Environmental impact of detonation of explosives in seismic survey operations

Seismic survey operations are short-term, although, they can cause annoyance to the surrounding inhabitants. These annoyances may be due to generation of ground vibrations and noise and their possible impact on the surrounding houses and other structures. The paper discusses a case study of experimental trials conducted at three different exploration sites of Oil India Limited in Assam, India. The impact of ground vibrations and noise generated due to detonation of explosives were investigated on the surrounding environment and structures in various working conditions. The maximum magnitude of vibration recorded near a residential house was 53.01 mm/s at a distance of 20 m from the blast site with the dominant peak frequency of 56.8 Hz. No adverse impact on the structure was observed. The analyses of data revealed that the ground vibrations generated due to the detonation of explosives were having their most of the energy in higher dominant frequency bands i.e. more than 30 Hz. The analyses of data clearly indicated that the magnitude of ground vibration enhances when the shot holes are stemmed. In general, the enhancement in vibration was 9 –29 % but in some cases, it was observed up to 31.7 %. The level of vibration also increases as the depth of burial of explosives is increased. It was observed that whenever the confinement of explosives will be more, higher magnitude of vibrations would be generated. The magnitude of noise generated during seismic survey operations were well within the safe limits