Critical-state soil mechanics parameters and their variation for Vertisols in eastern Australia
1991
Kirby, J.M.
Compression and shear tests were conducted on undisturbed samples from a range of Vertisols to determine the critical-state parameters, their variation, and the relationships between these parameters and the moisture content and density of the soil. The soils varied considerably in their characteristics, with the liquid limit ranging from 0.39 to 0.88, and were tested over a wide range of moisture contents, densities and saturations. The critical-state parameters describing compressional and shear properties varied with the moisture content, Atterberg limits and density of the soil, in contrast to saturated soils where these parameters are considered to be constants. It was found that the liquidity index (moisture content expressed as fractional distance between the liquid and plastic limits) explained the data significantly better than moisture content and also significantly better than did the suction. These data, therefore, supported suggestions that the Atterberg limits may serve as a useful basis for practical soil management guidelines. The measured parameters displayed considerable variation, demonstrating that any such guidelines need to be cast in terms of probabilities. The soil expanded when sheared if the normal stress during shear was less than about half the pre-consolidation stress and compressed when sheared if the normal stress during shear was more than about half the pre-consolidation stress. This behaviour was repeatable.
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