Due to the limitations in construction scope, blasting a medium-section tunnel is challenging as it often results in short circular footage and significant over and under excavation. To reduce costs and increase efficiency, it is essential to focus on long footage excavation and fine control of over and under excavation. In this study, a straight hole cutting blasting scheme was designed for a medium section tunnel project and 40 cycles of blasting excavation field tests were conducted. The results revealed that when designing the long footage blasting parameters for a medium section tunnel based on the blasting design manual, issues such as high block rate and uneven face frequently arise. However, by appropriately increasing the charge of the cut part (the proportion of charge of the cut part increased from 12.8% to 18.1% in our field test), better blasting effects were achieved. Additionally, by reducing the charge amount of peripheral holes and adjusting their distance from each other, smooth blasting effect was effectively ensured. During the field test, adjustments were made to the charge amount of peripheral holes based on preliminary design for blasting parameters. This resulted in good contour forming effects with a half-hole rate exceeding 90%. However, an average overcutting value of 18.6 cm was observed across all 40 excavation sections during the blasting cycle. The main cause for this overcutting was identified as platform irregularities along the contour line. To address this issue, it is necessary not only to reduce external drilling angles but also control platform width alongside reasonable parameter designs for surrounding holes. The straight hole cutting scheme proved compatible with three-arm rock drilling truck construction methods while enabling mechanized long-shot blasting excavations. Nevertheless, precise control over overcutting and undercutting remains challenging along with cost management during blast construction. It is necessary to optimize and improve the operation technology of drilling personnel and the management mode of site construction.

To study the explosion equivalent of DT-3 and its influencing factors caused by fire stimulus during storage, transportation and use, the propagate detonation ability of that was studied by the extremely insensitive to detonating substances (EIDS) gap test. High-speed cameras and a shock wave pressure acquisition system were utilized to obtain information on the deflagration processes and shock wave hazards of DT-3 under external flame effect. Additionally, an infrared thermal imager was employed to determine the highest temperature of the surface fireball. Further calculations were conducted to determine the explosive TNT equivalent of 18 kg and 120 kg DT-3 samples. The experimental results indicate that direct exposure to a strong shockwave does not cause DT-3 propagation detonation. However, different packing strengths can lead to deflagration events under external fire conditions, potentially resulting in an overall detonation reaction. The average TNT equivalents for standard packaged 18 kg and 120 kg DT-3 samples were found to be 0.629 and 0.0293 respectively. Furthermore, there is no positive correlation between the scale effect and shock wave impact. Under fire stimulus conditions, package design strength significantly influences the explosive characteristics of DT-3. To enhance safety measures, it is recommended that package design strength be reduced within acceptable limits for actual usage in order to effectively mitigate the risk of detonation hazard.

Due to the complex terrain and geological conditions in the blasting area, as well as errors in monitoring instruments, reflections of vibration propagation medium, and interference from magnetic fields, a significant amount of noise is often present in the original blasting vibration signals collected. To address this issue, a signal noise reduction smooth model based on complementary ensemble empirical mode decomposition (CEEMD) is proposed. Firstly, the measured blasting vibration signal is decomposed using CEEMD and an algorithm for low-pass filtering is established based on the obtained intrinsic mode function (IMF) component from the decomposition. Additionally, an objective function is constructed to calculate the optimal solution according to similarity and smoothness criteria for filtering algorithms. The resulting filtering algorithm model represents an optimal denoising smooth model for blasting vibration signals. To verify our noise reduction smooth model, a simulation signal is constructed and applied to actual open-pit deep-hole blasting vibration signal research. Finally, the noise reduction effects of empirical mode decomposition (EMD) method, wavelet threshold method, CEEMD-wavelet threshold method, and filter algorithm model BP3 are quantified and compared using two indexes: signal-to-noise ratio and root-mean-square error. It has been confirmed that the proposed noise reduction smooth model effectively reduces noise in open-pit blasting vibration signals. The findings demonstrate that our CEEMD-based noise reduction smooth model for open-pit deep-hole blasting vibrations possesses excellent denoising capabilities while preserving essential characteristic information from the original signals. Furthermore, the denoising effect of the proposed model surpasses that of EMD method, wavelet threshold method, and CEEMD-wavelet threshold method.

