To study the relationships between rock mass crack propagation and damage and confining pressure under blast impact loading during straight-hole cut blasting,tests were performed under different confining pressures.Th...To study the relationships between rock mass crack propagation and damage and confining pressure under blast impact loading during straight-hole cut blasting,tests were performed under different confining pressures.Then,the characteristics of rock mass crack development were analyzed,and the pressure resistance values of core samples before and after blasting were compared to study the trends of rock mass damage.Moreover,a three-dimensional numerical simulation model was established by LS-DYNA to analyze the stress wave propagation,cavity shape and crack propagation characteristics under different confining pressures.The propagation of rock blasting cracks is negatively correlated with the confining pressure.The greater the confining pressure,the shorter the crack development time.Additionally,the crack width is reduced from 0.4-1.7 to 0.04-1.4 mm,and the length is shortened from 280 to 120 mm.A comparison of the compressive strength revealed that blasting reduces the compressive strength of the rock mass.The greater the distance from the explosion source,the lower the degree of strength attenuation.An increase in the confining pressure can inhibit strength attenuation.Numerical simulations revealed that under the same confining pressure,the stress first peaks at the bottom of the blast hole.The greater the confining pressure,the longer the stress peak duration,the smaller the cavity volume,and the shorter the crack propagation length and depth.Under a confining pressure of 4 MPa,the longest crack was only 154.5 mm in length and 102 mm in depth.The research results provide a scientific basis for controlling rock damage and optimizing design in the excavation of deep rock roadways by blasting.展开更多
Drilling and blasting methods have been used as a common driving technique for shallow-hole driving and blasting in rock roadways.With the advent of digital electronic detonators and the need for increased production ...Drilling and blasting methods have been used as a common driving technique for shallow-hole driving and blasting in rock roadways.With the advent of digital electronic detonators and the need for increased production efciency,the traditional blasting design is no longer suitable for deep hole blasting.In this paper,a disperse charge cut blasting method was proposed to address the issues of low excavation depth and high block rate in deep hole undercut blasting.First,a blasting model was used to illustrate the mechanism of the deep hole dispersive charge cut blasting process.Then,continuous charge and dispersed charge blasting models were developed using the smooth particle hydrodynamics-fnite element method(SPHFEM).The cutting parameters were determined theoretically,and the cutting efciency was introduced to evaluate the cutting efect.The blasting efects of the two charging models were analyzed utilizing the evolution law of rock damage,the number of rock particles thrown,and the cutting efciency.The results show that using a dispersed charge improves the cutting efciency by about 20%and the rock breakage for the deep hole cut blasting compared to the traditional continuous charge.In addition,important parameters such as cutting hole spacing,cutting hole depth and upper charge proportion also have a signifcant impact on the cutting efect.Finally,the deep hole dispersed charge cut blasting technology is combined with the digital electronic detonator through the feld engineering practice.It provides a reference for the subsequent deep hole cutting blasting and the use of electronic detonators in rock roadways.展开更多
The cavity formation and propagation process of stress wave from parallel hole cut blasting was simulated with ANSYS/LS-DYNA 3D nonlinear dynamic finite element software. The distribution of element plastic strain, no...The cavity formation and propagation process of stress wave from parallel hole cut blasting was simulated with ANSYS/LS-DYNA 3D nonlinear dynamic finite element software. The distribution of element plastic strain, node velocity, node time-acceleration history and the blasting cartridge volume ratio during the process were analyzed. It was found that the detonation of charged holes would cause the interaction of stress wave with the wall of uncharged holes. Initial rock cracking and displacement to neighboring uncharged holes become the main mechanism of cavity formation in early stage.2008 University of Science and Technology Beijing. All rights reserved.展开更多
Pyramid cut blasting is an essential form of inclined hole cut blasting,but the in-situ stress effect of pyramid cut blasting is rarely studied.Based on the research background of pyramid cut blasting in a deep rock m...Pyramid cut blasting is an essential form of inclined hole cut blasting,but the in-situ stress effect of pyramid cut blasting is rarely studied.Based on the research background of pyramid cut blasting in a deep rock mass,the size,volume,and fragment size distribution of the blasting cavity before and after uniaxial compression were analysed by a model test.Otherwise,the damage and effective stress of the pyramid cut blasting were analysed with LS-DYNA numerical simulation.The results show that the damage and fragmentation of pyramid cut blasting are not only affected by blasting stress wave and blasting gas,but also affected by uniaxial compression.Under the influence of uniaxial compression,the blasting stress wave and blasting gas are more likely to damage the rock mass parallel to the uniaxial compression direction near the connecting line of blasting hole,and make the volume of cavity larger and the fragment rate lower.Additionally,uniaxial compression has a prominent influence during the middle and late stages of blasting.展开更多
