ORCID Profile
0000-0003-2988-7867
Current Organisation
China University of Mining and Technology
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Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 06-2021
Publisher: Hindawi Limited
Date: 2018
DOI: 10.1155/2018/5910437
Abstract: A shale gas reservoir is usually hydraulically fractured to enhance its gas production. When the injection of water-based fracturing fluid is stopped, a two-phase flowback is observed at the wellbore of the shale gas reservoir. So far, how this water production affects the long-term gas recovery of this fractured shale gas reservoir has not been clear. In this paper, a two-phase flowback model is developed with multiscale diffusion mechanisms. First, a fractured gas reservoir is ided into three zones: naturally fractured zone or matrix (zone 1), stimulated reservoir volume (SRV) or fractured zone (zone 2), and hydraulic fractures (zone 3). Second, a dual-porosity model is applied to zones 1 and 2, and the macroscale two-phase flow flowback is formulated in the fracture network in zones 2 and 3. Third, the gas exchange between fractures (fracture network) and matrix in zones 1 and 2 is described by a diffusion process. The interactions between microscale gas diffusion in matrix and macroscale flow in fracture network are incorporated in zones 1 and 2. This model is validated by two sets of field data. Finally, parametric study is conducted to explore key parameters which affect the short-term and long-term gas productions. It is found that the two-phase flowback and the flow consistency between matrix and fracture network have significant influences on cumulative gas production. The multiscale diffusion mechanisms in different zones should be carefully considered in the flowback model.
Publisher: Thomas Telford Ltd.
Date: 11-2010
DOI: 10.1680/MACR.2010.62.11.795
Abstract: This paper focuses on the wave propagation and compression damage in concrete through a plate impact problem. First, the Johnson–Holmquist concrete model is briefed. Then, a cross-format central finite difference scheme is formulated and coded in Fortran 90. After the damage constitutive model is implemented into the code, the stress-wave-induced compression damage in the concrete plate is subsequently simulated. The consistence of the predications between the one-dimensional finite difference code and LS-DYNA is corroborated. Finally, the effects of the magnitude and direction of impact velocity on compression damage are investigated in detail. Numerical results indicate that the proposed methodology is effective and useful. It can be further employed for the protection design of concrete structures against impact loading.
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 04-2014
Publisher: Elsevier BV
Date: 2009
Publisher: Springer Science and Business Media LLC
Date: 25-05-2014
Publisher: Elsevier BV
Date: 06-2014
Publisher: Elsevier BV
Date: 02-2020
Publisher: MDPI AG
Date: 19-12-2019
DOI: 10.3390/W12010027
Abstract: Many researchers have revealed that relative permeability depends on the gas-water-rock interactions and ultimately affects the fluid flow regime. However, the way that relative permeability changes with fractal porous media has been unclear so far. In this paper, an improved gas-water relative permeability model was proposed to investigate the mechanism of gas-water displacement in fractal porous media. First, this model took the complexity of pore structure, geometric correction factor, water film, and the real gas effect into account. Then, this model was compared with two classical models and verified against available experimental data. Finally, the effects of structural parameters (pore-size distribution fractal dimension and tortuosity fractal dimension) on gas-water relative permeability were investigated. It was found that the sticking water film on the surface of fracture has a negative effect on water relative permeability. The increase of geometric correction factor and the ignorance of real gas effect cause a decrease of gas relative permeability.
Publisher: MDPI AG
Date: 02-03-2020
DOI: 10.3390/SYM12030364
Abstract: Low-permeability porous medium usually has asymmetric distributions of pore sizes and pore-throat tortuosity, thus has a non-linear flow behavior with an initial pressure gradient observed in experiments. A threshold pressure gradient (TPG) has been proposed as a crucial parameter to describe this non-linear flow behavior. However, the determination of this TPG is still unclear. This study provides multi-scale insights on the TPG in low-permeability porous media. First, a semi-empirical formula of TPG was proposed based on a macroscopic relationship with permeability, water saturation, and pore pressure, and verified by three sets of experimental data. Second, a fractal model of capillary tubes was developed to link this TPG formula with structural parameters of porous media (pore-size distribution fractal dimension and tortuosity fractal dimension), residual water saturation, and capillary pressure. The effect of pore structure complexity on the TPG is explicitly derived. It is found that the effects of water saturation and pore pressure on the TPG follow an exponential function and the TPG is a linear function of yield stress. These effects are also spatially asymmetric. Complex pore structures significantly affect the TPG only in the range of low porosity, but water saturation and yield stress have effects on a wider range of porosity. These results are meaningful to the understanding of non-linear flow mechanism in low-permeability reservoirs.
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 05-2022
Publisher: World Scientific Pub Co Pte Lt
Date: 09-2020
DOI: 10.1142/S0218348X20501005
Abstract: The coupling of heat transfer and water flow in rock fractures is a key issue to geothermal energy extraction. However, this coupling in a rough fracture has not been well studied so far. This paper will study this coupling in a rock fracture with different roughness. First, multi-scale and self-affine rough fracture are constructed through the Weierstrass–Mandelbrot function and embedded into a rock block. Its single scale trend line is also derived. Second, a roughness factor is proposed based on the standard deviation of each segment from the trend line and introduced into the governing equation of fracture flow. After coupling with heat transfer and matrix deformation, a thermal-hydro-mechanical (THM) coupling model is formulated for a rough fracture flow. Third, an analytical solution is derived through the Laplace transform and Stehfest method and used for the validation of this THM coupling model. Finally, the effects of fracture roughness and matrix deformation on heat transfer and fracture flow are numerically investigated. The simulation results indicate that the rock fracture with lower fractal dimension has higher heat transfer efficiency. The effect of fracture roughness on heat transfer is much greater than that of aperture variation induced by the shrinkage of rock matrix.
Publisher: Elsevier BV
Date: 09-2002
Publisher: MDPI AG
Date: 30-10-2022
DOI: 10.3390/FRACTALFRACT6110632
Abstract: The in-situ combustion–explosion fracturing technology in shale reservoirs can promote continuous fracture expansion with a radial detonation wave first converging into a shock wave and then decaying into an elastic wave. The transformation scale of the shale reservoir is determined by the range of wave propagation during combustion–explosion. As wave propagation paths are usually tortuous and fractal, the previous integer wave models are not competent to describe the wave propagation and estimate the impact range of the combustion–explosion fracturing process. This study develops two fractional wave propagation models and seeks analytical solutions. Firstly, a novel fractional wave model of rotation angle is proposed to describe the process of detonation waves converting into shock waves in a bifurcated structure. The radial displacement gradient of the detonation wave is represented by the internal expansion and rotation deformation of the shale. Secondly, another fractional wave propagation model of radial displacement is proposed to show the process of a shock wave decaying into an elastic wave. Thirdly, the proposed models are analytically solved through the fractional variable separation method and variational iteration method, respectively. Analytical solutions for rotation angle and radial displacement with fractal time and space are obtained. Finally, the impacts of the branching parameter of the detonation wave converge bifurcation system, aggregation order of detonation compression wave, and different types of explosives on the rotation angle of the shock wave are investigated. The propagation mechanism of the primary wave (P-wave) with time and space is analyzed. The analytical solutions can well describe the wave propagation process in fractured shales. The proposed fractional wave propagation models can promote the research of wave propagation in the combustion–explosion fracturing process of shale reservoirs.
