Explosive Type Research Articles

FDEM simulation of rock damage evolution induced by contour blasting in the bench of tunnel at deep depth

One highly effective approach for tunnelling in rock at deep depth is blasting. The damage and in-situ stress redistribution in the surrounding rock mass induced by the blast loading during this process is, however, unavoidable. In this study, a powerful GPGPU-parallelized combined finite-discrete element method is implemented to study the damage evolution during controlled contour blasting in the bench of a deep-buried tunnel. The proposed method is characterized by the simulation of the blasting-induced pressure variation via the pressure-gas volume history curve and the modelling of the transition from continuum to discontinuum behaviour in the surrounding rock mass. The in-situ stress distribution, the blasting-induced stress wave propagation, and the corresponding rock fracture and fragmentation process are modelled and analysed. The numerical simulation results indicate that the in-situ stresses play a key role in the damage evolution around the tunnel, strongly influencing the stress redistribution pattern and thus the fracture initiation and propagation around the tunnel during blasting. Several different in-situ stress regimes are considered and discussed, revealing the dominating effects of the major principal stress and lateral pressure coefficient on the rock damage behaviour. Moreover, the blasting results obtained from employing the pressure–time history curve with varying decay time ratios and decoupling ratios are also studied. Longer decay time ratios and higher decoupling ratios induce additional rock fracture and fragmentation, indicating that the model can enable the selection of stemming and explosive type for effective breakage with limited damage around a tunnel.

Initiation of shaped charge into booster devices

ABSTRACT In this paper, the initiation capacity of shaped charges against booster devices is carefully examined using both experimental and simulation method. A booster device, which consists of insensitive charges, is investigated by shaped charge jet impact test. The results show that the response degree of the booster device with insensitive charge is detonation reaction. The numerical simulation results of jet initiation into booster devices are also compared with the witness board deformation performance. Furthermore, based on the validated numerical models and the corresponding parameters, a series of numerical simulations are performed to investigate the influence of the explosive types of booster devices, the locations of booster devices and the shell materials of booster devices. By assessing the peak pressure, maximum reaction degree and jet velocity, the influences of the key parameters on the booster device initiation are numerically discussed. The results indicate that, compared with traditional charge, the insensitive charge booster device has low jet initiation insensitivity. As the location of booster device changes, the anti-initiation performance of booster device changes. At the angle of 45°, the minimal initiation performance of the booster device is obtained. It is found that the density and strength of shell material have a slight effect on the jet initiation performance under the given thickness booster device. However, variations in the shell material property are found to impart significant effect on the jet penetration velocity, while variations in the strength impart a significant influence on the low-speed jet.

Air blast TNT equivalence concept for blast-resistant design

Trinitrotoluene (TNT) equivalence is a well-known concept, which has been extensively employed by the engineering community for the blast-resistant design of structures. It is invoked to predict the blast parameters generated from detonations of other types of high explosives. However, TNT equivalence factors available in the literature usually have significant variability, which may lead to large errors in estimating the blast loads. This study discusses the air blast TNT equivalence factors of seven types of high explosives (Composition A3, Composition B, Composition C4, PBX-9404, PBX-9501, Pentolite and Tetryl) for free air and surface bursts. The authors presented a numerical approach in the previous study, which used a curve fitting method to develop the empirical formulae of TNT equivalence factors. This paper extends the previous study by applying this numerical approach to the high explosives, which were extensively discussed by the blast engineering community in the past. The empirical formulae, which depict the TNT equivalence factors for overpressure and impulse as a function of the scaled distance Z, are developed for each explosive. To demonstrate the full potential of the developed empirical formulae, the results of TNT equivalence factors are verified against data collected from different sources. Two important conclusions are drawn. Firstly, the significant variance of TNT equivalence factors in the near field (Z from 0.1m/kg1/3 to 1.1-1.7m/kg1/3) requires different values depending on the scaled distance, as a constant value is insufficient for this range. Secondly, far-field detonations (Z from 1.1-1.7m/kg1/3 to 10m/kg1/3) allow a constant value of TNT equivalence to be used for each explosive, which is independent of the scaled distance, selected blast parameter for comparison (overpressure or impulse) and burst type (free air or surface burst).

