Pub Date : 2025-01-01DOI: 10.1016/j.gete.2024.100624
A. Gajo
This paper presents a general method for defining the macroscopic free-energy density function and its complementary forms for a porous medium saturated by two non-miscible fluids, in the case of compressible fluid and solid constituents, non-isothermal conditions and negligible interfacial surface energy.
The major advantage of the proposed approach is that no limitation or simplification is posed on the choice of the free energies of the fluid constituents. As a result, a fully non-linear equation of state for the pore fluids can be incorporated within the proposed framework.
The method is presented under the assumption that interfacial surface energy terms are negligible, thus recovering a Bishop parameter coinciding with the degree of saturation, which is expected to be applicable mostly to non-plastic soils. Moreover, small strains of the solid skeleton are assumed, but the method can be easily extended to a large strain formulation as discussed below. The paper analyzes also some particular cases concerning the incompressibility of all constituents, the geometric linearization and the incompressibility only of the solid constituent.
The knowledge of the free energy density function is the starting point for the evaluation of the dissipation function, of energy and entropy balance and, in general, for the formulation of thermodynamically consistent constitutive models.
{"title":"The free-energy density function and its complementary forms for porous media saturated by two non-miscible fluids under non isothermal conditions","authors":"A. Gajo","doi":"10.1016/j.gete.2024.100624","DOIUrl":"10.1016/j.gete.2024.100624","url":null,"abstract":"<div><div>This paper presents a general method for defining the macroscopic free-energy density function and its complementary forms for a porous medium saturated by two non-miscible fluids, in the case of compressible fluid and solid constituents, non-isothermal conditions and negligible interfacial surface energy.</div><div>The major advantage of the proposed approach is that no limitation or simplification is posed on the choice of the free energies of the fluid constituents. As a result, a fully non-linear equation of state for the pore fluids can be incorporated within the proposed framework.</div><div>The method is presented under the assumption that interfacial surface energy terms are negligible, thus recovering a Bishop parameter <span><math><mi>χ</mi></math></span> coinciding with the degree of saturation, which is expected to be applicable mostly to non-plastic soils. Moreover, small strains of the solid skeleton are assumed, but the method can be easily extended to a large strain formulation as discussed below. The paper analyzes also some particular cases concerning the incompressibility of all constituents, the geometric linearization and the incompressibility only of the solid constituent.</div><div>The knowledge of the free energy density function is the starting point for the evaluation of the dissipation function, of energy and entropy balance and, in general, for the formulation of thermodynamically consistent constitutive models.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100624"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-31DOI: 10.1016/j.gete.2024.100633
Jing Liu , Shuangying Zuo , Yunchuan Mo
To investigate the influences of the acid mine drainage (AMD) in a closed coal mine on the corrosion and seepage stability of limestone with rough fractures, both distilled water and AMD solution were employed to implement seepage-corrosion tests on the seven sets of a single fracture of limestone specimens under different hydraulic conditions. We investigated the effects of confining stress and solution on the seepage parameters. Also, the mechanism of seepage reduction of fractured limestone caused by AMD solution was proposed. Moreover, COMSOL numerical software was used to simulate the chemical-seepage coupling field characteristics of a rough fracture under condition 4. The results are as follows: (1) The permeability, the Ca2+ concentration gradually decreases, and the osmotic stress, the total iron concentration gradually increases during the seepage process. (2) Differences between the bedding and matrix corrosion exist, the roughness of the fracture surface decreases, and “passivation” occurs on the surface, which makes the permeability decrease rapidly in the early stages and stabilize later. (3) The real-time permeability of fractured limestone under high confining stress is smaller than that under low confining stress and the sensitivity of permeability decreased with the increase of confining stress. (4) The numerical simulated results show the diffusion area of the solution on the fracture wall expands with increasing seepage-corrosion time and osmotic stress of the entrance section. This work will be of great significance to guide the treatment of AMD and the stability analysis of engineering rock masses.
