Soil Strength Indices as Indicators of Consolidation

SHEAR strength indices are often used to estimate soil characteristics related to erosion. The purpose of this study was to evaluate the effectiveness of using soil strength indices as indicators of soil changes caused by consolidation. Fall-cone, torvane shear, and pocket penetrometer measurements were obtained on clay, silt loam, and fme sand soils as a function of soil water stress history and time. Also, wet aggregate stability was measured for the clay soil. Prestress suction was the dominant mechanism for strengthening the three soils. Time effects were less pronounced. The fall-cone was the best indicator of consolidation and the pocket penetrometer was also effective with some limitations. The torvane shear device was the least effective index for detecting strength changes, although it worked well on the silt loam soil. The three index tests did not rank the three soils the same in order of increasing strength, suggesting that the validity of using index tests to rank or compare soils is questionable. The results of the study indicated that proper strength index tests may be effective in characterizing relative changes in stability of a given soil over time.