万家寨水利枢纽工程施工导流暨截流

River Diversion and Closure of Wanjiazhai Key Water Project Liu Guiliang

枢纽采用分期导流的方式施工，先围左岸泄水建筑物坝段，河水由右岸束窄的河床渲泄；第二期围右岸电站厂房坝段，河水由左岸泄水建筑物坝段的临时导流底孔和导流缺口渲泄。一、二期上、下游横向围堰皆采用心墙式复合土工膜作防渗体，两侧填石渣的围堰型式，纵向围堰为混凝土围堰。二期上游围堰截流以立堵方式单向进占，龙口宽８７．５ｍ，实测截流流量范围为６７５ｍ３／ｓ～３４５ｍ３／ｓ，龙口合龙流量３４５ｍ３／ｓ，单宽流量５７．５ｍ３／ｓ·ｍ，最大落差３．４９ｍ，最大流速６．７５ｍ／ｓ，截流历时５２小时２７分，共抛投石料２．４万ｍ３。

The stage river diversion was adopted in the construction of the Wanjiazhai Key Water Project.In the first stage,the water release section of the dam near the left bank is enclosed,discharging the river flow by a narrow river channel in right bank. In the second stage,the right dam section,where the power house is to be built,is then surrounded while the river flow is changed its course towards the left bank,and discharged by a temporary bottom outlet and by a notch in the water release section of the dam near the left bank.The rockfill cofferdams with a composite geomembrane are built across the river both upstream and downstream.The cofferdams along the river being concrete structure.The closing dike upstream in the second stage,is advanced by one way and horizontal methods.The width of the final closure gap is reduced up to 87.5 m.During the closure operation,the discharge measured varies from 675 m 3/s 345 m 3/s.At the final closure gap,the unit discharge is 57.5 m 3/s.The maximum fall is 3.49m,and the maximum flow velocity is 6.75 m/s.From the beginning to the end,the closure operation took about 52 hours,with the stone riprap being 24,000 m 3.