{"title":"Experimental study on seepage–corrosion coupling characteristics of a single fracture in limestone subjected to acid mine drainage","authors":"Jing Liu , Shuangying Zuo , Yunchuan Mo","doi":"10.1016/j.gete.2024.100633","DOIUrl":"10.1016/j.gete.2024.100633","url":null,"abstract":"<div><div>To investigate the influences of the acid mine drainage (AMD) in a closed coal mine on the corrosion and seepage stability of limestone with rough fractures, both distilled water and AMD solution were employed to implement seepage-corrosion tests on the seven sets of a single fracture of limestone specimens under different hydraulic conditions. We investigated the effects of confining stress and solution on the seepage parameters. Also, the mechanism of seepage reduction of fractured limestone caused by AMD solution was proposed. Moreover, COMSOL numerical software was used to simulate the chemical-seepage coupling field characteristics of a rough fracture under condition 4. The results are as follows: (1) The permeability, the Ca<sup>2+</sup> concentration gradually decreases, and the osmotic stress, the total iron concentration gradually increases during the seepage process. (2) Differences between the bedding and matrix corrosion exist, the roughness of the fracture surface decreases, and “passivation” occurs on the surface, which makes the permeability decrease rapidly in the early stages and stabilize later. (3) The real-time permeability of fractured limestone under high confining stress is smaller than that under low confining stress and the sensitivity of permeability decreased with the increase of confining stress. (4) The numerical simulated results show the diffusion area of the solution on the fracture wall expands with increasing seepage-corrosion time and osmotic stress of the entrance section. This work will be of great significance to guide the treatment of AMD and the stability analysis of engineering rock masses.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100633"},"PeriodicalIF":3.3,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-12-27DOI: 10.1016/j.gete.2024.100632
Uy Vo , Mamadou Fall , Julio Ángel Infante Sedano , Maïwenn Humbezi-Desfeux , Jean-Michel Matray , Manuel Marcoux , Thanh Son Nguyen
Argillaceous rocks have many favourable characteristics for deep geological disposal of high-level radioactive waste (HLW) such as low permeability resulting in slow solute transport dominated by diffusion processes. However, waste-generated heat can increase pore pressure through Thermal-Hydraulic-Mechanical (THM) coupled processes, potentially enhancing advective transport. In this study, the authors developed a mathematical model to simulate a laboratory and a large-scale in situ experiment at an underground research facility (URF), to investigate (1) T-solute transport coupling (via the Soret effect and temperature-dependent diffusion coefficient) and (2) THM-solute transport coupling in argillaceous rock. The findings suggest that the Soret effect is significant in the laboratory experiments with relatively high thermal gradient, but negligible in the URF experiment where the thermal gradient is much smaller. Instead, the effect of temperature on the diffusion coefficient appears to play a more crucial role for the URF experiment. In addition, the advection enhancement due to thermal pressurization as a result of THM processes shows an insignificant effect on solute transport. The modelling of the URF experiment, as confirmed by observational evidence, shows the importance of anisotropy of the THM-transport properties as well as the effects of the excavation damage zone (EDZ). Finally, the model captures the key features of both experiments, highlighting its capability in enhancing comprehension of transport processes from a deep geological repository (DGR) built in argillaceous rocks. This improved understanding is valuable for safety assessments of DGRs in such rock types.
