Type of Document	Thesis
Author	Sheng, Biqing
Author's Email Address	sb08g@fsu.edu
URN	etd-07232010-180739
Title	Evaluation of Granular Subgrade Modulus from Field and Laboratory Tests
Degree	Master of Science
Department	Civil and Environmental Engineering, Department of
Advisory Committee	Advisor Name Title Wei-Chou Virgil Ping Committee Chair Ren Moses Committee Member Tarek Abichou Committee Member
Keywords	Modulus of Subgrade Reaction Resilient Modulus Granular Subgrade
Date of Defense	2010-06-30
Availability	unrestricted
Abstract The Resilient Modulus of pavement subgrade materials is an essential parameter for determining the stress-stain characteristics of pavement structures subjected to traffic loadings for a mechanistically based flexible pavement design procedure. The modulus of subgrade reaction is a required parameter for design of rigid pavements. The load-deformation characteristics of the granular subgrade soils were investigated using the laboratory triaxial test, test-pit plate load test, and field rigid plate load bearing test. Several typical subgrade soils used for pavement construction in Florida were obtained for evaluation. The resilient modulus of subgrade materials were evaluated by a laboratory triaxial testing program. The resilient properties of subgrade materials were found to be strongly influenced by moisture content and test procedure. A full-scale laboratory evaluation of the subgrade performance was then conducted in a test-pit facility to simulate the actual field conditions. The subgrade materials were tested under various moisture conditions that simulated different field groundwater levels. It was shown that the resilient modulus of subgrade materials increases with the decrease in groundwater level. In addition, the field plate load testing program was carried out to evaluate the bearing characteristics of pavement base, subgrade, and embankment soils. A hyperbolic model was used to represent the relationship of the load-deformation curve obtained from the field plate load bearing test. Correlation relationships were established between the laboratory resilient modulus and the resilient modulus measured using the test-pit facility. It was shown that the resilient modulus measured from the laboratory test could be used to predict the resilient deformation of the pavement subgrade layers if an appropriate calculation method was used. The correlation relationship between the subgrade soil resilient modulus and the modulus of subgrade reaction was also established; it was found to be close to the theoretical relationship from the AASHTO design guide. These correlation relationships could be utilized in the Florida pavement design guide in order to better predict the resilient deformation of pavement subgrades.
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