Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blas...Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blast method,as the short propagation distance amplifies blasting vibrations.A case of blasting damage is reported in this paper,where concrete cracks crossed construction joints in the twin-arch lining.To identify the causes of these cracks and develop effective vibration mitigation measures,field monitoring and numerical analysis were conducted.Specifically,a restart method was used to simulate the second peak particle velocity(PPV)of MS3 delays occurring 50 ms after the MS1 delays.The study found that the dynamic tensile stress in the tunnel induced by the blast wave has a linear relationship with the of the product of the concrete wave impedance and the PPV.A blast vibration velocity exceeding 23.3 cm/s resulted in tensile stress in the lining surpassing the ultimate tensile strength of C30 concrete,leading to tensile cracking on the blast-facing arch of the constructed tunnel.To control excessive vi-bration velocity,a mitigation trench was implemented to reduce blast wave impact.The trench,approximately 15 m in length,50 cm in width,and 450 cm in height,effectively lowered vibration ve-locities,achieving an average reduction rate of 52%according to numerical analysis.A key innovation of this study is the on-site implementation and validation of the trench's effectiveness in mitigating vi-brations.A feasible trench construction configuration was proposed to overcome the limitations of a single trench in fully controlling vibrations.To further enhance protection,zoned blasting and an auxiliary rock pillar,80 cm in width,were incorporated to reinforce the mid-wall.This study introduces novel strategies for vibration protection in tunnel blasting,offering innovative solutions to address blasting-induced vibrations and effectively minimize their impact,thereby enhancing safety and struc-tural stability.展开更多
To solve the uneven burden of same-type holes reducing the blasting efficiency due to the limitation of drilling equipment,we need a double-face program-controlled planning method for hole position parameters used on ...To solve the uneven burden of same-type holes reducing the blasting efficiency due to the limitation of drilling equipment,we need a double-face program-controlled planning method for hole position parameters used on a computer-controlled drilling jumbo.The cross-section splits into even and uneven areas.It also considers the uneven burden at the hole’s entrance and bottom.In the uneven area,various qualifying factors are made to optimize the hole spacing and maximize the burden uniformity,combined with the features of the area edges and gridbased segmentation methods.The hole position coordinates and angles in the even area are derived using recursion and iteration algorithms.As a case,this method presents all holes in a 4.8 m wide and 3.6 m high cross-section.Compared with the design produced by the drawing method,our planning in the uneven area improved the standard deviation of the hole burden by 40%.The improved hole layout facilitates the evolution of precise,efficient,and intelligent blasting in underground mines.展开更多
To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based sim...To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.展开更多
This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns ...This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns of blasting stress,characteristics of crack distribution,and rock fracture features in the specimens.First,blasting model experiments were carried out using the dynamic caustics principle to investigate the influence of bottom cushion layers and initiation methods on the integrity of the bottom rock mass.The experimental results indicate that the combined use of bottom cushion layers and inverse initiation effectively protects the integrity of the bottom rock mass.Subsequently,the process of stress wave propagation and dynamic crack propagation in rocks was simulated using the continuum-discontinuum element method(CDEM)and the Landau explosion source model,with varying thicknesses of bottom cushion layers.The numerical simulation results indicate that with increasing cushion thickness,the absorption of energy generated by the explosion becomes more pronounced,resulting in fewer cracks in the bottom rock mass.This illustrates the positive role of the cushion layer in protecting the integrity of the bottom rock mass.展开更多
