疏桩路基中基底垫层设置效应分析

Analysis of Setting Effect of Cushion in Sparse Pile Supported Roadbed

针对疏桩路基结构特点,对路基基底垫层作用效应进行了辨析,指出传统碎石垫层塑性流动特征不再适用于路基基础,提出灰土垫层应用于疏桩路基中的设想。采用路基-垫层双层体系模型,给出了考虑基底垫层作用效应的桩土荷载效应的计算方法,并对垫层的加筋兜提效应进行了分析。通过计算结果与工程实测结果的对比分析,验证了该方法的合理性;进而对碎石垫层、灰土垫层、加筋碎石垫层的作用效应进行了分析。结果表明,灰土垫层在桩体应力集中和抑制基底差异变形等方面都优于碎石垫层和加筋碎石垫层。同时,相比(加筋)碎石垫层,灰土垫层具有现场施工的便利性和经济的节约性,相对柔性路基基础的工程实践中可用灰土垫层取代传统碎石垫层或单层加筋碎石垫层。

According to the characteristics of embankment supported by sparse piles, the working mechanism of subgrade cushion is analyzed, and came to the conclusion that the plastic flow characteristic of traditional gravel cushion is no longer suitable for embankment foundation, then the idea that lime-soil cushion can be applied to sparse pile-supported embankment is proposed. The calculation method of pile-soil load effect is presented considering the action of basal cushion based on the embankment-cushion system model. The reinforcement effect of geosynthetic cushion is also analysed. The rationality of the presented method is validated by comparing the analytical solution with the test result, and the effect of gravel cushion, lime-soil cushion and reinforced gravel cushion are analyzed. It shows that lime-soil cushion is better than gravel cushion and reinforced gravel cushion in pile stress concentration and restrain differential deformation of subgrade. And lime-soil cushion is better than （reinforced） gravel cushion in terms of the convenience of site construction and economic savings, traditional gravel cushion or single-layer reinforced gravel cushion can be replaced by lime-soil cushion in flexible embankment engineering practice.