Publisher: MDPI AG
Date: 12-11-2022
DOI: 10.3390/MATH10224227
Abstract: The paths of a two-phase flow are usually non-linear and discontinuous in the production of shale gas development. To research the influence mechanism between shale gas and water, several integer two-phase flow models have been studied but few analytical solutions have been obtained on shale gas and water pressure. This study first developed a local fractional mathematical model for gas and water two-phase flow in shale gas production. The model thus created considers the effects of capillary pressure, the fractal dimension of the flow pipe, and the discontinuity of the flow path. Second, the local fractional traveling wave method and variational iteration method were applied to this model for the development of iterative analytical solutions. Both shale gas and water pressure were analytically derived. Third, the depressurization process of the shale gas and water was analyzed, and a parametric study was conducted to explore the impacts of fractional dimension, entry capillary pressure, and travel wave velocity on shale gas pressure. Finally, our conclusions are drawn, based on the results of these studies.
Publisher: Wiley
Date: 29-09-2022
DOI: 10.1002/DUG2.12018
Abstract: This paper introduces the establishment of deep underground infrastructure for science and engineering research. First, the representative deep underground research laboratories and facilities in the world and their functions were summarized and reviewed. Then, the plan and service target of China Yulong Lake Laboratory were proposed for the storage of resources and energy, as well as the sealing of hazardous waste in deep underground space. On this basis, this paper reveals how the facility addresses its key scientific issue on “The law of fluid matter migration in deep underground space” and engineering significance. Finally, the construction progress of the facility components was demonstrated in details. As is hoped, this paper would provide useful reference to the deep underground research community meanwhile, international collaboration on deep underground research is highly welcome.
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 09-2014
Publisher: Wiley
Date: 09-2022
DOI: 10.1002/DUG2.12019
Publisher: Elsevier BV
Date: 10-2011
Publisher: Hindawi Limited
Date: 07-11-2019
DOI: 10.1155/2019/3958583
Abstract: Previous studies on hydraulic fracturing mainly focus on the effects of the in-situ stress state, permeability, fracturing fluids, and approach angle in homogeneous rocks, but the impacts of joint mechanical properties in laminated shale reservoirs on the propagation and formation of the fracture network are still unclear. In this study, a coupled fluid-mechanical model was developed to investigate the impacts of joint mechanical properties on hydraulic fracture propagation. Then, this model was validated with Blanton’s criterion and some experimental observations on fracture morphology. Finally, a series of numerical simulations were conducted to comparatively analyze the impacts of joint mechanical properties on the total crack number, the percentage and distribution of each fracture type, the process of crack propagation, and the final fracture morphology. Numerical results show that the cracking behaviors induced by joint mechanical properties vary with the approach angle. Joint strength has a significant influence on the generation of matrix tensile cracks. The tensile-to-shear strength ratio plays an even more important role in the shear slips of bedding planes and is conducive to the formation of complex fracture morphology.
Publisher: MDPI AG
Date: 12-2022
DOI: 10.3390/SU142316072
Abstract: Refracturing can alleviate the rapid decline of shale gas production with a low drilling cost, but an appropriate fracture layout and optimal refracturing time have been unclear without a heavy computation load. This paper proposes a combination approach with a numerical simulation and data-driven analysis to quickly evaluate the impacts of the refracturing layout and refracturing time on shale gas production. Firstly, a multiphysical coupling model with the creep of natural fractures is established for the numerical simulation on shale gas production. Secondly, the effects of the refracturing layout and refracturing time on the shale gas production are investigated through a single factor sensitivity analysis, but this analysis cannot identify the fracture interaction. Thirdly, the influence of fractures interaction on shale gas production is explored through a combination of a global sensitivity analysis (GSA) and an artificial neural network (ANN). The GSA results observed that the adjacent fractures have more salient interferences, which means that a denser fracture network will not significantly increase the total gas production, or will reduce the contribution from each fracture, resulting in higher fracturing costs. The new fractures that are far from existing fractures have greater contributions to cumulative gas production. In addition, the optimal refracturing time varies with the refracturing layout and is optimally implemented within 2–3 years. A suitable refracturing scale and time should be selected, based on the remaining gas reserve. These results can provide reasonable insights for the refracturing design on the refracturing layout and optimal time. This ANN-GSA approach provides a fast evaluation for the optimization of the refracturing layout and time without enormous numerical simulations.
Publisher: Elsevier BV
Date: 08-2001
Publisher: Elsevier BV
Date: 10-2006
Publisher: MDPI AG
Date: 20-09-2018
DOI: 10.3390/EN11102503
Abstract: This paper develops a numerical model to study fracture network evolution during the nitrogen fracturing process in shale reservoirs. This model considers the differences of incompressible and compressible fluids, shear and tensile failure modes, shale heterogeneity, and the strength and permeability of both shale matrix and bedding planes through the coupling of mechanical-seepage-damage during fracturing fluid injection. The results show that nitrogen fracturing has a lower breakdown pressure and larger seepage zone than hydraulic fracturing under the same injection pressure. Tensile failure was identified as the major reason for the initiation and propagation of fractures. Ignoring the effect of bedding planes, the fracture initiation pressure, breakdown pressure, and fracturing effectiveness reached their maxima when the stress ratio is 1. Under the same strength ratio, the propagation path of the fractures was controlled by the stronger effect that was casused by the bedding angle and stress ratio. With increasing the strength ratio, the fracture number and shearing of the bedding plane increased significantly and the failure pattern changed from tensile-only mode to tensile-shear mode. These analyses indicated that the fracture network of bedding shale was typically induced by the combined impacts of stress ratio, bedding angle and strength ratio.
