Sediment incipient motion is the first step in sediment resuspension.Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary.A fl...Sediment incipient motion is the first step in sediment resuspension.Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary.A flume experiment was designed to innovatively divide the seabed into two parts to control the dynamic response of the seabed and control the seepage conditions.In the experiment,the seabed sediments and the amplitude of internal solitary waves(ISWs)were changed to compare and analyze the impact of seepage flow on the sediment resuspension by shoaling ISWs.Moreover,parametric research and verification were carried out.Results indicate that seepage flow can greatly influence fine sand,promote sediment resuspension,and increase the amount of suspension by two times on average.However,seepage flow had a little effect on the suspension of clayey silt and sandy silt.Besides,seepage force was added to the traditional gravity,drag force,and uplift force,and the parameterization of threshold starting shear stress of coarse-grained sediments was developed.The results of this parameterization were verified,and seepage force was critical to parameterization.The threshold starting shear stress was reduced by 54.6%after increasing the seepage force.The physical mechanism of this process corresponded to the vertical reciprocating transient seepage in and out the seabed interface caused by the wave-induced transient excess pore water pressure.This quantitative study on seepage flow for shear stress of coarse-grained sediments induced by ISWs is critical to geohazard assessment.展开更多
hi this paper. the author uses the theory of fluid mechanics. dynamics of fluids in Porous media. gas seepage flow in coal seams and combines the tests in the laboratory with the actual coal infusion to have an inves...hi this paper. the author uses the theory of fluid mechanics. dynamics of fluids in Porous media. gas seepage flow in coal seams and combines the tests in the laboratory with the actual coal infusion to have an investigating and study from the theory to the mechanism of coal infusion to wet coal seams. through the analysis to the process of coal infusion the author builds up the mathematical models and has a detailed discussion to the boundary conditions of coal infusion. Because the equation sets to describe coal infusion are non-linear. we have made a simplification to them to use the dimension analysis theory by leading into the non-dimensions of water pressure of coal infusion, seepage flow rate. increment of coal seam moisture and so on Besides the analytic and approximate solutions have also been discussed. At last. we use the scientific research item of the actual coal infusion to illustrate the effects and importance of the theory to direct actual coal infusion and its designs.展开更多
This paper focuses on the influence of permeability anisotropy of seepage flow on the face stability for a shied tunnel.An analytical model has been proposed to present the hydraulic head distribution around the tunne...This paper focuses on the influence of permeability anisotropy of seepage flow on the face stability for a shied tunnel.An analytical model has been proposed to present the hydraulic head distribution around the tunnel face in the anisotropic ground,considering the difference of permeability coefficient in the horizontal direction and the vertical direction.The rationality of the proposed model is ver-ified by a series of numerical simulations.Then,an analytical model of face stability for a tunnel under the anisotropic seepage has been established based on the limit analysis upper bound method.Comparisons of the analytical solutions and the numerical simulations are conducted,and the limit support pressure of the two methods is consistent.The effect of permeability anisotropy and water pressure on the stability of the tunnel face is analyzed through the three-dimensional analytical solution.Anisotropy of permeability has a significant impact on the stability of the tunnel face,and its impact gradually decreases.It can also be found that the water pressure coefficient of the tunnel face has a significant effect on the limit support pressure and the failure area when the ratio of the horizontal permeability to the vertical permeability is large.展开更多
The standing column well for ground source heat pump systems is a promising technology with high efficiency and environmental benefit, where groundwater is drawn from the bottom of a well and then re-injected to its t...The standing column well for ground source heat pump systems is a promising technology with high efficiency and environmental benefit, where groundwater is drawn from the bottom of a well and then re-injected to its top after transferring heat with heat pumps. Heat transfer analysis of great significance and aquifer involves complex problems. Determining the groundwater seepage flow is a precondition to solve the energy equation describing the heat transfer of the system. Only when piezometric head is obtained, the seepage velocity can be determined according to Darcy's law. In this article the groundwater seepage flow in an axial symmetrical geometry was studied under the assumption that gross groundwater flow is neglected. An analytical solution of the groundwater seepage flow for a confined aquifer was acquired by using the integral transform method, which may provide a foundation for heat transfer analysis of the standing column well system.展开更多
With the consideration of the visco―elasticity, the adsorption effect andthe variation of rheological parameters, a seepage flow model of visco-elastic polymer solutions wasestablished. The model was numerically trea...With the consideration of the visco―elasticity, the adsorption effect andthe variation of rheological parameters, a seepage flow model of visco-elastic polymer solutions wasestablished. The model was numerically treated with the finite difference method. Then curves ofBottom Hole Pressure (BHP) and formation pressure were drawn. The influences of the relaxation time,the injection rate, the permeability reduction coefficient, the consistency coefficient and thepower-law exponent of the injected fluid on pressure performance were analyzed. This study showsthat it is necessary to consider the visco-elasticity of non-Newtonian fluid in analyzing ofpressure performance in the polymer flooding.展开更多
