Porous sandwich structures are widely used in anti-explosion due to their excellent specific strength and stiffness. However, current explosion research mainly focuses on the failure mechanism of sandwich structures under small equivalent explosion loading. In contrast, the research on energy absorption characteristics of porous sandwich structures under actual large equivalent loading is rarely reported. To better guide the engineering application, ten kinds of sandwich structures with three kinds of sandwich materials (foam aluminum and honeycomb aluminum with 3 mm×10 mm side length) under different sandwich configurations (single-layer and two-layer sandwiches) and different thicknesses of face sheet/middle sheet/rear sheet were designed. The explosion tests with 0.5 kg TNT and 1 kg TNT equivalent explosion loading were respectively carried out on the above sandwich structures, and the overall deformation characteristics of the sandwich structures were analyzed. The effects of sandwich materials, sandwich configurations and other factors on energy absorption were discussed. Results show that both the foam sandwich structure and honeycomb sandwich structure could absorb energy through the large compression deformation of core material under explosion loading, while the deformation uniformity of the honeycomb structures is better. Furthermore, the energy absorption efficiency of the core is both related to its specific compressive strength and strength/stiffness of the face sheet/rear sheet. It is quite necessary to optimize those parameters to ensure that the core material can obtain a maximum compression and give full play to its energy absorption advantage. It is also found that the double-layer sandwich structure is superior to the single-layer sandwich structure on energy absorption and protection performance, which is an effective way to improve the overall energy absorption of the structure.

Husab Uranium Mine is a super-large-scale open-pit uranium mine. Currently, the mine adopts a “one-time design, long-term use” approach to blasting production, leading to issues such as a lack of dynamic adjustment of blasting parameters, high explosive consumption, and unsatisfactory blasting results. To address these issues, a solution can be achieved through dynamic blastability classification management of blasting blocks and feedbackcontrolled blast design. This study utilizes the production history big data of the mine's blasting blocks. It proposes a method to calculate the blasting index K using drilling rate (α), explosive consumption per unit volume (β), and fragmentation index (γ). Here, α represents the drill hole cross-sectional area per unit area, where a higher value indicates more drilling required and higher drilling costs. β represents the amount of explosives required per unit volume of crushed rock, where a higher value implies a more significant amount of explosives required and higher blasting costs. γ represents the distribution of fragment size after ore blasting, where a higher value indicates worse blasting effects, higher transportation costs, and greater difficulty in blasting. Based on the value of the blasting index K, the blastability of historical blasting blocks is classified into different levels. Uniaxial compressive strength (UCS) of the blasting blocks, rock quality designation (RQD) of the ore, and geological strength index (GSI) of the ore deposit are used as blastability indicators, establishing a dataset correlating blastability indicators with blastability levels. The dataset consists of 69 sets of historical data, with 20 sets classified as level one (easily blastable), 24 sets as level two (relatively difficult to blast), and 25 sets as level three (difficult to blast). Subsequently, a deep learning neural network model is constructed, comprising an input layer, five hidden layers, a dropout layer, and an output layer. The model is trained using blastability indicators as inputs and blastability levels as outputs. The traditional SVM model is used for comparison, revealing that the trained deep learning neural network model achieves higher prediction accuracy on the test set than the traditional SVM model. Finally, the reliability and accuracy of the trained deep learning neural network model in predicting the blastability level of blasting blocks are verified through on-site experiments, optimizing the blast design and blasting effects. The research findings indicate that the trained deep learning neural network model, based on a large amount of historical production data from Husab Uranium Mine, can be used for blastability classification of blasting blocks and optimization of blasting effects.

