Development of Design Charts for Unpaved Roads using NAUE Geosynthetics, Phase 1

The objective of this project is to develop a series of new design charts for NAUE geosynthetics used in unpaved roads based on mechanistic-empirical design principles.

Current design procedures for the stabilization of pavement subgrade are typically expressed in terms of design charts. These charts provide the recommended thickness of base course materials (compacted aggregate) required for haul roads. The thickness is calculated as a function of subgrade strength, based on a number of considerations, including whether the road will be built with reinforcement layers using geosynthetic materials. However, some design charts date back to the 1970s, and do not reflect design advancements, such as the development of mechanistic-empirical (M-E) design principles. M-E design integrates the application of engineering mechanics principles with the empirical computation of potential damage. The purpose of this project is to create new M-E design charts for NAUE, a German geosynthetic manufacturer. Previously, WTI researchers have developed a mechanistic-empirical design solution for base-reinforced flexible pavements, using a finite element model to calculate pavement response and empirical damage models to relate strain-response to long term rutting. This project will use these models as a starting point. To adapt them, researchers will construct and test field scale test sections on unpaved roadways with geosynthetic reinforcement layers. The results will be analyzed and compared with similar field tests recently completed by GeoTesting Express (also for NAUE). The findings will form the basis for calibration of the models used to develop the NAUE design charts.