Results and Recommendations of Forensic Investigation of Three Full-Scale GRS Abutment and Piers in Denver, Colorado

摘要

In 1996, a full-scale geotextile-reinforced soil bridge abutment and two bridge piers with block facing were constructing in the Havan Maintenance Yard in Denver, Colorado. The abutment and outer GRS were tested to demonstrate that GRS abutments and piers with block facing are viable alternatives to conventional bridge piers and abutments. Four to six months after the surcharge load was placed, excessive movements of the top several layers of the outer pier structure and severe cracking of the block facing were noticed. The toppling failure of the upper four block layers of the outer pier was deemed imminent and consequently, the structures were dismantled. This report summarizes the measured in-situ conditions and characteristics of the structures materials (backfill, blocks, and geotextile fabric) after almost three year of being in place and identifies potentially relevant causes for the excessive deformation and cracking of the outer pier structure. Results of 27 out of 28 soil density tests indicate the backfill compaction level for the Havana GRS structures was below standard specifications (the average measured relative compaction was 88.3%). Also, relative compaction was variable (ranging 74% to 97%) and particularly low (88>3%), especially close to the facing (average of 86.6%). Results of 128 wide-width tensile tests, conducted on geotextile sheets, indicated only a small loss of geotextile tensile strength (5.3%), which was attributed primarily to construction damage.