Triaxial Shear Testing of Polished Slickensided Surfaces

Christopher L. Meehan¹; Binod Tiwari²; Thomas L. Brandon³; J. Michael Duncan⁴

¹Assistant Professor, University of Delaware, Dept. of Civil and Environmental Engineering, 301 DuPont Hall, Newark, DE 19716, U.S.A.
E-mail: cmeehan@udel.edu (corresponding author)
²California State University, Fullerton, Dept. of Civil and Environmental Engineering, 800 N. State College Blvd. E-419, Fullerton, CA 92834, U.S.A.
E-mail: btiwari@fullerton.edu
³Associate Professor, Virginia Tech, Dept. of Civil and Environmental Engineering, 200 Patton Hall, Blacksburg, VA 24061, U.S.A.
E-mail: tbrandon@vt.edu
⁴Univ. Distinguished Professor, Virginia Tech, Dept. of Civil and Environmental Engineering, 200 Patton Hall, Blacksburg, VA 24061, U.S.A.
E-mail: jmd@vt.edu

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Landslides, 2011, Volume 8, Number 4, pp. 449-458

Abstract
A series of consolidated-drained triaxial tests were performed on precut and polished clay specimens to measure their drained residual strength. Two soils were tested during this research program: Rancho Solano Clay and San Francisco Bay Mud. Specimens were tested using a specially modified triaxial compression device which was developed to minimize the effects of end-platen restraint on the measured strengths. Special attention was paid to the influence of changing specimen area and membrane effects during the test. Triaxial test results were compared with baseline measurements of drained residual shear strength that were made for each of the clay soils using Bromhead ring shear tests and polished-specimen direct shear tests. Residual strength values measured in the triaxial device were higher than the drained residual strengths measured in the Bromhead ring shear apparatus and the direct shear device, indicating that this test approach is more challenging than the use of direct shear tests conducted on polished slickensided surfaces. Comparison of single stage and multistage triaxial test data indicates that multistage triaxial testing may work well for specimens that fail along a well-defined plane, provided that careful attention is given to the effects of end platen restraint, membrane restraint, and changes in specimen area during shear.

Keywords
Triaxial tests; Clays; Overconsolidated soils; Residual strength; Shear strength; Laboratory tests; Compression tests

Reference
Meehan, C. L., Tiwari, B., Brandon, T. L., and Duncan, J. M. (2011). “Triaxial Shear Testing of Polished Slickensided Surfaces.” Landslides, Journal of the International Consortium on Landslides, Springer, 8(4), 449-458. (doi:10.1007/s10346-011-0263-y)

DOI
10.1007/s10346-011-0263-y