In this paper,based on many experimental results,a creep damage equation for rocks with a creep modulus that can describe the history of damage has been deduced.According to the equation,a creep damage model for rock ...In this paper,based on many experimental results,a creep damage equation for rocks with a creep modulus that can describe the history of damage has been deduced.According to the equation,a creep damage model for rock materials is constructed,and it is shown that the extent of their damage,or damage degree,during creep can be determined by means of simple experiments.展开更多
There are many fracture zones crossing the dam foundation of the Xiangjiaba Hydropower Project in southwestern China. Clastic rock is the main media of the fracture zone and has poor physical and mechanical properties...There are many fracture zones crossing the dam foundation of the Xiangjiaba Hydropower Project in southwestern China. Clastic rock is the main media of the fracture zone and has poor physical and mechanical properties. In order to investigate the creep behavior of clastic rock, triaxial creep tests were conducted using a rock servo-controlling rheological testing machine. The results show that the creep behavior of clastic rock is significant at a high level of deviatoric stress, and less time-dependent deformation occurs at high confining pressure. Based on the creep test results, the relationship between axial strain and time under different confining pressures was investigated, and the relationship between axial strain rate and deviatoric stress was also discussed. The strain rate increases rapidly, and the rock sample fails eventually under high deviatoric stress. Moreover, the creep failure mechanism under different confining pressures was analyzed. The main failure mechanism of clastic rock is plastic shear, accompanied by a significant compression and ductile dilatancy. On the other band, with the determined parameters, the Burgers creep model was used to fit the creep curves. The results indicate that the Burgers model can exactly describe the creep behavior of clastic rock in the Xiangjiaba Hydropower Project.展开更多
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 co...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 m/s at confining pressure(σ3) of 2 MPa,and is about 3.9×10-9 m/s at σ3 of 6 MPa.It is seen that the seepage flow rate at σ3 of 2 MPa in this case is obviously larger than that at σ3 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
The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine Ⅲ were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic stra...The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine Ⅲ were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic strain, visco-elastic strain, instantaneous plastic strain and visco-plastic strain. The result shows that instantaneous deformation modulus tends to increase with the increase of creep stress; soft rocks enhance the ability to resist instantaneous elastic deformation and instantaneous plastic deformation during the multi-level of load and unload in the cyclic process. In respect of specimen JC1099, the ratio of visco-elastic strain to visco-plastic strain varies from 3.15 to 6.58, and the ratio has decreasing tendency with stress increase as a whole; creep deformation tends to be a steady state at low stress level; soft rocks creep usually embodies accelerated creep properties at high stress level. With the damaging variable and the hardening function introduced, a nonlinear creep model of soft rocks is established, in which the decay creep is described by the nonlinear hardening function H of viscidity coefficient. The model can describe the accelerated creep of soft rocks since the nonlinear damaging evolvement variable D of deformation parameter of rocks is introduced. Three stages of soft rocks creep can be described with the uniform creep equation in the nonlinear creep model. With this nonlinear creep model applied to the creep experiments of the ore-rock of Jinchuan Mine Ⅲ, the nonlinear creep model’s curves are in good agreement with experimental data.展开更多
The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test syste...The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test system,and the constitutive equations were established.It is found that fracture morphology of rock beams under no disturbance load is regular,cracking position of fractures is on part of loading concentration,the crack starts from a neutral plane.However,fracture morphology of rock beams under disturbance load is irregular,cracking position of fractures deviates from a neutral plane.Delayed instability of rock beam occurs for some time under constant disturbance load.When disturbance load is beyond a certain range,suddenly instability of occurs rock beam in a certain time.The results show that there is a guiding significance for creep stability in the geotechnical engineering fields.展开更多
By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures un...By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures under different lining circumstanceswere also analyzed on the basis of deducing the relationship between the generalizedKelvin creep model and implicit creep equations in ANSYS FEM software.The resultsshow that high stress of deep tunnels is the main factor in creep damage;the surroundingrock's deformation binding effect due to lining increases as the thickness increases but theeffect becomes very weak when it increases to a certain value;contact pressure on thelining decreases as its thickness decreases.展开更多
