UNDRAINED CYCLIC BEHAVIOR OF NONPLASTIC SILTY SAND

摘要

In this paper, an experimental program was undertaken to characterize the undrained cyclic behavior of nonplastic silly sands. A total number of sixty six constant volume stress-controlled cyclic tests using direct simple shear apparatus were performed on reconstituted specimens of sand with fines contents of 0, 20, and 40%. Specimens were prepared at relative densities of 40 and 80%; consolidated at vertical stresses of 50, 100, 200, and 400 kPa; and sheared at cyclic stress ratios of 0.05, 0.10, and 0.15. Results confirm that the failure criterion to be adopted in cyclic testing should be identified based on whether the soil behavior is contractive or dilative. It is shown that cyclic behavior of silty sand is better characterized in light of limiting silt content and relative density concepts. Cyclic resistance depends not on fines content but on whether that content is below or above the limiting silt content of the sand and is controlled by the soil relative density. Contradictory trends reported in the literature related to effect of fines content on cyclic behavior of sand based on laboratory and field measurements are attributed to the various density measures; relative density, gross void ratio, and sand skeleton void ratio; adopted when analyzing test results.