小浪底工程明流洞气减蚀设计研究

小浪底枢纽明流洞水头高、流速大，存在空蚀的可能性。为了减免空蚀对建筑物的危害，根据类似工程的经验，结合小浪底工程明流洞的具体情况，采用了掺气减蚀措施。设计过程中对掺气坎的形式、布置、保护长度等进行了充分的论证，取得了很好的效果

Application of full-face needle-beam steel formwork in the concrete lining of tunnel

The sections of No.3 and No.4 tunnels for intake head of Water Diversion Project From Yellow River To Shanxi Province are designed as circular section. Its excavation diameter is 6.4 m and the actual diameter after lining is 5.6 m. The total length of No.3 tunnel is 758.3 m, constructed by the steel formwork jack plane. The total length of No.4 tunnel is 1700 m, constructed by full-face needle-beam steel formwork. Analyzed and compared the concrete construction of such two tunnels, it is considered that the full-face needle-beam steel formwork construction has the advantages of low disturbance, good concrete appearance, high utilization rate of resources and labors, low investment and high progress. But its lump-sum investment is much larger than that of steel formwork jack plane, so that it is suitable to the concrete lining of long and fixed-section tunnel.