Abstract: The rock mass under the impervious wall of Nianpanshan Water Conservancy and Hydropower Project is moderately permeable red sandstone containing argillaceous siltstone, siltstone, medium coarse sandstone, and gravel-containing medium coarse sandstone (K₂P^3-1), etc. As the rock mass absorbs a small amount of slurry, cement grouting has unsatisfactory result with the water permeability after grouting still over 10 Lu. To tackle this problem, according to previous engineering experiences, we adopted acrylic chemical grouting and carried out indoor pressurized and pressureless groutability tests of rock samples and on-site chemical grouting tests. Test results demonstrate that the CW520 acrylate grouting material has good groutability for the red sandstone curtain. When the grout gelling time of the acrylate grouting material is controlled within 35-45 min and the unit grout consumption is 80 kg/m, the anti-seepage requirements of project design can be met, the grouting amount can be effectively controlled, and the project cost can be cut. The research findings have been applied to the design and construction of anti-seepage curtain grouting for the main works of Nianpanshan Water Conservancy and Hydropower Project.

Key words: permeable red sandstone, groutability, controlled grouting, curtain grouting, acrylate grouting material