Pub Date : 2025-12-02DOI: 10.1016/j.ijrmms.2025.106364
Timo Saksala , Mahmood Jabareen
The phase field method captures tensile (mode I) fracturing of brittle materials but has serious challenges in uniaxial compression of heterogeneous materials like rock and concrete. In this paper, we mend this drawback by combining a phase field model for mode I fracture with a viscoplastic damage model to capture the shear banding in uniaxial compression of rock. In the present phase field formulation, the mode I fracture is driven by Rankine type of crack driving force, while the Mohr–Coulomb criterion is employed in the viscoplastic damage part of the model to capture the compressive/shear failure. As the model is designed for transient dynamic problems, strain rate sensitivity of rock is accommodated, here by a linear viscous term in both the phase field and viscoplastic damage parts. The viscoplastic part is cast in the consistency format. The phase field variable and the damage variable operate, respectively, on the positive and negative parts of the principal stress returned to the (Mohr–Coulomb) yield surface. The performance of the model is demonstrated in uniaxial tension and compression tests. Finally, the dynamic Brazilian disc test and punch-through shear tests are simulated for further validation. The model captures the strain rate sensitive direct and indirect tensile strength as well as the correct failure modes in these tests.
{"title":"A combined viscoplastic damage-phase field model for rock fracture under dynamic loading","authors":"Timo Saksala , Mahmood Jabareen","doi":"10.1016/j.ijrmms.2025.106364","DOIUrl":"10.1016/j.ijrmms.2025.106364","url":null,"abstract":"<div><div>The phase field method captures tensile (mode I) fracturing of brittle materials but has serious challenges in uniaxial compression of heterogeneous materials like rock and concrete. In this paper, we mend this drawback by combining a phase field model for mode I fracture with a viscoplastic damage model to capture the shear banding in uniaxial compression of rock. In the present phase field formulation, the mode I fracture is driven by Rankine type of crack driving force, while the Mohr–Coulomb criterion is employed in the viscoplastic damage part of the model to capture the compressive/shear failure. As the model is designed for transient dynamic problems, strain rate sensitivity of rock is accommodated, here by a linear viscous term in both the phase field and viscoplastic damage parts. The viscoplastic part is cast in the consistency format. The phase field variable and the damage variable operate, respectively, on the positive and negative parts of the principal stress returned to the (Mohr–Coulomb) yield surface. The performance of the model is demonstrated in uniaxial tension and compression tests. Finally, the dynamic Brazilian disc test and punch-through shear tests are simulated for further validation. The model captures the strain rate sensitive direct and indirect tensile strength as well as the correct failure modes in these tests.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106364"},"PeriodicalIF":7.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145657714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01DOI: 10.1016/j.ijrmms.2025.106359
Bruce Gee , Mengsu Hu , Michael Manga
Deep geologic repositories are a proposed solution to safely dispose of nuclear waste at the end its useful life. As the contents decay, heat is released into the surrounding subsurface, creating stress and driving heat and fluid transport. While it is not expected that a repository would be placed in an area with recent geologic activity, an induced seismic event could have significant detrimental effects on the integrity of the repository and safety of the public. Here we examine the frictional stability of both locked and aseismic creeping faults subjected to nuclear waste decay heating for both granite and argillite rock masses. The stress in the rock mass is evaluated numerically using a volumetric thermo-poro-elastic response and a deviatoric visco-elastic Burgers model. Thermally-dependent rate and state friction models are used to evaluate the frictional stability. The risk of induced seismicity is generally low, as only small perturbations to the factor of safety are induced by the heating. Both rock types have advantages, as the higher friction of granites creates greater factors of safety, while the creep of argillite reduces the thermal stresses. The in-situ conditions have the greatest effect on the risk of induced seismicity, and higher mean in-situ stresses and hydrostatic conditions lower the risks of inducing a seismic event. Faults undergoing aseismic creep are likely to experience an increase in their creep rate but appear unlikely to experience rupture. This analysis provides guidance in site selection to minimize the risk of induced seismicity when building a deep geologic repository.
