Effectiveness of geosynthetic reinforcement for load transfer in column-supported embankments

Many column-supported embankment (CSE) design methods include geosynthetic reinforcement for vertical load transfer and/or settlement reduction regardless of project conditions. However, geosynthetic reinforcement may not be necessary for all applications, particularly if a sufficiently thick and strong soil layer overlies the compressible soil. A strong soil layer can transfer embankment loads to the columns without much differential settlement at the base of the embankment, limiting the development of tension in the reinforcement. If weak and compressible soil extends to the ground surface and the area replacement ratio is low, differential settlements may be so large that it may not be practically possible to provide enough reinforcement to avoid excessive strain or rupture. This paper describes parametric studies using the Load Displacement Compatibility method to investigate the influences of embankment height, geosynthetic stiffness, column diameter, and thickness of an upper sand layer on geosynthetic strain, differential settlement at the base of the embankment, and load distribution among the CSE components. Results of the parametric study show that site conditions, CSE system geometry, and performance requirements limit the range of circumstances for which geosynthetic reinforcement for settlement reduction is needed, effective, and practically possible.