The Influence of the Pore Fluid on Desiccation of a Deformable Porous Material H. P´ eron 1 , L.B. Hu 2 , T. Hueckel 2 , and L. Laloui 1 1 Soil Mechanics Laboratory, Ecole Polytechnique F´ ed´ erale de Lausanne – EPFL, Station 18, CH-1015 Lausanne, Switzerland herve.peron@epfl.ch, lyesse.laloui@epfl.ch 2 Department of Civil and Environmental Engineering, Duke University, Durham, N.C. 27706, U.S.A. lh19@duke.edu, hueckel@duke.edu Summary. This paper aims at elucidating the influence of pore fluid properties on the shrinkage strains of deformable materials subjected to drying. Results of isothermal drying tests of two kinds of silts saturated with three different pore fluids are presented. Results show different strain amounts during drying and the final void ratios, depending on pore fluid. The rates of drying are consistent with saturated vapor pressures, while their amount with the surface tension. The shrinkage limit appears also to be controlled by a limitation in skeleton compressibility. Introduction The study of deformation due to drying is fundamental in the understanding of the patterns of stress generated by the constrained shrinkage and cracking in soils. When drying shrinkage is constrained, reaction forces arising located at the constraints generate stresses, which depend on the amount of shrinkage. Our previous papers (P´ eron et al. 2006, Hu et al. 2006) revealed how the development of such stress in the elastic domain leads to soil cracking. Notably, several previous studies established that most of the desiccation shrinkage develops when soil is saturated (Croney and Coleman 1954, Fleureau et al. 1993). The state of full saturation when cracking initiates was hypoth- esized by several authors (Konrad and Ayad 1997, Abu-Hejleh and Znidarcic 1995, Lloret et al. 1998). Recently, P´ eron et al. (2006) showed that cracks occur at the end of saturation range or at the early stage of desaturation. The goal in this work is to investigate a possible relationship between the total amount of shrinkage, its rate and the mechanisms of liquid removal and deformation. In particular, the role of the evaporation flux versus surface tension, in addition to soil compressibility and transport properties are of in- terest. Slow, constant humidity environment, (isothermal) air-drying of thin and long rectangular soil slabs was carried out. Two different soil types were Page: 1 job: Peron macro: svmult.cls date/time: 26-Sep-2006/9:00