A study of short-term spatiotemporal clustering features of Greek seismicity

Clustering features of crustal seismicity for the period from 2008 up to 2018 in Greece in both space and time are investigated by means of the epidemic type aftershock sequence model. With a completeness threshold of mc = 3.5, the data set includes 8258 events, with 19 of them of Mw ≥ 6.0, encouraging the detailed analysis of the short–term clustering spatiotemporal characteristics. The estimation of the model parameters is performed via the maximum likelihood estimation technique using a simulated annealing approach, after considering a normal grid superimposed on the study area with 0.1° × 0.1° cells. The model is tested with a residual analysis procedure along with the application of both Numbers and Log Likelihood tests. The initial estimated model with the full dataset underestimates the observed seismicity, and appears unstable, implying an explosive type model (a model with infinite decay rate). The underestimation is observed during 2008, when five Mw ≥ 6.0 earthquakes occurred, which is an extreme rate for Greek seismicity. Excluding this part of the catalog, during the period 2009–2018, the estimated model exhibits good agreement with the observed seismicity. The classification between background and triggered events is made by measuring the contribution of each class to the total seismicity, which presents a considerable clustering behavior.

A Critical Review of Blast Wave Parameters and Approaches for Blast Load Mitigation

Casualty analysis of major terrorist attacks in recent decades shows an enormous increase in fatalities and economic losses. Due to frequent terrorist attacks and failure of engineering structures under blast load, this issue has gained the attention of scientists and structural engineers. Recently, threat due to explosions is considerably raised owing to the availability of small size explosive devices with powerful and high range explosive materials. Thus, there is an immediate need for the structures, vulnerable to such tragic events, to be analysed and designed to resist these extreme loading conditions. To predict the behavior of structure under explosion loads, blast load analysis needs to be done. The effective blast parameters such as standoff distance, angle of incidence, explosive type and charge weight with its damaging effects discussed by various researchers have been overviewed in the present work. Further, it is uneconomical to harden the structure to resist the blast load. Therefore, certain strategies which can be adapted to mitigate the effect of blast pressure have also been analysed, and discussed different analytical models for prediction of blast loads. The paper present basics of blast for beginner researchers and structural engineers to understand such complex loading scenario.

Effect of Type of Explosive and Blast Hole Diameter on Boulder Count in Limestone Quarry Blasting

Rock fragmentation due to blasting depends upon many parameters. The properties of the explosive are one of them. In limestone quarries, ammonium nitrate–fuel oil (ANFO) or site mixed emulsion (SME) are generally used for rock fragmentation. Both these explosives cause substantial changes in the breakage mechanism of rockmass thereby affecting the fragmentation. This paper reports the effect of type of the explosive and blast hole diameter on the boulder count in limestone quarry blasting. In all, 264 blasts using ANFO or SME explosives have been conducted in nearby limestone quarries. The blasts have been conducted for 152 mm diameter and 115/100 mm blast holes. The analysis of the results indicates that the SME explosives are more suitable explosive in limestone quarries than ANFO for reducing the boulder count. SME has caused a reduction in generation of boulders for both 152 and 100 mm diameter blast holes when compared to ANFO. Moreover, the blasts with larger diameter blast holes charged with SME have resulted in less boulders than smaller diameter blast holes charged with the same explosive.

Explosive phase transition in susceptible-infected-susceptible epidemics with arbitrary small but nonzero self-infection rate.

