Iso-velocity maps. A vibration control tool in quarries

Abstract

Urban growth around mining areas has brought problems such as neighborhood's discomfort due to blasting vibrations, which can cause structural damage to the houses, dust and atmospheric overpressure. In Brazil, environmental restrictions are increasingly rigorous and seismic monitoring is required as an environmental control measure. This study aims to analyze a methodology for application of iso-velocity maps in quarries located in urban areas and evaluate options for building iso-velocity maps. This work was performed in a quarry located in the State of Sao Paulo and four blastings were monitored. All blastings had similar features and they were evaluated in the same bench. For each equation, directional, scaled-distance parameters were estimated and different iso-velocity maps were made and compared. It is concluded that geophone disposition must adjust to the monitoring purposes. Eight to fifteen aligned geophones are adequate for a scaled-distance curve. Sixty-four or more geophones, spatially and homogeneously distributed, can generate an iso-velocity map concerning a single blasting. High variability of rock mass features seems to prevent obtaining good results when the seismographs are not homogeneously distributed surrounding the blasting.