Degree

Doctor of Philosophy (PhD)

Department

Civil Enginnering

Document Type

Dissertation

Abstract

Geosynthetic reinforced soil (GRS) is a special soil with geosynthetic fabric closely stacked in layers as soil stabilization and considered an alternative design method to the conventional bridge support technology. In this research study, a field case study of Maree Michel bridge, which is located in Route LA 91 Vermilion Parish in Louisiana, was instrumented with six different types of instrumentations to monitor the performance of GRS-IBS bridge abutment and to develop 2D and 3D finite element models. The instrumentations include Shape Acceleration Array (SAA), earth pressure cells, strain gauges, piezometers, and thermocouples. Additionally, surveying was conducted at the bridge surface upon the completion of the construction. Two and three-dimensional finite elements (FE) computer program PLAXIS 2016 was chosen to model the GRS abutment. First, the FE simulation is performed for the case study, in which the FE models were verified using the results of field monitoring program. A comprehensive parametric study was then conducted to evaluate the effect of different design variables on the performance of the GRS-IBS.

Based on the results of parametric study, the relationship between the reinforcement spacing and the reinforcement strength on the behavior of the GRS-IBS performance was evaluated. The results indicated that the reinforcement spacing has a higher impact than the reinforcement strength on the performance of GRS-IBS for a reinforcement spacing equal or greater than 0.2 m (8 in.), and similar impact for reinforcement spacing less than 0.2 m (8 in.). An analytical model was developed to calculate the required tensile strength of GRS-IBS abutment based on the composite behavior of the closely reinforcement soil. The equations were verified by using field measurements and by the results of the finite element (FE) method of analysis. The results of the analytical model were also compared with the current design procedure adopted by the Federal Highway Administration (FHWA). Finally, the FE analysis demonstrated that the possible potential failure envelope of the GRS-IBS abutment was found to be a combination of a punching shear failure at the top and Rankine failure surface at the bottom, in which the failure envelope is developed under the inner edge of the footing and extending vertically downward to intersect with the Rankine active failure surface.

Date

9-24-2018

Committee Chair

Murad Abu-Farsakh

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