The ɛ-susceptible-infected-susceptible (SIS) epidemic model on a graph adds an independent, Poisson self-infection process with rate ɛ to the "classical" Markovian SIS process. The steady state in the classical SIS process (with ɛ=0) on any finite graph is the absorbing or overall-healthy state, in which the virus is eradicated from the network. We report that there always exists a phase transition around τ_{c}^{ɛ}=O(ɛ^{-1/N-1}) in the ɛ-SIS process on the complete graph K_{N} with N nodes, above which the effective infection rate τ>τ_{c}^{ɛ} causes the average steady-state fraction of infected nodes to approach that of the mean-field approximation, no matter how small, but not zero, the self-infection rate ɛ is. For τ<τ_{c}^{ɛ} and small ɛ, the network is almost overall healthy. The observation was found by mathematical analysis on the complete graph K_{N}, but we claim that the phase transition of explosive type may also occur in any other finite graph. We thus conclude that the overall-healthy state of the classical Markovian SIS model is unstable in the ɛ-SIS process and, hence, unlikely to exist in reality, where "background" infection ɛ>0 is imminent.

Explosive exhalations by common bottlenose dolphins during Karenia brevis red tides

Harmful algal blooms (HABs) such as those produced by Karenia brevis have acute negative impacts on common bottlenose dolphins (Tursiops truncatus) in Florida coastal waters, frequently causing illness and death. However, much less is known about chronic, sub-acute effects on these important sentinel species. This study investigates whether bottlenose dolphin behavior in Sarasota Bay, Florida is influenced by the presence of severe red tide events, focusing on respiratory and other behaviors likely affected by abundant toxin aerosols produced during these blooms. Through focal animal behavioral follows, we observed free-ranging dolphin respiratory behavior, activity budgets, and movement patterns relative to K. brevis abundance in the study area. We compared behavior from dolphins observed during a 2005 K. brevis bloom to those observed during inter-bloom conditions where K. brevis was present at background concentrations. We found that the rate of “chuffing”, an explosive type of exhalation, was significantly greater in dolphins observed during the bloom. No apparent effect on respiratory rate, heading change rate or activity budgets was observed. We propose that this chuffing behavior is analogous to symptoms of respiratory irritation observed in humans exposed to such red tide events, and suggest that this may be a type of disturbance response. With an observed increase in both the frequency and severity of HABs, such disturbance responses may have large-scale chronic impacts to the health and fitness of bottlenose dolphins in regions where such HABs are common.

Finding, Organizing, and Preserving Legacy Nuclear Test Monitoring Data—Examples from the Livermore Nevada Network

AbstractA challenge for geophysical research is the relatively short time for which continuous digital data have been available. There are many events of research interest where much of the data were collected by analog or temporary digital means. These legacy data require special efforts to find, organize, and preserve for future research. Here, we focus on one type of legacy data, nuclear explosions, and associated events (e.g., collapses, aftershocks) of high interest for nuclear monitoring research and development. For nuclear tests conducted in Nevada, the Lawrence Livermore Nevada Network recorded valuable data on a variety of formats. In this article, we briefly review this network, and describe one set of data that previously was available via CD-ROM by request, and since 2018 has become available through Incorporated Research Institutions for Seismology as assembled dataset 18-001.

Observation of Variations in Condensed Carbon Morphology Dependent on Composition B Detonation Conditions

AbstractCarbon particulates generated during detonation depend upon high explosive type, composition, and detonation conditions. Although explosive composition greatly affects particulates, the focus of this work is on how detonation geometries that induce much higher temperatures and pressures in the high explosive lead to differing particulate morphologies. In this study, two geometries were used: Detonations were initiated in Composition B cylinders at one end in conventional detonations and initiated at both ends to produce colliding detonations. Each of these detonations was observed on the sub‐μs timescale using fast radiography capturing images of the front moving through the cylinder, and colliding detonation fronts in real‐time. These imaging experiments were complemented with time‐resolved small‐angle x‐ray scattering (SAXS) experiments that were able to observe and determine the varying condensed carbon morphologies at different locations and times in each detonation. The detonations could be timed in such a way that the spatial and temporal dependence of the carbon morphology could be superimposed onto radiography images collected at the same point in time. The complementary approach is able to show that the carbon condensates are much larger when formed in the elevated temperature and pressure conditions near the location of colliding detonation fronts. Thermochemical modeling suggests that these larger particulates form either in the diamond phase or on the liquidus line of the carbon phase diagram. The increase in size observed by SAXS may correlate well with the increased residence time deeply in the diamond phase. These particulates can be described as nano‐sized phases with some surface texture or otherwise near‐surface intra‐particle heterogeneity.

