JP2004285711A

JP2004285711A - Construction method for enlarged tunnel

Info

Publication number: JP2004285711A
Application number: JP2003079584A
Authority: JP
Inventors: Hideto Mashita; 英人真下; Hirohisa Kamata; 浩久蒲田; Akira Wakabayashi; 明若林; Masaaki Sato; 政昭佐藤; Michihiro Inao; 道裕稲生; Toshiro Kidokoro; 敏郎城所; Noriyuki Ito; 範行伊藤; Akihide Akutsu; 秋秀阿久津; Tomoaki Shimizu; 智明清水; Kenzo Mizuhara; 憲三水原
Original assignee: Mitsui Miike Machinery Co Ltd; Kajima Corp; Mitsui Miike Engineering Corp; Public Works Research Institute; Kumagai Gumi Co Ltd; Okumura Corp; Advanced Construction Technology Center ACTEC
Current assignee: Mitsui Miike Machinery Co Ltd; Kajima Corp; Mitsui Miike Engineering Corp; Kumagai Gumi Co Ltd; Okumura Corp; Advanced Construction Technology Center ACTEC; National Research and Development Agency Public Works Research Institute
Priority date: 2003-03-24
Filing date: 2003-03-24
Publication date: 2004-10-14
Anticipated expiration: 2023-03-24
Also published as: JP4144702B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method for an enlarged tunnel, increasing the width of one side part of an existing tunnel to construct a sidewalk or a vehicle road of one lane in the enlarged width part, securing the traffic during the period of works, and efficiently excavating to an enlargement scale while preventing landslide of the ground. <P>SOLUTION: After an enlarged width tunnel part T2 having a width 1/2 as large as that of the existing tunnel T1 is excavated on one side part of the existing tunnel T1, a lining wall body part 9A is formed on the excavating wall surface extending from the upper end part of excavation to the upper end of one side part of a lining body (t) of the existing tunnel T1, the lining wall body part 9A is supported on one side part of the lining body (t), and a partition wall partitioning between the enlarged width tunnel part T2 and the existing tunnel T1 is formed by the lining wall body part 9A and one side part of the lining body (t). After that, the enlarged width tunnel part T2 side is used for a road for the vehicle, and with the partition wall left undone, the existing tunnel T1 is knocked down and removed. While landslide of the ground is prevented, the ground of the upper peripheral part is excavated to an enlargement scale. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は既設トンネルの一側部を拡幅してその拡幅部に歩道や新たな車線を設ける拡大トンネルの築造方法に関するものである。
【０００２】
【従来の技術】
近年、交通量の増加に伴い、車線数の増加や歩道の増設を目的として既設トンネルの断面幅を拡大する工事が行われている。この際、拡大工事中においても一般車両の通行の迂回路を設けることなく、該既設トンネル内を通行路として使用することにより工期の短縮を図ると共に、工事期間中の安定した交通を確保することが提案されている。（例えば、特許文献１参照）。
【０００３】
【特許文献１】
特開２０００−３５６０９０号公報（第２〜４頁、第２、５図）。
【０００４】
この特許文献１に記載された既設トンネルの拡幅方法は、築造すべき拡幅トンネルの断面を、既設トンネルに隣接して掘削する先進坑と既設トンネルの断面を含む後進坑とに分け、上記先進坑を掘削すると共にこの先進坑と上記後進坑とを分割する仕切り面に仮支保工としての中壁を構築し、上記先進坑の掘削形成後、上記中壁を残してままで上記後進坑を掘削し、この後進坑の掘削形成後、上記中壁を撤去することにより既設トンネルの断面を拡幅するものである。
【０００５】
【発明が解決しようとする課題】
しかしながら、このような既設トンネルの拡幅方法において、上記中壁に最も要求される機能としては、先進坑と後進坑とを順次掘削して拡大トンネルを築造した際に、この拡大トンネルの天端周辺地盤の崩落を防止することにあり、そのため、中壁を拡大トンネルの断面形状の略中央部に施工する必要があるにもかかわらず、上記方法においては、中壁を既設トンネルの覆工体の一側方に施工されているために、先進坑の断面幅が狭くなればなる程、中壁の位置が拡大トンネルの一側部寄りに施工された状態となり、後進坑の掘削の際に拡大トンネルの天端周辺地盤が崩落する虞れがあった。また、上被りが浅い場合、崩落に限らず天端の大きな沈下により、地表面が沈下する虞れもあった。
【０００６】
従って、先進坑の断面幅が既設トンネルの断面幅の２倍以上、幅広い場合には上記拡幅方法を採用することができても、先進坑の断面幅が歩道や一車線の幅に等しい、例えば、既設トンネルの半分程度の狭い幅の場合には採用することが困難であるという問題点があった。
【０００７】
