JP2005048385A

JP2005048385A - Joint structure of steel pipe sheet pile

Info

Publication number: JP2005048385A
Application number: JP2003204250A
Authority: JP
Inventors: Kenji Saikai; 健二西海; Hisao Yamashita; 久男山下
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2003-07-31
Filing date: 2003-07-31
Publication date: 2005-02-24
Anticipated expiration: 2023-07-31
Also published as: JP4081412B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint structure increasing shear proof stress in the direction of a steel pipe shaft in a joint steel pipe (P-P joint) of a steel pipe sheet pile. <P>SOLUTION: In the steel pipe sheet pile 1 formed by laying the joint steel pipe having a slit 3 in the direction of the outside shaft of a steel pipe sheet pile main 2, in order to increase the shear proof stress between the joint steel pipe 4 and an infilled mortar 8 in a position opposed to a through-hole 7 opened in a joint long claw section 4a of the joint steel pipe 4 on the other side fitted to each other, a plurality of through-holes 7 having a hole diameter with a necessary and sufficient area for ensuring the shear proof stress of the joint steel pipes opposed to each other are arranged in the direction of the pipe shaft. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、土留め壁構造および井筒基礎構造など鋼管を連結して構築する鋼管矢板および鋼管矢板の継手鋼管構造に関する。
【０００２】
【従来の技術】
複数の鋼管矢板を井筒状に閉合してなる鋼管矢板井筒基礎においては、お互いの鋼管を連結するために一般にスリットを有する円形の継手鋼管（Ｐ−Ｐ継手）が用いられる。この継手を嵌合させて、鋼管矢板を連続して建て込んだ後に、継手鋼管内にモルタルを充填して構築する。図６以下によって説明すると、隣接する鋼管矢板１６の継手同士を互いに嵌合連結しながら、複数の鋼管矢板１６を平面に見て円形、小判形、矩形等の閉鎖形状になるように地盤中に打設し、その閉鎖形状の内部空間に頂版コンクリートを施工して鋼管矢板井筒基礎１７が構築され、その上面に橋脚１８が構築される。
【０００３】
前記鋼管矢板１６の継手部材としては、図７、図８に示されるように、通常、Ｐ−Ｐ型継手部材が採用される。この継手部材は、鋼管矢板本管１６ａより小径の円形鋼管（以下、継手鋼管という）１４からなり、その継手鋼管１４は、前記鋼管矢板本管１６ａの外面に溶接で固着されると共に、管軸方向に沿って伸びる嵌合用のスリット１９が設けられている。
【０００４】
施工にあたっては、各鋼管矢板１６について、その継手鋼管１４を、隣接する鋼管矢板１６の継手鋼管１４に嵌合させながら地盤中に打設し、継手鋼管１４における嵌合部の内部空間内の土砂を掘削、排土、洗浄した後、その空間内にモルタル２０を充填して鋼管矢板１６同士を連結して、閉鎖形状を形成する。
【０００５】
一般に、Ｐ−Ｐ型継手部材に用いる継手鋼管１４には、外形が１６５．２ｍｍ、板厚が１１ｍｍ（もしくは９ｍｍ）で、図８（Ｂ）に示すように内面に突起などの凸凹が無いものが使用される。一方、充填するモルタル２０としては、圧縮強度２０Ｎ／ｍｍ^２程度のものが使用されている。
【０００６】
ところで鋼管矢板井筒基礎１７に水平方向の外力が作用した場合には、鋼管矢板１６の継手鋼管１４に管軸方向のせん断力が作用する。この場合、継手部のせん断伝達力が小さいと、継手部で軸方向にずれが生じることとなり、鋼管矢板井筒基礎１７の構造全体の曲げ剛性はこの継手部で規定される。このことから鋼管矢板井筒基礎１７の曲げ剛性向上のためには、継手鋼管１４の鋼管軸方向のせん断耐力を向上させる必要がある。
【０００７】
継手部のせん断耐力を高める手法として、前記の図８（Ｃ）に示すような鋼管内面に突起部を設ける方法が知られており、この継手構造では、確かに突起部とモルタルとの摩擦力が高まるために、高いせん断耐力を発揮することができる。しかし、この場合には突起部での摩擦力は向上するが、鋼管の拘束効果が小さいために継手鋼管のスリット部に開き変形を生じ、このために継手せん断耐力の向上には限界がある。
【０００８】
