Evaluating the Effect of Large and Spread Explosives Loads

Journal of KONES. Powertrain and Transport, 2014

When an explosive charge is fired, the nature and mass of the explosive are the only parameters of importance usually considered. The shape however, also plays a major role in the effect of an explosive charge. Knowledge of shape effect can be important before the use of the explosive (in order to create a maximum effect with a given mass of explosive), or in post-explosion damage assessment. The shape effect however is only significant within a certain range from the charge. At longer distance, the produced blast wave tends to be spherical. The shock wave parameters studied in this work are the peak overpressure and the first positive impulse. A series of numerical test has been performed in order to determine the range of influence of the charge shape. Different locations of initiation were compared. A hemispherical charge was point detonated at its centre whereas a cylindrical shape was detonated at the centre of an upper or lower plane. Numerical simulations of near field burst were conducted using LS-DYNA software. During numerical tests a pressure fields were determined for different shapes of explosive charges as well as the pressure waveforms at points located 1000 mm from a centre. Additionally, reference pressure history curves from LOAD_BLAST_ENHANCED procedure were calculated.

2008

In case of terrorist attacks or other intentional actions using explosives, the information that can be obtained from the crater generated by the blast waves is extremely important. For example, the focus of the explosion and the mass of the explosive used in the attack can be deduced examining the location and dimensions of the crater. However, studies about craters produced by explosions on or above ground level, which would be the case when the explosive charge is situated in a vehicle, are rarely found in the open technical literature. A numerical study related to crater produced by small to medium explosive loads located on the soil surface was presented in previous papers. In this paper, a study about the craters created by exploding charges ranging from 120 kg to 1900 kg of TNT. The charge consists of different ordnances stacked in different configurations. The crater diameters and depths for all explosive loads tested at the Touwsrivier Training Area (South Africa) were obta...

Acta Physica Polonica A, 2015

Studies of craters produced by explosions above and underneath the ground surface are rarely found in the open technical literature. Most reports are confidential and access is limited to government agencies. Much of the information on explosively formed craters found in the literature is based on experimental data. Numerical studies were very limited until recently. An ablity to predict the anticipated size of crater is crucial to identification of the corresponding damage that might be caused by a given explosive charge, or to assessment of the magnitude of the charge if this is not known. In this paper a non-linear dynamic numerical analysis of the explosion phenomena in clay soils associated with different amounts of TNT explosive charge is performed using the ABAQUS/Explicit computer program. To validate the numerical procedure and material constitutive models used in the present work, a comparison with experimental results is first performed. The results obtained illustrate that the agreement between the numerical and the experimental results is reasonable. A study of the influence of soil density on the crater dimensions is then undertaken. From the numerical results obtained, a new prediction equation is proposed for the crater dimensions as a function of the explosive charge considered. This equation represents the approximation of the numerical results by least squares fitting.

MATEC Web of Conferences

When conducting a research concerning the propagation of a shock wave generated by the detonation of civil use explosives, the first thing that comes to mind should be if the detonation process takes place in an obstacle-free field, or the area has obstacles such as rocks, metals structures, wood etc, obstacles that can and will influence the final results, the shock wave curve being obturated by it. On one hand, the paper presents the experimental results obtained after the detonation of a freely suspended load, placed at 0.5m above a concrete surface. On the other hand, it compares the values of explosion pressure as shock wave, measured on 4 sensors linearly disposed at the same elevation to the ground, at a distance of 2,3,4 respectively 6 meters from the explosive charge. These values are determined through computerized simulation, using ANSYS AUTODYN software, by virtually reproducing the real scenario. Following the two experiments (real and virtual), one can conclude that co...

WIT Transactions on The Built Environment

Blast wave intensity depends on several parameters, namely: explosive material type, charge weight, shape and orientation, detonation point position, detonation initiator type (primary explosive type), the position (distance) of the explosive charge in relation to the intended target (standoff distance) and ground surface. Environmental conditions, particularly air temperature, humidity and atmospheric pressure, also influence blast pressures. It is difficult to accurately predict the blast wave action on target structures if all of these parameters are considered. This research concentrates on the influence of the shape of the explosive charge on blast pressure measurements. Spherical and hemispherical charge shapes are considered usual and, as such, accurate and reliable analytical expressions for the blast wave pressure approximation are available. The form and propagation of spherical charge blast waves are considered to have been thoroughly studied and known. In today's urban and guerrilla warfare, speed of action is a crucial factor. Rendering the careful shaping of explosive charges is time consuming and unnecessary, hence the need for investigating different charge shapes, other than spherical. This investigation consisted of field range experimental measurements of the incident (freefield) and reflected pressures caused by detonating differently shaped charges. The shapes considered were: spherical, cylindrical and rectangular. The experiments were numerically validated and verified using ANSYS Autodyn hydrocode software. Numerical simulations utilised a coupled Euler-Lagrange planar solver, using an ideal air environment and PEP500 explosive material. Charge shapes varied, according to the experimental outline, and the measuring points were constant, to allow comparison of the measured data.