This research is focused on the calculation of a reasonable detonator delay time for realizing cut blast vibration control.First,the viscoelastic rock mass parameters corresponding to the engineering rock mass quality...This research is focused on the calculation of a reasonable detonator delay time for realizing cut blast vibration control.First,the viscoelastic rock mass parameters corresponding to the engineering rock mass quality classification were determined based on wave theory of Kelvin medium.Then,a calculation model was obtained for the millisecond-delay cut blast vibration in Kelvin media using the Starfield charge superposition principle.Further,the influence of the delay time on the cut blast vibration was quantitatively analyzed and a method for calculating the reasonable cut blasting millisecond delay time is proposed according to the principle of dimensional analysis.Finally,field tests were used to verify the applicability of the method.The results show that 5 ms to 20 ms is a better detonator delay time range and cut blasting vibration can be effectively controlled using the delay time calculated by the calculation model described in this paper.展开更多
This paper analyses the fragmenting principle of static blasting agent (SBA) and the action of its cutting fragmentation. Using SBA for sterming material proved very useful and advantageous. Here we analyse in detail ...This paper analyses the fragmenting principle of static blasting agent (SBA) and the action of its cutting fragmentation. Using SBA for sterming material proved very useful and advantageous. Here we analyse in detail the cutting action of pre- stress and stress wave in pre-stressing force blasting.展开更多
The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters（such a...The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters（such as the hole spacing L and the empty hole diameter D） and damage zones were investigated by numerical simulation. A damage state index γ was introduced and used to characterize the crushing and crack damage zones through a user-defined subroutine. Two indices, i.e., η1 and η2 that can reflect the cutting performance, were also introduced. The simulation results indicate that an optimal value of L can be obtained so that the η1 and η2 can reach their optimal states for the best cutting performance. A larger D results in better cutting performance when the L value maintains its best. In addition, the influences of the loading rate and the in-situ stress on the cutting performance were investigated. It is found that an explosive with a high loading rate is suit for cutting blasting. The propagation direction and the length of the tensile cracks are affected by the direction and the magnitude of the maximum principal stress.展开更多
基金The National Natural Science Foundation of China(No.51874189)the Shandong Provincial Natural Science Foundation(Nos.ZR2023ME106 and ZR2023ME055)the Open Fund Project of the Engineering Research Center of the Ministry of Education for Mining Underground Engineering(No.JYBGCZX2021102).
文摘To study the relationships between rock mass crack propagation and damage and confining pressure under blast impact loading during straight-hole cut blasting,tests were performed under different confining pressures.Then,the characteristics of rock mass crack development were analyzed,and the pressure resistance values of core samples before and after blasting were compared to study the trends of rock mass damage.Moreover,a three-dimensional numerical simulation model was established by LS-DYNA to analyze the stress wave propagation,cavity shape and crack propagation characteristics under different confining pressures.The propagation of rock blasting cracks is negatively correlated with the confining pressure.The greater the confining pressure,the shorter the crack development time.Additionally,the crack width is reduced from 0.4-1.7 to 0.04-1.4 mm,and the length is shortened from 280 to 120 mm.A comparison of the compressive strength revealed that blasting reduces the compressive strength of the rock mass.The greater the distance from the explosion source,the lower the degree of strength attenuation.An increase in the confining pressure can inhibit strength attenuation.Numerical simulations revealed that under the same confining pressure,the stress first peaks at the bottom of the blast hole.The greater the confining pressure,the longer the stress peak duration,the smaller the cavity volume,and the shorter the crack propagation length and depth.Under a confining pressure of 4 MPa,the longest crack was only 154.5 mm in length and 102 mm in depth.The research results provide a scientific basis for controlling rock damage and optimizing design in the excavation of deep rock roadways by blasting.
基金the State Key Development Program for Basic Research of China(2016YFC0600903)the National Natural Science Foundation of China(51934001).
