Study on the mechanical properties of XG modified red clay under drying-wet cycle

Abstract To mitigate the adverse ecological impacts of inorganic solidified materials on modified red clay and address the issues of low bearing capacity and extensive cracking under hydraulic erosion, this study investigates the use of low-environmental-impact materials to improve the mechanical fracturing of red clay. In this context, the present study investigates the modification of red clay using an environmentally friendly biopolymer. Through a series of laboratory mechanical and microstructural tests, the effects of xanthan gum (XG) on the mechanical fracturing, California Bearing Ratio (CBR), and microstructural characteristics of red clay are examined. The results indicate that the shear strength of XG-modified soil increases approximately linearly with the increase in normal stress. The cohesion and internal friction angle of the modified soil first increases and then decrease with the increasing XG dosage. The compressive strength of the modified soil initially increases and then decreases with the addition of XG, with the most rapid growth occurring between 14 and 28 days. The deformation modulus of the modified soil initially increases and then decreases with increasing XG dosage, resulting in a 7.71% increase after 28 days. As the number of cycles increases, the development of fractures in the modified soil slows down, mainly due to the evolution of secondary fractures into primary fractures. The internal friction angle of the modified soil decreases with the increasing number of cycles, while the cohesion and compressive strength show a decreasing trend. The CBR of the modified soil first increases and then decreases with the increasing XG dosage, reaching a peak value of 24.1%. The addition of XG results in the formation of flake-like and needle-like hydration products that cover the soil particles, fill the pores, and form dense aggregates. After 28 days, the hydrophilic minerals in the modified soil are reduced by 53.99%. Pore analysis indicates a decrease in the average porosity and total pore size of the XG-modified soil. The research results provide a novel modification approach to address the ecological environmental issues associated with the treatment of red clay using inorganic solidifiers, offering valuable numerical references for similar engineering projects.