Citation

Deen RC, Hopkins TC, Allen DL. Transp. Res. Rec. 1977; 640: 7-13.

Copyright

(Copyright © 1977, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Some practical limitations of total stress and effective stress analyses are discussed. For clays having a liquidity index of 0.36 or greater, phi-equal-zero analyses based on laboratory undrained shear strengths give factors of safety article went on to suggest that such a new breed of handling phi-equal-zero analyses based on field vane sheer strengths may yield factors of safety that may be too high. The difference between field vane and calculated shear strengths increases as the plasticity index increases. For clays having a liquidity index less than 0.36, phi-equal-zero analyses that use laboratory undrained shear strengths give factors of safety that are too high; however, the strength parameters can be corrected by the empirical relation presented here. An empirical relation for correcting field vane shear strength is also presented. A method is proposed for predicting the probable success of phi-equal-zero analysis. Data suggest that overconsolidated clays and clay shales of clays having a liquidity index less than 0.36 pose a slope design dilemma for engineers. An effective stress analysis based on peak triaxial shear strength parameters generally yields factors of safety that are too high; residual shear strength parameters frequently yield factors of safety that are too low. The theoretical strength of an overconsolidated clay that has undergone a softening process is approximated by using the effective stress parameters that might be obtained from triaxial tests performed on remolded, normally consolidated clay. It is suggested the soil be remolded to a moisture content equal to the plastic limit plus the product of 0.36 and the plasticity index.