JP3912737B2

JP3912737B2 - Solidification improved ground

Info

Publication number: JP3912737B2
Application number: JP2002048024A
Authority: JP
Inventors: 健治緒方; 勇治福島; 太浩稲垣; 光夫野津; 誠大塚
Original assignee: Fudo Tetra Corp
Current assignee: Fudo Tetra Corp
Priority date: 2002-02-25
Filing date: 2002-02-25
Publication date: 2007-05-09
Anticipated expiration: 2022-02-25
Also published as: JP2003247227A

Description

【０００１】
【発明の属する技術分野】
本発明は、処理区域と非処理区域を有する固化処理改良地盤の盛り土などの載荷時において、該処理区域に造成される固化処理杭が受ける側方変形を抑制することができる固化処理改良地盤に関するものである。
【０００２】
【従来の技術】
地盤改良工法のひとつに固化処理杭造成工法がある。この固化処理杭造成工法は、例えば、機械式攪拌装置の先端を、施工する柱体の芯に合わせて攪拌軸を回転させ、装置先端から固化材を吐出しながら攪拌羽根を回転し、掘削土と混合攪拌しながら掘進を行い、設計深度に達したところで吐出を停止し、攪拌軸をそのままの回転又は逆転して、更に混合攪拌しながら地盤上に引き上げて柱状体を造成するものである。そして、柱状体の固化処理杭は軟弱地盤中、所定のピッチを有して多数造成されたり、接円断面状に多数造成して連続杭としたりする。
【０００３】
従来、例えば、図５に示すように、のり面５２を有する盛り土５１を支持する軟弱地盤を改良する場合、設計上、盛り土５１ののり面５２直下に所定のピッチで多数の固化処理杭５３を造成する。このため、盛り土を支持する改良地盤５０には、処理区域５４と、盛り土の中央部５５の直下に固化処理杭が造成されない非処理区域５６が存在する。また、図７に示すように、橋台構造物６１の背面部に造成される盛り土５５を支持する軟弱地盤を改良する場合、橋台６３の背面部の基礎部分６４に所定のピッチで多数の固化処理杭５３を造成する。このため、盛り土を支持する改良地盤６０には、処理区域５４と、橋台６３から離れた盛り土の直下に固化処理杭が造成されない非処理区域５６が存在する。
【０００４】
【発明が解決しようとする課題】
このような構造を有する改良地盤５０においては、図６に示すように、盛り土内側の固化処理杭５３ａは鉛直方向に盛り土の高さ分の荷重Ｚと、側方向の圧力によって、曲げ変形Ｘを生じる。盛り土外側の固化処理杭５３ｂは盛り土ののり尻の直下にあるため、鉛直方向の荷重は受けず、側方向の圧力を受けることになり、固化処理杭５３ｂは、下端５３１を中心に転倒変形Ｙを生じる。ここで、５３ａ以外の改良域の固化処理杭は、荷重をあまり負担していない状態となっており、不経済な改良となっていた。また、図７に示すような改良地盤６０においても、盛り土内側の固化処理杭５３ａは鉛直方向に盛り土の高さ分の荷重と、側方向の圧力によって、同様に曲げ変形を受ける一方で、その他の固化処理杭にはそれほどの曲げ変形が起こらない状態であり、効率的な荷重負担が行われていなかった。このような盛り土ののり面直下の固化処理杭５３に作用する偏荷重に効率的に対処する方法としては、地盤の改良率を高める方法が採られていたが、この方法は施工コストを上昇させるという問題があった。
【０００５】
従って、本発明の目的は、処理区域と非処理区域を有する固化処理改良地盤の盛り土などの載荷時において、該載荷に起因して発生する固化処理杭ごとに異なる不均一な応力状態を是正し、各固化処理杭に相応の荷重分担を行わせ地盤の側方変形を抑制する経済的な改良地盤を提供することにある。
【０００６】
【課題を解決するための手段】
かかる実情において、本発明者らは鋭意検討を行った結果、固化処理杭ごとの応力状態は弾塑性圧密変形有限要素法解析によって求められ、曲げ変形を受ける内側固化処理杭の特定位置に拡径の水平固化盤を形成し、該拡径の水平固化盤を、側方圧力が作用する方向に配置される固化処理杭に同様に形成するか、あるいは、前記処理区域内でかつ特定傾斜の斜め固化処理杭を更に造成するかすれば、固化処理杭ごとに異なる不均一な応力状態を是正し、各固化処理杭に相応の荷重分担を行わせ地盤の側方変形を抑制する経済的な改良地盤を得ることができること、などを見出し、本発明を完成するに至った。
【０００７】
すなわち、本発明（１）は、軟弱地盤中に所定のピッチで多数の固化処理杭が造成された処理区域と、固化処理杭が造成されない非処理区域を有し、非処理区域に直近する内側固化処理杭に構造物や盛り土による側方圧力が作用する固化処理改良地盤において、前記内側固化処理杭は、固化処理杭中、最大の曲げ変形を生じるものであって、且つ該内側固化処理杭の最大変位曲率位置又はその近傍に拡径の水平固化盤を有し、該拡径の水平固化盤は、側方圧力が作用する方向に配置される複数の固化処理杭列の少なくとも１列の固化処理杭に形成されると共に、固化処理杭列における隣接する水平固化盤同士を接合してなる固化処理改良地盤を提供するものである。また、本発明（２）は、軟弱地盤中に所定のピッチで多数の固化処理杭が造成された処理区域と、固化処理杭が造成されない非処理区域を有し、非処理区域に直近する内側固化処理杭に構造物や盛り土による側方圧力が作用する固化処理改良地盤において、前記内側固化処理杭は、該内側固化処理杭の最大変位曲率位置又はその近傍に拡径の水平固化盤を有し、該拡径の水平固化盤は、側方圧力が作用する方向に配置される複数の固化処理杭列の少なくとも１列の固化処理杭に形成されると共に、固化処理杭列における隣接する水平固化盤同士を接合してなり、且つ全ての固化処理杭に形成されるものではない固化処理改良地盤を提供するものである。
