To investigate the effect of saturation on the storage-dissipation properties and failure characteristics of red sandstone,as well as the energy mechanism of rockburst prevention by water,a series of uniaxial compress...To investigate the effect of saturation on the storage-dissipation properties and failure characteristics of red sandstone,as well as the energy mechanism of rockburst prevention by water,a series of uniaxial compression and uniaxial loading–unloading tests were conducted under five saturation levels.The effect of saturation on the mechanical properties and elastic energy density was analyzed,and a method for obtaining peak energy density was proposed.The effect of saturation on the energy evolution was examined,and the energy mechanism of water in preventing rockburst was revealed.The results indicate that an increase in saturation of red sandstone decreases the input energy density,elastic energy density,dissipated energy density,peak strength and peak strain;the compaction phase of the stress–strain curve becomes shorter;the failure mode transitions from X-conjugate oblique shear to single oblique shear;the variation in the debris ejection trajectory is as follows:radiation→X-ray→oblique upward parabola→horizontal parabola→oblique downward parabola;the degree of failure intensity and fragmentation is decreased gradually.Elastic energy density is interconnected with both saturation and stress but independent of the loading path.Saturation exhibits a dual effect on the energy storage property,i.e.,increasing saturation increases the energy storage efficiency and reduces the energy storage capacity.The ratio of peak elastic energy density to peak input energy density remains constant irrespective of saturation levels.Water prevents rockburst by decreasing the energy storage capacity of surrounding rock,alleviating the stress of surrounding rock to reduce energy storage,and elevating the energy release threshold of high-energy surrounding rock.The findings of this study contribute to understanding the effect of water on rock failure from an energy perspective,as well as provide theoretical guidance for rockburst prevention by water in deep tunnels.展开更多
To obtain the precise calculation method for the peak energy density and energy evolution properties of rocks subjected to uniaxial compression(UC)before the post-peak stage,particularly at s0.9sc(s denotes stress and...To obtain the precise calculation method for the peak energy density and energy evolution properties of rocks subjected to uniaxial compression(UC)before the post-peak stage,particularly at s0.9sc(s denotes stress and sc is the peak strength),extensive UC and uniaxial graded cyclical loading-unloading(GCLU)tests were performed on four rock types.In the GCLU tests,four unloading stress levels were designated when σ<0.9σc and six unloading stress levels were designated forσ≥0.9σc.The variations in the elastic energy density(ue),dissipative energy density(ud),and energy storage efficiency(C)for the four rock types under GCLU tests were analyzed.Based on the variation of ue whenσ≥0:9σc,a method for calculating the peak energy density was proposed.The energy evolution in rock under UC condition before the post-peak stage was examined.The relationship between C0.9(C atσ≥0:9σc)and mechanical behavior of rocks was explored,and the damage evolution of rock was analyzed in view of energy.Compared with that of the three existing methods,the accuracy of the calculation method of peak energy density proposed in this study is higher.These findings could provide a theoretical foundation for more accurately revealing the failure behavior of rock from an energy perspective.展开更多
To investigate the influence of unloading effect of a circular tunnel face on rockburst process,by innovatively combining rock drilling unloading devices and triaxial systems,the strain rockburst simulation under the ...To investigate the influence of unloading effect of a circular tunnel face on rockburst process,by innovatively combining rock drilling unloading devices and triaxial systems,the strain rockburst simulation under the entire stress path of“high initial stressþinternal unloadingþstress adjustment”(HUS test)was realized for the intact cubic red sandstone samples(100 mm×100 mm×100 mm).Comparative tests were conducted on cubic red sandstone samples with prefabricated circular holes(425 mm)under the stress path of“prefabricated circular hole+þhigh initial stress+stress adjustment”(PHS test),thereby highlighting the influence of internal unloading on rockburst failure.The test results revealed that with an increase in vertical stress,the sidewalls in both the HUS and PHS tests suffered strain rockburst failure.Compared with the PHS test,the initial failure stress in the HUS test is lower,and it is easier to induce sidewall rockbursts.This indicates that the internal unloading influences the sidewall failure,causing an obvious strength-weakening effect,which becomes more significant with an increase in buried depth.The strain rockburst failure was more severe in the HUS test owing to the influence of internal unloading.V-shaped rockburst pits were formed in the HUS tests,whereas in the PHS test,arcshaped rockburst pits were produced.It was also found that strain rockburst failure may occur only when the rock has a certain degree of rockburst proneness.展开更多
