三种工况下扩底楔形桩承载特性模型试验研究

Research on bearing capacity of belled wedge pile model under three working conditions

扩底楔形桩具有单位材料利用率高、竖向桩侧摩阻力和桩端阻力较常规等截面桩高的技术优点。然而,针对该桩型竖向及水平向承载力的定量模型试验研究相对较少。基于模型试验方法,开展砂性土中竖向、水平向荷载以及地面堆载等不同形工况荷载作用下扩底楔形桩的承载特性试验,测得不同荷载等级下桩侧摩阻力、桩端阻力、侧向土压力、桩顶下拽位移以及桩身下拽力等分布规律;同时,开展等混凝土用量常规等直径桩的承载特性试验作为对比分析,初步探讨了两种桩型的受力机制与异同点。研究结果表明,试验条件下,扩底楔形桩的单桩竖向承载力约为等直径圆桩的2.33倍,表现出侧阻力和端阻力都优于圆形桩的特点;水平承载力约为等直径圆桩的1.48倍,上部直径较大和扩大头的存在提高了其水平承载性能;与等直径圆桩相比,楔形角的存在可有效降低桩顶下拽位移,可见把传统桩型转变成扩底楔形桩是降低负摩阻力对桩基影响的有效方法之一。

Compared with traditional equal section pile, belled wedge pile has advantages of high unit material utilization, large pile side friction and tip resistances. However, there is little research focused on the quantitative model test on its vertical and lateral bearing capacities The bearing capacities of belled wedge pile embedded in sand under vertical load, lateral load, and surcharge load are tested experimentally to measure the pile shaft, tip resistances, lateral earth pressure, down-drag displacement, and drag load. At the same time, the bearing capacities of equal section pile with the same concrete usage are compared. The mechanism and differences of these piles are preliminary discussed. The results show that the vertical compressive bearing capacity of belied wedge pile are nearly 2.33 times that of equal circular pile, the side and tip resistance are higher than circular pile; the lateral bearing capacity of belled wedge pile is nearly 1.48 times that of circular pile, the larger diameter of the upper part of belled wedge pile and the expanded tip improve the lateral bearing capacity. Comparing with circular pile, the wedge angle can effectively reduce the down-drag displacement of pile top. It presents as one effective ways to reduce the negative friction resistance to the pile foundation by converting the traditional pile type into the belled wedge pile.