Blast Damage Research Articles

Investigation on the damage features and dynamic response of reinforced concrete slabs with polyurethane sacrificial cladding under close-range explosions

Sacrificial cladding has been widely used in the blast mitigation and protection of engineering structures, and its protection performance and mechanism have also attracted the extensive research interest of scholars. In order to study the blast damage mitigation effect of polyurethane (PU) sacrificial cladding on reinforced concrete structures, close-range explosion tests of the reinforced concrete slabs with polyurethane sacrificial cladding (PU-RCS) were carried out. At the same time, the reinforced concrete slabs (RCS) without polyurethane sacrificial cladding were set as the control group, and the influence of sacrificial cladding on the damage mode of the reinforced concrete slab was compared and analyzed. In addition, the SPH-FEM coupling model corresponding to the field explosion test was developed and verified by comparison with the test results. On this basis, numerical simulation analysis was used to investigate the dynamic response process of PU-RCS. Furthermore, the effects of the explosive charge and the thickness of polyurethane sacrificial cladding on the damage features of PU-RCS. Based on a large number of numerical simulation analyses, the prediction formula for the mid-span displacement of PU-RCS was proposed. The results show that under close-range explosion, the polyurethane sacrificial cladding can effectively disperse the blast loads, change the damage mode of the reinforced concrete slab, and demonstrate good mitigation ability. The proposed prediction formula can well predict the mid-span displacement of PU-RCS.

Study on a calculation method of the distribution of shock wave in ground buildings under internal explosion

In modern warfare, internal explosions have been taken as the main way of damage to ground buildings. Understanding the distribution of shock waves from an internal explosion is not only the basis of anti-explosion and explosion-proof design of structures but also the key to assess the damage effect of explosions on the battlefield. This paper identifies the propagation law of explosive shock waves in buildings using the LS-DYNA code and employs related test results to fit the engineering calculation algorithm of internal explosion-induced overpressure through numerical calculation, which can be used for the rapid assessment of damage to ground buildings. The development principle and process of the shock wave distribution calculation method are expected to provide a reference for the assess and analysis of blast damage to other ground engineering targets.

Analysis of the Ultimate Load-Bearing Capacity of Steel-Clad Concrete-Filled Steel Tube Arched Protective Doors under Blast Shock Waves

The mechanism of blast damage to steel-clad concrete-filled steel tube (SCCFST) arched protective doors is studied using the dynamic response characteristics of such loads under the action of blast shock wave loads, and the ultimate blast load-bearing capacity formula is derived based on the “plastic hinge” damage mode of the doors using limit analysis, which explores the effect of the blast shock wave. The effect of the design parameters of each component of the protective door on the load-bearing capacity subjected to blast shock waves is discussed. Results show that the damage mechanism under a uniform radial load on the outer surface of the SCCFST arched protective door is characterized by the plastic hinge lines at the two arch feet, which results in a slip fracture and renders the protective door unstable. The load-bearing capacity of the SCCFST arched protective door depends on the coordinated functioning of the cross-sectional outer cladding steel plate and inner connecting partition, concrete-filled steel tube, and restraining concrete outside the steel tube. The load-bearing capacity of each of the three parts differs with the varying cross-sectional occupancies.

Geotechnical analysis of blasting sequence and resulting shapes of drawbells in block cave mines

ABSTRACT Drawbells allow disassembled ore to be extracted from the production levels in block cave mines. As part of the construction process, blast damage must be minimised, enabling the remaining rock mass surrounding the drawbell to sustain the induced stress during the different stages of a block-caving operation for a successful mine plan extraction and ore recovery.This paper proposes two approaches for the geotechnical evaluation of drawbell blast performance. Initially, the expected dynamic burden is calculated along the length of the blasthole and used to assess surveyed blast holes. Secondly, the design compliance is evaluated using the Radial Distance of Over/Underbreak concept, which compares designed and scanned shapes relative to height and radial orientation.The results have identified confined blast zones at the top and around the corners of drawbells. Excessive confinement may cause damage to the pillars and negatively impact the stability of the production level.

