Graduation Year

2023

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Manjriker Gunaratne, Ph.D.

Co-Major Professor

Austin Gray Mullins, Ph.D.

Committee Member

Andres Tejada-Martinez, Ph.D.

Committee Member

Mohamed Elhamdadi, Ph.D.

Committee Member

Rasim R. Guldiken, Ph.D.

Keywords

Consolidation, Dynamic Compaction, Pore Water, Sand Column, Soil Improvement

Abstract

First a dynamic finite element methodology (FEM) was developed to simulate an entire dynamic replacement (DR) program of clay with sand involving multiple poundings. The main objective of this research was to employ FEM and geotechnical test data such as cone penetration test (CPT) data at the site to predict the maximum achievable sand column (SC) depth and the corresponding optimum levels of attributing parameters such as number and height of pounder drops. Another goal was to predict the pore pressure generated in clay due to pounding. A full-scale ground improvement project was used to guide the analytical process. Comparison of FEM predictions and field measurements showed the potential of using FEM to achieve the above objectives in advance of the field work. As a product of the first phase, a step–by-step procedure for using a FEM procedure to predict the optimum field setup and hence improve the efficacy of DR field implementation is illustrated.Secondly, this study also utilized the FEM to predict the pore pressure dissipation curves due to DR and the subsequent embankment construction. Using PLAXIS 3D software, a parametric analysis was conducted for the above purpose focusing on the area replacement ratio, width of SC to spacing ratio, the DR patterns (triangular and square) and the clay-to-sand permeability ratio. FEM predictions were validated by the above-mentioned full-scale ground improvement project. The results indicated that increasing the area replacement ratio accelerates pore pressure dissipation, regardless of the center-to-center spacing between SCs and the DR pattern. It also showed that pore pressure dissipation is proportional to clay-to-sand permeability ratio. In addition, the research provided a practical method to predict the time histories of pore pressure dissipation.

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