Failure modes and damage superposition effect of concrete gravity dams subjected to sequential underwater explosions

Abstract

Underwater explosion damage and failure modes in concrete gravity dams are crucial for understanding the blast resistance and protective capabilities of dam structures. With the increasing severity of international security and anti-terrorism concerns, the related research has received widespread attention. Existing research primarily focuses on single explosion. However, concrete gravity dams may suffer multiple attacks before its breaching. The damage and failure modes of dams under multiple explosions remain unclear. To analyze the failure mechanisms of the dams subjected to sequential underwater explosions, and enhance the blast resistance and protective capabilities of dams, this research establishes a fully coupled numerical model to determine the dynamic response process and failure mechanism of concrete gravity dams under double detonations conditions. The centrifuge tests of underwater explosions with double detonators on concrete gravity dams were conducted to validate the numerical simulation results. On this basis, the damage characteristics and failure modes of gravity dams under different delay intervals, initiation sequences, and equivalent combinations were investigated. The results indicate that underwater explosions of concrete gravity dam exhibit damage superposition effect under the condition of double detonations. There is a worst delay interval such that when the explosion equivalent is consistent, the damage of concrete dam is larger and the destruction is more pronounced. The worst delay interval is determined by the duration of dam dynamic response process, and is influenced by the combination of explosion equivalent and initiation sequence. This research can provide valuable insights for the dam safety protection.