In this paper, the algorithm developed on the concept of the Composite Element Method (CEM) is proposed for the seepage flow in discontinuous rock masses, The basic idea is that if an element contains one or more di...In this paper, the algorithm developed on the concept of the Composite Element Method (CEM) is proposed for the seepage flow in discontinuous rock masses, The basic idea is that if an element contains one or more discontinuity segments, it will be denoted as a composite element having a set of hydraulic potential values defined at its nodes. By the variation principle, the governing equation can be established to solve the unknown hydraulic potential values at the composite element nodes. The main advantage of the proposed model is that the generation of calculation mesh will not be restricted strongly by the number, the position and the orientation of the discontinuities, A numerical example is presented at the end of the paper, to show the validity of the proposed model.展开更多
On the basis of the generalized physical model of the riverbank, the experiments were conducted to study the mechanisms of riverbank failure under the coupling effect of seepage flow and river flow. The experimental s...On the basis of the generalized physical model of the riverbank, the experiments were conducted to study the mechanisms of riverbank failure under the coupling effect of seepage flow and river flow. The experimental setup was specially designed, as well as test point location, parameters and procedures, and the main influencing factors were analyzed affecting riverbank failure based on the failure types, the variations of pore water pressure and soil displacement. The results indicated that the coupling effect has different influences on the bank failure in three aspects: the failure type, the process and the extent. In addition, the river flow played a more important role than the seepage flow in the coupling effect on the bank failure.展开更多
To investigate the relationship between the structural characteristics and seepage flow behavior of rough single rock fractures,a set of single fracture physical models were produced using the WeierstrasseMandelbrot f...To investigate the relationship between the structural characteristics and seepage flow behavior of rough single rock fractures,a set of single fracture physical models were produced using the WeierstrasseMandelbrot functions to test the seepage flow performance.Six single fractures,with various surface roughnesses characterized by fractal dimensions,were built using COMSOL multiphysics software.The fluid flow behavior through the rough fractures and the influences of the rough surfaces on the fluid flow behavior was then monitored.The numerical simulation indicates that there is a linear relationship between the average flow velocity over the entire flow path and the fractal dimension of the rough surface.It is shown that there is good agreement between the numerical results and the experimental data in terms of the properties a of the fluid flowing through the rough single rock fractures.展开更多
The cut-off negative pressure method is one of effective approaches to solve the seepage flow with free surface. According to the characteristics of this method, however, it has been found out that the deficiency of t...The cut-off negative pressure method is one of effective approaches to solve the seepage flow with free surface. According to the characteristics of this method, however, it has been found out that the deficiency of the algorithms is to easily cause inaccurate simulation in the vicinity of free surface owing to the penalty function with only one controlling penalty parameter. Therefore, an improved cut-off pressure method was presented by constructing penalty function with two controlling penalty parameters. The improved algorithms were illustrated to be able to improve the simulation accuracy and raise the convergence speed through considering the effects of the partially saturated or unsaturated elements more reasonably and calculating the nodal external forces more accurately. Finally, the improved cut-off negative pressure method was applied to the simulation of unsteady seepage flow with free surface, and the corresponding program codes were developed with validation of some cases.展开更多
The BZ19-6 gas field is characterized by high temperature and high pressure (HTHP), high condensate content, little difference between the formation pressure and dew point pressure, and large amount of reverse condens...The BZ19-6 gas field is characterized by high temperature and high pressure (HTHP), high condensate content, little difference between the formation pressure and dew point pressure, and large amount of reverse condensate liquid. During the early stage of depletion development, the production gas-oil ratio (GOR) and production capacity remain relatively stable, which is inconsistent with the conventional reverse condensate seepage law. In view of the static and dynamic conflict in development and production, indoor high-temperature and high-pressure PVT experiment was carried out to reveal the mist-like condensation phenomenon of fluids in the BZ19-6 formation. And the seepage characteristics of condensate gas reservoirs with various degrees of depletion under the condition of HTHP were analyzed based on production performance. The change rule of fluid phase state was analyzed in response to the characterization difficulties of the seepage mechanism. The fluid state was described using the miscible mechanism. And the interphase permeability interpolation coefficient was introduced based on interfacial tension. By doing so, the accurate characterization of the “single-phase flow of condensate gas-near-miscible mist-like quasi single-phase flow-oil-gas two-phase flow” during the development process was achieved. Then the accurate fitting of key indicators for oilfield development was completed, and the distribution law of formation pressure and the law of condensate oil precipitation under different reservoir conditions are obtained. Based on research results, the regulation strategy of variable flow rate production was developed. Currently, the work system has been optimized for 11 wells, achieving a “zero increase” in the GOS of the gas field and an annual oil increase of 22,000 cubic meters.展开更多
