To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main compon...To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main components:a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state,a quantitative relationship between critical irreversible deformation and complex stress state,and evolution characteristics of strength parameters.The proposed model is implemented in a self-developed numerical code,i.e.CASRock.The reliability of the model is validated through experiments.It is indicated that the time-dependent fracturing potential index(xTFPI)at a given time during the attenuation creep stage shows a negative correlation with the extent of excavationinduced damage.The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress,thereby highlighting the 3D stress-dependent characteristic of the model.Finally,the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed.展开更多
Cucumber seedlings were sprayed with different concentrations of LaCl_3 for 3 d continuously. After 7 d of this treatment, the plants were treated with 1200 mg·L^(-1) 2,4-dichlorophennoxy(2,4-D) for 24 h. The lea...Cucumber seedlings were sprayed with different concentrations of LaCl_3 for 3 d continuously. After 7 d of this treatment, the plants were treated with 1200 mg·L^(-1) 2,4-dichlorophennoxy(2,4-D) for 24 h. The leaves were harvested and rinsed with 5 mmol·L^(-1) EDTA. The concentrations of photosynthetic pigments, soluble protein and metabolites related to oxidative stress and the activities of antioxidant enzymes in leaves were assayed. The results show that the treatment with appropriate concentration of LaCl_3 has resistant effect on oxidative stress induced by 2, 4-D. Proper concentration of LaCl_3 promotes the activity of antioxidant system in plants and alleviates the damage caused by 2, 4-D.展开更多
Piloti is commonly used in tropical and subtropical climate zones to get high wind velocity and create shadowed areas in order to optimize the living environment of residential blocks,but there are few studies to reve...Piloti is commonly used in tropical and subtropical climate zones to get high wind velocity and create shadowed areas in order to optimize the living environment of residential blocks,but there are few studies to reveal the influence of piloti on the radiant environment of residential blocks systematically. Taking the city of Guangzhou as an example,using 3-D Unsteady State Heat Balance Radiation Calculation Method,this paper shows that the mean radiant temperature( MRT) under piloti area increases with the increase of piloti ratio,and especially when piloti ratio is equal to 100%,the MRT increase trend becomes sharp. The MRT of exposed area decreases with the increase of piloti ratio,especially when piloti ratio reaches 100%,the decrease trend of MRT becomes sharp,which offers the reference for the study on piloti design in subtropical climate zones and further research on living environment by CFD simulation in residential blocks.展开更多
The time-domain BEM was developed to analyze the dynamic stress intensity factor ( DSIF) of 3-D elastodynamic crack problems. To simulate the stress singularity along the front of a crack, eight-node isoparametric sin...The time-domain BEM was developed to analyze the dynamic stress intensity factor ( DSIF) of 3-D elastodynamic crack problems. To simulate the stress singularity along the front of a crack, eight-node isoparametric singular elements were used, and the DSIF for a semi-circular surface crack was firstly calculated based on displacement equation using the time-domain BEM formulation. The new scheme to determine the time step was brought forward. By the dynamic analysis program of time-domain BEM compiled by its, several numerical examples are presented, which demonstrate the unconditional stability and high accuracy of time-domain BEM applied to 3-D elastodynamic crack problems.展开更多
The Shangzhuang altered-rock type gold ore deposit is located in the middle segment of and controlled by the Wang＇ershan fault zone in the northwestern part of the Jiaodong gold province, China. The deformation evolu...The Shangzhuang altered-rock type gold ore deposit is located in the middle segment of and controlled by the Wang＇ershan fault zone in the northwestern part of the Jiaodong gold province, China. The deformation evolution, the structure of strain and stress fields and its ore-controlling effect in the Shangzhuang deposit are discussed in this paper. It is revealed that the deformation evolution has mainly undergone four phases： the early ductile deformation, the second NE-striking horizontal simple shear, the third NE-striking compression-shear and the final NW-striking compression. The mineralization happened during the third stage in which the maximum principal stress gradually transited from NE to NW. The 3-D numerical simulations of the stress field show that, on the condition that the maximum principal stress is NE-striking, the fracture development in the fault zone is favored, while when the maximum principal stress is NW-striking, the fault zone is relatively extensional and it is suitable for the influx and emplacement of ore-forming fluids. The compression-shear strain field during the mineralization is characterized by the λ-type structure, the positive flower structure, etc. Orebodies are mostly equidistantly located in the dilatational spaces, which are distributed in the integral compressional circumstances. And the dilatational spaces are developed where the fault attitude changes or shear joint systems develop. In the overall compression-shear stress field, the strain field bears self-similarity at multiple scales, including the orebody, ore deposit and orefield. The selfsimilarity of the structure comprises the subequidistant distribution of fractures at the same scale and the similar shape of the fractures at various scales. Yet, due to the special geological structure, the orebodies are mostly located in the hanging wall in the Shangzhuang deposit, which is different from most deposits in the Jiaodong gold province. Analyses of the ore-controlling stress and strain fields in the deposit provide an important basis for deposit seeking.展开更多
