Simulation of damage-permeability coupling for mortar under dynamic loads
Résumé
The results reported in this paper deal with the simulation of damage in cohesive geomaterials such as rocks or concrete subjected to dynamic loads. The practical objective is to stimulate the production of tight gas reservoirs with a technique that is an alternative to hydraulic fracturing. The principle is that when subjected to dynamic loads, cohesive materials such as concrete, rocks or ceramics exhibit distributed micro-cracking as opposed to localised cracking observed under static loads. Hence, a low permeability rock containing gas trapped into occluded pores can be fragmented with the help of dynamic loads, and gas can be extracted in a much more efficient way compared with hydraulic fracturing, where only large macro cracks are formed with very few connections between occluded pores. At the stage of laboratory development of this technique, compressive underwater shock waves have been used to increase the intrinsic permeability of concrete specimens. In a previous study, pressure waves generated by pulsed arc electrohydraulic discharges in water were used in order to induce micro-cracking and an increase of average permeability of concrete hollow cylinders subjected to confinement stresses (equivalent to geostatic stresses). We discuss here a 3-D anisotropic constitutive model aimed at describing the dynamic response of these specimens. It is based on rate-dependent continuum damage constitutive relations. Crack closure effects and damage-induced anisotropy are included in the model. The directional growth of damage is related to the directional growth of material intrinsic permeability. Numerical simulations of damage induced by shock waves show good agreement with the experiments for various confinement levels of the specimens. © 2013 John Wiley & Sons, Ltd.
Mots clés
Anisotropic damage model
Concrete and rock fracture
Permeability Anisotropic damage model
Confining pressures
Damage induced anisotropy
Intrinsic permeability
Laboratory development
Low permeability rock
Pulsed arc electrohydraulic discharge
Rock fractures Engineering controlled terms: Anisotropy
Concretes
Dynamic loads
Hydraulic fracturing
Mechanical permeability
Rocks
Shock waves Engineering main heading: Cracks GEOBASE Subject Index: anisotropy
computer simulation
concrete
confining pressure
damage mechanics
dynamic response
hydraulic fracture
loading
microcrack
mortar
numerical model
permeability
rock mechanics
shock wave
static response