Assessment and Mitigation of Liquefaction Hazards to Bridge Approach Embankments in Oregon

摘要

The seismic performance of bridge structures and appurtenant components (i.e., approach spans, abutments and foundations) has been well documented following recent earthquakes worldwide. This experience demonstrates that bridges are highly vulnerable to earthquake-induced damages and loss of serviceability. These damages are commonly due to soil liquefaction and the associated impact of ground failures on abutments and pile foundations. This study has focused on numerical dynamic effective stress modeling to determine the seismic performance of sloping abutments and the effectiveness of soil improvement for reducing permanent ground deformations. Recommendations are provided for evaluating the dynamic behavior of regional silty soils, the application of soil improvement at bridge sites, and comparisons have been made between the deformations computed using the advanced numerical model and the rigid-black methods used in practice. The results have been presented in the form of design charts, where possible, that can be readily used by design engineers in preliminary design and incorporated into the ODOT Liquefaction Mitigation Policy. This study has demonstrated the utility, and limitations, of soil improvement solely by densification techniques.