{"title":"Evaluating the risk of induced seismicity in nuclear waste disposal","authors":"Bruce Gee , Mengsu Hu , Michael Manga","doi":"10.1016/j.ijrmms.2025.106359","DOIUrl":"10.1016/j.ijrmms.2025.106359","url":null,"abstract":"<div><div>Deep geologic repositories are a proposed solution to safely dispose of nuclear waste at the end its useful life. As the contents decay, heat is released into the surrounding subsurface, creating stress and driving heat and fluid transport. While it is not expected that a repository would be placed in an area with recent geologic activity, an induced seismic event could have significant detrimental effects on the integrity of the repository and safety of the public. Here we examine the frictional stability of both locked and aseismic creeping faults subjected to nuclear waste decay heating for both granite and argillite rock masses. The stress in the rock mass is evaluated numerically using a volumetric thermo-poro-elastic response and a deviatoric visco-elastic Burgers model. Thermally-dependent rate and state friction models are used to evaluate the frictional stability. The risk of induced seismicity is generally low, as only small perturbations to the factor of safety are induced by the heating. Both rock types have advantages, as the higher friction of granites creates greater factors of safety, while the creep of argillite reduces the thermal stresses. The in-situ conditions have the greatest effect on the risk of induced seismicity, and higher mean in-situ stresses and hydrostatic conditions lower the risks of inducing a seismic event. Faults undergoing aseismic creep are likely to experience an increase in their creep rate but appear unlikely to experience rupture. This analysis provides guidance in site selection to minimize the risk of induced seismicity when building a deep geologic repository.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106359"},"PeriodicalIF":7.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145651077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-29DOI: 10.1016/j.ijrmms.2025.106358
Shupeng Chai , Yuan Zou , Huanyu Wu , Mohammadreza Akbariforouz , Boyang Su , Giovanni Grasselli , Derek Elsworth , Yossef H. Hatzor , Qi Zhao
Laboratory shear tests are widely used to investigate the evolution of first and second-order frictional behavior and rupture nucleation on rock discontinuities. Average stress across the sample, instead of spatial stress distributions, is typically assumed in analysis. We provide a thorough numerical investigation of eight common laboratory shear test configurations, considering a linear velocity-weakening friction law on a planar sliding surface, to quantify the temporal and spatial nonuniformity of stress both before shear and during stick-slip cycles. Our results indicate that non-uniform stress distribution resulting from the test configuration exists in all laboratory shear tests, with stress concentration occurring at the edges of the shear plane, while the stress in the central portion of laboratory faults remains almost uniform. Stress heterogeneity is more pronounced in direct shear than in inclined and rotary shear configurations. During stick-slip cycles, the local shear stress significantly dropped as the rupture front propagated through, resulting in a more uniform stress distribution in the slip phase than in the stick phase. Stress concentration near the sample edge governs the rupture process and the resulting localization of damage. These findings highlight the importance of considering stress heterogeneity in laboratory investigations of damage evaluation on rock discontinuities. We suggest that test configuration-related stress heterogeneity should be distinguished from surface roughness-induced stress heterogeneity, and utilizing average stress may lead to misinterpretation of the rupture dynamics and damage patterns. Our results provide a guide on quantitative analysis of the shear behavior of rock discontinuities, considering stress heterogeneity in laboratory experiments.
{"title":"Influence of stress heterogeneity on shear behavior of rock discontinuities in laboratory experiments: New insights from numerical simulations","authors":"Shupeng Chai , Yuan Zou , Huanyu Wu , Mohammadreza Akbariforouz , Boyang Su , Giovanni Grasselli , Derek Elsworth , Yossef H. Hatzor , Qi Zhao","doi":"10.1016/j.ijrmms.2025.106358","DOIUrl":"10.1016/j.ijrmms.2025.106358","url":null,"abstract":"<div><div>Laboratory shear tests are widely used to investigate the evolution of first and second-order frictional behavior and rupture nucleation on rock discontinuities. Average stress across the sample, instead of spatial stress distributions, is typically assumed in analysis. We provide a thorough numerical investigation of eight common laboratory shear test configurations, considering a linear velocity-weakening friction law on a planar sliding surface, to quantify the temporal and spatial nonuniformity of stress both before shear and during stick-slip cycles. Our results indicate that non-uniform stress distribution resulting from the test configuration exists in all laboratory shear tests, with stress concentration occurring at the edges of the shear plane, while the stress in the central portion of laboratory faults remains almost uniform. Stress heterogeneity is more pronounced in direct shear than in inclined and rotary shear configurations. During stick-slip cycles, the local shear stress significantly dropped as the rupture front propagated through, resulting in a more uniform stress distribution in the slip phase than in the stick phase. Stress concentration near the sample edge governs the rupture process and the resulting localization of damage. These findings highlight the importance of considering stress heterogeneity in laboratory investigations of damage evaluation on rock discontinuities. We suggest that test configuration-related stress heterogeneity should be distinguished from surface roughness-induced stress heterogeneity, and utilizing average stress may lead to misinterpretation of the rupture dynamics and damage patterns. Our results provide a guide on quantitative analysis of the shear behavior of rock discontinuities, considering stress heterogeneity in laboratory experiments.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106358"},"PeriodicalIF":7.5,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145614045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-28DOI: 10.1016/j.ijrmms.2025.106361