"Generalized mobility"is used to realize the unification of tube flow and seepage in form and the unification of commonly used linear and nonlinear flow laws in form,which makes it possible to use the same f..."Generalized mobility"is used to realize the unification of tube flow and seepage in form and the unification of commonly used linear and nonlinear flow laws in form,which makes it possible to use the same form of motion equations to construct unified governing equations for reservoirs of different scales in different regions.Firstly,by defining the generalized mobility under different flow conditions,the basic equation governing fluid flow in reservoir coupling generalized tube flow and seepage is established.Secondly,two typical well test analysis models for coupling tube flow and seepage flow are given,namely,pipe-shaped composite reservoir model and partially open cylindrical reservoir model.The log-log pressure draw-down type-curve of composite pipe-shaped reservoir model can show characteristics of two sets of linear flow.The log-log pressure drawdown plot of partially opened cylindrical reservoir model can show the characteristics of spherical flow and linear flow,as well as spherical flow and radial flow.The pressure build-up derivative curves of the two models basically coincide with their respective pressure drawdown derivative curves in the early stage,pulling down features in the late stage,and the shorter the production time is,the earlier the pulling down feature appears.Finally,the practicability and reliability of the models presented in this paper are verified by three application examples.展开更多
Seepage flow through soils,rocks and geotechnical structures has a great influence on their stabilities and performances,and seepage control is a critical technological issue in engineering practices.The physical mech...Seepage flow through soils,rocks and geotechnical structures has a great influence on their stabilities and performances,and seepage control is a critical technological issue in engineering practices.The physical mechanisms associated with various engineering measures for seepage control are investigated from a new perspective within the framework of continuum mechanics;and an equation-based classification of seepage control mechanisms is proposed according to their roles in the mathematical models for seepage flow,including control mechanisms by coupled processes,initial states,boundary conditions and hydraulic properties.The effects of each mechanism on seepage control are illustrated with examples in hydroelectric engineering and radioactive waste disposal,and hence the reasonability of classification is demonstrated.Advice on performance assessment and optimization design of the seepage control systems in geotechnical engineering is provided,and the suggested procedure would serve as a useful guidance for cost-effective control of seepage flow in various engineering practices.展开更多
The study of flow behaviour of water-sand mixtures in fractured rocks is of great necessity to understand the producing mechanism and prevention of water inrush and sand gushing accidents.A self-developed seepage test...The study of flow behaviour of water-sand mixtures in fractured rocks is of great necessity to understand the producing mechanism and prevention of water inrush and sand gushing accidents.A self-developed seepage test system is used in this paper to conduct laboratory experiments in order to study the influence of the particle size distribution,the void ratio,and the initial mass of Aeolian sand on the flow behavior.It is concluded that the water flow velocity is insensitive to the initial mass of the Aeolian sand but increases with the power exponent in the Talbot formula and the specimen height.The outflow of the Aeolian sand increases with the power exponent in the Talbot formula,the specimen height,and the initial mass of the Aeolian sand.Besides,the outflow of the Aeolian sand changes exponentially with the water flow velocity.Finally,it is found that the fractured specimen has a maximum sand filtration capacity beyond which the outflow of the Aeolian sand significantly increases with the initial mass of the Aeolian sand.展开更多
Cemented tailings backfill(CTB) is made by mixing cement, tailings and water together, thus cement hydration and water seepage flow are the two crucial factors affecting the quality of CTB. Cement hydration process ca...Cemented tailings backfill(CTB) is made by mixing cement, tailings and water together, thus cement hydration and water seepage flow are the two crucial factors affecting the quality of CTB. Cement hydration process can release significant amount of heat to raise the temperature of CTB and in turn increase the rate of cement hydration. Meanwhile, the progress of cement hydration consumes water and produces hydration products to change the pore structures within CTB, which further influences the hydraulic behavior of CTB. In order to understand the hydraulic behavior of CTB, a numerical model was developed by coupling the hydraulic,thermal and hydration equations. This model was then implemented into COMSOL Multiphysics to simulate the evolutions of temperature and water seepage flow within CTB versus curing time. The predicted outcomes were compared with correspondent experimental results, proving the validity and availability of this model. By taking advantage of the validated model, effects of various initial CTB and curing temperatures, cement content, and CTB's geometric shapes on the hydraulic behavior of CTB were demonstrated numerically. The presented conclusions can contribute to preparing more environmentally friendly CTB structures.展开更多
Sediment resuspension is commonly assumed to be eroded from the seabed surface by an excess bottom shear stress and evolves in layers from the top down. Although considerable investigations have argued the importance ...Sediment resuspension is commonly assumed to be eroded from the seabed surface by an excess bottom shear stress and evolves in layers from the top down. Although considerable investigations have argued the importance of wave-induced seabed fluidization in affecting the sediment resuspension, few studies have been able to reliably evaluate its quantitative contribution till now. Attempt is made to preliminarily quantify the contribution of fluidization to resuspension using a series of large-scale wave flume experiments. The experimental results indicated that fluidization of the sandy silts of the Huanghe Delta account for 52.5% and 66.8% of the total resuspension under model scales of 4/20 and 6/20(i.e., relative water depth: the ratio of wave height to water depth), respectively. Some previously reported results obtained using the same flume and sediments are also summarized for a contrastive analysis, through which not only the positive correlation is confirmed, but also a parametric equation for depicting the relationship between the contribution of fluidization and the model scale is established. Finally, the contribution of fluidization is attributed to two physical mechanisms:(1) an attenuation of the erosion resistance of fluidized sediments in surface layers due to the disappearing of original cohesion and the uplifting effect resulting from upward seepage flows, and(2) seepage pumping of fines from the interior to the surface of fluidized seabed.展开更多
