Screening of Bridge Sites in Ontario for Liquefaction Susceptibility

Lateral ground deformation generally observed at river crossings is a pervasive type of liquefaction-induced ground failure. This can result in settlement of approach embankments, rotation and translation of abutment piles, and unseating of bridge decks. Since Ontario is situated in a generally low seismic activity region, liquefaction susceptibility and its consequences have not been comprehensively studied for its infrastructure. However, past earthquakes and seismic hazard maps of NBCC (2015) suggest that the infrastructure around the Niagara region, Ottawa region and along the Saint Lawrence River Valley can suffer earthquake-induced damage. All Ministry of Transportation bridge sites in Ontario were screened for liquefaction susceptibility using seismic microzonation maps and the most critical ones were identified. Seismic microzonation maps were developed by combining bedrock, surficial geology, groundwater and seismic hazard data in GIS software and Google Earth. Critical bridges were identified for liquefaction potential assessment using conservatively assumed site conditions and seismic demands following AASHTO and CHBDC design codes. AASHTO recommends detailed liquefaction assessment for four bridges in eastern and central regions of the province whereas CHBDC recommends evaluation of potential for liquefaction for a much larger number of bridges. The significant discrepancy between these codes points to a need for further study. Assumptions, details of the assessment, essential pieces of information needed, and future research are discussed.

Manmatharajan, M.V., M. Ghafghazi, D. Staseff, A. Sy and M. Snow. 2018. “Screening of Bridge Sites in Ontario for Liquefaction Susceptibility,” in Proceedings of GeoEdmonton, Transportation Geotechnique – Moving Forward, 71st Canadian Geotechnical Conference and the 13th Joint CGS/IAH-CNC Groundwater Conference, Edmonton, Alberta, 24-26 September 2018. Edmonton, AB: Canadian Geotechnical Society.

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