循环荷载下筋箍碎石桩复合地基动力特性数值分析

过7组三维有限差分数值模拟试验，研究了循环荷载作用下筋箍碎石桩复合地基的动力特性，着重分析了4个重要参数对其性能的影响，并将数值计算结果与室内模型试验结果进行了对比分析，验证了数值计算结果的合理性. 结果表明，在循环荷载作用下，筋箍碎石桩复合地基的应力和沉降变化具有明显的动力特性. 相同循环加载条件下，增大碎石密度可有效提高碎石桩的承载力. 筋材使碎石桩的力学性能得到了改善，不同长度的加筋会对碎石桩产生明显不同的效果，在一定范围内增加碎石桩的加筋长度可以有效提高碎石桩的承载力. 筋材对复合地基顶部的累积沉降和应力集中率有显著影响. 筋材能提高碎石桩的整体性，加筋长度越长的碎石桩的振动协调性越好. 桩径对筋箍碎石桩复合地基顶部累积沉降的影响比较明显，碎石桩的最佳L/d值为8/3. 数值计算结果与室内模型试验结果拟合较好，沉降值最大相差7%，桩侧应力值最大相差9%.

Numerical Analyses on Dynamic Characteristics of Composite Foundations with Encased Stone Piles under Cyclic Loading

In this study, seven groups of three-dimensional finite differential numerical simulation tests were performed to investigate the dynamic characteristics of the composite foundations of geogrid-encased piles under cyclic loading. The effects of four important parameters on the behavior of the encased piles were evaluated. The numerical calculation results are compared with those of laboratory model tests, which verifies the rationality of the numerical results. The results show that the stress and settlement of encased stone piles composite foundations have obvious dynamic characteristics under cyclic loading. Under the same cyclic loading condition, increasing the gravel density could effectively improve the bearing capacity of the piles. The encasement can improve the mechanical properties of the piles, and the encasements with different lengths have different effects on the piles. Increasing the encasement length in a certain range can effectively improve the bearing capacity of the stone piles. The encasement has a significant effect on the cumulative settlement and stress concentration at the top of composite foundations. The encasement can improve the integrity of the stone piles, and increasing reinforcement length can lead to better vibration coordination of the stone piles. Pile diameter has an obvious influence on the cumulative settlement at the top of encased stone pile composite foundations, and the optimal L/d value of the stone pile is 8/3. The results of numerical calculation fit well with those of laboratory model tests. The maximum difference in settlement value is 7%, and the maximum difference in lateral stress of the pile is 9%.