The Yinsong Water Diversion Project is a large-scale water diversion project aimed at solving the urban water supply problem in the central region of Jilin Province. The rock plug blasting at the intake is a key control engineering aspect of the project. The rock plug has a trumpet-shaped opening with a top width of 28.4 m, bottom width of 7.0 m, and thickness of 15.76 m. The construction site is located in a cold zone with temperatures ranging from-10℃ to-15℃ during the freezing period, resulting in an ice cover thickness of approximately 0.5 m. There are limited reference cases for implementing rock plug blasting operations under such low-temperature frozen conditions. To address the technical challenges faced, both 1∶1 scale rock plug blasting tests and low-temperature tests on explosive materials were conducted. The results of the 1∶1 scale rock plug blasting test were consistent with the original design, as confirmed through post-blast inspections which showed that the shape and dimensions of the intake met design requirements and achieved expected goals. This verified the feasibility of groove excavation hole layout, charge structure, amount of explosives used, and initiation network as planned in the design. The low-temperature test on explosive materials resolved issues related to phase separation and loss of sensitizing bubbles for ordinary emulsion explosives under low-temperature frozen environments. It also examined reliability by using physically treated solid particles for sensitized high-water-resistant emulsion explosives; experimental measurements met technical requirements. All communication, timing synchronization, and networking functions for high-precision digital electronic detonators operated normally. The high-energy detonation of the explosive charge was effectively controlled by implementing protective measures such as setting end caps and using epoxy resin. The sensitivity to detonation did not show any significant changes. Through a comparison with conventional blasting holes, it was observed that the equipment subjected to low-temperature testing met the design requirements satisfactorily. Based on the results of these two experiments, optimization of the blasting scheme was carried out. During actual operations, issues such as protruding ice formations on the inner walls of boreholes and difficulties in loading explosive charges were successfully resolved. The initiation network employed three main lines encircling the lining connection section, each distinguished by a different color. Electronic detonators were grouped according to their corresponding color-coded main line connections. This circular arrangement of blast initiation lines effectively prevented water leakage at low temperatures, ensuring waterproof integrity within connecting components and facilitating subsequent drilling and charging operations. To alleviate pressure build-up after blasting, relief holes were excavated in the upper ice layer above rock plugs for pressure release purposes. The resulting cross-section after blasting closely matched the design specifications without any noticeable collapse at tunnel entrances or excessive vibration levels at critical monitoring points during blasting operations. This study demonstrates that effective control over blast vibrations and environmental protection can be achieved through well-executed rock plug blasting techniques.

To optimize the initiation delay time of an open-pit mine and enhance blasting efficiency, a three-dimensional bench blasting model is developed using ANSYS/LS-DYNA software. The model consists of 2 blast holes in the front row and 1 blast hole in the back row arranged in a triangular pattern. The bottom initiation was employed, and 5 stress monitoring points were placed within the hole placement area. Simulated tests were conducted to evaluate rock fragmentation under different delay times between rows (42 ms) and between holes (11, 13, 15, 17, 19, 21, and 23 ms), while monitoring their effective stress levels. Additionally, a delayed detonation profile model for the two front row boreholes was established to observe the propagation characteristics of explosion stress waves. The results indicate that when the delay time between rows is set at 42 ms and between holes at 17 ms, it leads to peak values of maximum effective stress at each monitoring point which facilitates overall rock fragmentation. The advantage of time-delay blasting lies in its ability to enhance rock damage by utilizing the pre-blast hole as a foundation, while the front-row hole acts on the post-blast hole through pre-detonation effects, creating a new free surface. Through field testing and demonstration, we analyzed the distribution of rock fragmentation in blasting pile photos using split-desktop software. The findings indicate that with an inter-row delay time of 42 ms and an inter-hole delay time of 17 ms, approximately 77.24% of rocks are below 20 cm in size, while only a negligible proportion (0.31%) exceeds 50 cm. Overall, the crushing effect is satisfactory and meets both production and operational requirements for open-pit mining operations.

In order to investigate the influence mechanism of steel fiber content on the dynamic compression and tensile mechanical properties of concrete, this study conducted dynamic compression and dynamic Brazilian splitting tests on concrete samples with varying impact pressure and steel fiber volume contents (0% C50 element concrete, 2%, 3%, and 4%) using a Hopkinson pressure bar (SHPB) device. Additionally, high-speed photography was employed to reveal the dynamic evolution process of cracks. The test results demonstrate that under the same impact pressure, both the dynamic compressive strength and dynamic splitting tensile strength of steel fiber reinforced concrete samples exhibit a positive correlation with the content of steel fiber. Furthermore, there is also a positive correlation between energy absorption capacity and degree of crushing, indicating that steel fibers effectively inhibit concrete crushing while preventing excessive energy absorption and dissipation in these samples. The upper limit for energy absorption rate in steel fiber reinforced concrete samples ranges from 30% to 36%. Notably, compared to its effect on dynamic compressive strength, steel fibers significantly enhance the dynamic splitting tensile strength of concrete. For applications requiring high-strength or anti-violence characteristics in combination with cost-effectiveness, technical controllability, and test data analysis; incorporating a reasonable range for toughening can be achieved by including 2%~3% steel fiber content into high-strength concrete. Moreover, it is important to note that the action mechanism of steel fibers differs when considering their effects on both dynamic splitting and compression failure in concrete samples. Steel fibers significantly impede crack propagation during dynamic splitting processes; however, separation between the fibers themselves leads to ineffective toughening during dynamic compression."

