It is urgently required to establish performance verification methods for civil infrastructures as well as to rationally setup clear performance requirements. In particular, incorporating time-depending change in performance into the reliability-based design makes it possible to systematize performance verification methods of structure during the design lifetime.
　In this study, change in the failure risk due to time-depending deformation was evaluated for a shore protection facility with concrete-covered slope in its front face. For this purpose, an analytical model was created to express the transition of deformation based on the stochastic approach by using the Markovian-chain model.
　Through literature surveys, typical patterns of time-depending deformation of the facility during the lifetime were analyzed. Then, the following two patterns were focused as the most important and critical deformation: collapse of covering concrete due to wave forces and formation of a cave due to washing out of filling soils in consequence. The transition probability on formation of a cave was obtained by the cave growth rate. The failure probability on the collapse of concrete was evaluated by the first Gaussian approximation. Then these two probability models were incorporated in the Markovian-chain model. By the incorporation, we proposed the prediction method of the likelihood of the deformation of facility including the failure probability. The likelihood of the deformation was expressed by the probability vector of each state of deformation occurring in shore protection facilities. The applicability of the proposed system was confirmed by trial calculations.