PERFORMANCE OF A PRELOADED-PRESTRESSED
GEOGRID-REINFORCED SOIL PIER FOR A RAILWAY BRIDGE

TARO UCHIMURA, MASARU TATEYAMA, IKUO TANAKA, and FUMIO TATSUOKA

ABSTRACT: A new construction method, called "the preloaded and prestressed reinforced soil method", proposed in this paper, aims at making reinforced backfill structures very stiff and stable. To make the deformation of a reinforced backfill nearly elastic, sufficiently large preload is first applied by introducing tension into metallic tie rods that penetrate the reinforced backfill and are connected to top and bottom reaction blocks. High tensile force in the tie rods functions as prestress increasing the confining pressure in the backfill and thus keeping the stiffness and shear strength of the backfill soil sufficiently high. In 1996, in the northern Kyushu, Japan, a prototype pier of preloaded and prestressed geogrid reinforced backfill was constructed for the first time to support a pair of simple beam girders for a temporary railway bridge. An abutment of geogrid-reinforced soil retaining wall, which was neither preloaded nor prestressed, was also constructed for the same bridge by otherwise the same construction method. The behaviours of the pier and the abutment ware measured during the construction and the service period of about four and a half years and subsequently full-scale loading tests were performed. It is shown that the geogrid-reinforced backfill pier became substantially stiffer against static and dynamic load by having been preloaded and being prestressed, when compared to the geogrid-reinforced backfill abutment. 

Key words:  case history, cyclic loading, deformation, (long-term performance), preloading,  (prestressing),  reinforced soil (IGC: E12/K14)