JP4122641B2

JP4122641B2 - Frozen anti-frozen structure of ground anchor

Info

Publication number: JP4122641B2
Application number: JP21201299A
Authority: JP
Inventors: 山本　　彰
Original assignee: Obayashi Corp
Current assignee: Obayashi Corp
Priority date: 1999-07-27
Filing date: 1999-07-27
Publication date: 2008-07-23
Anticipated expiration: 2019-07-27
Also published as: JP2001032273A

Description

【０００１】
【発明の属する技術分野】
本発明は、地盤に埋め込んだテンドンをその地表に露出する外端部に固定した定着部により緊張し、その反力を該定着部により地盤に伝達させて地すべりを防止するグラウンドアンカーの耐凍上性能の向上を図った定着構造に関する。
【０００２】
【従来の技術】
従来、切土のり面などの地すべり対策工法として、図６に示すように格子状に成形されたコンクリート等からなる受圧板１をのり面５１上に敷設し、これと地盤５３，５５に適宜間隔に複数のグラウンドアンカー３を打設して前記受圧板１を介して地盤表層５３を地盤深部５５側に押し付けることで地盤表層５３の崩落を防止するものが知られている。この方法は、線状部材からなるテンドン５を地盤表面５１に対して略鉛直に受圧板１および地盤５３，５５に挿入し、その一端部１１を地盤深部５５に固着させるとともに、地盤表面５１に突出した他端部を定着部７を介して前記受圧板１に定着させて、前記テンドン５に緊張力を与えることで、その反力としての圧縮力を受圧板１を介して地盤５３，５５に伝達して地盤表層５３を締め付けるものである。つまり、前記テンドン５の一端部１１を地盤深部５５に固着するとともに、他端部を地盤表面５１に定着することで、地盤表層５３を地盤深部５５側に押し付けてのり面５１を安定化させるようになっている。
【０００３】
かようなグラウンドアンカー３の構造を図７によって詳しく説明すると、このグラウンドアンカー３は地盤５３，５５および受圧板１に形成された削孔５７、１ａにその大半を挿入されて機能する。そして、その構造は、複数のテンドン５をパイプ状のシース１３内に入れて構成されるアンカー部１５と、前記シース１３から突出したテンドン５の端部を前記受圧板１に定着する定着部７とからなる。
【０００４】
前記テンドン５は、長手方向の略半分に亘ってアンボンドチューブ５ｂにより被覆されたＰＣ鋼より線５ａからなる。
【０００５】
前記アンカー部１５は、その作用的観点から、前記アンボンドチューブ５ｂによりＰＣ鋼より線５ａが一本毎に被覆されたアンカー自由長部１９と、その残りの部分であって被覆されていないアンカー定着長部２３とに大別される。アンカー定着長部２３は、前記削孔５７において地盤深部５５に位置して該地盤深部５５に固着される部分である。すなわち、アンカー定着長部２３はシース１３内にてＰＣ鋼より線５ａがむき出しになっており、グラウンドアンカー３を地盤に挿入後にシース１３内外に各々注入・充填される内部グラウト２５ａおよび外部グラウト２５ｂによって、アンカー定着長部２３におけるＰＣ鋼より線５ａとシース１３および地盤深部５５の三者が一体的に固着される。そして、アンカー定着長部２３が地盤深部５５に定着される。
【０００６】
また、前記アンカー自由長部１９は、前記削孔５７において地盤表層５３に位置し、地盤表層５３とは固着されずに自由に摺動することができる部分である。詳細に述べると、アンカー自由長部１９は、ＰＣ鋼より線５ａの周囲にアンボンドチューブ５ｂが摺動可能に包皮されているので、前記内部グラウト２５ａおよび外部グラウト２５ｂとによって、ＰＣ鋼より線５ａと地盤表層５３とは固着されずに、互いに相対変位をすることができるようになっている。このため、前記アンカー定着部２３が地盤深部５５に定着されるとともに、ＰＣ鋼より線５ａの端部が前記定着部７によって受圧板１に定着されることで、アンカー自由長部１９のＰＣ鋼より線５ａに緊張力を付与できて地盤表層５３を締め付けることができる。
【０００７】
前記定着部７は、受圧板１の表面上に設置される。そして、その構成は、前記テンドン５が中心を挿通するとともにそのテンドン５の被覆されていない端部、すなわちＰＣ鋼より線５ａの端部が固着された裁頭円錐状のくさび部材７ａと、このくさび部材７ａが嵌合するテーパー孔を有する板状の定着具７ｂと、この定着具７ｂと前記受圧板１との間に介装されて、複数のテンドン５を挿通する孔７ｊが中央に形成された支圧板７ｃとからなる。このテーパー孔およびくさび部材７ａのテーパーは地盤より離れる方向に従って大径になるように形成されており、前記テーパー孔にくさび部材７ａが嵌合係止されることで、定着具７ｂおよび支圧板７ｃを介してテンドン端部が受圧板１に定着される。そして、テンドン５に付与された緊張力が定着部７および受圧板１を介して地盤表層５３に圧縮力として伝達されて、地盤表層５３は地盤深部５５に押し付けられる。
【０００８】
以上のように、グラウンドアンカー３は、アンカー定着長部２３が地盤深部５５に定着されるとともに、地盤表面５１に突出したテンドン端部が前記地盤表面５１に敷設された受圧板１に定着されることで、前記アンカー自由長部１９のテンドン５に緊張力を付与してこのアンカー自由長部１９に対応する深さの範囲の地盤表層５３を締め付けて地すべりを防止するようになっている。
【０００９】
しかし、寒冷地等、冬季に地盤表層５３が凍結しやすい地域にあっては、凍上（地盤表層５３が凍結して地盤表層５３が膨張すること）によって地盤表面５１が盛り上がる。その際、前記地盤表面５１に定着されたテンドン５は、テンドン長手方向の地盤表層の膨張量分引き伸ばされて、該テンドン５には前記緊張力に加えて前記膨張量分余計に力が作用し、結果過大な引張力・引張応力（但し、引張応力はテンドン単位横断面積当たりの引張力とする）が作用する。この時、テンドン５の引張強さが前記引張応力より小さい場合にはテンドン５はアンカー自由長部１９にて破断し、また地盤深部５５とテンドン５との固着強度が前記引張力よりも小さい場合には、前記アンカー定着長部２３にてテンドン５が引き抜けてしまい地すべり対策として機能しなくなる虞があった。
