In order to probe the mechanism of the phenomena of seismic electromagnetic radiation (EMR), we have completed field experiment on EMR caused by explosiom of rocks. In the experiments, the data of medium lo...In order to probe the mechanism of the phenomena of seismic electromagnetic radiation (EMR), we have completed field experiment on EMR caused by explosiom of rocks. In the experiments, the data of medium low freguency (<5000 Hz) EMR caused by 26 explosion tests of small dimension rocks have been obtained. This paper shows some representative observational results of the field experiment. The observational results show that, nearly 20 points of the 26 explosive points, the EMR phenomena are recorded at various degrees in the related explosive processes. The EMR intensities decay with the distance from explosive origins and increase with the explosive energy. The EMR records have certain repeatability (under the same condition), complexity( multiple EMR effects caused by one explosion) and regional characteristics such as rock structure and observational direction etc.展开更多
A numerical approach is presented to study the explosion-induced pressure load on an underground rock chamber wall and its resultant damage to the rock chamber.Numerical simulations are carried out by using a modified...A numerical approach is presented to study the explosion-induced pressure load on an underground rock chamber wall and its resultant damage to the rock chamber.Numerical simulations are carried out by using a modified version of the commercial software AUTODYN.Three different criteria,i.e.a peak particle velocity (PPV) criterion,an effective strain (ES) criterion,and a damage criterion,are employed to examine the explosion-induced damaged zones of the underground rock chamber.The results show that the charge chamber geometry,coupling condition and charge configuration affect significantly the dynamic pressure exerted on the rock chamber wall.Thus the chamber is damaged.An inaccurate approximation of pressure boundary ignoring the influences of these factors would result in an erroneous prediction of damaged area and damage intensity of the charge chamber.The PPV criterion yields the largest damaged zone while the ES criterion gives the smallest one.The presented numerical simulation method is superior in consideration of the chamber geometry,loading density,coupling condition and rock quality.The predicted damage intensity of rock mass can be categorized quantitatively by an isotropic damage scalar.Safe separation distance of adjacent chambers for a specific charge weight is also estimated.展开更多
The explosion effects and physical process in rock mass by cylindrical charges are discussed.The maximum explosion cavity radius and the coefficient of effective explosion work are found through mechanical model and n...The explosion effects and physical process in rock mass by cylindrical charges are discussed.The maximum explosion cavity radius and the coefficient of effective explosion work are found through mechanical model and numerical method.The dependance of explosion parameters on time is got.The results show that the maximum explosion cavity radius produced by cylindrical charge of ammonium trinitro-toluene No.2 explosive in limestone and diabase is 1.50 and 1.26 times respectively as much as that of blasthole;and the coefficient of effective explosion work is 0.71 and 0.54 respectively as much as that of the blasthole.展开更多
The application of the non-explosive expansion material (NEEM) is widely used as the controlled fracture method in quarry min- ing, especially in hard rocks. The pressure of NEEM is an important parameter in causing...The application of the non-explosive expansion material (NEEM) is widely used as the controlled fracture method in quarry min- ing, especially in hard rocks. The pressure of NEEM is an important parameter in causing rock fracture. An empirical model based on hole spacing was developed to determine the pressure of NEEM in the rock fracture process. Primarily, the empirical model was developed by the mathematical method, utilizing dimensional analysis. Then, the Phase2 code, which is based on the finite element method, was utilized to predict crack growth in rocks. The results of numerical analysis show slight deviations from the empirical model. Hence, the polynomial re- gression analysis was used to modify the model. Finally, the modified model shows a good agreement with the results gained from numerical modeling.展开更多
The seismic waves induced by underground explosions generate geological hazards affecting deep buried tunnels such as rockbursts and engineering-induced earthquakes. This issue is difficult to study through full-scale...The seismic waves induced by underground explosions generate geological hazards affecting deep buried tunnels such as rockbursts and engineering-induced earthquakes. This issue is difficult to study through full-scale testing due to the expense and unpredictable danger. To solve this problem, the authors developed experimental apparatus and presented a laboratory method to simulate seismic waves induced by underground explosions. In this apparatus, a combined structure of a diffusive-shaped water capsule and a special-shaped oil capsule was designed. This structure can provide an applied confining stress and freely transmit the stress wave generated by external impact. Therefore, the coupled loading of in situ stress and seismic waves induced by underground explosions in the deep rock mass was simulated. The positive pressure time and peak value of the stress wave could be adjusted by changing the pulse-shaper and the initial impact energy. The obtained stress waves in the experiments correspond to that generated by 0.15-120 kt of TNT equivalent explosion at a scaled distance of 89.9-207.44 m/kt.展开更多
