饱和南京细砂流动特性的振动台试验研究

Shaking table tests on fluid characteristics of saturated Nanjing fine sand

设计并完成了饱和南京细砂自由场振动台试验,采用频域分析手段对所采集到的加速度信号进行处理,并利用不同埋深处加速度换算得到模型地基土剪应力和剪应变,进一步基于流体动力学理论,得到地基土主震和余震作用下表观黏度的发展规律。试验结果表明,在主震和余震作用下表观黏度均随着剪应变率的增大而减小,表现出"剪切稀化"非牛顿流体特性,剪应变率相同时余震的表观黏度低于主震;主余震作用下表观黏度均随着孔压比的升高而降低,相同孔压比下余震的表观黏度明显大于主震的表观黏度;表观黏度的发展受到剪应变率和孔压比的双重影响。

Shaking table tests on the free ground consisting of saturated Nanjing fine sand are designed and accomplished. The collected acceleration signals are processed by the method of frequency-domain analysis, and the shear stress and strain of model soils are obtained using the accelerations measured at different depths. Furthermore, based on the theories of fluid mechanics, the evolution characteristics of the apparent viscosity under the action of the principal shock and aftershocks of foundation soils are obtained. The test results show that the apparent viscosity decreases with the growth of the shear strain rate under the action of the principal shock and aftershocks, and a typical shear-thinning non-Newtonian fluid feature is discovered. The apparent viscosity under the aftershocks is lower than that of the principal shock when it has the same shear strain rate. The apparent viscosity decreases as the pore pressure ratio increases under the action of the principal shock and aftershocks. The development of the apparent viscosity is affected by both the shear strain rate and the pore pressure ratio. The dual influences must be considered when the apparent viscosity is studied.