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, Available online , doi: 10.11883/bzycj-2026-0072
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Independent embedded steel sheet piles, characterized by convenient construction and strong damage resistance, are widely used in nearshore coastal protection engineering. The damage characteristics of steel sheet piles subjected to shallow-water explosions play a critical role in determining the reliability of blast-resistant design. However, existing studies remain insufficient to fully elucidate the damage mechanisms of steel sheet piles under shallow-water blast loading. Based on the attenuation law of underwater explosion loads, an engineering calculation model was established to evaluate the blast-induced damage of steel sheet piles in shallow water. Meanwhile, a coupled numerical simulation model accounting for the interaction among multiple materials was developed. Model tests were further conducted to validate the reliability of both the engineering calculation model and the numerical simulations. The effects of explosive charge equivalent, standoff distance, and water depth on the structural damage response were systematically analyzed. The results indicate that the weak zone of steel sheet piles is mainly concentrated near the water-soil interface, with punching shear fracture and bending deformation identified as the dominant failure modes. The scaled distance was found to be the key parameter governing the damage behavior. When the scaled distance is less than 0.086m/kg1/3, punching shear fracture occurs; when it exceeds 1.026 m/kg1/3, no significant damage is observed; and within the intermediate range, plastic bending deformation develops. Increasing water depth has a limited effect on fracture failure but can significantly extend the bending deformation zone, with an increase of up to 35%. Good agreement was achieved among the theoretical calculations, numerical simulations, and experimental results, with relative errors within 10%, satisfying the accuracy requirements for engineering prediction. These findings provide a reliable theoretical basis and practical guidance for the blast-resistant design, damage assessment, and protective reinforcement of independent embedded steel sheet pile structures.
Independent embedded steel sheet piles, characterized by convenient construction and strong damage resistance, are widely used in nearshore coastal protection engineering. The damage characteristics of steel sheet piles subjected to shallow-water explosions play a critical role in determining the reliability of blast-resistant design. However, existing studies remain insufficient to fully elucidate the damage mechanisms of steel sheet piles under shallow-water blast loading. Based on the attenuation law of underwater explosion loads, an engineering calculation model was established to evaluate the blast-induced damage of steel sheet piles in shallow water. Meanwhile, a coupled numerical simulation model accounting for the interaction among multiple materials was developed. Model tests were further conducted to validate the reliability of both the engineering calculation model and the numerical simulations. The effects of explosive charge equivalent, standoff distance, and water depth on the structural damage response were systematically analyzed. The results indicate that the weak zone of steel sheet piles is mainly concentrated near the water-soil interface, with punching shear fracture and bending deformation identified as the dominant failure modes. The scaled distance was found to be the key parameter governing the damage behavior. When the scaled distance is less than 0.086m/kg1/3, punching shear fracture occurs; when it exceeds 1.026 m/kg1/3, no significant damage is observed; and within the intermediate range, plastic bending deformation develops. Increasing water depth has a limited effect on fracture failure but can significantly extend the bending deformation zone, with an increase of up to 35%. Good agreement was achieved among the theoretical calculations, numerical simulations, and experimental results, with relative errors within 10%, satisfying the accuracy requirements for engineering prediction. These findings provide a reliable theoretical basis and practical guidance for the blast-resistant design, damage assessment, and protective reinforcement of independent embedded steel sheet pile structures.
, Available online , 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 0.06s, 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 0.06s, 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
, Available online , 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 , 2000, 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 (
, Available online , 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.
, Available online , 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 is 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 is proposed to predict the damage indices of RC columns under explosive loading. To train the model, a comprehensive database comprising
, Available online , 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.
