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Sheng-qi Yang - One of the best experts on this subject based on the ideXlab platform.
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Discrete element simulation on Failure Mechanical behavior of transversely isotropic rocks under different confining pressures
Arabian Journal of Geosciences, 2019Co-Authors: Peng-fei Yin, Sheng-qi Yang, Wen Ling Tian, Jian-long ChengAbstract:A large number of experimental investigations on anisotropic behavior of transversely isotropic rock have been conducted recently, and the strength and deformation anisotropy and macroscopic Failure behavior and Failure mechanism were studied in detail. However, the internal variation and microscopic Failure mechanism of transversely isotropic rock have been rarely determined by laboratory tests, and few studies have reported these types of results. This paper presents an investigation of particle flow code in 2 dimensions (PFC2D) simulation on transversely isotropic rock under different confining pressures based on laboratory experiments. The transversely isotropic PFC2D model is established by the bonded-particle model (BPM) and the smooth-joint model (SJ) to represent the layer materials and weak planes, respectively. To reflect the experimental specimens accurately, BPM and SJ microparameters are calibrated first. The simulated strength and deformation anisotropy of transversely isotropic rock under different confining pressures are all consistent with the experimental specimens and can reflect the macroscopic Failure behavior and Failure mechanism of experimental specimens very well. On a microscopic level, the internal variation and microscopic Failure mechanisms of transversely isotropic rock are studied in detail, and four types of microcracks, namely PB tensile cracks and PB shear cracks, which exist in the layer materials, and SJ tensile cracks and SJ shear cracks, which exist in the weak planes, are recorded and counted to reveal the microscopic Failure mechanisms of transversely isotropic rock at different orientation angles. The evolution processes of microcracks and PB forces are also analyzed to investigate internal variations during the Failure of transversely isotropic rock under different confining pressures.
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Failure Mechanical behavior of pre holed granite specimens after elevated temperature treatment by particle flow code
Geothermics, 2018Co-Authors: Sheng-qi Yang, Wen Ling Tian, Yan-hua HuangAbstract:Abstract Granite material, as an excellent medium for deep geological disposal rock projects may be affected by high temperature and macro-porosity. However, there are limited experiments and numerical simulations that have been adopted to investigate the Failure mechanism of granite specimens that contain pre-existing holes after high temperature treatment. As such, the cluster model in PFC 2D was used to explore the meso -mechanics of granite specimens containing pre-existing holes with different ligament angles (the angle between the line connecting the centers of two holes and the horizontal direction, and set as β = 0, 45 and 90°) after different temperature treatments (T = 25, 150, 300, 450, 600, 750 and 900 °C). The different mineral grains in the granite specimen were simulated by the cluster model with different linear thermal expansion coefficients. The phase transition is treated as a radius expansion with 1.0046 of quartz cluster. The results show that the numerical simulation method is reasonable and the numerical results show good consistency with experimental results. The Mechanical property curves can be divided into three phases, where the distribution of micro-cracks in a specimen has more scatter and fail more seriously with increasing temperature. The ligament angle has a significant effect on the crack evolution of a specimen. It was observed that more new micro-cracks with a scattered distribution existed in the high temperature treated specimen because the tensile force is concentrated at the temperature induced cracks. The ligament concentrates with compression in the H-model ( β = 0°) specimen, and concentrates with shear stress in the D-model ( β = 45°) specimen, while the ligament has almost no force concentration in the V-model ( β = 90°) specimen. The first crack coalesced with holes as a shear crack regardless of the ligament angle, and the maximum values of shear stress decrease with increasing temperature.
