In order to comprehensively evaluate the effect of deep hole bench blasting in Weijiamao Coal Mine, considering the three objectives of blasting quality, safety and economy, eight parameters such as block rate, root rate, back crack distance, loose coefficient, unit consumption, long-meter blasting amount, vibration speed and flying distance were selected as evaluation indexes. Through UAV, high-speed photography, vibration monitoring and other technical means, the field monitoring of four production blasting flat plates in Weijiamao Coal Mine was carried out. In the meantime, the data analysis was carried out by Split-desktop, Motion studio and other software, and the quantitative indexes of the above parameters were obtained. The subjective and objective weights of evaluation indexes are obtained by using analytic hierarchy process and CRITIC method respectively, and then the combined weights of each index are determined based on the principle of maximum sum of squares of deviations. The grey clustering method is optimized by using the center point triangle whitening weight function, and the grey clustering evaluation model of blasting effect is established. The deep hole bench blasting effect of Weijiamao Coal Mine is comprehensively evaluated, and the order of blasting effect of four flat plates is obtained according to the comprehensive clustering coefficient. Finally, the main problems of the flat plate with the worst blasting effect are analyzed by comparing the index data. The results show that the combined weight of explosive unit consumption, bulk rate and base rate is greater than 0.15, which has a great influence on the blasting effect. The order of blasting effect of four flat plates is that 1080 flat plate>1064 flat plate>1096 flat plate > 1112 flat plate. The 1112 flat plate needs to be combined with geological conditions to optimize the bench blasting parameters for the problems of large back crack distance, high unit consumption, small blasting amount per meter and large flying distance.

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 impact of blasting vibration on surrounding buildings has been widely concerned. Based on the deep hole bench blasting project of Changtan Open-pit Coal Mine, the characteristics of the adjacent 11-story frame-shear structure office building are comprehensively analyzed. After several blasting vibration tests, the distribution characteristics of vibration velocity and main frequency in different directions were analyzed. The significance of elevation difference on vibration velocity in various directions was obtained through single-factor analysis. Finally, based on the dimensional analysis method, a vibration velocity prediction model under the influence of multiple factors was studied, proposed, and applied to the blasting safety charge design. The main conclusions are as follows: with the increase of floors, the primary vibration direction changes from horizontal radial(X) to horizontal tangential(Y), and finally to vertical(Z). In most working conditions, the PPV_x and PPV_y are not more than 0.17 cm/s and 0.213 cm/s, respectively, and the elevation has little influence. The PPV_z is concentrated in 0.05~0.41 cm/s, and the elevation amplification effect is significant in 7~11 layers. The maximum charge per delay, total charge amount, and horizontal distance are substantial for the three-axis PPV_s. The elevation difference is not significant for the PPV_x but significant for the PPV_y and PPV_z. The main vibration frequency is concentrated in 3~12 Hz, and some reach 16~30 Hz. Based on the vibration prediction model for the office building, combined with the blasting safety regulations and the blasting parameters under the most dangerous working conditions, the total charge of the bottom blasting should be within 10 267 kg, and the total charge of the deep hole bench blasting should be between 8268~8883 kg.

In order to address the problem of predicting blasting vibration in complex geological conditions at open-pit mines, an improved BP neural network prediction model based on Mahalanobis distance discrimination(MD) and principal component analysis(PCA), namely MD-PCA-BP model, is proposed. By combining the monitoring data of blasting vibration at Changtan open-pit mine in Inner Mongolia, outliers in the monitoring data are eliminated using the Mahalanobis distance discrimination method. Then, the principal component analysis method is employed to reduce the dimensionality of factors affecting blasting vibration and obtain three principal component factors. The scores of each principal component factor are calculated, and finally a nonlinear relationship between blasting vibration and principal component scores is constructed through BP neural network to establish the prediction model based on MD-PCA-BP. The results show that the fitting degree between predicted values and measured values of blasting vibration velocity prediction model established based on MD-PCA-BP reaches 0.94, indicating high prediction accuracy of this model. When compared with Sadovsky empirical formula, two improved elevation empirical formulas, MD-BP model, PCA-BP model, and BP model, most of the prediction errors of MD-PCA-BP model are within 10%, demonstrating higher reliability and accuracy compared to empirical formulas and unimproved BP prediction models. The blast vibration prediction model based on MD-PCA-BP exhibits good predictive performance for blast vibration velocity in complex terrains.

In deep hole bench blasting, the classification of rock mass under different geological conditions according to its blastability is the premise for determining and optimizing blasting parameters. It is of great significance to improve blasting efficiency and effect and reduce blasting costs. Combined with the actual blasting excavation of Changtan open-pit coal mine, relevant indexes of rock mass blastability classification were obtained through on-site single-hole blasting crater tests, rock mass acoustic wave tests and laboratory rock mechanical tests. Furthermore, the blastability of stripped rock mass in Changtan open-pit coal mine was classified and evaluated based on the combination weighting(CWM) and cloud model(CM). The results show that the blastability of gray-green coarse sandstone at the 1130 platform is grade Ⅲ(medium). The blastability of yellow-green medium sandstone at the 1115 platform is grade Ⅱ(more difficult to be broken by blasting). The blastability of purple-red sandy mudstone at the 1100 platform is grade Ⅰ(difficult to be broken by blasting). The blastability of purple mudstone at the 1145 platform is grade Ⅲ(medium).

Ground blasting vibration control is one of the key contents in the blasting construction of subway tunnels in complex urban environment, and cut blasting is the key to determine the blasting vibration intensity. Combined with the actual project of the north extension line of WuHan Metro Line 7 (Qianchuan Line), an optimization design was carried out on the basis of the original blasting cut method. The numerical simulation and field vibration test verification methods were used to calculate and compare the blasting vibration effects of single wedge cutting, burn cut with four holes and double wedge cutting. Then, the optimization method of cut blasting was proposed. The results show that single wedge cutting, burn cut and double wedge cutting have similar propagation rules of blast vibrations along the axis of tunnel excavation. The peak vibration velocity along the x direction (horizontal radial) decreases with the increase of the distance from the working face in the range of 0~-5 m. When distance exceeds 5 m, the peak vibration velocity increases first and then decreases. The excavated area of the upper bench of the left pilot tunnel has an amplification effect on the surface vibration velocity, which is referred as a “cavity effect”. The distribution of the x-direction (horizontal radial) peak vibration velocity on the left and right sides of the tunnel is roughly similar, and gradually decreases with the increase of the horizontal absolute distance from the origin along the direction perpendicular to the axis of tunnel excavation. The upper bench of the left pilot tunnel has a free face, which makes the peak vibration velocity along the x direction (horizontal radial) on the left side of the tunnel bigger than that on the right side. Due to the delayed initiation, the peak vibration velocity along the x direction (horizontal radial) by double wedge cut blasting is the minimum. The surface vibration velocity of the excavated area is 1.35~2.02 times than that of the unexcavated area ahead during the tunnel blasting construction, due to the “cavity effect”. Compared with other cutting methods, the “cavity effect” of the double wedge cutting is weaker. The comparative analysis of blasting vibration intensity of the three kinds of cutting modes shows that the order of advantages and disadvantages of the three kinds of cutting modes is: double wedge cutting>single wedge cutting>four straight hole cutting.