the same diameter as the main shaft portion connected to the ready-made pile,Forming a lower shaft portion having a smaller diameter than the main shaft portion, forming a protrusion on the lower shaft portion, and forming the tip of the protrusion to be equal to or less than the maximum outer diameter of the main shaft portion;And forming a stepped portion on the lower surface of the large diameter portion,In the pile hole having a root-solidified portion filled with a root-solidifying solution on the supporting ground, the ready-made pile is connected to the tip fitting or "other pre-made pile" and the lower end of the ready-made pile is within the root-solidified portion of the pile hole. It is the foundation pile structure using the ready-made pile characterized by being embedded so that the said front-end metal fitting or "other ready-made pile" might be unitedly supported by the said support ground.
[0020]
  Further, in the above, the protruding portion is provided with a predetermined gap between the upper surface of the protruding portion and the lower surface of the step portion between the main shaft portion and the lower shaft portion, or with a predetermined gap between the upper and lower surfaces of the adjacent protruding portions. It is a foundation pile structure using the ready-made pile characterized by having filled with the soil cement into which the solidification strength becomes more than the intensity | strength of a support ground in the solidified part of the predetermined shape of a pile hole.
[0021]
  Further, the invention of another foundation pile structure is to connect a tip fitting or "other ready-made pile" to the lower end of a ready-made pile having a main shaft portion of a predetermined shaft diameter, and the tip fitting or "other ready-made pile"Having a large diameter portion of substantially the same diameter as the main shaft portion connected to the ready-made pile,At the lower end, form a lateral recess from the side to the shaft side,And forming a stepped portion on the lower surface of the large diameter portion,In the pile hole having a root consolidation part filled with root consolidation liquid on the supporting ground, the ready-made pile is connected to the tip metal fitting or “other ready-made pile” and the lower end portion of the ready-made pile in the root consolidation part of the pile hole. It is a foundation pile structure using a built-in ready-made pile so that the tip metal fitting or "other ready-made pile" may be integrated and supported on the supporting ground.
[0022]
  In addition, in the above, the ready-made pile is configured by attaching a cover that covers the lower end of the ready-made pile and the tip metal fitting or "other ready-made pile",The cover isPull the ready-made pile to the ground after burialConfigure as possibleIt is a foundation pile structure characterized by that.
[0023]
  The ready-made pile in the above is configured by connecting a tip fitting having a protrusion or a recess to the lower end of the ready-made pile, but when processing the lower end of one ready-made pile to have a predetermined structure having a protrusion or a recess. Alternatively, a structure in which one or a plurality of upper piles are joined to a lower pile having a predetermined structure having a protruding portion or a recessed portion may be used.
[0024]
  In addition, the ready-made pile in the above is mainly configured by connecting a steel tip metal fitting to the tip of a concrete-based ready-made pile, and the ready-made pile adopts a steel pipe system or a composite structure material thereof, A tip metal fitting and a ready-made pile can also be manufactured integrally.
[0025]
  Moreover, the outer diameter range in the above refers to a range that is equivalent to the maximum outer diameter of the ready-made pile and forms a cylindrical range and does not protrude radially from the cylindrical side surface.
[0026]
  In addition, the maximum outer diameter of the ready-made pile in the above usually refers to the outer diameter because a straight ready-made pile is used, but when using a ready-made pile having a different outer diameter, When the protrusions have a larger diameter than the bottom surface of the ready-made pile that connects the end fittings, the outer diameters of the large diameter part, the protrusions, and the like are referred to. That is, since the pile hole is excavated with a diameter corresponding to the maximum outer diameter of the ready-made pile, it means the maximum outer diameter of the ready-made pile defined by the excavation diameter of the pile hole.
[0027]
  The predetermined gap formed between the upper surface of the protrusion and the lower surface of the stepped portion between the main shaft portion and the lower shaft portion, or the predetermined gap formed between the upper and lower surfaces of the adjacent protrusions is effective shear. In order to propagate the force, it is desirable to set the projection interval so that the propagation of the shear force in each projection does not overlap in the vertical direction in consideration of the propagation angle of the shear force. For example, when two protrusions are formed on the top and bottom, when a vertical load is applied to the entire foundation pile structure, it adheres from the lower surface of the stepped portion, the lower surface of each protruding portion, and the lower surface of the ready-made pile (tip fitting). Shear force propagates to the soil cement layer (solidification). At this time, it has been confirmed by tests that the shear force propagates obliquely downward and at an angle of about 30 degrees with the vertical direction. Therefore, if this shearing force is propagated so that it does not hit the upper surface of the projecting part located below, the shearing force can be sufficiently expressed by the projecting part or the like. It is preferable that the height is √3 times or more. Based on the above assumptions, it is only necessary to design a projection with a predetermined gap in accordance with the required support force, but in general, a ready-made pile with a projection for consolidation that takes into account the predetermined gap It is desirable to manufacture in advance.
[0028]
  Further, when a pulling force is applied to the entire foundation pile structure, the shearing force is similarly applied upward, and the same predetermined gap as that when a vertical load is applied is required.