Publisher: MDPI AG
Date: 12-08-2020
DOI: 10.3390/MA13163563
Abstract: In this study, an approach is developed to estimate the density and effective elastic modulus of a lightweight bulk filling material made up of expanded polystyrene (EPS) and cement-reinforced clay (matrix). First, a representative volume element (RVE) is composed of cell A (an EPS and matrix) and cell B (matrix only). Then, an elastic interface is introduced to describe the discontinuity of displacement at the interface between EPS beads and matrix. Third, an Eshelby compliance tensor is modified in cell A to include the effects of imperfect interface and the compressibility of EPS beads. Finally, the approach for the density and effective elastic modulus of the EPS beads mixed cement-reinforced clay is verified with experimental data. The compressibility ratio of lightweight clay is compared under different confining pressures and curing times. It is found that the imperfect interface has salient impacts on the effective elastic modulus with the increase of volume fraction of inclusions. The interface parameters (α and β) vary with curing time and confining pressure. At the same curing time, the parameter α is almost constant regardless of confining pressure but the parameter β changes with confining pressure. The compressibility ratio is smaller for longer curing time if the confining pressure is constant.
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 2007
Publisher: Elsevier BV
Date: 06-2007
Publisher: Springer Science and Business Media LLC
Date: 25-07-2013
Publisher: Elsevier BV
Date: 10-2009
Publisher: Hindawi Limited
Date: 08-05-2019
DOI: 10.1155/2019/4943582
Abstract: The governing equations of a two-phase flow have a strong nonlinear term due to the interactions between gas and water such as capillary pressure, water saturation, and gas solubility. This nonlinearity is usually ignored or approximated in order to obtain analytical solutions. The impact of such ignorance on the accuracy of solutions has not been clear so far. This study seeks analytical solutions without ignoring this nonlinear term. Firstly, a nonlinear mathematical model is developed for the two-phase flow of gas and water during shale gas production. This model also considers the effects of gas solubility in water. Then, iterative analytical solutions for pore pressures and production rates of gas and water are derived by the combination of travelling wave and variational iteration methods. Thirdly, the convergence and accuracy of the solutions are checked through history matching of two sets of gas production data: a China shale gas reservoir and a horizontal Barnett shale well. Finally, the effects of the nonlinear term, shale gas solubility, and entry capillary pressure on the shale gas production rate are investigated. It is found that these iterative analytical solutions can be convergent within 2-3 iterations. The solutions can well describe the production rates of both gas and water. The nonlinear term can significantly affect the forecast of shale gas production in both the short term and the long term. Entry capillary pressure and shale gas solubility in water can also affect shale gas production rates of shale gas and water. These analytical solutions can be used for the fast calculation of the production rates of both shale gas and water in the two-phase flow stage.
Publisher: Emerald
Date: 09-2005
DOI: 10.1108/09615530510601468
Abstract: Develop a local radial point interpolation method (LRPIM) to analyze the dissipation process of excess pore water pressure in porous media and verify its numerical capability. Terzaghi's consolidation theory is used to describe the dissipation process. A local residual form is formulated over only a sub‐domain. This form is spatially discretized by radial point interpolation method (RPIM) with basis of multiquadrics (MQ) and thin‐plate spline (TPS), and temporally discretized by finite difference method. One‐dimensional (1D) and two‐dimensional consolidation problems are numerically analyzed. The LRPIM is suitable, efficient and accurate to simulate this dissipation process. The shape parameters, q =1.03, R =0.1 for MQ and η =4.001 for TPS, are still valid. The asymmetric system matrix in LRPIM spends more resources in storage and CPU time. Local residual form requires no background mesh, thus being a truly meshless method. This provides a fast and practical algorithm for engineering computation. This paper provides a simple, accurate and fast numerical algorithm for the dissipation process of excess pore water pressure, largely simplifies data preparation, shows that the shape parameters from solid mechanics are also suitable for the dissipation process.
Publisher: Elsevier BV
Date: 2002
Publisher: Elsevier BV
Date: 07-2010
Publisher: Trans Tech Publications, Ltd.
Date: 02-2012
DOI: 10.4028/WWW.SCIENTIFIC.NET/SSP.185.126
Abstract: The observation of scanning electron microscope (SEM) shows that a tibia bone is a kind of bioceramic composite consisting of hydroxyapatite layers and collagen protein matters. The hydroxyapatite layers are composed of hydroxyapatite sheets. The observation also shows there is a kind of interlaced microstructure of the hydroxyapatite sheets. The maximum pullout force of the interlaced microstructure was investigated and compared with that of the parallel microstructure. It is indicated that the maximum pullout force of the interlaced microstructure with a large interlaced angle is markedly larger than that of the parallel microstructure.
Publisher: Hindawi Limited
Date: 23-11-2020
DOI: 10.1155/2020/8875918
Abstract: The complex thermal-hydraulic-mechanical (THM) coupling is the key issue to the energy extraction from a geothermal reservoir, where fractures are the main channels for fluid circulation and heat transfer. However, the effects of matrix deformation-induced aperture variation and fracture roughness on heat recovery efficiency are unclear. In this paper, a fully coupling THM model based on a discrete fracture network is proposed to explore these coupling effects. First, the fracture roughness and the fracture aperture variation with effective stress are introduced. Second, the water flow and heat transfer in the matrix and fractures as well as the deformation of the geothermal reservoir are in idually formulated for a fractured geothermal reservoir. Third, the model is validated with analytical solution for its thermal-hydraulic (TH) coupling effect and literature data for its hydraulic-mechanical (HM) coupling effect. Finally, the features of heat transfer and fluid flow in the fractured geothermal reservoir are comparatively analyzed through four scenarios. The simulation results indicate that the discrete fracture network severely impacts the pressure distribution and temperature advance. The aperture variation induced by solid deformation can enhance heat transfer efficiency, and the fracture roughness can reduce the heat transfer efficiency.
Publisher: Elsevier BV
Date: 07-2010
Publisher: Elsevier BV
Date: 02-2019
Publisher: Elsevier BV
Date: 07-2010
Publisher: Elsevier BV
Date: 09-2003
Publisher: Informa UK Limited
Date: 12-2012
Publisher: MDPI AG
Date: 10-04-2020
DOI: 10.3390/EN13071857
Abstract: A fractal discrete fracture network based model was proposed for the gas production prediction from a fractured shale reservoir. Firstly, this model was established based on the fractal distribution of fracture length and a fractal permeability model of shale matrix which coupled the multiple flow mechanisms of slip flow, Knudsen diffusion, surface diffusion, and multilayer adsorption. Then, a numerical model was formulated with the governing equations of gas transport in both a shale matrix and fracture network system and the deformation equation of the fractured shale reservoir. Thirdly, this numerical model was solved within the platform of COMSOL Multiphysics (a finite element software) and verified through three fractal discrete fracture networks and the field data of gas production from two shale wells. Finally, the sensitivity analysis was conducted on fracture length fractal dimension, pore size distribution, and fracture permeability. This study found that cumulative gas production increases up to 113% when the fracture fractal length dimension increases from 1.5 to the critical value of 1.7. The gas production rate declines more rapidly for a larger fractal dimension (up to 1.7). Wider distribution of pore sizes (either bigger maximum pore size or smaller minimum pore size or both) can increase the matrix permeability and is beneficial to cumulative gas production. A linear relationship is observed between the fracture permeability and the cumulative gas production. Thus, the fracture permeability can significantly impact shale gas production.