MATEC Web of Conferences, 2016

For several decades, a blast wave due to explosive detonation has been investigated extensively. Base on a significant amount of experimental data, the blast wave propagation has been predicted at specific conditions. However, only spherical shape of explosive has been considered in most studies. Recently, it was noted that the shape of explosive influences the blast wave propagation significantly. In this study, a finite element analysis was carried out to investigate the effect of the shape of explosive on the blast wave propagation. Two different shapes of explosive were compared in blast wave propagation; spherical and cylindrical shape. It was found that the spherical and cylindrical shape blast show different characteristics in the blast wave propagation. The spherical blast showed the isotropic wave propagation as verified by experimental data. However, the cylindrical blast showed more concentrated and faster propagation in the axial direction.

International Journal of Structural and Civil Engineering Research, 2020

Explosives detonation could cause a partial or total destruction of equipment and installations, which in some cases derives in technical staff fatality. The present study aims to define blast wave parameters for spherical explosive in outdoor detonation. To achieve this purpose, a total of 30 blast wave tests were developed in samples of 1kg, 3kg and 5 kg of TNT; the experimental results were compared with standards and handbooks of explosion protection in order to evaluate the damage produced by blast wave effect in equipment, installations and technical professionals. The results reflect a range of safe-zones that varies from 7 m to 300 m according to explosives magnitude, furthermore the results also show the distance at which blast wave provoke lethal injuries. Finally, this research will be applied in further experimental tests related to the controlled demolition of building structural elements, to maximize safety ranges and minimize equipment damage, injuries and fatalities in these events. 

Defence Science Journal

A significant number of airblast test have been carried out with the purpose to characterise and analyse the properties of improvised explosive device (IED) with non-conventional explosives in terms of knowing the effects on people and/or structures. Small devices with 1.5 kg of explosive, initiated with a detonating cord have been studied. Seven different mixtures have been tested with two types of ammonium nitrate AN (technical and fertilizer) in different forms like prills or powder. In some cases, the ammonium nitrate has been mixed with fuel oil while in others, it has been mixed with aluminum. The TNT equivalent based on pressure, impulse, arrival time, positive phase duration and shock front velocity have been calculated and analysed for each mixture. Comparing the field test data obtained with respect to the representation of the UFC 3-340-02 values, it can be seen that the parameters measured are consistent. The IEDs with fertilizer ammonium nitrate do not detonate with the...

Journal of KONES. Powertrain and Transport, 2016

Explosives are broadly used today in many applications, both civilian and military. Many experiments involving explosives use either ball or cylinder charges. However, there can be raised a question whether an exact shape influences the resulting blast wave, and, additionally, if the length to diameter ratio of the cylinder influences the wave. To answer the question, numerical analysis was conducted. A 3D model of the charge was constructed in LS-Prepost software and calculated with use of an explicit FEM method in LS-DYNA software. To determine the change of character of the blast wave, the dimensions of the charge change, whereas the mass and distance from the centre of the charge are constant. Several length to diameter ratios was tested, starting from 0.25, to 2, in 0.25 increments. Two explosives, HMX and TNT, were used. As expected, the resulting Blast wave was different in each case, with 100% difference in pressure values between 0.25 and 2 L to D ratios, especially along the length axis of the cylinder. The results show that the exact diameters of the charges need to be taken into consideration while determining a type of charge to be used as well as determining the goal to be achieved during a particular conducted experiment.

International Journal of Protective Structures

Equivalency is often used to enable calculations of overpressures and impulses for explosives other than TNT. Equivalent mass factors are available for far field detonations but none are available for near field detonations. These reported factors are associated with incident overpressure and impulse and assumed appropriate for reflected overpressure and impulse. Numerical studies of TNT-equivalent mass factors for four high explosives (PETN, Composition B, Pentolite and Tetryl) for incident and normally reflected peak overpressure and impulse are presented for a wide range of scaled distance 0.06 ≤ Z ≤ 40 m/kg 1/3. Emphasis is placed on near-field detonations for which no reliable factors are currently available.