In order to study the influence of faults and internal karst on the propagation law of blasting seismic waves in open-pit mining, the change of seismic waves passing through faults and karst was analyzed. To collect the seismic data after blasting, monitoring points were arranged at the upper and lower walls of a large fault on the south slope and a karst cave at the+1014 m platform of the north slope of the Tangya limestone open pit mine. The Hilbert Huang transform method was used to process the original waveforms, and the changes of blasting seismic waves passing through the fault and the karst cave were analyzed by the time-spectrum energy spectrum, marginal spectrum, and instantaneous energy spectrum. The results showed that the energy attenuation of blasting seismic waves passing through the fault is very obvious. With the same vibration duration, the maximum instantaneous energy decreased from 1.7 10^-5 at the front of the fault to 6.0 10^-6 at the rear of the fault which was reduced to about 1/3 of the previous value. Among them, the energy at the rear of the fault in the frequency band of 60~80 Hz attenuated to 1/2 of that at front the fault. At the same time, the energy proportion of lower frequency band increased while the overall seismic wave energy decreased. The fault objectively hinders the propagation of blasting seismic waves. In addition, the energy change of blasting seismic wave was not obvious with the maximum instantaneous energy changed from 2.3 10^-4 to 1.9 10^-4 when it passed through the karst cave. However, the filtering effect of the high-frequency signal of seismic waves passing through the karst was obvious, and the energy distribution was more concentrated. The peak particle velocity on the rear part of the karst cave was slightly larger with an amplification coefficient of 1.10~2.53. The frequency band of energy generally developed to the low-frequency direction. Therefore, it is suggested to strengthen the support of rock mass above the karst.

In order to determine the degree of impact of blasting vibrations on main haulage roadways and surface buildings near an underground mine, and to control these effects, it is necessary to obtain field test data through industrial experimentation. The Blast-NET blasting monitoring instrument was first used to monitor the radial, tangential, and vertical vibration velocities and frequencies caused by the blasting. According to the Sadovsky formula, the K and α values related to geological conditions were calculated using single-factor regression analysis, and the actual blasting vibration velocity calculation formula was obtained. The reliability of the calculation formula was then verified through continuous vibration monitoring, and optimization experiments were conducted on three different blasting network configurations: row-by-row, segmented, and hole-by-hole. The research results showed that if the protection of surface buildings is considered, the minimum safe distance between the source of the explosion and the protected buildings is 250 meters, 200 meters, and 125 meters respectively for row-by-row, segmented, and hole-by-hole blasting. If the protection of underground haulage roadways is considered, the minimum safe distance between the source of the explosion and the protected roadways is 30 meters, 25 meters, and 25 meters respectively for row-by-row, segmented, and hole-by-hole blasting. Finally, it is concluded that when the predicted vibration velocity meets the requirements of row-by-row or segmented blasting, the mine can use nonel detonators for blasting. If the hole-by-hole blasting network is required, only digital electronic detonators or high-precision nonel detonators can be used.

When the local high voltage discharge occurs in the internal area of a converter transformer oil tank, the transformer oil in the discharge area will be vaporized instantly and explosion pressure wave will be generated. In order to study the propagation characteristics of the pressure wave in the transformer tank and elevated seat area in the above process, a three-dimensional geometric model was established and divided into polyhedral meshes according to the actual experimental situation. For numerical simulation, a fluent software was used. During the calculation, the actual discharge energy curve was loaded in the discharge area through the profile file, and the compressibility of gas and liquid was considered through the gas-liquid two-phase flow model. The results show that when the arc energy is 4.929 MJ and the duration is 58.6 ms, the peak pressures at the monitoring point on the top of the elevated seat, on the left and right top of the oil tank are 1.21 MPa, 4.62 MPa and 3.79 MPa, respectively. The pressure peak in the elevated seat area decreases with the increase of the distance from the fault point. The simulated pressure peak and pressure variation trends obtained by simulation at different monitoring points display a satisfied consistence with the experimental results, which verifies the effectiveness of the simulation calculation model. By establishing and solving the arc fault discharge simulation model in the oil tank through numerical simulation, the detailed pressure variation curve and the pressure wave propagation law in the three-dimensional space can be obtained. It can greatly reduce the loss of manpower and material resources caused by the discharge experiment, and provide an effective theoretical basis for the prevention of arc explosion accident in the transformer oil tank.

It is an important content in the course of "Blasting Engineering" to master the dynamic mechanical response of rock (body) under the action of blasting dynamic load. Since students majoring in civil or mining engineering lack basic theories such as wave mechanics and rock dynamics, the teaching effect is poor when the knowledge of dynamic mechanical properties of rock is explained in class, which will affect the subsequent learning of rock breakage mechanism. Therefore, the Split Hopkinson Pressure Bar (SHPB) experiment of rock materials is applied to the practical teaching of “Blasting Engineering”. By measuring the dynamic compression strength of rock samples and observing the failure forms of specimens, students are guided to understand the dynamic mechanical response of rock materials under different strain rates. The finite element software LS-DYNA is also used to simulate the SHPB experiment, and the process of stress wave propagation and rock failure is reproduced to achieve the demonstration function of dynamic impact. Practice shows that this teaching method enables students to intuitively perceive the stress wave propagation, clearly understand the dynamic failure mechanism of rock, master the relationship between dynamic mechanical properties of rock materials and strain rate, and lay a foundation for further study of blasting engineering theory.

