The influence of loading conditions on fracture initiation, propagation, and interaction in rocks with veins: Results from a comparative Discrete Element Method study

Abstract

We present the results of a comparative study of loading conditions on the interactions between extension fractures and veins. We model the fracture behavior of brittle discrete element materials each containing a tabular vein body of variable orientation and strength in two different loading conditions. The first is uniaxial tension, applied with servo‐controlled sidewalls. The second is a boudinage boundary condition in which a tensile triaxial stress state is induced in the brittle model volume by quasi‐viscous extensional deformation in the adjacent layers. Most of the fracture‐ vein interactions observed in uniaxial tension also exists in boudinage boundary conditions. However, the importance of each interaction mechanism for a given configuration of relative strength and misorientation of the vein may differ according to the loading mechanism. Nucleation and internal deflection is under both boundary conditions the dominating fracture‐vein interaction style in weak veins. In uniaxial tension models, strong veins tend to alter the fracture path by external deflection, while under boudinage loading these veins are more likely overcome by the fracture step over mechanism. Dynamic bifurcation of fractures was observed in uniaxial tension models but never for boudinage boundary conditions. This is because the acceleration of fracture tips in these conditions is suppressed by interaction with distributed fractures as well as viscous damping by the neighboring layers.

Forced folding and fracturing induced by differential compaction during post-depositional inflation of sandbodies: Insights from numerical modelling

“…This method has been thereby widely used for modelling structural deformations across a wide range of scales, especially for modelling development of detachment fold (Hardy and Finch, 2005;Vidal-Royo et al, 2011;Meng and Hodgetts, 2019), fault-bend fold (Benesh et al, 2007), fault-propagation fold (Finch et al, 2003(Finch et al, , 2004Cardozo et al, 2005;Hardy andFinch, 2006, 2007;Hughes et al, 2014;Meng and Hodgetts, 2019) and faults/fractures (e.g. Schöpfer et al, 2006Schöpfer et al, , 2007Schöpfer et al, , 2011Schöpfer et al, , 2016Schöpfer et al, , 2017Abe et al, 2011;Hardy, 2013;Spence and Finch, 2014;Virgo et al, 2013Virgo et al, , 2014Virgo et al, , 2016Finch and Gawthorpe, 2017). The extensive applications of discrete element modelling to structural geology research make it an ideal method for addressing questions related to the present study.…”

Influence of nodular structures on fracture development in fine-grained rocks: numerical simulations based on the discrete element method

“…The discrete element method has been extensively used for addressing problems in structural geology across a wide range of scales, such as the modelling of normal/ reverse faults (Saltzer, 1992;Strayer and Suppe, 2002;Yamada and Matsuoka, 2005;Abe et al, 2011;Smart et al, 2011;Hardy, 2011Hardy, , 2013Schöpfer et al, 2006Schöpfer et al, , 2007Schöpfer et al, , 2016Schöpfer et al, , 2017Finch and Gawthorpe, 2017), strikeslip fault (Liu and Konietzky, 2018), relay structures (Imber et al, 2004), fault gauge Mair, 2005, 2009;Morgan, 2006, 2007), detachment fold (Hardy and Finch, 2005;Vidal-Royo et al, 2011), fault-related fold (Finch et al, 2003(Finch et al, , 2004Cardozo et al, 2005;Finch, 2006, 2007;Benesh et al, 2007;Hughes et al, 2014), fold and thrust belt (Burbidge and Braun, 2002;Naylor et al, 2005;Hardy et al, 2009;Dean et al, 2013;Morgan, 2015;Morgan and Bangs, 2017), and salt tectonics (Pichel et al, 2017). In particular, the discrete element models can produce realistic fractures with a finite displacement due to the particle-based nature (Schöpfer et al, 2011;Virgo et al, 2013Virgo et al, , 2014Virgo et al, , 2016Spence and Finch, 2014), and provide a promising tool for fracture modelling and prediction.…”

The joint sets on the Lilstock Benches, UK. Observations based on mapping a full resolution UAV-based image

“…The presence of such low angle X-intersections is intriguing, because if joints are unsealed fractures, even with very high anisotropy of the horizontal stress, crosscutting is not possible at such a low angle (Renshaw and Pollard, 1995): instead, the younger joints would abut on the older one without crossing over into the adjacent block. However, joints can cross older joints if sealing of the older joint partly restores the shear strength (Virgo et al, 2013(Virgo et al, , 2014(Virgo et al, , 2016Laubach et al, 2019). If joints are completely invisible to the stress field because they are sealed with vein material of exactly the same strength and elastic modulus, joints can cross without any deflection.…”