Experimental study on the direct shear strength characteristics of silt treated with Xanthan gum under different drying and wetting paths.

The silt deposited in the Yellow River floodplains in China is weak and widely dispersed. In engineering practice, chemically modified agents such as lime and fly ash are frequently employed to enhance the hydro-mechanical behaviour of soils, which however generates significant amounts of CO 2. As an environmentally friendly soil improvement material, Xanthan gum has broad application prospects and is therefore being considered as a solidified material to improve silty soil, which meets the national strategy requirements of ecological protection and high-quality development in the Yellow River Basin. In this study, scanning electron microscope, WP4C apparatus, and an automatic direct shear test system were used to perform several microscopic, water-retention behaviour, and direct shear tests on Xanthan gum-treated silt in drying and wetting paths. According to test results, the differences in shear strength behavior were observed in drying and wetting paths. The average skeleton stress of untreated silt in the drying path is greater than that in the wetting path due to the hysteresis effect, and thus the shear strength in the drying path is higher than that in the wetting path. Xanthan gum-treated silt specimens in the wetting path first were cured at a relative humidity of 47% and temperature of 24°C for seven days, and then were wetted to different water contents. The microstructure of the Xanthan gum-treated silt in the wetting path became firmer, and thus the shear strength was higher than that in the drying path. There is also the hysteretic effect of Xanthan gum-treated silt. However, the curing age is the most important factor affecting this phenomenon. Our findings can serve as a scientific foundation for designing, constructing, and maintaining relevant geotechnical structures in the Yellow River flooded area. • The microstructure of Xanthan-treated silt is firmer than that of untreated silt. • Water retention characteristics of Xanthan-treated silt was obtained in wide suction range. • Shear strength of treated silt in drying and wetting paths was studied quantitatively. • Shear strength of untreated silt in drying path is higher than that in wetting path. • Shear strength of treated silt in wetting path is higher than that in drying path. [ABSTRACT FROM AUTHOR]