Andrea Lisjak

Andrea Lisjak
Geomechanica Inc.

PhD
Numerical modelling lead @ Geomechanica Inc.

About

54
Publications
42,751
Reads
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1,885
Citations
Introduction
Andrea Lisjak is the numerical modelling lead and a co-founder of Geomechanica Inc. in Toronto, Canada. Andrea leads the development of new simulation capabilities in Geomechanica's Irazu FDEM software and carries out consulting activities in several fields of geomechanics. His research interests focus on the numerical simulation of excavation-induced damage, rock support, rock seismicity, hydraulic fracturing, and THM processes in discontinuous rock masses.
Additional affiliations
April 2014 - March 2016
Geomechanica Inc.
Position
  • NSERC R&D Post-doctoral Fellow
September 2013 - present
Geomechanica Inc.
Position
  • Numerical Modelling Lead
May 2009 - August 2013
University of Toronto
Position
  • Research Assistant
Education
May 2009 - July 2013
University of Toronto
Field of study
  • Civil Engineering - Rock Mechanics
September 2006 - October 2008
University of Trieste
Field of study
  • Civil Engineering - Geoengineering and Georesources
September 2003 - July 2006
University of Trieste
Field of study
  • Civil Engineering

Publications

Publications (54)
Thesis
Full-text available
Clay shales are currently being assessed as possible host rock formations for the deep geological disposal of radioactive waste. However, one main concern is that the favourable long-term isolation properties of the intact rock mass could be negatively affected by the formation of an excavation damaged zone (EDZ) around the underground openings. Th...
Article
Full-text available
The purpose of this paper is to present Y-Geo, a new numerical code for geomechanical applications based on the combined finite-discrete element method (FDEM). FDEM is an innovative numerical technique that combines the advantages of continuum-based modeling approaches and discrete element methods to overcome the inability of these methods to captu...
Article
Stress waves, known as acoustic emissions (AEs), are released by localized inelastic deformation events during the progressive failure of brittle rocks. Although several numerical models have been developed to simulate the deformation and damage processes of rocks, such as non-linear stress-strain behaviour and localization of failure, only a limit...
Article
The Opalinus Clay (OPA) is an argillaceous rock formation selected to host a deep geologic repository for high-level nuclear waste in Switzerland. It has been shown that the excavation damaged zone (EDZ) in this formation is heavily affected by the anisotropic mechanical response of the material related to the presence of bedding planes. In this co...
Conference Paper
Full-text available
Enhanced geothermal systems (EGS) have been increasingly exploited as an alternative energy source. However, unexpected induced earthquakes bring uncertainty to their wider application. We employ a 2D thermal-hydro-mechanical (THM) coupled hybrid finite-discrete element method (FDEM) to investigate fault slip induced by injecting cold water into a...
Conference Paper
Full-text available
Coupled thermo-hydro-mechanical (THM) processes play a key role in a variety of geomechanical applications, including, enhanced oil recovery from unconventional reservoirs, deep geological disposal of heat-emitting nuclear waste, and enhanced geothermal systems (EGSs). The research work presented herein introduces a novel fully-coupled, THM formula...
Article
Full-text available
Rock bolt is a support system extensively utilized in Civil and Mining Engineering applications, especially for underground excavations projects. The main function of a rock bolt is to stabilize the rock mass around the opening of an excavation by fastening to further stable formations. Previous technical work developed pull-out testing in order to...
Preprint
Full-text available
Rock bolt is a support system extensively utilized in Civil and Mining Engineering applications, especially for underground excavations projects. The main function of a rock bolt is to stabilize the rock mass around the opening of an excavation by fastening to further stable formations. Previous technical work developed pull-out testing in order to...
Article
This paper presents a novel implementation of a hydro-mechanically coupled, finite-discrete element method (FDEM) optimized to exploit the computing parallelism of graphics processing units (GPUs). A co-processing approach is adopted with the control loop of FDEM executed serially on the CPU and compute-intensive tasks off-loaded to the GPU. A benc...
Chapter
Full-text available
The excavation damaged zone (EDZ) around the backfilled underground structures of a geological repository represents a release path for radionuclides, which needs to be addressed in the assessment of long-term safety. Additionally, the EDZ may form a highly efficient escape route for corrosion and degradation gases, thus limiting the gas overpressu...
Article
