沉渣预压处理的群桩模型试验研究

STUDY OF PILE GROUP MODEL TEST WITH PRELOADING BOTTOM SEDIMENT

为减小灌注桩桩底沉渣对承载力的影响,基于桩土共同作用原理,结合桩侧摩阻力发挥所需的位移对沉渣加以利用,并据此设计模型试验,试验包括两桩、三桩、四桩共3种桩基形式,分别对带沉渣与不带沉渣2种状况下群桩的承载性能展开研究。试验结果表明,相对不带沉渣的桩基而言,带沉渣的群桩在预压处理过程中,荷载–位移曲线在沉渣被压实前后会表现出台阶状的特点;经过预压处理后,桩体的位移较大,桩侧摩阻力发挥更充分;桩端阻力在沉渣被压实前很小,沉渣被压实后逐步发挥,并最终达到不带沉渣桩的水平。通过对带沉渣桩的荷载–位移曲线进行平移处理发现,桩基在牺牲一定沉降后承载力可恢复正常,且因沉降后的承台与土体接触紧密,使得桩土共同承载,往往使得处理后的桩基具有更高的竖向承载力和更好的水平承载性能。研究成果可为类似工程提供参考。

For reducing the influence of bottom sediment on bearing capacity of bored piles, a method of preloading sediment is proposed based on the principle of pile-soil interaction and the allowable displacement amount for frictional resistance. And the model tests are designed, which studied the bearing behavior of pile group with sediment and without sediment. The model experiment include two-pile foundation, three-pile foundation and four-pile foundation. For pile group without the sediment, the P-s curve of pile group represents step shape between pre-and post compacting the bottom sediment. The settlement of pile is greater after compacting the sediment. And the frictional resistance is greater than the general pile. Meanwhile, with the increase of load, the tip resistance experiences a process of small to great, and finally reaches the normal level. Through transferring the P-s curve of pile with sediment, the pile bearing capacity return to normal after the expense of certain settlement, and close contact between the pile cap and soil due to settlement, making the pile and soil common loading, which finally makes the pile has a higher vertical bearing capacity and a better horizontal bearing performance. The research results can provide a reference for similar projects.