Owing to the complexity of geo-engineering seepage problems influenced by different random factors, three-dimensional simulation and analysis of the stochastic seepage field plays an important role in engineering appl...Owing to the complexity of geo-engineering seepage problems influenced by different random factors, three-dimensional simulation and analysis of the stochastic seepage field plays an important role in engineering applications. A three-dimensional anisotropic heterogeneous steady random seepage model was developed on the basis of the finite element method. A statistical analysis of the distribution characteristics of soil parameters sampled from the main embankment of the Yangtze River in the Southern Jingzhou zone of China was conducted. The Kolomogorov-Smirnov test verified the statistical hypothesis that the permeability coefficient tensor has a Gaussian distribution. With the help of numerical analysis of the stochastic seepage field using the developed model, various statistical and random characteristics of the stochastic seepage field of the main embankment of the Yangtze River in the Southern Jingzhou zone of China were investigated. The model was also examined with statistical testing. Through the introduction of random variation of the upstream and downstream water levels into the model, the effects of the boundary randomness due to variation of the downstream and upstream water levels on the variation of simulated results presented with a vector series of the random seepage field were analyzed. Furthermore, the combined influence of the variation of the soil permeability coefficient and such seepage resistance measures as the cut-off wall and relief ditch on the hydraulic head distribution was analyzed and compared with the results obtained by determinate analysis. Meanwhile, sensitivities of the hydraulic gradient and downstream exit height to the variation of boundary water level were studied. The validity of the simulated results was verified by stochastic testing and measured data. The developed model provides more detail and a full stochastic algorithm to characterize and analyze three-dimensional stochastic seepage field problems.展开更多
Tunnel seepage is an important factor affecting the progress and safety of tunnel construction. In this paper, the mining method tunnel construction in the water-rich weathered granite stratum is taken as the research...Tunnel seepage is an important factor affecting the progress and safety of tunnel construction. In this paper, the mining method tunnel construction in the water-rich weathered granite stratum is taken as the research object. Through the analytical calculation method, the distribution law of tunnel seepage field under different waterproof and drainage types is studied, and the comparative analysis is carried out. According to the analytical solution, the influencing factors of grouting parameters are proposed. The sensitivity of the tunnel seepage field to the variation of grouting parameters is analyzed. A novel waterproof and drainage system, and construction technology suitable for subway tunnels with large buried depth below groundwater level were proposed.展开更多
In actual space, considering the heterogeneity and anisotropy of rock and soil, the difference of hydrogeological conditions and the influence of tunnel excavation, tunnel seepage problem is a very complex three-dimen...In actual space, considering the heterogeneity and anisotropy of rock and soil, the difference of hydrogeological conditions and the influence of tunnel excavation, tunnel seepage problem is a very complex three-dimensional seepage problem, which is very difficult to solve. The equivalent continuum model is one of the most commonly simplified models used in solving tunnel seepage problems. In this paper, the finite element software ABAQUS and the research results are used to establish a seepage numerical calculation model, study the influence of mining method construction on the seepage field in weathered granite, and clarify the influence of each stage of mining method construction on the groundwater environment. On this basis, the sensitivity of the seepage field to various factors such as natural environment, engineering geology and hydrogeology, tunnel construction and so on is analyzed, which provides a basis to establish the evaluation system of groundwater environment negative effect in weathered granite stratum by mining method tunnel construction.展开更多
Modifying the equivalent rotor resistivity with rotor end factor in 2-dimension(2-D)finite element analysis(FEA)is an effective way to analyze the 3-dimension(3-D)solid rotor problems.For the smooth solid rotor,five d...Modifying the equivalent rotor resistivity with rotor end factor in 2-dimension(2-D)finite element analysis(FEA)is an effective way to analyze the 3-dimension(3-D)solid rotor problems.For the smooth solid rotor,five different rotor end factors are discussed and compared with each other.It is theoretically clarified that the resistivity of rotor in 2-D FEA should be multiplied by the square of rotor end factors to take the 3-D end effect of solid rotor into account.For the slitted solid rotor,an improved rotor end factor is proposed based on the equivalent area algorithm of eddy currents in rotor,since the end factors of smooth solid rotor are not applicable.Finally,the time-harmonic finite element method(FEM)combined with the rotor end factor is applied to analyze the performance of solid rotor induction motor.The tested and computed results are in good agreement,which proves the effectiveness of rotor end factor for the simplication of 3-D solid rotor problems.展开更多
