【正文】 Overview Guangzhou Metro Line Road station turnback line of sports for sports Road station after the return line, structure plex, DK3 ~ varying crosssection set the doublearch structure, threearch structure of tunnels. Ranging from crossarch tunnel excavation span , excavation height of , crossvector ratio of 1:, after lining a hole span , large holes, after lining span , the wall thickness of m. Three doublearch tunnel excavation span , excavation height of , crossvector ratio of 1:. Arch tunnel section of rock from top to bottom are: artificial fill soil, red alluvial sand, alluvial alluvial soil, river and lake facies soil, plasticlike residual soil, hard plastic a hardlike residual soil, all weathered rock, strong weathering rock, the weathered layer and the breeze layer. Tunnel through the rock strata are more homogeneous, the intensity high, carrying ability, good stability. Thickness of the tunnel vault covering ~ 18m, of which grade Ⅳ Wai rock vault thickness ~ . Doublearch tunnel segment groundwater table is ~ , mainly Quaternary pore water and fissure water. Section 2 dualarch construction scheme parison As the doublearch tunnel segment structure more plex, the tunnel crosssection changes in large, plicated construction process, construction was very difficult, the construction cycle is long, so I chose a good quality and efficient pletion of the construction program segment arch tunnel construction is particularly important. Selection of a construction program, the main consideration the following aspects: (1) construction safety and structural safety。s main construction steps and measures are as follows: (1) The right line of doublearch tunnel hole within the return line side of temporary construction access, dualarch and the threearch in the wall construction, is pleted in a timely support for the wall, the construction to prevent bias. (2) construction of the wall lining is pleted, according to first small then big, closed into a ring principle, the right line with the step method of construction, with CRD engineering method returned a fourlane span tunnel construction. (3) When the return line side of the construction to the threearch tunnel in the wall, then in accordance with the right line of the wall construction method and the threearcharch in the wall construction, during which the right line to stop excavation until the pletion of construction of the wall. (4) The return line side of the wall construction is pleted, the right line to continue to move forward the construction. The construction method for the domestic doublearch tunnel of conventional construction method, Guangzhou Metro, Nanjing and Beijing Metro subway both applications, and can secure successful pletion of the construction of tunnels. However, examples of past engineering and construction Technology research can be found, the program has weaknesses and shortings. (1) The program used in this project, in a short span of of doublearch tunnel, the tunnel39。在廣州地鐵施工中首次提出了將連拱隧道改為單洞隧道施工技術(shù)，并對(duì)單一式中墻和分離式中墻結(jié)構(gòu)的技術(shù)方案進(jìn)行了比選，得出了滿足結(jié)構(gòu)安全、施工安全和經(jīng)濟(jì)效益較好的技術(shù)方案，可為今后類似工程的設(shè)計(jì)和施工提供借鑒和參考。 1 工程概況 廣州地鐵三號(hào)線體育西路站折返線為體育西路站站后折返線，結(jié)構(gòu)形式復(fù)雜，在 DK3+~+ 段設(shè)置了不等跨雙連拱結(jié)構(gòu)、三連拱結(jié)構(gòu)等隧道群。隧道通過地層巖質(zhì)較為均一，強(qiáng)度較高，承載能力強(qiáng)，穩(wěn)定性好。選擇施工方案時(shí)主要考慮以下幾個(gè)方面： (1)施工安全和結(jié)構(gòu)安全； (2)施工難度；(3)施工周期； (4)經(jīng)濟(jì)效益。 (3)當(dāng) 折返線側(cè)施工到三連拱隧道中墻后，再按照右線中墻施工方法進(jìn)行三連拱和雙連拱中墻施工，這期間右線停止掘進(jìn)，直到中墻施工完成。 (1)本方案運(yùn)用于本工程上，在短短的 的連拱隧道內(nèi)，隧道的初期支護(hù)和二次襯砌間將轉(zhuǎn)換 4 次， 轉(zhuǎn)換過于頻繁。 (2)對(duì)三連拱隧道先不施作中墻襯砌 ,按單線工況通過。 (2)降低了施工難度，縮短了施工周期。 3 三連拱段施工方案 從右線直接進(jìn)入三連拱隧道，其支護(hù)參數(shù)以原設(shè)計(jì)進(jìn)行，格柵全環(huán)安設(shè)，按設(shè)計(jì)全環(huán)噴射混凝土，并加強(qiáng)中墻拱頂處的錨桿設(shè)置 (折返側(cè)同右線施工方法 )，在中墻施工時(shí)需要破除隧道 格柵接頭處設(shè)一縱向加強(qiáng)梁。中墻施工完成后對(duì)中墻空隙進(jìn)行回填，加千斤頂支護(hù)。 4 施工時(shí)結(jié)構(gòu)受力性 態(tài)分析 將不等跨雙連拱的中墻取消，改為分離式中墻，在國(guó)內(nèi)城市地下鐵道工程中尚未有類似工程設(shè)計(jì)及施工經(jīng)驗(yàn)，也沒有類似隧道結(jié)構(gòu)設(shè)計(jì)，因此結(jié)構(gòu)是否安全，以及施工過程中工序轉(zhuǎn)換時(shí)施工是否安全，將是本方案研究的重點(diǎn)。 5 施工關(guān)鍵技術(shù)及對(duì)應(yīng)措施 連拱隧道段的施工是需要在嚴(yán)密的施工組織和強(qiáng)有力的技術(shù)保證措施下進(jìn)行的 ， 組織好各施工步驟 ， 準(zhǔn)備好各種技術(shù)預(yù)防措施是施工成功的關(guān)鍵。 中墻夾巖柱體注漿加固 中墻巖體最薄處為 ,經(jīng)過多次爆破開挖過程的影響，中墻周圍的圍巖松動(dòng)，其承載力受影響。 微差微震爆破技 術(shù) 隧道開挖全部采用鉆爆法施工。 (3)每次爆破使用多段位雷管起爆，采用非電毫秒雷管不對(duì)稱起爆網(wǎng)路微震動(dòng)技術(shù)。 輔助剪刀撐加強(qiáng)支護(hù) 通過 ANSYS 模擬分析，為確保小斷面隧道施工安全，必須對(duì)小斷面隧道進(jìn)行輔助支撐加固，抵御爆破產(chǎn)生的瞬時(shí)沖擊和巖層開挖時(shí)荷載釋放產(chǎn)生的偏壓。通過施工證明，支撐的設(shè)置是必要和有效的，小斷面隧道在加設(shè)輔助剪刀撐后收斂?jī)H為5mm。本工程為今后類似的地下鐵道建設(shè)取得了成功的經(jīng)驗(yàn)和應(yīng)用實(shí)例。因此在雙連拱薄弱的中墻處控制好微差弱爆破將是施工取得成功的重點(diǎn)。從受力分析看，仰拱與側(cè)墻連接處受影響最大，確保了初期支護(hù)承受足量荷載；其次是加強(qiáng)對(duì)中夾巖柱體的注漿加固，對(duì)其采用對(duì)拉錨桿、加強(qiáng)錨桿和注漿加固 ,確保了圍巖的穩(wěn)