The semi-analytical solutions to Fredlund and Hasan＇s one-dimensional （1D） consolidation for unsaturated soils with a semi-permeable drainage boundary are pre- seated. Two variables are introduced to transform the ...The semi-analytical solutions to Fredlund and Hasan＇s one-dimensional （1D） consolidation for unsaturated soils with a semi-permeable drainage boundary are pre- seated. Two variables are introduced to transform the two coupled governing equations of pore-water and pore-air pressures into an equivalent set of partial differential equations （PDFs）, which are easily solved by the Laplace transform method. Then, the pore-water pressure, pore-air pressure, and soil settlement are obtained in the Laplace domain. The Crump method is adopted to perform the inverse Laplace transform in order to obtain the semi-analytical solutions in the time domain. It is shown that the proposed solutions are more applicable to various types of boundary conditions and agree well with the existing solutions from the literature. Several numerical examples are provided to investigate the consolidation behavior of an unsaturated single-layer soil with single, double, mixed, and semi-permeable drainage boundaries. The changes in the pore-air and pore-water pres- sures and the soil settlement with the time factor at different values of the semi-permeable drainage boundary parameters are illustrated. In addition, parametric studies are con- ducted on the pore-air and pore-water pressures at different ratios （the air permeability coefficient to the water permeability coefficient） and depths.展开更多
It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on pr...It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on previous research on impermeable reservoir barrier, a mathematical flow model was derived for a horizontal well of a bottom water drive reservoir with a semi-permeable barrier. Besides, analytical equations were also presented to calculate critical parameters, such as production rate,pressure and potential difference. The effects of barrier, well and reservoir parameters on our model results were further investigated.The results show that the larger the barrier size is or the higher the barrier location is, the higher the critical production rate and potential difference of a horizontal well are. When the barrier permeability equals the formation permeability or the barrier width equals zero, the critical production rates converge to the values same to that of the case with no barrier. When the barrier permeability equals zero, the problem is regarded as a case of impermeable barrier. This model can be applied to predicting horizontal wells' critical production parameters in reservoirs with semi-permeable barriers.展开更多
The Group Ⅱ fresh groundwater bearing aquifers in the eastern plain of Tianjin underwent long term exploitation. This study shows that the area with greater water-level declining is associated with more rapid stratig...The Group Ⅱ fresh groundwater bearing aquifers in the eastern plain of Tianjin underwent long term exploitation. This study shows that the area with greater water-level declining is associated with more rapid stratigraphic compaction and consolidation. In the study area, the salty groundwater in the un-exploited overlying aquifers have the same dynamic characteristic of synchronization but different amplitude with the Group Ⅱ aquifers, showing that they have a close relationship. Cross-sectional study indicated that surface water, salty groundwater and underlying fresh groundwater belong to an integral water resources system. The compacted clay layers have the feature of semi-permeable membrane under alkaline condition. The infiltration of surface water is driven by the differences of osmotic pressure of salty water in each layer. When the water level difference between the Group Ⅱ aquifers and overlying salty aquifers is greater than osmotic water pressure difference, the salt water layer will desalinate downward and eventually, decreasing the water level of the upper aquifers, turning phreatic water amount supposed to evaporate to leakage recharge. Therefore, stopping mining groundwater in the Group Ⅱ aquifer will lead to other new environmental geology disaster.展开更多
Fracture analysis of a semi-permeable Yoffe-type interfacial crack propagating subsonically in magneto-electro-elastic （MEE） composites is presented based on the strip electro- magnetic polarization saturation （SE...Fracture analysis of a semi-permeable Yoffe-type interfacial crack propagating subsonically in magneto-electro-elastic （MEE） composites is presented based on the strip electro- magnetic polarization saturation （SEMPS） model. The electro-magnetic fields inside the crack are considered under the semi-permeable boundary condition. Nonlinear effects near the interfacial crack tip are represented by different electro-magnetic saturation zones. Utilizing the extended Stroh＇s method, we derive the moving dislocation densities as well as intensity factor and energy release rate for Yoffe-type MEE interracial crack. Numerical re- sults through an iterative approach are presented to show the characteristics of fracturedominant parameters with respect to propagation velocity and boundary condition category. The fracture-dominant parameters under the semi-permeable boundary condition are lower than those under the impermeable one, which implies that the electro-magnetic fields in the crack gap can retard the propagation of MEE interfacial crack.展开更多
