渗流作用下床面切应力响应机理

On the response of bed shear stress to seepage

由于河床底部渗流的引入,传统的床面切应力测量方法不再适用,床面切应力对渗流的响应机理研究目前仅限于基于相关假定的理论分析和间接的推算,不同学者得出不同甚至相反的结论。利用自行设计的渗流床面切应力直接测量装置,对不同明渠水流及渗流组合动力条件下的床面切应力进行了测量。结果表明渗流作用下床面切应力变化与相对渗流强度vs/U关系密切,一般在|vs/U|<0.2%时出现拐点,在0.2%<|vs/U|<0.4%时出现临界点,并指出相对渗流强度vs/U的取值是已有研究成果相矛盾的关键因素。

Since traditional methods to measure bed shear stress fail to work in the presence of seepage,alternative approaches to study the response mechanism of bed shear stress to seepage are limited to some theatrical analyses with some assumptions and indirect estimation.The issues of whether seepage reduces or enhances bed shear stress are still matters of considerable debate.To this end,a special-designed device is deployed to directly measure the bed shear stress in the open channel flume with varying seepage rates.Experimental results show a close relationship between changes in bed shear stresses and the relative seepage intensity vs/U.Variation in bed shear stresses with seepage has an inflexion and a critical value when the ｜vs/U｜ is about 0.2% and between 0.2% and 0.4%,respectively.Therefore,it is clear that the range of vs/U investigated experimentally is the leading cause of the contradiction in the literature.