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2026,
46(11):
111001.
doi: 10.11883/bzycj-2026-0132
Abstract:
Accurate sound velocity measurement under high pressure requires high-impedance window materials. However, no ideal candidates have been reported to date. In this study, the Hugoniot data and sound velocity of single-crystal lead fluoride (PbF2) in the pressure range from 64 GPa to 198 GPa were investigated by applying shock compression techniques and quantum molecular dynamics simulations. The theoretical simulation results of Hugoniot data and sound velocities are in excellent agreement with the experimental data. Along the Hugoniot curve, the sound velocities of liquid FbF2 increase linear with particle velocity. The signal from a displacement interferometer system for any reflector (DISAR) and simulation results confirm that PbF2 transforms into a liquid metal at 89.6 GPa, which enables efficient laser reflection at the shock front. Using a DISAR, both the shock wave velocity and the catch-up time of rarefaction waves can be accurately measured, providing critical technical support for the precise determination of sound velocity in materials under extremely high pressure. These superior properties, including high impedance, structural stability under high pressure, and pressure-induced metallization, enable PbF2 fully meet the core requirements for high-impedance standard windows.
Accurate sound velocity measurement under high pressure requires high-impedance window materials. However, no ideal candidates have been reported to date. In this study, the Hugoniot data and sound velocity of single-crystal lead fluoride (PbF2) in the pressure range from 64 GPa to 198 GPa were investigated by applying shock compression techniques and quantum molecular dynamics simulations. The theoretical simulation results of Hugoniot data and sound velocities are in excellent agreement with the experimental data. Along the Hugoniot curve, the sound velocities of liquid FbF2 increase linear with particle velocity. The signal from a displacement interferometer system for any reflector (DISAR) and simulation results confirm that PbF2 transforms into a liquid metal at 89.6 GPa, which enables efficient laser reflection at the shock front. Using a DISAR, both the shock wave velocity and the catch-up time of rarefaction waves can be accurately measured, providing critical technical support for the precise determination of sound velocity in materials under extremely high pressure. These superior properties, including high impedance, structural stability under high pressure, and pressure-induced metallization, enable PbF2 fully meet the core requirements for high-impedance standard windows.
2026,
46(11):
111501.
doi: 10.11883/bzycj-2026-0030
Abstract:
In recent years, with the widespread application of various explosive weapons, the number of explosion-induced traumatic brain injury (TBI) cases has surged. Current research on explosive blast injuries predominantly focuses on plain environments, while studies on the injury mechanisms, trauma characteristics, and treatment strategies under the special physical and chemical environment of the plateau remain relatively scarce. To investigate the kinematic response of the human head–neck system subjected to blast loading under low-ambient-pressure conditions, this study employed a high-fidelity physical anthropomorphic surrogate instrumented with overpressure transducers, accelerometers, angular-rate sensors, and a six-axis load cell. Experiments were conducted using a shock-tube test system at four ambient-pressure levels, with three blast overpressure magnitudes applied sequentially for each pressure condition. The results show that, under ambient pressures ranging from 54 kPa to 101 kPa, the free-field peak overpressure decreases with decreasing ambient pressure (relative to 101 kPa, the peak overpressure at 54 kPa is reduced by approximately 16.03%). The peak overpressure measured at various locations on the head surface also shows a decreasing trend in the low-pressure range. Meanwhile, translational metrics—such as the peak head center-of-gravity accelerations in the x and z directions and the peak neck forces in the x and z directions—decrease overall with decreasing ambient pressure, whereas rotational metrics such as the peak head center-of-gravity angular velocity in the y direction and the peak neck torque in the y direction—increase overall with decreasing ambient pressure. These findings indicate that, under the present test conditions, low ambient pressure exerts opposite effects on the translational and rotational responses of the head-neck system. The study reveals that the injury quantification assessment method established under normothermic and normobaric conditions exhibits applicability bias in high-altitude (hypobaric) environments. This bias arises because high-altitude (hypobaric) conditions can alter human physiological functions (e.g., hypoxia and hypothermia reduce tissue tolerance). Under identical blast loading conditions, injuries tend to be more severe than those at plain levels. Therefore, the method requires calibration and validation under hypobaric conditions. In summary, this study provides a mechanics-based reference for blast-induced injury research and for evaluating the applicability of injury criteria in plateau (low-ambient-pressure) environments.
In recent years, with the widespread application of various explosive weapons, the number of explosion-induced traumatic brain injury (TBI) cases has surged. Current research on explosive blast injuries predominantly focuses on plain environments, while studies on the injury mechanisms, trauma characteristics, and treatment strategies under the special physical and chemical environment of the plateau remain relatively scarce. To investigate the kinematic response of the human head–neck system subjected to blast loading under low-ambient-pressure conditions, this study employed a high-fidelity physical anthropomorphic surrogate instrumented with overpressure transducers, accelerometers, angular-rate sensors, and a six-axis load cell. Experiments were conducted using a shock-tube test system at four ambient-pressure levels, with three blast overpressure magnitudes applied sequentially for each pressure condition. The results show that, under ambient pressures ranging from 54 kPa to 101 kPa, the free-field peak overpressure decreases with decreasing ambient pressure (relative to 101 kPa, the peak overpressure at 54 kPa is reduced by approximately 16.03%). The peak overpressure measured at various locations on the head surface also shows a decreasing trend in the low-pressure range. Meanwhile, translational metrics—such as the peak head center-of-gravity accelerations in the x and z directions and the peak neck forces in the x and z directions—decrease overall with decreasing ambient pressure, whereas rotational metrics such as the peak head center-of-gravity angular velocity in the y direction and the peak neck torque in the y direction—increase overall with decreasing ambient pressure. These findings indicate that, under the present test conditions, low ambient pressure exerts opposite effects on the translational and rotational responses of the head-neck system. The study reveals that the injury quantification assessment method established under normothermic and normobaric conditions exhibits applicability bias in high-altitude (hypobaric) environments. This bias arises because high-altitude (hypobaric) conditions can alter human physiological functions (e.g., hypoxia and hypothermia reduce tissue tolerance). Under identical blast loading conditions, injuries tend to be more severe than those at plain levels. Therefore, the method requires calibration and validation under hypobaric conditions. In summary, this study provides a mechanics-based reference for blast-induced injury research and for evaluating the applicability of injury criteria in plateau (low-ambient-pressure) environments.
