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中性点位置的确定是负摩阻力作用下桩基下拽力与下拽位移,以及整体桩基承载力设计与计算的最关键环节之一;已有规范给定的中性点位置确定经验方法往往与实际存在一定的出入。基于人工合成透明土材料,采用非插入式测试方法开展负摩阻力作用下管桩中性点位置测定模型试验,测得桩体和桩周土体的沉降规律,续而分析桩-土相对位移、确定中性点位置;为了对比分析,同时进行负摩阻力作用下不同直径管桩中性点位置测定的模型试验,对比分析其中性点位置与地面堆载等级的关系。试验结果表明,本文试验条件下,管桩的中性点位置位于0.7 H-0.9 H(H为桩长)范围内,略低于建筑桩基规范中给出的砂性土中基桩建议参考值(0.7 H-0.8 H);桩顶下拽位移近似随地面堆载等级呈线性增长。
The determination of the neutral point position is one of the most crucial steps in the design and calculation of the overall pile foundation bearing capacity under the action of negative skin friction drag and pull; Methods tend to be different from the actual existence. Based on the synthetic transparent soil material, a non-inserting test method was used to carry out the model test of the neutral point position of the pipe pile under negative skin friction. The settlement law of the soil body around the pile body and the pile body was measured. , To determine the position of the neutral point. In order to comparatively analyze and test the neutral point position of different diameter pipe piles under negative skin friction at the same time, the relationship between neutral point position and ground loading level was analyzed. The experimental results show that under the experimental conditions, the neutral point position of the pipe pile lies within the range of 0.7 H-0.9 H (H is the pile length), which is slightly lower than the recommended reference for the pile found in sandy soil given in the code of construction pile foundation Value (0.7 H-0.8 H). The displacement of pile under the pile tip increases linearly with the ground loading level.