The excavation damaged zone (EDZ) around the backfilled underground structures of a geological repository represents a release path for radionuclides, which needs to be addressed in the assessment of long-term safety. Additionally, the EDZ may form a highly efficient escape route for corrosion and degradation gases, thus limiting the gas overpressu...
Article
This paper presents a new, fully-coupled, hydro-mechanical (HM) formulation for a finite-discrete element method computer code. In the newly-developed, hydraulic solver, fluid flow is assumed to occur through the same triangular mesh used for the mechanical calculations. The flow of a viscous, compressible fluid is explicitly solved based on a cubi...
Conference Paper
Full-text available
Standard laboratory testing of Georgian Bay shale and limestone was performed for an ongoing tunnel project in the Greater Toronto Area (GTA). The laboratory results were used as calibration targets to determine input parameters for numerical simulations using the Irazu simulation package based on the hybrid finite-discrete element method (FDEM). U...
Article
Full-text available
The excavation damaged zone (EDZ) around the backfilled tunnels of a geological repository represents a possible release path for radionuclides, corrosion and degradation gases that needs to be adequately addressed by safety assessment (SA) modelling tools. The hydrome-chanical phenomena associated with the creation and temporal evolution of the ED...
Conference Paper
Full-text available
This paper presents the development, verification and application of a new, fully-coupled, hydro-mechanical (HM) formulation for a finite-discrete element method (FDEM) software package called Irazu. FDEM is a general-purpose numerical approach which combines continuum mechanics principles with discrete element algorithms to simulate the mechanical...
Article
Full-text available
The study of acoustic emissions (AEs) is of paramount importance to understand rock deformation processes. AE recorded during laboratory experiments mimics, in a controlled geometry and environment, natural and induced seismicity. However, these experiments are destructive, time consuming and require a significant amount of resources. Lately, signi...
Conference Paper
Full-text available
This study aims at strengthening the understanding of the mechanical sealing process of the excavation damaged zone (EDZ) in Opalinus Clay, an indurated claystone currently being assessed as the host rock for a deep geological repository in Switzerland. To achieve this goal, hybrid finite-discrete element method (FDEM) simulations are applied to th...
Article
Full-text available
The analysis and prediction of the rock mass disturbance around underground excavations are critical components of the performance and safety assessment of deep geological repositories for nuclear waste. In the short term, an excavation damaged zone (EDZ) tends to develop due to the redistribution of stresses around the underground openings. The ED...
Conference Paper
Full-text available
This work demonstrates the potential of using the hybrid finite-discrete element method (FDEM) to model thermal and mechanical coupling mechanisms around a wellbore in shale formations. The simulated thermal and mechanical stresses were first validated in separate models by comparing them to closed-form solutions. Then, the stability of a borehole...
Conference Paper
Full-text available
Fluid-pressure-driven (or hydraulic) fracturing of rocks is used in several applications including stimulation of unconventional reservoirs, permeability enhancement of geothermal systems, and rock mass pre-conditioning in deep mining. In recent years, there has been a fast growing interest in the development and use of dvanced numerical methods to...
Conference Paper
Full-text available
In recent years, analyses based on the hybrid finite-discrete element method (FDEM) have been shown to provide a realistic representation of rock deformation and fracturing processes at laboratory and engineering scales. However, the ability to model linear rock reinforcement elements within FDEM has been largely limited. Through a collaborative re...
Conference Paper
Full-text available
Numerical simulations are widely adopted in the design of several types of rock structures, including tunnels, caverns, rock cuts, and open pit and underground mines. In recent years, analyses based on the hybrid finite-discrete element method (FDEM) have been shown to provide a realistic representation of rock mass deformation and fracturing proce...
Conference Paper
Full-text available
The goal of this paper is to present recent advances in the field of hydraulic fracturing modelling. In particular, a novel, fully 3D, hybrid finite-discrete element method (FDEM) approach was developed to numerically simulate fluid-pressure-driven fracturing. The effectiveness of the new approach is illustrated by simulating fracture nucleation an...
Conference Paper
Full-text available
Numerous research studies have shown that clay rock formations exhibit favourable characteristics for the deep geological disposal of radioactive waste. However, one main concern is that the favourable long-term isolation properties of the intact rock mass could be negatively affected by the formation of an excavation damaged zone (EDZ) around the...
Conference Paper