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Failure Mechanical and acoustic behavior of brine saturated-sandstone containing two pre-existing flaws under different confining pressures
Engineering Fracture Mechanics, 2018Co-Authors: Sheng-qi Yang, Yan-hua Huang, Pathegama Gamage RanjithAbstract:Abstract To better understand the Mechanical, acoustic and Failure behaviors of sandstone in deep saline aquifers, conventional triaxial compression tests were carried out on sandstone specimens containing two pre-existing three-dimensional (3D) flaws. First, pre-flawed sandstone specimens were saturated under NaCl solution with a salinity of 20 wt%. Then both dry and brine-saturated sandstone specimens were loaded under triaxial compression. As the flaw angle increased, the peak strength and crack damage stress of the dry and saturated pre-flawed sandstone specimens increased. The peak strength and crack damage stress of dry specimens increased linearly, while those of brine-saturated specimens increased nonlinearly with confining pressure. During triaxial loading, P-wave and AE signals were monitored in real-time for the sandstone specimens. The evolution of P-wave velocity and AE events can be characterized as having five stages based on the internal damage of sandstone specimens. In general, the accumulated AE count can be summarized as follows: very few or no AE counts, increases linearly, increases exponentially and increases stably. The P-wave velocity was also observed as: increases rapidly, increases stably, decreases unstably and keeps constant. Finally, by using X-ray micro CT observations, two crack coalescence modes between the two pre-existing flaws were identified, i.e., shear crack coalescence in the ligament region and indirect coalescence outside the ligament region. The second coalescence mode was only observed in the sandstone specimen with a flaw angle of 45° under low confining pressures. The internal opaque cracks were clearly displayed in the reconstruction images as a curved surface.
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Failure Mechanical behavior of Australian Strathbogie granite at high temperatures: Insights from particle flow modeling
Energies, 2017Co-Authors: Sheng-qi Yang, Wen Ling Tian, Pathegama Gamage RanjithAbstract:Thermally induced damage has an important influence on rock mechanics and engineering, especially for high-level radioactive waste repositories, geological carbon storage, underground coal gasification, and hydrothermal systems. Additionally, the wide application of geothermal heat requires knowledge of the geothermal conditions of reservoir rocks at elevated temperature. However, few methods to date have been reported for investigating the micro-mechanics of specimens at elevated temperatures. Therefore, this paper uses a cluster model in particle flow code in two dimensions (PFC2D) to simulate the uniaxial compressive testing of Australian Strathbogie granite at various elevated temperatures. The peak strength and ultimate Failure mode of the granite specimens at different elevated temperatures obtained by the numerical methods are consistent with those obtained by experimentation. Since the tensile force is always concentrated around the boundary of the crystal, cracks easily occur at the intergranular contacts, especially between the b-b and b-k boundaries where less intragranular contact is observed. The intergranular and intragranular cracking of the specimens is almost constant with increasing temperature at low temperature, and then it rapidly and linearly increases. However, the inflection point of intergranular micro-cracking is less than that of intragranular cracking. Intergranular cracking is more easily induced by a high temperature than intragranular cracking. At an elevated temperature, the cumulative micro-crack counts curve propagates in a stable way during the active period, and it has no unstable crack propagation stage. The micro-cracks and parallel bond forces in the specimens with elevated temperature evolution and axial strain have different characteristics than those at lower temperature. More branch fractures and isolated wider micro-cracks are generated with increasing temperature when the temperature is over 400 °C. Therefore, the total number of cracks is almost constant when the temperature is below 400 °C; next, it linearly increases when the temperature is over 400 °C. This trend is the same as that observed by experimentation.
