Observed Long-Term Performance of Geosynthetic Walls and Implications for Design

Abstract

Geosynthetic-reinforced walls have been viewed by the civil engineering profession as a new technology whose acceptable long-term performance is yet to be established. Nevertheless, geosynthetic walls have been in use for almost 25 years. Much of the uncertainty associated with acceptance of geosynthetic-reinforced wall technologies is related to time-dependent deformation. This paper summarizes the creep rates measured in full-scale walls and compares them to creep rates measured in-isolation in the laboratory where the applied load level matches values estimated for the same structures in the field. In the majority of cases, the laboratory in-isolation creep rates were the same as or greater than the measured reinforcement creep rates in full-scale walls, corroborating that reinforcement load levels can be estimated from measured strain data. At the end of wall construction, it appears that the reinforcement is primarily exhibiting creep, with only minor stress relaxation. However, in the long-term, there is a trend toward reinforcement stress relaxation. Furthermore, the long-term behavior observed in the full-scale walls indicates that the reinforcement loads are well below values required to cause creep rupture over the design life of the structures and, in some cases, creep appears to have stopped completely. Finally, the paper offers quantitative guidelines to delineate anticipated poor and good long-term wall performance based largely on level of reinforcement strains and magnitude of post-construction wall deformations.