Centrifuge evaluation of the time dependent behavior of geotextile reinforced soil walls
Abstract This paper presents the results of a centrifuge study performed to investigate the time dependent behavior of geotextile reinforced soil walls. To this effect, reduced scale centrifuge models were built using nonwoven fabrics as reinforcement elements and Monterey no. 30 sand as backfill. Digital image analysis techniques were used to quantify the internal displacements within the reinforced zone, where sand markers had been placed along the reinforcement layers. A sigmoid function was found to provide adequate fit to raw displacement data, allowing estimation of the strain distribution along the reinforcement layers. This investigation includes an initial series of centrifuge models designated as "Short term" tests, which were loaded to failure by continuously increasing the acceleration imparted to them. In addition, a series of models designated as "Long term" tests were conducted by subjecting them to constant accelerations corresponding to 25% 40% 60% and 80% of the g level at failure obtained from the "Short term" tests. The results revealed that walls subjected to constant acceleration showed a time dependent behavior that adversely affected their stability. Considerable time dependent deformations were observed to occur during the "Long term" tests. That is, time dependent deformations in the reinforcements, quantified using geosynthetic samples tested in isolation, were found to also develop under confinement in the centrifuge models. In particular, creep failure was observed in the "Long term" models subjected to comparatively high levels of constant acceleration. The time dependent deformations from confined geotextiles tested in the centrifuge testing program were compared against the results from unconfined geotextiles tested in a conventional creep testing program. The time to failure defined using data from centrifuge tests was found to be consistent with that obtained from conventional creep tests. The soil used in the centrifuge models in this study, frequently considered as having negligible creep, was ultimately found not to prevent the development of time dependent deformations.