人工冻结对南京砂液化特性的影响

针对长江中下游地区广泛分布的南京砂,使用GDS动三轴系统分别在地震荷载和地铁列车振动荷载作用下进行动三轴试验,研究人工冻结对南京砂液化特性的影响及其机理,并判别2种荷载对南京砂冻结施工的潜在危险。结果表明:在地震荷载和地铁列车振动荷载作用下,冻融循环均会明显降低南京砂的刚度和抗液化能力,首次冻融最为明显;冻融次数越多,冻融粉细砂的结构性越差,越容易发生液化;冻融循环将增大南京砂动孔压对动荷载响应的敏感度;冻结温度越低、有效围压越小,冻融循环后南京砂的抗液化能力越差;南京地区地震荷载对南京砂冻结施工的潜在危险较小,而来自地铁列车振动荷载的潜在危险较大。

Effects of Artificial Freezing on Liquefaction Characteristics of Nanjing Sand

Aiming at Nanjing sand widely distributed in the middle and lower reaches of the Yangtze River,the GDS dynamic triaxial system was used to carry out dynamic triaxial tests under seismic load and subway train vibration load respectively to study the influence of artificial freezing on the liquefaction characteristics of Nanjing sand and its mechanism,and distinguish the potential hazards of two kinds of loads to the freezing construction of Nanjing sand.Results show that the freeze-thaw cycle can significantly reduce the stiffness and liquefaction resistance of Nanjing sand under seismic and subway vibration loads,and the first freeze-thaw reduces most obviously.The more times of freeze-thaw,the worse the structure of the freeze-thaw silty fine sand,and the easier it is to liquefy.Freeze-thaw cycles will also increase the sensitivity of dynamic pore pressure to the dynamic load response of Nanjing sand.The lower the freezing temperature and the effective confining pressure,the worse the resistance to liquefaction of Nanjing sand after freeze-thaw cycle.The seismic load in Nanjing area has less potential hazard to the freezing construction of Nanjing sand,while the potential danger of vibration load from subway train is greater.