Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress ...Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure （tr3） of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.展开更多
This paper reports research on the effects of variations in injectio n velocity and perm eability on the heat transfer and flow through a highly porous medium betwee n two horizontal parallel plates situated at consta...This paper reports research on the effects of variations in injectio n velocity and perm eability on the heat transfer and flow through a highly porous medium betwee n two horizontal parallel plates situated at constant distance with constant suc tion by the upper plate.Due to this type of variation in injection velocity and in permeability the flow becomes three dimensional.The governing equations are sol ved by adopting complex variable notations to obtain the expressions for the ve locity and temperature field. The skin-friction along the main flow direction and rate of heat transfer are discussed with the help of graphs.展开更多
The mechanical behavior evolution characteristics of sandstone are important to the application and practice of rock engineering.Therefore,a new method and concept of deep rock mechanics testing are proposed to reveal...The mechanical behavior evolution characteristics of sandstone are important to the application and practice of rock engineering.Therefore,a new method and concept of deep rock mechanics testing are proposed to reveal the mechanical behavior evolution mechanism of deep roadway surrounding rock after excavation with a depth over 1000 m.High stress-seepage coupling experiments of deep sandstone under various confining pressures are conducted using GCTS.Stress−strain and permeability curves are obtained.The three-stage mechanical behavior of deep sandstone is better characterized.A platform and secondary compaction phenomena are observed.With the confining pressure increasing,the platform length gradually decreases,even disappears.In the stade I,the rigid effect of deep sandstone is remarkable.In the stage II,radial deformation of deep sandstone dominates.The transient strain of confining pressure compliance is defined,which shows three-stage evolution characteristics.In the stage III,the radial deformation is greater than the axial deformation in the pre-peak stage,but the opposite trend is observed in the post-peak stage.It is found that the dynamic permeability can be more accurately characterized by the radial strain.The relations between the permeability and stress−strain curves in various stages are revealed.展开更多
The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finit...The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finite element code DEFORM 3D.According to the effective plastic strain,the mean stress and the mean plastic strain distribution of the radial forging,the forging penetration efficiency(FPE) was studied throughout each operation.The results show that the effective plastic strain in the center of the forging is always greater than zero for the desirable larger axial drawing velocity.The mean stress in the center of the workpiece is proposed to describe hydrostatic pressure in this paper.There is compressive strain layer beneath the surface of the workpiece to be found,while there is tensile strain core in the center of the workpiece.These results could be a valuable reference for designing the similar forging operations.展开更多
Relative permeability is an indispensable property for characterizing the unsaturated flow and induced deformation in soils. The widely used Mualem model is inadequate for deformable soils because of its assumption of...Relative permeability is an indispensable property for characterizing the unsaturated flow and induced deformation in soils. The widely used Mualem model is inadequate for deformable soils because of its assumption of a rigid pore structure and the resultant unique dependence of the tortuosity factor on the volumetric water content. In this study, a unified relationship between the relative permeability and the effective degree of saturation was proposed for deformable soils by incorporating our newly developed water retention curve model into the original Mualem model, in which a new tortuosity factor was defined using the fractal dimension of flow paths and the mean radius of water-filled pores for representing the effect of pore structure variation. The modified deformation-dependent relative permeability model was verified using test data on five types of soils; the verification revealed a much better performance of the proposed model than the original model, which commonly overestimates the relative permeability of deformable soils. Finally, the proposed model was implemented in a coupled numerical model for examining the unsaturated flow and elastoplastic deformation processes in a soil slope induced by rain infiltration. The numerical results showed that the deformation-dependent nature of relative permeability has a remarkable effect on the elastoplastic deformation in the slope and that neglect of the deformation-dependent behavior of relative permeability causes overestimation of the depth of failure.展开更多
The carrier mobility of Si material can be enhanced under strain,and the stress magnitude can be measured by the Raman spectrum.In this paper,we aim to study the penetration depths into biaxially-strained Si materials...The carrier mobility of Si material can be enhanced under strain,and the stress magnitude can be measured by the Raman spectrum.In this paper,we aim to study the penetration depths into biaxially-strained Si materials at various Raman excitation wavelengths and the stress model corresponding to Raman spectrum in biaxially-strained Si.The experimental results show that it is best to use 325 nm excitation to measure the material stress in the top strained Si layer,and that one must pay attention to the distortion of the buffer layers on measuring results while 514 nm excitation is also measurable.Moreover,we established the stress model for Raman spectrum of biaxially-strained Si based on the Secular equation.One can obtain the stress magnitude in biaxially-strained Si by the model,as long as the results of the Raman spectrum are given.Our quantitative results can provide valuable references for stress analysis on strained materials.展开更多
基金Projects(11172090,51009052,51109069) supported by the National Natural Science Foundation of ChinaProject(2011CB013504) supported by the National Basic Research Program of China
文摘Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure （tr3） of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.
