Abstract: Partially drained CCP (constant confining pressure) and VCP (variable confining pressure) cyclic triaxial tests were carried out on Wenzhou soft clay by using GDS (Global Digital Systems) to investigate the permanent deformation behavior of saturated soft clay in subgrade under long-term traffic load more realistically.Special attention was paid to the influences of cyclic stress ratio (CSR),stress path (α) and length (L) on the permanent axial strain of saturated soft clay.The test results unveiled that at a give cycle number (N),the permanent axial strain increased with the increase of CSR and the decrease of α,which can be described by exponential function and logarithmic function respectively.The normalized permanent axial strain undergone 10,000 cycles (ε^p_{a,10 000}/ε^p,CCP_{a,10 000}) was in a logarithmic relationship with the normalized stress path length (L/L_CCP),and a linear relationship with the normalized mean principal stress amplitude (p^ampl/p^ampl_CCP),regardless of the CSR values.Furthermore,a logarithmic empirical model considering the combined effect of CSR,α,and N was established to predict the permanent axial strain under different stress paths,and the predicted results were in good agreement with the measured deformation.

Key words: saturated soft clay, strain accumulation characteristic, GDS dynamic triaxial test with variable confining pressure, partially drained stress path, permanent axial strain, empirical model