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.

The hydraulic conductivity of unsaturated soils with constant volume is a function of the saturation degree or matric suction, and can be obtained based on currently available procedures. However, each procedure has its limitations and consequently cares should be taken in the selection of a proper procedure. 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 soil-water characteristic curve and hydraulic conductivity function of unsaturated soils were derived from the fractal model for the pore-size distribution, and were expressed by only two independently physical parameters, the fractal dimension and the air-entry value. The predictions of the proposed soil-water characteristic curve and unsaturated hydraulic conductivity were in good accord with the published experimental data. Comparisons between the experimental results and the predictions of both the fractal model and the van Genuchten- Mualem model were performed, and it was found that the predictions of the fractal model were better than that of the van G-M model.

This paper describes the method of earth reinforcement using soilbags and illustrates its application for case studies involving a pond and the expansive soil slope protection for a highway. The strength properties of soilbags were investigated using unconfined compression tests and bearing capacity tests on real soilbags containing either medium grained sands or gravels. The test results show that soilbags have high strength when subjected to an external load. This is primarily attributed to the mobilization of tensile forces in the bags. It is concluded that earth reinforcement using soilbags could substantially improve the bearing capacity of soft ground as well as minimizing deformation under working loads.

Swelling deformation and swelling pressure tests of Tsukinuno bentonite and its mixtures with Toyoura sand were performed on a modified odometer. The swelling strain and swelling pressure of bentonite and its mixtures are dependent on the dry density, the increment of water content and the surface fractality of bentonite particle aggregates in voids. The water volume absorbed by bentonite is related to the surface fractal dimension (Ds) of bentonite. The correlation of the water volume to vertical overburden pressure (p) is obtained as Vw/Vm=KpDs 3 for Tsukinuno bentonite with fractal-textured surface. The maximum swelling strain is predicted according to the correlation of the water volume to vertical overburden pressure. The predictions of the maximum swelling strain are in satisfactory agreement with the experimental data. Furthermore, the good relationship between swelling strain and elapsed time is also proposed in this paper.

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.

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.

Soils are generally penetrated by a pore system. Most transport processes usually occur in pore space of soils. The description of pore space shape is necessary to quantify how the geometry in-uences the percolation of substances such as water and nutrients. In this paper, the pores in soils are described by fractal geometry, and the fractal dimension is obtained from porosimetric measurements. The water permeability function is studied to correlate with the pore-size distribution of unsaturated soils, and is derived from the fractal model of pore-size distribution. The comparisons between the collected data of permeability and the proposed permeability function show that the calculations of the proposed permeability function are in satisfactory agreements with the measurements.

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.

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.

Soil surface area does not keep constant and varies with the yardstick. Experimental results show that the amount of molecules absorbed in the surface monolayers is a function of absorbate size. The surface topography of soils from a few up to as many as thousand angstroms is very well described by fractal dimension, Ds. The surface fractal dimension, Ds is usually used to measure the irregularities of soil surface. The surface fractal dimensions of kaolin, montmorillonite and other six soils are measured using the adsorption method. The surface fractal dimensions of kaolin and montmorillonite are examined by the values measured using the nitrogen/water isotherm adsorption. The relationship between the surface fractal dimension and the content of clay is also discussed in this paper.