Publisher: World Scientific Pub Co Pte Lt
Date: 20-01-2010
DOI: 10.1142/S0217979210064125
Abstract: The observation of scanning electron microscope (SEM) showed that Tumblebug elytra consist of almost parallel upper and lower cuticles. Both of which are a kind of chitin-fiber-reinforced composite. There is a kind of chitin-fiber-reinforced composite pillars between the upper and lower cuticles, which support and connect the upper and lower cuticles uprightly. More careful observation showed that the chitin fibers in the pillars smoothly extend to the upper and lower composite cuticles forming a kind of fiber-continuous pillar-board composite (FCPBC) structure. Based on the observation, two kinds of pillar-board composite structure specimens, respective with continuous and discontinuous glass fibers, were fabricated with molding and felting processes. The rupture strengths of the two kinds of the specimens were tested and compared. It showed that the rupture strength of the specimens of the FCPBC structure is markedly larger than that of the specimens of the fiber-discontinuous pillar-board composite (FDPBC) structure. At last, the experimental result was analyzed for illumining the mechanism of the FCPBC structure in the enhancement of the strength.
Publisher: Elsevier BV
Date: 06-2018
Publisher: Springer Science and Business Media LLC
Date: 03-07-2023
Publisher: Elsevier BV
Date: 03-2006
Publisher: Elsevier BV
Date: 08-2004
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 03-2007
Publisher: Elsevier BV
Date: 07-2008
Publisher: Elsevier BV
Date: 08-2016
Publisher: Trans Tech Publications, Ltd.
Date: 02-2012
DOI: 10.4028/WWW.SCIENTIFIC.NET/SSP.185.133
Abstract: SEM observation on an abalone shell shows that the shell is a kind of bioceramic composite consisting of inorganic aragonite sheets and organic collagen protein matter. The aragonite sheets possess long and thin shape and are ided by the collagen protein matter, which compose a kind of laminated microstructure of the shell. The fracture surface energy of the laminated microstructure is investigated and compared with non-laminated microstructure based on its representative model. It shows that the fracture surface energy of the laminated microstructure is markedly larger than that of the non-laminated microstructure and endows the shell with high fracture toughness.
Publisher: Elsevier BV
Date: 10-2004
Publisher: Hindawi Limited
Date: 05-12-2022
DOI: 10.1155/2022/7202972
Abstract: The fluid front motion is an important phenomenon during anisotropic fluid flow in rock engineering. The pore pressure and mechanical responses may be significantly influenced and show an obvious difference near the moving fluid front. However, few studies have been conducted to investigate the front motion of different types of fluids during anisotropic fluid flow. In this work, a numerical model was proposed to detect the front motion of water, nitrogen, and CO2 in anisotropic shale reservoirs. The full coupling effects among mechanical deformation, fluid flow, and moving boundary in anisotropic porous media were considered in the model construction. The impacts of different fluid properties among water, nitrogen, and CO2 on the anisotropic fluid flow have been discussed. Then, the proposed model was applied to study the differences in front motion among different types of fluids in anisotropic shales. The impacts of permeability and mobility on fluid front motion were investigated. The theoretical equations for predicting the fluid front motion of different types of fluids were established by introducing corresponding correction coefficients to the previous formulas. The results showed that the model can well describe the anisotropic fluid permeation process. The fluid front motion increased with the increase of permeability and mobility. At the same permeability or mobility, the nitrogen front motion was the largest and the water front motion was the smallest. The difference in fluid front motion among water, nitrogen, and CO2 was caused by the difference of their viscosity and compressibility. The proposed formulas can fast and accurately predict the evolution of fluid front motion for different types of fluids.
Publisher: Springer Science and Business Media LLC
Date: 03-04-2019
Publisher: Springer Science and Business Media LLC
Date: 30-03-2006
Publisher: Elsevier BV
Date: 04-2009
Publisher: World Scientific Pub Co Pte Lt
Date: 20-01-2010
DOI: 10.1142/S0217979210064137
Abstract: Bone possesses excellent mechanical properties, which are closely related to its favorable microstructures optimized by nature through millions of years. In this work, a scanning electron microscope (SEM) was used to observe the microstructures of a shankbone. It showed that the bone is a kind of bioceramic composite consisting of hydroxyapatite layers and collagen protein matrix. The hydroxyapatite layers are further composed of long and thin hydroxyapatite sheets. The hydroxyapatite sheets in different hydroxyapatite layers distribute along different orientations, which composes a kind of intersectant microstructure. The maximum pullout force of the intersectant microstructure was investigated and compared with that of 0° microstructure with their representative models. The result indicated that the maximum pullout force of the intersectant microstructure is markedly larger than that of the 0° microstructure, which was experimentally verified.
Publisher: Elsevier BV
Date: 08-2004
Publisher: Elsevier BV
Date: 08-2004
Publisher: Thomas Telford Ltd.
Date: 11-2011
DOI: 10.1680/MACR.2011.63.11.883
Abstract: This paper investigates the compression strength and the energy absorption of steel fibre reinforced concrete under repetitive impact loadings. Cylindrical concrete specimens are fabricated with 0, 1·5 and 3·0% fibre volume fractions. For each fibre volume fraction, stress–strain curves are measured using split Hopkinson pressure bar tests. Also, post-test photographs are taken for each specimen after each impact. The data collected are used to evaluate the energy absorption and the damage evolution of concrete in compression. The results indicate that damage increases and strength decreases with the increase of impact times. Fibrous concrete is markedly superior to plain concrete in resisting dynamic failure. Furthermore, both impact velocity and fibre volume fraction exert a significant influence on the dynamic response of concrete.
Publisher: Elsevier BV
Date: 07-2011
Publisher: Wiley
Date: 2002
DOI: 10.1002/NME.489
Publisher: Elsevier BV
Date: 2007
Publisher: Thomas Telford Ltd.
Date: 08-2012
Abstract: The dynamic tensile strength of steel fibre reinforced concrete is experimentally investigated. Cylindrical specimens are first fabricated with three different fibre volume fractions of 0, 0·75% and 1·5%. These specimens are then tested by using the Hopkinson pressure bar technique. Their dynamic tensile strengths are measured under medium strain rate impact. In these tests, the stress histories are recorded by way of the strain gauges symmetrically mounted on the specimen and the post-test fracture modes are photographed. The test results indicate that the superposition of waves induces first compressive stress and then tensile stress. Once the tensile stress reaches its critical value, a spalling phenomenon occurs. Both volume fraction of fibres and strain rate exert a significant influence on the dynamic tensile strength of concrete. Furthermore, the strain-rate-induced enhancement of tensile strength is related to the compressive strength of the concrete matrix.