2026,
46(11):
111502.
doi: 10.11883/bzycj-2026-0027
Abstract:
In complex and sensitive environments, minimizing the disturbance of blasting vibration to surrounding residents is the primary concern during blasting construction. To explore a quantitative evaluation method for human dynamic response to blasting vibration, this study conducted single-subject in-situ blasting tests under strictly controlled safety conditions. By integrating digital image correlation (DIC) with a synchronous electrocardiogram (ECG) measurement system, the dynamic response characteristics of the human body surface under varying blasting vibration intensities were preliminarily analyzed. A height-dependent fitting relationship for peak particle velocity (PPV) was established under the present test conditions, with the body divided into two regions: below the waist and above the waist. Given the safety constraints of in-situ blasting tests, laboratory shake-table tests were also conducted. A comparative analysis using heart rate variability (HRV) evaluation indices was performed to preliminarily demonstrate the feasibility of using a shake table to simulate blasting vibration for human perception studies. The preliminary results indicate that under the present test conditions, the vertical vibration velocity of the human body is significantly higher than the horizontal velocity, with the vertical direction identified as the dominant vibration direction. The vertical vibration velocity exhibits a characteristic pattern of “attenuation below the waist and amplification above the waist”. Compared with the ground surface velocity, the attenuation rate in the lower body region ranges from 55.7% to 65.9%. The vibration velocity in the upper body region is amplified by a factor of 1.25 to 1.74. The horizontal vibration velocity decreases from the feet to the head, with an attenuation rate of 52.6% to 60%. The error in HRV indices obtained from the in-situ and shake-table tests is less than 10%, preliminarily confirming the feasibility of employing a shake table to simulate blasting vibration for human perception research. These exploratory in-situ tests provide a methodological reference for quantifying human vibration response and studying perceived ECG changes due to blasting vibrations.
In complex and sensitive environments, minimizing the disturbance of blasting vibration to surrounding residents is the primary concern during blasting construction. To explore a quantitative evaluation method for human dynamic response to blasting vibration, this study conducted single-subject in-situ blasting tests under strictly controlled safety conditions. By integrating digital image correlation (DIC) with a synchronous electrocardiogram (ECG) measurement system, the dynamic response characteristics of the human body surface under varying blasting vibration intensities were preliminarily analyzed. A height-dependent fitting relationship for peak particle velocity (PPV) was established under the present test conditions, with the body divided into two regions: below the waist and above the waist. Given the safety constraints of in-situ blasting tests, laboratory shake-table tests were also conducted. A comparative analysis using heart rate variability (HRV) evaluation indices was performed to preliminarily demonstrate the feasibility of using a shake table to simulate blasting vibration for human perception studies. The preliminary results indicate that under the present test conditions, the vertical vibration velocity of the human body is significantly higher than the horizontal velocity, with the vertical direction identified as the dominant vibration direction. The vertical vibration velocity exhibits a characteristic pattern of “attenuation below the waist and amplification above the waist”. Compared with the ground surface velocity, the attenuation rate in the lower body region ranges from 55.7% to 65.9%. The vibration velocity in the upper body region is amplified by a factor of 1.25 to 1.74. The horizontal vibration velocity decreases from the feet to the head, with an attenuation rate of 52.6% to 60%. The error in HRV indices obtained from the in-situ and shake-table tests is less than 10%, preliminarily confirming the feasibility of employing a shake table to simulate blasting vibration for human perception research. These exploratory in-situ tests provide a methodological reference for quantifying human vibration response and studying perceived ECG changes due to blasting vibrations.
2026,
46(11):
111503.