In this paper,transient electromagnetic method was used to carry out the feasibility study on the detection and recognition of chamber blasting misfire.Firstly,an electromagnetic background field was established in th...In this paper,transient electromagnetic method was used to carry out the feasibility study on the detection and recognition of chamber blasting misfire.Firstly,an electromagnetic background field was established in the test;secondly,a benign conductor was preset in the chamber,and then the background field was eliminated after the electromagnetic field was measured;thirdly,the transient electromagnetic field was measured again after blasting;at last,the chamber blasting misfire was detected and recognized by comparing the change of eddy current field of the preset benign conductor before and after blasting.The test results showed that:When the buried depth of aluminum box target was no more than 30 m,transient electromagnetic method can clearly identify the position of the aluminum box;when the buried depth of aluminum box was more than30 m,the buried depth and position of the aluminum box was not sure due to the unknown level of secondary eddy current field generated by aluminum box.展开更多
This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(S...This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(SDOF)and the experimentally validated Finite Element(FE)methods(LSDYNA).For this purpose,special atten-tion is given to calculating the response of H-shaped steel columns under blast.The damage amount is determined based on the support rotation criterion,which is expressed as a function of their maximum lateral mid-span dis-placement.To account for uncertainties in input parameters and obtain the failure probability,the Monte Carlo simulation(MCS)method is employed,complemented by the Latin Hypercube Sampling(LHS)method to reduce the number of simulations.A parametric analysis is hence performed to examine the effect of several input pa-rameters(including both deterministic and probabilistic parameters)on the probability of column damage as a function of support rotation.First,the MSDOF method confirms its higher accuracy in estimating the probability of column damage due to blast,compared to the conventional SDOF.The collected results also show that un-certainties of several input parameters have significant effects on the column behavior.In particular,geometric parameters(including cross-sectional characteristics,boundary conditions and column length)have major effect on the corresponding column response,in the same way of input blast load parameters and material properties.展开更多
For toe-shooting method, geomaterial constitutive models concerned are studied. Analysis shows that, although extensively applied in soil mechanics, due to its angular singularity of yielding surface, the Mohr-Coulomb...For toe-shooting method, geomaterial constitutive models concerned are studied. Analysis shows that, although extensively applied in soil mechanics, due to its angular singularity of yielding surface, the Mohr-Coulomb model is not suitable for numerical simulations in large deformation; in this case the rock-fills may be regarded as the Drucker-Prager model and the seaooze as the Prandtl-Reuss model. By comparing experimental data with numerical results, the constitutive model of the seaooze is numerically verified. It shows that, in high strain rate stage forming the blasting crater, the seaooze behaves as ideal non-compressible fluid, while in low strain rate stage during which the reck-fills flow to the blasting crater, the viscosity of the seaooze is negligible.展开更多
In this paper,dynamic caustic method is applied to analyze the blast-induced crack propagation and distribution of the dynamic stress field around an empty circular hole in polymethyl methacrylate(PMMA)material under ...In this paper,dynamic caustic method is applied to analyze the blast-induced crack propagation and distribution of the dynamic stress field around an empty circular hole in polymethyl methacrylate(PMMA)material under delayed ignition blasting loads.The following experimental results are obtained.(1)In directional-fracture-controlled blasting,the dynamic stress intensity factors(DSIFs)and the propagation paths of the blast-induced cracks are obviously influenced by the delayed ignition.(2) The circular hole situated between the two boreholes poses a strong guiding effect on the coelesence of the cracks,causing them to propagate towards each other when cracks are reaching the circular hole area.(3)Blast-induced cracks are not initiated preferentially because of the superimposed effect from the explosive stress waves on the cracking area.(4) By using the scanning electron microscopy(SEM)method,it is verified that the roughness of crack surfaces changes along the crack propagation paths.展开更多
With the application of electronic detonators, millisecond blasting is regarded as a signifi cant promising approach to improve the rock fragmentation in deep rock blasting. Thus, it is necessary to investigate the fr...With the application of electronic detonators, millisecond blasting is regarded as a signifi cant promising approach to improve the rock fragmentation in deep rock blasting. Thus, it is necessary to investigate the fracturing mechanisms of short-delay blasting. In this work, a rectangle model with two circle boreholes is modeled as a particles assembly based on the discrete element method to simulate the shock wave interactions induced by millisecond blasting. The rectangle model has a size of 12 × 6 m (L × W) and two blast holes have the same diameter of 12 cm. The