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An experimental study on deformation and Failure Mechanical behavior of granite containing a single fissure under different confining pressures
Environmental Earth Sciences, 2017Co-Authors: Sheng-qi Yang, Yan-hua HuangAbstract:Fissures in natural rocks play an important role in determining the strength, deformability and Failure behavior of rock mass. However in the past, triaxial compression experiments have rarely been conducted for rock materials containing three-dimensional (3-D) fissures and the Failure Mechanical behavior of fissured rocks is not well known due to the difficulty of conducting triaxial experiments on fissured rocks. Therefore in this research, conventional triaxial compression experiments were performed to study the strength, deformability and Failure behavior of granite specimens with one preexisting open fissure. Thirty-one specimens were prepared to perform conventional triaxial compression tests for intact and fissured granite. First, based on the experimental results, the effects of the confining pressure and the fissure angle on the elastic modulus and the peak axial strain of granite specimens are analyzed. Second, the influence of the confining pressure on the crack damage threshold and the peak strength of granite with respect to various fissure angles are evaluated. For the same fissure angle, the crack damage threshold and the peak strength of granite both increase with the confining pressure, which is in good agreement with the linear Mohr–Coulomb criterion. With increasing fissure angle, the cohesion of granite first increases and later decreases, but the internal friction angle is not obviously dependent on the fissure angle. Third, nine crack types are identified to analyze the Failure characteristics of granite specimens containing a single fissure under conventional triaxial compression. Finally, a series of X-ray microcomputed tomography (CT) observations were conducted to analyze the internal damage mechanism of granite specimens with respect to various fissure angles. Reconstructed 3-D CT images indicate obvious effects of confining pressure and fissure angle on the crack system of granite specimens. The study helps to elucidate the fundamental nature of rock Failure under conventional triaxial compression.
Yan-hua Huang - One of the best experts on this subject based on the ideXlab platform.
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Failure Mechanical behavior of pre holed granite specimens after elevated temperature treatment by particle flow code
Geothermics, 2018Co-Authors: Sheng-qi Yang, Wen Ling Tian, Yan-hua HuangAbstract:Abstract Granite material, as an excellent medium for deep geological disposal rock projects may be affected by high temperature and macro-porosity. However, there are limited experiments and numerical simulations that have been adopted to investigate the Failure mechanism of granite specimens that contain pre-existing holes after high temperature treatment. As such, the cluster model in PFC 2D was used to explore the meso -mechanics of granite specimens containing pre-existing holes with different ligament angles (the angle between the line connecting the centers of two holes and the horizontal direction, and set as β = 0, 45 and 90°) after different temperature treatments (T = 25, 150, 300, 450, 600, 750 and 900 °C). The different mineral grains in the granite specimen were simulated by the cluster model with different linear thermal expansion coefficients. The phase transition is treated as a radius expansion with 1.0046 of quartz cluster. The results show that the numerical simulation method is reasonable and the numerical results show good consistency with experimental results. The Mechanical property curves can be divided into three phases, where the distribution of micro-cracks in a specimen has more scatter and fail more seriously with increasing temperature. The ligament angle has a significant effect on the crack evolution of a specimen. It was observed that more new micro-cracks with a scattered distribution existed in the high temperature treated specimen because the tensile force is concentrated at the temperature induced cracks. The ligament concentrates with compression in the H-model ( β = 0°) specimen, and concentrates with shear stress in the D-model ( β = 45°) specimen, while the ligament has almost no force concentration in the V-model ( β = 90°) specimen. The first crack coalesced with holes as a shear crack regardless of the ligament angle, and the maximum values of shear stress decrease with increasing temperature.
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Failure Mechanical and acoustic behavior of brine saturated-sandstone containing two pre-existing flaws under different confining pressures
Engineering Fracture Mechanics, 2018Co-Authors: Sheng-qi Yang, Yan-hua Huang, Pathegama Gamage RanjithAbstract:Abstract To better understand the Mechanical, acoustic and Failure behaviors of sandstone in deep saline aquifers, conventional triaxial compression tests were carried out on sandstone specimens containing two pre-existing three-dimensional (3D) flaws. First, pre-flawed sandstone specimens were saturated under NaCl solution with a salinity of 20 wt%. Then both dry and brine-saturated sandstone specimens were loaded under triaxial compression. As the flaw angle increased, the peak strength and crack damage stress of the dry and saturated pre-flawed sandstone specimens increased. The peak strength and crack damage stress of dry specimens increased linearly, while those of brine-saturated specimens increased nonlinearly with confining pressure. During triaxial loading, P-wave and AE signals were monitored in real-time for the sandstone specimens. The evolution of P-wave velocity and AE events can be characterized as having five stages based on the internal damage of sandstone specimens. In general, the accumulated AE count can be summarized as follows: very few or no AE counts, increases linearly, increases exponentially and increases stably. The P-wave velocity was also observed as: increases rapidly, increases stably, decreases unstably and keeps constant. Finally, by using X-ray micro CT observations, two crack coalescence modes between the two pre-existing flaws were identified, i.e., shear crack coalescence in the ligament region and indirect coalescence outside the ligament region. The second coalescence mode was only observed in the sandstone specimen with a flaw angle of 45° under low confining pressures. The internal opaque cracks were clearly displayed in the reconstruction images as a curved surface.
