Effective stress vane shear strength correction factor correlations

A recent effective stress model of vane shear strength testing in soils can relate measured torques to vane shear strengths using theoretical analysis in terms of effective stress parameters. The strength estimates are based on known in situ stresses and soil parameters derived from laboratory testing. The model may be applied, for example, in obtaining theoretical estimates of conventional undrained vane shear strengths for comparison with field data and for use in stability analyses. However, the model incorporates a correction factor μ v , analogous to Bjerrum's field vane shear strength correction factor μ, intended to compensate for pore-pressure and shearing-rate effects. This correction factor must be evaluated before reliable torque or shear strength estimates can be made in any given case. To facilitate this, the paper presents correlations of μ v with both liquid limit and plasticity index, based on world-wide data from clays and silts. The correlations are compared with independent data from Norwegian clays. Key words : clay, correction factor, effective stress, liquid limit, plasticity index, silt, vane shear strength.