Geosynthetics Used in Unpaved and Paved Roads

May 18 12:00 pm - 1:30 pm

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Beginning in the 1930’s, geotextiles and then geogrids have been used in unpaved and paved roads for the purposes of reduced stone base thicknesses and/or improved serviceability. Today, they are used primarily in four discrete applications. This webinar will be subdivided accordingly. First, for use as unpaved road reinforcement, the theory is well developed such that benefit/cost of using geotextiles or geogrids can be assessed. This application is very well positioned and accepted. Second, for paved road stabilization, a number of geogrid design methods will be reviewed focusing on increased trafficability. Also, for paved roads under the assumption of lateral reinforcement, an observational approach to mitigate longitudinal cracks will be presented. Third, for paved roads, geotextiles have been used as separators to keep the crushed stone base course from mixing with the soil subgrade. Its “theory” is not well developed and reliance is on field studies. Fourth, both geotextiles and geogrids will be described insofar as prevention of reflective cracks through asphalt overlays. Both theory and field behavior are presented.

The topic of this webinar lies at the heart of pavement performance judged on the basis of benefit/cost as well as serviceability, both of which will also be illustrated in the four parts of the webinar.


  • federal, state and regional transportation, materials and geotechnical engineers;
  • engineers from municipal districts and townships;
  • private and municipal owners of all types of unpaved and paved roads
  • general engineering consulting engineers;
  • soils and geosynthetic testing laboratories servicing these organizations;
  • manufacturers and representatives of geotextiles and geogrids;
  • contractors and installers servicing these applications;
  • academic and research groups; and
  • others desiring technically related information on this important aspect of our infrastructure system.


This webinar, an essential aspect of geotextile and geogrid applications focuses on the following

  • Introduction and Background
    • amount of roads worldwide by country
    • geosynthetics being considered
    • soil subgrade strength categories and criteria
    • four major locations for geosynthetics in pavement cross-sections
  • Unpaved Roads Reinforcement With Geotextiles or Geogrids
    • Giroud and Noiray model
    • economics of reduced base courses
    • Giroud and Han revised model
    • related commentary
  • Paved Road Applications Using Geogrid Reinforcement
    • location within the stone base course
    • evolution of design models for increased trafficability
    • lateral reinforcement observations and hypothesis
    • Kinney’s torsional rotation laboratory test method
  • Paved Road Applications Using Geotextile Separators
    • concept and analytic; modeling difficulties
    • heuristic approach as to amount of saved stone base
    • long-term field performance studies
  • Geotextile and Geogrid lnterlayers for Asphalt Overlays
    • geotextile reinforcement design
    • geotextile waterproofing design
    • crack growth rate modeling
  • Summary and Conclusions
    • review of the four applications presented
    • acceptance status of these applications
    • comments going forward



The following Learning Objectives will be realized for Webinar participants.

This webinar focuses on a comprehensive presentation of the four major geosynthetic
applications with respect to unpaved and paved roads. Both geotextiles and geogrids are
involved depending on exactly where in the roadway cross-section they are placed. Of course,
the quality of the soil subgrade is significant and its role will be described accordingly.

More specifically, participants will learn about (i) design methodologies, (ii) the relevant test
methods and procedures required input data, (iii) numeric examples of the required stone or
asphalt thicknesses, and (iv) what an owner or design consultant can realistically expect insofar
as longterm field performance is concerned.


  • appreciate the very different applications of geotextiles and geogrids insofar as pavements are concerned
  • understand how the soil subgrade, stone base course, and pavement material function vis-a-vis the specific geosynthetic and its location in the cross-section
  • appreciate where design models are fully developed, moderately developed or quite nonexistent
  • understand how laboratory test values of the geosynthetic material are used in the various design processes.


  1. Introduction and Background
  2. Unpaved Roads Reinforced With Geotextiles or Geogrids
  3. Paved Road Applications Using Geogrid Reinforcement
  4. Paved Road Applications Using Geotextile Separators
  5. Geotextile and Geogrid lnterlayers for Asphalt Overlays
  6. Summary and Conclusions

WEBINAR INSTRUCTORRobert M. Koerner, Ph.D., P.E., Dist. M.ASCE, is the Director Emeritus of the Geosynthetic institute and Professor Emeritus of civil, architectural, and environmental engineering at Drexel University in Philadelphia, Pennsylvania. His interest in geosynthetics spans over thirty years of teaching, research, writing and consulting. He has received the Lindback Award for teaching excellence, along with many other honors and awards from professional organizations. Bob has authored or co-authored about 400 papers on geosynthetics in journals and at national and international conferences. His most authoritative publication is the textbook entitled “Designing With Geosynthetics; 6th Edition in 2012”. He is a member of the National Academy of Engineering (NIAE), and a Distinguished Member, Hero, and Diplomat of the Geo-Institute. He is also one of the first class of the recently formed Academy of Geo-Professionals (D.GE). Bob has been presenting ASCE Webinars since March 2, 2010 (fourteen to date), enjoys so-doing, and gets good “report cards” as well.


George R. Koerner is Director of the Geosynthetic Institute. He is in charge of laboratory accreditation, field certification and continuing education at the Institute. He also manages several research projects and has published over 300 technical papers in his 35-year association with polymers used in below ground construction. Dr. Koerner’s Ph.D. is from Drexel University in Geotechnical Engineering. He is a registered professional engineer and a certified quality auditor. George has received many awards over the years. The most notable being IFAI’s Environmental Technologies Award of Excellence 1995, ASCE’s DVGI Geotechnical Engineer of the year in 2004, the title of ASTM Fellow in 2013 and GMA’s first Koerner lecturer in 2017.


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May 18 12:00 pm

May 18 1:30 pm

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Jessica Kivijarvi