【００１０】
このため、従来は、前記テンドン５の長さを長くして、凍上時の膨張によってテンドン５に生じる引張歪み変形を小さくして、テンドン５に作用する前記引張応力を緩和するか、あるいはテンドン径を大きくして引張力上限値を大きくする等して対応してきた。
【００１１】
【発明が解決しようとする課題】
しかしながら、前者のテンドン長さを長くする方法では、テンドン５として使用する長いＰＣ鋼より線５ａ等が必要であるとともに、それを埋め込むための削孔５７も深くなって、グラウンドアンカー３の施工費は高くなり、また、後者のテンドン５の引張力上限値を大きくする方法にあっても、ＰＣ鋼より線径を太くするため、材料費および削孔５７の掘削費が高くなってしまい、いずれにせよ凍上対策に莫大な費用がかかるという課題があった。
【００１２】
本発明は、以上の課題を解決するものであって、その目的は、凍上時の地盤表層の膨張・収縮による地盤の伸縮を吸収して、前記テンドンの緊張力を一定に保持して、可及的に前記凍上によるテンドンの破損を防止できて、しかも廉価に施工することができるグラウンドアンカーの耐凍上定着構造を提供することにある。
【００１３】
【課題を解決するための手段】
かかる目的を達成するために請求項１に示す発明は、地盤に埋め込んだテンドンをその地表に露出する外端部に固定した定着部により緊張し、その反力を該定着部により受圧板を介して地盤に伝達させて地すべりを防止するグラウンドアンカーにおいて、前記テンドンの定着部と前記受圧板との間に、凍上時の地盤表層の膨張・収縮に応じて伸縮して、前記テンドンの緊張力を一定に保持する、中央に孔を有する皿ばねが配設され、前記皿ばねと前記受圧板との間に第１の支圧板が介装され、前記第１の支圧板は、前記皿ばねに当接する、前記テンドンを挿通する孔が形成された板状部と、この孔の周縁部に、前記受圧板側へ向けて立設されたパイプ部とを有し、前記皿ばねに前記第１の支圧板と反対側から当接する、前記テンドンを挿通する孔が形成された板状部と、当該板状部の孔の周縁部に、前記皿ばね側へ向けて立設されたパイプ部とを有する第２の支圧板が設けられ、前記第２の支圧板のパイプ部が、前記皿ばねの孔に差し込まれると共に、前記第１の支圧板のパイプ部の内周に嵌合されて、前記第１の支圧板の板状部と前記第２の支圧板の板状部との間に前記皿ばねが挟まれ、前記第１の支圧板のパイプ部が、前記受圧板に形成された前記テンドンを挿通する削孔に嵌合され、前記第２の支圧板の板状部が前記定着部に当接することで、前記テンドンが前記受圧板に定着されている、ことを特徴とすることを特徴とする。
【００１４】
上記構成によれば、凍上時に生じるテンドン長手方向の地盤の膨張は、前記定着部と受圧板との間に配設された、弾性部材の圧縮弾性変形によって吸収されるので、テンドンが地盤の膨張によって引き伸ばされることを抑えて、結果テンドンに過大な引張力が作用することを防止することが可能となり、更には前記テンドンの緊張力を一定に保持することができる。また、凍上時に膨張した地盤表層が解凍収縮する際にあっても、地盤の収縮を、弾性部材の前記圧縮変形が解放されて該弾性部材が伸長復帰することで吸収する。したがい、凍上後の地盤の解凍収縮の際にもテンドンの緊張力を一定に保持することができる。
【００１６】
また、上記構成によれば、皿ばねを使用したので、凍上時に生じるテンドン長手方向の地盤の膨張は、皿ばねの圧縮撓み変形で吸収される。この皿ばねは、撓み変形に対する弾発力変動が小さい弾発力変動不感帯領域を有しており、前記緊張力付与時の撓み変形に対する弾発力変動が小さくなるように設定されているため、前記圧縮撓み変形が生じても弾発力変動が生じず、これ故テンドンの緊張力を一定に保持することができる。また、弾発力と撓み変形の関係においてヒステリシスは無いため、前記圧縮撓み変形が解放される際にもテンドンの緊張力を一定に保持することができる。
【００１８】
さらに、上記構成によれば、皿ばねと受圧板との間に支圧板を介装したので、定着部から弾性部材に伝達されたテンドンの緊張力を支圧板の面で均等に受けて、均等な応力に変換して受圧板に伝達することができる。このため、受圧板に局所的に大きな応力が作用することを防止できて、受圧板の劣化を防止することが可能となる。
【００１９】
【発明の実施の形態】
以下、本発明の好ましい実施形態につき、添付図面を参照して詳細に説明する。尚、グラウンドアンカーの全体構造に関しては、前述した「従来の技術」のグラウンドアンカー３の構造とほぼ同じであり、よって同一の部材には同一の符号を付して、その相違点についてのみ説明する。
【００２０】
図１に本発明の第一実施形態を適用したグラウンドアンカーを示すが、同図は、グラウンドアンカー３の定着構造において、前述した「従来の技術」のグラウンドアンカー（図７参照）と相違する。すなわち、図１において定着部７の支圧板７ｃ’と受圧板１との間に皿ばね部８が介装されている点と、これに関連して前記支圧板７ｃ’の形状が異なる点の二点で相違する。
【００２１】
この支圧板７ｃ’は、前記支圧板７ｃと同形状の、中央に一つの孔７ｊが形成された板状部７ｄと、この孔７ｊの周縁部に位置して一体的に立設されたパイプ部７ｅとからなる。
【００２２】
また、前記皿ばね部８は、中央に一つの孔が形成された複数の皿ばね８ａを重ねた皿ばねセット８ｆと、この皿ばねセット８ｆと当接する、中央に一つの孔８ｈを有する板状部８ｅであって、この孔８ｈの周縁部に一体的にパイプ部８ｇが立設された支圧板８ｄとからなる。
【００２３】
そして、前記支圧板７ｃ’のパイプ部７ｅが、前記皿ばねセット８ｆの孔に差し込まれるとともに、前記支圧板８ｄのパイプ部８ｅの内周に嵌合されて、両支圧板７ｃ、８ｄの両板状部７ｄ、８ｅとによって皿ばねセット８ｆが挟まれる状態に組まれている。そして、この状態で、支圧板８ｄのパイプ部８ｇ外周が受圧板１の削孔１ａに嵌合されつつ板状部８ｅが受圧板１表面に固定されて、支圧板７ｃ’の板状部７ｄが定着具７ｂに当接することで、テンドン５が受圧板１に定着されている。
【００２４】
