水平偏心受荷桩基础在砂土中的群桩效应（英文）

Group effect in piles under eccentric lateral loading in sand

目的:p乘子法在水平受荷群桩非线性静力响应分析中应用广泛,是定量表征水平受荷群桩中群桩效应影响的有效方法。本文基于水平偏心受荷群桩中群桩效应的理论、实验和数值分析成果,提出一套定量表征水平偏心受荷群桩群桩效应的p乘子经验算法(为区别于水平受荷群桩p乘子,该p乘子被命名为广义p乘子)。创新点:1.提出表征水平偏心受荷群桩群桩效应的p乘子经验算法;2.分析水平偏心受荷群桩中任意两桩的运动规律,给出两桩运动方向角变化范围;3.给出两桩间产生桩-土-桩相互作用的临界条件。方法:1.通过理论分析给出两桩运动方向角变化范围和两桩间产生桩-土-桩相互作用的临界条件;2.利用离心模型实验和数值模拟获得折减系数随两桩运动方向的变化规律;3.采用数值拟合方法在相互作用存在的方向角范围内建立折减系数随两桩运动方向与两桩连线夹角之间的定量关系。结论:1.水平偏心受荷的两根桩,前桩运动方向与两桩连线之间的夹角η介于0°到90°之间,而后桩夹角θ介于-90°到90°之间;2.η和θ组合存在一个范围,在该范围内两桩存在相互作用,且相互作用对后桩的影响往往大于对前桩的影响;3.实验案例验证了本文提出的广义p乘子经验计算公式的合理性。

Group effect in a pile group under eccentric lateral loading is much more complicated than that in a pile group under lateral loading because the grouped piles have different motion directions due to the twist of the pile cap. The purpose of this study is to develop new p-multipliers quantifying group effect in pile groups subjected to eccentric lateral loading. Motions of two individual piles in a pile group under eccentric lateral loading were first studied and concepts of the leading pile and the trailing pile were defined to characterize the relative positions of the two piles. Then centrifuge model tests, numerical analysis, and theoretical analysis were carried out to study the interactions between two piles. It is found that the angles between the motion directions of the leading and trailing piles and the line through both piles, denoted as η and θ, vary in the ranges of 0°–90° and-90°–90°, respectively. The reduction factors of the leading and the trailing piles are both nonlinearly changed with η and θ. The reduction factor of the leading pile is larger than that of the trailing pile if interaction exists. There exist regions on the η-θ plane where the interaction between the two piles is negligible. A concept of critical angle θ0 was introduced to define the boundary with and without interaction for a given η. Finally, empirical equations of reduction factors and a procedure to calculate p-multiplier were proposed and examined using existing test results.