Explosive Charge Research Articles

Shock focusing effects on silica phase production during cyclotrimethylene trinitramine/2,4,6-trinitrotoluene detonations

Detonation is an increasingly studied method for the synthesis of nanomaterials due to the rapid reaction rate producing extreme pressures and temperatures for short durations, which can result in the production of ultra-hard and high-temperature nanomaterials. The present study shows that phase formation in detonation depends on the distribution of inert additives in the explosive charge. Numerical simulations and experimental validation were conducted on silica powders that were shock loaded by detonation of a 3.8 cm diameter cylindrical explosive charge composed of cyclotrimethylene trinitramine, 2,4,6-trinitrotoluene, and paraffin wax. Silica was incorporated into the explosive in three configurations and at two different starting particle sizes in both simulation and experiments. The detonation residues were purified to concentrate the silica and characterized via x-ray diffraction with Rietveld refinement and optical microscopy. Loading conditions and silica phase morphology were not consistent between the configurations and starting size of silica incorporated into the charge. The implication of these results is that the prediction of phase production in detonation synthesis experiments cannot be based on Chapman–Jouguet steady detonation parameters of the explosive matrix but must also include analysis of shock interaction and heat transfer into the additives incorporated into the explosive.

Prediction of residual strength of FRC columns under blast loading using the FEM method and regression approach

This study presents a development of empirical equation which can be used for predicting the residual strength of fiber reinforced concrete (FRC) columns subjected to a TNT explosion. For that purpose, numerical investigations on the structural behavior and damage of FRC column under blast loading were carried out. Finite element (FE) modelling of FRC column and TNT explosive charges were built using a robust program, LS-DYNA. Those FE modellings were then verified using relevant, recent test data. A series of parametric analyses was conducted with such various main parameters as section, scaled distance, scaled section, fiber type, and fiber content to investigate the effect of these parameters on the structural behavior and damage of the column under explosion. Some interesting discussions were then presented to thoroughly understand the role of each parameter on the resistant capacity of the column. To develop the empirical equation for predicting the residual strength of the FRC column, Multivariate Linear Regression (MLR) and Multilayer Perceptron for Regression (MLP-R) were employed to generate the fitting models. While the MLP-R showed a superior capacity for estimating the result, MLR, on the other hand, could easily achieve the regression coefficient with fairly good estimation. As a result, a reliable empirical equation that can be used to predict the residual strength of the FRC column in practical design was proposed as an important outcome of this study.

Numerical study and experimental tests on full-scale RC slabs under close-in explosions

This paper investigates the response of three reinforced concrete slabs subjected to a dynamic (explosive) load at close range, through full-scale testing and its subsequent simulation with numerical models. The first slab was subjected to 1.74 kg of TNT equivalent at one-meter distance and instrumented with pressure and acceleration sensors. In the second slab, the load was increased to 13.05 kg of TNT equivalent while maintaining the distance; finally, the load from the second case was maintained but the distance was decreased to half a meter. The results of the three slabs were compared with respect to the concrete damage surfaces. A well-known Finite Element (FE) model with LOAD BLAST ENHANCED (LBE) tool has been used to numerically describe the slab and the explosive charge, respectively. Three different concrete material models have been used for the description of the first slab with the FE-LBE model. Numerical models adopting coupled Finite Element (FE) and Smoothed Particle Hydrodynamics (SPH) (for the charge definition) have also been developed for the same slab, including the three concrete material models and two alternatives to describe the explosive mass. After comparing the damage evolution with different material models for the concrete in the first test, the remaining tests have been simulated with the concrete model that presented the best results. In the FE-SPH models the load has been simulated with three geometries (cylinder, cube and bag) to account for the uncertainty in geometry of the explosive charge. The cylindrical charge is the best replicating the detonation pressure, the cubic charge is the best reproducing the surface damage and the bag shaped gets the best results regarding the acceleration. FE-SPH models are able to reproduce the shape of the surface damage slightly better than the classic FE-LBE, an important finding when the explosive charges are not spherical. On the contrary, the ratio of surface damage is closer to that obtained in the tests for the FE-LBE models compared to the FE-SPH models.

