Civil and Environmental Engineering
First Advisor
Jongwan Eun
Committee Members
Jiong Hu, Jamilla Teixeira
Date of this Version
8-2024
Document Type
Thesis
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Civil Engineering
Under the supervision of Professor Jongwan Eun
Lincoln, Nebraska, August 2024
Abstract
Subgrade has a significant impact on the performance of a pavement as it serves as the foundation layer on which traffic loads are transferred. Many pavement failures can be attributed to weak subgrade strength. The integration of geosynthetics in road pavements has been identified as an effective solution for enhancing subgrade performance to withstand imposed traffic. This study evaluated the performance of unreinforced and geosynthetic-reinforced subgrades in Nebraska to quantify the contribution of geosynthetics to unpaved layer systems.
The strength and stiffness of different soil subgrades were assessed through unconfined compressive strength tests and repeated load triaxial (RLT) tests, which provided resilient modulus input essential for the Mechanistic-Empirical Pavement Design (MEPD). Stress-dependent models were calibrated for different soil types, with the Uzan and MEPDG models showing a good fit. Performance evaluation was conducted using Large-scale Tracking Wheel (LSTW) tests while the Dynamic Cone Penetrometer (DCP) tests were used for stiffness evaluation.
DCP tests revealed that geosynthetic reinforcement improved subgrade and base layer stiffness, indicated by higher penetration resistance. The confining effect of geosynthetics was evident, providing essential insights into their contribution to both subgrade and base layer reinforcement. The LSTW tests, which simulated real-world rolling wheel conditions, showed that sections reinforced with biaxial geogrid exhibited enhanced stiffness, reduced permanent deformation, and decreased stress on the subgrade. The results obtained from this comprehensive investigation can contribute towards the development of more resilient and longer-lasting pavement structures, aiding in the optimization of pavement designs in Nebraska.
Advisor: Jongwan Eun
Comments
Copyright 2024, Kenaz Owusu. Used by permission