基坑坑底抗隆起稳定安全系数计算方法改进研究

深基坑坑底抗隆起验算是基坑支护设计的重要内容之一，验算中如何考虑挡土构件嵌固段的作用是一个尚未较好解决的复杂问题。文章分析了国内现行技术标准中所建议基于地基承载力和圆形滑移面两种验算方法的不足，进而基于深入的理论及计算对比分析提出一套较为完善的验算方法。所提出的验算方法以现用两种方法为基础，对其进行适当改进，并研究给出其各自所适用的嵌深；研究给出一临界嵌深计算公式，用以界定不同嵌深时所应采用的计算方法，从而实现任意嵌深情况下的坑底抗隆起稳定性的简化验算。通过与有限元极限分析这一精细数值方法就大量算例的计算对比，对所提出的验算方法进行验证。

Improvement of calculation method for safety factor of#br# basal heave stability of deep excavation

The calculation of safety factor with regard to basal heave stability of deep excavation is an importance issue in the design of excavation support system, in which it is difficult to consider the effect of the retaining structural embedment depth. In this paper, the drawbacks of the current calculation methods are thoroughly analyzed, and then a set of improved methods are presented based on deep thinking and a large amount of comparative computations. The proposed method is based on the modification of the existing methods, with clear indication being given with regard to the applicable conditions of different methods in terms of the embedment depth of the retaining structures. A formula is proposed to determine the critical value of embedment depth, beyond which the safety factor will remain unchanged, and the safety factor should be evaluated by using that critical value. Thus the calculation of base stability safety factor of deep excavations can be reliably conducted. By comparing with the results calculated by the more refined finite element method of limit analysis for various deep excavation projects, the rationality and applicability of the presented method are validated.