Fig. 6: Summary of key results.
From: Deformation evolves from shear to extensile in rocks due to energy optimization
a Transition from shear- to extensile-dominated deformation observed in X-ray tomography triaxial compression experiments (a) and in numerical models that propagate fractures using energy optimization (b–e). a Increasing differential stress produces a larger volume of fractures oriented within the ranges expected for extensile deformation than shear deformation. b, c The most efficient numerical fracture geometries in the first stage of fracture growth do not include quasi-vertical fractures, but instead fractures oriented at 30–35° from the maximum compression direction, similar to the experiments, and consistent with the Mohr-Coulomb failure criterion for the applied internal friction coefficient. d The most efficient numerical fracture geometries in the second stage of fracture growth do not include an aligned array of fractures, but instead a distributed grid of fractures, indicating that fracture networks may delocalize. e The fracture network that develops from these distributed fractures form networks with an increasing proportion of extensile fractures, consistent with the experimental observations.
