INSTRUCTOR: Robert M. Koerner, Ph.D., P.E., D.GE, Dist. M.ASCE

Course Length:  90 minutes

Sponsored by ASCE Continuing Education and ASCE's Geo-Institute.

Purpose and Background

Polymeric fibers (usually polypropylene) are woven or nonwoven into fabrics which placed in the ground are called geotextiles. When used to filter liquids (very often water) they are commonly called filter fabrics. These geotextile filter fabrics are direct competition to sand filters which have a classical origin. Obviously, engineers must make the appropriate decision based on benefits, costs and likely success of the project. While the overall use of geotextile filters has been overwhelming successful there have been failures. This webinar describes and illustrates eighty-two such filter fabric failures. As such, the webinar can be considered as being of a lessons learned tutorial nature.

The presenter has been involved with geosynthetics since their origins in the 1970's and has collected situations where filtration performance has been inadequate. With regard to geotextile filters, eighty-two situations have arisen; approximately half of which are from personal files and half from published case histories. For presentation purposes, these failures have been subdivided into four categories: improper design, atypical soils, atypical permeants, and improper installation. In progressing through the categories, this webinar assesses adequate permeability, proper soil retention and long-term flow equilibrium. This webinar describes when and how the use of geotextile filters have been unsuccessful and how to prevent similar situations from occurring in the future. It concludes with a description of four long-term equilibrium tests (all standardized) which should be used by designers to preview if a sensitive situation is present and to make decisions accordingly.

Primary Discussion Topics

• A brief tutorial on proper design procedures
• Design failure illustrations and description
• Atypical soils failure illustrations and description
• Atypical permeant failure illustrations and description
• Installation failure Illustrations and description
• Summary in the context of long-term equilibrium laboratory test methods

Learning Objectives

• Explore proper geotextile filter design
• Determine which proper designs were not practiced
• Discuss extremely challenging situations involving upstream soils were encountered
• Explore situations where extremely challenging permeants were encountered
• Recognize situations where filter fabric installation was not practiced
• Identify long-term laboratory tests which are focused on site-specific field simulation to preview situations which will, or can, be troublesome over the life of the filter

Webinar Benefits

• Gain a sense of some of the nuances of proper geotextile filter design
• Understand cases where design was improper and caused failures
• Appreciate cases where extremely challenging upstream soils caused failures
• Learn about cases where extremely challenging permeants caused failures
• Comprehend cases where installation was improper and caused failures
• Understand what laboratory test methods are available to give insight into likely long-term field behavior

Intended Audiences

• Federal, state and regional geotechnical, transportation and hydraulic engineers 
• Engineers serving municipal districts and townships
• Private and municipal owners of all types of civil engineering filtration systems 
• Private owners of waste materials in need of dewatering and disposal
• General engineering consulting engineers
• Soils and geosynthetics testing laboratories servicing these organizations
• Manufacturers and representatives of geotextiles 
• Contractors and installers servicing these applications
• Academic and research groups
• Others desiring technically related information on this important aspect of our geotechnical, geoenvironmental and hydraulics related infrastructure system

Webinar Outline

• Background (Including Proper Design)
• Geotextile Design Failures
• Failures Involving Atypical Soils
• Failures Involving Atypical Permeants
• Geotextile Installation Failures
• Summary (Including Long-Term Lab Testing)