水力冲刷过程中塌岸淤床交互影响试验

An experimental study of interaction between bank collapse and river bed evolution

在弯道水槽中展开系列试验,研究水力冲刷过程中非粘性岸坡冲刷崩塌与河床冲淤交互作用过程及其影响因素,进一步分析塌岸淤床泥沙贡献率。试验成果表明,水流冲刷过程中岸坡破坏是水流淘刷岸坡坡脚、岸坡崩塌及崩塌体淤积坡脚并在河床上输移掺混的交互作用反复循环过程。塌岸淤床模式及掺混程度与近岸流速、主流贴岸程度、水位及河床边界条件等关系密切。近岸流速越大、水位越高,岸坡总冲刷坍塌量、河床总淤积量以及河床累计淤积率也越大,稳定后的岸坡越趋平缓;河床可动程度越大,岸坡总冲刷坍塌量及其在河床上的总淤积量也越大,但河床累计淤积率却越小;水位越高,在弯道段等横向输沙强度较大的地方,岸坡冲刷崩塌体与河床发生掺混的程度也越大。

This paper analyses the contribution rate of sediment in bank collapse and river bed evolution and presents a study on the patterns of non-viscous bank collapse and the interaction between it and the riverbed erosion/deposition through a series of experiments carried out in a bend flume. The experimental results reveal that the destruction of bank in the process of flow washout is a repeated interaction of water scouring the foot of bank, bank collapse along with the deposition and transportation of landslide substances. The mode and velocity of collapse and bed deposition rate and sediment interblending are largely affected by flow velocity distribution, flow turbulence and secondary flow, water level and the riverbed boundary conditions. The faster the near-bank flow and the closer the mainstream to bank is, the more unstable the bank will become. The extent of bank collapse and bed sediment deposition, the bed accu- mulative deposition rate is proportional to near-bank velocity and water level, but contrary when it comes to stable bank slope. When water level is higher, landslide substances interblend more violently with riverbed, especially on the bends where the transverse sediment transport happens tempestuously. The result reveals the mechanism and pat- terns of bank collapse and river bed evolution, which could provide a theoretical basis for the planning and design of flood control projects.