Full-text available
Between 2008 and 2012, several niches and tunnels were excavated within the Opalinus Clay of the Mont Terri underground research laboratory (URL) (see Fig. 1). During the excavation phases each newly-excavated section was geologically mapped in detail. The mapping focused on the orientation of the bedding and on the inventory of structural features...
Article
The mechanical response of a test tunnel in Opalinus Clay was characterized.•A strong directionality in the deformational behaviour was measured.•Numerical simulations were used to analyze the evolution of rock mass damage.•The importance of bedding plane slippage and extensional fracturing was shown.
Article
Full-text available
Over the past twenty years, there has been a growing interest in the development of numerical models that can realistically capture the progressive failure of rock masses. In particular, the investigation of damage development around underground excavations represents a key issue in several rock engineering applications, including tunnelling, minin...
Article
Full-text available
Hydraulic fracturing (HF) technique has been extensively used for the exploitation of unconventional oil and gas reservoirs. HF enhances the connectivity of less permeable oil and gas-bearing rock formations by fluid injection, which creates an interconnected fracture network and increases the hydrocarbon production. Meanwhile, microseismic (MS) mo...
Conference Paper
Full-text available
In this study, the hybrid Finite-Discrete Element Method (FEMDEM or FDEM) is used to investigate the influence of the rock fabric (e.g., joint sets and faults) on the mechanical response of rock masses in practical rock engineering problems. The first case study showcased focuses on the effects of pre-existing, cohesive discrete fracture networks (...
Chapter
Full-text available
Experimental evidence based on microseismic data clearly show that fluid-pressure-driven fractures interact with preexisting discontinuities, thus highlighting the strong influence of rock mass structures on hydraulic fracture development. However, these mechanisms are not well accounted for by analytical models and conventional continuum-based num...
Article
Pressure-driven fracturing, also known as hydraulic fracturing, is a process widely used for developing geothermal resources, extracting hydrocarbons from unconventional reservoirs such as tight sandstone and shale formations, as well as for preconditioning the rock-mass during deep mining operations. While the overall process of pressure-driven fr...
Article
Full-text available
The goal of this review paper is to provide a summary of selected discrete element and hybrid finite-discrete element modeling techniques that have emerged in the field of rock mechanics as simulation tools for fracturing processes in rocks and rock masses. The fundamental principles of each computer code are illustrated with particular emphasis on...
Chapter
Acoustic Emissions (AE) are stress waves released by localized inelastic deformation events during the progressive failure of brittle rocks. Although several numerical methods have been developed to simulate the deformation and damage processes of rocks, only a limited number have been capable of providing quantitative information regarding the ass...
Conference Paper
Full-text available
Opalinus Clay is an indurated over-consolidated argillaceous rock. The preferential orientation of clay platelets results in a strong anisotropy of its deformational and strength characteristics. The purpose of this study is two-fold: (i) to illustrate the new developments that have been introduced into the combined finite-discrete element method (...
Conference Paper
Full-text available
The present paper summarizes the work done on developing and validating the use of a hybrid Finite - Discrete Element (FEMDEM) code for modelling slope instability processes. The main advantages of the FEMDEM method are the ability (i) to analyze the slope failure without assuming any mode or mechanism a priori, and (ii) to explicitly model the pos...
Conference Paper
Full-text available
The accurate simulation of rock impact physics is a pivotal aspect of modeling rockfall phenomena. In the current study we present the im-plementation of a new dissipative contact interaction algorithm in the combined finite discrete-element method (FEM/DEM) Y-code. The numerical results show how the energy loss process during impact can be reprodu...

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Projects

Projects (3)
Project
Ultimate goal of this project is to provide critical rock mechanics input into the safety analyses of a deep geological repository for nuclear waste by carrying out physics-based, numerical simulations of the expected EDZ creation and evolution.
Project
This R&D project focuses on the development, implementation and validation of a 3D geomechanical simulation software based on the finite-discrete element method (FDEM). With this software, named Irazu, the parallel processing power of general-purpose graphics processing units (GPGPUs) is leveraged to gain significant computational performance boosts compared to existing sequential FDEM codes.