A suction- and temperature-controlled oedometric device

To characterize the influence of temperature and relative humidity on the mechanical behavior of geomaterials, an experimental device was designed based on a conventional oedometer testing device. The aim of this work is to provide fundamental information about Thermo-Hydro-Mechanical coupling of unsaturated porous geomaterials such as sand or clay. Several methods were tested and compared to impose relative humidity and temperature. Two systems of control of relative humidity were developed: one using salt solutions to impose constant relative humidity with accuracy in the range of ±4% and the other one using the variation of the saturated vapor pressure of water with temperature to impose relative humidities and potentially make them vary over time. A special attention was paid to thermal insulation of the entire system to reduce temperature variations. A Proportional–Integral–Derivative controller (PID controller) permits to control temperature of samples between 20 and 60 °C for a week with accuracy in the range of ±0.5 °C. This system makes it possible to test 3 samples in parallel, at the same temperature but at potentially different relative humidities. For each sample the vertical displacement, the temperature close to the sample, the relative humidity of the air injected into the sample and the lateral pressure (since zero lateral strain boundary conditions are imposed) are measured. Finally the experimental device was tested on Hostun sand at two temperatures and three relative humidities.