黑泉混凝土面板砂砾石坝设计与施工

Design and construction of Heiquan concrete face sand-gravel dam

黑泉坝址地处高海拔严寒地区 ,地震设防烈度 8度 ,坝基覆盖层深 2 5～ 2 9m。坝址下游距省会西宁市仅75km ,是国内在建的以砂砾石为主要筑坝材料的高混凝土面板砂砾石坝之一。设计中针对天然砂砾石分布不均 ,具离散性 ,易受冲蚀 ,在一定水力比降下有可能产生管涌破坏和丧失自由排水能力的特性 ,不仅考虑了面板坝的变形特点 ,充分发挥砂砾石变形模量高的特点 ,还特别注重坝体的抗渗稳定性 ,将渗流控制放在首位 ,以避免抗冲蚀能力差的缺点 ,确保大坝安全运行。这是有别于堆石混凝土面板坝的。另外 ,黑泉工程根据地形地质条件 ,在趾板上游做贴坡混凝土 ,下游做混凝土盖板或喷混凝土 ,以延长渗径 ;在河谷左岸段 ,左右坝肩做了高5 .8～ 17m的高趾墙 ,在坝体填筑施工中 ,采取了超前填筑 ,周边与界面填筑 ,坝内设临时“之”字路施工等措施 。

Heiquan dam is located in a frigid region of high elevation,75 km upstream from the provincial capital Xining,with an earthquake-resistant standard of intensity Ⅷ.The overburden depth of the foundation is 25～29 m.The dam is one of the high concrete face sand-gravel dams under construction in China.In view of nonuniform distribution,discreteness and erodibility of natural sand and gravel,and their potential of piping failure and losing free drainage capability in the case of a certain hydraulic gradient,in the dam design,not only the faced dam's deformation characteristics have been taken into account for making full use of the high deformation modulus of sand and gravel,but also the dam's stability against seepage has been stressed on,with seepage control put in the first place to ensure the dam's safe operation.These design considerations are different from those for concrete face rockfill dams.In addition,in accordance with topographic and geologic conditions at damsite,concrete blanket is placed on slopes before and after the toe plate,in order to prolong the seepage path.5.8～17-m-high toe walls are constructed in the left dam section and both abutments.In the construction,the left and right dam sections were embanked ahead of schedule before the river closure and special measures were taken for embankment at perimeter joints and interfaces,ensuring the project quality and progress