The Self-Similar Crack Expansion (SSCE) method is used to calculate stress intensity factors for three-dimensional cracks in an infinite medium or semi-infinite medium by the boundary integral element technique, where...The Self-Similar Crack Expansion (SSCE) method is used to calculate stress intensity factors for three-dimensional cracks in an infinite medium or semi-infinite medium by the boundary integral element technique, whereby, the stress intensity factors at crack tips are determined by calculating the crack-opening displacements over the crack surface. For elements on the crack surface, regular integrals and singular integrals are precisely evaluated based on closed form expressions, which improves the accuracy. Examples shaw that this method yields very accurate results for stress intensity factors of penny-shaped cracks and elliptical cracks in the full space, with errors of less than 1% as compared with analytical solutions. The stress intensity factors of subsurface cracks ate in good agreement with other analytical solutions.展开更多
In this study,the interaction between 3-D bedforms and submerged rigid vegetation has been investigated.Various laboratory experiments were conducted to study the distribution of flow velocity,Reynolds shear stress,tu...In this study,the interaction between 3-D bedforms and submerged rigid vegetation has been investigated.Various laboratory experiments were conducted to study the distribution of flow velocity,Reynolds shear stress,turbulent kinetic energy,and skewness coefficients for a constant density of vegetation.Results showed that the velocity profile in the pool section deviates from those in the upstream section of the pool.It has been found that the dip parameter varied between 0.6H and 0.9H depending on various factors including bed roughness,vegetation distribution,and pool entrance/exit slopes.However,scattered vegetation in the pool and differences in slopes created non-uniform flow conditions.Also,in the wake region behind each vegetated element,flow velocity reduced significantly,and small-scale eddies are formed,causing increased perturbations.By decreasing the entrance slope and bed roughness,relatively uniform flow and weaker turbulence was resulted,but the random distribution of vegetated elements counteracted this balance and intensified turbulence.With the decrease in the pool entrance slope,the contribution of sweep event decreased and the contribution of ejection event increased.展开更多
A generalized hend flow model, treating a 90° single bend and 60° continuous hends, was designed to quantitatively describe 3-D turhulenee mechanism of circulating notfully-developed flow in open channels wi...A generalized hend flow model, treating a 90° single bend and 60° continuous hends, was designed to quantitatively describe 3-D turhulenee mechanism of circulating notfully-developed flow in open channels with hends. The 3-D fluctuating veloeities of turbulent flow were measured and analyzed with a 3 D acoustic-Doppler velocimeter. Formula for 3 D turbulent intensity was derived using the dimension analysis approaeh. Expressions of vertical turbulent intensity distributions were obtained with the multivariant-rcgression theo ry, whieh agree with experiment data. Distrihutions of turbulent intensity and turbulent stress were characterized, and their relationships were concluded. In the bend-turbulent flow core region, longitudinal and lateral turbulent-intensity distri hutions are coincident with linear distribution, hut in nearwall region are coincident with the Gamma distribution. Verotical turbulent intensity distributions are coincident with the Rayleigh distribution. Herein, it is concluded that the bend turbulence is anisotropic.展开更多
The different physical states of saturated sand, including shear elasticity, positive dilatancy, and negative dilatancy (preliminary negative dilatancy, secondary negative dilatancy and reversal negative dilatancy) ar...The different physical states of saturated sand, including shear elasticity, positive dilatancy, and negative dilatancy (preliminary negative dilatancy, secondary negative dilatancy and reversal negative dilatancy) are revealed based on the pore water pressure response of saturated sand in undrained dynamic torsional tests of thin cylinder samples and also checked by the drained cyclic triaxial tests under a given mean effective normal stress. According to the effective stress path of different physical states under the undrained cyclic torsional tests the physical state transformation surface, stress history boundary and yield surface are determined, and the state boundary surface is also determined by the range of effective frictional stress state movement. Based on the moving yield surface without rotation, and the expanding stress history boundary surface relevant to the stress path variations under different physical states in 3D stress space, a physical state model is proposed to provide a new approach to calculating the transient pore water pressure under the undrained condition, and the volume strain of dilatation under drained condition in this paper.展开更多
Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture beha...Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52125903)the China Postdoctoral Science Foundation(Grant No.2023M730367)the Fundamental Research Funds for Central Public Welfare Research Institutes of China(Grant No.CKSF2023323/YT).
