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.
Highlights
A correct assessment 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
The magnitude of passive force is highly sensitive to the interface friction angle (δ) between the abutment wall and the adjacent backfill
A number of large-scale passive force tests have found that the logspiral approach generally provides the best agreement with measured passive force [2, 3, 4]
Summary
A correct assessment 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. The magnitude of passive force is highly sensitive to the interface (wall) friction angle (δ) between the abutment wall and the adjacent backfill. A proper assessment of interface friction is relatively straightforward for granular backfills such as sand or gravel; little guidance is available for other geomaterial backfills. Large scale test data has not been available for Geosynthetically Reinforced Earth (GRS) backfills or backfills where expanded polystyrene blocks (Geofoam) is placed as an inclusion between the concrete abutment wall and the compacted sand backfill behind it. Comparisons are provided between measured passive force and that computed using various methods and interface friction gles to determine the most reasonable approach. To evaluate the influence of the geotextile and geofoam interfaces between the concrete wall and the adjacent backfill, companion tests were performed. Tests were performed on a compacted sand backfill with and without geofoam blocks between the wall and the sand backfill
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
