The blasting fragment size of a mine is required to be less than 0.4 m. However, this area has a geological structure consisting of both hard and soft layers, which makes the traditional blasting method easy to produce boulders, and the blasting quality difficult to meet the requirements. In order to conquer the problem and save the construction cost, blasting tests on square hole layout with both deep and shallow holes were carried out with the middle shallow hole depths of 0 m, 4 m, 5 m, 6 m and 7 m. Firstly, ANSYS/LS-DYNA finite element software was used to carry out numerical simulations with a limestone model with RHT constitutive relation in the upper part and a marl model with HJC constitutive relation in the lower part, forming a hard-soft interlayer structure. Then, numerical tests were conducted to initially obtain more optimal middle hole depths, and the distribution characteristics of rock mass damage and the distribution law of blast effective stress under different test conditions were analyzed. Since ANSYS/LS-DYNA does not take the effect of detonation gas into account, the middle shallow hole depths of 4 m and 5 m were selected for on-site blast tests in order to obtain more accurate experimental conclusions and not to excessively increase explosive consumption. The research results show that it is effective to reduce the blasting boulder yield by square hole layout combining deep and shallow holes. When the depth of the middle shallow hole is 5m, the curvature coefficient Cc and the boulder yield can be reduced. Before the technology optimization, the average boulder yield was about 64.4%, and the rate of fragments larger than 0.4m have been reduced to about 38.1% after the technology improvement, making the blast fragmentation to a favorable level. So, the scheme of 5 m shallow holes has a better effect of reducing boulder yield than the original blasting scheme and the scheme of 4 m middle shallow hole.

In order to study the reasonable smooth blasting parameters such as smooth blasting range, hole spacing, line charge concentration and charge structure in a fault fracture zone, empirical formula is first used for calculation. Then the blasting effect is compared by field blasts to analyze the influencing factors of smooth blasting in a fault fracture zone, so that to improve the blasting parameters and charging structure. Research results and field applications show that the smooth blasting effect is relatively good when the charge column size is ϕ 60 mm×400 mm with an uncoupled charge structure, the hole spacing is 1.2~1.5 m, the smooth blasting range is 2.5~3.0 m, the linear charge concentration is 1.2~1.4 kg/m, and the air deck length is 0.6~0.8 m. When the charge column size is ϕ 60 mm×600 mm with an uncoupled charge structure, the hole spacing is 1.2~1.5 m, the smooth blasting range is 2.5~3.0 m, the linear charge concentration is 0.7~1.0 kg/m, the stemming length is 1m,, the air deck length under the stemming is 3.0~4.0 m and the normal air deck length is 1.5~2.0 m, the smooth blasting effect is the most ideal with a smooth and stable slope. Moreover, the latter scheme has a better economic return than the former one. The selection of blasting parameters, charge structure and charge column for this smooth blasting technology can provide reference for similar projects.

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 influence of blasting vibration on the stability of permanent slopes in an open-pit mine, this paper takes three pits in the Kamoya-Kazibizi mine as the research object, and compares the effects of blasting vibrations on the stability of the slopes with different rock characteristics. By collating the measured blasting vibration data, the maximum charge per delay and the distances from the measuring points to the center of the blast source, the blast vibration attenuation law and curve are obtained by regression analysis with a power function, which can be used to predict future blasting vibrations. In order to obtain the influence of the distance from the measuring point to the center of the blast source and the maximum charge per delay on the vibration velocity, the distance and charge are taken as the influence factor, and the blasting vibration velocity is taken as the dependent variable. Based on the vibration velocity calculated according to the fitted blasting vibration formula of each pit, nine groups of experimental schemes are designed. Using SPSS software to carry out variance analysis, it is concluded that the distance between the measuring point and the center of the blast source is highly sensitive to the blasting vibration velocity, and has a greater impact on the mine slope vibration. Therefore, for the soft rock slopes of Kazibizi mine and East No.2 mine, 2~3 rows of holes are reserved as a non-blasting area, and mechanical excavation is used to trim the slopes. For the medium hard rock slope of South No.2 mine, pre-split blasting is used to reduce the impact of blasting vibration on the slope stability. The research results have reference and application value for other open-pit copper-cobalt mines in Congo.

Prefabricated piers are widely used in the field of bridge construction and are often affected by accidental explosions or terrorist attacks. In order to study the influence law of the damage factors of prefabricated bridge piers under explosion load, a numerical model of the prefabricated bridge piers under near-field explosion load has been established by ANSYS. Based on the residual bearing capacity of bridge piers, the damage parameter D is proposed as the anti-explosion index. The influence of five damage factors, including the explosive equivalent, the distance from the explosion center, the initial prestress, the number of segments and the setting of shear keys, on the damage degree of bridge piers is analyzed. On this basis, grey correlation analysis method is used to measure the degrees of correlation and contribution among the damage factors. The results show that the comprehensive reduction rates of failure parameter D are 32.1% and 29.6% by increasing the initial prestress and setting shear keys between segments, which can effectively reduce the damage of the piers and have a good correlation with the blast resistance of prefabricated piers. However, increasing the shear key height and segment number to 12% and 7.2% has a small effect on pier damage. The order from largest to smallest of the five factors in the correlation degree on the damage of the fabricated bridge piers under blast loading is: TNT equivalent, blast center distance, initial tensile prestress, shear key setting and segment number. In the anti-explosion design of prefabricated bridge piers, the factors of large correlations such as increasing the initial tensile prestress and setting shear keys can be given priority. The grey correlation analysis method has certain reference value for the analysis of damage factors of prefabricated bridge piers under explosive load.

