Use of Geogrid-Reinforced and Pile-Supported Earth Structures

Abstract

When designing structures that will impose a significant load over a large area, such as buildings, tanks, walls, slopes or embankments, the geotechnical engineers must address the following situations, especially when dealing with weak foundation soils: bearing capacity failures, intolerable total and differential settlements, large lateral pressures and movement, and slope instability. Geogrid-reinforced and pile-supported platforms have been successfully used for supporting earth structures. In this system, geogrids create a stiffened platform that spans weak soils and prevents deflection between piles (or columns by ground improvement techniques) or pile caps from being reflected to the surface. This paper briefly discusses the mechanisms of this system and then focuses on three case studies in which geogrid-reinforced and pile-supported platforms were used for supporting segmental walls in Brazil, embankments, and a building in the US. The first two sites have peat deposits and the foundation soils are very soft. The third site had a large cut and fill situation and the anticipated differential settlement is substantial if no ground improvement is implemented. The three projects adopted three different deep foundation techniques: vibro-concrete columns (VCC), jet-grouting columns, and cast-in-place concrete piles. In this paper, each case study provides a description of the site, the design solution, construction, and performance. The performance of each project was investigated by survey, instrumentation, and/or observation. Satisfactory performances of these projects have proved the effectiveness of this technique in reducing total and differential settlements.