Finite Element Modeling of Field Performance of Permeable Bases under Asphalt Pavement

Abstract

The performance of permeable base materials used by the Ohio Department of Transportation (ODOT) was evaluated with a calibrated finite element modeling technique. Two bound permeable base materials (asphalt-treated base and cement-treated base) and four unbound base course materials (typical ODOT 304, 307-IA, 307-NJ, and 307-CE) were built on two monitoring sites on I-90 in Ashtabula County, Ohio. Moisture content measurements were made with time domain reflectometry. Movement of water through the six pavement sections at the project site was modeled by the finite element method. The two-dimensional finite element software (Seep/W) capable of simulating unsaturated water flow in layered systems was used. Precipitation recorded from an automated weather station at the monitoring site was used as an input in the model. Numerical simulation results showed that the finite element method can be used to simulate water flow through pavement layers. Accurate modeling of the boundary and initial conditions is important for results in accurate simulation of the measured field moisture regimes. The concept of time to drain outlined by AASHTO was used to evaluate the drainage efficiency of different permeable base materials. In general, both bound and unbound base materials specified in ODOT materials specifications meet drainage efficiency requirements. However, the ODOT 304 fill material, if it contains 13% of fines or more, cannot provide efficient drainage according to the time-to-drain criteria.