Proper selection of the explosive is an important part of blast design.The judicious selection of explosives is governed by economic considerations and site/field conditions.The mine management desires to select an ex...Proper selection of the explosive is an important part of blast design.The judicious selection of explosives is governed by economic considerations and site/field conditions.The mine management desires to select an explosive that will give the lowest cost per unit of rock broken,while assuring that fragmentation,fragment size distribution,muck pile profile,muck pile diggability,displacement of the rock,onset of movement,face movement,burden relief rate,ground vibration and noise remains within control limits.Factors which influence the selection of an explosive include explosive cost,charge diameter,cost of drilling,fragmentation difficulties and fragment size requirement with loose muck pile condition,water conditions,atmospheric temperature,propagating ground,storage considerations,sensitivity considerations,explosive atmospheres and nearness of communities from mine.All these concerns can be handled effectively by using the impedance matching technology where explosive impedance is matched with rock impedance for optimal blast performance with due concern to productivity,economics and environment.This paper discusses a case study in limestone mines where rock impedance was determined by carrying out surface refraction test and a patented algorithm was used to estimate the explosives’properties i.e.VOD(velocity of detonation)and density of explosives required.展开更多
It is important to investigate the dynamic behaviors of deep rocks near explosion cavity to reveal the mechanisms of deformations and fractures. Some improvements are carried out for Grigorian model with focuses on th...It is important to investigate the dynamic behaviors of deep rocks near explosion cavity to reveal the mechanisms of deformations and fractures. Some improvements are carried out for Grigorian model with focuses on the dilation effects and the relaxation effects of deep rocks, and the high pressure equations of states with Mie-Grüneisen form are also established. Numerical calculations of free field parameters for deep underground explosions are carried out based on the user subroutines which are compiled by means of the secondary development functions of LS-DYNA9703 D software. The histories of radial stress, radial velocity and radial displacement of rock particles are obtained, and the calculation results are compared with those of U.S. Hardhat nuclear test. It is indicated that the dynamic responses of free field for deep underground explosions are well simulated based on improved Grigorian model, and the calculation results are in good agreement with the data of U.S. Hardhat nuclear test. The peak values of particle velocities are consistent with those of test, but the waveform widths and the rising times are obviously greater than those without dilation effects. The attenuation rates of particle velocities are greater than the calculation results with classic plastic model, and they are consistent with the results of Hardhat nuclear test. The attenuation behaviors and the rising times of stress waves are well shown by introducing dilation effects and relaxation effects into the calculation model. Therefore, the defects of Grigorian model are avoided. It is also indicated that the initial stress has obvious influences on the waveforms of radial stress and the radial displacements of rock particles.展开更多
Rational rock-explosive matching is of great importance to enhancing explosive energy effective utilization and improving rock fragmentation effect.The traditionally emphasized method of acoustic impedance matching is...Rational rock-explosive matching is of great importance to enhancing explosive energy effective utilization and improving rock fragmentation effect.The traditionally emphasized method of acoustic impedance matching is not rational.Based on blasting breakage mechanism,a new theory of rock-explosive matching in drilling and blasting is proposed.The new approach chooses explosive parameters by reasonable control of the size of crushed zone under the condition of fully fragmentation between adjacent blast holes.This method can directly reflect the blasting fragmentation effect and energy effective utilization,which is easy to implement.Also,a modified model is developed,taken adjacent blast hole blasting loading into account.As a result,explosive parameters of different grades of rock are given in full coupling on-site mixed explosive charge for different project objectives.展开更多
The blasting operation plays a pivotal role in the overall economics of opencast mines.The blasting subsystem affects all the other associated sub-systems,i.e.loading,transport,crushing and milling operations.Fragment...The blasting operation plays a pivotal role in the overall economics of opencast mines.The blasting subsystem affects all the other associated sub-systems,i.e.loading,transport,crushing and milling operations.Fragmentation control through effective blast design and its effect on productivity are the challenging tasks for practicing blasting engineer due to inadequate knowledge of actual explosive energy released in the borehole,varying initiation practice in blast design and its effect on explosive energy release characteristic.This paper describes the result of a systematic study on the impact of blast design parameters on rock fragmentation at three mines in India.The mines use draglines and shoveledumper combination for removal of overburden.Despite its pivotal role in controlling the overall economics of a mining operation,the expected blasting performance is often judged almost exclusively on the basis of poorly defined parameters such as powder factor and is often qualitative which results in very subjective assessment of blasting performance.Such an approach is very poor substitutes for accurate assessment of explosive and blasting performance.Ninety one blasts were conducted with varying blast designs and charging patterns,and their impacts on the rock fragmentation were documented.A high-speed camera was deployed to record the detonation sequences of the blasts.The efficiency of the loading machines was also correlated with the mean fragment size obtained from the fragmentation analyses.展开更多
文摘In order to probe the mechanism of the phenomena of seismic electromagnetic radiation (EMR), we have completed field experiment on EMR caused by explosiom of rocks. In the experiments, the data of medium low freguency (<5000 Hz) EMR caused by 26 explosion tests of small dimension rocks have been obtained. This paper shows some representative observational results of the field experiment. The observational results show that, nearly 20 points of the 26 explosive points, the EMR phenomena are recorded at various degrees in the related explosive processes. The EMR intensities decay with the distance from explosive origins and increase with the explosive energy. The EMR records have certain repeatability (under the same condition), complexity( multiple EMR effects caused by one explosion) and regional characteristics such as rock structure and observational direction etc.
