SEDL / STP / STP599-EB / STP39075S

Effects of Specimen Type on the Residual Strength of Clays and Clay Shales

Townsend, FC
Research civil engineers, U.S. Army Engineer Waterways Experiment Station, Vicksburg, Miss.

Gilbert, PA
Research civil engineers, U.S. Army Engineer Waterways Experiment Station, Vicksburg, Miss.

Pages: 23    Published: Jan 1976

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Abstract

This investigation was an examination of the effects of testing apparatus, specimen type and density, normal stress, and sequence of loading on the residual strength of various clays and clay shales. Annular shear and repeated direct shear tests were conducted on intact shale specimens with precut failure planes, while comparison rotational shear tests were conducted on the same shale material subjected to various degrees of remolding. Test results indicate that comparable residual strengths can be obtained, regardless of equipment type and procedure or degree of remolding. Supplemental annular shear tests on residual clay and silty sand show that precutting of the failure plane or the specimen density has no effect on the ϕ^r' value. The residual friction angle is independent of stress history and normal load [when greater than 2 kg/cm² (1.96 × 10⁵ Pa)].