Experimental and Theoretical Research on Interaction Between Soil Wet Expansion and Pile Foundation
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摘要: 为研究同一湿度场环境下土体湿化膨胀与桩基相互作用的机理，设计了室内物理模拟试验，对土体湿化膨胀与桩基相互作用进行了分析。通过人工降雨入渗的方式模拟变化的湿度场环境，实时监测模型箱中不同入土深度的桩基抬升量以及膨胀土地基的变形和应力数据，研究桩基入土深度与抬升情况的关系，基于非饱和土力学理论、桩–土相互作用剪切位移理论，提出考虑土体刚度和隆起量变化的侧摩阻力计算方法，并将桩侧摩阻力理论计算结果与模型试验结果进行对比分析。结果表明：在土体吸水膨胀过程中，桩体的向上抬升会引起桩底端部的卸载作用；地层隆起量随着深度的增加呈线性递减，随着桩尖入土深度的增加，桩顶隆起量呈对数趋势减小，增加桩长可以在一定程度上抑制桩基抬升；同时，基于剪切位移理论得出的桩侧摩阻力与基于非饱和膨胀土理论得出的桩的侧摩阻力及试验测试数据分布基本一致，表明本文所提出侧摩阻力计算公式是可靠的。Abstract: To deeply study the stress and denaturation law of pile-expansive soil interaction in the humidity field, the physical simulation test of pile foundation uplift and the deformation or stress change of expansive soil foundation in the same humidity field at different soil depths was established. Through artificial rainfall infiltration to simulate the humidity field environment, and at the same time to monitor the change of pile foundation uplift at different soil depths in the model box, as well as the deformation and stress of expansive soil foundation, to obtain the impact of pile length on the uplift test results. Based on the theory of unsaturated soil mechanics, the distribution of pile lateral friction along pile length was analyzed. The theoretical formula of lateral friction resistance considering the change of soil stiffness and uplift is derived by combining with the shear displacement method, and compared with the results of the unsaturated soil mechanics theory and experiment. The results showed that the upward-lifting would cause unloading at the end of the pile body in the process of water absorption and expansion. With the increase of the pile tip's burial depth, the uplift of the pile tip tended to decrease as a logarithmic function, and the uplift decreased linearly with the increase of depth. The pile side friction theory formula and theory of unsaturated expansive soil pile side friction along the depth values were in good agreement. It was shown that the calculation formula of lateral friction was reliable, and based on the parameter limitation of the theoretical formula, the prediction method of lateral friction was put forward to determine the "neutral point" based on the theoretical formula and determine the value based on the unsaturated soil mechanics theory.
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Key words:
- pile /
- expansive soil /
- simulation test /
- shear displacement method /
- side friction
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表 1 渗透160 h后桩侧摩阻力计算数据汇总表
埋深/cm ${K_0}{\sigma _{\rm{s}}}$/kPa $({u_{\rm{ar}}} - {u_{\rm{wr}}})$
/kPa$S$ $f$/kPa 0 0 78.85 0.74 4.23 7 3.4 81.75 0.73 15.77 16 2.3 92.03 0.70 15.92 26 2.4 104.92 0.67 16.21 46 6.5 141.2 0.60 −17.14 
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