{"title":"Numerical simulation of solute transport in argillaceous rock under thermal gradient with a coupled THM-solute transport model","authors":"Uy Vo , Mamadou Fall , Julio Ángel Infante Sedano , Maïwenn Humbezi-Desfeux , Jean-Michel Matray , Manuel Marcoux , Thanh Son Nguyen","doi":"10.1016/j.gete.2024.100632","DOIUrl":"10.1016/j.gete.2024.100632","url":null,"abstract":"<div><div>Argillaceous rocks have many favourable characteristics for deep geological disposal of high-level radioactive waste (HLW) such as low permeability resulting in slow solute transport dominated by diffusion processes. However, waste-generated heat can increase pore pressure through Thermal-Hydraulic-Mechanical (THM) coupled processes, potentially enhancing advective transport. In this study, the authors developed a mathematical model to simulate a laboratory and a large-scale in situ experiment at an underground research facility (URF), to investigate (1) T-solute transport coupling (via the Soret effect and temperature-dependent diffusion coefficient) and (2) THM-solute transport coupling in argillaceous rock. The findings suggest that the Soret effect is significant in the laboratory experiments with relatively high thermal gradient, but negligible in the URF experiment where the thermal gradient is much smaller. Instead, the effect of temperature on the diffusion coefficient appears to play a more crucial role for the URF experiment. In addition, the advection enhancement due to thermal pressurization as a result of THM processes shows an insignificant effect on solute transport. The modelling of the URF experiment, as confirmed by observational evidence, shows the importance of anisotropy of the THM-transport properties as well as the effects of the excavation damage zone (EDZ). Finally, the model captures the key features of both experiments, highlighting its capability in enhancing comprehension of transport processes from a deep geological repository (DGR) built in argillaceous rocks. This improved understanding is valuable for safety assessments of DGRs in such rock types.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100632"},"PeriodicalIF":3.3,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-26DOI: 10.1016/j.gete.2024.100627
Jonny Rutqvist
A model for gas migration through clay-based buffer material is developed for modeling gas generation and migration associated with deep geologic nuclear waste disposal. The model is based on a multiphase fluid flow and geomechanics simulator that is adapted to consider enhanced gas flow when gas pressure is high enough to approach the confining stress magnitude. A key feature in the model is a direct coupling between gas permeability and stress, through a non-linear stress-dependent permeability function. The model was first tested and calibrated by modelling two different laboratory gas migration tests on Wyoming (MX-80) bentonite samples. The calibrated model was then applied to model gas migration through a bentonite buffer of a large-scale gas injection test (Lasgit) conducted at the Äspö Hard Rock Laboratory in Sweden. Observed preferential gas migration along interfaces (between compacted blocks and along the canister surface) required explicit representation of such interfaces in the model. The model with the stress-dependent gas permeability accurately captured observed experimental responses in terms of gas breakthrough time, peak gas pressure, and cumulative gas flow rates. The calibrated model was finally applied to simulate migration of hydrogen gas generated within a breached nuclear waste canister over 10,000 years, involving migration of much larger gas volumes. For the considered gas generation rate and host rock properties, the generated gas could migrate through the bentonite buffer and released into the surrounding host rock at a maximum gas pressure somewhat higher than the initial total stress, though a significant amount of hydrogen remained within the buffer. This modelling sets the stage for further detailed analysis of the impact of hydrogen gas generation on the long-term performance of nuclear waste repositories.
{"title":"Modeling gas migration through clay-based buffer material using coupled multiphase fluid flow and geomechanics with stress-dependent gas permeability","authors":"Jonny Rutqvist","doi":"10.1016/j.gete.2024.100627","DOIUrl":"10.1016/j.gete.2024.100627","url":null,"abstract":"<div><div>A model for gas migration through clay-based buffer material is developed for modeling gas generation and migration associated with deep geologic nuclear waste disposal. The model is based on a multiphase fluid flow and geomechanics simulator that is adapted to consider enhanced gas flow when gas pressure is high enough to approach the confining stress magnitude. A key feature in the model is a direct coupling between gas permeability and stress, through a non-linear stress-dependent permeability function. The model was first tested and calibrated by modelling two different laboratory gas migration tests on Wyoming (MX-80) bentonite samples. The calibrated model was then applied to model gas migration through a bentonite buffer of a large-scale gas injection test (Lasgit) conducted at the Äspö Hard Rock Laboratory in Sweden. Observed preferential gas migration along interfaces (between compacted blocks and along the canister surface) required explicit representation of such interfaces in the model. The model with the stress-dependent gas permeability accurately captured observed experimental responses in terms of gas breakthrough time, peak gas pressure, and cumulative gas flow rates. The calibrated model was finally applied to simulate migration of hydrogen gas generated within a breached nuclear waste canister over 10,000 years, involving migration of much larger gas volumes. For the considered gas generation rate and host rock properties, the generated gas could migrate through the bentonite buffer and released into the surrounding host rock at a maximum gas pressure somewhat higher than the initial total stress, though a significant amount of hydrogen remained within the buffer. This modelling sets the stage for further detailed analysis of the impact of hydrogen gas generation on the long-term performance of nuclear waste repositories.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100627"},"PeriodicalIF":3.3,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-26DOI: 10.1016/j.gete.2024.100635
