A PREDICTIVE MODEL FOR THE WATER-RETENTION CURVE - APPLICATION TO TAILINGS FROM HARD-ROCK MINES

It is now commonly recognized that many geotechnical problems are rela ted to the unsaturated behavior of soils. Such is the case for phenome na occurring at shallow depths in the so-called vadose zone. Unsaturat ed flow is also very important for the management of milling wastes, e specially for seepage in and around tailings ponds. Suction properties constitute a key element for the functional representation of unsatur ated flow conditions. These are usually shown by the water retention c urve, which gives the relationship between volumetric water content (t heta) and matric suction (psi) Laboratory measurements have been perfo rmed on three different tailings from hard-rock mines in the Abitibi r egion to study the effect of various factors, including grain size and porosity, on the theta-psi relationship. The main results are present ed in this paper. The data are first analyzed using a well-known descr iptive model. The experimental results are also used to estimate the a ir-entry value according to various procedures including a simple meth od proposed by the authors. Then, it is shown how an existing predicti ve model can be modified to obtain, from basic material properties, th e complete water retention curve.