Abstract: Nazixia hydropower dam is a concrete face-slab sand gravel dam. It is located in Menyuan county, Qinghai province, a high-altitude and extremely cold area. The surface water stop of the faceslab joint is sealed with SR filler. The EPDM-reinforced SR anti-seepage cover is applied and the water stop is fixed by expansion bolts on both sides. After operation for three years (2015~2017), due to the water freezing in winter, plastic filler on the surface of face-slab joints was extruded along the lower part of plate on both sides, the sealing cover was torn, and the impervious cover had some defects, such as screw loosening and strip warping. This paper introduces the structure improvement scheme for water stop on face-slab joint surface in winter water level variation area, which adopts the scheme of slotted plastic filler + overcoating (SK brush polyurea) water stop. By improvement, the adaptability of surface water stop to the winter water freezing is improved.

Key words: face-slab sand gravel dam, surface water stop, structure improvement, winter water freezing, SK brush polyurea

摘要： 纳子峡水电站大坝为混凝土面板砂砾石坝，位于青海省门源县，地处高海拔严寒地区，大坝面板接缝表面止水采用SR填料，上敷三元乙丙增强型SR防渗盖片，两侧采用膨胀螺栓固定。经过2015～2017年运行，由于面板接缝表面止水结构不适应抗冰冻要求，出现塑性填料沿两侧压板下部挤出、止水盖片撕裂、防渗保护盖片螺丝松动脱落和压条翘起等缺陷。笔者介绍了冬季水位变化区面板接缝表面止水采用缝口塑性填料与面板平齐+覆涂式（SK刮涂聚脲）盖片止水结构改进方案及施工工艺。通过对纳子峡电站冬季水位变化区大坝面板接缝表面止水结构的改进，提高了抗冰冻能力。

关键词: 面板砂砾石坝, 表面止水, 结构改进, 冬季库区结冰, SK刮涂聚脲