doi: 10.11883/bzycj-2025-0383
Abstract:
To address the high cost and low sample efficiency of deep learning-based blast loading prediction in urban environments, a Bayesian deep active learning (BDAL) method is proposed. The objective is to significantly reduce the dependency on large-scale, high-fidelity numerical simulation data while maintaining prediction accuracy and providing reliable uncertainty quantification. A three-dimensional typical urban building cluster consisting of a 3×3 regular array of cuboid buildings was constructed. A seven-dimensional parameter space was defined, including explosive charge equivalence(1000 , 2000 , 3000 kt), detonation distance (1000 , 2 000, 3000 m), building length (10, 20, 30 m), building width (20, 40 m), building height (75, 100 m), street length (50, 75, 100 m), and street width (50, 75 m). A full factorial experimental design was employed, generating 648 parameter combinations. For each combination, the open-source computational fluid dynamics (CFD) software blastFoam was used to perform three-dimensional numerical simulations of blast wave propagation. The background mesh size was set to 30 m based on grid sensitivity analysis, and adaptive mesh refinement (AMR) with local refinement level 2 and dynamic refinement level 1 was applied to capture shock wave details. Peak overpressure values were recorded at 12 points of interest (POIs) in the building cluster, resulting in a dataset of 7776 samples. A BDAL framework was then developed. Bayesian inference was integrated into a deep neural network to enable probabilistic modeling of parameters. Monte Carlo (MC) dropout was adopted as an approximate variational inference method to estimate predictive uncertainty. An uncertainty-driven active sampling strategy was designed: the predictive variance of each unlabeled sample was computed via 30 stochastic forward passes with dropout enabled. Samples with variance exceeding 85% of the maximum variance were selected as candidates, and the top 28 cases (336 samples) with the highest variance were chosen in each active learning cycle. These selected samples were labeled by the blastFoam simulator and added to the training set. The model was retrained iteratively until the relative improvement in mean absolute percentage error (MAPE) fell below 1% or the labeled set reached the full training size. On a test set of 780 unseen samples (65 cases), the proposed BDAL method achieved an MAPE of 13.1% and an R2 of 0.972 for peak overpressure prediction. The 95% prediction interval covered the true values in 85.9% of the cases, with a normalized mean prediction interval width (NMPIW) of 0.026. Single-point prediction response time was below 20 ms, representing a speedup of more than 105 compared to high-fidelity numerical simulations. Compared to passive deep learning models trained on the full dataset, the BDAL method required only about 50% of labeled data to reach comparable prediction accuracy. In a comparative experiment with 50% training data, BDAL achieved a MAPE of 17.2%, while a conventional fully connected neural network (FCNN) and a three-dimensional direction-encoded Bayesian neural network (3D-DeBNN) gave MAPEs of 52.9% and 22.6%, respectively. The proposed Bayesian deep active learning method enables efficient and low-cost blast loading prediction in typical regularized urban environments. It effectively reduces the dependency on large-scale numerical simulation data, maintains high prediction accuracy and reliable uncertainty quantification, and meanwhile achieves millisecond-level inference speed. The method shows strong potential for disaster prevention and mitigation applications, such as pre-disaster anti-blast design and post-disaster emergency response.
To address the high cost and low sample efficiency of deep learning-based blast loading prediction in urban environments, a Bayesian deep active learning (BDAL) method is proposed. The objective is to significantly reduce the dependency on large-scale, high-fidelity numerical simulation data while maintaining prediction accuracy and providing reliable uncertainty quantification. A three-dimensional typical urban building cluster consisting of a 3×3 regular array of cuboid buildings was constructed. A seven-dimensional parameter space was defined, including explosive charge equivalence(
2026,
46(11):
111504.
doi: 10.11883/bzycj-2025-0409
Abstract:
Reinforced concrete (RC) columns are critical load-bearing members in engineering structures. Under explosive loading, they may sustain severe damage and potentially trigger the collapse of the entire structure. Therefore, rapid and accurate assessment of the damage state of RC columns subjected to explosive loading is essential for ensuring structural safety and implementing effective protective measures. Accordingly, a data-driven machine learning (ML) model was proposed to predict the damage indices of RC columns under explosive loading. To train the model, a comprehensive database comprising3133 samples was established by integrating 259 samples collected from the literature and 2874 supplementary samples generated through numerical simulations. The database includes both RC columns with uniformly spaced stirrups and those with densified stirrups satisfying seismic design requirements. Eleven key parameters were selected as input features, with the RC column damage index taken as the output. Six ML models were employed to predict the damage indices under explosive loading, and their predictive performance was comparatively evaluated using four regression metrics. The results indicate that the tabular prior-data fitted network (TabPFN) achieved the best predictive accuracy and generalization performance, with a coefficient of determination of 0.989 on the test set and a mean absolute error and a root mean square error of 0.018 and 0.030, respectively. The interpretability of the TabPFN model was further analyzed using SHAP (Shapley additive explanations). The results show that charge mass, standoff distance, and column cross-sectional depth are the key features governing the damage severity of RC columns. Notably, the volumetric stirrup reinforcement ratio contributes more significantly to improving the blast resistance of RC columns than the longitudinal reinforcement ratio. Finally, comparison with independent finite element simulation results confirmed that the TabPFN model exhibits good predictive stability as a surrogate model under unseen loading conditions. In terms of computational efficiency, the proposed model achieves a single-prediction inference time of approximately 0.5 s, representing an efficiency improvement of nearly four orders of magnitude compared with conventional numerical simulation methods. The established model enables rapid surrogate prediction of RC column damage under explosive loading and provides guidance for preliminary parameter analysis in blast-resistant structural optimization design.
Reinforced concrete (RC) columns are critical load-bearing members in engineering structures. Under explosive loading, they may sustain severe damage and potentially trigger the collapse of the entire structure. Therefore, rapid and accurate assessment of the damage state of RC columns subjected to explosive loading is essential for ensuring structural safety and implementing effective protective measures. Accordingly, a data-driven machine learning (ML) model was proposed to predict the damage indices of RC columns under explosive loading. To train the model, a comprehensive database comprising
2026,
46(11):
113301.
doi: 10.11883/bzycj-2026-0002
Abstract:
To further analyze the damage effects of projectile penetration into concrete targets and their influence on the penetration process, a systematic theoretical investigation was carried out. A spalling effect model was established based on the spalling phenomenon observed during normal perforation of concrete targets by projectiles. By integrating this model with the cratering effect model and the target resistance function, a theoretical model for penetration that comprehensively accounts for both cratering and spalling effects was developed. By means of the presented model, the influence of target thickness and impact velocity on the penetration process and target damage parameters were analyzed. The results show that as the concrete target thickness decreases or the impact velocity increases, the influence of the spalling effect on penetration resistance and residual velocity diminishes, while the proportion of the splash zone during the spalling stage increases, making the splash effect the dominant factor affecting resistance in the spalling stage. When the target thickness exceeds 4.5 times the projectile diameter, the influence of the spalling effect on the residual velocity exceeds 10%, rendering the spalling effect non-negligible. Cratering depth increases linearly with thickness when the thickness is not more than 4 times the projectile diameter, and then tends to stabilize. Spalling depth increases linearly with thickness when the thickness is not more than 6.9 times the projectile diameter, and then decreases linearly. During the linear increase stage, both cratering depth and spalling depth are approximately half of the concrete target thickness. Compared with perforation of thin concrete targets, variations in impact velocity exhibit a more pronounced influence on the crater depth and spalling depth during the penetration of thick concrete targets. The proposed model effectively characterizes the damage effects of concrete targets and can provide a theoretical basis for penetration analysis and protective design of concrete targets.
