An experimental investigation on engineering properties of undisturbed loess under acid contamination

Even though soil acidification can cause significant destabilizing effects on various geotechnical issues, studies have rarely been conducted to determine the influence of soil structure on the impact of acid-contaminated soil. The current work aims to understand the effect of acid fluids on engineering behavior of undisturbed loess through laboratory tests. The sampling site is in a typical region of Loess Plateau, China. The variations in particle size distribution, Atterberg limits, uniaxial compression strength, and permeability were investigated with the help of microstructure for a better understanding of the governing mechanism of undisturbed loess subjected to acid fluids. It was found that exposure to acid fluids can improve the particle size distribution of loess. In contrast, the experimental results indicated that acid fluids can decrease Atterberg limits and strength and permeability of loess, although Atterberg limits and strength of loess are considerably increased in a highly sulfuric acid environment. Then, analyzing the engineering response in the light of microstructure revealed that the face-to-face contacts primarily exist in loess prepared with hydrochloric acid and nitric acid, respectively, whereas the mosaic structure is indeed active in sulfur-contaminated loess. Furthermore, a micro-conceptual structure was proposed based on the experiment led to the conclusion that the cementitious salt and structural characteristics play a dominant role in governing the engineering behavior of loess under acidic conditions.