本発明は上記のような問題点に鑑みてなされたもので、その目的とするところは、既設トンネルの一側部に拡幅トンネル部を掘削、形成する際に、該既設トンネルの覆工体の一側部を拡幅トンネル部との仕切壁の一部に使用して、築造すべき拡大トンネルの天端周辺地盤をこの仕切壁を介して支持し得るようにした拡大トンネルの築造方法を提供するにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するために本発明の拡大トンネルの築造方法は、請求項１に記載したように、覆工体で覆工されている既設トンネルを拡幅してアーチ状の拡大トンネルを築造する方法であって、既設トンネルの一側部に沿って該既設トンネルの覆工体の一側部外周面を露出させ且つ高さがこの露出した覆工体一側部の上端よりも高い所定幅の拡幅トンネル部を掘削する第１工程と、この拡幅トンネル部の上端部と上記露出した覆工体の一側部の上端部間に壁体部を施工する第２工程と、この壁体部と拡幅トンネルに露出している上記覆工体部分とによって形成した仕切壁を残して覆工体の上周部側の地盤の掘削と該仕切壁以外の既設トンネルの壁体部分を撤去する第３工程と、仕切壁を撤去する第４工程とからなることを特徴としている。
【０００９】
また、請求項２に係る発明は、上記拡大トンネルの築造方法における、拡幅トンネル部の上端部と露出した既設トンネル覆工体の一側部の上端部間に壁体部を施工する第２工程において、該壁体部の下端を既設トンネル覆工体の露出した一側部の上端に連結、支持させると共にその支持部の下方における既設トンネル覆工体の一側内周面側に、既設トンネル内に車両が通行可能な空間を残して既設トンネル覆工体の補強体を施工することを特徴とする。
【００１０】
一方、請求項３に係る発明においては、上記拡幅トンネル部の上端部と既設トンネルにおける露出した覆工体の一側部の上端部間に壁体部を施工する第２工程より前に、該壁体部の下端の下方における既設トンネル覆工体の一側部内に、既設トンネル内に車両が通行可能な空間を残して既設トンネル覆工体の補強体を施工し、この補強体の上端部を既設トンネル覆工体の一側部に貫通させておき、第２工程において、該補強体の上端を上記壁体部の下端に一体に連結させることを特徴とする。
【００１１】
【作用】
既設のトンネル、例えば、２車線の通行路幅を有する小径の既設トンネルの一側部に既設トンネルの断面幅よりも幅狭い一車線の通行路又は歩道を増設する場合、まず、既設トンネルの一側部に上記一車線分又は歩道の幅に等しい幅を有する拡幅トンネル部を掘削形成する。この際、既設トンネル側においては車両規制を行うことなく自由に通行させる。この拡幅トンネル部は、上記既設トンネルの覆工体における一側部外周面を露出させながら掘削され、且つ、その高さは既設トンネルの上記露出した覆工体の一側部の上方に達する高さ、即ち、築造すべき拡大トンネルの天端近傍部に達する高さとなるように掘削される。従って、拡幅トンネル部の両側掘削壁面における他側壁面の大部分は、上記既設トンネルの露出した覆工体の一側部外周面によって形成された構造となる。
【００１２】
そして、上記露出した覆工体を他側壁面としてこの他側壁面に対向している拡幅トンネル部の一側方の掘削壁面を吹き付けコンクリート等によって覆工すると共に、この一側部の上端と上記露出した覆工体の上端間の掘削壁面に吹き付けコンクリート等による壁体部を施工し、この壁体部と拡幅トンネルに露出している上記覆工体部分とによって拡幅トンネル部と既設トンネルとを仕切っている仕切壁を形成する。
【００１３】
この際、この壁体部の下端を露出した覆工体の一側部上端外周面に連結、支持させると共にこの支持部の下方における既設トンネル覆工体の一側内周面側に、既設トンネル覆工体の補強体を施工してこの補強体により上記壁体部にかかる土圧等を既設トンネルの覆工体を介して支持させるか、或いは、上記補強体の上端部を既設トンネルの覆工体の一側上端部を貫通させてその上端面で上記壁体部の下端を支持させておくことが望ましい。なお、この場合も、既設トンネルの一側部内に補強体を施工するにもかかわらず、既設トンネル内での車両の通行を妨げないようにする。
【００１４】
次いで、上記仕切壁を残して既設トンネル覆工体の上周部側の地盤を掘削する。この際、仕切壁の上部を形成している上記壁体部は、築造すべき拡大トンネルの天端近傍部に設けられた構造としているので、既設トンネル覆工体の上周部側の地盤掘削時には、この壁体部によって拡大トンネルの天端周辺地盤が崩落するのを防止することができる。そして、既設トンネルの上記覆工体部分を解体、撤去すると共に該覆工体の上周部側の地盤を掘削してこの掘削壁面を吹き付けコンクリート等によって覆工する。この作業中においては上記仕切壁を残しておき、この仕切壁によって仕切られた拡幅トンネル部側を車両通行路として使用する。
【００１５】
既設トンネルの覆工体における上周部側の地盤の掘削作業や掘削壁面に対する覆工作業、及び、既設トンネルの覆工体部分の撤去作業が全線或いは所定長さ完了した後、上記仕切壁を撤去することによって拡大トンネルを築造するものである。
【００１６】
【発明の実施の形態】
次に、本発明の実施の形態を図面について説明すると、図１において、Ｔ１は例えば２車線の通行路を設けている小径の既設トンネルであって、本発明の実施の形態においては、この小径の既設トンネルＴ１の一側部に該既設トンネルＴ１の断面幅よりも幅狭い一車線分の通行路又は歩道を有する拡幅トンネル部Ｔ２を掘削、形成して図６に示すような拡大トンネルＴを築造する方法について説明する。まず、拡幅トンネル部Ｔ２を掘削、形成する前に既設トンネルＴ１の覆工体ｔを補強しておく。
【００１７】
この補強作業は、覆工体ｔの内周面に沿ってアーチ状に湾曲したＨ形鋼からなる支保工１を既設トンネルＴ１の長さ方向に所定間隔毎に建込むと共に、隣接する支保工１、１間に対する金網（図示せず）の張設や既設トンネルＴ１の覆工背面に対する薬液注入処理を行ったのち、拡幅トンネル部Ｔ２を掘削する側の覆工体ｔの一側部以外の覆工体ｔ部分に、既設トンネルＴ１内から覆工体ｔの周辺地盤中に向かってロックボルト２、２・・・を放射状に打設し、後述するように覆工体ｔの周辺地盤を掘削する際において、該周辺地盤が崩壊するのを予め防止した構造としておく。
【００１８】
また、既設トンネルＴ１の一側部内において、覆工体ｔの一側部内周面の上部と床面一側部との間にＨ形鋼からなる型枠兼用の補強縦枠材３を既設トンネルＴ１の長さ方向に一体間隔毎に建て込み、その上下端を覆工体ｔの一側部内周面の上部と床面一側部とにそれぞれ固着すると共に隣接する補強縦枠材３、３間に矢板４を嵌め込んで型枠を形成し、この型枠と既設トンネルＴ１の覆工体ｔの一側部内周面とで囲まれた空間部にコンクリート５を打設、充填して硬化させることにより、既設トンネルＴ１の一側部に覆工体ｔの一側部と一体化して該一側部を補強した補強体Ａを形成する。なお、この補強体Ａは既設トンネルＴ１内で車両の通行を妨げない通路幅を残して既設トンネルＴ１の一側部内に施工される。また、この補強体Ａの施工作業や上記ロックボルト２、２・・・の打設による覆工体ｔの補強作業等は夜間において、車両を一時通行止めすることにより行われ、これらの作業終了後は既設トンネルＴ１内を自由に通行させる。
【００１９】
一方、既設トンネルＴ１の覆工体ｔの一側部外周面から外側方部に、図２に示すように、この既設トンネルＴ１の長さ方向に沿って、該既設トンネルＴ１の断面幅の１／２程度の幅を有し、内部を一車線分の車両の通行路または歩道とするための拡幅トンネル部Ｔ２を掘削形成する。この拡幅トンネル部Ｔ２の掘削形成は、まず、既設トンネルＴ１の覆工体ｔの一側部側の周辺地盤における上半部を掘削する。
【００２０】
この際、該上半部の上端部の高さ、即ち、形成すべき拡幅トンネル部Ｔ２の上端部Ｂの高さが覆工体ｔの天端部よりも高くなるように、且つ、該上端部Ｂが既設トンネルＴ１の覆工体ｔの一側部の上方に位置するように掘削すると共に、この上端部Ｂから既設トンネルＴ１側に対して、その覆工体ｔの一側部上端に向かって斜め下方に傾斜した傾斜掘削壁面Ｂ１となるように掘削する一方、該上端部Ｂから外側下方に向かって円弧状に湾曲した掘削壁面Ｂ２となるように掘削する。さらに、上記傾斜掘削壁面Ｂ１の下端が既設トンネルＴ１の覆工体ｔの一側部上端に達するまで掘削されると、該覆工体ｔの一側部外周面の上部を露出させながら既設トンネルＴ１の上半部における下部を図２の仮想線Ｄに示す位置まで掘削形成する。
