Three-dimensional finite-element analysis of panel installation of a ultra-deep diaphragm wall
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摘要: 当前的研究和实践成果已表明,水平向应力较大的重超固结土层中,地下连续墙的施工会引起较大的地层位移,影响墙体在主开挖阶段的力学性状。对于正常固结土层中的超深地下连续墙的施工影响,尚无相应的研究成果。基于大型商业有限元程序ABAQUS,土体本构模型选用能够较好反映正常固结和弱超固结黏土单向受荷性状的修正剑桥模型,分析研究正常固结黏性土中超深下连续墙槽段施工所诱发的地层变形特点。首先探讨ABAQUS软件中,多孔介质弹性模型及临界状态塑性模型中有关参数的物理含义,以及参数值根据室内试验的确定方法,并根据需要推导K0状态下土体初始孔隙比的计算公式。通过建立对成槽和泥浆护壁、混凝土浇筑、墙体成型硬化等过程合理再现的三维数值模型,分析研究槽段施工诱发地层变形的特点,并研究槽段宽度、泥浆重度等参数对地层变形的影响。Abstract: It is well known that installation of diaphragm walls in heavily overconsolidated soils will cause substantial ground deformation and can influence the behaviour of the wall during the main excavation process. However, it has not been considered that the installation effect of the panels of ultra-deep diaphragm wall in normally consolidated soils. A popular commecial finite element software, ABAQUS, is employed to simulate the panel installation process of a ultra-deep diaphragm wall in normally consolidated clay. The clay plasticity soil model in ABAQUS, which is based on the modified Cam clay model, is selected to simulate the clay characteristic. The physical meanings of the parameters for the clay model in ABAQUS are discussed, and the methods to decide the parameter values from triaxial compression tests or oedometer tests are presented. A formula for the initial void ratio and the mean effective stress in the field is deduced and used in the simulating by ABAQUS. Three-dimensional numerical models are established to simulate the installation process of the panels, including excavation under a bentonite support, placing and subsequent hardening of concrete. The deformation characteristics of the soil layers induced by the construction of wall panels as well as the influences from the width of the wall panels and the weight of the bentonite slurry are studied.
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