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Abstract:
How to accurately define “close-in explosion” has always been a hotspot in the field of protection engineering research. In this paper, based on the fully validated 2D axisymmetric fine finite element model, the characteristics and laws of the propagation of air shock waves and high-speed expansion of detonation products generated by TNT spherical charge were studied. It is found that there is a significant influence of the detonation products on the blast load on rigid wall when the range of the scaled distance less than 0.8 m/kg1/3. It is recommended to use the scaled distance range from 0.30 m/kg1/3 to 0.80 m/kg1/3 as the definition criterion of close-in explosion for spherical TNT charge explosion. It was found that: due to the inhomogeneity and randomness of the detonation product rapid expansion, the peak value of the rigid-wall reflected overpressure experienced a sharp drop within a range of incident angle of 0°～5° in the case of close-in explosion defined in the paper. In addition, there were two peaks on the reflected overpressure curve in close-in explosion cases, and the first peak overpressure was caused by the interaction between the shock wave and rigid wall while the second peak overpressure was generated by the interaction between the detonation products and rigid wall. Based on curve fitting, the formulas for calculating the two peak values were proposed, respectively, and a simplified load model suitable for calculation of engineering structure response was put forward; The distribution law of the reflected overpressure on the rigid wall under close-in explosion was revealed.
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