An Optimized Radio Follow-up Strategy for Stripped-envelope Core-collapse Supernovae

Abstract Several ongoing or planned synoptic optical surveys are offering, or will soon be offering, an unprecedented opportunity for discovering larger samples of the rarest types of stripped-envelope core-collapse supernovae, such as those associated with relativistic jets, mildly relativistic ejecta, or strong interaction with the circumstellar medium. Observations at radio wavelengths are a useful tool to probe the fastest moving ejecta, as well as denser circumstellar environments, and can thus help us identify the rarest type of core-collapse explosions. Here, we discuss how to set up an efficient radio follow-up program to detect and correctly identify radio-emitting stripped-envelope core-collapse explosions. We use a method similar to the one described in Carbone &amp; Corsi, and determine the optimal timing of GHz radio observations assuming a sensitivity comparable to that of the Karl G. Jansky Very Large Array. The optimization is done so as to ensure that the collected radio observations can identify the type of explosion powering the radio counterpart by using the smallest possible amount of telescope time. We also present a previously unpublished upper limit on the late-time radio emission from supernova iPTF 17cw. Finally, we conclude by discussing implications for follow-up in the X-rays.

Empirical analysis of a steam explosion in a slag yard based on a field investigation and 3D explosion damage simulation

Many types of explosions often occur in industrial settings, and research is being conducted to identify the causes and establish preventive measures. The aim of this study is to investigate slag yards, where metal residues are cooled in the steel industry, often causing steam explosions. The cause of accidents and explosion simulation analyses were used to investigate the sources of steam explosions in a slag yard. The explosion intensity of 4kg of TNT was measured for the purpose of predicting the intensity of a steam explosion. This was compared with a simulation of explosion damage that occurred in 2017. These results could not be produced from small-scale experiments, and they indicate that damage resulting from actual explosions poses a potential risk to pipes that cannot be directly observed. We conclude that this damage can lead to a domino accident, and this study provides results for estimating the possibility of future damage.

Određivanje kritičnog rastojanja u postupku eksplozivnog zavarivanja

Introduction/purpose: When performing the explosive welding procedure, for the safety of workers, it is necessary to take into account the minimum distance between the workers and the place of explosion at the time of explosion. Negligence can cause temporary hearing loss, rupture of the eardrum and in some cases even the death of workers. The aim of this paper is to determine the critical distance based on the mass of explosive charge required for explosive welding, provided that the limit pressure is 6.9 kPa in the case of temporary hearing loss and 35 kPa in the case of eardrum rupture. This paper does not take into account other effects of the explosion than those caused by the shock wave. Methods: Depending on the type of explosion, the equivalent explosive mass was calculated. Based on the equivalent explosive mass and the limit pressure, the minimum distances were calculated using the Sadovsky and Kingery-Bulmash equations. Results: The corresponding tables show the results of the calculation of the critical distance of workers from the place of the explosion when there may be temporary hearing loss or rupture of the eardrum. The calculated value of the critical explosion distance by the Kingery-Bulmash method, under the condition of the maximum pressure for temporary hearing loss, is 5.62% lower than the distance value obtained by the Sadovsky method while the value of the critical explosion distance calculated by the Kingery-Bulmash method, under the condition of the maximum pressure for eardrum rupture, is 7.83% lower than the value obtained by the Sadovsky method. Conclusion: The results of the calculation showed that the critical distance from the explosion can be successfully calculated and that the obtained values have small differences depending on the applied calculation method.

