A NEW MODEL OF VANE SHEAR-STRENGTH TESTING IN SOILS

Using experimental data on the total and effective stresses acting within the shearing zone surrounding a rotating shear vane, a new theoretical model of the vane shear test has been developed. The model accounts for the initial stress state of the soil, assumed to be axisymmetric, as well as some of the phenomena affecting the effective stresses during shearing. An empirical correction factor mu(V) is introduced to account for some phenomena not directly incorporated in the model, which depend on the test procedure and the soil tested. The theoretical contributions of the sides and ends of the vane to the measured torque can be assessed using the model. The model is consistent with limited experimental vane shear data for soft Leda clay, Osaka marine clay and London Clay. However, the limited number of soils and initial stress states considered is too small to fully validate the model. Values of mu(V) have been obtained for the Leda and Osaka clays which suggest that the variation of mu(V) with plasticity index may resemble that of Bjerrum's vane shear correction factor mu(R).