Blasting Engineering is an essential core course for civil engineering and mining majors. To improve the students' understanding on dynamic mechanical response and damage mechanism of rock materials, the experimental teaching contents of explosion and impact dynamics of rock materials were set up in a training plan to achieve the teaching goal of the course of Blasting Engineering. In view of students' lack of theoretical knowledge and experimental basis of impact dynamics in blasting engineering, the split Hopkinson pressure bar (SHPB) experiment technology and two-dimensional plate blasting (TDPB) experiment technology were applied to the practical teaching of Blasting Engineering. Firstly, the experimental system compositions and calculation principles of SHPB and TDPB were introduced. Secondly, the course contents of SHPB impact compression experiment and TDPB central blasting experiment of rock materials were designed. Thirdly, the dynamic mechanical behavior and energy evolution characteristics of sandstone material under the SHPB experiment and the strain wave evolution and dynamic damage and fracture behavior mechanism of sandstone-like material under the TDPB experiment were analyzed. Finally, the students′ in-depth discussion on the critical problems of rock impact dynamics was guided. The innovative combination of SEM testing technology and impact dynamics experimental technology revealed the damage mechanism of rock materials under SHPB and TDPB experiments to students from the micro-level, which gave the students a clear understanding of meso-damage and macro-failure. The effect of teaching practice shows that the student's theoretical and practical ability is exercised by combining the experimental course of SHPB and TDPB with the theoretical course of Blasting Engineering, which leads to the improvement of students' scientific research ability and the sense of teamwork, and the fulfillment of the teaching goals.

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.

This study aims to analyze the damage evolution law of the surrounding rock mass in an ultra-deep shaft under blasting load. To achieve this, a numerical simulation method is adopted based on the blasting construction practice of Xiling Auxiliary Shaft in Sanshandao Gold Mine. The simulation utilizes a restart technology based on ANSYS/LS-DYNA and adopts the equivalent explosion load method according to the blasting design scheme. The surrounding rock mass damage of the ultra-deep shaft is calculated under four different ground stresses (15 MPa, 30 MPa, 45 MPa, and 60 MPa) and four different side pressure coefficients (1.0, 1.25, 1.5, and 2.0). Furthermore, this study analyzes the damage effect on the shaft's surrounding rock mass and investigates how ground stress and side pressure coefficient influence the extent of damage to the surrounding rock. The numerical results demonstrate that as ground stress increases from 15 MPa to 60 MPa, there is a significant inhibition in the damage area with a decrease in radius from 5.75 m to 3.4 m. Additionally, it is observed that with an increase in lateral pressure coefficient, there is anisotropy in terms of blasting damage area distribution where greater ground stress leads to concentrated damage areas.

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.

In response to the poor excavation effect of traditional blasting in complex lithology tunnels, a method called advanced cutting control blasting is proposed based on the research of traditional smooth blasting and pre-splitting blasting. This method involves conducting the blasting around weak surrounding rock areas after tunnel contouring hole blasting. A quasi-three-dimensional model was established, and numerical simulations were conducted using the fluid-structure interaction (ALE) algorithm and ANSYS/LS-DYNA finite element analysis software to compare the advanced cutting control blasting method with traditional pre-splitting and smooth blasting methods. The results show that compared to smooth blasting and pre-splitting, advanced cutting control blasting reduced the depth of damage around the tunnel contour by 6.85% and 10.08%, respectively. Based on simulation results, field blast test plans were designed, and comparative tests between smooth surface blasting and advanced cutting control blasting methods were carried out. The blast results demonstrated that after adopting the advanced cutting control method, the tunnel contour had good shaping effects without block falling or collapse in weak surrounding rock areas, while over-excavation was effectively controlled. Three-dimensional cross-sectional scanning data and statistical results of post-blast sections indicated that compared to well-performing smooth surface blasting, maximum over-excavation decreased by 35.98%, average over-excavation decreased by 25.60%, concrete consumption decreased by 26.3%, and flatness standard deviation increased by 24.29%. This method has been verified through field practice as it reduces over-excavation while mitigating blast damage in complex lithology areas, thereby improving tunnel retaining rock flatness.

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.

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 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.