Liangchen Zhao , Yixin Zhao , Xinze Li , Zhe Yang , Jihong Guo , Hua Bian
Rock fracture networks have a major impact on rock mass mechanical behavior, and their accurate characterization is important for various engineering disciplines. However, traditional manual topological analysis of these networks suffers from subjectivity and inefficiency, limiting its application, particularly for dynamic fracture processes. This study bridges this fundamental gap by introducing FisTopNet, a novel deep learning approach for direct and automated estimation of fracture network topology from image sequences. FisTopNet employs a multi-task learning architecture to perform semantic segmentation of fractures, fracture edge detection, and the extraction of the fracture topological graph, including its constituent nodes and connecting branches. Proposed FisTopNet utilizes the temporal information in the image sequences and takes into account the dynamic evolution of the fracture network thereby improving the accuracy of topology estimation. Furthermore, we constructed and meticulously annotated a unique dataset comprising image sequences from uniaxial compression tests on rock samples, featuring ground truth labels for semantic segmentation, edge detection, and evolving fracture network topology. Extensive experiments demonstrate FisTopNet's superior performance over established baseline methods. FisTopNet achieved an Intersection over Union (IoU) of 88.14 % and a Topological Similarity of 96.48 %. The IoU score, which quantifies the overlap between predicted and ground truth areas, represents a 12.74 % improvement over the leading competitor, SegFormer. Furthermore, Topological Similarity, an index evaluating the consistency of network connectivity, represents a 1.63 % improvement over the HRNet. In addition, ablation studies further validate the importance of the multi-task design and the temporal processing module. Moreover, our approach proficiently characterized the three-stage evolution of fracture topology and revealed strong correlations between dynamic topological parameters and macroscopic rock mechanical behavior, such as failure mode and peak stress. By leveraging FisTopNet, we propose a robust and automatic methodology for analyzing dynamic fracture processes, thereby facilitating a greater insight into rock failure mechanisms and enhancing engineering design and hazard assessment, with potential applications in geothermal energy extraction, CO2 geological sequestration, and stability analysis for underground mining and civil engineering projects.
{"title":"FisTopNet: A deep learning framework for automated estimation of evolving rock fracture network topology from image sequences","authors":"Liangchen Zhao , Yixin Zhao , Xinze Li , Zhe Yang , Jihong Guo , Hua Bian","doi":"10.1016/j.ijrmms.2025.106361","DOIUrl":"10.1016/j.ijrmms.2025.106361","url":null,"abstract":"<div><div>Rock fracture networks have a major impact on rock mass mechanical behavior, and their accurate characterization is important for various engineering disciplines. However, traditional manual topological analysis of these networks suffers from subjectivity and inefficiency, limiting its application, particularly for dynamic fracture processes. This study bridges this fundamental gap by introducing FisTopNet, a novel deep learning approach for direct and automated estimation of fracture network topology from image sequences. FisTopNet employs a multi-task learning architecture to perform semantic segmentation of fractures, fracture edge detection, and the extraction of the fracture topological graph, including its constituent nodes and connecting branches. Proposed FisTopNet utilizes the temporal information in the image sequences and takes into account the dynamic evolution of the fracture network thereby improving the accuracy of topology estimation. Furthermore, we constructed and meticulously annotated a unique dataset comprising image sequences from uniaxial compression tests on rock samples, featuring ground truth labels for semantic segmentation, edge detection, and evolving fracture network topology. Extensive experiments demonstrate FisTopNet's superior performance over established baseline methods. FisTopNet achieved an Intersection over Union (IoU) of 88.14 % and a Topological Similarity of 96.48 %. The IoU score, which quantifies the overlap between predicted and ground truth areas, represents a 12.74 % improvement over the leading competitor, SegFormer. Furthermore, Topological Similarity, an index evaluating the consistency of network connectivity, represents a 1.63 % improvement over the HRNet. In addition, ablation studies further validate the importance of the multi-task design and the temporal processing module. Moreover, our approach proficiently characterized the three-stage evolution of fracture topology and revealed strong correlations between dynamic topological parameters and macroscopic rock mechanical behavior, such as failure mode and peak stress. By leveraging FisTopNet, we propose a robust and automatic methodology for analyzing dynamic fracture processes, thereby facilitating a greater insight into rock failure mechanisms and enhancing engineering design and hazard assessment, with potential applications in geothermal energy extraction, CO<sub>2</sub> geological sequestration, and stability analysis for underground mining and civil engineering projects.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106361"},"PeriodicalIF":7.5,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145611883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1016/j.ijrmms.2025.106360
