Three-dimensional characterization of a fractured granite and transport properties

International audienceA three-dimensional fracture network in a granite block is reconstructed from a series of experimental serial sections. It is visualized and its most important geometrical characteristics are studied, namely the orientation of the fractures, the connectivity of the fractures, the number of cycles, per unit volume, the distributions of surface areas and of the intersection lengths, and the number of finite solid blocks isolated in the solid matrix by the network. Though the network mostly consists of two families of fractures, it is interesting to note that a simple model of randomly oriented, monodisperse hexagons often yields a good order of magnitude for the various geometrical properties, which have been measured on the real block. The flow properties are then studied; examples of velocity field are provided as well as histograms of velocities; the permeability tensor is determined and is found to be in good agreement with Snow's formula. Finally, dispersion is analyzed by means of a random walk method; histograms of arrival times are provided and interpreted in terms of dispersion tensor

Thermal stability of different siliceous and calcareous aggregates subjected to high temperature

The goal of this study is to improve the knowledge of the deterioration of aggregates subject to high temperature phenomena and to characterise the physical and chemical transformations they undergo. Twenty one (21) aggregates of different mineralogical composition were exposed at temperatures up to 750 °C. The behaviour of siliceous and calcareous aggregates undergoing high temperature has been examined with respect to the evolution of physical, chemical and mineralogical properties

History of fluid circulation in an alteration zone of the Soultz-Sous-Forêts granite (Alsace, France)

International audienceThe Soultz-sous-Forêts area (Alsace, France), a pilot site for geothermal "Hot Dry Rock" exploitation, is characterized by a high surface heat flow induced by circulations of hot fluids percolating through the thick (1 to 3 km) sedimentary cover and the granitic basement (Soultz granite). Three main deep drill holes have been made around the Soultz HDR geothermal site at various depths (EPS-1: 2227 m. GPK-1: 3590 m, GPK-2: 3900 m)

3D electrical resistivity imaging of the near-surface structure of mud-volcano vents

International audienc