Introduction to FEM/DEM technology and its application to model of Excavation Damaged Zone (EDZ) in anisotropic rock formation
Event details
| Date | 28.02.2013 |
| Hour | 12:15 › 13:15 |
| Speaker | Prof. Giovanni Grasselli |
| Location |
GC C330
|
| Category | Conferences - Seminars |
The combined finite/discrete element method (FEM/DEM) is a numerical technology that combines DEM algorithms, which capture the interaction and fracturing of different solids, with FEM principles that describe the elastic deformation of discrete bodies. Damage and failure of rock material is simulated in FEM/DEM by explicitly modelling crack initiation and propagation using principles of non-linear elastic fracture mechanics.
The purpose of this presentation is three-fold:
(i) to present the basic concepts of the hybrid finite-discrete element method (FEM/DEM);
(ii) to illustrate the new approaches that have been introduced into the FEM/DEM technology to model layered materials; and
(iii) to demonstrate the effectiveness of this new modelling approach in simulating the development of fractures around a tunnel excavated in layered rock formation.
In this context, the term excavation damaged zone (EDZ) refers to the volume of rock close to an underground opening that has experienced irreversible deformation due to the excavation and where new fractures have occurred. With respect to the original host rock, EDZ is characterized by a reduced mechanical strength and a significant increase in its flow and transport properties. Thus, for both rock support design and permeability studies it is important to estimate the extent and the geometry of the EDZ, which is also influenced by the type of material and its internal microstructure. In particular, it has been observed that the EDZ in layered rock formations is heavily affected by the anisotropic mechanical response of the material due to the presence of bedding planes and it cannot be properly modeled using a continuum approach.
This presentation will also present how a transversely isotropic elastic constitutive law was implemented into FEM/DEM to account for the anisotropy in global elastic modulus, while procedures to incorporate a distribution of preferentially oriented defects and the presence of bedding planes were devised to capture the anisotropic strength of metamorphic and sedimentary rocks.
Finally, an example of model calibration and simulated fracture patterns around circular excavations will be then discussed in the context of the theory of brittle rock failure and analyzed with reference to the EDZ formation mechanisms observed at the Mont Terri Underground Research Laboratory, Switzerland.
Bio sketch:
Dr. Giovanni Grasselli is a full faculty member at the University of Toronto, Canada. He holds an undergraduate degree in Civil Engineering (1995) from the University of Parma, Italy, and a PhD in Rock Mechanics (2001) from the Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland. His doctoral thesis ‘‘Shear Strength of Rock Joints based on Quantified Surface Description’’ was awarded with the 2004 ISRM Rocha Medal. Previously to join University of Toronto, he has been research fellow at the Imperial College London (UK), and at the Sandia National Laboratories (USA). He has served as associate director of the Geomechanis Research Centre at Mirarco (Canada) in 2005 and of the Lassonde Institute for Mining at the University of Toronto in 2007-2009.
The purpose of this presentation is three-fold:
(i) to present the basic concepts of the hybrid finite-discrete element method (FEM/DEM);
(ii) to illustrate the new approaches that have been introduced into the FEM/DEM technology to model layered materials; and
(iii) to demonstrate the effectiveness of this new modelling approach in simulating the development of fractures around a tunnel excavated in layered rock formation.
In this context, the term excavation damaged zone (EDZ) refers to the volume of rock close to an underground opening that has experienced irreversible deformation due to the excavation and where new fractures have occurred. With respect to the original host rock, EDZ is characterized by a reduced mechanical strength and a significant increase in its flow and transport properties. Thus, for both rock support design and permeability studies it is important to estimate the extent and the geometry of the EDZ, which is also influenced by the type of material and its internal microstructure. In particular, it has been observed that the EDZ in layered rock formations is heavily affected by the anisotropic mechanical response of the material due to the presence of bedding planes and it cannot be properly modeled using a continuum approach.
This presentation will also present how a transversely isotropic elastic constitutive law was implemented into FEM/DEM to account for the anisotropy in global elastic modulus, while procedures to incorporate a distribution of preferentially oriented defects and the presence of bedding planes were devised to capture the anisotropic strength of metamorphic and sedimentary rocks.
Finally, an example of model calibration and simulated fracture patterns around circular excavations will be then discussed in the context of the theory of brittle rock failure and analyzed with reference to the EDZ formation mechanisms observed at the Mont Terri Underground Research Laboratory, Switzerland.
Bio sketch:
Dr. Giovanni Grasselli is a full faculty member at the University of Toronto, Canada. He holds an undergraduate degree in Civil Engineering (1995) from the University of Parma, Italy, and a PhD in Rock Mechanics (2001) from the Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland. His doctoral thesis ‘‘Shear Strength of Rock Joints based on Quantified Surface Description’’ was awarded with the 2004 ISRM Rocha Medal. Previously to join University of Toronto, he has been research fellow at the Imperial College London (UK), and at the Sandia National Laboratories (USA). He has served as associate director of the Geomechanis Research Centre at Mirarco (Canada) in 2005 and of the Lassonde Institute for Mining at the University of Toronto in 2007-2009.
Practical information
- General public
- Free
Organizer
- Prof. Nikolas Geroliminis and Prof. Katrin Beyer
Contact
- Prof. Jian Zhao