[0029]
  In addition, the above-mentioned solidified root portion is a size (layer thickness, outer diameter, long length) that matches the strength of the solidified soil cement layer required when the shearing force propagates downward or upward. Meaning). The layer thickness of the soil cement layer between the lower surface of the ready-made pile (tip fitting) and the bottom of the pile hole is equal to or greater than the pile diameter of the ready-made pile (tip fitting) (for example, about 50 cm). It is desirable that the diameter is about 1.5 times the diameter of the protrusion.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
(1) The tip metal fitting 12 of the present invention has a structure that can be attached to the lower end portion (end plate portion or the like) of the ready-made pile 14 with a bolt or the like, and has a large diameter portion 2 for connection to the upper end portion of the steel pipe main body 1. Annular projections 10 and 10 are formed on the intermediate portion and the lower end portion (the portion excluding the large diameter portion) of the steel pipe main body 1. The outer diameter D of the annular protrusion 10₄Is the large diameter part 2, that is, the maximum outer diameter D of the ready-made pile 14₅It is equivalent to or smaller than Here, the tip of the annular protrusion 10 is formed so as not to protrude outwardly from the maximum outer diameter of the large-diameter portion 2, that is, the ready-made pile 14 (FIG. 1). If it is below a shaft part excavation diameter, it can also project a little.
[0031]
  The ready-made pile 14 to which the tip metal fitting 12 is connected is lowered into the pile hole 32 filled with a solidified material such as soil cement so that the tip metal fitting 12 is positioned at the rooting portion 34 formed at the lower end portion of the pile hole. Then, the ready-made pile 14 is buried to form a foundation pile structure 37 (FIG. 3). It is desirable that the soil cement has a predetermined solidification strength equal to or higher than the ground strength.
[0032]
  An upper structure such as a foundation base and a building is constructed on the upper end of the foundation pile structure 37.
[0033]
(2) Function and structure of the end fitting 12 to be mounted
[0034]
  The load of the building or the like transmitted from the ready-made pile 14 is propagated to the supporting ground or the like as a shearing force or the like from the surface of the annular protrusion 10 of the tip fitting 12, and the tip fitting 12 is solidified soil cement in the pile hole 32. It has a function of supporting the supporting ground integrally with the layer.
[0035]
  The upper surface of the large-diameter portion 2 at the upper end of the tip fitting 12 is in close contact with the lower surface of the lower end plate 17 of the ready-made pile 14 and functions as a connecting portion to be attached to the ready-made pile 14. The large-diameter portion 2 is formed by being welded to the steel pipe main body 1 or molded integrally with the steel pipe main body 1.
[0036]
  Moreover, the outer side surface 8 of the steel pipe main body 1 adheres to the solidified soil cement in the pile hole 32 and functions so as to be embedded integrally. The annular protrusion 10 has an outer diameter D of the annular protrusion 10.₄Is the depth L between the annular projections 10, 10.₇This is the same as the formation of the recess 40.
[0037]
(3) Explanation of each component
[0038]
  (a) The large-diameter portion (connecting portion) 2 positioned at the upper end portion of the tip fitting 12 transmits the load of the building or the like transmitted from the ready-made pile 14 positioned above the steel pipe body 1 and the annular protrusion 10. To do. Furthermore, it has the function of increasing the supporting force together with the annular protrusion 10 by propagating a vertical shearing force from the lower surface of the outer edge of the large-diameter portion 2 (stepped portion with the steel pipe body) through the soil cement layer in the pile hole.
[0039]
  The large-diameter portion 2 and the steel pipe body 1 are connected and fixed by welding or forming process, etc., and a steel material having an integrated structure is used so that the transmission of stress smoothly propagates. In addition, an annular connecting plate is formed in the large diameter portion 2, and the thickness can be adjusted by stacking a plurality of stress dispersions on the connecting plate depending on the necessity for strength. In addition, a plurality of oblique reinforcing ribs can be formed between the lower surface of the peripheral edge of the connecting plate and the outer surface of the steel pipe body.
[0040]
  (b) The annular protrusion 10 is integrally attached and buried in the soil cement layer in the pile hole 32, and the upper and lower surfaces of the annular protrusion 10 are attached to the soil cement layer corresponding to the desired bearing force and the strength (thickness). In general, steel is used. Accordingly, a plurality of annular protrusions 10 are formed, and a predetermined shearing force from the upper and lower surfaces 42 and 41 of each annular protrusion 10 and the stepped portion lower surface 43 can be sufficiently propagated obliquely downward (about 30 degrees). Interval L₁It is desirable to provide Such an annular protrusion 10 is fixed to the outer surface 8 of the steel pipe body 1 by welding or the like, and is configured integrally with the steel pipe body 1.
[0041]
  The structure of the annular protrusion 10 may be, for example, a donut shape made of a steel plate and attached to the steel pipe body 1 (FIG. 1), or a structure attached two to a donut shape made of a steel plate (FIG. 5A). it can. In this case, reinforcing ribs 11 can be formed between the upper and lower surfaces of the annular protrusion 10 and the outer surface 8 of the steel pipe main body 1 (FIG. 5A). In addition, the formation of the donut shape can be formed by overlapping a steel rod in place of the steel plate and winding the same (not shown).
[0042]
  Moreover, the annular protrusion 10 can also be made into the structure which twisted the donut-shaped steel plate and formed the spiral wing | blade shape in two places (FIG.5 (b)). In this case, considering the propagation of the shearing force in the soil cement layer, it is necessary to make the inclination angle of the spiral blade smaller and to make it less than one round.
[0043]
  Moreover, the annular protrusion 10 can also be formed in a donut shape having a thick trapezoidal cross section (FIG. 5C). In this case, the annular protrusion 10 can be either hollow or solid.
