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Pentaerythritol tetranitrate (PETN) is a widely studied high explosive (HE), most commonly used in detonator applications. In this work, we use a spray drying technique to manufacture a new “nano-powder” morphology of PETN. The spray dried PETN is several orders of magnitude smaller in particle size than traditionally prepared PETN powders. The spray dried PETN has a mostly spherical and smooth morphology, while traditional crystalline PETN typically has sharp edges and crystal facets. Small-scale sensitivity tests including drop-weight impact, friction, and electrostatic discharge (ESD) indicate the spray dried PETN is less sensitive than traditionally used forms of PETN powders. We also observed no changes in chemical properties (melt temperature and onset of decomposition) after spray drying, and the material remains in the tetragonal, crystalline phase.

The particle velocity created in beds of both low-density inert sugar and explosive PETN as a function of distance from an exploding bridgewire was measured using optical velocimetry and a silvered PMMA window. As expected, more violent bridge-bursts (from a greater-stored-energy capacitive discharge unit) resulted in greater particle velocities and a better supported compaction wave in sugar. In all cases, ramp waves, not shocks, were observed in the inert sugar. Large window velocities were observed for very powerful bursts (up to 270 m/s), but bursts required for stochastic detonator operation conditions resulted in sugar/PMMA window velocities of only 8–10 m/s 0.85 mm from the bridge location. In contrast, after a distance of only 0.65 mm, a building shock wave was observed in PETN under both threshold and reliable firing conditions. Subsequently a hot-spot-driven shock-to-detonation (SDT) process was observed prior to full detonation. The measured buildup process accounts for $$\approx $$ ≈ 66% of the so-called excess transit time (ETT) between the observed and theoretical total function time for the particular exploding-bridge-wire (EBW) detonator studied. The remainder must occur in the powerful output pellet region. In contrast to a common understanding, the ETT is found to be a weak function of the discharge energy. Thus, the operation of the detonator after a bridge-burst energy-to-powder reaction transition process is found to be hot-spot-driven SDT in both the low- and high-density pellets.

Pre-detonators are commonly used in rotating detonation engine (RDE) experiments. Current experimental studies focus on the performance of pre-detonator while ignoring the influence of pre-detonator on the flow field. In numerical simulations one-dimensional detonation wave is usually used to ignite the fresh gas in RDE. This is a simplification of the pre-detonator used in practical hotfire tests. But the coupling between the pre-detonator and the combustor is ignored. The aim of the present study is to study the influence of pre-detonator on the flow field in the RDE. A model of RDE with a pre-detonator is built, in which three-dimensional numerical simulations fueled with hydrogen/air is performed. The influence of pre-detonator on the combustor in different stages is studied. After initiation, detonation wave from the pre-detonator forms two counter-rotating detonation waves. The tangential installation of pre-detonator fails in directional initiation of detonation wave. The coupling effect is shown as the reflection and expulsion of shock wave. Detonation wave or oblique shock wave in the combustion chamber enters the pre-detonator and turns into shock wave before colliding with the end and re-entering the combustion chamber. Under some circumstances, the reflected shock wave will initiate a detonation wave and affect the wave structure in the combustion chamber. In the stable stage, the reflected shock wave has no effect on the flow field. However, periodic collision of reflected shock wave with detonation wave at the junction causes ablation in long-time experiments. Increasing the axial distance between pre-detonator and injection wall is expected to be a solution for the ablation problem.

The application of explosives has never been considered as a major influencing factor during either the designing of a mine or the selection of the mining method. However, this has changed with the launch of WebGenTM wireless blasting system, which allowed underground mines to exploit their orebody applying methods previously not possible due to limitations imposed by the use of wired detonators. The wireless blasting system is based on magnetic induction communication, and its signal is capable of overcoming hundreds of meters through rock, water, and air, to reach individual primers in the blastholes without any physical connection.A noble application of wireless detonators is being used in Vazante mine, Brazil, an underground zinc mine where ore pillars are left in the mined stope to secure stability and minimize dilution by limiting the hydraulic radius. The recovery of these pillars is financially desirable but involves extra time and costs associated with scaling, backfilling, reinstalling infrastructure, accessing areas previously blasted (less stable), drilling, charging with explosives, and subsequently, firing and mucking out the blasted material with expected high dilution. Applying 100% wireless detonators made it possible to safely preload the pillar together with production blasts before losing access to the area, a method named Temporary Rib Pillar (TRP). After all the stope is mined and the pillar accomplished its objectives, the primers are initiated without neither the need for the extra cycles described previously, nor the need to re-enter the area. Thus, it was possible to reduce the exposure of people and equipment, reduce operational cycles, and increase ore recovery, directly contributing to anticipate the ore production while guaranteeing the safety of the teams involved.

