Experimental study on migration and deposition of particles under alternating dynamic and static loads

The study on the migration and deposition of suspended particles in subgrade is important to reveal the generation and disaster-causing mechanism of mud pumping. The effects of magnitude of dynamic loads, intermittent duration of static loads and repetition number of alternating dynamic and static loads on the migration and deposition of particles are studied by carrying out the mud pumping tests on the layered gravel-sandy silt column. According to the hydrodynamic response characteristics of specimens, the driving mechanism of particle migration is analyzed. The test results show that the suspended particles migrate upward under hydrodynamic force and settle under gravity during the interval of static loads, which results in the fluctuating growth of slurry turbidity in the gravel layer. The particle suspension increment tends to decrease with the increasing repetition of alternating dynamic and static loads, and these particles gradually clog gravel pores and inhibit mud pumping to a certain extent. Increasing the dynamic frequency and stress can further reduce the internal stability of the sandy silt surface layer. However, compared with increasing the dynamic stress, increasing the loading frequency is more beneficial to increase the particle migration mass and vertical migration distance.