Performance of Geogrid-Reinforced and PTC Pile-Supported Embankment in a Highway Widening Project over Soft Soils

A case study of a widened highway embankment is presented, in which prestressed tubular concrete (PTC) piles and geogrids were used to reinforce the embankment and to reduce construction time. In situ measurements of earth pressures, settlements, and lateral displacements were reported and analyzed to evaluate the effectiveness of the reinforcement technologies. The instrumentation data confirm that a large portion of the embankment load is supported by the PTC piles, as quantified by a large stress concentration ratio of 6.6. Consequently, the resulting total settlement at the embankment surface and lateral displacement during and after the embankment construction were significantly reduced by using geogrids and two groups of PTC piles at different elevations of the embankment. The measurement data will be valuable for numerical simulations on pile-supported embankments and highway widening projects in the future. Lastly, a design procedure was proposed for highway widening projects based on the literature studies, and its validity was verified by this case study.