Assessment of Structural Damage Due to Blasting in Hydro Power Tunnel

Abstract

AbstractExcavation is a major activity in construction of mega underground hydropower project. Successful excavation of access and water conducting tunnels and caverns of different size and shapes by adopting highly economical and efficient method of excavation like drilling and blasting in extreme geological conditions makes the hydropower project a manmade marvel. The national codes which regulates the safety of structures while using explosives are successfully adopted where the tolerable limits for blast induced seismic waves are provided for different type of structures. This paper deals with impact of 9 m(W) and 8 m(H) tunnel blast induced seismic vibrations on the underground and surface concrete structures. The outcome of tunnel blasting with reference to peak particle velocity and related displacements gave a unique results where the seismic wave produced displacements up to 0.04 mm at large underground openings (250 m(L) × 18 m(W) × 59 m(H)) when compared to displacements of 0.016 mm in small openings of 9 m(W) × 8 m(H) with similar peak particle velocity levels of 20 mm/sec. These results subjected the structures which are located in the larger underground openings to lose their strength easily when compared to the structures located in small openings. Further, the structures located in the surface are more vulnerable to get damaged due to higher displacement recordings up to 0.123 mm. Experimental outcome was recorded for various blast design and results were further analyzed to optimize the blast parameters for successful control of blast induced vibration zone within 60 m. The relation between the structure locations where blast induced seismic wave propagates seems to play a key role in influencing on the structural damage, where less influence of peak particle velocity is observed.KeywordsCracksDisplacementSurface structureUnderground structure and Tunnel blast