In collapsible loess area, the negative skin friction of pile foundation will cause many engineering problems such as failure of pile strength and reduction of bearing capacity of pile foundation, which will bring great harm to engineering construction. In order to study the change and distribution law of negative friction of pile foundation in collapsible loess area, the scale model test of negative friction of pile considering loess collapsibility was designed and completed. Through finite element numerical simulation, the test results are verified, and the distribution law of negative friction of pile and the number and position of neutral points are obtained. The test results show that under the condition of immersion, the loess has layered settlement, and there are both negative friction and positive friction on the pile surface, and there are two neutral points. Negative friction drags the pile downward, which makes the axial force of the pile increase obviously. The numerical simulation results verify the feasibility and validity of the test results. The research results of this paper have certain guiding significance for pile foundation design in collapsible loess area.

在湿陷性黄土地区，桩基的负表面摩擦力会引起桩体强度失效、桩基承载力降低等诸多工程问题，给工程建设带来很大危害。为研究湿陷性黄土地区桩基负摩擦力的变化及分布规律，设计并完成了考虑黄土湿陷性的桩基负摩擦力比例模型试验。通过有限元数值模拟，对试验结果进行了验证，得到了桩身负摩擦力的分布规律以及中性点的数量和位置。试验结果表明，在浸水条件下，黄土发生层状沉降，桩面既有负摩擦，也有正摩擦，并且有两个中性点。负摩擦力将桩向下拖，使桩的轴力明显增大。数值模拟结果验证了试验结果的可行性和有效性。本文的研究成果对湿陷性黄土地区的桩基设计具有一定的指导意义。