Fracture patterns in nonplane strain boudinage—insights from 3‐D discrete element models

Abstract

We use 3‐D Discrete Element Method simulations to model the evolution of boudin structures in a layered material under nonplane strain conditions. As the models are shortened perpendicular to the layer orientation, they are extended at different rates in the two layer‐parallel directions. The particular emphasis of the study is on the orientation of fractures between the boudin blocks. The results show that the fracture orientation distribution is closely connected to the ratio of the two layer‐parallel extension rates. The anisotropy of the fracture orientation distribution increases systematically from no anisotropy at isotropic layer‐parallel extension to a highly anisotropic distribution in case of uniaxial extension. We also observe an evolution of the anisotropy of fracture orientation distribution with increasing deformation in each individual model from a high‐initial anisotropy towards a value characteristic for the ratio of the layer‐parallel extension rates. The observations about the relation between the strain ratios and the fracture patterns do have the potential to serve as the basis for a new method to analyze strains in naturally boudinaged rocks.