前記皿ばねセット８ｆは、中央に孔を有する裁頭円錐状の皿ばね８ａを同じ向きに２枚直列重ねした皿ばね積層体８ｂおよびこれと同様構成の皿ばね積層体８ｃの互いの向きを違えて２段に配して構成される。この皿ばねセット８ｆは、その皿ばね積層体当たりの皿ばね枚数・皿ばね積層体の体の数・皿ばね積層体の向き等の重ね方の組み合わせを変えることで、弾発力レベルと撓み量とを自由に変更できる。このため、重ね方の組み合わせは所期の弾発力レベルと撓み量とを満足するように設定すれば良く、本実施形態に限られるものではない。但し、前記皿ばね８ａは、図２に示すように皿ばね厚みｔと皿ばね高さＨの比Ｈ／ｔのみで決定する非線形な荷重−撓み特性を有しており、本実施形態にあっては、撓み変形に対する弾発力変動が小さい弾発力変動不感帯を利用するため、Ｈ／ｔ＝１．４の皿ばねを使用するのが望ましい。尚、前記皿ばね８ａの素材としては高強度のばね鋼などが適当である。
【００２５】
前記皿ばねセット８ｆの端部が当接する支圧板８ｄの板状部８ｅは、局所的に過大な応力が作用しても耐え得るように鋼等の金属材料が用いられる。そして、その板状部８ｆの中央には、複数のテンドン５を挿通する円形状の孔８ｈを有しており、その孔径や板状部８ｆの外形状・外寸法は、前記皿ばねセット８ｆより伝達された緊張力を均等な応力に変換して受圧板１に伝達するように設定される。
【００２６】
また、前記孔８ｈの周縁部に位置して一体的に立設している前記パイプ部８ｅは、後述もするが、受圧板１に形成された削孔１ａにその外周が嵌合固定され、その内周に支圧板７ｃ’のパイプ部７ｅが摺動自在に嵌合されることで、定着部７のアンカー部１５に対する位置決めをするとともに、前記パイプ部７ｅの軸方向の動きを円滑に案内して前記皿ばねセット８ｆの撓み変形を安定化する案内ガイドとして機能する。
【００２７】
前記支圧板７ｃ’も鋼系の金属材料であり、前記板状部７ｄに皿ばね８ａの端縁が当接して、局所的に過大な応力が作用しても耐え得るようになっている。その板状部８ｆの中央にはテンドン５を挿通する円形状の孔７ｊが形成されて、その孔７ｊの周縁部に位置して前記パイプ部７ｅが一体的に立設している。
【００２８】
このパイプ部７ｅは、皿ばねセット８ｆの孔を挿通して、皿ばねセット８ｆがスラスト方向に離脱しないように保持する機能を有するとともに、前記支圧板８ｄのパイプ部８ｇと組み合わされて、皿ばねセット８ｆが安定して撓み変形をできるようにする案内ガイドとしての機能も有する。すなわち、その外周の先端が前記支圧板８ｄのパイプ部８ｅ内周と隙間をもって嵌合し軸方向に摺動自在に相対変位することで、板状部８ｅ、７ｄの間に介装された皿ばねセット８ｆが安定して撓み変形をできるようになっている。
【００２９】
したがい、このパイプ部７ｅの内径は、その内側に前記テンドン５が隙間をもって挿通できるように設定されるとともに、その外径は、前記皿ばね８ａの孔径および前記支圧板８ｄのパイプ部８ｇ内径よりも若干小さく設定される。
【００３０】
また、前記パイプ部７ｅの先端とシース１３端との間には、長手方向に伸縮自在の蛇腹パイプ状シース１３ａが設けられて、皿ばねセット８ｆの撓み変形時の前記パイプ部７ｅとシース１３との間隔の変動を吸収するようになっている。
【００３１】
尚、本実施形態にあっては、前記定着部７および皿ばね部８の両者を覆って有蓋円筒状のヘッドキャップ９が支圧板８ｄにボルト９ｂ固定されており、風雨から定着部７やテンドン５のみならず皿ばね部８をも防いで、耐久性を向上することができるようになっている。このヘッドキャップ９内に防錆油を充填することでその耐久性を更に向上することも可能である。
【００３２】
次に第一実施形態にかかるグラウンドアンカーの耐凍上定着構造の作用について図１、図２を用いて説明する。
【００３３】
図１に示すように切土のり面たる地盤表面５１にグランドアンカー３の打設が完了した状態にあっては、アンカー定着長部２３が地盤深部５５に定着されるとともに、地盤表面５１のテンドン外端部が定着部７および皿ばね部８を介して受圧板１に定着されており、アンカー自由長部１９のテンドン５に緊張力が付与されて、アンカー自由長部１９に対応する深さ範囲の地盤表層５３を締め付けている。
【００３４】
また、前記定着部７と受圧板１との間に介装された皿ばね８ａは前記緊張力分撓み変形をしているが、図２に示す弾発力変動不感帯の弾発力が前記緊張力と一致するように皿ばねの重ね方の組み合わせが調整されている。
【００３５】
かような状態において、凍上によって地盤表層５３が膨張して地盤表面５１が盛り上がった際には、前記地盤表層５１の盛り上がり量分、受圧板１と定着部７との間に介装された皿ばね８ａが、パイプ部８ｇ、７ｅによって案内されつつ安定した状態で圧縮撓み変形をする。この時、受圧板１と定着部７との間が狭くなるだけで、定着部７とアンカー定着長部２３との間が伸長することはなく、つまりテンドン５が引き伸ばされることはない。このため、テンドン５に過大な引張力が作用する事を防止することができる。
【００３６】
また、皿ばね８ａの前記圧縮撓み変形は、図２に示す弾発力変動不感帯領域であるので、弾発力が変動することなく圧縮撓み変形のみが生じてテンドン５の緊張力は変動することなく一定に保持される。そして、凍上時に膨張した地盤表層５３が解凍収縮する際には、前記圧縮撓み変形が解放されて伸長復帰することで前記解凍収縮を吸収できるので、凍上後の解凍収縮の際にもテンドン５の緊張力は一定に保持される。
【００３７】
このように、グラウンドアンカー３の耐凍上定着構造によれば、定着部７と受圧板１との間に皿ばね部８を介装するという簡単な構成によって、凍上時にあってもテンドン５の緊張力を変動することなく維持できてグラウンドアンカー３の破損を確実に防止できる。
【００３８】
また、皿ばねセット８ｆと受圧板１との間に鋼系の支圧板８ｄを介装したので、この支圧板８ｄが皿ばね８ａとの当接によって破損することなく、定着部７から皿ばねセット８ｆに伝達されたテンドン５の緊張力を支圧板８ｄの面で均等に受けて、その均等な荷重を受圧板１に均等な応力に変換して伝達することができる。このため、脆弱なコンクリート等からなる受圧板１に局所的に大きな応力が作用することを防止できて、受圧板１の破損・摩滅などの劣化を防止してその耐久性が向上する。
【００３９】
尚、本発明に係る第二実施形態として、皿ばねの破損防止用フェールセーフ機構を設けた耐凍上定着構造を図３に示す。図示するようにこのフェールセーフ機構７ｃ”は、支圧板７ｃ”の板状部７ｄの片面の外周縁全周に亘り、支圧板８ｄに向かって突出するリブ７ｈを形成したリブ付き支圧板７ｃ”であり、前記リブ７ｈ端面と支圧板８ｄとの間には皿ばねセット８ｆの圧縮撓み変形相当分の隙間が設けられている。そして、前記圧縮撓み変形の限界を超えるような地盤収縮が生じた際に、リブ７ｈ端面と支圧板８ｄとが当接して、皿ばね８ａの限界以上の撓み変形を規制してその塑性変形による破損を防止するものである。