In deep geological disposal of high-level nuclear waste,one of the most important subjects is to estimate long-term stability and strength of host rock under high temperature conditions caused by radioactive decay of ...In deep geological disposal of high-level nuclear waste,one of the most important subjects is to estimate long-term stability and strength of host rock under high temperature conditions caused by radioactive decay of the waste.In this paper,some experimental researches on the thermo-mechanical characteristics of soft sedimentary rock have been presented.For this reason,a new temperature-controlled triaxial compression and creep test device,operated automatically by a computer-controlled system,whose control software has been developed by the authors,was developed to conduct the thermo-mechanical tests in different thermal loading paths,including an isothermal path.The new device is proved to be able to conduct typical thermo-mechanical element tests for soft rock.The test device and the related testing method were introduced in detail.Finally,some test results have been simulated with a thermo-elasto-viscoplastic model that was also developed by the authors.展开更多
Based on the results of triaxial compressive creep tests for five kinds of rock under the different stress loading,unloading and cycle-loading-unloading conditions,the creep deformation is not only a function of stres...Based on the results of triaxial compressive creep tests for five kinds of rock under the different stress loading,unloading and cycle-loading-unloading conditions,the creep deformation is not only a function of stress and time,but also it has the corresponding relations to the triaxial stress-strain curves of rock.The deformation properties of soften-strain,harden-strain and ideal plasticity presented by conventional triaxial compressive test curves under the different stress states were utilized,and the creep characteristics,the creep starting stress and the different entire creep process curves of rock were studied systematically according to creep experiment results,and the relations of the triaxial stress-strain curves to the creeping starting stress,the terminating curve,the different creep processes,and the different creep fracture properties were established.The relations presented in this paper were verified partially by the creep experiment results of five types of rock.展开更多
In order to investigate the time-dependent behaviors of deep hard rocks in the diversion tunnel of Jinping II hydropower station, uniaxial creep tests were carried out by using the triaxial testing machine RC-2000. Th...In order to investigate the time-dependent behaviors of deep hard rocks in the diversion tunnel of Jinping II hydropower station, uniaxial creep tests were carried out by using the triaxial testing machine RC-2000. The axial compressive load was applied step by step and each creep stage was kept for over several days. Test results show that: (1) The lateral deformation of rock specimens is 2-3 times the axial compressive deformation and accelerates drastically before damage, which may be employed as an indicator to predict the excavation-induced instability of rocks. (2) The resultant deformation changes from compression to expansion when the Poisson's ratio is larger than 0.5, indicating the starting point of damage. (3) In the step-loading stages, the Poisson's ratio approximately remains constant; under constantly imposed load, the Poisson's ratio changes with elapsed time, growing continuously before the specimen is damaged. (4) When the applied load reaches a certain threshold value, the rock deteriorates with time, and the strength of rocks approximately has a negative exponent relation with time. (5) The failure modes of the deep marble are different in long- and short-term loading conditions. Under the condition of short-term loading, the specimen presents a mode of tensile failure; while under the condition of long-term loading, the specimen presents a mode of shear failure, followed by tensile failure.展开更多
文摘In this paper,based on many experimental results,a creep damage equation for rocks with a creep modulus that can describe the history of damage has been deduced.According to the equation,a creep damage model for rock materials is constructed,and it is shown that the extent of their damage,or damage degree,during creep can be determined by means of simple experiments.
基金supported by the National Natural Science Foundation of China(Grants No.51409261 and 11172090)the Natural Science Foundation of Shandong Province(Grants No.ZR2014EEQ014)the Applied Basic Research Programs of Qingdao City(Grant No.14-2-4-67-jch)
文摘There are many fracture zones crossing the dam foundation of the Xiangjiaba Hydropower Project in southwestern China. Clastic rock is the main media of the fracture zone and has poor physical and mechanical properties. In order to investigate the creep behavior of clastic rock, triaxial creep tests were conducted using a rock servo-controlling rheological testing machine. The results show that the creep behavior of clastic rock is significant at a high level of deviatoric stress, and less time-dependent deformation occurs at high confining pressure. Based on the creep test results, the relationship between axial strain and time under different confining pressures was investigated, and the relationship between axial strain rate and deviatoric stress was also discussed. The strain rate increases rapidly, and the rock sample fails eventually under high deviatoric stress. Moreover, the creep failure mechanism under different confining pressures was analyzed. The main failure mechanism of clastic rock is plastic shear, accompanied by a significant compression and ductile dilatancy. On the other band, with the determined parameters, the Burgers creep model was used to fit the creep curves. The results indicate that the Burgers model can exactly describe the creep behavior of clastic rock in the Xiangjiaba Hydropower Project.
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 m/s at confining pressure(σ3) of 2 MPa,and is about 3.9×10-9 m/s at σ3 of 6 MPa.It is seen that the seepage flow rate at σ3 of 2 MPa in this case is obviously larger than that at σ3 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.