In-situ collapse blasting demolition technology is a new blasting demolition technology which can break through the condition of serious shortage of collapse space for towering chimneys. The difficulty of this technology is to set up efficient operation platforms at multiple locations at hundreds of meters to quickly complete drilling, charging, stemming and networking, thus forming multiple ring blasting cuts. According to the requirements, a variable diameter hanging basket as a construction platform is developed. The overall design idea of the new operation platform is as follows: The core function of the platform is defined based on the analysis of the operation process, and the variable section basket platform with a sliding plate is selected by comprehensively considering various factors such as efficiency, reliability, adaptability and cost. A parametric model is established to determine the optimal values of the length and included angle of the fixed section and the sliding plate of the hanging basket for different chimney dimensions, which is according to the adaptability of the platform to the overall dimension of the chimney. The technical schemes of the telescopic structure are compared and selected, and finally the steel wire rope traction scheme together with the resistance reduction scheme by tetrafluoroethylene plate is selected. On the basis of the above technical scheme, the structural scheme, safety guarantee scheme, adaptive design scheme, installation, disassembly and using scheme of the platform are determined. In order to verify the reliability of the structural design, the stress analysis of the structure under various working conditions is carried out by using the finite element software. Meanwhile, a special test frame is set up, and a series of tests including functional test, load test and reliability test are carried out on the first test prototype to verify the safety and functional reliability of the platform structure. The test results show that all the functions of the platform reach the design expectations, and the structural safety and functional reliability meet the requirements. The platform can meet the needs of in-situ collapse of towering chimneys by blasting demolition, and can also be used as a construction platform for the demolition of other high-rise structures with variable cross-sections.

In order to analyze the failure characteristics and strain evolution law of reinforced concrete columns after blasting under different amount of explosives per unit area and section stresses, blasting tests of 12 reinforced concrete columns were carried out by using a self-developed test system with uniaxial inertial dynamic loading model, which is based on the theory of elastic mechanics. When the upper section stress of the reinforced concrete columns was 0 MPa, the corresponding amounts of explosives per unit area were 0.11 kg/m², 0.23 kg/m², 0.27 kg/m², respectively. When the upper section stress was 2 MPa, the corresponding amounts of explosives per unit area were 0.13 kg/m², 0.18 kg/m², 0.23 kg/m², respectively. When the upper section stress was 3 MPa, the corresponding amounts of explosives per unit area were 0.18 kg/m², 0.23 kg/m², 0.32 kg/m², respectively. When the upper cross-sectional stress was 4 MPa, the corresponding amounts of explosives per unit area were 0.13 kg/m², 0.18 kg/m², 0.23 kg/m², respectively. In addition, numerical simulation software was used to analyze the impact of different section stresses on blasting effect. The longitudinal central axis crushing distance is defined to describe the crushing range of the column after blasting, and the central axis crushing distance and strain evolution law are analyzed under different influencing factors through theoretical deduction, field experiment and numerical simulation. The analysis results show that with the increase of section stress, the greater the coupling tangential stress close to the central axis, and the coupling tangential tensile stress which is perpendicular to the loading direction is relatively reduced. When the amount of explosive per unit area is less than 0.15 kg/m², the crushing range of the central axis of the column decreases with the increase of the section stress. When the amount of explosive per unit area is more than 0.15 kg/m², with the increase of section stress, the crushing range continues to increase. The peak of tangential tensile strain shows an upward trend, and the absolute value of the peak radial compressive strain gradually decreases. When the section stress is fixed, the crushing range of the column increases with the increase of the amount of explosive per unit area, but the growth rate decreases with the increase of the amount of explosive per unit area. Meanwhile, the peak of the tangential tensile strain of the column increases, and the absolute value of the peak radial compressive strain also shows an upward trend. With the increase of section stress, the crushing range in the column damage cloud is increasing, and the crack tends to extend axially with the load, which further verifies the correctness of the test conclusions.

