Performance evaluation of geogrid reinforced soil walls with marginal backfills through centrifuge model tests

Marginal fill materials that do not follow the guidelines are used in constructional activities due to ease in its availability and economic benefits. But several cases of geogrid reinforced soil wall failures indicate the loss of interfacial shear resistance due to wetting of backfill as a possible reason. In the present study, centrifuge tests were performed on geogrid reinforced soil wall models with wrap-around facing using a 4.5 m radius large beam centrifuge facility available at IIT Bombay at 40 gravities. A marginal soil with 21% fines was chosen as backfill in the study. Two geogrid types of different stiffnesses were modelled based on scaling considerations and used in the study. The models were prepared at wet of optimum to simulate wet backfill conditions. The surface settlements of the models during centrifuge tests were monitored with the help of Linear Variable Differential Transformers (LVDTs). Digital Image Analysis (DIA) was performed on photographs of the front elevation of the model captured during flight, to obtain face movements and reinforcement strain distribution along geogrid layers during centrifuge tests. Interpretations of centrifuge model test results reveal that the soil wall reinforced with low stiffness geogrid layers was observed to deform excessively and undergo pullout failure along soil–geogrid interface. However, the provision of geogrid layers with higher stiffness limited the excessive outward deformations of geogrid reinforced soil walls with marginal backfills. Further, the effect of moulding water content and stiffness of the geogrid on the mobilization of pullout resistance was evaluated through pullout tests in the laboratory. Based on the observations made from pullout tests and centrifuge tests, provision of stiffer geogrids in geogrid reinforced soil walls was found to be one of the viable options to mitigate the problems posed by marginal backfills.