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An experimental study on deformation and Failure Mechanical behavior of granite containing a single fissure under different confining pressures
Environmental Earth Sciences, 2017Co-Authors: Sheng-qi Yang, Yan-hua HuangAbstract:Fissures in natural rocks play an important role in determining the strength, deformability and Failure behavior of rock mass. However in the past, triaxial compression experiments have rarely been conducted for rock materials containing three-dimensional (3-D) fissures and the Failure Mechanical behavior of fissured rocks is not well known due to the difficulty of conducting triaxial experiments on fissured rocks. Therefore in this research, conventional triaxial compression experiments were performed to study the strength, deformability and Failure behavior of granite specimens with one preexisting open fissure. Thirty-one specimens were prepared to perform conventional triaxial compression tests for intact and fissured granite. First, based on the experimental results, the effects of the confining pressure and the fissure angle on the elastic modulus and the peak axial strain of granite specimens are analyzed. Second, the influence of the confining pressure on the crack damage threshold and the peak strength of granite with respect to various fissure angles are evaluated. For the same fissure angle, the crack damage threshold and the peak strength of granite both increase with the confining pressure, which is in good agreement with the linear Mohr–Coulomb criterion. With increasing fissure angle, the cohesion of granite first increases and later decreases, but the internal friction angle is not obviously dependent on the fissure angle. Third, nine crack types are identified to analyze the Failure characteristics of granite specimens containing a single fissure under conventional triaxial compression. Finally, a series of X-ray microcomputed tomography (CT) observations were conducted to analyze the internal damage mechanism of granite specimens with respect to various fissure angles. Reconstructed 3-D CT images indicate obvious effects of confining pressure and fissure angle on the crack system of granite specimens. The study helps to elucidate the fundamental nature of rock Failure under conventional triaxial compression.
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Three-Dimensional Numerical Simulation on Triaxial Failure Mechanical Behavior of Rock-Like Specimen Containing Two Unparallel Fissures
Rock Mechanics and Rock Engineering, 2016Co-Authors: Yan-hua Huang, Sheng-qi Yang, Jian ZhaoAbstract:A three-dimensional particle flow code (PFC3D) was used for a systematic numerical simulation of the strength Failure and cracking behavior of rock-like material specimens containing two unparallel fissures under conventional triaxial compression. The micro-parameters of the parallel bond model were first calibrated using the laboratory results of intact specimens and then validated from the experimental results of pre-fissured specimens under triaxial compression. Numerically simulated stress–strain curves, strength and deformation parameters and macro-Failure modes of pre-fissured specimens were all in good agreement with the experimental results. The relationship between stress and the micro-crack numbers was summarized. Crack initiation, propagation and coalescence process of pre-fissured specimens were analyzed in detail. Finally, horizontal and vertical cross sections of numerical specimens were derived from PFC3D. A detailed analysis to reveal the internal damage behavior of rock under triaxial compression was carried out. The experimental and simulated results are expected to improve the understanding of the strength Failure and cracking behavior of fractured rock under triaxial compression.
Wen Ling Tian - One of the best experts on this subject based on the ideXlab platform.
