Pullout evaluation of uniaxial geogrids embedded in dredged material

With the ever increasing need for MSE walls, the study of the interaction between soil and geosynthetics has become increasingly relevant. New concepts are constantly being researched, including the use of industrial byproducts as alternative backfill materials. The idea that byproduct material could somehow be a suitable fill for these MSE walls may spark new opportunities. One such byproduct being researched is dredged material. The suitability of dredged material as a backfill would not only contribute to lower construction costs, but would also benefit local confined disposal facilities looking to reduce their already overflowing dredged material accumulation.
This thesis further considers the use of dredged material by evaluating its interface shear strength with uniaxial geogrids. A series of laboratory pullout tests were conducted using two types of uniaxial geogrids (UX1400 and UX1700) embedded in three different soil types (Monterey Sand and two different dredged materials). The laboratory results are used to examine the effect on the coefficient of interaction of the various parameters governing the pullout resistance. The results of this study show that: (1) the presence of adhesion to characterize the soil-reinforcement interface shear strength causes a decrease in the coefficient of interaction with increasing normal stress, (2) the reinforcement length of the geogrid was found not to affect the coefficient of interaction; provided that boundary effects are minimized, (3) the dredged material, tested wet of optimum, showed a response consistent with an undrained behavior, which produced pullout resistances significantly lower than that of the Monterey Sand, (4) the coefficient of interaction for the UX1700 was comparatively higher than that for the UX1400; however the differences obtained when testing Monterey Sand were similar to those obtained when testing the dredged materials.