Effect of Interface Friction on Passive Force on Bridge Abutments

¹ Civil & Environ. Engrg. Dept., Brigham Young University, 430 EB, Provo, UT 84602, USA
² AECOM, 756 E. Winchester St #400, Salt Lake City, UT 84107 USA
³ CKR Engineers, 1295 N State St., Orem, UT 84057 USA

^* Corresponding author: rollinsk@byu.edu

Abstract

A correct understanding of passive force-deflection response is important for lateral load evaluations of bridges during extreme events such as earthquakes and from thermal expansion and contraction of the superstructure. In these cases, the ultimate passive force is highly sensitive to the interface friction between the abutment wall and the adjacent geomaterials. These geomaterials may simply consist of compacted sand or gravel; however, for geosynthetic reinforced soil (GRS) backfill a geosynthetic fabric may be placed between the abutment wall and soil which can reduce the interface friction. In still other cases, a zone of compressible material such as geofoam may be used as a barrier between the soil and abutment to reduce lateral earth pressures. To evaluate the effect of the interface friction on passive force-deflection curves, large-scale testing was performed with a test abutment that was 3.35 m wide and 1.68 m high. Backfill materials consisted of sand, gravel, GRS backfill, and a geofoam inclusion between a sand backfill and the abutment. As a result of lower interface friction, the GRS backfills only developed 80% of the force developed by the unreinforced gravel. The geofoam inclusion decreased the passive force by about 70% as a result of reduced interface friction.