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The consequences of dam damage caused by explosions, wars, and terrorist attacks are extremely serious, and they can cause casualties among downstream residents. Studying the damage behaviors of dams is a prerequisite for improving their anti-knock performance. Researchers view the dam as homogeneous for research; but in reality, the concrete strength of the dam decreases from bottom to top. The partitioning of dam concrete strength can meet the different functional and economic requirements of a concrete gravity dam (referred to as concrete strength partition gravity dam (CSPGD)). Therefore, CSPGD shows a more complex dynamic performance and failure characteristics under the impact load of an underwater explosion. First, by investigating the current status of anti-knock research on CSPGDs, a fully coupled finite element numerical model for an underwater explosion of CSPGD was established. Considering the initial stress such as the self-weight of the dam, the upstream reservoir hydrostatic pressure, and the uplift pressure of the dam foundation during the service period, the anti-knock performance of CSPGD was studied. The results showed that the interface of CSPGD had a strain rate effect under the action of blast load, and it was easy to produce tensile failure at a low strain rate. In addition, the dynamic response and damage characteristics under different explosion scenarios such as explosive charge weight (w), detonation depth (D), and standoff distance (R) were further studied. The dam crest was always a weak anti-knock part, and the foundation anti-sliding stability was also very important to dam safety. Therefore, it was proposed and suggested to use the crack length of the dam crest and dam foundation to evaluate the overall anti-knock capacity of CSPGD. The study also found that the detonation depth affected the response time of dam damage and had a significant impact on the anti-knock performance of CSPGD. [ABSTRACT FROM AUTHOR]

Steel fiber foamed concrete (SFFC) combines the impact resistance of steel fiber concrete (SFC) and the energy absorption characteristics of foamed concrete (FC), and it has brought attention to the impact field. Using the mechanical properties of SFFC expanded polystyrene concrete, we prepared (EPSC) specimens with 10%, 20%, 30%, 40%, 50% by volume of expanded polystyrene (Veps), and steel fiber expanded polystyrene concrete (SFEPSC) specimens by adding 1% steel fiber (SF) based on the EPSC in this study. The relationship between compressive strength, the Veps and apparent density was revealed. The relationship between the first crack and the ultimate failure impact of SFEPSC specimens was obtained by a drop-weight test. The impact resistance of SFEPSC and EPSC and the variation law of Veps were studied by mathematical statistics. The log-normal and the two-parameter Weibull distributions were used to fit the probability distribution of impact resistance of the SFEPSC and EPSC specimens. Finally, both types of specimens' destruction modes and mechanisms were analyzed. The mechanism of the EPS particles and the SFs dissipating impact load energy was analyzed from the energy point of view. [ABSTRACT FROM AUTHOR]