Ring Shear Test : Development And Fundamentals

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Ring Shear Test: Development and Fundamentals
K.D. Heiter, EIT
HDR Inc., 4470 Cox Rd, Suite 200, Glen Allen, VA 23223; PH (712) 210-6263; email: kdheiter@ncsu.edu


Drained Residual Strengths Drained residual strength develops during the reactivation of a preexisting shear surface (F). Pre-existing shear surfaces may be present in old landslides, sheared bedding planes, sheared joints or faults, or embankment failures (A). Common materials that develop residual strengths include mudstone, claystone, shale, silt, and clay. The drop in drained shear strength to residual shear strength can be attributed to flocculated clay particles being oriented parallel to the direction of shear, decreasing the tendency for volume change and development of excessive pore-water pressures (F). This change in orientation tend to require 1 to 2 meters of field displacement to fully develop (A).
Methods of Measurement Several devices have been developed to measure the drained residual shear strength. Examples of these devices include, laboratory vane, cone penetrometer, plane strain and independent stress control ‘triaxial’ cells, direct shear box and the ring shear device. The direct shear box and the ring shear device are the two most commonly used because they give more accurate results (E). The direct shear method however has several limitations in comparison with the torsional ring shear test, making it less preferred than the torsional ring shear (H). The primary
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