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...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.展开更多
The final anomalous sag distortion of the ship girder subjected to the near field underwater explosion （undex） below the middle ship is studied. The sinking exercise of Spruance class destroyer DD973 sunk by one MK4...The final anomalous sag distortion of the ship girder subjected to the near field underwater explosion （undex） below the middle ship is studied. The sinking exercise of Spruance class destroyer DD973 sunk by one MK48 torpedo is first presented, and a simulation model is established. The exponential attenuation phase, the reciprocal attenuation phase, the post reciprocal attenuation phase, and the negative pressure phase of the undex load are precisely applied in this model. The fluid-solid interaction, the added water mass, the gravity, and the change of buoyancy are also taken into account. The similarity theory is then used to analyze the dynamic response of the ship girder. Similarity parameters and theory prediction formulae of the dynamic response of the ship girder are presented, The physical meaning and influences of these similarity parameters are analyzed.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.51879283 , 51339006)。
文摘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.
基金supported by the National Security Major Basic Research 973 Project of China(No.51335020101)
文摘The final anomalous sag distortion of the ship girder subjected to the near field underwater explosion （undex） below the middle ship is studied. The sinking exercise of Spruance class destroyer DD973 sunk by one MK48 torpedo is first presented, and a simulation model is established. The exponential attenuation phase, the reciprocal attenuation phase, the post reciprocal attenuation phase, and the negative pressure phase of the undex load are precisely applied in this model. The fluid-solid interaction, the added water mass, the gravity, and the change of buoyancy are also taken into account. The similarity theory is then used to analyze the dynamic response of the ship girder. Similarity parameters and theory prediction formulae of the dynamic response of the ship girder are presented, The physical meaning and influences of these similarity parameters are analyzed.