前記の問題を解決する手段として、特開２０００−２２０１３５には、鋼管矢板本管の円弧部と継手鋼管の円弧部の間に補強板を溶接する方法が開示されている。この先行技術は、先の突起付き継手鋼管の技術と、継手鋼管の大径化により継手せん断耐力を増加した場合に、継手鋼管のせん断降伏により継手せん断耐力が規定される場合があることに着目し、継手せん断耐力を増加するために、鋼管矢板円弧部に別途補強板を溶接により配置した構造である。しかし、前記先行技術は補強板の溶接量が多くなり、かつ、加工が煩雑となるために、継手製作費が高価となるという問題があった。
【０００９】
他方、特開２０００−３５５９３３には、円形の継手鋼管（Ｐ−Ｐ継手）における継手嵌合区間に貫通孔を有する技術が開示されている。この先行技術では、継手せん断耐力は、該継手鋼管の長爪側（鋼管矢板本管との溶接部からスリットまでが長い側）の嵌合区間でのせん断抵抗が最も重要であることに着目し、かつ、施工時の土砂洗浄状態が継手せん断耐力に大きな影響を及ぼすことに着目し、長爪側嵌合区間に小径の貫通孔を複数開孔している。すなわち、この開孔は、モルタル充填前の継手管内洗浄の向上を主たる目的としたものである。
【００１０】
前記の先行技術において、発明の詳細な説明には、貫通孔の配置により継手鋼管とモルタルの付着強度が向上することが記載されているが、積極的にずれ止めとしての使用は考慮されていない。また、そこに記載されている実験データからは、貫通孔を配置することによりモルタル付着強度の増加は認められず、継手鋼管の管軸方向のずれ止めとしての機能、スリット部を介して継手鋼管に開き変形を生じるのを拘束するアンカーとしての機能は期待できない。
【００１１】
【特許文献１】
特開２０００−２２０１３５号公報
【特許文献２】
特開２０００−３５５９３３号公報
【００１２】
【発明が解決しようとする課題】
本発明者は、鋼管矢板の継手鋼管の軸方向のせん断耐力向上につき独自の研究を行った。その結果、従来技術に見られるように、単に鋼材に開設の小孔にモルタルを回り込ませることでモルタルと鋼材との付着強度を向上するのではなく、特に、一定の条件が整うように継手管に貫通孔を設けることで、相対する継手鋼管の対向する貫通孔の内外に硬化したモルタルを行き渡って存在させることによりアンカー軸として機能させ、これにより継手鋼管を拡開させようと作用する力に抵抗させてその拡開を拘束し、以って継手部に大きなせん断耐力を発揮させることができることの知見を得た。
【００１３】
すなわち、本発明者の研究によると、鋼管矢板の継手鋼管に一定条件の下で貫通孔を設けることにより、この貫通孔部にずれ力が作用した場合には、継手鋼管貫通孔の板厚部でモルタルに支圧力が作用すると同時に、貫通孔法線方向に割裂力が作用する。この割裂力を抑制する拘束効果を付与することにより、せん断耐力は飛躍的に大きくなる。また、拘束力が作用した条件では、せん断耐力はおおよそ貫通孔面積に比例することの知見を得た。
【００１４】
本発明は、前記の研究結果にもとづいて提案するもので、鋼管矢板の継手鋼管（Ｐ−Ｐ継手）において、鋼管軸方向のせん断耐力を高める継手構造を提供することが課題である。
【００１５】
【課題を解決するための手段】
本発明は、前記の目的を達成するため、次のように構成する。
【００１６】
第１の発明は、鋼管矢板本管の外面軸方向にスリットを有する継手鋼管を配管してなる鋼管矢板において、前記継手鋼管の継手長爪部でかつ、互いに嵌合する相手側の継手鋼管の継手長爪部に開設する貫通孔と対向する位置に、継手鋼管と充填モルタルとのせん断耐力を増加すべく、相対する継手鋼管同士のせん断耐力を確保するに必要かつ十分な面積の孔径を持つ複数の貫通孔を管軸方向に配置したことを特徴とする。
【００１７】
第２の発明は、第１の発明において、継手長爪部の先端から相手側の継手鋼管のスリットまでの範囲を長爪側嵌合区間とし、前記貫通孔の直径（Ｄ）は、前記長爪側嵌合区間の１／４から１／２の範囲に設定することを特徴とする。
【００１８】
第３の発明は、第１又は第２の発明において、前記継手鋼管の継手長爪部に開設の貫通孔の中心軸を、相対する継手鋼管の矢板本管との溶接部を通る中心軸よりも先端側に配置したことを特徴とする。
【００１９】
第４の発明は、第１〜第３の何れかの発明において、前記継手鋼管に内面突起鋼管を用いたことを特徴とする。
【００２０】
第５の発明は、第１〜第４の何れかの発明において、前記継手鋼管の継手長爪部の側端部の軸方向に充填モルタル拘束用の突起部を配置したことを特徴とする。
【００２１】
【作用】
本発明によると、互いに嵌合する相手側の継手鋼管の長爪部に開設する貫通孔と対向する位置に、相対する継手鋼管同士のせん断耐力を確保するに必要かつ十分な面積の孔径を持つ複数の貫通孔を管軸方向に配置したので、前記対向する貫通孔に存在する硬化したモルタルがアンカー軸部として機能し、これにより貫通孔部にせん断耐力が作用した場合に、継手鋼管の板厚部でモルタルに支圧力が作用すると同時に、貫通孔法線方向に割裂力が作用しても、前記アンカー軸部がこの割裂力を抑制する拘束効果を発揮し、この拘束効果によって継手鋼管のせん断耐力は大きくなる。モルタルにアンカー軸部としての機能を発揮させるための前記貫通孔の大きさは、継手鋼管に拘束力が作用した条件下では、せん断耐力はおおよそ貫通孔の面積に比例することの知見を得たことに基づき、それに適した大きさに開設されている。
【００２２】
【発明の実施の形態】
以下、本発明の実施形態を図を参照して説明する。
【００２３】
図１は、本発明の実施形態１を示し、（Ａ）は、鋼管矢板における相対する継手鋼管（Ｐ−Ｐ継手）の嵌合状態を示す平面図、（Ｂ）は、継手鋼管を単体で示す斜視図である。同図に示すように鋼管矢板１は、鋼管矢板本管２の外面軸方向にスリット３を有する円形鋼管からなる継手鋼管４を溶接して構成されている。この継手鋼管４は、溶接部５からスリット３の側端までが長い方を継手長爪部４ａとし、溶接部５からスリット３の側端までが短い方を継手短爪部４ｂとする。また、スリット３を介して互いに嵌合した継手鋼管４において、継手長爪部４ａの先端から相手側の継手鋼管４のスリット３までの範囲を長爪側嵌合区間６とする。
