Interaction between lattice dislocations and grain boundaries in high purity iron. Fiche cinematographique ONERA n° 1173 ( 1986 )

No abstract availabl

Interaction between lattice dislocations and grain boundaries in high purity iron. Fiche cinematographique ONERA n° 1173 ( 1986 )

No abstract availabl

Electromagnetic/Acoustic Coupling in Partially Saturated Porous Rocks: An Extension of Pride’s Theory

International audienceIn this paper a set of equations governing the electromagnetic/acoustic coupling in partially-saturated porous rocks in the low-frequency regime is derived. The equations are obtained by volume averaging of fundamental electromagnetic and mechanical equations valid at the porescale, following the same procedure as the one developed in the seminal paper of S. Pride for porous media where the fluid electrolyte fully saturates the pore space. In the present approach it is assumed that the porous rock is partially saturated with a wetting-fluid electrolyte (water) Electromagnetic/acoustic coupling in partially-saturated porous rocks and a non-wetting fluid (air). We also assume that an electromagnetic/mechanical coupling exists at the water-solid and water-air contact surfaces through adsorbed excess charges balanced by mobile ions in the water. The proposed approach is valid at the low-frequency regime, where capillary pressure perturbations can be safely neglected. The governing equations thus derived are similar to the ones obtained by Pride with the main difference that the various coefficients, including the electrokinetic coupling coefficient and electric conductivity appearing in the transport equations are functions of the water saturation and depend on electrical and topological properties of both electric double layers

Seismoelectric Signals Produced by Mesoscopic Heterogeneities: Spectroscopic Analysis of Fractured Media

International audienceIn fluid-saturated porous rocks, the presence of mesoscopic heterogeneities such as, for example, fractures, can produce measurable seismoelectric signals. The conversion of mechanical energy into electromagnetic energy is related to wave-induced fluid flow (WIFF) between the heterogeneities and the embedding background. This physical mechanism is a well-known cause of seismic attenuation, which exhibits a strong frequency dependence related to rock physical and structural properties. Consequently, seismoelectric signals arising from WIFF are also expected to depend on various material properties, such as the background permeability and fracture characteristics. We present analytical and numerical approaches to study the effects of mesoscopic heterogeneities on seismoelectric signals. We develop an energy-based approach to quantify the total energy converted to seismoelectric signals at the sample scale. In particular, we apply our theoretical framework to synthetic models of fractured rock samples and study the spectral signature of the resulting seismoelectric signals. This study highlights the influence of the mechanical and hydraulic properties, as well as the geometrical characteristics, such as degree of fracture connectivity, of the probed medium on the resulting seismoelectric signal