| In Japan，there are many rock-sheds over mountain and coastal roads．Sand cushion is commonly used to reduce the impact force by rock falling on the roof of rock-sheds．However，sand cushion is said to have a limited shock-absorbing capability．And distribution of impact force using sand cushion is narrow．In order to improve the safety of rock-sheds，a three-layered cushion system was developed which is composed of a top sand layer，a RC core slab and a bottom EPS layer．Full scale tests on shock absorbing capacity of three-layered cushion system and sand cushion are performed．In this paper，to study the application of three-layered cushion system to PC rock-shads，PC rock-sheds using various cushion are designed |
