Long-Term Mechanical Properties of Solidified Municipal Sludge Under Freeze-Thaw Cycles

The municipal sludge was solidified with a new curing agent developed independently.Considering the impact of the climatic environment, we analyzed the long-term deformation and strength development properties of the solidified sludge by using a series of triaxial creep tests under freeze-thaw cycles.The experimental results show that with the number of freeze-thaw cycles increasing, the shear strength of the solidified sludge tends to reduce significantly first and then becomes steady.When the deviatoric stress applied to the soil samples was less than the yield stress of the solidified sludge, the duration curves of creep all presented an attenuated creep pattern.Moreover, the overall trends of the curves under different stress levels were similar.When the deviatoric stress level reached failure stress, the creep deformation increased sharply.When other conditions are the same, the lower the freeze-thaw temperature is, the faster the creep deformation rate will be, and the larger the amount of deformation will be when each level of creep is stable.The isochronous curves of the solidified sludge have an obvious yield point;compared with the curves at other times, the isochronous curve at t=0h shows an obvious discrete phenomenon.Based on the stress-strain logarithmic curves and the inflection point method of isochronous curves, a creep model of solidified sludge and its long-term strength prediction formula that can consider the effects of freeze-thaw cycles have been established, which can provide relevant engineering practice references.