, Available online , doi: 10.11883/bzycj-2026-0057
Abstract:
To address the issues of insufficient cycle advance and low blast-hole utilization resulting from inappropriate cut blasting layouts during roadway excavation, the empty-hole effect was employed to establish a three-dimensional cut blasting model using FEM-SPH（finite element method-smooth particle hydrodynamics）coupled numerical simulation. In the numerical modeling, the rock mass was described by the RHT constitutive model, which accounts for strain-rate sensitivity and confinement effects under high-strain-rate loading. The explosive was modeled using the Jones-Wilkins-Lee equation of state. A central charged hole was surrounded by four, five, or six empty holes with a spacing of 210 mm determined theoretically. SPH particles were applied to the central zone to capture large deformation, fragmentation, and rock ejection, while the FEM was used for the outer region to reduce computational cost. Non-reflecting boundaries were set to avoid stress wave reflection. The model was then used to simulate and analyze the influence of different cut blasting arrangements on rock mass damage, rock throw efficiency, and fragmentation patterns. Furthermore, field engineering tests were conducted in a copper mine roadway to validate the simulation results by examining the residual hole depth after blasting and the achieved cycle advance. The research findings indicate that a cut blasting layout with one central charged hole and five empty holes provides a moderate number of free surfaces, allowing for more sufficient superposition of stress waves and resulting in better blasting performance. Compared to layouts with four or six empty holes, the five-empty-hole configuration demonstrates optimal rock throw effects, with the slot cavity opening size increasing by 42.5% and 20.3%, respectively, and the slot cavity cross-sectional size improving by 52.4% and 34.7%, respectively. Field test results show that the cycle advance achieved with the five-empty-hole layout is 10.2% and 3.2% higher than that of the four-empty-hole and six-empty-hole layouts, respectively. The research reveals a nonlinear relationship between the number of empty holes and blasting effects, demonstrating that the optimal balance between stress wave superposition and energy concentration can be achieved using a moderate number of empty holes, providing a basis for the design and optimization of cut blasting schemes in roadway excavation.
To address the issues of insufficient cycle advance and low blast-hole utilization resulting from inappropriate cut blasting layouts during roadway excavation, the empty-hole effect was employed to establish a three-dimensional cut blasting model using FEM-SPH（finite element method-smooth particle hydrodynamics）coupled numerical simulation. In the numerical modeling, the rock mass was described by the RHT constitutive model, which accounts for strain-rate sensitivity and confinement effects under high-strain-rate loading. The explosive was modeled using the Jones-Wilkins-Lee equation of state. A central charged hole was surrounded by four, five, or six empty holes with a spacing of 210 mm determined theoretically. SPH particles were applied to the central zone to capture large deformation, fragmentation, and rock ejection, while the FEM was used for the outer region to reduce computational cost. Non-reflecting boundaries were set to avoid stress wave reflection. The model was then used to simulate and analyze the influence of different cut blasting arrangements on rock mass damage, rock throw efficiency, and fragmentation patterns. Furthermore, field engineering tests were conducted in a copper mine roadway to validate the simulation results by examining the residual hole depth after blasting and the achieved cycle advance. The research findings indicate that a cut blasting layout with one central charged hole and five empty holes provides a moderate number of free surfaces, allowing for more sufficient superposition of stress waves and resulting in better blasting performance. Compared to layouts with four or six empty holes, the five-empty-hole configuration demonstrates optimal rock throw effects, with the slot cavity opening size increasing by 42.5% and 20.3%, respectively, and the slot cavity cross-sectional size improving by 52.4% and 34.7%, respectively. Field test results show that the cycle advance achieved with the five-empty-hole layout is 10.2% and 3.2% higher than that of the four-empty-hole and six-empty-hole layouts, respectively. The research reveals a nonlinear relationship between the number of empty holes and blasting effects, demonstrating that the optimal balance between stress wave superposition and energy concentration can be achieved using a moderate number of empty holes, providing a basis for the design and optimization of cut blasting schemes in roadway excavation.
, Available online , 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.
, Available online , 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
, Available online , 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.
, Available online , 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.
, Available online , 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.
, Available online , doi: 10.11883/bzycj-2025-0419
Abstract:
Addressing the high probability of injury and fatality associated with traditionalanti-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 traditionalanti-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.
