Geosynthetic design methods used in roadway applications: Fid-Bau Portal

Geosynthetic design methods used in roadway applications

Koerner, Robert M.

From the very beginnings of geosynthetics roadways have been a major application area. Geotextiles were used successfully on soft subgrade soils for unpaved roads since the 1970's. Geotextiles for prevention of reflective cracking in asphalt overlays began in the 1980's. Geogrids within stone base aggregate for paved and unpaved roads, as well as railroads, began shortly thereafter. Considering the tremendous amount of roadways of all types, however, many feel (the author included) that the full potential of geotextiles and geogrids in roadway applications is largely unfulfilled. One reason is perhaps because the necessary design methodology is either unavailable or overlaps the various functions that may be simultaneously occurring, i.e., a specific design methodology for each mechanism is yet to be developed and moreover accepted by the owner/regulatory community. This paper, essentially a review of available design methods for each mechanism, purposely distinguishes between four unique functions that geosynthetics provide in roadway applications. They are the following: (1) Geotextiles and/or geogrids used for reinforcement of soft soil subgrades for unpaved roads. (2) Geotextiles used for separation on firm soil subgrades for paved and unpaved roads (3) Geogrids used for reinforcement within stone base aggregates on firm subgrades for paved and unpaved roads (4) Geotextiles or geogrids used for waterproofing or reinforcement of reflective cracking in asphalt overlays of paved roads The state-of-the-practice insofar as design is concerned will be presented in each of these four discrete areas. The perceived status of geosynthetics in roadways and recommendations going forward will be offered as well.