A predictive model for the water retention curve: application to tailings from hard-rock mines

Abstract

It is now commonly recognized that many geotechnical problems are related to the unsaturated behavior of soils. Such is the case for phenomena occurring at shallow depths in the so-called vadose zone. Unsaturated flow is also very important for the management of milling wastes, especially for seepage in and around tailings ponds. Suction properties constitute a key element for the functional representation of unsaturated flow conditions. These are usually shown by the water retention curve, which gives the relationship between volumetric water content ( theta ) and matric suction ( psi ). Laboratory measurements have been performed on three different tailings from hard-rock mines in the Abitibi region to study the effect of various factors, including grain size and porosity, on the theta - psi relationship. The main results are presented in this paper. The data are first analyzed using a well-known descriptive model. The experimental results are also used to estimate the air-entry value according to various procedures including a simple method proposed by the authors. Then, it is shown how an existing predictive model can be modified to obtain, from basic material properties, the complete water retention curve.Key words: unsaturated flow, tailings, water retention curve, moisture content, saturation ratio, porosity.