双层车站密贴下穿既有隧道案例分析及隧道沉降变形特征
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摘要
长春地铁1号线卫星广场站下穿轻轨3号线工程中,下穿段负一层顶板与轻轨隧道底板密贴接触,形成"叠合板结构"。施工中,先注浆加固下穿段土体,然后采用六导洞PBA法配合千斤顶顶升支撑修建下穿段,具体方法为:于1~#+4~#导洞冠梁上布置液压千斤顶,对上层板形成两端临时支撑;再于3~#+5~#、2~#+4~#导洞内各施作一组钢管混凝土立柱及纵梁,对下层板形成永久支撑,纵梁兼做负一层顶板。然后逐步移除千斤顶、拆除导洞初支、浇筑负一层顶板,实现上下层板密贴;最后修建剩余下穿段结构。为评估施工对轻轨隧道的影响,建立数值模型验算轻轨隧道底板弯矩,结果为安全;数值结果表明,底板沉降经历了先下沉、后抬升、再下沉的复杂过程,最终沉降曲线为单凹槽状。实测数据表明:沉降曲线可划分为振荡型、掉落型两种;曲线类型与测点位置有很大关系,震荡型曲线测点位于下穿段两端,掉落型曲线测点位于下穿段中部,分别受千斤顶、5~#及6~#导洞开挖控制;底板中线最终沉降为单凹槽状,最大沉降量与数值结果相符;变形缝差异沉降在千斤顶作用下一直处于可控状态。
The construction of new subway stations under the existing subway tunnels has high risks and strict requirements for settlement control. The ceiling of Satellite Square station, which belongs to Changchun metro line No.1, contacts tunnel baseplate of light rail line No.3 directly. There is no soil layer between the upper tunnel and lower station, under such circumstances it is described as dual-layer formation. The engineering approach is introduced in this paper. Soil was reinforced firstly by grouting before any excavation, then ten hydraulic jacks were arranged in pilot tunnels No.1 & No.4 right beneath baseplate of upper tunnel to mitigate adverse settlement. Then two groups of concrete-filled tubes, together with longitudinal beams, were forged in pilot tunnels No.3 & No.5 and pilot tunnels No.2 & No.4 as permanent supporting. As soon as these tubes were operative, hydraulic jacks and preliminary supports of pilot tunnels were removed orderly while ceiling of station was cast piece by piece, and the rest of station was cast conventionally at last. In the second part, bearing capacity and settlement of upper tunnel are discussed by numerical simulation. It shows that the maximum bending moment on the baseplate of upper tunnel is allowable, and the settlement on central of baseplate is variable from w-shaped to v-shaped. Analysis of filed monitoring about this case is introduced in the third part, the settlement curves fall into two distinctive categories and highly depend on physical positions of monitoring points. The observed settlements on central of baseplate are consistent to numerical results both in maximum value and overall profile. Due to effective control of hydraulic jacks, the differential settlements on movement joints are also manageable.
The construction of new subway stations under the existing subway tunnels has high risks and strict requirements for settlement control. The ceiling of Satellite Square station, which belongs to Changchun metro line No.1, contacts tunnel baseplate of light rail line No.3 directly. There is no soil layer between the upper tunnel and lower station, under such circumstances it is described as dual-layer formation. The engineering approach is introduced in this paper. Soil was reinforced firstly by grouting before any excavation, then ten hydraulic jacks were arranged in pilot tunnels No.1 & No.4 right beneath baseplate of upper tunnel to mitigate adverse settlement. Then two groups of concrete-filled tubes, together with longitudinal beams, were forged in pilot tunnels No.3 & No.5 and pilot tunnels No.2 & No.4 as permanent supporting. As soon as these tubes were operative, hydraulic jacks and preliminary supports of pilot tunnels were removed orderly while ceiling of station was cast piece by piece, and the rest of station was cast conventionally at last. In the second part, bearing capacity and settlement of upper tunnel are discussed by numerical simulation. It shows that the maximum bending moment on the baseplate of upper tunnel is allowable, and the settlement on central of baseplate is variable from w-shaped to v-shaped. Analysis of filed monitoring about this case is introduced in the third part, the settlement curves fall into two distinctive categories and highly depend on physical positions of monitoring points. The observed settlements on central of baseplate are consistent to numerical results both in maximum value and overall profile. Due to effective control of hydraulic jacks, the differential settlements on movement joints are also manageable.
引文
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[13]张成平,张顶立,骆建军,等.地铁车站下穿既有线隧道施工中的远程监测系统[J].岩土力学,2009,30(6):1861-1866.ZHANG Cheng-ping,ZHANG Ding-li,LUO Jian-jun,et al.Remote monitoring system applied to the construction of metro station undercrossing existing metro tunnel[J].Rock and Soil Mechanics,2009,30(6):1861-1866.
