The shock load of underwater explosion usually includes shock wave load and bubble pulsation load. The structural damage caused by shock wave and bubble load is always a hot topic in ship design. It is generally believed that the impact of shock wave load on the structure is mainly local damage, while the impact of bubble pulsation load on the structure is mainly global damage. The actual damage process of underwater explosion load is often the result of the joint action of the two kinds of loads. However, it is difficult to quantify the contribution of the two kinds of elements to ship damage. In order to study the damage effects of two kinds of loads on ships, a variable section box girder was used to simulate the surface ship structure, and its response process under the impact of underwater explosion was experimentally studied. Both the influence of distance on shock wave and the conditions for utilizing bubble energy were considered in the design of the experiment. The results show that plastic hinge was formed in the box beam structure near water surface under the action of near-field explosion load, and the energy transferred by explosion load to the beam structure was mainly converted into the deformation energy of the plastic hinge. In addition, the dynamic strain response of the structure gradually decreased from the middle to the end of the box beam, and the residual plastic deformation mainly occurred near the middle of the structure. The continuous large opening mode on the upper surface of the box beam resulted in larger plastic deformation of the deck side plate and the upper part than that at the bottom of the hull.

In the teaching of demolition blasting, the structure modeling period and the cost of single experiment are both too excessive, and the experiment cannot be repeated in a short time. In addition, the experiment is transient, irreversible, and dangerous, which is not conducive to close observation and learning. Aiming at the difficult problems of experimental teaching in blasting demolition engineering, a platform of virtual simulation experiment is established for teaching design schemes. Firstly, through the two interactive operation links of “toppling scheme selection” and “cut design”, the learners can master the basis for the selection of toppling scheme and the design method of blasting cut, and understand the design content of blasting cut such as cut shape, orientation window and positioning window. It is easy by the platform for the learners to understand the stress conditions for cut design according to the mechanical principle of chimney toppling. They also should be familiar with the knowledge of tension zone, compression zone and neutral axis, and master the calculation formula of the extreme stress of the cut section and the application of strength conditions. Secondly, the platform system can make the learners participate in the design of powder factor, blast hole parameters and initiation network through “blasting parameter design”, and correctly select the detonators inside and outside hole. Then, through the interactive learning of “safety check” and “arrangement of shock absorption measures”, the learners can master the data collection steps, the safety check methods and measures to control the negative blasting effects. Finally, the learners can experience the on-site blasting operation process by the “blasting site” module, and gradually establish their understanding of the blasting operation process by participating in the design and organizing each construction step. In addition, the experimental system has a knowledge introduction for each module, which is convenient for learners to learn independently. The construction of the virtual simulation experiment platform not only optimizes the teaching methods, but also improves the teaching quality, and enriches the characteristics and innovative ideas of the experiment teaching of engineering blasting.

Electronic detonators are the main initiation method currently used in the field of explosives engineering. However, they cannot be used in classroom or experimental teaching due to their high risk and special control requirements. It is urgent to develop a safe, reliable and reusable simulation device. Based on the STC15 microcontroller technology, a kind of analog electronic detonator for teaching was designed and tested. The simulated electronic detonators can be manufactured by 3D printing technology an they have been successfully applied to detonator detection and detonation network simulation experiments. The analog electronic detonator is mainly composed of power circuits, detonator simulation circuits, and PCB boards. A pair of leads protruding from one end of the detonator are connected to the power supply. Then, the microcontroller control chip, the drive circuit and the acousto-optic simulator are powered by the power supply circuit. After being powered on, the microcontroller control chip can drive the acous-to-optic simulator device according to the written program to simulate the operation of the electronic detonators. Thus, adjustable delay times have been implemented. In addition, the real blasting scene can be simulated, the internal structure can be visually observed, and series parallel stable operation can be realized. Through the experimental teaching, students can understand the structure and characteristics of electronic detonators, master the detonator performance detection method and detonation network connection method. The new analog electronic detonators can fully mobilize students' enthusiasm of learning the “blasting safety” course, give full play to the subjective initiative, and effectively improve their practical ability.

