【作者】 徐洋；

【导师】 谢康和；

【作者基本信息】 浙江大学 ， 岩土工程， 2004， 博士

【摘要】 复合地基工后沉降是复合地基设计必需考虑的重要内容之一，对其如何合理地进行计算已逐渐成为工程界所关注的问题，但有关研究至今尚不多见。本文从解析计算和有限元分析两方面着手对复合地基固结与变形问题展开了较全面、深入的研究。主要研究工作如下： 1．在对若干试验结果分析的基础上，提出了刚性基础下复合地基桩侧摩阻力分布形状的假定，然后基于总应力法分析了单桩复合地基中桩体和桩间土的沉降变形，并编制了相应的计算程序。 2．基于Biot理论，分别对在桩顶受外荷载作用和桩土共同受外荷载作用的情况下考虑桩土相互作用的单桩复合地基固结问题建立了基本方程和求解条件，并在Laplace变换域和Hankel变换域内得到了土体和桩体的变形解答。 3．编制了可以进行平面应变、轴对称以及三维情况下复合地基固结与变形分析的有限元程序。该程序对土体可采用弹性、非线性弹性、弹塑性等多种本构模型并可考虑基础筏板、垫层等复杂条件。同时通过多种算例对该程序进行了验证。 4．在假定复合地基桩土间竖向和切向变形协调、应力平衡以及复合元模型的平均固结度与单桩轴对称复合地基的平均固结度相等的条件下，用有效应力分析法建立了三维复合有限元模型，提出了基于此模型的复合地基固结变形分析有限元法。该法无需将桩单元和土单元分别进行网格剖分，从而能极大地减少有限元分析的工作量，特别是对于群桩复合地基固结分析，其优势更为突出。 5．用编制的有限元程序对单桩、群桩复合地基的固结变形性状进行了大量的计算分析，阐述了弱排水桩也能加速地基固结的机理，提出了将强排水桩成层复合地基固结简化为均质单层复合地基固结的计算方法，并通过工程实例分析说明了该程序在实际中的应用。 本文工作较全面地揭示了复合地基固结性状，并为复合地基工后沉降的计算提供了新的理论和技术支持，从而丰富和完善了复合地基变形计算理论和技术。更多还原

【Abstract】 The settlement induced by consolidation of composite foundation is one of the important items that must be considered in design of such foundation, and its reasonable evaluation has been becoming a problem deeply concerned by engineers. However, the relevant study was rarely reported. In this dissertation, the consolidation and deformation problem of composite foundation was studied both by analytical method and by FEM. The main work includes:1. On the basis of analyzing data from several field tests, assumption was proposed for the distribution of side friction along column under rigid raft, and settlements of column and soil in the composite foundation with single column were analyzed by totally stress method. The corresponding computer program was developed at the same time.2. Based on Biot’s theory, the basic equations and solution conditions were established for the consolidation problem of the composite foundation with single column considering soil-column interactions when load was applied on the top of column only or applied on the top of both column and soil, and the solution for deformations of soil and column were obtained in the forms of Laplace and Hankel transformation.3. Computer program was developed by FEM that can be used to perform consolidation and deformation analyses of composite ground for plane strain, axial symmetry and three-dimensional conditions, in which, the soil model can be linear elastic, non-linear elastic or elasto-plastic, and complicate factors such as raft, cushion et al. can be taken into consideration. Meanwhile, the program was verified by many examples.4. By assuming that distortion is coordinative and stress is in equilibrium at the interfaces of columns and soil in composite foundation and that the average consolidation degree in composite model was equal to the one in composite foundation, a three-dimensional composite model was established by effective stress analysis method. The corresponding finite element method is then developed for consolidation analysis of composite foundation. This method is advantaged by no need to distinguish column and soil and thus raises greatly the efficiency of FEM analysis, especially in consolidation analysis of composite foundation with columns group.5. The consolidation behavior of composite foundation with single column or with columns group was analyzed extensively by the computer program developed, and the mechanism that the column with low permeability can also accelerate the consolidation of soil was illustrated. Moreover, a simplified method was proposed for consolidation analysis of layered composite foundation with column of high permeability. Finally, a case study was made to show the practical application of this computer program.The work presented herein not only reveals the consolidation behavior of composite foundation, but also provides new theory and technique support for the computation of settlement induced by consolidation of composite foundation, and thus makes the computation theory for the settlement of composite foundation more perfect.更多还原