【００２１】
従って、拡幅トンネル部Ｔ２の上半部における上部の断面形状は上端部Ｂから下方に向かって徐々に幅広くなってあたかも竹の子の先端部の断面形状に等しい形状に形成され、覆工体ｔの一側部の上部外周面が露出したのちは、この露出面と上記一側方の円弧状掘削壁面Ｂ２との間の幅が下方に向かって僅かに幅広くなるように掘削するか、或いは、略等しい幅でもって掘削する。
【００２２】
こうして、拡幅トンネル部Ｔ２における上端部Ｂから仮想線Ｄに達する上半部が掘削されると、その掘削壁面Ｂ１、Ｂ２にコンクリートを吹き付けて一次吹き付けコンクリート層６を形成したのち、これらの掘削壁面Ｂ１、Ｂ２にトンネル長さ方向に所定間隔毎にＨ形鋼よりなる鋼製支保工７ａ、７ｂをそれぞれ建て込む。この際、傾斜掘削壁面Ｂ１に建て込まれた鋼製支保工７ａはその上端を上記円弧状掘削壁面Ｂ２側に建て込まれた鋼製支保工７ｂの上端に一体に連結されると共に下端は拡幅トンネル部Ｔ２の覆工体ｔにおける露出した一側部上端に連結、支持させる。
【００２３】
さらに、これらの鋼製支保工７ａ、７ｂの建て込み後、二次吹き付けコンクリート層８を設けると共に鋼製支保工７ａ、７ｂの長さ方向に所定間隔毎にロックボルト２ａ、２ｂをそれぞれ打設することにより、掘削壁面Ｂ１、Ｂ２からの地盤の崩落を防止した覆工壁体部９Ａ、９Ｂをそれぞれ形成する。
【００２４】
図３は上記傾斜掘削壁面Ｂ１側の覆工壁体部９Ａを支持した既設トンネルＴ１における覆工体ｔ部分の拡大断面図であって、既設トンネルＴ１の一側部内に築造された上記補強体Ａの上端上方部における既設トンネル覆工体ｔの露出している一側部上端に切欠段部１０を削成し、この切欠段部１０に上記鋼製支保工７ａの下端エンドプレート７ａ’ を当接、受止させ、このエンドプレート７ａ’ をアンカーボルトとナット１１によって切欠段部１０に固定、支持させ、上記補強体Ａによって補強された既設トンネル覆工体ｔにおける露出した一側部上端に、上記鋼製支保工７ａを有する覆工壁体部９Ａを介して拡幅トンネル部Ｔ２の上端側地盤を支持させ、該地盤の崩壊を防止した構造としている。そして、上記覆工壁体部９Ａと補強体Ａにより補強されてこの覆工壁体部９Ａを支持している既設トンネル覆工体ｔの一側部とによって、後述する拡大トンネルＴを築造する際における拡幅トンネル部Ｔ２に対する仕切壁Ｅを構成している。
【００２５】
次いで、拡幅トンネル部Ｔ２において、上記仮想線Ｄから底面に達するまでの拡幅トンネル部Ｔ２の下半部を掘削する。この掘削は既設トンネルＴ１の覆工体ｔの一側部側においてはその一側部における覆工体ｔの下部外周面を露出させながら下端まで掘削する一方、円弧状に湾曲した掘削壁面Ｂ２側においては、この掘削壁面Ｂ２を下方に延長するようにして上記上半部の幅でもって、或いは、その幅を徐々に広がらせながら掘削する。
【００２６】
しかるのち、図２に示すように、この下半部における円弧状に湾曲した掘削壁面Ｂ２’ 、即ち、拡幅トンネル部Ｔ２の一側掘削壁面にコンクリートを吹き付けて上記一次吹き付けコンクリート層６の下端に連続する一次吹き付けコンクリート層６’を形成したのち、トンネル長さ方向に所定間隔毎に上記上半部側の鋼製支保工７ｂから連続したＨ形鋼よりなる鋼製支保工７ｂ’ を建て込み、次いで、上記上半部側の二次吹き付けコンクリート層８の下端に連続する二次吹き付けコンクリート層８’を設けると共に鋼製支保工７ｂ’ の長さ方向（掘削壁面Ｂ２’ の円弧長方向）に所定間隔毎にロックボルト２ｂを打設することにより、掘削壁面Ｂ２’ からの地盤の崩落を防止した覆工壁体部９Ｂ’ （上記覆工壁体部９Ａの下端に連続している）を形成する。
【００２７】
このように拡幅トンネル部Ｔ２の掘削、及び掘削壁面Ｂ１、Ｂ２を補強した覆工壁体部９Ａ、９Ｂの形成が終了すると、図４に示すように、既設トンネルＴ１の覆工体ｔ一側部に沿って拡幅トンネル部Ｔ２内に上端が上記上端部Ｂに連続し、下端がこの拡幅トンネル部Ｔ２の底面他端部に固定した垂直な防護壁１２を設置すると共に既設トンネルＴ１の底部と略面一状となるように掘削された拡幅トンネル部Ｔ２の底面に仮舗装１３を施工する一方、円弧状に湾曲した覆工壁体部９Ｂ、９Ｂ’ の内面に防水シート１４を張設する。なお、上記防護壁１２は拡幅トンネル部Ｔ２に面している既設トンネルＴ１の覆工体ｔの一側部を隠蔽して拡幅トンネル部Ｔ２内を車両が一層安全に走行できるように設けられたものであり、この防護壁１２から一車線路の幅を存して拡幅トンネル部Ｔ２の一下側覆工壁体部９Ｂ’ に沿ってガードレール１５をトンネル長さ方向に立設する。
【００２８】
こうして、拡幅トンネル部Ｔ２内を車両が交互通行可能な状態にしてのち、既設トンネルＴ１内からこの拡幅トンネル部Ｔ２内に車線を変更し、既設トンネルＴ１側の掘削作業を開始する。この掘削作業は、図５に示すように、上記補強体Ａによって補強されている既設トンネルＴ１の一側覆工体部分と上記覆工壁体部９Ａとからなる仕切壁Ｅを残して、既設トンネルＴ１の覆工体ｔの撤去と、仕切壁Ｅの覆工壁体部９Ａで仕切られた既設トンネルＴ１の覆工体ｔの上周部側の地盤を掘削することにより行われる。
【００２９】
即ち、既設トンネルＴ１内から、該既設トンネルＴ１の一側部以外の覆工体ｔを支保工１の解体後に破砕、撤去して該覆工体上周部側の地盤を露出させたのち、この地盤を適宜な掘削機械を使用してその掘削壁面ｔ１が上記拡幅トンネル部Ｔ２の円弧状に湾曲した一側掘削壁面Ｂ２の上端からこの掘削壁面Ｂ２と略同じ湾曲度でもって該掘削壁面Ｂ２を覆工体ｔの他側部に向かって延長するように掘削し、該掘削壁面Ｔ１を覆工体ｔの他側部下端に連続させるものである。
【００３０】
詳しくは、上記仕切壁Ｅの上部を形成している覆工壁体部９Ａ側が最も上下掘削幅が広くなり、この覆工壁体部９Ｂ側から既に撤去している既設トンネルＴ１の覆工体ｔの上周部外周面に沿うようにして該既設トンネルＴ１の覆工体ｔの他側部に向かうに従って覆工体ｔとの間の上下掘削幅が徐々に狭くなるように円弧状に掘削し、既設トンネルＴ１を拡大した空間部Ｃを形成するものである。なお、既設トンネルＴ１の覆工体ｔの撤去時及び地盤の掘削時には、その掘削すべき地盤内に存在しているロックボルト２部分を切除する。
【００３１】
こうして、既設トンネルＴ１の覆工体ｔの撤去と共にその上周部側の地盤を掘削して拡大空間部Ｃを形成したのち、この拡大空間部Ｃの円弧状に湾曲した掘削壁面ｔ１に一次吹き付けコンクリート層１６を施工し、次いで、上記拡幅トンネル部Ｔ２の一側掘削壁面Ｂ２にトンネル長さ方向に所定間隔毎に建て込んでいる各鋼製支保工７ｂの上端に一端を連続させて、上記掘削壁面ｔ１に同じくＨ形鋼よりなる支保工７ｃを順次建て込み、しかるのち、該掘削壁面ｔ１に二次吹き付けコンクリート層１７を施工することによって覆工壁面１８を形成する。
【００３２】
次いで、上記補強体Ａによって補強された既設トンネル覆工体ｔの一側部と壁体部９Ａとからなる仕切壁Ｅを解体、撤去したのち、底面に上記拡幅トンネル部Ｔ２の仮舗装１３と面一状となるように仮舗装１９すると共に、掘削壁面ｔ１に、上記拡幅トンネル部Ｔ２の円弧状掘削壁面Ｂ２に張設した防水シート１４と連続するように防水シート１４’ を張設する。この状態にして、上記拡幅トンネル部Ｔ２と防護壁１２を介して区画されている既設トンネルＴ１を拡大した拡大トンネル部内で車両の通行を可能にして拡幅トンネル部Ｔ２側からこの拡大トンネル部内に車線変更を行う。
【００３３】
しかるのち、図６に示すように、拡幅トンネル部Ｔ２側から防護壁１２を解体、撤去することによって拡大トンネルＴを構成し、拡幅トンネル部Ｔ２側の掘削壁面Ｂ２に張設している防水シート１４と拡大トンネル部Ｔ’側の掘削壁面ｔ１に張設している防水シート１４’ とを接続させると共にこの拡大トンネルＴ内での車線の位置変更等を行い、さらに、舗装や覆工工事、内装設備工事等を行って拡大トンネルＴの築造を終了するものである。