Sotirios Nik. Longinos, Dastan Begaliyev, Randy Hazlett
The purpose of this research is to investigate the effects of elevated heating and cooling with liquid nitrogen (LN2) on the mechanical properties of two different granites from the Akmola region in Kazakhstan. While trends regarding behavior of treated samples are similar, the differences observed between the two compositions of granite are asserted to be due to the difference in quartz versus feldspar ratios and the contrast in coefficients of thermal expansion at heterogeneous grain contacts. The results showed that high initial temperature along with LN2 cooling increased the deformation of specimens leading to smaller peak stress values under load in both granite specimens. For granite 1, stress values decreased from a baseline value of 158.13 MPa to 123.24 MPa after heating to 400 °C and immersion in LN2; while for granite 2, the stress values decreased from 181.42 MPa to 118.33 MPa under similar conditions. There was a positive correlation observed between Young's modulus and the degree of thermal shock, whereas a negative correlation was noted for Poisson's ratio. The failure mode classification in Brazilian tests progressed with increasing initial sample initial temperature from Type I to Type III, indicating increasing complexity in rock integrity with larger thermal shock. Adding to the study’s novelty, numerical simulations were performed to investigate the distribution of stress in granite samples that were cryogenically treated utilizing von Mises stress analysis to monitor changes over time. The close match between the simulation results and the experimental data confirmed the model's reliability. These findings offer strong evidence in favor of the feasibility of increasing granite permeability by LN2-based treatments, which may improve the effectiveness and security of geothermal extraction techniques.
{"title":"Experimental and simulation study of cryogenic stimulation of granites from Akmola region in Kazakhstan","authors":"Sotirios Nik. Longinos, Dastan Begaliyev, Randy Hazlett","doi":"10.1016/j.gete.2024.100635","DOIUrl":"10.1016/j.gete.2024.100635","url":null,"abstract":"<div><div>The purpose of this research is to investigate the effects of elevated heating and cooling with liquid nitrogen (LN<sub>2</sub>) on the mechanical properties of two different granites from the Akmola region in Kazakhstan. While trends regarding behavior of treated samples are similar, the differences observed between the two compositions of granite are asserted to be due to the difference in quartz versus feldspar ratios and the contrast in coefficients of thermal expansion at heterogeneous grain contacts. The results showed that high initial temperature along with LN<sub>2</sub> cooling increased the deformation of specimens leading to smaller peak stress values under load in both granite specimens. For granite 1, stress values decreased from a baseline value of 158.13 MPa to 123.24 MPa after heating to 400 °C and immersion in LN<sub>2</sub>; while for granite 2, the stress values decreased from 181.42 MPa to 118.33 MPa under similar conditions. There was a positive correlation observed between Young's modulus and the degree of thermal shock, whereas a negative correlation was noted for Poisson's ratio. The failure mode classification in Brazilian tests progressed with increasing initial sample initial temperature from Type I to Type III, indicating increasing complexity in rock integrity with larger thermal shock. Adding to the study’s novelty, numerical simulations were performed to investigate the distribution of stress in granite samples that were cryogenically treated utilizing von Mises stress analysis to monitor changes over time. The close match between the simulation results and the experimental data confirmed the model's reliability. These findings offer strong evidence in favor of the feasibility of increasing granite permeability by LN<sub>2</sub>-based treatments, which may improve the effectiveness and security of geothermal extraction techniques.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100635"},"PeriodicalIF":3.3,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143133429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-12-25DOI: 10.1016/j.gete.2024.100628
Minseop Kim , Changsoo Lee , Sugita Yutaka , Jin-Seop Kim , Min-Kyung Jeon
This study investigates the influence of primary variables selection on modeling non-isothermal two-phase flow, using numerical simulation based on the full-scale engineered barrier system (EBS) experiment conducted at the Horonobe Underground Research Laboratory (URL) as part of the DECOVALEX-2023 project. A thermal-hydraulic coupled model was validated against analytical solution and experimental data before being applied to simulate the heterogeneous porous media within the EBS. Two different primary variable schemes were compared for discretizing the governing equations, revealing substantial differences in results. Notably, using capillary pressure as a primary variable instead of saturation resulted in closer alignment with analytical solutions and real-world observations. While the modeling work at the Horonobe URL generally exhibited trends consistent with experimental data, discrepancies were attributed to the operational conditions of the heater and the influence of the Excavation Damaged Zone (EDZ) near the borehole.