The effect of explosive charge backing in close-proximity air-blast loading

This paper presents new insights into the influence of explosive charge backing on the impulse transfer and transient response characteristics of plates subjected to close-proximity air blast loading. The results of the combine experimental and computational studies show the critical influence of charge backing, which caused between a 3-5 times increase in the impulse transfer when the charge was metal-backed. The permanent deflections from the metal-backed detonations were larger than for air, but not to the same degree as the impulse increase. These findings demonstrate the important influence of charge backing, in close proximity detonations, which greatly exceeded anything previously measured. These valuable insights will assist blast protection engineers considering the effects of explosions in situations when the charge backing is something other than air, which is a frequent occurrence in explosion scenarios.

STUDY ON THE VELOCITY POTENTIAL FIELD OF THE GROUP OF PARALLEL LONG CYLINDRICAL CHARGES

Previous theoretical studies have addressed the velocity potential of single charges. In practice, the group of explosive charges are commonly used. In this paper, the velocity potential field of a group of parallel long cylindrical charges is established by analytical method. The calculation program of the velocity potential of any element in the environment caused by a group of long cylindrical charges is written based on the Matlab programming language. This program allows to survey the velocity potential around a group of parallel long cylindrical charges. The analytical results showed that this velocity potential is on a plane and with the same specific conditions of the rockmass and the same blasting condition. Surveying results also showed that, the velocity potential of a group of parallel long cylindrical charges also decreases gradually as far as the case of single cylindrical charge. When the distance between the long cylindrical charges is reasonable, it will form an area, which has the velocity potential field close to the plane. This is the flat explosion wave area. This area has good implications for controlling the uniform breaking quality of rocks.

Deformation of Armox 440T plates subject to buried explosive charge detonations: A benchmark for appliqué systems

Loading of vehicle undercarriages from the detonation of shallow-buried explosives remains a serious threat to life in conflict and post-conflict zones. One method to protect lightly-armoured vehicles is to retrofit them with appliqué armour, which must be strong enough to provide adequate protection, but light enough to maintain vehicle manoeuvrability. A key performance metric of this armour is its deformation under loading, which must be limited to avoid impact upon vehicle occupants. The high-strength steel Armox 440T is commonly used due to its high load capacity, strength-to-weight ratio, ductility and low cost: as other protection systems are developed, it would be of great benefit to compare their deformation against an Armox 440T benchmark. However, no definitive benchmarking study has been published to date, mainly due to the difficulties in ensuring repeatable loading from complex buried detonations.This paper presents experiments which underpin such a benchmarking study, building on the authors’ previous work to establish a methodology which produces very consistent loading from shallow-buried detonations. Tests were conducted with a range of explosive masses and plate thicknesses, with target plates secured in a purpose-designed frame to produce simple, consistent boundary conditions. Plate deformations captured by stereo high-speed digital image correlation were compared to a commonly-used low-cost peak deflection method. High-speed digital image correlation was found to make highly reproducible displacement measurements with a standard deviation of 2% of the mean. The low-cost method provided slightly higher variability up to 5% of the mean value, and measurements of peak deformation were systematically 20% higher, but in a consistent manner, with a low unit cost and without risk to expensive test equipment. The low-cost method therefore allowed the development of a multivariate regression relationship between deformation, charge size and plate thickness, which provides a benchmark for the assessment of future protection solutions.

Airblast variability and fatality risks from a VBIED in a complex urban environment

Explosive blasts and prediction of fatality risks in urban environments is a complicated task due to the variability in blast wave reflection and propagation. The terrorist threats considered in this paper are vehicle-borne improvised explosive devices (VBIED) containing 225 kg or 450 kg of TNT or ammonium nitrate fuel oil (ANFO) detonated in an open street. This paper uses Viper::Blast CFD software to estimate the variability of explosive blast loads using Monte-Carlo sampling. To probabilistically model the blast wave, the paper takes into consideration the variability of explosive charge mass, detonation location, height of detonation, net equivalent quantity, atmospheric pressure and temperature, and model errors. The fatality risk assessment combines lung-rupture, whole-body displacement and skull fracture dependant on the pressure and impulse. It was found that the mean fatality risk for a 450 kg home-made ANFO explosive device detonated at a road T-intersection is 16% for people exposed in the street. If bollards were placed 10 m from the main street then fatality risk for people in the main street is reduced by over 90%. It was found that a deterministic analysis yielded fatality risks 10–60% higher than a probabilistic analysis, leading to an overly conservative assessment of safety risks.

