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This webinar was co-sponsored by ASCE's Geo-Institute (G-I) and ASCE Continuing Education
Instructor: Robert M. Koerner, Ph.D., P.E., Dist.M.ASCE
Course Length: 1.5 Hours
Purpose and Background
This webinar presents an alternative to classical deep foundations and concrete pile caps for construction over soft soil foundations. It applies to roadways, levees and dikes, storage areas, parking lots and related “low-to-medium capacity surface loads”. Focus is twofold; a high strength geotextile or geogrid reinforced load transfer platform (LTP), and an underlying deep foundation support system which should not have sharp edges, e.g., a geogrid encased stone column or a geotextile encased sand column is suggested.
The webinar is indeed design oriented. Five different published methods based on limit equilibrium for the LTP will be presented and compared to one another. The comparison is poor. This is followed by examples using the FLAC computer code (based on finite differences) which is a 3-D depiction of the situation. Its results highlight the critical issue of geosynthetic edge stresses when placed against a rigid pile or pile cap. This suggests the possibility of using a deep foundation system which is accommodating to the LTP reinforcement. This can be accomplished using geogrid encased stone columns or geotextile encased sand columns. A 2.4 km long dike construction case history encompassing the various points of the webinar is also illustrated.
Primary Discussion Topics
- Concept of construction on soft foundation soils using geosynthetic reinforcement of a soil mattress
- Concept of the support of the mattress with geosynthetic related deep foundations
- Five design methods for the reinforced mattress and how they compare to one another
- Two computer designs and recommendations for this situation
- Methods of constructing compliant deep foundations (stone or sand) using geosynthetics as encasement
- A large case history embodying both the reinforced mattress and a compliant pile system
Learning Outcomes
Upon completion of this course, you will be able to:
- Identify geosynthetic reinforced LTP
- Recognize differences in design methods using limit equilibrium as contrasted to computer codes
- Become familiar with the danger of high edge stress on the geosynthetic reinforcement of the mattress
- Recognize laboratory testing of high strength geosynthetics and their seams
- Discover new deep foundation systems using encasing geosynthetics which provide low edge stress accommodation
- Identify how each of the above topics are integrated and deployed in a large case history
Webinar Benefits
- Understand that a geosynthetic-related system for moderate load support over soft foundation soils is available
- Appreciate that major design differences exist in using limit equilibrium methods
- In contrast, learn that computer codes based on finite differences or finite elements result in better understanding of the tensile stresses in the reinforcement
- Understand that alternatives to “hard” (classical) deep foundation systems exist and are based on geosynthetic encasement of granular soils
- Understand elements of the laboratory testing of high-strength geosynthetics which is necessary for proper design
- Appreciate that each aspect of the webinar can be incorporated into a case history as is described and illustrated
Assessment of Learning Outcomes
Students' achievement of the learning outcomes will be assessed via a short post-assessment (true-false, multiple choice and fill in the blank questions).
Intended Audience
- Federal, state and regional geotechnical and materials engineers
- Geotechnical and geoenvironmental engineers serving private clients in heavy industries
- Private and municipal owners of all types of civil engineering systems
- Private and public owners of construction sites with soft foundations soils
- General engineering consulting engineers
- Soils and geosynthetics testing laboratories servicing these organizations
- Manufacturers and representatives of geotextiles
- Contractors and installers servicing these situations
- Academic and research groups
- Others desiring technically related information on this important aspect of our infrastructure system
Webinar Outline
- Concept and Overview
- Limit State Design of Load Transfer Platform
- Finite Difference and Finite Element Modeling
- Geosynthetic Encased Stone and Sand Columns
- Case History
- Conclusions and Recommendations
How to Earn your CEUs/PDHs and Receive Your Certificate of Completion
To receive your certificate of completion, you will need to complete a short on-line post-test and receive a passing score of 70% or higher within 1 year of purchasing the course.
How do I convert CEUs to PDHs?
1.0 CEU = 10 PDHs [Example: 0.1 CEU = 1 PDH]