Abstract:

To demolish concrete cutoff wall successfully in one blasting is a difficulty which arose in the demolition blasting of downstream cofferdams in the second stage of Three Gorges Project (TGP). The problem was caused by grouting steel tubes and supports to immobilize them, both of which were pre-buried in concrete cutoff wall. This kind of structure was never encountered before in demolition blasting of cofferdams’ underwater cutoff wall. If the demolition blasting just exploded concrete into pieces, leaving those steel tubes unbroken and their supports compact, the underwater excavation of explosion residues could not proceed. The key element of the demolition blasting of downstream cofferdams in the second stage was to destroy both the grouting steel tubes and their supports. To solve this problem, this paper used ANSYS/LS-DYNA computational software and in-situ experiments to study the effects of different charge structures and diameters of cartridges on the destruction of steel tubes in explosions. The relationships between the destruction configurations of steel tubes after explosions and charge structures are discussed; and the proper blasting parameters and charge structure are determined based on these discussions. The research achievements are proved by the results of the demolition blasting.

Key words: TGP, concrete cutoff wall, explosion of steel tube, numerical analysis, field test