Simulation Analysis of Factors Affecting the Distribution of Internal Blast Reflection Overpressure on Tunnel Linings with Grey Relational Theory

Investigating the influence level and law of various factors on the distribution of reflected overpressure resulting from explosions in vehicles carrying hazardous chemicals or explosives is of great significance for accounting for the impact of load distribution in the blast-resistant design of structures. This paper uses LS-DYNA software to simulate and investigate the effects of five factors (charge mass (M), charge eccentricity (X), the aspect ratio of cuboid charge (δL/H), charge inclination (θ), and tunnel diameter (D)) on the distribution of reflected overpressure on the lining. The grey relational degree reveals the relative influence of each factor on the reflected overpressure parameters of the lining cross-section (RPPCS) at the blast center. The results show that M, X, and D have the greatest influence on the RPPCS of the blast center. An independent analysis of each factor revealed that the distribution of reflected overpressure from the central charge changes from two-dimensional symmetry to one-dimensional symmetry. Non-central charge disrupts its symmetric distribution. Inclined charge results in an asymmetric distribution. The intensity and incident angle of the shock wave have a significant effect on the location of the maximum reflected overpressure on the lining cross-section (RPCS-max) at the blast center. In the RPCS-max at the blast center, X and θ change their location. θ can alter its distribution shape. When δL/H is too large, increasing M or δL/H will both reduce the reflected overpressure. The influence of various factors on RPPCS is different. Increases in M and D reduce the non-uniform distribution of RPCS, but other factors have the opposite effect. The research findings provide a basis for considering the effects of load distribution in the design of structures resistant to internal explosions.