Vibrations induced due to blasting in mines may damage the nearby houses and disturb the habitants. The monitoring, prediction, and control of vibration in terms of peak particle velocity (PPV) has been an area of concern for blasting engineers since many decades. The frequency of vibration has a very critical role to play in damaging the structures. To minimize the adverse effects of blast vibration, it is required to reduce the PPV and increase the frequency of the blast vibration waves. In past research work, studies have been done to reduce the PPV due to blasting, but it has been found the prediction and control of blast vibration frequency still remains a difficult task. With the availability of most precise electronic detonators, the precise detonation timings can be used to superimpose the waveforms of different holes in a manner to achieve the required targets. In this paper, an attempt has been made to analyze the signature hole waveform and use the delay timings in such manner to destructively superimpose the blast vibration waveforms. Utilizing the concept, production/multi-hole blasts were conducted with the estimated delay timing obtained through signature hole’s waveform. It has been found that the concept of frequency channeling has been successful in reducing the PPV values in almost 70% of the cases, whereas the frequency values increased successfully in 91.3% cases.

The Empirical Mode Decomposition (EMD) of blasting seismic wave monitoring signal with noise can get IMFs with serious mode confusion and divergent end points. The Hilbert transform is constrained by the Bedrosian theorem, when it dealing with such IMFs will get negative instantaneous frequency, which leads to serious error in the identification of non-electric millisecond detonator initiation delay. EP-CEEMDAN-INHT is proposed and applied to the delay analysis of blasting network of deep buried diversion tunnel crossing fault zone. Comparing EP-CEEMDAN-INHT with EMD-HHT, it is found that EP-CEEMDAN-INHT can clearly display the time-frequency information contained in the measured blasting vibration signal, and EMD mode confusion and endpoint effect are well suppressed. The actual millisecond time interval obtained by EP-CEEMDAN-INHT can judge whether the detonator is in normal service. At the same time, the blasting millisecond interval with the best damping effect is 54.51ms to 59.75ms, which can realize the optimization of blasting network and has important practical significance for blasting safety control.

Procesi, ki se izvajajo v kamnolomih, ob uporabi eksplozivnih sredstev predstavljajo tveganje, ki lahko v večji ali manjši meri vplivajo na varnost ter zdravje delavcev in drugih vpletenih oseb. Posledično je zelo pomembno usposabljanje delavcev in drugih ključnih oseb, ki morajo biti seznanjene z vsemi tveganji, ki lahko pri tem delu nastanejo. Pomembno je tudi poznavanje in seznanitev z varno uporabo eksplozivov in z njimi povezanih sredstev s katerimi rokujejo delavci. Prav tako je ključnega pomena, da delavci upoštevajo varnostne ukrepe za preprečevanje tveganj, ki bi ogrožale varnost in zdravje delavcev. Processes carried out in quarries using explosives pose a risk that can affect the safety and health of workers and others involved in these processes. Therefore, it is very important to prepare workers and other relevant persons who must be aware of all the risks that may occur during this work. It is also important that workers know and master the safe handling of explosives and related materials. It is also crucial that workers follow safety measures to avoid risks that would endanger the safety and health of workers.

Based on wavelet transform, the blasting vibration signals are analyzed here. For millisecond blasting, the blasting effect is mostly affected by the actual delay time. Local characteristics of the analyzed signals could be highlighted by the wavelet transform. The simultaneous initiation of large explosive quantity could be avoided by the use of multistage detonators, while the vibration resistance effect could be better. For the same level of detonator segment, the larger the arranged time interval, the less the possibility of initiation at the same time, which is not conducive to the vibration resistance. Therefore, it is suggested to use high-level detonators with detonating cord or high-precision digital electronic detonators to minimize the initiation error. Furthermore, by identifying the delay time using wavelet transform, the interval delay time of different detonator segments could be obtained. Moreover, the nominal delay time, actual delay time, and interval delay time are further compared and analyzed. It is suggested that the millisecond delay series of detonators should be selected in the whole section blasting, and the segment should be jumped as much as possible, so as to increase the secondary breakage time. Detonators with longer interval delay time should be avoided to the full.