shock waves are simplifi ed as time-varying forces applied at the particles of walls of the two boreholes. Among a series of numerical tests in this study, the spacing between two adjacent boreholes and delay time of millisecond blasting are considered as two primary variables, and the decoupling charge with a coeffi cient of 1.5 is taken into account in each case. The results show that stress superposition is not a key factor for improving rock fragmentation (tensile stress interactions rather than compressive stress superposition could aff ect the generation of cracks), whereas collision actions from isolated particles or particles with weakened constraints play a crucial role in creating the fracture network. The delay time has an infl uence on causing cracks in rock blasting, however, whether it works heavily depends on the distance between the two holes.展开更多
Three-dimensional rock fracture induced by blasting is a highly complex problem and has received considerable attention in geotechnical engineering.The material point method is firstly applied to treat this challengin...Three-dimensional rock fracture induced by blasting is a highly complex problem and has received considerable attention in geotechnical engineering.The material point method is firstly applied to treat this challenging task.Some inherent weaknesses can be overcome by coupling the generalized interpolation material point(GIMP)and the convected particle domain interpolation technique(CPDI).For the media in the borehole,unchanged GIMP-type particles are used to guarantee a homogenous blast pressure.CPDITetrahedron type particles are employed to avoid the fake numerical fracture near the borehole for the rock material.A blasting experiment using three-dimensional single-borehole rock was simulated to examine the applicability of the coupled model under realistic loading and boundary conditions.A good agreement was achieved between the simulation and experimental results.Moreover,the mechanism of three-dimensional rock fracture was analyzed.It was concluded that rock particle size and material parameters play an important role in rock damage.The reflected tensile waves cause severe damage in the lower part of the model.Rayleigh waves occur on the top face of the rock model to induce a hoop failure band.展开更多
The threshold control of safety blasting vibration velocity is a significant process for the underground mining of complicated ore deposit under construction,road,and water.According to the equivalent principle of dis...The threshold control of safety blasting vibration velocity is a significant process for the underground mining of complicated ore deposit under construction,road,and water.According to the equivalent principle of displacement and velocity of mass point,differential evolution is put forward based on 3DEC dynamic analysis,making the calculation more efficient and accurate.The 3DEC model of the complicated orebody under railway is established according to the topographic maps and geological data of the eastern Pyrite Mine.The stimulus-response distribution of internal stress and displacement fields are demonstrated by analyzing the on-site monitoring vibration displacement and velocity data of the mass point.The reliability of parameter selection,such as blasting simulation waveforms,rock damping,is identified.The safety vibration velocity of railway is set to 4.5 cm/s in line with the requirement of safety blasting rules.Thus,the maximum amount of single-stage explosive in this region is 44.978 kg.The simulation result is in good agreement with the on-site monitoring datum.No displacement and settlement of the 701 railway special line was achieved by choosing the critical amount of the single-stage explosive.展开更多
The applications of numerical simulation in demolition blasting were reviewed.Several methods of numerical simulation in demolition blasting were introduced.The strength and weakness of the numerical methods mentioned...The applications of numerical simulation in demolition blasting were reviewed.Several methods of numerical simulation in demolition blasting were introduced.The strength and weakness of the numerical methods mentioned in this paper were also indicated,respectively.Furthermore,the solid lattice model in the frame of discrete element method(DEM),which was developed by the author and his team,was detailedly described.The existed problems in the current numerical simulation methods of demolition blasting were presented and the future trend of the numerical simulation is finally prospected.展开更多
