加厚冰盖渗流对渠道输水能力的影响

输水渠道冰期输水能力日益成为工程运行管理、学者研究关注的焦点。输水能力的研究不能仅仅局限在正常输水期(明流期和封冻期),还应该考虑非常工况下工程的输水能力,比如流凌期的输水能力。普遍认为流凌期输水能力将可能成为束缚冰期输水能力的瓶颈。为提高流凌期输水能力,可以采用加厚冰盖下的输水方式运行。通过理论分析和物理模型试验相结合的方法,针对加厚冰盖渗流对输水工程冰期输水能力的影响进行了研究,结果表明:由于结冰期加厚冰盖孔隙率较大,其渗透系数大于融冰期加厚冰盖;冰凌形状系数t/L对加厚冰盖渗透系数影响较小;随着冰厚的增加,加厚冰盖渗透系数逐渐减小,尤其当冰厚小于0.1m时,渗透系数衰减迅速;随着渠道总流量的增加,加厚冰盖渗流量相应增大,但是渗流量在总流量中的比重却随总流量的增大而减小;加厚冰盖渗流在渠道输水流量中所占比重很小,一般情况下,对输水渠道冰期输水能力的影响可以忽略不计。

Impact Analysis of Seepage Flow in Thickened Ice Cover on the Water Diversion Capacity in Canal

The water diversion capacity during the ice age has received more and more attention from the aspects of project management and scientific research.The research on the water diversion capacity should not be limited to the normal flow conditions,such as the free-flowing period and ice covered period,and it should further extend to the special situations during the ice-flowing period.In general,the water diversion capacity during the ice-flowing period may affect and limit the water diversion capacity during the ice age.Adopting the operating measure of water diversion under a thickened ice cover can improve the water diversion capacity during the ice-flowing period.In this paper,based on the theoretical analysis and physical model experiments,the effects of seepage flow in the thickened ice cover on the water diversion capacity during the ice age were analyzed.The results showed(1) Due to the high porosity of the thickened ice cover during the frozen period,the permeability coefficient of the thickened ice cover is larger than that during ice-melting period;(2) The shape factor of ice slush(t/L) has insignificant effects on the permeability coefficient of thickened ice cover;(3) With the increasing of the thickness of ice cover,the permeability coefficient of thickened ice cover decreases gradually.Especially when the thickness is less than 0.1m,the permeability coefficient decreases rapidly;(4) With the increasing of the total flow in canal,the seepage flow in the thickened ice cover becomes larger,while the proportion of the seepage flow to the total flow decreases;and(5) The seepage flow in the thickened ice cover only accounts for a very small proportion of the total flow.Therefore,the effects of seepage flow on the water diversion capacity during the ice age are negligible.