, Available online , doi: 10.11883/bzycj-2026-0035
Abstract:
Aiming at the problems of complex characteristics of blast load induced by fuel-rich explosives in confined spaces, as well as the high cost of high-precision solution and engineering application, a numerical calculation method for confined blast loading considering the afterburning effect was established. The method was verified for its reliability by comparing the calculated quasi-static pressure, impulse within the saturation response time and residual deformation of the target with the experimental results, with all relative errors controlled within 10%. The spatiotemporal distribution law of confined blast loading in confined spaces was systematically analyzed, and a simplified equivalent loading method considering both the saturation response time and quasi-static pressure was proposed. The reliability of the simplification method was validated by comparing the calculated first peak deformation and residual deformation at the central point with the results from fully coupled calculation, with all errors within 10%. Through an investigation into the spatial distribution form of the equivalent load and the influence of quasi-static pressure on structural response, the results show that within the scope of the current research, the spatial distribution of the equivalent load has a relatively minor effect on structural response, while the contribution of quasi-static pressure cannot be neglected. On the basis of the above findings, a two-stage load simplification model based on the load characteristics at the central point of the target plate was proposed. The reliability of the simplified model was confirmed by comparing the residual deformation values obtained from 10 groups of simplified model calculations with the experimental data, with all errors within 15%. The research results indicate that the proposed model exhibits good applicability under different working conditions; it can significantly improve the calculation efficiency while ensuring the calculation accuracy, and thus provides a technical approach for the simplified analysis of engineering problems related to confined space explosions.
Aiming at the problems of complex characteristics of blast load induced by fuel-rich explosives in confined spaces, as well as the high cost of high-precision solution and engineering application, a numerical calculation method for confined blast loading considering the afterburning effect was established. The method was verified for its reliability by comparing the calculated quasi-static pressure, impulse within the saturation response time and residual deformation of the target with the experimental results, with all relative errors controlled within 10%. The spatiotemporal distribution law of confined blast loading in confined spaces was systematically analyzed, and a simplified equivalent loading method considering both the saturation response time and quasi-static pressure was proposed. The reliability of the simplification method was validated by comparing the calculated first peak deformation and residual deformation at the central point with the results from fully coupled calculation, with all errors within 10%. Through an investigation into the spatial distribution form of the equivalent load and the influence of quasi-static pressure on structural response, the results show that within the scope of the current research, the spatial distribution of the equivalent load has a relatively minor effect on structural response, while the contribution of quasi-static pressure cannot be neglected. On the basis of the above findings, a two-stage load simplification model based on the load characteristics at the central point of the target plate was proposed. The reliability of the simplified model was confirmed by comparing the residual deformation values obtained from 10 groups of simplified model calculations with the experimental data, with all errors within 15%. The research results indicate that the proposed model exhibits good applicability under different working conditions; it can significantly improve the calculation efficiency while ensuring the calculation accuracy, and thus provides a technical approach for the simplified analysis of engineering problems related to confined space explosions.
, Available online , doi: 10.11883/bzycj-2026-0056
Abstract:
To clarify the ultimate load-bearing capacity characteristics of prestressed concrete T-girder bridges under typical blast loads and address the technical difficulties in the residual load-bearing capacity evaluation of blast-damaged bridge structures, a two-stage test method combining blast damage test and post-blast static loading test is adopted in this study. A full-scale (1:1) prestressed concrete T-girder bridge specimen consistent with practical engineering structural parameters is taken as the test object to carry out large-equivalent field blast tests. Multi-stage graded static loading tests are further implemented on the blast-damaged specimen to obtain structural damage evolution features and deflection response data under post-blast service conditions. Based on the measured damage morphologies, deformation data and mechanical response laws acquired from physical tests, a refined three-dimensional finite element (FE) numerical simulation model for prestressed concrete T-girder bridges is established. Key structural characteristics including concrete and reinforcement strain-rate effects, material nonlinearity, prestress loss and structural contact interaction are fully considered in model establishment. The accuracy and reliability of the numerical model are validated through comparative calibration with experimental results. The validated model is subsequently employed to quantitatively investigate the ultimate load-bearing performance of bridges under three typical blast working conditions, including deck central contact blast, combined blast of deck central explosion and inter-girder internal explosion, and bilateral inter-girder internal explosion. The research results demonstrate distinct structural damage and bearing degradation characteristics under different blast scenarios. Contact blast acting on the bridge deck mainly induces local slab perforation failure and concentrated plastic deformation of deck concrete. For internal explosion occurring between main girders, structural damage presents a more severe and extensive pattern. In addition to concrete spalling and fragmentation on the bottom surface of the bridge deck, obvious outward bulging deformation, concrete crushing and local collapse failure occur on the webs and transverse diaphragms of T-girders. Among the three typical blast damage states, the combined blast condition with deck central explosion followed by secondary inter-girder explosion causes the most significant degradation of structural ultimate load-bearing capacity due to the superimposed synergistic damage effect. Reasonable optimization of live load layout effectively avoids severe damage areas of blast-affected bridges, eliminates the adverse influence of blast-induced structural defects, and achieves a remarkable improvement in the ultimate load-bearing capacity of damaged bridges. An integrated evaluation system covering the whole process from blast damage characterization to ultimate load-bearing capacity quantification is established in this research. The proposed evaluation method provides a systematic theoretical basis and feasible technical support for residual load-bearing capacity assessment, damage prediction and blast-resistant reinforcement design of prestressed concrete T-girder bridges suffering blast loads.
