ABSTRACT
Two steps are needed to reduce the nuisance resulting from blasting-generate less fines/dust during blasting and then reduce the dispersion of dust which gets airborne. Fines/dust generation and dispersion are influenced by blast design parameters and execution (Bhandari et al, 2004). The fine material is assumed to originate from a cylindrical crushed zone around the blast hole, within which particles are generated by the crushing of the rock due to comprehensive-shear failure (Kanchibotla et al, 1999). The radius of zone is assumed as the distance from the blast hole zone to the point where radial stresses exceed the compressive strength of rock mass. However, Svahn, (2003) and others have shown that much of the fines generated in blasting do not originate in the crushed zone around the blasthole. Efforts are needed to understand the process of fines/dust generation and dispersion. Labozratory blasting experiments carried out by Bhandari (1975a and b), Bhandari (1983), Bhandari and Badal (1990), Badal (1990) have been reassessed. Size distribution has been analyzed by Ouchterlony (2011) using Swebrec function which throws important light on the generation of fines. During the intervening period there has been new understanding of mechanism of rock fracture and fragmentation (Fourney, 1993, Bhandari, 1997, Liu and Kastabnis, 1997) and it
1 INTRODUCTION
Fines and dust resulting from blasting operations sometimes become both an environmental issue and an economical loss for the producers. Dust is a general term-fine particles (below 75 micron range) that are suspended in the atmosphere. Dust is formed when fine particles become entrained in the atmosphere by the turbulent action of wind, by the mechanical disturbance of fine materials, or through the release of particulate-rich gaseous emissions. In reality fines may be useful or detriment to the operation. Most often less fines generation is needed in overburden blasting, aggregate production or in steel grade limestone production (where anything less than 40/30 mm size is not used) and often this material becomes waste. Whereas in situations where material is further crushed and processed, it is better to break the material by blasting to the smallest size (Mine to Mill concept-JKMRC, 1998). Even in later situation dust continues to be a matter of concern. Fines and dust resulting from mining operations is a serious nuisance and a health hazard to mine workers and population living in the vicinity of a mine. Though the blasting dust cloud is raised for few minutes but most of the dust settles in and around mining area and some of it is dispersed before settling down. Depending on meteorological conditions this dust can disperse to substantial distances endangering health of communities. Some of the settled dust is raised again by mining activities for example by travelling vehicles. Damage to vegetation and agriculture is possible.
