冰塞渗流阻力特性的实验研究

冰塞引起的上下游水位变化与内部水流阻力有关,其堆积演变形成的固液多孔介质中存在渗流问题,且渗流阻力对上下游水头压力具有一定影响。本研究基于实验室冰水力学模型实验,通过设定不同的水力条件,获取不同冰塞剖面形状及沿冰塞剖面累积方向冰盖下流速分布,采用非达西渗流理论对冰塞内渗流阻力进行率定,获得了渗流阻力能量损失的变化特征。结果表明,渗流阻力能量损失占总能量损失的比例为11%～21%,冰厚较大位置可达到42%,沿冰塞累积方向,渗流能量损失占比与冰厚和水深之比呈典型的正相关。渗流流量为河道内重要的槽蓄水量,孔隙率在0.39～0.51之间,冰厚与水深之比在0.6～1.4之间时,渗流流量占总流量的9%～26%。渗流流量的变化受孔隙率、冰塞结构及水力特征等共同影响,冰颗粒均匀且随机堆积情况下,冰塞厚度越厚,冰体排列越紧密,孔隙率和渗流系数越小,流体通过多孔介质的比表面积越大,渗流能量损失也越多。本研究进一步明晰了冰塞阻力机理及渗流阻力在冰塞中的重要性,为受凌汛灾害困扰流域解决实际问题提供理论科学依据。

A laboratory study on seepage flow resistance of ice jams

The head loss of ice jams is mainly related to the seepage flow resistance. A laboratory study is conducted to evaluate this head loss. By setting different hydraulic conditions, the ice jam profile and undercover velocity distribution are obtained along ice jams. The non-Darcy seepage flow theory is used to calculate the seepage head loss. The results show that the seepage head loss is an important part of the flow resistance of ice jams, which accounts for 11%~21% of the total energy loss, especially near the jam toe,up to 42%. There is a positive correlation between seepage head loss and the ratio of ice thickness to water depth. The seepage discharge is an important storage water, which accounts for 9%~26% of the total discharge when the jam porosity is 0.39~0.51, and the ratio of ice thickness to water depth is 0.6~1.4. The porosity, ice jam structure and hydraulic characteristics have all effect on the seepage discharge. In the case of uniform and random accumulation of ice particles, the thicker and the more compact the ice jam thickness is,the smaller the porosity and seepage coefficient will be,which cause the larger seepage head loss due to the larger specific surface area of fluid passing through porous media. The mechanism of ice jam resistance and the significance of seepage resistance in the ice jam are examined to provide information for solving ice jam problems in the basin troubled by the ice flood disaster.