The governing differential equations of the coupled problem of temperature and seepage fields with phase change are first derived from the theory of heat transfer and the theory of seepage. The finite element formulae...The governing differential equations of the coupled problem of temperature and seepage fields with phase change are first derived from the theory of heat transfer and the theory of seepage. The finite element formulae of this problem are obtained from Galerkin’ s method. And considering the seepage influence, an illustrative example of thetemperature field in a cold-region tunnel is provided.The example shows that the influence of seepage on the frozen depth of the tunnel is very great, and thus the effect of the seepage factor should be taken into account in the engineering design.展开更多
To study the distribution characteristics and variation regularity of the temperature field during the process of seepage freezing,a simulated-freezing test with seepage of Xuzhou sand was completed by using a model t...To study the distribution characteristics and variation regularity of the temperature field during the process of seepage freezing,a simulated-freezing test with seepage of Xuzhou sand was completed by using a model test developed in-house equipment.By means of three group freezing tests with different seepage velocities,we discovered the phenomenon of the asymmetry of the temperature field under the influence of seepage.The temperature upstream was obviously higher than that downstream.The temperature gradient upstream was also steeper than that downstream.With a higher seepage velocity,the asymmetry of the temperature field is more pronounced.The asymmetry for the interface temperature profile is more strongly manifest than for the main surface temperature profile.The cryogenic barrier section is somewhat"heartshaped".With the increasing velocity of the seepage flow,the cooling rate of the soil decreases.It takes much time to reach the equilibrium state of the soil mass.In our study,seepage flow velocities of 0 m/d,7.5 m/d,and 15 m/d showed the soilcooling rate of 4.35°C/h,4.96°C/h,and 1.72°C/h,respectively.展开更多
Currently,the water inrush hazards during tunnel construction,the water leakage during tunnel operation,and the accompanying disturbances to the ecological environment have become the main problems that affect the str...Currently,the water inrush hazards during tunnel construction,the water leakage during tunnel operation,and the accompanying disturbances to the ecological environment have become the main problems that affect the structural safety of tunnels in water-rich regions.In this paper,a tunnel seepage model testing system was used to conduct experiments of the grouting circle and primary support with different permeability coefficients.The influences of the supporting structures on the water inflow laws and the distribution of the water pressure in the tunnel were analyzed.With the decrease in the permeability coefficient of the grouting circle or the primary support,the inflow rate of water into the tunnel showed a non-linear decreasing trend.In comparison,the water inflow reduction effect of grouting circle was much better than that of primary support.With the increase of the permeability coefficient of the grouting ring,the water pressure behind the primary lining increases gradually,while the water pressure behind the grouting ring decreases.Thus,the grouting of surrounding rock during the construction of water-rich tunnel can effectively weaken the hydraulic connection,reduce the influence range of seepage,and significantly reduce the decline of groundwater.Meanwhile,the seepage tests at different hydrostatic heads and hydrodynamic heads during tunnel operation period were also conducted.As the hydrostatic head decreased,the water pressure at each characteristic point decreased approximately linearly,and the water inflow rate also had a gradual downward trend.Under the action of hydrodynamic head,the water pressure had an obvious lagging effect,which was not conducive to the stability of the supporting structures,and it could be mitigated by actively regulating the drainage rate.Compared with the hydrostatic head,the hydrodynamic head could change the real-time rate of water inflow to the tunnel and broke the dynamic balance between the water pressure and water inflow rate,thereby affecting the stress state on the supporting structures.展开更多
Energy utilization in the aquifers is a new technology closely related to development of heat pump technique. It is significant for the flow distribution to be predicted in the aquifer surrounding the Groundwater Sour...Energy utilization in the aquifers is a new technology closely related to development of heat pump technique. It is significant for the flow distribution to be predicted in the aquifer surrounding the Groundwater Source Heat Pump System （GSHPS）. The authors presented a new concept of ＂flow transfixion＂ by analyzing general features of aquifers, and then discussed interaction of the flow transfixion with the beat transfixion, which has practical significance to projects. A numerical model of groundwater flow was established based on the basic tenets of water-heat transferring in the aquifer. On this basis the flow field and the temperature field of GSHPS for a site in Shenyang City were numerically simulated. The basis of the flow transfixion was obtained; it was discussed for the influence of the flow transfixion on the heat transfixion. To a certain extent, the study offers some reference for the projects＇ design of GSHP in the studied area.展开更多
