Evolution of Dynamic Characteristics of Solidified Dredge Sludge during Long-Term Traffic Loading under Environmental Actions

Abstract

This study investigates the evolution of the dynamic characteristics of a solidified dredge sludge, including the resilient modulus (M_R), accumulative plastic strain (ε_p) and damping ratio (λ) during long-term traffic loadings considering influences of environmental actions (dry-wet, DW, and freeze–thaw, FT cycles), stress states (confining stress σ_c and deviator stress σ_d) and loading frequency (f). The experimental results indicate that the dynamic characteristics continuously change with increasing loading cycles and the influences of environmental actions, external stress state, and loading frequency are coupled. The resistance of the solidified sludge against traffic loading decreases after both DW and FT cycles, which is manifested by the decrease in the M_R and the increase in the λ and ε_p. DW cycles induce greater reductions in the dynamic characteristics than the FT cycles. The increasing σ_c improves the resistance of the soil against cyclic loadings, resulting in higher M_R and lower ε_p and λ. Besides, their rates of change with loading cycles (i.e., δM_R, δε_p and δλ) reduce. The M_R, ε_p, λ, and δε_p increase while the δM_R and δλ decrease with the σ_d, indicating that the increase in the cyclic loading level contributes to the accumulation of plastic strain and energy assumption while the resultant densification effect leads to the increase in the M_R and decrease in the δM_R and δλ. The soil dissipates less energy when loaded under higher f, resulting in higher M_R and lower ε_p and λ. Results reported in this paper are helpful for better understanding the dynamic responses of solidified sludge under complex loading and environmental conditions.