Experimental study on dynamic characteristics of marine soil under multi-frequency loading

In order to explore the dynamic characteristics of marine soil and their dynamic influential factors, the laboratory dynamic triaxial tests are carried out on the undisturbed marine soil from an investigated site in Yellow Sea, China by using the GCTS dynamic apparatus. The influences of the deviator stress, dynamic stress amplitude and dynamic load frequency on the dynamic stress-strain behavior and dynamic pore pressure of the marine soil are discussed, and the variation characteristics of dynamic shear modulus and damping ratio are analyzed. The test results show that the dynamic strain of the marine soil increases with the increase of the deviator stress and dynamic stress amplitude, and that the behavior of the marine clay is significantly affected by the loading frequency, i.e., in the low frequency band (0.02~0.1 Hz) of loading, the dynamic strain accumulation is much higher than that happens in the high frequency band (5~10 Hz) of loading. The excess pore water pressure increases sharply during low frequency loading cycles, but within the high frequency of loading, it is scarcely accumulated. The dynamic shear modulus of the marine clay exhibits weak response to the frequency of dynamic loading, i.e., within the low frequency band of loading, the dynamic shear modulus drops a little with the frequency transition, and it increases with the increase of the dynamic stress amplitude and decreases with the increase of the deviator stress level. In the high frequency band (1~10 Hz), the damping ratio of the soil samples increases significantly with the increase of the dynamic load frequency, and the increase range can reach more than 1 time. The damping ratio decreases slightly with the increase of the dynamic stress amplitude, and increases slightly with the increase of the deviator stress level.