Based on bound water characteristics study of microporosity characteristics and mechanical properties evolution of...

The potential impact of heavy metal ion infiltration on macroscopic and microscopic soil properties is a subject of academic interest. Laterite has an extensive distribution in southern China and is extensively utilized as a vertical containment wall for landfills. Consequently, there is a need to investigate how heavy metal ions affect laterite's microstructure and mechanical properties. To examine the impact of Cu²⁺ on laterite's microporous characteristics and mechanical properties, laboratory tests were conducted on the permeability, shear strength, microporous characteristics, and strong absorbed water content of Cu²⁺-contaminated laterite. The results show that Cu²⁺ hydrolysis generates an acidic environment, which leads to erosion of the cementing substance between the laterite particles, increasing the laterite's porosity and decreasing the soil's cohesive strength, thus affecting the shear strength and permeability of the laterite. When the concentration of Cu²⁺ is 5.0 g/L, the laterite demonstrated the most significant decrease in shear strength, 43.01%, while the permeability coefficient increased from 3.24 × 10^-8 cm/s to 1.32 × 10^-7 cm/s. Meanwhile, Cu²⁺ changes the content of strong absorbed water in laterite. The change of strong absorbed water content will affect the Van der Waals between laterite particles, promote the evolution of soil micropore structure, and lead to a decrease in the proportion of intra-aggregate pores (d < 1 μm) and an increase in the proportion of inter-aggregate pores (1 μm < d < 10 μm), which in turn affects the macroscopic shear strength and permeability. This study has improved our understanding of the mechanisms underlying the microporosity and mechanical property evolution of laterite when subjected to heavy metal attack.