Non-local criteria for the borehole problem: Gradient Elasticity versus Finite Fracture Mechanics

Abstract Two nonlocal approaches are applied to the borehole geometry, herein simply modelled as a circular hole in an infinite elastic medium, subjected remote biaxial loading and/or internal pressure. The former approach lies within framework of Gradient Elasticity (GE). Its characteristic is material behaviour and local failure criterion, hence related stress concentration factor. latter Finite Fracture Mechanics (FFM), well-consolidated model brittle fracture. non-local fracture since crack onset occurs when two (stress energy) conditions front point simultaneously met. Although have completely different origin, they present some similarities, both involving length. Notably, lead almost identical critical load predictions far lengths properly related. A comparison with experimental data available literature also provided.