A Novel Torsional Kolsky Bar Apparatus for Investigating Dynamic Frictional Resistance of Granular Materials Under Seismically Relevant Conditions

Abstract

In the present study, a modified torsional Kolsky bar apparatus is utilized to investigate the dynamic frictional behavior of confined granular geo-materials under seismically relevant normal stresses, slip velocities and accelerations. The frictional resistance of the granular specimens is evaluated under both dry and wet conditions. Using the apparatus, slip speeds ranging between 2 and 6 m/s are achieved at normal stresses ranging between 50 and 125 MPa. The maximum slip displacement obtained during the frictional slip is about 5 mm. The usefulness of the experimental configuration is validated by presenting results for Talc under both wet and dry conditions, and 50/50 Montmorillonite/Ottawa sand under wet conditions. For the experiments on Talc, the dry specimens are found to have a coefficient of kinetic friction in the range of 0.2–0.4, with the wet specimens exhibiting lower values of 0.1–0.2. The wet 50/50 Montmorillonite/Ottawa sand specimens exhibit a low average friction coefficient value of about 0.1 for all the test conditions.