Research on Strain Softening Characteristics of Saturated Soft Clay Considering Accumulative Plastic Strain under Traffic Load

Long-term cyclic traffic loads will cause significant roadbed settlement, while the existing long-term operation settlement analysis of roadbeds is mostly based on cyclic triaxial tests, ignoring the deflection effect of the principal stress axis of the soil element under traffic load. Through the stress-controlled hollow cylinder torsional shear test of Hangzhou undisturbed soft clay, the relationship between cyclic stress ratio (CSR), deviatoric consolidation ratios (K0), loading frequency change (f), degradation index and accumulative plastic strain was studied. The results show that for the consolidated isotropic soft clay, the initial cumulative plastic strain is negative strain, which gradually increases with the increase of the number of vibrations (negative strain), while the initial cumulative plastic strain of K0consolidation is positive strain. The decrease of K0and the vibration frequency increases the initial cumulative plastic strain of the soil sample and accelerates the failure rate of the soil sample. Based on the test results, the logarithmic relationship expression between the softening index and the vibration frequency is determined. The cumulative plastic strain influence factor ζ is introduced to establish the cumulative plastic strain model of the undisturbed soft clay, which provides a theoretical basis for predicting and calculating the long-term settlement and deformation of the foundation soil. © 2023 Science Press. All rights reserved.