Reliability Analysis of Revetments near Canti Pier, South Lampung

Canti pier is located in Southern Lampung and faces the Sunda strait water areas. Locals use this pier sailing to Sebesi island, and tourists need it as the closest starting point from the mainland to explore Krakatoa’s natural reserve. As a volcano tsunami occurred last December of 2018, Canti was one of the affected locations. Previous study shows measured wave height of 3-7 m in Way Muli and Kahai beach, located around 10 km from Canti. Field observation clearly shows the damaged concrete structure of the T-shaped Canti pier’s end tip due to the tsunami. This research focuses on analyzing the reliability of the north and south revetments of the Canti pier that still exists using statistic and probability methods. Van der Meer’s rock stability formula is adopted as the basis of determining the Limit State Function (LSF). For the reliability method, the FORM (First Order Reliability Method) is applied and produces the probability of failure of the revetment’s system during particular designed service times. The result shows that the northern revetment is relatively more robust than the southern revetment as its probability of failure is slightly lower. The expected failure probabilities are acceptable during regular operation for both revetments (less than 15%). If there is a stormy condition, the chance of collapse south revetment is relatively higher. One could also foresee the total collapse of revetments if tsunami waves attack. This condition also describes the 2018 tsunami wave height in Canti is much lower than in Way Muli since this area is sheltered by some islands, such as Sebuku and Sebesi. To conclude, considering the normal wave condition, the revetment’s structures are still reliable. However, if extreme waves occur, the revetments’ reliability is noticeably low or even unreliable (tsunami waves).