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根据桩基现场原位试验,对比分析了旋挖钻成孔和正循环钻成孔两种施工工艺对成桩前期桩基承载力性状的影响。试验结果表明:旋挖钻成孔消除了桩侧泥皮的影响,改善了桩的荷载传递性能,使桩侧摩阻力增加,轴力衰减速度加快;旋挖钻成孔桩的桩侧最大摩阻力提高30%以上,达到桩侧最大摩阻力时的沉降约为正循环钻成孔桩的50%;旋挖钻成孔消除了桩端沉渣的影响,其最大端阻力提高136%,相同沉降量下旋挖钻成孔桩桩端阻力提高较大;旋挖钻成孔对桩侧阻力及桩端阻力的综合影响提高了桩的极限承载力。
According to the in-situ test of pile foundations, the influence of two kinds of construction techniques, ie rotary drilling and counterbore forming and positive cyclic drilling and boring on the bearing capacity of pre-pile foundations was analyzed. The test results show that the rotary drilling drilled holes eliminate the influence of the mud piles on the pile side and improve the load transfer performance of the pile, which increases the frictional resistance of the pile and accelerates the attenuation of axial force. The resistance increased by more than 30%. When the maximum frictional force on pile side was reached, the settlement was about 50% of that of the positive circulation drilling pile. The drilling drilled hole eliminated the influence of pile bottom sediment, the maximum resistance increased by 136% and the same settlement The lateral resistance of the drilled bored pile increased greatly. The combined effect of bored drilled holes on pile side resistance and pile end resistance increased the ultimate bearing capacity of pile.