Investigation and optimization of main materials consumption when mining iron ores at deep levels of the Underground Mine Group of the PJSC “ArcelorMittal Kryvyi Rih”

The work considers conditions of deep levels of the Underground Mine Group for underground ore mining (as underground mines) of the Mining Department of the PJSC “ArcelorMittal Kryvyi Rih” (the PJSC “ArcelorMittal Kryvyi Rih”). The research aims to improve indicators of mined ore mass extraction when mining rich iron ores through studying and optimizing consumption of explosives, enhancing mining technology to provide fulfilment of the underground iron ore mining program. During the research, there are analyzed mining geological and technical conditions of the deposit mining as well as current technologies of iron ore mining at the Underground Mine Group of the PJSC “ArcelorMittal Kryvyi Rih”. The work analyzes the achieved indices and consumption of explosives for drilling and blasting at the Underground Mine Group. The mining geological and technical conditions of the deposit mining as well as current technologies of mining, parameters of preparatory operations, the nomenclature and qualitative characteristics of many types of explosives are determined to have changed. This complicates planning consumption of explosives and making their estimates for work sites. However, this is a reason for selecting highly efficient technology and machinery in deteriorating mining and geological conditions of operating at over 1200 m depths. The work determines dependencies of a stress value on a mining depth and physical properties of rocks, as well as parameters of drilling and blasting operations considering the stress-strain state of the massif under high rock pressure at deep levels of the Mining Group of the PJSC “ArcelorMittal Kryvyi Rih”.

Numerical simulation for determining detonation parameters of explosive substances using EXPLO5 thermo-chemical prediction software

The article presents the theoretical and practical research results regarding the development of the IT and methodological infrastructure for assessing the parameters which define explosive substances. The software us intended for estimating, based on the chemical composition of substances, parameters which define such substances (detonation velocity, detonation energy, detonation pressure etc.), as well as for determining the probability of explosion. EXPLO5 is a specialized software which allows to solve thermo-dynamic equations between different reaction products in order to determine the balance composition, having incorporated a filtering algorithm for estimating Jones-Wilkins-Lee (JWL) state equations coefficients which are used for calculating the detonation energy of explosives. For the proper performance of pilot tests of numerical simulations upon certain representative types of explosives (civil use explosives and double-use explosives: civil and military) there have been taken into account the special characteristics of EXPLO5 provided by the EOS BKW (BKW standard with set of BKWN constants and BKW EOS modified with the set of constants and volumes BKWN-M) and EXP-6 EOS function which is based more on theoretical concepts.

A refined model of viscoelastic-plastic deformation of flexible plates with spatial reinforcement structures

A refined model of viscoelastic-plastic deformation of flexible plates with spatial reinforcement structures has been developed. Strains of the composition materials are assumed to be small and decomposed into plastic and viscoelastic components. Instant plastic deformation of these materials is described by the flow theory with isotropic hardening. Viscoelastic deformation obeys the equations of a linear model of a five-constant body. The geometric nonlinearity of the problem is taken into account in the Karman approximation. The possible weak resistance of composite plates to lateral shear is modeled in the framework of a refined theory of bending. This allows one to determine the displacements of plate points and the stress-strain state in the components of the composition with varying degrees of accuracy. In a first approximation, from the obtained equations and boundary conditions, we obtain relations corresponding to the traditional nonclassical Reddy theory. A numerical solution to the formulated initial-boundary-value problem is sought according to an explicit “cross-type” scheme The viscoelastic-plastic dynamic deformation of rectangular, relatively thin fiberglass plates under the influence of an explosive type load is investigated. The plates have a traditional plane-cross (orthogonal) or spatial reinforcement structure. It is shown that even in the case of relatively thin composite plates the Reddy theory is unacceptable for adequate calculations of their dynamic viscoelastic-plastic deformation. It has been demonstrated that the magnitude and shape of the residual deflections depend not only on the reinforcement structure, but also on the magnitude of the viscoelastic characteristics of the materials of the composition components. It was found that, after dynamic inelastic deformation, the composite plate can have a corrugated residual shape with folds oriented in the longitudinal direction. It is shown that even in the case of a relatively thin plate, replacing the planar-cross reinforcement structure with a spatial structure can significantly reduce the amount of residual deflection and the intensity of residual deformation in the binder material and some fiber families. For relatively thick plates, the effect of such a replacement of the reinforcing structures manifests itself much more.

