Effects of apparatus design details on constant height simple shear test results

May 6, 2026

Simple shear testing is one of the few practical laboratory techniques in geotechnical engineering. This is partly because constant height simple shear tests offer a cost-effective way of replicating undrained conditions without the need to saturate specimens through a constant volume approach. Maintaining truly constant specimen height is analogous to obtaining full saturation in undrained tests. This study evaluates how apparatus design details and system compliance influence height control under constant volume conditions. Enhancements including frame reinforcement, prestressing of components, and the implementation of a real-time height adjustment feedback loop were made to increase system rigidity. The apparatus' compliance was measured before and after the modifications. Cyclic tests were conducted on Ottawa F-65 silica sand under constant height condition with varying compliances. The findings indicated a substantial increase in the number of cycles required for liquefaction as compliance increased. Current standards and practices were found to be generally inadequate for handling compliance in simple shear testing.

Soltan, A. Ghafghazi, M., Cross, R., Eden, D. 2026 " Effects of Apparatus Design Details on Constant Height Simple Shear Test Results,” in Proceedings of the21st International Conference on Soil Mechanics and Geotechnical Engineering 2026, 14-19 June 2026, Vienna, Austria: Austrian Geotechnical Society and Austrian Society for Geomechanics