南水北调中线干渠冰期拦冰索水力控制条件研究

通过控制水力条件,使拦冰索能够有效拦截浮冰、使得浮冰能够在拦冰索前停滞堆积而形成冰盖,是保证南水北调中线工程冰盖下安全输水的关键。本文基于中线干渠冰期原型观测数据,分析了浮冰下潜的临界水力条件,表明传统的第二临界Fr(0.08~0.09)只适用于判别冰盖前缘的浮冰运动状态,对于判别拦冰索前浮冰运动状态、分析拦冰索的拦冰能力具有局限性,并论证了采用Ashton孔口排冰公式来判断拦冰索前的流冰运动状态的合理性。研究表明,同一水力条件下,拦冰索的水下淹没深度越大,其拦冰性能越好,拦冰索前冰凌下潜的临界Fr越大;并在此基础上确定了中线工程各渠池拦冰索的最小淹没深度。研究成果可为中线工程冰期输水方案制定和拦冰索技术改造提供依据。

Study on hydraulic control conditions of main canal in South-to-North Water Diversion Middle Route Project

The key to water transfer under the ice cover in South-to-North Water Diversion Middle Route Project during winter is to control the hydraulic conditions, under which the ice boom can intercept the ice floes effectively and ice floes can accumulate and form ice cover in front of the ice boom. In this paper, based on the prototype observation data of South-to-North Water Diversion Middle Route Project, the critical hydraulic conditions of floating ice diving are analyzed. The analysis result shows that the traditional second critical Fr (0.08~0.09) is only applicable to identifying the ice floe motion in front of the leading edge of the ice cover, but has eimieaeions identifying the ice floe motion in front of the ice boom. Then according to the research results of the ice drowning at the submerged orifice, the formula of the critical Froude number of the ice diving is recommended in front of the ice boom,and the rationality of the formula is verified. The study shows that the greater the submerged depth of the ice boom,the better the ice intercepts,and the greater the critical Fr value for ice diving in front of the ice boom. At last the minimum submerged depths of the ice booms of South-to-North Water Diversion Middle Route Project are deter-mined. The results provide a theoretical basis for making water transfer plan and ice booms modification of South-to-North Water Diversion Middle Route Project.