堆载条件下单桩负摩阻力模型试验研究

Model test study of negative skin friction for single pile under surface load

通过对粉土中混凝土单桩竖向静载荷的模型试验,分析了在桩周土堆载条件下,端承桩、摩擦端承桩在桩周土含水率变化时,桩侧摩阻力、桩端阻力的变化规律及不同土层的沉降、"中性点"位置和下拽力的变化。研究发现,摩擦端承桩"中性点"位置随桩周土含水率、堆载等级的变化而变化,在最优含水率附近,土层的下陷量较大,致桩体沉降量也大,故"中性点"的位置会有所上升;随着桩周土堆载的增大,桩周土对桩侧的下拽力也增大,桩体进一步下陷,使桩土相对位移反而减少,"中性点"有所上升。

Through the vertical static load model experiment of concrete single pile in silt, the change rule of the resistance of pile side and pile tip, the subsidence situation of different soil strata, and the changes of ＂neutral point＂ position and dragload of end-bearing pile and friction end-bearing pile are analyzed under the variety of the water content change of the soil around the pile. It is found that the ＂neutral point＂ position of friction end-bearing pile changes while the variety of water content and load grade of soil around the pile change; ＂neutral point＂ position reaches the tiptop near optimum moisture content and becomes higher along with the load increase.