【００２４】
本発明の実施形態１では、互いに嵌合した継手鋼管４の長爪側嵌合区間６において、相手側の長爪側嵌合区間６に開設する貫通孔７と対向する位置に、同じく貫通孔７を開設した点に特長がある。しかもこの貫通孔７は、継手鋼管４とその内部に充填するモルタル８とのせん断耐力を増加すべく、相対する継手鋼管同士の軸方向のせん断耐力を確保するに必要かつ十分な面積の孔径を有していることが条件であり、かつ、この貫通孔７は管軸方向に列状に配置している（なお貫通孔７は千鳥配置でもよいが図は省略する）。また、貫通孔７が相手側の貫通孔７と対向する位置設けられるとは、後述の図４（Ｂ）、図５（Ｃ）に示すように、互いに嵌合した継手鋼管４の溶接部５を通る中心線（イ）上に位置して対向する貫通孔７と、図５（Ａ）、（Ｂ）に示すように、中心線（イ）に対し平面的に見てある角度θ傾斜した位置で対向する貫通孔７とを含むものである。
【００２５】
前記のように継手鋼管４に貫通孔７を配置することにより、該貫通孔７に充填されるモルタル８（図４、図５に示す）のせん断伝達により継手鋼管４にスリット３を介して開き方向の力が作用したとき、該モルタルがアンカー軸として機能し、該継手鋼管４の継手せん断耐力が増大する。このせん断耐力は、概ね貫通孔７の孔面積に比例することが判明した。したがって、大きなせん断耐力を確保するためには、大きな面積の貫通孔７を配置することが効果的である。したがって、この点で、継手嵌合区間６において管軸方向に貫通孔７を列状に配置することが最も効果的な孔配置方法である。勿論、貫通孔７の孔の大きさを調整することで該貫通孔７を複数列配置することは構わない。また、貫通孔７の形状は、円形でも矩形でも構わない。さらに、以上の知見に基づけば、孔が縦長形状である場合には、さらに貫通孔７を効果的に配置することができる。
【００２６】
前記貫通孔７の孔サイズとしては、継手嵌合区間６の長さの１／４から１／２程度の直径（Ｄ）を有することが望ましい。したがって、Φ１６５．２ｍｍの継手鋼管４の場合には、孔が３５ｍｍ〜７０ｍｍ程度の幅寸法の貫通孔７となる。また、継手鋼管４に大きなサイズを用いる場合には、該継手鋼管４の寸法に応じて貫通孔７の寸法も大きくなる。互いに嵌合した継手鋼管４内に充填するモルタル８としては、高強度のほうが継手鋼管４のせん断耐力が大きくなる。一般の充填モルタルは、２０Ｎ／ｍｍ^２程度であるが、４０〜６０Ｎ／ｍｍ^２程度の高強度モルタルを充填してもよい。
【００２７】
次に、図２は実施形態２を示し、貫通孔７の配置の部位を特別に規定することで、継手鋼管４のモルタルとのせん断耐力を一層向上させる例を示す。すなわち、この実施形態２では、スリット３を介して互いに嵌合した両継手鋼管４の鋼管矢板本管２との溶接部５を通る中心線（イ）よりも継手長爪部４ａの先端側に貫通孔７の中心軸を配置する例を示すが、貫通孔７の中心を中心線（イ）よりも先端側に寄せた配置でもよい。
【００２８】
実施形態２において、継手鋼管４の中心線（イ）よりも先端側に貫通孔７を配置することにより、モルタル８との一層大きなせん断耐力を発揮することができる。実施形態２の継手鋼管４によると、貫通孔７とモルタル８のせん断耐力は、鋼管軸方向と同様に鋼管周方向にも抵抗することができる。したがって、貫通孔７を継手鋼管４の中心線（イ）よりも先端側に配置することにより、貫通孔７の周囲のコンクリートに拘束力が作用するために、長爪側嵌合区間において長爪部の抜け出しを抑制し、継手鋼管同士のせん断耐力を増加することができる。
【００２９】
また、実施形態１、２で説明したように貫通孔７を有する継手鋼管４において、本発明においても内面に突起を有する継手鋼管４を用いることは一層効果的である。図３には、継手鋼管４の内面に突起部を設けた例を示し、同図（Ａ）は、チェッカー状の突起１０を示し、同図（Ｂ）は、スパイラル状の突起１１を示し、同図（Ｃ）は、横方向に平行の突起１２の例を示す。このように継手鋼管４の内面に突起部を設けることによって、鋼管とモルタルの付着を確保し、そのために飛躍的に優れたせん断耐力を発揮することができる。継手鋼管４の内面の突起は、縞鋼管を用いてもよいし、チェッカープレートにより製造してもよい。
【００３０】
しかし、継手鋼管４において、内面突起部と充填モルタルの付着性状は、突起部でのせん断破壊時のモルタルに体積膨張が生じるため、継手部の閉鎖空間内では高い付着力を発揮するが、継手鋼管４には、反力として剥離力が作用するために、鋼管にスリット３があるような本発明の継手鋼管４の場合には、継手短爪部が開くとともに、継手長爪部に抜け出しが生じ、低強度でせん断破壊に至る。
【００３１】
継手鋼管４における長爪側嵌合区間６の抜け出しを抑制する手段として、図５（Ｃ）には、継手鋼管４の端部、つまり長爪側嵌合区間６の先端に定着部として内側屈曲部１３を設けた例を示す。前記の内側屈曲部１３を設けることによって継手鋼管４の長爪側嵌合区間６の抜け出しに抵抗させることができ、これにより飛躍的に大きなせん断耐力を発揮することができる。継手鋼管４の長爪側嵌合区間６の先端に設ける鋼管端部の定着部は、図の内側屈曲部１３のようにスリット部の鋼管を折り曲げ加工により設けてもよいし、鋼板や丸鋼などを溶接で配置してもよい。
【００３２】
すなわち、内面突起鋼管の場合に、継手鋼管内のモルタルの拘束力が作用すれば、大きなせん断耐力を発揮するために、長爪側嵌合区間６に貫通孔７や先端定着部を配置することにより、長爪側嵌合区間６の抜け出し抑制アンカーとして機能し、継手鋼管のせん断耐力が飛躍的に増大させることができる。
【００３３】
