Development and Application of Bender Element Field Sensor for Pavement Base/Subbase Modulus Characterization and Geogrid Effectiveness Evaluation
Advisor: Professor Erol Tutumluer
Abstract
Despite the importance of accurately assessing granular base/subbase modulus, a crucial mechanistic layer property for pavement analysis and design, currently available evaluation methods do not allow continuously monitoring the aggregate layer modulus behavior. This deficiency is noteworthy as the role of pavement is progressively evolving towards enabling applications of smart sensing and connected vehicles for managing roadway infrastructure.
This doctoral research is focused on the development and application of a Bender Element (BE) field sensor for the estimation of pavement base and subbase stiffness characteristics. The newly developed BE field sensor is embedded in the pavement unbound aggregate layers to measure the shear wave velocity of the material, which is linked to its small-strain modulus behavior. In this research, a new design and development of the BE field sensor was carried out in detail in a controlled laboratory environment. An extensive experimental study was conducted to investigate the linkage between laboratory-tested resilient modulus (MR) and small-strain elastic modulus (Emax) characteristics estimated based on the BE instrumentation. BE field sensors were installed in two full-scale pavement test sections to monitor in-situ modulus characteristics during construction and traffic testing. One of the two full-scale test sections was the Construction Cycle 9 (CC9) tests of the National Airport Pavement Test Facility (NAPTF), operated by Federal Aviation Administration (FAA). The pavement modulus behavior to controlled aircraft gear loadings were analyzed, and the response predictions were compared to the pavement responses measured using other embedded sensors, i.e., coil sensors and pressure cells. Further, the BE sensor technology was applied to quantify the local stiffness enhancement near geogrid when installed in unbound aggregate assemblies through laboratory and full-scale experiments; the effectiveness of geogrid stabilization was substantiated.
Findings from this comprehensive study provided valuable information on the modulus behavior of unbound aggregates and the lateral restraint mechanism of geogrid stabilization and demonstrated the potential of the BE field sensor technology for transportation infrastructure.
