Effect of Repeated Blast Vibrations on Rock Mass Damage in Tunnels

Abstract

Blasting is the most common method of rock excavation technique in mining and civil construction and infrastructure projects. General blast-induced damage was extensively studied globally, but the studies on repeated blast induced damage is not yet reported, quantitatively. This chapter deals with the research work carried on the effect of repeated dynamic loading imparted on the jointed rock mass from subsequent blasts in the vicinity, on the jointed rock mass at Lohari Nag Pala Hydroelectric Power Construction Project. The blast-induced damage was monitored by borehole extensometers, borehole camera inspection surveys and triaxial geophones installed at three test sites of different joint orientations at the Main Access Tunnel of power house. The study reveals that the repeated blast vibrations resulted in extra damage of 60%. The results of the study indicate that repeated vibrations, resulted in inducing damage even at 23-33% of the critical vibrations (Vc) levels.