超长桩在基坑开挖时承载性状分析

Analysis of Bearing Characteristics of Super Long Piles in Foundation Pit Excavation

建立了成层土中超长桩考虑桩土相互作用的三维非线性有限元数值模型,选取摩尔库伦准则为土体本构模型,通过对计算域、地应力平衡、边界条件等设定,使结构能反映实际工作情况,并与试验结果进行对比,验证了模型的准确性。模拟计算了单桩在基坑开挖工况下的竖向受力模型。针对工程试桩中常用到的套筒技术,模拟了套筒桩的承载性状,对比套筒桩与基坑开挖桩的桩顶荷载-沉降曲线,证明了套筒桩作为工程试桩高估了其在开挖后的承载力。

A 3D nonlinear finite element model is built to analyze the super long pile driven into stratified soil by taking the interaction of soil and pile into consideration.The criterion of Mohr-Coulomb is selected as the constitutive model of soil mass.Furthermore,the model can reflect the actual working state by setting the calculation domain,geostress equilibrium and boundary conditions.The accuracy of the model is verified by comparing the above information with the experimental results.The vertical load of single pile is calculated under the condition of foundation pit excavation.In addition,the influence of excavation depth on pile foundation bearing capacity is more than that of excavation length.The sleeve pile technique commonly used in pile test is studied so as to simulate its bearing characteristics The Q-S curves of sleeve pile and excavating pile are compared,which shows that the bearing capacity of sleeve pile as the test pile is lower than the estimated value after the excavation of foundation pit.