[0044]
  (c) The steel pipe body 1 is integrated with the large-diameter portion 2 and the annular protrusion 10, and further, when embedded, it is integrated with the solidified soil cement layer in the pile hole 32 to transmit and support stress in the vertical direction. It is the structure used as the base | substrate which carries out. Therefore, the steel pipe body 1 has a required thickness t suitable for stress transmission and support.₁, Material is required. Moreover, the inside of the steel pipe main body 1 communicates with the hollow part of the ready-made pile 14 to connect with the same internal diameter, and it forms so that soil cement can be uniformly filled in a hollow part. Moreover, when it forms with the same internal diameter as the hollow part of the ready-made pile 14 to connect, when applying to a medium digging method, a drilling rod can be penetrated without trouble.
[0045]
(4) Dimensions of tip bracket 12
[0046]
  Inside diameter D of steel pipe body 1₂May be equal to or larger than the inner diameter of the hollow portion of the ready-made pile 14 positioned at the upper portion, but in order to increase the effective area of the protrusion, an inner diameter of approximately the same size as the inner diameter of the hollow portion of the ready-made pile 14 is desirable (FIG. 1). .
[0047]
  Further, the outer diameter D of the annular protrusion 10₄Is the outer diameter D of the ready-made pile 14 located in the upper part₅The following dimensions are possible, but the outer diameter D of the ready-made pile 14₅Are substantially the same in terms of strength design, support force, etc. (FIGS. 1 and 4). Further, when the ready-made pile 14 is set in the pile hole, it is necessary to limit it to at least an outer diameter dimension within a range in which the pile hole can be penetrated without any trouble when penetrating into the shaft portion. In other words, it is desirable to be less than the shaft excavation diameter of the pile hole.
[0048]
  Further, the length L of the annular protrusion 10 from the outer surface of the steel pipe body 1₇(= “D₄-D₁)) And the installation interval L₁With the propagation angle θ of the downward shear force (≈30 degrees), so that the shear force can be sufficiently expressed,
  L₇<L₁× tanθ
In order to secure the surface area of the annular protrusion 10 from both the surface of propagation of shearing force to the soil cement layer and the surface of adhesion to the soil cement, L is as much as possible.₇It is desirable to increase (FIG. 1 (a)).
[0049]
(5) Moreover, from the technical idea as described above, a steel pipe pile with a spiral wing (smaller diameter than the ready-made pile to be installed) is fixed to the lower end of the ready-made pile instead of the tip fitting, and the ready-made pile of this invention is configured. You can also
[0050]
[Example 1]
  An embodiment of the tip metal fitting of the present invention will be described based on the drawings.
[0051]
(1) Outer diameter D₁(= 450mm), inner diameter D₂(= 420) steel pipe body (thickness t₁= 15 mm) At the upper end of 1, the outer diameter D₃A large-diameter portion 2 of (= 600 mm) is formed and used as a connection portion with the ready-made pile 14. On the outer periphery on the upper end side of the large-diameter portion 2, an annular groove portion 3 for fitting the connecting band 23 is formed. The outer diameter of the connecting portion, that is, the outer diameter D of the large diameter portion 2₃Is substantially the same as the outer diameter of the ready-made pile 14 to be connected (the outer diameter of the lower end plate). Bolt holes 4 and 4 for connection are formed in the annular groove 3.
[0052]
  On the outer periphery of the large-diameter portion 2, a cylindrical surface material 5 having an annular groove portion 3, a donut-shaped contact material 6 that is in contact with the lower surface of the ready-made pile 14 continuously from the upper end inside the cylindrical surface material 5, Is embedded. The bolt holes 4 and 4 are formed in the cylindrical surface material 3.
[0053]
  The distance L from the outer surface 8 of the steel pipe to the outer periphery of the intermediate part and the lower end part of the steel pipe body 1₇(= 75 to 90 mm) (ie outer diameter D₄= 600-630mm), thickness t₂An annular projection 10 (= 10 to 40 mm) is projected. The annular protrusion 10 is formed in a thin disk shape, and the distance L is set so that the distance from the lower end of the steel pipe body 1 to the lower portion of the large diameter portion 2 is equally divided.₁Three (= 500 mm) are formed. If the annular protrusion 10 is expressed in another way, the reference diameter D₄To depth L₇The recess 40 is formed.
[0054]
  As described above, the end fitting 12 is configured (FIGS. 1A, 1B, and 1C).
[0055]
  Interval L in the above₁In consideration of effective propagation of the shearing force from the lower surface 41, the upper surface 42 of the annular protrusion 10, and the stepped portion lower surface 43 of the large diameter portion 2,
  L₁> √3 × L₇
It is formed to become.
[0056]
(2) Next, the use of the tip metal fitting 12 of the present invention based on the above-described embodiment, that is, the configuration of the ready-made pile 14 will be described (FIGS. 2A and 2B).
[0057]
  A steel connection fitting 16 is integrally attached to a lower end portion of the ready-made pile 14 made of concrete. The connection bracket 16 includes a disk-shaped lower end plate 17 and a cylindrical side plate 18 that is connected to the lower end plate 17 and is provided around the side surface of the ready-made pile 14. The side plate 18 is formed at a portion that is continuous with the lower end plate 17. The thick portion 19 has a thicker material. An annular groove portion 20 having substantially the same shape as the annular groove portion 3 of the end fitting 12 is formed on the side plate 18. Bolt holes 21 and 21 corresponding to the bolt holes 4 of the end fitting 12 are formed in the annular groove portion 20. The annular groove portion 20 and the bolt hole 21 are formed in the thick portion 19.