【０００８】
また、本発明（３）は、軟弱地盤中に所定のピッチで多数の固化処理杭が造成された処理区域と、固化処理杭が造成されない非処理区域を有し、非処理区域に直近する内側固化処理杭に構造物や盛り土による側方圧力が作用する固化処理改良地盤において、側方圧力が作用する方向に配置される複数の固化処理杭列間に、前記内側固化処理杭の上端から外側固化処理杭の下端にかけて傾斜する斜め固化処理杭を更に造成することを特徴とする固化処理改良地盤を提供するものである。
【０００９】
また、本発明（４）は、軟弱地盤中に所定のピッチで多数の固化処理杭が造成された処理区域と、固化処理杭が造成されない非処理区域を有し、非処理区域に直近する内側固化処理杭に構造物や盛り土による側方圧力が作用する固化処理改良地盤において、側方圧力が作用する方向に配置される複数の固化処理杭列間に、前記内側固化処理杭の最大主応力方向に沿った角度で斜め固化処理杭を前記処理区域内に更に造成することを特徴とする固化処理改良地盤を提供するものである。
【００１０】
【発明の実施の形態】
次に、本発明の第１の実施の形態における固化処理改良地盤を図１および図２を参照して説明する。図１は第１の実施の形態例の固化処理改良地盤の断面図、図２は図１の固化処理杭の構造を説明する模式図で、（ａ）が側方圧力が作用する方向に配置されるひとつの固化処理杭列を示し、（ｂ）が４列の固化処理杭列の平面図をそれぞれ示す。但し、図２では、図の簡略化のため、杭本数を１列当たり３本で示した。
【００１１】
本例の固化処理改良地盤１Ａは、のり面２を有する盛り土４を支持する軟弱地盤５を改良するため、盛り土４ののり面２の直下に所定のピッチで多数の固化処理杭３を造成したものである。すなわち、盛り土４は図１中、紙面の表裏方向にも連続しており、従って、固化処理杭３も同様に図１中、紙面の表裏方向に所定のピッチで連続して造成されている。このため、盛り土４を支持する改良地盤５には、処理区域７と、盛り土の中央部４１の直下に固化処理杭が造成されない非処理区域８が存在し、処理区域７内の固化処理杭３のうち、非処理区域８に直近の内側固化処理杭３ａに盛り土４による側方圧力が作用することになる。
【００１２】
第１の実施の形態例において、内側固化処理杭３ａは、該内側固化処理杭３ａの最大変位曲率位置ｈに拡径で所定の厚みを有する第１水平固化盤６ａを、更にその下方に拡径で所定の厚みを有する第２水平固化盤６ｂを有している。このように、内側固化処理杭３ａの最大変位曲率位置ｈに拡径の水平固化盤６ａを設けることにより、極めて効率的に側方変形を抑制することができる。また、内側固化処理杭３ａの第１水平固化盤６ａ及び第２水平固化盤６ｂは、側方圧力が作用する方向に配置される複数の固化処理杭列３Ａ、３Ｂ、３Ｃ、３Ｄ・・・のうち、固化処理杭列３Ｂおよび３Ｄの固化処理杭３ａ、３ｂ、３ｃに形成されると共に、隣接する水平固化盤６はオーバーラップして、固化処理杭３同士を接合している。このように、接合された固化処理杭は互いに一体化しているため、各固化処理杭に相応の荷重分担を行なわせることができる。
【００１３】
本例において、内側固化処理杭３ａの最大変位曲率位置ｈは、地表面から内側固化処理杭３ａの最大変位曲率位置までの深さであり、弾塑性圧密変形有限要素法解析により求められるもので、詳しくは、第４６回地盤工学シンポジウム−地盤・構造物の変形とその評価−平成１３年１１月２１日発行（社団法人地盤工学会）第２７５頁から第２８０頁に開示された方法、あるいは、当該有限要素解析により求めた簡易なノモグラフが適用できる。この弾塑性圧密変形有限要素法解析は、固化処理杭および軟弱地盤を含むモデル領域を要素メッシュに分割し、各要素の内部応力と外力とが等しいとする“つりあい方程式”と、水の流れる速さが動水勾配と透水係数の積に等しいとする“水の連続方程式（ダルシー則）”を、連立方程式とみなし、これをモデル領域全体に足し合わせ、全体の方程式をマトリックスで解くものであり、公知の解析方法である。本例では図５及び図６で示される内側固化処理杭５３ａが解析の対象となり、このような固化処理杭５３ａの場合、最大変位曲率位置ｈは地表面から地層底（硬質層の表面）までの厚みＨの１／３〜１／４の深度に現れる。
【００１４】
本例において、固化処理杭における拡径の水平固化盤の設置位置は、第１の実施の形態例のように、内側固化処理杭３ａの最大変位曲率位置ｈの他、最大変位曲率位置ｈの近傍であっても、内側固化処理杭３ａに作用する曲げ応力に抗することができる点でその設置範囲内である。また、本例において、拡径の水平固化盤６は、少なくとも内側固化処理杭３ａの最大変位曲率位置ｈ又はその近傍に形成されていればよく、第１の実施の形態例のような合計設置数が２個の他、３個以上の設置数であってもよい。また、水平固化盤６の厚みも適宜決定されるが、余り厚すぎても施工に多くの時間を要したり、固化材が不必要に多く使用するなど不経済となる。
【００１５】
また、第１の実施の形態例において、処理区域７に造成される固化処理杭３は、その下端が硬質層５１に着底しているものの他、硬質層５１に到達していない浮き杭にも適用できる。この浮き杭の場合、その下端が硬質層５１の近傍まで達している固化処理杭、すなわち、軟弱地盤層の深さＨの相当長さまで形成されている固定処理杭が、盛り土の荷重を実質的に支えることができる点で好ましい。また、拡径の水平固化盤６は、側方圧力が作用する方向に配置される複数の固化処理杭列３Ａ、３Ｂ、３Ｃ、３Ｄ・・・の少なくともいずれかひとつの列の固化処理杭３ａ、３ｂ、３ｃに形成されていればよく、上記の例の他、更に、固化処理杭列３Ａ及び３Ｃにも形成されるものであってもよい。この場合、隣接する固化処理杭列の固化処理杭の水平固化盤６同士も接合されると共に、処理区域７に造成される全ての固化処理杭３に水平固化盤を形成させることになる。拡径の水平固化盤６を、側方圧力が作用する方向に配置される複数の固化処理杭列のいずれの列の固化処理杭に形成するかは、軟弱地盤の土質、側方圧力の程度、固化処理杭の強度などを考慮して適宜決定される。また、水平固化盤６の接合形態としては、上記の例のオーバーラップの他、接円断面形状のものであってもよい。
