The geological structure of the Ying Liang-bao hydroelectric underground power-house is complex due to the development of surrounding rock fissures, messy lithology, and a rock body with "hard, broken, miscellaneous" characteristics. Excavation and molding pose difficulties while pre-splitting blasting has poor effects. To address this issue, we conducted a systematic blasting test combined with pre-splitting for central groove construction on layer III of the power-house. In initial tests, both sides of the wall exhibited significant breakage after blasting and traces of presplitting holes were not clearly visible when linear charge density was nearly 100 g/m lower than standardized calculation values. Acoustic testing data revealed that average longitudinal wave velocity in the rock mass body was 4.03 km/s indicating overall poor integrity. Additionally, segmental wave velocities along axial depths from 0~1.5 m, 1.5~3.9 m and 3.9~7.4 m were found to be 2.59 km/s, 3.58 km/s and 4.70 km/s respectively suggesting segmented integrity differences in depth direction. Based on these findings an average single-hole linear charge density for pre-splitting blasts during excavation was determined to be between 0.123~0.284 kg/m with different densities selected according to varying depths while small charge rolls were evenly spaced for each section. The results obtained through testing and application have been positive ensuring basic formation of wall surfaces while significantly increasing half-porosity levels.

The non-pillar sublevel caving method is extensively employed in underground metal deposits due to its advantages of high mining efficiency, simple structure, and enhanced safety. In order to address the issues associated with the laborious design process and insufficiently intuitive simulation effect of medium-length hole blasting using traditional pillarless sublevel caving methods, this study conducted a simulation and application research on the medium deep hole blasting process based on the Aegis blasting design and analysis software. Firstly, this paper introduces the module composition and functions of the software while summarizing the simulation analysis process. Secondly, two key technologies were investigated: utilizing model boundaries to confine the blasting space and employing staggered states of blasting energy to verify borehole network parameters. Finally, numerical simulations were performed on medium-length hole blasting in a specific underground mine with non-pillar sublevel caving method using this software. The research findings suggest that the explosion energy in a single row of blast holes is concentrated and fills the entire explosion chamber. The design of continuously coupled charging structure and a powder factor of 0.3 kg/t is deemed reasonable in this context. It appears that there exists a tangential state for the blasting cavity walls between adjacent blast holes, indicating that the energy between rows may not be sufficient to completely break the rock mass. The distance between blast holes, which is approximately 2.2 m, seems slightly larger. Multiple routes were analyzed to predict the distribution of blasting fragmentation masses, all showing a high proportion of large blocks, consistent with field engineering practice results. For instance, based on photos taken after one blasting event, it was observed that large blocks accounted for 18.03% of the total pile volume. Simulation results from Aegis software analysis indicate that the large spacing between blast holes may be a primary factor contributing to this high block rate. Furthermore, through conducting 12 blasting tests on six mining routes within an experimental section and verifying these results through simulation analysis, consistent outcomes regarding proportions of block size and mass were obtained. This effectively supports the practical application efficiency of the software on-site. Overall, these findings contribute valuable insights into optimizing blasting techniques in rock excavation projects by considering factors such as explosion energy concentration and hole spacing to achieve desired fragmentation outcomes while minimizing undesirable block formation.

Abstract: This study aims to address the challenge of rapid tunnel excavation without the use of explosive. A new oxygen expansion rock breaking technology suitable for general tunnel excavation such as cutting, expanding, auxiliary and peripheral holes is explored, researched, and summarized. The drilling and blasting parameters optimized for tunnel excavation are also provided in detail. The experimental study section consists of granite with a compressive strength ranging from 90 to 100 MPa, developed cleavage cracks, and average blastability. Through field tests and continuous improvement, an average cycle footage of 2.5 m per two-day cycle is achieved for a tunnel area of approximately 65 m², meeting the requirements for rapid excavation when explosives cannot be used. The research demonstrates that the new gas expansion rock-breaking technology can effectively excavate tunnels in hard rock masses. It offers advantages such as safe operation, high efficiency in rock breaking, no involvement with civil explosives or dangerous chemicals used in explosive production, absence of explosion shock waves and low vibration amplitude. This technology provides a solution to situations where civil explosives are prohibited due to complex environmental conditions or slow progress using mechanical methods.

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.

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.

