粘性土层中挤扩支盘桩的承载力性状

Capacity behavior of cast-in-place pile with branches and plates in cohesive soils

分析了杭州粘性土地层中一根桩身埋设量测元件的挤扩支盘桩的载荷试验资料 ,揭示了挤扩支盘桩的承载力性状 ,即荷载由桩顶向下传递 ,盘阻力也自上至下在不同的荷载阶段发挥出来。结果表明 ,即使在可塑甚至接近软塑状态的粘性土中 ,只要层位、层厚合适 ,并满足盘距的构造要求 ,盘阻力是能够很好发挥的 ,但发挥程度受土的粘性和稠度影响 ,在液性指数小于 0 .7的粉质粘土中成盘性能良好。将试桩结果与现行规范做了比较 ,对支盘桩承载力计算参数的选用提出了有用的建议。

Data of the loading test on a cast\|in\|place pile with branches & plates instrumented with re\|bar gauge in cohesive soils in Hangzhou are analyzed. The capacity behavior of this type of pile in the soils is clarified, that is to say, the load is transferred from above to below, and so is the mobilization sequence of the resistance of the plates. The results show where there are suitable position and enough thickness of the strata and if the distance between the plates is proper, the resistance of the plates can well be mobilized even if the clay soil is in a near soft\|plastic state. The degree of mobilization is influenced by the cohesiveness and consistency of cohesive soils. The plates can well be formed in silty clay with a liquidity index of less then 0.7. After having compared the data of the loading test with present technical code, useful suggestions about the choice of parameters for the prediction of the load carrying capacity of the pile is presented.