Collaborative Research on Column-Supported Embankments with Geosynthetic-Reinforced Bridging Layers (05-2630)
George M. Filz, Virginia Polytechnic Institute and State University
Raymond H. Plaut, Virginia Polytechnic Institute and State University

The U.S. National Science Foundation is sponsoring a three-year research project on vertical columns installed in soft ground with overlying bridging layers that are reinforced with geosynthetics. A principal application is column-supported embankments. Motivation for the research is based on widespread uncertainty and disagreement regarding the magnitude and mechanisms of arching and load transfer to geosynthetic reinforcement in such systems. Existing methods for calculating the vertical loads on geosynthetic layers differ by an order of magnitude for common system geometries. None of these methods incorporates the compressibility of the soft ground between columns as an input parameter, even though numerical analyses demonstrate that this factor has an important influence on system performance. Both excessive deformation and capacity failures have occurred, and improvements in the state of practice are needed. The NSF-sponsored research project includes (a) pilot-scale tests with well-defined boundary conditions and material property values to disclose fundamental mechanisms, (b) numerical analyses of the pilot-scale tests and instrumented full-scale projects to calibrate and verify the numerical procedures, (c) mathematical analyses of geogrid reinforcement to optimize arrangements and provide guidance for geogrid modeling in the numerical analyses, (d) parametric numerical analyses of the composite systems, and (e) development of simple yet reliable methods for cost-effective design. The authors intend to collaborate with other interested individuals and organizations domestically and internationally, and comments and suggestions regarding the research are sought. Case-history data from instrumented full-scale projects are needed.