Effects Of Blast Waves Research Articles

Use of explainable machine learning models in blast load prediction

The effects of blast waves and their consequent damage to structures have been an increasingly popular research topic in the past decade. Various methods are used in blast load prediction on structures, including experimental, semi-empirical and numerical approaches. However, there is a demand for developing time-efficient predictive methods that help various professionals, such as engineering practitioners and first responders, in their regular activities. Machine learning (ML), as a subset of artificial intelligence (AI), has gained significant attention in various engineering applications over the past decades for its ability to aid decision-making. However, a critical gap exists in the comprehensive analysis of these ML models' transparency and interpretability levels. This paper presents a novel approach to employing explainable machine learning (XML) to predict the blast loads generated by high explosives. The primary objective is to assess the validity of utilising a machine learning (ML) framework for blast load predictions, examining the scientific consistency of the model's prediction process. This research utilises XML to interpret the ML model-based blast load prediction framework, marking the first documented use of XML in published literature for blast load prediction. This research study utilised three ML models, namely a) Decision Tree, b) Random Forest, and c) Extreme Gradient Boost (XGB) models, to predict blast loads on rigid structures. Validated numerical model results were used to generate the dataset to train the ML models, and the respective dataset consists of approximately 600 independent blast events. The models were evaluated for their predictability using error metrics: adjusted coefficient of determination (adjusted R2), root mean square error (RMSE), and mean absolute error (MAE). The overall ML model performance evaluation showed that the best-performing model, XGB, could make predictions with 98 % accuracy compared to validated numerical predictions. The XML explanations for the XGB models showcased that the blast load prediction procedure of the models aligns with the blast physics principles, ensuring the credibility of the developed ML models. In summary, these XML predictive models can be considered accurate and reliable for blast load prediction on structures.

Effect of blast orientation, multi-point blasts, and repetitive blasts on brain injury

Explosions in the battlefield can result in brain damage. Research on the effects of shock waves on brain tissue mainly focuses on the effects of single-orientation blast waves, while there have been few studies on the dynamic response of the human brain to directional explosions in different planes, multi-point explosions and repetitive explosions. Therefore, the brain tissue response and the intracranial pressure (ICP) caused by different blast loadings were numerically simulated using the CONWEP method. In the study of the blast in different directions, the lateral explosion blast wave was found to cause greater ICP than did blasts from other directions. When multi-point explosions occurred in the sagittal plane simultaneously, the ICP in the temporal lobe increased by 37.8 % and the ICP in the parietal lobe decreased by 17.6 %. When multi-point explosions occurred in the horizontal plane, the ICP in the frontal lobe increased by 61.8 % and the ICP in the temporal lobe increased by 12.2 %. In a study of repetitive explosions, the maximum ICP of the second blast increased by 40.6 % over that of the first blast, and that of the third blast increased by 61.2 % over that of the second blast. The ICP on the brain tissue from repetitive blasts can exceed 200 % of that of a single explosion blast wave.

Dynamic behaviors of concrete gravity dam against combined blast wave and bubble pulsation of underwater explosion

Underwater explosion process mainly includes the preceding blast wave and the succeeding bubble pulsation, while the effect of bubble pulsation on hydraulic structures is always neglected. This paper aims to numerically study the dynamic behaviors of prototype concrete gravity dam against underwater explosion, considering the combined effects of blast wave and bubble pulsation. Firstly, a finite element analysis (FEA) approach for predicting the underwater explosion loadings, as well as the damage evolution and dynamic responses of dam against underwater explosions was proposed, in which the hydrostatic pressure of reservoir and the dead load of dam were considered. Based on Cole's formula and the existing underwater explosion tests, the reliability of FEA approach, including the mesh sizes, material models and the corresponding parameters, as well as the mapping, Fluid-Structure Interaction and contact algorithms, was comprehensively validated. Secondly, to realize the simulation of the prototype gravity dam impeded by the validated small Lagrange mesh size, a mesh transition strategy was proposed based on the equivalence of dam damage modes and total eroded element mass. Finally, the dynamic behaviors of a typical 120 m-height concrete gravity dam against underwater explosion, i.e., 1 t of TNT equivalence detonated at a depth of 35 m and standoff distances of 4–16 m, were examined. The dimensionless distance λR, i.e., the ratio of the standoff distance to the maximum bubble radius, was introduced to quantitatively evaluate the underwater explosion loadings and dynamic behaviors of the dam. It indicates that, the blast wave firstly leads to the local compressive damage on the upstream surface, as well as the tensile damage on the downstream folded slope and dam heel. The succeeding free vibration and bubble pulsation will further aggravate the damage degree, resulting in the cracking of dam neck and heel. Especially for the scenarios when λR ≤ 1.22, the overall sliding of dam is highly prone to occur.

