Towards Standardization of Torsional Shear Testing

The use of torsional shear testing devices as a means to study the monotonic and cyclic behavior of soils is increasing at a steady, if slow, rate. While the range of different test devices and procedures that have been developed all typically follow the same general guidelines for applying torsional loading to the specimens, there are also significant differences among many of them which can potentially result in variations in the measured soil properties which makes use of the test results by others less viable. These differences range from factors such as (i) specimen type (solid versus hollow), (ii) specimen diameter, (iii) length-to-diameter ratio, (iv) wall thickness for hollow specimens, (v) applied boundary stresses, (vi) method of loading, and (vii) means of measuring specimen response. ASTM Subcommittee D18.09 on Cyclic and Dynamic Properties of Soils is currently in the initial stages of developing a standard test method for the performance of torsional shear testing. This paper provides references and summarizes the findings of an initial review which was conducted as part of this standardization effort. The significance of membrane effects are discussed. Recommendations are made on items to include in the proposed standard.