In this paper based on investigation on the structural types of sea embankments in the southeast coastal area of China, as well as the related tidal stages, waves and strength of marine soils, the finite element metho...In this paper based on investigation on the structural types of sea embankments in the southeast coastal area of China, as well as the related tidal stages, waves and strength of marine soils, the finite element method (FEM) calculations for seepage flow stability, including the overall stability against sliding and local stability of sloping surface under the action of tidal stage and waves are carried out. A comparison of the computational results of FEM for single circular slip, composite circular slip and geogrid reinforcement against sliding shows that for calculation of stability against sliding of marine soft soil foundation it is even more reasonable to use the composite circular slip. The stability of sloping type sea embankment against sliding is slightly better than that of the vertical face type; for the combination of three defences (wave, scour and seepage defences) the sea embankment structural type of a composite cross section with a platform should be a good one, but it still should be suitable to local conditions. For the local stability of riprap slope blocks and wall face loose masonry blocks, according to the analyses of wave-induced seepage flow fields, calculating formulas are given and they are verified by model test on block stability of breakwaters.展开更多
In this paper, a three-dimensional seepage flow problem was solved by use of boundary-fitted curvilinear coordinates transformation technique. The application of the presented method in a practical project was briefly...In this paper, a three-dimensional seepage flow problem was solved by use of boundary-fitted curvilinear coordinates transformation technique. The application of the presented method in a practical project was briefly described.展开更多
A fissured aquifer model used in petroleum engineering has been studied by the author. It is found that thefissure-induced inhomogeneity which appeared in reservoir media can be expressed by a delay timeτ whichcharac...A fissured aquifer model used in petroleum engineering has been studied by the author. It is found that thefissure-induced inhomogeneity which appeared in reservoir media can be expressed by a delay timeτ whichcharacterizes the process of transition from unsteady to steady seepage flow. Comparison between the fissured aquifer model mentioned above and corresponding homogeneous media is given in this paper. The expression of the characteristic delay timeτis independently derived by using the fissured porous media modeland by solving the characteristic time of an one-dimensioned diffusion equation in turn. The result shows thatthe τ value is in direct proportion to L2. L is the average size of aquifer rock blocks cut by fissures network.The larger the L value, the longer the fissures is and the less the density of fissure is. For identifying the inhomogeneity manifestation of aquifer, a criterion related with the characteristic time of external force action isproposed. In addition, a suggestion on the in-situ measurement of the new aquifer parameter, the 1 value, isgiven.展开更多
Even though a large number of large-scale arch dams with height larger than 200 m have been built in the world, the transient groundwater flow behaviors and the seepage control effects in the dam foundations under dif...Even though a large number of large-scale arch dams with height larger than 200 m have been built in the world, the transient groundwater flow behaviors and the seepage control effects in the dam foundations under difficult geological conditions are rarely reported. This paper presents a case study on the transient groundwater flow behaviors in the rock foundation of Jinping I double-curvature arch dam, the world's highest dam of this type to date that has been completed. Taking into account the geological settings at the site, an inverse modeling technique utilizing the time series measurements of both hydraulic head and discharge was adopted to back-calculate the permeability of the foundation rocks,which effectively improves the uniqueness and reliability of the inverse modeling results. The transient seepage flow in the dam foundation during the reservoir impounding was then modeled with a parabolic variational inequality(PVI) method. The distribution of pore water pressure, the amount of leakage, and the performance of the seepage control system in the dam foundation during the entire impounding process were finally illustrated with the numerical results.展开更多
A stochastic simulation of fluid flow in porous media using a complex variable expression method (SFCM) is presented in this paper. Hydraulic conductivity is considered as a random variable and is then expressed in ...A stochastic simulation of fluid flow in porous media using a complex variable expression method (SFCM) is presented in this paper. Hydraulic conductivity is considered as a random variable and is then expressed in complex variable form, the real part of which is a deterministic value and the imaginary part is a variable value. The stochastic seepage flow is simulated with the SFCM and is compared with the results calculated with the Monte Carlo stochastic finite element method. In using the Monte Carlo method to simulate the stochastic seepage flow field, the hydraulic conductivity is assumed in three different probability distributions using random sampling method. The obtained seepage flow field is examined through skewness analysis, and the skewed distribution probability density function is given. The head mode value and the head comprehensive standard deviation are used to represent the statistics of calculation results obtained by the Monte Carlo method. The stochastic seepage flow field simulated by the SFCM is confirmed to be similar to that given by the Monte Carlo method from numerical aspects. The range of coefficient of variation of hydraulic conductivity in SFCM is larger than used previously in stochastic seepage flow field simulations, and the computation time is short. The results proved that the SFCM is a convenient calculating method for solving the complex problems.展开更多
