Effect of using blast wave trap in tunnels with 90 degrees bend on reduction of Pressure produced by a explosion outside the tunne

Blast wave trap is one of the ways to deal with and reduce the effects of blast wave inside the secure underground structures. In this paper, the effect of blast wave trap on reducing the overpressure in the main route of the tunnel has been studied. Accordingly, the blast wave propagation of different explosives in various distances from the tunnel entrance including blast wave trap is simulated. Autodyn software is employed for numerical simulation. Based on the ratio of the overpressure applied to blast wave trap to obtained overpressure of the main route after blast wave trap, the appropriate distance and optimum length of the blast wave trap is calculated. The results presents that using blast wave trap can significantly reduce the overpressure applied to the blast wave trap zone. Besides, higher values of overpressure before blast wave trap zone leads to an increase of optimum length of blast wave trap along with more pressure reduction.