This study designs four types of liquid-filled cylindrical shell structures to investigate their protection characteristics against explosive shock waves and high-speed fragments.Bare charge and charge-driven prefabri...This study designs four types of liquid-filled cylindrical shell structures to investigate their protection characteristics against explosive shock waves and high-speed fragments.Bare charge and charge-driven prefabricated fragments are employed to examine the damage under blast shock waves and combined blast and fragments loading on various liquid-filled cylindrical shell structures.The test results are compared to numerical calculations and theoretical analysis for the structure's deformation,the liquid medium's movement,and the pressure waves'propagation characteristics under different liquid-filling methods.The results showed that the filling method influences the blast protection and the struc-ture's energy absorption performance.The external filling method reduces the structural deformation,and the internal filling method increases the damage effect.The gapped internal filling method improves the structure's energy absorption efficiency.The pressure wave loading on the liquid-filled cylindrical shell structure differs depending on filling methods.Explosive shock waves and high-speed fragments show a damage enhancement effect on the liquid-filled cylindrical shell structure,depending on the thickness of the internal liquid container layer.The specific impulse on the inner surface of the cylindrical shell positively correlates to the radial deformation of the cylindrical shell structure,and the external liquid layer limits the radial structural deformation.展开更多
The protective bulkhead of the large surface warship need to be designed working in the membrane mode. In this paper, a formula is derived for calculating the plastic deformation of the protective bulkhead subjected t...The protective bulkhead of the large surface warship need to be designed working in the membrane mode. In this paper, a formula is derived for calculating the plastic deformation of the protective bulkhead subjected to blast loading by the energy method, and the ultimate capability of the protective bulkhead can be calculated. The design demand of the protective bulkhead is discussed. The calculation is compared with external experiments, which indicates that the formula is of great application value.展开更多
To create a new prediction model, the unbiased GM （1,1） model is optimized by the five-point slide method in this paper. Then, based on the occurrence areas of dce blast in Enshi District during 1995 -2004, the new ...To create a new prediction model, the unbiased GM （1,1） model is optimized by the five-point slide method in this paper. Then, based on the occurrence areas of dce blast in Enshi District during 1995 -2004, the new model and unbiased GM （1, 1 ） model are applied to predict the occurrence areas of rice blast during 2005 -2010. Predicting outcomes show that the prediction accuracy of five-point unbiased sliding optimized GM （1, 1 ） model is higher than the unbiased GM （1,1） model. Finally, combined with the prediction results, the author provides some suggestion for Enshi District in the prevention and control of rice blast in 2010.展开更多
基金supported by the Shenzhen Stability Support Plan(Grant No.20231122095154003)National Natural Science Foundation of China(Grant Nos.51978671 and 52378425)Guizhou Provincial Department of Transportation Science and Technology Program(Grant No.2023-122-003)。
文摘Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blast method,as the short propagation distance amplifies blasting vibrations.A case of blasting damage is reported in this paper,where concrete cracks crossed construction joints in the twin-arch lining.To identify the causes of these cracks and develop effective vibration mitigation measures,field monitoring and numerical analysis were conducted.Specifically,a restart method was used to simulate the second peak particle velocity(PPV)of MS3 delays occurring 50 ms after the MS1 delays.The study found that the dynamic tensile stress in the tunnel induced by the blast wave has a linear relationship with the of the product of the concrete wave impedance and the PPV.A blast vibration velocity exceeding 23.3 cm/s resulted in tensile stress in the lining surpassing the ultimate tensile strength of C30 concrete,leading to tensile cracking on the blast-facing arch of the constructed tunnel.To control excessive vi-bration velocity,a mitigation trench was implemented to reduce blast wave impact.The trench,approximately 15 m in length,50 cm in width,and 450 cm in height,effectively lowered vibration ve-locities,achieving an average reduction rate of 52%according to numerical analysis.A key innovation of this study is the on-site implementation and validation of the trench's effectiveness in mitigating vi-brations.A feasible trench construction configuration was proposed to overcome the limitations of a single trench in fully controlling vibrations.To further enhance protection,zoned blasting and an auxiliary rock pillar,80 cm in width,were incorporated to reinforce the mid-wall.This study introduces novel strategies for vibration protection in tunnel blasting,offering innovative solutions to address blasting-induced vibrations and effectively minimize their impact,thereby enhancing safety and struc-tural stability.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.FRF-AT-19-005)the National Natural Science Foundation of China(No.51934001).