文摘To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main components:a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state,a quantitative relationship between critical irreversible deformation and complex stress state,and evolution characteristics of strength parameters.The proposed model is implemented in a self-developed numerical code,i.e.CASRock.The reliability of the model is validated through experiments.It is indicated that the time-dependent fracturing potential index(xTFPI)at a given time during the attenuation creep stage shows a negative correlation with the extent of excavationinduced damage.The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress,thereby highlighting the 3D stress-dependent characteristic of the model.Finally,the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed.
文摘Cucumber seedlings were sprayed with different concentrations of LaCl_3 for 3 d continuously. After 7 d of this treatment, the plants were treated with 1200 mg·L^(-1) 2,4-dichlorophennoxy(2,4-D) for 24 h. The leaves were harvested and rinsed with 5 mmol·L^(-1) EDTA. The concentrations of photosynthetic pigments, soluble protein and metabolites related to oxidative stress and the activities of antioxidant enzymes in leaves were assayed. The results show that the treatment with appropriate concentration of LaCl_3 has resistant effect on oxidative stress induced by 2, 4-D. Proper concentration of LaCl_3 promotes the activity of antioxidant system in plants and alleviates the damage caused by 2, 4-D.
基金Sponsored by the Strategic Japanese-Chinese Cooperation Program (Grant No.2011DFA91210)the Fundamental Research Funds for the Central Universities (Grant No.HIT.NSRIF.2014075),the Fundamental Research Funds for the Central Universities (Grant No.HIT.KISTP.201419)the Natural Science Foundation of Heilongjiang Province (Grant No.E201316)
文摘Piloti is commonly used in tropical and subtropical climate zones to get high wind velocity and create shadowed areas in order to optimize the living environment of residential blocks,but there are few studies to reveal the influence of piloti on the radiant environment of residential blocks systematically. Taking the city of Guangzhou as an example,using 3-D Unsteady State Heat Balance Radiation Calculation Method,this paper shows that the mean radiant temperature( MRT) under piloti area increases with the increase of piloti ratio,and especially when piloti ratio is equal to 100%,the MRT increase trend becomes sharp. The MRT of exposed area decreases with the increase of piloti ratio,especially when piloti ratio reaches 100%,the decrease trend of MRT becomes sharp,which offers the reference for the study on piloti design in subtropical climate zones and further research on living environment by CFD simulation in residential blocks.
文摘The time-domain BEM was developed to analyze the dynamic stress intensity factor ( DSIF) of 3-D elastodynamic crack problems. To simulate the stress singularity along the front of a crack, eight-node isoparametric singular elements were used, and the DSIF for a semi-circular surface crack was firstly calculated based on displacement equation using the time-domain BEM formulation. The new scheme to determine the time step was brought forward. By the dynamic analysis program of time-domain BEM compiled by its, several numerical examples are presented, which demonstrate the unconditional stability and high accuracy of time-domain BEM applied to 3-D elastodynamic crack problems.
基金This paper is supported by the National Natural Science Foundation of China （Grant Nos. 40572063 and 40272051）；the Fostering Plan Fund for Trans-Century Excellent Talents and the Project 111 （No. B07011）.
