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
Recently,the application of detrital coral as an alternative to natural aggregates in marine structures has attracted increased attention.In this study,research on the compressive performance of coral aggregate concre...Recently,the application of detrital coral as an alternative to natural aggregates in marine structures has attracted increased attention.In this study,research on the compressive performance of coral aggregate concrete(CAC)confined using steel stirrups with anti-rust treatment was experimentally conducted.A total of 45 specimens were cast,including 9 specimens without stirrups and under different strength grades(C20,C30,and C40)and 36 specimens under different strength grades(C20,C30,and C40).Moreover,three stirrup levels(rectangular,diamond-shaped compound,and spiral stirrups)and different stirrup spacings(40,50,60,and 70 mm)were used.Subsequently,the stress−strain curves of specimens subjected to axial loading were measured.The effects of the stirrup spacing and stirrup configurations on the stress and strain were investigated,respectively,and the lateral effective stress of the different stirrups was calculated based on the cohesive-elastic ring model and modified elastic beam theory.Moreover,a damageconstitutive model of CAC considering the lateral stress was set up based on damage mechanics theory.The results indicated an increase in the stress and strain with a decrease in the stirrup spacing,and the adopted stirrup ratio had a better strengthening effect than the different concrete grades,and the variation in the deformation was restricted by the performance of coral coarse aggregate(CA).However,an increment in the lateral strain was observed with an increase in the axial strain.The lateral stress model showed a good agreement with the experimental data,and the proposed damageconstitutive model had a good correlation with the measured stress−strain curves.展开更多
Compacted graphite iron(CGI)is considered to be an ideal diesel engine material with excellent physical and mechanical properties,which meet the requirements of energy conservation and emission reduction.However,knowl...Compacted graphite iron(CGI)is considered to be an ideal diesel engine material with excellent physical and mechanical properties,which meet the requirements of energy conservation and emission reduction.However,knowledge of the microstructure evolution of CGI and its impact on flow stress remains limited.In this study,a new modeling approach for the stress–strain relationship is proposed by considering the strain hardening effect and stored energy caused by the microstructure evolution of CGI.The effects of strain,strain rate,and deformation temperature on the microstructure of CGI during compression deformation are examined,including the evolution of graphite morphology and the microstructure of the pearlite matrix.The roundness and fractal dimension of graphite particles under different deformation conditions are measured.Combined with finite element simulation models,the influence of graphite particles on the flow stress of CGI is determined.The distributions of grain boundary and geometrically necessary dislocations(GNDs)density in the pearlite matrix of CGI under different strains,strain rates,and deformation temperatures are analyzed by electron backscatter diffraction technology,and the stored energy under each deformation condition is calculated.Results show that the proportion and amount of low-angle grain boundaries and the average GNDs density increase with the increase of strain and strain rate and decreased first and then increased with an increase in deformation temperature.The increase in strain and strain rate and the decrease in deformation temperature contribute to the accumulation of stored energy,which show similar variation trends to those of GNDs density.The parameters in the stress–strain relationship model are solved according to the stored energy under different deformation conditions.The consistency between the predicted results from the proposed stress–strain relationship and the experimental results shows that the evolution of stored energy can accurately predict the stress–st展开更多
基金Project(2022YFB3705103)supported by the National Key R&D Program,ChinaProject(2023CDJXY-020)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(cstc2021jcyj-msxmX1085)supported by Chongqing Natural Science Foundation General Project,China。
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.
基金This study was supported by the National Natural Science Foundation of China(Grant No.51868005)the Innovation Project of Guangxi Graduate Education(No.YCBZ2022010)Their sponsorships are sincerely appreciated.
文摘Recently,the application of detrital coral as an alternative to natural aggregates in marine structures has attracted increased attention.In this study,research on the compressive performance of coral aggregate concrete(CAC)confined using steel stirrups with anti-rust treatment was experimentally conducted.A total of 45 specimens were cast,including 9 specimens without stirrups and under different strength grades(C20,C30,and C40)and 36 specimens under different strength grades(C20,C30,and C40).Moreover,three stirrup levels(rectangular,diamond-shaped compound,and spiral stirrups)and different stirrup spacings(40,50,60,and 70 mm)were used.Subsequently,the stress−strain curves of specimens subjected to axial loading were measured.The effects of the stirrup spacing and stirrup configurations on the stress and strain were investigated,respectively,and the lateral effective stress of the different stirrups was calculated based on the cohesive-elastic ring model and modified elastic beam theory.Moreover,a damageconstitutive model of CAC considering the lateral stress was set up based on damage mechanics theory.The results indicated an increase in the stress and strain with a decrease in the stirrup spacing,and the adopted stirrup ratio had a better strengthening effect than the different concrete grades,and the variation in the deformation was restricted by the performance of coral coarse aggregate(CA).However,an increment in the lateral strain was observed with an increase in the axial strain.The lateral stress model showed a good agreement with the experimental data,and the proposed damageconstitutive model had a good correlation with the measured stress−strain curves.
基金the National Natural Science Foundation of China(Grant Nos.52275464 and 52075300)the Scientific Research Project for National High-level Innovative Talents of Hebei Province Full-time Introduction,China(Grant No.2021HBQZYCXY004).
文摘Compacted graphite iron(CGI)is considered to be an ideal diesel engine material with excellent physical and mechanical properties,which meet the requirements of energy conservation and emission reduction.However,knowledge of the microstructure evolution of CGI and its impact on flow stress remains limited.In this study,a new modeling approach for the stress–strain relationship is proposed by considering the strain hardening effect and stored energy caused by the microstructure evolution of CGI.The effects of strain,strain rate,and deformation temperature on the microstructure of CGI during compression deformation are examined,including the evolution of graphite morphology and the microstructure of the pearlite matrix.The roundness and fractal dimension of graphite particles under different deformation conditions are measured.Combined with finite element simulation models,the influence of graphite particles on the flow stress of CGI is determined.The distributions of grain boundary and geometrically necessary dislocations(GNDs)density in the pearlite matrix of CGI under different strains,strain rates,and deformation temperatures are analyzed by electron backscatter diffraction technology,and the stored energy under each deformation condition is calculated.Results show that the proportion and amount of low-angle grain boundaries and the average GNDs density increase with the increase of strain and strain rate and decreased first and then increased with an increase in deformation temperature.The increase in strain and strain rate and the decrease in deformation temperature contribute to the accumulation of stored energy,which show similar variation trends to those of GNDs density.The parameters in the stress–strain relationship model are solved according to the stored energy under different deformation conditions.The consistency between the predicted results from the proposed stress–strain relationship and the experimental results shows that the evolution of stored energy can accurately predict the stress–st
基金Projects(52225404, 51808545) supported by the National Natural Science Foundation of ChinaProject(SKLCRSM21LH04) supported by the Joint Fund of State Key Laboratory of Coal Resources and Safe Mining-the Beijing Outstanding Young Scientist Program,ChinaProject(2023ZKPYLJ05) supported by the Fundamental Research Funds for the Central Universities,China。
