Abstract: The large-scale triaxial apparatus is indispensable in the experimental application of soil materials with gravel for which have much larger grains in high core rockfill dams. Also the great percentage of clay has increased the level of challenge in the experimental work because of low permeability coefficient, difficulties of saturated and consolidation, long test period and so on for large scale specimens. To solve these practical problems effectively, sand cores has been reserved to accelerate saturation and consolidation in this paper’s tests. Analyses have been conducted on the creep strain and the creep model parameters of clay material with gravel tested by large-scale rheological triaxial apparatus. The results indicate that the rational power function relationship between creep strain and load time could exactly be described by the creep model of Yangtze River Scientific Research Institute. It is also revealed that the clay materials with gravel have smaller creep strain and lower model parameter indexes than the same materials without gravel. Consequently, mixing appropriate amount of gravel into clay soil could improve the engineering characteristics. The creep indexes of unsaturated materials are obviously lower than them of saturated materials in conditions of clay or clay with gravels. This fully shows that the sand cores reserved to accelerate draining play an very apparent role in the test process.

Key words: clay materials with gravel, large-scale triaxial, rheological test, creep model