丁坝局部冲刷坑形态演变及冲刷平衡临界条件

Morphological evolution of spur dike local scour hole and the scour balance critical condition

丁坝局部冲刷坑垂向冲深、平面宽度及上下游边坡构成了冲刷坑几何形态的三维特征。局部冲刷达到平衡状态时,冲刷坑上下游边坡保持相对稳定的斜率。其与泥沙颗粒水下休止角大小及冲刷平衡临界条件的关系仍不太明确。一系列清水冲刷试验表明,不同来流强度条件下冲深与展宽速率存在非对称特征,坝体上下游边坡斜率随时间演变振荡衰减至相对稳定坡度。坝体上游坡度均较下游陡,比值近似常量为0.5。边坡斜率略小于泥沙颗粒水下休止角,比值下限近似为常量0.7。

Roughly several parameters controlled the 3-D characteristics of the scour hole geometry, which were the scour hole depth and width geometry and the side slope of upstream and downstream. The inclina- tions of the upstream and downstream side-slope kept relatively stable in the stage of scour equilibrium, while the relationship between the wet angle of repose of the sediment particle and the critical condition of scour equilibrium is not clear. A series of clear-water experiments showed that the variation of the scour depth and length possessed asymmetrical characteristic in different flow condition and the angel of inclina- tions of the upstream and downstream side-slope oscillated damply with time until stability. The scour hole side slope is steeper at upstream than that at downstream, which has a approximate constant of inclination ratio, namely about 0.5. The angel of inclination of side-slope is close to that of repose of the sediment particle, and its lower limit angle ratio approximated to 0.7.