苏通长江大桥北引桥二期试桩试验研究

苏通长江大桥北引桥二期试桩工程采用自平衡试桩法对4根桩进行了测试,其中2根采用U管桩端压浆技术。根 据未压浆桩端阻实测值与计算结果的比较,计算值偏大,实测值为计算值的0.75～0.95倍。未压浆桩发挥端阻所需位移分别 为16mm、38mm,压浆桩发挥端阻所需位移有所减少,分别为12mm、21mm。压浆后桩端阻力测试值是未压浆桩端阻力测试值 的2.46～3.32倍,是规范计算值的2.46～2.50倍。压浆后,桩端阻力在总荷载中所占比例明显提高,由14.42%～15.39%提 高到22.83%～27.22%。桩端压浆对桩侧摩阻力有较大影响,其显著影响范围约为桩端以上14.27m～19.12m,且发挥摩阻 力所需位移明显减小。

TESTING PILES FOR THE SECOND STAGE OF NORTH BRIDGE APPROACH OF SUTONG YANGTZE RIVER BRIDGE

Static load tests were carried out with the self-balanced test method on four bored piles of which two use the U-tube base grouting technique, for the second stage of the north bridge approach at the Sutong Yangtze River Bridge. The test results of the pile-tip bearing capacity are about 5% to 25% smaller than the calculation results from the standard. The critical displacements of un-grouted piles are 16 mm and 38 mm respectively, which are larger than those of the grouted piles: 12 mm and 21 mm respectively. The pile-tip bearing capacity for the grouted piles is 2.46 to 3.32 times of that of the un-grouted ones, or 2.46 to 2.50 times of the calculated value from the standard. After grouting, ratios of the pile-tip bearing capacity over total capacity increase from 14.42%¹5.39% to 22.83%²7.22%. The shaft resistances are also affected by grouting. The apparent affecting zone ranges from 14.27 m to 19.12 m above the pile tip with reduced critical displacements.