【００３４】
なお、以上の実施の形態において、既設トンネルＴ１の一側方に拡幅トンネル部Ｔ２を掘削形成した時に、その上端部Ｂから既設トンネルＴ１の覆工体ｔの一側部上端に向かって施工している覆工壁体部９Ａは、図３に示すように、その下端を上記覆工体ｔの一側部上端に連結、支持させているが、図７に示すように、既設トンネルＴ１の一側部内に形成している補強体Ａにおける補強縦枠材３の上端部を覆工体ｔの一側部上端を貫通させて覆工体ｔから外周方に突出させ、その突出上端面に上記覆工壁体部９Ａにおける鋼製支保工７ａの下端面を突き合わせ状態にしてボルト２０により一体に連結した構造としておいてもよい。
【００３５】
また、上記実施の形態においては、既設トンネル覆工体ｔの補強体Ａは、補強縦枠材３とコンクリート５とから構成しているが、本発明の既設トンネル覆工体ｔの補強体はこれに限らず、例えば、補強縦枠材３のみ、或いはコンクリート５のみで形成しておいてもよい。
【００３６】
【発明の効果】
以上のように本発明の拡大トンネルの築造方法によれば、請求項１に記載したように、覆工体で覆工されている既設トンネルを拡幅してアーチ状の拡大トンネルを築造する方法であって、既設トンネルの一側部に沿って該既設トンネルの覆工体の一側部外周面を露出させ且つ高さがこの露出した覆工体一側部の上端よりも高い所定幅の拡幅トンネル部を掘削する第１工程と、この拡幅トンネル部の頂部と上記露出した覆工体の一側部の上端部間に壁体部を施工する第２工程と、この壁体部と拡幅トンネルに露出している上記覆工体部分とによって形成した仕切壁を残して覆工体の上周部側の地盤の掘削と該仕切壁以外の既設トンネルの壁体部分を撤去する第３工程と、仕切壁を撤去する第４工程とからなることを特徴とするものであるから、拡幅トンネル部の掘削形成時には既設トンネル内を車両の通行路として使用することができると共にこの拡幅トンネル部の形成後、既設トンネルの拡大作業時においては上記拡幅トンネル部内を車両の通行路として使用することができ、従って、車両の通行を全面的に遮断したり迂回させたりすることなく、拡大トンネルの築造が能率よく行うことができ、工期の短縮を図ることができる。
【００３７】
さらに、上記拡幅トンネル部における既設トンネル側の掘削壁面の大部分をこの既設トンネルの露出した覆工体の一側部外周面によって形成しているので、該掘削壁面に対する地盤崩落防止処理等が省略することができて工費の低減と作業能率の向上を図ることができると共に、拡幅トンネル部の最上端と既設トンネルにおける上記露出した覆工体の一側部の上端部間の掘削壁面に壁体部を施工するので、この壁体部を拡幅トンネル部の覆工体側に強固に支持させることができ、その上、この壁体部を設けている掘削壁面は既設トンネルにおける上記露出した覆工体の一側部上方に位置するので、壁体部を築造すべき拡大トンネルの幅方向の中央部、即ち、天端部分に設けることができ、従って、既設トンネルの周辺上方地盤を掘削して拡大トンネルを築造する際に、その天端周辺の地盤をこの壁体部によって確実に支持して地盤の崩落を防止することができる。
【００３８】
また、既設トンネルの周辺上方地盤を掘削する際には、上記壁体部と既設トンネルの覆工体における露出した一側部を、拡幅トンネル部側に対する仕切壁として使用して拡幅トンネル部内での車両の通行に支障を及ぼすことなく拡大掘削作業を行うことができるものであり、拡幅トンネル部が一車線、或いは歩道用としての幅狭いトンネル部であって、このトンネル部を既設トンネルの一側部に設けることにより拡大トンネルを築造することができる好適な方法を提供し得るものである。
【００３９】
このような拡大トンネル築造方法において、請求項２に係る発明は、上記拡幅トンネル部の頂部と露出した覆工体の一側部の上端部間に壁体部を施工する際に、該壁体部の下端を覆工体の露出した一側部の上端に連結、支持させるので、覆工体の一側部を壁体部の支持体として利用して壁体部と共に上述したように拡幅トンネル部側に対する仕切壁を形成することができ、且つ、拡大トンネルの掘削時における天端周辺の地盤を壁体部を介して既設トンネルの覆工体の一側部に確実に支持させることができる。さらに、その支持部の下方における既設トンネル覆工体の一側内周面側に、既設トンネル内に車両が通行可能な空間を残して既設トンネル覆工体の補強体を施工するので、上記壁体部の支持力が一層強大となり、この壁体部を介しての拡大トンネルの掘削時における天端周辺の地盤崩落を確実に防止することができる。
【００４０】
一方、請求項３に係る発明によれば、拡幅トンネル部の上端部と露出した覆工体の一側部の上端部間に壁体部を施工する際に、該壁体部の下端の下方における既設トンネル覆工体の一側部内に、既設トンネル内に車両が通行可能な空間を残して上記既設トンネル覆工体の補強体を施工し、この補強体の上端部を既設トンネル覆工体の一側部を貫通させて上記壁体部の下端に一体に連結させるので、補強体を既設トンネル内における車両通路側に対する仕切部材としての役目と共に壁体部を強固に支持した支持部材として共用させることができ、壁体部を介しての掘削壁面の確実にして安定した支持構造を構成することができる。
【図面の簡単な説明】
【図１】既設トンネルの一側部内に補強壁体部を施工している状態の縦断正面図、
【図２】既設トンネルの一側部に沿って拡幅トンネル部を掘削形成している状態の縦断正面図、
【図３】覆工壁体部の支持構造を示す既設トンネルの一部の拡大縦断正面図、
【図４】拡幅トンネル部内に防護壁等を施工した状態の縦断正面図、
【図５】既設トンネル側を拡大して拡大トンネルを形成している状態の縦断正面図、
【図６】拡大トンネルの縦断正面図、
【図７】覆工壁体部の支持構造の別な形態を示す一部の拡大縦断正面図。
【符号の説明】
Ｔ拡大トンネル
Ｔ１既設トンネル
ｔ覆工体
Ｔ２拡幅トンネル部
Ａ補強壁体部
Ｂ拡幅トンネル部の掘削上端部
Ｅ既設トンネル覆工体の補強体
９Ａ覆工壁体部
１支保工
２ロックボルト
３補強縦枠材
７鋼製支保工
１２防護壁[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for constructing an enlarged tunnel in which one side of an existing tunnel is widened and a sidewalk or a new lane is provided in the widened portion.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the increase in traffic volume, construction for increasing the cross-sectional width of an existing tunnel has been performed for the purpose of increasing the number of lanes and increasing the number of sidewalks. At this time, even during the expansion work, the construction time will be shortened by using the existing tunnel as a passageway without providing a detour for general vehicles, and the stable traffic during the construction period will be secured. Has been proposed. (For example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-2000-356090 (pages 2 to 4, FIGS. 2 and 5).
