The seepage of groundwater and the strain-softening of rock mass in a submarine tunnel expand the plastic region of rock,thereby affecting its overall stability.It is therefore essential to study the stress and strain...The seepage of groundwater and the strain-softening of rock mass in a submarine tunnel expand the plastic region of rock,thereby affecting its overall stability.It is therefore essential to study the stress and strain fields in the rocks surrounding the submarine tunnel by considering the coupled effect of strainsoftening and seepage.However,the evolution equation for the hydro-mechanical parameters in the existing fully coupled solution is a uniform equation that is unable to reproduce the characteristics of rock mass in practice.In this study,an updated numerical procedure for the submarine tunnel is derived by coupling strain-softening and seepage effect based on the experimental results.According to the hydro-mechanical coupling theory,the hydro-mechanical parameters such as elastic modulus,Poisson's ratio,Biot's coefficient and permeability coefficient of rocks are characterized by the fitting equations derived from the experimental data.Then,the updated numerical procedure is deduced with the governing equations,boundary conditions,seepage equations and fitting equations.The updated numerical procedure is verified accurately compared with the previous analytical solution.By utilizing the updated numerical procedure,the characteristics of stress field and the influences of initial pore water pressure,Biot's coefficient,and permeability coefficient on the stress,displacement and water-inflow of the surrounding rocks are discussed.Regardless of the variations in hydro-mechanical parameters,the stress distribution has a similar trend.The initial permeability coefficient exerts the most significant influence on the stress field.With the increases in initial pore water pressure and Biot's coefficient,the plastic region expands,and the water-inflow and displacement increase accordingly.Given the fact that the stability of the tunnel is more sensitive to the seepage force controlled by the hydraulic parameters,it is suggested to dewater the ground above the submarine tunnel to control the initial pore water pressure.展开更多
A detailed mathematical procedure of the optimization of the fluid flow in a tundish water model with and without flow control devices （weir and dam） was carried out using the commercial CFD eode FLUENT 6.0. The （...A detailed mathematical procedure of the optimization of the fluid flow in a tundish water model with and without flow control devices （weir and dam） was carried out using the commercial CFD eode FLUENT 6.0. The （k- ε） two-equation model was used to model turbulence. The residence time distribution （RTD） curves were used to analyze the behavior of the flow in tundish. The location of flow control devices in the tundish was studied. The results show that the flow modifiers play an important role in promoting the floatation of nonmetallic inclusions in steel. Comparing the three geometric configurations that are considered （bare tundish, weir, weir＋dam）, the tundish equipped with the arrangement （weir＋dam） is a best and optimal geometric configuration of tundish.展开更多
The structural engineering design of not conventional typologies imposes a complex path that begins evaluating procedures of a preliminary design and ends with complex procedures to validate the analysis response. Any...The structural engineering design of not conventional typologies imposes a complex path that begins evaluating procedures of a preliminary design and ends with complex procedures to validate the analysis response. Any guide lines to follow are often available. About complex shapes, in particular, any details are presented in the codes to evaluate wind action and so wind tunnel experiments are necessary to valuate this. The evaluation of wind tunnel data is a complex process that often needs new and specific subroutines programmed by researchers. The difficult increases when the objective is to study a not specific building but general aspects as for examples the dependence of a generic phenomenon by a geometric sample;in this case it is necessary to design and to program numerical subroutines before and then the wind tunnel experiments. Often, these subroutines are left detached and are non-generalizable process. Purpose of this paper is to describe a complete procedure to pre- and post-process wind tunnel data with the objective to design a not convectional structure as a tensile structure. In this particular case the research aim is a parametrization of the aerodynamic behavior of Hyperbolic Paraboloid roofs, shape used for cables net. The reason of the experiments is the absence in the international codes of the pressure coefficients for these geometries. The paper describes the numerical procedure evaluated to choose a sufficient representative geometric sample, the numerical procedure evaluated to design and to construct the wind tunnel models and FE models, the numerical procedure to evaluate and to use for FEM analyses of the wind tunnel data, the numerical procedure to calculate nonlinear structural analysis, and, finally some applications. All these numerical procedures use basic theory derived for example by the cable theory, the fluid mechanic, the nonlinear geometric analysis and other. However specific codes were necessary and were programmed to apply the theories on the specific case of study;the complete methodology followed is presented. The goal is to create a free open domain where the numerical procedures evaluated are merged, added, modified by researchers with the aim to obtain a common space of use for wind engineering of not conventional structure.展开更多
This study focuses on the stress and displacement of a circular opening that is excavated in a strain-softening rock mass under hydraulic-mechanical coupling.It follows the generalized Hoek-Brown(H-B) failure criterio...This study focuses on the stress and displacement of a circular opening that is excavated in a strain-softening rock mass under hydraulic-mechanical coupling.It follows the generalized Hoek-Brown(H-B) failure criterion.Moreover,an improved numerical method and stepwise procedure are proposed.This method considers the deterioration of the strength,deformation,and dilation angle.It also incorporates the hydraulic-mechanical coupling and the variation of elastic strain in the plastic region.Several examples are conducted to demonstrate the validity and accuracy of the proposed solution through MATLAB programming and FLAC software.Parametric studies are also conducted to highlight the influence of hydraulic–mechanical coupling on stress and displacement.Results show that in this case,stress confinement is lower and tunnel convergences are higher than the corresponding stresses and displacements obtained when those factors are not considered.The displacement and plastic radius are also larger than those obtained when hydraulic-mechanical coupling is not considered.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52279118 and U21A20159)Sub-project of National Key Research and Development(Grant No.2023YFC3007403).
