Effects of wetting–drying cycles and NaCl solution on the hydro-mechanical behaviour and microstructure of compacted red clay-bentonite mixtures

作者：Kao-fei Zhu, Yong He, Ke-neng Zhang, Yu-Jun Cui · 发表于：Journal of Rock Mechanics and Geotechnical Engineering · 年份：2025 · DOI：10.1016/j.jrmge.2025.01.028 · 被引用次数：9 · 研究领域：Soil and Unsaturated Flow、Landfill Environmental Impact Studies、Grouting, Rheology, and Soil Mechanics

Compacted clays are widely used as barriers in municipal solid waste (MSW) landfills due to their low permeability, and the hydro-mechanical behaviour of such materials can be greatly affected by the environmental conditions. In this study, a series of wetting-drying (W-D) cycle tests and hydraulic conductivity tests were conducted on compacted red clay-bentonite mixtures. Various concentrations of NaCl solution were introduced during wetting to investigate the chemical effects. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests were performed to analyze the evolution of soil microstructure. Results indicate that the compacted mixtures undergo cumulative shrinkage during W-D cycles, reaching an elastic state after three cycles. The hydraulic conductivity decreased as bentonite content increases, becoming lower than 1 × 10 -9 m/s when the bentonite content exceeds 10%, which satisfies the requirement for the waste barriers. For a given bentonite content, the relationship between the logarithm of hydraulic conductivity and the void ratio can be well described by a linear regression equation. Additionally, the hydraulic conductivity initially increases and then decreases during the W-D cycles, peaking during the second wetting process. The presence of NaCl solution accelerates the microstructural evolution and cumulative shrinkage, particularly for pure red clay. Therefore, adding an appropriate amount of bentonite mitigates the effect of NaCl solut...