The effect of periodic intermittency on the cyclic behavior of marine sedimentary clay

Abstract

For subway systems built in coastal areas, the marine sediments are subjected to regular load sequences of waves and intermittencies, resulting in more complex reactions in their cyclic behaviors compared with those under the uniform cyclic loading applied in common studies. This research involved a series of experimental investigations into the undrained behavior of undisturbed saturated marine sedimentary clay subjected to cyclic loading with periodic intermittency considering the initial deviator stress and the conventional uniform cyclic triaxial tests for comparison. The results indicate that periodic intermittency significantly increases cyclic resistance, manifested by weakening of the long-term response and decreases in the number of vibration times required to achieve a steady state. The effect is greater with longer intermittency durations. Furthermore, changes in the pore water volume during cyclic loading were analyzed via nondestructive detection based on nuclear magnetic resonance. A conversion from bound water to free water was observed, referring to vibration magnitude and times. Lastly, the macroscopic results observed in triaxial tests and the microscopic results obtained in the nuclear magnetic resonance test appear to be closely related, indicating that the use of the variation in pore water is an applicable approach to delineate microchanges.