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Discrete element simulation on Failure Mechanical behavior of transversely isotropic rocks under different confining pressures
Arabian Journal of Geosciences, 2019Co-Authors: Peng-fei Yin, Sheng-qi Yang, Wen Ling Tian, Jian-long ChengAbstract:A large number of experimental investigations on anisotropic behavior of transversely isotropic rock have been conducted recently, and the strength and deformation anisotropy and macroscopic Failure behavior and Failure mechanism were studied in detail. However, the internal variation and microscopic Failure mechanism of transversely isotropic rock have been rarely determined by laboratory tests, and few studies have reported these types of results. This paper presents an investigation of particle flow code in 2 dimensions (PFC2D) simulation on transversely isotropic rock under different confining pressures based on laboratory experiments. The transversely isotropic PFC2D model is established by the bonded-particle model (BPM) and the smooth-joint model (SJ) to represent the layer materials and weak planes, respectively. To reflect the experimental specimens accurately, BPM and SJ microparameters are calibrated first. The simulated strength and deformation anisotropy of transversely isotropic rock under different confining pressures are all consistent with the experimental specimens and can reflect the macroscopic Failure behavior and Failure mechanism of experimental specimens very well. On a microscopic level, the internal variation and microscopic Failure mechanisms of transversely isotropic rock are studied in detail, and four types of microcracks, namely PB tensile cracks and PB shear cracks, which exist in the layer materials, and SJ tensile cracks and SJ shear cracks, which exist in the weak planes, are recorded and counted to reveal the microscopic Failure mechanisms of transversely isotropic rock at different orientation angles. The evolution processes of microcracks and PB forces are also analyzed to investigate internal variations during the Failure of transversely isotropic rock under different confining pressures.
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Failure Mechanical behavior of pre holed granite specimens after elevated temperature treatment by particle flow code
Geothermics, 2018Co-Authors: Sheng-qi Yang, Wen Ling Tian, Yan-hua HuangAbstract:Abstract Granite material, as an excellent medium for deep geological disposal rock projects may be affected by high temperature and macro-porosity. However, there are limited experiments and numerical simulations that have been adopted to investigate the Failure mechanism of granite specimens that contain pre-existing holes after high temperature treatment. As such, the cluster model in PFC 2D was used to explore the meso -mechanics of granite specimens containing pre-existing holes with different ligament angles (the angle between the line connecting the centers of two holes and the horizontal direction, and set as β = 0, 45 and 90°) after different temperature treatments (T = 25, 150, 300, 450, 600, 750 and 900 °C). The different mineral grains in the granite specimen were simulated by the cluster model with different linear thermal expansion coefficients. The phase transition is treated as a radius expansion with 1.0046 of quartz cluster. The results show that the numerical simulation method is reasonable and the numerical results show good consistency with experimental results. The Mechanical property curves can be divided into three phases, where the distribution of micro-cracks in a specimen has more scatter and fail more seriously with increasing temperature. The ligament angle has a significant effect on the crack evolution of a specimen. It was observed that more new micro-cracks with a scattered distribution existed in the high temperature treated specimen because the tensile force is concentrated at the temperature induced cracks. The ligament concentrates with compression in the H-model ( β = 0°) specimen, and concentrates with shear stress in the D-model ( β = 45°) specimen, while the ligament has almost no force concentration in the V-model ( β = 90°) specimen. The first crack coalesced with holes as a shear crack regardless of the ligament angle, and the maximum values of shear stress decrease with increasing temperature.
