Simulation of rock subjected to underground blast using FLAC3D.

Abstract

In recent past, effects of blast loads on structures/foundations have gained considerable attention due to increase in threat from various man-made activities. Protecting foundation systems from such threat has become a major concern for designers. Terrorist attack as a source of blast may be in the form of missile attack which will penetrate the ground and then explode. Mining, quarrying, construction activities and all other operations which involve the use of explosives for rock breaking are some of the other sources of blast load. Blast phenomenon can lead to excessive settlement or distortion of foundation systems which in turn may collapse the building. Full-scale experiments of blast are expensive and model tests are found to be unrealistic many a times, numerical simulation of blast is required to be done to understand the complex response of foundation subjected to blast. The finite difference method is a powerful numerical method to solve geo-mechanical problems which can be used to analyze soil foundation interaction. In the present paper, finite difference software Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC 3D) is used to model ground shock wave propagation in rock. In order to study the response of foundations to blast loads through numerical modeling, many factors such as fixity conditions, constitutive models, mesh size, time step need to be calibrated. Blast load is applied and Particle velocity time-history is obtained. Peak Particle Velocity (PPV) is estimated at various points away from blast. The FLAC3D result has been compared with field data to arrive at suitable constitutive model, mesh size, time step etc. Calibration of FLAC3D model is achieved. Effects of Young’s modulus and Poisson’s ratio have also been presented. The results will be very useful for evaluation of response of foundation subjected to blast.