In order to improve the efficiency of the directional cracking of hard rocks, starting from the mechanism of cracking from hard rocks to breaking rocks, based on the empty hole effect theory, the stress variation law of the empty hole wall under the 200 mm、250 mm、300 mm、400 mm hole spacing and the 20 mm、40 mm、90 mm、120 mm hole radius is studied, and the theoretical calculation and numerical simulation are compared and analyzed to verify. The results show that the existence of empty hole makes the stress concentration near the expansion hole, with the increase of empty hole spacing and the decrease of empty hole radius, the stress concentration of empty hole effect becomes weaker. The maximum tensile stress appears on the connection line of the empty hole and the expansion hole. The maximum pressure stress appears near the empty hole circle 70°. The stress intensity factor of type I rock on the inter-hole connection line corresponds to the law of stress variation. When the hole spacing reaches 400 mm, the stress intensity factor K_I is smaller than the fracture toughness K_IC of rock and the condition for formation of through cracks cannot be reached. According to the research results, set the parameters of the empty hole and in Shenzhen Tiegang-Shiyan reservoir Shiyan North clear water diversion tunnel to carry out the rock breaking test. The test results show that empty holes play a guiding role in the direction of crack propagation, which can cause the main crack to form on the connecting line between the empty hole and the expansion hole and is beneficial to improving the efficiency of the breaking rocks in hard rocks, which can provide reference for similar projects.

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.

Shallow hole blasting is com in roadway or tunnel excavation, which has the disadvantages of more work cycles, less footage per cycle and low excavation speed. Meanwhile, deep-hole blasting which is widely used in mining engineering usually adopts continuous charge structure. This brings problems such as high charge quantity per delay, significant blast-induced harmful effect and high boulder yield. To overcome these problems, it is effective to adopt the in-hole sectional blasting technique. Firstly, key factors such as charging structure, charging materials, decking length, sectional delay and charging method are emphatically introduced based on the patents of in-hole sectional blasting in recent years. Then, taking the open-pit bench blasting of a mine adjacent to a railway as an example, the new two-deck charge blasting technology with rock powder barrier as the decking material was presented and compared with the traditional continuous charge blasting technology. After application of the new technique, the boulder yield was reduced by 54%, preventing secondary blasting. At the same time, the explosive usage was saved by 20%. The blasting vibration at the nearest monitoring point to the railway was reduced by 7.62%, and the flying rocks were all within the allowable range. The new technical scheme can also make the bench surface smoother after loading and transporting, which is more conducive to the subsequent stage of blasting operations.

Smooth blasting is of great significance to roadway stability and safety. The conventional smooth blasting method has some disadvantages when applied to the full-section blasting of a small section roadway in hard rock. Due to the selection of unreasonable charge quantity of the contour hole, hole spacing and decoupling coefficient, the phenomenon of backbreak or underbreak occurs after blasting. This approach can also lead to increased support work, decreased efficiency, and problems such as sidewall collapse and roof caving. To achieve a one-time full-section smooth blasting of the tunnel and reduce damage to the surrounding rock, an optimized smooth blasting method was developed. Six large-diameter empty holes with a diameter of 70 mm were designed at the periphery of the tunnel using the stress concentration effect of empty holes. The distance between the contour holes was reduced from 544~600 mm to 400 mm and evenly distributed around the tunnel contour. The contour holes were charged with the air decking structure and spaced at intervals of 0.4 m. The optimized smooth blasting method was applied in a test of a hard rock tunnel in the middle roadway of Heilangou Gold Mine at a depth of 500 m. Results show that compared with the traditional smooth blasting method, the optimized smooth blasting is more remarkable in technical, economic and safety aspects. The average footage increased by 0.03 m, the average half-hole rate increased by 34%, the explosive consumption decreased by 0.42 kg/m³, and the blasting operation cost decreased by 7.82 yuan/m³. The tunnel walls were smooth, and the roof stability was better, effectively reducing the disturbance to the surrounding rock, providing valuable experience for deep hard rock mining.

At present, there are some problems such as inadequate implementation of safety management measures and heavy burden of supervision departments in the special storage for civil explosives in commercial blasting operation units. Thus, the damage and economic burden to the blasting operation unit caused by explosion accidents of civil explosives storage are analyzed and illustrated by case studies. Combined with the new requirements of “fundamentally eliminate hidden dangers of accidents” in the “14th Five-Year Plan for the Safety Development of the Civil Explosives Industry” for the civil explosives industry, it is considered feasible to cancel the commercial blasting operation units owning or renting civil explosive storages that have passed the safety evaluation, from the perspective of the intrinsic safety of the civil explosive industry. Therefore, it is suggested that the Ministry of Public Security to modify or cancel the requirement of the item of 6.2.2.1 "a) (having or renting a civil explosive storage that has passed the safety evaluation) when revising the standard of the Qualification and management requirements for unit of blasting operation (GA990—2012). This measure can improve the safety production management system of the civil explosive industry, reduce the burden of the safety supervision department and the economic burden of the commercial blasting operation units, which is more conducive to the improvement of the intrinsic safety level of the civil explosive industry.

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.

