Underwater implosion of re-enforced concrete piers

Abstract

From 2015 through 2018, 18 reinforced concrete piers formally supporting the east span of the San Francisco-Oakland Bay Bridge were removed using underwater demolition. The events ranged from one pier to up three piers at one time with the number of charges ranging from 92 to 688 and weights from 12 to 35 pounds. In all cases, a bubble curtain, blast attenuation system was used to reduce the blast pressures. Although the blast plans varied, more variation in the monitored peak sound pressure levels and sound exposure levels was observed than was expected from initial predictions. Potential causes of this variability were examined including varying charge confinement, directionality due to self-shielding of the structures as the individual blasts progressed, the effect of varying distance to the monitoring location for the individual charges, obscuration of the monitoring location due to intervening structures, and varying effectiveness of the blast attenuation system. Each of these potential causes are examined in this presentation.