[0058]
  The band 23 for joining is comprised with the steel which has the internal diameter which can be fitted to the large diameter part 2 of the front-end metal fitting 12, and the lower end board 17 of the ready-made pile 14. FIG. The band 23 is formed with an annular convex portion 25 projecting inward so that it can be fitted into the annular groove portion 20 on the upper inner surface, and a similar annular convex portion 26 corresponding to the annular groove portion 3 on the lower side. Is formed. In addition, through holes 27 and 27 corresponding to the bolt holes 4 and 21 are formed in the annular convex portions 25 and 26 of the band 23, and an accommodating portion 28 having an enlarged diameter of the through holes 27 and 27 is formed on the outer surface of the band 23. It is formed and can accommodate the head of the bolt 30 for joining. Further, the band 23 is equally divided into three band pieces 24 and 24 so as to facilitate the connecting operation.
[0059]
  In the state where the ready-made pile 14 is lifted vertically or the ready-made pile 14 is laid on the ground, the upper surface of the tip metal fitting 12 (the upper surface of the large-diameter portion 2) is brought into contact with the lower end plate 17 of the ready-made pile 14, Band pieces 24, 24 are arranged in abutment with the contact portion to form a band 23, and the annular convex portions 25, 26 of the band 23 are inserted into the annular groove portion 20 of the ready-made pile 14 and the annular groove portion 3 of the tip fitting 12, respectively. Bolts 30 are inserted through the through holes 27, 27, the tip portions of the bolts 30 are screwed and fastened to the bolt holes 21, 4, and the band 23 is fixed to the ready-made pile 14 and the tip fitting 12. The metal fitting 12 is fixed integrally.
[0060]
  In this state, the inner diameter of the ready-made pile 14 and the inner diameter of the tip fitting 12 are formed to be substantially the same diameter. That is, the inner side surface 15 of the ready-made pile 14 and the inner side surface 9 of the tip metal fitting 12 are formed substantially flush with each other (FIG. 2B).
[0061]
(3) Other embodiments
[0062]
  Moreover, in the said Example, although the ready-made pile 14 fixed the tip metal fitting 12 to the lower end, it formed, the tip metal fitting 12 was formed integrally with the ready-made pile, and it can also be set as the ready-made pile 14 (FIG. 6). ). Even in this case, the distance L between the protrusions 10 is₁In consideration of effective propagation of the shearing force from the lower surface 41, the upper surface 42, and the stepped portion lower surface 43 of the annular protrusion 10,
  L₁> √3 × L₇
It is formed to become. Further, if the annular protrusion 10 is expressed in another way, the reference diameter D₄To depth L₇The recess 40 is formed.
[0063]
[Example 2]
  Next, the foundation pile structure of this invention is demonstrated.
[0064]
(1) Predetermined aperture D₁₁(D₁₁= D₅The shaft portion 33 of the pile hole 32 of about +30 mm) has a predetermined depth L₂Drilled until the shaft portion 33 of the pile hole 32 continues to the depth L₃Over the diameter D₁₂The bottom is excavated to form a solidified portion 34 of the pile hole 32. The pile hole 23 is filled with a root-solidifying solution in the root-solidifying portion 34, and a shaft portion 33 is filled with a pile circumference fixing liquid, respectively. The root hardening liquid and the pile circumference fixing liquid are composed of a solidifying material such as cement milk, or a soil cement formed by stirring and mixing a solidifying material with excavated soil. The root hardening liquid is adjusted so as to have a solidification strength equivalent to the ground strength of the supporting ground (FIG. 3). The diameter D of the root hardening part 34₁₂Is the shaft outer diameter D of the ready-made pile 14 due to the supporting force required in the design.₅It is desirable to adjust up to about 1.5 times.
[0065]
(2) A prefabricated pile (lower pile, straight shape) 14 having a tip metal fitting 12 attached to the lower end is buried in the pile hole 32, and the prefabricated pile 14 is opened at the opening of the pile hole 32 at a predetermined depth. And the other ready-made pile (upper pile, straight shape) 14 </ b> A is connected to the upper end of the ready-made pile 14.
[0066]
  Subsequently, the ready-made piles 14, 14 </ b> A are lowered into the pile holes 32, the tip metal fitting 12 is completely accommodated in the rooted portion 34, and the lower end 22 of the ready-made pile 14 has a predetermined length L.₅Only into the root consolidation part 34, and the lower surface 13 of the end fitting 12 is a predetermined length L from the bottom 35 of the root consolidation part 34.₄The descent of the ready-made pile 14 is stopped at such a position as to be located only above, and the ready-made piles 14 and 14A are held in that state (FIG. 4).
[0067]
(3) The foundation pile structure 37 of this invention is comprised in the state which the root hardening liquid and the pile circumference fixing liquid solidified and expressed (FIG. 3).
[0068]
(4) Other embodiments
[0069]
  In the above example, the so-called pre-digging method in which the ready-made pile is buried after the completion of the excavation of the pile hole has been explained, but the foundation pile is applied to the so-called medium excavation method in which the ready-made pile is buried while excavating the pile hole. Can also be built.
