【作者】 黄春娥；

【导师】 龚晓南；

【作者基本信息】 浙江大学 ， 岩土工程， 2001， 博士

【摘要】 基坑是一种特殊的临时性边坡，其稳定分析理论沿用了土坡稳定分析的理论，并随着土坡稳定分析理论的发展而发展。在各种影响土坡稳定安全的因素中，地下水渗流的作用是最难确定的，经过多年的工程经验的积累、总结，前人提出了多种计算地下水渗流的简化方法，最常用的是代替容重法和静水压力法。但是，基坑施工中常常采取治水措施，如设置抽水井、回灌井及阻水帷幕等，使得基坑周围的渗流场分布复杂化，大多与简化方法假定的水压力分布形态相去甚远。而实际基坑工程稳定验算中，也沿用了代替容重法和静水压力法等土坡稳定分析中的简化渗流计算方法，这样必然产生较大误差，有时甚至得出错误的结果。用错误的结果去指导工程实践是非常危险的，实际工程中由于地下水处理不当而导致的工程事故已给人民生命财产带来了巨大损失。因此，基坑工程实践亟待适合的理论来指导。 本文从研究基坑周围的渗流场入手，结合土坡稳定分析理论，建立了一套分析渗流作用下基坑稳定性的新的计算模型： ·根据稳定渗流理论，考虑基坑工程中常见的复杂边界条件，建立了复杂边界条件下稳定渗流场的计算模型。 根据实际基坑治水措施，区分有压渗流与无压渗流。有自由面的无压渗流计算采用虚单元法，融合了固定网格法和移动网格法的优点。 在边界条件的处理中，提出以沟代井模拟大井径渗水井、同点异号法模拟小井径抽水井及无厚度阻水结构的计算模型。 ·建立了有限元法与条分法结合计算渗流作用下基坑稳定性的计算模型。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。 ·本文对核心计算程序作了一定的前后处理工作，有限元计算网格的自动剖分及输入输出数据的图形化均提高了程序的实用性。 ·通过对阻挡治水基坑的稳定分析，探讨了各种计算方法在该工况下的适用性，对工程设计有一定的指导意义。 ·最后用本文提出的计算模型分析了—采用抽水——回灌治水措施的深基坑工程的稳定性。 本文提出的计算模型既在理论上有创新性又不脱离工程实际，为渗流作用下的基坑稳定分析开辟了一条新的途径。更多还原

【Abstract】 Foundation Pit is a special temporary slope. The theories of stability analysis of Foundation Pit stemmed from those of slope and developed with them. Among the various factors that affect the safety of slope, seepage flow is the most difficult one to determine. Several simplified methods, including the common used methods such as hydrostatic pressure method and replaced weight method, were developed on the basis of many years’ experience in slope stability analysis. The instalment of seepage-control equipment in the construction of Foundation Pit will make the distribution of seepage pressure much different from what the simplified methods had supposed. In this situation, using the simplified methods to determine the effect of seepage flow will lead to inaccurate even incorrect results. To avoid the great losses arising from the disastrous collapse of Foundation Pit due to the inappropriate treatment of underground water, a fit theory for the stability analysis of Foundation Pit with seepage flow must be developed.In this dissertation, a new model for stability analysis of Foundation Pit with seepage flow was developed by studying the seepage flow field around Foundation Pit and the theories of stability analysis of slope. numerical model simulating the seepage flow field with complicate boundary conditions was proposed according to the theory of steady state flow and the actual boundaries of Foundation Pit.According to the actual measures of seepage control, seepage flow within confined boundaries and that with free water surface were classified. The latter was computed by Dummy Element Method, which united the merits of fixed mesh method and changing mesh method.To simulate the boundary conditions, the models of using ditch to simulate large-diameter well, same node with different numbers method to simulate small-diameter well and baffle-wall were put forwarded.?A new model for stability analysis of Foundation Pit, which integrated FEM and the method of slices, was developed. 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.?Adding Pro- and Post-processing functions, including auto element-partition and data conversion, to the core program improved its application.?In analyzing a Foundation Pit with baffle-wall, several methods were compared and the evaluation of their applicability was useful in engineering design..?The new model also was used to analyze one deep Foundation Pit involving pumping.?The new model developed in this dissertation blazed a new path for stability analysis of Foundation Pit.更多还原