Tourists’ Perception on Volcanic Hazard and Risk in Guci Hot Spring, Slamet Volcano, Indonesia

Guci Hot Spring is one of the tourist destinations in Central Java Province renowned for its beautiful scenery as well as its health-healing benefit. In 2016, this touristic destination attracted more than 650.000 visitors, this number is growing each year. However, this touristic spot has its hidden hazard and risk of the Slamet Volcano eruption. The historical eruptions of this volcano, recorded since the 18th century, have shown that this volcano is known for its explosive type of eruption. Despite its potential hazard and risk, this hot spring area is growing continuously as a touristic spot. Therefore, this study aims to understand tourists’ perception on volcanic hazard and risk in this area, by interviewing 31 respondents using questionnaires. The results show that 74% of respondents are aware that Slamet Volcano has different potential hazards such as volcanic ashfall, lahars, lava and pyroclastic flows. Although Guci Hot Spring is located in Slamet volcanic hazard area, only a few tourists know this information (42%). Majorities of the respondents did not have any experience on volcanic disaster (68%). Most of the respondents did not get any information on Slamet volcanic hazard (58%), while others only get information through television and/or social media. Nevertheless, almost all of the respondents claimed that they will follow any instructions given by government or related institutions if any volcanic eruption occurs (97%). Therefore, awareness program towards tourists in the volcanic touristic spot should be strengthened through different means to give information on volcanic hazard, its risk as well as mitigation and crisis management.

Forensic Investigation of Explosions: A Review

An explosion is defined as a violent, shattering action caused by a bomb. The main chemical ingredient of a bomb is the explosive – an endothermic substance which serves as a storehouse of energy. When this energy is suddenly released, in the confined space of the bomb, it causes a devastating effect, resulting in loss of lives and property. As compared to conventional crime scenes, explosion sites are more difficult to process. In many cases a building may have collapsed and the crime scene evidence may have become buried beneath the debris. A vital aspect of forensic investigation of bomb blasts is to establish the explosion seat. Equally important is to identify the type of chemical explosives used to commit the crime. This communication highlights the complications encountered in the management of explosion sites and the difficulties experienced in processing the evidence collected there from. The types of injuries which the victims of explosion suffer are also briefly described.

Improving the Chemical Selectivity of an Electronic Nose to TNT, DNT and RDX Using Machine Learning.

We used a 16-channel e-nose demonstrator based on micro-capacitive sensors with functionalized surfaces to measure the response of 30 different sensors to the vapours from 11 different substances, including the explosives 1,3,5-trinitro-1,3,5-triazinane (RDX), 1-methyl-2,4-dinitrobenzene (DNT) and 2-methyl-1,3,5-trinitrobenzene (TNT). A classification model was developed using the Random Forest machine-learning algorithm and trained the models on a set of signals, where the concentration and flow of a selected single vapour were varied independently. It is demonstrated that our classification models are successful in recognizing the signal pattern of different sets of substances. An excellent accuracy of 96% was achieved for identifying the explosives from among the other substances. These experiments clearly demonstrate that the silane monolayers used in our sensors as receptor layers are particularly well suited to selecting and recognizing TNT and similar types of explosives from among other substances.

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.