In deep hole bench blasting in open-pit mines, several issues arise including high consumption of explosives per blast, large bulk and foundation ratio, increased overall cost, inadequate loose blasting pile for shovel loading, and excessive blasting vibrations that affect slope stability. This study focuses on the controlled blasting project of deep-hole benches in Duobaoshan open-pit mine. Theoretical analysis was conducted to establish an analytical formula for the stress field caused by hole-by-hole blasting. The parameters such as hole and row spacings, minimum bottom resistance line, and delay time between holes were determined based on this formula. The LS-DYNA software was utilized to analyze the blasting stress and crushing range under these parameters. Furthermore, six groups of industrial field tests were carried out at Duobaoshan open pit mine using different blasting parameters. These tests aimed to determine the variation patterns of powder factor, fragmentation size, and looseness characteristics among different explosives. The optimized parameters for controlled deep hole bench blasting in Duobaoshan open-pit mine were verified and determined through these experiments. The main research findings are as follows: (1) Under the coupling charge condition of Duobaoshan open-pit blasts and utilizing theoretical derivation and analysis of stress fields from hole-by-hole initiation method, it was found that the influence of stress field distribution is limited to front and rear holes with a delay time between holes set at 17 ms. (2) UAV tilt photography technology along with mobile phone photography can be employed to collect data on detonation piles' characteristics and lumpiness size at blast sites. Analysis based on collected data provides effective insights into looseness levels. (3) For the 178 mm of the hole diameter and 17 ms of the holes' delay time of the deep hole bench blasting in Duobaoshan open-pit mine, the powder factor is 0.60 kg/m³ and the hole row spacing is 7 m×5 m under the conditions that the blast lumpiness is less than 60 cm and the looseness is greater than 1.45 shovel loading.

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 blasting effect of cut holes has a significant impact on the overall quality of blasting in large section tunnels. To address the challenges associated with difficult excavation and low utilization rate of blast holes, this study employs a fluid structure coupling algorithm based on ANSYS/LS-DYNA to compare and analyze the internal effective force and damage range between single wedge cut blasting and compound wedge cut blasting. The research findings confirm that compound wedge cut blasting yields better results compared to single wedge cut blasting, providing an explanation for this improved performance. The results indicate that in single wedge cutting, peak stress occurs at the bottom of the hole, gradually decreasing from the bottom to the stemming section before dropping sharply from the stemming section to the palm surface. In contrast, double wedge cutting exhibits higher peak stress values at the bottom of the first level cutting hole compared to single wedge cutting. The damage area cross-sections are found to be similar for both types of cutting models. However, in single wedge cutting models, rock from the blockage section to the palm face area remains unbroken and disconnected. Conversely, in compound wedge cutting models, there is complete connectivity throughout the entire groove cavity. Based on these numerical simulation results, an improved blasting scheme was implemented for a specific highway tunnel project. On-site experiments were conducted accordingly. Compound wedge cuts proved more effective in addressing issues such as low utilization rate of blast holes in large section tunnels and multiple large blocks after blasting.

Feed and its additive dusts have a high combustion heat, which poses significant risks of dust explosions during production, thereby threatening life and property safety. Currently, premix inhibitors are widely used as explosion suppression measures. However, traditional inhibitors are inedible and cannot be added to feed dust to achieve explosion suppression. Therefore, this study focuses on the dust of DL-methionine (DLM), a primary additive in feed, and investigates the effect of self-synthesized phytic acid-cytosine (PA-CY), an edible biomass-based compound with nutritional value and environmental friendliness, on the flame propagation characteristics of DLM dust explosions. The flame propagation process was recorded through high-speed photography and visualized in a vertical pipe while calculating the flame velocity. Additionally, thermocouples were used to monitor changes in flame temperature. The results indicate that as the mass fraction of PA-CY increases, the luminosity of DLM dust explosion flames consistently decreases, severely disrupting the flame structure. After adding 20% PA-CY, there is a reduction of 50.0%, 52.2%, and 46.7% in peak velocity (from 27.66 m/s to 13.83 m/s), average velocity (from 14.39 m/s to 6.88 m/s), and peak temperature (from 1014℃ to 540℃) respectively. Moreover, when the mass fraction of PA-CY reaches 30%, ignition of the dust cannot occur indicating significant inhibitory effects provided by PA-CY.

In order to investigate the mechanical properties and energy transfer law of jointed deep tuff under one-dimensional dynamic loading, seven kinds of tuff specimens with specified natural joint inclinations were tested by SHPB test device. During the tests, the dynamic process was recorded by high-speed camera in real time. The influence of joint inclination angle on the dynamic response characteristics of deep tuffs was systematically analyzed in terms of dynamic strength, energy dissipation and macroscopic damage. The results show that tuffs has the lowest dynamic strength when the joint inclination is 45°, and the dynamic compressive strength and peak strain show a tendency of decreasing firstly and then increasing in the range of joint inclination angle increasing from 0° to 90°. Besides, the final damage modes of the specimens are controlled by the nodal inclination, and the final damage modes of tuff specimens with different nodal inclinations can be classified into tensile damage, tensile-shear composite damage and shear damage. When the incident energy is roughly the same, the reflection energy ratio and transmission energy ratio of tuff present a decrease-increase trend with the increase of natural joint inclination angle, with the lowest energy ratio at 45°. However, the trend of the dissipation energy ratio is opposite. The energy-time density increased first and then decreased with the increase of joint inclination angle. When the direction of load and joint is within 45°~60°, more energy is absorbed and used for self-crack propagation.