To further analyze the damage effects of projectile penetration into concrete targets and their influence on the penetration process, a systematic theoretical investigation was carried out. A spalling effect model was established based on the spalling phenomenon observed during normal perforation of concrete targets by projectiles. By integrating this model with the cratering effect model and the target resistance function, a theoretical model for penetration that comprehensively accounts for both cratering and spalling effects was developed. By means of the presented model, the influence of target thickness and impact velocity on the penetration process and target damage parameters were analyzed. The results show that as the concrete target thickness decreases or the impact velocity increases, the influence of the spalling effect on penetration resistance and residual velocity diminishes, while the proportion of the splash zone during the spalling stage increases, making the splash effect the dominant factor affecting resistance in the spalling stage. When the target thickness exceeds 4.5 times the projectile diameter, the influence of the spalling effect on the residual velocity exceeds 10%, rendering the spalling effect non-negligible. Cratering depth increases linearly with thickness when the thickness is not more than 4 times the projectile diameter, and then tends to stabilize. Spalling depth increases linearly with thickness when the thickness is not more than 6.9 times the projectile diameter, and then decreases linearly. During the linear increase stage, both cratering depth and spalling depth are approximately half of the concrete target thickness. Compared with perforation of thin concrete targets, variations in impact velocity exhibit a more pronounced influence on the crater depth and spalling depth during the penetration of thick concrete targets. The proposed model effectively characterizes the damage effects of concrete targets and can provide a theoretical basis for penetration analysis and protective design of concrete targets.
2026,
46(11):
113401.
doi: 10.11883/bzycj-2025-0312
Abstract:
During the high-speed water entry of a projectile, cavitation occurs, forming a cavity bubble that alters the flow field and subsequently affects the projectile’s motion stability. Our study investigates the characteristics of flow field changes after double-cone projectiles with different head cone angles traverse the free surface. High-speed water entry experiments were conducted by using an electromagnetic launch device, and a numerical simulation model of high-speed water entry was established basing on the overset mesh technique and the volume-of-fluid multiphase flow model. The validity of the simulation model was verified through experiments, and the flow field characteristics after the vertical water entry of projectiles with different head types were obtained. The research findings are as follows: After the vertical water entry of a double-cone projectile, the cavity bubble develops symmetrically. Following surface closure of the cavity bubble, its total length increases while its maximum width gradually decreases. As the head cone angle of the projectile's cavitator increases: during the initial entry phase, the closure point and wetted surface position move closer to the tail; the cavity contour becomes wider; the resistance experienced at the moment of entry and during underwater motion increases, leading to faster velocity decay; the time of surface closure for the cavity bubble is delayed. At the same moment during underwater motion, the longer the length of the tail cavity bubble, the shorter the length of the vortex structures within the water domain.
During the high-speed water entry of a projectile, cavitation occurs, forming a cavity bubble that alters the flow field and subsequently affects the projectile’s motion stability. Our study investigates the characteristics of flow field changes after double-cone projectiles with different head cone angles traverse the free surface. High-speed water entry experiments were conducted by using an electromagnetic launch device, and a numerical simulation model of high-speed water entry was established basing on the overset mesh technique and the volume-of-fluid multiphase flow model. The validity of the simulation model was verified through experiments, and the flow field characteristics after the vertical water entry of projectiles with different head types were obtained. The research findings are as follows: After the vertical water entry of a double-cone projectile, the cavity bubble develops symmetrically. Following surface closure of the cavity bubble, its total length increases while its maximum width gradually decreases. As the head cone angle of the projectile's cavitator increases: during the initial entry phase, the closure point and wetted surface position move closer to the tail; the cavity contour becomes wider; the resistance experienced at the moment of entry and during underwater motion increases, leading to faster velocity decay; the time of surface closure for the cavity bubble is delayed. At the same moment during underwater motion, the longer the length of the tail cavity bubble, the shorter the length of the vortex structures within the water domain.
2026,
46(11):
113901.