[0070]
  That is, the drilling rod for medium digging is inserted into the hollow portion of the ready-made pile 14 to which the tip metal fitting 12 is attached, and the ready-made pile 14 is lowered while the excavation head is protruded from the lower end of the tip metal fitting to excavate the pile hole (see FIG. Not shown). The excavated earth and sand are discharged to the ground through the hollow portion of the tip fitting 12 and the ready-made pile 14 by a spiral provided around the excavating rod while using compressed air. Subsequently, the ready-made pile 14A is connected, the excavation rod is added, excavated while pouring water, the ready-made piles 14 and 14A are lowered and lowered to a predetermined position. The excavation rod is pulled up to the ground through the inside of the hollow portions of the ready-made piles 14 and 14A and the tip fitting 12 while stirring and pouring cement milk.
[0071]
  Thereafter, while lowering the ready-made pile 14, the end fitting 12 is completely accommodated in the rooted portion 34, and the lower end 22 of the ready-made pile 14 has a predetermined length L, as in the pre-digging method.₅Only into the root consolidation part 34, and the lower surface 13 of the end fitting 12 is a predetermined length L from the bottom 35 of the root consolidation part 34.₄The descent of the ready-made pile 14 is stopped at such a position as to be located only above, and the ready-made piles 14 and 14A are held in this state. With the above, the root hardening liquid is solidified and the foundation pile structure is constructed.
[0072]
[Example 3]
  The comparison when the foundation pile structure of the present invention and the foundation pile structure of the conventional example C are applied to the same ground will be described (FIG. 8).
[0073]
(1) Invention of the present application
  Like the said Example 1, the front-end | tip metal fitting 12 is attached to the lower end of the ready-made pile 14, and it embeds in the pile hole 32 which has the root hardening part 34 (FIG. 1, FIG. 3). The dimensions of each part are as follows.
[0074]
  Ready-made pile 14
      SC pile (steel pipe covered concrete pile)
      Pile length 13.5m
      Outer diameter D₅= 600mm
      Hollow part inner diameter D₂= 420mm
  Tip bracket 12
    Steel pipe body 1 t₁= 15mm
                  D₁= 450mm
                  D₂= 420mm
    Large diameter part 2 D₃= 600mm
    Annular projection 10 L₇= 75-90mm
                  D₄= 600-630mm
                  t₂= 10-40mm
                  L₁= 3 pieces at 500mm
[0075]
  D₄= Even if it is 630mm, the excavation diameter D of the pile hole shaft₁₁And D₃The range is equivalent to (= 600 mm).
[0076]
  Pile hole 32
    Shaft 33 length L₂= 13500mm
                  Diameter D₁₁= D₅+ 30mm
                            = 630mm
                (At least D₁₁≧ D₄Adjust slightly so that
    Rooting part 34 Length L₃= 3000-3500mm
                  Diameter D₁₂= 900mm
[0077]
(2) Comparative example (conventional example C)
  A foundation pile structure is constructed in a comparative example corresponding to the conventional example C in which the same ready-made pile 14 is an upper pile 14A, and a lower pile 14B with a joint 39 is connected instead of the end fitting 12 (FIG. 7).
[0078]
(a) Upper pile 14A
    SC pile (steel pipe covered concrete pile)
    Pile length = 12m
    Pile thickness = 80mm
    Steel pipe thickness = 9mm
    Outer diameter D₅= 500mm
    Hollow part inner diameter = 340mm
(b) Lower pile 14B
    Knotted concrete pile
    Pile length = 4m
    Pile thickness = 80mm
    Pile shaft outer diameter D₆= D₅= 500mm
    Pile node outer diameter D₇= 650mm
    Pile hollow inner diameter = 340mm
(c) Pile hole 32
    Shaft 33 length L₂= 13500mm
                  Diameter D₁₁= 650mm + 30mm
                            = 680mm
    Rooting part 34 Length L₃= 2500mm
                  Diameter D₁₂= 950mm
[0079]
(3) Effects
[0080]
  (a) In the loading test, the maximum load is 6.5MN or more. In the third embodiment, the number of annular protrusions formed is three, but by increasing or decreasing this number, it is possible to increase or decrease the adhesion area with the soil cement in the rooting portion and increase or decrease the propagation area of shear force. In addition, by further increasing the solidification strength of the soil cement in the root consolidation portion and appropriately selecting the soil quality of the supporting ground, a higher load resistance can be achieved.
[0081]
  (b) In the case of a foundation pile structure that exhibits the same supporting force, the shaft diameter of the pile hole can be reduced to a little less than 10% of the conventional diameter. Along with this, the amount of excavated soil can be similarly reduced, and the construction time is also shortened. Therefore, in proportion to the reduction of the amount of soil and the excavation time, it is possible to reduce the soil discharged from the site as industrial waste and reduce the exhaust gas of the excavator. Become.
[0082]
  Moreover, the gap between the ready-made pile and the shaft portion of the pile hole is reduced to about 1/6, and the cement milk used is also reduced by 40%.
[0083]
  (c) Since the outer diameter of the pile shaft can be increased by about 20% with respect to the high bearing capacity of the hardened part, the selection range is about twice as strong as that of the SC pile as the bending moment strength of the ready-made pile material. Spread.
[0084]
  (d) As the inner diameter dimension of the hollow portion of the ready-made pile, when the inner diameter of the ready-made pile for demonstrating high supporting force is 340 mm when compared with the same supporting force, the ready-made pile having the same outer diameter is used. In this case, the inner diameter of the ready-made pile is only 420 mm in the present invention.
