中文摘要：

当前在评价复合地基稳定性时通常采用极限平衡法进行分析,即采用复合地基理论,把刚性桩的黏结力和摩擦角等效为地基整体的黏聚力和内摩擦角,然后采用圆弧条分法计算其整体安全系数。显然,该计算方法假定了桩体与土体皆发生剪切破坏。但相关研究成果表明,群桩中存在多种破坏模式,单纯采用剪切破坏模式计算出的安全系数可能偏安全。从刚性群桩的实际破坏模式出发,提出一种适用于刚性桩破坏特征的强度折减法,即通过强度折减法搜索复合地基系统的临界状态时,刚性桩的破坏模式应符合实际破坏情况。同时,根据刚性桩的变形破坏特征,探讨强度折减法临界状态判别方法,通过算例比较只折减抗剪切强度参数和笔者所提方法的差异,验证了本文方法的可行性和合理性。

英文摘要：

At present the limit equilibrium method is generally used to evaluate the stability of composite foundation. In this procedure, the composite foundation theory assumes the cohesion and friction angle of rigid pile are equivalent to that of the whole foundation, and then the safety factor of the whole foundation is obtained by circular slice method. This theory considers the shear failure at critical state for all rigid pile and the soil. However, according to the relevant research results, shear failure is not exclusive for group piles, and the safety factor based on the shear failure mode may tend to be overestimated. Based on the actual failure mode of rigid pile group, a strength reduction method is developed for rigid pile failure. That is, when the critical state of composite foundation system is searched by strength reduction method, the failure mode of rigid pile should meet the actual damage. At the same time, on the basis of the deformation and failure characteristics of the rigid pile, methods for identifying critical state are discussed. The feasibility and validity of the proposed method are verified through comparing the proposed method and the traditional method only considering shear failure.