Liquefaction Behavior of Mississippi River Silts

Civil infrastructure built on alluviums and recent deposits, such as dams, contain significant amount of silts. The static and dynamic behavior of these fine-grained soils has been investigated less than the clay-like or sand-like soils. Low plasticity silts (PI = 6) obtained east of St. Louis in Illinois are known as loess that has been re-deposited by water in the floodplains of the Mississippi River. These silts were reconstituted in the laboratory by slurry at water content above the liquid limit and then consolidated to an initial effective stress. The initial laboratory characterization under monotonic loading included a series of consolidated undrained triaxial compression tests at different effective confinement to determine the critical state parameters. A series of stress-controlled cyclic triaxial compression tests were run under normally and overconsolidated conditions. The liquefaction behavior of the silt at different over consolidation ratios and its relationship to the monotonic behavior is presented and discussed.