Shock Tube based Study on Damage Prediction of Soft Rocks

The principal objective of thispaperis to develop a controlled laboratory testfor predicting the damage of soft rocks when exposed to blast or shock waves. Shock tube experiment is proposed to generate shock/blast waves that are strong enough to create fracture in soft rocks by release of tremendous amount of energy over a small duration of time. Plaster of Parisis used as test sample in this study, as a substitute for soft rocks. The evaluation of damage is based on the energy absorbed by the sampleonexposing to the incoming shock waves. The critical energy is the measure,where the sample resistance is surpassed and the absorbed energy isreleased in the form of crack or fracture. The incident, transmitted (absorbed) and residual energy is evaluated based on the principles of gas dynamics and global mass, momentum and energy conservation equations. The rate of loading is varied by producing shock waves of different Mach number (strength). It is observed that energy absorbed by the sample varies linearly with impulseimparted.