不同水深拱坝坝身泄水孔形态变化规律研究

Research on the pattern of arch dam body outlet influented by different water depth

在拱坝坝身泄水孔设计布置时,随着水深的增加,坝身泄水孔的宽高比不断减小,减小到一定数值(略小于1.0)后,随着水深增加不再变化。通过分析可知,孔口面积保持不变时,孔口宽高比越小,孔口的泄水能力就越强。同时,拱坝可看作由一根根固结在基岩的悬臂梁和一层层固结在坝肩的拱圈组成,随着水深增加,悬臂梁对整个拱坝承受荷载的作用逐渐增大,拱的作用逐渐减弱。增大孔口宽度,可削弱悬臂梁的作用,而增加孔口高度,可削弱拱的作用。因此随着水深的增加,可适当减小孔口宽高比。

When the outlet of arch dam is designed,with the increasing of water depth,the width-to-height ratio of the outlet is reduced continuously,after the ratio is reduced to a certain value(slightly less than 1.0),and then along with the water depth increased,the ratio is no longer changed.Through the analysis,when the area of outlet is invariable,the smaller the ratio of beam-to-depth is,the stronger discharging capacity of outlet was.Meanwhile arch dam can be seen as the composition of some cantilever girders held on the bedrock and some layers of arches held on the utment,with the water depth increased,the effect of cantilever girder is increased,which gradually occupied the largely load of arch dam,and the effect of arch is fallen gradually.Then increasing the width of outlet,may weakened cantilever girder's effect,while increasing the height of outlet,may weakened the effect of arch.Thus with water depth increased,the ratio should be reduced appropriately.