【作者】 童磊；

【导师】 谢康和；

【作者基本信息】 浙江大学 ， 岩土工程， 2010， 博士

【摘要】 在土体内部进行隧道施工,无论隧道埋深大小,其开挖会使开挖面周围土体因卸荷而发生变形,造成地表短期沉降；同时,对土体产生的扰动及新边界条件的形成导致应力场和渗流场重分布,土体重新固结及流变变形,引起整个地层的长期沉降。当沉降变形发展到一定程度,将影响地下管线等设施的正常使用,甚至危及地面建筑物的安全。因此,如何预测和控制隧道的地表沉降已成为工程界关心的重要问题。随着城市化进程的加快,地铁、市政管道等隧道工程的建设在我国蓬勃发展,而目前薄弱的理论研究还滞后于蓬勃发展的工程实践。本文从解析理论和数值分析两方面出发,结合已有的工程背景,对软土浅埋隧道工程中渗流、固结和沉降问题展开系统、深入的研究,以期为工程实践提供技术支撑。主要创新工作如下：1.通过将Sagaseta提出的通用地层变形方式,即考虑径向收缩、椭圆化变形和竖向位移独立影响下的隧道周边复杂位移边界条件引入Airy应力函数,推导了浅埋隧道周边土体变形计算公式,并提出适用于正常固结土的简化计算方法。在此基础上分析了隧道径向收缩、椭圆化变形和竖向位移对土体变形的影响及其规律,并通过与四个隧道工程实测数据的对比,对公式中各参数取值的合理性进行了探讨,同时给出了预估隧道沉降的推荐参数值。2.通过引入以隧道边界径向收缩、椭圆化变形和竖向位移表示的隧道周边复杂位移边界条件,并将该边界条件转化为映射后的复平面边界条件,利用复变函数解法,给出了盾构隧道任意衬砌变形复变函数的精确解答。进而通过数值分析,对所提出的复变函数求解方法进行验证,并结合本文已给出的应力函数解答,分析了两种不同解析理论及数值分析所得结果的差异。3.对考虑衬砌和土体渗透特性的半无限空间中隧洞周边渗流问题进行了研究。采用土体与衬砌分算,分别得到了两者渗流方程,在此基础上利用边界条件和流量连续条件,给出了半无限含水层中带衬砌隧洞渗流问题的复变函数解析解。进而通过数值分析对该复变函数解进行了验证,并分析了隧道径深比、土体与衬砌渗透系数相对值、内壁水压力等因素对渗流量和衬砌周边水头的影响及其规律。4.根据四元件流变模型和Terzaghi-Rendulic固结理论,建立了衬砌透水与封闭条件下的超静孔隙水压力的控制方程,并得到了处于饱和粘弹性土体中隧道的超静孔隙水压力解析解,由此可确定求解域中任意点任意时刻的超静孔隙水压力。5.以上海地铁二号线工程为研究背景,利用通用有限元程序Abaqus,考虑隧道施工和运营的多工况的特点,对盾构隧道的长期沉降进行了数值分析。程序中选用prony级数拟合的四元件粘弹性本构模型,考虑地基土的成层性,耦合了Biot固结理论进行计算,并与实测所得长期沉降进行了对比。更多还原

【Abstract】 During the process of tunnel construction, regardless of the tunnel depth, tunnel excavation causes soil convergence around the tunnel face and results in short-term surface settlement; meanwhile, soil disturbance and the resulting new boundary conditions lead to re-distribution of stress field and seepage field, and consolidation and creep of the soft soil, which bring about long-term subsidence. Excessive subsidence caused by tunnel construction may affect the safety and normal use of the surface structures, foundations and adjacent pipelines, etc. Therefore, how to predict and control the tunnel settlement becomes an important engineering issue. With the accelerated urbanization process, a large number of tunnels are built and put into use; however, the relevant theoretical study lags far behind the booming engineering practice. To give technique supports for the tunnel construction, the seepage field, consolidation behavior and land subsidence of the soil around shallow tunnel are systematically studied using both analytical and numerical methods in this dissertation. The main original work includes:1. The general ground deformation pattern suggested by Sagaseta, which can consider uniform convergence, pure distortion and vertical translation of tunnel individually, is incorporated into Airy stress function as the complex boundary condition of the displacement around the tunnel section. An elastic solution for the prediction of the tunneling-induced ground deformations for shallow tunnels in the soft ground is derived, and the simplified solution for normal consolidated soil is proposed. The influences of uniform convergence, pure distortion and vertical translation on land subsidence are analyzed. The comparisons of the solutions with the data observed in four different tunnels are made and the reasonable values of the parameters in the solution are investigated. Finally, three deformation types for different soils are suggested for practical purpose.2. A general ground deformation pattern is assumed as the displacement boundary condition around the tunnel section, and the elastic half plane with a hole is mapped conformably onto a ring, a solution for complex boundary condition of the displacement around a circular tunnel is deduced by the complex variable method. The results given by the solution are compared with the ones given by FEM and the data observed. Differences between the complex variable method and Airy stress function method are discussed.3. An analytical solution is derived for steady flow into a lined tunnel in a semi-infinite aquifer firstly by assuming the soil and lining are saturated, homogeneous and isotropic media. Using the conformal mapping, the flow in the soil region, as well as in the lining region, can be described by Laplace equation in a ring domain. Water inflow volume and hydraulic head along the tunnel circumference are solved by Fourier method for the Dirichlet problem. The influences of the ratio of radius to depth of tunnel, the hydraulic conductivity of both soil and lining and the internal water pressure on the water inflow volume and hydraulic head along the tunnel circumference are discussed and compared with numerical stimulation.4. Based on Burges viscoelastic constitutive model and Terzaghi-Rendulic consolidation theory, the governing equation about excess pore pressure is established with drainage and no-drainage boundary. An analytical solution for the excess pore pressure of tunnel in viscoelastic saturated soil is obtained. By this solution, the excess pore pressure of any position can be determined at any time in the considered region.5. Using the FEM code-Abaqus, a part of Shanghai metro line NO.2 shield tunnel is simulated to investigate the behavior of long-term ground subsidence. Burgers viseoelastic constitutive model fitted by prony series is implemented in the code coupled with Biot’s consolidation theory, and the multi-layered characteristics of soil are also taken into account. A multiple-step numerical procedure is designed to simulate the mechanical behavior of shield tunnel in different period during the long-term duration. Finally, comparison with the observed data shows that the long-term response of shield tunnel can be predicted by such numerically simulation.更多还原