Based on the construction interfaces in rolled control concrete dam(RCCD), the methods were proposed to calculate the influence thickness of construction interfaces and the corresponding physical mechanics parameters....Based on the construction interfaces in rolled control concrete dam(RCCD), the methods were proposed to calculate the influence thickness of construction interfaces and the corresponding physical mechanics parameters. The principle on establishing the coupling model of seepage_field and stress_field for RCCD was presented. A 3_D Finite Element Method(FEM) program was developed. Study shows that such parameters as the thickness of construction interfaces,the elastic ratio and the (Poisson's) ratio obtained by tests and theoretical analysis are more reasonable, the coupling model of seepage_field and stress_field for RCCD may indicate the coupling effect between the two fields scientifically, and the developed 3_D FEM program can reflect the effect of the construction interfaces more adequately. According to the study, many scientific opinions are given both to analyze the influence of the construction interfaces to the (dam's) characteristic, and to reveal the interaction between the stress_field and the seepage_field.展开更多
Purpose–This paper aims to study the impacts of groundwater seepage on artificial freezing process of gravel strata,the temperature field characteristics of the strata,and the strata process,closure time and thicknes...Purpose–This paper aims to study the impacts of groundwater seepage on artificial freezing process of gravel strata,the temperature field characteristics of the strata,and the strata process,closure time and thickness evolution mechanism of the frozen wall.Design/methodology/approach–In this paper several laboratory model tests were conducted,considering different groundwater seepage rate.Findings–The results show that there is a significant coupling effect between the cold diffusion of artificial freezing pipes and groundwater seepage;when there is no seepage,temperature fields upstream and downstream of the gravel strata are symmetrically distributed,and the thickness of the frozen soil column/frozen wall is consistent during artificial freezing;groundwater seepage causes significant asymmetry in the temperature fields upstream and downstream of the gravel strata,and the greater the seepage rate,the more obvious the asymmetry;the frozen wall closure time increases linearly with the increase in the groundwater seepage rate,and specifically,the time length under seepage rate of 5.00 m d1 is 3.2 times longer than that under no seepage;due to the erosion from groundwater seepage,the thickness of the upstream frozen wall decreases linearly with the seepage velocity,while that of the downstream frozen wall increases linearly,resulting in a saddle-shaped frozen wall.Originality/value–The research results are beneficial to the optimum design and risk control of artificial freezing process in gravel strata.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50379046)the Doctoral Fund of the Ministry of Education of China (Grant No. A50221)
文摘Owing to the complexity of geo-engineering seepage problems influenced by different random factors, three-dimensional simulation and analysis of the stochastic seepage field plays an important role in engineering applications. A three-dimensional anisotropic heterogeneous steady random seepage model was developed on the basis of the finite element method. A statistical analysis of the distribution characteristics of soil parameters sampled from the main embankment of the Yangtze River in the Southern Jingzhou zone of China was conducted. The Kolomogorov-Smirnov test verified the statistical hypothesis that the permeability coefficient tensor has a Gaussian distribution. With the help of numerical analysis of the stochastic seepage field using the developed model, various statistical and random characteristics of the stochastic seepage field of the main embankment of the Yangtze River in the Southern Jingzhou zone of China were investigated. The model was also examined with statistical testing. Through the introduction of random variation of the upstream and downstream water levels into the model, the effects of the boundary randomness due to variation of the downstream and upstream water levels on the variation of simulated results presented with a vector series of the random seepage field were analyzed. Furthermore, the combined influence of the variation of the soil permeability coefficient and such seepage resistance measures as the cut-off wall and relief ditch on the hydraulic head distribution was analyzed and compared with the results obtained by determinate analysis. Meanwhile, sensitivities of the hydraulic gradient and downstream exit height to the variation of boundary water level were studied. The validity of the simulated results was verified by stochastic testing and measured data. The developed model provides more detail and a full stochastic algorithm to characterize and analyze three-dimensional stochastic seepage field problems.
文摘Tunnel seepage is an important factor affecting the progress and safety of tunnel construction. In this paper, the mining method tunnel construction in the water-rich weathered granite stratum is taken as the research object. Through the analytical calculation method, the distribution law of tunnel seepage field under different waterproof and drainage types is studied, and the comparative analysis is carried out. According to the analytical solution, the influencing factors of grouting parameters are proposed. The sensitivity of the tunnel seepage field to the variation of grouting parameters is analyzed. A novel waterproof and drainage system, and construction technology suitable for subway tunnels with large buried depth below groundwater level were proposed.