図４、図５は、鋼管矢板１に水平方向の外力が作用した場合において、モルタル８が充填された互いに嵌合するスリット付き継手鋼管４にせん断力が作用した場合に、該継手鋼管のモルタル８に作用する割裂力の方向を矢印で示す説明図である。図４（Ａ）は、比較例として示す継手鋼管１４であり、図４（Ｂ）と図５（Ａ）、（Ｂ）、（Ｃ）は、本発明に係る継手鋼管４の例を示す。
【００３４】
図４（Ａ）の継手鋼管１４では、内面にモルタル２０との付着力を増す突起部（図示せず）を有しているが貫通孔を有していない。この継手鋼管１４にせん断力が作用したとき、モルタル２０には矢印（ロ）のように剥離力が作用する。このために、継手短爪部は外側に開く方向に変形し、継手長爪部は抜け出す方向に変形し、両継手鋼管１４は嵌合が外れやすくなると共に、せん断耐力の増大が阻害される。
【００３５】
これに対して、図４（Ｂ）に示す本発明の継手鋼管４においては、貫通孔７が継手鋼管４の溶接部５を通る中心線（イ）上に対向して設けられている。この継手鋼管４にせん断力が作用したとき、モルタル８には矢印（ハ）のような割裂力が作用する。しかし、貫通孔７が相対する位置に配置されているため、割裂力が相殺されることにより、点線で示す領域にモルタルアンカー軸部１５が形成される。このモルタルアンカー軸部１５の存在によって、モルタルの割裂破壊を拘束されるために、継手鋼管のせん断耐力が飛躍的に増大することとなる。
【００３６】
図５（Ａ）、（Ｂ）に示す本発明の継手鋼管４においては、貫通孔７が継手鋼管４の溶接部５を通る中心線（イ）に対し平面的に見てある角度θ傾斜した位置で対向して設けられている。この継手鋼管４にせん断力が作用したとき、モルタル８に作用する割裂力は矢印（ニ）のようになる。すなわち、中心線（イ）に対し傾斜した角度位置で対向する貫通孔７の存在により、割裂力が相殺されモルタルアンカー軸部に大きな拘束力が作用する。また、モルタルアンカー軸が長爪側に傾斜しているために、継手短爪部は開く方向の変形は生じない。
【００３７】
また、図４（Ｂ）は継手鋼管４の内面に突起を設けた場合を示している。内面突起部にせん断力が作用すると、前述のように継手鋼管のスリットが開き、継手長爪部が抜け出す方向に剥離力が作用するが、貫通孔７における継手鋼管の周方向のせん断抵抗により、継手長爪部の抜け出しを抑制するアンカーとして機能する。このために、継手鋼管のせん断耐力は飛躍的に増大することとなる。
【００３８】
図５（Ｃ）に示す、継手鋼管４とモルタル８の剥離力に抵抗し、継手鋼管４における長爪側嵌合区間６の抜け出しを一層抑制する手段として、端部、つまり長爪側嵌合区間６の先端に定着部として内側屈曲部１３を設けた例においては、継手鋼管４にせん断力が作用したとき、モルタル８に作用する剥離力は図４（Ｂ）で示したのと同様になる。すなわち、継手長爪部に抜け出し力が発生した場合に前記の内側屈曲部１３によって鋼管とコンクリートの定着を確保して抜け出しに抵抗し、とくに、対向する継手鋼管４のスリット３の拡開を確実に止めることができ、それにより飛躍的に優れたせん断耐力を発揮することができるものである。
【００３９】
なお、本発明は、実施形態に示した構成を適宜変更して実施することは構わない。
【００４０】
【発明の効果】
本発明に係る鋼管矢板の継手構造によると、▲１▼継手が高いせん断耐力を発揮する。▲２▼鋼管矢板本管と継手鋼管との接合部を補強しなくてよいから、補強プレートなどの溶接が不要である。▲３▼継手構造のせん断耐力が向上するので、井筒基礎構造の全体曲げ剛性が向上し、井筒基礎の寸法を小さくすることができ、経済性が向上する。
【図面の簡単な説明】
【図１】（Ａ）は、実施形態１を示し、鋼管矢板における相対する継手鋼管（Ｐ−Ｐ継手）の嵌合状態を示す平面図、（Ｂ）は、継手鋼管を単体で示す斜視図である。
【図２】（Ａ）は、実施形態２を示し、鋼管矢板における相対する継手鋼管の嵌合状態を示す平面図、（Ｂ）は、前記継手鋼管を単体で示す斜視図である。
【図３】（Ａ）、（Ｂ）、（Ｃ）は、継手鋼管内面に付形する内面突起の３例を示す説明図である。
【図４】鋼管矢板において互いに嵌合した継手鋼管にせん断力が作用したとき、充填モルタルに作用する割裂力の方向を矢印で示す図で、（Ａ）は比較例として示す貫通孔を有しない互いに嵌合した継手鋼管の平面図、（Ｂ）は、本発明の貫通孔を有する互いに嵌合した継手鋼管の第１、第２例の平面図である。
【図５】（Ａ）、（Ｂ）、（Ｃ）は、同じく本発明の貫通孔を有する互いに嵌合した継手鋼管の第３例と第４例と第５例の平面図である。
【図６】従来例の鋼管矢板井筒基礎の斜視図である。
【図７】従来の鋼管矢板における相対する継手鋼管の嵌合状態を示す平面図、（Ｂ）は、鋼管矢板を単体で示す斜視図である
【図８】図７の鋼管矢板における相対する継手鋼管の嵌合状態を示す平面図、（Ｂ）、（Ｃ）は、前記継手鋼管の内面突起の有る場合と無い場合の２例を単体で示す斜視図である。
【符号の説明】
１鋼管矢板
２鋼管矢板本管
３スリット
４継手鋼管
４ａ継手長爪部
４ｂ継手短爪部
５溶接部
６長爪側嵌合区間
７貫通孔
８モルタル
１１スパイラル状突起
１２平行突起
１３内側屈曲部
１４継手鋼管
１５モルタルアンカー軸部
１５ａモルタルアンカー軸部
１６鋼管矢板
１６ａ鋼管矢板本管
１７鋼管矢板井筒基礎
１８橋脚
１９スリット
２０モルタル
２１凸凹[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a steel pipe sheet pile constructed by connecting steel pipes such as a retaining wall structure and a well foundation structure, and a steel pipe sheet pile joint steel pipe structure.
