堆载和桩顶荷载组合作用下的桩土响应分析

摘要

Negative skin friction is an important factor which affects the performance of pile foundation.As pile head load and surface load exert significant effect on the distribution of skin friction,Lagrangian difference method was used to analyze the skin friction and the variation discipline of neutral point position as well as axial stress distribution of pile to study their coupled effect.The results show that negative skin friction occurs in the range of 0.37-0.64 pile length from the pile top.When the surface load is 60 kPa or less,the negative skin friction firstly increases with the increase of depth,and then decreases,and finally changes to the positive skin friction.The surface load is greater than 60 kPa.The negative skin friction firstly decreases then changes to the positive friction.The relationship between the maximum value of pile-axial forces with surface load and pile head load is a significant duality.The variation discipline of neutral point position is affected by the combination values of surface load and pile head load.In addition,the relationship between neutral point position with pile head load and surface load can be described by a binary equation,which can be used to calculate the neutral point position.%桩侧负摩阻力是影响桩基工作性能的重要因素,而堆载和桩顶荷载对桩侧摩阻力的分布影响很大,为了研究其组合作用机理,采用拉格朗日差分法分析堆载和桩顶荷载组合作用下桩侧摩阻力分布、中性点位置变化规律以及桩体轴力分布.研究结果表明:负摩阻力主要出现在0.37～0.64倍桩长位置;当堆载小于或等于60 kPa时,负摩阻力沿桩身向下先增大后减小并逐渐过渡到正摩阻力;当堆载大于60 kPa时,负摩阻力沿桩身向下逐渐减小然后过渡到正摩阻力;桩体最大轴应力与堆载和桩顶荷载具有明显的二元线性相关性;中性点位置变化规律受桩顶荷载和堆载组合值的影响,根据此规律得出二元方程式,可用于快速估算中性点的位置.