The Experts below are selected from a list of 33255 Experts worldwide ranked by ideXlab platform
Ling-ling Zeng - One of the best experts on this subject based on the ideXlab platform.
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State of compacted bentonite inside a Fractured granite cylinder after infiltration
Applied Clay Science, 2020Co-Authors: Xia Bian, Yu-jun Cui, Ling-ling ZengAbstract:A small-scale mock-up test was carried out on a Fractured hollow granite cylinder with compacted MX80 bentonite inside, to study the interaction between engineered barrier (compacted bentonite) and natural barrier (host Rock with the presence of Rock Fracture). The swelling pressure and relative humidity of bentonite were monitored with respect to the position of the Rock Fracture during 349 days of infiltration. Herein, the variation of water content, dry density, suction and microstructure along bentonite column after dismantling were reported, focusing on the changes in the vicinity of the Rock Fracture, to evaluate the effect of the Rock Fracture on the swelling behaviour of compacted bentonite. Results showed that the presence of Rock Fracture disturbed the water content distribution, with a lower water content at a position closer to the Fracture. A significant decrease in dry density was also observed in the vicinity of the Rock Fracture; the closer the positions to the Fracture the larger the decrease of dry density. This decrease coincided with the reduction of swelling pressure recorded by the pressure sensors, suggesting the occurrence of Rock Fracture filling-up by bentonite. Further examination showed that when the soil suction was higher than 9 MPa, the decrease in dry density in the near field of Rock Fracture was mainly attributable to the increase in large pore porosity (>2 μm). This suggests that at this suction the mechanism involving intrusion of bentonite into the Rock Fracture with Fracture width higher than the size of bentonite gains was related to the pushing effect under the swelling of bentonite behind. By contrast, when the suction became lower than 9 MPa, the bentonite gel formed from the exfoliation of clay particles might fill up the Rock Fracture with smaller aperture width.
Le Zhang - One of the best experts on this subject based on the ideXlab platform.
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experimental study of convective heat transfer of carbon dioxide at supercritical pressures in a horizontal Rock Fracture and its application to enhanced geothermal systems
Applied Thermal Engineering, 2017Co-Authors: Peixue Jiang, Le ZhangAbstract:Abstract Enhanced geothermal systems create Fractured reservoirs to extract economic quantities of heat from low-permeability and/or low-porosity geothermal resources. Convective heat transfer characteristics of fluids at supercritical pressures in Rock Fractures are important for optimizing the heat transfer model, which is a key tool for simulating heat extraction and improving the heat recovery factor for such projects. This paper presents the results of experimental investigations of laminar convective heat transfer of CO 2 at supercritical pressures in a horizontal Fracture with an aperture of 0.2 mm. The laboratory apparatus operated at temperatures up to 280 °C, fluid pressures up to 14 MPa, and confining pressures up to 28 MPa. The effects of mass flow rate and initial Rock temperature on the Rock wall and fluid temperatures were examined. A method was proposed for processing the experimental data and local heat transfer performance in the Fracture was obtained. Considering the effects of variations in thermophysical properties, a correlation of heat transfer performance in the Rock Fracture was proposed to improve field simulation models for enhanced geothermal systems.
Katriona Edlmann - One of the best experts on this subject based on the ideXlab platform.
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Modelling Rock Fracture Induced By Hydraulic Pulses
Rock Mechanics and Rock Engineering, 2021Co-Authors: Shangtong Yang, Christopher I. Mcdermott, Zoe K. Shipton, Andrew Fraser-harris, Katriona EdlmannAbstract:Soft cyclic hydraulic fracturing has become an effective technology used in subsurface energy extraction which utilises cyclic hydraulic flow pressure to Fracture Rock. This new technique induces fatigue of Rock to reduce the breakdown pressure and potentially the associated risk of seismicity. To control the fracturing process and achieve desirable Fracture networks for enhanced permeability, the Rock response under cyclic hydraulic stimulation needs to be understood. However, the mechanism for cyclic stimulation-induced fatigue of Rock is rather unclear and to date there is no implementation of fatigue degradation in modelling the Rock response under hydraulic cyclic loading. This makes accurate prediction of Rock Fracture under cyclic hydraulic pressure impossible. This paper develops a numerical method to model Rock Fracture induced by hydraulic pulses with consideration of Rock fatigue. The fatigue degradation is based on S–N curves ( S for cyclic stress and N for cycles to failure) and implemented into the constitutive relationship for Fracture of Rock using in-house FORTRAN scripts and ABAQUS solver. The cohesive crack model is used to simulate discrete crack propagation in the Rock which is coupled with hydraulic flow and pore pressure capability. The developed numerical model is validated via experimental results of pulsating hydraulic fracturing of the Rock. The effects of flow rate and frequency of cyclic injection on borehole pressure development are investigated. A new loading strategy for pulsating hydraulic fracturing is proposed. It has been found that hydraulic pulses can reduce the breakdown pressure of Rock by 10–18% upon 10–4000 cycles. Using the new loading strategy, a slow and steady Rock Fracture process is obtained while the failure pressure is reduced.
Han H - One of the best experts on this subject based on the ideXlab platform.