文摘The Shangzhuang altered-rock type gold ore deposit is located in the middle segment of and controlled by the Wang＇ershan fault zone in the northwestern part of the Jiaodong gold province, China. The deformation evolution, the structure of strain and stress fields and its ore-controlling effect in the Shangzhuang deposit are discussed in this paper. It is revealed that the deformation evolution has mainly undergone four phases： the early ductile deformation, the second NE-striking horizontal simple shear, the third NE-striking compression-shear and the final NW-striking compression. The mineralization happened during the third stage in which the maximum principal stress gradually transited from NE to NW. The 3-D numerical simulations of the stress field show that, on the condition that the maximum principal stress is NE-striking, the fracture development in the fault zone is favored, while when the maximum principal stress is NW-striking, the fault zone is relatively extensional and it is suitable for the influx and emplacement of ore-forming fluids. The compression-shear strain field during the mineralization is characterized by the λ-type structure, the positive flower structure, etc. Orebodies are mostly equidistantly located in the dilatational spaces, which are distributed in the integral compressional circumstances. And the dilatational spaces are developed where the fault attitude changes or shear joint systems develop. In the overall compression-shear stress field, the strain field bears self-similarity at multiple scales, including the orebody, ore deposit and orefield. The selfsimilarity of the structure comprises the subequidistant distribution of fractures at the same scale and the similar shape of the fractures at various scales. Yet, due to the special geological structure, the orebodies are mostly located in the hanging wall in the Shangzhuang deposit, which is different from most deposits in the Jiaodong gold province. Analyses of the ore-controlling stress and strain fields in the deposit provide an important basis for deposit seeking.
基金the National Institute of Standards and Technologythe Army Office of Research
文摘The Self-Similar Crack Expansion (SSCE) method is used to calculate stress intensity factors for three-dimensional cracks in an infinite medium or semi-infinite medium by the boundary integral element technique, whereby, the stress intensity factors at crack tips are determined by calculating the crack-opening displacements over the crack surface. For elements on the crack surface, regular integrals and singular integrals are precisely evaluated based on closed form expressions, which improves the accuracy. Examples shaw that this method yields very accurate results for stress intensity factors of penny-shaped cracks and elliptical cracks in the full space, with errors of less than 1% as compared with analytical solutions. The stress intensity factors of subsurface cracks ate in good agreement with other analytical solutions.
文摘In this study,the interaction between 3-D bedforms and submerged rigid vegetation has been investigated.Various laboratory experiments were conducted to study the distribution of flow velocity,Reynolds shear stress,turbulent kinetic energy,and skewness coefficients for a constant density of vegetation.Results showed that the velocity profile in the pool section deviates from those in the upstream section of the pool.It has been found that the dip parameter varied between 0.6H and 0.9H depending on various factors including bed roughness,vegetation distribution,and pool entrance/exit slopes.However,scattered vegetation in the pool and differences in slopes created non-uniform flow conditions.Also,in the wake region behind each vegetated element,flow velocity reduced significantly,and small-scale eddies are formed,causing increased perturbations.By decreasing the entrance slope and bed roughness,relatively uniform flow and weaker turbulence was resulted,but the random distribution of vegetated elements counteracted this balance and intensified turbulence.With the decrease in the pool entrance slope,the contribution of sweep event decreased and the contribution of ejection event increased.
文摘A generalized hend flow model, treating a 90° single bend and 60° continuous hends, was designed to quantitatively describe 3-D turhulenee mechanism of circulating notfully-developed flow in open channels with hends. The 3-D fluctuating veloeities of turbulent flow were measured and analyzed with a 3 D acoustic-Doppler velocimeter. Formula for 3 D turbulent intensity was derived using the dimension analysis approaeh. Expressions of vertical turbulent intensity distributions were obtained with the multivariant-rcgression theo ry, whieh agree with experiment data. Distrihutions of turbulent intensity and turbulent stress were characterized, and their relationships were concluded. In the bend-turbulent flow core region, longitudinal and lateral turbulent-intensity distri hutions are coincident with linear distribution, hut in nearwall region are coincident with the Gamma distribution. Verotical turbulent intensity distributions are coincident with the Rayleigh distribution. Herein, it is concluded that the bend turbulence is anisotropic.
基金Project supported by the National Natural Science Foundation of China (No.10172071) the Natural Science Foundation of Shaanxi Province.
文摘The different physical states of saturated sand, including shear elasticity, positive dilatancy, and negative dilatancy (preliminary negative dilatancy, secondary negative dilatancy and reversal negative dilatancy) are revealed based on the pore water pressure response of saturated sand in undrained dynamic torsional tests of thin cylinder samples and also checked by the drained cyclic triaxial tests under a given mean effective normal stress. According to the effective stress path of different physical states under the undrained cyclic torsional tests the physical state transformation surface, stress history boundary and yield surface are determined, and the state boundary surface is also determined by the range of effective frictional stress state movement. Based on the moving yield surface without rotation, and the expanding stress history boundary surface relevant to the stress path variations under different physical states in 3D stress space, a physical state model is proposed to provide a new approach to calculating the transient pore water pressure under the undrained condition, and the volume strain of dilatation under drained condition in this paper.
文摘Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.
