Blast Damage Research Articles

Numerical simulation of damage effect for runway subjected to explosive loading

In order to study the blast damage effect of kinetic energy warhead. It is concerned with use the hydro code AUTODYN for the simulation of explosive loading interactions to multilayer runway. A study is presented including an investigation of the effect of blasting depth, layer of runway, boundary of target. Comparisons and analysis are made with crater size, crunch area radius, damage area and the peak pressure. Based on this analysis Based on the theoretical analysis and numerical simulation results, Preliminary rule between explosive effect and influence parameter is obtained. The simulated results have reference value for the design of the penetrator and damage evaluation.

Influence of critical parameters on UHPFRC structural elements subjected to blast loading

Response of structures subjected to blast loading is a highly complex phenomena involving time-dependent deformation, geometric and material nonlinearities and loading rate based material properties. During an explosion, blast loads act as an impulsive load of very short duration developing enormous heat and pressure. With increasing terrorist threats, attention is needed to study dynamic response of structures under blast loading. Ultra high strength concrete (UHPC) has been found to considerably enhance strength, member size, weight reduction and workability and is now a day used due to improved energy absorption capacity, workability and anti-abrasion ability. Investigations conducted by several researchers to study blast-resistant capacities of UHPC have demonstrated possibilities of using the material in structures susceptible to terrorist attack. The present paper provides comprehensive review of published research to study blast loading effect on Ultra high performance fibre reinforced concrete (UHPFRC) structural elements in terms of variables like standoff distance, charge weight, types of blast loadings, grades of UHPFRCs, etc., both analytically and experimentally. UHPFRC slab panels, beams, columns, and other fibre composite structures have been studied at structural level to draw fruitful inferences and conclusions. It has been found that UHPFRC possesses increased capacity to disseminate large amount of energy during blast loading and demonstrates better performance after blast damage contrasted with normal strength concrete and High strength concrete. Detailing in UHPFRC structural elements under seismic condition offers improved blast performance, and UHPFRC can more effectively resist compression and shock waves. Low Strength and low ductility fibres added to UHPFRC further illustrates minimal influence on the blast performance and fracture energy. Shear failure is also found to be one of the dominant modes in UHPFRC under blast loading at close standoff. Based on extensive review, further research is proposed to solve complex problems to achieve appropriate design of structural UHPFRC members.

Blast mitigation of RC column using polymeric foam

In the present investigation, the effect of blast load on column of a multi-storied building is studied using Coupled Eulerian Lagrangian (CEL) method with the help of ABAQUS®/Explicit software. Concrete and reinforcement are modeled using Lagrangian formulation while explosive and air are modeled using Eulerian formulation. Jones-Wilkins-Lee (JWL) equation of state is used to define the behavior of TNT modeled herein. Response of the column is measured in terms of deflection at mid-height at varying TNT charge weights. Blast damage is mitigated by fitting the column with a layer of energy absorbing polymeric foam sandwiched with a steel sheet. Further, parametric analysis is conducted considering foam thickness and stand-off distance of the explosive from the column as variables. The results indicate that the displacement reduces significantly on application of foam on the column by absorbing the blast energy up to a considerable amount.

A critical analysis of recent research into the prediction of flyrock and related issues resulting from surface blasting activities

SYNOPSIS Since 2010, a number of researchers have investigated the development of new models to generate accurate predictions relating to the risks from flyrock. The purpose of this paper is to summarize and analyse these recent studies in order to determine the validity of the findings as a global solution. Recent publications have proposed a wide range of potential approaches and techniques to predict or investigate flyrock. Several authors have proposed viable solutions based on assumed causative parameters and their impact as inputs. However, the results were concluded to be site-specific and could not be applied to other environments. Since the actual impact of blast design parameters on the risk of flyrock remains debatable, based on the varying assumptions made in recent research, it is important to use an objective methodology for evaluating the impact of design parameters as well as environmental considerations. The testing methodologies used to measure the actual flyrock distance are not scientific and are highly dependent on the scrutiny of the researcher. In order to present results that are objective and uncriticizable, an accurate, quantitative and objective method of measuring the travel distance of flyrock is required. Keywords: flyrock, flyrock prediction, flyrock measurement, blast safety, blast analysis, blast damage.

Does Tympanic Membrane Perforation Have a Protective Affect on the Inner Ear in Blast-Injured Patients?

