ABSTRACT
The retention of water in unsaturated soil is dictated by the interaction between different phases. The equilibrium of air, water, vapor and soil (or ice) particles leads to the capillary phenomena usually termed as suction. This component, defined by the difference between air pressure (ua) and water pressure (uwl), is widely used for the description of the mechanical response of soils. The value of suction ranges from 0 to more than 10 MPa according to most reviews (Fleureau et al. 1993). The French ANR project TerreDurable (Boutonnier et al. 2012) is dedicated to the study of fine grain soil for the construction of embankments, situation where the soil is typically unsaturated (Pendular to hygroscopic domain). Although some concern have been made regarding such suction values and their actual mechanical effect on soil (Baker & Frydman 2009). This paper presents the mechanical response of water at negative pressure through its capillary pressure and nucleation process. Corresponding physical phenomenon leads to desaturation. Furthermore desaturation at a single pore scale will be examined. Then evolution of porosity and behavior associated is discussed. The absolute pressure is used with a vacuum pressure equal to zero.