Prediction of the pervious surround performance of blast damage zone to reduce groundwater flow in backfilled open-pits

ABSTRACT Reducing groundwater flow in backfilled open-pit to limit interactions of the backfilled wastes with the environment often relies on the creation of preferential flow paths around the disposed wastes in the form of a pervious surround. The blast damage zone, which consists of an enhanced permeability zone near the pit walls, could naturally contribute to creating such preferential flow, thus eliminating the need to build a permeable envelope, reducing costs and maximising the volume for wastes deposition. The objective of this research was thus to propose parameters that could easily be accessed on the field, so practitioners could predict the flow deviation and evaluate if the BDZ is a sufficient containment structure to reduce interactions between backfilled wastes and the environment. Results showed the BDZ deviation could be predicted using the BDZ size and pit wall permeability only, and within a precision of 15% without prior assumptions on the wastes or rock permeability. Three abacuses and one semi-analytical equation were proposed, and several criteria were derived to ensure the BDZ would act as a natural pervious surround. The results of these study should help mining operators and regulatory agencies to assess the BDZ effect on groundwater flow in backfilled open-pits.

Mitigation of the blast load on RC column by hanging granite slabs

Reinforced concrete (RC) column, which is the critical axial load carrying structural component, is vulnerable to blast loads, especially to close-in blast loads. The blast damage of the RC column might lead to the progressive collapse of the whole building structure. Therefore, it is necessary to ensure that the RC column could survive under design blast loads once the building structure is at the risk of terrorist or accidental explosions. One of the solutions is that the RC column is designed to be strong enough to resist the blast loads, which is very expensive. While the other method is to protect the RC column against blast loads with energy absorb materials. The granite slab, which is often used as the decoration hanging outside the structural components, is utilized to mitigate the blast loads applied on the RC column. In this study, firstly the concept of hanging granite slab for mitigating blast load on RC columns is proposed. Furthermore, the finite element (FE) model for simulation of the blast wave interaction with the dry-hanging granite slab is established to reveal the protection mechanism of RC column hanging with granite slab based on the platform LS-DYNA. The accuracy of FE model is validated by comparing the numerical results and the test results from blast field test. The influences of slab thickness T and hanging distance D on blast mitigation are investigated. Finally, the blast load mitigation factors are proposed and their empirical model are established as a function of scaled distance Z, hanging slab thickness T and hanging standoff distance D.

Residual seismic resistance of CFDST columns after a close-in explosion: Experimental study

This paper examines the residual seismic resistance of a concrete filled double-skin steel tube (CFDST) column after a close-in explosion experimentally. First, six 1/4 scaled CFDST columns were fabricated and tested under a close-in explosion with scaled distances ranging from 0.116 m/kg1/3 to 0.232 m/kg1/3. After that, the failure mode and seismic behaviours of the CFDST columns, including one intact specimen, three postblast specimens, and three postblast specimens with retrofitting, were investigated via the cyclic loading test. Additionally, a modified composite damage index was proposed. The results showed that: (i) The CFDST column exhibited a combined localized crater and overall deformation under a close-in explosion, which became more severe as the scaled distance decreased. (ii) As the initial damage degree of the specimen increased, the likelihood of a plastic hinge developing in the blast-induced crater region to consume the hysteretic energy increased. (iii) A weak hinge formed at the crater caused by slight blast damage can assist the plastic hinge induced by the repeated lateral loading to enhance the energy dissipation capacity of the specimen. (iv) In the cyclic loading test, the lateral loading capacity, initial stiffness and energy dissipation of the specimens decreased with the increase in the initial degree of the blast-induced damage. (v) The deformation of the inner steel tube had an unfavourable influence on the stiffness and energy dissipation capacity of the postblast specimen with and without retrofitting. (vi) Among all the specimens, the retrofitted columns exhibited the worst lateral loading capacity, ductility, and energy dissipation capacity due to weld joint failure at the column foot. (vii) When the damage index is less than 0.5, the postblast CFDST column should be retrofitted for further use. In particular, the inner steel tube should be repaired. When the damage index exceeds 0.5, demolishing the postblast CFDST column is suggested.

