Effects of Pisha sandstone additions on microstructural stability of sandy soil in Mu Us Sandy Land, China

The degradation of soil structure in sandy regions undermines soil functionality and poses a significant threat to environmental sustainability. The incorporation of Pisha sandstone, a natural soil amendment, has been recognized as an effective intervention to reduce soil erosion and expand arable land in the Mu Us Sandy Land, China. However, the microstructural stability and resilience of amended sandy soil formed by mixing Pisha sandstone with sandy soils remain inadequately understood. This study aims to evaluate the effects of Pisha sandstone addition on the microstructural stability of sandy soils. Four amendment rates of Pisha sandstone (16.7 %, 33.3 %, 50 %, and 100 % w/w) and five water content levels (40 %-80 %) were tested. Key parameters related to microstructural stability and structural resilience were assessed using amplitude sweep and rotational shear tests via a rheometer. Results indicated that soil shear resistance (τLVR, τmax, τy), storage modulus (G'YP) and viscosity (η0) decreased with the addition of Pisha sandstone, attributed to its lubricating effect and swelling properties. Additionally, Pisha sandstone enhanced physical elasticity (γLVR) and structural recovery of sandy soil under conditions of low disturbance. However, when water content exceeded 50 %, the fluidity of the amended sandy soil increased with Pisha sandstone addition. The sandy soil with a Pisha sandstone addition rate of 16.7 % exhibited optimal structural elasticity, shear resistance, and stiffness. These findings provide valuable insights into the enhancement of sandy soil structural stability using Pisha sandstone, offering a scientific foundation for refining amendment ratios and advancing agricultural management practices.