Article
Engineering, Geological
Julia Leuthold, Eleni Gerolymatou, Theodoros Triantafyllidis
Summary: This paper evaluates the performance of a constitutive model for the hydro-mechanical behavior of soft rock and calibrates it using experimental results. An analytical model based on the Kozeny-Carman equation is proposed to describe the effect of compaction bands on the permeability of soft rocks and is discussed.
ROCK MECHANICS AND ROCK ENGINEERING
(2021)
Article
Engineering, Geological
Julia Leuthold, Eleni Gerolymatou, Maximiliano R. Vergara, Theodoros Triantafyllidis
Summary: Experimental studies on soft porous rocks showed that discrete compaction bands form under high confining stresses, while shear bands form under low confining stresses. Axial permeability decreases with increasing axial strain, with a maximum permeability decrease of three orders of magnitude at 40% axial strain.
ROCK MECHANICS AND ROCK ENGINEERING
(2021)
Article
Materials Science, Multidisciplinary
Fanbao Meng, Lingcao Huang, Patrick Baud, Teng-fong Wong
Summary: By analyzing the data set obtained through Digital Volume Correlation (DVC) from the in situ CT imaging during shear-enhanced compaction in Leitha limestone, we confirmed the occurrence of two stages of inelastic compaction: macro-pore collapse and sequential growth of compaction bands. DVC analysis provided more constraints on the geometric attributes of the bands and the spatio-temporal development of strain.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2023)
Article
Materials Science, Multidisciplinary
Yunteng Wang, Ronaldo I. Borja, Wei Wu
Summary: We propose a new phase-field formulation to model the formation and propagation of compaction bands in high-porosity rocks. This formulation takes into account the effects of inertia on the rate of development of compaction bands, as well as degradation mechanisms in tension, compression, and shear. We also present a robust numerical technique to handle the spatiotemporal formation and evolution of the compaction band, and validate the model using a benchmark problem involving a notched cylindrical specimen of Bentheim sandstone.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2023)
Article
Computer Science, Interdisciplinary Applications
Quanshui Huang, Xing Zhou, Biao Liu
Summary: Combining experimental and numerical study, this paper investigates the effect of realistic shape on grain crushing behavior. The results show significant differences in force-displacement curves, fragmentation modes, and Weibull survival probabilities between rounded and angular rock grains. The discrete element method (DEM) simulation reproduces the experimental results and reveals that realistic irregular shape enhances the variability of grain crushing strength. The role of particle microstructure in weakening or strengthening the effect of grain shape is also confirmed. These findings provide deeper insights into the effect of morphological features on grain crushing behaviors.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Engineering, Geological
Chara Prassa, Sotiris Alevizos, Manolis Veveakis, Yannis F. Dafalias
Summary: Compaction bands are localized failure patterns that appear in highly porous rock material under the effect of relatively high confining pressure. The study focused on the mechanism leading to the onset of compaction bands using a viscoplasticity model, showing that isotropic hardening promotes compaction localization while rotational hardening has a slightly negative effect on the onset of compaction localization.
INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS
(2022)
Article
Engineering, Geological
Sabrina C. Y. Ip, Ronaldo Borja
Summary: In this study, a phase-field approach is proposed to capture the formation and propagation of compaction bands. By interpreting fracture energy as driven by grain crushing and introducing a new decomposition of the free energy function, the model accurately predicts different types of compaction bands. Numerical simulations also reveal the role of confining pressure, plasticity, and critical breakage energy on the styles of the predicted compaction bands.
INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS
(2022)
Article
Engineering, Geological
Antoine B. Jacquey, Klaus Regenauer-Lieb, Mauro Cacace
Summary: Observations show that the mechanical behavior of porous rocks under external loading is influenced by factors such as confining pressure, fluid pressure, and deformation rate. The multiscale and poromechanical behavior of geomaterials is significant for various applications including civil engineering, reservoir engineering, geological, and geodynamic studies. The use of thermodynamic-consistent approaches is important in constructing constitutive laws that cover a wide range of time scales.
ROCK MECHANICS AND ROCK ENGINEERING
(2021)
Article
Engineering, Geological
Antoine B. Jacquey, Klaus Regenauer-Lieb
Summary: The lack of consensus in applying equilibrium thermodynamics in geomechanics and geological applications is due to the non-equilibrium nature of the problems, such as rate-dependence and poromechanical complexity, which prevent the local equilibrium assumption. The extension of the theory of thermomechanics offers a thermodynamic-consistent modeling approach for civil engineering, geological, and geodynamic problems.
