Characteristic propagation features of the explosion air shock wave at the corner of tunnel

This paper is aimed at presenting the authors' numerical calculation and their theoretic analyses of the air shock wave propagation process as well as the corresponding principles in case of the explosion taking place in the mining tunnel. For this purpose, a piece of particular research into the overpressure changing process when the explosion shock wave goes through 45° turning corner. As is known, since inside a tunnel, its wall is limited in its rigidity, the propagation of shock wave must differ from that in an open space. According to the results of our research, the overpressure tends to increase noticeably with the air shock wave becoming more complicated and therefore difficult to give a clear description at a turning corner inside. Nevertheless, it is there the outer wall of the tunnel that has to suffer the peak overpressure and then begins to attenuate quickly in a radial form with its minimum overpressure at the inner wall side. It is just for this reason that the peak overpressure strength can thus be estimated by the shock wave reflection formula. That is to say, the air shock wave should resume to plane front form after propagation continuing through a distance of 4 times equivalent to the tunnel diameter, which can therefore be calculated in accordance with the cross-section area, till then the overpressure would have been attenuating monotonously with the distance increase from the epicenter of the explosion.