Full-Scale Investigation of Differential Settlements beneath a Geosynthetic-Reinforced Soil Bridge Abutment

Abstract

Geosynthetic-reinforced soil bridge abutments can be constructed quickly and at lower cost than traditional alternatives. However, the lack of deep foundation elements contributes to a perceived vulnerability to differential settlements at the foundation level, either because of scour undermining or compressible soils beneath the foundation. A full-scale abutment was constructed, instrumented, and subjected to carefully controlled differential settlements. Data collected during construction indicate that the abutment adequately supported the surcharge load. Subsequent large differential settlements imposed at the foundation level resulted in small surface expression of differential settlements, redistribution of stresses within the reinforced fill, and adequate support at the level of the superstructure. However, the facing units appeared vulnerable to removal, potentially exposing the reinforced fill to erosion. Three measures to help mitigate this risk are discussed: pinning the concrete masonry units (CMUs) near the corner of the abutment, adding a protective wrap behind the CMUs to encapsulate the fill, and increasing the reinforcement length at the base of the abutment.