[0002]
[Prior art]
In a steel pipe sheet pile well foundation in which a plurality of steel pipe sheet piles are closed in a tubular shape, a circular joint steel pipe (PP joint) having a slit is generally used to connect the steel pipes to each other. After fitting this joint and continuously building the steel pipe sheet pile, the joint steel pipe is filled with mortar and constructed. 6 and below, the joints of adjacent steel pipe sheet piles 16 are fitted and connected to each other, and a plurality of steel pipe sheet piles 16 are viewed in a plan view so as to have a closed shape such as a circle, an oval shape, or a rectangle. The steel pipe sheet pile well foundation 17 is constructed by placing the top concrete in the closed internal space, and the pier 18 is constructed on the upper surface thereof.
[0003]
As a joint member of the steel pipe sheet pile 16, a PP joint member is usually adopted as shown in FIGS. The joint member includes a circular steel pipe (hereinafter referred to as a joint steel pipe) 14 having a diameter smaller than that of the steel pipe sheet pile main pipe 16a, and the joint steel pipe 14 is fixed to the outer surface of the steel pipe sheet pile main pipe 16a by welding and a pipe shaft. A fitting slit 19 extending in the direction is provided.
[0004]
In the construction, each steel pipe sheet pile 16 is placed in the ground while fitting the joint steel pipe 14 to the joint steel pipe 14 of the adjacent steel pipe sheet pile 16, and the earth and sand in the internal space of the fitting portion in the joint steel pipe 14. After excavating, discharging and cleaning, the mortar 20 is filled in the space and the steel sheet piles 16 are connected to form a closed shape.
[0005]
Generally, the joint steel pipe 14 used for the PP joint member has an outer shape of 165.2 mm, a plate thickness of 11 mm (or 9 mm), and has no irregularities such as protrusions on the inner surface as shown in FIG. Is used. On the other hand, as the mortar 20 to be filled, one having a compressive strength of about 20 N / mm ² is used.
[0006]
By the way, when a horizontal external force is applied to the steel pipe sheet pile well foundation 17, a shearing force in the pipe axis direction is applied to the joint steel pipe 14 of the steel pipe sheet pile 16. In this case, when the shear transmission force of the joint portion is small, a displacement occurs in the axial direction at the joint portion, and the bending rigidity of the entire structure of the steel pipe sheet pile well foundation 17 is defined by this joint portion. Therefore, in order to improve the bending rigidity of the steel pipe sheet pile well foundation 17, it is necessary to improve the shear strength in the steel pipe axial direction of the joint steel pipe 14.
[0007]
As a technique for increasing the shear strength of the joint, there is known a method of providing a protrusion on the inner surface of the steel pipe as shown in FIG. 8C. In this joint structure, the frictional force between the protrusion and the mortar is surely obtained. Therefore, high shear strength can be exhibited. However, in this case, the frictional force at the protrusion is improved, but the restraining effect of the steel pipe is small, so that the slit part of the joint steel pipe is deformed open, and there is a limit to the improvement of the joint shear strength.
[0008]
As means for solving the above problem, Japanese Patent Laid-Open No. 2000-220135 discloses a method of welding a reinforcing plate between an arc portion of a steel pipe sheet pile main pipe and an arc portion of a joint steel pipe. This prior art focuses on the joint steel pipe with a projection and the joint shear strength of the joint steel pipe when the joint shear strength is increased by increasing the diameter of the joint steel pipe. In order to increase the joint shear strength, a reinforcing plate is separately arranged on the steel pipe sheet pile arc portion by welding. However, the prior art has a problem that the amount of welding of the reinforcing plate is increased and the processing becomes complicated, so that the joint manufacturing cost becomes expensive.
[0009]
On the other hand, Japanese Patent Application Laid-Open No. 2000-355933 discloses a technique having a through hole in a joint fitting section in a circular joint steel pipe (PP joint). In this prior art, focusing on the joint shear strength, the shear resistance in the fitting section on the long claw side of the joint steel pipe (the side from the welded portion to the steel pipe sheet pile main pipe to the slit) is the most important. Moreover, paying attention to the fact that the state of soil washing during construction has a great influence on the joint shear strength, a plurality of small-diameter through-holes are opened in the long claw-side fitting section. That is, this opening is mainly intended to improve the cleaning of the joint pipe before filling with mortar.
[0010]
In the above prior art, the detailed description of the invention describes that the adhesion strength between the joint steel pipe and the mortar is improved by the arrangement of the through holes, but the use as a detent is not considered actively. . Also, from the experimental data described there, no increase in the mortar adhesion strength was observed by arranging the through-holes, and the function as a detent in the pipe axis direction of the joint steel pipe, the joint steel pipe through the slit part Therefore, it cannot be expected to function as an anchor that restrains opening deformation.
[0011]
[Patent Document 1]
JP 2000-220135 A [Patent Document 2]
JP 2000-355933 A
[Problems to be solved by the invention]
The present inventor conducted original research on the improvement of the shear strength in the axial direction of the steel pipe sheet pile joint steel pipe. As a result, as seen in the prior art, it is not necessary to improve the adhesion strength between the mortar and the steel material by simply wrapping the mortar in the small holes established in the steel material. By providing a through-hole, the hardened mortar spreads inside and outside the opposing through-holes of the opposing joint steel pipe to function as an anchor shaft, thereby increasing the force acting to expand the joint steel pipe. It was found that it was possible to resist and constrain its expansion, thereby allowing the joint to exhibit a large shear strength.
