Abstract: The research of explosive shockwave can be significant for the weapon's damage efficiency evaluation, and also important for measuring the system security in mine explosive accidents.  When propagating through the bend tunnel, due to the limitation of rough wall, the explosive shockwave will produce reflection and superimposition to form a turbulence area, disturbing the energy distribution inside the tunnel. And the shockwave will recover to become “plane” in certain distance. In this paper, LS-DYNA software is utilized to simulate certain weak shockwave propagating through the bend tunnel and to find out the rule and characteristic of shockwave turbulence area inside the bend tunnel. The “plane wave” is quantitatively redefined using the overpressure/momentum ratio benchmarks by analyzing the numerical simulation results. The research result shows that the momentum ratio benchmark can be used to better define the “plane shockwave”, and the shockwave will assuredly recover to become plane in a distance of 5 times equivalent tunnel diameter behind the tunnel bending. In case of a bend corner angle  of 20°,45°,90°or 135°, the momentum attenuation coefficient is 0.993 7, 0.955 9, 0.911 5 or 0.816 7 correspondingly. The max peak overpressure inside the turbulence area can be estimated using the fitting formula listed in the paper.

Key words: Explosion mechanics, Bend tunnel, Plane shockwave, Numerical simulation