Development of a Hollow Cylinder Torsional Apparatus for Pre-failure Deformation and Large Strains Behaviour of Sand

Abstract

A hollow cylindrical torsional apparatus (HCTA) recently developed at University of Bristol, UK is presented. The HCTA apparatus is testing granular soils in drained and undrained, in monotonic but also dynamic loading conditions, and it is equipped with a complex strain measurement system based on high resolution non-contact transducers. The experimental developments are designed to allow the study of the pre-failure deformation characteristics and the large strains behaviour, via a continuous test on a single specimen and, thus, analyze the soil stiffness with the evolution of the strain and stress levels. While the experimental developments and apparatus capabilities in large strains have been explored and validated in an earlier study, this paper describes mainly the precision measurement system, including the assessment of its performance with reference to the soil stiffness.