Abstract
This paper describes an improvement and an estimation of the in-situ shear equipment for an accurate testing. This equipment, which is referred to as Borehole torsional shear test (BTST), consists of a shearing part for shearing soils, a pressure control part to apply a vertical stress and a recorder part. First, the place of shear plane was observed to realize the mechanism of shear failure in this test. Second, the effect of the length of a confining ring was examined by comparison with the results from ring shear tests. It is shown that these experimental results from the BTST have a similar tendency with the results from ring shear tests in both constant pressure and constant volume conditions.
