【作者】 吴刚刚；

【导师】 何世秀；

【作者基本信息】 湖北工业大学 ， 岩土工程， 2006， 硕士

【摘要】 土质堤防因具有能就地取材等优点而为水利及防洪工程广泛采用,合理分析与计算高洪水位作用下堤防的渗流及稳定性、为除险加固提供技术支撑具有重要的工程实际意义。因实际工程中堤防的作用水头、堤身断面、填土性质、地质条件等均千变万化,导致难以全面而准确地分析其渗流场分布并采取有效的防渗措施。为此,本文论述了不同条件下渗流微分方程的建立及其定解条件,简要介绍了常用的渗流计算和稳定分析方法。在介绍了渗流问题有限元公式的基础上,通过对各种计算渗流自由面的方法进行比较,运用变单元渗透系数法的原理,利用APDL语言开发了二维稳定和非稳定渗流的程序,使用该程序计算自由面只需进行一次网格剖分,通过迭代即可较准确地求出自由面的位置;通过算例验证了变单元渗透系数法的正确性。在阐述了ANSYS软件在渗流稳定计算中的应用、边坡稳定性分析的方法和原理及水位下降时边坡失稳机理后,探讨了水位下降时自由面位置随时间的变化规律,同时针对具体算例,利用所编写的非稳定渗流计算程序对其进行了渗流的有限元分析,并用简化的毕肖普法进行稳定性计算,得出了不同下降速度时的稳定系数。这种方法既利用了有限元法计算渗流场的有效性,又不脱离条分法多年使用积累的工程经验,融合了两种算法的优点。最后,还分析了水位下降时各种因素对稳定性的影响。此外,考虑到应力场中的应力会改变土体渗透系数进而影响渗流场,而渗流场也因其产生的渗透力会导致应力场发生变化,两者之间存在耦合作用,针对某一具体算例,通过ANSYS软件和自编程序,分别对不考虑应力影响下的渗流场和不考虑渗流影响下的应力场以及两场相互耦合时的稳定性进行了研究,得出了一定规律。本文的研究工作在改进和完善计算渗流自由面的方法方面进行了有益的尝试。通过对算例进行数值计算和较为深入细致的分析,对水位变化渗流场的分布以及由此引起的滑坡失稳的机理和规律有了进一步的认识。可为非稳定渗流下边坡稳定分析、滑坡灾害预报和边坡治理等方面提供有用的参考,具有一定的理论意义和使用价值。更多还原

【Abstract】 Soil Embankment is widely used in water conservancy and flood prevention projects because of its being able to drawing on local resources and other advantages. How to analyze and calculate the seepage and stabilities of levees under high level flood reasonably, and supply reliable technological support for dangers removing and strengthening are of great engineering significances.As for actual embankments, the hydraulic head, cross section shapes, properties of filled soil, geological conditions and so on all vary greatly, it’s hard to define precisely the distribution of seepage field and take effective seepage prevention measures. So the setup of various kinds of seepage differential equations as well as their solving terms, and methods in common use to analyze and calculate the seepage and stabilities are discussed in this paper. On the foundation of the seepage problem finite element method formula, Compared to various kinds of calculating seepage free surface methods, by using the principle of variable seepage coefficient method and APDL language, two-dimension finite element calculation program of steady and unsteady seepage problem has been empoldered. Using the method to calculate free surface which only one gridding is needed, the position of free surface can be gained precisely through reiterative calculation. The examples show that variable seepage coefficient of element method is correct.After expatiating on the application of ANSYS in seepage’s stabilization calculation, the methods and principles of stability analysis of slope, and the mechanism of slopes losing stability when water level falls, the changing rules of the free surface with time when water level falls. At the same time, aiming at material case, the FEM analysis of its seepage has been carried through by the variable seepage-calculating program, which is compiled. And the stability coefficients under various falling velocities have been educed through the stability calculation with predigested Bishop. This model not only could bring the efficiency and accuracy of FEM into full play but also could utilize the rich experience in using the method of slices. At last, the influence on stability of various factors when water level falls has been analyzed.Furthermore, as stresses in the stress field influence the value of seepage coefficient, which will results in the change of seepage field in the end, while on the other hand, the seepage field also has an effect on the stress field because of seepage forces. Aiming at a material example, using ANSYS and program which compiled by更多还原