砂土中单桩基础冲刷的修正应变楔计算

Modified Strain Wedge Calculation of Single Pile in Sand under Scour

由冲刷引起的深水结构物桩基础周围土体损失致使基础水平承载性能下降的问题越发受到重视。应变楔方法假设桩前土体抵抗为三维楔形体,其尺寸发展与楔形体区域土体发挥的内摩擦角有关,从而得到水平受荷桩的p-y曲线。本文对应变楔方法进行修正和拓展,建立非线性位移假设以考虑桩前楔形体区域土体应变沿深度的非均匀分布,将冲刷坑底以上土体的有效自重作用等效为竖向荷载,对楔形体的深度进行修正,以解决楔形体方法只适用于地表水平的情况,得到砂土中单桩基础冲刷的修正应变楔计算方法;并通过与模型试验及三维有限元分析的对比来验证该方法的合理性。分析结果表明:冲刷深度增加会显著降低桩基水平承载性能,冲刷深度3.2D和6.4D情况下的桩顶位移比平均值分别趋近于1.8和3.0;相比有限元方法,本文修正SW方法计算的p-y曲线结果与实测结果更为接近。

Scour can induce soil loss around the pile foundations of engineering structures in deep water and the degeneration of the lateral bearing capacity of pile foundations caused by scour is being paid more and more attention.The strain wedge（SW）method is an effective p-y curve technique for predicting the response of piles under lateral loading.It assumes that a threedimensional passive soil wedge forms to resist the movement of a laterally loaded pile and that the dimensions and mobilized friction angle of the soil wedge develop as the lateral load increases.However,in order to improve and extend the ability of the SW method,a modified SW method is developed which introduces the assumption of nonlinear lateral deflection of the pile resulting in non-uniform soil strain,rather than uniform strain in the soil wedge.In addition,by equating the soil weight above the bottom of the scour hole to a vertical load,the problem of the SW method being only suitable for horizontal ground surfaces is solved.The validity of the method is confirmed by the measured results of a model test and the finite element method.Results show that the lateral bearing capacity of the pile sharply declines as scour depth increases.The average ratio of lateral displacements at the pile head tended to 1.8and 3.0when scour depths were 3.2D and 6.4D（D=outer diameter of pile）,respectively.Compared with the results of p-ycurves from the finite element method,the results from the modified SW method are much more satisfactory than those measured.