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Failure Mechanical behavior of Australian Strathbogie granite at high temperatures: Insights from particle flow modeling
Energies, 2017Co-Authors: Sheng-qi Yang, Wen Ling Tian, Pathegama Gamage RanjithAbstract:Thermally induced damage has an important influence on rock mechanics and engineering, especially for high-level radioactive waste repositories, geological carbon storage, underground coal gasification, and hydrothermal systems. Additionally, the wide application of geothermal heat requires knowledge of the geothermal conditions of reservoir rocks at elevated temperature. However, few methods to date have been reported for investigating the micro-mechanics of specimens at elevated temperatures. Therefore, this paper uses a cluster model in particle flow code in two dimensions (PFC2D) to simulate the uniaxial compressive testing of Australian Strathbogie granite at various elevated temperatures. The peak strength and ultimate Failure mode of the granite specimens at different elevated temperatures obtained by the numerical methods are consistent with those obtained by experimentation. Since the tensile force is always concentrated around the boundary of the crystal, cracks easily occur at the intergranular contacts, especially between the b-b and b-k boundaries where less intragranular contact is observed. The intergranular and intragranular cracking of the specimens is almost constant with increasing temperature at low temperature, and then it rapidly and linearly increases. However, the inflection point of intergranular micro-cracking is less than that of intragranular cracking. Intergranular cracking is more easily induced by a high temperature than intragranular cracking. At an elevated temperature, the cumulative micro-crack counts curve propagates in a stable way during the active period, and it has no unstable crack propagation stage. The micro-cracks and parallel bond forces in the specimens with elevated temperature evolution and axial strain have different characteristics than those at lower temperature. More branch fractures and isolated wider micro-cracks are generated with increasing temperature when the temperature is over 400 °C. Therefore, the total number of cracks is almost constant when the temperature is below 400 °C; next, it linearly increases when the temperature is over 400 °C. This trend is the same as that observed by experimentation.
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an experimental investigation on thermal damage and Failure Mechanical behavior of granite after exposure to different high temperature treatments
Geothermics, 2017Co-Authors: Sheng-qi Yang, P G Ranjith, Hong Wen Jing, Wen Ling TianAbstract:Abstract A detailed understanding of the thermal damage and Failure Mechanical behavior of granite at elevated temperatures is a key concern in nuclear waste disposal engineering, underground coal gasification, and heat mining in enhanced geothermal energy. In this research, uniaxial compression tests were first carried out to evaluate the effect of high temperature treatments (200, 300, 400, 500, 600, 700 and 800 °C) on the crack damage, strength and deformation Failure behavior of a granite. The results demonstrated that, in all cases, the crack damage threshold, the strength and static elastic modulus of granite were increased at 300 °C, before decreasing up to our maximum temperature of 800 °C. However, the static Poisson’s ratio of granite first decreased at 600 °C, and then increased rapidly with the temperature. The crack damage and peak axial strain always showed an increase when the temperature was increased. However, the dynamic elastic modulus decreased with the temperature, whereas the dynamic Poisson’s ratio did not depend on the temperature. The gradual increase of temperature results in a more ductile Failure of granite. Next, the thermal damage mechanism of uncompressed granite was analyzed by optical microscopic observation. At T = 25–300 °C, the mechanisms were favored by the thermal expansion of mineral grains but no microcracks were observed; at T = 400–600 °C, the mechanisms were contributed by boundary cracks and transgranular cracks in feldspar and quartz grains; and at T = 700–800 °C, the mechanisms were associated with the coalescence of boundary cracks and transgranular cracks. The internal crack evolution process was then monitored during deformation using acoustic emission (AE) monitoring. The results showed that the cracking process of granite depended on the heat treatment temperature. Finally, the deformation mechanism of failed granite at various temperatures was analyzed using X-ray micro CT. During loading, the uniaxial compression stress direction dominated the more brittle fracture process of granite at T = 25–600 °C, which led to splitting tensile main cracks induced along the axial stress, and thermal damage determined the larger ductile fracture process of granite at T = 700–800 °C, which resulted in a more ductile deformation after the peak strength.
Okechukwu Ojogho - One of the best experts on this subject based on the ideXlab platform.
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Pancreaticoduodenectomy in a patient with previous left ventricular assist device: a case report with specific emphasis on peri-operative logistics.
Journal of surgical case reports, 2017Co-Authors: Juan C. Mejia, Mei Dong, Okechukwu OjoghoAbstract:To the best of our knowledge this is the first case of this nature described in the literature. Sharing the authors experience with this case, particularly the technical challenges and post-operative management may aid other physicians facing similar scenarios. In this report, we describe a pancreaticoduodenectomy for pancreatic adenocarcinoma in a patient with a previous left ventricular assist device (LVAD). A multidisciplinary approach, particularly close involvement of the advanced heart Failure, Mechanical heart and pancreas surgery teams was key to the success of this case. Major abdominal surgery in the setting of previous LVAD should be considered carefully, however, the LVAD should not be generalized as an absolute contraindication.
