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The use of CSE technology is rapidly expanding across the US as a viable alternative to more conventional methods of constructing embankments over soft soils. This rapid growth has occurred predominately because of the inclusion of a Load Transfer Platform (LTP), which more effectively transfers the load from the embankment to the columns across the soft soil layer and onto a firm foundation. This allows the columns to be spaced further apart increasing the economy of the technology. Strata manufacturers a variety of the geosynthetic products that can be incorporated into the design of the LTP.

Researchers at Virginia Tech (Dr. Filz and Joel Sloan) and the University of Kansas (Dr. Han), in partnership with Dr. Collin, are conducting full scale tests in order to validate and or modify current design procedures and will make recommendations to National Academy of Sciences in the summer of 2011, so that best practices and guidelines can be established and used by engineers throughout the US.

There are two main techniques being used: The Catenary Approach and the Beam Approach. The primary difference between each approach is the type of Load Transfer Platform that is placed over the piles. The Catenary Approach uses one or more layers of geosynthetic reinforcement placed as a catenary to transfer the embankment load to the columns. The Beam Approach uses multiple layers of soil and geosynthetics which form a geosynthetic reinforced beam.

There also are many other variables to consider including the types of the piles and the arrangement of the columns, both of which depend on the tributary area of soil surrounding each column. Columns are typically arranged in a square, triangle or hexagon formation. Typical center-to-center column spacing ranges from 1.5 to 3.0 meters.

Is Your Application A Candidate For A CSE?

Your project may benefit from the use of this technology (CSE) if the site consists of a soft layer of soil underlain by a firm layer. The embankment fill above the column foundation (vertical space) must also be adequate to transfer the load to the columns without differential settlement at the surface. The Catenary approach requires 1.4 times the clear span, and the Beam approach requires at least ½ the clear span between columns and surface of the embankment.

Contact The Collin Group for information on currently available guidelines.  www.thecollingroup.com/index.php/contact-us