[0004]
The method of widening an existing tunnel described in Patent Document 1 divides the cross section of the widening tunnel to be built into an advanced pit excavated adjacent to the existing tunnel and a reverse pit including the cross section of the existing tunnel, And constructing an intermediate wall as a temporary support on a partition surface separating the advanced pit and the reverse pit, and excavating the reverse pit while leaving the intermediate wall after forming the excavation of the advanced pit After the excavation of the backward shaft, the cross section of the existing tunnel is widened by removing the inner wall.
[0005]
[Problems to be solved by the invention]
However, in such a widening method of the existing tunnel, the most required function of the middle wall is to construct an enlarged tunnel by sequentially digging an advanced pit and a reverse pit, and constructing an enlarged tunnel around the top end of the enlarged tunnel. In order to prevent the ground from collapsing, it is necessary to construct the middle wall at the approximate center of the cross-sectional shape of the enlarged tunnel. Because it is constructed on one side, as the section width of the advanced pit becomes narrower, the position of the inner wall is enlarged.It is constructed closer to one side of the tunnel, and it expands when excavating the reverse tunnel. There was a risk that the ground around the top of the tunnel would collapse. In addition, when the top cover is shallow, there is a possibility that the ground surface may sink due to a large sink at the top end as well as the collapse.
[0006]
Therefore, even if the cross-sectional width of the advanced pit is at least twice the cross-sectional width of the existing tunnel and is wide, even if the widening method can be adopted, the cross-sectional width of the advanced pit is equal to the width of the sidewalk or one lane. However, there is a problem that it is difficult to adopt the case where the width is about half as narrow as the existing tunnel.
[0007]
The present invention has been made in view of the above problems, and an object thereof is to excavate and form a widened tunnel portion on one side of an existing tunnel, and to form a lining body of the existing tunnel. Provided is a method of constructing an enlarged tunnel in which one side portion is used as a part of a partition wall with the widened tunnel portion so that the ground around the top end of the enlarged tunnel to be built can be supported through the partition wall. It is in.
[0008]
[Means for Solving the Problems]
To achieve the above object, a method for constructing an enlarged tunnel according to the present invention is a method for constructing an arch-shaped enlarged tunnel by widening an existing tunnel covered with a lining body, as described in claim 1. And an outer peripheral surface of one side of the lining of the existing tunnel is exposed along one side of the existing tunnel, and the height of the predetermined width is higher than the upper end of the one side of the exposed lining. A first step of excavating the widened tunnel, a second step of constructing a wall between the upper end of the widened tunnel and the upper end of one side of the exposed lining, Excavating the ground on the upper peripheral side of the lining body while leaving the partition wall formed by the above-mentioned lining body part exposed to the widening tunnel, and removing the wall part of the existing tunnel other than the partition wall; And a fourth step of removing the partition wall.
[0009]
The invention according to claim 2 is a second step of constructing a wall portion between the upper end portion of the widened tunnel portion and the upper end portion of one side portion of the existing tunnel lining body in the method of constructing the enlarged tunnel. The lower end of the wall portion is connected to and supported by the upper end of one exposed side of the existing tunnel lining body, and the existing tunnel lining body is provided with an existing tunnel lining below the supporting portion on one inner peripheral surface side of the existing tunnel lining body. It is characterized by constructing a reinforcement of the existing tunnel lining body while leaving a space in which vehicles can pass.
[0010]
On the other hand, in the invention according to claim 3, before the second step of constructing a wall portion between the upper end portion of the widening tunnel portion and the upper end portion of one side of the exposed lining in the existing tunnel, On one side of the existing tunnel lining below the lower end of the wall, a reinforcement of the existing tunnel lining is constructed, leaving a space where vehicles can pass in the existing tunnel, and the upper end of this reinforcing body Is penetrated through one side of the existing tunnel lining, and in a second step, the upper end of the reinforcing body is integrally connected to the lower end of the wall.
[0011]
[Action]
When an existing one-lane traffic lane or sidewalk narrower than the cross-sectional width of the existing tunnel is added to one side of the existing tunnel, for example, a small-diameter existing tunnel having a two-lane lane width, the existing tunnel must first be reconstructed. A widened tunnel portion having a width equal to the width of the one lane or the sidewalk is formed in the side portion. At this time, the existing tunnel is allowed to pass freely without restricting the vehicle. The widened tunnel portion is excavated while exposing an outer peripheral surface of one side of the lining body of the existing tunnel, and has a height reaching above one side of the exposed lining body of the existing tunnel. That is, it is excavated so as to reach a height near the top end of the enlarged tunnel to be built. Therefore, most of the other side wall surface of the excavated wall surface on both sides of the widening tunnel portion has a structure formed by the outer peripheral surface of one side of the exposed lining of the existing tunnel.
[0012]
The exposed lining body is used as the other side wall surface, and the excavated wall surface on one side of the widening tunnel portion facing the other side wall surface is laid by spraying concrete or the like. A wall part made of sprayed concrete or the like is constructed on the excavation wall between the upper ends of the exposed lining body, and the widening tunnel part and the existing tunnel are connected by the wall part and the lining part exposed to the widening tunnel. Forming partition walls.
