JP2004003324A

JP2004003324A - Foundation pile structure using prefabricated pile, prefabricated pile, and tip fitting for prefabricated pile

Info

Publication number: JP2004003324A
Application number: JP2003121272A
Authority: JP
Inventors: Yoshinobu Kitani; 木谷　好伸; Tatsu Matsuda; 松田　竜
Original assignee: Mitani Sekisan Co Ltd
Current assignee: Mitani Sekisan Co Ltd
Priority date: 2002-04-26
Filing date: 2003-04-25
Publication date: 2004-01-08
Anticipated expiration: 2023-04-25
Also published as: JP4706994B2

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an amount of removed earth, excavation time, and the the removed earth as industrial waste discharged from a job site, by exerting a greater bearing force in a state in which an excavation diameter of a posthole shaft is made smaller; to reduce exhaust gas from an excavator by reducing the excavation time; and to impart greater friendliness to the environment. <P>SOLUTION: In a tip fitting 12, a large-diameter part 2 for being mounted at the lower end of a prefabricated pile 14 is provided in a steel pipe body 1, and an annular protrusion 10 is provided below the large-diameter part 2. The annular protrusion 10 is formed in such a manner that an outside diameter D<SB>4</SB>thereof is as large as or smaller than a maximum outside diameter D<SB>5</SB>of the prefabricated pile 14. The prefabricated pile 14, to which the tip fitting 12 is coupled, is sunk in a posthole 32. A foundation pile structure 37 is formed by burying the prefabricated pile 14 so that the tip fitting 12 can be located in a consolidated foundation 34 filled with soil cement in which solidification strength is set to be a ground strength or more. An installation interval between the annular protrusions 10 is set at √3×L<SB>7</SB>or longer, in consideration of efficient propagation of a shear force from an under surface 41, a top surface 42 and the like. <P>COPYRIGHT: (C)2004,JPO

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、既製杭、既製杭用の先端金具に関する。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部を、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、根固め部を有する杭穴内に、前記既製杭を、突起部が前記杭穴の根固め部内に位置するように、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部に、側面から軸側に向けての横方向の凹部を形成して、所定形状の根固め部を有する杭穴内に、前記既製杭を、前記凹部が前記杭穴の根固め部内に位置するように、埋設した既製杭を使用した基礎杭の構造であって、前記凹部の上下壁間の距離を、前記凹部の深さの√３倍以上に形成すると共に、根固め部内に固化強度が支持地盤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。
【００２２】
また、前記において、既製杭の突起部又は凹部は、総て根固め部内に配置すると共に、前記既製杭の下端と根固め部の底とにより所定長さの間隙を形成し、前記既製杭の前記突起部又は凹部の直上部分で既製杭の主軸部の軸径を有する部分を根固め部の上端部に配置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。
【００２３】
また、既製杭の発明は、所定外径の上部軸部の下方に下部軸部を有する既製杭において、前記下部軸部を上部軸部より小径に形成し、該下部軸部に突起部を形成し、前記突起部の先端を、上部軸部の外径範囲と同等又はそれ以下の大きさに形成したことを特徴とする既製杭である。
【００２４】
また、先端金具の発明は、鋼管本体の上端部に大径部を形成し、該大径部に既製杭との連結部を形成し、前記鋼管本体の外周に、突起部を形成してなり、前記突起部の外径を、前記大径部の外径と同等又は大径部より小径に形成したことを特徴とする既製杭用の先端金具である。また、大径部の外径を、連結すべき既製杭の外径と略同一とした既製杭用の先端金具である。
【００２５】
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。
【００２６】
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。
【００２７】
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。
【００２８】
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。
【００２９】
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。
【００３０】
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。
【００３１】
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。
【００３２】
【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。
【００３３】
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。
【００３４】
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。
【００３５】
（２）装着する先端金具１２の機能、構造等
【００３６】
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。
【００３７】
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。
【００３８】
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。
【００３９】
（３）各構成部分の説明
【００４０】
（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。
【００４１】
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。
【００４２】
（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。
【００４３】
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）。
【００４４】
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。
【００４５】
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。
【００４６】
（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。
【００４７】
（４）先端金具１２の寸法
【００４８】
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）。
【００４９】
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。
【００５０】
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））。
【００５１】
（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。
【００５２】
【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。
【００５３】
（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。
【００５４】
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。
【００５５】
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。
【００５６】
以上のようにして、先端金具１２を構成する（図１（ａ）（ｂ）（ｃ））。
【００５７】
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。
【００５８】
（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））。
【００５９】
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。
【００６０】
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。
【００６１】
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。
【００６２】
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））。
【００６３】
（３）他の実施例
【００６４】
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。
【００６５】
【実施例２】
次に、この発明の基礎杭構造について説明する。
【００６６】
（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。
【００６７】
（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。
【００６８】
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）。
【００６９】
（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）。
【００７０】
（４）他の実施例
【００７１】
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。
【００７２】
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。
【００７３】
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。
【００７４】
【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）。
【００７５】
（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。
【００７６】

