长短桩复合地基稳定承载可靠度分析

Stability bearing reliability analysis on long-short-pile composite foundation

以稳定性分析为基础,提出长短桩复合地基承载力可靠度计算的优化方法。数据表法利用可靠度指标的几何意义,在基本变量空间中直接求解可靠度;它与稳定分析中的圆弧滑动法有着相似的计算求解过程,将两者结合起来形成相对简单的、可用于计算长短桩复合地基承载力可靠度指标的优化方法。用圆弧滑动法建立长短桩复合地基的两种破坏模型,推导出极限状态函数,采用数据表法在Excel2007中处理数据,求得安全系数和可靠度指标。结合实例,计算出可靠度指标,并用蒙特卡罗法验证。从可靠度分析角度确定了最危险滑弧的位置,发现滑动破裂面穿过了长短桩复合地基的上下两个加固层,同时对可靠度的影响因素进行了讨论,发现土体重度γs、内摩擦角φs和上部荷载p的变异对可靠度指标影响较大。

On the basis of stability analysis, put forward an optimization method to calculate the long-short-pile composite foundation bearing capacity reliability index. By using the graphic meaning of reliability index, spreadsheet method can calculate the reliability index in the basic variable space directly. This method has a similar calculation principle with circular sliding stability analysis. It will become a relatively simple method if combining the two methods, which could be used to calculate the reliability index of the long-short-pile composite foundation bearing capacity. Establishe two circular sliding foundation damage models by Arc sliding method and derive the limit state function. The Excel 2007 software was applied to process the data with diagram method to seek safety factor and reliability index. Combined with examples, it shows that the sliding rupture of foundation will pass through both of the two reinforcement layers of the long-short-pile composite foundation, and the most dangerous slip surface location were determined from the perspective of reliability analysis. The results were verified by Monte Carlo method and the factors impacting the reliability of this sliding model was discussed. The variation of the soil parameters γs,φs and load p have large influence on the reliability index.