水库区低Froude数的典型涉水滑坡涌浪缩尺物理模型试验研究——以王家山滑坡为例

Scaled experimental study on impulse wave generated by a typical semi-submerged landslide with a low Froude number in reservoir areas—Taking Wangjiashan landslide as an example

大型水库涉水滑坡涌浪大多是低Froude(Fr)数的滑坡涌浪事件,它的冲击效应和涌浪特征尚需进一步揭示。以白鹤滩水库王家山滑坡为典型案例,遵循Froude相似准则,以1∶150的比例尺构建30 m×27 m×1.5 m的大型三维缩尺滑坡涌浪试验场,开展Fr数为0.08~0.32的9组滑坡涌浪试验,系统深入研究低Fr数下涉水滑坡涌浪规律。研究结果表明:当Fr数≤0.15时,运动初期水下运动产生的拖曳效应要大于水上滑体入水的冲击效应,涌浪波先出现小的波谷。低Fr数滑坡形成的首浪波类型多为过渡波,传播过程中波浪易从具有推移能力的波浪类型转化为弱或无推移能力的波浪类型。无量纲最大波幅、涌浪衰减率分别与Fr数满足线性和对数函数关系。低Fr数的涉水滑坡造浪效率低于高Fr数的水上滑坡。Fr数的增加会导致滑坡涌浪危害面积强烈扩大,增加的涌浪红色预警面积倍数约是Fr数增加倍数的10倍。这些新认识揭示了水库涉水滑坡涌浪的隐蔽性和危害性,支撑了库区涌浪防灾减灾工作。

Impulse wave generated by semi-submerged landslides in large reservoir mostly has a low Froude number,and its impact effect and wave characteristics need to be further revealed.Taking the Wangjiashan landslide of Baihetan reservoir as an example,a large-scale three-dimensional scaled landslide-induced impulse wave(LIW)experiment with the size of 30 m×27 m×1.5 m was constructed with a geometric scale of 1∶150,following the Froude similarity criterion.Nine groups of LIW experiments with Froude number of 0.08–0.32 were carried out to study the wave regularity of wading landslide under low Froude number.The research results show that as Fr≤0.15,the drag effect caused by the underwater motion is greater than the impact effect caused by the subaerial sliding mass at the beginning of motion,and the wave appears with a small trough at first.The type of primary wave generated by the landslide with a low Froude number is mostly transition wave.In the process of wave propagation,the wave type is easily transformed from the wave type with big translation capacity to that with low or nontranslation capacity.The dimensionless wave amplitude and wave attenuation rate are linear and logarithmic functions with Froude number,respectively.Wave making efficiency of wading landslide with a low Froude number is lower than that of subaerial landslide with a high Froude number.The increase of the Froude number will lead to the strongly expansion of the hazard zone of impulse wave,and the increased red warning area multiple is about 10 times that of the increase of Froude number.These new understandings revealed the concealment and hazardous of LIW in the reservoir,supporting prevention and mitigation of impulse waves in the reservoir area.