[0013]
At this time, the lower end of the wall portion is connected to and supported by the outer peripheral surface of the upper end of the exposed side of the lining body, and the existing tunnel lining body is provided with the existing tunnel below the supporting portion. Either a reinforced body of the lining is applied and the earth pressure or the like applied to the wall portion is supported by the reinforced body through the lining of the existing tunnel, or the upper end of the reinforcing body is covered with the lining of the existing tunnel. It is desirable to penetrate the upper end of one side of the body and to support the lower end of the wall at the upper end surface. In this case as well, despite the construction of the reinforcing member in one side of the existing tunnel, the traffic of the vehicle in the existing tunnel is not obstructed.
[0014]
Next, the ground on the upper peripheral side of the existing tunnel lining body is excavated while leaving the partition wall. At this time, since the wall portion forming the upper portion of the partition wall is provided near the top end of the enlarged tunnel to be built, the ground excavation on the upper peripheral side of the existing tunnel lining body is performed. At times, the ground can prevent the ground around the top end of the enlarged tunnel from collapsing. Then, the above-mentioned lining body portion of the existing tunnel is dismantled and removed, and the ground on the upper peripheral side of the lining body is excavated. During this operation, the above-mentioned partition wall is left, and the widened tunnel section side partitioned by this partition wall is used as a vehicle passage.
[0015]
After the excavation work of the ground on the upper peripheral side in the lining body of the existing tunnel and the lining work on the digging wall surface, and the removal work of the lining body part of the existing tunnel are completed on the entire line or a predetermined length, the partition wall is removed. By removing it, an enlarged tunnel is built.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, T1 is an existing small-diameter tunnel provided with a two-lane traffic path, for example. In one side of the existing tunnel T1, a widened tunnel T2 having a traffic lane or sidewalk for one lane narrower than the cross-sectional width of the existing tunnel T1 is excavated and formed to form an enlarged tunnel T as shown in FIG. The method of building will be described. First, before excavating and forming the widened tunnel portion T2, the lining body t of the existing tunnel T1 is reinforced.
[0017]
In this reinforcing work, the support 1 made of H-shaped steel curved in an arch shape along the inner peripheral surface of the lining body t is erected at predetermined intervals in the length direction of the existing tunnel T1, and the adjacent support After stretching a wire mesh (not shown) between the first and the first and performing a chemical solution injection process on the back surface of the lining of the existing tunnel T1, excluding the one side of the lining body t on the side where the widening tunnel portion T2 is excavated. In the lining body t, the rock bolts 2, 2,... Are radially driven from the existing tunnel T1 into the surrounding ground of the lining body t, and the surrounding ground of the lining body t is formed as described later. When excavating, the surrounding ground is prevented from collapsing in advance.
[0018]
Further, in one side of the existing tunnel T1, a reinforcing vertical frame member 3 made of H-shaped steel and serving as a formwork is formed between the upper part of the inner peripheral surface of one side of the lining body t and one side of the floor surface. It is erected at an integral interval in the length direction of T1, and its upper and lower ends are fixed to the upper part of the inner peripheral surface of one side of the lining body t and one side of the floor, respectively, and the adjacent reinforcing vertical frame members 3, 3 The sheet pile 4 is inserted between the molds to form a formwork, and concrete 5 is poured into a space surrounded by the formwork and the inner peripheral surface of one side of the lining body t of the existing tunnel T1, filled and cured. By doing so, a reinforcing body A that is integrated with one side of the lining body t on one side of the existing tunnel T1 and reinforced the one side is formed. The reinforcing member A is installed in one side of the existing tunnel T1 except for a passage width that does not hinder the traffic of the vehicle in the existing tunnel T1. Also, the construction work of the reinforcement body A and the reinforcement work of the lining body t by driving the lock bolts 2, 2,... Are performed by temporarily closing the vehicle at night. Is allowed to freely pass through the existing tunnel T1.
[0019]
On the other hand, as shown in FIG. 2, along the longitudinal direction of the existing tunnel T1, one section of the cross-sectional width of the existing tunnel T1 extends from the outer peripheral surface of one side of the lining body t of the existing tunnel T1 to the outside. A widened tunnel portion T2 having a width of about / 2 and having the inside as a traffic lane or a sidewalk for one lane is formed by excavation. In the excavation of the widened tunnel portion T2, first, the upper half of the surrounding ground on one side of the lining body t of the existing tunnel T1 is excavated.
[0020]
At this time, the height of the upper end of the upper half, that is, the height of the upper end B of the widened tunnel portion T2 to be formed is higher than the top end of the lining body t, and Excavation is performed so that the part B is located above one side of the lining body t of the existing tunnel T1, and from the upper end B to the upper end of one side of the lining body t with respect to the existing tunnel T1. Excavation is performed so as to form an inclined excavation wall surface B1 that is inclined diagonally downward, while excavation is performed so as to form an excavation wall surface B2 that is curved in an arc shape from the upper end portion B outward and downward. Further, when the lower end of the inclined excavation wall B1 is excavated until reaching the upper end of one side of the lining body t of the existing tunnel T1, the existing tunnel is exposed while exposing the upper part of the outer peripheral surface of one side of the lining body t. The lower part of the upper half of T1 is excavated and formed to the position shown by the imaginary line D in FIG.
[0021]
Therefore, the cross-sectional shape of the upper part in the upper half portion of the widening tunnel portion T2 is gradually increased from the upper end portion B downward, and is formed as if the cross-sectional shape is equal to the cross-sectional shape of the tip of the bamboo shoot. After the upper outer peripheral surface of the side portion is exposed, the excavation is performed such that the width between the exposed surface and the one sided arc-shaped excavation wall surface B2 is slightly widened downward, or substantially equal. Excavate with width.
[0022]
When the upper half of the widened tunnel portion T2 reaching the imaginary line D from the upper end portion B is excavated in this way, concrete is sprayed on the excavated wall surfaces B1 and B2 to form a primary sprayed concrete layer 6, and then these excavated wall surfaces are formed. Steel supports 7a and 7b made of H-section steel are erected at predetermined intervals in the length direction of the tunnel in B1 and B2, respectively. At this time, the upper end of the steel support 7a built on the inclined excavation wall B1 is integrally connected to the upper end of the steel support 7b installed on the arc-shaped excavation wall B2, and the lower end is widened. The tunnel part T2 is connected to and supported on the exposed upper end of one side of the lining body t.
[0023]
Further, after the steel supports 7a, 7b are erected, a secondary sprayed concrete layer 8 is provided, and lock bolts 2a, 2b are driven at predetermined intervals in the length direction of the steel supports 7a, 7b. Thereby, the lining wall portions 9A and 9B which prevent the ground from collapsing from the excavation wall surfaces B1 and B2 are formed, respectively.
[0024]
FIG. 3 is an enlarged cross-sectional view of a lining body t portion of the existing tunnel T1 supporting the lining wall portion 9A on the side of the inclined excavation wall surface B1, and the reinforcing body built in one side of the existing tunnel T1. A notch step 10 is formed at the upper end of the exposed side of the existing tunnel lining body t above the upper end of A, and the notch step 10 is provided with the lower end plate 7a 'of the steel support 7a. The end plate 7a 'is fixed to and supported by the notch step 10 with an anchor bolt and a nut 11, and the exposed upper end of one side of the existing tunnel lining body t reinforced by the reinforcing body A In addition, the ground on the upper end side of the widened tunnel portion T2 is supported via a lining wall portion 9A having the steel support 7a to prevent collapse of the ground. Then, an enlarged tunnel T, which will be described later, is constructed by the lining wall 9A and one side of the existing tunnel lining t which is reinforced by the reinforcing member A and supports the lining wall 9A. In this case, a partition wall E for the widened tunnel portion T2 is formed.