In order to solve the problem of blasting demolition of tall reinforced concrete water towers in restricted space, a vertical in-situ blasting demolition technology was developed. The impact failure mechanism, collapse process and touchdown vibration of the water tower were analyzed comprehensively by means of high-speed photography, vibration monitoring and numerical simulation. It was found that the collapse process of the tower by vertical in-situ blasting demolition is similar to free fall motion with an acceleration of 9.4 m/s² calculated by regression analysis, which was slightly smaller than the gravity acceleration. By using the “separated” finite element model, the collapse process of the water tower could be approximately simulated and the impact time of each section cylinder could be accurately captured. In general, cumulative damage by multiple impacts is the main characteristic of the complex failure process of the water tower, which can be simulated by the No.159 concrete material model. The main frequency band of the vibration is mainly concentrated in the range of 5~60 Hz. The high frequency part of the vibration signal attenuates rapidly, and the energy is mainly concentrated in the low frequency part. Moreover, the total energy of the vibration signal decreases significantly with the increase of distance. The test results show that the successive vertical collapse of the tower and the simultaneous blasting on the top water tank can control not only the collapse range of the tower, but also the touchdown vibration and blasting dusts.

Ground surface settlement caused by explosion-induced liquefaction of saturated sand foundation is an important subject in the seismic safety evaluation and explosion compaction of dam foundation. In this paper, the characteristics of ground surface settlement caused by liquefaction under contained explosions are studied for layered saturated sand foundation with roller compaction. Based on the existing empirical prediction models of explosion-induced liquefaction and surface settlement, the calculation formula of liquefaction volume is derived, and the rapid prediction model of surface settlement area is established and verified for reliability. Based on the above model, the characteristics of the explosion-induced liquefaction zone of saturated sand foundation and the resulted surface settlement funnel are investigated by changing the control factors such as compactness, explosive amount and burial depth, and the influence of stratified ground compaction on the characteristics of the surface settlement funnel is also discussed. The results show that the explosion liquefaction zone of saturated sand foundation has three types from small to large, including ellipsoid type, funnel type and pot bottom type. From small to large, there are two types of surface settlement area: inverted cone type and butterfly type. The liquefaction and settlement zones increase with the increase of explosive amount and the decrease of burial depth and compactness. For the layered saturated sand foundation with rolling compaction, the explosion-induced liquefaction and the resulted surface settlement are not only affected by the amount of explosive, buried depth and density, but also determined by the relative size of delamination thickness compared with the initiation depth, which further affects the range of surface settlement area.

To improve stemming effectiveness for tunnel excavation and blasting, a stemming device was designed utilizing the expansion characteristics of aluminum tubes under explosive action. The expansion-induced circumferential strain of the stemming device colliding with the steel tube was then measured using a dynamic strain gauge. The simulated explosive stemming devices were subjected to uniaxial compression deformation tests using a universal testing machine. The stemming effects were evaluated by recording the blasting process of cement pillars through high-speed photography. Results showed that the peak circumferential strain of the steel tube under the impact of the stemming device reached 0.02, indicating that the expansion impact force of the device on the blast hole wall was substantial which helped the device adhere to the wall. The compressive strength of the stemming device after adhesion to the blast hole wall was between 4.1 MPa and 5.5 MPa and its shear strength ranged from 0.49 MPa to 0.66 MPa, far greater than the conventional stemming material's shear strength of 0.09 MPa. In practical use, the stemming device together with the stemming material could effectively prevent its movement. When the traditional stemming material was used for stemming cement pillars, punching phenomenon appeared while no damage was observed after blasting. However, when the stemming device was used instead, there was no punching, and the stemming device only shattered after creating cracks at the collar of the blast hole, resulting in the cement pillar being split into three parts. Therefore, the stemming device significantly improved the stemming effects, and helped increase rock-breaking efficacy of the explosive gas while also enhancing the throwing effect, which is of great significance in improving blasting effects for cut holes.

