Aiming at the blasting demolition problems of a 180 m reinforced concrete chimney in Wuhan Iron and Steel plant, which contains a herringbone large volume lining and an adjacent gas pipe, the feasibility of the optimization scheme of “digging large arched guide window and raising blasting incision” was demonstrated by the ANSYS/LS-DYNA finite element software. The calculation results show that the collapse and accumulation speed of the inner lining is obviously greater than the closing speed of the blasting incision after it is generated. Meanwhile, the chimney may not be topple over under the influence of the accumulation body by using a general directional dumping scheme. However, the chimney will collapse by raising the height of blasting incision to 5.6 m and digging a large arched guide window which is 6.09 m wide and 8 m high. In addition, to ensure a good effect of blasting demolition, the auxiliary measures of mechanically removing the lining around the blasting incision and covering the surface of the blasting incision and gas pipeline with flexible protective layers composed of safety nets, barbed wires, geogrids and other composite materials were put forward. The actual demolition blasting results show that the chimney collapse process is smooth after the incision detonation, and the numerical simulation results are in good agreement with the actual situation. At the same time, the gap between the chimney root cylinder wall and the ground is filled with the accumulated objects after the collapse, and there is no damage to the adjacent gas pipe. Besides, the excavation of the oversized arched guide window not only realizes the relief of the accumulation materials, but also greatly reduces the workload of charging and protection.

A monitoring method based on the characteristics of weak grating sensors is proposed for long-term monitoring of the uneven settlement and horizontal displacement of segments in shield subway tunnels during the operation period. The cable type weak grating sensor is fixed on the wall of the shield tunnel in a diamond patten after prestretching. By monitoring the deformation of the weak grating sensor, the tunnel deformations corresponding to different tunnel structure modes can be distinguished and calculated to meet the real-time and precision requirements for engineering. According to the similarity ratio principle, a 1∶5 tunnel displacement model is designed and manufactured to simulate the local expansion, settlement and horizontal displacement of the tunnel segments. The grating sensors are also fixed on the wall surface of the tunnel model. Sensitivity tests of the weak grating sensors are first conducted before displacement monitoring. Then, the weak grating monitoring results with different diamond layout angles are compared. The following step is to monitor the vertical settlement and horizontal displacement of the tunnel model, which are compared with the actual displacement values. The results show that the strain of weak grating with the diamond layout is larger than that with a linear layout under the same settlement condition, which means the sensitivity of the diamond layout method to settlement change is better than that of traditional linear layout. Furthermore, 10°~20° is the optimal angle interval of the diamond layout for weak grating, for the monitoring result error is low. Additionally, the inversion equation of weak grating wavelength change and segment displacement is established based on the test data of diamond layout with an angle of 15°.

For the purpose of studyingTo study the influence of hydration rate of static explosives on the mechanical behavior and damage mechanism of coal ore body, numerical simulations of ore body mechanical damage were carried out using a stress-damage coupling model under different hydration rates. The impact of hydration rate on the evolution of stress field and damage zone in the ore body was analyzed, and the mechanism of the effect of drilling arrangement model on hydration rate was revealed. The research results indicate that the development of the damage zone in static blasting can be divided into four stages: compaction stage, micro-damage formation stage, damage zone development stage, and damage zone connection stage. Among them, the stages of damage zone development and connection stages show the most significant stress effects. The stress field and damage zone increaseincreases with the increase in of hydration rate. Specifically, and the influence of hydration rate on the stress field and damage zonesuch kind of influence is relatively small during the initial rapid energy release phase, but becomes significantly different in the later stages. Besides, Tthe borehole arrangement model affects the mechanism of hydration rate. withUnder the single-hole mechanical model, the hydration rate promotes expansion pressure differences, while However, the under the double hole mechanical model, hydration rate promotes stress superimposition forunder the double hole mechanical model. The guided hole arrangement model has the most significant effect, where the initial hydration rate accelerates stress transfer and the later hydration rate promotes stress superimposition, leading to the expansion and connection of the damage zone under the combined effects of time and stress dimensions. In the numerical simulation and field tests scheme of this study, the hydration rate of the static blasting agent was 1.8 MPa/min, the blast orehole diameter was 113 mm, the borehole spacing was 1000 mm, and the reasonable ratio of borehole spacing to diameter (η) was 9. The guided hole arrangement model can effectively fractures the ore body and generatees a large number ofmany damage zones. This research provides a reference basis for improving the fracturing effect and construction arrangement of static blasting technology.