文摘To solve the uneven burden of same-type holes reducing the blasting efficiency due to the limitation of drilling equipment,we need a double-face program-controlled planning method for hole position parameters used on a computer-controlled drilling jumbo.The cross-section splits into even and uneven areas.It also considers the uneven burden at the hole’s entrance and bottom.In the uneven area,various qualifying factors are made to optimize the hole spacing and maximize the burden uniformity,combined with the features of the area edges and gridbased segmentation methods.The hole position coordinates and angles in the even area are derived using recursion and iteration algorithms.As a case,this method presents all holes in a 4.8 m wide and 3.6 m high cross-section.Compared with the design produced by the drawing method,our planning in the uneven area improved the standard deviation of the hole burden by 40%.The improved hole layout facilitates the evolution of precise,efficient,and intelligent blasting in underground mines.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52271317 and 52071149)the Fundamental Research Funds for the Central Universities(HUST:2019kfy XJJS007)。
文摘To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.
基金financially supported by the National Natural Science Foundation of China(Nos.52204085 and 52104074)the Youth Science and Technology Foundation Key Laboratory for Mechanics in Fluid Solid Coupling System,Institute of Mechanics(No.E0XM040401)。
文摘This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns of blasting stress,characteristics of crack distribution,and rock fracture features in the specimens.First,blasting model experiments were carried out using the dynamic caustics principle to investigate the influence of bottom cushion layers and initiation methods on the integrity of the bottom rock mass.The experimental results indicate that the combined use of bottom cushion layers and inverse initiation effectively protects the integrity of the bottom rock mass.Subsequently,the process of stress wave propagation and dynamic crack propagation in rocks was simulated using the continuum-discontinuum element method(CDEM)and the Landau explosion source model,with varying thicknesses of bottom cushion layers.The numerical simulation results indicate that with increasing cushion thickness,the absorption of energy generated by the explosion becomes more pronounced,resulting in fewer cracks in the bottom rock mass.This illustrates the positive role of the cushion layer in protecting the integrity of the bottom rock mass.
文摘In this paper,transient electromagnetic method was used to carry out the feasibility study on the detection and recognition of chamber blasting misfire.Firstly,an electromagnetic background field was established in the test;secondly,a benign conductor was preset in the chamber,and then the background field was eliminated after the electromagnetic field was measured;thirdly,the transient electromagnetic field was measured again after blasting;at last,the chamber blasting misfire was detected and recognized by comparing the change of eddy current field of the preset benign conductor before and after blasting.The test results showed that:When the buried depth of aluminum box target was no more than 30 m,transient electromagnetic method can clearly identify the position of the aluminum box;when the buried depth of aluminum box was more than30 m,the buried depth and position of the aluminum box was not sure due to the unknown level of secondary eddy current field generated by aluminum box.
文摘This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(SDOF)and the experimentally validated Finite Element(FE)methods(LSDYNA).For this purpose,special atten-tion is given to calculating the response of H-shaped steel columns under blast.The damage amount is determined based on the support rotation criterion,which is expressed as a function of their maximum lateral mid-span dis-placement.To account for uncertainties in input parameters and obtain the failure probability,the Monte Carlo simulation(MCS)method is employed,complemented by the Latin Hypercube Sampling(LHS)method to reduce the number of simulations.A parametric analysis is hence performed to examine the effect of several input pa-rameters(including both deterministic and probabilistic parameters)on the probability of column damage as a function of support rotation.First,the MSDOF method confirms its higher accuracy in estimating the probability of column damage due to blast,compared to the conventional SDOF.The collected results also show that un-certainties of several input parameters have significant effects on the column behavior.In particular,geometric parameters(including cross-sectional characteristics,boundary conditions and column length)have major effect on the corresponding column response,in the same way of input blast load parameters and material properties.
基金Sponsored by the National Natural Science Foundation of China (10072070)
文摘For toe-shooting method, geomaterial constitutive models concerned are studied. Analysis shows that, although extensively applied in soil mechanics, due to its angular singularity of yielding surface, the Mohr-Coulomb model is not suitable for numerical simulations in large deformation; in this case the rock-fills may be regarded as the Drucker-Prager model and the seaooze as the Prandtl-Reuss model. By comparing experimental data with numerical results, the constitutive model of the seaooze is numerically verified. It shows that, in high strain rate stage forming the blasting crater, the seaooze behaves as ideal non-compressible fluid, while in low strain rate stage during which the reck-fills flow to the blasting crater, the viscosity of the seaooze is negligible.