Publisher: Wiley
Date: 22-08-2023
DOI: 10.1002/DUG2.12051
Publisher: Wiley
Date: 28-09-2023
DOI: 10.1002/ESE3.1574
Publisher: Elsevier BV
Date: 2017
Publisher: American Physical Society (APS)
Date: 23-12-2021
Publisher: Thomas Telford Ltd.
Date: 12-2008
DOI: 10.1680/GEIN.2008.15.6.428
Abstract: New mining technologies not only exploit lower-grade ores but also produce a much higher volume of tailings as mining waste. The disposal of these tailings is a challenge for mine operators. A tailings dam is usually constructed to store these wastes safely. The dam continuously increases its height and changes geometry with the disposal of tailings, which is different from conventional dams. Therefore the stability of tailings dams is a challenge. Geosynthetics have been widely used as reinforcement in retaining walls and embankments, but their applicability to the construction of tailings dams has not previously been studied. Their applicability depends largely on the interaction between geosynthetics and fine tailings. In this paper, the interaction of geosynthetics (geobelt and geogrid) with fine copper ore tailings is studied through laboratory pullout tests. The test results reveal that the interaction characteristics are influenced by tailings particle size, density, moisture content, and vertical load. It is found that the maximum friction coefficient between geosynthetics and the fine tailings is less than 0.22, which is lower than the published data for natural soils.
Publisher: MDPI AG
Date: 04-03-2023
DOI: 10.3390/SU15054597
Abstract: Hydraulic fracturing technology can be used to jointly exploit unconventional natural gas such as coalbed methane and tight sandstone gas in coal-measure superimposed reservoirs for the enhancement of natural gas production. Hydraulic fracturing usually induces mixed fractures of I and II modes, but existing studies have not considered the influence of reservoir lithology on the stress intensity factor of I/II mixed fractures in coal-measure superimposed reservoirs. This paper develops an analytical stress model and a seepage-mechanical-damage numerical model for the vertical propagation of I/II mixed fractures in coal-measure superimposed reservoirs. The variation of stress intensity factor of I/II mixed fractures is analyzed when the fractures are close to the interface of different lithologic reservoirs and the effects of elastic modulus difference, stress state, fracturing fluid viscosity, shear and tensile failure modes on the vertical propagation of hydraulic fractures are investigated. Finally, the ratio of elastic modulus of adjacent reservoirs is proposed as an evaluation index for the fracture propagation through reservoir interface. These investigations revealed that hydraulic fracture propagation through the reservoir interface is a process of multi-physical interactions and is mainly controlled by the injection pressure and the elastic modulus ratio of adjacent reservoirs. A critical line is formed in the coordinates of elastic modulus ratio and injection pressure. A fracture can propagate through the reservoir interface when the combination of injection pressure and the elastic modulus ratio is in the breakthrough zone. These results can provide theoretical support for the site selection of horizontal wells in coal-measure gas exploitation.
Publisher: MDPI AG
Date: 06-11-2022
Abstract: Carbon dioxide (CO2) may infiltrate into the caprock and displace brine water in the caprock layer. This causes two effects: one is the caprock swelling induced by the CO2 adsorption and the other is the caprock dehydration and shrinkage due to CO2–brine water two-phase flow. The competition of these two effects challenges the caprock sealing efficiency. To study the evolution mechanism of the caprock properties, a numerical model is first proposed to investigate the combined effects of CO2 adsorption-induced expansion and dehydration-induced shrinkage on the caprock sealing efficiency. In this model, the caprock matrix is fully saturated by brine water in its initial state and the fracture network has only a brine water–CO2 two-phase flow. With the diffusion of CO2 from the fractures into the caprock matrix, the CO2 sorption and matrix dehydration can alter the permeability of the caprock and affect the entry capillary pressure. Second, this numerical model is validated with a breakthrough test. The effects of the two-phase flow on the water saturation, CO2 adsorption on the swelling strain, and dehydration on the shrinkage strain are studied, respectively. Third, the permeability evolution mechanism in the CO2–brine water mixed zone is investigated. The effect of dehydration on the penetration depth is also analyzed. It is found that both the shale matrix dehydration and CO2 sorption-induced swelling can significantly alter the sealing efficiency of the fractured caprock.
Publisher: World Scientific Pub Co Pte Lt
Date: 03-2019
DOI: 10.1142/S0218348X19500063
Abstract: A multiple fractured shale gas reservoir is ided into three zones, namely the single-porosity zone, the dual-porosity zone, and the hydraulic fracture zone. The distributions of pore size, fracture length, and fracture aperture vary in each zone and affect shale gas productivity. This paper developed a fractal numerical model to investigate the impacts of zone fractal properties on the shale gas productivity of a multiple fractured horizontal well. In this model, a fractal permeability model was developed, in which the diameter/aperture distribution of circular/slit pores and the length of fractures all follow fractal scaling law. This numerical model was solved by finite element method within the platform of COMSOL Multiphysics and verified through the history matching of production data from the Marcellus and Barnett shale reservoirs. Finally, the effects of the fractal dimension ([Formula: see text], [Formula: see text], [Formula: see text]) and the maximum diameter ([Formula: see text]) of the pores on gas productivity (measured by gas production rate and cumulative gas production) were investigated. Numerical results show that increasing the maximum pore diameter [Formula: see text] can enhance gas productivity, but increasing the pore diameter fractal dimension [Formula: see text] makes the gas productivity decrease and increasing tortuous fractal dimension [Formula: see text] decreases the gas productivity, too. The length fractal dimension [Formula: see text] of fractures is sensitive to the gas flow in the dual-porosity zone.
Publisher: American Chemical Society (ACS)
Date: 14-06-2023
Publisher: MDPI AG
Date: 20-06-2018
DOI: 10.3390/EN11061608
Publisher: Springer Science and Business Media LLC
Date: 04-2011
Publisher: Elsevier BV
Date: 07-2012
Publisher: Springer Science and Business Media LLC
Date: 24-02-2012
Publisher: Informa UK Limited
Date: 15-04-2008
Publisher: Elsevier BV
Date: 11-2008
Publisher: Elsevier BV
Date: 11-2008
Publisher: Springer Science and Business Media LLC
Date: 11-2018
Publisher: Elsevier BV
Date: 06-2008
Publisher: Elsevier BV
Date: 03-2006
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 03-2022
Publisher: Elsevier BV
Date: 2003
Publisher: Thomas Telford Ltd.