Multiphysics modeling of the initiating capability of detonators. I. The underwater test

Detonators are explosive devices used for the initiation of secondary explosives in commercial and military applications. They are characterized by their initiating capability, which is a critical factor for their safe and effective use but challenging to assess accurately. In this two-part study, we employ numerical simulations to investigate the blast wave generated by detonators and examine their initiating capability. The first part, presented here, follows the European underwater test of initiating capability, which evaluates detonators in isolation (direct method) and the second part considers detonators placed within a receiving explosive charge (indirect method). In the underwater test, the detonator is ignited inside a water tank and the initiating capability is assessed through pressure measurements in the far field. We employ a multiphysics methodology that allows the use of distinct mathematical models for each component such as two-phase reactive materials, elastic–plastic solids, and inert fluids. The computational implementation is validated against underwater experiments and is employed for the simulation of the blast wave generated by different types of detonators. The initial focus is on the general characteristics of the blast wave and subsequently on the differences between detonators of different shell material and thickness. Results show that the blast wave in the near field is asymmetric and varies significantly between detonators, but these features do not persist in the far field. The underwater test considers only the far field and is thus unable to capture the near field differences, which have a significant impact on the initiation of secondary explosives.

Multiphysics modeling of the initiating capability of detonators. II. Booster initiation

Detonators are explosive devices used for the initiation of secondary explosives in commercial and military applications. They are characterized by their initiating capability, which is a critical factor for their safe and effective use but challenging to assess accurately. In this two-part study, we employ numerical simulations to investigate the blast wave generated by detonators and examine their initiating capability. The first part follows the European underwater test, which evaluates detonators in isolation (direct method). The second part, presented here, investigates detonators placed within a receiving explosive charge (indirect method). Specifically, the detonator is placed inside a booster device, which contains secondary explosives and together forms an initiating system used to ignite mining blastholes. The physical system is modeled using a multiphysics methodology to accurately capture the response of the materials present in the configuration (explosives, metals, and fluids). The reactive model is extended to account for shock desensitization where explosives become more difficult to initiate after the passage of weak shock waves. The variability of the blast wave generated by detonators, observed in the first part of the study, can lead to partial desensitization resulting in pockets of unreacted explosives, which inhibit booster initiation and performance. The computational implementation is extensively validated and calibrated against the experiment before being employed for the study of booster initiation by a range of detonators. Results show that the booster is susceptible to shock desensitization, which occurs in varying degrees for different types of detonators and can significantly impact the performance of the initiating system.

Substantiation of parameters of mine working drivage with blasting technique and cleaning charges in advance cutting holes

Drilling and blasting operations (D&B) are the most difficult and laborious operations in the process of mineral extraction, requiring permanent development and upgrading of methods and equipment. The aim of the study is to substantiate the parameters of drilling and blasting drivage of horizontal and inclined (up to 12o) mine workings on the basis of high-performance self-propelled equipment and new designs of box cuts with cleaning explosive charges (0.2 kg of 6ZhV ammonite), placed in advance holes of 65 to 105 mm in diameter. The paper presents the results of the analysis of practical experience and scientific achievements in the field of drilling-andblasting rupture of solid media and continuum mechanics. The need for new designs of box cuts, reliability of which in the formation of high-quality (clean) cut cavity reaches 0.95-1.00, was substantiated. New design options of box cuts have been developed, the peculiarity of which consists in provision of sufficient compensation (peripheral) volume with the use of blast hole cut charges for blasting rupture of trapezoidal partitions, with the compensation volume factor of 2.50 to 1.34. Promising areas of research were shown using the example of complicated structure ore deposits and large faults in the Kirovograd ore district and crystalline rocks of the Ukrainian shield at the following mines of Ukraine: PJSC KZhRK, CJSC Sukhaya Balka (Kryvyi Rih), Vostok-Ruda LLC, SE VostGOK (Zheltye Vody), CJSC ZZhRK, etc. Promising areas of research were proposed using the example of complicated structure ore deposits typically formed at the junction of large faults; besides, the use of environmentally friendly emulsion explosives and self-propelled emulsion explosive chargers was recommended.