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.

Nayong Weima stone arch bridge and the new simply supported beam bridge have a 41° diagonal crossing in the horizontal direction, with a total length of 68 m. It passes 28.5 m below the fifth span of the new bridge, and is only 0.8 m away from the #4 column of the new bridge. In order to ensure the successful blasting demolition of the old stone arch bridge, the in-situ buffer collapse control blasting technology is adopted to ensure the safety of the adjacent new bridge. Considering the damage to the surrounding environment caused by the blasting demolition of the stone arch bridge, especially the damage to 4# column and the pier foundation, the horn blasting notches is used based on the structural characteristics of the stone arch bridge and the analysis of blasting and collapse vibrations. At the same time, the blasting notch of the East-West arch foot is moved to the second abdominal arch, and the crushing notch close to #4 column is added. For the initiation network, the sequence of "west to east and south to north" is adopted. Other methods include adjusting the resistance line of the blast hole close to the #4 column and taking different powder factors for different blasting notches, etc. All those measures are taken to make the stone arch bridge tends to collapse to the south with a minimum collapse size and reduce the impact of blasting on the surrounding environment. Furthermore, the reliability and safety of the blasting demolition of the stone arch bridge are ensured by the safety protection measures such as stacking of slag and soft soil to cushion dikes and setting up protective shelving. According to the collapse vibration formula, the vibration velocity of the bridge deck corresponding to the #4 column of the new bridge is calculated to be 3.9~5.2 cm/s, which is close to the maximum vibration velocity of 3.879 cm/s measured by the vibration meter. It is verified that the design idea of the blasting demolition of the stone arch bridge and the selection of the relevant parameters are scientific and reasonable. The blasting demolition has achieved ideal results, which could provide reference for similar blasting demolition projects.

Field tests of blast vibrations were conducted based on the concept of interference between blast-induced seismic waves for the purpose of reducing blasting vibration intensity and controlling blasting vibration hazards. Three different blast schemes were realized by using electronic detonators, and nonel detonators were used for the fourth blast scheme as comparison. Monitoring points were arranged at the locations of 15 m, 30 m, 45 m and 60 m away from the working face. By studying variation law of the blasting vibration velocity, the optimal delay intervals between holes and rows were selected as those of the third scheme based on the characteristics of accurate timing of electronic detonators. In the third scheme, the cut holes were initiated every two holes from top to bottom with an inter-hole delay of 8 ms. The slashing holes were arranged symmetrically along the center of the working face, and initiated hole by hole with an inter-hole delay of 16 ms and inter-row delay of 100 ms. In addition, the roof holes and bottom holes were initiated with a delay interval of 100ms. This scheme was used to obtain a vibration reduction effect by wave destruction interference. The test results show that the blast parameters are the key to reduce the blast vibration intensity. With the same distance to the blast source, the peak particle velocity when electronic detonators are used is much smaller than that when nonel detonators are used. At the same time, the dominant frequency of electronic detonators is higher than that of the nonel detonators. This engineering technology has achieved significant vibration reduction effect in the blasting construction of the flood discharge tunnel of Luoning pumped-storage power station in Henan Province.

The stability calculation is the key to prevent and control the geological disaster of dangerous rock collapse, which is of great practical and prediction significance. However, the quasi-static method cannot depict the influence of factors as the shape and geometric size of the dangerous rock mass, the frequency and initial phase on the actual blasting vibration load. Based on conventional pseudo-static analysis and the slice method, a blasting dynamic stability analysis method considering size effect is established. This calculation program is compiled by using MATLAB. The results indicate that the calculated minimum stability coefficients of dangerous rock mass vary periodically with the initial phase of the blasting seismic waves. For a given calculation with specific parameters, the coefficients are proximate to those calculated by conventional quasi-static analysis. The relative difference of these two calculations is between 5.1% and 8.2%, which indicates the calculation method and program are reasonable and effective. When the number of slices is 1, the calculated results of the program are equivalent to those calculated by traditional quasi-static method. The method proposed in this study provides a reference for dynamic stability analysis and evaluation for dangerous rock mass.

Rock foundation excavation plays an important role in the entire project of hydraulic structures. The key and difficult point of the blasting excavation is how to reduce the damage of the rock mass on the foundation surface under the premise of ensuring the excavation of the structural foundation to the specified elevation. In this paper, ANSYS/LS-DYNA finite element software is used to numerically simulate the blasting damage of the rock mass 40 m underwater. The blasting and excavation simulation of composite energy dissipation structure, flexible cushion and traditional charge structure is carried out in a 24.5 cm×24.5 cm×30 cm rock mass model, respectively. Fluid-structure coupling algorithm is used in the simulation process, and 0.4 MPa water pressure is added to simulate the 40 m water depth environment. The simulation results found that the damage depth of the basement, the energy transfer of the retained bedrock and the damage degree of the retained bedrock can be reduced by 38.89%, 30.52%, and 30.90% respectively by using the composite energy dispassion blasting technology under the same conditions. The results also show that the energy dissipation structure can effectively control the damage form and scope of the rock mass retained on the foundation surface, which can be applied to the protection of foundation surface of underwater rock excavation.