[0013]
That is, according to the research of the present inventor, by providing a through hole under a certain condition in the joint steel pipe of the steel pipe sheet pile, when a displacement force acts on this through hole part, the plate thickness part of the joint steel pipe through hole At the same time as the supporting pressure acts on the mortar, the splitting force acts in the normal direction of the through hole. By providing a restraining effect that suppresses the splitting force, the shear strength is dramatically increased. In addition, it was found that the shear strength is roughly proportional to the through-hole area under the condition where the restraining force is applied.
[0014]
This invention proposes based on the said research result, and it is a subject to provide the joint structure which raises the shear strength of a steel pipe axial direction in the joint steel pipe (PP joint) of a steel pipe sheet pile.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0016]
1st invention is a steel pipe sheet pile formed by piping the joint steel pipe which has a slit in the outer surface axial direction of a steel pipe sheet pile main pipe, and is a joint long claw part of the above-mentioned joint steel pipe, In order to increase the shear strength between the joint steel pipe and the filling mortar at a position facing the through-hole established in the joint long claw, the hole diameter is necessary and sufficient to ensure the shear strength between the joint steel pipes facing each other. A plurality of through holes are arranged in the tube axis direction.
[0017]
According to a second invention, in the first invention, a range from the tip of the joint long claw portion to the slit of the mating joint steel pipe is a long claw side fitting section, and the diameter (D) of the through hole is the length of the long hole. It is characterized by being set to a range of ¼ to ½ of the nail side fitting section.
[0018]
According to a third invention, in the first or second invention, the central axis of the through hole established in the joint long claw portion of the joint steel pipe is more than the central axis passing through the welded portion of the opposing joint steel pipe with the sheet pile main pipe. Is also arranged on the tip side.
[0019]
According to a fourth invention, in any one of the first to third inventions, an internally projecting steel pipe is used as the joint steel pipe.
[0020]
A fifth invention is characterized in that, in any of the first to fourth inventions, a filling mortar restraining projection is arranged in the axial direction of the side end of the joint long claw of the joint steel pipe.
[0021]
[Action]
According to the present invention, the hole diameter of the area necessary and sufficient to ensure the shear strength of the opposed joint steel pipes is provided at a position facing the through hole formed in the long claw portion of the mating joint steel pipe to be fitted to each other. Since a plurality of through-holes are arranged in the tube axis direction, the hardened mortar present in the opposing through-holes functions as an anchor shaft portion, whereby when the shear strength acts on the through-hole portion, the joint steel pipe plate At the same time as the support pressure acts on the mortar at the thick part, even if splitting force acts in the normal direction of the through-hole, the anchor shaft portion exerts a restraining effect that suppresses this splitting force, and this restraining effect causes the joint steel pipe to Shear strength is increased. The size of the through hole for causing the mortar to function as an anchor shaft was obtained under the condition that a binding force was applied to the joint steel pipe, and the shear strength was approximately proportional to the area of the through hole. Based on that, it has been established in a size suitable for it.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0023]
FIG. 1 shows Embodiment 1 of the present invention, (A) is a plan view showing a fitting state of opposing steel pipes (PP joints) in a steel pipe sheet pile, and (B) is a single joint steel pipe. It is a perspective view shown. As shown in the figure, a steel pipe sheet pile 1 is configured by welding a joint steel pipe 4 made of a circular steel pipe having a slit 3 in the outer surface axial direction of the steel pipe sheet pile main pipe 2. In this joint steel pipe 4, the longer one from the welded portion 5 to the side end of the slit 3 is a joint long claw portion 4 a, and the shorter one from the welded portion 5 to the side end of the slit 3 is a joint short claw portion 4 b. Further, in the joint steel pipe 4 fitted to each other through the slit 3, the range from the tip of the joint long claw portion 4 a to the slit 3 of the mating joint steel pipe 4 is a long claw side fitting section 6.
[0024]
In Embodiment 1 of the present invention, in the long claw-side fitting section 6 of the joint steel pipe 4 fitted to each other, the through-hole is located at a position facing the through-hole 7 established in the counterpart long-claw-side fitting section 6. The feature is that 7 was established. Moreover, the through hole 7 has a hole diameter having a sufficient and sufficient area to ensure the shear strength in the axial direction between the joint steel pipes facing each other in order to increase the shear strength of the joint steel pipe 4 and the mortar 8 filled therein. The through holes 7 are arranged in a row in the tube axis direction (the through holes 7 may be arranged in a staggered manner, but the illustration is omitted). Further, the fact that the through-hole 7 is provided at a position facing the counterpart through-hole 7 means that the welded portion 5 of the joint steel pipe 4 fitted to each other as shown in FIGS. 4B and 5C described later. As shown in FIGS. 5 (A) and 5 (B), the through-hole 7 located on the center line (A) passing through and facing is inclined at an angle θ as viewed in plan with respect to the center line (A). The through-hole 7 which opposes in a position is included.
[0025]
By disposing the through hole 7 in the joint steel pipe 4 as described above, it opens to the joint steel pipe 4 through the slit 3 by shear transmission of the mortar 8 (shown in FIGS. 4 and 5) filled in the through hole 7. When a directional force is applied, the mortar functions as an anchor shaft, and the joint shear strength of the joint steel pipe 4 increases. It was found that this shear strength was approximately proportional to the hole area of the through hole 7. Therefore, in order to ensure a large shear strength, it is effective to arrange the through holes 7 having a large area. Therefore, in this respect, it is the most effective hole arrangement method to arrange the through holes 7 in a row in the pipe axis direction in the joint fitting section 6. Of course, the through holes 7 may be arranged in a plurality of rows by adjusting the size of the through holes 7. The shape of the through hole 7 may be circular or rectangular. Furthermore, based on the above knowledge, when the hole has a vertically long shape, the through hole 7 can be further effectively arranged.