基金Project(2007CB209400) supported by the Major State Basic Research and Development Program of ChinaProject(50774093) supported by the National Natural Science Foundation of ChinaProject(200801) supported by Open Research Fund of Hunan Provincial Key of Safe Mining Techniques of Coal Mines
文摘The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine Ⅲ were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic strain, visco-elastic strain, instantaneous plastic strain and visco-plastic strain. The result shows that instantaneous deformation modulus tends to increase with the increase of creep stress; soft rocks enhance the ability to resist instantaneous elastic deformation and instantaneous plastic deformation during the multi-level of load and unload in the cyclic process. In respect of specimen JC1099, the ratio of visco-elastic strain to visco-plastic strain varies from 3.15 to 6.58, and the ratio has decreasing tendency with stress increase as a whole; creep deformation tends to be a steady state at low stress level; soft rocks creep usually embodies accelerated creep properties at high stress level. With the damaging variable and the hardening function introduced, a nonlinear creep model of soft rocks is established, in which the decay creep is described by the nonlinear hardening function H of viscidity coefficient. The model can describe the accelerated creep of soft rocks since the nonlinear damaging evolvement variable D of deformation parameter of rocks is introduced. Three stages of soft rocks creep can be described with the uniform creep equation in the nonlinear creep model. With this nonlinear creep model applied to the creep experiments of the ore-rock of Jinchuan Mine Ⅲ, the nonlinear creep model’s curves are in good agreement with experimental data.
基金Projects(50474029,50174035) supported by the National Natural Science Foundation of China
文摘The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test system,and the constitutive equations were established.It is found that fracture morphology of rock beams under no disturbance load is regular,cracking position of fractures is on part of loading concentration,the crack starts from a neutral plane.However,fracture morphology of rock beams under disturbance load is irregular,cracking position of fractures deviates from a neutral plane.Delayed instability of rock beam occurs for some time under constant disturbance load.When disturbance load is beyond a certain range,suddenly instability of occurs rock beam in a certain time.The results show that there is a guiding significance for creep stability in the geotechnical engineering fields.
基金Supported by Open Foundation Project of Education Ministry Key Laboratory about Mine Disaster Prevention and Control(MDPC0811)Research Project"Spring Bud Plan"of Shandong University of Science and TechnologyShandong University of Science and Technology Innovation Fund Grant(yca2008-04-01)
文摘By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures under different lining circumstanceswere also analyzed on the basis of deducing the relationship between the generalizedKelvin creep model and implicit creep equations in ANSYS FEM software.The resultsshow that high stress of deep tunnels is the main factor in creep damage;the surroundingrock's deformation binding effect due to lining increases as the thickness increases but theeffect becomes very weak when it increases to a certain value;contact pressure on thelining decreases as its thickness decreases.
文摘In deep geological disposal of high-level nuclear waste,one of the most important subjects is to estimate long-term stability and strength of host rock under high temperature conditions caused by radioactive decay of the waste.In this paper,some experimental researches on the thermo-mechanical characteristics of soft sedimentary rock have been presented.For this reason,a new temperature-controlled triaxial compression and creep test device,operated automatically by a computer-controlled system,whose control software has been developed by the authors,was developed to conduct the thermo-mechanical tests in different thermal loading paths,including an isothermal path.The new device is proved to be able to conduct typical thermo-mechanical element tests for soft rock.The test device and the related testing method were introduced in detail.Finally,some test results have been simulated with a thermo-elasto-viscoplastic model that was also developed by the authors.
基金Project(50774090) supported by the National Natural Science Foundation of China
文摘Based on the results of triaxial compressive creep tests for five kinds of rock under the different stress loading,unloading and cycle-loading-unloading conditions,the creep deformation is not only a function of stress and time,but also it has the corresponding relations to the triaxial stress-strain curves of rock.The deformation properties of soften-strain,harden-strain and ideal plasticity presented by conventional triaxial compressive test curves under the different stress states were utilized,and the creep characteristics,the creep starting stress and the different entire creep process curves of rock were studied systematically according to creep experiment results,and the relations of the triaxial stress-strain curves to the creeping starting stress,the terminating curve,the different creep processes,and the different creep fracture properties were established.The relations presented in this paper were verified partially by the creep experiment results of five types of rock.
基金Supported by the National Natural Science Foundation of China(50909092)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences (Z000802)the Natural Science Foundation of Hubei Province (2009CDB120)
文摘In order to investigate the time-dependent behaviors of deep hard rocks in the diversion tunnel of Jinping II hydropower station, uniaxial creep tests were carried out by using the triaxial testing machine RC-2000. The axial compressive load was applied step by step and each creep stage was kept for over several days. Test results show that: (1) The lateral deformation of rock specimens is 2-3 times the axial compressive deformation and accelerates drastically before damage, which may be employed as an indicator to predict the excavation-induced instability of rocks. (2) The resultant deformation changes from compression to expansion when the Poisson's ratio is larger than 0.5, indicating the starting point of damage. (3) In the step-loading stages, the Poisson's ratio approximately remains constant; under constantly imposed load, the Poisson's ratio changes with elapsed time, growing continuously before the specimen is damaged. (4) When the applied load reaches a certain threshold value, the rock deteriorates with time, and the strength of rocks approximately has a negative exponent relation with time. (5) The failure modes of the deep marble are different in long- and short-term loading conditions. Under the condition of short-term loading, the specimen presents a mode of tensile failure; while under the condition of long-term loading, the specimen presents a mode of shear failure, followed by tensile failure.