Characteristics of blasting vibration in presence of weak interlayers

A numerical model is proposed in this paper to consider the effect of thin weak layers within semi-infinite homogeneous elastic media when explosives are at different locations. Using this model, we have studied the different features of blasting vibrations generated by explosives placed at different locations and for different dimensions (different areas) of weak layers through LS_DYNA. The numerical results reveal that the longer the layer length is, the larger vibration amplitude is and the less the characteristic frequencies of vibration signals are. The amplitude of vibration signals has a maximum value when blasting source is in the weak layer, and will decrease when the blasting source go away from the weak layer. There is a significant shading effect when the dimension of weak layer is large and the relative stiffness of the weak layer compared to surrounding medium is low. These findings are helpful to identify underground weak interlayer. In-situ experiments also confirm above findings qualitatively.