【００１６】
第１の実施の形態例における拡径を有する固化処理杭３は、例えば、特公昭５９-５０８１３号公報に記載の攪拌翼を拡大縮小自在の上段攪拌翼と一定直径の下段攪拌翼の２段構造を有する拡径時攪拌翼変化型の機械攪拌混合処理装置を使用する方法、あるいは、例えば、地盤中に所定深度まで貫入した中空ロッドを回転させ、かつその下端の下向きノズルから固化材を噴出させながら引き上げ、この間、地盤表面から深さｈのところでは中空ロッドの下端の横向きノズルからも固化材の高圧噴出を行なう拡径時高圧噴射併用型複合攪拌混合処理方法など公知の方法で形成させることができる。
【００１７】
第１の実施の形態の固化処理改良地盤によれば、固化処理杭ごとの応力状態は前述の弾塑性圧密変形有限要素法解析によって求められ、曲げ変形を受ける内側固化処理杭の最大変位曲率位置に拡径の水平固化盤を形成し、該拡径の水平固化盤を、側方圧力が作用する方向に配置される固化処理杭に同様に形成したため、発生応力を拡径の水平固化盤が形成されたすべての固化処理杭で負担させることができる。このため、曲げ変形に対して、ほとんど改良率を高めることなく、改良率が高められたと同様の効果を奏する。
【００１８】
次に、本発明の第２の実施の形態における固化処理改良地盤を図３及び図４を参照して説明する。図３は第２の実施の形態例の固化処理改良地盤の断面図、図４は図３の固化処理杭の構造を説明する模式図で、（ａ）が側方圧力が作用する方向に配置されるひとつの固化処理杭列と斜め固化処理杭を示し、（ｂ）が４列の固化処理杭列のそれぞれの列間に造成された斜め固化処理杭の平面図をそれぞれ示す。但し、図４では、図の簡略化のため、杭本数を１列当たり３本で示した。図３及び図４において、図１及び図２と同一の構成要素には同一符号を付して、その説明を省略し、異なる点についてのみ主に説明する。
【００１９】
すなわち、図３及び図４において、図１及び図２と異なる点は、側方圧力が作用する方向に配置される固化処理杭に水平固化盤を形成させる代わりに、内側固化処理杭３ａの上端から外側固化処理杭３ｂの下端にかけて傾斜する斜め固化処理杭９を造成した点にある。また、この斜め固化処理杭９は、側方圧力が作用する方向に配置される複数の固化処理杭列３Ａ、３Ｂ、３Ｃ、３Ｄ・・・の、各列の間に造成されている。この斜め固化処理杭９の造成により、盛り土の荷重は斜め固化処理杭９の圧縮強度によっても支えることができるため、側方変形を抑制することができる。
【００２０】
また、この斜め固化処理杭９は、図４（ａ）に示すように、上端の芯部９１を内側固化処理杭３ａの上端の芯部３１に略合わせ、その傾斜が最大主応力方向（鉛直方向に対して、時計回りでα度の方向）に沿った角度となるように処理区域７内に造成してもよい。これにより、盛り土荷重を効率的に支えることができ、改良率を極端に高めることなく、比較的少ない処理杭で改良率を高めた場合と同等の改良効果を得ることができる。内側固化処理杭３ａの最大主応力方向とは、第１の実施の形態例と同様に、弾塑性圧密変形有限要素法解析、あるいは、当該有限要素解析により求めた簡易なノモグラフにより求められるものである。すなわち、本例では図５及び図６で示される内側の固化処理杭５３ａが解析の対象となり、具体的には固化処理杭５３ａにおいて、地表面から地層底（硬質層の表面）までの厚みＨの上部１／４部分程度の要素での解析結果における平均の最大主応力方向をその値とする。要素単位が上記１／４程度を越えると、杭の角度が過大となって効果が薄れ、また、１／４程度未満であると、杭の角度が過小となって効果が薄れるため好ましくない。一般に、固体の１点の任意面の応力は、垂直応力とせん断応力で表現でき、このとき、せん断応力が０の面が必ず存在し、その面の方向を主方向といい、その面の垂直応力を主応力と言う。そして、最大主応力とは、一般に、外力が作用する固体内の任意の１点には３つの主応力が存在するが、それらのうちの最大の主応力を言い、最大主応力方向とはその最大主応力が作用する方向を言う。最大主応力方向αは、例えば、図５の地盤の遠心模型実験における固化処理杭５３ａの場合、盛土高さを６ｍ、のり面勾配を１：１.６、軟弱層（カオリン粘土）の厚みを１３ｍ、軟弱層のせん断強度を１８kN/m²、軟弱地盤の含水比４８％、軟弱地盤の湿潤密度１．７１g/cm³、固化処理杭の本数を５本、固化処理杭の一軸圧縮強さを３００kN/m²とした条件で解析した場合、５２度である。
【００２１】
第２の実施の形態例において、斜め固化処理杭９の設置位置は、上記位置に限定されず、内側固化処理杭３ａの最大主応力方向の±１５度の角度（図４中、βの範囲）に沿った範囲に造成され、且つ斜め固化処理杭９の上端芯部９１が、側面視で内側固化処理杭３ａの上端芯部３１から側方圧力が作用する方向に隣接する固化処理杭３ｃの上端芯部３２の範囲に存在するものであってもよい。すなわち、例えば、上端芯部９１が内側より２番目の固化処理杭３ｃの上端芯部と一致させた位置である場合、斜め固化処理杭９は当該上端芯部９１を中心に角度βの範囲、すなわち、ｌ-ｌ線からｍ-ｍ線に亘る範囲内で造成してもよい。当該範囲内にあれば、内側固化処理杭３ａの最大主応力方向に沿って造成される斜め固化処理杭９と同様に、盛り土荷重を支えることができるため、側方変形を抑制することができる。
【００２２】
