Abstract: The maximum height of the core-wall rockfill dam of Nuozhadu Hydropower Station is 261.5 m. The core-wall impervious materials are composed of natural clay mixed with artificially graded crushed stones, namely gravel clay. For solving the technical difficulties associated with the impervious materials for the super high rockfill dam, comprehensive researches are carried out, including survey and characteristic tests of natural soils, in-situ tests of construction techniques, filling and compaction quality control, safety monitoring and feedback analysis. The research and design achievements in the above aspects are introduced.