Background Blast-induced hearing loss is an acoustic trauma commonly caused by high-energy explosions of improvised explosive devices, and the auditory system may be affected by blast damage. This study aims to evaluate the protective effect of tympanic membrane perforation (TMP) on the inner ear against blast injury. Methods In this study, 43 adult patients who had suffered blast injury were divided into three subgroups: intact tympanic membranes in both ears, unilateral TMP, and bilateral TMP. Each patient underwent a comprehensive audiogram, including bone conduction, in the audiology department. Results Evaluation was performed on 43 (100%) males with a mean age of 31.44±8.01 years (range, 18-52 years). When the type of hearing loss was evaluated separately for each ear, sensorineural hearing loss (SNHL) was observed in 31 (36%), high-frequency SNHL in 26 (30.2%), conductive hearing loss in eight (9.3%), and mixed type hearing loss in 21 (24.4%) ears. TMP was detected in 21 (48.8%) of 43 blast-injured patients, on the right side in four (9.3%) patients, on the left side in seven (16.3%), and bilateral in 10 (23.3%). When the type of acoustic trauma was evaluated, 15 (34.9%) patients were observed to have suffered from the explosion of an IED, 12 (30.2%) from weapon explosion, six (14%) were a vehicle bomb explosion, three (7%) were projectile missile explosion, three (7%) were mortar explosion, two (4.7%) were mine explosion, and two (4.7%) were exposed to the explosion in an armored vehicle (Table 1). Conclusion No significant difference was observed in the majority of the frequencies whether the tympanic membrane was perforated or not in the blast-injured patients and it was concluded that tympanic membrane perforation caused by blast injury had no protective effect on the inner ear.

Evaluating the Impact of Blast‐Induced Damage on the Rock Load Supported by Liner in Construction of a Deep Shaft: A Case Study of Ventilation Shaft of Micangshan Road Tunnel Project

The rock load acting on the lining of an underground excavation is influenced by multiple factors, including rock type, rock mass condition, depth, and construction method. This study focuses on quantifying the magnitude and distribution of the radial loads on the lining of a deep shaft constructed in hard rock by the so‐called short-step method. The blasting‐induced damage zone (BDZ) around the shaft was characterized using ultrasonic testing and incorporated into the convergence‐confinement method (CCM) and 3D numerical analyses to assess the impact of BDZ on rock loading against the liner. The results show that excavation blasting of shafts is an important controlling factor for the degradation of the rock mass, while the orientation and magnitude of the principal stress had a minimal influence on the distribution of blast‐induced damage. The analysis shows that increasing the depth of blast damage in the walls can increase the loads acting on the lining, and the shear loads acting on the liner could be significant for shafts sunk by the short‐step method in an area with anisotropic in situ stresses.

Numerical formulation of P-I diagrams for blast damage prediction and safety assessment of RC panels

A numerical study is carried out to assess the dynamic response and damage level of one- and two-way reinforced concrete (RC) panels subjected to explosive loads by using finite element LS-DYNA software. The precision of the numerical models is validated with the previous experimental test. The calibrated models are used to conduct a series of parametric studies to evaluate the effects of panel wall dimensions, concrete strength, and steel reinforcement ratio on the blast-resistant capacity of the panel under various magnitudes of blast load. The results are used to develop pressure-impulse (P-I) diagrams corresponding to the damage levels defined according to UFC-3-340-02 manual. Empirical equations are proposed to easily construct the P-I diagrams of RC panels that can be efficiently used to assess its safety level against blast loads.

A novel approach to distinguish the uniform and non-uniform distribution of blast loads in process industry

The blast load distribution is an important factor affecting the accuracy of structural damage and domino effect analysis caused by explosions in petroleum and chemical industries. The distribution is usually treated as the uniform or non-uniform and the latter is more suitable for the real scenarios. However, the applicability of the uniform distribution has not been studied in details. In the present study, both the blast load intensity model (BLIM) and blast damage intensity model (BDIM) are developed to represent uniform or non-uniform blast loads quantitatively. Three explosion types (free air burst, air burst and surface burst) and three target structural surfaces (rectangular plates, cylindrical shells and spherical shells) are considered in BLIM and BDIM. The element superposition method based on finite element model (FEM) is proposed, which can solve BLIM and BDIM accurately. Furthermore, the relative difference between the uniform and non-uniform distribution can be obtained on basis of BLIM and BDIM. Finally, the application condition for the rectangular plates - critical stand-off distances with the relative difference of 5%, is defined and verified to distinguish the uniform and non-uniform distribution. The study can provide an insight into the proper application of blast load distribution.

