Experimental study on the deterioration characteristics of the remolded loess with Na2SO4 under freezing-thawing cycles

Freezing-thawing cycles and salinization are the two important factors inducing the deterioration of the loess. In this study, the unconfined compressive strengths of the remolded loess with different Na2SO4 contents (i.e., 0.0 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, and 3.0 wt%) under different freezing-thawing cycles (0, 1, 3, 5, 10) were investigated to study the strength deterioration characteristics. The pore size distributions of the remolded loess samples were also investigated based on the mercury intrusion porosimetry (MIP) test. The modified disturbed state concept (MDSC) based constitutive model was proposed to establish relationship of the unconfined compressive strength and porosity of the remolded loess sample. Results showed that:1) the unconfined compressive strengths of the remolded loess decreased linearly with the Na2SO4 contents, and decreased exponentially with the freezing-thawing cycles; 2) the ratio of freezing-thawing cycles to salinization corrosion deterioration factor decreased exponentially with the Na2SO4 contents, and increased linearly with the freezing-thawing cycles; 3) three peaks were clearly found in the pore size distribution of the remolded loess sample, and the porosity firstly increased rapidly and then slowly increased with the Na2SO4 contents and freezing-thawing cycles; 4) the predicted stress-strain curves from the proposed constitutive model can generally match with the measured stress-strain curve with a consistency index higher than 0.80, while the predicted unconfined compressive strengths were relatively lower than that measured value, which was approximately 89% of the measured strength. This study is helpful for engineering construction in the Chinese Loess Plateau.