云南田坝电站尾水闸前水下混凝土围堰拆除爆破

Blasting Technique for removal of Underwater Concrete Cofferdam Upstreamfrom Draft-tube Gate for Tianba Hydropower station in Yunnan Province

云南田坝电站尾水洞是利用漫湾电站２＃导流洞后段改造而成，由于先修造围堰，造成田坝电站尾水闸室布置离围堰较近，给后期围堰拆除施工增大了难度。在爆破拆除设计中采用分区分块进行，实际施工中采用了各种保护措施，减少单响量，爆破时飞石及声响控制较好，爆破后经水下测量，底坎光爆面成型较好，达到设计要求。

The Tianba Hydropower station has a tailrace tunnel which was converted from the downstream section of the No.2 river diversion tunnel for the Manwan Hydropower Station. Since the cofferdam was constructed first, the draft-tube gate chamber had to be arranged close to the cofferdam for the Tianba Hydropower Station. As a result, it was difficult to remove the cofferdam at the late stage of the construction. The cofferdam was desinged to be removed by blasting zone by zone and block by block, and various protective measures were taken in the construction to reduce charge for one blasting, which is resulted in good control of flying stone pieces and sound during blasting. The measuring under water after blasting indicated a proper shape of smooth blasting surface on the bottom sill, satisfying the design criteria.