【００４０】
以上、本発明の実施形態について説明したが、本発明は、かかる実施形態に限定されるものではなく、その要旨を逸脱しない範囲で種々の変形が可能である。
【００４１】
例えば、本実施形態では、弾性部材として皿ばね８ａを使用したが、テンドン５の縦弾性定数と比較して小さな弾性係数を有して、撓み変形に対する弾発力変動が小さいものであればこれに限るものではなく、コイルバネ、板バネなどの弾性部材を適用することができる。尚、前記皿ばね８ａと同様の弾発力変動不感帯領域を有するばね特性の弾性部材として、図４に示すようなハニカム型ダンパや図５に示すようなセル型ダンパが挙げられる。
【００４２】
このハニカム型ダンパ３１は、図４に示すように、複数の断面六角形の角パイプを一体的に連結したような形状で、全体として略対称の蜂の巣状の外観を呈する。そして、六角形空間３１ｃを画成する一側片３１ａ，３１ｂの肉厚は同一に設定されているが、そのパイプ軸方向長さは配置部位によって異なり、長さが長い長側片３１ａと短い短側片３１ｂとからなる。このハニカムダンパ３１にパイプ軸方向の圧縮荷重が作用した際には図２と同様の特性を示す。この長側片３１ａ長さ、短側片３１ｂ長さ、長側片３１ａおよび短側片３１ｂの配置パターン、肉厚、六角形空間３１ｃの配置パターンは、要求される弾発力特性に応じて設定される。尚、前述した皿ばね８ａに代えて該ハニカム型ダンパ３１を介装した場合、テンドン５はハニカム型ダンパの六角形空間３１ｃに挿通されることは言うまでもない。
【００４３】
また、図５に示すセル型ダンパ４１は、略円筒パイプ４１ａの両端に円盤状のフランジ４１ｂを同心的にかつ一体的に設けたものであって、前記フランジ４１ｂには、パイプ内径と同じ孔４１ｅが形成されている。そして、前記略円筒パイプ４１ａのパイプ内径は軸方向に亘って一定であるが、軸方向中央を境にしたパイプの半分部分４１ｃは、その外径がフランジ４１ｂに近づくに従って縮径する裁頭円錐状の外観を呈する裁頭円錐状部４１ｃとなっている。すなわち、略円筒パイプ４１ａの軸方向の半分は前記裁頭円錐状部４１ｃで残りの半分が円筒状部４１ｄとなっている。このセル型ダンパ４１も、パイプ軸方向に圧縮荷重が作用した際に図２と同様の特性を示す。このパイプ高さ、裁頭円錐状部４１ｃ寸法、円筒状部寸法、フランジ厚、孔径は、要求される弾発力特性に応じて設定される。前述した皿ばね８ａに代えて該セル型ダンパ４１を介装した場合、テンドン５はセル型ダンパ４１の略円筒パイプ４１ａ内側を挿通されることは言うまでもない。
【００４４】
本実施形態の場合は、皿ばね８ａをヘッドキャップ９で覆って防錆油を封入して防錆処置としたが、防錆効果があればこれに限るものではなく、皿ばね表面にグリース等の固形状油分を塗布しても良い。尚、この処置は皿ばね表面の摺動摩耗防止も兼ねるものでもある。
【００４５】
【発明の効果】
以上説明したように、請求項１に示す発明によれば、テンドンの定着部と受圧板との間に弾性部材を配設するという簡単な構成によって、凍上時にテンドンに過大な引張力が作用しないようにして確実にその破損を防止できる。したがい、テンドン径を大きくする必要もなく凍上対策を廉価に施工するが可能となる。また、凍上時および解凍時にあってもテンドンの緊張力を一定に保持することができるので、地すべりを確実に防止して該地すべり災害を大幅に減少することができる。
【００４６】
請求項２に示す発明によれば、前記弾性部材に弾発力変動不感帯領域を有する皿ばねを使用したので、前記凍上時にテンドンの緊張力を一定に保持することができる。したがい、常時、地盤表層を地盤深部側に押し付けて地すべりを確実に防止して該地すべり災害を大幅に減少することができる。
【００４７】
請求項３に示す発明によれば、弾性部材と受圧板との間に支圧板を介装したので、受圧板に局所的に大きな応力が作用することを防止できて、受圧板の破損・摩耗などの劣化を防止することが可能となる。この結果、受圧板の耐久性が向上して地すべり対策の信頼性も向上する。
【図面の簡単な説明】
【図１】本発明の第一実施形態の耐凍上定着構造を有するグラウンドアンカーの側断面図である。
【図２】本発明に係る弾性部材として使用される皿ばねの非線形ばね特性を示す概念図である。
【図３】本発明の第二実施形態の耐凍上定着構造の断面図である。
【図４】皿ばねと同様のばね特性を有するハニカム型ダンパの図であって、図４（ａ）は、その平面図、図４（ｂ）はその側面図である。
【図５】皿ばねと同様のばね特性を有するセル型ダンパの図であって、図５（ａ）は、その平面図、図５（ｂ）はその側面図である。
【図６】地すべり対策工法の概要を示す、切土のり面を有する地山の斜視一部断面図である。
【図７】グラウンドアンカーの構造を示す断面図である。
【符号の説明】
１受圧板１ａ削孔
３グラウンドアンカー５テンドン
５ａＰＣ鋼より線５ｂアンボンドチューブ
７定着部７ａくさび部材
７ｂ定着具７ｃ支圧板
７ｃ’支圧板７ｄ板状部
７ｅパイプ部７ｊ孔
７ｃ”リブ付き支圧板７ｈリブ
８皿ばね部８ａ皿ばね
８ｂ，８ｃ皿ばね積層体８ｄ支圧板
８ｅ板状部８ｇパイプ部
８ｇ孔８ｆ皿ばねセット
９ヘッドキャップ９ｂボルト
１３シース１３ａ蛇腹パイプ状シース
１５アンカー部１９アンカー自由長部
２３アンカー定着長部２５グラウト
２５ａ内部グラウト２５ｂ外部グラウト
３１ハニカム型ダンパ３１ａ長側片
３１ｂ短側片３１ｃ六角形空間
４１セル型ダンパ４１ａ略円筒パイプ
４１ｂフランジ４１ｃ裁頭円錐状部
４１ｄ円筒状部
５１地盤表面，切土のり面，のり面
５３地盤表層
５５地盤深部
５７削孔[0001]
BACKGROUND OF THE INVENTION
The present invention is a tense anchor embedded in the ground is tensioned by a fixing part fixed to the outer end exposed to the ground surface, and the reaction force is transmitted to the ground by the fixing part to prevent landslides. The present invention relates to a fixing structure that is improved.