The present investigation of the crack problem in piezoelectric materials is performed based on the non-local theory. After some manipulations, the impermeable crack, the permeable crack （the crack gap is full of NaC...The present investigation of the crack problem in piezoelectric materials is performed based on the non-local theory. After some manipulations, the impermeable crack, the permeable crack （the crack gap is full of NaCI solution）, and the semi-permeable crack （the crack gap is full of air or silicon oil） are reduced to a uniform formulation by assuming the normal electric displacement on the crack surfaces to be an unknown variable. Thus, a triple integral equation with the unknown normal electric displacement is established. By using the Newton iterative method and solving the triple integral equation, it is found that the normal electric displacement on the crack surfaces is no longer a constant as determined by previous studies, rather, it depends upon the remote combined electromechanical loadings. Numerical results of the stresses and electric displacement fields show that there are no singularities at the crack tips so that the stresses remain finite. It is of great significance that the concrete electric boundary condition on the crack surfaces exerts significant influence on the near-tip fields and in this way plays an important role in evaluating the crack stability in the non-local piezoelectric materials. More specifically, the impermeable crack model always overestimates the finite stresses at the crack tips, whereas the permeable crack model always underestimates them.展开更多
Reservoir deposition occurs over geologic periods of time. Although reservoirs are assumed to be homogenous for simplicity of analysis, most reservoirs are heterogeneous in nature. Some common forms of hetergeneity ar...Reservoir deposition occurs over geologic periods of time. Although reservoirs are assumed to be homogenous for simplicity of analysis, most reservoirs are heterogeneous in nature. Some common forms of hetergeneity are the presence of layers and the presence of different zones of fluids and/or rock in the formation. A modified semi-permeable model for multi-layered gas reservoirs with pseudo-steady state interlayer crossflow was developed. The model accounted for the effect of skin and wellbore storage, considers all layers open to a single well, which flows at constant total rate. This new numerical solution was proved to be computationally very efficient, and it has been validated by comparing the results with those of some simple, well known models in the well testing literature. The effects of the reservoir parameters such as permeability, vertical permeability, skin, wellbore storage on the wellbore response, pressure and layer production rate were investigated. Numerical solutions of the problem for the modified semi-permeable model were used to find the structure of crossflow in typical cases.展开更多
The cost of dairy manure treatment and bedding material purchase increases the operating cost of the dairy farm.Membrane-covered aerobic fermentation system has been widely used for dealing with dairy manure and recyc...The cost of dairy manure treatment and bedding material purchase increases the operating cost of the dairy farm.Membrane-covered aerobic fermentation system has been widely used for dealing with dairy manure and recycling the final product as bedding material.However,the microbial safety in each processing step is still uncertain.To better understand the bacterial community dynamics during the whole bedding conversion process,a full-chain and large-scale experiment including 16-day membrane-covered aerobic fermentation and 11-day bedding material application was conducted.The results showed that the pile temperatures in the fermentation stage rapidly increased to 80°C and maintained>50°C for more than 11 days and the use of fermentation product as bedding material provided cows with a stable and comfortable bedding environment.The Chao1 and Shannon index decreased at the end of the fermentation stage and remained stable in the application stage,indicating that membrane-covered aerobic fermentation effectively killed some pathogenic bacteria and guaranteed both the maturity and stability of the final product.The dominant bacteria in the fermentation stage were Acinetobacter,Thermus,and Rhodothermus at genus level.Seven common potential pathogens of mastitis(Staphylococcus,Enterococcus,Serratia,Pseudomonas,Corynebacterium,Mycobacterium,and Bacillus)were found at the end of fermentation stage but the relative abundance was low(0.0025%-0.2727%).The dominant bacteria in the application stage mainly included Acinetobacter,Pseudomonas,and Flavobacterium at the genus level.The relative abundance of Pseudomonas increased in the application stage,which was a reminder to the dairy farm to pay attention to the disinfection and timely replacement of bedding material to prevent the occurrence of dairy mastitis.The results of this study contributed deep understanding of the microorganism-driven bedding conversion process and provide practical guidance and cautions for the bedding materials application.展开更多
A new model called semi-permeable wall model is presented for multilayer gas reservoir. The model is used to study the influence of crossflow on pressure transient well tests and other single-phase flow problems. It i...A new model called semi-permeable wall model is presented for multilayer gas reservoir. The model is used to study the influence of crossflow on pressure transient well tests and other single-phase flow problems. It is suggested here to use this model to approximate the actual multilayer gas reservoir, so that the problem is greatly simplified mathematically. Its differential equation is established here for multilayer gas reservoirs, and is linearized by normalized pseudo pressure and pseudo time. Simulation program is developed by finite-difference method when all layers are perforated. The feature of wellbore pressure and rate is clarified by analyzing the results of numerical simulation.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.41630633 and11672172)
