Final Report Summary - FAILFLOW (Failure and Fluid Flow in Porous Quasibrittle Materials)
The objective of the Failflow project is to investigate the relationship between the microstructure of quasi-brittle materials and their permeability to fluid flow. This relationship plays a pivotal role in the production of fossil resources, the development of enhanced oil recovery, the geological storage of carbon dioxide, or the serviceability and durability of concrete structures. Although the project focuses on geo-materials (rocks, mortar and concrete), the scientific questioning concerns also many industrial processes involved in the food or medicine industry.
Among the difficulties addressed within the Failflow project there is:
(i) the issue of the evolution of the microstructure – micro-cracking and damage growth – due to applied mechanical loads and the induced variation of intrinsic permeability of the material.
(ii) when the porous material exhibit pores at the nanoscale, the fluid is confined, the interaction with the solid phase are modified and the overall mechanical and transport properties change.
(iii) the issue of multiphase and multispecies fluids in porous materials which influences again the permeability.
The scientific outcomes of the project are:
Continuum to discrete transition in continuous non local damage models: a new model with non-local interactions during failure in quasi-brittle materials has been proposed. Interactions are computed in the course of damage, on the basis of micromechanical arguments.
Failure and size effect for notched and unnotched concrete beams: Structural size effect tests data on the same material and different geometries are very scarce in the literature. We have performed a unique experimental campaign of three point bending fracture tests showing size effect for geometrically similar specimens with different notch lengths.
Meso-mechanical approaches to damage in quasi-brittle materials: a meso-scale model for fracture of heterogeneous quasi-brittle materials has been developed. Experimental results on geometrically similar specimens under three point bending loading have been reproduced, and the local failure process as well.
Fluids in porous materials - Interfacial properties: an original coupling between the Gradient Theory of fluid interfaces and a molecular equation of state (SAFT-VR Mie) allowed to obtain for the first time together bulk, equilibrium and interfacial properties of water/hydrocarbon mixtures. The model was extended to fluid/solid interfaces and to associative compounds.
Fluid-solid interactions in microporous materials: Fluid-solid interactions in microporous materials yield at the macroscopic level interactions between adsorption and swelling. A novel phenomenological model inspired by MC simulations, which captures this phenomenon, has been devised.
Fluid flow in microporous materials - molecular simulations: molecular dynamics has been used in order to revisit the fluid flow in very narrow pores. Partial slip occurs not only between fluid and solid phases, but also between non miscible dense fluid phases. The apparent slippage amplitude is guided by the species that are the most adsorbed on the surface. The density inhomogeneities induced by physic-sorption and confinement induce local variations of the transport properties.
Computations of permeabilities in tight materials: tools for the prediction of the permeability of a porous material from the knowledge of their pore size distribution have been developed yielding an equivalent Darcy-type relationship. Permeability was also extracted from CT Scans directly.
Multicomponent adsorption on micro and mesoporous materials: an experimental technique performing multicomponent adsorption measurements, coupled to a gas chromatograph was designed. Such a device represents an innovative step forward regarding selective adsorption measurement techniques.
This project is based upon an assembly of skills in the fields of solid mechanics, fluid mechanics, molecular simulation, thermodynamics and physics of interfaces. Developments in the field of micro-porous materials have a strong potential impact on candidate technologies for gas production from very tight rocks such as coal seams or gas shales.
Among the difficulties addressed within the Failflow project there is:
(i) the issue of the evolution of the microstructure – micro-cracking and damage growth – due to applied mechanical loads and the induced variation of intrinsic permeability of the material.
(ii) when the porous material exhibit pores at the nanoscale, the fluid is confined, the interaction with the solid phase are modified and the overall mechanical and transport properties change.
(iii) the issue of multiphase and multispecies fluids in porous materials which influences again the permeability.
The scientific outcomes of the project are:
Continuum to discrete transition in continuous non local damage models: a new model with non-local interactions during failure in quasi-brittle materials has been proposed. Interactions are computed in the course of damage, on the basis of micromechanical arguments.
Failure and size effect for notched and unnotched concrete beams: Structural size effect tests data on the same material and different geometries are very scarce in the literature. We have performed a unique experimental campaign of three point bending fracture tests showing size effect for geometrically similar specimens with different notch lengths.
Meso-mechanical approaches to damage in quasi-brittle materials: a meso-scale model for fracture of heterogeneous quasi-brittle materials has been developed. Experimental results on geometrically similar specimens under three point bending loading have been reproduced, and the local failure process as well.
Fluids in porous materials - Interfacial properties: an original coupling between the Gradient Theory of fluid interfaces and a molecular equation of state (SAFT-VR Mie) allowed to obtain for the first time together bulk, equilibrium and interfacial properties of water/hydrocarbon mixtures. The model was extended to fluid/solid interfaces and to associative compounds.
Fluid-solid interactions in microporous materials: Fluid-solid interactions in microporous materials yield at the macroscopic level interactions between adsorption and swelling. A novel phenomenological model inspired by MC simulations, which captures this phenomenon, has been devised.
Fluid flow in microporous materials - molecular simulations: molecular dynamics has been used in order to revisit the fluid flow in very narrow pores. Partial slip occurs not only between fluid and solid phases, but also between non miscible dense fluid phases. The apparent slippage amplitude is guided by the species that are the most adsorbed on the surface. The density inhomogeneities induced by physic-sorption and confinement induce local variations of the transport properties.
Computations of permeabilities in tight materials: tools for the prediction of the permeability of a porous material from the knowledge of their pore size distribution have been developed yielding an equivalent Darcy-type relationship. Permeability was also extracted from CT Scans directly.
Multicomponent adsorption on micro and mesoporous materials: an experimental technique performing multicomponent adsorption measurements, coupled to a gas chromatograph was designed. Such a device represents an innovative step forward regarding selective adsorption measurement techniques.
This project is based upon an assembly of skills in the fields of solid mechanics, fluid mechanics, molecular simulation, thermodynamics and physics of interfaces. Developments in the field of micro-porous materials have a strong potential impact on candidate technologies for gas production from very tight rocks such as coal seams or gas shales.