Stability of embankment on clay : Hamel, JV Discussion of paper by Wu et al, Sept. 1975 1T, 2R J. Geotech. Engng Div. ASCE, V102, GT5, 1976, P574–576

Abstract

Comments are made on the possible role of residual strength in effective stress analyses of the embankment failure. It is noted that the minimum effective shear strength likely to occur laong structural discontinuities or progressively developed failure surfaces in clay is the residual strength. The residual friction angle (14 deg.) determined by the authors for slickensides in the foundation is used to estimate safety factors for the three cross sections. Details of the estimation procedure are described, and the estimated safety factors are tabulated. Previous work is quoted that pointed out that stability of embankments on slightly overconsolidated highly plastic clay foundations is generally overestimated by both total and effective stress analyses using shear strengths from conventional laboratory tests. It was proposed that a shear strength reduction factor be used to account for progressive failure of foundation behavior which reduce field mobilized shear strengths. Later studies have shown that rsidual or near-residual shear strengths are mobilized as described.