黄土地基微型桩基础上拔及下压承载性能研究

Uplift and press bearing capacity of micro-pile foundation for transmission line on loess ground

在软土地基中,微型桩常用作输电线路杆塔基础,而在黄土地区的应用相对较少。为了研究黄土地基微型桩基础的上拔及下压承载性能,本研究基于微型桩原位静载荷试验,分析了桩长、桩径及黄土湿陷性等不同参数对微型桩承载性能的影响;同时创建了三维桩土相互作用的有限元模型,对比其数值模拟结果与试验数据,验证了有限元模型的正确性,进一步分析了桩长、桩径及桩身弹性模量对其抗拔及抗压承载性能的影响。结果表明:相比其抗拔承载力而言,黄土湿陷性对微型桩抗压承载力的影响更大,且浸水后微型桩基础的破坏曲线斜率更大。黄土地基微型桩的竖向承载特性主要取决于桩侧摩阻力,桩长对抗拔、抗压极限承载力影响较桩径显著。上述研究对微型桩基础在黄土地区的应用具有较好的参考价值。

The micro-piles have been widely used in transmission line tower foundation on soft soil foundation,but it is relatively less used on loess foundation.In order to study the uplift and press bearing capacity of micro-pile foundation on loess foundation,the effects of pile length,pile diameter and loess collapsibility on the bearing capacity of micropiles are analyzed based on the field static load test.To overcome the limitation of the field test,the three-dimensional finite element models of pile-soil interaction are established to compare the results of numerical analysis and experimental results.The finite element model is verified,and then used to analyze the effects of different pile length and pile diameter pile elastic modulus on the uplift and the compressive load performance.The results could be drawn from this study show that the impact of loess collapsibility on the compressive bearing capacity of micro-pile is greater than that of uplift bearing capacity,and the failure curve of the micro-pile foundation after immersion in water presents a more obvious steep drop.The vertical bearing capacity of micro-pile on loess foundation is mainly determined by pile lateral friction resistance.The influence of pile length on ultimate bearing capacity is more significant than that of pile diameter.The above research has good reference value for the application of micro-pile foundation on loess ground.