水布垭工程岩溶研究与帷幕优化

Research on karst of Shuibuya hydroproject and curtain optimization

水布垭水电站位于清江中游河段,大坝为混凝土面板堆石坝,地下式引水发电系统,装机1 840 MW,大坝正常蓄水位400 m,相应库容43.28亿m3,最大坝高233 m,坝高居世界同类坝首位。该电站是一个石灰岩坝址,岩溶化程度很高,坝基及绕坝渗漏问题十分突出,计算表明,如果坝址不作防渗处理,其渗漏量可达7 m3/s,水量及电能损失严重,还将对坝基中的剪切带产生冲刷破坏,埋藏在坝基下的多条岩溶管道系统在洪水期将直接冲刷大坝的堆石体。为此需要设置一条总长2 588.3 m,面积达44.14万m2,钻灌总进尺达39.2万m的地下帷幕工程。防渗帷幕初期采用了全封闭方案,投资4.76亿元(与大坝投资相当)。经大量的地质科学研究,包括岩溶发育规律、控制因素及岩体渗透特性等;提出了Ⅰ号岩溶管道具有独立的补、迳、排系统,邹家沟一带存在“弱岩溶化地块”,该地块隔断Ⅰ号岩溶系统与库水的联系;对于帷幕线上的强岩溶发育区通过封堵岩溶洞穴可以实现“变岩溶化岩体为裂隙性岩体”,同时提出了在复杂岩溶地区帷幕优化的原则和类型。水布垭工程按地质提出的帷幕优化图形实施后,钻灌进尺将小于30万m,初步估算可节省投资近亿元。

Shuibuya hydroproject is located at the middle reach of the Qingjiang river,the dam is concrete faced rockfill one with underground power generation system with 1840 MW generation capacity equipped,the normal storage water level is 400 m with correspondent capacity of 4.328 billion m^3,the maximum dam height is 233 m,ranking first in the world.The dam site is in a comparably higher karsted area,the seepage of dam foundation and around the dam is very serious.The calculation results demonstrate that if no measure is taken,the seepage volume can reach 7 m^3/s,With large water volume loss and water power loss ,and scour and damage the shearing belt in the dam foundation.The water in karst passage systems embedded in the dam foundation will directly scour rockfill body.To solve this problem,a underground curtain with total length of(2 588.3) m,area of 441.4 thousand m^2 and drilling and grouting length of 392 thousand m should constructed.The whole-closed scheme is adopted for seepage curtain in initial period with the investment of 476 million RMB(nearly equal to the investment in dam body works).Through large amount of scientific research on karst development law,controlling factor and rock body seepage features,the author puts forward that No.1 karst passage possesses independent supplementary,running,drainage system,' weak karst block zone' exists in Zoujiagou area,separating the connection of karst system and the reservoir water;for strong karst area on the curtain line,through blocking karst caves, 'changing karst body into fissure body' can be realized.In the meantime,the author suggests the principle and classification of curtain optimization in complicated karst area.