No matter violent & terrorist incidents or explosion accidents, parameters related to the explosion source, such as explosive equivalent, are always important for the post-explosion accident investigation. The characteristic trace of the medium under explosion load is an important basis for tracing the cause of an explosion accident and obtaining the corresponding explosion source parameters. After reviewing the typical research progress of explosive characteristic traces, including explosion crater, damage of surrounding buildings, and personnel damage degree, it is found that there are significant differences in the shape and size among the explosion craters created by near surface explosions, exposed surface explosions and explosions with certain depth. This research is based on an underground explosion accident in a gold mine in 2021, which was caused by that the dropped welding slag from the shaft ignited the underground combustible materials and explosive equipment. According to the sizes of three explosion craters formed at the accident site, the TNT equivalents are calculated as 654.17 kg, 232.49 kg and 193.83 kg, respectively. Then, the particle vibration velocity and the shock wave overpressure of the shaft wall are calculated as 40 cm/s and 2129 Pa, according to the TNT equivalents. The calculation results are consistent with the damage degree of the cage and shaft wall.

Quartz sandstone samples were tested under cyclic impact loadings by the drop weight impact test equipment to study its mechanical properties and failure process under medium strain rates. Three specimens were selected at each impact height of 0.3~0.6 m, and each specimen was subjected to 8 cycles of impact with medium strain rates of 26.33 s^-1, 29.7 s^-1, 32.03 s^-1 and 35.17 s^-1, respectively. Then, the influence of cyclic loading times on the dynamic compressive strength, elastic modulus and energy efficiency of quartz sandstone were discussed. The results show that under different medium strain rates, the dynamic compressive strength of the specimens under the impact loading of the 8th cycle is about 13 MPa, which is lower than that of the first cycle. During the process, the resistance to deformation is weakened, and the elastic modulus is significantly reduced. The dynamic compressive strength of the specimens has a positively correlation with the elastic modulus. From the perspective of energy, the dissipated energy, energy efficiency and unit volume dissipated energy of the specimen are improved after 8 cycles of impact loading. The effect is most obvious when the impact energy is 70.27 J, the dissipated energy of rock is increased by 6 J, the energy efficiency is increased by 8.8%, and the unit volume dissipated energy is increased by 50%. For fracture fractal, the fracture morphology of rock under medium strain rates includes splitting failure, edge collapse failure, block failure and crushing failure. When the strain rate increases from 26.33 s^-1 to 35.17 s^-1, the characteristic value of the average particle size of the sample fragments decreases from 24.49 mm to 21.15 mm. The fractal dimension increases from 1.07 to 1.75 linearly.

Based on the actual production in jilangde open pit coal mine, the application of air interval charging blasting technology was clarified, defining two test significance: one is “reducing cost and increasing efficiency”, the other is “controlling blasting fragmentation”. Three groups of orthogonal tests are used to evaluate the application effect of air interval blasting technology. The photo photography method is used to identify the fragmentation distribution after blasting. Firstly, the matlab program is optimized with reference to relevant literature to process the fragmentation image into fragmentation distribution data. Secondly, the data is imported into Origin software to generate fragmentation distribution curve to evaluate the blasting effect. The test results show that the fragment size distribution of 17.3% interval blasting is close to continuous charging blasting. Conclusions 1: The air interval height has no positive correlation with the final effect., There is a reasonable interval height which is in line with the purpose of reducing cost and increasing efficiency of enterprises. The fragmentation grading evaluation method is used to analyze the uniformity of blasting effects of different charges. Firstly, the fragmentation distribution data is imported into Origin software to fit the blasting fragmentation grading curve. Secondly, five fragmentation evaluation indexes are summarized with reference to relevant literature. The analysis results are the uniformity of blasting block: continuous charge > interval 17.3% > interval 11.5% Conclusion 2: The charging amount can be reduced through the control of central air interval charging technology, so that the blasting effect is close to the traditional continuous charging, which can achieve the purpose of controlling blasting fragmentation.

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.