Graduate Thesis Or Dissertation
 

Enhancing Design of Geosynthetic-Reinforced Soil Supporting Spread Footings

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/4j03d465c

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  • Internal stability of Geosynthetic-Reinforced Soil (GRS) walls are conventionally assessed using lateral earth pressure methods. Determination of these pressures is a key component of limit state design as it enables determination of mobilized resisting forces in reinforcements needed to ensure stability and function of the GRS structure. However, conventional methods (e.g. Rankine) are not directly applicable for an increasingly common application of GRS structures: support of surcharge loading stemming from bridge superstructures or other structural functions. The third chapter of this dissertation presents an analytical model that was developed to determine mobilized reinforcement loading considering a log-spiral mechanism and discrete surcharges using limit analysis. Lateral earth pressures attained from this approach are consistent with simplified analyses presented in the literature, realizing reinforcement loads that are more reasonable when compared with observed reinforcement loading than conventional limit equilibrium-based methods. To demonstrate the effects of various design parameters, the relationship between soil strength properties, interface friction between the soil, facing and toe, wall height, wall batter and reinforcement loads were studied. The fourth chapter of this dissertation presents an approach towards assessing the bearing capacity on Geosynthetic-Reinforced Soil walls through consideration of five different failure mechanisms that capture potential failure modes. These include a logarithmic spiral, two-part wedge, two-sided general shear, one-sided general shear and failure above the uppermost geosynthetic. Each of these mechanisms is assessed considering geometry, geotechnical properties, whereupon a customized algorithm selects the minimum, critical bearing capacity and associated failure mechanism for design. The mechanisms and bearing capacity attained from this analysis are compared with rigorous numerical models demonstrating good agreement. Furthermore, the multi-mechanism approach was extended to a series of normalized design charts considering varying reinforcement spacing, reinforcement tensile strength, footing location, footing width, wall height, and wall batter. Chapter 5 discusses the influence of non-uniform reinforcement spacing on realized bearing capacity and internal stability for surcharged GRS structure through application of using upper-bound Limit Analysis using the Discontinuity Layout Optimization (DLO) discretization algorithm. The effects on stability are evaluated for two scenarios: (1) a “top-down” approach where reinforcement spacing density is progressively increased from the top of the wall downwards and (2) a “bottom-up” approach where the spacing density is progressively increased from the toe of the wall upwards. Presented within this study are the results of comprehensive parametric analysis varying reinforcement spacing, reinforcement strength and footing location, highlighting the stability benefits of top-down and bottom-up reinforcement density approaches. Placement of dense reinforcements near the crest of surcharge-supporting walls had a notable benefit for stability, while placement of dense reinforcements at the toe improves stability for walls without surcharge loading.
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  • Pending Publication
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  • 2018-01-29 to 2018-08-28

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