Laboratory scale investigation of stress wave propagation and vibrational characteristics in sand when subjected to air-blast loading

The main objective of this study is to develop a new approach for evaluating the effects of air-blast on protective barrier made of sand. The air-blast loading is simulated experimentally laboratory using the shock tube test facility. The stress wave propagation in medium dense and dense sand medium are investigated under simulated air-blast loading. Synchronised pressure and accelerometer measurement system is used to capture peak stress wave pressure and peak particle velocity (PPV). The blast wave impact generates a stress wave in the medium leading to the compaction of the soil skeleton, which has led to stress enhancement (4-5 times of peak overpressure) in top most sand layer, following which the high-pressure gas behind the shock front permeates through the sample. The intensity of stress waves and gas permeation rate gradually decrease with depth. Further, from the result of the simulated air-blast experiments, an empirical equation has been developed with a power law index of 1.88 and 1.36 for medium dense and dense sand respectively, to predict PPV against scaled blast distance. Visualisation of the sand deformation was possible with the help of a high-speed camera; displacement trajectories and strain contours are obtained through digital image correlation (DIC) analyses.