Alette Kleven

• Kleven, Alette; Barras, Fabian & Galland, Olivier (2025). Tensile versus shear failure of the host rocks at the tip of a pressurized dyke. Fulltekst i vitenarkiv Vis sammendrag

  Sheet intrusions are the most fundamental magma pathways through the crust. Field observations suggest a variety of dyke propagation modes, ranging from tensile failure of the host rock in agreement with the Linear Elastic Fracture Mechanics (LEFM) theory, to shear failure of the host rock in agreement with the viscous indenter model. Under which conditions tensile versus shear failure occur at the propagating dyke tips is currently unknown. This is a key question as the LEFM and viscous indenter dyke propagation mechanisms may produce drastically distinct geophysical and geodetic signals. Here we present a Finite Element Model (FEM) that simulates the elastoplastic behavior of crustal rocks following a Drucker-Prager yield criterion. The host rock is deformed by the increasing pressure in an elliptical dyke until failure is reached at its tip. In our elastoplastic model, either tensile or shear failure occurs, depending on the host rock cohesion, the dyke dimension and depth. By exploring the parameter space, we built phase diagrams to map under which conditions tensile versus shear failure occur at dyke tips. Our results show that shear failure is favored when (1) the host rock cohesion is low, and/or (2) the dyke tip is deep and/or (3) the thickness-to-length aspect ratio of the dyke is high. Our study and phase diagram provide insights for the interpretation of geophysical and geodetic data collected at active volcanoes.

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