泥石流流变特性的试验研究

为了研究泥石流体的流变特性，专门研制了一台环形锥板式流变仪，其特点是能保证切变率场分布均匀.用四种颗粒材料和不同粘度的液相试料配制成不同特性的试样进行了一系列试验，成功地测得了试样受剪时的切应力和法应力变化.试验表明，两相体内颗粒间的作用不只是惯性碰撞，还有接触支承、摩擦滑动等作用.颗粒切应力与法应力之比基本为常数，其值只随颗粒外表特征而异.随着浓度增大，应力曲线的屈服值益超显著.外形不规则颗粒的试样在低切变率区具有一个与高切变率区不同变化规律的初始段，出现应力随切变率减小而增大的逆向变化和更大的屈服值.这些现象对于研究泥石流运动机理有重要意义。

Experiment of rheology of debris flow

Experiment of two-phase mixtures consisting of neutrally buoyant grains and interstitial liquid are performed on a special designed rheometer in order to investigate the stress constitutive relation of debris flow. This rheometer is equipped with an annular cone-plate type shear cell in which shear-rates can be kept in uniform. Four types of grain and various liquids are used to mix the test mixtures. The shear stress and normal pressure are measured simultaneoursly. The results show that, the granular stress occurred during shearing is not only caused by collision but also by supporting and friction. The ratios of shear stress to normal pressure are independent of grain concentration and liquid viscosity, roughly approach to a constant value. When the concentration becomes higher, the yield strenght of mixture becomes obvious even though the liquid medium of mixture are Newtonian fluids. In the initial part of flow curves, there exists a special section which has a property other than that of higher shear-rate region. Sometimes, a negative slope appears in initial section. This section can not be explained with a single rheological model. These phenomena may be important in study of debris flow mechanism.