堆积体作用下陡坡河道流速沿程及横向分布规律

Streamwise and lateral velocity distribution of steep river underthe action of deposit body

滑坡、泥石流等灾害过程,常在河流岸边形成大型堆积体,缩窄了主河道过流宽度,对主河道水流运动产生影响.通过水槽试验,研究了堆积体作用下陡坡急流河道流速沿程及横向分布规律.试验结果表明:受堆积体影响,水流流态一般可分为上游低速区、主流区、下游回流区及堆积体下游段折冲水流与隐蔽区缓流相遇而形成的斜向水跃.堆积体的壅水作用对主流区流速沿程分布影响较大,随堆积体尺度的增加,对主流流速影响增大,影响范围加大.堆积体上游段,主流流速受堆积体影响减小;急流条件下,堆积体段的过流断面束窄,过流能力降低,主流流速较天然状态有所降低,出现急、缓流过渡,堆积体末端逐步恢复至天然状态.堆积体下游临近断面流速大小与天然状态基本一致,沿横断面的流速比天然状态略有增大,对岸流速则略有降低,随堆积体规模的增加,流速横向变化幅度增大.

The disasters such as landslides and debris flows, often form large deposit in the river bank, which can exert an influence on the river flow through minishing the riverway. Based on the flume experiment, the streamwise and lateral velocity distributions of steep channel under the impact of deposit body are analyzed herein. The results show that ： under the impact of deposit, the flow pattern can be divided into four sections, i.e. the low speed zone upstream, the main flow zone, the backflow zone downstream and the ROEUP caused by the encounter of the skijump flow downstream and the low speed flow in shadow zone. The backwater significantly affects the streamwise velocity distribution of the main flow. With the increase of deposit body shape, the influence extent and range both augment. The influence of deposit on the mainstream velocity of upstream decreases, while on the condition of rapids flow in the region of deposit, because the cross-section is narrower and the conveyance capacity is lessened, the mainstream velocity is lower compared to natural condition and the flow will change between the rapids and tranquil flow, and then return to natural condition. The velocity in sections near the downstream of deposit body is approximately in accordance with natural condition. Compared with natural condition, the lateral distribution of velocity has a little increase in the bank of deposit body and a little decrease in another bank. The larger the scale of deposit is, the more the change extent of lateral distribution of flow will be.