【作者】 胡强；

【导师】 刘宁； 邵国建；

【作者基本信息】 河海大学 ， 工程力学， 2004， 博士

【摘要】 基坑工程中的数值仿真存在着许多的技术难题，本文在系统总结基坑工程中存在的关键问题的基础上，从基坑的建模、反分析方法、稳定性分析及临界变形指标几个方面进行了深入研究，提出了相应的解决方法。传统有限元模拟大型深基坑施工时，模型难以真实反映挡墙和支护结构的弯曲变形效应，故其计算结果与实际相差较大，这对工程是不利的。为了在数值模拟方面力求合理地反映基坑工程中复杂结构体系的实际效应，迫切需要建立一种新的数值计算模型，一方面可以提高传统有限元的计算精度，另一方面，既可直接应用于三维实体和中厚度板壳结构又易于与其它带转动自由度的梁单元相容，并且在处理复杂组合结构体时无需引入任何过渡单元就可完成数值实施。本文首先建立了一种新型单元——RH8单元，推导了该单元的确定性有限元及随机有限元列式，建立了基坑的有限元数值模拟的新模型；在此基础上本文对基坑的动态模拟及基坑的稳定性进行了研究。全文的主要内容如下： 1．基于非协调元理论和修正的Reissner泛函中引入独立转动场的变分原理，将转角自由度作为独立自由度，创建了一种新的三维八结点单元——RH8单元，并根据变分原理推导了相应的有限元列式，最后还对其适用性进行了讨论。 2．将本文所建立的单元用于梁、板、块体同时存在的复杂组合结构体系问题当中，讨论了该单元在处理联结问题的优势，通过若干考例验证了该单元在计算组合结构时的合理性。针对大型结构中计算量较大的问题，讨论了提高新型单元计算效率的处理方法。 3．提出了带独立转动自由度的随机变分原理，在此基础上推导了新型单元的随机有限元列式。 4．基于新型单元模式对连续墙、支撑及土体进行模拟，从而建立了基坑施工模拟的新模型，对实际工程应用中该模型存在的问题及解决方法进行了探讨。 5．系统综述了反分析计算方法，对目前反分析中存在的问题进行了总结。针对实际存在的问题，提出了并行进化演化反演算法，采用面向对象的编程思想编制了相应的程序，验证了该算法的有效性。 6．在干扰能量法和超变形法的基础上，提出了基坑稳定评判的广角度综合评判法。同时考虑参数的随机性，以杆件的干扰能量作为功能函数，提出了支撑体系的体系可靠度计算方法，采用可靠度来对基坑的稳定性进行评价。最后还对基坑临界摘要变形指标问题进行了探讨。 7.针对国内某一特大型深基坑施工，利用本文方法进行了应力和变形分析、土层参数反分析、基坑支撑体系的体系可靠度分析，对基坑的安全稳定性进行了评价，得到合理的研究结果。关键词:深基坑、建模理论、稳定性、转动自由度、体系可靠度、临界变形指标更多还原

【Abstract】 For the critical problems in the foundation-pit, the corresponding solutions are indicated from several aspects, i.e. the model of foundation-pit numerical value simulation, back-analysis, stability, critical target of the foundation-pit strain. When the excavation of deep foundation is simulated in three-dimension with isoparametric elements which have eight nodes, the result is difficult to reflect the influence of bending-strain exactly because of the model itself. Therefore the safety of the project is threaten. In order to simulate the excavation more exactly, a model, which can not only improve the precision but also predigest the coupling of the different structure, is urgent to be established. This paper proposes one new elements - RH8 elements(Rotation Hexahedron element of 8 nodes). The determined finite element formula and random finite element formula of the new element is also presented. Then the new model of the foundation which give facilities for the finite element numerical simulation is developed. Ultimately, the dynamic simulation and stability of the foundation is studied. The main contents of the dissertation are as follows:1. Based on the inconsistent element theory and the Reissner variational principle which is modified to the independent rotation fields, the rotation degree is considered as independent degree and a new three-dimensional eight-node element-RH8 element is developed. Then the finite element formula is presented based on the variational principle. Finally this paper discussed the appropriate range of the new element.2. The new element is introduced into the problem of composite structures in which the girder, plate and block exists at the same time. Then this paper discussed the advantages of the elements when dealing with the connect problem. Ultimately, a classical problem calculating connect structures demonstrated the new elements is rational.3. The random variational principle with independent rational degree is proposed. Then on the basis of it, the random finite element formula of the new element is presented.4. This paper simulates the continuous wall, supports and soil mass adopting the new elements. Then it established a new model for simulating the excavation and discussed the existing issues, then gives some advices to this problem.5. The method of back-analysis and the existing problem is comprehensively summarized. This paper proposed the method of back-analysis with Parallel-Genetic-Algorithm and corresponding program has been validated correctly.6. Based on the Inteference-Energy method and Over-deformation method, the extensive angle method is applied in the judgement of the stability of ground foundation pit. At the same time, considering the uncertainty of the parameters, a system reliability method of the supports whose performance function is the inteference energy is presented. And the stability of the foundation is evaluated based-on the reliability method. Finally this paper bring forward the method to attain the critical target of the strain7. For certain project of deep foundation, stress-deformation analysis, soil parameters back-analysis, system reliability analysis of the support and the evaluation of the stability are done. The result is demonstrated rationally.更多还原