【００７７】
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。
【００７８】

【００７９】
（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）。
【００８０】

【００８１】
（３）効果等
【００８２】
（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。
【００８３】
（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。
【００８４】
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。
【００８５】
（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。
【００８６】
（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。
【００８７】
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。
【００８８】
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。
【００８９】
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。
【００９０】
【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。
【００９１】
（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）。
【００９２】
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。
【００９３】
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。
【００９４】
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））。
【００９５】
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。
【００９６】
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。
【００９７】
（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）。
【００９８】
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。
【００９９】
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。
【０１００】
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）。
【０１０１】
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。
【０１０２】
（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。
【０１０３】
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。
【０１０４】
（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。
【０１０５】
【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。
【０１０６】
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。
【０１０７】
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。
【０１０８】
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。
【０１０９】
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
４９　ＰＣ鋼棒
５２　円盤状治具[0001]
TECHNICAL FIELD OF THE INVENTION
At the lower end of the pile, a ready-made pile formed with a projection such as a node, a spiral wing, a steel rod, a steel plate, etc., is installed on a soil cement layer of a predetermined rooting portion, and the projection is used to provide a high bearing capacity. The present invention relates to a foundation pile structure, a ready-made pile, and a tip metal fitting for a ready-made pile exhibiting the above. It should be noted that the root stiffening portion can be applied with or without expanding.
[0002]
[Prior art]
Conventionally, in a pile foundation, an invention has been made in which projections are formed at the lower end of a pile buried in a bolster and a supporting strength of the entire foundation pile is increased integrally with a ready-made pile buried 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 bar between the reinforcing bars of the expanded reinforcing bars (Patent Document 1. Japanese Unexamined Patent Application Publication No. 11-61811 and Japanese Patent No. 3054389). (Hereinafter, Conventional Example A)), and a structure in which an H-shaped steel having a convex portion on the flange outer surface is fixed to the tip of a ready-made pile (Patent Document 2. Japanese Patent Application Laid-Open No. 2001-271347 (hereinafter, Conventional Example B)). In addition, a structure using a ready-made concrete pile having a protrusion on the outer periphery of a lower end portion (Patent Document 3, Japanese Patent Application Laid-Open No. H11-280067 (hereinafter, Conventional Example C)) and the like are known.
[0003]
According to FIGS. 1 to 5 and the like 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 is formed. It is stated that a high supporting force can be obtained by pushing the reinforcing bar 6 into the expanding portion 2 to expand the expanding reinforcing bar 6 and burying and solidifying the reinforcing bar 6 as shown in FIG. Although the excavation size of the pile hole is not specifically described, according to FIGS. 3 and 5, the size of the pile hole 1 in the shaft portion is at least “pile diameter + expanded reinforcing bar thickness” or more. Pile holes with a large diameter of about 30% or more of the diameter are excavated. Therefore, the gap between the pile and the pile hole is extra than that required for the required dimension of the shaft pile hole of the ordinary pile foundation, ie, “pile diameter + 30 mm (10% or less of the pile diameter)”. The excavation diameter of the root consolidation portion is also twice as large as the pile diameter, which is a large diameter as compared with a normal bearing capacity (pile diameter × about 1.25 to 1.5).
[0004]
Further, according to the example on page 3 of the conventional example B, the steel H steel is formed at the lower end of the outer shell steel pipe concrete pile 1 (usually referred to as SC pile) having an outer diameter D (500 mm). And the hole diameter D of the shaft₁Is excavated at 650 mm. The required shaft excavation diameter of the conventional foundation pile is about "pile diameter + 30 mm (10 m% or less of the pile diameter)", and the space between the inner wall of the pile hole and the outer surface of the pile is extra than in the past. Also, in order to express high bearing capacity, the excavated diameter D₀In this case, a large-diameter excavation is performed, which is 1000 mm, which is about twice as large as the pile diameter, and which is much larger than the ordinary bearing capacity (pile diameter x about 1.25 to 1.5).
[0005]
According to FIG. 2A, the H steel 2 and the reinforcing ribs 4 formed at the lower end of the pile 1 seem to be formed to be smaller than the outer diameter of the upper pile 1 at first glance. Compared to FIGS. 1, 3 and the like, the drawing is made with substantially the same dimensions as those of the embodiment, and it is presumed that the large-diameter excavation is performed for both the shaft excavation and the excavation of the bottom-fixing portion as in the embodiment.
[0006]
Furthermore, as shown in FIG. 2 of JP-A-2001-27347, in the case of a structure in which the projection closes the lower end of the pile, especially in the high-concentration soil cement of the root consolidation portion, the center of the lower end of the pile and the hollow portion of the pile hole. In addition, there is anxiety about the uniformity of the projections and the like, and furthermore, the shearing force cannot be sufficiently utilized due to, for example, the upper and lower portions of each of the plug-shaped projections. In addition, since the excavation head cannot penetrate the hollow portion of the pile hole due to the projection, there is a problem in versatility such that construction by the middle digging method cannot be performed.
[0007]
In addition, according to the pile foundation 10 according to the first embodiment shown in FIG. 1 of the conventional example C in FIG. 1, the structure of the lower part of the pile is formed at the lower end of the pile buried in the expanded bottom stiffening part 3, and the projection part contributes to the development of high holding power. Is an annular rib (node shape), and three