This study investigated the sidewall rockburst characteristics of highly stressed circular tunnel subjected to impact loads resulting from rock blasting or other mining-related dynamic disturbances,aiming at exploring...This study investigated the sidewall rockburst characteristics of highly stressed circular tunnel subjected to impact loads resulting from rock blasting or other mining-related dynamic disturbances,aiming at exploring the influence of vertical prestress and dynamic load on sidewall rockburst.Using a biaxial Hopkinson pressure bar(BHPB)system,we studied the sidewall rockburst of a circular tunnel by applying various prestresses(horizontal and vertical static stresses)to a sand prefabricated circular hole specimen,followed by impact loads.The real-time process and strain field of the sidewall rockburst around the specimen were tracked by the high-speed camera and digital image correlation(DIC).The tests reveal that the sidewall rockburst process can be summarized as:calm stage,slab buckling and spalling stage,rock slabs ejection stage,and V-shaped notch formation stage.Furthermore,the sidewall rockbursts exhibit typical dynamic tensile failure.The mechanism of sidewall rockburst under the coupled static-impact loads was summarized,i.e.the static prestress determines the initial stress and strain distribution,and the vertical prestress influences the affected range and strain values of the strain concentration zone;the impact load disrupts the original static stress equilibrium,inducing alterations in the stress and strain of the surrounding rock and triggering sidewall rockburst.展开更多
This study aims to clarity the failure mechanism of sidewall rockburst of highly stressed D-shape tunnel triggered by impact load.Using the biaxial Hopkinson pressure bar(BHPB)system,we have developed experimental cap...This study aims to clarity the failure mechanism of sidewall rockburst of highly stressed D-shape tunnel triggered by impact load.Using the biaxial Hopkinson pressure bar(BHPB)system,we have developed experimental capabilities to study the sidewall rockburst of D-shape tunnel by applying various prestresses,including horizontal and vertical static stresses,to sand prefabricated D-shape hole specimen,followed by impact loads.High-speed(HS)camera and digital image correlation(DIC)were used to tracked the process and strain field of the sidewall rockburst.The test results reveal that the process of sidewall rockburst can be summarized as:calm stage,crack initiation,propagation,and coalesce stage,spalling stage and rock fragments ejection stage.During the rockburst process,the surrounding rock experienced spalling and violent ejection,involving both tensile and tensile-shear failure.The mechanism of sidewall rockburst under the coupled of static stress and impact loads has been elucidated,i.e.,the static prestress determines the initial stress and strain distribution,and the horizontal prestress influences the affected range and strain values of strain concentration zone;the impact load disrupts the original static stress equilibrium,inducing alterations in the stress and strain of the surrounding rock and triggering sidewall rockburst.展开更多
Rockburst has always been a challenge for the safe construction of deep underground engineering.This study investigated the rockburst characteristics in highly-stressed D-shape tunnels under impact loads from rock bla...Rockburst has always been a challenge for the safe construction of deep underground engineering.This study investigated the rockburst characteristics in highly-stressed D-shape tunnels under impact loads from rock blasting and other mining-related dynamics disturbances.The biaxial Hopkinson pressure bar was utilized to apply varying biaxial prestress and the same impact loads to cube specimens with D-shape hole.High-speed camera and digital image correlation(DIC)were used to capture the failure process and strain field of specimen.The test results demonstrate that the D-shape hole specimen experience rockburst under coupled static stress and impact load.Under this circumstance,the rockburst mechanism of the D-shaped hole specimens involves spalling in sidewall induced by impact load,indicating dynamic tensile failure.The high static prestress provides the initial stress field,while the impact load disrupts the stress equilibrium,result in the stress or strain concentration in the sidewall of the D-shape hole,inducing rockburst.Moreover,the rockburst process can be divided into(1)calm stage,(2)crack initiation,propagation,and coalesce stage,(3)spalling stage and(4)rock fragments ejection stage.Impact load triggers rockburst occurrence,while vertical stress further determines the rockburst characteristics.The influence range and magnitude of strain concentration zone and displacement deformation of the tunnel surrounding rock increases with increasing vertical stress,thus inducing more severe rockburst.展开更多
基金supported by the National Natural Science Foundation of China(52104133,52304227)the Natural Science Foundation of Hunan Province(2021JJ40465,2023JJ40548)the Opening Foundation of the State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines(SKLMRDPC20KF03).
