乌江渡水电站坝基水质特征及帷幕性状评价

Evaluation on water quality characteristics and curtain behavior of dam foundation of Wujiangdu Hydropower Station

以岩溶地区乌江渡水电站为典型案例,针对pH值、水化学类型、析出物、渗漏量等坝基防渗评价因素,结合历史、近期水样检测资料及坝址地层岩性和帷幕材料,对比库水与防渗帷幕后水样的pH值和水化学类型的变化,研究析出物成分的来源变化、渗漏量的趋势,分析坝基防渗帷幕性能。结果表明:水化学类型以CO_3^(2-)或OH^-型、HCO_3^-型为主,白色碳酸钙析出物由水—岩—混凝土三者间互相作用而成。水库在蓄水后,库底变为高压缺氧的还原环境,同时有机物的堆积会使得库底水呈弱酸性,侵蚀性CO_2含量会有所增加。这对坝基帷幕体不利。坝基防渗帷幕体的防渗性能整体上仍然完整有效;水的流动是析出物沉淀的必要条件之一。将水的pH值与渗流量或渗透压力及析出物沉淀情况综合分析,可以作为判别防渗帷幕防渗性能的依据。该研究结果可以为其他相似水库判断防渗帷幕性能提供参考。

By taking Wujiangdu Hydropower Station in karst region as a typical case,the pH value and the hydrochemical types of both the reservoir water and the water behind the anti-seepage curtain are compared in combination with the historical and recent water sample detection data,stratum lithologies within the dam site and the materials of the curtain for the factors for evaluating the anti-seepage of the dam foundation,such as pH value,hydrochemical types,precipitates,seepage amount,etc.,and then the change of the sources of the precipitate contents and the trend of the seepage are studied,while the performance of the anti-seepage curtain for the dam foundation is analyzed as well. The result shows that the hydrochemical types are mainly CO3^2-or OH^- type,HCO3^- type,the precipitate of white calcium carbonate is created from the effects among water-rock-concrete. After the impoundment of the reservoir,the bottom of the reservoir becomes a high pressure and oxygen-deficient reducing environment,while the organic accumulation is to make the reservoir bottom water present faintly acid and the corrosive CO2 content is to be increased somewhat. This is unfavorable to the curtain body of the for the dam foundation. The anti-seepage performance of the anti-seepage curtain for the dam foundation is still integrally effective,while the flow of water is one of the necessary conditions for the settlement of the precipitates. The comprehensive analysis made on the statuses of pH value and seepage amount or the seepage pressure and the settlements of the precipitates can be taken as the basis for judging the performance of the anti-seepage curtain. The study result can provide a reference for judging the performance of anti-seepage curtain for the other similar reservoir.