基金Supported by the Opening Fund of the State Key Laboratory of Explosion Science and Technology of Beijing Institute of Technology(KFJJ17-01M)
文摘In this paper,dynamic caustic method is applied to analyze the blast-induced crack propagation and distribution of the dynamic stress field around an empty circular hole in polymethyl methacrylate(PMMA)material under delayed ignition blasting loads.The following experimental results are obtained.(1)In directional-fracture-controlled blasting,the dynamic stress intensity factors(DSIFs)and the propagation paths of the blast-induced cracks are obviously influenced by the delayed ignition.(2) The circular hole situated between the two boreholes poses a strong guiding effect on the coelesence of the cracks,causing them to propagate towards each other when cracks are reaching the circular hole area.(3)Blast-induced cracks are not initiated preferentially because of the superimposed effect from the explosive stress waves on the cracking area.(4) By using the scanning electron microscopy(SEM)method,it is verified that the roughness of crack surfaces changes along the crack propagation paths.
基金National Science Foundation for Young Scientists of China under Grant No.51709176National Natural Science Foundation of China under Grant No.51979170+2 种基金Key Project of Hebei Natural Science Foundation under Grant No.F2019210243Hebei Province Science Foundation for Young Scientists under Grant No.E2018210046Open Project of State Key Laboratory of Advanced Electromagnetic Engineering and Technology under Grant No.AEET 2019KF005
文摘With the application of electronic detonators, millisecond blasting is regarded as a signifi cant promising approach to improve the rock fragmentation in deep rock blasting. Thus, it is necessary to investigate the fracturing mechanisms of short-delay blasting. In this work, a rectangle model with two circle boreholes is modeled as a particles assembly based on the discrete element method to simulate the shock wave interactions induced by millisecond blasting. The rectangle model has a size of 12 × 6 m (L × W) and two blast holes have the same diameter of 12 cm. The shock waves are simplifi ed as time-varying forces applied at the particles of walls of the two boreholes. Among a series of numerical tests in this study, the spacing between two adjacent boreholes and delay time of millisecond blasting are considered as two primary variables, and the decoupling charge with a coeffi cient of 1.5 is taken into account in each case. The results show that stress superposition is not a key factor for improving rock fragmentation (tensile stress interactions rather than compressive stress superposition could aff ect the generation of cracks), whereas collision actions from isolated particles or particles with weakened constraints play a crucial role in creating the fracture network. The delay time has an infl uence on causing cracks in rock blasting, however, whether it works heavily depends on the distance between the two holes.
基金This research was funded by the Natural Science Foundation of Sichuan,China(No.2022NSFSC1915)the National Natural Science Foundation of China(No.U19A2098)+1 种基金State Key Laboratory of Precision Blasting and Hubei Key Laboratory of Blasting Engineering,Jianghan University(No.PBSKL2022B06)the Fundamental Research Funds for the Central Universities。
文摘Three-dimensional rock fracture induced by blasting is a highly complex problem and has received considerable attention in geotechnical engineering.The material point method is firstly applied to treat this challenging task.Some inherent weaknesses can be overcome by coupling the generalized interpolation material point(GIMP)and the convected particle domain interpolation technique(CPDI).For the media in the borehole,unchanged GIMP-type particles are used to guarantee a homogenous blast pressure.CPDITetrahedron type particles are employed to avoid the fake numerical fracture near the borehole for the rock material.A blasting experiment using three-dimensional single-borehole rock was simulated to examine the applicability of the coupled model under realistic loading and boundary conditions.A good agreement was achieved between the simulation and experimental results.Moreover,the mechanism of three-dimensional rock fracture was analyzed.It was concluded that rock particle size and material parameters play an important role in rock damage.The reflected tensile waves cause severe damage in the lower part of the model.Rayleigh waves occur on the top face of the rock model to induce a hoop failure band.
