强震作用下饱和粉细砂液化振动台试验

针对强震区饱和粉细砂液化问题,依托海南铺前大桥实体工程,基于振动台模型试验,选用叠层剪切式模型箱,模拟自由场在地震作用下的振动反应,分析0.15g～0.80g地震动强度下不同深度饱和细粉砂孔压比的变化规律,探讨饱和粉细砂的液化判别方法.结果表明:饱和粉细砂超静孔隙水压力、孔压比的增长滞后于地震动应力,且粉细砂深度越深,滞后时间越长,上覆土层厚度对于饱和粉细砂的抗液化性能有重要影响;深度为5 cm、60 cm和110 cm的饱和粉细砂,当地震动强度分别≥0.15g、0.20g和0.25g时发生液化,此时孔压比稳定值均≥0.8,提出以0.8作为饱和粉细砂液化的临界孔压比;对比讨论现有常用方法的液化判定结果,提出一种以饱和粉细砂深度、地震动强度和孔压比为判据的饱和粉细砂液化判别新方法,可为铺前大桥基础的合理设计与施工提供科学依据,也可为类似工程提供技术支持.

Shaking table test of saturated fine sand liquefaction under strong earthquake

Aiming at liquefaction of saturated fine sand in meizoseismal area and taking the Puqian Bridge project as the test site, this study simulated the vibration response of the free field under seismic action by the vibration table model test and the laminated shear model box. The variation law of pore pressure ratio of saturated fine sand at different depths under ground vibration intensity of 0.15g~0.80g (g represents gravity acceleration) was analyzed, and the liquefaction discrimination method of saturated fine sand was discussed. Results show that the growth of ultra-quiet pore water pressure and pore pressure ratio of saturated fine sand lagged behind ground motion stress, and the deeper the sand was, the longer the lag time. The saturated fine sand with a depth of 5 cm, 60 cm, and 110 cm was liquefied when the local vibration intensity was greater than or equal to 0.15g, 0.20g, and 0.25g respectively, and the pore pressure ratio stability value was greater than or equal to 0.8, which was proposed as a critical pore pressure ratio of saturated fine sand liquefaction. The liquefaction determination results of the existing common methods were discussed and a new method for discriminating the liquefaction of saturated fine sand by the criterion of saturated fine sand depth, ground motion intensity, and pore pressure ratio was proposed. It provides technical reference for similar projects and scientific basis for rational design and construction of bridge foundation before paving.