A.K. Raina

Rock mass characterization by fractal dimension

Fractal theory is used in the present study to develop a more reliable method for rock mass characterization. Field studies have been carried out in opencast mines of dolomite, limestone, fluorite; sandstone and shale in coalmines. Fractal dimension of blasted fragments (Dfrag) and in situ rock blocks (Din situ) is calculated using size distribution curves according to Schumanns model. Based on the co-relation between Uniaxial Compressive Strength (UCS) and Dfrag, it is observed that change in fractal dimension is nominal beyond the UCS value of 20. From the co-relation between Bieniawaskis Rock Mass Rating (RMR) and Din situ, it is found that there is a sharp increase in fractal dimension for RMR greater than 40. Co-relation between RMR and Dfrag/Din situ shows that as RMR increases, Dfrag/Din situ ratio decreases. Rock mass classification based on fractal geometry is suggested.

Impact of blast induced transitory vibration and air-overpressure/noise on human brain – an experimental study

Human response to blast induced ground vibration and air-overpressure/noise is a major concern of current mining activity. This is because the fact that mines are fast transgressing the habitats and people are getting educated. Consequently the response of humans is changing and expectedly will increase in days to come with no viable and economic alternative to blasting – an essential component of mining. The response of humans can be purely physiological or psychological in nature or combination of both depending upon the situation and conditions of mining. Where physiological response is documented in terms of effects on ears and lungs there is a meager amount or no literature available regarding effects of blasting on the brain. Moreover, the studies on transitory phenomenon like the effects of blasting on humans are rare in comparison to the whole body vibration studies. This study was designed to address the issues as a precursor to a major initiative. The preliminary investigations conducted with the monitoring of EEG responses of humans to vibration and air-overpressure/noise due to blasting revealed that there is no major response of the brain to transitory vibrations and noise.