[0002]
[Prior art]
Conventionally, as a landslide countermeasure method such as a cut slope, a pressure receiving plate 1 made of concrete or the like formed in a lattice shape is laid on a slope 51 as shown in FIG. It is known that a plurality of ground anchors 3 are placed and the ground surface layer 53 is pressed against the ground deep portion 55 side through the pressure receiving plate 1 to prevent the ground surface layer 53 from collapsing. In this method, the tendon 5 made of a linear member is inserted into the pressure receiving plate 1 and the grounds 53 and 55 substantially perpendicularly to the ground surface 51, and one end 11 thereof is fixed to the ground deep portion 55 and the ground surface 51 is fixed to the ground surface 51. The protruding other end portion is fixed to the pressure receiving plate 1 via the fixing portion 7, and tension is applied to the tendon 5, so that the compressive force as the reaction force is applied to the ground 53, 55 via the pressure receiving plate 1. And the ground surface layer 53 is tightened. That is, one end portion 11 of the tendon 5 is fixed to the ground deep portion 55 and the other end portion is fixed to the ground surface 51 so that the ground surface layer 53 is pressed against the ground deep portion 55 side to stabilize the slope 51. It has become.
[0003]
The structure of the ground anchor 3 will be described in detail with reference to FIG. 7. The ground anchor 3 functions by inserting most of the ground holes 53 and 55 in the ground holes 53 and 55 and the pressure receiving plate 1. The structure includes an anchor portion 15 configured by putting a plurality of tendons 5 in a pipe-shaped sheath 13, and a fixing portion 7 that fixes an end portion of the tendon 5 protruding from the sheath 13 to the pressure receiving plate 1. It consists of.
[0004]
The tendon 5 is made of a PC steel wire 5a covered with an unbonded tube 5b over almost half of the longitudinal direction.
[0005]
From the viewpoint of its function, the anchor portion 15 includes an anchor free length portion 19 in which PC steel strands 5a are covered one by one by the unbonded tube 5b, and an anchor fixing portion that is the remaining portion and is not covered. It is roughly divided into a long part 23. The anchor fixing long portion 23 is a portion that is located at the ground deep portion 55 in the drilling hole 57 and is fixed to the ground deep portion 55. That is, the anchor fixing length portion 23 is exposed from the PC steel wire 5a in the sheath 13, and after inserting the ground anchor 3 into the ground, the inner grout 25a and the outer grout 25b are injected and filled in and out of the sheath 13, respectively. Accordingly, the three pieces of the PC steel strand 5a, the sheath 13, and the ground deep portion 55 in the anchor fixing long portion 23 are integrally fixed. Then, the anchor fixing length portion 23 is fixed to the deep ground portion 55.
[0006]
The anchor free length portion 19 is a portion that is located on the ground surface layer 53 in the drilling hole 57 and can slide freely without being fixed to the ground surface layer 53. More specifically, the anchor free length portion 19 is covered with the inner grouting 25a and the outer grouting 25b so that the unbonded tube 5b is slidably wrapped around the PC stranded wire 5a. And the ground surface layer 53 are not fixed to each other and can be displaced relative to each other. For this reason, the anchor fixing portion 23 is fixed to the ground deep portion 55 and the end portion of the wire 5a is fixed to the pressure receiving plate 1 by the fixing portion 7 so that the PC steel of the anchor free long portion 19 is fixed. Tension can be applied to the stranded wire 5a and the ground surface layer 53 can be tightened.
[0007]
The fixing unit 7 is installed on the surface of the pressure receiving plate 1. And, the configuration is such that the end of the tendon 5 is inserted through the center and the end of the tendon 5 is not covered, that is, the truncated conical wedge member 7a to which the end of the PC steel wire 5a is fixed, A plate-like fixing device 7b having a tapered hole into which the wedge member 7a is fitted, and a hole 7j inserted between the fixing device 7b and the pressure receiving plate 1 and through which the plurality of tendons 5 are inserted are formed in the center. It consists of the supported pressure plate 7c. The taper hole and the taper of the wedge member 7a are formed to have a larger diameter in the direction away from the ground, and the fixing member 7b and the pressure bearing plate 7c are fitted and locked to the taper hole. The end of the tendon is fixed to the pressure receiving plate 1 via Then, the tension applied to the tendon 5 is transmitted as a compressive force to the ground surface layer 53 via the fixing unit 7 and the pressure receiving plate 1, and the ground surface layer 53 is pressed against the ground deep portion 55.
[0008]
As described above, in the ground anchor 3, the anchor fixing length portion 23 is fixed to the ground deep portion 55, and the tendon end protruding from the ground surface 51 is fixed to the pressure receiving plate 1 laid on the ground surface 51. Thus, a tension force is applied to the tendon 5 of the anchor free length portion 19 and the ground surface layer 53 in a depth range corresponding to the anchor free length portion 19 is tightened to prevent a landslide.
[0009]
However, in an area such as a cold region where the ground surface layer 53 is likely to freeze in winter, the ground surface 51 rises due to frost heaving (the ground surface layer 53 freezes and the ground surface layer 53 expands). At that time, the tendon 5 fixed to the ground surface 51 is stretched by the amount of expansion of the ground surface layer in the longitudinal direction of the tendon, and a force acts on the amount of the expansion amount in addition to the tension force on the tendon 5. As a result, excessive tensile force / tensile stress (however, the tensile stress is the tensile force per tendon unit cross-sectional area) acts. At this time, when the tensile strength of the tendon 5 is smaller than the tensile stress, the tendon 5 is broken at the anchor free length portion 19 and the fixing strength between the ground deep portion 55 and the tendon 5 is smaller than the tensile force. In some cases, the tendon 5 may be pulled out at the anchor fixing length portion 23 and may not function as a landslide countermeasure.
[0010]
For this reason, conventionally, the length of the tendon 5 is lengthened, the tensile strain deformation generated in the tendon 5 due to expansion during freezing is reduced, and the tensile stress acting on the tendon 5 is relaxed, or the tendon diameter is reduced. Has been increased by increasing the upper limit of tensile force.
[0011]
[Problems to be solved by the invention]
However, in the former method for increasing the length of the tendon, a wire 5a or the like is required from the long PC steel used as the tendon 5, and the drilling hole 57 for embedding the wire 5a is also deepened. In addition, even in the latter method of increasing the upper limit of the tensile force of tendon 5, the wire diameter is made thicker than that of PC steel, so that the material cost and the drilling cost of the hole 57 are increased. In any case, there was a problem that enormous costs were required for measures against frost heaving.
[0012]
The present invention solves the above-mentioned problems, and its purpose is to absorb the expansion and contraction of the ground due to the expansion and contraction of the ground surface layer during freezing, and to keep the tension of the tendon constant. Another object of the present invention is to provide a freeze-fixing structure for ground anchors that can prevent tendon breakage due to frosting and can be constructed at low cost.
