Volume 32, Issue 3 (May 2009)
A New Ring Shear Device to Measure the Large Displacement Shearing Behavior of Sands
Among devices commonly used to measure the shearing behavior of sands, only the ring shear device can shear a soil to virtually unlimited displacements without creating substantial nonuniformities in stress and strain distributions. However, some limitations have precluded its widespread use. A new ring shear device was constructed at the University of Illinois that has large specimen dimensions to reduce stress and strain nonuniformities, has auxiliary load and torque cells to measure any wall friction that develops along the confining rings, and utilizes quad-rings along the confining rings to prevent soil extrusion. Sample ring shear tests on a dry fine-grained, silty sand specimen demonstrate that the new ring shear device operates properly in both constant volume and drained conditions, providing identical effective stress friction angles at large displacements when shear and effective normal stresses on the shear plane are considered. Parallel drained and undrained triaxial compression tests on saturated specimens illustrate that the new ring shear device provides reasonable values of effective stress friction angle and show that the triaxial test does not shear specimens to sufficient displacement to reach critical state shear strengths for this sand, which was reached at displacements ranging from about 1 to 10 m.