Date: 2011
Publisher: Elsevier BV
Date: 2004
Publisher: SAGE Publications
Date: 11-10-2012
Abstract: Rapid development of China’s economy demands for more mineral resources. At the same time, a vast quantity of mine tailings, as the waste byproduct of mining and mineral processing, is being produced in huge proportions. Tailings impoundments play an important role in the practical surface disposal of these large quantities of mining waste. Historically, tailings were relatively small in quantity and had no commercial value, thus little attention was paid to their disposal. The tailings were preferably discharged near the mines and few tailings storage facilities were constructed in mainland China. This situation has significantly changed since 2000, because the Chinese economy is growing rapidly and Chinese regulations and legislation require that tailings disposal systems must be ready before the mining operation begins. Consequently, data up to 2008 shows that more than 12 000 tailings storage facilities have been built in China. This paper reviews the history of tailings disposal in China, discusses three cases of tailings dam failures and explores failure mechanisms, and the procedures commonly used in China for planning, design, construction and management of tailings impoundments. This paper also discusses the current situation, shortcomings and key weaknesses, as well as future development trends for tailings storage facilities in China.
Publisher: American Chemical Society (ACS)
Date: 17-02-2023
Publisher: Elsevier BV
Date: 10-2014
Publisher: Elsevier BV
Date: 02-2007
Publisher: MDPI AG
Date: 22-05-2019
DOI: 10.3390/MA12101662
Abstract: The variation of physical and mechanical properties of the lightweight bulk filling material with cement and expanded polystyrene (EPS) beads contents under different confining pressures is important to construction and geotechnical applications. In this study, a lightweight bulk filling material was firstly fabricated with Singapore marine clay, ordinary Portland cement and EPS. Then, the influences of EPS beads content, cement content, curing time and confining pressure on the mass density, stress–strain behavior and compressive strength of this lightweight bulk filling material were investigated by unconsolidated and undrained (UU) triaxial tests. In these tests, the mass ratios of EPS beads to dry clay (E/S) were 0%, 0.5%, 1%, 2%, and 4% and the mass ratios of cement to dry clay (C/S) were 10% and 15%. Thirdly, a series of UU triaxial tests were performed at a confining pressure of 0 kPa, 50 kPa, 100 kPa, and 150 kPa after three curing days, seven curing days, and 28 curing days. The results show that the mass density of this lightweight bulk filling material was mainly controlled by the E/S ratio. Its mass density decreased by 55.6% for the C/S ratio 10% and 54.9% for the C/S ratio 15% when the E/S ratio increased from 0% to 4% after three curing days. Shear failure more easily occurred in the specimens with higher cement content and lower confining pressure. The relationships between compressive strength and mass density or failure strain could be quantified by the power function. Increasing cement content and reducing EPS beads content will increase mass density and compressive strength of this lightweight bulk filling material. The compressive strength with curing time can be expressed by a logarithmic function with fitting correlation coefficient ranging from 0.83 to 0.97 for five confining pressures. These empirical formulae will be useful for the estimation of physical and mechanical properties of lightweight concretes in engineering application.
Publisher: Elsevier BV
Date: 08-2019
Publisher: World Scientific Pub Co Pte Lt
Date: 12-2004
DOI: 10.1142/S0219581X04002565
Abstract: Most structural materials existing in nature take the form of a composite. After centuries of evolution, these materials have gained highly optimized microstructures and performance. In this work, a natural biocomposite, chafer cuticle, was observed with SEM, and it was found that the insect cuticle has a laminated structure with chitin fiber and protein matrix. Special helicoidal layups of chitin fibers were found with the chitin fiber being of nanometer scale. The relationship between the nanometer scale of the chitin fiber and the fracture strength of the cuticle was analyzed. The results show that the nanometer scale of the chitin fiber is profitable to maintain and improve the fracture strength of the biocomposite.
Publisher: Elsevier BV
Date: 04-2012
Publisher: Mary Ann Liebert Inc
Date: 10-2006
Abstract: To screen diagnostic markers of Deficiency-Cold syndrome by gene expression profile and to establish a discriminant mathematical milliliters model for the clinical diagnosis of this syndrome based on a support vector machine (SVM). A family suffering from Deficiency-Cold syndrome is chosen for this study. This family has 5 patients with Deficiency-Cold syndrome and 10 normal members. The peripheral blood s les for these 5 patients and 5 normal members are tested by using cDNA microarray with 18,816 clones to get their differential expression genes. These genes are further explored to understand their biological functions and pathways through existing databases. A SVM model for clinical diagnosis is then developed based on these differential expression genes. A total of 83 differential expression genes were identified between patients and normal members, in which 21 genes were recorded in the FATIGO database and 16 genes were related to metabolism. Eight (8) pathways were sorted out in the KEGG database, and half pathways were associated with human metabolism. A discriminant mathematical model based on a support vector machine successfully predicted a normal person and a patient with heavy Deficiency-Cold syndrome based on their gene differential expression profiles. Thus, this model may classify the Deficiency-Cold syndrome. This work demonstrates that the differential expression genes can be used to identify normal persons and patients with Deficiency-Cold syndrome. Deficiency-Cold syndrome is mainly associated with the metabolism-related gene regulations. In addition, the discriminant mathematical model based on a support vector machine is applicable to the clinical diagnosis for Deficiency-Cold syndrome.
Publisher: Elsevier BV
Date: 2004
Publisher: Elsevier BV
Date: 12-2021
Publisher: MDPI AG
Date: 06-11-2020
DOI: 10.3390/W12113114
Abstract: The migration of hazardous substances in a bentonite barrier layer is a key issue for the safety of nuclear waste storage. This study develops a thermo-hydro-mechanical coupling model to simulate the contaminant migration in a bentonite barrier layer of the nuclear waste storage chamber. In particular, the Richard’s equation is used to describe the groundwater flow in the bentonite barrier layer with variable saturation. Thermal diffusion and concentration diffusion are coupled with the layer deformation and fluid flow. The migration rate and diffusion range of hazardous substances in the bentonite barrier layer are numerically simulated. These numerical simulations show that the heat release from nuclear waste can induce a temperature gradient and deformation, and thus significantly affects both transfer rate and concentration distribution of dilute substances. These multi-physical couplings under different initial saturation may significantly modify the sealing efficiency of an unsaturated bentonite barrier layer and thus this model is of great significance in the safety evaluation of a nuclear waste disposal repository.