{"title":"Comparative analysis of primary variables selection in modeling non-isothermal two-phase flow: Insights from EBS experiment at Horonobe URL","authors":"Minseop Kim , Changsoo Lee , Sugita Yutaka , Jin-Seop Kim , Min-Kyung Jeon","doi":"10.1016/j.gete.2024.100628","DOIUrl":"10.1016/j.gete.2024.100628","url":null,"abstract":"<div><div>This study investigates the influence of primary variables selection on modeling non-isothermal two-phase flow, using numerical simulation based on the full-scale engineered barrier system (EBS) experiment conducted at the Horonobe Underground Research Laboratory (URL) as part of the DECOVALEX-2023 project. A thermal-hydraulic coupled model was validated against analytical solution and experimental data before being applied to simulate the heterogeneous porous media within the EBS. Two different primary variable schemes were compared for discretizing the governing equations, revealing substantial differences in results. Notably, using capillary pressure as a primary variable instead of saturation resulted in closer alignment with analytical solutions and real-world observations. While the modeling work at the Horonobe URL generally exhibited trends consistent with experimental data, discrepancies were attributed to the operational conditions of the heater and the influence of the Excavation Damaged Zone (EDZ) near the borehole.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100628"},"PeriodicalIF":3.3,"publicationDate":"2024-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-12-25DOI: 10.1016/j.gete.2024.100630
Kwang-Il Kim , Saeha Kwon , Changsoo Lee , Jin-Seop Kim , Jeoung-Seok Yoon , Li Zhuang
In deep geological repositories (DGRs), decay heat from spent nuclear fuel raises the temperature, causing thermal stress and shear slip in pre-existing fractures in crystalline rocks, a phenomenon known as thermoshearing. An in-depth understanding of the thermoshearing mechanism in fractured rock masses is crucial for assessing the safety and stability of DGRs, as irreversible increase in permeability due to fracture shear slip can elevate fluid flow containing radionuclides and can compromise the integrity and performance of engineered barrier systems. This study presents a numerical reproduction of the laboratory thermoshearing experiments conducted on granite samples with planar and rough fractures using the three-dimensional discontinuum-based coupled code, TOUGH-3DEC. The calculated and measured temperatures at the heater and rock samples show reasonable agreement. The numerical models effectively capture the characteristic fracture shear behavior related to fracture roughness, as observed in the experiments. Irregular fracture roughness and relatively greater differential stress conditions applied in the rough fracture (RF) model induce shear slip before heating, differentiating the initiation timing of shear slip in the planar fracture (PF) and RF models. After heating, the maximum shear displacements for the PF and RF models are 68 μm and 74 μm, respectively, occurring near the top and bottom boundaries, where the temperature increase is the greatest. Among the five locations analyzed by digital image correlation, the largest shear displacement but the smallest dilation occurs at a specific location, indicating that intensified stress concentration at local protruding contacts can restrain the fracture dilation. The seismic events calculated using the developed seismic analysis algorithm show similarities with the measured acoustic emission events in terms of relative size and temporal distributions.