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Combined finite-discrete element modelling of dynamic Rock Fracture and fragmentation during mining production process by blast
'Hindawi Limited', 2021Co-Authors: An H, Song Y, Liu H, Han HAbstract:A combined finite-discrete element method (FDEM) is proposed to model the dynamic Fracture, fragmentation, and resultant muck-piling process during mining production by blast in underground mine. The key component of the proposed method, that is, transition from continuum to discontinuum through Fracture and fragmentation, is introduced in detail, which makes the proposed method superior to the continuum-based finite element method and discontinuum-based discrete element method. The FDEM is calibrated by modelling the crater formation process by blast. The FDEM has well modelled the stress and Fracture propagation and resultant fragmentation process. In addition, the proposed method has well captured the crushed zone, cracked zone, and the radial long crack zone. After that, the FDEM is employed to model the dynamic Fracture and resultant fragmentation process by blast during sublevel caving process in an underground mine. Then the FDEM has well modelled the stress propagation process, as well as the Fracture initiation and fragmenting process. Finally, the effects of borehole spacing and initial gas pressure are discussed. It is concluded that the FDEM is a value numerical approach to study the dynamic Rock Fracture process by blast
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Hybrid finite-discrete element modelling of Rock Fracture process in intact and notched Brazilian disc tests
'Informa UK Limited', 2021Co-Authors: An H, Liu H, Han HAbstract:A hybrid finite–discrete element method is proposed to model the Rock Fracture behaviour under various loading rates. Three Fracture models are proposed to predict the Fracture initiation and propagation for modelling the transition from continuum to discontinuum. The modelling transition from continuum to discontinuum makes the hybrid method superior to the traditional continuum-based finite element method and discontinuum-based discrete element method. Moreover, the hybrid method considers the effect of the loading rate by implementing an empirical relationship between the static strengths and the dynamic strengths derived from the dynamic Rock Fracture experiments. Then, the Brazilian tensile strength tests are modelled to calibrate the proposed method under various loading rate, and demonstrate its ability in modelling the dynamic Rock behaviours. The Notched Brazilian Disc tests are modelled to illustrate the capabilities of the proposed method in modelling different Fracture modes. The hybrid finite element method has well modelled the stress propagation, Fracture initiation and propagation, even the pure mode I, pure mode II and mixed-mode I–II Fractures. It is concluded that the hybrid finite element method is superior to the continuum-based finite element method and discontinuum-based discrete element method in modelling the Fracture behaviours of Rock under various loading rates
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Combined finite-discrete element modelling of Rock Fracture and fragmentation induced by contour blasting during tunnelling with high horizontal in-situ stress
'Elsevier BV', 2020Co-Authors: Han H, Liu H, Fukuda D, Fathi Salmi E, Sellers E, Liu T, Chan AAbstract:A combined finite-discrete element method (FDEM) parallelized on the basis of GPGPU is implemented to model the Rock Fracture and fragmentation process and the resultant excavation damaged zone (EDZ) development induced by the controlled contour blasting, which was conducted in the TASQ tunnel with high in-situ stresses in the Äspö Hard Rock Laboratory in Sweden. The combination of in-situ stress field, equation-of-state based blast loading, fracturing in tension and shear with gas flow loading of Fractures enables the modelling of complex dynamic interactions from multiple blast rounds. For the contour blasting under high horizontal in-situ stresses, blasting-induced Fractures initially propagate horizontally, even though the holes are decoupled. Later, these Fractures coalesce into larger cracks, which prevents the formation of smooth tunnel walls and increases the EDZ. Smoother surfaces are created at the crown and invert by the propagation of long Fractures in the horizontal direction. Due to the combined effect of the free surfaces provided by the adjacent blast-holes and the maximum principal stress induced by in-situ stresses, the Fractures at the lower part of the tunnel sidewalls have the tendency to propagate upwards with a diagonal direction about 60° relative to vertical, in accordance with the field test results. Removing the in-situ stresses results in smoother sidewall fracturing with more damage in the crown and invert. Increase in Rock heterogeneity, above a threshold, induces more Fractures. Increasing the detonation timing between blast-holes induces more damage into the Rock mass and fragmentation in the burden. Outcomes of this study show that the GPGPU-parallelized Y-HFDEM IDE provides a powerful tool to replicate the mechanisms of Rock Fracture and fragmentation induced by blasting
Xia Bian - One of the best experts on this subject based on the ideXlab platform.
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State of compacted bentonite inside a Fractured granite cylinder after infiltration
Applied Clay Science, 2020Co-Authors: Xia Bian, Yu-jun Cui, Ling-ling ZengAbstract:A small-scale mock-up test was carried out on a Fractured hollow granite cylinder with compacted MX80 bentonite inside, to study the interaction between engineered barrier (compacted bentonite) and natural barrier (host Rock with the presence of Rock Fracture). The swelling pressure and relative humidity of bentonite were monitored with respect to the position of the Rock Fracture during 349 days of infiltration. Herein, the variation of water content, dry density, suction and microstructure along bentonite column after dismantling were reported, focusing on the changes in the vicinity of the Rock Fracture, to evaluate the effect of the Rock Fracture on the swelling behaviour of compacted bentonite. Results showed that the presence of Rock Fracture disturbed the water content distribution, with a lower water content at a position closer to the Fracture. A significant decrease in dry density was also observed in the vicinity of the Rock Fracture; the closer the positions to the Fracture the larger the decrease of dry density. This decrease coincided with the reduction of swelling pressure recorded by the pressure sensors, suggesting the occurrence of Rock Fracture filling-up by bentonite. Further examination showed that when the soil suction was higher than 9 MPa, the decrease in dry density in the near field of Rock Fracture was mainly attributable to the increase in large pore porosity (>2 μm). This suggests that at this suction the mechanism involving intrusion of bentonite into the Rock Fracture with Fracture width higher than the size of bentonite gains was related to the pushing effect under the swelling of bentonite behind. By contrast, when the suction became lower than 9 MPa, the bentonite gel formed from the exfoliation of clay particles might fill up the Rock Fracture with smaller aperture width.