また、本第２の実施の形態例において、処理区域７に造成される固化処理杭３は、その下端が硬質層５１に着底しているものの他、硬質層５１に到達していない浮き杭にも適用できる。この浮き杭の場合、その下端が硬質層の近傍まで達している固化処理杭、すなわち、軟弱地盤層の深さＨの相当長さまで造成されている固定処理杭が、盛り土の荷重を実質的に確実に支えることができる点で好ましい。第２の実施の形態例における斜め固化処理杭９は、例えば、リーダー及び攪拌軸を傾斜して施工できる固化処理杭造成装置を使用して造成される。
【００２３】
本例において、斜め固化処理杭の造成箇所及び個数としては、上記の例に限定されず、例えば、側方圧力が作用する方向に配置される複数の固化処理杭列３Ａ、３Ｂ、３Ｃ、３Ｄ・・・の間をひとつ飛び、又は任意の数飛びにして形成されるものであってもよく、更に、既設の鉛直固化処理杭３ａ、３ｂ、３ｃにオーバーラップして造成されるものであってもよい。既設の鉛直固化処理杭３ａ、３ｂ、３ｃへのオーバーラップ施工は、既設杭が既に固化している場合は、施工が困難となる場合があり、その場合は、既設の固化処理杭列３Ａ、３Ｂ、３Ｃ、３Ｄ・・・のそれぞれの間に造成することが好ましい。
【００２４】
第２の実施の形態の固化処理改良地盤１Ｂによれば、固化処理杭３ごとの応力状態は弾塑性圧密変形有限要素法解析によって求められ、盛り土４の荷重を鉛直固化処理杭３と斜め固化処理杭９の双方で支えるため、側方変形を効率的に抑制することができる。
【００２５】
【発明の効果】
本発明によれば、固化処理杭ごとの応力状態は弾塑性圧密変形有限要素法解析によって求められ、拡径の水平固化盤を、側方圧力が作用する方向に配置される固化処理杭の特定位置に形成するか、あるいは、斜め固化処理杭を前記処理区域内に造成するかするため、固化処理杭ごとに異なる不均一な応力状態を是正し、各固化処理杭に相応の荷重分担を行わせる地盤の側方変形を抑制する経済的な改良地盤を得ることができる。
【図面の簡単な説明】
【図１】第１の実施の形態例の固化処理改良地盤の断面図である。
【図２】図１の固化処理杭の構造を説明する模式図で、（ａ）が側方圧力が作用する方向に配置されるひとつの固化処理杭列を示す、（ｂ）が４列の固化処理杭列の平面図を示す。
【図３】第２の実施の形態例の固化処理改良地盤の断面図である。
【図４】図３の固化処理杭の構造を説明する模式図で、（ａ）が側方圧力が作用する方向に配置されるひとつの固化処理杭列と斜め固化処理杭を示し、（ｂ）が４列の固化処理杭列のそれぞれの列間に造成された斜め固化処理杭の平面図を示す。
【図５】従来の固化処理改良地盤の断面図である。
【図６】従来の固化処理杭の構造を説明する模式図で、（ａ）が側方圧力が作用する方向に配置されるひとつの固化処理杭列を示す、（ｂ）が３列の固化処理杭列の平面図を示す。
【図７】従来の他の固化処理改良地盤の断面図である。
【符号の説明】
１Ａ、１Ｂ固化処理改良地盤
２、５２のり面
３、５３固化処理杭
３Ａ、３Ｂ、３Ｃ、３Ｄ固化処理杭列
３ａ、５３ａ内側の固化処理杭
３ｂ、５３ｂ外側の固化処理杭
４、５１盛り土
５軟弱地盤
６ａ第１水平固化盤
６ｂ第２水平固化盤
７、５４処理区域
８、５６非処理区域
９斜め固化処理杭
４１盛り土の中央部
５０、６０改良地盤
ｈ最大変位曲率位置
Ｈ軟弱地盤層の厚み[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solidification improved ground that can suppress lateral deformation received by a solidified pile piled up in the treatment area when loading the embankment of the solidification improved ground having a treatment area and a non-treatment area. Is.
[0002]
[Prior art]
One of the ground improvement methods is the solidification pile construction method. This solidification pile construction method is, for example, rotating the stirring shaft with the tip of the mechanical stirring device aligned with the core of the column to be constructed, rotating the stirring blade while discharging the solidified material from the tip of the device, and excavating soil. When the design depth is reached, the excavation is stopped, the discharge is stopped, the stirring shaft is rotated or reversed as it is, and the columnar body is formed by further pulling up on the ground while mixing and stirring. And many solidification piles of a columnar body are formed in a soft ground with a predetermined pitch, or a large number of solid piles are formed in a contiguous cross section to form a continuous pile.
