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Earth-covered magazine has some characteristics that are safer than the above-ground magazine and are more economical than underground magazine. To investigate the pressure distribution and the structural failure under the internal explosion, the scaled tests of the earth-covered magazine were conducted under a 0.5 kg TNT explosive charge. The overpressure in the 0°, 90°, and 180° directions outside the structure and the debris distribution were obtained. The numerical simulations were constructed in LS-DYNA software to analyze the test results. The results show that the external overpressure has a directional characteristic that the maximum and minimum overpressure appear in 0° and 180° directions, respectively. In the double logarithmic coordinate system, the overpressure peaks in three directions are linearly related to the scaled distance. Most of the fragments in the 0° direction hit the ground within the front range of ±60°, and the further fragments (40 m or more) were confined to a limited sector within the front range of ±30°. The internal explosion numerical simulation shows that the concrete cracks first appeared at the roof and the ground, and then the damage occurred at the intersection of the walls, and then the damage occurred at each surface. The maximum debris velocity of the side and rear walls is lower than that of the front wall due to the limitation of the soil. The motion equations of the debris combined with numerical simulation can be adopted to predict the projection distance of fragments. [ABSTRACT FROM AUTHOR]

Methane-air mixtures initiated by Hexogen (RDX) were experimentally investigated in a custom-designed rectangular venting device. By changing the methane concentration, the overpressure characteristics and flame propagation were studied under the conditions of RDX detonation and electric spark ignition, respectively. The results indicate that, compared with spark ignition, the RDX explosion shock wave leads to the structural vibration and interacts with the flame, shortening the methane reaction time and substantially increasing the explosion overpressure. When the methane concentration is close to the equivalence ratio of unity, only one pressure peak occurs after the vent plate opening. The pressure peak caused by the interaction between acoustic waves and flames, P 3 , appears only at methane concentrations of 8 vol% and 13 vol% under RDX detonation. The acoustic vibration of the structure induced by different masses of RDX has a nonlinear impact on the increase of P 3. The long reaction duration and the weakening of the shock wave result in a relatively small frequency of high-frequency oscillations at high concentrations. [ABSTRACT FROM AUTHOR]

Gas explosion accidents under shock wave stimulation cause more severe hazards than electric spark ignition. To explore the initiation mechanism and explosion characteristics of methane induced by shock waves. A series of experimental investigations of methane-air mixtures initiated by hexogen (RDX) was performed based on a self-developed closed pipeline. The effects of incident shock wave intensity and methane concentration on the characteristics of methane explosion were studied. The results indicate that methane participating in the reaction can significantly increase the positive pressure duration compared with RDX explosion. With the increase of incident shock Mach number (Ma), methane deflagration pressure increases and counteracts the attenuation of RDX detonation pressure. When the ignition distance is 0 cm, the overpressure inside the pipeline is directly proportional to the methane concentration from 5 vol% to 13 vol%. When the concentration approaches the upper explosion limit, the flame velocity exceeds the theoretical detonation velocity, resulting in the unstable detonation of methane in the pipeline. • The methane combustion mechanism initiated by RDX was investigated in a closed pipeline. • The effect of the shock wave intensity on the explosion characteristics was analyzed. • Significant influence of methane concentration on overpressure peak and flame velocity was obtained. [ABSTRACT FROM AUTHOR]