ORCID Identifier(s)

0000-0002-1420-582X

Graduation Semester and Year

2021

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Sahadat MD Hossain

Abstract

Mechanically Stabilized Earth (MSE) walls constructed on unsuitable foundation soil are prone to large deformation and bearing capacity failure. A variety of techniques can be applied to address this issue, such as removal and replacement of existing soil with competent soil, staged construction, dynamic compaction, stone columns, geosynthetic reinforcement. One common traditional approach followed by Texas Department of Transportation (TxDOT) for the improvement of unsuitable foundation soil is removal of the in-situ soil and replacement with suitable fill material. However, this method can be time-consuming and expensive. A pile-supported system in combination with geosynthetic reinforcement can provide a sustainable solution for ground improvement. The use of Recycled Plastic Pins (RPPs) can be a viable alternative to other conventionally used piles. So, to minimize construction time and cost, the use of RPPs for ground improvement needs to be evaluated as an effective and sustainable technique. The objective of this study is to assess the effectiveness of RPPs for improving unsuitable foundation soil. An extensive field-testing program was conducted on RPP reinforced soil. Four identical test sections were constructed; among which three were reinforced with RPPs having different sizes and spacings, and the fourth one was left unreinforced to use as a control section. Performance monitoring for all four test sections was conducted using inclinometer and pressure plates for more than two years. The field monitoring data indicated that the settlement of the reinforced section was reduced up to 84%, and RPPs were carrying 78% of the total surcharge load. Based on the available field data, RPPs show a promising potential for improving the unsuitable foundation soil. The performance of the test sections was further evaluated in numerical modeling using finite element software PLAXIS 2D. A parametric study was conducted using the calibrated model to evaluate the effect of foundation and backfill soil strength, RPP size, and spacing on settlement and pressure distribution of the RPP reinforced system. Finite element studies showed that larger cross-sections and closer spacing of RPPs provided better resistance. Settlement, stress reduction ratio, and stress concentration ratio prediction models were developed using the modeling results will help determining the settlement and pressure distribution of RPP reinforced foundation. Based on the performance monitoring results and further analyses, it can be concluded that the RPPs can be effectively used to increase the bearing capacity of MSE wall foundation.

Keywords

Foundation soil, Recycled plastic pins, Bearing capacity

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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