doi: 10.11883/bzycj-2026-0022
Abstract:
Current transformers are core components of power systems used for current measurement and relay protection. During long-term service under coupled multiphysical-field conditions, the internal insulation structure is susceptible to breakdown under locally intensified electric fields, triggering arc discharge in the insulating oil. The resulting oil cracking and rapid gas expansion produce a sharp rise in internal pressure. If this pressure is not relieved promptly, the resulting pressure surge may lead to combustion and explosion accidents. Therefore, the rapid-response capability of pressure relief devices under explosive loading is critical to the operational safety of current transformers. This study focuses on the expander–rupture disc pressure relief assembly of an LVB-220 current transformer and systematically investigates its dynamic mechanical behavior and failure mechanism under explosive impact loading. An equivalent hydrogen-air premixed-gas explosion test platform was constructed. The test system consisted of two stainless-steel flame-acceleration tubes with an inner diameter of 168.3 mm and a total length of4250 mm, a gas-filling and mixing unit, an ignition device, and a high-speed data-acquisition system. A hydrogen-air mixture with a volume ratio of 27∶75 was used as the combustible gas to reproduce the most severe explosion conditions caused by arc-generated cracking gas in transformer oil. Pressure and flame signals were recorded synchronously using a high-temperature pressure transducer and two flame detectors installed along the tube. The tested assembly consisted of a positive-arch, cross-scored rupture disc made of 316L stainless steel, with a static burst pressure of 0.2 MPa, and a nine-convolution expander. In addition, an explicit dynamic finite element model was developed using ANSYS/LS-DYNA. The Johnson-Cook constitutive model was adopted to describe the strain-rate-dependent behavior of 316L stainless steel. The cross-scored region of the rupture disc was finely meshed with a minimum element size of approximately 0.02 mm to accurately capture crack initiation and propagation. The measured pressure-time history was applied as the loading boundary condition. The model was validated by comparing the simulated opening pressure and expander deformation with the experimental results. The results show that, during the early stage of the explosion, the pressure wave reaches the relief port ahead of the flame front and triggers the opening of the rupture disc. The measured peak pressure before disc opening is 0.72 MPa, which is significantly higher than the static calibration value of 0.2 MPa because of strain-rate hardening, structural inertia, and the spatial nonuniformity of the pressure field under rapid loading. The expander exhibits limited plastic deformation, with the axial deformation of the nine convolutions ranging from 0.60 to 2.30 mm. The deformation distribution is characterized by larger values at both ends and smaller values in the middle, reflecting an energy-absorption mechanism dominated by low-order bending modes. The asymmetric curling of the rupture-disc petals is closely associated with stress-wave reflections and fluid-structure interaction induced by high-speed venting. The numerical simulation reproduces the crack-growth sequence, opening morphology, and stress distribution in good agreement with the experimental observations. The proposed integrated experimental-numerical approach provides a reliable mechanical basis and engineering guidance for optimizing the blast-resistant design of pressure relief devices for current transformers.
Current transformers are core components of power systems used for current measurement and relay protection. During long-term service under coupled multiphysical-field conditions, the internal insulation structure is susceptible to breakdown under locally intensified electric fields, triggering arc discharge in the insulating oil. The resulting oil cracking and rapid gas expansion produce a sharp rise in internal pressure. If this pressure is not relieved promptly, the resulting pressure surge may lead to combustion and explosion accidents. Therefore, the rapid-response capability of pressure relief devices under explosive loading is critical to the operational safety of current transformers. This study focuses on the expander–rupture disc pressure relief assembly of an LVB-220 current transformer and systematically investigates its dynamic mechanical behavior and failure mechanism under explosive impact loading. An equivalent hydrogen-air premixed-gas explosion test platform was constructed. The test system consisted of two stainless-steel flame-acceleration tubes with an inner diameter of 168.3 mm and a total length of
2026,
46(11):
113902.
doi: 10.11883/bzycj-2025-0348
Abstract:
The present investigation examines the effectiveness of a composite cushion charging structure, placed at the bottom of underwater boreholes, to mitigate bedrock damage induced by blasting excavation during cross-sea engineering. With reference to the embedded open caisson blasting project for a major cross-sea bridge, this research adopted a combined methodology of field sampling and controlled underwater explosion model tests. A piezoelectric ceramic detection system was employed to quantitatively analyze how the composite cushion, composed of iron-sand concrete layers with varying wave impedances, affects rock sample damage. Piezoelectric signals were processed via wavelet packet analysis to calculate the axial damage factor (DI) of the blast hole. Furthermore, by integrating fractal dimension theory with damage mechanics, a quantitative assessment was performed on the propagation behavior of cracks formed on the top surfaces of rock specimens under different test conditions. Results demonstrate that the implemented composite bottom cushion effectively mitigates blast-induced damage by significantly inhibiting macroscopic crack propagation, reducing surface crack density, and decreasing the axial penetration depth of cracks into the rock mass. Detailed analysis of axial damage reveals a clear trend, showing that the reduction in DI becomes more pronounced as the wave impedance of the cushion material increases. Specifically, within the borehole-affected zone (0–12 cm), the maximum achievable reduction in DI reaches 10.70%. At the bottom measurement point, reductions exceeding 90% are observed for the higher-impedance cushion configurations. In conclusion, this work confirms that employing a composite cushion charging structure in underwater drilling and blasting operations can significantly alleviate blast-induced damage to foundational bedrock. The findings also establish that axial damage to the rock mass can be effectively controlled by adjusting the wave impedance of the iron-sand concrete in the cushion layer. These outcomes offer valuable insights for optimizing blasting design and enhancing damage control in marine engineering projects.
The present investigation examines the effectiveness of a composite cushion charging structure, placed at the bottom of underwater boreholes, to mitigate bedrock damage induced by blasting excavation during cross-sea engineering. With reference to the embedded open caisson blasting project for a major cross-sea bridge, this research adopted a combined methodology of field sampling and controlled underwater explosion model tests. A piezoelectric ceramic detection system was employed to quantitatively analyze how the composite cushion, composed of iron-sand concrete layers with varying wave impedances, affects rock sample damage. Piezoelectric signals were processed via wavelet packet analysis to calculate the axial damage factor (DI) of the blast hole. Furthermore, by integrating fractal dimension theory with damage mechanics, a quantitative assessment was performed on the propagation behavior of cracks formed on the top surfaces of rock specimens under different test conditions. Results demonstrate that the implemented composite bottom cushion effectively mitigates blast-induced damage by significantly inhibiting macroscopic crack propagation, reducing surface crack density, and decreasing the axial penetration depth of cracks into the rock mass. Detailed analysis of axial damage reveals a clear trend, showing that the reduction in DI becomes more pronounced as the wave impedance of the cushion material increases. Specifically, within the borehole-affected zone (0–12 cm), the maximum achievable reduction in DI reaches 10.70%. At the bottom measurement point, reductions exceeding 90% are observed for the higher-impedance cushion configurations. In conclusion, this work confirms that employing a composite cushion charging structure in underwater drilling and blasting operations can significantly alleviate blast-induced damage to foundational bedrock. The findings also establish that axial damage to the rock mass can be effectively controlled by adjusting the wave impedance of the iron-sand concrete in the cushion layer. These outcomes offer valuable insights for optimizing blasting design and enhancing damage control in marine engineering projects.
