Geogrid-Reinforced and Pile-Supported Roadway Embankment

Abstract

Settlement is one of the major concerns in roadway embankment construction in areas where soft soil deposits constitute the major portion of subsurface soil. A pile foundation system is an effective way to support an embankment in order to minimize total settlement. In recent years, geosynthetic reinforcement has been successfully incorporated with pile foundations to improve settlement performance. Referred to as Load Transfer Platform (LTP), or Geosynthetic Reinforced Platform (GRP), the system combines vertical piles and horizontal geosynthetics to form a relatively stiff platform that transfers embankment load to a deeper, competent bearing layer. The geosynthetic layers serve as the tensioned platform that bridges over the piles and reduces the differential settlement at top of the platform, which in turn reduces the differential settlement of the embankment. After a brief discussion of the system mechanism, this paper focuses on a case study of a roadway embankment supported by a geogrid-reinforced platform and precast concrete piles in Colon City, Republic of Panama. The embankment, a MSE (Mechanically Stabilized Earth) retaining wall with a maximum height of 3.2 meters, was built on a 1.0-meter thick geogrid reinforced crushed stone LTP, which is supported by 30 cm diameter precast piles. Piles penetrate through 6 meters of organic clay to a very dense sandy silt bearing layer, 10 meters below the existing ground surface. Due to the complexity of the system a numerical method was used to model the system and evaluate settlement behavior. This paper presents a detailed discussion of the project information, the design methodology and the numerical modeling. In addition, field instrumentation is also presented in comparison with the design and analysis.