The adsorption of contaminants is one of the key mechanisms governing the transport of contaminants in the clay liner at landfill sites. This study presents an investigation of some factors controlling the adsorption of potassium (K+) onto two soils, named Ariake clay and Akaboku soil. The KCl solution and multi-salt solution containing KCl, NaCl and CaCl2 were selected as the synthetic leachates. The results show that with the increase of the solid/solution ratio, the adsorbed amount of K+ decreased for both soils. This dependence of adsorption behavior on the solid/solution ratio was found more significant for the Ariake clay. Both soils arrived an equilibrium condition in short time less than the contact time prescribed by the ASTM and US EPA standard batch-type tests. It was observed that both soils adsorbed larger amount of K+ in the case of KCl solution condition than in the case of multi-salt condition.

The disturbance of Shanghai silty clay during earth pressure balance (EPB) tunnelling hasbeen studied through field monitoring, field measurement and laboratory test. The soil disturbance during tunnelling consists of two parts: stress disturbance, which is the change of effective stress; and strain disturbance, which is caused by the soil movement. The definition of stress disturbance degree of Shanghai silty clay is given by the change in the in situ effective stress before and just after tunnelling at the same site. According to the changes in the static cone penetrometer resistance, the extent of stress disturbance in a transverse section is determined. The relationships between the mechanical properties and stress disturbance degree are also studied.

A significant 'size effect' is observed in ice failure strength: the ice strength is not independent of ice fragment size, but decreases with increasing size. The fractal approach to the ice mechanics with a multiscale microstructure provides an elegant and unified explanation of the size effect on ice failure strength. Ice fragments are found to have a fractal size distribution, with a fractal dimension (D) close to 2.50 over a remarkably wide range of ice fragment size. The size effect on ice strength can be well predicted using the fractal dimension D=2.50 of the ice fragment size distribution.

Great efforts have been made to determine the shear strength of unsaturated soils using both elaborate laboratory tests and empirical methods. However, elaborate laboratory tests are difficult and time consuming to perform, and the physical meaning of empirical parameters is not obvious in empirical methods. A simple method to determine the unsaturated shear strength is proposed based on a fractal model for the pore surface. The unsaturated shear strength can be easily estimated using the surface fractal dimension and air-entry value, which can be calculated from the soil-water characteristic curves. The unsaturated shear strength obtained from the proposed method is in satisfactory agreement with the experimental data found in the literature. The proposed method is critically examined and its advantages and limitations are also discussed.

Modelling flow and solute transport in unsaturated porous media on the basis of the Richards equation requires specifying values for unsaturated hydraulic conductivity and water potential as a function of saturation. The high cost and large spatial variability of measurements makes the prediction of these properties a viable alternative. Fractal approach seems to be a potentially useful tool to describe hierarchical systems and is suitable to model the structure and hydraulic properties of porous media. In this paper, the fractal model for the pore-size distribution of unsaturated soils is constructed. The soil-water characteristics, hydraulic conductivity and soil-water diffusivity of unsaturated soils are derived and expressed by only two parameters, the fractal dimension and the air-entry value, which can be evaluated from the fractal model for the pore-size distribution. The predictions of the soil-water characteristics, hydraulic conductivity and soil-water diffusivity of unsaturated soils are in good accord with the published experimental data. Correlation between the pore-size distribution and the grain-size distribution is also studied, and it is found that both the pore-size distribution and the grain-size distribution satisfy the fractal model and they have the same fractal dimension. The fractal dimension of the grain-size distribution can be used to determine the unsaturated hydraulic conductivity, instead of the fractal dimension of the pore-size distribution.