The impacts of freeze-thaw cycles on saturated hydraulic conductivity and microstructure of saline-alkali soils

Study on the microscopic structure of saline-alkali soil can reveal the change of its permeability more deeply. In this paper, the relationship between permeability and microstructure of saline-alkali soil with different dry densities and water content in the floodplain of southwestern Shandong Province was studied through freeze-thaw cycles. A comprehensive analysis of soil samples was conducted using particle-size distribution, X-ray diffraction, freeze-thaw cycles test, saturated hydraulic conductivity test and mercury intrusion porosimetry. The poor microstructure of soil is the main factor that leads to the category of micro-permeable soil. The porosity of the local soil was only 6.19-11.51%, and ultra-micropores (< 0.05 mu m) and micropores (0.05-2 mu m) dominated the pore size distribution. Soil saturated water conductivity was closely related to its microscopic pore size distribution. As the F-T cycles progressed, soil permeability became stronger, with the reason the pore size distribution curve began to shift to the small pores (2-10 mu m) and mesopores (10-20 mu m), and this effect was the most severe when the freeze-thaw cycle was 15 times. High water content could promote the effects of freeze-thaw cycles on soil permeability and pore size distribution, while the increase of dry density could inhibit these effects. The results of this study provide a theoretical basis for the remediation of saline-alkali soil in the flooded area of Southwest Shandong.

Automated summary

This study investigated the relationship between permeability and microstructure of saline-alkali soil in the floodplain of southwestern Shandong Province through freeze-thaw cycles. The results showed that soil microstructure and pore size distribution play a crucial role in determining soil permeability. The increase in freeze-thaw cycles led to stronger soil permeability, with a shift towards smaller pore sizes in the soil.