Numerical analysis of internal blast effects on underground tunnel in soils

The response of underground structures subjected to internal blasts is an important topic in protective engineering. Due to various constraints, pertinent experimental data are extremely scarce. Adequately detailed numerical simulation thus becomes a desirable alternative. However, the physical processes involved in the internal explosion and blast wave propagation are very complex, and hence, a realistic and detailed reproduction of the phenomena would require sophisticated numerical models for the loading and material responses. In this article, a fully coupled numerical model is established to simulate dynamic responses of tunnel structure in soils under internal blasting loads. The approach considers all the stages of the process: detonation of the internal charge; shock wave propagation in the internal gas; coupled fluid-structure interaction between explosive wave and tunnel structure; structure damage; soil-structure dynamic interaction; and wave propagation in the surrounding soil medium. Effects of soil-structure interactions, soil stiffnesses, buried depths, cross-sectional shapes and locations of charge are thoroughly investigated on dynamic responses of tunnel structures subjected to internal blasting loads. Results show that the tunnel responses are driven by the soil stiffness rather than by the interface friction, and the location of charge has a significant effect on the tunnel responses.