Jinjie Suo , Jinyang Fan , Deyi Jiang , Arezoo Rahimi , Daniel Nelias , Zhenyu Yang , Zongze Li
This study investigates the fatigue behavior of mudstone under cyclic triaxial loading conditions, with a focus on the effects of stress amplitude and confining pressure relevant to underground Compressed Air Energy Storage (CAES) operations. Graded triaxial intermittent fatigue tests (GTIF) were conducted to simulate the stress path of intermittent loading. The results show that the fatigue life of mudstone exhibits a non-monotonic dependence on confining pressure: the longest life occurs at 3 MPa, while higher confining pressures (6–12 MPa) cause a pronounced reduction followed by a plateau, indicating a threshold-like confinement effect. The elastic modulus decreases with increasing stress amplitude but, at a given stress ratio, increases with confining pressure, reflecting a trade-off between stress-induced damage and confinement-enhanced stiffness. Residual strain behavior was found to depend on the stress limit interval pattern: upper limit intervals led to reduced residual strain post-rest, whereas lower limit intervals caused strain reversal due to internal stress relaxation. These trends reveal that the loading history significantly influences deformation recovery and potential damage evolution. The damping ratio decreased with increasing confining pressure but increased with stress amplitude, implying that while confining pressure suppresses internal defect activity, higher stress promotes energy dissipation through microcracking. Dissipated energy showed distinct patterns under different loading modes: it increased with stress ratio but decreased with cycle number, highlighting the fatigue softening effect. Interestingly, confining pressure enhanced energy dissipation in upper-limit loading but reduced it under lower-limit conditions. Overall, these results clarify how confining pressure, stress amplitude, and loading intervals jointly govern fatigue life, residual strain, and energy dissipation in mudstone interlayers, and identify measurable damage indicators that can support safer mechanical design and long-term performance assessment of CAES in layered geological formations.
{"title":"Experimental study on triaxial fatigue properties of mudstone interlayers in CAES under synergistic effects of stress amplitude and time interval","authors":"Jinjie Suo , Jinyang Fan , Deyi Jiang , Arezoo Rahimi , Daniel Nelias , Zhenyu Yang , Zongze Li","doi":"10.1016/j.ijrmms.2025.106360","DOIUrl":"10.1016/j.ijrmms.2025.106360","url":null,"abstract":"<div><div>This study investigates the fatigue behavior of mudstone under cyclic triaxial loading conditions, with a focus on the effects of stress amplitude and confining pressure relevant to underground Compressed Air Energy Storage (CAES) operations. Graded triaxial intermittent fatigue tests (GTIF) were conducted to simulate the stress path of intermittent loading. The results show that the fatigue life of mudstone exhibits a non-monotonic dependence on confining pressure: the longest life occurs at 3 MPa, while higher confining pressures (6–12 MPa) cause a pronounced reduction followed by a plateau, indicating a threshold-like confinement effect. The elastic modulus decreases with increasing stress amplitude but, at a given stress ratio, increases with confining pressure, reflecting a trade-off between stress-induced damage and confinement-enhanced stiffness. Residual strain behavior was found to depend on the stress limit interval pattern: upper limit intervals led to reduced residual strain post-rest, whereas lower limit intervals caused strain reversal due to internal stress relaxation. These trends reveal that the loading history significantly influences deformation recovery and potential damage evolution. The damping ratio decreased with increasing confining pressure but increased with stress amplitude, implying that while confining pressure suppresses internal defect activity, higher stress promotes energy dissipation through microcracking. Dissipated energy showed distinct patterns under different loading modes: it increased with stress ratio but decreased with cycle number, highlighting the fatigue softening effect. Interestingly, confining pressure enhanced energy dissipation in upper-limit loading but reduced it under lower-limit conditions. Overall, these results clarify how confining pressure, stress amplitude, and loading intervals jointly govern fatigue life, residual strain, and energy dissipation in mudstone interlayers, and identify measurable damage indicators that can support safer mechanical design and long-term performance assessment of CAES in layered geological formations.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106360"},"PeriodicalIF":7.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1016/j.ijrmms.2025.106355
Changdi He , Brijes Mishra , David Oskar Potyondy