annular ribs

5, 6, 7 are formed. In order to sufficiently exert the shear force of the projection, the annular rib outer diameter D of the projection is₁(75cm) is the outside diameter D of the shaft of the pile 4.₀(60 cm) to increase the projection surface area. Therefore, the outer diameter of the upper part of the ready-made pile is the outer diameter D of the shaft part.₀And the excavation dimension of the pile hole shaft 2 is a dimension D that the annular rib easily penetrates.₀₀(80 cm), the gap between the inner wall of the pile hole and the outer surface of the pile is wide, and the expanded dimension D of the reinforced portion₁₁In addition, large-diameter excavation at an unprecedented ratio was required, and both the shaft portion and the expanded bottom consolidation portion required new technical measures for unprecedented large-diameter excavation work.
[0008]
In addition, many pile foundations have been proposed in the past, in which projections or recesses are formed in the embedded portion of the piles of the ready-made piles to increase the supporting force, but the shear force due to the projections adjacent to the projections or the recesses has been proposed. The spacing between the protrusions or the recesses is not sufficient to express sufficiently, and it is also considered that the shear force including the required solidification strength of the soil cement layer is fully expressed and the supporting force is obtained. It seems that only those foundation piles utilizing the invention of Conventional Example C have a large number of construction records.
[0009]
Also, in general, the shaft pile with a small diameter is used for the high bearing capacity that appears at the root consolidation part, and the horizontal strength of the shaft pile itself is insufficient, and the pile The choice of materials was limited, and it was difficult to construct a pile foundation that maximized the vertical bearing capacity.
[0010]
[Patent Document 1] Japanese Patent Application Laid-Open No. 11-61811
[0011]
[Patent Document 2] Japanese Patent Application Laid-Open No. 2001-271347
[0012]
[Patent Document 3] JP-A-11-280067
[0013]
[Problems to be solved by the invention]
The conventional technique has the following problems.
[0014]
(1) At the lower end of the pile, as a simple method, the projection is formed on the outer surface of the pile in order to increase the area of the projection for adhering to the soil cement layer and expressing its shearing force. The diameter of the excavated root and the diameter of the shaft of the pile hole are larger in the pile diameter ratio than the conventional ordinary bearing pile foundation. The gap between the pile diameter of the pile-hole shaft and the diameter of the pile-hole shaft must also be increased excessively.
[0015]
(2) (1) The piles in the shaft of the pile hole need to have a well-balanced large strength (strength that satisfies both the load transfer and the bending strength), while the high bearing capacity that is about twice as much as the conventional one that appears at the root consolidation part is required. However, since the diameter of the pile is small, the selection range of the pile material is limited, and it has been difficult to make full use of the high bearing capacity of the rooted portion.
[0016]
(3) Pile hole diameter required to express the frictional force of the pile diameter buried in the pile hole shaft part due to excavation of the pile hole shaft part (the normal distance between the pile hole inner wall and the pile is 30 mm and the pile diameter 10% or less) (e.g., 20% or more), the excavation area is wasted (about 40%), and the excavation diameter of the expanded root consolidation part is relatively large in comparison with the conventional pile diameter ratio. As a result, the excavation time is long, excavation excavation is large, and it is economically and environmentally problematic. Furthermore, there are many wasteful points, such as the need to procure an excavator for a large-diameter pile hole, which is not available in the past.
[0017]
In particular, in the case of middle digging, there are many issues to be solved in terms of digging equipment technology for stable digging because the diameter of the expanded pile hole is larger than the conventional one (compared to the inner diameter of the hollow portion of the pile).
[0018]
[Means for Solving the Problems]
However, according to 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 of the ready-made pile located at the root consolidation part has a smaller diameter than the upper shaft part. Since the lower shaft portion is formed with a projection or the like having an outer diameter equal to or smaller than the maximum outer diameter of the upper shaft portion, the above-described problem is solved.
[0019]
That is, the invention of the foundation pile structure is that the lower end of the ready-made pile having a main shaft portion having a predetermined shaft diameter is formed with a lower shaft portion having a smaller diameter than the main shaft portion, and a projection is formed on the lower shaft portion. The tip of the protrusion is formed to be equal to or less than the maximum outer diameter of the main shaft portion, so that the ready-made pile is located in the pile hole having the root fixing portion, and the protrusion is located in the root fixing portion of the pile hole. In addition, a foundation pile structure using a ready-made pile characterized by being buried.
[0020]
Further, in the above, the protrusion is provided with a predetermined gap between the upper surface of the protrusion and the lower surface of the step portion between the main shaft portion and the lower shaft portion, or a predetermined gap is provided between the upper and lower surfaces of the adjacent protrusion. A foundation pile structure using a ready-made pile, characterized in that soil cement, whose solidification strength is equal to or higher than the strength of the supporting ground, is filled in a solidified portion of a pile hole having a predetermined shape.
[0021]
Further, another invention of the foundation pile structure is to form a laterally concave portion from the side surface toward the shaft side at the lower end portion of the ready-made pile having a main shaft portion with a predetermined shaft diameter, and to form a rooting portion of a predetermined shape. In the pile hole having, the ready-made pile, the concave portion is located in the solidified portion of the pile hole, the structure of the foundation pile using the buried ready-made pile, the distance between the upper and lower walls of the concave portion A foundation pile structure using a ready-made pile, characterized in that it is formed at least three times the depth of the concave portion and is filled with soil cement whose solidification strength is equal to or higher than the support ground strength in the root consolidation portion.
[0022]
Further, in the above, all the projections or recesses of the ready-made pile are arranged in the rooting part, and a gap of a predetermined length is formed by the lower end of the ready-made pile and the bottom of the rooting part. A foundation pile structure using a ready-made pile, characterized in that a portion having a shaft diameter of a main shaft portion of the ready-made pile immediately above the projection or the concave portion is arranged at an upper end portion of the bolster.
[0023]
Also, the invention of a ready-made pile is that in a ready-made pile having a lower shaft portion below an upper shaft portion having a predetermined outer diameter, the lower shaft portion is formed to have a smaller diameter than the upper shaft portion, and a projection is formed on the lower shaft portion. The tip of the protruding portion is formed to have a size equal to or smaller than the outer diameter range of the upper shaft portion.
[0024]
Further, the invention of the tip metal fitting is such that a large diameter portion is formed at an upper end portion of a steel pipe main body, a connection portion with a ready-made pile is formed at the large diameter portion, and a projection is formed on an outer periphery of the steel pipe main body. An outer diameter of the protruding portion is formed to be equal to or smaller than an outer diameter of the large diameter portion. In addition, this is a tip fitting for a ready-made pile in which the outer diameter of the large diameter portion is substantially the same as the outside diameter of the ready-made pile to be connected.
[0025]
The ready-made pile in the above is formed by connecting a tip fitting having a protrusion or a concave portion to the lower end of the ready-made pile, but the lower end of one ready-made pile is processed to have a predetermined structure having a protrusion or a concave portion. Alternatively, a structure in which one or a plurality of upper piles are joined to a lower pile having a predetermined structure having a protrusion or a concave portion may be employed.
[0026]
In addition, the ready-made pile in the above is mainly configured by connecting a steel tip fitting to the tip of a concrete-based ready-made pile, and the ready-made pile is made of a steel pipe system or a material of a composite structure of these, and further, The tip fitting and the ready-made pile can also be manufactured integrally.
[0027]
Further, the outer diameter range in the above refers to a range that forms a cylindrical range equal to the maximum outer diameter of the ready-made pile and does not radially protrude from the cylindrical side surface.
[0028]
In addition, the maximum outer diameter of the ready-made pile in the above usually refers to the outer diameter because a straight-shaped ready-made pile is used, but when using a ready-made pile having a different outer diameter, the large-diameter portion or the like is used. When the projections and the like have a diameter larger than the lower surface of the ready-made pile to which the tip fitting is connected, the outer diameters of the large diameter portions and the projections 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, the maximum outside diameter of the ready-made pile defined by the excavation diameter of the pile hole is referred to.
[0029]
In addition, a predetermined gap formed between the upper surface of the protrusion and the lower surface of the step portion between the main shaft portion and the lower shaft portion, or a predetermined gap formed between the upper and lower surfaces of the adjacent protrusions, is an effective shear. In order to propagate the force, it is desirable to set the projection interval such that the propagation of the shear force in each projection does not overlap the upper and lower portions in consideration of the propagation angle of the shear force. For example, when two protrusions are formed on the upper and lower sides, when a vertical load is applied to the entire foundation pile structure, it adheres from the lower surface of the step portion, the lower surface of each protrusion, and the lower surface of the ready-made pile (tip fitting). Shear force propagates to the existing soil cement layer (solidification). At this time, it has been confirmed by a test that the shear force propagates obliquely downward at an angle of about 30 degrees with the vertical direction. Therefore, if the shear force is propagated so that it does not hit the upper surface of the projection located below it, the shear force can be sufficiently generated by the projection or the like. Is preferably at least √3 times the height of On the premise of the above, in implementation, the design may be such that the projections are set in the predetermined gap in accordance with the required supporting force, but usually, a ready-made pile with a projection for fixing the ground taking the predetermined gap into account. It is desirable to manufacture in advance.
[0030]
Further, when a pulling force acts on the entire foundation pile structure, the shear force similarly acts upward, and a predetermined gap similar to that when a vertical load acts is required.
[0031]
In addition, the above-mentioned rooting portion having a predetermined shape is a size (layer thickness, outer diameter, and length) commensurate with the required strength of the solidified soil cement layer when the above-described shear force propagates downward or upward. Etc.). 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 larger than the pile diameter of the ready-made pile (tip fitting) (for example, about 50 cm). It is desirable that the diameter be less than 1.5 times the diameter of the projection.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
(1) The tip 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 the upper end portion of the steel pipe main body 1 is a large diameter portion 2 for connection.

