砂土液化及液化后流动特性试验研究

Laboratory tests on flow characteristics of liquefied and post-liquefied sand

根据流体力学中的绕球定常黏性流动理论,在振动台试验的基础上,设计了一套砂土液化及液化后流动特性的试验装置。在振动台模型箱的砂土中埋入可以水平滑动的钢球,当砂土发生液化时使钢球发生水平运动,通过测量钢球所受的阻力来反算液化及液化后砂土的表观动力黏度,进而研究液化及液化后砂土的流动特性。试验中考虑了砂土的初始相对密度、钢球的运动速率、液化后砂土的超孔压比等因素的影响。试验结果表明,液化及液化后状态下砂土的表观动力黏度随着应变率的增大而减小,液化砂土呈现出剪切稀化的非牛顿流体特性。随着液化后超孔压比的降低,表观动力黏度也逐渐增大,通常随着应变率的增大,表观动力黏度–超孔压比曲线逐渐变缓。

According to the theory of dropping ball viscosimeter, the test apparatus of flow characteristics of liquefied and post-liquefied sand is developed based on the shaking table tests. A steel sphere, embedded in the sand box, can be moved in the horizontal direction when the soil liquefaction occurs. Resistance force and velocity are measured during sphere dragging and apparent viscosity is evaluated. The initial relative density of the deposited sand, 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 liquefied and post-liquefied sand decreases with the increase of the strain rate. The liquefied and post-liquefied sand is shear thinning non-Newtonian fluid. The apparent viscosity of the post-liquefied sand increases with the decrease of the excess pore pressure ratio, and the curve slope of the apparent viscosity vs. the excess pore pressure ratio decreases with the increase of the strain rate.