In this paper, 3D elasto-plastic impact response analysis on H-section steel posts of H200×200×8×12 used for a 4 m high rockfall protection fence placed on the 3 m high plain concrete retaining wall was conducted varying the anchoring depth of the post and the top width of the wall. The results obtained from this study are as follows: 1) even though the required anchoring depth of the post for normally constructed wall is estimated as 800 mm, the depth may be decreased up to 600 mm due to increasing width of the wall by 700 mm; and 2) then the required anchoring depth may be decreased and damage of the wall may be more restrained due to increasing the top width of the wall.