To clarify the ultimate load-bearing capacity characteristics of prestressed concrete T-girder bridges under typical blast loads and address the technical difficulties in the residual load-bearing capacity evaluation of blast-damaged bridge structures, a two-stage test method combining blast damage test and post-blast static loading test is adopted in this study. A full-scale (1:1) prestressed concrete T-girder bridge specimen consistent with practical engineering structural parameters is taken as the test object to carry out large-equivalent field blast tests. Multi-stage graded static loading tests are further implemented on the blast-damaged specimen to obtain structural damage evolution features and deflection response data under post-blast service conditions. Based on the measured damage morphologies, deformation data and mechanical response laws acquired from physical tests, a refined three-dimensional finite element (FE) numerical simulation model for prestressed concrete T-girder bridges is established. Key structural characteristics including concrete and reinforcement strain-rate effects, material nonlinearity, prestress loss and structural contact interaction are fully considered in model establishment. The accuracy and reliability of the numerical model are validated through comparative calibration with experimental results. The validated model is subsequently employed to quantitatively investigate the ultimate load-bearing performance of bridges under three typical blast working conditions, including deck central contact blast, combined blast of deck central explosion and inter-girder internal explosion, and bilateral inter-girder internal explosion. The research results demonstrate distinct structural damage and bearing degradation characteristics under different blast scenarios. Contact blast acting on the bridge deck mainly induces local slab perforation failure and concentrated plastic deformation of deck concrete. For internal explosion occurring between main girders, structural damage presents a more severe and extensive pattern. In addition to concrete spalling and fragmentation on the bottom surface of the bridge deck, obvious outward bulging deformation, concrete crushing and local collapse failure occur on the webs and transverse diaphragms of T-girders. Among the three typical blast damage states, the combined blast condition with deck central explosion followed by secondary inter-girder explosion causes the most significant degradation of structural ultimate load-bearing capacity due to the superimposed synergistic damage effect. Reasonable optimization of live load layout effectively avoids severe damage areas of blast-affected bridges, eliminates the adverse influence of blast-induced structural defects, and achieves a remarkable improvement in the ultimate load-bearing capacity of damaged bridges. An integrated evaluation system covering the whole process from blast damage characterization to ultimate load-bearing capacity quantification is established in this research. The proposed evaluation method provides a systematic theoretical basis and feasible technical support for residual load-bearing capacity assessment, damage prediction and blast-resistant reinforcement design of prestressed concrete T-girder bridges suffering blast loads.