A new calculation model of blasting damage degree—Based on fractal and tie rod damage theory

Based on blasting engineering experience, the damage degree model of a blasting pressure relief zone is constructed. The energy conservation principle is applied in the blasting pulverization zone. The shock wave energy formed via the explosion is divided into surface energy of rock fragmentation and strain energy inside the rock. Consequently, the prediction model of rock fragmentation particle size in the blasting area was established using rock fracture theory. Also, using the rock fragmentation particle size model combined with fractal theory, a calculation method of fractal dimension related to broken rock particle blockiness was proposed. The correspondence between fractal dimension and blast damage degree was established, and the damage degree of the blasting crushing zone was determined. The rock rupture in the blasting rupture zone is along the direction of the initial weak damage, and the damage model of the fracture zone is analyzed using a weak-face parallel bar damage model. Then, the LS-DYNA numerical software and engineering practice are used to fit the theoretical calculation results. The results show that the fits of the two models reach 95% and 94%, respectively, and these results verify the model applicability, providing a new method for studying the evolution law of rock blasting damage.

Controlled blasting in underground construction: A case study of a tunnel plug demolition in the Neelum Jhelum hydroelectric project

Blasting is a popular method of excavation in underground construction. Blast-induced vibrations, however, if not properly controlled, can negatively affect the rock mass surrounding the tunnel. During the drill-and-blast (D&B) excavation of twin headrace tunnels through a major fault zone below the Jhelum River, a 180-m3/h groundwater inflow occurred from the tunnel invert. A 610-m3 concrete plug and high-pressure grouting around the tunnel periphery were formed to stabilize the tunnel and control inflow. To complete the tunnel, the temporary tunnel plug was ultimately demolished using controlled blasting. Ground vibration monitoring data from the regular D&B operations were used to develop a site-specific vibration attenuation model. Using geotechnical data from the feasibility stage and tunnel mappings during construction, a critical particle velocity above which tensile cracking could be initiated was determined for the rock mass surrounding the plug. The critical particle velocity was incorporated into the vibration attenuation model to obtain permissible charge weights to limit blast damage to within a short distance from the charge. Using this approach, an innovative blasting pattern was adopted in which the tunnel plug was sequentially demolished by detonating a burn cut and separate contour blast rows. During blasting, rigorous supervision and data collection helped to record, evaluate, and when needed, adjust the blasting program. Overall, the tunnel plug demolition was completed in a safe and cost-effective manner.

Retrofit scheme of FRP jacketing system for blast damage mitigation of non-ductile RC building frames

Non-ductile reinforced concrete building structures built before the 1970s have been significantly damaged and collapsed under man-made disasters (e.g., blast loads) due to their inadequate column details. The structural deficiencies can be mitigated by a fiber-reinforced polymer jacketing system. This research investigated the blast performance of a low-rise non-ductile building frame strengthened with the jacketing system. Based on the investigation, a retrofit scheme was established to mitigate the blast-induced damage and maximize the effectiveness of the retrofit system. The retrofitted models varied with the main parameters of the retrofit system associated with the confinement effect and flexural stiffness, and blast simulation was performed under various loading scenarios. The retrofit effect was examined in terms of confinement and stiffness ratios. Since the effects of the retrofit parameters on the blast performance depend on the blast loads, the retrofit scheme needs to be established in terms of expected blast loading scenarios.

The effect of blast overpressure on the mechanical properties of the human tympanic membrane

The rupture of the tympanic membrane (TM) is one of the major indicators for blast injuries due to the vulnerability of TM under exposure to blast overpressure. The mechanical properties of the human TM exhibit a significant change after it is exposed to such a high intensity blast. To date, the published data were obtained from measurement on TM strips cut from a TM following an exposure to blast overpressure. The dissection of a TM for preparation of strip samples can induce secondary damage to the TM and thus potentially lead to data not representative of the blast damage. In this paper, we conduct mechanical testing on the full TM in a human temporal bone. A bulging experiment on the entire TM is carried out on each sample prepared from a temporal bone following the exposure to blast three times at a pressure level slightly below the TM rupture threshold. Using a micro-fringe projection method, the volume displacement is obtained as a function of pressure, and their relationship is modeled in the finite element analysis to determine the mechanical properties of the post-blast human TMs, the results of which are compared with the control TMs without an exposure to the blast. It is found that Young's modulus of human TM decreases by approximately 20% after exposure to multiple blast waves. The results can be used in the human ear simulation models to assist the understanding of the effect of blast overpressure on hearing loss.