Publisher: Cambridge University Press (CUP)
Date: 06-2007
Abstract: The gene expression profile of a normal-suffering monozygotic twin pair is investigated to explore biological mechanisms of spastic type cerebral palsy. Main works include following three aspects: First, a cDNA microarray test is carried out to get the differentially expressed genes of the patient with cerebral palsy compared to her monozygotic twin sister. Second, these differentially expressed genes are searched for their bioinformation within 4 biological databases: FatiGO, FatiGOPlus, KEGG, and SOURCE. Third, a set of special genes and gene families are screened out from the spastic type cerebral palsy patient. These biological analyses reveal that those genes for cell junction are mostly down-regulated, while those genes for metabolism are mostly up-regulated. The in idual genes, gene family, and their associated biological functions can reflect the pathological and physiological characteristics of the cerebral palsy.
Publisher: Springer Science and Business Media LLC
Date: 19-09-2017
Publisher: MDPI AG
Date: 15-03-2018
DOI: 10.3390/EN11030654
Publisher: Hindawi Limited
Date: 04-03-2019
DOI: 10.1155/2019/7692490
Abstract: Water permeation into a porous medium is a common but important phenomenon in many engineering fields such as hydraulic fracturing. The water permeation front moves with time and may significantly impact the field variable evolution near the water front. Many algorithms have been developed to calculate this water front motion, but few numerical algorithms have been available to calculate the water front motion in anisotropic fluid-solid couplings with high computational efficiency. In this study, a numerical model is proposed to investigate the front motion of water permeation into an anisotropic porous medium. This model fully couples the mechanical deformation, fluid flow, and water front motion. The water front motion is calculated based on a directional Darcy’s flow in the anisotropic porous medium, and a revised formula with a correction coefficient is developed for the estimation of permeation depth. After verification with three sets of experimental data, this model is used to numerically investigate the impacts of permeability, viscosity, permeability anisotropy, and mechanical anisotropy on water front motion. Numerical results show that the proposed model can well describe the anisotropic water permeation process with reasonable accuracy. The permeation depth increases with permeability, mobility, and mechanical anisotropy but decreases with viscosity and permeability anisotropy. The correction coefficient mainly depends on porosity evolution, flow pattern, mobility, permeability anisotropy, and mechanical anisotropy.
Publisher: Thomas Telford Ltd.
Date: 11-2011
DOI: 10.1680/MACR.2011.63.11.829
Abstract: Steel fibre reinforced concrete (SFRC) has been gaining popularity in load-carrying members because of its positive contribution to both concrete strength and energy absorption capacity. This paper presents both experimental and theoretical study of the fibre reinforcing effect on the concrete failure mechanism. The compression/shear tests of cubic steel fibre reinforced concrete specimens with fibre volume fractions of 0%, 1·5% and 3% are conducted in the wedge shear apparatus. Their failure patterns are analysed at macro- and meso-scale levels. Subsequently, these experimental data are analysed by a twin-shear strength theory. One concise compression/shear failure criterion is then developed for SFRC. It is found that the predicted results by this criterion agree well with those by experiments. Finally, the changes of concrete twin-shear strength parameters with the fibre volume fraction are explored.
Publisher: MDPI AG
Date: 06-04-2023
DOI: 10.3390/APP13074639
Abstract: The comfort of a bus running on different road conditions is a matter of public concern. In this paper, the differential equations of motion are established for a bus running on different road conditions and the whole driving process is mechanically analyzed. Firstly, the bump degree at different positions is quantitatively analyzed and it is found that the rear row is bumpier on different roads. Then, the relationship between the speed of the bus and the vertical displacement and acceleration is quantitatively described. Regardless of the speed, a similar displacement and acceleration will be eventually achieved, but the speed is higher, and the duration of maximum displacement and acceleration is longer. When the speed is 8 m/s, resonance occurs on the bus during road condition II. Finally, the change in vertical displacement and acceleration under the action of different spring stiffness coefficient ratios of the front and rear wheels is quantitatively analyzed. High stiffness ratios mean less displacement and acceleration. By establishing an actual excitation road surface, the differential equations and analytical solutions in this paper can be used to roughly analyze the mechanical response of a traveling bus. These results can provide some guidance for the design and driving of buses.
Publisher: Elsevier BV
Date: 07-2008
Publisher: Elsevier BV
Date: 09-2004
Publisher: Elsevier BV
Date: 03-2002
Publisher: Elsevier BV
Date: 06-2015
Publisher: Elsevier BV
Date: 12-2006
Publisher: Elsevier BV
Date: 04-2013
Publisher: Elsevier BV
Date: 10-2020
Publisher: World Scientific Pub Co Pte Lt
Date: 12-2019
DOI: 10.1142/S0218348X19501299
Abstract: Previous studies ignore the evolutions of pore microstructure parameters (pore diameter fractal dimension [Formula: see text] and tortuosity fractal dimension [Formula: see text]) but these evolutions may significantly impact the gas transport during gas extraction. In order to investigate these evolutions of fractal dimension properties during gas extraction, following four aspects are studied. Firstly, surface diffusion in adsorbed multilayer is modeled for fractal shale matrix. Our new matrix permeability model considers the slip flow, Knudsen diffusion and surface diffusion. This model is verified by experimental data. Secondly, a new fracture permeability model is proposed based on fractal theory and the coupling of viscous flow and Knudsen diffusion. Thirdly, the multilayer adsorption and these permeability models are introduced into the equations of gas flow and reservoir deformation. Finally, sensitivity analysis is performed to determine the key factors on fractal dimension evolution. The results show that the multilayer adsorption can accurately describe the adsorption properties of real shale reservoir. Shale reservoir deformation and gas desorption govern the evolutions of fractal dimensions. The multilayer adsorption and adsorbed gas porosity [Formula: see text] play an important role in the evolutions of fractal dimensions during gas extraction. The monolayer saturated adsorption volume [Formula: see text] is the most sensitive parameter affecting the evolution of fractal dimensions. Therefore, the effects of gas adsorption on the evolution of fractal dimensions cannot be neglected in shale reservoirs.
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 08-2010
Publisher: Springer Science and Business Media LLC
Date: 11-05-2016
Publisher: MDPI AG
Date: 23-09-2022
DOI: 10.3390/MATH10193473
Abstract: Heat treatment on shale reservoirs can promote the development of secondary fractures in a matrix on the basis of hydraulic fracturing, forming multi-scale gas–water seepage channels and strengthening the gas desorption. Experimental evidence shows that heat treatment can enhance gas recovery in the same mining life. Heat treatment on a shale gas reservoir is a multi-physical and multi-phase coupling process. However, how the thermal stimulation interacts with nonlinear two-phase flow in heterogeneous shale volume fracturing has not been clear. In this paper, a fully coupled THGM model for heating-enhanced shale-gas recovery in heterogeneous shale reservoirs is proposed. First, the governing equations are formulated for the shale-reservoir deformation involving both gas adsorption and thermal expansion, the permeability evolution model for the cracking process of fractured shale, the gas–water two-phase continuity equation considering the effects of gas solubility and the heat transfer equation for heat conduction and convection. The interactions among stress, temperature and seepage in a heterogeneous shale reservoir were studied. Secondly, a test on shale permeability after 50 °C temperature treatment was conducted. The evolution of temperature, capillary pressure, water and gas saturation and the permeability of shale during the heat treatment of the reservoir were numerically analyzed. Finally, the gas production from a shale gas reservoir was numerically simulated with this THGM model. The numerical results indicated that the thermal-induced fracturing, gas desorption and separation from water make predominant contributions to the evolution of permeability. The heat treatment can enhance cumulative gas production by 58.7% after 27.4 years of heat injection through promoting gas desorption and matrix diffusion.
