波浪作用下液化粉土流动特性拖球试验研究

Dragging ball test on flow characteristics of liquefied silt under wave loading

粉质土大量存在于黄河水下三角洲地区,粉土液化过程中具有类似流体的性质,可以把液化过程中的粉土视为黏性流体进行研究。基于流体力学中Stokes黏滞阻力原理,在波浪水槽试验基础上,设计了一套测量液化过程中粉土流变特性的拖球装置,并对其实用性进行验证。在铺设有粉土底床的波浪水槽中埋入可以水平滑动的小球,通过拖动小球在粉土中水平运动,测量小球所受阻力值的大小,用以计算液化粉土表观动力黏度。充分考虑试验中波浪要素、超孔压比等因素的影响。结果表明,该装置能够满足试验要求;波浪循环荷载作用下,观察到了孔压的累积至液化的过程;波浪参数对结果有较大影响,其中波高越大,表观黏度值越小;同一波高情况下,表观黏度随时间缓慢增加;随着超孔压比的升高,波浪作用下粉土表观黏度值逐渐减小。

Silty seabed exists widely in the Yellow River Subaqueous Delta.Liquefied silt has properties similar to fluid.It has found that the behavior of liquefied silt can be simulated appropriately by modeling the liquefied silt as viscous fluid.According to the theory of Stokes Law,the test apparatus of flow characteristics of liquefied silt is developed based on the wave flume tests.A steel sphere,embedded in the wave flume,can be moved in the horizontal direction when the silt liquefaction occurs.Resistance force and velocity of the steel sphere are measured during sphere dragging,then apparent viscosity can be evaluated.Considering fully the infection of wave parameters and excess pore pressure ratio in the tests.The results indicate that this apparatus can meet the test requirements.It can be observed the processes of pressure buildup when it is forced by the cyclic loading of wave.Wave parameters have great influence on the results,apparent viscosity decreased as wave height increase.Apparent viscosity slowly enlarge with the passing of time at the same wave heights.Along with the increasing of pore pressure ratio,the apparent viscosity of the liquefied silt apparently decreases.