Ranking and Assessment of Seismic Stability of Highway Embankments in Kentucky (KYSPR 96-173)

This report presents the findings of three independent studies under the same grant. These were (a) assess and rank highway embankments along priority routes in western Kentucky according to seismic stability, (b) assess the seismic stability of the approach embankment for the U.S. 51 Ohio River crossing near Wickliffe, Kentucky, and (c) evaluate the seismic stability of the U.S. 41 Ohio River twin spans north of Henderson, Kentucky. Seismic stability of bridge foundations was not a part of this study. The highway ranking assessed over 400 embankments and delineated each as having high, moderate, or little risk of significant failure for both the 50 and 500 year events. For the 50 year event, 6 were designated as high risk, while 145 were designated as high risk for the 500 year event. The report recommends evaluation of all high risk embankments and any moderate risk embankments along particularly critical sections of roadway. The US 51 bridge embankment assessment indicated a high risk of embankment failure for the 500 year event, and a moderate risk of some deformation requiring repair for the 50 year event. The findings suggested the need for an emergency repair plan in the event of either earthquake, and suggested a more detailed evaluation if a higher confidence about the risk of failure was required. The US 41 bridge embankment evaluation indicated little to no risk of major liquefaction for the 50 and 500 year events. A factor of safety of about 1.0 was estimated for seismic slope stability of the embankment at the bridge abutments, but a detailed stratigraphic section was not possible due to limited project budget. There thus remains some uncertainty about the overall seismic slope stability. The factor of safety is not likely to be significantly less than 1.0. This is acceptable for seismic loading, as a factor of safety of 1.0 implies some deformation of the embankment may occur, but the extent of damage should be repairable on relatively short notice