Nadia Saiyouri

Microstructural approach and transfer water modelling in highly compacted unsaturated swelling clays

A compacted smectite clay was studied in order to understand the swelling phenomenon. The influence of the sample initial state on the swelling mechanisms was demonstrated. A complete physical–chemical and mineralogical characterization of the clay was achieved using X-ray by reflexion and thermal methods. The X-ray diffraction by transmission method allowed to describe the various levels of the hydrated clay organization and the microstructure evolution. The pore distribution and the water partition are shown. Other important parameters: water retention, inter-layer distances, particle size, number of layers per particle were examined. This information gives the ability to follow the swelling which occurred in two steps, and to calculate the swelling potential versus the water content, or the void ratio. In application to this study, a water transfer in unsaturated clay was studied with the laws of continuous medium mechanics. A finite difference program was used to examine two cases: prevented and free swelling in an oedometer. In order to take into account the material deformation, the swelling potential was introduced in the diffusion coefficients. The simulation results of the water transfer obtained on this basis, were in good agreement with the experiments. Copyright

Permeability and porosity improvement of grouted sand

Over the past twenty years, growing technology allowed to treat a wide range of subsurface conditions for construction. When a properly designed cement grout is injected into sand soil, homogeneous grout bulbs are formed which make dense and thus strengthen the surrounding soil. For successful growing, the knowledge of subsurface conditions is important. Ground improvement can be assessed by permeability testing and mercury porosimetry testing. Laboratory experiments were conducted to examine grout injection through Loire sand columns under saturated conditions. These tests were performed in order to highlight the effect of some key factors: cement-to-water ratio, relative density of the granular skeleton on the properties of the grouted sand. Subsequently Mercury Intrusion Porosimetry tests showed that both porosity and its distribution are modified. Besides, the intrinsic permeability was measured by a gas permeability device. Then, an evaluation of intrinsic permeability using the Katz-Thompson equation on these tests is proposed and compared to gas permeability which is still commonly used in civil engineering to measure this intrinsic parameter.