Comparative Study on Response of Natural and Artificial Granular Media Towards Blast Loading

Conventionally, naturally available sand and soil are used to form a protective layer around the critical military structures. In the recent past, the use of manufactured granular media like glass spheres for protective purposes is increasing. The damping of blast waves due to a granular media is primarily studied from the data obtained from full-scale field experiments. The focus of the present study is to develop a blueprint of an intermediate media between a structure of importance and the region of blast wave impact so that there is minimum or no damage to the structure using shock tubes. At the Laboratory for Hypersonic and Shockwave Research, Indian Institute of Science, to study the effect of a protective layer on the propagation of blast waves, two different granular materials, namely naturally available river sand and artificially manufactured glass spheres of the same particle size, are being used. The Vertical Shock Tube facility is used to create blast wave pressure profiles analogous to free field explosions, and blast waves of different intensities are imparted on the granular media held in a test chamber. For similar packing densities, pressure profiles from the experiments showed that the blast wave through the sand decays faster as compared to the glass spheres. This may be due to the absence of particle interlocking, which is seen prominently in the sand, on account of its uniform spherical shape. Additionally, experiments on glass spheres showed some uncharacteristic pressure jumps at random locations.