[14]张晓丽,张顶立,王梦恕.既有地铁注浆抬升合理位置的确定[J].岩土工程学报,2008,30(5):712-717.ZHANG Xiao-li,ZHANG Ding-li,WANG Meng-shu.Determination of proper position of grouting during lifting the existing subway[J].Chinese Journal of Geotechnical Engineering,2008,30(5):712-717.
[2]李倩倩,张顶立,房倩,等.浅埋暗挖法下穿既有盾构隧道的变形特性分析[J].岩石力学与工程学报,2014,33(增刊2):3911-3918.LI Qian-qian,ZHANG Ding-li,FANG Qian,et al.Study of deformation characteristics of tunnels traversing adjacently under shield tunnels by shallow tunneling method[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(Suppl.2):3911-3918.
[3]ZHANG Z,HUANG M.Geotechnical influence on existing subway tunnels induced by multiline tunneling in Shanghai soft soil[J].Computers&Geotechnics,2014,56(03):121-132.
[4]张旭,张成平,韩凯航,等.隧道下穿既有地铁车站施工结构沉降控制案例研究[J].岩土工程学报,2017,39(4):759-766.ZHANG Xu,ZHANG Cheng-ping,HAN Kai-hang,et al.Case study on control technology of structural settlements due to tunnelling beneath a subway station[J].Chinese Journal of Geotechnical Engineering,2017,39(4):759-766.
[5]王剑晨,张顶立,张成平,等.浅埋暗挖隧道近距施工引起的上覆地铁结构变形分析[J].岩石力学与工程学报,2014,33(1):90-97.WANG Jian-chen,ZHANG Ding-li,ZHANG Cheng-ping,et al.Analysis of structural deformation of overlying subway station induced by approaching tunnel excavation in shallow depth[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(1):90-97.
[6]刘蕾,尹亚坡.北京地铁四号线宣武门站下穿运营车站沉降控制综合施工技术[J].隧道建设,2009,29(1):112-119.LIU Lei,YIN Ya-po.Comprehensive construction techniques for settlement control of Xuanwumen metro station crossing underneath existing metro station on No.4line of Beijing metro[J].Tunnel Construction,2009,29(1):112-119.
[7]陶连金,安军海,边金,等.密贴下穿地下工程施工新工艺“CRD+多重预顶撑”研究[J].湖南大学学报(自然科学版),2015,42(1):97-103.TAO Lian-jin,AN Jun-hai,BIAN Jin,et al.Study on new technology of CRD+top-bracing applied in closely-attached intersecting underground structures[J].Journal of Hunan University(Natural Science),2015,42(1):97-103.
[8]PARK Y H,KIM J P,CHO K H.Stability analysis of subway box structure supported by modified underpinning method[J].Tunnelling&Underground Space Technology Incorporating Trenchless Technology Research,2015,50(4):199-208.
[9]LI X,ZHANG C,YUAN D.An in-tunnel jacking above tunnel protection methodology for excavating a tunnel under a tunnel in service[J].Tunnelling&Underground Space Technology,2013,34(1):22-37.
[10]陈孟乔,杨广武.新建地铁车站近距离穿越既有地铁隧道的变形控制[J].中国铁道科学,2011,32(4):53-59.CHEN Meng-qiao,YANG Guang-wu.Deformation control of a newly-built subway station crossing the adjacent existing subway tunnel[J].China Railway Science,2011,32(4):53-59.
[11]沈良帅,贺少辉.复杂环境条件上跨下穿同一既有地铁隧道的变形控制分析及施工方案优化[J].岩石力学与工程学报,2008,27(增刊1):2893-2900.SHEN Liang-shuai,HE Shao-hui.Subsidence controlling and construction scheme optimization of cutting across and underpassing an existing metro tunnel under complex environmental conditions[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(Suppl.1):2893-2900.
[12]王占生,张顶立.浅埋暗挖隧道近距下穿既有地铁的关键技术[J].岩石力学与工程学报,2007,26(增刊2):4208-4214.WANG Zhan-sheng,ZHANG Ding-li.Key techniques on shallow embedded tunnel constructed beneath existing subway tunnel[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(Suppl.2):4208-4214.
[13]张成平,张顶立,骆建军,等.地铁车站下穿既有线隧道施工中的远程监测系统[J].岩土力学,2009,30(6):1861-1866.ZHANG Cheng-ping,ZHANG Ding-li,LUO Jian-jun,et al.Remote monitoring system applied to the construction of metro station undercrossing existing metro tunnel[J].Rock and Soil Mechanics,2009,30(6):1861-1866.
[14]张晓丽,张顶立,王梦恕.既有地铁注浆抬升合理位置的确定[J].岩土工程学报,2008,30(5):712-717.ZHANG Xiao-li,ZHANG Ding-li,WANG Meng-shu.Determination of proper position of grouting during lifting the existing subway[J].Chinese Journal of Geotechnical Engineering,2008,30(5):712-717.