海底泥流的流变试验及强度模型

Rheological test and strength model of submarine mud flow

海底泥流是海底斜坡发生失稳滑动后,经复杂的水土交换作用演变成的稀式海底滑坡体,表现出土体和流体的双重特征,而现有的测试方法难以获得低剪切应变率下连续变化的强度值,不能很好地揭示其综合强度特性。利用新型全流动贯入仪和RST流变仪,对模拟海底泥流在不同剪切应变率下的流变和强度特性进行了多组试验研究,并基于试验结果分析了不排水剪切强度、屈服应力和表观黏度与含水率的相关性。基于剪切稀化理论,提出分阶段拟合模式来描述海底泥流从低剪切应变率到中高剪切应变率的流变关系;通过多种常规流变模式拟合结果的对比分析,显示出新流变模式的适用性和优势。考虑强度软化的影响,建立了全剪切应变率范围内海底泥流的不排水剪切强度模型,为海底泥流运动过程的数值模拟和灾害评价提供科学依据。

Submarine mud flow is a kind of dilute submarine landslide body which is evolved by complex soil and water exchange after the unstable sliding of submarine slope. It shows the dual characteristics of soil and fluid. However, it is difficult to obtain the continuous changing strength under low shear strain rate by the existing testing methods, and the comprehensive strength characteristics can not be well revealed. The rheological and strength properties of the simulated submarine mud flow at different shear strain rates are investigated by using new full-flow penetrometer and RST rheometer, and the relevance of the undrained shear strength, yield stress and apparent viscosity with moisture content are analyzed according to the experimental results. Based on the shear thinning theory, a piecewise fitting model is developed to describe the rheological relation of submarine mud flow from low to high shear strain rate. Then, the new rheological model shows a good applicability and advantages through the comparison with other conventional models. In addition, an undrained shear strength model of submarine mud flow is established by considering the effect of strength softening, which provides a scientific basis for the numerical simulation and disaster assessment of submarine mud flow movement.