[0013]
[Means for Solving the Problems]
In order to achieve such an object, the invention shown in claim 1 is that a tendon embedded in the ground is tensioned by a fixing portion fixed to an outer end portion exposed to the ground surface, and the reaction force is passed through a pressure receiving plate by the fixing portion. by transmitting to the ground in a ground anchor to prevent landslides Te, between the fixing portion and the pressure receiving plate of the tendon, and expands and contracts in response to expansion and contraction of the ground surface at the time of frost heave, the tension of the tendon kept constant, the disc spring having a hole at the center is disposed, the first Bearing plate is interposed between said pressure receiving plate and said disc spring, said first bearing capacity plate, the disc spring A plate-like portion formed with a hole through which the tendon is inserted, and a pipe portion erected on the periphery of the hole toward the pressure-receiving plate side. Insert the tendon that comes in contact with the pressure plate opposite to A second support plate having a plate-like portion in which a hole is formed and a pipe portion erected toward the disc spring side at a peripheral portion of the hole of the plate-like portion; The pipe portion of the pressure plate is inserted into the hole of the disc spring and is fitted to the inner periphery of the pipe portion of the first pressure plate so that the plate-like portion of the first pressure plate and the second portion The disc spring is sandwiched between the plate-like portion of the pressure plate, and the pipe portion of the first pressure plate is fitted into a hole formed through the tendon formed in the pressure plate. The tendon is fixed to the pressure receiving plate by abutting the plate-like portion of the pressure plate on the fixing portion .
[0014]
According to the above configuration, since the expansion of the ground in the longitudinal direction of the tendon that occurs during freezing is absorbed by the compressive elastic deformation of the elastic member disposed between the fixing portion and the pressure receiving plate, the tendon expands the ground. As a result, it is possible to prevent the tensile force from acting on the tendon and to keep the tension force of the tendon constant. Further, even when the ground surface layer expanded upon freezing is defrosted and contracted, the contraction of the ground is absorbed by releasing the compression deformation of the elastic member and restoring the elastic member. Therefore, even when the ground is thawed and contracted after freezing, the tendon tension can be kept constant.
[0016]
Moreover, according to the said structure, since the disk spring was used, the expansion | swelling of the ground of the tendon longitudinal direction which arises at the time of freezing is absorbed by the compression deformation of a disk spring. This disc spring has a resilient force fluctuation dead zone region in which the elastic force fluctuation with respect to the bending deformation is small, and is set so that the elastic force fluctuation with respect to the bending deformation at the time of applying the tension force is small. Even if the compressive bending deformation occurs, the elastic force does not fluctuate, so that the tendon tension can be kept constant. Further, since there is no hysteresis in the relationship between the elastic force and the bending deformation, the tendon tension can be kept constant even when the compression bending deformation is released.
[0018]
Further, according to the above configuration, since the bearing plate is interposed between the disc spring and the pressure receiving plate, the tension force of tendon transmitted from the fixing portion to the elastic member is evenly received by the surface of the bearing plate, and It can be converted into a stress and transmitted to the pressure receiving plate. For this reason, it can prevent that a big stress acts on a pressure receiving plate locally, and it becomes possible to prevent deterioration of a pressure receiving plate.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The overall structure of the ground anchor is substantially the same as the structure of the ground anchor 3 of the above-mentioned “prior art”. Therefore, the same members are denoted by the same reference numerals, and only the differences will be described. .
[0020]
FIG. 1 shows a ground anchor to which the first embodiment of the present invention is applied. This figure is different from the above-described “prior art” ground anchor (see FIG. 7) in the fixing structure of the ground anchor 3. That is, in FIG. 1, the disc spring portion 8 is interposed between the pressure bearing plate 7 c ′ of the fixing unit 7 and the pressure receiving plate 1, and the shape of the pressure bearing plate 7 c ′ is related to this. There are two differences.
[0021]
The bearing plate 7c ′ has a plate-like portion 7d having the same shape as the bearing plate 7c, with a single hole 7j formed in the center, and a pipe that is integrally provided upright at the peripheral edge of the hole 7j. Part 7e.
[0022]
The disc spring portion 8 includes a disc spring set 8f in which a plurality of disc springs 8a each having a single hole formed at the center thereof, and a plate having a single hole 8h in contact with the disc spring set 8f. It is a shape portion 8e, and is composed of a pressure bearing plate 8d in which a pipe portion 8g is erected integrally with a peripheral portion of the hole 8h.
[0023]
And the pipe part 7e of the said bearing plate 7c 'is inserted in the hole of the said disc spring set 8f, and it is fitted by the inner periphery of the pipe part 8e of the said bearing plate 8d, and both both bearing plates 7c and 8d are carried out. The disc spring set 8f is assembled between the plate-like portions 7d and 8e. In this state, the plate portion 8e is fixed to the surface of the pressure receiving plate 1 while the outer periphery of the pipe portion 8g of the pressure supporting plate 8d is fitted in the hole 1a of the pressure receiving plate 1, so that the plate portion 7d of the pressure supporting plate 7c ′ is fixed. Is in contact with the fixing tool 7b, whereby the tendon 5 is fixed to the pressure receiving plate 1.
[0024]
The disc spring set 8f has a disc spring stack 8b in which two conical disc springs 8a each having a hole in the center are stacked in series in the same direction, and a disc spring stack 8c having the same configuration as each other. Differently arranged in two stages. This disc spring set 8f changes the combination of the number of disc springs per disc spring laminate, the number of disc spring laminate bodies, the direction of the disc spring laminate, and the like, thereby changing the elasticity level and the deflection. You can change the quantity freely. For this reason, the combination of the overlapping methods may be set so as to satisfy the desired elasticity level and the amount of deflection, and is not limited to this embodiment. However, the disc spring 8a has a non-linear load-deflection characteristic determined only by the ratio H / t of the disc spring thickness t and the disc spring height H as shown in FIG. Therefore, it is desirable to use a disc spring of H / t = 1.4 in order to use a resilient force fluctuation dead zone in which the resilient force fluctuation with respect to the bending deformation is small. Note that high strength spring steel or the like is suitable as the material of the disc spring 8a.
[0025]
The plate-like portion 8e of the bearing plate 8d with which the end of the disc spring set 8f abuts is made of a metal material such as steel so that it can withstand even if a local excessive stress is applied. And in the center of the plate-shaped part 8f, it has the circular hole 8h which penetrates several tendons 5, The hole diameter and the external shape and external dimension of the plate-shaped part 8f are the said disc spring set 8f. It is set so that the transmitted tension is converted into a uniform stress and transmitted to the pressure receiving plate 1.
