拱坝水垫塘内水舌合理间距的分析计算

Analysis of Reasonable Distance of Water Jets in Water Cushion Pool behind an Arch Dam

首次提出了上、下水垫深度的概念．以射流理论为基础推导了上、下水垫深度与双股入水水舌的水力要素之间的关系，指出了这两个水垫深度可用来划分拱坝水垫塘底板上最大动水压力区（“１＋１＝１”、“１＋１＞１”和“１＋１＜１”区）．结合小湾电站水垫塘的实验成果，给出了可用来迅速求解上、下水垫深度的图表．分析结果表明，当小湾电站水垫塘内水深为３７．８７ｍ时，中孔水舌入水的较优间距为１３．３～４０．５ｍ，与实验所得的１３～１７．

The concepts of upper depth and lower depth of water cushion are proposed for the first time. The relations between these two depths and the hydraulic factors of the two jets are derived from jet theory. It is pointed out that these two depths could be used to divide different areas of maximum water pressure on the pool bottom (that is :“1+1=1”, “1+1>1”, and “1+1<1” area). By used of the experimental data of Xiaowan project, a set of diagrams are given from which the two depths can be obtained easily. As for Xiaowan project, the reasonable distance of two water jets from the middle outlets in “1+1<1” area is from 13 3m to 40 5m for the depth of water cushion of 37 87m, which agrees with the data 13～17 5m to 40～49m obtained in the experiment.