Explosions can result in massive fatalities and severe damage to structures and facilities in tunnels. Therefore, it is of crucial importance to incorporate disaster mitigation strategies against potential blast scenarios in the design of such structures and implement viable solutions to attenuate the destructive effect of blast waves caused by explosions. To this end, we propose an innovative layout design strategy called symmetric multi-path branching, where multiple closed-end paths with relatively small cross-sectional areas branch out laterally from the sides of a straight and prismatic tunnel. To exploit the neutralizing effect of colliding pressure waves, a reflective symmetry with respect to the longitudinal mid-plane of the tunnel is considered in the layout design. To examine the effectiveness and efficiency of this strategy in reducing the effect of the pressure wave caused by the explosion, a series of layout designs are produced and investigated numerically and experimentally. After verifying the simulation method, the effect of the branching angles, cross-sectional geometry, drilling depth, and location of the branches, as well as the mass of the explosive charge, are studied systematically. The results illustrate an acceptable match between the numerical and the scaled experimental test methods. Moreover, it is shown that using three pairs of branches with an appropriate geometry and branching angles can attenuate the pressure waves passing through the tunnel up to 50% without obstructing the main route. The findings of this study can be applied to designing blast-resilient layouts in the development of underground tunnels and other corridor-like structures.