文摘This paper reports research on the effects of variations in injectio n velocity and perm eability on the heat transfer and flow through a highly porous medium betwee n two horizontal parallel plates situated at constant distance with constant suc tion by the upper plate.Due to this type of variation in injection velocity and in permeability the flow becomes three dimensional.The governing equations are sol ved by adopting complex variable notations to obtain the expressions for the ve locity and temperature field. The skin-friction along the main flow direction and rate of heat transfer are discussed with the help of graphs.
基金Projects(51974319,52034009)supported by the National Natural Science Foundation of ChinaProject(2020JCB01)supported by the China University of Mining and Technology(Beijing)。
文摘The mechanical behavior evolution characteristics of sandstone are important to the application and practice of rock engineering.Therefore,a new method and concept of deep rock mechanics testing are proposed to reveal the mechanical behavior evolution mechanism of deep roadway surrounding rock after excavation with a depth over 1000 m.High stress-seepage coupling experiments of deep sandstone under various confining pressures are conducted using GCTS.Stress−strain and permeability curves are obtained.The three-stage mechanical behavior of deep sandstone is better characterized.A platform and secondary compaction phenomena are observed.With the confining pressure increasing,the platform length gradually decreases,even disappears.In the stade I,the rigid effect of deep sandstone is remarkable.In the stage II,radial deformation of deep sandstone dominates.The transient strain of confining pressure compliance is defined,which shows three-stage evolution characteristics.In the stage III,the radial deformation is greater than the axial deformation in the pre-peak stage,but the opposite trend is observed in the post-peak stage.It is found that the dynamic permeability can be more accurately characterized by the radial strain.The relations between the permeability and stress−strain curves in various stages are revealed.
文摘The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finite element code DEFORM 3D.According to the effective plastic strain,the mean stress and the mean plastic strain distribution of the radial forging,the forging penetration efficiency(FPE) was studied throughout each operation.The results show that the effective plastic strain in the center of the forging is always greater than zero for the desirable larger axial drawing velocity.The mean stress in the center of the workpiece is proposed to describe hydrostatic pressure in this paper.There is compressive strain layer beneath the surface of the workpiece to be found,while there is tensile strain core in the center of the workpiece.These results could be a valuable reference for designing the similar forging operations.
基金supported by the CRSRI Open Research Program(Grant No.CKWV2015209/KY)the National Natural Science Foundation of China(Grant Nos.51409198,51179136&51222903)
文摘Relative permeability is an indispensable property for characterizing the unsaturated flow and induced deformation in soils. The widely used Mualem model is inadequate for deformable soils because of its assumption of a rigid pore structure and the resultant unique dependence of the tortuosity factor on the volumetric water content. In this study, a unified relationship between the relative permeability and the effective degree of saturation was proposed for deformable soils by incorporating our newly developed water retention curve model into the original Mualem model, in which a new tortuosity factor was defined using the fractal dimension of flow paths and the mean radius of water-filled pores for representing the effect of pore structure variation. The modified deformation-dependent relative permeability model was verified using test data on five types of soils; the verification revealed a much better performance of the proposed model than the original model, which commonly overestimates the relative permeability of deformable soils. Finally, the proposed model was implemented in a coupled numerical model for examining the unsaturated flow and elastoplastic deformation processes in a soil slope induced by rain infiltration. The numerical results showed that the deformation-dependent nature of relative permeability has a remarkable effect on the elastoplastic deformation in the slope and that neglect of the deformation-dependent behavior of relative permeability causes overestimation of the depth of failure.
基金supported by the Research Fund for the Doctoral Program of Higher Education of China(Grant No.JY0300122503)the NLAIC Research Fund(Grant No.P140c090303110c0904)
文摘The carrier mobility of Si material can be enhanced under strain,and the stress magnitude can be measured by the Raman spectrum.In this paper,we aim to study the penetration depths into biaxially-strained Si materials at various Raman excitation wavelengths and the stress model corresponding to Raman spectrum in biaxially-strained Si.The experimental results show that it is best to use 325 nm excitation to measure the material stress in the top strained Si layer,and that one must pay attention to the distortion of the buffer layers on measuring results while 514 nm excitation is also measurable.Moreover,we established the stress model for Raman spectrum of biaxially-strained Si based on the Secular equation.One can obtain the stress magnitude in biaxially-strained Si by the model,as long as the results of the Raman spectrum are given.Our quantitative results can provide valuable references for stress analysis on strained materials.
