Microcrack growth during progressive compressive failure in brittle rocks strongly influences the safety of deep underground engineering.The external shear stressτxy on brittle rocks greatly affects microcrack growth...Microcrack growth during progressive compressive failure in brittle rocks strongly influences the safety of deep underground engineering.The external shear stressτxy on brittle rocks greatly affects microcrack growth and progressive failure.However,the theoretical mechanism of the growth direction evolution of the newly generated wing crack during progressive failure has rarely been studied.A novel analytical method is proposed to evaluate the shear stress effect on the progressive compressive failure and microcrack growth direction in brittle rocks.This model consists of the wing crack growth model under the principal compressive stresses,the direction correlation of the general stress,the principal stress and the initial microcrack inclination,and the relationship between the wing crack length and strain.The shear stress effect on the relationship between y-direction stress and wing crack growth and the relationship between y-direction stress and y-direction strain are analyzed.The shear stress effect on the wing crack growth direction during the progressive compressive failure is determined.The initial crack angle effect on the y-direction peak stress and the wing crack growth direction during the progressive compressive failure considering shear stress is also discussed.A crucial conclusion is that the direction of wing crack growth has a U-shaped variation with the growth of the wing crack.The rationality of the analytical results is verified by an experiment and from numerical results.The study results provide theoretical support for the evaluation of the safety and stability of surrounding rocks in deep underground engineering.展开更多
The strain energy density ratio criterion for predicting cracking direction in composite materials is proposed. The Tsai-Hill criterion and Norris criterion of composite materials are extended to predict the cracking ...The strain energy density ratio criterion for predicting cracking direction in composite materials is proposed. The Tsai-Hill criterion and Norris criterion of composite materials are extended to predict the cracking direction in composites. The three criteria are used to analyse the crack propagation problem of the unidirectional fibre composite sheet with various fibre directions. The predicted results are compared with those of the existing normal stress ratio criterion and strain energy density criterion.展开更多
This paper presents a directional large-area rock fracturing method.The method had distinctive features compared with other common fracturing methods.The area of the fracturing surface could reach 10–500m^(2).The fra...This paper presents a directional large-area rock fracturing method.The method had distinctive features compared with other common fracturing methods.The area of the fracturing surface could reach 10–500m^(2).The fractured rock was sheet-like in shape,with a thickness of 6–8cm.The main fracturing tools and procedures used were described in the paper.This paper analyzed the reason for controllable and directional(also mode-I)rupturing in rock from the view of fracture mechanics.Counter-intuitively,the fracturing surface of the rock sheet had an angle(approximately 25°)to the loading direction(i.e.,the orientation of the maximum principal compressive stress).The rupture behavior was controlled by the relationship between the load and the geometric boundary of the rock.It is found that the fracturing surface can suddenly and rapidly propagate after a certain strike by calculating the energies of the rock sheet.The striking energy could be converted into elastic strain energy,which accumulates in a very-slightly bent rock sheet step by step until exceeds the bearing limit of rock sheet.Most of the stored elastic strain energy was subsequently released in the form of splitting energy,leading to rock fracturing.This study provides insights into the occurrence of tectonic earthquakes.展开更多
The dynamic stress-fields and their distribution characteristics around boreholes in the directed crack blasting were measured with the dynamic photo-elastic laser holography apparatus and the ultradymamic measurement...The dynamic stress-fields and their distribution characteristics around boreholes in the directed crack blasting were measured with the dynamic photo-elastic laser holography apparatus and the ultradymamic measurement system. The directed crack mechanism and its mechanical model have been analysed and expounded. Through the 43 production experiments using slotted cartridges and the double triangle center cut-holes for directed crack blasting in underground rock drift, the results of which the rates of half-hole marks and efficiency of borehole,and the nonsmooth grades of the cut contours are 96%, 98% and 10cm respectively have been achieved.展开更多
In this contribution,the microscopic fracture mechanism and extension criterion for mixed type crack in ductile material under plane mixed mode loading are investigated in details.A universal extension criterion for t...In this contribution,the microscopic fracture mechanism and extension criterion for mixed type crack in ductile material under plane mixed mode loading are investigated in details.A universal extension criterion for the mixed type crack,i.e.the crack propagates along the direction of the maximum gradient of equivalent stress,is suggested.This new criterion is used to predict the propagation direction of mixed type crack,showing a good agreement with other theories for different types of mode mixity.Moreover,the numerical verification is also carried out for the case of an edge crack with different mixed mode loadings.Finally,a potential application to three-dimensional fracture in the ductile material induced by holes is also discussed.展开更多
By revisiting the three stage theory for the progress of science proposed by Taketani in 1942, the footmarks of fluidization research are examined. The bubbling and fast fluidization issues were emphasized so that the...By revisiting the three stage theory for the progress of science proposed by Taketani in 1942, the footmarks of fluidization research are examined. The bubbling and fast fluidization issues were emphasized so that the future offluidization research can be discussed among scientists and engineers in a wider perspective. The first cycle of fluidization research was started in the early 1940s by an initial stage of phenomenology. The second stage of structural studies was kicked off in the early 1950s with the introduction of the two phase theory. The third stage of essential studies occurred in the early 1960s in the form of bubble hydrodynamics. The second cycle, which confirmed the aforementioned three stages closed at the turn of the century, established a general understanding of suspension structures including agglomerating fluidization, bubbling, turbulent and fast fluidizations and pneumatic transport; also established powerful measurement and numerical simulation tools.After a general remark on science, technology and society issues the interactions between fluidization technology and science are revisited. Our future directions are discussed including the tasks in the third cycle, particularly in its phenomenology stage where strong motivation and intention are always necessary, in relation also to the green reforming of the present technology. A generalized definition of ＇fluidization＇ is proposed to extend fluidization principle into much wider scientific fields, which would be effective also for wider collaborations.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:51708016,12172036R&D Program of Beijing Municipal Education Commission,Grant/Award Number:KM202110016014+1 种基金Government of Perm Krai,Research Project,Grant/Award Numbers:СED-26-08-08-28,С-26/628Graduate Innovation Program of Beijing University of Civil Engineering and Architecture,Grant/Award Number:PG2024035。
文摘Microcrack growth during progressive compressive failure in brittle rocks strongly influences the safety of deep underground engineering.The external shear stressτxy on brittle rocks greatly affects microcrack growth and progressive failure.However,the theoretical mechanism of the growth direction evolution of the newly generated wing crack during progressive failure has rarely been studied.A novel analytical method is proposed to evaluate the shear stress effect on the progressive compressive failure and microcrack growth direction in brittle rocks.This model consists of the wing crack growth model under the principal compressive stresses,the direction correlation of the general stress,the principal stress and the initial microcrack inclination,and the relationship between the wing crack length and strain.The shear stress effect on the relationship between y-direction stress and wing crack growth and the relationship between y-direction stress and y-direction strain are analyzed.The shear stress effect on the wing crack growth direction during the progressive compressive failure is determined.The initial crack angle effect on the y-direction peak stress and the wing crack growth direction during the progressive compressive failure considering shear stress is also discussed.A crucial conclusion is that the direction of wing crack growth has a U-shaped variation with the growth of the wing crack.The rationality of the analytical results is verified by an experiment and from numerical results.The study results provide theoretical support for the evaluation of the safety and stability of surrounding rocks in deep underground engineering.
