Civil and Environmental Engineering Presentations
Document Type
Conference Proceeding
Publication Date
10-4-2017
Abstract
Despite extensive amount of research on liquefaction analysis of sands, reliquefaction behavior and cyclic liquefaction resistance of cohesionless soils under a repeated cyclic load have not received the same amount of consideration. This is important as most soil deposits in high seismic areas have been subjected to repeated number of earthquakes. This paper presents series of laboratory cyclic simple shear tests on specimens of a local carbonate sand from London, Ontario. Sand specimens are reconstituted at relative densities of 25%, 45%, and 65% and subjected to effective vertical stresses of 50, 100, 200, 400, and 600 kPa. Reconstituted samples are subjected to two consecutive cyclic loads and sand behavior and liquefaction resistance are examined and compared following both cyclic loads. Reliquefaction is simulated by unloading the specimens after the first cyclic load and re-consolidating the specimen under the same initial vertical stress. A similar cyclic load is then re-applied on the sand specimen. The results show a moderate increase in relative density after re-consolidation, which is greater for loose sand specimens. However, a complicated change in cyclic liquefaction resistance is observed for loose and dense specimens which also varies with stress level. Despite the larger increase in relative density, the loose specimens exhibit a dramatic decrease in cyclic resistance following the first cyclic load. The reduction in cyclic resistance increases with decreasing effective stress (from 600 to 50 kPa). On the other hand, dense samples experience an increase in cyclic resistance, particularly at lower stress levels.
Notes
Paper presented at GeoOttawa 2017, the 70th Canadian Geotechnical Conference and the 12th Joint CGS/IAH-CNC Groundwater Conference held in Ottawa, Ontario, Canada from October 1-4, 2017.