An interpretation of the seismic behaviour of reinforced-earth retaining structures

This paper provides an interpretation of the behaviour of retaining structures made of geosynthetic-reinforced earth, subjected to a severe seismic loading. It is seen that during strong ground motion the main source of energy dissipation derives from the transient activation of plastic mechanisms within the soil mass: these mechanisms can be global, local, or a combination of the two. Using numerical pseudo-static analyses and limit analysis methods it is shown that three retaining structures having a similar overall seismic resistance, expressed by their critical seismic coefficient, activate different – global, local, or combined – plastic mechanisms. The seismic performance of the different retaining structures is then evaluated through a series of dynamic analyses in which acceleration–time histories are imposed to the bottom boundary of the same numerical models used for the pseudo-static analyses. The results of the dynamic analyses are interpreted in the light of the plastic mechanisms evaluated with the pseudo-static procedure. They show that for the reinforced-earth structures there is always a local contribution to the dissipation of energy during strong motion, evidenced by the attainment of the available strength in different portions of the soil-reinforcement system, and that this energy dissipation has a substantial influence on the seismic performance of the system. These results extend the current understanding on the seismic behaviour of reinforced-earth retaining structures and can be used to provide some guidance for design.