Abstract:

The dynamic strength and deformation characteristics of gravelly soils are the basis for analyzing the seismic permanent deformation of gravelly soil foundation and their structures. Therefore, a series of undrained cyclic triaxial tests on two kinds of gravelly soils were performed by use of a large dynamic triaxial apparatus in this paper. The effects of cyclic stress ratio, mean consolidation stress, consolidation stress ratio, initial void ratio and number of loading cycles on the deformation and excess pore pressure characteristics of gravelly soils were investigated in detail. The test results showed that the cumulative axial strain and excess pore pressure ratio of gravelly soils increased with the increase of cyclic stress ratio, mean consolidation stress and initial void ratio, and the excess pore pressure ratio decreased with the increase of consolidation stress ratio. When the number of loading cycles was less than 20, the consolidation stress ratio had little influence on the cumulative axial strain. When the number of loading cycles was more than 20, the cumulative axial strain decreased with the increase of consolidation stress ratio. Based on the test results, the empirical models of undrained dynamic strength and excess pore pressure were proposed in which the effects of mean consolidation stress, initial void ratio, number of loading cycles, and cumulative axial strain were taken into account. Comparisons of the computed values by models with the measured ones by tests showed that the proposed models could accurately describe variations in undrained dynamic strength, excess pore pressure and cumulative deformation for two kinds of gravelly soils under cyclic loading.

Key words: gravelly soil, cyclic loading, triaxial test, dynamic strength, cumulative deformation