浑水推移质分组输沙研究

Fractional bedload transport in turbid waters

天然河流的泥沙输移大多在浑水条件下进行,浑水条件与清水条件下的输沙机理存在一定差异。基于近底泥沙交换三状态随机-力学模式,考虑了床沙与推移质向悬移质的净交换,引入扬动概率,建立了浑水中非均匀推移质分级输沙率公式,进而导出总输沙率及推移质级配的计算式。浑水条件下进行的推移质输移水槽试验和野外实测资料验证了该理论公式的合理性与可靠性,并发现浑水条件下推移质级配可能粗于原始床沙级配。研究结果表明:在浑水中,以悬移质形式存在的砂质泥沙含量对有效估算推移质输沙率有着不容忽视的影响。在某粒级运动泥沙总量不变的前提下,由于一部分沙粒悬浮于水体中,将使得推移质数量相对减少。

The mechanism of sediment transport in turbid water is different from that in clear water. According to the concept of three states exchange mode of non-uniform sediment at riverbed surface, an analytical formula for calculating the fractional bedload transport rate in turbid was established. In the formula the parameter expressing the drawn up possibility was introduced and the net exchange of bedload towards water flow was considered. The reliability of the proposed formula was verified by experimental and field observation data. It is found that the bedload particles may become coarser than that of original in turbid water. Furthermore, for exactly estimating the sandy bedload transport rate the content of suspended load which comes from bedload should be neglected.