Formation of converging cylindrical detonation front

Purpose. To develop a laser method for initiating a converging cylindrical front of a detonation wave and a method for calculating the kinematic parameters of the cylindrical shell walls, accelerated by the pressure of the detonation products of an external explosive charge. Methodology. An experimental technology for the manufacture of a photosensitive explosive composite and an experimental technique for igniting the surface of its layer with an extended laser beam without the use of a fiber-optic cable are used. The results of simulation modeling the Monte Carlo method were used to study the effect of illumination on the process of ignition of explosives by laser pulsed radiation. For the selected type of photosensitive explosive composite, its explosive and optical characteristics, the distance from the surface of the explosive charge to the lens scattering the laser beam, and taking into account the total area of the expanded beam, the regularities of the distribution of the radiation energy density over the vertical and horizontal sections of the laser beam were studied. Findings. The analysis of the scientific and technical level of methods of shock-wave processing of materials in the region of ultrahigh pressures from the point of view of the fundamental value of the cumulation of energy in the waves of a converging cylindrical detonation and shock front is carried out. Physicomathematical modeling was carried out and the regularities of pressure increase in the wave front were established in the process of approaching the shell walls to the axis. The scientific results of modeling converging cylindrical shells under the influence of the pressure of the explosion products have been analyzed. A method for laser initiation of a converging cylindrical front of a detonation wave has been developed, and a method for calculating the kinematic parameters of the converging walls of a cylindrical shell has been proposed. Originality. A technique has been developed for determining the energy characteristics of an expanded laser beam, calculating the laser radiation energy required to initiate detonation simultaneously on the entire lateral cylindrical surface of a photosensitive explosive composite. The idea of technical implementation of the cumulation of converging cylindrical detonation and shock waves was developed further. A technique has been developed for the numerical determination of the change in the internal average compression rate of the shell during the movement of its walls towards the axis for various ratios of its external radius to the wall thickness and taking into account the increase in pressure in the converging detonation front. Practical value. For the first time, a method for laser initiation of a converging cylindrical front of a detonation wave was developed and a device was tested that forms a converging cylindrical front of a detonation wave and a corresponding shock front in the material under study by the impact of a metal shell converging to the axis. The core of the device is a laser explosive initiation system that uses light-sensitive explosive composites to initiate an explosive charge.

Rational crushing of mineral raw materials by well charges as a factor of environmental safety of blasting works in quarries

Purpose. Improving the environmental safety of blasting operations in quarries for the extraction of non-metallic and construction materials based on their rational explosive crushing, aimed at reducing the effect of overgrinding, accompanied by the formation of fine fractions of materials and significant dust emissions. The research methodology provided a theoretical analysis of the destruction processes of a rock massif by well charges of explosives on the basis of calculations of shock adiabats of an explosive wave in rocks at different speeds of detonation of explosives. Experimental verification of the identified patterns was performed by assessing the quality of blasting by the particle size distribution of the rock in the collapse. Research results. The scientific and practical task of ensuring rational explosive crushing of materials in quarries with the use of elongated borehole charges has been solved. Mechanisms for the destruction of rock massifs and the peculiarities of the distribution of destruction zones by dispersed composition have been established, which contributes to the reduction of dust emissions into the atmosphere to an acceptable level of environmental safety of blasting operations in quarries. Comparative estimates of the shock load during the explosion of the explosive charge for the main rocks at different levels of the rate of detonation of charges are given. The dependence of the volume of overgrinding rock in the zone of its adjacency to the charge on the detonation velocity of explosives has been established. An experimental verification of the identified patterns in the current quarry by assessing the quality of blasting by the particle size distribution of rock mass in its collapse after experimental explosions with different parameters is done. Scientific novelty. The multiphase process of rock destruction by explosion was investigated by the calculated determination of the parameters of the shock adiabats of the blast wave in different rocks and at different detonation velocities of explosives. It is shown that during the destruction of a rock mass by the explosion of an elongated borehole charge of explosives, several specific zones of destruction are formed, the characteristics of which differ in particle size distribution. The area of controlled crushing is highlighted, where the intensity of rock destruction can be changed by adjusting the parameters of the explosive load and the area of little or almost unregulated crushing. The possibility of managing the process of dust formation and, accordingly, the level of environmental safety of blasting works in quarries for the extraction of non-metallic and construction materials is substantiated. Practical meaning. The identified patterns and provisions to reduce the effect of mineral overgrinding were used in the development of measures to improve the environmental safety of blasting in the quarry, which, in particular, provided an increase in well spacing in the range up to 3.0-3.4 m and reduce specific energy consumption from 1.27 g/cm3 to 0.97 g/cm3.

