Prediction of Blast-Induced Overbreak Based on Geo-mechanical Parameters, Blasting Factors and the Area of Tunnel Face

Abstract

Determination of blast-induced overbreak is a very critical factor in underground excavations where drilling and blasting method is used. Overbreak, as an inevitable side effect, significantly affect the cost and safety of underground constructions. A lot of researches have been conducted by many scholars so as to minimize overbreak and excavation damage zone. There is a need for a contractor to quantitatively assess overbreak area. Unfortunately, as a result of complexity of the parameters influencing overbreak and little understanding of the phenomenon, there is no systematic and quantitative model for predicting overbreak considering the geological conditions, blast parameters, and geometry of the tunnels. At the present time, the constant magnitude of 10–15 cm is allowable in contracts, due largely to imprecise prediction about the quality and magnitude of overbreak. The main objective of this paper is to present a linear multiple regression analysis model for predicting the blast-induced overbreak of the tunnels driven in sedimentary rocks. This model is developed considering all the factors affecting the damage. The performance of the best model was evaluated showing the suitability of the model for assessing overbreak.