2026,
46(11):
113903.
doi: 10.11883/bzycj-2025-0419
Abstract:
Addressing the high probability of injury and fatality associated with traditional anti-riot kinetic energy projectiles represented by rubber bullets, a novel low-kinetic-energy frangible projectile with the characteristics of reliable shell fragmentation and the energy release of powder dispersion was designed based on the existing launch platforms of non-lethal weapons, aimed to improve the application safety of anti-riot kinetic energy projectiles. Through shooting tests on anthropomorphic dummy targets and ballistic gelatin targets, the dynamic impact responses of the two targets under the blunt impacts of frangible projectiles were obtained. In the dummy target tests, the frangible projectile achieved reliable fragmentation and exhibited a significant kinetic energy slow-release effect; the calculated injury assessment indicators for different parts of the dummy were all within the safety threshold. Comparative analyses with the blunt impact test results of rubber bullets show that this type of frangible projectile has significantly higher safety than rubber bullets while maintaining effective pain-inducing performance. In the ballistic gelatin target shooting tests, under the same projectile mass and impact velocity, the peak pressure generated in the gelatin measured by the internal sensor differed by approximately one order of magnitude between the frangible projectile and the rubber bullet. The test results show that the novel low-kinetic-energy frangible projectile can effectively attenuate the peak impact pressure of the projectile and greatly reduce its injury potential through the fragmentation of the projectile shell and the dispersion of the powder filled inside the projectile, which provides technical support for improving the application safety of anti-riot kinetic energy ammunition.
Addressing the high probability of injury and fatality associated with traditional anti-riot kinetic energy projectiles represented by rubber bullets, a novel low-kinetic-energy frangible projectile with the characteristics of reliable shell fragmentation and the energy release of powder dispersion was designed based on the existing launch platforms of non-lethal weapons, aimed to improve the application safety of anti-riot kinetic energy projectiles. Through shooting tests on anthropomorphic dummy targets and ballistic gelatin targets, the dynamic impact responses of the two targets under the blunt impacts of frangible projectiles were obtained. In the dummy target tests, the frangible projectile achieved reliable fragmentation and exhibited a significant kinetic energy slow-release effect; the calculated injury assessment indicators for different parts of the dummy were all within the safety threshold. Comparative analyses with the blunt impact test results of rubber bullets show that this type of frangible projectile has significantly higher safety than rubber bullets while maintaining effective pain-inducing performance. In the ballistic gelatin target shooting tests, under the same projectile mass and impact velocity, the peak pressure generated in the gelatin measured by the internal sensor differed by approximately one order of magnitude between the frangible projectile and the rubber bullet. The test results show that the novel low-kinetic-energy frangible projectile can effectively attenuate the peak impact pressure of the projectile and greatly reduce its injury potential through the fragmentation of the projectile shell and the dispersion of the powder filled inside the projectile, which provides technical support for improving the application safety of anti-riot kinetic energy ammunition.
2026,
46(11):
114901.
doi: 10.11883/bzycj-2025-0401
Abstract:
Coupling and stemming coefficients are essential for predicting ground shock magnitude and damage zones from underground explosions, yet their variation with burial depth and dependence on media and explosion types remain insufficiently understood. Experimental and theoretical methods for determining these coefficients in concrete, rock, and soil under both chemical and nuclear explosions were systematically reviewed. Based on collected data from published tests, definitions of different coupling coefficients (energy coupling, ground shock parameter coupling, equivalent yield, and stemming coefficients) were clarified, and conversion relationships among them were derived using energy conservation and wave attenuation principles. The critical burial depth for full coupling was analyzed separately for peak quantities (e.g., peak stress, particle velocity) and integral quantities (e.g., impulse, surface vibration). Experimental results show that peak quantities reach full coupling at a depth approximately equal to the contained explosion cavity radius, which is much shallower than the critical depth for contained explosions. In contrast, impulse and ground motion require depths close to the contained explosion threshold. The coupling energy is proportional to the volume of the damaged zone, and the evolution of coupling coefficients with scaled depth of burial follows a Boltzmann function, requiring only two parameters to define the entire curve. For chemical explosions, the fully coupled equivalent yield coefficient (relative to contained explosions) in concrete, limestone, and soils was quantified, with stemming coefficients ranging from 1.4−1.8 in rocks and 2.4−2.6 in soils. It is concluded that different ground shock parameters exhibit distinct coupling behaviors, challenging the assumption of a universal coupling coefficient. The proposed empirical formulas provide conservative estimates for engineering design, while the underlying mechanisms of free-surface unloading require further quantitative investigation.
