GEOMEC: Geomechanics Platform (Nantes)

Liste of equipement

The geomechanics platform is equipped with several machines for characterising geomaterials as well as analogue materials. The simple shear and pure shear devices are used to study the shear behaviour of soils.

The experimental earthquake simulation setup makes it possible to reproduce seismic-type events in the laboratory at a scale of a few tens of millimetres. It comprises a 3D-printed specimen holder capable of applying a controlled displacement, a triangular specimen made of a paraffin oil-based gel, and a digital camera that records image sequences during dynamic rupture propagation. The specimen interface can be homogeneous or heterogeneous, allowing the study of dynamic rupture propagation.


Laboratory experimental simulation of earthquakes


A growing number of earthquakes are associated with fluid injection into the subsurface, particularly in connection with geothermal energy production. Preliminary studies (Stefanou, JGR, 2019; Gutierrez-Oribio et al., IEEE Trans. Control Syst. Technol., 2023) have shown that injection-induced earthquakes can be mitigated through control strategies that modulate the pressure of the injected fluid. To further investigate the possibilities for controlling induced seismicity in the laboratory, a new experimental earthquake simulation setup has been developed as part of a PhD thesis. This setup is capable of producing spontaneous ruptures and sustaining dynamic rupture propagation, and it is currently used to study dynamic propagation behaviour along homogeneous and heterogeneous interfaces. Ultimately, it will serve as an experimental platform for developing and testing control algorithms aimed at limiting rupture propagation.

Examples of slip velocity maps (left panels) and time histories of local slip velocity (right panels) during the first 50 milliseconds following rupture nucleation. The upper panels show a rupture propagating along a homogeneous interface, while the lower panels show a rupture interacting with a zone of higher shear strength located at x0.



Hydromechanical instabilities in geomaterials in the context of underground fluid storage

The coupling between two-phase flow and the mechanical response of a granular medium is studied at laboratory scale in order to highlight the interactions between the fingering phenomenon occurring during fluid flow and localised deformation within the granular medium. The proposed experimental campaign makes it possible to perform drainage flows under mechanical stress.

While many experimental studies have focused on the morphology of two-phase flow in a Hele-Shaw cell or a 3D medium, full-field quantification of fluid-induced skeleton deformation under hydromechanical loading is still lacking. The aim of the research carried out within the ANR STOWENG project (underground STOrage of reneWable ENergies in low permeability Geomaterials) was, on the one hand, to identify the relationship between the unstable gas flow observed during drainage and localised deformation, using digital image correlation coupled with interface detection, and on the other hand, to highlight the influence of mechanical loading on the level of deformation and the characteristics of the interface.

 

Volumetric strain maps for the right finger detected during drainage. The black lines represent the interface detected using the phase-field method for d = 0.25.

 
 

Blast Project


Reduced-scale explosion simulator
Investigating the response of structures to explosions is highly challenging when relying solely on numerical and analytical tools. To improve our understanding and validate existing models, these tools must be complemented by experimental testing. However, experiments specifically designed for blast scenarios remain scarce compared with tests carried out under other dynamic conditions, such as earthquakes. This scarcity can be attributed to the many complexities of conducting large-scale explosion experiments, mainly due to the nature of the loading involved.


Nevertheless, reduced-scale experiments offer an alternative approach with greater flexibility. In this context, this device opens up new opportunities by allowing us to carry out experiments specifically designed to study the dynamic behaviour of structures subjected to blast loading. For the first time, it enables us to explore and draw valuable conclusions from reduced-scale experiments that faithfully simulate explosion scenarios.



 

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