There was a special working face with an ultra-high bench and a large resistance at the 410 platform of a mine in Qingyuan city, which required one-time blasting. This working face had a bench height of 30m, a length of 80 m, and a face angle of 45°~80°. Due to the large bench height, small face angle, and the different face angles of the upper and lower parts, it was difficult to conduct the blasting construction. Before blasting design, the RTK measuring instrument and total station were used to measure the topography of the detailed working face, and then calculate the slope angle of each position of the face according to the topographic map. According to the rock properties, the construction experience and the drilling rig type, the powder factor and blast hole diameter were determined. Based on the above results, the toe burden, drilling angle, depth and spacing of the first row of blast holes were then deigned. Similarly, the burden, drilling angle, depth, spacing of the following rows of holes were also determined. After the hole parameters were determined, the charging structure was designed according to the burden of each row of holes, the rock volume of each hole, powder factor, and the principle of uniform blasting action. Finally, the initiation network was designed by the software of 3Dmine based on the direction of rock movement and the earthquake-proof requirements of the protected objects. During the construction process, the key links such as hole layout, hole depth measurement, drilling, charging, and network connection were strictly controlled, and positive results were obtained after blasting.

Since continuous charge structure is adopted in the bench blasting of Heigou open-pit mining area, the boulder yield is high and the secondary crushing workload is large, which seriously affects the operation efficiency of the mine's subsequent production and loading shovel loading process. In order to optimize the open-pit blasting charge structure, the 2DBench module for open-pit mining in the blasting simulation software JKSimBlast is used. Taking the length and the position of the commonly used air decking as the research objects and the boulder yield as the evaluation index, 25 groups of experiments with two factors and five levels are designed with the hole depth of 17.5 m and the charge length of 10 m. The simulation results show that with the same air deck length, the boulder yield decreases first and then increases with the deck position moving down, and thus there is an optimal deck position. With the same deck position, the boulder yield decreases first and then increases with the increase of the air deck length. Furthermore, the optimal air deck length is determined as 2 m and the optimal deck position is 11.5 m from the orifice. Finally, field industrial tests with the optimized structure are carried out in 5 different blasting areas. The blasting muck pile photos before and after optimization in area 3 is selected as the reference group. By comparison, the results show that the optimized charge structure reduces the boulder yield by an average of 9.24% and effectively improves the blasting effect, which provides a useful reference for the selection and optimization of the charge structure in open pit mines.

While excavating the rock mass by drilling and blasting method, it is bound to cause a certain degree of damage to the surrounding rock. Therefore, it has an important guiding role for the tunnel support design and longterm stability to make clear the damage characteristics of the surrounding rock during tunnel blasting excavation. Taking the blasting excavation of the Longnan Tunnel of the Ganzhou-Shenzhen High-speed Railway under Class Ⅲ surrounding rock as an example, the cross-hole ultrasonic detection method was used to detect the acoustic wave velocity of the surrounding rock in different parts of the same cross-section of the tunnel, and the distribution characteristics of the acoustic wave reduction rate were analyzed. Based on the analysis, the damage depth of the surrounding rock in different parts of the tunnel was determined, and the relationship between the damage degree and the damage depth of the surrounding rock was revealed. Based on LS-DYNA numerical simulation software, the damage evolution and distribution characteristics of the surrounding rock under 8 cyclic bench blasting under the same working conditions are simulated, which are basically consistent with the damage distribution characteristics evaluated by the acoustic wave test. The analysis results show that the surrounding rock at the foot of the arch at the upper bench has the greatest degree of damage, but with the shallowest damage depth. The maximum depth of damage to the surrounding rock is located at the bottom of the inversion arch. Based on the damage distribution characteristics, and according to the engineering analogy and relevant standards, the length of the initial supporting bolts of the grade Ⅲ surrounding rock of Longnan Tunnel should be 3.5~4 m.

Aiming at the problem of high boulder yield under different thicknesses of frozen soil in high latitude and alpine region, blasting crater tests were carried out at low temperatures in winter in Unugtushan copper-molybdenum mine. According to the test results, the relationship between the charge parameters and the blasting crater parameters is determined by using the Livingston blasting crater theory. Simultaneously, the deformation energy coefficient of the frozen soil layer is calculated, and the blasting crater characteristic curves of different frozen soil thicknesses are analyzed. When the charging amount is 4 kg, the critical depth of the frozen soil is 1.3 m, the optimal depth is 0.84 m, and the deformation energy coefficient is 1.06. When the charging amount is 8kg, the critical depth of the frozen soil is 1.7 m, the optimal depth is 1.2 m, and the deformation energy coefficient is 1.05. When the charging amount is 12kg, the above parameters are 2.2 m, 1.34 m and 0.95, respectively. According to the similarity law, the optimal charging parameters which are suitable for the frozen soil area on the site are derived, the blasting effect under multiple blasting parameters of different frozen soil thicknesses is compared and analyzed. In addition, the blasting effect is optimized by the principle of “sub-regions and stages”. For weak frozen soil, the blasting effect can be improved with shorter stemming length and longer charge length. For strong frozen soil area, auxiliary holes are added around the main blasting holes to reduce the boulder yield. Furthermore, the optimization scheme of blasting parameters which is suitable for the change of frozen soil layer thickness in Alpine region is summarized. As a result, the blasting effect is significantly improved, which greatly reduces the boulder yield after blasting of the frozen soil layer and improves the ore supply rate.