Electrically exploded wires find uses throughout high-energy physics. For example, they are commonly used as high-temperature sources, X-ray generators, and in precision timing detonators. However, the detailed and complete physics that occurs is complex and still poorly understood. A full mechanistic description of these complex phenomena is beyond the scope of a single paper. Instead, we focus on the formation of metal vapor and its transition to plasma. This single transition is commonly assumed to comprise “bridge-burst”. We use a suite of diagnostics including a novel, fiber-based, high-speed, optical pyrometer to better characterize this transition. The primary finding from this project is that peak light output from an exploding wire does not temporally match the peak temperature. Additionally, it is found that peak light does not align with peak bridge-burst voltage and that the peak temperature is not voltage-dependent. These findings are non-intuitive and will allow for the correction of false assumptions previously made about this topic.

On limestone blasting activities besides safety there are two other important factors that must be highly considered, that are productivity and environmental impacts that caused, along with the replacement of the blasting contractor at PT Semen Baturaja (Persero) Tbk and accompanied by the strategy of explosive type change that used from ANFO with electric detonator to DABEX with non electric detonator. So, it is necessary an analysis of productivity and environmental impacts that caused, whether for the better or vice versa. The research method that used is qualitative triangulation research using data from direct observation in field, managing documentation data and conducting deep interview with parties who are directly or indirectly involved on limestone blasting activities. Interview was conducted with 10 samples representing representatives of Mining Division work unit with representatives from Echelon 1, Echelon III, Echelon IV and daily workers. From the testing data obtained that the strategy of explosive type change from productivity side is better and more efficient whereas from environmental impacts caused side is not better especially with the use of DABEX which cause an increased level of vibration. Based on these results, it is necessary to make improvements to the blasting method or to find for other alternative explosives that can increase productivity but have minimal environmental impact.

In the present study, commercially available detonators with pentaerythritol tetranitrate (PETN) were subjected to elevated temperatures. The detonators were thermally ignited over a range of heating rates to measure ignition delay time and assess detonator violence. The violence of the detonator was quantified by measuring the velocity of the detonator closure disc (or “flyer”). The maximum flyer velocity of a thermally ignited detonator was comparable in magnitude to that obtained by initiating a room temperature pristine detonator with an exploding bridge wire (under the same confinement); however, the high flyer velocity was not an indication of deflagration to detonation transition (DDT) in the thermally ignited detonator. The detonator responded more violently than a thermally ignited detonator when initiated at 95% of the ignition delay time. Inoperability thresholds were also measured by varying the detonator temperature and the threshold was found to be sensitive at detonator temperatures below the melting point of PETN.

Accurate knowledge of post-detonation fireball temperatures is important for understanding device performance and for validation of numerical models. Such measurements are difficult to make even under controlled laboratory conditions. In this work temperature measurements were performed in the fireball of a commercial detonator (RP-80, Teledyne RISI). The explosion and fragments were contained in a plastic enclosure with glass windows for optical access. A hybrid femtosecond-picosecond (fs-ps) rotational coherent anti-Stokes Raman scattering (CARS) instrument was used to perform gas-phase thermometry along a one-dimensional measurement volume in a single laser shot. The 13-mm-thick windows on the explosive-containment housing introduced significant nonlinear chirp on the fs lasers pulses, which reduced the Raman excitation bandwidth and did not allow for efficient excitation of high-J Raman transitions populated at flame temperatures. To overcome this, distinct pump and Stokes pulses were used in conjunction with spectral focusing, achieved by varying the relative timing between the pump and Stokes pulses to preferentially excite Raman transitions relevant to flame thermometry. Light scattering from particulate matter and solid fragments was a significant challenge and was mitigated using a new polarization scheme to isolate the CARS signal. Fireball temperatures were measured 35–40 mm above the detonator, 12–25 mm radially outward from the detonator centerline, and at 18 and 28 µs after initiation. At these locations and times, significant mixing between the detonation products and ambient air had occurred thus increasing the nitrogen-based CARS thermometry signal. Initial measurements show a distribution of fireball temperatures in the range 300–2000 K with higher temperatures occurring 28 µs after detonation.

