In order to explore the mechanical characteristics and failure characteristics of water-saturated frozen cement mortar with different transfixion degree joints under impact load, a cyclic freezing impact test was performed on six kinds of water-saturated frozen cement mortar specimens with different transfixion degrees (0%, 20%, 40%, 60%, 80%, 100%) by split Hopkinson pressure bar (SHPB), and the microscopic damage of specimens was tested by an MRI analyzer. The results show that the dynamic compressive strength of the water-saturated frozen cement mortar increases first and then decreases with the increase of the number of cycles, with the increase of joint transfixion degree the peak stress showing a clear linear downward trend. An 80% transfixion degree joint specimen has the weakest ability to carry impact loads, and the 40% transfixion degree joint specimen has the strongest ability to carry impact loads. With the increase of joint transfixion degree, there was a similar trend of first decreasing and then rising in the average change of porosity and the change of energy density per unit time index. The joint transfixion degree controls the crack development trend and the final destruction mode of the specimen. With the increase of joint transfixion degree, the failure sequence gradually evolved from pull-shear composite failure to split-tensioned failure.

Drop hammer impact tests were conducted to study crack features and the ductile–brittle transition in sea ice under low-speed impact. Crack images were analyzed using Hessian filtering and Hough transform methods, and a finite element model was created. Material parameters were validated using the crack tip strength factor. Energy dissipation, focusing on kinetic energy, was analyzed to understand energy conversion and crack propagation in sea ice during low-speed impact. The results indicate that the angular distribution of the crack mode exhibits central symmetry, with the peak frequency at each angle approximately 5°. As the initial impact kinetic energy increases, the dynamic response of the sea ice plate transitions from toughness to brittleness; the kinetic energy dissipation increases linearly, while its utilization efficiency declines. The variation in the kinetic energy conversion rate (η) is associated with the mode of ice plate failure. The crack propagation rate follows a normal distribution in relation to changes in time and kinetic energy. The stress wave effect predominates in the fracture formation mode, further elucidating the ductile–brittle transition behavior of sea ice. This research holds significant implications for ice-breaking operations.