{"title":"Discontinuum-based numerical analysis of thermoshearing in planar and rough granite fractures: A comparison with laboratory observations","authors":"Kwang-Il Kim , Saeha Kwon , Changsoo Lee , Jin-Seop Kim , Jeoung-Seok Yoon , Li Zhuang","doi":"10.1016/j.gete.2024.100630","DOIUrl":"10.1016/j.gete.2024.100630","url":null,"abstract":"<div><div>In deep geological repositories (DGRs), decay heat from spent nuclear fuel raises the temperature, causing thermal stress and shear slip in pre-existing fractures in crystalline rocks, a phenomenon known as thermoshearing. An in-depth understanding of the thermoshearing mechanism in fractured rock masses is crucial for assessing the safety and stability of DGRs, as irreversible increase in permeability due to fracture shear slip can elevate fluid flow containing radionuclides and can compromise the integrity and performance of engineered barrier systems. This study presents a numerical reproduction of the laboratory thermoshearing experiments conducted on granite samples with planar and rough fractures using the three-dimensional discontinuum-based coupled code, TOUGH-3DEC. The calculated and measured temperatures at the heater and rock samples show reasonable agreement. The numerical models effectively capture the characteristic fracture shear behavior related to fracture roughness, as observed in the experiments. Irregular fracture roughness and relatively greater differential stress conditions applied in the rough fracture (RF) model induce shear slip before heating, differentiating the initiation timing of shear slip in the planar fracture (PF) and RF models. After heating, the maximum shear displacements for the PF and RF models are 68 μm and 74 μm, respectively, occurring near the top and bottom boundaries, where the temperature increase is the greatest. Among the five locations analyzed by digital image correlation, the largest shear displacement but the smallest dilation occurs at a specific location, indicating that intensified stress concentration at local protruding contacts can restrain the fracture dilation. The seismic events calculated using the developed seismic analysis algorithm show similarities with the measured acoustic emission events in terms of relative size and temporal distributions.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100630"},"PeriodicalIF":3.3,"publicationDate":"2024-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-12-25DOI: 10.1016/j.gete.2024.100634
Suman Saurabh, Natalia Zakharova
This study demonstrates a successful application of scratch test to characterizing geomechanical anisotropy in weakly to moderately anisotropic sedimentary rocks. Scratch tests were performed in three orthogonal directions on four sedimentary rock samples: one limestone and three shales, and the scratch-derived mechanical properties were compared to anisotropic parameters calculated from acoustic velocities. Results showed a similar pattern of anisotropy in the scratch-derived unconfined compressive strength (UCS) and fracture toughness (KIC), and velocity-derived Thomsen’s parameters. The measured values also compared well to previous studies of anisotropy in shales. The UCS and KIC for shale samples were correlated: shales with higher UCS were also characterized by higher KIC, and vice versa. The lowest values for both were observed perpendicular to bedding planes. All parameters consistently indicated that three out of four samples were transversely isotropic, and one sample exhibited more orthotropic behavior. Overall, our results indicate that scratch tests provide a simple and reliable tool for screening and potentially quantifying mechanical properties of anisotropic rocks. Compared to the majority of conventional geomechanical methods, which are destructive and require multiple directional samples, scratch test provides an opportunity to characterize mechanical anisotropy with very limited rock material and/or on a single sample.
{"title":"Characterizing mechanical anisotropy in rocks using instrumented scratch test","authors":"Suman Saurabh, Natalia Zakharova","doi":"10.1016/j.gete.2024.100634","DOIUrl":"10.1016/j.gete.2024.100634","url":null,"abstract":"<div><div>This study demonstrates a successful application of scratch test to characterizing geomechanical anisotropy in weakly to moderately anisotropic sedimentary rocks. Scratch tests were performed in three orthogonal directions on four sedimentary rock samples: one limestone and three shales, and the scratch-derived mechanical properties were compared to anisotropic parameters calculated from acoustic velocities. Results showed a similar pattern of anisotropy in the scratch-derived unconfined compressive strength (UCS) and fracture toughness (K<sub>IC</sub>), and velocity-derived Thomsen’s parameters. The measured values also compared well to previous studies of anisotropy in shales. The UCS and K<sub>IC</sub> for shale samples were correlated: shales with higher UCS were also characterized by higher K<sub>IC</sub>, and vice versa. The lowest values for both were observed perpendicular to bedding planes. All parameters consistently indicated that three out of four samples were transversely isotropic, and one sample exhibited more orthotropic behavior. Overall, our results indicate that scratch tests provide a simple and reliable tool for screening and potentially quantifying mechanical properties of anisotropic rocks. Compared to the majority of conventional geomechanical methods, which are destructive and require multiple directional samples, scratch test provides an opportunity to characterize mechanical anisotropy with very limited rock material and/or on a single sample.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100634"},"PeriodicalIF":3.3,"publicationDate":"2024-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-12-25DOI: 10.1016/j.gete.2024.100629