[0003]
Conventionally, for example, as shown in FIG. 5, when improving the soft ground that supports the embankment 51 having the slope 52, a large number of solidified piles 53 are arranged at a predetermined pitch immediately below the slope 52 of the embankment 51 by design. Create. For this reason, in the improved ground 50 that supports the embankment, there are a treated area 54 and a non-treated area 56 in which a solidified pile is not formed immediately below the central portion 55 of the embankment. In addition, as shown in FIG. 7, when the soft ground supporting the embankment 55 formed on the back surface portion of the abutment structure 61 is improved, a number of solidification treatments are performed on the foundation portion 64 of the back surface portion of the abutment 63 at a predetermined pitch. A pile 53 is created. For this reason, in the improved ground 60 that supports the embankment, there are a treatment area 54 and a non-treatment area 56 in which a solidified pile is not formed immediately below the embankment away from the abutment 63.
[0004]
[Problems to be solved by the invention]
In the improved ground 50 having such a structure, as shown in FIG. 6, the solidified pile 53 a inside the embankment is subjected to bending deformation X by the load Z corresponding to the height of the embankment in the vertical direction and the pressure in the lateral direction. Arise. Since the solidified pile 53b on the outer side of the embankment is directly below the bottom edge of the embankment, it does not receive a load in the vertical direction and receives a lateral pressure, and the solidified pile 53b falls over the lower end 531 as a center. Produce. Here, the solidification processing pile of the improvement area | regions other than 53a has been in the state which has not borne much load, and was an uneconomic improvement. In addition, in the improved ground 60 as shown in FIG. 7, the solidified pile 53a inside the embankment is similarly bent and deformed by the load corresponding to the height of the embankment in the vertical direction and the pressure in the lateral direction. In the solidified pile, no significant bending deformation occurred, and an efficient load bearing was not performed. As a method for efficiently dealing with the uneven load acting on the solidified pile 53 just below the slope of the embankment, a method for increasing the improvement rate of the ground has been adopted, but this method increases the construction cost. There was a problem.
[0005]
Accordingly, an object of the present invention is to correct uneven stress states that differ depending on the solidified piles generated due to the loading when loading the embankment of the solidification improved ground having a treated area and a non-treated area. It is to provide an economically improved ground that suppresses lateral deformation of the ground by applying a corresponding load sharing to each solidified pile.
[0006]
[Means for Solving the Problems]
In such a situation, the present inventors have intensively studied, and as a result, the stress state of each solidified pile is obtained by elastoplastic consolidation deformation finite element method analysis, and the diameter of the inner solidified pile subjected to bending deformation is expanded to a specific position. A horizontal solidifying disk of the same diameter is formed in the same manner as the solidified pile piled in the direction in which the lateral pressure acts, or in the processing area and at a slant with a specific inclination. If the solidified piles are further constructed, an economically improved ground that corrects uneven stress conditions that differ from one solidified pile to another and distributes the load appropriately to each solidified pile and suppresses lateral deformation of the ground. As a result, the present invention has been completed.
[0007]
That is, the present invention (1) has a treated area in which a number of solidified piles are created at a predetermined pitch in soft ground, and a non-treated area where solidified piles are not created, and the inner side closest to the untreated area. In the solidification improved ground in which a lateral pressure due to a structure or embankment acts on the solidified pile, the inner solidified pile generates the largest bending deformation in the solidified pile , and the inner solidified pile A horizontal solidifying board having an enlarged diameter at or near the maximum displacement curvature position of the horizontal diameter, the horizontal solidifying board having an enlarged diameter is at least one of a plurality of solidified pile rows arranged in a direction in which a lateral pressure acts. The present invention provides a solidification improved ground which is formed in a solidified pile and is formed by joining adjacent horizontal solidified plates in a solidified pile row . Further, the present invention (2) includes a treated area where a number of solidified piles are created at a predetermined pitch in soft ground, and an untreated area where no solidified pile is created, and an inner side closest to the untreated area. In the solidification improved ground where lateral pressure due to structures and embankments acts on the solidified pile, the inner solidified pile has a horizontal solidified plate with an enlarged diameter at or near the maximum displacement curvature position of the inner solidified pile. The horizontal solidification board having an enlarged diameter is formed in at least one solidification pile of a plurality of solidification piles arranged in a direction in which the lateral pressure acts, and adjacent horizontal solidification piles in the solidification pile The present invention provides a solidification improved ground which is formed by joining solidification boards and is not formed on all solidification piles.
[0008]
In addition, the present invention ( 3 ) includes a treated area in which a number of solidified piles are created at a predetermined pitch in soft ground, and a non-treated area where solidified piles are not created, and an inner side closest to the non-treated area. In the solidification improved ground where lateral pressure due to structures and embankments acts on the solidified pile, between the multiple solidified pile rows arranged in the direction in which the lateral pressure acts, from the upper end of the inner solidified pile The present invention provides a solidification improved ground characterized by further forming an oblique solidification pile that inclines toward the lower end of the solidification pile.