Comparative study of the influence of charge shapes on the distribution of blast pressure on a structural unit

Since limited research results are available in the area of blast wave interactions with structural surfaces, a comparative study is undertaken to ascertain the interaction effects of blast waves generated by exploding spherical and cylindrical charges on the surface of a concrete structural unit. The effective blast pressure experienced by a concrete unit is evaluated and its distribution across the front face is studied here for two distinct charge shapes, namely spherical and cylindrical. The finite element analysis is carried out for nine different scaled distances. Random forests algorithm was utilized to analyze the 450 observations to evaluate the results and build predictive models. The best models were selected based on standard performance indicators. For cylindrical charges, the aspect ratio was also factored in the analysis. The distribution of effective pressure indicates unique patterns for the two different charge shapes in the graphical comparison. The effective pressures caused by the cylindrical charge shape for the specific aspect ratios considered here are lower by 84 % on average compared to the effect caused by a spherical charge, which results from the distinct characteristics of blast waves generated by the explosion of cylindrical charges.

The fatal effect of shock waves on the head of a person wearing a polyurea-reinforced ballistic helmet

Ballistic helmets are an important part of personal protective equipment in war and are specifically designed to protect a person’s head. The future trend is to improve the protective performance of helmets through the use of lightweight coatings, and polyurea, as one of the hottest elastomeric polymer coating materials in recent years, has excellent physical properties, especially its ability to improve the target’s protection against blast shock waves. Therefore, in this study, using a validated head model, a blast impact model under the fluid-solid coupling method was constructed to study the effect of blast wave on the model and to analyse its effect on intracranial pressure and skull deformation. In addition, the effect of the position of the polyurea lightweight protective coating on the bending deformation of the skull under the effect of the blast wave was also investigated. The results showed that the polyurea coating could reduce the skull deformation under the same surface density condition. However, spraying polyurea on the blast surface of the helmet’s blast-facing surface does not effectively reduce skull deformation caused by blast waves.

Symmetric multipath branching as a layout design strategy for blast-resilient tunnel structures

Explosions can result in massive fatalities and severe damage to structures and facilities in tunnels. Therefore, it is of crucial importance to incorporate disaster mitigation strategies against potential blast scenarios in the design of such structures and implement viable solutions to attenuate the destructive effect of blast waves caused by explosions. To this end, we propose an innovative layout design strategy called symmetric multi-path branching, where multiple closed-end paths with relatively small cross-sectional areas branch out laterally from the sides of a straight and prismatic tunnel. To exploit the neutralizing effect of colliding pressure waves, a reflective symmetry with respect to the longitudinal mid-plane of the tunnel is considered in the layout design. To examine the effectiveness and efficiency of this strategy in reducing the effect of the pressure wave caused by the explosion, a series of layout designs are produced and investigated numerically and experimentally. After verifying the simulation method, the effect of the branching angles, cross-sectional geometry, drilling depth, and location of the branches, as well as the mass of the explosive charge, are studied systematically. The results illustrate an acceptable match between the numerical and the scaled experimental test methods. Moreover, it is shown that using three pairs of branches with an appropriate geometry and branching angles can attenuate the pressure waves passing through the tunnel up to 50% without obstructing the main route. The findings of this study can be applied to designing blast-resilient layouts in the development of underground tunnels and other corridor-like structures.

