Constant Volume Cyclic Direct Simple Shear Test Validation on a Clean Sand Using Published Quality Control Measures

The cyclic direct simple shear (CDSS) test is increasingly being used to evaluate the cyclic resistance of clean sands. However, there are differences related to equipment manufacturers, sample preparation techniques, testing procedures, failure criteria, and quality control (QC) measures, all of which lead to uncertainties in CDSS results even for the same sand. In particular, system stiffness of the equipment has been shown to greatly affect test results. As a result, accurate evaluation of the cyclic behavior in clean sands using CDSS tests requires rigorous QC measures. In this study, several active control constant volume CDSS tests were conducted on samples of Monterey and Ottawa sand with different stress histories and relative densities. Various quality assurance/QC (QA/QC) measures published in the literature were applied and evaluated. The results of tests that passed the QA/QC checks compared well with recently published “high-quality” results despite differences in equipment and some testing procedures. Preconditioning (i.e., many cycles of low shear stress during the consolidation stage) was also evaluated. There appeared to be no significant effect of preconditioning on the cyclic resistance of dense Monterey sand, but it increased the cyclic resistance of medium-dense Ottawa sand. Unexpectedly, the cyclic resistance results for Monterey sand reveal a stress-dependent trend (i.e., Kσ) that does not follow the commonly accepted pattern in the literature, and more work is needed to better understand the role of confining stress on cyclic strength in simple shear. Improved communication and transparency regarding QA/QC procedures in CDSS testing is recommended to ensure comparability of results across different studies and ensure that CDSS test results are reproducible.