三峡大坝泄水建筑物水力学原型观测与分析

三峡大坝泄水建筑物具有下泄流量大(102 500 m3/s)、泄洪落差大(97.3 m)、孔口数量多(22个表孔和23个深孔)、运行水头高(90 m)、库水位变幅大(135～180 m)等特点,其泄洪运行备受关注。采用现场原型观测手段,2003年以来历时十余年,系统观测了深孔135 m、156 m、172 m和表孔162 m、172 m特征库水位泄洪消能水动力特性,重点考察了水流流态、动水压强、水流流速、水流空化噪声、通气风速、水流掺气浓度、坝下冲刷等参数,获得了宝贵的原型系列观测数据,并与模型试验成果对比分析补充完善。观测显示,泄水建筑物过流面虽有初生空化信号但未见空蚀和泥沙磨损破坏,坝下消能区冲坑最深点高程20.8 m,折算其上游坡比1∶6,表明三峡大坝泄水建筑物布置总体是成功的。

Hydraulic prototype observation and analysis of Three Gorges Dam discharge structures

The water discharge buildings of the Three Gorges Dam are characterized by large downward discharge (102500m³/s), large spillway drop (97.3m), large number of orifices (22 surface holes and 23 deep holes), and high running head (90m) and large variation of reservoir water level (135-180m), which attract much attention in its flood discharge operation. In this study,through more than ten years of prototype observation since the impoundment of the Three Gorges reservoir in 2003, hydraulic characteristics of flood discharge and energy dissipation of bottom outlets (135m, 156m, 172m) and surface outlets (162m,172m) at various reservoir water level conditions have been observed systematically,which focused on flow patterns, hydrodynamic pressure, flow velocity, flow cavitation noise, ventilation speed, aerated concentration, discharge atomization and downstream scour. The observations show that although there are cavitation signals in the overflow surface of the discharge structures,no cavitation erosion or sediment abrasion damage occurs. The lowest elevation of the scouring pit in the downstream energy dissipation area is 20.8m, which is higher than the base level. The observation results indicate that the discharge structures worked normally in 16 flood seasons it has experienced, and the layout of the Three Gorges Dam discharge structures have been successfully designed in general.