[0025]
Next, in the widening tunnel portion T2, the lower half of the widening tunnel portion T2 from the imaginary line D to the bottom is excavated. In this excavation, on one side of the lining body t of the existing tunnel T1, the digging is performed to the lower end while exposing the lower outer peripheral surface of the lining body t on the one side, and the digging wall B2 side curved in an arc shape. In this case, digging is performed by extending the digging wall B2 downward with the width of the upper half portion or while gradually increasing the width.
[0026]
Thereafter, as shown in FIG. 2, concrete is sprayed on the excavated wall surface B 2 ′ curved in an arc shape in the lower half portion, that is, on one excavated wall surface of the widened tunnel portion T 2, so that the lower end of the primary sprayed concrete layer 6 is formed. After forming the continuous primary sprayed concrete layer 6 ', a steel support 7b' made of a continuous H-section steel is erected from the upper half-side steel support 7b at predetermined intervals in the length direction of the tunnel. Then, a continuous secondary sprayed concrete layer 8 'is provided at the lower end of the secondary sprayed concrete layer 8 on the upper half side, and the length direction of the steel support 7b' (the arc length direction of the excavated wall surface B2 '). The lining wall 9B '(which is continuous with the lower end of the lining wall 9A) is provided with the lock bolts 2b at predetermined intervals to prevent the ground from collapsing from the excavation wall B2'. Form That.
[0027]
When the excavation of the widened tunnel portion T2 and the formation of the lining wall portions 9A and 9B that reinforce the excavation wall surfaces B1 and B2 are completed as shown in FIG. 4, one side of the lining body t of the existing tunnel T1 as shown in FIG. Along the portion, inside the widened tunnel portion T2, an upper end is continuous with the upper end portion B, and a lower end is provided with a vertical protective wall 12 fixed to the other end portion of the bottom surface of the widened tunnel portion T2. The temporary pavement 13 is constructed on the bottom surface of the widened tunnel portion T2 excavated so as to be substantially flush, and the waterproof sheet 14 is stretched on the inner surfaces of the lining wall portions 9B and 9B 'curved in an arc shape. . The protective wall 12 is provided so as to cover one side of the lining body t of the existing tunnel T1 facing the widened tunnel portion T2 so that the vehicle can travel in the widened tunnel portion T2 more safely. A guardrail 15 is erected in the length direction of the tunnel along the lower lining wall portion 9B 'of the widened tunnel portion T2 with a width of one lane from the protective wall 12.
[0028]
Thus, after the vehicle is allowed to pass alternately in the widened tunnel portion T2, the lane is changed from the existing tunnel T1 to the widened tunnel portion T2, and the excavation work on the existing tunnel T1 side is started. As shown in FIG. 5, this excavation work is performed while leaving a partition wall E composed of one side lining body part of the existing tunnel T1 reinforced by the reinforcing body A and the lining wall part 9A. The removal is performed by removing the lining body t of the tunnel T1 and excavating the ground on the upper peripheral side of the lining body t of the existing tunnel T1 partitioned by the lining wall portion 9A of the partition wall E.
[0029]
That is, from inside the existing tunnel T1, the lining body t other than one side of the existing tunnel T1 is crushed and removed after disassembly of the support 1 to expose the ground on the upper peripheral side of the lining body. Using an appropriate excavating machine, the excavated wall surface t2 of the excavated wall surface t1 is formed from the upper end of the one-side excavated wall surface B2 curved in an arc shape of the widening tunnel portion T2 with substantially the same degree of curvature as the excavated wall surface B2. Is excavated so as to extend toward the other side of the lining body t, and the excavated wall surface T1 is connected to the lower end of the other side of the lining body t.
[0030]
Specifically, the lining wall portion 9A forming the upper portion of the partition wall E has the largest vertical excavation width, and the lining of the existing tunnel T1 already removed from the lining wall portion 9B side. Excavation in an arc shape so that the vertical excavation width between the lining body t and the lining body t of the existing tunnel T1 is gradually reduced toward the other side of the lining body t along the upper peripheral part of the existing tunnel T1. Then, a space portion C in which the existing tunnel T1 is enlarged is formed. At the time of removing the lining body t of the existing tunnel T1 and excavating the ground, the rock bolt 2 existing in the ground to be excavated is cut off.
[0031]
In this way, after removing the lining body t of the existing tunnel T1 and excavating the ground on the upper peripheral side to form the enlarged space C, the primary spraying is performed on the excavated wall surface t1 curved in an arc shape of the enlarged space C. The concrete layer 16 is constructed, and then one end is connected to the upper end of each steel support 7b which is erected at predetermined intervals in the length direction of the tunnel on one side excavation wall B2 of the widened tunnel portion T2. Supports 7c, also made of H-section steel, are sequentially built on the excavated wall surface t1, and then a secondary sprayed concrete layer 17 is applied to the excavated wall surface t1 to form the lining wall surface 18.
[0032]
Next, after separating and removing the partition wall E including one side portion of the existing tunnel lining body t reinforced by the reinforcing member A and the wall portion 9A, the temporary pavement 13 of the widening tunnel portion T2 is provided on the bottom surface. A temporary pavement 19 is formed so as to be flush, and a waterproof sheet 14 'is stretched on the excavated wall surface t1 so as to be continuous with the waterproof sheet 14 stretched on the arc-shaped excavated wall surface B2 of the widened tunnel portion T2. In this state, vehicles are allowed to pass in the enlarged tunnel portion obtained by enlarging the existing tunnel T1 partitioned by the widened tunnel portion T2 and the protective wall 12, and lanes are inserted from the widened tunnel portion T2 side into the enlarged tunnel portion. Make changes.
[0033]
Thereafter, as shown in FIG. 6, the protection wall 12 is dismantled and removed from the widening tunnel portion T2 side to form the widening tunnel T, and the waterproof sheet stretched on the excavation wall surface B2 on the widening tunnel portion T2 side. 14 and the waterproof sheet 14 'stretched on the excavation wall surface t1 on the side of the enlarged tunnel portion T', the lane position in the enlarged tunnel T is changed, and the like. The construction of the enlarged tunnel T is completed by performing interior equipment work and the like.
[0034]
In the above-described embodiment, when the widened tunnel portion T2 is excavated and formed on one side of the existing tunnel T1, construction is performed from the upper end portion B toward the upper end of one side of the lining body t of the existing tunnel T1. The lower end of the lining wall 9A is connected to and supported by the upper end of one side of the lining t as shown in FIG. 3, but as shown in FIG. The upper end of the reinforcing vertical frame member 3 in the reinforcing body A formed in one side is made to penetrate through the upper end of one side of the lining body t and protrudes outward from the lining body t. The steel support 7a in the lining wall portion 9A may have a lower end face abutting against each other and be integrally connected by bolts 20.