Blast Damage Simulation With the Discontinuous Galerkin Finite Element Method of Bond-Based Peridynamics

Blast Damage Simulation With the Discontinuous Galerkin Finite Element Method of Bond-Based Peridynamics

Simulation of an explosion-proof bin made of relaxation material

The article discusses the numerical simulation of a blast wave interaction with a relaxation multiphase material used in design of the destructible protection bin with combined method of suppression of the blast damage effects. Numerical simulation of shock-wave systems and processes occurring during the detonation of a condensed high explosive (HE) in semi-open (open at the top) explosion-proof bins was obtained, including when one which uses multiphase gas-liquid material (at a first approximation – water-bubble mechanical foam) as relaxation substance that absorbs the explosion energy and thus reduces the damaging effect of the blast waves.

Functional Changes in the Adult Mouse Retina using an Alpha7 Nicotinic Acetylcholine Receptor Agonist after Blast Exposure

Currently, there is a lack of treatments for retinal neurotrauma. To address this issue, this study uses an alpha7 nAChR agonist, PNU-282987, to determine it effects on functional activity in the retina shortly after a traumatic blast exposure. The objectives of this research include: (1) examination of the cellular and functional damage associated with ocular blast exposure, and (2) evaluation of structural and functional changes that occur post PNU-282987 treatment. Significant ocular blast damage was induced in adult mice after exposure to a single blast of 35 psi to the left eye. Blast-exposed transgenic mice expressing tdTomato Müller glia were treated daily with eyedrops containing PNU-282987 for 4 weeks following the blast exposure. Antibody staining studies in these transgenic mice was conducted to examine lineage tracing and electroretinograms (ERGs) were obtained to examine functional changes. Blast exposure caused a significant loss of cells in all retinal layers after 4 weeks. Immunohistochemical analysis demonstrated tdTomato-positive labeled photoreceptors and retinal ganglion cells in blast-exposed mice treated with PNU-282987. ERG recordings were taken from control animals, from blast-damaged animals and from animals exposed to blast followed by 4 weeks of PNU-282987 treatment. Scotopic ERG recordings from blast-exposed mice had significantly decreased amplitudes of a-wave, b-wave, oscillatory potentials and flicker frequencies, which were prevented after PNU-282987 treatment. In photopic experiments, the PhNR response was reduced significantly after blast exposure but the decrease was prevented after treatment with PNU-282987. These are the first experiments that demonstrate preservation of retinal function after blast exposure using an alpha7 nAChR agonist.

Blast damage zone influence on groundwater fluxes through backfilled open pits

The blast damage zone (BDZ) surrounding backfilled pits could significantly influence groundwater flow, increase flowrate through backfilled wastes, and potentially increase the dispersion of contaminants to the environment. A conceptual model of the fracture network of the BDZ was first proposed, which consisted of circular fracture oriented along the pit walls, and with a decreasing density with the distance to it. Realistic model parameters were also estimated based on the literature; BDZ equivalent permeability was analytically derived and used in 3D numerical models of conic open pits considering different backfilling scenarios. A total of 16 500 BDZ models were generated to assess the general influence of the BDZ on the flow and the influence of each parameter (fracture trace and attenuation length and fracture radius, aperture, and anisotropy). Results showed that the BDZ generally contributes to reduce (up to three orders of magnitude) the groundwater flow through backfilled tailings, but contributes to increase (by up to 250%) the flow in backfilled waste rocks, especially for wide and fractured BDZ in small pits. This study therefore suggests that the BDZ could be a self-sufficient containment structure to limit contaminant transports from backfilled tailings to the environment, but increases the risk considering waste rock.

