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Platform of Physics Modeling of Earth Sciences Process

Project Manager: M. Pessel

Objective:

The objective of this platform is to perpetuate the ongoing projects and develop new cooperation between the two laboratories, so this platform gathers a range of facilities to integrate various projects in synergy with the two laboratories. Indeed the approach of laboratory IDES passes through the understanding of the processes studied by field studies: they do not explain their origin and their possible effectiveness. Numerical modeling are found so often needed to quantify the processes involved and, secondly, to identify or prioritize the parameters. These models should be complemented by analogy validations and are usually followed by a return to the field to new achievements and measures. The expertise of laboratory FAST is complementary and represents a considerable potential contribution to the numerical modeling and processes studied in laboratory. The work of FAST has indeed a large part of small-scale experiments well controlled for understanding the influence of specific parameters of complex processes. The laboratory IDES has also an activity recognized for conducting experiments in cold environments and the high expertise of the laboratory FAST on the thermal exchanges and physicochemical processes provides an excellent complement.

Major works in progress in this platform

Comparison between 2D electrical imaging and video observation of monitoring of plumes of pollutants:

Tomography of electrical resistivity is a common method of geophysics of subsurface allowing, among other things, to detect the plume of pollutants spreading in the saturated zone. However, the complexity and variability of hydrodynamic parameters of the environment and the non-uniqueness of inversion models limit the qualitative interpretations. The objective of this work is to test the various devices of electrodes and inversion processes associated with measures of tracers in porous environments to quantitatively determine hydrodynamic parameters of a diffusion front.

Studies of river dynamic in periglacial environment - Case of the evolution of islands in the valleys of defeat

The purpose of this study designed to promote the understanding of the dynamics of river flows in periglacial environment through an analogic experience in cold storage. It uses various skills of physicists, geologists and geomorphologists between FAST and IDES. It is a sharing of these skills in understanding and quantification of an elementary erosion process under the effect of a flow in cold environments. We will focus in this program on an analogic and numeric modeling of the interaction between an island consisting of a permafrost in contact with a turbulent flow. Our goal is a morphometric, analogic and numeric study of the formation, development or destruction of the islands in a river system in periglacial environment.

Figure 1: Hydraulic channel in cold storage and image of an island formed in the channel


Measurement of surface rupture

For several years the laboratory FAST teams interest in flows in heterogeneous environments. In natural environments, the fractures change profoundly the structure of the flows by locating a significant part of flows along some preferential paths. At the range of the single fracture, roughness of the fracture surfaces and its influence on the structure of voids in the fracture is the cause of the appearance of this phenomenon of localization. To characterize the geometry of the roughness of fracture surfaces we have developed a mechanical profilometer. This device allows to measure the surface elevation with a precision micrometer on surfaces of a few square centimeters. The repetition of the measure with a minimum pitch of 25 microns allows to acquire cards containing nearly 60 000 points maximum.

Figure 2 : Map of the heights of a fracture surface of granite: the asperities appear at all scales highlighting the multi-scale roughness of such surfaces

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