Mineralogical features, including mineral spatial distribution, shape, and orientation, are important in determining the mechanical behaviors of granite. This effect was investigated by using the X-ray micro-computed tomography (micro-CT) scan on granite specimens (10 mm diameter and 15 mm height) before and after uniaxial compressive strength (UCS) testing. The X-ray micro-CT scan generated thousands of CT images, which were processed using advanced digital image processing (DIP) techniques. Specifically, the Residual Network–Visual Geometry Group16–UNet (Res–VGG16–UNet) model and the circular threshold segmentation technique were applied to identify and map minerals within the CT images. The coordinate information extracted from these mapped minerals was then used to create 3D Subspring Network Breakable Voronoi (SNBV) microstructural models that incorporate the mineral characteristics of tested granite specimens. The models consist of a mesh (3D Voronoi tessellation) of rigid, breakable, Voronoi blocks. The extracted coordinate information, forming a large dataset, was managed by the -Dimensional Tree (KD-Tree) algorithm to facilitate mineral type assignment in SNBV models. The models were calibrated by comparing their results with the experimental data obtained from UCS tests. This study further explored the variations in biotite grain spatial distribution, shape, and orientation within a calibrated SNBV model, and examined their impact on the UCS and fracture behaviors of granite, based on a set of simplified microproperties. The results illustrate that as the SNBV model resolution (defined by the number of rigid blocks contained in models with identical physical dimensions) increases, mechanical properties, including UCS and crack initiation and damage strains and stresses, reach constant values. Additionally, the spatial distribution, shape, and orientation of biotite grain affect the UCS of granite, while their effect on the failure strain is minimal. The aspect ratio of biotite grains affects UCS, with -axis elongation (aligned with compression) yielding higher UCS than -axis elongation (perpendicular to compression).
{"title":"Impact of mineralogical features on the mechanical behaviors of granite: A study using physically informed 3D microstructural model","authors":"Changdi He , Brijes Mishra , David Oskar Potyondy","doi":"10.1016/j.ijrmms.2025.106355","DOIUrl":"10.1016/j.ijrmms.2025.106355","url":null,"abstract":"<div><div>Mineralogical features, including mineral spatial distribution, shape, and orientation, are important in determining the mechanical behaviors of granite. This effect was investigated by using the X-ray micro-computed tomography (micro-CT) scan on granite specimens (10 mm diameter and 15 mm height) before and after uniaxial compressive strength (UCS) testing. The X-ray micro-CT scan generated thousands of CT images, which were processed using advanced digital image processing (DIP) techniques. Specifically, the Residual Network–Visual Geometry Group16–UNet (Res–VGG16–UNet) model and the circular threshold segmentation technique were applied to identify and map minerals within the CT images. The coordinate information extracted from these mapped minerals was then used to create 3D Subspring Network Breakable Voronoi (SNBV) microstructural models that incorporate the mineral characteristics of tested granite specimens. The models consist of a mesh (3D Voronoi tessellation) of rigid, breakable, Voronoi blocks. The extracted coordinate information, forming a large dataset, was managed by the <span><math><mi>k</mi></math></span>-Dimensional Tree (KD-Tree) algorithm to facilitate mineral type assignment in SNBV models. The models were calibrated by comparing their results with the experimental data obtained from UCS tests. This study further explored the variations in biotite grain spatial distribution, shape, and orientation within a calibrated SNBV model, and examined their impact on the UCS and fracture behaviors of granite, based on a set of simplified microproperties. The results illustrate that as the SNBV model resolution (defined by the number of rigid blocks contained in models with identical physical dimensions) increases, mechanical properties, including UCS and crack initiation and damage strains and stresses, reach constant values. Additionally, the spatial distribution, shape, and orientation of biotite grain affect the UCS of granite, while their effect on the failure strain is minimal. The aspect ratio of biotite grains affects UCS, with <span><math><mi>z</mi></math></span>-axis elongation (aligned with compression) yielding higher UCS than <span><math><mi>x</mi></math></span>-axis elongation (perpendicular to compression).</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106355"},"PeriodicalIF":7.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145598600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1016/j.ijrmms.2025.106352
Yan Li , Miguel Herbón-Penabad , Jorge Castro , Marina Miranda , Tonglu Li , Jordi Delgado-Martín
Understanding mode I fracture behavior in rocks is essential for handling geomechanical problems, including tunneling, mining, and hydraulic fracturing. This study investigates the mode I fracture toughness (KIC) and specific fracture energy (Gc and Gf) in one sandstone, one limestone and two marble lithologies using the pseudo-compact tension (pCT) test. To assess the influence of the notch radius, specimens were prepared with two notch radii: 0.15 mm (thin) and 0.5 mm (thick). The key novelty lies in comparing notch radius effects across multiple lithologies while explicitly accounting for heterogeneity via ultrasonic wave velocities and micro X-ray fluorescence elemental mapping. Results show that, for the limestone and the marbles, the thick notch yields higher values of KIC, Gc, Gf. In contrast, the sandstone shows the opposite trend, with higher values for thin-notch specimens. This behavior is likely attributed to its high porosity, where stress concentration around pores can generates secondary crack tips near the blunt notch tip, that reduce the fracture toughness and energy dissipation. Across all rocks, Gf > Gc, indicating substantial dissipation by microcracking and grain-boundary processes beyond pure surface-energy creation. In addition, a thinner notch improves repeatability and reduces data dispersion, thereby mitigating heterogeneity effects on measured parameters. These findings provide practical guidance on selection of notch radius and highlight the importance of multiscale heterogeneity characterization for advancing rock mechanics research and refining fracture testing methods, thereby improving accuracy and reducing variability.