文摘Drilling and blasting methods have been used as a common driving technique for shallow-hole driving and blasting in rock roadways.With the advent of digital electronic detonators and the need for increased production efciency,the traditional blasting design is no longer suitable for deep hole blasting.In this paper,a disperse charge cut blasting method was proposed to address the issues of low excavation depth and high block rate in deep hole undercut blasting.First,a blasting model was used to illustrate the mechanism of the deep hole dispersive charge cut blasting process.Then,continuous charge and dispersed charge blasting models were developed using the smooth particle hydrodynamics-fnite element method(SPHFEM).The cutting parameters were determined theoretically,and the cutting efciency was introduced to evaluate the cutting efect.The blasting efects of the two charging models were analyzed utilizing the evolution law of rock damage,the number of rock particles thrown,and the cutting efciency.The results show that using a dispersed charge improves the cutting efciency by about 20%and the rock breakage for the deep hole cut blasting compared to the traditional continuous charge.In addition,important parameters such as cutting hole spacing,cutting hole depth and upper charge proportion also have a signifcant impact on the cutting efect.Finally,the deep hole dispersed charge cut blasting technology is combined with the digital electronic detonator through the feld engineering practice.It provides a reference for the subsequent deep hole cutting blasting and the use of electronic detonators in rock roadways.
文摘The cavity formation and propagation process of stress wave from parallel hole cut blasting was simulated with ANSYS/LS-DYNA 3D nonlinear dynamic finite element software. The distribution of element plastic strain, node velocity, node time-acceleration history and the blasting cartridge volume ratio during the process were analyzed. It was found that the detonation of charged holes would cause the interaction of stress wave with the wall of uncharged holes. Initial rock cracking and displacement to neighboring uncharged holes become the main mechanism of cavity formation in early stage.2008 University of Science and Technology Beijing. All rights reserved.
基金supported by the National Natural Science Foundation of China(Grant No.51974316)the National Key R&D Program of China(Grant No.2021YFB3401500)the National Key Research and Development Program of China(Grant No.2016YFC0600903)。
文摘Pyramid cut blasting is an essential form of inclined hole cut blasting,but the in-situ stress effect of pyramid cut blasting is rarely studied.Based on the research background of pyramid cut blasting in a deep rock mass,the size,volume,and fragment size distribution of the blasting cavity before and after uniaxial compression were analysed by a model test.Otherwise,the damage and effective stress of the pyramid cut blasting were analysed with LS-DYNA numerical simulation.The results show that the damage and fragmentation of pyramid cut blasting are not only affected by blasting stress wave and blasting gas,but also affected by uniaxial compression.Under the influence of uniaxial compression,the blasting stress wave and blasting gas are more likely to damage the rock mass parallel to the uniaxial compression direction near the connecting line of blasting hole,and make the volume of cavity larger and the fragment rate lower.Additionally,uniaxial compression has a prominent influence during the middle and late stages of blasting.
基金National Natural Science Foundation of China under Grant Nos.51979205 and 51939008。
文摘This research is focused on the calculation of a reasonable detonator delay time for realizing cut blast vibration control.First,the viscoelastic rock mass parameters corresponding to the engineering rock mass quality classification were determined based on wave theory of Kelvin medium.Then,a calculation model was obtained for the millisecond-delay cut blast vibration in Kelvin media using the Starfield charge superposition principle.Further,the influence of the delay time on the cut blast vibration was quantitatively analyzed and a method for calculating the reasonable cut blasting millisecond delay time is proposed according to the principle of dimensional analysis.Finally,field tests were used to verify the applicability of the method.The results show that 5 ms to 20 ms is a better detonator delay time range and cut blasting vibration can be effectively controlled using the delay time calculated by the calculation model described in this paper.
文摘This paper analyses the fragmenting principle of static blasting agent (SBA) and the action of its cutting fragmentation. Using SBA for sterming material proved very useful and advantageous. Here we analyse in detail the cutting action of pre- stress and stress wave in pre-stressing force blasting.
基金Projects(2016YFC0600706,2016YFC0600802) supported by the National Key Research and Development Program of ChinaProject(2017zzts186) supported by Cultivating Excellent Doctors of Central South University,China
文摘The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters（such as the hole spacing L and the empty hole diameter D） and damage zones were investigated by numerical simulation. A damage state index γ was introduced and used to characterize the crushing and crack damage zones through a user-defined subroutine. Two indices, i.e., η1 and η2 that can reflect the cutting performance, were also introduced. The simulation results indicate that an optimal value of L can be obtained so that the η1 and η2 can reach their optimal states for the best cutting performance. A larger D results in better cutting performance when the L value maintains its best. In addition, the influences of the loading rate and the in-situ stress on the cutting performance were investigated. It is found that an explosive with a high loading rate is suit for cutting blasting. The propagation direction and the length of the tensile cracks are affected by the direction and the magnitude of the maximum principal stress.
