G. Mesri et Mem. Abdelghaffar, COHESION INTERCEPT IN EFFECTIVE STRESS-STABILITY ANALYSIS, Journal of geotechnical engineering, 119(8), 1993, pp. 1229-1247
The cohesion intercept in the Coulomb shear-strength equation has a si
gnificant influence on the location of the slip surface and the factor
of safety. The cohesion intercept results from a linear approximation
of a segment of a nonlinear shear strength against effective normal s
tress relationship. Shear strength on a slip surface, at the instant o
f a global instability, may range from residual strength to peak stren
gth for stiff clays, and from large strain strength to peak strength f
or soft clays. Peak strength controls local development of slip surfac
e. but it may not be available during global failure. The critical sli
p surface for an initial slide is determined using the peak shear stre
ngth. However, a mobilized strength equal to or less than the peak str
ength is used to define the factor of safety. Effective stress-stabili
ty analysis of slope failures has resulted in a reduction factor to th
e peak strength in order to obtain the mobilized strength for first ti
me slides. For over 60 slope failures in soft and stiff clays. the val
ues of c' (mob) are in the range of 0-26 kPa as compared to 1-150 kPa
for c' of the clays involved in the failures.