[0026]
In addition, the pipe portion 8e that is integrally standing and positioned at the peripheral edge of the hole 8h is fitted and fixed to the hole 1a formed in the pressure receiving plate 1, as will be described later. The pipe portion 7e of the pressure bearing plate 7c ′ is slidably fitted to the inner periphery thereof, thereby positioning the fixing portion 7 with respect to the anchor portion 15 and smoothly guiding the axial movement of the pipe portion 7e. Thus, it functions as a guide for stabilizing the bending deformation of the disc spring set 8f.
[0027]
The bearing plate 7c ′ is also a steel metal material, and the end of the disc spring 8a abuts on the plate-like portion 7d, so that it can withstand even excessive local stress. A circular hole 7j through which the tendon 5 is inserted is formed at the center of the plate-like part 8f, and the pipe part 7e stands integrally at the peripheral part of the hole 7j.
[0028]
The pipe portion 7e has a function of holding the disc spring set 8f through the hole of the disc spring set 8f so as not to be detached in the thrust direction, and is combined with the pipe portion 8g of the bearing plate 8d. The spring set 8f also has a function as a guide that allows the spring set 8f to bend and deform stably. That is, the outer peripheral tip is fitted with an inner periphery of the pipe portion 8e of the bearing plate 8d with a gap and is slidably displaced in the axial direction so that the plate is interposed between the plate-like portions 8e and 7d. The spring set 8f can be bent and deformed stably.
[0029]
Accordingly, the inner diameter of the pipe portion 7e is set so that the tendon 5 can be inserted inside with a gap, and the outer diameter thereof is larger than the hole diameter of the disc spring 8a and the inner diameter of the pipe portion 8g of the bearing plate 8d. Is also set slightly smaller.
[0030]
Also, a bellows pipe-shaped sheath 13a that is extendable in the longitudinal direction is provided between the tip of the pipe portion 7e and the sheath 13 end, and the pipe portion 7e and the sheath 13 at the time of bending deformation of the disc spring set 8f are provided. It is designed to absorb fluctuations in the interval.
[0031]
In the present embodiment, a covered cylindrical head cap 9 is fixed to the bearing plate 8d so as to cover both the fixing portion 7 and the disc spring portion 8, and the fixing portion 7 and tendon are protected from wind and rain. 5 can prevent not only the disc spring portion 8 but also the durability. The durability of the head cap 9 can be further improved by filling the head cap 9 with anti-rust oil.
[0032]
Next, the operation of the antifreeze fixing structure of the ground anchor according to the first embodiment will be described with reference to FIGS.
[0033]
As shown in FIG. 1, in the state where the ground anchor 3 has been placed on the ground surface 51 which is the cut slope, the anchor fixing length portion 23 is fixed to the ground deep portion 55 and the tendon of the ground surface 51 is fixed. The outer end portion is fixed to the pressure receiving plate 1 via the fixing portion 7 and the disc spring portion 8, and tension is applied to the tendon 5 of the anchor free length portion 19, and the depth corresponding to the anchor free length portion 19. The ground surface layer 53 of the range is tightened.
[0034]
Further, the disc spring 8a interposed between the fixing portion 7 and the pressure receiving plate 1 is deformed by the tension force, but the elasticity of the elastic force fluctuation insensitive zone shown in FIG. The combination of disc springs is adjusted to match the force.
[0035]
In such a state, when the ground surface layer 53 expands due to freezing and the ground surface 51 rises, the plate interposed between the pressure receiving plate 1 and the fixing unit 7 by the amount of the ground surface layer 51 raised. The spring 8a is compressed and deformed in a stable state while being guided by the pipe portions 8g and 7e. At this time, only the space between the pressure receiving plate 1 and the fixing portion 7 is narrowed, and the space between the fixing portion 7 and the anchor fixing length portion 23 is not expanded, that is, the tendon 5 is not stretched. For this reason, it is possible to prevent an excessive tensile force from acting on the tendon 5.
[0036]
Further, since the compression deformation of the disc spring 8a is in the elastic force fluctuation dead zone region shown in FIG. 2, only the compression deformation occurs without changing the elastic force, and the tension force of the tendon 5 changes. Is kept constant. When the ground surface layer 53 expanded upon freezing is defrosted and contracted, the compression deformation can be released and restored by expansion, so that the defrosting can be absorbed. The tension is kept constant.
[0037]
As described above, according to the frost-proof fixing structure of the ground anchor 3, the tension of the tendon 5 can be maintained even during frosting by a simple configuration in which the disc spring portion 8 is interposed between the fixing portion 7 and the pressure receiving plate 1. The force can be maintained without fluctuation, and the ground anchor 3 can be reliably prevented from being damaged.
[0038]
In addition, since the steel bearing plate 8d is interposed between the disc spring set 8f and the pressure receiving plate 1, the bearing plate 8d is not damaged by contact with the disc spring 8a, and the disc spring is removed from the fixing portion 7. The tension force of the tendon 5 transmitted to the set 8f can be evenly received by the surface of the bearing plate 8d, and the uniform load can be converted into a uniform stress and transmitted to the pressure receiving plate 1. For this reason, it is possible to prevent a large stress from acting locally on the pressure receiving plate 1 made of fragile concrete or the like, and to prevent deterioration of the pressure receiving plate 1 such as breakage or abrasion, thereby improving its durability.
[0039]
As a second embodiment according to the present invention, FIG. 3 shows an anti-freezing and fixing structure provided with a fail-safe mechanism for preventing breakage of a disc spring. As shown in the drawing, this fail-safe mechanism 7c ″ includes a rib-supported pressure plate 7c ″ formed with ribs 7h projecting toward the pressure-bearing plate 8d over the entire outer periphery of one surface of the plate-like portion 7d of the pressure-bearing plate 7c ″. A gap corresponding to the compression deformation of the disc spring set 8f is provided between the rib 7h end surface and the bearing plate 8d, and ground contraction exceeding the limit of the compression deformation occurs. In this case, the end face of the rib 7h and the pressure bearing plate 8d come into contact with each other, and the bending deformation exceeding the limit of the disc spring 8a is restricted to prevent the damage due to the plastic deformation.
[0040]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, A various deformation | transformation is possible in the range which does not deviate from the summary.
[0041]
For example, in the present embodiment, the disc spring 8a is used as the elastic member. However, if the elastic member has a small elastic coefficient as compared with the longitudinal elastic constant of the tendon 5 and has a small change in the elastic force against the bending deformation, this is used. The elastic member such as a coil spring or a leaf spring can be applied. As the elastic member having a spring characteristic having the elastic force fluctuation dead zone similar to the disc spring 8a, a honeycomb type damper as shown in FIG. 4 and a cell type damper as shown in FIG.