Annular projections

10 and 10 are formed at the middle and lower ends (excluding the large diameter portion) of the steel pipe main body 1. Outer diameter D of annular projection 10₄Is the maximum outer diameter D of the large diameter portion 2, that is, the ready-made pile 14.₅It is formed equal to or smaller than. Here, the tip of the annular projection 10 is formed so as not to protrude outward from the large diameter portion 2, that is, the maximum outer diameter of the ready-made pile 14 (FIG. 1). If it is less than the shank excavation diameter, it can be formed to protrude slightly.
[0033]
The ready-made pile 14 to which the tip fitting 12 is connected is lowered into the pile hole 32 filled with the solidified material such as soil cement or the like so that the tip fitting 12 is located at the root fixing portion 34 formed at the lower end 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.
[0034]
At the upper end of the foundation pile structure 37, an upper structure such as a foundation base and a building is constructed.
[0035]
(2) Function, structure, etc. of the tip fitting 12 to be attached
[0036]
The load of the building or the like transmitted from the ready-made pile 14 is propagated to a supporting ground or the like as a shearing force or the like from the surface of the annular projection 10 of the tip fitting 12, and the tip fitting 12 is solidified soil cement in the pile hole 32. It has the function of being supported on the supporting ground integrally with the layer.
[0037]
The large-diameter portion 2 at the upper end of the tip fitting 12 has an upper surface 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 welding to the steel pipe main body 1 or by integrally molding with the steel pipe main body 1.
[0038]
Further, the outer side surface 8 of the steel pipe main body 1 functions so as to adhere to the solidified soil cement in the pile hole 32 and be buried integrally therewith. The annular projection 10 has an outer diameter D of the annular projection 10.₄, The depth L between the

annular projections

10, 10₇This is the same as the formation of the concave portion 40 of FIG.
[0039]
(3) Description of each component
[0040]
(A) The large-diameter portion (connecting portion) 2 located at the upper end of the tip fitting 12 transmits the load of a building or the like transmitted from the ready-made pile 14 located above to the steel pipe main body 1 and the annular projection 10. I do. Further, it has a function of transmitting a vertical shearing force from the lower surface of the outer edge of the large-diameter portion 2 (the step portion with the steel pipe main body) through the soil cement layer in the pile hole, thereby enhancing the supporting force together with the annular projection 10.
[0041]
The large-diameter portion 2 and the steel pipe main body 1 are connected and fixed by welding, molding, or the like, and an integrated steel material is used so that the transmission of stress is smoothly propagated. Further, an annular connecting plate is formed in the large-diameter portion 2, and it is possible to adjust the thickness by laminating a plurality of stress distributions on the connecting plate if necessary for strength. In addition, a plurality of oblique reinforcing ribs may be formed between the lower peripheral edge of the connecting plate and the outer surface of the steel pipe main body.
[0042]
(B) The annular projection 10 is integrally attached to and embedded in the soil cement layer in the pile hole 32, and the upper and lower surfaces of the annular projection 10 are attached to the soil cement layer and the strength (thickness) corresponding to the desired supporting force. , Material), and usually a steel material is used. Therefore, a plurality of annular protrusions 10 are formed, and a predetermined shape is set so that the upward and downward shear forces from the upper and

lower surfaces

42 and 41 and the lower surface 43 of each annular protrusion 10 can sufficiently propagate obliquely downward (about 30 degrees). Interval L₁It is desirable to provide. Such an annular projection 10 is fixed to the outer surface 8 of the steel pipe main body 1 by welding or the like, and is formed integrally with the steel pipe main body 1.
[0043]
The structure of the annular projection 10 is, for example, a donut shape made of a steel plate, and a structure in which three pieces are attached to the steel pipe main body 1 (FIG. 1), and a structure in which two pieces are made in a donut shape made of a steel plate (FIG. 5A). it can. In this case, reinforcing