{"title":"Experimental assessment of mode I fracture toughness and fracture energy in four rock types using the pCT testing method with two notch radii","authors":"Yan Li , Miguel Herbón-Penabad , Jorge Castro , Marina Miranda , Tonglu Li , Jordi Delgado-Martín","doi":"10.1016/j.ijrmms.2025.106352","DOIUrl":"10.1016/j.ijrmms.2025.106352","url":null,"abstract":"<div><div>Understanding mode I fracture behavior in rocks is essential for handling geomechanical problems, including tunneling, mining, and hydraulic fracturing. This study investigates the mode I fracture toughness (<em>K</em><sub>IC</sub>) and specific fracture energy (<em>G</em><sub>c</sub> and <em>G</em><sub>f</sub>) in one sandstone, one limestone and two marble lithologies using the pseudo-compact tension (<em>p</em>CT) test. To assess the influence of the notch radius, specimens were prepared with two notch radii: 0.15 mm (thin) and 0.5 mm (thick). The key novelty lies in comparing notch radius effects across multiple lithologies while explicitly accounting for heterogeneity via ultrasonic wave velocities and micro X-ray fluorescence elemental mapping. Results show that, for the limestone and the marbles, the thick notch yields higher values of <em>K</em><sub>IC</sub>, <em>G</em><sub>c</sub>, <em>G</em><sub>f</sub>. In contrast, the sandstone shows the opposite trend, with higher values for thin-notch specimens. This behavior is likely attributed to its high porosity, where stress concentration around pores can generates secondary crack tips near the blunt notch tip, that reduce the fracture toughness and energy dissipation. Across all rocks, <em>G</em><sub>f</sub> > <em>G</em><sub>c</sub>, indicating substantial dissipation by microcracking and grain-boundary processes beyond pure surface-energy creation. In addition, a thinner notch improves repeatability and reduces data dispersion, thereby mitigating heterogeneity effects on measured parameters. These findings provide practical guidance on selection of notch radius and highlight the importance of multiscale heterogeneity characterization for advancing rock mechanics research and refining fracture testing methods, thereby improving accuracy and reducing variability.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106352"},"PeriodicalIF":7.5,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145598601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1016/j.ijrmms.2025.106357
Xuyang Guo , Yan Jin , Tingting Miu , Shiming Wei , Yang Xia , Jizhou Tang
Depressurization-induced gas hydrate dissociation is widely employed for gas hydrate production but simultaneously introduces substantial geomechanical challenges, including sediment deformation, formation damage, and subsidence. Such issues have significantly limited the duration of field production tests worldwide, typically causing production to cease within around one month. The reliance on time-independent and quasi-static geomechanical assumptions in many existing models may lead to significant underestimation of depressurization-induced irreversible deformation and overlook time-dependent creep effects. This study develops a fully coupled poro-elasto-viscoplastic-dynamic model specifically designed to analyze realistic dynamic geomechanical responses induced by depressurization in gas hydrate-bearing sediments. The novelty of this work lies in incorporating both the inertial effects and a validated time-dependent elasto-viscoplastic constitutive relationship within a unified poromechanical framework, representing one of the first numerical efforts to capture these coupled effects and their impact on progressive irreversible deformation. The numerical framework integrates thermal, hydraulic, mechanical, and chemical processes. Comprehensive validations against established benchmarks and experimental data substantiate the accuracy and reliability of the model. Results demonstrate distinctive dynamic behaviors, capturing stress rebound phenomena at hydrate dissociation fronts, characterized by sudden stiffness reductions followed by transient stress recovery. The model identifies significant tertiary creep deformation occurring rapidly consistent with global field observations where production frequently terminates due to severe geomechanical deterioration. Comparative analyses further indicate that conventional quasi-static and time-independent constitutive models underestimate cumulative irreversible plastic deformation, potentially misrepresenting short-term geomechanical risks. Unique stress path evolution patterns captured by the dynamic model also provide quantification of transient yielding, stress redistribution, and progressive deformation mechanisms. This study explains the geomechanical reasons underlying the un-sustained and limited-duration gas hydrate production commonly observed in field operations. It also quantifies risks often overlooked or underestimated by simplified modeling approaches.
