In this study, the effect of coal dust particle size on the intensity of coal dust explosion was investigated using an explosion test in a 2-liter chamber. Samples of coal have been collected from various coal mines in the country and they are used for coal dust preparation. To determine the index of explosion capability (KST), the distribution of the explosion intensity of each sample should be evaluated by measuring the maximum pressure (Pmax) and the maximum explosion pressure rise rate (dp/dtmax) in different experiments. Coal dust particles at constant concentrations and different sizes (149µm, 125µm, 105µm, 74µm, 63µm, 53µm, 44µm, 37µm) were evaluated. The results of the sieving analysis show that almost all samples of the prepared coal dust have a minimum optimum explosive concentration (250 g/m3 ). In this analysis, all tests were carried out at 1.5 bar and the initial temperature was 25 °C. According to the results, coal dust particles with dimensions of 44 and 37 microns have higher explosive index than other dimensions. Therefore, both parameters of maximum explosion pressure (Pmax) and the maximum explosion pressure rise rate (dp/dtmax) show an increasing trend with decreasing particle size. Also an increasing concentration of coal dust shows an increasing trend at the first and then a decrease in the intensity of the explosion. The presence of small coal particles increases the effective level, thus increasing the explosion rate and the rate of instability, which accelerates the process of coal dust explosion. Therefore, according to the results obtained in the process of checking coal dust explosion, in addition to the inherent characteristics of coal dust, particle size coal dust should also be taken into account. The results obtained in this mechanism are useful not only in the research and development of knowledge of coal dust blasting processes, but also in taking the necessary measures to prevent the explosion of coal dust in coal mines.

Underwater explosion is a common phenomenon to be considered for marine and coastal structures. Although it is not wise to design such structures based on explosion loads, but having studied the explosion wave and its demotic effects, location and geometries of these structures can be improved. In this study after introducing underwater explosion mechanism a summary of the numerical methods used for propagation of explosion waves in water is introduced and finally a preferable method is proposed for modeling the phenomenon. Based on such considerations numerical results using multipurpose commercial codes are successfully compared with empirical relations.

Various structures are subject to explosion for terrorist and non-terrorist reasons. The study of effective factors in reducing the damage caused by the explosion is one of the most important issues of passive defense. One of these factors is the presence of openings in the structure under confined explosion. In this study, the effect of opening on the loading caused by the explosion has been examined in terms of pressure-time and impulse-time graphs. In this regard, using the UFC 3-340-02 regulations and numerical simulation of the AUTODYN hydrocode, the confined explosion of a TNT explosive with different masses in a cubic chamber, with different openings in terms of size and location, has been investigated. The investigation results of the effect of each of the opening position factors specify the number of pop-ups with openings and the size of the opening on the loading exerted on the inner surface of the structure due to the confined explosion. Finally, in addition to determining the parametric optimal optimization, the results of the confined explosion resulting from numerical simulation are compared and examined with the UFC 3-340-02 regulations.

Explosion problems can be examined in different environments. Due to the lesser-known nature of soil types and extent of the equations of state,explosion problems need careful analysis.Because of difficulties in laboratory explosion modeling, numerical models use to analyze this phenomenon Using the SPH methodology avoids the disadvantages of traditional numerical methods in treating large diformations in the extremely transient explosion process. Since explosion crater in the soil is an important problem and most of the studies are experimental, In this article it is tried to investigate the craters diameter and height caused by the different amounts of explosives. The model is programmed with Fortran language and smooth particle hydrodynamics,SPH, the craters, pressure caused by the explosion in the soil and the soil surface changes are also studied. To validate the model, the results of a laboratory study were used and it is shown that they are consistent with the numerical results of this study.Finally,craters in a two layer soil is studied.This program can be used for modeling of soil explosion and craters.

In this research, a deep explosion in the reservoir of a concrete gravity dam has simulated by the coupled Euler –Lagrange finite element method. The validity of explosion hydrodynamics pressure has compared with Taylor empirical formula.  The surface sloshing not considered due to deep explosion. The dam and its retained water excited by detonating large explosive charges in deep water upstream from the dam. The damage plastic model of Lee has applied for concrete and damage pattern detection of dam. The dam responses to the underwater explosion were recorded as crest displacement time history. The result of explosion simulation of one ton TNT has compared with actual damage of Koyna dam due to 6.5 Richter earthquakes in 1976. The crack pattern was similar in two cases, but in underwater explosion test, the crack propagation is stopped before reaching to downstream of dam. Evolution of result was shown that controlled explosion test in the reservoir of a dam can be used as a method for study of hydrodynamics effects on dam body safety.