[0042]
As shown in FIG. 4, the honeycomb type damper 31 has a shape in which a plurality of hexagonal cross-section square pipes are integrally connected, and has a substantially symmetrical honeycomb-like appearance as a whole. The thickness of the one side pieces 31a and 31b that define the hexagonal space 31c is set to be the same, but the length in the pipe axial direction differs depending on the arrangement site, and is shorter than the long side piece 31a having a long length. It consists of a short side piece 31b. When a compressive load in the pipe axial direction is applied to the honeycomb damper 31, the same characteristics as in FIG. The length of the long side piece 31a, the length of the short side piece 31b, the arrangement pattern of the long side piece 31a and the short side piece 31b, the thickness, and the arrangement pattern of the hexagonal space 31c depend on the required elasticity characteristics. Is set. Needless to say, when the honeycomb type damper 31 is interposed instead of the above-described disc spring 8a, the tendon 5 is inserted into the hexagonal space 31c of the honeycomb type damper.
[0043]
A cell type damper 41 shown in FIG. 5 is formed by concentrically and integrally providing disc-shaped flanges 41b at both ends of a substantially cylindrical pipe 41a. The flange 41b has the same hole as the pipe inner diameter. 41e is formed. The pipe inner diameter of the substantially cylindrical pipe 41a is constant over the axial direction, but the half portion 41c of the pipe with the axial center as the boundary is a truncated cone whose diameter decreases as the outer diameter approaches the flange 41b. It is a truncated cone-shaped part 41c which exhibits the shape-like appearance. That is, the half of the substantially cylindrical pipe 41a in the axial direction is the truncated conical portion 41c, and the other half is the cylindrical portion 41d. This cell-type damper 41 also exhibits the same characteristics as FIG. 2 when a compressive load is applied in the pipe axial direction. The height of the pipe, the size of the truncated conical portion 41c, the size of the cylindrical portion, the flange thickness, and the hole diameter are set according to the required elasticity characteristics. Needless to say, when the cell type damper 41 is interposed instead of the above-described disc spring 8a, the tendon 5 is inserted through the inside of the substantially cylindrical pipe 41a of the cell type damper 41.
[0044]
In the case of this embodiment, the disc spring 8a is covered with the head cap 9 and rust preventive oil is enclosed to prevent rust. However, the anti-rust effect is not limited thereto, and the surface of the disc spring may be grease or the like. The solid oil component may be applied. This measure also serves to prevent sliding wear on the surface of the disc spring.
[0045]
【The invention's effect】
As described above, according to the first aspect of the present invention, an excessive tensile force does not act on the tendon during freezing due to a simple configuration in which the elastic member is disposed between the fixing portion of the tendon and the pressure receiving plate. Thus, the breakage can be surely prevented. Therefore, it is possible to construct frost heaving measures at low cost without the need to increase the tendon diameter. In addition, since the tension of tendon can be kept constant even during freezing and thawing, landslides can be reliably prevented and the landslide disaster can be greatly reduced.
[0046]
According to the second aspect of the present invention, since the disc spring having the elastic force fluctuation dead zone region is used as the elastic member, the tension force of tendon can be kept constant during the freezing. Therefore, the landslide disaster can be greatly reduced by always preventing the landslide by pressing the ground surface layer toward the deep part of the ground at all times.
[0047]
According to the third aspect of the present invention, since the bearing plate is interposed between the elastic member and the pressure receiving plate, it is possible to prevent a large stress from acting locally on the pressure receiving plate, and the pressure receiving plate is damaged or worn. It is possible to prevent such deterioration. As a result, the durability of the pressure receiving plate is improved and the reliability of the landslide countermeasure is also improved.
[Brief description of the drawings]
FIG. 1 is a side cross-sectional view of a ground anchor having a frost-proof top fixing structure according to a first embodiment of the present invention.
FIG. 2 is a conceptual diagram showing nonlinear spring characteristics of a disc spring used as an elastic member according to the present invention.
FIG. 3 is a cross-sectional view of a frost-proof fixing structure according to a second embodiment of the present invention.
4A and 4B are views of a honeycomb type damper having spring characteristics similar to those of a disc spring, in which FIG. 4A is a plan view and FIG. 4B is a side view thereof.
5A and 5B are diagrams of a cell type damper having spring characteristics similar to those of a disc spring, in which FIG. 5A is a plan view and FIG. 5B is a side view thereof.
FIG. 6 is a perspective partial cross-sectional view of a natural ground having a cut slope, showing an outline of a landslide countermeasure construction method.
FIG. 7 is a cross-sectional view showing the structure of a ground anchor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pressure receiving plate 1a Drilling hole 3 Ground anchor 5 Tendon 5a PC steel strand 5b Unbonded tube 7 Fixing part 7a Wedge member 7b Fixing tool 7c Bearing plate 7c 'Bearing plate 7d Plate-like part 7e Pipe part 7j Hole 7c "Supporting plate with rib 7h rib 8 disc spring portion 8a disc spring 8b, 8c disc spring laminated body 8d pressure plate 8e plate-like portion 8g pipe portion 8g hole 8f disc spring set 9 head cap 9b bolt 13 sheath 13a bellows pipe-like sheath 15 anchor portion 19 anchor free Long part 23 Anchor fixing long part 25 Grout 25a Internal grout 25b External grout 31 Honeycomb type damper 31a Long side piece 31b Short side piece 31c Hexagonal space 41 Cell type damper 41a Substantially cylindrical pipe 41b Flange 41c Cone cone part 41d Cylindrical shape Part 51 Ground surface, cut slope, slope 5 3 Ground surface layer 55 Deep ground portion 57 Drilling hole

Claims

In the ground anchor that prevents the landslide by tensioning the tendon embedded in the ground by the fixing part fixed to the outer end exposed on the ground surface and transmitting the reaction force to the ground through the pressure receiving plate by the fixing part.
Between the fixing portion and the pressure receiving plate of the tendon, and expands and contracts in response to expansion and contraction of the ground surface at the time of frost heave, holds the tension of the tendons constant, the disc springs having a hole in the center distribution I am set,
A first support plate is interposed between the disc spring and the pressure plate,
The first pressure plate has a plate-like portion that is in contact with the disc spring and has a hole through which the tendon is inserted, and a pipe portion that is erected on the periphery of the hole toward the pressure-receiving plate side. And
A plate-like portion that is in contact with the disc spring from the side opposite to the first bearing plate and has a hole through which the tendon is inserted, and a peripheral portion of the hole of the plate-like portion toward the disc spring side A second bearing plate having a standing pipe portion is provided,
The pipe portion of the second bearing plate is inserted into the hole of the disc spring and is fitted to the inner periphery of the pipe portion of the first bearing plate, and the plate-like portion of the first bearing plate The disc spring is sandwiched between the plate-like portion of the second bearing plate,
The pipe portion of the first pressure plate is fitted into a drilling hole through which the tendon formed in the pressure plate is inserted, and the plate-like portion of the second pressure plate is in contact with the fixing portion. The tendon is fixed to the pressure receiving plate,
Frozen anti-frozen structure for ground anchors.