The earth pressure behind full-height frame integral abutments supporting granular fill

Abstract

Compared with conventional bridges, integral bridges have no bearings or joints between the deck and abutments and thus can significantly reduce maintenance requirements and costs over the bridge's lifetime. However, there is uncertainty about the ultimate magnitude of the lateral earth pressure behind such abutments, as they are forced to move with the deck length change caused, for example, by daily and annual variations in the effective bridge temperature. This research investigated the earth pressure that would be expected to occur behind full-height frame integral abutments backfilled by granular materials. Radial strain-controlled cyclic stress path testing has been conducted on coarse sand specimens and a glass ballotini specimen. The results suggest that for integral abutments retaining uniform coarse sand, the lateral earth pressure will experience systematic increases for almost all cyclic strain levels, eventually reaching states of stress close to both active and passive. The mechanism of the buildup of lateral stress is explored, and it appears to be associated with nonspherical granular particle shape. The implications for frame integral abutment design are discussed.Key words: integral abutments, granular, particle shape, earth pressure, stiffness.