Ground shock mitigation with explosion energy coupling reduction

Underground structures have been widely employed as they are relatively difficult to locate, and more resistant to airbursts and surface explosions. With the development of penetrating weapons, subsurface explosions could couple a large portion of the blast energy into the surrounding soil, generating strong ground shock and posing a great threat to buried structures. Different from the existing ground shock mitigation methods, in the present study, a new ground shock mitigation approach based on explosion energy coupling reduction was proposed and was realized by installing specially designed buried multi-layer concrete honeycomb array. Firstly, the numerical model was established with ANSYS/LS-DYNA and verified by the empirical formula in the design code and field test data. Then, the validated model was employed to investigate the ground shock mitigation effect of the single concrete honeycomb cell and multi-layer honeycomb cell array. Furthermore, the important governing factors influencing the ground shock mitigation effect, including the thickness of the cell walls, the strength of the concrete, the configuration of the cell array, and the location of the explosion, were discussed. Based on the analysis and parametric study, it was found that in the concerned scaled distance range meaningful in buried structure protection, the proposed approach exhibited a favorable mitigation effect. Increasing the thickness of the hollow honeycombs or the strength of the concrete would increase ground shock intensity. Furthermore, recommendations regarding the hollow cell array design that balanced the ground shock mitigation effect and practical engineering consideration were provided, facilitating the protective design of underground structures against subsurface explosions.