ribs

11 and 11 can be formed between the upper and lower surfaces of the annular projection 10 and the outer surface 8 of the steel pipe main body 1 (FIG. 5A). In addition, the donut-shaped formation may be performed by stacking and winding steel rods instead of steel plates to obtain a similar structure (not shown).
[0044]
Alternatively, the annular projection 10 may be formed by twisting a donut-shaped steel plate to form a spiral wing shape at two locations (FIG. 5B). In this case, in consideration of the propagation of the shearing force in the soil cement layer, it is necessary to reduce the inclination angle of the spiral blade and to form the spiral blade less than one round.
[0045]
In addition, the annular projection 10 can be formed in a donut shape having a thick wall and a trapezoidal cross section (FIG. 5C). In this case, the annular projection 10 can be hollow or solid.
[0046]
(C) (1) The steel pipe main body 1 is integrated with the large diameter portion 2 and the annular projection 10, and when embedded, is integrated with the solidified soil cement layer in the pile hole 32 to transmit and support vertical stress. This is a structure serving as a base material. Accordingly, the steel pipe main body 1 has a thickness t of a required strength suitable for stress transmission and support.₁, Material is required. Further, the inside of the steel pipe main body 1 is formed so as to communicate with the hollow portion of the ready-made pile 14 to be connected with the same inner diameter so that soil cement can be uniformly filled in the hollow portion. Further, by forming the same diameter as the hollow portion of the ready-made pile 14 to be connected, the drilling rod can be inserted without any trouble when applied to the middle digging method.
[0047]
(4) Dimensions of tip fitting 12
[0048]
Inner diameter dimension D of steel pipe body 1₂May be equal to or larger than the inner diameter of the hollow portion of the prefabricated pile 14 located at the upper portion. However, in order to increase the effective area of the protrusion, the inner diameter of the hollow portion of the prefabricated pile 14 is desirably substantially the same as the inner diameter (FIG. 1). .
[0049]
Also, the outer diameter D of the annular projection 10₄Is the outer diameter D of the ready-made pile 14 located at the top.₅The following dimensions are possible, but the outer diameter D of the ready-made pile 14 is:₅It is desirable from the point of view of strength design, supporting force, and the like (FIGS. 1 and 4). Further, when the ready-made pile 14 is sunk into the pile hole, it is necessary to limit the diameter of the pile to at least the outer diameter dimension within a range that can be penetrated without hindrance when penetrating the shaft portion. That is, it is desirable that the diameter of the shaft hole excavation of the pile hole is smaller than the diameter.
[0050]
The length L of the annular projection 10 from the outer surface of the steel pipe body 1₇(= “D₄-D₁) And the installation interval L₁Means that when the propagation angle θ of the shearing force is downward (≒ 30 degrees), the shearing force can be sufficiently expressed.
L₇<L₁× tanθ
In order to secure the surface area of the annular projection 10 from both the surface for transmitting the shearing force to the soil cement layer and the surface for adhering to the soil cement,₇Is desirably increased (FIG. 1A).
[0051]
(5) In addition, from the above-mentioned technical idea, a steel pipe pile with a spiral blade (smaller in diameter than the ready-made pile to be attached) is fixed to the lower end of the ready-made pile instead of the tip fitting, to constitute the ready-made pile of the present invention. You can also.
[0052]
Embodiment 1
An embodiment of a tip fitting according to the present invention will be described with reference to the drawings.
[0053]
(1) Outer diameter D₁(= 450 mm), inner diameter D₂(= 420) steel pipe body (thickness t₁= 15mm) The outer diameter D₃(= 600 mm) large-diameter portion 2 is formed as a connection portion with ready-made pile 14. An annular groove 3 for fitting the connecting band 23 is formed on the outer periphery on the upper end side of the large diameter portion 2. 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). The annular groove 3 is provided with bolt holes 4 for connection.
[0054]
On the outer periphery of the large-diameter portion 2, a cylindrical surface material 5 having an annular groove portion 3, and a donut-shaped contact material 6 that is continuous with the inside of the upper end of the cylindrical surface material 5 and abuts on the lower surface of the ready-made pile 14. Is embedded. The bolt holes 4 are formed in the cylindrical surface member 3.
[0055]
A distance L from the outer surface 8 of the steel pipe around the middle and lower ends of the steel pipe body 1.₇(= 75 to 90 mm) (ie, outer diameter D₄= 600-630 mm), thickness t₂(= 10 to 40 mm) annular projections 10 are provided. The annular protrusion 10 is formed in a thin disk shape, and has an interval L such that the distance from the lower end of the steel pipe main body 1 to the lower portion of the large diameter portion 2 is equally divided.₁(= 500 mm), and three sheets are formed. In addition, if the annular protrusion 10 is expressed in another way, the reference diameter D₄From depth L₇Is formed.
[0056]
The tip fitting 12 is configured as described above (FIGS. 1A, 1B, and 1C).
[0057]
The interval L in the above₁Considering the effective propagation of the shear force from the lower surface 41, the upper surface 42 of the annular protrusion 10, and the lower surface 43 of the step portion of the large diameter portion 2,
L₁> √3 × L₇
It is formed so that it becomes.
[0058]
(2) Next, the use of the tip fitting 12 of the present invention based on the above embodiment, that is, the configuration of the ready-made pile 14 will be described (FIGS. 2A and 2B).
[0059]
A steel connection fitting 16 is integrally attached to the lower end of the ready-made concrete pile 14. The connection fitting 16 includes a disc-shaped lower end plate 17 and a tubular side plate 18 connected to the lower end plate 17 and provided around the side surface of the ready-made stake 14. And a thicker portion 19 having a thicker material. An annular groove 20 having substantially the same shape as the annular groove 3 of the end fitting 12 is formed on the side plate 18. Bolt holes 21, 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.
[0060]
The joining band 23 is made of steel having an inner diameter that can be fitted to the large diameter portion 2 of the tip fitting 12 and the lower end plate 17 of the ready-made pile 14. In the band 23, an annular convex portion 25 protruding inward is formed on the upper inner surface so as to be inserted into the annular groove portion 20, and a similar annular convex portion 26 corresponding to the annular groove portion 3 is formed on the lower side. Is formed. Further, through

holes

27, 27 corresponding to the bolt holes 4, 21 are formed in the annular

convex portions

25, 26 of the band 23, and a housing portion 28 in which the diameter of the through

holes

27, 27 is increased 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, 24 so that the connecting operation is easy.
[0061]
With the ready-made pile 14 suspended vertically or with the ready-made pile 14 laid on the ground, the upper surface of the tip 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 to be fitted.

Band pieces

24, 24 are arranged in annular contact with the contact portion to form a band 23, and annular

convex portions

25, 26 of band 23 are fitted into annular groove 20 of ready-made pile 14 and annular groove 3 of tip fitting 12, respectively. The bolt 30 is inserted through the through

holes

27, 27, and the tips of the bolts 30 are screwed and tightened into 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.
[0062]
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. That is, the inner surface 15 of the ready-made pile 14 and the inner surface 9 of the tip fitting 12 are formed substantially flush (FIG. 2B).
[0063]
(3) Other embodiments
[0064]
Further, in the above-described embodiment, the ready-made stake 14 is formed by fixing the tip fitting 12 to the lower end. However, the tip-fitting 12 may be formed integrally with the ready-made stake to form the ready-made stake 14 (FIG. 6). ). Even in this case, the distance L between the protrusions 10₁Considering the effective propagation of the shear force from the lower surface 41, the upper surface 42, and the lower surface 43 of the stepped portion of the annular projection 10,
L₁> √3 × L₇
It is formed so that it becomes. When the annular projection 10 is expressed in another way, the reference diameter D₄From depth L₇Is formed.
[0065]
Embodiment 2
Next, the foundation pile structure of the present invention will be described.
[0066]
(1) Predetermined diameter D₁₁(D₁₁= D₅The shaft 33 of the pile hole 32 with a predetermined depth L₂Excavation to the shaft 33 of the pile hole 32 and the depth L₃Diameter D over₁₂Bottom excavation is performed to form the root-fixing portion 34 of the pile hole 32. The pile hole 23 is filled with a root compaction liquid in the root compaction part 34 and the shaft part 33 is filled with the pile circumference fixing liquid. The root consolidation liquid and the pile circumference fixing liquid are made of a solidifying material such as cement milk or soil cement formed by stirring and mixing the solidifying material with excavated soil. The root consolidation liquid is adjusted to have a consolidation strength equivalent to the ground strength of the supporting ground (FIG. 3). In addition, the diameter D of the₁₂Is the shaft outer diameter D of the ready-made pile 14 due to the supporting force required in the design.₅It is desirable that the adjustment be made up to about 1.5 times.
[0067]
(2) In the pile hole 32, a ready-made pile (lower pile; straight shape) 14 having the tip metal fitting 12 attached to the lower end is buried and buried to a predetermined depth. And another ready-made pile (upper pile, straight shape) 14 </ b> A is connected to the upper end of the ready-made pile 14.
[0068]
Subsequently, the ready-made

