Drained Shear Displacement Rates in Fully Softened Strength Torsional Ring Shear Testing

Abstract

Abstract To measure the fully softened strength, the normally consolidated and reconstituted specimen must be drained, i.e., no development of shear-induced pore-water pressures, during shearing. This article investigates (1) typical shear displacement rates in torsional ring shear tests that yield drained shearing conditions for a range of fine-grained soils and (2) the problems that can develop if the porous discs in a torsional ring shear device are not clean and saturated prior to placement of the reconstituted soil paste in the specimen container. The data presented herein show that using a clogged or unsaturated porous disc will require a drained shear displacement rate that is one to two orders of magnitude slower than required, e.g., 0.018 mm/min, if the porous discs are clean, maintained, and saturated as recommended by the original equipment manufacturer and the ASTM D7608, Standard Test Method for Torsional Ring Shear Test to Measure Drained Fully Softened Shear Strength and Stress Dependent Strength Envelope of Fine-Grained Soils.