J.P. Giroud and Jie Han
Since its publication in 2004, the Giroud-Han design method for geosynthetic-reinforced unpaved roads has received considerable attention from the geosynthetics industry. This article is the first of two that provides practical information for the users of the method as well as for those who want to learn about the method.
Part 1 | Method development and calibration
The Giroud-Han (G-H) design method provides a design tool to determine the thicknesses of unreinforced and geosynthetic-reinforced aggregate bases for unpaved roads over soft subgrade. The method was published in two parts (Giroud and Han, 2004a, b) in the ASCE Journal of Geotechnical and Geoenvironmental Engineering.
The G-H method replaces the widely used method published by Giroud and Noiray (1981) and has been included in the updated “Geosynthetic Design and Construction Guidelines” manual by the Federal Highway Administration (FHWA, 2008).
Development of the G-H method was a long and complex effort in the late 1990s and early 2000s. The length and complexity were justified by the authors’ desire to openly provide all details and calculations pertaining to the development of the method. However, the need for a summary of the method has been expressed. This article presents a summary of the method’s features.
Even though the G-H design method has been adopted by consultants and geosynthetic manufacturers, a number of issues have arisen, which are clarified in this article. In particular, this article clearly indicates the equations that are generic—and can be used with any geosynthetic with appropriate calibration—and the equations that were calibrated for specific geosynthetics. This distinction between generic and calibrated equations is crucial because it was not clear to some readers of the original publications of the G-H method.
Also, the calibration steps were not easy to follow due to the length and complexity of the original papers. In this article, they are presented in a concise manner.