Influence of Joint Conditions and Blast Design on Pre-split Blasting Using Response Surface Analysis

Blasting is a major method of excavation in mining, civil construction and infrastructure projects. The integrity of the rockmass of the final wall after excavation is important for the stability and economics of the operation. Perimeter blasting achieves a planned surface of the rockmass. The pre-split is one such technique, deployed when there is no free face and, thus, involving several interactions of rockmass properties, including strength, joint spacing and joint orientation, with respect to blastholes, blast design, explosive configuration, blasthole deviations and other variables. The mechanism and models of the pre-split are perfunctory, particularly in defining interactions of pre-splitting variables. The basis of pre-splitting vis-a-vis dominant variables affecting performance is, accordingly, discussed here. Since the half cast factor, generally used for damage assessment, has its limitations, the index of blast damage has been compared while modelling performance. Models using response surface analysis for pre-splitting, for both blast damage index and half cast factor, were developed using historical data. The angle of the blasthole with respect to the major joint orientation, spacing of the joints, blasthole spacing, drill deviation, linear charge concentration and compressive strength has been used to compare the above-mentioned damage criteria. Blast damage index has been found to be a better predictor for determining rockmass damage due to blasting. The desirability of the variables deployed has been determined using optimization procedures. A fresh impetus to pre-split studies is expected to provide a ground for future research, particularly studies using advanced computational and numerical algorithms.

Reprint of “Effects of asteroid property distributions on expected impact rates”

Assessments of the risk posed by asteroid impacts depend implicitly upon estimates of how frequently asteroids of different sizes and properties are expected to strike Earth. These impact rates are generally based upon populations of near-Earth objects as a function of absolute magnitude, which are then translated to equivalent size frequencies by assuming an average albedo. However, this simplified approach neglects the broad distribution of sizes and properties among objects of a given absolute magnitude. In this study, we use a probabilistic asteroid impact risk model to more rigorously investigate the effects of asteroid property distributions on estimated impact rates as a function of diameter, energy, mass, and blast damage radius. We also use impact damage modeling results to compare the effects of the new distribution-based results on expected casualty rates for two sample risk assessment cases. The current study focuses on mid-sized objects with diameters of 20–300m, which could cause substantial local ground damage but are unlikely to produce larger-scale regional or global effects. Particular emphasis is placed on sizes similar to the 1908 Tunguska event, which provides a unique source of evidence for such impacts and is often used as a reference point for damage potential and impact rates in the literature. Results demonstrate that accounting for realistic distributions of asteroid properties can significantly reduce expected impact intervals for these size ranges compared to estimates based on mean albedo, density, and velocity assumptions. These lower impact intervals, in turn, result in higher expected casualty estimates in impact risk assessment applications.

Failure of reinforced concrete and tuff stone masonry buildings as consequence of hydrogen pipeline explosions

Pipelines are the most efficient method of transporting large quantities of hydrogen, and the low volumetric energy density of gaseous hydrogen requires that the gas must be compressed to extremely high pressure to be used as a transport fuel. The failure of high pressure hydrogen gas pipelines and subsequent explosion may induce heavy damage to buildings. In this paper, such an issue is addressed for existing reinforced concrete framed buildings and tuff stone masonry buildings. Physical features such as the gas jet release process, flammable cloud size, blast generation and propagation, and explosion effects on structural components of buildings are considered and evaluated through the SLAB integral model, Multi-Energy Method and pressure‒impulse diagrams. Damage to both types of structural components was evaluated and the maximum distance of blast damage was derived in several environmental conditions, contributing to land-use planning and performance-based design/assessment of pipelines and buildings.

Multivariate evaluation of blast damage from emulsion explosives in tunnels excavated in crystalline rock

Blast damage in tunnels is usually regulated in Swedish infrastructure contracts as it can influence the quality and lifecycle cost for tunneling projects. The topic is important for underground constructions with a long operation period such as tunnels for public transport, permanent access tunnels in mines or underground repositories for nuclear waste. This paper aims to evaluate the influence of design and geology variables on the resulting blast fracture length and frequency by means of multivariate data analysis. The analysis was based on data from five field investigations carried out at tunnel sites in Sweden and Finland where emulsion explosives were used. Data was compiled and analyzed using Principal Component Analysis (PCA). Charge concentration was found to be the most influential design variable and hole spacing had limited influence on blast fracturing. Results from the PCA suggest that blast fractures length could be dependent also on geology and natural fractures. Three main groups of fracture patterns were identified, one group with relatively few and short blast fractures, a group with several longer blast fractures and a group with few or a single long blast fracture. The result shows differences in fracture length between the column and bottom charge part of the contour holes, with blast fracture lengths up to approx. 40 cm for the column charge and up to approx. 60 cm for the bottom charge.

