Time-dependent rheological properties and thixotropy of reconstituted debris-flows samples taken from channel bank deposits are examined using a commercial rheometer equipped with a vane rotor geometric system. Sweep tests and creep tests were carried out involving mixtures having different grain concentrations ranging between 50% and 58%. Different initial conditions of the mixtures were considered in order to analyze the effects of aging and rejuvenation (thixotropy) over a short period of time and long period of time. Tested slurries show viscosity bifurcation, yield stress and time-dependent behavior. According to the experimental results, three different regimes were identified: a lower shear rate regime, corresponding to a shear rate lower than the critical value; an intermediate banding shear rate regime characterized by static and dynamic yield stress level; and a higher shear rate regime where the flowing debris behaves as a non-Newtonian fluid characterized by a constant steady state ultimate apparent viscosity. In any case, the initial state of the mixture and the sediment concentration affects the ultimate steady state rheology and the time-dependent (thixotropy) slurries’ behavior.

中文翻译：

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再生泥石流混合物的触变性

使用装备有叶片转子几何系统的商用流变仪，对从河道堤岸沉积物中提取的再生碎屑流样品的随时间变化的流变性质和触变性进行了检查。进行了扫掠测试和蠕变测试，涉及到不同颗粒浓度在50％到58％之间的混合物。考虑了混合物的不同初始条件，以便分析短期和长时间内的老化和回春作用（触变性）。经测试的浆料显示出粘度分叉，屈服应力和随时间变化的行为。根据实验结果，确定了三种不同的状态：较低的剪切速率状态，对应于低于临界值的剪切速率；以及较低的剪切速率状态。以静态和动态屈服应力水平为特征的中间带剪切速率状态；较高的剪切速率范围，其中流动的碎屑表现为非牛顿流体，其特征是恒定的稳态极限表观粘度。在任何情况下，混合物的初始状态和沉积物浓度都会影响最终的稳态流变性和时间依赖性（触变性）浆液的行为。