piles

14 and 14A are lowered into the pile holes 32, the tip metal fittings 12 are completely accommodated in the rooted portions 34, and the lower ends 22 of the ready-made piles 14 have a predetermined length L.₅And the lower surface 13 of the tip metal fitting 12 extends a predetermined length L from the bottom 35 of the root fixing part 34.₄The descent of the ready-made stake 14 is stopped at a position that is located only above, and the ready-made

stakes

14 and 14A are held in that state (FIG. 4).
[0069]
(3) (1) The foundation pile structure 37 of the present invention is configured in a state where the root compaction liquid and the pile circumference fixing liquid are solidified and developed (FIG. 3).
[0070]
(4) Another embodiment
[0071]
In the above example, the so-called pre-digging method of burying a ready-made pile after completion of excavation of a pile hole has been described. Can also be constructed.
[0072]
That is, the excavation rod for middle excavation is inserted into the hollow portion of the ready-made pile 14 to which the tip fitting 12 is attached, and the excavation head is protruded from the lower end of the tip fitting to excavate the pile hole, and the ready-made pile 14 is lowered (FIG. Not shown). The excavated earth and sand is discharged to the ground through the tip fitting 12 and the hollow portion of the ready-made pile 14 by using a spiral provided around the excavation rod while using compressed air. Subsequently, the ready-made piles 14A are connected, a drilling rod is added, and excavation is performed while pouring water. When the ready-made

piles

14 and 14A are lowered to a predetermined position, a root consolidation part is formed, and cement milk is formed. The excavating rod is lifted to the ground through the ready-made

piles

14, 14A and the hollow portion of the tip fitting 12 while injecting and stirring and discharging cement milks.
[0073]
Hereinafter, while descending the ready-made stake 14, the tip fitting 12 is completely accommodated in the solidified portion 34, and the lower end 22 of the ready-made stake 14 is set to the predetermined length L, as in the above-mentioned excavation method.₅And the lower surface 13 of the tip metal fitting 12 extends a predetermined length L from the bottom 35 of the root fixing part 34.₄The descent of the ready-made stake 14 is stopped at a position which is located only above, and the ready-made

stakes

14 and 14A are held in that state. With the above, the root compaction liquid and the like are solidified and developed, and the foundation pile structure is constructed.
[0074]
Embodiment 3
A comparison between the case where the foundation pile structure of the present invention and the foundation pile structure of Conventional Example C are applied to the same ground will be described (FIG. 8).
[0075]
(1) The present invention
As in the first embodiment, the tip fitting 12 is attached to the lower end of the ready-made stake 14, and is buried in the stake hole 32 having the root fixing portion 34 (FIGS. 1 and 3). The dimensions of each part are as follows.
[0076]

[0077]
Note that D₄= 630 mm, the excavation diameter D of the pile hole shaft₁₁And D₃(= 600 mm).
[0078]

[0079]
(2) Comparative example (conventional example C)
A foundation pile structure is constructed in a comparative example corresponding to Conventional Example C in which the same ready-made pile 14 is used as an upper pile 14A and a lower pile 14B with a node 39 is connected instead of the tip fitting 12 (FIG. 7).
[0080]

[0081]
(3) Effects
[0082]
(A) In the loading test, 6.5 MN or more was obtained as the maximum load in both cases. In the third embodiment, the number of the annular protrusions is three, but by increasing or decreasing the number, it is possible to increase or decrease the area of adhesion to the soil cement in the root consolidation part and increase or decrease the propagation area of the shear force. In addition, by further increasing the solidification strength of the soil cement at the root consolidation portion and appropriately selecting the soil quality of the supporting ground, a higher load capacity can be achieved.
[0083]
(B) In the case of a foundation pile structure exhibiting the same supporting force, the diameter of the shaft portion of the pile hole can be reduced to less than 10% of the conventional one. Along with this, the amount of excavated soil discharged can be similarly reduced, and the construction time can be similarly reduced. Therefore, in proportion to the reduction of the earth removal amount and the excavation time, it is possible to reduce the earth removal discharged as industrial waste from the site and the exhaust gas of the excavator, and to create a more environmentally friendly foundation pile. Become.
[0084]
In addition, the gap between the ready-made pile and the shaft of the pile hole is reduced to about 1/6, and the cement milk used is reduced by 40%.
[0085]
(C) (4) Since the outer diameter of the pile shaft can be increased by about 20% against the high bearing capacity of the root compaction part, the bending moment strength of the ready-made pile material can be selected to be about twice as strong as the SC pile. Spreads.
[0086]
(D) As for the inner diameter of the hollow part of the ready made pile, when compared with the same supporting force, when the inner diameter of the ready made pile for exhibiting the high supporting force is 340 mm, the ready made pile having the same outer diameter was used. In this case, according to the present invention, the inner diameter of the ready-made pile may be 420 mm.
[0087]
That is, when a ready-made pile of a normal standard is used, the inner diameter becomes the same as that when a ready-made pile having a large outer diameter of one rank is used, and the inner diameter can be increased by 20% or more.
[0088]
Therefore, in the excavation method, the maximum outer diameter of the excavation rod inserted into the hollow portion can be increased, so that excavation rods having excavation heads of various structures can be selected. In addition, the excavation size of the consolidation portion can be further increased. Therefore, by increasing the diameter of the rooted portion, it is possible to further develop a high supporting force. It is also effective in terms of equipment technology, such as being able to excavate using a conventional excavation rod and obtaining a high bearing capacity.
[0089]
Conventionally, it is difficult to excavate the bottom with the middle digging method, and even if possible, it is possible to excavate only about 1.3 to 1.4 times the outer diameter of the ready-made pile at most. Although it was difficult to construct a foundation pile structure that exerts a supporting force, according to the invention of the present application, the bottom of an expanded bottom portion that is 1.5 to 1.6 times the outer diameter of a ready-made pile that is one rank higher with the conventional construction technology is obtained. Excavation is possible, and the applicable range of the excavation method can be expanded.
[0090]
Embodiment 4
In each of the above embodiments, the distal end fitting 12 has the

