Experimental study on permeability and its influencing factors for sandy gravel of Dashixia dam

A super-large cubic permeability meter (1000 mm×1000 mm) and a traditional cylindrical large-scale permeability meter (Φ300 mm) are used to conduct systematic experiments on the permeability characteristics of gravel materials to be used in Dashixia concrete face gravel dam (CFGD). It is found that the content of fine particles smaller than 5 mm has important effects on the permeability coefficient, the seepage failure resistance and the relevant failure modes. Scaling of specimens tends to result in an overestimation of the drainage behavior and seepage failure resistance of the test gravel. Evident particle segregation phenomenon is observed in compacted and prepared specimens, particularly in those prepared in the super-large cubic permeability meter. Therefore, to improve the reliability of the test results, the in-situ compaction condition should be taken into account carefully. The test results also show that the content of particles smaller than 5 mm is high in the gravel materials to be used in Dashixia CFGD, which is responsible for the low permeability measured in the tests. It is necessary to set a transition and filter zone between the main gravel zone and the cushion so as to enhance the seepage failure resistance of the cushion materials.