文摘The semi-analytical solutions to Fredlund and Hasan＇s one-dimensional （1D） consolidation for unsaturated soils with a semi-permeable drainage boundary are pre- seated. Two variables are introduced to transform the two coupled governing equations of pore-water and pore-air pressures into an equivalent set of partial differential equations （PDFs）, which are easily solved by the Laplace transform method. Then, the pore-water pressure, pore-air pressure, and soil settlement are obtained in the Laplace domain. The Crump method is adopted to perform the inverse Laplace transform in order to obtain the semi-analytical solutions in the time domain. It is shown that the proposed solutions are more applicable to various types of boundary conditions and agree well with the existing solutions from the literature. Several numerical examples are provided to investigate the consolidation behavior of an unsaturated single-layer soil with single, double, mixed, and semi-permeable drainage boundaries. The changes in the pore-air and pore-water pres- sures and the soil settlement with the time factor at different values of the semi-permeable drainage boundary parameters are illustrated. In addition, parametric studies are con- ducted on the pore-air and pore-water pressures at different ratios （the air permeability coefficient to the water permeability coefficient） and depths.
基金Project(51404201)supported by the National Natural Science Foundation of ChinaProject(2011ZX05024-003)supported by the National Science and Technology Major Project of China+1 种基金Project(14ZB0045)supported by the Scientific Project of Sichuan Provincial Education Department,ChinaProject(2015JY0076)supported by Basic Application Research of Science and Technology Department of Sichuan Province,China
文摘It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on previous research on impermeable reservoir barrier, a mathematical flow model was derived for a horizontal well of a bottom water drive reservoir with a semi-permeable barrier. Besides, analytical equations were also presented to calculate critical parameters, such as production rate,pressure and potential difference. The effects of barrier, well and reservoir parameters on our model results were further investigated.The results show that the larger the barrier size is or the higher the barrier location is, the higher the critical production rate and potential difference of a horizontal well are. When the barrier permeability equals the formation permeability or the barrier width equals zero, the critical production rates converge to the values same to that of the case with no barrier. When the barrier permeability equals zero, the problem is regarded as a case of impermeable barrier. This model can be applied to predicting horizontal wells' critical production parameters in reservoirs with semi-permeable barriers.
文摘The Group Ⅱ fresh groundwater bearing aquifers in the eastern plain of Tianjin underwent long term exploitation. This study shows that the area with greater water-level declining is associated with more rapid stratigraphic compaction and consolidation. In the study area, the salty groundwater in the un-exploited overlying aquifers have the same dynamic characteristic of synchronization but different amplitude with the Group Ⅱ aquifers, showing that they have a close relationship. Cross-sectional study indicated that surface water, salty groundwater and underlying fresh groundwater belong to an integral water resources system. The compacted clay layers have the feature of semi-permeable membrane under alkaline condition. The infiltration of surface water is driven by the differences of osmotic pressure of salty water in each layer. When the water level difference between the Group Ⅱ aquifers and overlying salty aquifers is greater than osmotic water pressure difference, the salt water layer will desalinate downward and eventually, decreasing the water level of the upper aquifers, turning phreatic water amount supposed to evaporate to leakage recharge. Therefore, stopping mining groundwater in the Group Ⅱ aquifer will lead to other new environmental geology disaster.
基金sponsored by the National Science Foundation of China (Nos.11090334 and 11572227)
文摘Fracture analysis of a semi-permeable Yoffe-type interfacial crack propagating subsonically in magneto-electro-elastic （MEE） composites is presented based on the strip electro- magnetic polarization saturation （SEMPS） model. The electro-magnetic fields inside the crack are considered under the semi-permeable boundary condition. Nonlinear effects near the interfacial crack tip are represented by different electro-magnetic saturation zones. Utilizing the extended Stroh＇s method, we derive the moving dislocation densities as well as intensity factor and energy release rate for Yoffe-type MEE interracial crack. Numerical re- sults through an iterative approach are presented to show the characteristics of fracturedominant parameters with respect to propagation velocity and boundary condition category. The fracture-dominant parameters under the semi-permeable boundary condition are lower than those under the impermeable one, which implies that the electro-magnetic fields in the crack gap can retard the propagation of MEE interfacial crack.