The seismic wave signal acquisition will result in the mixed noise in the measured signal due to the monitoring environment, test system and other factors, and the existence of noise will lead to the distortion of the time-frequency analysis results of the signal Hilbert-Huang Transform. There are two reasons. One is that the empirical mode decomposition (EMD) algorithm will obtain the intrinsic mode function (IMF) component with modal confusion phenomenon when processing the blasting seismic wave signal containing noise; The other reason is that because the Hilbert transform is constrained by the Bedrosian theorem, which will produce negative instantaneous frequencies when dealing with modal confusion components. These lead to huge analytical errors. In order to obtain real blasting vibration properties, HHT should be improved. Complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) can be obtained by adding adaptive noise signal to EMD. Then normalized Hilbert transform is performed on the IMF obtained by CEEMDAN, and an improved normalized Hilbert transform (INHT) is obtained. Through the above two steps, the CEEMDAN-INHT time-frequency analysis algorithm can be established. In order to verify that the algorithm can effectively improve the time-frequency analysis accuracy of the noise-containing blasting seismic wave vibration signal, a comparative study on the time-frequency analysis of the HHT and CEEMDAN-INHT noise-containing simulated vibration signals is carried out. Finally, CEEMDAN-INHT is used in the time-frequency analysis of blasting seismic wave signals in an underground cavern, and it is found that the algorithm can effectively overcome the inherent mode confusion of EMD, and at the same time obtain the time-frequency-energy characteristic parameters reflecting the real blasting vibration attributes. It is of practical significance to carry out resonance analysis of blasting excavation in caverns from the perspective of frequency and energy, and to realize blasting seismic wave hazard control.

The primary support is the main load-bearing structure in the tunnel construction stage, the response rule and safety control of the primary support under dynamic disturbance are of great significance to ensure the safe and rapid construction. Figuring out the dynamic response characteristics and the safety control of the primary support is an important issue for the blasting excavation of a soft rock tunnel with reserved core soil. A three-dimensional finite-element numerical model was established by ANSYS/LSDYNA for the Linchang tunnel blasting excavation, and the reliability of the numerical model was verified by the field vibration monitoring data. The stress distribution characteristics of the primary tunnel support under the simultaneous action of two blast sources was studied combined with the construction characters of the reserved core soil method. The attenuation law of blasting vibration was obtained by using Sadovsky empirical formula. The safety criterion of blasting vibration velocity for the primary tunnel support under the simultaneous blasting excavation of both sides of the lower bench was proposed by taking stress as the control standard. The results show that the maximum vibration velocity appears at the arch foot of the primary support rather than at the tunnel floor or vault, which is different from the full section method and bench blasting method. Meanwhile, the propagation path of the blasting stress wave is dramatically affected at the un-backfilled area of the tunnel invert. The vibration velocity of the primary tunnel support is larger and attenuates faster on the left arch foot versus right arch foot. The maximum tensile stress and shear stress appear on the left arch foot of the tunnel under simultaneous blasting with 7.544 MPa and 2.78 MPa, respectively, which exceed the allowable value of the specification. According to the established linear stress-vibration velocity relationship, a blasting vibration safety criterion of primary tunnel support is proposed based on the ultimate strength. In addition, the safety vibration velocity threshold of the primary support in Linchang tunnel is 10 cm/s.

The explosion of premixed gas in a closed vessel is very complicated. In order to study the effect of ignition position on the explosion characteristics of methane/air premixed gas, the central ignition explosion experiment with 10 vol. % methane concentration in a 1 m³ closed spherical explosive vessel was carried out under an initial pressure of 101 kPa and an initial temperature of 300 K. Besides, the effect of different ignition positions (center ignition, 0.5R ignition, R ignition) on the explosion characteristics of methane/air premix in the vessel was studied by LES turbulence model and Zimont combustion model of the Fluent numerical simulation software. It includes flame structure evolution, explosion temperature, explosion pressure and explosion pressure rise rate. The results show that the flame expands around until the wall and profile of the vessel gradually change from the initial “left thin and right thick” to the “left raised sharp angle” and gradually stretch from the “circular arc” to the “sharp shape” to the left when the flame is ignited at the center, 0.5R and R. And then, there is a temperature gradient in the temperature field at different ignition positions. The heating law is continuously released from the energy of the ignition center, and the temperature continuously accumulates and rises. Furthermore, the variation trend of explosion pressure under different ignition positions is basically the same. The final maximum explosion pressure is stable at about 766 kPa due to the wall insulation. Finally, the rise rate of the maximum explosion pressure in the center ignition is the highest, which is 94.5% and 141.8% higher than that in 0.5R ignition and R ignition, respectively.

