Pore-scale study on the characteristic hydraulic conductivity of a dispersive lean clay affected by salinity and freeze-thaw

Research into the permeability of dispersive soils featuring high erodibility remains rather limited, especially from a pore-scale perspective. This study focused on the relationship between permeability of remolded dispersive soil (lean clay) and its initial pore scale characteristics, via constant-head permeation and mercury intrusion porosimetry (MIP) tests, with consideration of soil salinity and freeze-thaw (F-T) effects. Main findings are as follows. The peak hydraulic conductivity (k(max)) appeared at the initial permeation stage linked initial pore-scale parameters. Pores inside of soil could be classified into two groups (> 10 and < 10 mu m) based on MIP results. Increase in salt contents led to increased volume of pores > 10 mu m (V-p>10) and porosity (n), but decreasing tortuosity (tau) and fractal dimension (D-f). In addition, 5 F-T cycles maximized V-p>10 and n but minimized tau, and D-f reached its maximum after 10 cycles. Correlation analyses found that V-p>10, n and tau correlated with k(max); a combined variable nd(ave)(2) showed better correlation to k(max) than others regarding pore diameter; besides, and no correlation was found between D-f and k(max), but D-f should not be ignored as it described the complexity of pore structure. Finally, based on grey relation entropy method, the above pore-scale parameters were extracted to compare their contributions under coupled effects of salinity and F-T to the variation in k(max). The following order of importance was found: nd(ave)(2) approximate to V-p>10 > n > D-f > tau. Moreover, single impact of F-T on the contribution ranking was less intense than that of salinity.

Automated summary

The relationship between the permeability of dispersive soil and its pore-scale characteristics was investigated in this study. The results showed that salt content and freeze-thaw cycles have different effects on pore structure and permeability. Pore diameter and pore volume were found to be the major factors affecting permeability.