非均质泥石流起动判别关系式

Distinguish relations for the critical intitiation of non-homogeneous debris flow

在我国西部山区每年汛期发生不同程度的泥石流灾害,认识非均质泥石流(又称黏性泥石流)的形成机理,判识泥石流的发生条件是准确预测预报泥石流的基础。本文通过48组正交的水槽实验,模拟非均质泥石流形成的动力过程,分析相关起动因子的量化关系。基于泥沙运动力学理论,将Shields数(又称希尔兹数)列为判识泥石流固体颗粒起动的重要参数,分析非均质系数(颗粒铺设方式)、水流量等水沙因子对泥石流起动的响应关系。进一步从泥沙颗粒的受力角度,以水流剪切力与颗粒起动临界剪切力的比值(即起动判别式)作为表征泥石流颗粒起动的参数(其值大于1时表示泥石流颗粒处于起动状态),分别应用Shields起动拖曳力曲线的整体拟合公式和分段拟合公式两种形式,初步建立了非均质泥石流颗粒起动判别式。通过应用蒋家沟实测资料进行验证,表明以Shields起动拖曳力曲线的整体拟合公式得出的起动判别式误差较小,可以应用于泥石流起动条件与致灾临界条件的判识,对我国泥石流防灾减灾具有重要参考价值。

As one of natural disasters,non-homogeneous debris flow is common in nature,occurring widely throughout the world in flood seasons especially in the southwest China. The formation mechanism of de-bris flow is highly concerned by scholars around the world. Studying the formation mechanism of debrisflow and occurrence conditions is the basis for debris flow forecast and prevention. With 48 flume simulation experiments,the mechanism of debris flow and the quantitative relations of factors related to debrisflow formation are revealed. According to sediment movement mechanics,Shields number is important to de-termine solid particle starting of debris flow. With the Shields number results classified by water quantity,vertical distribution of solid particle（non-homogeneous coefficient Ψ） and d50,the Shields number showspositive relations with particle median diameter d50 and water discharge Q with analysis. The vertical distri-bution of solid particle reflects the non-homogeneous properties and the starting order of particles. Whenparticles at the upper layer are much coarser than those at the lower layer,the Shields number is the largest. In the aspect of the particle shear stress,the critical expression of particle starting（the ratio of watershear stress to critical particle starting stress, if the calculation value of the discriminant is larger than1.0,then particles start.） are preliminarily established separately based on the overall fitting formula andbreak fitting formula of Shields starting drag curve. Through verification with the field data from JiangjiaGully,the critical expression of the particle initiation based on the overall fitting formula has a smaller deviation,having the better applicability. These results above is very significant for both preventing and reducing debris flow disasters.