津滨轻轨基础托换桩基承载力的自平衡试验

Self-balanced loading test for pile bearing capacity of pile underpinning on Jin-bin light track

津滨轻轨基础托换工程采用了直径2.0m、桩长90m的大直径超长钻孔灌注桩,且该桩位处于北方地区软土地基环境.受津滨轻轨高架桥的限制,桩基施工净空仅有7m.采用自平衡测桩技术,对该工程托换桩基极限承载力进行了原位测试.试验在桩端附近位置安设荷载箱,测试荷载箱上部和下部的承载力,根据测试数据并进行荷载转换,从而得出试验桩基的极限承载力.试验同时分析了各土层的实际摩阻力和桩端阻力.数据显示桩端承载力较低,桩端阻力仅为其承载力的5.7%,原位试验验证了桩基承载力满足设计要求.

The foundation underpinning of Jin-bin light tracks uses large diameter bored piles,2.0m diameter and 90m long,located at the northern areas of the soft foundation.Restrictions on the viaduct of Jinbin light tracks,pile construction clearance is only 7m high.An in-site test of the pile underpinning＇s bearing capacity is performed by self-balanced loading technique.Load cells are put around the pile tips.The utmost bearing capacity of the pile tips is obtained by testing the bearing behavior of the top and bottom of the load cells.The real friction resistance and pile tip resistance of different stratum layers are also analyzed.The result of the test shows a lower pile-tip capacity,only 5.7% of its bearing capacity.The insite test shows that the bearing capacity of the pile foundation satisfies the design requirements.