Due to the propagation characteristics of explosion shock waves, the stiffness of the structure and its components has an important influence on the explosion effects of the reticulated shell. However, the current research on this problem is insufficient. In this paper, a parametric model for the numerical simulation of spherical reticulated shell structure under internal explosion was established using the finite-element software. Based on the built model, the dynamic responses of a spherical reticulated shell under internal explosion were numerically simulated and analyzed. In addition, the influence of the stiffness of the reticulated shell bars, the stiffness of the connectors, and the stiffness of the roof panels on the explosion effects of the spherical reticulated shell structure under internal explosions were researched. The results show that with an increase in the flexural stiffness of the reticulated shell bars, the kinetic energy and the maximum node displacement responses of the spherical reticulated shell are reduced. However, the magnitude of these decreases gradually decline. The results also reveal that the greater the stiffness of the connectors, the greater the internal energy, the kinetic energy and the maximum node displacement responses. The increase in the stiffness of the connectors is disadvantageous to the anti-explosion properties of the spherical reticulated shell structure. In addition, the research indicated that there is a threshold value to the stiffness (thickness) of the roof panels with regard to the influence of the explosion effects of the spherical reticulated shell, in the case of a certain amount of explosives. With an increase in the stiffness (thickness) of the roof panels, the displacement responses of the spherical reticulated shell under internal explosion decrease if the stiffness (thickness) of the roof panels exceeds the threshold value. Finally, some suggestions for explosion proof and anti-explosion design of the long-span spherical reticulated structures are proposed.

Fire and explosion are often synergistic. A fire may occur after an explosion or a fire may occur first and then an explosion occurs. The consequences of a combined fire and explosion scenario about each component must be considered in the design or evaluation of the structure. The analysis of fire and explosion should be done together and the effects of one on the other should be carefully analyzed. In most researches and design guidelines, fire and explosion phenomena are investigated independently and their interaction is less considered. In this research, this issue is addressed and the fire after the explosion and the interaction and synergy of these two phenomena are studied together. The studied structure is a two-story steel structure with different occupancy (dwelling, office, etc.). which is subject to various explosions and as a result fire caused by the equipment inside the building. Explosive loading has been calculated using UFC 3-340-02 instruction charts and fire load using the concept of fire density and relationships of EUROCODE 1 and EUROCODE 3 regulations. In order to simulate explosive and thermal loading, Abaqus finite element software and combined thermal-deformation dynamic analysis have been used. The temperature caused by the fire has been used as a natural fire, and the cooling and post-cooling stages of the fire have also been investigated. After validating the proposed simulation with two valid laboratory works, the analysis of the structure's response against various types of explosive loads and subsequent fires was performed by a numerical model. The results of these investigations showed that the response and deformation of the structure in the chain combined analysis (applying the interaction of explosion and fire on the structure) compared to the independent combined analysis (independent analysis of the structure against explosion and fire and collecting the responses together) It increases by 15%, and considering the interaction of explosion and fire is not only important but also necessary, and not considering this interaction in most cases will cause the response of the structure to be less than the reality, and as a result, it will cause an unsafe design.

The explosion occurrence is the most likely events that may occur during a fire incident. This paper studies on nonlinear response of steel column against an explosion during fire event by using dynamic explicit finite element scheme. In this study, the effect of temperature of steel surface at the moment of explosion and scaled distance parameter are investigated. The results show that increasing temperature to more than 400 °C may cause large displacements and ultimately led to collapse the column. It is shown that increasing the temperature of the instant explosion for more intense explosions is less effective than explosions with larger scaled distance (Z).

One of the regular tests used for designing explosive materials for internal explosion is doing the explosion in a closed or partially closed environment to detect and analyzing the blast wave parameters. In this regard, the test so-called two- room test is considered among researchers. The test is performed in two reinforced concrete- built rooms which are connected by a door. The explosive material is detonated in one room and the effects of that are measured and analyzed in both of them. The purpose of the current study is to predict the maximum number of explosions which leads to destruction of the prefabricated rooms. Hence, after validation of the solution, the numerical simulation of the successive explosions was performed by AUTODYN hydrodynamic software. The damage parameter in RHT model of concrete was used as a basis to determine the number of allowable explosions. According to the mentioned basis and with extrapolating the simulation results, maximum number of the allowable explosions was determined for different amount of explosives.

Explosions at the entrance of tunnels and underground spaces can lead to losses. To decrease side effects of such explosions, some approaches like dead_end, bends, geometric barriers and anti-explosion doors are available. Using geometric barriers, especially the waveguides, is the most commonly used and economical way. The purpose of this paper is to investigate the effect of the angle of rotation of the longitudinal axis (bend) and the local variation of the tunnel area on reducing the impact of explosions. Appropriate angle of rotation of the longitudinal axis and suitable location for local variation of the tunnel cross section in line with the tunnel are calculated, by numerical analysis, using Abaqus software.  Finally, proper characteristics are used to propose a method, requiring the least drilling in construction (the most economical method), and generating the highest reduction in the effects of the explosion (the highest vulnerability reduction) in explosions near and away from the span. The results show that the localized change in the tunnel cross-section at the end of the direct path and the change in the angle of rotation of the long axis from 135 ° to 90 ° (90 °) will lead to the greatest reduction in pressure.