三峡水利枢纽大江截流设计

Design of main river channel closure for TGP

三峡工程施工导流采用“三期导流、明渠通航”方案。二期施工围左岸，进行主河床截流，迫使江水从右岸导流明渠下泄。截流流量为11月下旬的20年一遇最大日平均流量14000m3／s，截流时间选在1997年11月中旬，采用上游单戗堤立堵截流方案。龙口位于主河床深槽右侧，龙口宽130m，最大水深达60m。为防止戗堤头部坍塌，在龙口段先行平抛垫底。龙口进占由两岸同时进行，投抛材料为块石和石渣。设计龙口水位落差0．51～0．71m，口门流速2．13～2．73m／s。

The in-three-stage river diversion scheme with the diversion open channel used as a temporary navigable water way is adopted for the construction of TGP. During the second stage construction period, the main river channel will be closed to form a spillway construction pit adjacent to the left bank powerplant construction pit, and the river flow will be diverted downstream through the right bank diversion open channel. The closure now discharge is 14 000 m3/s, a 20-year return flood. The river closure is planned to be carried out on middle ten days of November, 1997. The upstream single dike end dumping closure scheme is adopted. The closure gap will be located in the right part of the main river channel, with its width of some 130 m and maximum water depth of up to 60 m. In order to prevent the closure dike's end parts from slumping, the rock riprap front dumping will be carried out in advance on the location of the closure gap to form a floor and reduce the water depth for end dumping. The gap closing will be conducted simultaneously from both right and left ends, with the rock blocks and the stone ballasts used as the dumped materials, The design water head and flow velocity at the closure gap are 0. 51~0. 71 m and 2. 13~2. 73 m/s respectively.