[0085]
  That is, when using a standard-made ready-made pile, the inner diameter becomes the same as when using a ready-made pile having a large one-rank outer diameter, and the inner diameter can be increased by 20% or more.
[0086]
  Therefore, in the medium excavation method, the maximum outer diameter of the excavation rod inserted into the hollow portion can be increased, and therefore an excavation rod having excavation heads of various structures can be selected. Moreover, the excavation dimension of the root hardening part can be expanded more. Therefore, it is possible to develop a higher support force by expanding the root diameter of the root. It is also effective from the viewpoint of equipment technology, such as the ability to excavate using a conventional excavating rod and high bearing capacity.
[0087]
  Conventionally, it is difficult to expand the bottom with the medium digging method, and even if possible, it is only possible to excavate the bottom of the bottom of 1.3 to 1.4 times the outer diameter of the ready-made piles. Although it was difficult to construct a foundation pile structure that exerts a supporting force, according to the invention of the present application, it is possible to increase the bottom of the bottomed portion up to 1.5 to 1.6 times the outer diameter of a ready-made pile that is one rank higher than conventional construction technology. Drilling is possible, and the application range of the medium digging method can be expanded.
[0088]
[Example 4]
  In each of the above-described embodiments, the tip metal fitting 12 is formed with the annular protrusions 10 and 10 at the intermediate portion and the lower end portion of the steel pipe main body 1.
[0089]
(1) Outer diameter D₁Outer diameter D having a connecting portion with a ready-made pile at the upper end of the steel pipe body 1₃The outer diameter D is formed at the lower end.₄These annular projections are connected to each other (FIG. 9).
[0090]
  Outer diameter D₁, Inner diameter D₂On the upper end of the steel pipe body 1, the outer diameter D₃The large-diameter portion 2 is formed, and the large-diameter portion 2 is used as a connection portion with the ready-made pile 14. The large-diameter portion 2 is formed with a stepped portion lower surface 43 having a partially conical inclined slope whose upper surface is a horizontal flat surface and whose lower surface side is gradually reduced in diameter. The outer diameter of the connecting portion, that is, the outer diameter D of the large diameter portion 2₃Is substantially the same as the outer diameter of the ready-made pile 14 to be connected (the outer diameter of the lower end).
[0091]
  On the outer surface of the lower end of the steel pipe body 1, the outer diameter D₄A disc-shaped (doughnut-shaped) annular projection 10 is projected. The upper surface 44 of the annular protrusion 10 is formed in a horizontal plane, the lower surface 45 forms a partially conical inclined slope, and the lower end of the inclined slope reaches the lower end of the steel pipe body 1.
[0092]
  As described above, the end fitting 12 is configured (FIG. 9A). Inner diameter D of end fitting 12₂Is formed from the upper end (the upper end of the large-diameter portion 2) to the lower end substantially the same as the inner diameter of the ready-made pile 14. That is, the inner side surface 15 of the ready-made pile 14 and the inner side surface 9 of the tip metal fitting 12 are formed substantially flush with each other (FIG. 10B).
[0093]
  Moreover, the space | interval of the large diameter part 2 and the cyclic | annular protrusion 10 is formed similarly to the said each Example, Furthermore, the cyclic | annular protrusion 10 of a present Example or the said Example 1 is further connected between the cyclic | annular protrusions 10. FIG. In this case as well, an interval in the vertical direction is formed as in the first embodiment.
[0094]
  Here, for example,
    D₁= 620mm
    D₂= 580mm
    D₃= 800mm
    D₄= 856mm
As D₃Compared to D₄Is formed to have a slightly larger diameter, so that a greater supporting force can be expected. In addition, in the work of burying ready-made piles, the workability may be inferior due to the large diameter, but if the required supporting force is obtained, D₄≦ D₃It can also be said. In the above, D₄(= 856mm) is less than the excavation diameter (830mm) of the pile hole shaft, and D₃The range is equivalent to (= 800 mm).
[0095]
(2) The upper surface of the large-diameter portion 2 of the end fitting 12 is the same outer diameter D as in the first embodiment.₃The large-diameter portion 2 and the lower end plate 17 are fixed together with bolts, welding or the like, and embedded in a pile hole to constitute a foundation pile structure (shown) Not)
[0096]
  When embedding the ready-made pile 14, use the cylindrical cover 47 that covers the entire steel pipe body 1 including the large-diameter portion 2 and the lower end of the ready-made pile 1, and prevents mud from adhering to the portion. Is desirable. In this case, the lower end of the cover 47 is temporarily locked to the outer peripheral portion 46 of the annular protrusion 10 via the stopper 5, and the lower end of the PC steel rod 49 is screwed to the couplers 48, 48 at the upper end of the cover 47. The upper end of the steel rod 49 is screwed to the disc-shaped jig 52 provided continuously with the upper end of the ready-made pile 14 with a nut 51 and a coupler 50 (FIG. 10A). In this state, if the ready-made pile 14 is buried, as will be described later, mud soil hardly adheres or stays on the upper surface 44 and the lower surface 45 of the annular protrusion 10 protected by the cover 47, and the tip metal fitting 12 and the ready-made pile 14 This can be installed in the root of the pile hole without mud sticking to the lower end of the pile.