[0035]
In the above embodiment, the reinforcing member A of the existing tunnel lining body t is composed of the reinforcing vertical frame member 3 and the concrete 5, but the reinforcing member of the existing tunnel lining body t of the present invention is However, the present invention is not limited to this. For example, the reinforcing vertical frame member 3 alone or the concrete 5 alone may be used.
[0036]
【The invention's effect】
As described above, according to the method for constructing an enlarged tunnel of the present invention, as described in claim 1, a method of constructing an arch-shaped enlarged tunnel by widening an existing tunnel covered with a lining body. A widening of a predetermined width that exposes an outer peripheral surface of one side of the lining of the existing tunnel along one side of the existing tunnel and has a height higher than an upper end of the one side of the exposed lining; A first step of excavating the tunnel, a second step of constructing a wall between the top of the widened tunnel and an upper end of one side of the exposed lining, and a step of excavating the wall and the widened tunnel Excavating the ground on the upper peripheral side of the lining body while leaving the partition wall formed by the lining body part exposed to the outside, and removing the wall part of the existing tunnel other than the partition wall; And the fourth step of removing the partition wall. When the wide tunnel is excavated, the existing tunnel can be used as a traffic path for the vehicle, and after the wide tunnel is formed, when the existing tunnel is expanded, the wide tunnel is used as a traffic path for the vehicle. Therefore, the construction of the enlarged tunnel can be efficiently performed without completely blocking or bypassing the traffic of the vehicle, and the construction period can be shortened.
[0037]
Furthermore, since most of the excavated wall surface on the existing tunnel side in the widened tunnel portion is formed by the outer peripheral surface of one side of the exposed lining body of the existing tunnel, ground collapsing prevention processing for the excavated wall surface is omitted. The excavation wall between the top end of the widening tunnel and the upper end of one side of the exposed lining in the existing tunnel can be reduced while reducing the construction cost and improving the work efficiency. Since the wall portion is constructed, the wall portion can be firmly supported on the lining side of the widening tunnel portion, and the excavated wall surface on which the wall portion is provided is the exposed lining portion in the existing tunnel. Because it is located above one side of the tunnel, it can be provided at the center in the width direction of the enlarged tunnel where the wall is to be built, that is, at the top end. When construction of the tunnel, it is possible to prevent the collapse of the ground and securely support the ground around the top end by the wall portion.
[0038]
Also, when excavating the ground above the existing tunnel, the exposed side of the wall and the lining of the existing tunnel are used as a partition wall for the widened tunnel and the inside of the widened tunnel is used. Enlarged excavation work can be performed without hindering the passage of vehicles. The widened tunnel is a narrow lane for one lane or sidewalk, and this tunnel is connected to one side of the existing tunnel. It is possible to provide a suitable method by which an enlarged tunnel can be built by providing the part in a part.
[0039]
In such an enlarged tunnel construction method, the invention according to claim 2 is characterized in that when the wall is constructed between the top of the widened tunnel and the upper end of one side of the exposed lining, Since the lower end of the portion is connected to and supported by the upper end of the exposed one side of the lining, one side of the lining is used as a support for the wall, and the widening tunnel is used together with the wall as described above. It is possible to form a partition wall for the tunnel side, and to reliably support the ground around the top end when excavating the enlarged tunnel to one side of the lining of the existing tunnel via the wall. . Further, the reinforcing member of the existing tunnel lining body is constructed on one inner peripheral surface side of the existing tunnel lining body below the supporting portion, leaving a space where vehicles can pass in the existing tunnel lining body. The supporting force of the body portion is further increased, and the collapse of the ground around the top end during excavation of the enlarged tunnel through the wall portion can be reliably prevented.
[0040]
On the other hand, according to the invention according to claim 3, when the wall is constructed between the upper end of the widened tunnel and the upper end of one side of the exposed lining, the lower part of the lower end of the wall is constructed. In one side of the existing tunnel lining, a reinforcing body of the above-mentioned existing tunnel lining is constructed while leaving a space where vehicles can pass in the existing tunnel, and an upper end of the reinforcing body is attached to the existing tunnel lining. Of the wall is integrally connected to the lower end of the wall, so that the reinforcing member serves as a partition member for the vehicle passage side in the existing tunnel and is used as a support member for firmly supporting the wall. This makes it possible to form a stable and stable support structure for the excavated wall surface via the wall portion.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional front view showing a state in which a reinforcing wall is being constructed in one side of an existing tunnel;
FIG. 2 is a longitudinal sectional front view showing a state in which a widening tunnel is excavated along one side of an existing tunnel;
FIG. 3 is an enlarged vertical sectional front view of a part of an existing tunnel showing a support structure of a lining wall portion;
FIG. 4 is a longitudinal sectional front view showing a state in which a protective wall and the like are constructed in the widening tunnel,
FIG. 5 is a longitudinal sectional front view showing a state in which an existing tunnel is enlarged to form an enlarged tunnel;
FIG. 6 is a longitudinal front view of the enlarged tunnel,
FIG. 7 is a partially enlarged longitudinal sectional front view showing another form of the support structure of the lining wall.
[Explanation of symbols]
T Expanding tunnel T1 Existing tunnel t Lining body T2 Widening tunnel part A Reinforcement wall part B Excavation top end of widening tunnel part E Reinforcement body 9A of existing tunnel lining body Lining wall part 1 Supporting 2 Lock bolt 3 Reinforcement Vertical frame material 7 Steel support 12 Protective wall

Claims

A method for widening an existing tunnel covered with a lining body to build an arch-shaped enlarged tunnel, wherein the outer peripheral surface of one side of the lining body of the existing tunnel along one side of the existing tunnel A first step of excavating a widened tunnel portion having a predetermined width whose height is higher than the upper end of one side of the exposed lining body, and exposing the upper end portion of the widening tunnel portion and the exposed lining body A second step of constructing a wall between the upper ends of one side, and leaving a partition wall formed by the wall and the above-mentioned lining exposed to the widening tunnel; A method for constructing an enlarged tunnel, comprising: a third step of excavating ground on a peripheral side and removing a wall portion of an existing tunnel other than the partition wall; and a fourth step of removing a partition wall.

In the second step of constructing the wall between the upper end of the widening tunnel and the upper end of one side of the exposed lining in the existing tunnel, the lower end of the wall is exposed to the exposed lining. Before the third step, a space through which vehicles can pass in the existing tunnel is provided on one inner peripheral surface side of the existing tunnel lining body below the above-mentioned support portion, while being connected to and supported by the upper end of the side portion. The method for constructing an enlarged tunnel according to claim 1, wherein a reinforcing body of the existing tunnel lining body is constructed by using the reinforcing member.

Before the second step of constructing the wall between the upper end of the widening tunnel and the upper end of one side of the exposed lining in the existing tunnel, the existing tunnel lining below the lower end of the wall is In one side of the body, a reinforcement of the existing tunnel lining body is installed leaving a space where vehicles can pass in the existing tunnel, and the upper end of this reinforcement body penetrates through one side of the existing tunnel lining body 2. The method according to claim 1, wherein, in the second step, the upper end of the reinforcing member is integrally connected to the lower end of the wall.