Coupling and stemming coefficients are essential for predicting ground shock magnitude and damage zones from underground explosions, yet their variation with burial depth and dependence on media and explosion types remain insufficiently understood. Experimental and theoretical methods for determining these coefficients in concrete, rock, and soil under both chemical and nuclear explosions were systematically reviewed. Based on collected data from published tests, definitions of different coupling coefficients (energy coupling, ground shock parameter coupling, equivalent yield, and stemming coefficients) were clarified, and conversion relationships among them were derived using energy conservation and wave attenuation principles. The critical burial depth for full coupling was analyzed separately for peak quantities (e.g., peak stress, particle velocity) and integral quantities (e.g., impulse, surface vibration). Experimental results show that peak quantities reach full coupling at a depth approximately equal to the contained explosion cavity radius, which is much shallower than the critical depth for contained explosions. In contrast, impulse and ground motion require depths close to the contained explosion threshold. The coupling energy is proportional to the volume of the damaged zone, and the evolution of coupling coefficients with scaled depth of burial follows a Boltzmann function, requiring only two parameters to define the entire curve. For chemical explosions, the fully coupled equivalent yield coefficient (relative to contained explosions) in concrete, limestone, and soils was quantified, with stemming coefficients ranging from 1.4−1.8 in rocks and 2.4−2.6 in soils. It is concluded that different ground shock parameters exhibit distinct coupling behaviors, challenging the assumption of a universal coupling coefficient. The proposed empirical formulas provide conservative estimates for engineering design, while the underlying mechanisms of free-surface unloading require further quantitative investigation.
2026,
46(11):
115401.
doi: 10.11883/bzycj-2025-0342
Abstract:
Efficiently achieving plane wave loading on the test specimen is a key technical issue in the design of blast wave simulators. Based on the existing device, testing data of large-scale shock tubes, and LS-DYNA software, numerical models of blast wave propagation in simulators were established. Numerical simulations were conducted to develop a safe, economical, and reusable blast wave simulator. A quantitative method for assessing the uniformity of overpressure load on the loading area was proposed. Numerical analyses were performed to investigate the influence of the shape and length of the expansion section and the length of the conditioning section on the uniformity of overpressure load on the loading area. Key structural parameters, including the wall thickness of the expansion and conditioning sections, as well as the spacing and height of the stiffeners, were numerically optimized. Validation tests were conducted on the blast wave simulator. It is found that the established numerical model can accurately reproduce the blast wave propagation, and the prediction results show good agreement with the testing data. Taking the errors of overpressure peak value and arrival time as indicators, the quantitative evaluation of overpressure load uniformity on the loading area is achieved. Considering the balance between technical and economic factors, the developed blast wave simulator is designed with a symmetrically configured expansion section 3 m in length. The length of the conditioning section can be extended as much as the actual investment allows. Based on the numerical results, the wall thickness of both the expansion and conditioning sections is determined to be 30 mm. The height and spacing of the stiffeners are both recommended to be 150 mm. The results of validation tests confirm that the geometric and structural design meets the requirements of blast loads and structural resistance, and the developed simulator is suitable for component-level tests.
Efficiently achieving plane wave loading on the test specimen is a key technical issue in the design of blast wave simulators. Based on the existing device, testing data of large-scale shock tubes, and LS-DYNA software, numerical models of blast wave propagation in simulators were established. Numerical simulations were conducted to develop a safe, economical, and reusable blast wave simulator. A quantitative method for assessing the uniformity of overpressure load on the loading area was proposed. Numerical analyses were performed to investigate the influence of the shape and length of the expansion section and the length of the conditioning section on the uniformity of overpressure load on the loading area. Key structural parameters, including the wall thickness of the expansion and conditioning sections, as well as the spacing and height of the stiffeners, were numerically optimized. Validation tests were conducted on the blast wave simulator. It is found that the established numerical model can accurately reproduce the blast wave propagation, and the prediction results show good agreement with the testing data. Taking the errors of overpressure peak value and arrival time as indicators, the quantitative evaluation of overpressure load uniformity on the loading area is achieved. Considering the balance between technical and economic factors, the developed blast wave simulator is designed with a symmetrically configured expansion section 3 m in length. The length of the conditioning section can be extended as much as the actual investment allows. Based on the numerical results, the wall thickness of both the expansion and conditioning sections is determined to be 30 mm. The height and spacing of the stiffeners are both recommended to be 150 mm. The results of validation tests confirm that the geometric and structural design meets the requirements of blast loads and structural resistance, and the developed simulator is suitable for component-level tests.
2026,
46(11):
115402.
doi: 10.11883/bzycj-2025-0355
Abstract:
The design of blast wave simulators for prototype or large-scale engineering structures and components must carefully balance safety, cost, and performance. To address this challenge, a blast wave simulator driven by methane-air deflagration was developed in this study. Numerical models of methane-air deflagration in large-scale tubes were established using the CFD software OpenFOAM and validated against experimental data. On the basis of the validated model, numerical simulations were performed to investigate the effects of gas cloud length, venting conditions, and obstacle configurations on overpressure loads, thereby revealing the mechanisms of blast wave and flame propagation in the methane-air deflagration-driven simulator. A testing scheme was subsequently proposed to generate different levels of blast loading. The results show that the developed numerical model can reasonably predict the overpressure time histories and spatial distributions of gas explosions in large-scale tubes. In the simulator, increasing the gas cloud volume and placing obstacles near the ignition zone of the driven section can significantly intensify the deflagration of methane-air mixtures. Moreover, side venting effectively separates the pressure wave from the flame, thereby preventing high-temperature effects in the loading area. An optimized loading configuration was proposed, in which four obstacles (1×50% blockage ratio and 3×25% blockage ratio, spaced at 3 m intervals) were arranged, and different blast load levels were achieved by varying the gas cloud length from 1.5 m to 6 m in the driven section. Trial tests of the developed simulator showed that the measured peak overpressures agree well with the numerical predictions, with deviations less than 12%, and the results exhibit good uniformity and high repeatability. These findings demonstrate that the proposed methane-air deflagration-driven blast wave simulator is suitable for blast testing of structural components such as reinforced concrete slabs.