[0097]
  If the ready-made pile 14 is installed in a predetermined position, the upper end of the PC steel bar is pulled up, the temporary fixing of the cover 47 and the annular protrusion 10 by the stopper 53 is released, and the cover 47 and the PC steel bar 49 are pulled up to the ground.
[0098]
  Therefore, when the cover 47 is used, the lower end portions of the end fitting 12 and the ready-made pile 14 can be firmly adhered and fixed in the cement milk layer formed in the rooting portion, and a high-quality foundation pile structure can be constructed. Further, here, a cylindrical thin steel pipe is used as the cover 47. However, the material and the structure are arbitrary as long as the cover can be embedded and buried and then pulled up. Similarly, the cover 47 can be applied to the end fitting 12 of the first embodiment (not shown).
[0099]
  By using the protective cover 47, it is possible to prevent sticky mud from adhering to the lower end of the ready-made pile 14 and the soil cement, so that the outer diameter and the pile hole of the ready-made pile 14 (lower end) can be prevented. Even if the outer diameter and gap of the shaft portion are small, the adhesion between the lower end of the ready-made pile 14 and the soil cement layer can be maintained regardless of the soil quality, and a stable tip support force can be obtained with the foundation pile structure.
[0100]
(3) Since the tip fitting 12 of this embodiment provides a stable support force using the protective cover 47, the tip fitting 12 of the first embodiment (FIGS. Compared to), the total surface area and the surface through which shearing force is transmitted are small, so the supporting force is designed to be somewhat small, but it is easy to handle in construction and the drilling diameter of the pile-solidified part can be made small There are advantages such as.
[0101]
  Specifically, the following advantages can be stably obtained by using the end fitting 12 having the above structure and further using the protective cover 47.
[0102]
    (a) The length of the steel pipe body 1 (cylindrical base) is shortened (about 1.0 m in length. In Example 1, the length is about 2.5 m), and the contribution of the support force in the end fitting 12 is small. The area of the side surface of the steel pipe body 1 was reduced. As a result, the length of the bottom-excavated excavation of the root consolidation portion of the pile hole can be shortened, and as a result, the construction time can be shortened and the amount of cement milk used can be reduced.
    (b) Further, the root portion of the annular protrusion 10 (side closer to the steel pipe body 1) was thickened to increase the mechanical strength.
    (c) Moreover, since the lower surface 45 of the annular protrusion 10 is a partially conical inclined slope, the stress to the soil cement layer and the ground in the root consolidation portion is efficiently propagated.
    (d) Since the annular protrusion 10 having a large surface area is formed at the tip portion considered to contribute most to the generation of the vertical supporting force, a larger vertical supporting force can be exhibited with a small number of protrusions having a small outer diameter.
    (e) Since the lower surface 45 of the annular protrusion 10 that contributes to the generation of the vertical support force is formed to be inclined, mud is difficult to adhere to the lower surface 45 of the annular protrusion 10 when the tip fitting is embedded in the pile hole. Therefore, the adhesion between the soil cement layer and the lower surface 45 can be enhanced, and the propagation of the shearing force to the soil cement layer can be ensured.
    (f) Since the largest-diameter portion is formed at the forefront of the ready-made pile 14, when the ready-made pile 14 is embedded, centering of the ready-made pile 14 (centering with the core of the pile hole) becomes easy. .
[0103]
【The invention's effect】
  For a prefabricated pile with a protruding metal fitting fixed to the lower end of the prefabricated pile, or with a protrusion or recess formed on the lower end, the adhesion area with the soil cement is widened, Arranged so that the shearing force can be sufficiently propagated without hindrance from the lower surface of the head, the upper and lower surfaces of the projection of the tip bracket, the stepped portion of the main shaft and lower shaft of the ready-made pile, the upper and lower walls of the projection, Since it is embedded in the root consolidation part filled with soil cement having a solidification strength equal to or higher than the supporting ground strength, there is an effect that a shear force can be effectively propagated in the root consolidation part and a foundation pile structure having a high bearing capacity can be formed.
[0104]
  Moreover, since the outer diameter of the protrusion part of the tip metal fitting is formed to be equal to or smaller than the maximum outer diameter of the ready-made pile, there is an effect that a larger supporting force can be exhibited with a smaller excavation diameter of the pile hole shaft part. In addition, since the bearing capacity can be increased compared to the drilling diameter of the pile hole shaft, the drilling diameter can be reduced with the same supporting force, reducing the amount of soil removed and reducing the drilling time of the pile hole. There is. Therefore, it is possible to reduce the soil discharged as industrial waste discharged from the site, reduce the exhaust gas of the excavator by reducing the excavation time, and build a foundation pile that is more environmentally friendly.
[0105]
  Also, when the shaft diameter of the pile hole and the outer diameter of the ready-made pile are made the same, and the same support force as before can be demonstrated, the inner diameter of the ready-made pile can be increased. The foundation pile which has higher bearing capacity by the medium digging method can be easily constructed with conventional equipment.
[0106]
  Also, when using a tip fitting, even when using a ready-made pile of the same diameter, if the required tip support force is different, change the number of protrusions formed on the tip fitting according to the tip support force. By increasing or decreasing the effective area or increasing or decreasing the solidification strength of the soil cement, there is an effect that a more efficient foundation pile structure can be easily constructed.