Control of density and velocity of emulsion explosives detonation for ore breaking

Purpose.Development of a new procedure for calculating the density of emulsion explosives (EE), that will allow determining the detonation velocity along the charging length, depending on the inclination of boreholes during ore breaking. Methodology.A calculation method for the redistribution of EE density and mass in boreholes at different angles of inclination has been developed by using the well-known laws of hydrostatics. Measurement of the detonation velocity of the EE Ukrainit-PP-2B was conducted by using the method of polygon experimental tests. The numerical simulation of changes in the detonation velocity of explosives in boreholes was conducted by using the proposed method and established regularities. Findings.Methods of calculation of EE density changing along the charging column length under the action of hydrostatic pressure at different angles of inclination of both ascending and descending boreholes have been developed. Based on experimental data, regularities of detonation rate changing from density and charge diameter for EE Ukrainit-PP-2B, varying according to exponential law have been established. The rational initial density of EE Ukrainit-PP-2B has been established for ores breaking by boreholes, which is equal to 8001000 kg/m3, at which the detonation rate along the length of the charge column at different angles of inclination of the boreholes is maintained. The obtained results will allow controlling density and detonation velocity during ore breaking. Originality.The density of EE increases in the formed charging column under the action of hydrostatic pressure: in ascending boreholes from the face, while in descending boreholes from the brow. Practical value.Application of the calculation results of EE density at different inclination angles of boreholes makes it possible to determine in the charge column sections with its critical values more than 1410 kg/m3, at which a sharp attenuation of the detonation rate begins. Consideration of this phenomenon makes it possible to prevent the occurrence of failures at the explosion of charges in boreholes during ore breaking.

Active protection of work area against explosion of dust\u2013gas mixture

Potentially explosive atmosphere can occur not only in the production systems of the food, energy, chemical and petrochemical industries but also in the production processes of the mining industry. Gases, vapours, mists and dusts arise can escape in an uncontrolled way during production, processing, transportation and storage of flammable substances. In combination with oxygen, they create explosive atmospheres that, if ignited, lead to an explosion causing catastrophic damage to people's lives and property. To protect against the results of hazardous dust–gas mixtures explosions in a confined work space, where employees can stay, various control and protection mechanisms are used in the form of an active explosion-proof system. The article presents the results of tests on an active system for limiting the effects of ignition of gas and/or dust based on a highly efficient explosion suppression system—equipped with an ignition detection system, high-pressure fire extinguisher and a power supply and trigger system. Smokeless powder was used as the explosive charge and sodium bicarbonate as the suppressive material. Tests of the effectiveness of the active explosion suppression system were carried out on two devices: a small-size dry dust collector and a zone extinguishing system adapted for direct explosion suppression in closed working spaces. In both cases, the explosion suppression process took place through the action of extinguishing powder blown out of the fire extinguisher after membrane perforation by compressed combustion products.

