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利用已有的离心机预固结加荷装置,开发了一套可以有效控制超固结比的模型桩竖向加荷系统,进行了开挖条件下饱和黏土中单桩竖向承载特性的室内模型试验。在模型试验用高岭土单元体试验的基础上,考虑开挖引起土体K0系数和不排水抗剪强度变化对桩侧极限摩阻力的影响,提出了开挖卸荷条件下饱和黏土中单桩竖向承载特性的非线性简化计算方法,并通过与模型试验结果进行对比验证了计算方法的正确性,算例分析表明:开挖将会使得竖向桩顶刚度和极限承载力的降低,合理的预测方法应该既要考虑开挖卸荷引起的桩侧土上覆压力的减少,又要考虑桩侧土体K0值和不排水抗剪强度的提高。
Using the existing centrifuge pre-consolidation load device, a set of model pile vertical loading system that can effectively control the overconsolidation ratio was developed. The indoor vertical load-bearing characteristics of single pile in saturated clay Model test. Based on the experiment of kaolin unit in model test and considering the effect of excavation on the ultimate frictional resistance of pile due to the change of K0 coefficient and undrained shear strength of soil under excavation, The nonlinear calculation method of bearing characteristics is simplified, and the correctness of the calculation method is verified by comparison with the model test results. The analysis shows that excavation will reduce the rigidity and ultimate bearing capacity of vertical pile, The prediction method should consider both the reduction of the overburden pressure on the pile side caused by excavation and unloading and the increase of K0 value and undrained shear strength of the pile side soil.