Vane borer. An apparatus for determining the shear strength of clay soils directly in the ground

Abstract

Laboratory shear strength tests on clay samples extracted from boreholes often give too small strength values as compared with values obtained in stability analyses, especially when samples are taken from great depths. This may largely be due to changes in the pressure conditions during the extraction of samples. A method for determining the shear strength of clay soils directly in the ground is described. The strength test is made by driving a vane into the soil and rotating it, while measuring the resistance to rotation. The shear strength is calculated from the torsional moment thus obtained.