Analysis of crack propagation and degree of damage due to explosion on dimensional variations of laboratory scale models

Blasting activities as a method of breaking rocks often occur near free areas, such as the surface of the ground or mine walls which are not solid, the pressure waves produced by the explosion can bounce back towards the source of the explosion after reaching the free area. In this research, an explosion simulation was carried out on a laboratory scale to model the interaction between explosion and rock. Two domain model sizes, in the form of cubes made of concrete with dimensions of 30x30x30cm and 40x40x40cm, were exploded using electric detonator no.8 to evaluate their impact on rock damage. Monitoring was carried out by measuring the primary wave velocity (Vp) on the cube model at 49 points before and after the detonation. The results obtained were that the 30x30x30 cm model was broken into 6 parts so that Vp measurements could not be carried out after blasting. In the 40 × 40 × 40 cm cube model, the specimen remained largely intact after blasting, although visible cracks and partial spalling were observed. Despite this damage, the P-wave velocity (Vp) test could still be conducted, revealing a reduction in rock strength of approximately 38%.