嵌岩灌注桩初始后屈曲性状分析

Analysis of the Behavior of Initial Post-Buckling of Cast-in-situ Rock-Socketed Piles

为了探讨桥梁工程中广泛使用的嵌岩灌注桩的初始后屈曲性状,先基于弹性地基梁理论假定桩身后屈曲分析模型与相应的桩身挠曲位移函数,由此建立桩土体系的总势能方程;然后采用扰动法,基于能量原理导得不同约束情况下桩顶临界荷载的变化式,并据此讨论了桩土刚度比、桩身埋置率及桩顶自由长度等对桩身后屈曲性状的影响规律.结果表明,当桩周土趋于软弱而桩身刚度越大时,桩身初始后屈曲平衡路径将越趋于不稳定,且可能因桩身初始缺陷的存在而导致其屈曲荷载的显著降低.

To discuss the behavior of initial post-buckling of cast-in-situ rock-socketed piles widely used in bridge engineering, the total potential energy equation of the pile-soil system was first obtained from the simplified beam model on elastic foundation and oorresponding flexure function of the pile shaft. Then, variation forrnulas of the buckling load under different constrain conditions were deduced respectively by applying the minimum potential energy principle. Based on the obtained solutions, influencing rules by the stiffness ration of pile shaft to the surrounding soil, the embedded proportion of pile shaft and the length of unsupported part of pile top were discussed in detail. The result showed that, when the soil around the pile shaft was weaker or the pile shaft was stiffer, the initial post-buckling equilibrium path of pile shaft tended to be trustable, and a remarkable decrease of the critical load for piles with initial imperfections was possible, which couldn＇ t be neglected in engineering practice.