三峡工程导流底孔长管方案研究

Study on Long Pipe Scheme for the Diversion Conduit of the Three Gorges Project

三峡大坝河床溢流坝段内设有泄洪深孔、表孔和第三期导流底孔。后者系三期导流时用以泄水和实现围堰挡水发电的主要建筑物，孔口尺寸为6m×8．5m，进出口均为56．0m，型式有短管和长管两种。导流孔上游短管为管长16．09m，下游明流段98．78m；长等方案是上游管长77m，下游明渠长33m。短管方案由于坝体挖空大不利施工和坝体应力条件不良等而选用长管方案。长管方案在闸门布置、体型、水力学特征等四方面均能解决好。

In the spillway dam section at the riverbed of the Three Gorges Dam there are a low level outlet works,a crest spillway and a diversion conduit in the 3rd stage. The diversion conduit, with an opening dimension of 6m x 8. 5m and an elevation of 56. 0m for both its entrance and exit, is a major structure to discharge water and retain water for generating electricity together with the cofferdam during the 3rd stage of diversion. The diversion conduit involves the short pipe scheme, in which the upstream pipe is 16. 09m long and the downstream open channel section has a length of 98. 78m,and the long pipe scheme, in which the upstream pipe is 77m long and the downstream open channel section has a length of 33m. The long pipe scheme for the diversion conduit was adopted in consideration of the fact that for the short pipe scheme, the much hollowed dam body is unfavorable to the construction and the stress condition in the dam body is defective,while compared with the short pipe scheme,the long pipe scheme can give a good solution to problems on lock arrangement, type of build, hydraulic property and so on.[