基金Supported by the Natural Science Foundation of Jiangsu Province(No.BK20210527)the Open Research Fund of Key Laboratory of Coastal Science and Integrated Management,Ministry of Natural Resources(No.2021COSIMQ002)+1 种基金the National Natural Science Foundation of China(Nos.42107158,41831280)the Fundamental Research Funds for the Central Universities(No.2021QN1096)。
文摘Sediment incipient motion is the first step in sediment resuspension.Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary.A flume experiment was designed to innovatively divide the seabed into two parts to control the dynamic response of the seabed and control the seepage conditions.In the experiment,the seabed sediments and the amplitude of internal solitary waves(ISWs)were changed to compare and analyze the impact of seepage flow on the sediment resuspension by shoaling ISWs.Moreover,parametric research and verification were carried out.Results indicate that seepage flow can greatly influence fine sand,promote sediment resuspension,and increase the amount of suspension by two times on average.However,seepage flow had a little effect on the suspension of clayey silt and sandy silt.Besides,seepage force was added to the traditional gravity,drag force,and uplift force,and the parameterization of threshold starting shear stress of coarse-grained sediments was developed.The results of this parameterization were verified,and seepage force was critical to parameterization.The threshold starting shear stress was reduced by 54.6%after increasing the seepage force.The physical mechanism of this process corresponded to the vertical reciprocating transient seepage in and out the seabed interface caused by the wave-induced transient excess pore water pressure.This quantitative study on seepage flow for shear stress of coarse-grained sediments induced by ISWs is critical to geohazard assessment.
文摘hi this paper. the author uses the theory of fluid mechanics. dynamics of fluids in Porous media. gas seepage flow in coal seams and combines the tests in the laboratory with the actual coal infusion to have an investigating and study from the theory to the mechanism of coal infusion to wet coal seams. through the analysis to the process of coal infusion the author builds up the mathematical models and has a detailed discussion to the boundary conditions of coal infusion. Because the equation sets to describe coal infusion are non-linear. we have made a simplification to them to use the dimension analysis theory by leading into the non-dimensions of water pressure of coal infusion, seepage flow rate. increment of coal seam moisture and so on Besides the analytic and approximate solutions have also been discussed. At last. we use the scientific research item of the actual coal infusion to illustrate the effects and importance of the theory to direct actual coal infusion and its designs.
基金the financial support provided by National Natural Science Foundation of China(Grant No.51978019)Beijing Natural Science Foundation(Grant No.8222004).
文摘This paper focuses on the influence of permeability anisotropy of seepage flow on the face stability for a shied tunnel.An analytical model has been proposed to present the hydraulic head distribution around the tunnel face in the anisotropic ground,considering the difference of permeability coefficient in the horizontal direction and the vertical direction.The rationality of the proposed model is ver-ified by a series of numerical simulations.Then,an analytical model of face stability for a tunnel under the anisotropic seepage has been established based on the limit analysis upper bound method.Comparisons of the analytical solutions and the numerical simulations are conducted,and the limit support pressure of the two methods is consistent.The effect of permeability anisotropy and water pressure on the stability of the tunnel face is analyzed through the three-dimensional analytical solution.Anisotropy of permeability has a significant impact on the stability of the tunnel face,and its impact gradually decreases.It can also be found that the water pressure coefficient of the tunnel face has a significant effect on the limit support pressure and the failure area when the ratio of the horizontal permeability to the vertical permeability is large.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50476040).
文摘The standing column well for ground source heat pump systems is a promising technology with high efficiency and environmental benefit, where groundwater is drawn from the bottom of a well and then re-injected to its top after transferring heat with heat pumps. Heat transfer analysis of great significance and aquifer involves complex problems. Determining the groundwater seepage flow is a precondition to solve the energy equation describing the heat transfer of the system. Only when piezometric head is obtained, the seepage velocity can be determined according to Darcy's law. In this article the groundwater seepage flow in an axial symmetrical geometry was studied under the assumption that gross groundwater flow is neglected. An analytical solution of the groundwater seepage flow for a confined aquifer was acquired by using the integral transform method, which may provide a foundation for heat transfer analysis of the standing column well system.
文摘With the consideration of the visco―elasticity, the adsorption effect andthe variation of rheological parameters, a seepage flow model of visco-elastic polymer solutions wasestablished. The model was numerically treated with the finite difference method. Then curves ofBottom Hole Pressure (BHP) and formation pressure were drawn. The influences of the relaxation time,the injection rate, the permeability reduction coefficient, the consistency coefficient and thepower-law exponent of the injected fluid on pressure performance were analyzed. This study showsthat it is necessary to consider the visco-elasticity of non-Newtonian fluid in analyzing ofpressure performance in the polymer flooding.
