双缆网式拦冰索布设间距研究

南水北调中线工程自丹江口水库向北京、天津方向输水,冬季南北冻融不同步将可能会导致严重冰情的出现。同时,南水北调中线工程由串联渠池组成,为降低下游渠池发生冰害的可能性,实现南水北调中线工程各渠池冰凌"自产自销",在物理模型试验的基础上,研发了双缆网式新型拦冰索。现重点在新型拦冰索拦冰效果研究的基础上,结合冰水力学相关理论,对新型拦冰索有效拦冰距离的计算方法进行探讨,并结合南水北调中线工程的特点,研究了新型拦冰索的布设间距。研究认为:拦冰索拦滞的加厚冰盖极限长度以及有效拦冰距离均随锚固位置与水面距离的增大而减小、随加厚冰盖糙率的增大而减小、随冰凌厚度的增加而减小;当冰凌厚度较大时,冰凌不再下潜,形成平铺冰盖,此时拦冰索拦滞的加厚冰盖极限长度与有效拦冰距离相等。对于南水北调中线工程总干渠典型渠段,在极端气候条件下,拦冰索的布设间距以4～6km为宜。

Research on Layout Distance between Net-style Ice Boom with Two Axes

The asynchronous ice melting between the north and south in winter may lead to a serious ice condition for the Middle Route of the South-to-North Water Diversion from the Danjiangkou reservoir to Beijing and Tianjin.In view of that the Middle Route of the South-to-North Water Diversion Project is composed of the canals and ponds in series,the net-style ice boom with two axes on the basis of physical model experiments was developed to reduce the possibility of ice hazards emerging in the downstream canals and to achieve the goals of ice forming and disappearing by itself in canals and ponds.Based on the research on the intercepting effects of this new type of net-style ice boom and the theory of ice hydraulics,this paper focuses on the calculation method about the effective intercepting distance between the new ice booms Moreover,according to the characteristics of the Middle Route of the South-to-North Water Diversion Project,this paper further researches on the reasonable layout distances between the ice booms.The results show that(1) The limit length of the ice cover intercepted by the net-style ice boom and the effective intercepting distance decrease with the increasing of the distance between anchor end and water surface,with the increasing of the roughness of thickened ice cover,and also with the increasing of the thickness of ice slushes;(2) When the thickness of ice slushes become larger,ice slushes stop submerging and form the surface ice cover.Under such circumstances,the limit length of the ice cover intercepted by the net-style ice boom is equal to the effective intercepting distance;(3) Under the extreme weather conditions,the reasonable layout distance between the ice booms is from 4km to 6km in view of the typical canal in the Middle Route of the South-to-North Water Diversion Project.