Rosie C. Leone , Paul E. Mariner , Emily R. Stein , Jeffrey D. Hyman , Jan Thiedau , Carlos R. Guevara Morel , Zhenze Li , Son Nguyen , Yong-Min Kim , Jung-Woo Kim , Chieh-Chun Chang , Ondrej Mikláš , Nicholas I. Osuji , Auli Niemi
Performance Assessment (PA) is important in ensuring the isolation and long-term containment of spent nuclear fuel from the geosphere. It plays a crucial role in evaluating the long-term safety and effectiveness of underground nuclear waste storage, considering factors such as radionuclide release rates, transport mechanisms, and the performance of engineered barriers. This paper presents the findings of DECOVALEX 2023 Task F, which aimed to compare various models and conceptual approaches used in PA of a generic deep geologic repository in crystalline rock. The objective was to explore the contribution of modeling choices to uncertainty in PA model outputs. The study highlights the importance of characterizing the crystalline rock properties and the engineered barrier system in PA. The so-called reference case, a simplified version of a PA focused on the transport of two conservative tracers from the deposition hole to the surface, neglecting waste package performance was used as an example. Seven international teams (Canada, Czech Republic, Germany, Korea, Sweden, Taiwan, and United States) developed and simulated the generic reference case, tracking tracer releases from waste package locations to the near field and ground surface. Quantities of Interest (QOI) such as remaining tracer in the repository and fluxes across the domain were compared. Technical and time constraints led some teams to exclude parts of the engineered barrier system which resulted in faster release of tracers and radionuclides from the repository region. Comparing all models highlighted the importance of explicitly including drifts, buffer, and backfill in the reference case models. The results also emphasize the utility of a diverse set of modeling approaches in building confidence with performance assessment analysis.
{"title":"Comparison of performance assessment models and methods in crystalline rock: Task F1 DECOVALEX-2023","authors":"Rosie C. Leone , Paul E. Mariner , Emily R. Stein , Jeffrey D. Hyman , Jan Thiedau , Carlos R. Guevara Morel , Zhenze Li , Son Nguyen , Yong-Min Kim , Jung-Woo Kim , Chieh-Chun Chang , Ondrej Mikláš , Nicholas I. Osuji , Auli Niemi","doi":"10.1016/j.gete.2024.100629","DOIUrl":"10.1016/j.gete.2024.100629","url":null,"abstract":"<div><div>Performance Assessment (PA) is important in ensuring the isolation and long-term containment of spent nuclear fuel from the geosphere. It plays a crucial role in evaluating the long-term safety and effectiveness of underground nuclear waste storage, considering factors such as radionuclide release rates, transport mechanisms, and the performance of engineered barriers. This paper presents the findings of DECOVALEX 2023 Task F, which aimed to compare various models and conceptual approaches used in PA of a generic deep geologic repository in crystalline rock. The objective was to explore the contribution of modeling choices to uncertainty in PA model outputs. The study highlights the importance of characterizing the crystalline rock properties and the engineered barrier system in PA. The so-called reference case, a simplified version of a PA focused on the transport of two conservative tracers from the deposition hole to the surface, neglecting waste package performance was used as an example. Seven international teams (Canada, Czech Republic, Germany, Korea, Sweden, Taiwan, and United States) developed and simulated the generic reference case, tracking tracer releases from waste package locations to the near field and ground surface. Quantities of Interest (QOI) such as remaining tracer in the repository and fluxes across the domain were compared. Technical and time constraints led some teams to exclude parts of the engineered barrier system which resulted in faster release of tracers and radionuclides from the repository region. Comparing all models highlighted the importance of explicitly including drifts, buffer, and backfill in the reference case models. The results also emphasize the utility of a diverse set of modeling approaches in building confidence with performance assessment analysis.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100629"},"PeriodicalIF":3.3,"publicationDate":"2024-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-12-20DOI: 10.1016/j.gete.2024.100616
