液化砂土流动效应的振动台试验研究

采用振动台激励使饱和砂土发生液化，并侧向拖拽埋入砂土中的铝管，模拟液化土体与管体相对运动以分析液化砂土流动的力学效应。引入流体力学理论与方法，推导出以拉力反算表观黏度的表达式以及液化土体作为流体对管壁作用的黏滞剪切力。分析和比较了振时拖动、振后拖动下土体的流体性质及其流动效应的率相关性和孔压相关性，探讨了砂土密实度对土体流动效应的影响。结果表明，土体初始密实度与液化后土体的表观黏度正相关；液化土体的表观黏度以及因流动产生的黏滞剪切力与孔压反相关；液化砂土流动产生的黏滞剪切力具有强烈的率相关性。针对可液化场地中的结构抗震分析，应考虑土-结构率相关相互作用。

Shaking table tests on flow effects of liquefied sands

A series of shaking table tests on the saturated sands are conducted. The embedded aluminous tube in the sands is pulled laterally to simulate relative motion between liquefied sands and tube. The theories and methods of fluid mechanics are introduced to analyze the mechanical effects induced by the flows of liquefied sands. The real-time apparent viscosity of liquefied soils and the viscous shear force acting on the tube wall are calculated according to the measured pulling force. Fluid characteristics and flow effects of the liquefied soils are analyzed. For the soils during shaking and after shaking, their flow effects are rate-dependent and dependent on the excess pore water pressure. The influences of initial relative density on the flow effects are also discussed. The experimental results show that apparent viscosity of the liquefied sands is positively correlated with their initial relative density. The apparent viscosity and the viscous shear forces acting on the tube wall are negative correlated with the excess pore water pressure in the soils. Furthermore, the viscous shear forces acting on the tube wall are strongly rate-dependent. Therefore, the rate-dependent soil-structure interaction is suggested to be considered for the seismic analysis of structures in the liquefiable site.