基金Project supported by the National Natural Science Foundation of China (Grant Nos:50379039,50239070).
文摘In this paper, the algorithm developed on the concept of the Composite Element Method (CEM) is proposed for the seepage flow in discontinuous rock masses, The basic idea is that if an element contains one or more discontinuity segments, it will be denoted as a composite element having a set of hydraulic potential values defined at its nodes. By the variation principle, the governing equation can be established to solve the unknown hydraulic potential values at the composite element nodes. The main advantage of the proposed model is that the generation of calculation mesh will not be restricted strongly by the number, the position and the orientation of the discontinuities, A numerical example is presented at the end of the paper, to show the validity of the proposed model.
基金supported by the Chinese Key Technology R and D Program of the Eleventh Five-year Plan (Grant No.2008BAB29B04)the Non-Profit Industry Financial Program of Ministry of Water Resources (Grant Nos. 200801030,S111001)supported by the Nanjing Hydraulic Research Institute Science Fund Program (Grant No. Y110001)
文摘On the basis of the generalized physical model of the riverbank, the experiments were conducted to study the mechanisms of riverbank failure under the coupling effect of seepage flow and river flow. The experimental setup was specially designed, as well as test point location, parameters and procedures, and the main influencing factors were analyzed affecting riverbank failure based on the failure types, the variations of pore water pressure and soil displacement. The results indicated that the coupling effect has different influences on the bank failure in three aspects: the failure type, the process and the extent. In addition, the river flow played a more important role than the seepage flow in the coupling effect on the bank failure.
基金The authors are grateful to the National Natural Science Funds for Distinguished Young Scholars of China(Grant No 51125017)the National Natural Science Foundation of China(Grant No 51374213)+3 种基金the Creative Research Group Program of Jiangsu Province(Grant No 2014-27)the Priority Academic Program Development of Jiangsu Higher Education Institutions(Grant No PAPD-2014-12)the Open Research Project of State Key Laboratory for Geomechanics and Underground Engineering(Grant No SKLGDUEK1318)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No 51421003)for their financial supports.
文摘To investigate the relationship between the structural characteristics and seepage flow behavior of rough single rock fractures,a set of single fracture physical models were produced using the WeierstrasseMandelbrot functions to test the seepage flow performance.Six single fractures,with various surface roughnesses characterized by fractal dimensions,were built using COMSOL multiphysics software.The fluid flow behavior through the rough fractures and the influences of the rough surfaces on the fluid flow behavior was then monitored.The numerical simulation indicates that there is a linear relationship between the average flow velocity over the entire flow path and the fractal dimension of the rough surface.It is shown that there is good agreement between the numerical results and the experimental data in terms of the properties a of the fluid flowing through the rough single rock fractures.
文摘The cut-off negative pressure method is one of effective approaches to solve the seepage flow with free surface. According to the characteristics of this method, however, it has been found out that the deficiency of the algorithms is to easily cause inaccurate simulation in the vicinity of free surface owing to the penalty function with only one controlling penalty parameter. Therefore, an improved cut-off pressure method was presented by constructing penalty function with two controlling penalty parameters. The improved algorithms were illustrated to be able to improve the simulation accuracy and raise the convergence speed through considering the effects of the partially saturated or unsaturated elements more reasonably and calculating the nodal external forces more accurately. Finally, the improved cut-off negative pressure method was applied to the simulation of unsteady seepage flow with free surface, and the corresponding program codes were developed with validation of some cases.
文摘The BZ19-6 gas field is characterized by high temperature and high pressure (HTHP), high condensate content, little difference between the formation pressure and dew point pressure, and large amount of reverse condensate liquid. During the early stage of depletion development, the production gas-oil ratio (GOR) and production capacity remain relatively stable, which is inconsistent with the conventional reverse condensate seepage law. In view of the static and dynamic conflict in development and production, indoor high-temperature and high-pressure PVT experiment was carried out to reveal the mist-like condensation phenomenon of fluids in the BZ19-6 formation. And the seepage characteristics of condensate gas reservoirs with various degrees of depletion under the condition of HTHP were analyzed based on production performance. The change rule of fluid phase state was analyzed in response to the characterization difficulties of the seepage mechanism. The fluid state was described using the miscible mechanism. And the interphase permeability interpolation coefficient was introduced based on interfacial tension. By doing so, the accurate characterization of the “single-phase flow of condensate gas-near-miscible mist-like quasi single-phase flow-oil-gas two-phase flow” during the development process was achieved. Then the accurate fitting of key indicators for oilfield development was completed, and the distribution law of formation pressure and the law of condensate oil precipitation under different reservoir conditions are obtained. Based on research results, the regulation strategy of variable flow rate production was developed. Currently, the work system has been optimized for 11 wells, achieving a “zero increase” in the GOS of the gas field and an annual oil increase of 22,000 cubic meters.