文摘A numerical approach is presented to study the explosion-induced pressure load on an underground rock chamber wall and its resultant damage to the rock chamber.Numerical simulations are carried out by using a modified version of the commercial software AUTODYN.Three different criteria,i.e.a peak particle velocity (PPV) criterion,an effective strain (ES) criterion,and a damage criterion,are employed to examine the explosion-induced damaged zones of the underground rock chamber.The results show that the charge chamber geometry,coupling condition and charge configuration affect significantly the dynamic pressure exerted on the rock chamber wall.Thus the chamber is damaged.An inaccurate approximation of pressure boundary ignoring the influences of these factors would result in an erroneous prediction of damaged area and damage intensity of the charge chamber.The PPV criterion yields the largest damaged zone while the ES criterion gives the smallest one.The presented numerical simulation method is superior in consideration of the chamber geometry,loading density,coupling condition and rock quality.The predicted damage intensity of rock mass can be categorized quantitatively by an isotropic damage scalar.Safe separation distance of adjacent chambers for a specific charge weight is also estimated.
文摘The explosion effects and physical process in rock mass by cylindrical charges are discussed.The maximum explosion cavity radius and the coefficient of effective explosion work are found through mechanical model and numerical method.The dependance of explosion parameters on time is got.The results show that the maximum explosion cavity radius produced by cylindrical charge of ammonium trinitro-toluene No.2 explosive in limestone and diabase is 1.50 and 1.26 times respectively as much as that of blasthole;and the coefficient of effective explosion work is 0.71 and 0.54 respectively as much as that of the blasthole.
文摘The application of the non-explosive expansion material (NEEM) is widely used as the controlled fracture method in quarry min- ing, especially in hard rocks. The pressure of NEEM is an important parameter in causing rock fracture. An empirical model based on hole spacing was developed to determine the pressure of NEEM in the rock fracture process. Primarily, the empirical model was developed by the mathematical method, utilizing dimensional analysis. Then, the Phase2 code, which is based on the finite element method, was utilized to predict crack growth in rocks. The results of numerical analysis show slight deviations from the empirical model. Hence, the polynomial re- gression analysis was used to modify the model. Finally, the modified model shows a good agreement with the results gained from numerical modeling.
基金financial support from the National Natural Science Foundation of China (Grant Nos. 51527810,51679249, 12002171 and 51909120)Postgraduate Research&Practice Innovation Program of Jiangsu Province (Grant No.KYCX20_0312)。
文摘The seismic waves induced by underground explosions generate geological hazards affecting deep buried tunnels such as rockbursts and engineering-induced earthquakes. This issue is difficult to study through full-scale testing due to the expense and unpredictable danger. To solve this problem, the authors developed experimental apparatus and presented a laboratory method to simulate seismic waves induced by underground explosions. In this apparatus, a combined structure of a diffusive-shaped water capsule and a special-shaped oil capsule was designed. This structure can provide an applied confining stress and freely transmit the stress wave generated by external impact. Therefore, the coupled loading of in situ stress and seismic waves induced by underground explosions in the deep rock mass was simulated. The positive pressure time and peak value of the stress wave could be adjusted by changing the pulse-shaper and the initial impact energy. The obtained stress waves in the experiments correspond to that generated by 0.15-120 kt of TNT equivalent explosion at a scaled distance of 89.9-207.44 m/kt.
