不同加荷顺序下单桩负摩阻力模型试验研究

发布时间：2018-06-05 09:22

本文选题：堆载 + 桩载　；参考：《铁道工程学报》2017年07期

【摘要】：研究目的:基桩负摩阻力对桩产生下拉荷载,增大桩身轴力和端阻力,甚至导致桩身破坏。由于桩周土和桩体承受荷载后的沉降发展过程不同,桩载与堆载施加顺序必然对桩体负摩阻力产生较大影响。本文通过模型试验,研究不同桩端持力层条件下堆载和桩载施加顺序对单桩负摩阻力的影响。研究结论:(1)先堆载后桩载工况下,堆载完成后,中性点离桩顶最远,随着桩载增加,中性点逐渐上移,最终黄土和粗砂持力层中性点位置分别在桩顶下0.49l和0.56l处;桩身轴力呈先增加后减小的趋势,单桩承载力发挥系数分别为0.69和0.57;(2)先桩载后堆载工况下,施加桩载时,桩身轴力沿深度逐渐减小,无中性点,施加堆载时,轴力呈先增加后减小的趋势,中性点出现并逐渐下移,最终黄土和粗砂持力层的中性点位置分别在0.41l和0.50l附近,单桩承载力发挥系数分别为0.86和0.69;(3)同种持力层情况下,先桩载后堆载的承载力发挥系数较先堆载后桩载的大,安全储备小,实际工程中应严格控制堆载宽度、集度及堆载边缘距桩中心的距离;(4)在实际工程中应综合分析地质条件、桩基的受力特点及承载要求,选取合适的加载顺序来减小桩身负摩阻力;(5)该研究成果可为堆载条件下桩基的设计提供参考。
[Abstract]:The purpose of the study is that negative frictional resistance of foundation pile produces pull-down load on pile, increases axial force and end resistance of pile body, and even leads to pile body failure. Because the settlement development process of soil around pile and pile body under load is different, the order of pile load and pile load application must have great influence on negative friction resistance of pile body. In this paper, the influence of pile load and pile load on the negative friction resistance of single pile under different pile end bearing layer is studied by model test. The results show that the neutral point is farthest from the top of the pile when the pile load is completed, and the neutral point moves up gradually with the increase of pile load. Finally, the neutral point of loess and coarse sand bearing layer is 0.49l and 0.56l under the pile top, respectively. The axial force of pile body increases first and then decreases. The bearing capacity of single pile is 0.69 and 0.57 / 2 respectively. When pile load is applied, the axial force of pile body decreases gradually along the depth, no neutral point, and when pile load is applied, The axial force increased first and then decreased, the neutral point appeared and gradually moved down, the neutral point of loess and coarse sand bearing layer was about 0.41l and 0.50l respectively, and the exertion coefficient of bearing capacity of single pile was 0.86 and 0.69 / 3 respectively) in the same bearing layer. The bearing capacity exertion coefficient of the first pile load and the later pile load is larger than that of the first pile load and the pile load, and the safety reserve is small. In actual engineering, the width of the pile load should be strictly controlled, the set degree and the distance between the heaped load edge and the pile center should be strictly controlled, and the geological conditions should be comprehensively analyzed in the actual engineering. The stress characteristics and bearing requirements of pile foundation and the proper loading sequence are selected to reduce the negative frictional resistance of pile. The research results can provide a reference for the design of pile foundation under the condition of heaped load.
【作者单位】：兰州交通大学;
【基金】：国家自然科学基金项目(41562014)
【分类号】：TU473.1

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