Numerical investigation of the impact of rock mass properties on propagation of ground vibration

Ground vibrations induced by the blasting of explosives can cause damage to the slope stability of mines. The important indicators of rock mass such as the geological discontinuities, physical and mechanical properties of rock can affect the creation and prediction of blast damage. This paper aims to assess the simultaneous effects of the above properties. For that purpose, peak particle velocity as the indicator of damage at two rock slopes was examined through a three-dimensional distinct element code (3DEC). The developed model simulated the dynamic pressure of detonation and provided useful results for analysis. The qualitative analysis demonstrated how significant it is to incorporate the rock mass properties in the model. Moreover, a statistical analysis was performed to quantify the effects of these properties. Therefore, the distance from blast, dip/direction of discontinuities, blast damage factor (Hoek–Brown failure criterion) and Geological Strength Index have the most influences on the slope damage, respectively. The moment failure analysis of 3DEC explained the Shear–Tension and Shear–Shear failures associated with the rock mass damage caused by blasting. The dip/direction of discontinuities plays a major role in the control or propagation of dynamic pressure and should be considered in blast damage control. If necessary, artificial discontinuities such as pre-splitting should be employed for better control and use of the favorable effects of geological discontinuities.

Three-dimensional Numerical Analysis of Blast-induced Damage Characteristics of the Intact and Jointed Rockmass

This article reports numerical results investigating the damage evolution and spatial distribution characteristics of intact and jointed rockmass subjected to blast loading. The behaviors of rock material are described by the Holmquist- Johnson-Cook (HJC) constitutive model incorporated in the finite element software LS-DYNA. Results indicate that the damage distribution shows a reverse S-shape attenuation with the increase of the distance from borehole, and a better goodness of fit with the Logistic function is observed. In the single-hole blasting of jointed rockmass, there are two types of regions around the intersection of borehole and joint in which the damage degree is quite different. The crushing damage develops in a Ψ-shape path along the joint. In the radial direction, the crushing damage and cracking damage of rock show different distribution forms with the increase of joint dip angle. As for the double-hole blasting, due to the superposition of the blast waves, the damage degree in the region between the two boreholes of intact rockmass is significantly large. For jointed rockmass, the joint has local enhancement or inhibition effect on the blast damage in the region between the two boreholes.

Structural damage analysis of explosive testing experimental bay using HEXDAM Modelling software

Modelling of structural damages is a tool for making blast damage assessments resulting from an explosion on a localized area. This can be used as a damage/ injury assessment tool to determine the amount of blast damage/injury done to individual structures/ persons in a certain geographical area due to the detonation of explosives at ground level or at a specified height above the ground. This paper deals with prediction the structural damages of an experimental bay building when subjected to explosive testing, using HEXDAM (High Explosive Damage Assessment Modelling) software. The modelling software helps to predict the blast parameters at various points and the structural damages caused to the structures with in a facility. The basic outputs of HEXDAM are designed to provide data such as before/after blast display; damage/injury table; damage vs distance; pressure contours; damage/injury contours and the data tables for overpressure, dynamic pressure and damage/injury at each grid point. The experimental bay building along with the facility building was scientifically modelled with the trial set up using this software. The structural damages to the experimental bay and the nearby facilities are analysed when the building set up is subjected to the explosive loading at the height of 1m. The over pressure data at various points from the ground level to the height of 9m have been generated in this modelling. The Outputs are in the form of Damage vs injury tables, before and after blast displays, pressure and damage vs injury contour plots and Damage, injury-versus-distance graphs.

Effects of asteroid property distributions on expected impact rates

Assessments of the risk posed by asteroid impacts depend implicitly upon estimates of how frequently asteroids of different sizes and properties are expected to strike Earth. These impact rates are generally based upon populations of near-Earth objects as a function of absolute magnitude, which are then translated to equivalent size frequencies by assuming an average albedo. However, this simplified approach neglects the broad distribution of sizes and properties among objects of a given absolute magnitude. In this study, we use a probabilistic asteroid impact risk model to more rigorously investigate the effects of asteroid property distributions on estimated impact rates as a function of diameter, energy, mass, and blast damage radius. We also use impact damage modeling results to compare the effects of the new distribution-based results on expected casualty rates for two sample risk assessment cases. The current study focuses on mid-sized objects with diameters of 20–300 m, which could cause substantial local ground damage but are unlikely to produce larger-scale regional or global effects. Particular emphasis is placed on sizes similar to the 1908 Tunguska event, which provides a unique source of evidence for such impacts and is often used as a reference point for damage potential and impact rates in the literature. Results demonstrate that accounting for realistic distributions of asteroid properties can significantly reduce expected impact intervals for these size ranges compared to estimates based on mean albedo, density, and velocity assumptions. These lower impact intervals, in turn, result in higher expected casualty estimates in impact risk assessment applications.