基金Supported by the Scientific Research Project of Key Laboratory of Shaanxi Provincial Department of Education(13JS090)。
文摘"Generalized mobility"is used to realize the unification of tube flow and seepage in form and the unification of commonly used linear and nonlinear flow laws in form,which makes it possible to use the same form of motion equations to construct unified governing equations for reservoirs of different scales in different regions.Firstly,by defining the generalized mobility under different flow conditions,the basic equation governing fluid flow in reservoir coupling generalized tube flow and seepage is established.Secondly,two typical well test analysis models for coupling tube flow and seepage flow are given,namely,pipe-shaped composite reservoir model and partially open cylindrical reservoir model.The log-log pressure draw-down type-curve of composite pipe-shaped reservoir model can show characteristics of two sets of linear flow.The log-log pressure drawdown plot of partially opened cylindrical reservoir model can show the characteristics of spherical flow and linear flow,as well as spherical flow and radial flow.The pressure build-up derivative curves of the two models basically coincide with their respective pressure drawdown derivative curves in the early stage,pulling down features in the late stage,and the shorter the production time is,the earlier the pulling down feature appears.Finally,the practicability and reliability of the models presented in this paper are verified by three application examples.
基金Supported by the National Natural Science Foundation of China(51079107,50839004)the Program for New Century Excellent Talents in University(NCET-09-0610)
文摘Seepage flow through soils,rocks and geotechnical structures has a great influence on their stabilities and performances,and seepage control is a critical technological issue in engineering practices.The physical mechanisms associated with various engineering measures for seepage control are investigated from a new perspective within the framework of continuum mechanics;and an equation-based classification of seepage control mechanisms is proposed according to their roles in the mathematical models for seepage flow,including control mechanisms by coupled processes,initial states,boundary conditions and hydraulic properties.The effects of each mechanism on seepage control are illustrated with examples in hydroelectric engineering and radioactive waste disposal,and hence the reasonability of classification is demonstrated.Advice on performance assessment and optimization design of the seepage control systems in geotechnical engineering is provided,and the suggested procedure would serve as a useful guidance for cost-effective control of seepage flow in various engineering practices.
基金financially supported by the National Natural Science Foundation of China(Nos.41807209,51778215,51708185,and 51974293)the Young Teacher Foundation of HPU(No.2019XQG-19)+3 种基金the Henan Provincial Youth Talent Promotion Program(No.2020HYTP003)the Jiangsu Province Science Foundation for Youths(No.BK20180658)the Doctor Foundation of Henan Polytechnic University(Nos.B2017-51 and B2017-53)China Postdoctoral Science Foundation(No.2018M632422)。
文摘The study of flow behaviour of water-sand mixtures in fractured rocks is of great necessity to understand the producing mechanism and prevention of water inrush and sand gushing accidents.A self-developed seepage test system is used in this paper to conduct laboratory experiments in order to study the influence of the particle size distribution,the void ratio,and the initial mass of Aeolian sand on the flow behavior.It is concluded that the water flow velocity is insensitive to the initial mass of the Aeolian sand but increases with the power exponent in the Talbot formula and the specimen height.The outflow of the Aeolian sand increases with the power exponent in the Talbot formula,the specimen height,and the initial mass of the Aeolian sand.Besides,the outflow of the Aeolian sand changes exponentially with the water flow velocity.Finally,it is found that the fractured specimen has a maximum sand filtration capacity beyond which the outflow of the Aeolian sand significantly increases with the initial mass of the Aeolian sand.
基金Project(SKLCRSM13KFB05)supported by State Key Laboratory for Coal Resources and Safe Mining(China University of Mining&Technology)
文摘Cemented tailings backfill(CTB) is made by mixing cement, tailings and water together, thus cement hydration and water seepage flow are the two crucial factors affecting the quality of CTB. Cement hydration process can release significant amount of heat to raise the temperature of CTB and in turn increase the rate of cement hydration. Meanwhile, the progress of cement hydration consumes water and produces hydration products to change the pore structures within CTB, which further influences the hydraulic behavior of CTB. In order to understand the hydraulic behavior of CTB, a numerical model was developed by coupling the hydraulic,thermal and hydration equations. This model was then implemented into COMSOL Multiphysics to simulate the evolutions of temperature and water seepage flow within CTB versus curing time. The predicted outcomes were compared with correspondent experimental results, proving the validity and availability of this model. By taking advantage of the validated model, effects of various initial CTB and curing temperatures, cement content, and CTB's geometric shapes on the hydraulic behavior of CTB were demonstrated numerically. The presented conclusions can contribute to preparing more environmentally friendly CTB structures.
