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.

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.

Bentonite with a low hydraulic conductivity is often used as engineered barriers to prevent groundwater contamination by leachate from the nuclear waste. When bentonite is immersed into the water solution, swelling deformation and swelling pressure will occur to create a tight contact with confining rock. The swelling deformation and swelling pressure are proportional to the amount of water volume absorbed by bentonite. The water volume absorbed by bentonite is related to its surface fractality. The correlation of the normalized water volume by bentonite volume (Vw=Vm) to vertical overburden pressure (p) is obtained as Vw=Vm ¼ KpDs 3, which presents a method to determine the surface fractal dimension of bentonite using the swelling tests. The surface fractal dimensions (Ds) of Wyoming bentonite and Tsukinuno bentonite are 2.64, 2.65, respectively obtained from the swelling tests. The surface fractal dimension of bentonite can be used to estimate the maximum swelling strain and swelling pressure in the disposal system f nuclear waste.

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.