泥石流运动阻力特性及其研究进展

Research Progress of Resistance Character of Debris-flow

泥石流是一种由液相浆体和固相粗颗粒构成的特殊两相流体,其运动和动力性质研究的关键在于科学认识和描述其阻力特性。泥石流的阻力可以分为内部阻力和外部阻力:外部阻力是沟道底床和侧壁与泥石流体相互作用的结果,与沟床的粗糙度、几何形态及泥石流体的性质相关。内部阻力与泥石流体的物质构成有关,黏性细颗粒含量较多的黏性泥石流在运动过程中固、液两相的相对速度不明显,可以将黏性泥石流看成是一种均匀的混合流体,用伪一相流进行模拟,但其内部阻力仍应分为液相浆体阻力和固相颗粒间的阻力;黏性细颗粒含量较少的泥石流,液相浆体对粗颗粒的约束作用较小,存在明显的相间速度,诸如黏性拖曳力、附加质量力等相间作用力的影响非常重要。浆体中的细颗粒物质对泥石流运动阻力具有非常重要的影响,细颗粒物质的含量改变了液相浆体的阻力特性,包括屈服应力和黏性系数,而浆体的黏性将进一步改变固相颗粒间的相互作用。通过分析黏性泥石流的阻力特性,初步提出泥石流的综合阻力模型。

Debris-flow is a kind of two-phase fluid,which contains liquid-phase with slurry and solid-phase with coarse grains. The resistance characteristics,which can be divided into internal resistance and external resistance,is a critical factor for the study of kinematic and dynamic of debris-flow. The external resistance caused by interaction between debris-flow and gully-bed and gully- wall depends on the roughness,geometric shape of gully and properties of debris-flow. The debris-flow can be classified into viscosity debris-flow and two-phase debris-flow for understanding their internal resistance characteristics. For the former, the solid- phase and liquid-phase during the motion have no obvious slip velocity, therefore viscosity debris-flow could be identified as a kind of homogeneous mixing fluid and modeled by pseudo-homogenous fluid. However, for the two-phases debris-flow, the solid- phase and liquid-phase itave obvious slipvelocity;the stress forces due to solid-liquid interaction, such as viscosity drag force and virtual mass force etc. ,play critical role,and thus the stress due to interactions of solid grains,which comes from granular flow, is a key factor. The Fine contents in liquid-phase slurry has a huge effect on the resistance character of a debris flow and can change the resistance character of liquid-phase slurry,including yield stress and viscosity coefficient. Furthermore,the viscosity co- efficient of slurry can have effects on stress due to interaction of solid grains. A comprehensive resistance model of debris-flow, including internal resistance and external resistance,was proposed.