高海拔地区宽级配泥石流冲击拦砂坝试验研究

Experimental study on the impact of wide graded debris flow on check dam in high altitude area

在高海拔地区,由于山高谷深,坡表物质受物理风化严重,物源级配宽度范围大,泥石流的发育频率高,冲击力大,导致拦砂坝损毁严重。为研究高海拔地区宽级配泥石流对拦砂坝的冲击规律,以西藏地区发育的泥石流为原型,建立宽级配泥石流冲击拦砂坝的物理试验模型,选取泥石流容重、水槽坡度与泥石流固相最大粒径为变量,进行27组水槽试验,研究冲击力特征。结果表明:(1)宽级配泥石流在冲击拦砂坝过程中经历“冲击爬高、旋滚回流、堆积回淤”3个接触演化阶段,泥石流容重越小,爬高越大,冲淤过程的阶段性表现越明显;(2)拦砂坝的坝前冲击力随宽级配泥石流容重的增大而减小,在相同坡度和级配的条件下,容重越大,水流携带固体物源运动越困难,泥石流流速降低,泥石流的冲击力减小;(3)拦砂坝的坝前冲击力随沟槽坡度增大而增大,沟槽坡度越大,宽级配泥石流的流速和流深越大,泥石流冲击力就越大,并且泥石流固相粒径越大,坡度对冲击力的影响效果越明显;(4)拦砂坝的坝前冲击力随宽级配泥石流固相最大粒径增大而增大,且变化趋势较泥石流容重及沟槽坡度条件改变时更加显著,最大粒径与泥石流流速、流深没有明显规律关系。研究成果将为宽级配泥石流防治和研究提供一定的数据参考。

The impact force of debris flow is the main cause of damage and destruction of check dam.In high altitude area,due to high mountains and deep valleys,serious physical weathering of surface materials,a wide range of source materials gradation,high frequency of debris flow occurence and high impact force,the damages induced by debris flow to the check dam are significant.To study the impact characteristics of the wide graded debris flow on check dam in high altitude area,the debris flow developed in Tibet is taking as a prototype.A physical test model of the impact check dam of wide graded debris flow is established.The unit weight of debris flow,the slope of flume and the maximum particle size of debris flow solid are selected as variable factors.27 groups of flume tests were carried out to study the characteristics of impact force.The results show that:(1)Wide-graded debris flow mainly undergoes three contact evolution stages during the process of impact retaining dam,i.e.impact climbing-rolling return flow-accumulation and silting.The smaller of the debris flow volume weight could lead to a higher climbing distance,and more obvious stage performance of sourcing and sliting process.(2)The impact force in front of the dam decreases with the increase of the bulk weight of wide-graded debris flow.Under the same slope and gradation,a larger the bulk weight of debris flow materials lead to a lower velocity of the debris flow materials and less impact force,because it is more difficult to carry solid material sources.(3)The impact force in front of the dam increases with the increase of the groove gradient.The larger the groove gradient,the greater the flow velocity and flow depth of wide-graded debris flow,the greater the impact force of debris flow.The larger the particle size of solid phase of debris flow,the more significant the impact of slope on impact force.(4)The impact force in front of the sand bar increases with the increase of the maximum particle size of the solid phase of the wide graded debris flow,and the change trend is more significant than when the volume density of the debris flow and the slope conditions of the groove change.The maximum particle size has no obvious regular relationship with the velocity and depth of the debris flow.The research results will provide certain data reference for the prevention and research of wide graded debris flows.