Workshop on Discrete Fracture ProcessModelling: Fundamentals of the hybridFinite-Discrete Element Method (FEMDEM)and its applications to engineeringcharacterization of fractured rock masses

Lecturers: Dr. Omid Mahabadi and Dr. Andrea Lisjak, Geomechanica Inc.

Introduction

The Hybrid Finite-Discrete Element method (FEMDEM) is an explicit numerical technology whichcombines continuum mechanics principles (FEM) with discrete element algorithms (DEM) to simulatemultiple interacting deformable bodies. In FEMDEM, the progressive failure of rock material iscaptured using cohesive elements inserted at the interface of each FEM element. With this technique,fracturing can be explicitly modelled solely based on the strength degradation of these dedicated“crack” elements. Inherent to this approach, material damage emerges as a natural outcome of thedeformation process without employing any additional macroscopic failure criterion. For this ability toclosely reproduce failure processes in brittle materials, FEMDEM is gaining increasing importance incivil, petroleum, mining, and geological engineering applications where fracture and fragmentationprocesses are key to fully understand the studied phenomenon and characterize the rock masses.

Learning goals

By attending this workshop students and professionals will learn the basic concepts and algorithmsembedded into FEMDEM and how to work with it. To achieve these learning objectives, the coursewill combine theoretical lectures to modelling sessions where the participants will be guided throughseveral numerical simulations. Attendees should leave the workshop with a basic understanding of theFEMDEM technology, its strengths, limitations, and how it can be applied to model complexengineering problems as those observed in continuous and discontinuous rock masses.

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Course program overview

After introducing the main modelling philosophy and algorithms behind FEMDEM, emphasis will beplaced on the role of fracture and fragmentation processes on the overall modelling results. Theworkshop will start with a general introduction to the FEMDEM technology and its application toengineering geology, rock mechanics, and geophysics problems. After a quick review of the basicalgorithms such as deform, contact detection, and contact interaction, the fracture model will bediscussed in more depth. More advanced features of the FEMDEM code, including dynamic boundaryconditions, excavation function, and the incorporation of Discrete Fracture Networks will beintroduced.

Next, the participants will learn how to build simple FEMDEM models in Y-Geo code*, assign correctinputs, and post-process the results. This way, each participant will have the opportunity to gain“hands-on” experience with the Y-Geo FEMDEM code.

Target Audience

This workshop is specifically designed for mining, geological and geotechnical engineers, graduate andpost-graduate students who wish to use FEMDEM in their work and research.

* Mahabadi OK, Lisjak A, Munjiza A and Grasselli G (2012). "Y-Geo: a new combined finite-discrete element numericalcode for geomechanical applications". International Journal of Geomechanics. 12(6), 676-688.

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