Behaviour of reinforced earth marine walls under the effect of wave loading

One of the most contemporary applications for reinforced earth is in marine works. In this application, the reinforced earth wall acts as a seawall for the protection and stabilization of the shoreline against the marine environment or as a quay wall or wharf structure for providing a deep vertical face for ship berthing in harbours. In these cases, the reinforced soil structure must withstand marine environmental factors such as saturation, submergence, changing water levels due to tide action, and impact forces due to sea wave or ship collision. This paper evaluates the effects of sea wave loading on the stability of a reinforced soil marine wall. This study was carried out by doing numerical analysis on a reinforced earth wall with 6.1m height using finite element modelling. The study shows that cyclic sea wave loading can seriously affect the external and internal stability of the reinforced soil wall by changing various characteristics such as lateral displacement of the facing, effective vertical stress in the backfill, tensile forces in the reinforcements, and bond resistance of the reinforcements. After a wave impact, free vibration of the wall causes a significant increase in tensile force in the reinforcements which seriously reduces the safety factor of the wall against rupture and bond failures. The dynamic portion of the tensile force is due to the transient effect of a single wave impact (inertia effect), or cumulative residual force from preceding repeating loads (residual load). The numerical analysis of a reinforced soil wall under a transient wave impact showed that the tensile forces in the reinforcements are periodically changing with high amplitude which can seriously reduce the lifespan of the reinforcement’s bond. This study also showed that the dynamic portion in the tensile force for the upper layers is more prominent and critical than that for the bottom layers of reinforcements. The wave loading also causes a significant increase in the lateral deflection of the wall. For the wall studied in this paper, the amount of increase in lateral deflection of the wall facing was about 100 percent. It also affects the vertical pressure in the reinforced soil wall. For the case study, the vertical pressure at the toe of the wall under wave loading was about 25 percent more than that of under static loading. This increase is associated with a decreasing safety factor of the structure against tilting.