超长大直径钻孔灌注桩群桩效应系数研究

Research on Effect Coefficient of Extra-long Large Diameter Bored Pile Groups

针对超长大直径钻孔灌注群桩效应系数,研究了5种计算公式或方法,其中基于应力叠加的群桩效应系数计算公式,考虑了桩长、桩径、土层的内摩擦角以及地基土应力叠加等影响因素,适合计算超长大直径钻孔灌注群桩效应系数。然后,基于苏通长江公路大桥主5号墩超长大直径钻孔灌注群桩基础桩长、桩径和地基土层条件,分别计算了2×2群桩与3×3群桩的群桩效应系数值,并与相应类型群桩离心模型试验的群桩效应系数值进行比较。研究结果表明,计算值仅低于试验值7.2%-12.7%,说明该群桩效应系数计算公式具有一定的合理性,可为超长大直径钻孔灌注群桩设计提供参考。

In order to study the effect coefficient of extra-long large diameter bored pile groups, five formulas or methods for effect coefficient of pile groups were analyzed. It is found that the formula based on stress superposition fits the calculation of the effect coefficient of extra-long large diameter bored pile groups. The formula takes into the pile length, pile diameter, friction angle of soil layers and stress superposition. The effect coefficients of 2 × 2 pile groups and 3 × 3 pile groups were calculated based on the data of the soil layers, pile length and diameter for the pile groups under the fifth main pier in the Sutong Yangtse River Highway Bridges in P. R. China. The calculated theoretical values are compared with those of the centrifugal model test. The calculated ones are lower only by 7. 2 -12. 7 percent. This shows that the formula based on stress superposition for calculating the effect coefficient of extra-long large diameter bored pile groups is reasonable and can serve as a reference to design types of pile groups.