文摘In actual space, considering the heterogeneity and anisotropy of rock and soil, the difference of hydrogeological conditions and the influence of tunnel excavation, tunnel seepage problem is a very complex three-dimensional seepage problem, which is very difficult to solve. The equivalent continuum model is one of the most commonly simplified models used in solving tunnel seepage problems. In this paper, the finite element software ABAQUS and the research results are used to establish a seepage numerical calculation model, study the influence of mining method construction on the seepage field in weathered granite, and clarify the influence of each stage of mining method construction on the groundwater environment. On this basis, the sensitivity of the seepage field to various factors such as natural environment, engineering geology and hydrogeology, tunnel construction and so on is analyzed, which provides a basis to establish the evaluation system of groundwater environment negative effect in weathered granite stratum by mining method tunnel construction.
基金This work was supported by the National Natural Science Foundation of China under Grant No.51177077.
文摘Modifying the equivalent rotor resistivity with rotor end factor in 2-dimension(2-D)finite element analysis(FEA)is an effective way to analyze the 3-dimension(3-D)solid rotor problems.For the smooth solid rotor,five different rotor end factors are discussed and compared with each other.It is theoretically clarified that the resistivity of rotor in 2-D FEA should be multiplied by the square of rotor end factors to take the 3-D end effect of solid rotor into account.For the slitted solid rotor,an improved rotor end factor is proposed based on the equivalent area algorithm of eddy currents in rotor,since the end factors of smooth solid rotor are not applicable.Finally,the time-harmonic finite element method(FEM)combined with the rotor end factor is applied to analyze the performance of solid rotor induction motor.The tested and computed results are in good agreement,which proves the effectiveness of rotor end factor for the simplication of 3-D solid rotor problems.
基金Project supported by the National Natural Science Foundation of China (Grant No. 49671020), and the Key Project of the Chinese Academy of Sciences (Grant No. KZ952-J1-216).
文摘The governing differential equations of the coupled problem of temperature and seepage fields with phase change are first derived from the theory of heat transfer and the theory of seepage. The finite element formulae of this problem are obtained from Galerkin’ s method. And considering the seepage influence, an illustrative example of thetemperature field in a cold-region tunnel is provided.The example shows that the influence of seepage on the frozen depth of the tunnel is very great, and thus the effect of the seepage factor should be taken into account in the engineering design.
基金financially supported by the National Natural Science Foundation of China (No. 41201070)Project of Education Department of Jiangxi Province (GJJ14494)+1 种基金Development Fund Project of State Key Laboratory of Frozen Soil Engineering (SKLFSE 201508)Development Fund Project of State Key Laboratory for Geomechanics & Deep Underground Engineering (SKLGDUEK1505)
文摘To study the distribution characteristics and variation regularity of the temperature field during the process of seepage freezing,a simulated-freezing test with seepage of Xuzhou sand was completed by using a model test developed in-house equipment.By means of three group freezing tests with different seepage velocities,we discovered the phenomenon of the asymmetry of the temperature field under the influence of seepage.The temperature upstream was obviously higher than that downstream.The temperature gradient upstream was also steeper than that downstream.With a higher seepage velocity,the asymmetry of the temperature field is more pronounced.The asymmetry for the interface temperature profile is more strongly manifest than for the main surface temperature profile.The cryogenic barrier section is somewhat"heartshaped".With the increasing velocity of the seepage flow,the cooling rate of the soil decreases.It takes much time to reach the equilibrium state of the soil mass.In our study,seepage flow velocities of 0 m/d,7.5 m/d,and 15 m/d showed the soilcooling rate of 4.35°C/h,4.96°C/h,and 1.72°C/h,respectively.
