Blast-induced fractures are simulated by a novel gas-solid interaction model, which combines an immersed-body method and a cohesive zone fracture model. The approach employs a finite element fluid model and a combined finite-discrete element solid model. This model is fully coupled and simulates the whole blasting process including gas pressure impulse, shock wave propagation, gas expansion, fragmentation and burden movement phases. In the fluid model, the John-Wilkins-Lee equation of state is introduced to resolve the relationship between pressure and density of the highly compressible gas in blasts and explosions. A Q-scheme is used to stabilise the model when solving extremely high pressure situations. Two benchmark tests, blasting cylinder and projectile fire, are used to validate this coupled model. The results of these tests are in good agreement with experimental data. To demonstrate the potential of the proposed method, a blasting engineering simulation with shock waves, fracture propagation, gas-solid interaction and flying fragments is simulated.