文摘To investigate the effect of saturation on the storage-dissipation properties and failure characteristics of red sandstone,as well as the energy mechanism of rockburst prevention by water,a series of uniaxial compression and uniaxial loading–unloading tests were conducted under five saturation levels.The effect of saturation on the mechanical properties and elastic energy density was analyzed,and a method for obtaining peak energy density was proposed.The effect of saturation on the energy evolution was examined,and the energy mechanism of water in preventing rockburst was revealed.The results indicate that an increase in saturation of red sandstone decreases the input energy density,elastic energy density,dissipated energy density,peak strength and peak strain;the compaction phase of the stress–strain curve becomes shorter;the failure mode transitions from X-conjugate oblique shear to single oblique shear;the variation in the debris ejection trajectory is as follows:radiation→X-ray→oblique upward parabola→horizontal parabola→oblique downward parabola;the degree of failure intensity and fragmentation is decreased gradually.Elastic energy density is interconnected with both saturation and stress but independent of the loading path.Saturation exhibits a dual effect on the energy storage property,i.e.,increasing saturation increases the energy storage efficiency and reduces the energy storage capacity.The ratio of peak elastic energy density to peak input energy density remains constant irrespective of saturation levels.Water prevents rockburst by decreasing the energy storage capacity of surrounding rock,alleviating the stress of surrounding rock to reduce energy storage,and elevating the energy release threshold of high-energy surrounding rock.The findings of this study contribute to understanding the effect of water on rock failure from an energy perspective,as well as provide theoretical guidance for rockburst prevention by water in deep tunnels.
基金the National Natural Science Foundation of China(Grant Nos.52104133 and 52304227)the Postdoctoral Foundation of Henan Province(Grant No.HN2022015)are appreciated.
文摘To obtain the precise calculation method for the peak energy density and energy evolution properties of rocks subjected to uniaxial compression(UC)before the post-peak stage,particularly at s0.9sc(s denotes stress and sc is the peak strength),extensive UC and uniaxial graded cyclical loading-unloading(GCLU)tests were performed on four rock types.In the GCLU tests,four unloading stress levels were designated when σ<0.9σc and six unloading stress levels were designated forσ≥0.9σc.The variations in the elastic energy density(ue),dissipative energy density(ud),and energy storage efficiency(C)for the four rock types under GCLU tests were analyzed.Based on the variation of ue whenσ≥0:9σc,a method for calculating the peak energy density was proposed.The energy evolution in rock under UC condition before the post-peak stage was examined.The relationship between C0.9(C atσ≥0:9σc)and mechanical behavior of rocks was explored,and the damage evolution of rock was analyzed in view of energy.Compared with that of the three existing methods,the accuracy of the calculation method of peak energy density proposed in this study is higher.These findings could provide a theoretical foundation for more accurately revealing the failure behavior of rock from an energy perspective.
基金This work was supported by the National Natural Science Foundation of China(Grant No.42077244)the Open Research Fund of State Key Laboratory of Deep Earth Science and Engineering(Sichuan University)(Grant No.DESE 202201)the Fundamental Research Funds for the Central Universities(Grant No.2242022k30054).
文摘To investigate the influence of unloading effect of a circular tunnel face on rockburst process,by innovatively combining rock drilling unloading devices and triaxial systems,the strain rockburst simulation under the entire stress path of“high initial stressþinternal unloadingþstress adjustment”(HUS test)was realized for the intact cubic red sandstone samples(100 mm×100 mm×100 mm).Comparative tests were conducted on cubic red sandstone samples with prefabricated circular holes(425 mm)under the stress path of“prefabricated circular hole+þhigh initial stress+stress adjustment”(PHS test),thereby highlighting the influence of internal unloading on rockburst failure.The test results revealed that with an increase in vertical stress,the sidewalls in both the HUS and PHS tests suffered strain rockburst failure.Compared with the PHS test,the initial failure stress in the HUS test is lower,and it is easier to induce sidewall rockbursts.This indicates that the internal unloading influences the sidewall failure,causing an obvious strength-weakening effect,which becomes more significant with an increase in buried depth.The strain rockburst failure was more severe in the HUS test owing to the influence of internal unloading.V-shaped rockburst pits were formed in the HUS tests,whereas in the PHS test,arcshaped rockburst pits were produced.It was also found that strain rockburst failure may occur only when the rock has a certain degree of rockburst proneness.