[0009]
In addition, the present invention ( 4 ) includes a treatment area in which a number of solidified piles are formed at a predetermined pitch in soft ground, and a non-treated area where solidified piles are not created, and an inner side that is closest to the non-treated area. The maximum principal stress of the inner solidified pile between the solidified piles arranged in the direction in which the lateral pressure acts in the solidification improved ground where the lateral pressure due to the structure or embankment acts on the solidified pile It is another object of the present invention to provide a solidification improved ground characterized in that an oblique solidification pile is further created in the treatment area at an angle along the direction.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, the solidification improved ground in the first embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 1 is a cross-sectional view of the solidification improved ground of the first embodiment, FIG. 2 is a schematic diagram for explaining the structure of the solidification pile of FIG. 1, and (a) is arranged in the direction in which the lateral pressure acts. One solidified pile pile to be processed is shown, and (b) shows a plan view of four solidified pile piles. However, in FIG. 2, the number of piles is shown as three per row for simplification of the drawing.
[0011]
The solidification-improved ground 1A of this example has created a large number of solidified piles 3 at a predetermined pitch directly below the slope 2 of the bank 4 in order to improve the soft ground 5 that supports the bank 4 having the slope 2. Is. That is, the embankment 4 is also continuous in the front and back direction of the paper surface in FIG. 1, and accordingly, the solidified pile 3 is also continuously formed at a predetermined pitch in the front and back direction of the paper surface in FIG. For this reason, in the improved ground 5 that supports the embankment 4, there is a treated area 7 and a non-treated area 8 in which a solidified pile is not formed immediately below the central portion 41 of the embankment, and the solidified pile 3 in the treated area 7. Among these, the side pressure by the embankment 4 acts on the inner solidified pile 3 a closest to the non-treatment area 8.
[0012]
In the first embodiment, the inner solidified pile 3a further expands the first horizontal solidified plate 6a having a predetermined diameter and a larger diameter at the maximum displacement curvature position h of the inner solidified pile 3a. A second horizontal solidifying board 6b having a predetermined thickness in diameter is provided. Thus, by providing the horizontal solidification board 6a having an enlarged diameter at the maximum displacement curvature position h of the inner solidification processing pile 3a, lateral deformation can be suppressed extremely efficiently. Moreover, the 1st horizontal solidification board 6a and the 2nd horizontal solidification board 6b of the inner side solidification processing pile 3a are several solidification processing pile row | line | columns 3A, 3B, 3C, 3D ... arrange | positioned in the direction where a side pressure acts. Among them, the solidification piles 3a, 3b, and 3c of the solidification treatment pile rows 3B and 3D are formed, and the adjacent horizontal solidification disks 6 are overlapped to join the solidification treatment piles 3 to each other. In this way, since the solidified piles that have been joined are integrated with each other, each solidified pile can be assigned a corresponding load.
[0013]
In this example, the maximum displacement curvature position h of the inner solidified pile 3a is the depth from the ground surface to the maximum displacement curvature position of the inner solidified pile 3a, and is obtained by elastoplastic consolidation deformation finite element analysis. In detail, the 46th Geotechnical Engineering Symposium-Deformation of Ground and Structure and its Evaluation-The method disclosed on pages 275 to 280 issued on November 21, 2001 (Japan Geotechnical Society), or A simple nomograph obtained by the finite element analysis can be applied. This elasto-plastic consolidation deformation finite element method analysis divides the model region including the solidified pile and soft ground into element meshes, and the “balance equation” where the internal stress and external force of each element are equal, The water continuity equation (Darcy's law), which is assumed to be equal to the product of the hydrodynamic gradient and the hydraulic conductivity, is regarded as a simultaneous equation, and is added to the entire model region to solve the entire equation in a matrix. This is a known analysis method. In this example, the inner solidified pile 53a shown in FIGS. 5 and 6 is the object of analysis, and in the case of such a solidified pile 53a, the maximum displacement curvature position h is from the ground surface to the bottom of the stratum (the surface of the hard layer). Appears at a depth of 1/3 to 1/4 of the thickness H.
[0014]
In this example, the setting position of the horizontal solidification board with the enlarged diameter in the solidified pile is the maximum displacement curvature position h in addition to the maximum displacement curvature position h of the inner solidified pile 3a as in the first embodiment. Even in the vicinity, it is within the installation range in that it can resist bending stress acting on the inner solidified pile 3a. Moreover, in this example, the expanded horizontal solidification board 6 should just be formed at the maximum displacement curvature position h of the inner side solidification processing pile 3a or its vicinity, and is total installation like a 1st embodiment. The number of installations may be three or more in addition to two. Moreover, although the thickness of the horizontal solidification board | substrate 6 is also determined suitably, even if it is too thick, it will become uneconomical, for example, it will require much time for construction, or an excessive amount of solidification materials will be used.
[0015]
Further, in the first embodiment, the solidified pile 3 formed in the treatment area 7 is a floating pile not reaching the hard layer 51 in addition to the bottom end of the solid pile piled on the hard layer 51. Is also applicable. In the case of this floating pile, the solidification treated pile whose lower end reaches the vicinity of the hard layer 51, that is, the fixed treated pile formed to a length equivalent to the depth H of the soft ground layer substantially reduces the load of the embankment. It is preferable in that it can be supported. Moreover, the horizontal solidification board 6 of an enlarged diameter is the solidification processing pile 3a of at least any one row | line | column of several solidification processing pile row | line | columns 3A, 3B, 3C, 3D ... arrange | positioned in the direction where a side pressure acts. What is necessary is just to be formed in 3b, 3c, and also other than said example, it may be formed also in the solidification process pile row | line | column 3A and 3C. In this case, the horizontal solidification discs 6 of the solidification treatment piles of adjacent solidification treatment pile rows are joined together, and the horizontal solidification discs are formed in all the solidification treatment piles 3 formed in the treatment area 7. Whether the horizontal solidification board 6 of the expanded diameter is formed in the solidification pile of a plurality of solidification piles arranged in the direction in which the lateral pressure acts depends on the soil quality of the soft ground and the degree of the lateral pressure It is determined appropriately in consideration of the strength of the solidified pile. Moreover, as a joining form of the horizontal solidification board 6, in addition to the overlap in the above example, a shape with a contact cross section may be used.
