The coefficient of permeability for an unsaturated soil is primarily determined by the pore-size distribution of the soil and can be predicted from the soil-water characteristic curve. A general eq...

Predicting the permeability function for unsaturated soils using the soil-water characteristic curve

Unsaturated soil mechanics has rapidly become a part of geotechnical engineering practice as a result of solutions that have emerged to a number of key problems (or challenges). The solutions have emerged from numerous research studies focusing on issues that have a hindrance to the usage of unsaturated soil mechanics. The primary challenges to the implementation of unsaturated soil mechanics can be stated as follows: (1) The need to understand the fundamental, theoretical behavior of an unsaturated soil; (2) the formulation of suitable constitutive equations and the testing for uniqueness of proposed constitutive relationships; (3) the ability to formulate and solve one or more nonlinear partial differential equations using numerical methods; (4) the determination of indirect techniques for the estimation of unsaturated soil property functions, and (5) in situ and laboratory devices for the measurement of a wide range of soil suctions. This paper explains the nature of each of the previous challenges and...

http://keshavarz.persiangig.com/document/Fredlund2006.pdf

Unsaturated Soil Mechanics in Engineering Practice

Water permeability, water retention and microstructure of unsaturated compacted Boom clay

Practical applications of unsaturated soil mechanics still lag behind the state-of-the-art knowledge The main stumbling block is the time-consuming processes involved in the measurement of the unsaturated soil parameters required for the constitutive models Recent research has shown that the soil-water characteristic curves of a soil can be used in the establishment of a number of the unsaturated soil parameters In many applications, it has become obvious that a satisfactory equation for describing the soil-water characteristic curve will simplify the determination of the soil parameters Over the years a number of equations have been suggested Most of these equations have limited success depending on soil types This paper evaluates the more popular equations that have been suggested and shows that all the equations can be derived from a single generic form One equation has been identified that performs very well for all soil types If this equation is in common usage, useful databases on unsaturated soil parameters can be more easily established for practical applications of unsaturated soil mechanics

Review of soil-water characteristic curve equations

Use of indicators and pore volume-function characteristics to quantify soil physical quality

The soil-water characteristic curve can be used to estimate various parameters used to describe unsaturated soil behaviour. A general equation for the soil-water characteristic curve is proposed. A nonlinear, least-squares computer program is used to determine the best-fit parameters for experimental data presented in the literature. The equation is based on the assumption that the shape of the soil-water characteristic curve is dependent upon the pore-size distribution of the soil (i.e., the desaturation is a function of the pore-size distribution). The equation has the form of an integrated frequency distribution curve. The equation provides a good fit for sand, silt, and clay soils over the entire suction range from 0 to 106 kPa. Key words : soil-water characteristic curve, pore-size distribution, nonlinear curve fitting, soil suction, water content.

Anqing Xing

Papers

Equations for the soil-water characteristic curve

Predicting the permeability function for unsaturated soils using the soil-water characteristic curve