Exploring the saturated permeability of remolded loess under inorganic salt solution seepage
2021
Xu, Panpan | Qian, Hui | Zhang, Qiying | Zheng, Le
The seepage of remolded loess with inorganic salt solutions can deteriorate its engineering properties. To gain insight into the mechanism responsible for changes in the permeability of remolded loess due to the invasion of inorganic pollutants, the saturated permeability tests were performed on remolded loess samples using deionized water (DW) and NaCl, CaCl₂, AlCl₃, and NaHCO₃ solutions. Leaching tests were designed to determine the chemical components of leachates. Zeta potentials were measured to evaluate the electrochemical properties, and mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) tests were used to estimate changes in microstructure before and after seepage. The results indicate that the saturated hydraulic conductivity (Kₛₐₜ) was positively correlated with the cation valence. With the increase of cation valence, the compression degree of double diffusion layer on the surface of clay particles increases, and a larger space for free water movement is formed. The salt effect promoted the dissolution of carbonate minerals of loess and enhanced permeability, for example, NaCl; while the common-ion effect of HCO₃⁻ inhibited their dissolution and even led to the calcite precipitation. In addition, the hydrolysis of Al³⁺ also significantly affected Kₛₐₜ. Therefore, under the seepage of inorganic salt solutions, the order of Kₛₐₜ of remolded loess samples was NaHCO₃ < DW < NaCl < CaCl₂ < AlCl₃.
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