Investigating the causes of rock underbreak during blasting :

Abstract

Rock fragmentation is a fundamental. goal of drilling and blasting Where the most effective blasts can be achieved. Drill and blast system has been used in hard rock excavation due to its economics and adaptability to changing rock mass conditions. The blasting method is broadly used for rock excavation worldwide because of its efficiency. The blasting induced rock under break occur in the vicinity of both surface and underground openings. Common question during mining operations is whether rock under break has been caused by blasting practice or poor rock mass quality. Critical evaluation of the factors influencing. rock under break was required to address such questions. In order to understand the mysterious nature of blast damage prediction and control the field work involved the assessment of rock mass quality during blasting operations. Therefore, the influence of rock mass features, explosive characteristics and blast design parameters on rock under break has been. examined in this study. Implications of rock underbreak have also been outlined in this paper. Investigations at Aljouda Mining company have showed increased under break as a result of low explosive strength compared to the rock strength and large spacing between the blast holes.