{"title":"Investigation of the time-dependent and dynamic geomechanical behaviors induced by depressurization in natural gas hydrate-bearing sediments based on a poro-elasto-viscoplastic-dynamic model","authors":"Xuyang Guo , Yan Jin , Tingting Miu , Shiming Wei , Yang Xia , Jizhou Tang","doi":"10.1016/j.ijrmms.2025.106357","DOIUrl":"10.1016/j.ijrmms.2025.106357","url":null,"abstract":"<div><div>Depressurization-induced gas hydrate dissociation is widely employed for gas hydrate production but simultaneously introduces substantial geomechanical challenges, including sediment deformation, formation damage, and subsidence. Such issues have significantly limited the duration of field production tests worldwide, typically causing production to cease within around one month. The reliance on time-independent and quasi-static geomechanical assumptions in many existing models may lead to significant underestimation of depressurization-induced irreversible deformation and overlook time-dependent creep effects. This study develops a fully coupled poro-elasto-viscoplastic-dynamic model specifically designed to analyze realistic dynamic geomechanical responses induced by depressurization in gas hydrate-bearing sediments. The novelty of this work lies in incorporating both the inertial effects and a validated time-dependent elasto-viscoplastic constitutive relationship within a unified poromechanical framework, representing one of the first numerical efforts to capture these coupled effects and their impact on progressive irreversible deformation. The numerical framework integrates thermal, hydraulic, mechanical, and chemical processes. Comprehensive validations against established benchmarks and experimental data substantiate the accuracy and reliability of the model. Results demonstrate distinctive dynamic behaviors, capturing stress rebound phenomena at hydrate dissociation fronts, characterized by sudden stiffness reductions followed by transient stress recovery. The model identifies significant tertiary creep deformation occurring rapidly consistent with global field observations where production frequently terminates due to severe geomechanical deterioration. Comparative analyses further indicate that conventional quasi-static and time-independent constitutive models underestimate cumulative irreversible plastic deformation, potentially misrepresenting short-term geomechanical risks. Unique stress path evolution patterns captured by the dynamic model also provide quantification of transient yielding, stress redistribution, and progressive deformation mechanisms. This study explains the geomechanical reasons underlying the un-sustained and limited-duration gas hydrate production commonly observed in field operations. It also quantifies risks often overlooked or underestimated by simplified modeling approaches.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106357"},"PeriodicalIF":7.5,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145593044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1016/j.ijrmms.2025.106344
Lishan Zhang , Chongyuan Zhang , Yifan Wu , Manchao He , Mohua Bu
Understanding the mechanisms underlying fluid-induced fault instability is essential for mitigating the risk of triggered seismicity. This study integrates laboratory experiments on granite samples containing a pre-cut fault zone and field data from the Gonghe Enhanced Geothermal System (EGS) to examine how injection rate and confining pressure govern fault slip modes, energy partitioning, and precursor signals. Experimental results demonstrate that injection rate critically modulates slip behavior: low injection rates promote cascades of small, low-energy slip events, whereas high rates induce a three-stage evolution (initiation-creep-instability) that culminates in larger seismic energy release. For stably slipping faults, total hydraulic energy shows a linear correlation with shear displacement. An interesting finding is the identification of a precursory stress drop, marked by a nonlinear transition in the pore pressure growth curve. A precursory time window exists between macro-slip initiation and catastrophic stick-slip. This precursor window shortens with increasing injection rate, underscoring that injection rate control is a primary strategy for seismic hazard management. Field observations from the Gonghe EGS confirm that higher injection rates are associated with reduced hydraulic diffusivity and increased seismic energy release, consistent with the mechanism identified in the laboratory.