文摘The strain energy density ratio criterion for predicting cracking direction in composite materials is proposed. The Tsai-Hill criterion and Norris criterion of composite materials are extended to predict the cracking direction in composites. The three criteria are used to analyse the crack propagation problem of the unidirectional fibre composite sheet with various fibre directions. The predicted results are compared with those of the existing normal stress ratio criterion and strain energy density criterion.
基金the National Natural Science Foundation of China for financial support(Grant No.42272336).
文摘This paper presents a directional large-area rock fracturing method.The method had distinctive features compared with other common fracturing methods.The area of the fracturing surface could reach 10–500m^(2).The fractured rock was sheet-like in shape,with a thickness of 6–8cm.The main fracturing tools and procedures used were described in the paper.This paper analyzed the reason for controllable and directional(also mode-I)rupturing in rock from the view of fracture mechanics.Counter-intuitively,the fracturing surface of the rock sheet had an angle(approximately 25°)to the loading direction(i.e.,the orientation of the maximum principal compressive stress).The rupture behavior was controlled by the relationship between the load and the geometric boundary of the rock.It is found that the fracturing surface can suddenly and rapidly propagate after a certain strike by calculating the energies of the rock sheet.The striking energy could be converted into elastic strain energy,which accumulates in a very-slightly bent rock sheet step by step until exceeds the bearing limit of rock sheet.Most of the stored elastic strain energy was subsequently released in the form of splitting energy,leading to rock fracturing.This study provides insights into the occurrence of tectonic earthquakes.
文摘The dynamic stress-fields and their distribution characteristics around boreholes in the directed crack blasting were measured with the dynamic photo-elastic laser holography apparatus and the ultradymamic measurement system. The directed crack mechanism and its mechanical model have been analysed and expounded. Through the 43 production experiments using slotted cartridges and the double triangle center cut-holes for directed crack blasting in underground rock drift, the results of which the rates of half-hole marks and efficiency of borehole,and the nonsmooth grades of the cut contours are 96%, 98% and 10cm respectively have been achieved.
基金supported by the Natural Science Foundation of Shannxi (No. 2005A19)the Open Foundation of Engineering Key Laboratory of Disaster Prevention and Structural Safety,Guangxi Univ.(No. 2008TMKF004)the National Natural Science Foundation (Nos. 10932007 and 11172228)
文摘In this contribution,the microscopic fracture mechanism and extension criterion for mixed type crack in ductile material under plane mixed mode loading are investigated in details.A universal extension criterion for the mixed type crack,i.e.the crack propagates along the direction of the maximum gradient of equivalent stress,is suggested.This new criterion is used to predict the propagation direction of mixed type crack,showing a good agreement with other theories for different types of mode mixity.Moreover,the numerical verification is also carried out for the case of an edge crack with different mixed mode loadings.Finally,a potential application to three-dimensional fracture in the ductile material induced by holes is also discussed.
文摘By revisiting the three stage theory for the progress of science proposed by Taketani in 1942, the footmarks of fluidization research are examined. The bubbling and fast fluidization issues were emphasized so that the future offluidization research can be discussed among scientists and engineers in a wider perspective. The first cycle of fluidization research was started in the early 1940s by an initial stage of phenomenology. The second stage of structural studies was kicked off in the early 1950s with the introduction of the two phase theory. The third stage of essential studies occurred in the early 1960s in the form of bubble hydrodynamics. The second cycle, which confirmed the aforementioned three stages closed at the turn of the century, established a general understanding of suspension structures including agglomerating fluidization, bubbling, turbulent and fast fluidizations and pneumatic transport; also established powerful measurement and numerical simulation tools.After a general remark on science, technology and society issues the interactions between fluidization technology and science are revisited. Our future directions are discussed including the tasks in the third cycle, particularly in its phenomenology stage where strong motivation and intention are always necessary, in relation also to the green reforming of the present technology. A generalized definition of ＇fluidization＇ is proposed to extend fluidization principle into much wider scientific fields, which would be effective also for wider collaborations.
