【作者】 曹奕；

【导师】 谢康和； 朱向荣； 蒋军；

【作者基本信息】 浙江大学 ， 岩土工程， 2014， 博士

【摘要】 目前对软土盾构隧道的研究主要集中于开挖造成的短期地表及隧道沉降、施工扰动,及盾构开挖对隧道支护内力的影响。然而对已建成地铁盾构隧道的现场监测表明：软土地铁盾构隧道的长期沉降量很大,达到沉降稳定状态所需的时间亦十分漫长,且沉降在隧道纵向呈现出很大的不均匀性。地铁隧道长期沉降的影响因素十分复杂,其中初始超孔隙水压力分布、隧道衬砌和周边土体的相对渗透性等对地铁长期沉降造成的影响尤为显著。对于埋置于深厚软土地区的地铁隧道而言,列车荷载的长期作用会引起隧道周边饱和软土应力、应变和孔隙水压力变化,导致土的刚度降低、强度衰减、变形加剧。本文采用解析方法,结合已有工程实测数据,对渗漏隧道周边土体长期非线性固结过程中稳定渗流状态、超孔隙水压力消散、地表沉降等问题展开研究,主要创新工作如下：1.采用经典的e-lgσ’和e-lg k经验公式模拟土体非线性固结过程中体积压缩性和渗透性的变化,根据土体自由应变和连续性条件得到了土体非线性固结控制方程。2.将隧道衬砌透水条件理想化为完全透水及完全不透水极端边界条件,从而得到了隧道作为一个排水边界时,对土体非线性固结过程中超孔压消散、固结度增长、地面沉降发展影响的上下限。并进一步采用Li(1999)提出的半渗透边界条件将存在局部渗漏通道的隧道衬砌等效为均质透水体,建立局部渗漏边界条件,求解隧道周边土体的非线性固结本构方程,得出了不同程度的衬砌局部渗漏条件下的隧道周边软土非线性固结解析解。进而对衬砌不同程度渗漏对隧道周边土体长期固结、超孔隙水压力压力消散、长期沉降的影响进行了分析。3.通过将列车荷载等效为矩形循环荷载,求得了列车荷载作用下理想化渗漏隧道周边土体非线性固结解析解。通过等效矩形循环荷载参数的调整,分析了列车荷载对土体固结、地表沉降的影响规律,以及列车荷载与衬砌渗漏情况的耦合作用。4.采用Merchant三元件模型模拟土体长期变形的粘弹性,建立隧道周边土体粘弹性流变固结控制方程,并引入e-lg k关系考虑土体渗透性在固结过程中的非线性变化,并采用迭代递推的办法获得了列车荷载作用下局部渗漏隧道周边土体的长期沉降解析解。5.以上海地铁1号线和2号线为工程背景,通过本文得到的解析解预测值和上海地铁三个测点实测沉降数据的对比验证了本文非线性固结解析解以及粘弹性流变固结解析解的合理性。更多还原

【Abstract】 Many theoretical and field studies have been performed on tunneling induced response of surrounding soil and interaction of soil-structure, yet most of these studies are concerned with short-term response by tunnel construction. However, many field measurements comfirmed that long-term deformation of surrounding soft soil of shield tunnels could be very large and last for a long time after construction, and the longitudinal settlement of shield tunnel is uneven. In the various factors that affect the long-term settlement of metro tunnel, the initial excess pore pressure induced by tunneling, partially sealed lining, and relative permeability of soil-lining are more significant. Meanwhile, for shield tunnel buried in deep soft soil, train loading during long-term operation after construction could induce the variation of stress, strain, and pore pressure, leading to reduction of soil stiffness, enlarging of soil deformation. In this dissertation, steady seepage state, dissipation of excess pore pressure, and land subsidence of soil around shield tunnel are systematically studied by both analytical method and field study. The main original work of this dissertation includes:1. The empirical e-lg σ’ and e-lg k relation are introduced to simulate nonlinear behavior of soil during long-term consolidation. Then based on the free strain assumption and continuity equation, the governing equation of two-dimensional nonlinear consolidation of soil around shield tunnel is derived.2. The linings of shield tunnel are idealized as completely permeable or completely impermeable, which represents the upper and lower limits of the induced soil consolidation behavior. Then the partial sealed linings of tunnel are idealized as a homogeneous body by introducing a relative parameter of soil-lining permeability κ which is first proposed by Li(1999). The analytical solutions of governing equation of nonlinear consolidation are derived by introducing the partially permeable condition κ to discuss the influence on soil consolidation, dissipation of excess pore pressure, and long-term consolidation settlement.3. The train loading is simplified as equivalent rectangular cyclic loading q to obtain the analytical solution of nonlinear consolidation of soil around shield tunnel with both idealized sealed linings and partially sealed linings. By the adjusting of equivalent rectangular cyclic loading and relative parameter of soil-lining permeability, the influence of train loading and coupled effects of both partially sealed lining and train loading on soil consolidation, ground settlement, and settlement rate are discussed.4. Merchant model is employed to simulate the visco-elastic deformation of soil, and the governing equation of consolidation of visco-elastic soil around shield tunnel with partially sealed linings is established. Then a recursive method is used to introduce e-lg k relation to consider the variation of soil permeability during consolidation. The analytical solution of long-term ground settlement of shield tunnel in creep soil under train loading is obtained.5. Three case studies from Shanghai metro line No.l and No.2are simulated to investigate the behavior of nonlinear consolidation of soil around shield tunnel. The rationality of analytical solutions of nonlinear consolidation and visco-elastic model are verified by the comparison between predicted and observed long-term settlements。更多还原