Publisher: Informa UK Limited
Date: 12-2006
DOI: 10.1080/15287390600751322
Abstract: Family investigation is a reliable model to study the effects of both genetic and environmental factors on human health. This article studies kidney-yang deficiency syndrome and cold syndrome through family investigation and cDNA microarray technology, exploring the effects of both genetic and environmental factors on the health of family members. Particularly, these two syndromes were first assessed by the accumulated clinical scores measured by 40-item scoring tables among 15 family members. The family patterns were obtained and the correlation of these two syndromes was determined. Then the gene differential expression profiles among 12 family members were obtained using an 18,816 clones cDNA microarray. The profiles of the patients with typical kidney-yang deficiency syndrome and cold syndrome were compared to those of normal members and 89 differential expression genes were found. Further, only 22 genes were identified as known functions, and most (16 genes) were associated with the regulation of metabolism, temperature feeling, and growth. Therefore, the formation and development of these two syndromes have not only genetic but also environmental factors, including living conditions and lifestyle.
Publisher: Elsevier BV
Date: 03-2015
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2022
Publisher: Elsevier BV
Date: 12-2002
Publisher: Elsevier BV
Date: 09-2006
Publisher: World Scientific Pub Co Pte Lt
Date: 2006
DOI: 10.1142/S0192415X06003928
Abstract: It is essential to explore the molecular therapeutic effect of warm and tonic herb treatment for in iduals with typical kidney-yang deficiency. In this report, we have identified members of a family with a history of suffering from cold and kidney-yang deficiency syndromes. First, we have employed the accumulated scores of the 40-items clinical scoring indicators for kidney-yang deficiency and cold syndromes to clinically assess the presence or absence of the deficiency for 15 family members. We then proceeded to compare the gene expression profiles of RNA isolated from blood s les, prior to and post-herbal treatment, of a sibling (brother and younger sister) that are suffering from the deficiency using cDNA microarrays with 18816 genes. Following treatments with the warming and tonic herb, the accumulated clinical scores obtained from the 40-items clinical scoring indicators were compared to those obtained pre-treatment. It was observed that the accumulated clinical scores were reduced by 1/3 for the brother and 2/3 for his younger sister following the treatments. Furthermore, we have demonstrated that the level of gene expression for a total of 33 genes at pre-treatment was modulated after treatments with the warming and tonic herb and correlated well with the clinical improvements of their syndromes. These results suggest that the combination of gene profiling and the accumulated clinical scores obtained from the 40-items clinical scoring indicators may provide an accurate clinical assessment and a way to monitor the therapeutic efficacy of the warming and tonic herb treatment.
Publisher: MDPI AG
Date: 08-08-2020
DOI: 10.3390/APP10165496
Abstract: The micro-cracking morphology in laminated shale formation plays a critical role in the enhancement of shale gas production, but the impacts of bedding strength parameters on micro-cracking morphology have not been well understood in laminated shale formation. This paper numerically investigated the initiation and evolution of micro-cracking morphology with bedding strength parameters in laminated shale under uniaxial compression. First, a two-dimensional particle flow model (PFC2D) was established for laminated shale. Then, the micro-mechanical parameters of this model were calibrated using stress-strain curves and final fracture morphology measured in the laboratory. Finally, the impacts of bedding strength parameters on the uniaxial compressive strength (UCS), crack type and the complexity of fracture network were analyzed quantitatively. Numerical simulation results indicate that the UCS of shale varies linearly with the bedding strength, especially when the shear failure of beddings is dominant. Matrix cracks mainly depend on bedding strength, while the generation of tensile cracks is determined by the shear-to-tensile strength ratio of beddings (STR). The shale with a higher STR is likely to produce a more complex fracture network. Therefore, the bedding strength parameters should be carefully evaluated when the initiation and evolution of micro-cracking morphology in laminated shale formation are simulated.
Publisher: Elsevier BV
Date: 08-2022
Publisher: Wiley
Date: 05-05-2023
DOI: 10.1002/DUG2.12040
Abstract: Precipitation or dissolution due to geochemical reactions has been observed in the caprocks for CO 2 geosequestration. Geochemical reactions modify the caprock sealing efficiency with self‐limiting or self‐enhancement. However, the effect of this modification on the caprock sealing efficiency has not been fully investigated through multiphysical‐geochemical coupling analysis. In this study, a multiphysical‐geochemical coupling model was proposed to analyze caprock sealing efficiency. This coupling model considered the full couplings of caprock deformation, two‐phase flow, CO 2 concentration diffusion, geochemical reaction, and CO 2 sorption. The two‐phase flow only occurs in the fracture network and the CO 2 may partially dissolve into water and diffuse through the concentration difference. The dissolved CO 2 has geochemical reactions with some critical minerals, thus altering flow channels. The CO 2 in the fracture network diffuses into matrix, causing the matrix swelling. This fully coupling model was validated with a penetration experiment on a cement cube and compared with two other models for CO 2 storage plumes. Finally, the effects of geochemical reactions on penetration depth and pore pressure were studied through parametric study. The numerical simulations reveal that the coupling of geochemical reactions and matrix diffusion significantly affect the caprock sealing efficiency. Geochemical reactions occur at a short time after the arrival of CO 2 concentration and modify the fracture porosity. The CO 2 diffusion into the matrix requires a much longer time and mainly induces matrix swelling. These effects may produce self‐enhancement or self‐limiting depending on the flow rate in the fracture network, thus significantly modifying caprock sealing efficiency.
Publisher: Elsevier BV
Date: 03-2002
Publisher: Springer Science and Business Media LLC
Date: 05-06-2010
Publisher: Wiley
Date: 2003
DOI: 10.1002/NAG.286
Publisher: Elsevier BV
Date: 09-2017
Publisher: Wiley
Date: 23-05-2023
DOI: 10.1002/DUG2.12045
Publisher: Elsevier BV
Date: 05-2020
No related grants have been discovered for J.G. Wang.