March 15, 2022

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Thierno Kane Coauthored a Paper on Fully Softened Shear Strength in the Canadian Geotechnical Journal

Thierno Kane, Ph.D., (Illinois) coauthored a paper entitled "Meaning, Measurement, and Field Application of Fully Softened Shear Strength of Stiff Clays and Clay Shales" published in the Canadian Geotechnical Journal on September 20, 2021.

Gholamreza Mesri of the University of Illinois at Urbana-Champaign was the lead author, and Cai Wang of Mott MacDonald was an additional coauthor.

Theirno Kane is an Engineer based in Illinois who focuses on landslide movement and slope stability, geotechnical laboratory testing and analyses, and shear strength and consolidation. He also has experience in civil and geotechnical engineering consulting and design, including the design of foundations and earth retention systems, liquefaction analyses, and seepage analyses.

The Canadian Geotechnical Journal features work related to new developments in geotechnical and geoenvironmental engineering and applied sciences. The topics of papers include soil and rock mechanics, material properties and fundamental behavior, site characterization, foundations, excavations, tunnels, dams and embankments, slopes, landslides, geological and rock engineering, ground improvement, hydrogeology and contaminant hydrogeology, geochemistry, waste management, geosynthetics, offshore engineering, ice, frozen ground and northern engineering, risk and reliability applications, and physical and numerical modelling.

Canadian Science Publishing, publisher of the Journal, is Canada's independent, not-for-profit source for science-based knowledge. As Canada's largest publisher of scientific journals, their goal is to strengthen the integrity, relevance, reach, and impact of vital knowledge and research, across the nation and the world.


Fully softened shear strength mobilized in first-time slope failures, introduced by Skempton in 1970, corresponds to a random edge-face arrangement and interaction of clay particles in an entirely destructured fabric of stiff clays and clay shales. A series of triaxial compression tests were conducted on reconstituted normally consolidated specimens of 15 stiff clay and clay shale compositions. Based on the laboratory results an empirical correlation for secant fully softened friction angle, ϕ'fssσ'n, was developed for clay compositions with plasticity index in the range of 10 to 250%, in effective normal stress range of 10 to 700 kPa. The laboratory measurements confirm an empirical equation for fully softened shear strength in terms of parameters ϕ'fss100 and mfs. The field application of secant fully softened friction angle was examined by stability analyses of 63 first-time slope failures in 38 geologic materials. These include 45 slope failures with a segment of observed slip surface at the residual condition and the back-scarp mobilizing fully softened shear strength, and 18 slope failures with entire observed slip surface at fully softened condition. The back-calculated fully softened secant friction angles for first-time slope failures are in good agreement with ϕ'fssσ'n correlation based on laboratory tests.

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