饱和砂土液化前高孔压状态的流动特性试验研究

The flow characteristics of pre-liquefied sand under high excess pore pressure

将液化及液化后状态的砂土视为流体状态,研究发现液化及液化后砂土是一种剪切稀化非牛顿流体。对于液化前高孔压状态下的流动特性也值得探讨。根据落球黏度计的原理,开发了饱和砂土液化前流动特性的模型试验装置。在模型箱中铺设饱和砂土,模型箱底部与一水箱相连,提高水箱高度可以使模型箱中的饱和砂土产生超孔压。模型箱的砂土中埋设一个可以水平拉动的钢球,通过监测钢球水平运动的速度和所受的阻力来计算砂土的表观黏度,得到饱和砂土液化前高孔压状态下的流动特性。试验中考虑了超孔压比、钢球运动速度对结果的影响。试验表明,饱和砂土在液化前高孔压状态下,表观黏度均随着应变率的增大而减小,呈现出剪切稀化非牛顿流体特性,同时随着超孔压比的提高,表观黏度也逐渐减小。

Liquefied and post-liquefied sand can be treated as a kind of fluid.Past research has suggested that liquefied and post-liquefied sand is a shear-thinning non-Newtonian fluid.It's worth discussing the flow characteristics of pre-liquefied sand under high pore pressure ratio state.According to the theory of dropping ball viscosimeter,the test apparatus of flow characteristics of pre-liquefied sand is developed.The saturated sand was laid in a model box.A water box is linked with the bottom of the sand box.The height of water box can be enhanced to obtain the excess pore pressure in the sand soil.A steel sphere,embedded in the sand box,can be moved in the horizontal direction.Resistance force and velocity are measured during sphere dragging and apparent viscosity is evaluated.The velocity of the sphere and excess pore pressure ratio are the main factors in the tests.The results show that the apparent viscosity of the pre-liquefied sand decreases with the increase of the strain rate.The pre-liquefied sand is shear thinning non-Newtonian fluid,which is similar with liquefied and post-liquefied sand.The apparent viscosity of the pre-liquefied sand decreases with the increase of the excess pore pressure ratio.