Finite element modeling of frictional contact and stress intensity factors in three-dimensional fractured media

Abstract:

Understanding the mechanical response of fractured media subjected to different mechanical loads is of vital importance and great interest to a variety of scientific and engineering fields. Both elastic and inelastic responses of fractured media to mechanical loads are significantly influenced by the presence of cracks. The size of cracks varies from micron-sized micro-cracks, to kilometre-scale rock faults. Pre-existing natural fractures in rock masses act as local mechanical weaknesses and flow pathways, and therefore control not only the deformation and strength behavior of the rock mass, but also its flow and transport properties.

In this seminar, a three-dimensional (3D) finite element formulation is introduced for accurately modeling the linear elastic deformation of fractured media under tensile and compressive loadings. The model includes several novel components: (i) the singular stress field near the crack front is modeled using quarter-point tetrahedral finite elements, (ii) the frictional contact between the crack faces is modeled using a gap-based augmented Lagrangian method, and (iii) accurate stress intensity factors of 3D cracks under extension and compression are computed using a disk-shaped domain integral. The results of contact and stress intensity factors are validated for several cases involving single and multiple cracks. Two geomechanical applications of this methodology are also discussed: (i) the hysteretic behavior of rock deformation due to frictional sliding along micro-cracks; and (ii) simulating 3D brittle crack growth under mixed-mode loading conditions.

This presentation is a summary of the work undertaken during my PhD project at Imperial College, carried out from 2012-2015 under the supervision of Dr. Adriana Paluszny and Prof. Robert Zimmerman.

Biography:

2003-2007: BSc, Mechanical Engineering, Isfahan University of Technology, Iran.

2007-2010: MSc, Mechanical Engineering, Iran University of Science and Technology, Iran.

2012-Date: PhD Candidate, Computational Geomechanics, Imperial College London, UK.