The simulation test of blade loss in an aero engine plays a crucial role in casing containment design. The main challenge lies in controlling the breaking of rotor blades when they reach their maximum allowable speed. To investigate the optimal separation structure for rotor blades with artificial separation, two types of TC4 titanium alloy plates with Ⅴ-shaped grooves, one with a single hole and another with double holes at the center, were designed using explosive separation method. The selected size for the TC4 titanium alloy plate was 100 mm×80 mm×23 mm. The AUTODYN numerical simulation software's Smoothed Particle Hydrodynamics (SPH) algorithm was employed to conduct simulation calculations. Experimental comparisons were made on the damage and additional kinetic energy caused by five different schemes involving these two structures. Results indicated that scheme Ⅱ and Ⅴ failed to break off successfully, while scheme Ⅲ resulted in significant damage to the template. On the other hand, schemes Ⅰ and Ⅳ demonstrated better ability to separate the template. Under identical charge conditions, it was observed that the displacement of double-hole structured plates after fracture was significantly greater than that of single-hole structured plates with Ⅴ-grooves on both sides. Further analysis revealed that the Ⅴ-shaped slotted structure could reduce plate damage, enhance explosive energy efficiency, and minimize additional kinetic energy exerted on the plate. Moreover, compared to double-hole structures, this slotted structure also reduced peak speed by 20% and escape speed by 40%.

Air overpressure generated from the blasting excavation may affect the safety of surrounding structures. The blasting operation area of the horizontal tunnel of the second phase of Meizhou Pumped storage power station is only 81 m away from the steel accident gate of the upper drainage tunnel of the second phase project, which has been built and put into the operation in the first phase. However, the blasting may affect the operation stable of the accident gate. Therefore, taking the blasting excavation of the horizontal hole above the water diversion of the second phase of Meizhou pumped storage power station as the object, the field monitoring of blasting air overpressure was carried out. The distribution rule of blasting air overpressure and its influence on the safety of the emergency gate in the upper reservoir of Meizhou pumped storage power station were analyzed, which provided support for analyzing the influence of blasting air overpressure on the safety of the emergency gate in the upper reservoir. The blasting air overpressure monitoring data show that the air overpressure level in front of the accident gate about 80 m away from the blasting master surface is distributed at 0.63~3.46 kPa, which is much smaller than the suggested corresponding blasting safety control standard of 100 kPa. The protective facilities before the gate can effectively reduce the air overpressure at the gate position, and the measured air overpressure in the fourth and fifth blasting is reduced by more than 55%. When the single and total charge volume are effectively controlled, the measured air overpressure value is much smaller than the suggested control standard value. Besides, there is no abnormality in the field macro investigation and other detection data, the blasting construction does not affect the safe operation of the accident gate on the reservoir.

The contour forming effect of a hard rock tunnel is of significant importance in enhancing the stability of surrounding rock and reducing support costs. This paper aims to optimize the single-hole charge and charge structure for tunnel contour holes. The theoretical range of charge parameters for blasting contour holes in tunnels is proposed initially. Subsequently, blasting tests were conducted on a hard rock tunnel using single-hole charges of 1200 g, 900 g, 750 g, and 600 g respectively, with all tunnel contours analyzed by a laser scanner. Finally, a fracture mechanics model was employed to simulate the contour blasting of the hard rock tunnel with different single-hole charges. The results indicate that when charging parameters are within a reasonable range, smaller single-hole charges result in fewer cracks between blasting holes and less damage to the surrounding rock. Although decreasing the charging amount from 1200 g to 600 g reduces over-excavation volume from 6.53 m³ to 2.02 m³, it also increases under-excavation volume caused by hole position error from 0.15 m³ to 0.26 m³ along the tunnel contour. Furthermore, compared to the damage mechanics model, the fracture mechanics model proves superior in simulating contour blasting for hard rock tunnels as evidenced by good agreement between calculated results and experimental data regarding half hole numbers on the tunnel's contour.

Although the rock stratum can be blasted into blocks in advance on the ground when the shield machine bores through silt-rock strata, the vibrations generated by blasting in silt-rock strata will threaten the safety of the water supply pipeline near the blast area. Based on the blasting vibrations of field tests and numerical simulations, the physical and mechanical parameters of the materials on sites were verified, and the dynamic response of the water supply pipeline near the blast area was studied. The research results show that the peak particle velocity (PPV) decreases with the increase of the horizontal distance from the explosion source on the pipeline along the axial direction. The PPV also decreases with the increase of the horizontal distance from the explosion source on the ground surface above the pipeline along the axial direction, and there is a relationship between the PPVs of the pipeline and the PPVs of the ground surface above the pipeline. The maximum PPV of the pipeline's inner wall is 3.97 times the minimum PPV, and the PPV is the highest at 90° of the inner wall. Meanwhile, the maximum PPV of the pipeline's outer wall is 1.03 times the minimum PPV, and the PPV is the highest at 150° of the outer wall. Besides, the PPV of each node is different from that of the other, and the PPV on the pipeline's inner wall is more significant than that on the pipeline's outer wall. Although the PPV on the pipeline's inner wall changes significantly, the PPV on the pipeline's outer wall is relatively close. The maximum peak effective stress of the element is 4.06 times the minimum peak effective stress of the element, and the peak effective stress of the element is the highest at 240°~270° of the pipeline's outer wall.