文摘The seepage of groundwater and the strain-softening of rock mass in a submarine tunnel expand the plastic region of rock,thereby affecting its overall stability.It is therefore essential to study the stress and strain fields in the rocks surrounding the submarine tunnel by considering the coupled effect of strainsoftening and seepage.However,the evolution equation for the hydro-mechanical parameters in the existing fully coupled solution is a uniform equation that is unable to reproduce the characteristics of rock mass in practice.In this study,an updated numerical procedure for the submarine tunnel is derived by coupling strain-softening and seepage effect based on the experimental results.According to the hydro-mechanical coupling theory,the hydro-mechanical parameters such as elastic modulus,Poisson's ratio,Biot's coefficient and permeability coefficient of rocks are characterized by the fitting equations derived from the experimental data.Then,the updated numerical procedure is deduced with the governing equations,boundary conditions,seepage equations and fitting equations.The updated numerical procedure is verified accurately compared with the previous analytical solution.By utilizing the updated numerical procedure,the characteristics of stress field and the influences of initial pore water pressure,Biot's coefficient,and permeability coefficient on the stress,displacement and water-inflow of the surrounding rocks are discussed.Regardless of the variations in hydro-mechanical parameters,the stress distribution has a similar trend.The initial permeability coefficient exerts the most significant influence on the stress field.With the increases in initial pore water pressure and Biot's coefficient,the plastic region expands,and the water-inflow and displacement increase accordingly.Given the fact that the stability of the tunnel is more sensitive to the seepage force controlled by the hydraulic parameters,it is suggested to dewater the ground above the submarine tunnel to control the initial pore water pressure.
文摘A detailed mathematical procedure of the optimization of the fluid flow in a tundish water model with and without flow control devices （weir and dam） was carried out using the commercial CFD eode FLUENT 6.0. The （k- ε） two-equation model was used to model turbulence. The residence time distribution （RTD） curves were used to analyze the behavior of the flow in tundish. The location of flow control devices in the tundish was studied. The results show that the flow modifiers play an important role in promoting the floatation of nonmetallic inclusions in steel. Comparing the three geometric configurations that are considered （bare tundish, weir, weir＋dam）, the tundish equipped with the arrangement （weir＋dam） is a best and optimal geometric configuration of tundish.
文摘The structural engineering design of not conventional typologies imposes a complex path that begins evaluating procedures of a preliminary design and ends with complex procedures to validate the analysis response. Any guide lines to follow are often available. About complex shapes, in particular, any details are presented in the codes to evaluate wind action and so wind tunnel experiments are necessary to valuate this. The evaluation of wind tunnel data is a complex process that often needs new and specific subroutines programmed by researchers. The difficult increases when the objective is to study a not specific building but general aspects as for examples the dependence of a generic phenomenon by a geometric sample;in this case it is necessary to design and to program numerical subroutines before and then the wind tunnel experiments. Often, these subroutines are left detached and are non-generalizable process. Purpose of this paper is to describe a complete procedure to pre- and post-process wind tunnel data with the objective to design a not convectional structure as a tensile structure. In this particular case the research aim is a parametrization of the aerodynamic behavior of Hyperbolic Paraboloid roofs, shape used for cables net. The reason of the experiments is the absence in the international codes of the pressure coefficients for these geometries. The paper describes the numerical procedure evaluated to choose a sufficient representative geometric sample, the numerical procedure evaluated to design and to construct the wind tunnel models and FE models, the numerical procedure to evaluate and to use for FEM analyses of the wind tunnel data, the numerical procedure to calculate nonlinear structural analysis, and, finally some applications. All these numerical procedures use basic theory derived for example by the cable theory, the fluid mechanic, the nonlinear geometric analysis and other. However specific codes were necessary and were programmed to apply the theories on the specific case of study;the complete methodology followed is presented. The goal is to create a free open domain where the numerical procedures evaluated are merged, added, modified by researchers with the aim to obtain a common space of use for wind engineering of not conventional structure.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2013CB036004)the National Natural Science Foundation of China(Grant No.51208523)China Postdoctoral Science Foundation(Grant No.2003034468)
文摘This study focuses on the stress and displacement of a circular opening that is excavated in a strain-softening rock mass under hydraulic-mechanical coupling.It follows the generalized Hoek-Brown(H-B) failure criterion.Moreover,an improved numerical method and stepwise procedure are proposed.This method considers the deterioration of the strength,deformation,and dilation angle.It also incorporates the hydraulic-mechanical coupling and the variation of elastic strain in the plastic region.Several examples are conducted to demonstrate the validity and accuracy of the proposed solution through MATLAB programming and FLAC software.Parametric studies are also conducted to highlight the influence of hydraulic–mechanical coupling on stress and displacement.Results show that in this case,stress confinement is lower and tunnel convergences are higher than the corresponding stresses and displacements obtained when those factors are not considered.The displacement and plastic radius are also larger than those obtained when hydraulic-mechanical coupling is not considered.