基金Fund for New Teacher of the Doctoral Program of Higher Education(No. 200805611092)the Fundamental Research Funds for the Central Universities(No.2009zm0064)the Key Program of the National Natural Science Foundation of China(No.50934002) for its financial support
文摘The threshold control of safety blasting vibration velocity is a significant process for the underground mining of complicated ore deposit under construction,road,and water.According to the equivalent principle of displacement and velocity of mass point,differential evolution is put forward based on 3DEC dynamic analysis,making the calculation more efficient and accurate.The 3DEC model of the complicated orebody under railway is established according to the topographic maps and geological data of the eastern Pyrite Mine.The stimulus-response distribution of internal stress and displacement fields are demonstrated by analyzing the on-site monitoring vibration displacement and velocity data of the mass point.The reliability of parameter selection,such as blasting simulation waveforms,rock damping,is identified.The safety vibration velocity of railway is set to 4.5 cm/s in line with the requirement of safety blasting rules.Thus,the maximum amount of single-stage explosive in this region is 44.978 kg.The simulation result is in good agreement with the on-site monitoring datum.No displacement and settlement of the 701 railway special line was achieved by choosing the critical amount of the single-stage explosive.
文摘The applications of numerical simulation in demolition blasting were reviewed.Several methods of numerical simulation in demolition blasting were introduced.The strength and weakness of the numerical methods mentioned in this paper were also indicated,respectively.Furthermore,the solid lattice model in the frame of discrete element method(DEM),which was developed by the author and his team,was detailedly described.The existed problems in the current numerical simulation methods of demolition blasting were presented and the future trend of the numerical simulation is finally prospected.
基金the National Natural Science Foundation of China(Grant Nos.52371342,52271338,52101378 and 51979277)。
文摘This study designs four types of liquid-filled cylindrical shell structures to investigate their protection characteristics against explosive shock waves and high-speed fragments.Bare charge and charge-driven prefabricated fragments are employed to examine the damage under blast shock waves and combined blast and fragments loading on various liquid-filled cylindrical shell structures.The test results are compared to numerical calculations and theoretical analysis for the structure's deformation,the liquid medium's movement,and the pressure waves'propagation characteristics under different liquid-filling methods.The results showed that the filling method influences the blast protection and the struc-ture's energy absorption performance.The external filling method reduces the structural deformation,and the internal filling method increases the damage effect.The gapped internal filling method improves the structure's energy absorption efficiency.The pressure wave loading on the liquid-filled cylindrical shell structure differs depending on filling methods.Explosive shock waves and high-speed fragments show a damage enhancement effect on the liquid-filled cylindrical shell structure,depending on the thickness of the internal liquid container layer.The specific impulse on the inner surface of the cylindrical shell positively correlates to the radial deformation of the cylindrical shell structure,and the external liquid layer limits the radial structural deformation.
文摘The protective bulkhead of the large surface warship need to be designed working in the membrane mode. In this paper, a formula is derived for calculating the plastic deformation of the protective bulkhead subjected to blast loading by the energy method, and the ultimate capability of the protective bulkhead can be calculated. The design demand of the protective bulkhead is discussed. The calculation is compared with external experiments, which indicates that the formula is of great application value.
基金Supported by Science Research Project of Department of Education of Hubei Province (B20092901)~~
文摘To create a new prediction model, the unbiased GM （1,1） model is optimized by the five-point slide method in this paper. Then, based on the occurrence areas of dce blast in Enshi District during 1995 -2004, the new model and unbiased GM （1, 1 ） model are applied to predict the occurrence areas of rice blast during 2005 -2010. Predicting outcomes show that the prediction accuracy of five-point unbiased sliding optimized GM （1, 1 ） model is higher than the unbiased GM （1,1） model. Finally, combined with the prediction results, the author provides some suggestion for Enshi District in the prevention and control of rice blast in 2010.
