孔压增长后的饱和砂土流体特性及其孔压相关性

Fluid characteristics dependent on excess pore water pressure of saturated sand after growth of pore pressure

设计并完成了可液化饱和南京细砂自由场地基振动台试验。利用不同埋深处量测的加速度反应时程,采用线性插值法通过换算得到模型地基土剪应力和剪应变。进一步基于流体力学方法,研究了饱和砂土在孔压增长过程中表观动力黏度的变化规律。试验结果表明,在正弦波荷载作用下,饱和砂土液化前的表观动力黏度随着剪应变和剪应变率的增大而减小,表现出典型的"剪切稀化"非牛顿流体特性;超孔压比在饱和砂土的表观动力黏度发展变化中起着显著作用,表观动力黏度随着超孔压比的增大而减小,并且利用幂函数可以很好的拟合表观动力黏度与超孔压比的关系曲线。此外,表观动力黏度与孔压比的关系似乎不依赖有效上覆压力,该结论有待进一步验证。

Shaking table model tests on free ground consisting of saturated liquefiable Nanjing fine sand are designed and accomplished.According to the acceleration response measured at different depths,the shear stress and strain of the model soils are obtained using the linear interpolation method conversion.Furthermore,based on the principles of fluid mechanics,the evolution characteristics of dynamic apparent viscosity of the saturated sand during the build-up of the pore water pressure are studied.The test results show that the dynamic apparent viscosity decreases with the growth of shear strain as well as the increase of shear strain rate during the sinusoidal wave excitations.In addition,a typical shear-thinning non-Newtonian fluid feature is discovered.Moreover,the excess pore pressure ratio plays a significant role in the development and change of apparent dynamic viscosity of saturated sand,and the apparent dynamic viscosity decreases as the excess pore pressure ratio increases;besides,the relationship curve of the apparent dynamic viscosity and pore pressure ratio can be well fitted using the power function.Additionally,the relationship curve of the apparent dynamic viscosity and pore pressure ratio might not be dependent on the effective overburden pressure.However,this conclusion needs further verification.