Impact of host-rock heterogeneities on failure mechanism around magmatic intrusions
Seminar by post-doc Alban Souche
Rock failure mechanism accommodating the emplacement of magmatic intrusions is controlled by the local stress regime within the host-rock. Most of the mechanical models addressing rock failure conditions simplify the stress calculation by assuming the homogeneity of the host-rock properties. In this study, we highlight the importance of local heterogeneities in controlling the failure mechanism ahead of a magmatic intrusion. The heterogeneities are introduced by mean of a self-affine stochastic perturbation with given wave-length and amplitude on the host-rock cohesion. In this talk, I will show numerical results of elastoplastic deformation around an overpressurised circular intrusion and document the development of plastic strain zones representative of either tensile or shear failure. From those idealised numerical results, I will argue that shear failure is the dominant deformation mechanism in the vicinity of a magmatic intrusion as soon as heterogeneities are introduced, even for relatively large dilatancy property of the host-rock (up to the limit of associative plasticity). I will further show that the localisation of the deformation is function of the characteristic wavelength of the heterogeneities. Any comments, discussions, critics, and inputs will be appreciated.