[0026]
As the hole size of the through hole 7, it is desirable to have a diameter (D) of about 1/4 to 1/2 of the length of the joint fitting section 6. Therefore, in the case of the joint steel pipe 4 having a diameter of 165.2 mm, the hole is a through hole 7 having a width of about 35 mm to 70 mm. In addition, when a large size is used for the joint steel pipe 4, the dimension of the through-hole 7 is increased according to the dimension of the joint steel pipe 4. As the mortar 8 filled in the joint steel pipe 4 fitted to each other, the shear strength of the joint steel pipe 4 is higher when the strength is higher. General filling mortar is a 20 N / mm ² approximately, may be filled with high-strength mortar of about 40~60N / mm ^2.
[0027]
Next, FIG. 2 shows Embodiment 2, and shows the example which improves the shear strength with the mortar of the joint steel pipe 4 further by prescribing | regulating the site | part of arrangement | positioning of the through-hole 7. FIG. That is, in the second embodiment, the joint long claw portion 4a is closer to the distal end side than the center line (A) passing through the welded portion 5 of the steel pipe sheet pile main pipe 2 of the two joint steel pipes 4 fitted to each other through the slit 3. Although the example which arrange | positions the center axis | shaft of the through-hole 7 is shown, the arrangement | positioning which put the center of the through-hole 7 near the front end side rather than the centerline (A) may be sufficient.
[0028]
In the second embodiment, by disposing the through hole 7 on the tip side of the center line (A) of the joint steel pipe 4, a greater shear strength with the mortar 8 can be exhibited. According to the joint steel pipe 4 of Embodiment 2, the shear strength of the through-hole 7 and the mortar 8 can resist the steel pipe circumferential direction as well as the steel pipe axial direction. Therefore, by placing the through hole 7 on the tip side of the center line (A) of the joint steel pipe 4, a binding force acts on the concrete around the through hole 7. The part can be prevented from coming out and the shear strength between the jointed steel pipes can be increased.
[0029]
In addition, in the joint steel pipe 4 having the through hole 7 as described in the first and second embodiments, it is more effective to use the joint steel pipe 4 having a protrusion on the inner surface in the present invention. In FIG. 3, the example which provided the projection part in the inner surface of the joint steel pipe 4 is shown, The same figure (A) shows the checker-like protrusion 10, The same figure (B) shows the spiral-shaped protrusion 11, FIG. 3C shows an example of the protrusions 12 parallel to the horizontal direction. Thus, by providing a projection part in the inner surface of the joint steel pipe 4, adhesion between the steel pipe and the mortar can be ensured, and for this reason, a significantly superior shear strength can be exhibited. The protrusion on the inner surface of the joint steel pipe 4 may be a striped steel pipe or may be manufactured by a checker plate.
[0030]
However, in the joint steel pipe 4, the adhesive property between the inner surface protruding portion and the filling mortar exhibits a high adhesive force in the closed space of the joint portion because volume expansion occurs in the mortar at the time of shear fracture at the protrusion portion. Since the peeling force acts on the steel pipe 4 as a reaction force, in the case of the joint steel pipe 4 of the present invention in which the steel pipe has the slit 3, the joint short claw portion is opened and the joint long claw portion is pulled out. Resulting in low strength and shear failure.
[0031]
As a means for preventing the long-claw-side fitting section 6 from slipping out of the joint steel pipe 4, FIG. 5C shows an inward bending as a fixing portion at the end of the joint-steel pipe 4, that is, the tip of the long-claw side fitting section 6. The example which provided the part 13 is shown. By providing the inner bent portion 13, it is possible to resist the withdrawal of the long-claw-side fitting section 6 of the joint steel pipe 4, and thereby it is possible to exhibit a significantly large shear strength. The steel pipe end fixing portion provided at the tip of the long claw side fitting section 6 of the joint steel pipe 4 may be provided by bending the steel pipe of the slit portion as in the inner bent portion 13 in the figure, or a steel plate or a round steel. Etc. may be arranged by welding.
[0032]
That is, in the case of an internally protruded steel pipe, if a mortar restraining force in the joint steel pipe is applied, in order to exert a large shear strength, the through-hole 7 and the tip fixing portion are arranged in the long claw side fitting section 6. Thus, it functions as an escape restraining anchor for the long claw side fitting section 6, and the shear strength of the joint steel pipe can be dramatically increased.
[0033]
4 and 5 show a mortar of the jointed steel pipe when a shearing force is applied to the jointed steel pipe 4 with slits fitted to each other and filled with the mortar 8 when a horizontal external force is applied to the steel pipe sheet pile 1. 8 is an explanatory diagram showing the direction of the splitting force acting on 8 by arrows. FIG. 4 (A) shows a joint steel pipe 14 shown as a comparative example, and FIGS. 4 (B) and 5 (A), (B), (C) show examples of the joint steel pipe 4 according to the present invention.
[0034]
The joint steel pipe 14 in FIG. 4A has a protrusion (not shown) that increases the adhesion with the mortar 20 on the inner surface, but does not have a through hole. When a shearing force acts on the joint steel pipe 14, a peeling force acts on the mortar 20 as indicated by an arrow (b). For this reason, the joint short claw part is deformed in the direction of opening outward, the joint long claw part is deformed in the direction of pulling out, and the joint steel pipes 14 are easily disengaged, and the increase in shear strength is inhibited.
[0035]
On the other hand, in the joint steel pipe 4 of the present invention shown in FIG. 4 (B), the through hole 7 is provided facing the center line (A) passing through the welded portion 5 of the joint steel pipe 4. When a shearing force is applied to the joint steel pipe 4, a splitting force as indicated by an arrow (C) is applied to the mortar 8. However, since the through-holes 7 are arranged at opposing positions, the splitting force is canceled, so that the mortar anchor shaft portion 15 is formed in the region indicated by the dotted line. The presence of the mortar anchor shaft portion 15 restrains the fracture fracture of the mortar, so that the shear strength of the joint steel pipe is dramatically increased.
