OTREC-RR-13-05

Liquefaction and liquefaction induced damage in pile supported structures is seen in earthquakes around the world. The Pacific Northwest has seismic hazard conditions as a Cascadia Subduction Zone (CSZ) with an expected earthquake magnitude of 9.0 (Mw) and a 300 year return period. Oregon Dept. of Transportation found thousands of Oregon bridges to be vulnerable to a CSZ earthquake, with repair and replacement costs estimated at over $1 billion. This research sought to evaluate the seismic performance of bridge foundations and liquefaction mitigation alternatives. The main objectives were to develop design charts for mitigation alternatives and to develop methodologies for assessing the performance of bridge pile foundations in laterally spreading ground. Research focuses are: 1) ground improvement methods, particularly using stone columns and deep soil mixing grids, and 2) assess the seismic performance of bridge foundations and seismic retrofitting alternatives for the bridge foundation.