A fueled cavity in a supersonic crossflow was ignited via a pulse detonator (PD) producing detonation waves that were then decoupled to produce varying degrees of shock-flame separation at the exit of the PD tube. This decoupling allowed for observation of the cavity ignition mechanism, and the key parameters required for successful cavity ignition were identified. Measurements were made using high-frame-rate OH Planar Laser-Induced Fluorescence (PLIF) and schlieren and chemiluminescence imaging. It was shown that the entrainment of high-temperature intermediate species into the forward region of the cavity, immediately behind the step, is the principal criterion for cavity ignition. Both coupled and slightly decoupled detonation cases induced significant OH shedding into the step region, leading to ignition and flame stabilization within the cavity. At conditions where OH shedding into the step region did not occur, cavity ignition was not observed. In coupled and slightly decoupled cases, there is more shedding of OH behind the step due to the greater disturbances created in the flowfield. As the degree of detonation decoupling increases, there is less shedding of OH and therefore a lower likelihood of ignition. Additionally, the time required for cavity combustion to reach its steady-state condition varied with the degree of decoupling of the detonation. Coupled detonation cases were shown to be more disruptive to the cavity and thus required more time to reach steady state than the decoupled cases.

The possibilities of controlling the edge effect of the explosion of the conic primer in the lower part of the borehole charge on the level of the bench sole are considered. The data from the analytical studies of the formation of the strain field in the corner area of the borehole bottom are shown. The feasibility and efficiency of using an intermediate detonator (cone-shaped primer) at the lower end of the borehole charge to reduce the depth of the subdrilling are confirmed.

A CCDS2000 detonator for acetylene, ethylene, propylene, and a multicomponent methylacetylene–allene fraction (MAF) fuel is used to perform experiments on measuring the detonation velocity and recording a detonation front cell in a tube 26 mm in diameter and 2 m in length. The experiments are carried out at atmospheric pressure in stoichiometric mixtures diluted by nitrogen to air concentrations and in air–fuel mixtures with a varying fuel content in them. In the case where the explosive mixture components are fed as a flow by stratifying an explosive charge in an initiation zone, a self-sustaining detonation is stably ignited up to limiting (spin) modes. The concentration limits of the detonation existence are determined. In the air–fuel mixtures of acetylene and ethylene, as the values become lower than the limits, there is multiheaded detonation. For propylene and MAF, a tube diameter of 26 mm is near-critical: only single- and two-headed spin is observed in the entire range of existence. Calculation results are in good agreement with the experiment.

A method for exciting the detonation process and its development in onboard low-pulse shatter-proof separation devices and in the units for initiating detonation equipped by high-energy elastic materials (HEEM) is examined. The relationships for calculating detonation initiation reliability for the HEEM charge are presented and practical recommendations for increasing it are given.

Ridge-cut explosive bolts are a type of pyrotechnic release devices in which two connected structures are separated by explosives. They are designed such that shock waves can interact with and cut their body. Furthermore, they provide a clean separation surface and require a smaller explosive amount compared with other types of explosive bolts. In this study, ridge-cut explosive bolts of various diameters and with an exploding bridge wire (EBW) detonator were developed for use in sled testing. Their initial shapes were designed using an established procedure. Initial separation tests for the initial designs of the explosive bolts showed that considerable debris was produced for some models and that the explosive amount should be reduced. For the minimization of the number of experiments, the appropriate explosive amount was determined in advance through numerical analysis, which was performed using Autodyn, a commercial hydrocode. The numerical analysis technique used was improved to analyze the complete separation phenomena. The numerical results clearly revealed the separation mechanism and characteristics of the explosive bolts and helped determine an appropriate explosive amount for achieving a small amount of debris. Verification tests confirmed that explosive amounts determined using the numerical results were appropriate for separation and generated a small amount of debris.

Rock breakage using blasting is one of the important operations of the mining industry. The delay timing decides the initiation sequence of holes in the blasts and is a crucial factor to improve the overall blast performance. Blast-induced ground vibration is an undesired yet unavoidable outcome of blasting. Peak particle velocity (PPV) is commonly used to measure the magnitude of blast-induced ground vibration. Channelization and better utilization of explosive energy delay are provided between blast holes using initiating systems. The use of different initiation systems even on the same site results in a very significant difference in the values of PPV generated. Due to scattered delay timings of pyrotechnic detonators, the scaled distance predictor equations obtained become unreliable. The error/scatter in delay timing leads to overlapping of holes and hence increases in maximum charge per delay. In this paper, an analytical approach has been discussed to measure the overlapping of holes during blasting with initiation systems having inherent cap scatter. The analytical approach will be calculating the probable overlapping of holes due to scatter in delay timing and will help blasting engineers to understand the variation in maximum charge per delay due to pyrotechnic based initiating systems. In this study, a total number of 102 blasts were conducted using different initiation systems at two different opencast coal mine and 221 corresponding blast vibrations events were recorded.

Exploding bridgewire (EBW) detonators work by electrically exploding a thin conducting wire as a result of a high voltage discharge from a capacitor. The process creates a strong UV (ultraviolet) e...