Attenuation of blast waves from an intense explosion in dusty gases: a case study

An intense explosion in dusty gas is analyzed considering the Beirut ammonium nitrate explosion of 2020 as a case study. The data available from various sources for the Beirut explosion are used to determine the energy released and the possible reduction in damage radius if there were additional dust particles in the atmosphere. The relationship derived in our previous article ( Proc. R. Soc. A 476 , 2020) between the blast radius and the time of arrival of the shock seems quite accurate, and here the energy released by the explosion and the mass of trinitrotoluene (TNT) equivalent based on energy considerations and blast damage are estimated for dusty gases. These estimates depend on Γ , the ratio of specific heats of the dusty gas mixture. The hydrostatic overpressure and dynamic pressure are calculated from previous results by using the data available. The variation of the three dust parameters in the atmosphere, i.e. (i) mass concentration of dust particles ( k p ) , (ii) specific heat ratio ( β ) , and (iii) density ratio ( G ) , gives the estimated TNT equivalence as ≈ 0.1 kt to 2.5 kt up to a distance of 500 m. Enhanced decay and reduced pressure is evident for dusty gases with appropriate dust parameters.

Comparative Study on Blast Damage Features of Reinforced Concrete Slabs with Polyurethane Sacrificial Cladding Based on Different Numerical Simulation Methods.

The defense effects of sacrificial cladding have been extensively studied in the field of blast resistance. As a polymer material with a cellular structure, polyurethane also has the potential to act as sacrificial cladding due to its good mechanical properties. The purpose of this study is to compare and select a numerical simulation method that is suitable for exploring the blast damage mitigation effect of polyurethane sacrificial cladding on reinforced concrete slabs. To this end, three numerical models were developed using the Fully Coupled Eulerian–Lagrangian (CEL) method, the Arbitrary Lagrangian–Eulerian (ALE) coupling method, and the Smoothed Particle Hydrodynamics and Finite Element Method (SPH–FEM) coupling method, respectively. These three numerical models were used to investigate the damage features of reinforced concrete slabs with polyurethane sacrificial cladding (PU–RCS) under contact explosions. A field test was also carried out to provide a comparison for numerical simulation results. Moreover, the advantages and disadvantages of the three simulation results and the applicability of the three coupled models were discussed. The results show that compared with the CEL model and the ALE coupling model, the SPH–FEM coupling model can better simulate the damage features of PU–RCS, such as the cracks on the bottom surface of the RC slab and the large deformation failure state of polyurethane sacrificial cladding, while the CEL model and the ALE coupling model can simulate the propagation process of shock waves and have a lower computational cost. In conclusion, the SPH–FEM coupling method is the most applicable method for exploring the blast damage features of PU–RCS in this study.

Experimental investigation into the close-in blast performance of RC columns with axial loading

The high cost and long consuming time of field blast test result in that the experimental study on the blast performance of reinforced concrete (RC) column subjected to blast loads and axial loading is limited in the previous study which focuses on the numerical investigation. As the critical reference which is utilized to verify the accuracy of the numerical simulation, it is necessary to carry out the experimental study for the RC column subjected to close-in blast loads and axial loadings. In this study, the lateral displacement and failure characteristic of RC column with initial axial loading subjected to close-in blast loads are analyzed based on the field blast test. The influence of charge mass, detonation distance and axial load on the lateral displacement and failure mode of RC column subjected to close-in blast loads is discussed. The experimental result shows that the close-in blast loads can induce serious local damage, which is characterized as the concrete crushing at the front blast surface and concrete spallation at the rear blast surface. The decrease of scaled distance has a negative influence on the close-in blast performance of RC column, while the increase of axial compression ratio has different influences on the close-in blast performance of RC column under different scaled distances. In order to assess the damage degree of RC column subjected to close-in blast loads, the residual bearing capacity test of blast-damaged RC column is carried out. The decrease of scaled distance makes the blast damage degree of RC column transform from low damage to medium damage under the certain combination of scaled distance and axial loads. The increase of axial compression ratio makes the blast damage degree of RC column transform from low damage to medium damage under the certain combination of scaled distance and axial loads.

