【作者】 马飞；

【导师】 王国体；

【作者基本信息】 合肥工业大学 ， 岩土工程， 2007， 硕士

【摘要】 随着我国对西部地区开发力度的加强，湿陷性黄土地区工程建设速度近年来有了很大的提高。因此对湿陷性黄土的土性及其处理方法的研究不仅在理论上具有一定意义，而且具有重要的工程实践意义。在本文第一章，主要介绍了水泥土挤密桩在国内发展的一些情况。在本文第二章，结合工程中的具体实例，主要介绍了水泥土挤密桩的作用原理以及施工工艺，本章结束之时，着重分析现实中水泥土挤密桩的特点和实际中存在的问题。在本文第三章，在水泥土挤密桩复合地基中，水泥土挤密桩起着竖向增强体的作用，它的强度直接决定着复合地基的承载力，因此研究水泥土的物理力学性质是有必要的。同样夯击能量的大小也会对水泥土挤密桩的强度有一定的影响。首先通过对水泥土和水泥砂土在不同水泥掺入比、不同龄期下的无侧限抗压强度试验，对无侧限抗压强度、模量以及应力—应变规律进行了研究，分析了水泥掺入比、龄期、土性对水泥土性能的影响。并且对水泥砂土在浸水和不浸水情况下的力学性能进行了研究。上述试验为工程实践提供了试验依据。在本文第四章，主要论述了复合地基有限元分析的基本理论及一些计算问题，着重讨论土体单元类型、桩体单元类型及土体、桩体的本构模型的建立，以及当采用非线本构模型模拟土体时，明确土体非线性分析中需要注意的问题和有限元解题步骤等内容，再者主要论述了在ANSYS中所建立的桩基及复合桩基的三维有限元模型、单元选取、网格划分等问题以及在ANSYS中的计算结果，并与两个实际工程中的水泥挤密桩实测数据进行了对比分析，认为所选取的模型及参数是合理的，并为进一步的分析提供了基础。最后主要分析了复合地基、双层地基以及天然地基下卧层的应力和沉降随加固区模量、下卧层模量不同的变化情况，说明复合地基下卧层沉降计算不能采用基于双层地基模型的各种计算方法，将其应用于工程中是偏于不安全的。结合水泥土挤密桩在郑西客运专线灵宝段的湿陷性黄土处理地基的应用实例，依据水泥土挤密桩的作用原理，进行现场施工试验和现场质量监控。并利用大型有限元软件ANSYS对竖向荷载下水泥土单桩与土的相互作用进行了计算分析，结果表明，计算分析基本与实际测量吻合，说明水泥土挤密桩对处理湿陷性黄土是十分有效的。更多还原

【Abstract】 Although composite foundation has widely used in engineering during recent years, the research on the mechanical behavior has lagged behind the engineering applications。In the first chapter, the main research studies are about the situations of the soil-cement pile in the country。In the second chapter, by an example of application, the main research studies are the function and the construction techniques, In the last, it emphasize that the characteristic of the soil-cement pile and the problem of it。In the third chapter, firstly, in the soil-cement pile, the soil-cement plays an important role in strengthen the vertical substance. Its intensity determined the bearing capacity of the composite foundation, So it is necessary to study the physics character of the soil-cement, also the size of the energy has a determine influence on the soil-cement pile, According to the unconfined compression tests on the cement and the sand soil cement with different cement ratio and different curing time, and studying on rules of the unconfined compression and modulus, and summarizing of the characteristic of stress-strain diagram of soil cement, this dissertation analyzes the influence of cement ratio and curing time and characteristic of soil on unconfined compressive strength, and study the mechanicbehaviors of sand soil cement on the condition of soaking or dryness. The tests provide some data to the application of these two kinds of soil cementThe basic theory and some computations of FEM for composite foundation are discussed in the four chapter. The element types of soil and pile, models of soil and pile and calculation steps in FEM are focused on. Some notes are mentioned when nonlinear characteristics are applied. In the four chapter, the establishment of 3D FEM models, the selection of elements and meshing are discussed. Further analysis on the numerical result is presented, and then some contrasts are made with the test data. The conclusion is drawn that the selection of model and parameters are reasonable. The contrasts also supply a base for further analysis. And the stress and displacement of the composite group piles, two-layer foundation are computed respectively when varying modulus in the last. It’s concluded that the method based on two-layer foundation does not fit to computing the displacement of composite foundation, and it causes to in security if applied to engineeringBy an example of application of the soil-cement pile in collapsible loess foundation treatment in ZhengZhou-Xi’an passenger dedicated railway line (in LingBao) the paper analyses and discusses the theory of the soil-cement pile, and make the field test, field quality control。And the Goodman interface elements were defined to contribute a nonlinear numerical model for the coupling finite elements and interface elements the interaction of a pile-soil system analyzed by ANSYS, case studies showed the results are fairly well consistent with the field observation, so it is so vivid that the soil-cement pile treat with collapsible loess foundation.更多还原