变刚度调平设计中桩基承载性状研究

Bearing capacity of piles in optimized design of pile foundation stiffness to reduce differential settlement

桩基变刚度调平设计的框筒结构体系大比尺模型试验和实际工程桩顶反力测试结果均显示工作荷载作用下,核心筒不同区位桩顶反力随荷载水平的提高而增加,核心筒外围框架柱下桩顶反力也与核心筒下桩顶反力一样趋于均匀。可见,变刚度调平设计可调整反力分布,改善筏板的受力性状。模型试验中核心筒桩顶反力提高的比率是角桩最大、边桩次之、中心桩最小,角桩、边桩、中心桩反力与平均值的比值为:1.15∶1.02∶0.83。工程实测中外框架角桩下桩反力>外框架边柱下桩反力>核心筒下桩反力。这主要由于群桩效应引起的桩基竖向支撑刚度弱化,外框架柱下角桩处桩数少,群桩效应影响较弱。

The measured results of forces at pile top of tube frame structural system and large-scale model tests by applying the optimized design of pile foundation stiffness to reduce differential settlement show that the forces at pile top in different tube areas increase with the increase of loading level, and those under the tube and peripheral frame columns tend to be uniform under the working loads. The optimized design of pile foundation stiffness to reduce differential settlement can adjust distribution of forces and improve stress behavior of rafts. In model tests, the improvement ratio for tubes is in the decreasing order of angle pile, side pile and center pile. The corresponding pile butt force ratio of the forces to mean values is 1.15∶1.02∶0.83. The measured pile forces are in the decreasing order of peripheral frame columns, peripheral frame edge columns and piles under the tube. This is mainly due to the weakening of support stiffness caused by the vertical pile group effect. The pile group effect is weaker due to the fewer number of piles under the peripheral frame columns and angle piles.