A conceptual framework integrating numerical simulation with system theory based method for quantitative explosion process hazard analysis

Explosion is a significant threat to chemical process safety, which often occurs suddenly with a wide range of impact, resulting in catastrophic disasters. Predictions of explosion hazards are required for regional safety assessment and disaster resilience enhancement of chemical industrial parks (CIPs). This paper, therefore, aims to develop a conceptual framework for systematically analyzing explosion evolutions and quantifying the potential hazards by combining system-theoretic process analysis (STPA) method with numerical simulation. The proposed framework consists of 5 steps: (i) establishment of hierarchical safe control structures (SCSs) of important chemical processing zones in the CIP, (ii) computational fluid dynamics (CFD) modeling for potential explosion evolutions in each zone by changing the examined parameters randomly, (iii) development of a convolutional neural network (CNN) prediction model through constant self-learning of CFD pressure field data, (iv) comprehensive assessment of blast damage by incorporating the outputs of the above numerical models into existing evaluation methods, (v) identification of unsafety control actions and causes, and safety constraints for the improvement of SCSs. Provided with monitoring data, the developed analysis architecture can predict explosion process hazards and recommend appropriate safety strategies in real time. This would service the multi-level requirements for explosion prevention and protection, supporting better-informed decision-making. The paper describes the concepts and implementation process of the method as a first step.

Review: Atomic Doctors: Conscience and Complicity at the Dawn of the Nuclear Age, by James L. Nolan, Jr.

Review: <i>Atomic Doctors: Conscience and Complicity at the Dawn of the Nuclear Age</i>, by James L. Nolan, Jr.

Combined Effects of Soil Silicon and Host Plant Resistance on Planthoppers, Blast and Bacterial Blight in Tropical Rice.

Simple SummaryRice is often attacked by several herbivores and plant pathogens at the same time. Public research has mainly focused on enhancing rice resistance against these biotic stresses by selecting rice lines with resistance genes during breeding programs. However, rice resistance to biotic stresses is also affected by soil nutrients, including available nitrogen and silicon. Nitrogen tends to reduce resistance, but silicon can increase resistance. We assessed the effects of combining soil silicon with host plant resistance against rice planthoppers, blast disease, and bacterial blight disease. We used pure silicon (SiO2) to avoid the confounding effects of nutrients associated with silicates. We also assessed the effects of nitrogenous fertilizer on silicon-augmented resistance to planthoppers. We found that high nitrogen diminishes the capacity of soil silicon and host resistance to reduce planthopper fitness (i.e., nitrogen was antagonistic); but that silicon counters nitrogen-related reductions in rice antixenosis defenses (e.g., repellency) against gravid female planthoppers (i.e., an additive effect of silicon and resistance). Silicon augmented resistance against blast and bacterial blight, but the effects were most apparent on susceptible varieties. Plants infected with bacterial blight generally grew larger in silicon amended soils. We discuss how silicon improves seedling quality by augmenting broad-spectrum resistance.Soil silicon enhances rice defenses against a range of biotic stresses. However, the magnitude of these effects can depend on the nature of the rice variety. We conducted a series of greenhouse experiments to examine the effects of silicon on planthoppers (Nilaparvata lugens [BPH] and Sogatella furcifera [WBPH]), a leafhopper (Nephotettix virescens [GLH]), blast disease (Magnaporthe grisea) and bacterial blight (Xanthomonas oryzae) in susceptible and resistant rice. We added powdered silica gel (SiO2) to paddy soil at equivalent to 0.25, 1.0, and 4.0 t ha−1. Added silicon reduced BPH nymph settling, but the effect was negligible under high nitrogen. In a choice experiment, BPH egg-laying was lower than untreated controls under all silicon treatments regardless of nitrogen or variety, whereas, in a no-choice experiment, silicon reduced egg-laying on the susceptible but not the resistant (BPH32 gene) variety. Stronger effects in choice experiments suggest that silicon mainly enhanced antixenosis defenses. We found no effects of silicon on WBPH or GLH. Silicon reduced blast damage to susceptible and resistant (Piz, Piz-5 and Pi9 genes) rice. Silicon reduced damage from a virulent strain of bacterial blight but had little effect on a less virulent strain in susceptible and resistant (Xa4, Xa7 and Xa4 + Xa7 genes) varieties. When combined with resistance, silicon had an additive effect in reducing biomass losses to plants infested with bacterial blight (resistance up to 50%; silicon 20%). We discuss how silicon-containing soil amendments can be combined with host resistance to reduce biotic stresses in rice.

