Ring Shear Apparatus for Measuring Residual Strengths and it's Measurement Accuracy

Abstract

This paper describes the introduction of a newly developed ring shear apparatus and its measurement accuracy. It has been pointed out that the conventional ring shear apparatus has the following disadvantages: sample loss by the squeezing during shearing process, periodic variation in the stress-displacement relation ship, and detection of normal stress acting on the shear surface. The new apparatus, as a goal, aims at solving the problems mentioned above, and attaining the high accuracy of measurement. In the new apparatus, the gap between the upper and lower confining rings can be made as small as 5μm-10μm, and the normal stress on the shear surface is improved to be measured directly from the actual vertical load. Furthermore, the time required for residual strength measurement was remarkably shortened by adoption of the function of the constant volume shear. The residual strength parameters measured with the new apparatus were found to be more appropriate than the parameters measured with the direct shear test. They also well corresponded to the parameters of the field-mobilized shear strength analyzed by the back analysis of a actual case.