Yan Jun Du

Swelling–shrinkage properties and soil improvement of compacted expansive soil, Ning-Liang Highway, China

Abstract In this paper, the swelling–shrinkage properties of the compacted expansive soil in the Huaiyin Section of the Ning-Lian Highway are introduced, and swelling–shrinkage mechanisms are discussed based on changes in soil water content, dry density, material composition and fabric. The improvement of the compacted expansive soil by lime is also discussed briefly. It is concluded that careful attention should be paid to this type of compacted expansive soil.

Effect of Leachate Composition on the Adsorption Properties of Two Soils

The experimental results show that the composition of the contaminant leachate affects the adsorption behavior for the soil tested. However, this conclusion is based on the assumption that the soil adsorption isotherm is linear. To investigate this effect when the adsorption isotherm is nonlinear, a series of batch tests were conducted with a single-salt solution (KCl, CaCl2, and NaCl solution, respectively) and multi-salt solution (aqueous miscible solution containing KCl, CaCl2, and NaCl) for the selected two soils from Japan. A comparison of the test results between these two conditions indicated that for a specified cation of interest, soils adsorbed larger amounts of cations in the case of the single-salt condition relative to the multisalt condition. The Freundlich equation was adopted to fit the experimental data, and the model parameters are presented. The relative cation adsorption of soils is provided and the controlling factors are discussed.

A laboratory study on migration of K+ in a two-layer landfill liner system

Contaminant transport through the clay liner and the underlying secondary leachate drain layer (SLDL) in landfills was studied through a laboratory test, and analysis method on the transport of K+ in a two-layer soil system. The soils used for this study were Ariake clay and the underlying layer, Shirasu soil from the Kyushu region of Japan, representing the clay liner material and SLDL material, respectively. The effective diffusion coefficients (D e) of the selected target chemical species, potassium (K+) for the Ariake clay and Shirasu soil were back-calculated using a computer program, and it was found that values of D e derived from this study were consistent with those previously published. The hypothesis that the mechanical dispersion process can be negligible has been proved to be reasonable based on both the observation that the predicted values fit the experimental data and the analyses of two dimensionless parameters. Parametric analysis showed the transport of K+ through the soils is controlled by advection–diffusion rather than diffusion only, whereas at low Darcy velocity (i.e. ≤ 10–9 m s–1), transport of K+ would be controlled by diffusion. The test results and parametric analysis may be applied in design of landfill liners and SLDLs, particularly in coastal areas.