Geometric modeling of blast waves reflected from the cylindrical surface of a sineusidal profile

A method is proposed for geometric modeling of a family of blast wave fronts reflected from a cylindrical surface of a sinusoidal profile. The model of “optical” reflection is adopted as a basis, when for each incident virtual explosive “ray” the angle of reflection is equal to the angle of incidence. To illustrate the graphic-analytical approach, a test model of the formation of a family of reflected wave fronts for a cylindrical parabolic surface has been developed. A cylindrical surface of a sinusoidal profile obtained by bending a rectangular metal sheet by longitudinal forces is considered. Geometric models of a family of blast wave fronts reflected from a cylindrical surface of a sinusoidal profile are described. Maple has been compiled – programs for visualizing models of a family of blast wave fronts reflected from a cylindrical surface. Conducted studies of sinusoidal cylindrical reflectors designed to demonstrate the effect of multiplying the effects of shock blast waves directed towards the fire zone. For their practical use, it is necessary to find the bending parameters of the cylinder such that the virtual beams of the “point” explosive are transformed into a system of beams that are close to parallel in the fire zone. As a result of the research, the parameters of bending of a metal rectangular sheet by longitudinal forces were calculated, and the coordinates of the location of the “point” explosive substance were determined. It is taken into account that cylindrical reflectors with a sinusoidal profile can be manufactured at the site of their use. To do this, a rectangular sheet of metal must be bent by longitudinal forces and the bend must be fixed by welding reinforcement rods. The research carried out is aimed at developing the technology of extinguishing forest fires with directed explosions.

Roadways fracture response under varying dominant blasting frequencies and lateral pressure coefficients

Dominant frequency of blasting waveform attenuates with increasing propagation distance, leading to diverse diffractive effects on a roadway located in different sublevels. To investigate the roadway fracture characteristics in response to varying blasting wave frequencies and geo-stresses. Numerical simulation and experiments were performed by using discrete element methods and acoustic emission (AE) techniques, respectively. Roadway response differences in terms of microcracks propagation regions were primarily investigated, to reveal the relationships between damage-prone regions and the lateral pressure coefficient and blast waveform frequencies. The results showed that the excavation damage zone (EDZ) and the types of microcracks developed are primarily influenced by the principal stress direction. Low-frequencies blast waves contribute significantly to the overall damage to the surrounding rock around the roadway, while high-frequencies blast waves mainly damage the sides of the facing blast. Under the coupling effect of principal stress and blast wave, microcracks are more prone to generate in regions coupling with high-stress concentration regions induced by principal stress and disturbed regions diffracted by blast waves. With the results from this study, the roadway support should consider the difference in damage-prone regions triggered by blasting waves with varying dominant frequencies under different lateral pressure coefficients.

Modeling and analysis of domino effect in petrochemical storage tank farms under the synergistic effect of explosion and fire

The synergistic effect of explosion and fire (SEEF) is one of the challenges of domino effect risk assessment for petrochemical storage tank farms. However, the domino effect probabilities at different orders and accident propagation patterns in storage tank farms under the SEEF are still unclear. An approach based on Bayesian networks is developed to model the propagation of domino effects in storage tank farms under the SEEF. The method accounts for the temporal and spatial synergistic effects of blast wave and fire thermal radiation in multiple accidents during domino accident escalation and the damage enhancement effect caused by the SEEF on the target units. Application of the method to a real tank farm highlights that the SEEF has a significant impact on the domino effect probabilities. Compared with only considering a single accident type, the SEEF leads to an increase in the domino effect probabilities of the tank farm. Installing water deluge systems and blast walls for all tanks at the same time is an effective safety measure to mitigate domino effects due to the SEEF. When safety resources are limited, the priority to equip critical tanks with water deluge systems and blast walls can also mitigate the domino effects.

Performance of honeycomb sandwich structure under combined blast and impact of fragments

The response of sandwich structures under the synergistic effects of blast wave and fragments is a topic of interest for researchers and designers. Thus, the performance of a sandwich structure used for enhancing the protection of a target structure is numerically investigated because it may experience such complex loading conditions resulting from combined blast and fragment impact. A conventional sandwich structure modelled using aluminium alloy resists a bare blast load imposed on it. Analysis, however, reveals that fragments penetrate through the front facesheet of a conventional sandwich structure, indicating a lower resistance of the front facesheet to combined blast and fragment effects. Thus, the behaviour of conventional aluminium honeycomb sandwich structures is compared with enhanced sandwich configurations consisting of a front facesheet covered with multilayer lightweight composite Kevlar fabric material. The Kevlar fabric arrests the maximum number of fragments, and reduces their momentum, thereby reducing the damage level in the sandwich structure. The effect of the charge weight and shape of the fragments on the damage modes of the sandwich structure is also assessed. With the increase in charge weight, the momentum of the fragments is found to increase, and these penetrate the back facesheet of the sandwich structure.

