黏性泥石流冲起爬高计算

Determination of Run-up of Viscous Debris Flow

泥石流冲起爬高是泥石流防治工程设计中的一个重要参数。黏性泥石流是一种特殊的固、液两相流体,固、液两相间的相互作用很弱,流体整体性表现为粘塑性流体。在运动过程中,由于黏粒含量高,液相浆体表现出非常大的宏观黏性,而浆体的屈服应力和固相颗粒间的摩擦作用使得泥石流体表现出了很强的塑性特性。本文以黏性泥石流作为研究对象,考虑泥石流龙头的运动平衡方程,建立了一个简单的黏性泥石流运动爬高的物理模型。结合运动平衡方程的解和障碍物的几何特性,推导了黏性泥石流的冲起爬高的计算公式。参数敏感性分析表明,泥石流的冲起爬高随着障碍物迎面坡度和泥石流流速的增加而增加,随着障碍物坡面的摩擦系数和泥石流密度的增加为减小,而泥石流的泥深、液相浆体的屈服应力及动力粘性对泥石流的爬高影响较小。进一步的分析表明,黏性泥石流冲起爬高的计算公H_p=aV^2/2g主中的动能修正系数a与泥石流的密度及障碍物的迎面坡度和摩擦系数有关,可表示为a=sinθ/[sinθ+C_s(ρ_s-ρ_f)/ρ cosθ tanφ]。利用水槽实验和云南蒋家沟野外采集的泥石流动力学参数和爬高数据,验证了本文提出的黏性泥石流冲起爬高的计算公式的可靠性。

Debris flow run-up is one of the key considerations in engineering mitigation design,particularly in the case of viscous debris flow,which usually was considered as granular-liquid two-phase flow. Due to its high clay content,viscous debris flow travels with higher viscosity,usually treated as visco-plastic flow in the modelling.Such plastics behavior of debris flow was ascribed to the interaction result of yield stress of liquid phase and friction stress between particles. In this study,run-up of viscous debris flow was addressed and a simplified physical model was developed based on momentum equilibrium equation for the debris flow front. The bottom shear stresses consisted of the stress of liquid slurries and was simulated by Bingham model and the friction stress between coarse particles and the surface of barrier. The calculation formula of viscous debris flow run-up was obtained through combining the solution of momentum equation for debris flowfront with the geometric characteristics of the barrier.The sensitivity analysis of the parameters showed that debris flow run-up increased with the increasing of velocity of debris flow and slope of barrier,and decreased with the decreasing of density of debris flow and friction coefficient between coarse particles and the surface of barrier. However,height of debris flow and dynamical parameters of liquid-slurry had less effect on the run-up of debris flow. Therefore,viscous debris flow run-up depended mainly on velocity of debris flow,slope of barrier and friction coefficient between coarse particles and the surface of barrier.Ignoring the resistance due to liquid slurry,the debris flow run-up could be calculated with the model,i. e. Hp=a V^2/2 g. Furthermore,the coefficient a in the debris flow run-up model,was depends on the density of debris flow,the slope of barrier and friction coefficient between coarse particles and the surface of barrier and can be modeled as a = sin θ/[sin θ ＋ Cs（ ρs-ρf）/ρ cos θ tan φ]. The proposed model was verified using experiment data and field measurement at the Jiangjia Gully.