Abstract: Dam structures are prime targets during wars, and a tragedy is likely to happen in a populated area downstream of a dam exposed to explosions. However, experimental investigations of the failure of a concrete gravity dam subjected to underwater explosion (UNDEX) are extremely scarce. In this study, centrifuge tests and numerical simulations were performed to investigate the failure of a concrete gravity dam subjected to a near-field UNDEX. The results revealed the existence of two tensile fractures inside the dam, one in the upper part and the other in the lower part. Due to the narrowness of the upper part, there were coupled effects of bending tensile loads in the upstream face and a reflected tensile stress wave in the downstream face, resulting in severe tensile damage to the upper part in both the upstream and downstream faces. The fracture in the lower part was measured at around one third of the height of the dam. This fracture was produced mainly by the bending tensile loads in the upstream face. Driven by those loads, this fracture started from the upstream face and developed towards the downstream face, with a horizontal angle of about 15°. The underlying mechanisms behind the two tensile fractures were confirmed by recorded strain histories. The dam failures presented in this study are similar to those produced in historical wars, in which dams were under similar attack scenarios.

Key words: Centrifuge test; Numerical simulation; Concrete gravity dam; Underwater explosion (UNDEX); Bending failure

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