The blast wave generated by a high explosive detonation is dependent not only on the shape of the charge but on the location of the detonator or detonators. Even for a spherical charge, the blast wave can be very asymmetric if the initiation is not at the center of the charge. The asymmetry is even greater for cylindrical charges. High-resolution, high-fidelity calculations of the blast wave generated by several spherical and cylindrical charges have been used to quantify these differences for free-field blast propagation. Except for the center-detonated spherical charge, the blast wave never becomes spherical. Several examples are shown to demonstrate and quantify the asymmetries and to illustrate that the blast wave, once asymmetric, can never regain spherical symmetry. At distances of over 40 charge radii, the asymmetries are clearly defined. As the overpressure at the shock front decays below half a bar, the propagation velocity approaches ambient sound speed. At half a bar (50 kPa), the Mach number of the shock is 1.19 and at a tenth of a bar (10 kPa) the shock velocity is only Mach 1.04. If the shock front is asymmetric at low overpressures, all parts of the shock front are moving at very nearly the same velocity and can therefore never “catch up” to other parts of the front: once asymmetric, always asymmetric. Results of several calculations have been analyzed to determine the quantitative differences in shock properties resulting from detonator placement and charge shape. Properties are significantly different behind the shock fronts, especially in the density distribution.

Pyrotechnic compositions are usually employed in time delay detonators to facilitate controlled initiation of explosive charges in mining and quarrying operations. Traditional slow-burning formulat...

Defects such as voids, pores, and joints will transform into big scale cracks in the rock of tunnel surrounding under dynamic load like blasting and earthquake. In this paper, three kinds of symmetrical cracks were chosen as an example, and experiments and numerical simulations were conducted to study the effect of symmetric cracks on a blast-induced crack. The relationship of main crack propagation characteristic and distribution of symmetrical cracks was investigated. Some circular specimens using two kinds of material, PMMA and sandstone, including a center hole charged with a detonator and pre-existing cracks were used in the experiments. The test system consisted of an oscilloscope and an ultradynamic strain amplifier and crack propagation gauges (CPGs) were employed in monitoring propagation velocity. AUTODYN code was applied in numerical simulation to investigate the propagation behavior of main crack between symmetrical cracks. Linear equation of state and a modified major principal stress failure criterion was utilized to describe the status of rock material. Based on experimental and numerical results, it can be concluded that (1) the pre-existing symmetrical cracks have arrest effect on main crack propagation, (2) compressive stress in y-direction plays very important roles in crack arrest, and (3) the spacing of parallel cracks has a great influence on crack propagation length and velocity.

The well-developed theory of Lorentz plasma that is dominated by electron–ion interactions is used to calculate the PETN arc characteristics. The spark-gap discharge current is a ramp with 10 to 25...

Exploding bridgewire (EBW) detonators work by bursting a thin conducting wire as a result of a high voltage discharge. This process is known to produce a strong UV emission. The roles of optical ab...

A highly stable and highly efficient electroexplosive device for initiating powerful shock waves that contained a detonator based on a narrow copper foil coated with a polymer film and a semiconductor generator of submicrosecond current pulses that provides an electric explosion of the foil in a time of ~70 ns are considered. The possibility of using the developed device for detonating powerful explosives that are resistant to thermal and mechanical external influences is demonstrated.

A prototype of WiFi based wireless blasting system aimed to achieve simple and easy detonation techniques. Since the invention of explosives world has used various detonation techniques, this prototype is developed to further simplify the detonation techniques. The speciality of this detonator is that it can trigger most forms of explosives and can also ignite a controlled fire without any explosive.

Everybody knows TNT, the most widely used explosive material and a universal measure of the destructiveness of explosions. A long history of use and extensive manufacture of toxic TNT leads to the accumulation of these materials in soil and groundwater, which is a significant concern for environmental safety and sustainability. Reliable and cost-efficient technologies for removing or detoxifying TNT from the environment are lacking. Despite the extreme urgency, this remains an outstanding challenge that often goes unnoticed. We report here that highly controlled energy release from explosive molecules can be accomplished rather easily by preparing TNT–perovskite mixtures with a tailored perovskite surface morphology at ambient conditions. These results offer new insight into understanding the sensitivity of high explosives to detonation initiation and enable many novel applications, such as new concepts in harvesting and converting chemical energy, the design of new, improved energetics with tunable characteristics, the development of powerful fuels and miniaturized detonators, and new ways for eliminating toxins from land and water.