Failure mode and blast resistance of polyurea coated metallic cylinders under internal multi-field coupled loading

The failure mode and blast resistance of polyurea-coated metallic cylinders were investigated under internal multi-field coupled loading. Experiments were conducted to study the synergistic effect of detonation products, blast waves, and fragments loadings, as well as the following damages on polyurea-coated cylinders. The results indicated that polyurea coating could not only reduce substrate deformation and damage caused by shock waves and products, but also prevent fragment dispersion due to its excellent glassy transition capabilities. Micromorphology failure revealed that the glassy transition of polyurea was initiated by fragments penetration, and shock waves were responsible for the tension failure and extension of the penetration hole. The verified finite element mode was utilized to perform equivalent numerical simulations of the tests, allowing for further analysis of the cylinder response. Simulation results revealed that severe perforation and local damage were caused by the first arriving high-velocity fragments, while the following shock wave and detonation products exacerbated the previous damage and crack propagation. Damage extension and the synergistic effects of coupled loading were reduced owing to the glassy transition of the polyurea coating, which prevented fragments in their tracks, and the coating’s superelastic properties, which limited the substrate cylinder’s expansion during shock waves.

Nuclear explosion impact on humans indoors

This study investigates the nuclear blast effects on humans inside a building within a moderate damage zone. These effects depend on many parameters that must be better understood. In addition, the nuclear blast effects will spread further away than the devastating destruction zone, where most people are killed instantly. However, these injuries will vary depending on a person's position in the building and the air velocities attained when the blast wave enters indoors. The blast wave effects are examined for an indicative, easily reproducible indoor arrangement. The airspeed behind the blast wave accelerates to even higher velocities in the interior. The supersonic shock waves arising from the blast undergo expansion as they enter a room through an opening leading to channeling effects. The results show that most of the air is directed toward the corridor rather than through the opposite room's door, leading to high airspeed developed in rooms further down the aisle. The airspeed attained in the interior is calculated for two blast wave overpressures, 3 and 5 pounds per square inch, for which most concrete buildings do not collapse. The data reveal that the force applied to a standing person from the speed of the gusts formed at several locations in the interior is equivalent to several g-forces of body mass acceleration capable of lifting and throwing any person off the ground. It is then the impact onto solid surfaces that can lead to severe injury or death. Finally, the results reveal preferential areas in the rooms where a human can avoid the risk of exposure to the highest wind forces.

Study on chest injury and bulletproof vest protection under the combined action of blast wave and fragments

Using a simulation based method, this paper analysis the damage effect of blast wave and fragments on human body and the protective effect of bulletproof vest. The results show that compared with the single blast shock wave, the chest injury is more serious under the combined action of blast shock wave and fragments. The peak stress of sternum, costal cartilage and rib increases by 334.34%, 170.23% and 39.72%, respectively. The peak stress on the side of the lung decreases by 3.95%, with little change. The peak stress on the front and back of the lung increases by 83.58% and 409.09% respectively. Overall, the lung injury is aggravated. With the addition of the bulletproof vest, the damage caused by fragments is reduced, and the peak stress of the sternum and the costal cartilage decreases by 48.77% and 69.78%, respectively. Due to the interaction of the blast wave with the vest and the chest, the damage caused by blast wave is aggravated. The peak stress of rib increases by 13.55%, and the peak stress of lung front, side and back increases by 1.22%, 6.51% and 3.57%, respectively.

Blast enhanced façade design by means of an optimal balance between security and sustainability

The major objective of this paper is to show that glazed curtain wall has a surprising potential for blast enhancement. However, often this potential is partially lost because of inaccurate and only presumed safe side approach. Indeed, in curtain wall it is much important to assess properly the beneficial effect of the deformable supports, framing and possibly brackets, on the glazing response under blast wave effects. Only in this way a true balanced design approach can be carried out and the protective requirement can be integrated into the façade design by preserving the architectural requirements, comfort, classical energy efficiency requirements and novel demand for sustainability. On the other side the large variability of materials and component behaviour under nonlinear range and the uncertainties related to the blast threat recommend a flexible calculation tool, which must be coupled with a sensitivity analysis on the most relevant inputs. For this reason, a Multi Degree of Freedom approach shows several advantages with respect to the Explicit Dynamic Finite Element Analysis, considering also the large number of geometry, component design and blast load variations are existing in a typical application of the protection on a high rise building. The impact of the calculation method is demonstrated by means of a comparative exercise and by means of real case applications.