基金supported by the National Natural Science Foundation of China(Grant No.42077244).
文摘This study investigated the sidewall rockburst characteristics of highly stressed circular tunnel subjected to impact loads resulting from rock blasting or other mining-related dynamic disturbances,aiming at exploring the influence of vertical prestress and dynamic load on sidewall rockburst.Using a biaxial Hopkinson pressure bar(BHPB)system,we studied the sidewall rockburst of a circular tunnel by applying various prestresses(horizontal and vertical static stresses)to a sand prefabricated circular hole specimen,followed by impact loads.The real-time process and strain field of the sidewall rockburst around the specimen were tracked by the high-speed camera and digital image correlation(DIC).The tests reveal that the sidewall rockburst process can be summarized as:calm stage,slab buckling and spalling stage,rock slabs ejection stage,and V-shaped notch formation stage.Furthermore,the sidewall rockbursts exhibit typical dynamic tensile failure.The mechanism of sidewall rockburst under the coupled static-impact loads was summarized,i.e.the static prestress determines the initial stress and strain distribution,and the vertical prestress influences the affected range and strain values of the strain concentration zone;the impact load disrupts the original static stress equilibrium,inducing alterations in the stress and strain of the surrounding rock and triggering sidewall rockburst.
基金supported by the National Natural Science Foundation of China(Grant No.42077244).
文摘This study aims to clarity the failure mechanism of sidewall rockburst of highly stressed D-shape tunnel triggered by impact load.Using the biaxial Hopkinson pressure bar(BHPB)system,we have developed experimental capabilities to study the sidewall rockburst of D-shape tunnel by applying various prestresses,including horizontal and vertical static stresses,to sand prefabricated D-shape hole specimen,followed by impact loads.High-speed(HS)camera and digital image correlation(DIC)were used to tracked the process and strain field of the sidewall rockburst.The test results reveal that the process of sidewall rockburst can be summarized as:calm stage,crack initiation,propagation,and coalesce stage,spalling stage and rock fragments ejection stage.During the rockburst process,the surrounding rock experienced spalling and violent ejection,involving both tensile and tensile-shear failure.The mechanism of sidewall rockburst under the coupled of static stress and impact loads has been elucidated,i.e.,the static prestress determines the initial stress and strain distribution,and the horizontal prestress influences the affected range and strain values of strain concentration zone;the impact load disrupts the original static stress equilibrium,inducing alterations in the stress and strain of the surrounding rock and triggering sidewall rockburst.
基金supported by the National Natural Science Foundation of China(Grant No.42077244)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z020005)。
文摘Rockburst has always been a challenge for the safe construction of deep underground engineering.This study investigated the rockburst characteristics in highly-stressed D-shape tunnels under impact loads from rock blasting and other mining-related dynamics disturbances.The biaxial Hopkinson pressure bar was utilized to apply varying biaxial prestress and the same impact loads to cube specimens with D-shape hole.High-speed camera and digital image correlation(DIC)were used to capture the failure process and strain field of specimen.The test results demonstrate that the D-shape hole specimen experience rockburst under coupled static stress and impact load.Under this circumstance,the rockburst mechanism of the D-shaped hole specimens involves spalling in sidewall induced by impact load,indicating dynamic tensile failure.The high static prestress provides the initial stress field,while the impact load disrupts the stress equilibrium,result in the stress or strain concentration in the sidewall of the D-shape hole,inducing rockburst.Moreover,the rockburst process can be divided into(1)calm stage,(2)crack initiation,propagation,and coalesce stage,(3)spalling stage and(4)rock fragments ejection stage.Impact load triggers rockburst occurrence,while vertical stress further determines the rockburst characteristics.The influence range and magnitude of strain concentration zone and displacement deformation of the tunnel surrounding rock increases with increasing vertical stress,thus inducing more severe rockburst.
