Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science in Civil and Environmental Engineering

Department

Civil and Environmental Engineering

First Advisor

Aaron Bradshaw

Abstract

This thesis presents the results of two studies. The first is a study performed to characterize the resilient modulus properties of unbound subbase material containing Reclaimed Asphalt Pavement (RAP) that has been previously reclaimed. The Rhode Island Department of Transportation (RIDOT) is moving toward the use of the Mechanistic-Empirical Pavement Design Guide (MEPDG) for pavement design. The guidelines require the resilient modulus of the pavement structure as an input including both the bound (i.e. asphalt) and unbound layers (i.e. subbase/subgrade). This study characterizes the resilient moduli of RAP/aggregate blends sampled from an existing roadway subbase layer in Rhode Island. The RAP content of the samples tested ranged from approximately 15% to 40%. The test results showed that the average resilient modulus ranged from approximately 120 MPa to 520 MPa, with increasing values occurring with higher confining stress and cyclic stress levels. Neither the percentage of RAP nor the relative compaction had an effect on the resilient modulus value.

The second portion of this thesis presents the results of a study of cyclic triaxial tests performed on Monterey sand to investigate the influence of initial effective confining stress on the dissipated energy at initial liquefaction. Energy-based liquefaction procedures have been proposed as a more fundamental alternative to the more commonly used cyclic stress-based procedures. It is well known that in the shear stress-based simplified procedures, for example, that initial confining pressure has an influence on the cyclic resistance. These effects are accounted for by multiplying the Cyclic Resistance Ratio (CRR) by an overburden stress correction factor (K-sigma). However, it is uncertain at this point if a similar overburden correction factor is required for energy-based simplified procedures (K-sigma-energy). Therefore, this thesis performs cyclic triaxial tests on Monterey sand at various relative densities and initial effective confining stresses to investigate this effect. The results suggest that no overburden stress correction factor is needed for use with energy-based liquefaction procedures.

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