Dynamic responses of steel cylindrical tanks subjected to sequential loadings of earthquake and explosion

The earthquake-explosion sequence is one of the typical multi-hazard coupling scenarios in chemical industrial parks (CIPs), of which hazardous installation units are easily damaged by the combined loadings. However, the structural dynamic responses behavior is extremely complex and associated with non-stationary relations. It is still challenging to capture a clear insight into the structural failure caused by sequential multi-hazards. This work focuses on the damage amplified phenomena of the steel cylindrical tank under the earthquake-explosion sequence. Specifically, a consecutive coupling approach is established, considering the interaction between the tank and stored liquid. The coupling effects of earthquake loading and blast wave on the deformation characteristics, stress response, energy absorption, and anti-blasting ability of the tank are investigated. Additionally, the effects of the seismic intensity and explosion intensity are analyzed. The results indicate that the failure of the tank probably appears in the upper portion under combined loadings. Compared to the tank without earthquake action, the seismic damage status results in multiple stress concentrations. The dynamic responses of the seismic damage tank under explosions are higher, which are 1.0–2.4 times than the case without earthquake action. Moreover, with the explosion intensity decreasing, the damage amplification effect of the tank under combined loadings becomes more apparent. Negative pressure and the impact of convective pressure formed by the liquid sloshing are the main factors causing the depression deformation of tank structure under the coupling effect. With the plastic deformation of the tank caused by earthquakes, the anti-blast performance of the tank will further reduce. The coupling scenarios of bi-directional earthquakes will cause more severe consequences than the uni-directional earthquake, while there are no significant differences in the coupling amplification effects in this work. These conclusions contribute to exploring the complex failure mechanisms of the tank exposed to post-earthquake explosion scenarios.

Escalation probabilistic model of atmospheric tank under coupling effect of thermal radiation and blast wave in domino accidents

Statistical analyses of accidents have suggested that fires are frequently accompanied by explosions in domino accidents at atmospheric storage tank farms. Owing to the complexity of the escalation probability under the coupling effect of multiple accidents, determining an escalation criterion is of considerable significance for high-accuracy risk assessment of an accident chain. In this study, by establishing the propagation mode of domino accidents and calculating their physical effects, an escalation probability model under the coupling effect of thermal radiation and blast waves is constructed based on a dynamic Bayesian network. To verify the rationality of the model, it is compared to Cozzani's model under a single thermal radiation by conducting case studies. The escalation probability at each stage of a domino accident was calculated using the two models; the results indicated that the former reached 303 times that of the latter in 30 min. Finally, the influence of the layout on the domino accident was studied. The results indicated that the maximum deviation of different layouts on the total escalation probability of the domino accident reached 181.4%. Therefore, the coupling effect between different accidents should be considered for domino accidents. Tank layout should be considered during construction, alteration, and expansion.

Effect of minocycline and its nano-formulation on central auditory system in blast-induced hearing loss rat model

Blast injuries are common among the military service members and veterans. One of the devastating effects of blast wave induced TBI is either temporary or permanent hearing loss. Treating hearing loss using minocycline is restricted by optimal drug concentration, route of administration, and its half-life. Therefore, therapeutic approach using novel therapeutic delivery method is in great need. Among the different delivery methods, nanotechnology-based drug delivery is desirable, which can achieve longer systemic circulation, pass through some biological barriers and specifically targets desired sites. The current study aimed to examine therapeutic effect of minocycline and its nanoparticle formulation in moderate blast induced hearing loss rat model through central auditory system. The I.v. administered nanoparticle at reduced dose and frequency than regularly administered toxic dose. After moderate blast exposure, rats had hearing impairment as determined by ABR at 7- and 30-days post exposure. In chronic condition, free minocycline also showed the significant reduction in ABR threshold. In central auditory system, it is found in this study that minocycline nanoparticles ameliorate excitation in inferior colliculus; and astrocytes and microglia activation after the blast exposure is reduced by minocycline nanoparticles administration. The study demonstrated that in moderate blast induced hearing loss, minocycline and its nanoparticle formulation exhibited the optimal therapeutic effect on the recovery of the ABR impairment and a protective effect through central auditory system. In conclusion, targeted and non-targeted nanoparticle formulation have therapeutic effect on blast induced hearing loss.