In view of the problem that mining and crushing of magnetite ore require huge energy consumption, the split Hopkinson pressure bar (SHPB) is used to test and analyze the dynamic mechanical properties and energy dissipation characteristics of magnetite ore during crushing process under different strain rates. Meanwhile, the complete dynamic failure process of the sample is simulated by ANSYS/LS-DYNA software. The results show that the dynamic compressive strength of the magnetite ore samples has a significant strain rate correlation, and increases from 126.77 MPa to 220.62 MPa when the strain rate ranges from 43.94 s^-1 to 147.75 s^-1. Besides, The analysis of energy transfer law shows that the increase trend of reflected energy become more obvious with the increase of incident energy, and the maximum proportion accounts for about 22% of the total incident energy. However, The increase trend of transmission energy become weaker, and the proportion of transmission energy decreases from 78% at low incident energy to 38% at high incident energy. At the same time, the dissipated energy used for specimen crushing increases gradually, which has a linear relationship with the incident energy. The failure mode changes from the splitting failure at low and medium strain rates to crushing failure at a high strain rate. In terms of the crushing scale, most of the fragments at low and medium strain rates are large, while the fragments at high strain rates are small and mostly fine-grained and needle shaped. Numerical simulation results indicate that the initial failure is caused by the "cross" shaped reflected tensile waves on the incident end of the specimen. The results of this study can provide a reference for judging the difficulty of dynamic crushing of magnetite ore and improving the efficiency of rock breaking by impact.

In order to study the crushing energy dissipation characteristics of graphite ore rock under impact loads, ϕ 50 mm diameter split Hopkinson pressure bar (SHPB) test device is used to conduct impact compression tests. The crushing energy dissipation law of the graphite ore rock samples is analyzed under different loading rates with five different impact pressures from 0.2 MPa to 0.6 MPa with a 0.1 MPa interval. The test results show that the dynamic compressive strength of the samples have a strong third-order polynomial relationship with the average strain rate under impact loads. The graphite ore rock has dynamic hardening under impact loads, and its dynamic compressive strength increases nonlinearly with the increase of strain rate, which shows an obvious strain rate effect. In addition, there is an obvious logarithmic relationship between the crushing dissipation energy and the incident energy. With the increase of incident energy, the crushing dissipation energy also increases. However, the proportion of the crushing energy gradually decreases from 0.38 to 0.11. The crushing energy dissipation density of the samples has an obvious strain rate effect, and its value increases with the increase of strain rate. Besides, the average particle size of the broken samples is strongly correlated with the energy dissipation density of the samples. As the energy dissipation density increases, the crushing degree of the sample becomes more severe. Therefore, the average particle size of the crushing fragments can be used to quantitatively describe the crushing degree of the samples.

Understanding the classification of rock mass blastability is an important basis for determining reasonable blasting parameters and improving engineering efficiency. Combined with the practice of bench blasting in Weijiamao mining area, the protodyakonov coefficient and the tensile strength of rock samples are obtained according to the engineering geological data of the mining area, on the basis of site investigation and sampling. The density and acoustic wave velocity of the rock samples on the exposed step surface are measured and analyzed by wax sealing density tests and acoustic wave tests. According to the four indexes obtained, the rock mass blastability in the mining area is studied based on the principle of weighted cluster analysis. The research shows that there are coarse sandstone, medium sandstone, fine sandstone, sandy conglomerate and argillaceous sandstone in the Wejiamao mining area. The density of the marl sandstone is the highest, which is 2.75 g/cm³. The density of the coarse sandstone is the lowest, 2.01 g/cm³, while the density of the sandy conglomerate, fine sandstone and medium sandstone lies between the marl sandstone and the coarse sandstone. In the acoustic wave test, the longitudinal wave velocity of the rock in the 1064 platform is the highest, which is 2.615 km/s, while that in the 1096 platform is the lowest, which is 2.029 km/s. According to the distribution of the rock samples at the corresponding platform, the blastability of the rock mass in Weijiamao mining area gradually decreases from 1112 platform to 1064 platform. Among them, the 1112 platform is mainly sandy conglomerate with a medium blastability. The 1096 platform is mainly coarse sandstone with an easy blastability. The 1080 platform is medium sandstone with a medium blastability. The 1064 platform is mainly composed of fine sandstone with a difficult blastability.

The safety control standard of buildings subjected to blast vibrations should not ignore the influence of the cyclic blasts. It is suggested that the critical peak vibration velocity which makes each part in elastic deformation stage is taken as the safety control standard and damage law of brick-concrete buildings or structures under frequent blast vibrations based on the cumulative damage theory and numerical simulations. According to the specific material parameters and model conditions, the critical peak vibration velocity of an intact brick-concrete structure is 0.67 cm/s, and tensile damage occurs in the stress concentration parts. It is therefore recommended that for buildings with weak anti-vibration ability, such as brick-concrete structures, the range of the safety control standard under frequent blast vibrations can be determined by multiplying the lower limit value set by the most unfavorable frequency in the current blasting safety regulations for general civil buildings by a reduction factor, which can be 0.45~0.55. When determining the safety control standard of damaged structures under frequent blast vibrations, the actual damage situation of the buildings should be comprehensively considered. The vibration safety control standard is taken as the smaller value between the critical peak vibration velocity which does not lead to crack propagation and the critical peak vibration velocity which ensures that all parts of the structure are in elastic deformation stage.