The design of blast wave simulators for prototype or large-scale engineering structures and components must carefully balance safety, cost, and performance. To address this challenge, a blast wave simulator driven by methane-air deflagration was developed in this study. Numerical models of methane-air deflagration in large-scale tubes were established using the CFD software OpenFOAM and validated against experimental data. On the basis of the validated model, numerical simulations were performed to investigate the effects of gas cloud length, venting conditions, and obstacle configurations on overpressure loads, thereby revealing the mechanisms of blast wave and flame propagation in the methane-air deflagration-driven simulator. A testing scheme was subsequently proposed to generate different levels of blast loading. The results show that the developed numerical model can reasonably predict the overpressure time histories and spatial distributions of gas explosions in large-scale tubes. In the simulator, increasing the gas cloud volume and placing obstacles near the ignition zone of the driven section can significantly intensify the deflagration of methane-air mixtures. Moreover, side venting effectively separates the pressure wave from the flame, thereby preventing high-temperature effects in the loading area. An optimized loading configuration was proposed, in which four obstacles (1×50% blockage ratio and 3×25% blockage ratio, spaced at 3 m intervals) were arranged, and different blast load levels were achieved by varying the gas cloud length from 1.5 m to 6 m in the driven section. Trial tests of the developed simulator showed that the measured peak overpressures agree well with the numerical predictions, with deviations less than 12%, and the results exhibit good uniformity and high repeatability. These findings demonstrate that the proposed methane-air deflagration-driven blast wave simulator is suitable for blast testing of structural components such as reinforced concrete slabs.
2026,
46(11):
115901.
doi: 10.11883/bzycj-2025-0148
Abstract:
To address the challenges of rapid deployment for heavy-duty unmanned platforms and impact protection during drop-landing, a buffer airbag system was designed to ensure the safe landing of the unmanned platform. First, theoretical modeling was used to preliminarily determine the geometric parameters of the buffer airbag and the size of the vent holes. A finite element simulation model that included the buffer airbag, the unmanned platform and the ground was established using the control volume method (CVM) to simulate the cushioning process of the airbag. The impact dynamics response during the landing attenuation process was analyzed, and the specific energy absorption (SEA) of the buffer airbag system was introduced to evaluate its cushioning performance. The analysis results indicate that during the landing buffer process, the unmanned platform reached a maximum overload value of 16.8g at 0.06 s, and the platform velocity reached a post-rebound maximum of 0.79 m/s at 0.1 s. At 0.18 s, the platform shifted laterally due to the center of gravity, and one side of the platform first contacted the ground. This led to fluctuations in overload value and velocity, but the overall landing process remained stable. The calculated SEA of the buffer airbag system was1527 J/kg. Using the control variable method, the influence of key parameters on the buffer performance of the airbag was analyzed, revealing the effects of vent hole size, critical exhaust pressure, airbag base area and airbag height on the performance of the buffer. The study found that the influence of airbag height on the two key indicators (maximum overload and SEA) was consistent, presenting no optimization conflict. However, after the height exceeded 0.37 m, a diminishing returns effect appeared. When the other three variables were changed individually, they caused a conflict between the goals of minimizing maximum overload and maximizing SEA, making it impossible to improve both simultaneously through independent optimization. To resolve this issue, an optimal latin hypercube design was used for sampling, and a three-layer neural network was employed to construct proxy models for the objective functions. The root mean square error (RMSE) and coefficient of determination (R2) of these two types of proxy models were calculated to evaluate their regression performance. The NSGA-Ⅱ genetic algorithm was integrated for multi-objective optimization. The results showed that for the proxy models predicting maximum overload and SEA, the RMSEs were 0.4895 and 0.7262 , and the R2 values were 0.9833 and 0.9364 , respectively. All R2 values were greater than the industry benchmark of 0.9, indicating high reliability of the proxy models. When the vent hole area was 3952 mm2, the critical exhaust pressure, the airbag base area were 158 kPa and 1.08 m2, respectively. Meanwhile, the maximum overload was reduced from 16.8g to 14.5g, and the SEA remained stable at 1529 J/kg. Based on the characteristics of the airbag's buffer process, a gantry crane-based simulation test method for unmanned platform airdrop and lifting was designed. A piezoelectric IEPE acceleration sensor was used to measure the overload value of the unmanned platform. Experimental verification showed that the measured maximum overload value was 15.2g, with a mere 4.8% error compared to the simulation result, confirming the correctness of the optimization scheme. This research provides efficient and low-cost design technical support for the soft landing systems of unmanned platforms, enhancing the safety and efficiency of operational deployment.
To address the challenges of rapid deployment for heavy-duty unmanned platforms and impact protection during drop-landing, a buffer airbag system was designed to ensure the safe landing of the unmanned platform. First, theoretical modeling was used to preliminarily determine the geometric parameters of the buffer airbag and the size of the vent holes. A finite element simulation model that included the buffer airbag, the unmanned platform and the ground was established using the control volume method (CVM) to simulate the cushioning process of the airbag. The impact dynamics response during the landing attenuation process was analyzed, and the specific energy absorption (SEA) of the buffer airbag system was introduced to evaluate its cushioning performance. The analysis results indicate that during the landing buffer process, the unmanned platform reached a maximum overload value of 16.8g at 0.06 s, and the platform velocity reached a post-rebound maximum of 0.79 m/s at 0.1 s. At 0.18 s, the platform shifted laterally due to the center of gravity, and one side of the platform first contacted the ground. This led to fluctuations in overload value and velocity, but the overall landing process remained stable. The calculated SEA of the buffer airbag system was