[0016]
The solidified pile 3 having an expanded diameter in the first embodiment is, for example, a two-stage stirring blade described in Japanese Patent Publication No. 59-50813, an upper stirring blade that can be expanded and contracted and a lower stirring blade having a constant diameter. A method of using a mechanical stirring and mixing apparatus of a stirring blade change type having a diameter expansion structure, or, for example, rotating a hollow rod penetrating to a predetermined depth in the ground and ejecting a solidified material from a downward nozzle at its lower end In the meantime, at a depth h from the ground surface, it is formed by a known method such as a high-pressure jet combined use composite agitation and mixing method for high-pressure jetting of the solidified material from the horizontal nozzle at the lower end of the hollow rod. be able to.
[0017]
According to the solidification improved ground of the first embodiment, the stress state of each solidification pile is obtained by the above-described elastic-plastic consolidation deformation finite element analysis, and the maximum displacement curvature position of the inner solidification pile subjected to bending deformation The horizontal solidification board with an enlarged diameter is formed in the same manner as the solidified piles arranged in the direction in which the lateral pressure acts. It can be borne by all the solidified piles formed. For this reason, with respect to bending deformation, there is almost no increase in the improvement rate, and the same effect as that obtained when the improvement rate is increased is obtained.
[0018]
Next, a solidification improved ground in the second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a cross-sectional view of the solidification improved ground of the second embodiment, FIG. 4 is a schematic diagram illustrating the structure of the solidification pile of FIG. 3, and (a) is arranged in the direction in which the lateral pressure acts. 1 shows a solidified pile pile and a diagonal solidified pile, and (b) shows a plan view of the diagonal solidified pile formed between each of the four solidified pile rows. However, in FIG. 4, the number of piles is shown as three per row for simplification of the drawing. 3 and 4, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, description thereof is omitted, and only different points will be mainly described.
[0019]
That is, in FIGS. 3 and 4, the difference from FIGS. 1 and 2 is that instead of forming a horizontal solidification disk on the solidification pile arranged in the direction in which the lateral pressure acts, the upper end of the inner solidification pile 3 a It is in the point which created the diagonal solidification processing pile 9 which inclines toward the lower end of the outer side solidification processing pile 3b. Moreover, this diagonal solidification processing pile 9 is formed between each row | line | column of several solidification processing pile row | line | columns 3A, 3B, 3C, 3D ... arrange | positioned in the direction where a side pressure acts. By forming the diagonally solidified pile 9, the load of the embankment can be supported also by the compressive strength of the diagonally solidified pile 9, and thus lateral deformation can be suppressed.
[0020]
In addition, as shown in FIG. 4A, the diagonally solidified pile 9 has its upper end core portion 91 substantially aligned with the upper end core portion 31 of the inner solidified pile 3a, and its inclination is the maximum principal stress direction (vertical). You may create in the process area 7 so that it may become an angle along the direction (alpha direction clockwise). Thereby, the embankment load can be supported efficiently, and the improvement effect equivalent to the case where the improvement rate is increased with relatively few treated piles can be obtained without extremely increasing the improvement rate. The maximum principal stress direction of the inner solidified pile 3a is obtained by an elasto-plastic consolidation deformation finite element method analysis or a simple nomograph obtained by the finite element analysis, as in the first embodiment. is there. That is, in this example, the inner solidified pile 53a shown in FIG. 5 and FIG. 6 is the object of analysis. Specifically, in the solidified pile 53a, the thickness H from the ground surface to the bottom of the stratum (the surface of the hard layer) The average maximum principal stress direction in the analysis result of the element of the upper quarter portion is taken as the value. If the element unit exceeds about 1/4, the angle of the pile is excessive and the effect is reduced, and if it is less than about 1/4, the angle of the pile is excessively reduced and the effect is reduced. In general, the stress of an arbitrary surface of a solid can be expressed by normal stress and shear stress. At this time, there is always a surface with zero shear stress, and the direction of the surface is called the main direction. Stress is called principal stress. The maximum principal stress generally has three principal stresses at an arbitrary point in a solid to which an external force acts. The largest principal stress is the largest principal stress. The direction in which the maximum principal stress acts. For example, in the case of the solidified pile 53a in the centrifugal model experiment of the ground in FIG. 5, the maximum principal stress direction α is the height of the embankment 6m, the slope of the slope 1: 1.6, and the thickness of the soft layer (kaolin clay). 13m, the shear strength of the soft layer 18 kN / m ^2, water content of 48% soft ground, the soft ground wet density 1.71 g / cm ^3, 5 present the number of solidification pile, uniaxial compressive strength of the solidification pile Is 52 degrees when analyzed under the condition of 300 kN / m ² .
[0021]
In the second embodiment, the installation position of the diagonally solidified pile 9 is not limited to the above position, but is an angle of ± 15 degrees in the maximum principal stress direction of the inner solidified pile 3a (the range of β in FIG. 4). ) And the upper end core portion 91 of the diagonally solidified pile 9 adjacent to the direction in which the side pressure acts from the upper end core portion 31 of the inner solidified pile 3a in a side view. The upper end core portion 32 may be present in the range. That is, for example, in the case where the upper end core portion 91 is at a position aligned with the upper end core portion of the second solidification processing pile 3c from the inside, the oblique solidification processing pile 9 has a range of an angle β around the upper end core portion 91, That is, it may be formed within a range from the l-l line to the m-m line. If it exists in the said range, since the embankment load can be supported similarly to the diagonal solidification processing pile 9 constructed | assembled along the largest principal stress direction of the inner side solidification processing pile 3a, it can suppress a side deformation. .