Damage assessment of aircraft wing subjected to blast wave with finite element method and artificial neural network tool

Damage assessment of the wing under blast wave is essential to the vulnerability reduction design of aircraft. This paper introduces a critical relative distance prediction method of aircraft wing damage based on the back-propagation artificial neural network (BP-ANN), which is trained by finite element simulation results. Moreover, the finite element method (FEM) for wing blast damage simulation has been validated by ground explosion tests and further used for damage mode determination and damage characteristics analysis. The analysis results indicate that the wing is more likely to be damaged when the root is struck from vertical directions than others for a small charge. With the increase of TNT equivalent charge, the main damage mode of the wing gradually changes from the local skin tearing to overall structural deformation and the overpressure threshold of wing damage decreases rapidly. Compared to the FEM-based damage assessment, the BP-ANN-based method can predict the wing damage under a random blast wave with an average relative error of 4.78%. The proposed method and conclusions can be used as a reference for damage assessment under blast wave and low-vulnerability design of aircraft structures.

Local damage of precast concrete columns with grout sleeve connections under contact detonation

Over the past several decades, the global terrorism is looming large and public buildings have become targets of terrorist bomb attacks. To obtain the blast performance of precast concrete (PC) columns with grout sleeve connections at the background of terrorist attacks, the contact detonation is concerned in this paper. An experimental program with six PC columns and one reinforced concrete column against contact detonation was conducted in a blast testing vessel, in which the effects of charge weight and location as well as connection type of columns on blast damage were studied. Then the finite-element-based (FE) numerical models were built up with LS-DYNA and validated with comparison of experimental results. In the FE model, blast load is simulated using multi-material Arbitrary-Lagrangian-Eulerian (MM-ALE) algorithm. After careful validation, the numerical models are extended to conduct parametric studies, including the effects of longitudinal and transverse reinforcement ratio, column section depth (or aspect ratio), charge weight and location, axial compression ratio on the blast damage of PC columns. Finally, curve-fitting-based models are derived to build up relationships between local damage sizes and the studied parameters, and then verified with part of numerical results. The results show that contact detonation destroyed all the concrete cover at the front face supporting the charge, and resulted in severe spall damage along the four corners and side faces, in which the corner connecting the side and rear face suffered larger damage than that connecting the side and front face. Moreover, the grout sleeves are able to mitigate the damage if the detonation is at the splicing segments. Increasing reinforcement ratio, section depth and axial compression ratio are able to reduce damage sizes, but the beneficial effect differs for the local damage at the column corners and front face.

Blast resistance of a folded arch cross-section immersed tunnel subjected to internal explosion

With the completion of the subsea immersed tunnel of the Hong Kong–Zhuhai–Macao Bridge (HZMB), the tunnel structure in a closed environment for a long time will inevitably be threatened by sudden extreme accidents such as car accidents and car bombs. However, intensive research efforts have been devoted to understanding their performance under service and seismic loads, and the vulnerability of the tunnels against accidental blast loads is seldom discussed. The present study performs an immersed tunnel model of HZMB was constructed at a scale of 1:5 to carry out the explosion test. The results showed that after an internal explosion of a van-type bomb, the roof subsidence of the tunnel model doubled under the same water pressure. The test also revealed that the peak overpressure load on the roof was up to 50 MPa, which showed the multi-peak characteristics, and evident cracks appeared on the top slab and at the junction of the roof and middle wall. In addition, based on the fully verified constitutive model of high strain rate materials, a refined finite element model was established. The propagation characteristics of the blast wave in the tunnel, dynamic response characteristics, and failure process and modes of the tunnel structure were discussed in the developed FE model. The results showed that the ultimate blast resistance of the tunnel model was 41.8 kg TNT (scaled distance is 0.363 m/kg1/3). Furthermore, a resonance effect was observed between the middle wall and roof. The deformation and damage of the roof could be significantly reduced for the explosion height of 1.06–1.25 m. This height range could be very useful for developing traffic standards guiding the safe transportation of hazardous chemicals in tunnels. Based on the numerical and test data, four blast damage levels were finally identified and categorized according to the scaled distance to the tunnel roof.