Olaf Kolditz , Christopher McDermott , Jeoung Seok Yoon , Mostafa Mollaali , Wenqing Wang , Mengsu Hu , Tsubasa Sasaki , Jonny Rutqvist , Jens Birkholzer , Jung-Wook Park , Chan-Hee Park , Hejuan Liu , Peng–Zhi Pan , Thomas Nagel , Son Nguyen , Saeha Kwon , Changsoo Lee , Kwang-Il Kim , Bond Alexander , Teklu Hadgu , Andrew Fraser-Harris
The paper presents the key findings of Task G SAFENET of the DECOVALEX 2023 project “Safety Assessment of Fluid Flow, Shear, Thermal and Reaction Processes within Crystalline Rock Fracture NETworks”. It utilizes a systematic and experimental approach to numerically simulate mechanical (M), hydro-mechanical (HM), and thermo-mechanical (TM) fracture processes in brittle rocks. The Task team introduced, applied, and compared a wide range of numerical methods, including both continuum and discontinuum methods, for simulating related fracture processes. Task G is based on three key experiments: the Freiberg, GREAT cell, and KICT experiments, which analyze M, HM, and TM processes respectively. Classic HM and THM benchmark exercises serve as a common basis by using analytical solutions for a plane line discontinuity in a poro-elastic medium (Sneddon and Lowengrub, 1969) and a point heat source in a thermo-poro-elastic medium (Booker and Savvidou, 1985), (Chaudhry et al., 2019). These solutions also serve as a reference for rough fractures and simple fracture networks. A systematic set of new benchmark cases has been derived based on the GREAT cell experiments. An analysis of the constant normal load (CNL) experiment has been conducted using micro- and macroscopic approaches, based on the Freiberg experiment. The GREAT cell experiments provided a database for evaluating the mechanical and hydro-mechanical responses of various rock samples (resin, greywacke, gneis) in triaxial tests with a rotational stress field. Fracture permeability was determined as a function of normal stresses in the rotational stress field. The KICT experiments were used to investigate thermally induced shear slip and dilation processes. The SAFENET Task contributed to the Open Science concept in DECOVALEX by providing a freely accessible Jupyter notebooks for selected benchmark exercises.
{"title":"A systematic model- and experimental approach to hydro-mechanical and thermo-mechanical fracture processes in crystalline rocks","authors":"Olaf Kolditz , Christopher McDermott , Jeoung Seok Yoon , Mostafa Mollaali , Wenqing Wang , Mengsu Hu , Tsubasa Sasaki , Jonny Rutqvist , Jens Birkholzer , Jung-Wook Park , Chan-Hee Park , Hejuan Liu , Peng–Zhi Pan , Thomas Nagel , Son Nguyen , Saeha Kwon , Changsoo Lee , Kwang-Il Kim , Bond Alexander , Teklu Hadgu , Andrew Fraser-Harris","doi":"10.1016/j.gete.2024.100616","DOIUrl":"10.1016/j.gete.2024.100616","url":null,"abstract":"<div><div>The paper presents the key findings of Task G SAFENET of the DECOVALEX 2023 project “Safety Assessment of Fluid Flow, Shear, Thermal and Reaction Processes within Crystalline Rock Fracture NETworks”. It utilizes a systematic and experimental approach to numerically simulate mechanical (M), hydro-mechanical (HM), and thermo-mechanical (TM) fracture processes in brittle rocks. The Task team introduced, applied, and compared a wide range of numerical methods, including both continuum and discontinuum methods, for simulating related fracture processes. Task G is based on three key experiments: the Freiberg, GREAT cell, and KICT experiments, which analyze M, HM, and TM processes respectively. Classic HM and THM benchmark exercises serve as a common basis by using analytical solutions for a plane line discontinuity in a poro-elastic medium (Sneddon and Lowengrub, 1969) and a point heat source in a thermo-poro-elastic medium (Booker and Savvidou, 1985), (Chaudhry et al., 2019). These solutions also serve as a reference for rough fractures and simple fracture networks. A systematic set of new benchmark cases has been derived based on the GREAT cell experiments. An analysis of the constant normal load (CNL) experiment has been conducted using micro- and macroscopic approaches, based on the Freiberg experiment. The GREAT cell experiments provided a database for evaluating the mechanical and hydro-mechanical responses of various rock samples (resin, greywacke, gneis) in triaxial tests with a rotational stress field. Fracture permeability was determined as a function of normal stresses in the rotational stress field. The KICT experiments were used to investigate thermally induced shear slip and dilation processes. The SAFENET Task contributed to the Open Science concept in DECOVALEX by providing a freely accessible Jupyter notebooks for selected benchmark exercises.</div></div>","PeriodicalId":56008,"journal":{"name":"Geomechanics for Energy and the Environment","volume":"41 ","pages":"Article 100616"},"PeriodicalIF":3.3,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143132786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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