An evaluation of the effects of microstructural characteristics and frost heave on the remediation of saline-alkali soils in the Yellow River Delta, China

In the Yellow River Delta of China, soil salinization is of serious concern from both agricultural and environmental perspectives. In this study we investigated the microstructural characteristics of saline-alkali soils in this region and explored the influence of frost heave on soil microstructure. Soil mineral composition, pore distribution, particle arrangement, and pore characteristics were measured using X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). Soil pore characteristics, overall porosity, and unconfined compressive strength (UCS) were measured at water content of 10, 15, 20, 25% (w/w) before and after freezing at -10 degrees C. The results showed that deterioration of soil physical properties was largely caused by dense particle arrangement, high proportion of ultra-micropore-specific surface area, and poor pore distribution, rather than mineral content or particle size distribution. The microstructure of saline-alkali soil was greatly improved by frost heave with the overall porosity and UCS of frost heave-treated soil samples significantly higher than for the control. Moreover, particle cementation decreased with increasing soil water content. This study demonstrated that a combination of XRD, SEM, and MIP offers accurate evaluation of the microstructural characteristics of saline-alkali soils, and frost heave may serve as an economically sustainable and technically feasible method for saline-alkali soil amelioration in the Yellow River Delta.