The performance of flexible and rigid pavements is known to be closely related to properties of the base, subbase, and/or subgrade. Recent research studies, however, indicate the procedures contained in the American Association of State Highway and Transportation Officials’ (AASHTO’s) design guidance need to be evaluated. TRB hosted a webinar on Tuesday, August 3, 2021 from 2:00-3:30 PM to highlight the importance of applying unsaturated geomaterial mechanics during pavement foundation design. The webinar covered the fundamentals of unsaturated soil mechanics, including fine-grained (subgrade) coarse-grained materials and recycled materials. They discussed the relationship between matric suction and geomaterial engineering properties, novel and practical field moisture measurement techniques, field implementation of the research findings, and department of transportation experience.

This webinar was organized by the TRB Standing Technical Committees on Aggregates and Mechanics & Drainage of Saturated and Unsaturated Geomaterials. It also features research from NCHRP Web-Only Document 264: Proposed Enhancements to Pavement ME Design: Improved Consideration of the Influence of Subgrade and Unbound Layers on Pavement Performance.

The slides are linked in the meeting materials below. Click here to view the recording.

Webinar agenda and presenters

1. Fundamentals of unsaturated soil/geomaterial mechanics: William Likos, University of Wisconsin-Madison
2. Impact of matric suction on pavement foundation materials: Bora Cetin, Michigan State University
3. Influence of moisture content on compaction quality for geomaterials: David White, Ingios Geotechnics, Inc.
4. Question and answer session: Moderated by John Siekmeier, Minnesota Department of Transportation

The first 60 minutes of the webinar will be for presentations and the final 30 minutes will be reserved for audience questions.

Learning Objectives

At the end of this webinar, participants will be able to:

1. Identify unsaturated geomaterial mechanisms
2. Discuss the impact of moisture/matric suction on geomaterial performance
3. Identify implementation options during pavement foundation design

Professional Development Hours

Professional Development Hours (PDHs) earned on completion of this program were reported to the Registered Continuing Education Program (RCEP). Certificates of Completion are issued to all participants via the RCEP.net online system. Complaints about registered providers may be addressed to RCEP, 1015 15th Street, NW, 8th Fl., Washington, DC, 20005.