Computational performance evaluation of sacrificial protective walls composed of lightweight concrete blocks: a parametric study of blast loads in a tunnel

Sacrificial wall systems consisting of lightweight concrete blocks have several advantages including versatility and high installation speed, making them effective tools for reducing the destructive effects of blast waves. Particularly, in confined structures, they can be placed along the path of potential explosion waves such that internal failure mechanisms in the concrete blocks cause the explosion wave energy to be dissipated. Numerous factors can affect the performance of such wall systems, including the material properties, location, and physical dimensions of the concrete blocks. This research presents an in-depth computational study on parameters influencing the performance of such sacrificial wall systems.

Numerical Analysis of Blast Effects and Mitigation in the Far-Field from Small Explosions

Requirements for explosive safety are often given in terms of a “K-Factor”, correlating incident blast effects with the distance and TNT equivalent weight of an explosion. Traditionally, this is conducted using empirical correlations to experimental measurements (e.g., the Kingery–Bulmash equations). In the far-field, empirical verification of incident overpressure and impulse magnitudes can be difficult; extrapolations from data give expected values at reasonable standoff distances that sometimes are too small to measure on available equipment but are larger than some regulations require. The present paper describes the results of numerical hydrocode analysis to verify the expected incident overpressure and impulse from small hemispherical ground charges of TNT at these relatively large distances. Furthermore, the dynamic effect of incident blast waves on lightweight, modular mitigation barriers is studied to gauge their effectiveness at providing safety standard compliance.

Experimental Study on Intracranial Pressure and Biomechanical Response in Rats Under the Blast Wave.

Explosion overpressure propagates extracranially and causes craniocerebral injury after being transmitted into the brain. Studies on the extent of skull to reduce impact overpressure are still lacking. Therefore, it is necessary to study the relationship between intracranial pressure (ICP) and external field pressure and the situation of craniocerebral injury under the blast wave. Pressure sensor of 1.2 mm was disposed 3 mm posterior to the bregma of rat skull, and type I biological shock tube (BST-I) was used as the source of injury while a side-on air pressure sensor was installed at the horizontal position of the ICP sensor. Eleven groups of blast experiments with peak air overpressure ranging from 167 kPa to 482 kPa were performed to obtain the variation law of ICP and injury of rats. Data measured by sensors show that the peak pressure formed in the rat brain are lower than the external air overpressure; the differential pressure between the inside and outside of the brain is 27-231 kPa. When side-on air overpressure is ≤363 kPa, ICP is ≤132 kPa, and the hemorrhage area of the rat's brain is <15%, the injury is minor. When side-on air overpressure is 363 kPa-401 kPa, ICP range is from 132 kPa to 248 kPa, hemorrhage area is about 15%-20%, and the injury increases. When side-on air overpressure is 401 kPa-435 kPa, ICP range from 248 kPa to 348 kPa, the hemorrhage area is about 20%-24%, and the injury is serious. When side-on air overpressure ≥482 kPa, the peak ICP surged to 455 kPa and the peak negative ICP reached -84 kPa, the hemorrhage area exceeded 26%. When the external blast wave is weak, skull can absorb the blast wave better, reducing the pressure by 81.4%, when the external shockwave is strong, skull only reduces the pressure by 5.6%, but both can play certain protective role. The fitting curve of air overpressure and ICP can be used to predict the changes of ICP under different external blast overpressure. Analysis of cranial injury showed that the area of cranial hemorrhage with extremely severe injury increased by 107.9% compared with mild injury, increased by 53.3% compared with moderate injury, and increased by 21.6% compared with severe injury. This work may provide references for the dynamic response of biological cranial and brain injury mechanism under the effect of blast wave.