基金The project was supported by the National Natural Science Foundation of China(10572110)the Doctor Foundation of the Chinese Education Ministry.
文摘The present investigation of the crack problem in piezoelectric materials is performed based on the non-local theory. After some manipulations, the impermeable crack, the permeable crack （the crack gap is full of NaCI solution）, and the semi-permeable crack （the crack gap is full of air or silicon oil） are reduced to a uniform formulation by assuming the normal electric displacement on the crack surfaces to be an unknown variable. Thus, a triple integral equation with the unknown normal electric displacement is established. By using the Newton iterative method and solving the triple integral equation, it is found that the normal electric displacement on the crack surfaces is no longer a constant as determined by previous studies, rather, it depends upon the remote combined electromechanical loadings. Numerical results of the stresses and electric displacement fields show that there are no singularities at the crack tips so that the stresses remain finite. It is of great significance that the concrete electric boundary condition on the crack surfaces exerts significant influence on the near-tip fields and in this way plays an important role in evaluating the crack stability in the non-local piezoelectric materials. More specifically, the impermeable crack model always overestimates the finite stresses at the crack tips, whereas the permeable crack model always underestimates them.
文摘Reservoir deposition occurs over geologic periods of time. Although reservoirs are assumed to be homogenous for simplicity of analysis, most reservoirs are heterogeneous in nature. Some common forms of hetergeneity are the presence of layers and the presence of different zones of fluids and/or rock in the formation. A modified semi-permeable model for multi-layered gas reservoirs with pseudo-steady state interlayer crossflow was developed. The model accounted for the effect of skin and wellbore storage, considers all layers open to a single well, which flows at constant total rate. This new numerical solution was proved to be computationally very efficient, and it has been validated by comparing the results with those of some simple, well known models in the well testing literature. The effects of the reservoir parameters such as permeability, vertical permeability, skin, wellbore storage on the wellbore response, pressure and layer production rate were investigated. Numerical solutions of the problem for the modified semi-permeable model were used to find the structure of crossflow in typical cases.
基金the China Agriculture Research System of MOF and MARA(CARS 36)Fundamental Research Funds for the Central Universities(Grant No.2021TC039)the National Natural Science Foundation of China(Grant No.31771684).
文摘The cost of dairy manure treatment and bedding material purchase increases the operating cost of the dairy farm.Membrane-covered aerobic fermentation system has been widely used for dealing with dairy manure and recycling the final product as bedding material.However,the microbial safety in each processing step is still uncertain.To better understand the bacterial community dynamics during the whole bedding conversion process,a full-chain and large-scale experiment including 16-day membrane-covered aerobic fermentation and 11-day bedding material application was conducted.The results showed that the pile temperatures in the fermentation stage rapidly increased to 80°C and maintained>50°C for more than 11 days and the use of fermentation product as bedding material provided cows with a stable and comfortable bedding environment.The Chao1 and Shannon index decreased at the end of the fermentation stage and remained stable in the application stage,indicating that membrane-covered aerobic fermentation effectively killed some pathogenic bacteria and guaranteed both the maturity and stability of the final product.The dominant bacteria in the fermentation stage were Acinetobacter,Thermus,and Rhodothermus at genus level.Seven common potential pathogens of mastitis(Staphylococcus,Enterococcus,Serratia,Pseudomonas,Corynebacterium,Mycobacterium,and Bacillus)were found at the end of fermentation stage but the relative abundance was low(0.0025%-0.2727%).The dominant bacteria in the application stage mainly included Acinetobacter,Pseudomonas,and Flavobacterium at the genus level.The relative abundance of Pseudomonas increased in the application stage,which was a reminder to the dairy farm to pay attention to the disinfection and timely replacement of bedding material to prevent the occurrence of dairy mastitis.The results of this study contributed deep understanding of the microorganism-driven bedding conversion process and provide practical guidance and cautions for the bedding materials application.
基金the National NatualScience Foundation of China (No.59995460).
文摘A new model called semi-permeable wall model is presented for multilayer gas reservoir. The model is used to study the influence of crossflow on pressure transient well tests and other single-phase flow problems. It is suggested here to use this model to approximate the actual multilayer gas reservoir, so that the problem is greatly simplified mathematically. Its differential equation is established here for multilayer gas reservoirs, and is linearized by normalized pseudo pressure and pseudo time. Simulation program is developed by finite-difference method when all layers are perforated. The feature of wellbore pressure and rate is clarified by analyzing the results of numerical simulation.
