冲刷作用下砂土地层中桩的侧向力学性质分析

Analysis of Laterally Loaded Piles in Sand Considering Scour Hole Dimensions

[目的]冲刷是在水流以及波浪作用下土体流失的一个过程,它通常发生在桥梁、港口码头、以及海岸平台等结构的基础周围,造成基础的承载力下降,危及上部结构的安全。目前在分析桩的侧向力学行为时,只考虑了冲刷深度对桩的侧向承载力的影响,而忽略了冲刷形成的冲刷孔的影响。事实上,冲刷孔的几何形状不仅包括冲刷深度、还包括了冲刷孔的宽度以及冲刷孔的坡度。目前,工程设计中广泛采用的侧向桩分析方法,即p-y曲线方法无法考虑冲刷孔三维几何形状对桩的侧向力学性质的影响。[方法]针对这个问题,文章提出了一种修正的p-y曲线方法以用于分析砂土地层中桩在冲刷作用下的侧向力学响应。[结果]该方法改进了基于锲形体破坏模型的Reese p-y曲线法,从而能考虑冲刷孔三维几何形状的影响。将计算得到的结果与三维有限差分数值分析的结果进行了比较,验证该修正方法的可靠性。[结论]计算结果表明:在冲刷孔的几何形状参数里,冲刷深度对桩的侧向力学性质的影响最大,其次是冲刷孔的宽度与坡度。忽略冲刷孔几何形状的影响,桩在地面位置的侧向位移会增加49%~68%。

[Introduction]Scour is a process of soil erosion,which can occur around the foundations of bridges or offshore structures through the action of flowing water; it can,therefore,reduce the capacity of the foundations and sometimes lead to the failure of structures. During an analysis of scour effects on laterally loaded piles,scour hole geometry is often ignored. Instead,scour effects are considered by simply removing the whole soil layer to the scour depth. However,a scour hole has not only depth,but also width and a slope. At present,the widely used p-y method for analyzing laterally loaded piles cannot consider three-dimensional scour hole dimensions. [Method]For this reason,a simplified method was developed herein for the analysis of laterally loaded piles in sand under a scour condition. [Result]The p-y curves in this method were based on a wedge type of failure. The effects of the scour hole dimensions on the response of laterally loaded piles in sand were evaluated using this simplified method. The computed results from the simplified method compared well with those from the three-dimensional finite-difference method. Scour depth was identified as the most influential factor on the pile response compared with scour width and scour hole angle. [Conclusion]Based on the parameters investigated,a model that removes the entire soil layer to the scour depth resulted in 49% - 68% higher groundline lateral displacements of the pile than a model that incorporates the three-dimensional scour hole dimensions.