Pressure Load Characteristics of Explosions in an Adjacent Chamber

To learn more about dynamite explosions in confined spaces, we focused on the chamber adjacent to the main chamber, the main chamber being the location of the explosion. We investigated the characteristics of two damaging pressure loads: first reflected shock wave and quasistatic pressure. In this work, we analyzed the characteristics of the first reflected shock wave and the quasistatic pressure formed by the explosion of the chamber charge. Simulated chamber explosion experiments were carried out, where high‐frequency piezoelectric sensors were used to measure the first reflected shock wave, and low‐frequency piezo‐resistive sensors were used to measure the quasistatic pressure. Valid and reasonable experimental data were obtained, and the experimental values of the pressure load were compared with those calculated from the classical model. The results showed that when the main chamber was partially damaged by the explosion load, the adjacent chambers were not subjected to the shock wave load, and the quasistatic pressure load was less than that in the main chamber. The presence of adjacent chambers did not affect the shock wave load in the main chamber. Using the mass of the explosive and the blast distance as input parameters, the internal explosion shock wave load parameters, including those in adjacent chambers, can be calculated. The presence of the adjacent chamber did not affect the theoretically calculated quasistatic overpressure peak in the main chamber. Using the mass of the explosive and the spatial volume of the chamber as input parameters, the quasistatic pressure load parameters of the internal explosion can be calculated, including those in the adjacent chambers.

Calculation of crack formation radius by modeling the explosive charge with a radial clearance

This article discusses the effect of explosion pulse on the process of cracking in a rock mass and shows the possibility of calculating the radius of a cracking zone by the theoretical value of the dynamic strength of rocks, based on their main physical and mechanical characteristics.

Development of an Optimized Regression Model to Predict Blast-Driven Ground Vibrations

Ground vibrations caused by blasting operations in cement canisters is among the main mining issues that cause significant disruptions to nearby buildings and infrastructure. This research was performed in a limestone quarry situated southeast of Helwan City, Egypt, to investigate the impact of ground motion vibration due to cement blast action in limestone rocks. To reduce the environmental impact of quarry blasting, continuous monitoring, and accurate medium's peak particle velocity (PPV) assessment are required. Recently, machine learning (ML) models are employed in diverse applications. The default hyperparameters of such models must be modified to fit the problem concerned. The hyperparameters optimization for ML models impacts the employed model's performance and efficiency. In this research, different regression models are implemented for predicting the PPV values. A dataset representing 1438 blast incidents in the Helwan area was built and utilized to evaluate the considered ML models. This dataset incorporates the relationship of the ground vibration amplitude to both the explosive charge weight per delay and distance from the blast. The predictive models' output performance has been evaluated using the root-mean-squared error (RMSE) and the coefficient of determination ($R^{2}$ ). The PPV dataset has been divided into training and testing data to produce statistically significant results and to make the dataset more representative to avoid overfitting. The utilized test PPV dataset acts as a proxy for any new PPV data prediction. There was evidence of higher performance in the developed Decision Trees model with the lowest RMSE and the highest $R^{2}$ on training and testing data. The decision tree is, therefore, an acceptable algorithm for the construction of a predictive PPV model for other quarry blasting areas with conditions identical to those in Helwan. Finally, comparative experimental results have shown that optimized models can predict PPV values with lower errors and greater prediction accuracy.

Experimental Study on the Damage Characteristics of Polymer Slabs Subjected to Air Contact and Close‐In Explosions

As a new antiseepage reinforcement material, polyurethane grouting material has been widely studied in terms of its static mechanical properties. However, research on its dynamic mechanical properties is relatively rare. In this research, considering the influence of the explosive charge weight, the air contact and close‐in explosion experiments of polymer slabs were carried out. The failure mode and damage spatial distribution characteristics of polymer slabs were explored. Pressure time history curve of air shock wave was obtained using an air shock wave tester. The influence of polymer slabs on the propagation of air explosion shock wave was compared and analyzed. The results show that, under the air contact explosion, the polymer slab mainly suffers local damage, while under close‐in explosion, overall damage is the main damage mode. With the increase of the explosive charge weight, the failure mode of the polymer slab transits from surface crack and slight spalling to local and whole crushing.

Detonation Parameters of Mixtures Produced by Injecting Gaseous Components into the Barrel of a Pulse Gas Detonation Installation

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.

Evaluation of some parameters of the interaction between detonating explosive charge and environment

Both strain waves, generated by the shock wave, and expanding gaseous products of the explosion contribute to the destruction of the rocks. The role of these factors is especially obvious at explosion of soft and moderately hard rocks. The article considers some aspects of the phenomena accompanying the explosion of the detonating explosive charge on example of the unworked coal.