A new methodology to improve backcalculation of flexible pavements with stabilized foundations

Abstract

Flexible pavements with stabilized foundations are often used in parts of the U.S. where subgrade and aggregate base materials are sub-optimal. Though common, there is precious little mechanistic-empirical data and few mechanistic studies featuring these pavement types. To improve the fundamental understanding and overall design and performance of flexible pavements with stabilized foundations, there is a need for full scale evaluation. To address this need, the Mississippi Department of Transportation sponsored a full-scale pavement section at the National Center for Asphalt Technology Test Track beginning in 2018. While studying many aspects of M−E analysis and design, the aim of this investigation was to overcome the challenges of backcalculating layer moduli of a flexible pavement with a stabilized foundation. Falling weight deflectometer testing was conducted three times per month on this section to characterize structural behavior over time. The backcalculation process using conventional methods yielded unrealistic results with high variability. To resolve the issue, a new backcalculation computer program (MASTIC) was developed to add additional features such as partial friction for layer interfaces which showed significant improvement over traditional full bonding conditions but did not entirely address the problem of high variability. To obtain less variable results, a new methodology was developed to examine the actual deflection basins. The “x-intercept” method filtered out deflection basins that resulted in erroneous estimation of layer moduli by examining measurements from the four outermost sensors. This study showed that integration of partial friction method and x-intercept analysis is necessary to obtain acceptable moduli of stabilized foundation sections.