annular projections

10 and 10 formed at the intermediate portion and the lower end of the steel pipe main body 1, but is an embodiment in which the distal end fitting 12 has another structure.
[0091]
(1) Outer diameter D₁Outer diameter D having a connection portion with a ready-made pile at the upper end of the steel pipe body 1₃Formed with a large diameter portion, and an outer diameter D at the lower end.₄(FIG. 9).
[0092]
Outer diameter D₁, Inner diameter D₂The 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 formed in a horizontal plane and whose lower surface 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 (outer diameter of the lower end) of the ready-made pile 14 to be connected.
[0093]
An outer diameter D is provided on the outer surface of the lower end of the steel pipe main body 1.₄(Projection) of a disk-shaped (donut-shaped) annular projection 10 is provided. The upper surface 44 of the annular projection 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 main body 1.
[0094]
The tip fitting 12 is configured as described above (FIG. 9A). Inner diameter D of tip fitting 12₂Is formed from the upper end (the upper end of the large-diameter portion 2) to the lower end so as to be substantially the same as the inner diameter of the ready-made pile 14. That is, the inner surface 15 of the ready-made pile 14 and the inner surface 9 of the tip fitting 12 are formed substantially flush (FIG. 10B).
[0095]
The distance between the large-diameter portion 2 and the annular projection 10 is formed in the same manner as in each of the above embodiments, and the annular projection 10 of the present embodiment or the first embodiment is further connected between the annular projections 10. In this case as well, a vertical interval is formed as in the first embodiment.
[0096]
Here, for example,
D₁= 620mm
D₂= 580mm
D₃= 800mm
D₄= 856mm
As D₃Compared to D₄Is formed to have a somewhat larger diameter, so that a larger supporting force can be expected. In addition, the workability may be inferior in the work of burying the ready-made piles due to the large diameter, but if the required supporting force is obtained, D₄≤D₃, Can also be. In the above, D₄(= 856 mm) is set to be equal to or less than the excavation diameter (830 mm) of the shaft₃(= 800 mm).
[0097]
(2) The upper surface of the large-diameter portion 2 of the tip fitting 12 has the same outer diameter D as in the first embodiment.₃The large diameter portion 2 and the lower end plate 17 are integrally fixed by bolts, welding, or the like to the lower surface of the lower end plate 17 of the ready-made pile 14, and buried in the pile hole to form a foundation pile structure (illustrated). Not).
[0098]
When the ready-made pile 14 is buried, a tubular cover 47 that covers the entire steel pipe main body 1 including the large-diameter portion 2 and the lower end of the ready-made pile 1 and that can prevent mud from sticking to this portion is used. Is desirable. In this case, the lower end of the cover 47 is temporarily fixed to the outer peripheral portion 46 of the annular projection 10 via the stopper 5, and the lower end of the PC steel bar 49 is screwed to the

couplers

48, 48 at the upper end of the cover 47. The upper end of the steel bar 49 is screwed with a nut 51 and a coupler 50 to a disk-shaped jig 52 connected to the upper end of the ready-made pile 14 (FIG. 10A). In this state, if the ready-made pile 14 is buried, as described later, the mud is unlikely to adhere or stay on the upper surface 44 and the lower surface 45 of the annular projection 10 protected by the cover 47, and the tip fitting 12 and the ready-made pile 14 This portion can be installed in the stake of the pile hole without the mud sticking to the lower end of the pile hole.
[0099]
When the ready-made pile 14 is installed at a predetermined position, the upper end of the PC steel bar is pulled up, the temporary fixing of the cover 47 and the annular projection 10 by the stopper 53 is released, and the cover 47 and the PC steel bar 49 are pulled up to the ground.
[0100]
Therefore, when the cover 47 is used, the tip metal fittings 12 and the lower ends of the ready-made piles 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. As the cover 47, a cylindrical thin steel pipe is used here, but the material and structure are arbitrary as long as the cover can be covered and buried and then pulled up. Further, the cover 47 can be similarly applied to the tip fitting 12 of the first embodiment (not shown).
[0101]
By using the protective cover 47, it is possible to prevent adhesion of the adhesive mud which lowers the adhesion between the lower end portion of the ready-made pile 14 and the soil cement, so that the outer diameter of the ready-made pile 14 (lower end portion) and the pile hole can be prevented. Even if the outer diameter and the gap of the shaft portion are small, the adhesion between the lower end portion of the ready-made pile 14 and the soil cement layer can be maintained irrespective of the soil quality, and a stable tip support force can be obtained with the foundation pile structure.
[0102]
(3) In the tip fitting 12 of this embodiment, a stable supporting force can be obtained by using the protective cover 47. Therefore, when the outer diameter is the same, the tip fitting 12 of the first embodiment (see FIGS. 1 and 5). ), The bearing surface is designed to be slightly smaller because of the smaller total surface area and the surface to which the shear force is transmitted, but it is easy to handle in construction and the excavation diameter of the piled-up portion of the pile hole can be made smaller. There are advantages such as.
[0103]
That is, specifically, the following advantages can be stably obtained by using the tip fitting 12 having the above-described structure and further using the protective cover 47.
[0104]
(A) (1) The length of the steel pipe main body 1 (tubular base) is reduced (about 1.0 m in length; about 2.5 m in Example 1), and little contributes to exerting the supporting force on the tip fitting 12. Thus, the area of the side surface of the steel pipe main body 1 was reduced. This shortens the length of the excavated bottom of the pile consolidation portion, thereby shortening the construction time and reducing the amount of cement milk used.
(B) The thickness of the root of the annular projection 10 (the side close to the steel pipe main body 1) is increased to increase the mechanical strength.
(C) Since the lower surface 45 of the annular projection 10 is formed as a partially conical inclined slope, the stress on the soil cement layer and the ground in the consolidation portion is efficiently propagated.
(D) Since the annular projection 10 having a large surface area is formed at the tip portion which is considered to most contribute to the generation of the vertical supporting force, a larger vertical supporting force can be exhibited with a small number of projecting portions having a small outer diameter.
(E) Since the lower surface 45 of the annular projection 10 that contributes to the generation of the vertical support force is formed to be inclined, the mud is less likely to adhere to the lower surface 45 of the annular projection 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 transmission of the shearing force to the soil cement layer can be reliably performed.
(F) Since the largest diameter portion is formed at the forefront of the ready-made pile 14, centering of the ready-made pile 14 (alignment with the core of the pile hole) becomes easy when the ready-made pile 14 is buried. .
[0105]
【The invention's effect】
At the lower end of the ready-made pile, a tip fitting having a projection is fixed, or for a ready-made pile having a projection or recess formed at the lower end, the area of attachment with soil cement is increased, and the diameter of the tip fitting is increased. From the lower surface, the upper and lower surfaces of the protrusion of the tip fitting, the step between the main shaft and the lower shaft of the ready-made pile, the upper and lower walls of the protrusion, and the upper and lower walls of the recess, they are arranged so that the shear force can be propagated without obstacles. Since it is buried in the solidified portion filled with the soil cement having the solidification strength equal to or higher than the supporting ground strength, there is an effect that the shear force can be effectively propagated in the solidified portion to form a foundation pile structure having a high supporting force.
[0106]
In addition, since the outer diameter of the protrusion of the tip 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 exerted with a smaller excavation diameter of the shaft portion of the pile hole. In addition, the drilling diameter can be reduced with the same supporting force because it can exert a larger supporting force than the drilling diameter of the pile hole shaft part, so the amount of earth removal and the drilling time of the pile hole can be reduced. There is. Therefore, it is possible to reduce the amount of soil discharged as industrial waste discharged from the site, reduce the excavation time by reducing the excavation time, and build a foundation pile that is more environmentally friendly.
[0107]
In addition, when the shaft diameter of the pile hole and the outer diameter of the ready-made pile are the same and the same bearing capacity is exhibited as before, the inner diameter of the ready-made pile can be increased, so the hollow part of the ready-made pile can be used effectively. In addition, there is an effect that a foundation pile having a higher bearing capacity can be easily constructed with the conventional equipment by the inside digging method.
[0108]
In addition, when using the tip metal fitting, even when using a pre-made pile having the same diameter, if the required tip supporting force is different, the number of protrusions of the tip metal fitting is changed according to the tip supporting force. By increasing or decreasing the effective area, or increasing or decreasing the solidification strength of the soil cement, it is possible to easily construct a more efficient foundation pile structure.
[0109]
In addition, when the lower end portion of the ready-made pile and the tip support device related to the tip support force are covered with the protective cover, the adhesion between the portion and the soil cement layer is improved without muddy soil fixing or stagnation at the portion. You. Therefore, stable bearing capacity can be obtained even on highly adhesive ground, and even if the gap between the shaft diameter of the pile hole and the outer diameter of the ready-made pile and tip metal fittings is small, the stable foundation pile structure will be stable. High supporting force is obtained.
[Brief description of the drawings]
FIG. 1 is an embodiment of a tip fitting according to the present invention, wherein (a) is a front view, (b) is a bottom view, and (c) is a longitudinal sectional view.
FIGS. 2A and 2B are partially enlarged longitudinal sectional views showing a connection between a tip fitting and a ready-made stake of the present invention, wherein FIG. 2A shows a state before connection and FIG.
FIG. 3 is a longitudinal sectional view of the foundation pile structure according to the embodiment of the present invention.
FIG. 4 is an enlarged vertical sectional view of the root compaction part.
FIG. 5 is a front view of another tip fitting of the present invention.
FIG. 6 is a front view of another ready-made pile according to the present invention.
7A and 7B are diagrams illustrating 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 ready-made piles (upper and lower piles) are embedded. is there.
FIG. 8 is a diagram for explaining the ground to which the third embodiment is applied and the state of installation of ready-made piles.
9 (a) is a longitudinal sectional view and FIG. 9 (b) is a front view of a ready-made pile according to the fourth embodiment, which is mounted on a pile driver.
FIG. 10 is a partially enlarged longitudinal sectional view of the ready-made stake, wherein (a) shows an upper end portion and (b) shows a lower end portion, respectively.
[Explanation of symbols]
1 Steel pipe body
2 Large diameter part
3 annular groove
4mm bolt hole
5 mm cylindrical surface material
6 Contact material
8mm outer surface
9 inner surface
10 ° annular projection
11 Rib of annular projection
12mm tip fitting
13 Lower surface of tip fitting
14, 14A Ready-made pile
15 Inner surface of ready-made pile
16 Connection fittings for ready-made piles
17 Lower end plate of ready-made pile
18 Side plate of ready-made pile
19 Thick part of side plate of ready-made pile
20mm annular groove of ready made pile
21 Bolt hole of ready made pile
22 Lower end of ready-made pile
23mm band for connection
24 band piece
25, 26 band convex ring
27 band through hole
28 band storage
30mm bolt
32 pile hole
33 Shaft hole shaft
34 Pile hole fixing part
35 底 Bottom of the root of the pile hole
37 foundation pile structure
40 ° recess
41 Lower surface of protrusion (upper side surface of concave portion)
42 Upper surface of protrusion (lower side surface of concave portion)
43mm stepped bottom surface
44 ° Upper surface of annular projection 11
45 ° Lower surface of annular projection 11
47 cover
49 PC steel bar
52 disc-shaped jig