, Available online , doi: 10.11883/bzycj-2026-0054
Abstract:
Impact fatigue refers to the phenomenon in which materials or structures, subjected to repeated impact loading, experience localized stress concentrations and rapid strain accumulation, leading to the initiation of internal micro-damage and ultimately the fracture failure. Impact fatigue loads are characterized by their short duration, rapid loading rates and significantly elevated strain-rates, which has greater threat than conventional fatigue. The wheel-rail dynamic contact forces of high-speed trains exhibit typical characteristics of impact fatigue loading, which induces the accumulation of impact fatigue damage, accelerates the deterioration of material’s mechanical properties; and consequently, compromises the operational safety of high-speed trains. The present study integrates a material-based impact fatigue damage-coupled constitutive model to develop a comprehensive three-dimensional wheel-rail rolling contact finite element model. The stress-strain states and adhesion-slip characteristics of wheel-rail rolling/sliding contact are clarified, and the distribution features and accumulation evolution of wheel-rail impact fatigue damage are analyzed. Meanwhile, the effects of train speed, friction coefficient, and traction coefficient on impact fatigue damage are studied, and the influence of material constitutive model on typical wheel-rail contact mechanical behavior is examined. The results clearly indicate that the proposed impact fatigue model is able to well represent the wheel-rail contact responses, adhesion-slip distribution characteristics and damage accumulation. Under repeated rolling contact, the impact fatigue damage of the rail exhibits a nonlinear cumulative increasing trend with the increase of rolling cycles; however, the growth rate gradually decreases and eventually tends to stabilize approximately. Compared with the elastoplastic constitutive model, the wheel-rail contact mechanical responses predicted by the impact fatigue constitutive model are more severe and dangerous. Moreover, the coupling effect of impact fatigue damage gradually intensifies with the increase of wheel passages. These findings provide valuable theoretical insights and technical support for fatigue damage assessment and life prediction of high-speed wheel-rail systems.
Impact fatigue refers to the phenomenon in which materials or structures, subjected to repeated impact loading, experience localized stress concentrations and rapid strain accumulation, leading to the initiation of internal micro-damage and ultimately the fracture failure. Impact fatigue loads are characterized by their short duration, rapid loading rates and significantly elevated strain-rates, which has greater threat than conventional fatigue. The wheel-rail dynamic contact forces of high-speed trains exhibit typical characteristics of impact fatigue loading, which induces the accumulation of impact fatigue damage, accelerates the deterioration of material’s mechanical properties; and consequently, compromises the operational safety of high-speed trains. The present study integrates a material-based impact fatigue damage-coupled constitutive model to develop a comprehensive three-dimensional wheel-rail rolling contact finite element model. The stress-strain states and adhesion-slip characteristics of wheel-rail rolling/sliding contact are clarified, and the distribution features and accumulation evolution of wheel-rail impact fatigue damage are analyzed. Meanwhile, the effects of train speed, friction coefficient, and traction coefficient on impact fatigue damage are studied, and the influence of material constitutive model on typical wheel-rail contact mechanical behavior is examined. The results clearly indicate that the proposed impact fatigue model is able to well represent the wheel-rail contact responses, adhesion-slip distribution characteristics and damage accumulation. Under repeated rolling contact, the impact fatigue damage of the rail exhibits a nonlinear cumulative increasing trend with the increase of rolling cycles; however, the growth rate gradually decreases and eventually tends to stabilize approximately. Compared with the elastoplastic constitutive model, the wheel-rail contact mechanical responses predicted by the impact fatigue constitutive model are more severe and dangerous. Moreover, the coupling effect of impact fatigue damage gradually intensifies with the increase of wheel passages. These findings provide valuable theoretical insights and technical support for fatigue damage assessment and life prediction of high-speed wheel-rail systems.
, Available online , 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%. In the adjacent bedrock zone, damage mitigation is even more evident, with DI decreasing by 95.7% to 95.8%, depending on the specific wave impedance. 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%. In the adjacent bedrock zone, damage mitigation is even more evident, with DI decreasing by 95.7% to 95.8%, depending on the specific wave impedance. 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.
, Available online , doi: 10.11883/bzycj-2025-0401
Abstract:
Coupling coefficients 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 compared. 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. Proposed empirical formulas provide conservative estimates for engineering design, while the underlying mechanisms of free-surface unloading require further quantitative investigation.
Coupling coefficients 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 compared. 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. Proposed empirical formulas provide conservative estimates for engineering design, while the underlying mechanisms of free-surface unloading require further quantitative investigation.
