Secondary Settlement of Geosynthetic-Reinforced Soil Piers: Preliminary Results

Four geosynthetic-reinforced soil (GRS) piers, each built with different reinforcement strengths and aggregate backfill material, were constructed at the FHWA's Turner-Fairbank Highway Research Center in collaboration with the Long-Term Bridge Performance Program. The objective of the research is to assess the secondary deformation characteristics of GRS for load-bearing applications under service load conditions. The experiment consisted of axially loading the piers with 490 kN decommissioned prestressed concrete girders, resulting in an equivalent vertical applied stress of 200 kPa. The geometry of each GRS composite was 1.2 m square by 2.3 m in height, for an approximate base to height ratio of 0.5. The facing element for each GRS pier is a simple, split-faced concrete masonry unit (CMU) that is frictionally connected to the GRS composite at a nominal vertical reinforcement spacing of 0.2 m. The piers were instrumented to record reinforcement strain, earth pressures, and deformations. This paper will discuss the objectives of the experiment, explain the testing program, and share some of the vertical deformation results after almost four months in service. In addition, the results will be compared with the results of a long-term (since 1999) study on secondary settlement of a GRS abutment.