Claims

A lower end portion of a ready-made pile having a main shaft portion having a predetermined shaft diameter is formed with a lower shaft portion having a smaller diameter than the main shaft portion, and a projection is formed on the lower shaft portion. Formed equal to or less than the outer diameter,
A foundation pile structure using a ready-made pile, wherein the ready-made pile is buried in a pile hole having a rock-solid portion so that a protrusion is located in the rock-solid portion of the pile hole.

The protrusions are arranged so as to provide a predetermined gap between the upper surface of the protrusion and the lower surface of the step portion between the main shaft portion and the lower shaft portion, or to provide a predetermined gap between the upper and lower surfaces of the adjacent protrusions.
The foundation pile structure using a ready-made pile according to claim 1, characterized in that soil cement having a solidification strength equal to or higher than the strength of the supporting ground is filled in a fixed part of the pile hole having a predetermined shape.

At the lower end of the ready-made pile having a main shaft portion having a predetermined shaft diameter, a lateral concave portion is formed from the side surface toward the shaft side,
A structure of a foundation pile using a pre-built pre-built pile, wherein the pre-made pile is embedded in a pile hole having a pre-fixed part, and the recess is located in the consolidation part of the pile hole. The distance between the upper and lower walls is formed at least 3 times the depth of the concave portion, and a solid pile having a solidified strength equal to or more than the supporting ground strength is filled in the reinforced portion, and a ready-made pile is used. Foundation pile structure.

The protrusions or recesses of the ready-made piles are all arranged in the rooting portion, and a gap of a predetermined length is formed by the lower end of the ready-made pile and the bottom of the rooting portion,
The ready-made pile according to any one of claims 1 to 3, wherein a portion having a shaft diameter of a main shaft portion of the ready-made pile immediately above the projecting portion or the concave portion of the ready-made pile is arranged at an upper end portion of the stiffening portion. Using foundation pile structure.

In a ready-made pile having a lower shaft portion below an upper shaft portion having a predetermined outer diameter, the lower shaft portion is formed to have a smaller diameter than the upper shaft portion, a projection is formed on the lower shaft portion, and a tip of the projection portion Is formed in a size equal to or less than the outer diameter range of the upper shaft portion.

A large diameter portion is formed at the upper end of the steel pipe main body, a connection portion with a ready-made pile is formed at the large diameter portion, and a projection is formed on the outer periphery of the steel pipe main body. A tip fitting for a ready-made stake, wherein the tip has a diameter equal to or smaller than the outer diameter of the large diameter portion.

The tip metal fitting for a ready-made pile according to claim 6, wherein the outer diameter of the large diameter portion is substantially the same as the outer diameter of the ready-made pile to be connected.