ABSTRACT
Abstract The controlled blastin g methods available for localized cuttin g and partia l demolition o f concrete are presented. Th e first is a blasting method utilizin g th e charge holder with two wedge-shaped air cavities. Th e charge holder produces shock converging effect s in a borehole and the shock wave pressure acts effectively o n the cavity walls. Th e tensile stress fields are produced o n the borehole at the locations of the apexes of cavities and controlled crack s are initiated. The second i s a combined method o f a split-tube charge holder and a notched borehole . The dynamic deformations of the split tube under th e action of shock waves and gases driven by the explosion produc e highly concentrated tensil e stresses on the borehole at the notch locations . Th e stress fields initiate cracks which form the controlled fractur e plane . Th e effectiveness of these methods is demonstrated b y a series of model experiments with electric detonators , mortar specimens and lead ones . Keywords: Controlle d blasting , Partia l demolition, Charge holder, Notched borehole .
