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The numerical experiments investigate the dynamic response of a pile-slab retaining wall under the impact of rockfall. Firstly, a full-scale numerical model of a four-span pile-slab retaining wall satisfying specification requirements is established. Secondly, the numerical experiments investigate the dynamic response of a pile-slab retaining wall under different impact centers and velocities. Finally, the maximum impact energy that the structure can resist is predicted. Results reveal that: (1) During the impact process, the stress, strain, and concrete damage of the structure gradually spread from the impact center to the entire structure and ultimately result in permanent deformation; (2) The lateral displacement of pile at ground surface and the number of damage failure units under the pile as the impact center is greater than those under the slab as impact center. It shows that the impact position has a significant effect on the stability of the structure.(3) The impact force, interaction force, lateral displacement of pile at ground surface, and concrete damage is increased with the increase of impact velocity. Under pile as the impact center (slab as the impact center), when the velocity increases from 15 m/s to 30 m/s, the impact force increases by 1.42, 1.91, and 2.41 times (1.41, 1.90, and 2.41 times), the interaction force increases by 1.25, 1.47, and 1.68 times (1.24, 1.47, and 1.68 times), and the maximum lateral displacement of pile at ground surface increases by 1.57, 2.24, and 3 times (1.55, 2.23, and 3 times). (4) Utilizing this relationship between the impact velocity and the maximum lateral displacement of pile at ground surface, the estimated maximum impact energy that the pile-slab retaining wall can withstand is 905 kJ in this study when the structure top is taken as the impact point. Impact resistance of the structure optimized 1.814 times compared to traditional reinforced concrete retaining walls.