基金The National Natural Science Foundation of China under contract Nos 41272316 and 41372287the Joint Fund of NSFC and Marine Science Research Centers of Shandong Province of China under contract No.U1606401the Key Research and Development Program of Shandong Province of China under contract No.2016ZDJS09A03
文摘Sediment resuspension is commonly assumed to be eroded from the seabed surface by an excess bottom shear stress and evolves in layers from the top down. Although considerable investigations have argued the importance of wave-induced seabed fluidization in affecting the sediment resuspension, few studies have been able to reliably evaluate its quantitative contribution till now. Attempt is made to preliminarily quantify the contribution of fluidization to resuspension using a series of large-scale wave flume experiments. The experimental results indicated that fluidization of the sandy silts of the Huanghe Delta account for 52.5% and 66.8% of the total resuspension under model scales of 4/20 and 6/20(i.e., relative water depth: the ratio of wave height to water depth), respectively. Some previously reported results obtained using the same flume and sediments are also summarized for a contrastive analysis, through which not only the positive correlation is confirmed, but also a parametric equation for depicting the relationship between the contribution of fluidization and the model scale is established. Finally, the contribution of fluidization is attributed to two physical mechanisms:(1) an attenuation of the erosion resistance of fluidized sediments in surface layers due to the disappearing of original cohesion and the uplifting effect resulting from upward seepage flows, and(2) seepage pumping of fines from the interior to the surface of fluidized seabed.
文摘In this paper based on investigation on the structural types of sea embankments in the southeast coastal area of China, as well as the related tidal stages, waves and strength of marine soils, the finite element method (FEM) calculations for seepage flow stability, including the overall stability against sliding and local stability of sloping surface under the action of tidal stage and waves are carried out. A comparison of the computational results of FEM for single circular slip, composite circular slip and geogrid reinforcement against sliding shows that for calculation of stability against sliding of marine soft soil foundation it is even more reasonable to use the composite circular slip. The stability of sloping type sea embankment against sliding is slightly better than that of the vertical face type; for the combination of three defences (wave, scour and seepage defences) the sea embankment structural type of a composite cross section with a platform should be a good one, but it still should be suitable to local conditions. For the local stability of riprap slope blocks and wall face loose masonry blocks, according to the analyses of wave-induced seepage flow fields, calculating formulas are given and they are verified by model test on block stability of breakwaters.
文摘In this paper, a three-dimensional seepage flow problem was solved by use of boundary-fitted curvilinear coordinates transformation technique. The application of the presented method in a practical project was briefly described.
文摘A fissured aquifer model used in petroleum engineering has been studied by the author. It is found that thefissure-induced inhomogeneity which appeared in reservoir media can be expressed by a delay timeτ whichcharacterizes the process of transition from unsteady to steady seepage flow. Comparison between the fissured aquifer model mentioned above and corresponding homogeneous media is given in this paper. The expression of the characteristic delay timeτis independently derived by using the fissured porous media modeland by solving the characteristic time of an one-dimensioned diffusion equation in turn. The result shows thatthe τ value is in direct proportion to L2. L is the average size of aquifer rock blocks cut by fissures network.The larger the L value, the longer the fissures is and the less the density of fissure is. For identifying the inhomogeneity manifestation of aquifer, a criterion related with the characteristic time of external force action isproposed. In addition, a suggestion on the in-situ measurement of the new aquifer parameter, the 1 value, isgiven.
基金financially supported through NSERC Discovery Grant(RGPIN/4994-2014)
文摘Even though a large number of large-scale arch dams with height larger than 200 m have been built in the world, the transient groundwater flow behaviors and the seepage control effects in the dam foundations under difficult geological conditions are rarely reported. This paper presents a case study on the transient groundwater flow behaviors in the rock foundation of Jinping I double-curvature arch dam, the world's highest dam of this type to date that has been completed. Taking into account the geological settings at the site, an inverse modeling technique utilizing the time series measurements of both hydraulic head and discharge was adopted to back-calculate the permeability of the foundation rocks,which effectively improves the uniqueness and reliability of the inverse modeling results. The transient seepage flow in the dam foundation during the reservoir impounding was then modeled with a parabolic variational inequality(PVI) method. The distribution of pore water pressure, the amount of leakage, and the performance of the seepage control system in the dam foundation during the entire impounding process were finally illustrated with the numerical results.
基金supported by the National Natural Science Foundation of China(GrantNos.51079039,51009053)
文摘A stochastic simulation of fluid flow in porous media using a complex variable expression method (SFCM) is presented in this paper. Hydraulic conductivity is considered as a random variable and is then expressed in complex variable form, the real part of which is a deterministic value and the imaginary part is a variable value. The stochastic seepage flow is simulated with the SFCM and is compared with the results calculated with the Monte Carlo stochastic finite element method. In using the Monte Carlo method to simulate the stochastic seepage flow field, the hydraulic conductivity is assumed in three different probability distributions using random sampling method. The obtained seepage flow field is examined through skewness analysis, and the skewed distribution probability density function is given. The head mode value and the head comprehensive standard deviation are used to represent the statistics of calculation results obtained by the Monte Carlo method. The stochastic seepage flow field simulated by the SFCM is confirmed to be similar to that given by the Monte Carlo method from numerical aspects. The range of coefficient of variation of hydraulic conductivity in SFCM is larger than used previously in stochastic seepage flow field simulations, and the computation time is short. The results proved that the SFCM is a convenient calculating method for solving the complex problems.