The Geosynthetic Institute (GSI) will sponsor a webinar, “Geosynthetic Reinforced MSE Walls; Overview, Failures and Items for Improvement” on Dec. 11, from 11:30 a.m. to 1 p.m. EST. Geosynthetic Materials Association (GMA) member companies and their employees receive discounted rates on all GSI webinar and short course registrations.

Mechanically stabilized earth (MSE) walls represent a grade separation structure which functions at a slope between unreinforced soil to classical (i.e., vertical) concrete walls. The soil mass itself is layered with geogrids or geotextiles such that a coherent stable mass is formed. The facing is usually either vegetated or masonry block, including many aesthetic variations. MSE walls have reached to 25 meters in height, supported railroads and heavy surcharge loads, buildings of moderate bearing capacity and can readily function adjacent to water courses and seismic conditions.

Furthermore, they are shown by a recent survey to be the least costly of any other type of retaining wall by 20 to 50%.

Design of such MSE walls is well within the state-of-the-practice and is usually addressed using a computer code. The six essential elements of design being the following; each of which are numerically addressed.

Internal Stability

• tensile overstress (spacing)
• retained soil pullout (length)
• facing connection overstress

External Stability

• mass sliding
• mass overturning
• bearing capacity

Unfortunately, there have been failures consisting of either excessive deformation or actual collapses. The presenter has been collecting such failures since 2000, and the worldwide database includes more than 300. They will be analyzed to learn where ongoing concerns exist. In this regard, five areas appear to be fundamental insofar as remedies are concerned. They will be described accordingly.

• use of fine-grained backfill soils
• poor compaction of backfill soils
• inclusion of drainage facilities within the backfill
• surface and adjacent water issues
• miscellaneous design details

Summarizing comments and conclusions will be offered accordingly.

Participants will learn about this new class of retaining walls (and steep slopes), cost comparison to other wall types, elements of design and where problems have existed in the past. These past problems have been classified into groups, which give clear insight into the mechanisms involved. Five aspects of design and/or construction will be offered which, if followed, would minimize such failures from occurring in the future.

The webinar is intended for owners of sites needing grade separation in both the public and private sectors; federal, state, and regional geotechnical, transportation and environmental engineers; engineers from municipal districts and townships; private and municipal land developers, architectural and landscape designers; general civil consulting engineers; hardscape designers; testing laboratories servicing these organizations; manufacturers and representatives of geosynthetic and masonry block materials; ground modification contractors; academic and research groups; and others desiring technically related information on this important aspect of our constructed infrastructure.

The webinar’s instructor, Dr. Robert M. Koerner, is professor emeritus of civil engineering at Drexel University, and founder and director emeritus of the Geosynthetic Institute.

Webinars cost $200.00 for GSI and GMA members, and $250.00 for nonmembers. Successful completion of a multiple-choice test after the webinar carries 1.5 professional development hours (PDH).

For more information or to register, visit http://www.geosynthetic-institute.org/webinar.htm.