Pathegama Gamage Ranjith - One of the best experts on this subject based on the ideXlab platform.
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Failure Mechanical and acoustic behavior of brine saturated-sandstone containing two pre-existing flaws under different confining pressures
Engineering Fracture Mechanics, 2018Co-Authors: Sheng-qi Yang, Yan-hua Huang, Pathegama Gamage RanjithAbstract:Abstract To better understand the Mechanical, acoustic and Failure behaviors of sandstone in deep saline aquifers, conventional triaxial compression tests were carried out on sandstone specimens containing two pre-existing three-dimensional (3D) flaws. First, pre-flawed sandstone specimens were saturated under NaCl solution with a salinity of 20 wt%. Then both dry and brine-saturated sandstone specimens were loaded under triaxial compression. As the flaw angle increased, the peak strength and crack damage stress of the dry and saturated pre-flawed sandstone specimens increased. The peak strength and crack damage stress of dry specimens increased linearly, while those of brine-saturated specimens increased nonlinearly with confining pressure. During triaxial loading, P-wave and AE signals were monitored in real-time for the sandstone specimens. The evolution of P-wave velocity and AE events can be characterized as having five stages based on the internal damage of sandstone specimens. In general, the accumulated AE count can be summarized as follows: very few or no AE counts, increases linearly, increases exponentially and increases stably. The P-wave velocity was also observed as: increases rapidly, increases stably, decreases unstably and keeps constant. Finally, by using X-ray micro CT observations, two crack coalescence modes between the two pre-existing flaws were identified, i.e., shear crack coalescence in the ligament region and indirect coalescence outside the ligament region. The second coalescence mode was only observed in the sandstone specimen with a flaw angle of 45° under low confining pressures. The internal opaque cracks were clearly displayed in the reconstruction images as a curved surface.
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Failure Mechanical behavior of Australian Strathbogie granite at high temperatures: Insights from particle flow modeling
Energies, 2017Co-Authors: Sheng-qi Yang, Wen Ling Tian, Pathegama Gamage RanjithAbstract:Thermally induced damage has an important influence on rock mechanics and engineering, especially for high-level radioactive waste repositories, geological carbon storage, underground coal gasification, and hydrothermal systems. Additionally, the wide application of geothermal heat requires knowledge of the geothermal conditions of reservoir rocks at elevated temperature. However, few methods to date have been reported for investigating the micro-mechanics of specimens at elevated temperatures. Therefore, this paper uses a cluster model in particle flow code in two dimensions (PFC2D) to simulate the uniaxial compressive testing of Australian Strathbogie granite at various elevated temperatures. The peak strength and ultimate Failure mode of the granite specimens at different elevated temperatures obtained by the numerical methods are consistent with those obtained by experimentation. Since the tensile force is always concentrated around the boundary of the crystal, cracks easily occur at the intergranular contacts, especially between the b-b and b-k boundaries where less intragranular contact is observed. The intergranular and intragranular cracking of the specimens is almost constant with increasing temperature at low temperature, and then it rapidly and linearly increases. However, the inflection point of intergranular micro-cracking is less than that of intragranular cracking. Intergranular cracking is more easily induced by a high temperature than intragranular cracking. At an elevated temperature, the cumulative micro-crack counts curve propagates in a stable way during the active period, and it has no unstable crack propagation stage. The micro-cracks and parallel bond forces in the specimens with elevated temperature evolution and axial strain have different characteristics than those at lower temperature. More branch fractures and isolated wider micro-cracks are generated with increasing temperature when the temperature is over 400 °C. Therefore, the total number of cracks is almost constant when the temperature is below 400 °C; next, it linearly increases when the temperature is over 400 °C. This trend is the same as that observed by experimentation.