文摘Proper selection of the explosive is an important part of blast design.The judicious selection of explosives is governed by economic considerations and site/field conditions.The mine management desires to select an explosive that will give the lowest cost per unit of rock broken,while assuring that fragmentation,fragment size distribution,muck pile profile,muck pile diggability,displacement of the rock,onset of movement,face movement,burden relief rate,ground vibration and noise remains within control limits.Factors which influence the selection of an explosive include explosive cost,charge diameter,cost of drilling,fragmentation difficulties and fragment size requirement with loose muck pile condition,water conditions,atmospheric temperature,propagating ground,storage considerations,sensitivity considerations,explosive atmospheres and nearness of communities from mine.All these concerns can be handled effectively by using the impedance matching technology where explosive impedance is matched with rock impedance for optimal blast performance with due concern to productivity,economics and environment.This paper discusses a case study in limestone mines where rock impedance was determined by carrying out surface refraction test and a patented algorithm was used to estimate the explosives’properties i.e.VOD(velocity of detonation)and density of explosives required.
基金Project(51378498)supported by the National Natural Science Foundation of ChinaProject(BK20141066)supported the Natural Science Foundation of Jiangsu Province,China+1 种基金Project(SKLGDUEK1208)supported by State Key Laboratory for Geo Mechanics and Deep Underground Engineering(China University of Mining & Technology),ChinaProject(DPMEIKF201301)supported by State Key Laboratory of Disaster Prevention & Mitigation of Explosion & Impact(PLA University of Science and Technology),China
文摘It is important to investigate the dynamic behaviors of deep rocks near explosion cavity to reveal the mechanisms of deformations and fractures. Some improvements are carried out for Grigorian model with focuses on the dilation effects and the relaxation effects of deep rocks, and the high pressure equations of states with Mie-Grüneisen form are also established. Numerical calculations of free field parameters for deep underground explosions are carried out based on the user subroutines which are compiled by means of the secondary development functions of LS-DYNA9703 D software. The histories of radial stress, radial velocity and radial displacement of rock particles are obtained, and the calculation results are compared with those of U.S. Hardhat nuclear test. It is indicated that the dynamic responses of free field for deep underground explosions are well simulated based on improved Grigorian model, and the calculation results are in good agreement with the data of U.S. Hardhat nuclear test. The peak values of particle velocities are consistent with those of test, but the waveform widths and the rising times are obviously greater than those without dilation effects. The attenuation rates of particle velocities are greater than the calculation results with classic plastic model, and they are consistent with the results of Hardhat nuclear test. The attenuation behaviors and the rising times of stress waves are well shown by introducing dilation effects and relaxation effects into the calculation model. Therefore, the defects of Grigorian model are avoided. It is also indicated that the initial stress has obvious influences on the waveforms of radial stress and the radial displacements of rock particles.
基金Foundation items: National Science Fund for Distinguished Young Scholars, China (No. 51125037) Natio- nal Basic Research Program of China (No. 2011CB013501) National Natural Science Foundation of China (No. 51279135)
文摘Rational rock-explosive matching is of great importance to enhancing explosive energy effective utilization and improving rock fragmentation effect.The traditionally emphasized method of acoustic impedance matching is not rational.Based on blasting breakage mechanism,a new theory of rock-explosive matching in drilling and blasting is proposed.The new approach chooses explosive parameters by reasonable control of the size of crushed zone under the condition of fully fragmentation between adjacent blast holes.This method can directly reflect the blasting fragmentation effect and energy effective utilization,which is easy to implement.Also,a modified model is developed,taken adjacent blast hole blasting loading into account.As a result,explosive parameters of different grades of rock are given in full coupling on-site mixed explosive charge for different project objectives.
基金The financial support from Coal S&T grant of Ministry of Coal,Government of India
文摘The blasting operation plays a pivotal role in the overall economics of opencast mines.The blasting subsystem affects all the other associated sub-systems,i.e.loading,transport,crushing and milling operations.Fragmentation control through effective blast design and its effect on productivity are the challenging tasks for practicing blasting engineer due to inadequate knowledge of actual explosive energy released in the borehole,varying initiation practice in blast design and its effect on explosive energy release characteristic.This paper describes the result of a systematic study on the impact of blast design parameters on rock fragmentation at three mines in India.The mines use draglines and shoveledumper combination for removal of overburden.Despite its pivotal role in controlling the overall economics of a mining operation,the expected blasting performance is often judged almost exclusively on the basis of poorly defined parameters such as powder factor and is often qualitative which results in very subjective assessment of blasting performance.Such an approach is very poor substitutes for accurate assessment of explosive and blasting performance.Ninety one blasts were conducted with varying blast designs and charging patterns,and their impacts on the rock fragmentation were documented.A high-speed camera was deployed to record the detonation sequences of the blasts.The efficiency of the loading machines was also correlated with the mean fragment size obtained from the fragmentation analyses.