Liquefaction testing of stratified silty sands

The cyclic behavior of stratified silty sandy soils is at present poorly un derstood, yet these materials are commonly found in alluvial deposits and h ydraulic fill, which have a history of liquefaction during earthquakes. The main objective of this research project was to compare the behavior of str atified and homogeneous silty sands during seismic liquefaction conditions for various silt contents and confining pressures. A comprehensive experime ntal program was undertaken in which a total of 150 stress-controlled undra ined cyclic triaxial tests were performed. Two methods of sample preparatio n were used for each soil type. These methods included moist tamping (repre senting uniform soil conditions) and sedimentation (representing layered so il conditions). The silt contents ranged from 10 to 50%, and confining pres sures in the range of 50 to 250 KPa were considered. The results indicated that the Liquefaction resistances of layered and uniform soils are not sign ificantly different, despite the fact that the soil fabric produced by the two methods of sample preparation is totally different. The findings of thi s study justify applying the laboratory test results to the field condition s for the range of variables studied.