公路桥超长群桩的有效桩长研究

Study of effective length of super-long pile group in highway bridges

针对公路桥梁超长群桩的有效桩长问题,对国内公路桥梁桩基的荷载状况进行统计分析,得出桩顶应力主要分布在6～21 MPa范围。进行了长径比为96的桩间距分别为3D、4.5D和6D的3组不同群桩的超长群桩模型试验,得到3种不同桩间距的超长群桩中单桩轴力随着不同荷载的分布图,按照桩身轴力趋于0的桩截面的深度确定有效桩长,并利用指数函数关系分别拟合了3种不同桩间距的桩顶应力与有效桩长之间的关系。根据竖向荷载作用下群桩模型试验与实际原型之间的相似关系,确定公路桥超长群桩与荷载对应的有效桩长取值范围,研究了超长群桩的有效桩长与桩间距之间的关系,并对桥梁桩基有效桩长的取值与桩间距提出了建议。

In light of the effective length problem of super-long pile of the pile group in highway bridges,the loading status of pile foundation for highway bridges in China is statistically analyzed.The resulting stress distribution range at the top of the pile is basically 6-21 MPa.The model tests of the super long pile groups have been carried out,in which the length-diameter ratio is 96 and the pile spans are respectively 3D,4.5D and 6D.The axial force distributions of different loadings in the super-long pile group with different pile spans are obtained.According to the depth of pile section for axial forces of the pile tending to zero,the effective length of pile is determined.The relations between the pile top stress and the effective length of pile for three different pile spans are drawn up by utilizing the exponential functions.By exploring the resemble principles about model test of pile groups under the vertical loads,the effective length of piles corresponding to pile top loading of the super long pile group in highway bridges are yielded.Also the relations between the effective lengths of piles in the super long pile group and the pile spans are researched.At last,some suggestions are proposed for the concrete choice data of the pile spans and effective lengths of super-long piles.