In order to solve the problems of large displacement, high boulder yield and low shovel loading efficiency in the front row of Husab mine blasting operations, a series of buffer blasting trials were designed and conducted. The project has successively completed the buffer blasting tests in 5 large blocks, and each section has 360 000 tons to 530 000 tons of ores, 15~21 rows of holes, and 5~40 meters wide buffer materials on the free surface. The muck pile shape, shovel productivity, fragmentation and floor elevation deviation were measured and compared with the non-buffer blasting results in the same period. The test results show that there are forward pounce and uplift phenomenon to the blasting pile under the impact of explosion. Meanwhile, the muck pile surface presents a shape with unequal heights, and the maximum height difference varies from 4.06 m to 5.85 m. The productivity of a hydraulic shovel is 2722 t/h in the buffer blasting blocks, which is 4.69% higher than that in the non-buffer blasting blocks in the same period. Moreover, the results of fragmentation analysis reveal that the buffer blasting is better than non-buffer blasting on the fragmentation performance, and the buffer blasting has the advantage in reducing boulders. Finally, the test results show that the buffer blasting has certain advantages in floor elevation control. It is the first time to promote buffer blasting technology to the blasting of large sections with multiple rows of holes (15 to 21 rows), which is not only in line with the objective needs of large-scale mine production, but also an inevitable trend as large-scale equipment is used.

Aiming at the problems of high boulder yield, high explosive consumption and poor blasting effect in an open-pit mine with complex lithology in Xinjiang, 59 blasting tests for the optimal inter-hole and inter-row delays in rock masses with different blastabilities were carried out on four levels (between 445 m and 595 m) at the east side of the mine. The optimal delays between holes and rows were determined by the shape of blasting pile, ore rock fragmentation and powder factor. The test results show that the blasting pile is flat and the fragmentation is uniform for benches of mudstone with some fine sands when the delays between holes and rows are 5.9 ms/m and 14 ms/m, respectively. For sandstone with part of mudstone lithologic, when the delays between holes and rows are taken as 2.7 ms/m and 14.2 ms/m respectively, the blasting pile shape and fragmentation are reasonable and the boulder yield is low. The test results are applied to the field production of the mine, and the average powder factor and boulder yield are 4.03% and 1.8%, respectively, which are lower than those of previous years. The research shows that reasonable selecting of delay time between holes and rows for complex geological conditions can obtain flat blasting pile and the uniform block size, which can effectively reduce the powder factor, and save costs. The delay time determined in this test can provide important field data for selecting the delay time of mudstone and sandstone mixed bench blasting under the same geological conditions in Zhundong area.

In order to study the development track and hot spot changing trends of blasting technology in openpit mining, 1116 valid journal articles were retrieved as a sample from the China National Knowledge Infrastructure (CNKI) database by selecting “open-pit mining” and “blasting” as the search criteria. According the visual analysis reports from CNKI and utilizing the visual knowledge graph tool CiteSpace, a comprehensive and in-depth study has been conducted on the state of the art, distribution characteristics, research hotspots, and cutting-edge trends in the field of open-pit mining blasting research in China. The research findings indicate that the study of open-pit mining blasting has undergone three distinct stages: the establishment and development of open-pit mining blasting theory (pre—2010), the phase of modern technology application and innovation (2010—2015), and the stage of green, intelligent, and precision development (2015—present). The disciplinary distribution primarily focuses on mining engineering and general industrial technology and equipment. The prominent journals for publication include Blasting, Engineering Blasting, and other journals in the field of mining engineering. The majority of authors and institutions are affiliated with mining-related universities, enterprises and research institutes. The research topics encompass various aspects, including the development and application of blasting design software, optimization of blasting parameters (such as blast hole pattern, powder factor and charge structure), deep-hole blasting, bench blasting, cast blasting, pre-splitting blasting, control and monitoring of blasting vibration, numerical simulation, and application of artificial intelligence algorithms, analysis of factors affecting blasting quality and evaluation of blasting effects. The future of open-pit mining blasting will continue to evolve towards automation, intelligence, precision and environmental friendliness. Through technological innovation and interdisciplinary integration, the industry aims to provide more efficient, safer and sustainable blasting solutions for the mining sector.

Boulder yield is an important index to evaluate the blasting quality in the blasting process of an open pit mine. Since a high boulder yield will not only greatly reduce the mining efficiency, but also increase the cost of secondary rock breaking, so fragments size statistics is an important work in open pit mining. Aiming at the problem that the statistics of fragment size is complex and not accurate enough, a statistical model of boulder yield was built by deep learning based on the takes the image data of blasting piles collected in the Unugetushan copper and molybdenum mine. Firstly, the annotated data set was initially segmented into an initial effect diagram of the mine rock contour based on the U-net image segmentation model. And then, the annotated data for training was optimized and the Resu-net model was improved on the basis of the residual learning module, which resulted in the final segmentation effect map of mine rock contour. Finally, the fragment size information of the blasting pile was obtained through the minimum external rectangle method combined with OpenCV image processing technology. The results show that the segmentation accuracy of U-net+Resu-net fragment size optimization model proposed in this study is 97.84% with an accurate image data segmentation. The statistics of fragment size in an inclined blasting pile is realized by OpenCV technology combined with the camera monocular imaging principle. In addition, the developed interactive interface is simple to operate and can quickly calculate the boulder yield.