[0036]
In the joint steel pipe 4 of the present invention shown in FIGS. 5 (A) and 5 (B), the through hole 7 is inclined at an angle θ as viewed in plan with respect to the center line (A) passing through the welded portion 5 of the joint steel pipe 4. It is provided facing in position. When a shearing force acts on the joint steel pipe 4, the splitting force acting on the mortar 8 is as indicated by an arrow (d). That is, due to the presence of the through-holes 7 that are opposed to each other at an inclined angle with respect to the center line (A), the splitting force is offset and a large restraining force acts on the mortar anchor shaft. Further, since the mortar anchor shaft is inclined toward the long claws, the joint short claws are not deformed in the opening direction.
[0037]
FIG. 4B shows a case where a protrusion is provided on the inner surface of the joint steel pipe 4. When a shearing force acts on the inner surface protrusion, the slit of the joint steel pipe opens as described above, and a peeling force acts in the direction in which the joint long claw comes out, but due to the shear resistance in the circumferential direction of the joint steel pipe in the through hole 7, It functions as an anchor that prevents the joint long claws from coming out. For this reason, the shear strength of the joint steel pipe will increase dramatically.
[0038]
As a means for resisting the peeling force between the joint steel pipe 4 and the mortar 8 shown in FIG. 5C and further preventing the long claw side fitting section 6 from coming out of the joint steel pipe 4, the end, that is, the long claw side fitting In the example in which the inner bent portion 13 is provided as a fixing portion at the tip of the section 6, when a shearing force acts on the joint steel pipe 4, the peeling force acting on the mortar 8 is the same as that shown in FIG. Become. That is, when a pull-out force is generated in the joint long claw portion, the inner bent portion 13 secures fixing of the steel pipe and the concrete and resists the pull-out, and in particular, the slit 3 of the opposite joint steel pipe 4 is surely expanded. Therefore, the shear strength can be remarkably improved.
[0039]
Note that the present invention may be implemented by appropriately changing the configuration shown in the embodiment.
[0040]
【The invention's effect】
According to the steel pipe sheet pile joint structure according to the present invention, (1) the joint exhibits high shear strength. (2) Since it is not necessary to reinforce the joint between the steel pipe sheet pile main pipe and the joint steel pipe, welding of a reinforcing plate or the like is unnecessary. (3) Since the shear strength of the joint structure is improved, the overall bending rigidity of the well foundation structure is improved, the dimensions of the well foundation can be reduced, and the economy is improved.
[Brief description of the drawings]
1A is a plan view showing a fitting state of opposing joint steel pipes (PP joints) in a steel pipe sheet pile according to Embodiment 1, and FIG. 1B is a perspective view showing a joint steel pipe alone; It is.
2A is a plan view showing a fitting state of opposing joint steel pipes in a steel pipe sheet pile according to Embodiment 2, and FIG. 2B is a perspective view showing the joint steel pipe alone.
FIGS. 3A, 3B and 3C are explanatory views showing three examples of inner surface protrusions formed on the inner surface of the joint steel pipe. FIGS.
FIG. 4 is a diagram showing the direction of the splitting force acting on the filling mortar when a shearing force is applied to the joint steel pipes fitted to each other in the steel pipe sheet pile, and (A) does not have a through hole shown as a comparative example. The top view of the joint steel pipe fitted together, (B) is a top view of the 1st and 2nd example of the joint steel pipe fitted together which has a penetration hole of the present invention.
FIGS. 5A, 5B, and 5C are plan views of third, fourth, and fifth examples of joint steel pipes that are fitted with each other and that have through holes according to the present invention.
FIG. 6 is a perspective view of a conventional steel pipe sheet pile well foundation.
7 is a plan view showing a fitting state of opposing steel pipe sheet piles in a conventional steel pipe sheet pile, and FIG. 7B is a perspective view showing the steel pipe sheet pile as a single body. FIG. The top view which shows the fitting state of a steel pipe, (B), (C) is a perspective view which shows the two examples with and without the internal surface protrusion of the said joint steel pipe.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel pipe sheet pile 2 Steel pipe sheet pile main pipe 3 Slit 4 Joint steel pipe 4a Joint long claw part 4b Joint short claw part 5 Welding part 6 Long claw side fitting section 7 Through-hole 8 Mortar 11 Spiral protrusion 12 Parallel protrusion 13 Inner bending part 14 Joint steel pipe 15 Mortar anchor shaft part 15a Mortar anchor shaft part 16 Steel pipe sheet pile 16a Steel pipe sheet pile main pipe 17 Steel pipe sheet pile well foundation 18 Bridge pier 19 Slit 20 Mortar 21 Unevenness

Claims

In steel pipe sheet pile made by piping a joint steel pipe having a slit in the outer surface axial direction of the steel pipe sheet pile main pipe, it is opened at the joint long claw part of the joint steel pipe and the joint long claw part of the mating joint steel pipe to be fitted to each other In order to increase the shear strength between the joint steel pipe and the filling mortar, a plurality of through holes having a hole diameter of an area necessary and sufficient to secure the shear strength between the opposing joint steel pipes are provided at positions opposite to the through holes. A steel pipe sheet pile joint structure characterized by being arranged in the axial direction.

The range from the tip of the joint long claw part to the slit of the mating joint steel pipe is the long claw side fitting section, and the diameter (D) of the through hole is from 1/4 to 1/1 of the long claw side fitting section. 2. The steel pipe sheet pile joint structure according to claim 1, wherein the joint structure is set to a range of 2.

The center axis of the through-hole established in the joint long claw part of the joint steel pipe is arranged on the tip side from the center axis passing through the welded part with the sheet pile main pipe of the opposing joint steel pipe. 2. A steel pipe sheet pile joint structure according to 2.

The steel pipe sheet pile joint structure according to any one of claims 1 to 3, wherein an internally projecting steel pipe is used as the joint steel pipe.

The steel pipe sheet pile joint structure according to any one of claims 1 to 4, wherein a projection for restraining filling mortar is disposed in an axial direction of a side end portion of a joint long claw portion of the joint steel pipe.