Influence of the freeze-thaw effect on the Duncan-Chang model parameter for lean clay

Using undrained triaxial shear tests, this study investigates the mechanical properties of lean clay under the freeze-thaw (F-T) and thermostatic-curing (T-C) cycles. The shear strength and Duncan-Chang model parameters, considering both the number of cycles and the freezing temperatures, were calculated from the hardening strain-stress curves. Compared to the shear strength in the T-C group, the F-T effect causes irreversible attenuation of shear strength in specimens with water content of 17.6%. Except for the damage ratio, the other four model parameters in the T-C group are all greater than those in the F-T group at the same cycle. Different fitting functions simply and directly reveal the trend of the model parameters with the cycles. The freezing rate due to freezing temperature induces a significant difference in water redistribution and dry density from the core to the surface layer of the specimen, which is why the model parameter and its fitting parameters don't monotonically decrease with stepwise-reduced freezing temperatures. The gray correlation degree shows that the freezing temperature cannot be ignored when considering the F-T effect. The generalized Hooke's Law in principal-stress form demonstrates the applicability of the Duncan-Chang model while considering the F-T effect and the T-C effect.