夯扩挤密碎石桩加固液化砂土地基的动力数值分析

砂土液化问题一直是土动力学与岩土地震工程研究领域的重要课题之一。基于南水北调中线某工程，通过现场和室内试验获取土体的物理力学参数，利用岩土数值分析软件FLAC3D对夯扩挤密碎石桩加固干渠液化砂土地基进行了动力数值分析。结果表明，由于夯扩挤密碎石桩的排水作用，干渠底部饱和砂土地基中的超静孔隙水压力和孔压比与加固前相比明显减小；干渠渠道底部饱和砂土中的监测曲线表明，随着地震荷载持续时间的增加，饱和砂土地基中超静孔隙水压力和孔压比峰值较加固前大幅值降低，且时程曲线达到峰值之后也由加固前的基本保持不变改为迅速消减降低；由于夯扩挤密碎石桩的排水和挤密作用，有效消除了干渠渠道底部以及渠堤坡面外侧平台至坡脚底部砂土层的液化现象，加固后干渠底部饱和砂土地基中没有液化现象产生。

Dynamic numerical analysis of liquefiable sand soil foundation reinforced by compacted gravel pile

The sand liquefaction problem has been one of the important topics in soil dynamics and geotechnical earthquake engineering. Based on a project of the Middle Route of South-to-North Water Transfer, physico-mechanical parameters of soil have been obtained through field and laboratory tests. And the dynamic numerical analysis on the liquefied sand foundation of the main canal which has been reinforced by compacted gravel piles is conducted with FLAC3D. The results show that, for the drainage of the compacted gravel piles, the excess pore water pressure and pore pressure ratio in the saturated sand foundation of the main canal bottom have been significantly reduced compared to ones before reinforcement. Monitoring curves of the saturated sand in the bottom of the main canal show that, with the duration of the seismic loading, the peak values of the excess pore water pressure and pore pressure ratio in the saturated sand foundation decrease significantly compared to ones before reinforcement; and the time-history curve declines quickly when to the peak value, which keeps essentially unchanged before reinforcement. For the drainage and compaction effect of the compacted gravel piles, the liquefaction of the sand layers, in the bottom of the main canal, and from the outside platform of the embankment to the bottom of the slope foot, is eliminated effectively. And no liquefaction occurs in the saturated sand foundation of the main canal bottom after reinforcement.