The prediction of blast-induced ground vibrations across fractured rock masses is of great concern to rock engineers in evaluating the stability of rock slopes in open pit mines. At the present work, the ‘hybrid method’ was used at the Gol-e-Gohar iron ore mine to simulate the production blast. Then, the simulated production blast seismograms were used as input to predict particle velocity time histories of blast vibrations in the mine wall using the three-dimensional distinct element method. By back analysis of measured blast waveforms, mechanical properties of in-filled faults of the study area were determined. In combination with the numerical model, a ‘simulated annealing’ search algorithm was employed to find the optimum values of unknown parameters. Simulated time histories of particle velocity showed a good agreement with the measured production blast time histories.
Wave propagation through surface rock structures and their dynamic response are very complicated especially when the rock masses are regarded as discontinuous media containing various types of fractures (in the form of micro-cracks to faults). When a blast-induced shock wave propagates in an intact medium, it is attenuated simultaneously by material damping and geometrical spreading. However, when a shock wave propagates in a jointed rock mass, wave attenuation is controlled by the characteristics of joints surfaces, the rock wave impedance of both walls of each discontinuity, and the angles between discontinuities and the direction of propagation. Hence, many researchers have studied effects of blastinduced wave propagation through rock slopes and tried to simulate the complexities using analytical, empirical, and numerical methods. Based on results of blasts monitoring, many empirical relationships have been presented which predict the peak particle velocity (PPV) at any points considering mostly two parameters namely the maximum charge per delay and distance from the blast to the measuring point .