水力学计算在导流明渠及挡水围堰选型和优化设计中的应用

水利工程建设施工中，为保证施工干场作业，大部分水利工程建设过程中都需要考虑导流问题，例如目前中国南水北调工程中已经开工或将要相继开工的多个穿河倒虹吸或暗涵工程，都涉及到施工导流课题。简易导流方案一般为修围堰全断面挡水断流、另挖明渠导流或修围堰束窄河床导流等。根据相应施工防洪标准，对河床水流和明渠水流进行正确的水力学计算，确定导流渠（或束窄河床）最佳过水断面尺寸，并结合现场实际情况，考虑经济指标，修正最佳水力断面，最终可确定经济适用导流渠断面及挡水围堰高程，既能满足防洪安全要求，又充分利用了现场条件，可降低工程成本，且效果明显。

Hydraulics Calculation in the Type-Chosen and Optimal Design of Open Diversion Channel & Water-Retaining Cofferdam

Many crossing river inverted works or underground culvert works in the South-to-North Water Transfer Project are involved in the diversion construction to ensure the hydraulic projects constructing in the dry site. Simple methods for diversion usually are to build a water retaining cofferdam to completely control water flow, to dig an open diversion channel, or to build a cofferdam to narrow the riverbed Based on the corresponding flood-preventing standards, we can obtain an economical cross section for the diversion channel and the altitude of the water-retaining cofferdam which can meet the requirements of flood-preventing and can make full use of the spot situation. The method is to have a right hydraulics calculation for the riverbed flow and the open channel flow, to decide the optimal discharge cross section dimension for the diversion channel (or the narrow riverbed), and to revise the optimal hydraulic cross section.