ROCK MECHANICS AND ROCK ENGINEERING
(2021)
Article
Materials Science, Multidisciplinary
Sabrina C. Y. Ip, Ronaldo I. Borja
Summary: This study proposes a coupled hydromechanical,
phase-field approach for studying the formation and evolution of compaction bands in heterogeneous porous media. Numerical simulations demonstrate that the model is able to capture the phenomena of compaction band formation, porosity reduction, and permeability evolution. The results provide insights into the factors affecting the formation styles of compaction bands.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2023)
Article
Crystallography
Lei Cai, Mohamed Jebahi, Farid Abed-Meraim
Summary: This paper investigates the abilities and limitations of strain gradient crystal plasticity (SGCP) theories in capturing different kinds of localization modes in single crystals. By simulating several single crystal localization problems with different slip system configurations, the study demonstrates the good capabilities of the applied model in regularizing various types of localization bands.
Article
Mathematics, Interdisciplinary Applications
Zhaocheng Li, Baowen Liu, Dongdong Han, Yichang Xie, Yongli Zhao
Summary: The relationship between microcracks of a single particle and crushing strength was investigated through virtual experiments. CT-scanning technology was used to obtain the three-dimensional profile of a single particle. The particle bonding model was employed to construct virtual particles based on the three-dimensional contour, and virtual crushing experiments were conducted using the discrete element method. The influence of microcracks on the Weibull distribution of crushing strength was considered in terms of quantity, location, and direction.
COMPUTATIONAL PARTICLE MECHANICS
(2023)
Article
Nanoscience & Nanotechnology
Qingge Xie, Zhi Li, Hongchua Ma, Shuang Liu, Xingwei Liu, Jinxu Liu, Jurij J. Sidor
Summary: Studying the hardening variation inside and outside of Geometrically Necessary Bands (GNBs) helps understand their formation to accommodate deformation heterogeneity. The slip activities induced by prismatic and basal slips were verified using a crystal plasticity model and electron backscatter diffraction microstructures. Abundance of GNBs was observed, and the hardening/softening effect in GNBs is compensated by softening/hardening behavior near GNBs. The high and low GNDD regions share the same shape and peak positions in frequency-strength profiles, confirming the correlation between high GNDDs and low GNDDs.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Multidisciplinary Sciences
Shuo Zhou, Antoinette Tordesillas, Mehdi Pouragha, James Bailey, Howard Bondell
Summary: The study introduces a new metric called s-LID to identify and quantify hierarchies of kinematic patterns in heterogeneous media. Results show that the evolution of failure in deforming granular materials is governed by a complex symbiosis among different coexisting structures, with particle rotation playing an essential role in the transition to the shearband-dominated regime.
SCIENTIFIC REPORTS
(2021)
Article
Engineering, Geological
Tyler J. J. Oathes, Ross W. W. Boulanger
Summary: A numerical study was conducted to investigate the effects of viscoplasticity on localization processes in sensitive clays and plastic silts. The study employed a viscoplastic constitutive model to simulate laboratory specimens under monotonic, undrained, direct simple shear loading. Parametric analyses were performed to assess the influence of soil sensitivity, strain-softening rate, strain rate dependency, specimen size, mesh discretization, and loading rate. The results showed that the strain rate dependency of the soil's shearing resistance relative to its rate of postpeak strain softening primarily determines the global strain at which localization occurs. A regression model relating the onset of localization to the soil's strain rate dependency and postpeak strain-softening rate was proposed. The findings indicate that the inclusion of reasonable levels of viscoplasticity increases the strain development before localization in clays and plastic silts.
JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING
(2023)
Article
Engineering, Civil
Filippo Masi, Ioannis Stefanou, Victor Maffi-Berthier, Paolo Vannucci
ENGINEERING STRUCTURES
(2020)
Article
Engineering, Geological
Sergio Samat, Laurant Brochard, Ioannis Stefanou
INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS
(2020)
Article
Geosciences, Multidisciplinary
G. Tzortzopoulos, P. Braun, I. Stefanou
Summary: Earthquakes occur when stored elastic energy in the earth's crust is suddenly released due to sliding over a fault, and fluid injections can reactivate and trigger earthquakes. By wetting a porous paper model, the process of wetting-induced earthquakes can be quantified, gradually releasing stored energy. Injection strategies initiated at high stress levels may lead to large earthquakes, while starting at low stress levels could reduce earthquake magnitude.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geochemistry & Geophysics
Youssouf Abdallah, Jean Sulem, Michel Bornert, Siavash Ghabezloo, Ioannis Stefanou
Summary: The study investigates the formation mechanisms of compaction bands using Digital Volume Correlation and X-Ray Computed Tomography images of Saint-Maximin limestone samples. A new analysis method is proposed to identify the type of observed localization bands. Results show that compaction bands are found at different confining pressures compared to shear bands, with porosity heterogeneity significantly affecting strain localization. Scanning Electron Microscopy observations reveal differences in grain crushing and cement cracking in high and low-porosity zones.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Materials Science, Multidisciplinary
Filippo Masi, Ioannis Stefanou, Paolo Vannucci, Victor Maffi-Berthier
Summary: TANNs is a physics-based neural network method for constitutive modeling, where thermodynamic principles are encoded into the network architecture using automatic differentiation. Its advantages include efficiency, robustness, accuracy in predictions, and maintaining thermodynamic consistency.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2021)
Article
Geochemistry & Geophysics
Philipp Braun, Georgios Tzortzopoulos, Ioannis Stefanou
Summary: Laboratory experiments using sand-based 3D-printed materials were conducted to investigate frictional properties, bulk mechanical parameters, and viscous behavior. A special focus was placed on the post-peak softening behavior, with a model designed to simulate earthquake-like instabilities and oscillating friction coefficients during slip. The study also examined the creation of a gouge-like layer due to granular debonding during sliding, showing potential for new surrogate experiments in fault mechanics and geomechanics.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Construction & Building Technology
Cyril Douthe, Ioannis Stefanou
Summary: The study focuses on the long-term behavior of composites subjected to permanent bending, confirming the recommendations for using composites in civil engineering and demonstrating the safety and long-term robustness of double curvature structures.
