泥石流的固液两相分界粒径

The critical grain size of debris flow

固液两相分界粒径的划分是采用两相流理论研究非均质泥石流的关键问题之一。通过分析泥石流液相浆体的组成机理,以及泥石流野外实测资料和试验数据发现,分界粒径与泥石流的容重、黏度和流速等因素密切相关;根据不同粒径颗粒的物理力学性质和运动特征,以及浆体中所含颗粒主要处于悬浮状态且不发生分选的特点认为,泥石流的分界粒径将随自身的演进过程在某个范围内发生变化,且其最大变化值与泥石流的颗粒组成和运动特征有关。根据各类泥石流中固相和液相的应力特征,分别讨论了不同输沙模式下分界粒径的确定方法。基于非均匀悬移质输沙理论,从泥石流运动过程中粗细颗粒交换的角度出发,利用挟沙力的概念建立了一套适用于两相紊流输沙模式下分界粒径的确定方法,其同时考虑了泥石流容重、黏度及流速等因素的影响,比较切合实际且能与实测资料的分析结果相吻合。

Critical grain size is one of key study topics of heterogeneous debris flow based on the two phase flow theory. By mechanism analysis of slurry composition in the debris flow with observed data,the result indicates that the critical grain size closely relates with the density,viscosity,and velocity of the debris flow. According to the physical and mechanical properties and motion characteristics of particles with different sizes,and the characteristics of the particles contained in the slurry are mainly in suspended state without sorting.It’s sure that the change of the critical grain size will only occur within a certain range. According to the stress characteristics of solid phase and liquid phase in debris flow,methods to determine the critical grain size in different sediment transport modes are discussed. Based on the theory of non-uniform suspended sediment transport,and the view of the exchange of coarse and fine particles in the process of debris flow movement,we established a method to determine the critical grain size in the two-phase turbulent sediment transport mode,which includes the effects of density,viscosity and velocity based on the concept of sediment transport capacity. Furthermore,the method can conform to the actual and be consistent with the results of the analysis of observed data.