{"title":"Characteristics of fault slip, energy budget, and precursory stress drop revealed by fluid-induced fault instability experiments with varied injection rates","authors":"Lishan Zhang , Chongyuan Zhang , Yifan Wu , Manchao He , Mohua Bu","doi":"10.1016/j.ijrmms.2025.106344","DOIUrl":"10.1016/j.ijrmms.2025.106344","url":null,"abstract":"<div><div>Understanding the mechanisms underlying fluid-induced fault instability is essential for mitigating the risk of triggered seismicity. This study integrates laboratory experiments on granite samples containing a pre-cut fault zone and field data from the Gonghe Enhanced Geothermal System (EGS) to examine how injection rate and confining pressure govern fault slip modes, energy partitioning, and precursor signals. Experimental results demonstrate that injection rate critically modulates slip behavior: low injection rates promote cascades of small, low-energy slip events, whereas high rates induce a three-stage evolution (initiation-creep-instability) that culminates in larger seismic energy release. For stably slipping faults, total hydraulic energy shows a linear correlation with shear displacement. An interesting finding is the identification of a precursory stress drop, marked by a nonlinear transition in the pore pressure growth curve. A precursory time window exists between macro-slip initiation and catastrophic stick-slip. This precursor window shortens with increasing injection rate, underscoring that injection rate control is a primary strategy for seismic hazard management. Field observations from the Gonghe EGS confirm that higher injection rates are associated with reduced hydraulic diffusivity and increased seismic energy release, consistent with the mechanism identified in the laboratory.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106344"},"PeriodicalIF":7.5,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145593046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-22DOI: 10.1016/j.ijrmms.2025.106353
Kwang-Il Kim , Changsoo Lee , Dongkeun Cho , Jin-Seop Kim , Jonny Rutqvist
This study numerically investigates the influence of the excavation damaged zone (EDZ) on the long-term coupled thermo-hydro-mechanical (THM) behaviors of the Korean deep geological repository (DGR) concepts in granitic rock masses. Using the extent and properties of the EDZ derived from Korean Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT), numerical results reveal that the EDZ exerts a minor influence on thermal behavior but accelerates the resaturation of the buffer and backfill due to its increased permeability. Notably, the EDZ leads to a smaller extent of potential rock failure compared to simulation cases without the EDZ. This is attributed to a more pronounced reduction in thermal stresses relative to the decrease in rock mass strengths. A sensitivity analysis reveals that uncertainties in the rock mass stiffness within the EDZ have a more pronounced effect on the predicted rock failure volume than variations in thermal conductivity and permeability have on the temperature and saturation evolutions. Reducing disposal spacing to increase disposal density defined as the amount of disposed uranium per unit area significantly raises thermal loading and the risk of rock mass failure, potentially inducing continuous failure zones connecting neighboring deposition holes and disposal tunnels under relatively weak rock conditions. These findings suggest that while the EDZ may not be a critical factor in determining disposal spacing, DGR designs to enhance the disposal density necessitate careful consideration of the rock mass strength to ensure long-term safety.
{"title":"Effect of excavation damaged zone on the long-term coupled thermo-hydro-mechanical behaviors of deep geological repositories in granitic rock masses","authors":"Kwang-Il Kim , Changsoo Lee , Dongkeun Cho , Jin-Seop Kim , Jonny Rutqvist","doi":"10.1016/j.ijrmms.2025.106353","DOIUrl":"10.1016/j.ijrmms.2025.106353","url":null,"abstract":"<div><div>This study numerically investigates the influence of the excavation damaged zone (EDZ) on the long-term coupled thermo-hydro-mechanical (THM) behaviors of the Korean deep geological repository (DGR) concepts in granitic rock masses. Using the extent and properties of the EDZ derived from Korean Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT), numerical results reveal that the EDZ exerts a minor influence on thermal behavior but accelerates the resaturation of the buffer and backfill due to its increased permeability. Notably, the EDZ leads to a smaller extent of potential rock failure compared to simulation cases without the EDZ. This is attributed to a more pronounced reduction in thermal stresses relative to the decrease in rock mass strengths. A sensitivity analysis reveals that uncertainties in the rock mass stiffness within the EDZ have a more pronounced effect on the predicted rock failure volume than variations in thermal conductivity and permeability have on the temperature and saturation evolutions. Reducing disposal spacing to increase disposal density defined as the amount of disposed uranium per unit area significantly raises thermal loading and the risk of rock mass failure, potentially inducing continuous failure zones connecting neighboring deposition holes and disposal tunnels under relatively weak rock conditions. These findings suggest that while the EDZ may not be a critical factor in determining disposal spacing, DGR designs to enhance the disposal density necessitate careful consideration of the rock mass strength to ensure long-term safety.</div></div>","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"197 ","pages":"Article 106353"},"PeriodicalIF":7.5,"publicationDate":"2025-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145567443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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