Semester of Graduation

Summer 2021

Degree

Master of Science in Civil Engineering (MSCE)

Department

Department of Civil and Environmental Engineering (CEE)

Document Type

Thesis

Abstract

This study directed at investigating the performance of the pile-supported embankment system utilizing a geosynthetic reinforced load transfer platform (GRLTP) using Finite Element numerical modeling. A 2D Finite Element Modeling (FEM) methodology was first developed using PLAXIS 2D 2021 computer software and verified by well-documented case studies in the literature of this system. Second, a performance prediction was made for a field case study of the Amite River Project near French Settlement, which is located along Route LA 16 Livingston Parish in Louisiana State. A comprehensive FEM parametric study was then carried out to evaluate the performance of the system by changing the subsoil profiles, the GRLTP and the piles' extent under the embankment slope, embankment height, and pile spacing. Key performance measures included: settlement, lateral displacement, stress transfer, excess pore water pressure, and geosynthetic reinforcement strain. The subsoil profiles included very soft clay and very loose sand layers which were considered problematic layers. The GRLTP and the piles' extent were changed under the embankment slope as no support under the slope, one-quarter of the slope, mid-slope, three-quarters of the slope, and full length up to the embankment toe. Embankment heights were varied to be 3.05 m (10 ft), 6.10 m (20 ft), and 9.15 m (30 ft). An extensive parametric study of the performance of the system with changing the center-to-center pile spacing of 0.915 (3 ft), 1.22 m (4 ft), 1.525 m (5 ft), and 1.83 m (6 ft) was then conducted with each proposed embankment height. The results of the FEM parametric study showed a significant improvement in the system by utilizing a combination between timber piles and GRLTP in terms of the settlement, the differential settlement, and global stability. Better arching effect development was observed for the very soft clay cases compared to that of the very loose sand cases. Furthermore, the very loose sand cases showed less required GRLTP and piles to be extended under the slope compared to the very soft clay cases. The FEM parametric study design recommendations were also compared with the Federal Highway Administration (FHWA) design recommendations for this system. The FHWA design recommendations showed an overestimation of the values obtained in the FEM parametric study for both the required horizontal distance between the outer pile edge and the embankment toe, and the required tensile stiffness of geosynthetics for support.

Committee Chair

Abu-Farsakh, Murad

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