CONSTRUCTION AND BUILDING MATERIALS
(2021)
Article
Engineering, Multidisciplinary
Alexandros Stathas, Ioannis Stefanou
Summary: Strain softening is responsible for mesh dependence in numerical analyses in various fields. Regularizing strain localization is crucial for engineering product and system design. Revisiting a model involving elastoviscoplastic properties reveals possible strain localization on a mathematical plane under certain conditions.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
Article
Engineering, Mechanical
Filippo Masi, Ioannis Stefanou, Victor Maffi-Berthier
Summary: Investigating masonry structures' response to explosions requires experimental tests for validation, especially in full-scale blast experiments. New scaling laws for dynamic response and failure modes under blast loads are proposed for further study and validation through numerical simulations and examples.
JOURNAL OF ENGINEERING MECHANICS
(2021)
Article
Geochemistry & Geophysics
Ioannis Stefanou, Georgios Tzortzopoulos
Summary: This study proposes a control theory for preventing instabilities and inducing controlled, slow-slip in frictionally unstable systems. By exploiting the dependence of friction on pressure, the dynamics of the system can be altered to stabilize chaos, guarantee slow frictional dissipation, and tune the system towards lower energy equilibria. The control approach is robust and does not require precise knowledge of the system's frictional or elastic behavior.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Engineering, Multidisciplinary
Filippo Masi, Ioannis Stefanou
Summary: The mechanical behavior of inelastic materials with microstructure is complex and difficult to predict accurately using traditional methods. This paper proposes a Thermodynamics-based Artificial Neural Networks (TANN) approach for modeling such materials. Several examples demonstrate the high accuracy and physical consistency of TANN in predicting macroscopic and microscopic mechanical behavior.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
Article
Geochemistry & Geophysics
E. Papachristos, I. Stefanou, J. Sulem
Summary: This study uses discrete elements simulations to investigate the frictional response of fault gouges, considering their previous ultra-cataclastic flow and long-time consolidation loading. The impact of particle characteristics (such as size, polydispersity) and shearing velocities on the gouge's response under seismogenic zone conditions is explored. Monte-Carlo analyses show that local stick-slip events disappear when a large number of numerical samples are averaged. The apparent material frictional response is largely unaffected by the spatial randomness of particles' position and particle size distribution, but is controlled by the mean particle size and the formation of shear bands.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Engineering, Mechanical
Alexandros Stathas, Ioannis Stefanou
Summary: Earthquake faults result from severe strain localization in rocks, which is controlled by the size of the microstructure and various Thermo-Hydro-Mechanical (THM) couplings. Our modeling using the Cosserat theory and considering large shear deformations during seismic slip justifies the rate and state friction law. We find the presence of traveling shear bands along the thickness of the fault, leading to oscillations in the fault's frictional response.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Materials Science, Multidisciplinary
Filippo Masi, Ioannis Stefanou
Summary: Data-driven and deep learning approaches have the potential to replace classical constitutive models for complex materials. However, current approaches suffer from issues such as the dependence on incremental formulations and poor generalization. This study proposes a new approach called eTANN, which decouples material representation from incremental formulation and utilizes continuous-time evolution equations. The proposed approach demonstrates excellent results in various applications and offers the possibility to describe both macroscopic and micromechanical behavior of complex materials.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2023)
Article
Automation & Control Systems
Diego Gutierrez-Oribio, Georgios Tzortzopoulos, Ioannis Stefanou, Franck Plestan
Summary: This article explores the possibility of using robust control theory to prevent earthquakes by injecting fluids into the Earth's crust. Two types of robust controllers are designed based on reduced-order nonlinear models to mitigate uncertainties and external disturbances. Both controllers are tested extensively through numerical simulations and laboratory experiments. This work opens new perspectives for applying robust nonlinear control theory to complex geosystems, earthquakes, and sustainable energy production.
IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY
(2023)