基金supported by the Chongqing Natural Science Foundation(No.cstc2020jcyjmsxm X0904)the Chongqing Talent Plan(No.CQYC2020058263)+3 种基金the Chongqing Technology Innovation and Application Development Project(No.cstc2021ycjh-bgzxm0246)the China Postdoctoral Science Foundation(No.2021M693739)the Sichuan Science and Technology Program(No.2021YJ0539)the Natural Science foundation of Jiangsu higher education institutions of China(Grant No.19KJD170001)。
文摘Currently,the water inrush hazards during tunnel construction,the water leakage during tunnel operation,and the accompanying disturbances to the ecological environment have become the main problems that affect the structural safety of tunnels in water-rich regions.In this paper,a tunnel seepage model testing system was used to conduct experiments of the grouting circle and primary support with different permeability coefficients.The influences of the supporting structures on the water inflow laws and the distribution of the water pressure in the tunnel were analyzed.With the decrease in the permeability coefficient of the grouting circle or the primary support,the inflow rate of water into the tunnel showed a non-linear decreasing trend.In comparison,the water inflow reduction effect of grouting circle was much better than that of primary support.With the increase of the permeability coefficient of the grouting ring,the water pressure behind the primary lining increases gradually,while the water pressure behind the grouting ring decreases.Thus,the grouting of surrounding rock during the construction of water-rich tunnel can effectively weaken the hydraulic connection,reduce the influence range of seepage,and significantly reduce the decline of groundwater.Meanwhile,the seepage tests at different hydrostatic heads and hydrodynamic heads during tunnel operation period were also conducted.As the hydrostatic head decreased,the water pressure at each characteristic point decreased approximately linearly,and the water inflow rate also had a gradual downward trend.Under the action of hydrodynamic head,the water pressure had an obvious lagging effect,which was not conducive to the stability of the supporting structures,and it could be mitigated by actively regulating the drainage rate.Compared with the hydrostatic head,the hydrodynamic head could change the real-time rate of water inflow to the tunnel and broke the dynamic balance between the water pressure and water inflow rate,thereby affecting the stress state on the supporting structures.
文摘Energy utilization in the aquifers is a new technology closely related to development of heat pump technique. It is significant for the flow distribution to be predicted in the aquifer surrounding the Groundwater Source Heat Pump System （GSHPS）. The authors presented a new concept of ＂flow transfixion＂ by analyzing general features of aquifers, and then discussed interaction of the flow transfixion with the beat transfixion, which has practical significance to projects. A numerical model of groundwater flow was established based on the basic tenets of water-heat transferring in the aquifer. On this basis the flow field and the temperature field of GSHPS for a site in Shenyang City were numerically simulated. The basis of the flow transfixion was obtained; it was discussed for the influence of the flow transfixion on the heat transfixion. To a certain extent, the study offers some reference for the projects＇ design of GSHP in the studied area.
文摘Based on the construction interfaces in rolled control concrete dam(RCCD), the methods were proposed to calculate the influence thickness of construction interfaces and the corresponding physical mechanics parameters. The principle on establishing the coupling model of seepage_field and stress_field for RCCD was presented. A 3_D Finite Element Method(FEM) program was developed. Study shows that such parameters as the thickness of construction interfaces,the elastic ratio and the (Poisson's) ratio obtained by tests and theoretical analysis are more reasonable, the coupling model of seepage_field and stress_field for RCCD may indicate the coupling effect between the two fields scientifically, and the developed 3_D FEM program can reflect the effect of the construction interfaces more adequately. According to the study, many scientific opinions are given both to analyze the influence of the construction interfaces to the (dam's) characteristic, and to reveal the interaction between the stress_field and the seepage_field.
基金supported by the National Natural Science Foundation of China(Grant No.51978426)the NSFC Young Scientists Fund(Grant No.41801277)+1 种基金the Science and Technology Research Program of Hebei Education Department(Grant No.QN2018072)the Program for High-level Talent Fund of Hebei Province(Grant No.A201903010).
文摘Purpose–This paper aims to study the impacts of groundwater seepage on artificial freezing process of gravel strata,the temperature field characteristics of the strata,and the strata process,closure time and thickness evolution mechanism of the frozen wall.Design/methodology/approach–In this paper several laboratory model tests were conducted,considering different groundwater seepage rate.Findings–The results show that there is a significant coupling effect between the cold diffusion of artificial freezing pipes and groundwater seepage;when there is no seepage,temperature fields upstream and downstream of the gravel strata are symmetrically distributed,and the thickness of the frozen soil column/frozen wall is consistent during artificial freezing;groundwater seepage causes significant asymmetry in the temperature fields upstream and downstream of the gravel strata,and the greater the seepage rate,the more obvious the asymmetry;the frozen wall closure time increases linearly with the increase in the groundwater seepage rate,and specifically,the time length under seepage rate of 5.00 m d1 is 3.2 times longer than that under no seepage;due to the erosion from groundwater seepage,the thickness of the upstream frozen wall decreases linearly with the seepage velocity,while that of the downstream frozen wall increases linearly,resulting in a saddle-shaped frozen wall.Originality/value–The research results are beneficial to the optimum design and risk control of artificial freezing process in gravel strata.