[0022]
In the second embodiment, the solidified pile 3 formed in the treatment area 7 is a floating pile that does not reach the hard layer 51 in addition to the bottom end of the solid pile piled on the hard layer 51. It can also be applied to. In the case of this floating pile, the solidified pile whose lower end has reached the vicinity of the hard layer, that is, the fixed pile that has been built up to a length equivalent to the depth H of the soft ground layer substantially reduces the load of the embankment. It is preferable in that it can be reliably supported. The diagonally solidified pile 9 in the second embodiment is formed using, for example, a solidified pile forming apparatus that can be constructed with the leader and the stirring shaft inclined.
[0023]
In this example, the creation location and the number of diagonally solidified piles are not limited to the above example, and, for example, a plurality of solidified pile rows 3A, 3B, 3C, 3D arranged in the direction in which the lateral pressure acts. ... may be formed with one jump or any number of jumps between them, and is further formed by overlapping with existing vertical solidification piles 3a, 3b, 3c. May be. Overlap construction to the existing vertical solidification piles 3a, 3b, 3c may be difficult if the existing pile has already solidified, in which case the existing solidification pile pile 3A, It is preferable to create between 3B, 3C, 3D.
[0024]
According to the solidification improved ground 1B of the second embodiment, the stress state of each solidification pile 3 is obtained by elasto-plastic consolidation deformation finite element analysis, and the load of the embankment 4 is obliquely solidified with the vertical solidification pile 3. Since it supports with both the process piles 9, a side deformation | transformation can be suppressed efficiently.
[0025]
【The invention's effect】
According to the present invention, the stress state of each solidified pile is determined by elasto-plastic consolidation deformation finite element method analysis, and the horizontal solidified plate with an enlarged diameter is specified in the direction in which the lateral pressure acts. In order to form in the position or to construct the diagonally solidified piles in the treatment area, correct the uneven stress state that is different for each solidified pile and perform the corresponding load sharing to each solidified pile An economically improved ground that suppresses lateral deformation of the ground to be removed can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a solidification improved ground according to a first embodiment.
FIG. 2 is a schematic diagram for explaining the structure of the solidified pile shown in FIG. 1, in which (a) shows one solidified pile row arranged in the direction in which the lateral pressure acts, and (b) shows four rows. The top view of a solidification processing pile row is shown.
FIG. 3 is a cross-sectional view of a solidification improved ground according to a second embodiment.
FIG. 4 is a schematic diagram for explaining the structure of the solidified pile shown in FIG. 3. FIG. 4A shows one solidified pile row and an oblique solidified pile arranged in the direction in which the lateral pressure acts; ) Shows a plan view of the diagonally solidified piles formed between the four rows of solidified piles.
FIG. 5 is a cross-sectional view of a conventional solidification improved ground.
FIG. 6 is a schematic diagram illustrating the structure of a conventional solidified pile, where (a) shows one solidified pile row arranged in a direction in which lateral pressure acts, and (b) shows three solidified piles. The top view of a processing pile row is shown.
FIG. 7 is a cross-sectional view of another conventional solidification improved ground.
[Explanation of symbols]
1A, 1B Solidification improved ground 2, 52 Slope 3, 53 Solidification pile 3A, 3B, 3C, 3D Solidification pile 3a, 53a Inner solidification pile 3b, 53b Outer solidification pile 4, 51 Fill 5 Soft ground 6a 1st horizontal solidification board 6b 2nd horizontal solidification board 7, 54 Treatment area 8, 56 Non-treatment area 9 Diagonal solidification pile 41 Central part of embankment 50, 60 Improved ground h Maximum displacement curvature position H of soft ground layer Thickness

Claims

There is a treated area where a number of solidified piles are created at a predetermined pitch in soft ground, and an untreated area where solidified piles are not created. In the solidification improved ground where the side pressure acts, the inner solidification pile has the largest bending deformation in the solidification pile , and at or near the maximum displacement curvature position of the inner solidification pile. The expanded horizontal solidifying board is formed in at least one solidified pile of a plurality of solidified piles arranged in a direction in which the lateral pressure acts, Solidification improved ground obtained by joining adjacent horizontal solidification machines in a solidification pile row .

There is a treated area where a number of solidified piles are created at a predetermined pitch in soft ground, and an untreated area where solidified piles are not created. In the solidification improved ground in which a lateral pressure acts, the inner solidification pile has an enlarged horizontal solidification board at or near the maximum displacement curvature position of the inner solidification pile, and the enlarged horizontal solidification board. Is formed in at least one solidification pile of a plurality of solidification piles arranged in the direction in which the lateral pressure acts, and is formed by joining adjacent horizontal solidification boards in the solidification pile rows, And the solidification process improvement ground which is not formed in all the solidification process piles.

There is a treated area where a number of solidified piles are created at a predetermined pitch in soft ground, and an untreated area where solidified piles are not created. In the solidification-improved ground where the side pressure acts, between the plurality of solidification piles arranged in the direction in which the side pressure acts, the diagonal slanting from the upper end of the inner solidification pile to the lower end of the outer solidification pile Solidification improved ground characterized by further creating solidification piles.

There is a treated area where a number of solidified piles are created at a predetermined pitch in soft ground, and an untreated area where solidified piles are not created. In the solidification improved ground where the side pressure acts, between the plurality of solidification piles arranged in the direction in which the side pressure acts , diagonal solidification treatment at an angle along the maximum principal stress direction of the inner solidification pile A solidified improved ground, wherein a pile is further created in the processing area.

The oblique solidified pile is formed in a range along an angle of ± 15 degrees of the maximum principal stress direction of the inner solidified pile, and the upper end core portion of the oblique solidified pile is the inner solidified treatment in a side view. The solidification improved ground of Claim 4 which exists in the range of the upper end core part of the solidification process pile adjacent to the direction where a side pressure acts from the upper end core part of a pile.