[0107]
  In addition, when covering the lower end of the prefabricated pile related to the tip support force and the tip support with a protective cover, the adhesion between the portion and the soil cement layer is improved without mud soil adhering or staying in the portion. The Therefore, stable support force can be obtained even on highly sticky ground, so even if the gap between the shaft diameter of the pile hole and the outer diameter of the ready-made pile and the tip metal fitting is reduced, it is stable in the built foundation pile structure. High bearing capacity.
[Brief description of the drawings]
1A is a front view, FIG. 1B is a bottom view, and FIG. 1C is a longitudinal sectional view of an embodiment of a tip metal fitting of the present invention.
FIGS. 2A and 2B are partially enlarged longitudinal sectional views showing the connection between the end fitting of the present invention and a ready-made pile, wherein FIG. 2A shows before connection and FIG. 2B shows after connection.
FIG. 3 is a longitudinal sectional view of a foundation pile structure according to an embodiment of the present invention.
FIG. 4 is an enlarged vertical cross-sectional view of the root hardening part.
FIG. 5 is a front view of another tip fitting according to the present invention.
FIG. 6 is a front view of another ready-made pile according to the present invention.
7A and 7B are diagrams for explaining a conventional example C of the present invention, in which FIG. 7A is a longitudinal sectional view of an upper pile and a lower pile, and FIG. 7B is a longitudinal sectional view of a foundation pile structure in which an existing pile (upper and lower piles) is embedded. is there.
FIG. 8 is a diagram for explaining the ground to which Example 3 is applied and the state of ready-made pile installation.
9A and 9B are ready-made piles of Example 4, wherein FIG. 9A is a longitudinal sectional view, and FIG. 9B is a front view of the pile mounted on a pile driving machine.
FIGS. 10A and 10B are partially enlarged longitudinal sectional views of a ready-made pile, in which FIG. 10A shows an upper end portion and FIG. 10B shows a lower end portion.
[Explanation of symbols]
1 Steel pipe body
2 Large diameter part
3 annular groove
4 Bolt holes
5 Tubular surface material
6 Contact material
8 Outside
9 Inner side
10 Annular projection
11 Rib of annular projection
12 Tip bracket
13 Underside of the end fitting
14, 14A Ready-made pile
15 Inside surface of ready-made piles
16 Ready-made pile connection fittings
17 Lower end plate of ready-made pile
18 Side plates of ready-made piles
19 Thick part of side plate of ready-made pile
20 Annular groove of ready-made pile
21 Bolt holes in ready-made piles
22 Lower end of ready-made pile
23 Band for connection
24 Band pieces
25, 26 Banded convex part
27 Band through hole
28 Band housing
30 volts
32 Pile hole
33 Shaft hole shaft
34 Root consolidation part of pile hole
35 Bottom of pile hole root
37 Foundation pile structure
40 recess
41 Lower surface of protrusion (upper side of recess)
42 Top surface of protrusion (lower side of recess)
43 Lower surface of step
44 Upper surface of the annular protrusion 11
45 The lower surface of the annular protrusion 11
47 Cover
49 PC steel bar
52 Disc-shaped jig

Claims

A tip fitting or “other ready-made pile” is connected to the lower end of the ready-made pile having a main shaft portion with a predetermined shaft diameter, and the tip fitting or “other ready-made pile” is substantially the same as the main shaft portion connected to the ready-made pile. Having a large diameter portion of the same diameter, forming a lower shaft portion having a diameter smaller than that of the main shaft portion, forming a projection portion on the lower shaft portion, and a tip of the projection portion being equal to the maximum outer diameter of the main shaft portion or Formed below that, and formed by forming a stepped portion on the lower surface of the large-diameter portion,
In the pile hole having a root-solidified portion filled with a root-solidifying solution on the supporting ground, the ready-made pile is connected to the tip fitting or "other pre-made pile" and the lower end of the ready-made pile is within the root-solidified portion of the pile hole. The foundation pile structure using the ready-made pile characterized by being embedded so that the said front-end metal fitting or "other ready-made pile" might be unitedly supported by the said support ground.

The protrusion is disposed so as to provide a predetermined gap between the upper surface of the protrusion and the lower surface of the stepped portion between the main shaft and the lower shaft, or to provide a predetermined gap between the upper and lower surfaces of the adjacent protrusions. The foundation pile structure using the ready-made pile according to claim 1, wherein a solid cement having a solidification strength equal to or higher than the strength of the supporting ground is filled into a root-solidified portion of a predetermined shape of the pile hole.

A tip fitting or “other ready-made pile” is connected to the lower end of a ready-made pile having a spindle portion of a predetermined shaft diameter, and the tip fitting or “other ready-made pile” is substantially the same as the spindle portion connected to the ready-made pile. Having a large diameter portion of the same diameter, forming a concave portion in the lateral direction from the side surface toward the shaft side at the lower end portion, and forming a stepped portion on the lower surface of the large diameter portion;
In the pile hole having a root consolidation part filled with root consolidation liquid on the supporting ground, the ready-made pile is connected to the tip metal fitting or “other ready-made pile” and the lower end portion of the ready-made pile in the root consolidation part of the pile hole. The foundation pile structure which used the embedded ready-made pile so that the said front-end metal fitting or "other ready-made pile" may be unitedly supported by the said support ground.

A cover covering the lower end of the ready-made pile and the tip metal fitting or “other ready-made pile” is attached to form the ready-made pile, and the cover is configured to be able to be pulled up to the ground after being buried. The foundation pile structure of Claim 1 thru | or 3.