ABSTRACT
Probabilistic risk methodologies applied to geotechnical problems, in the sense that we now think of them, began to appear in the late 1960s with the work of Lumb (1966), Wu and Kraft (1967), Folayan et al. (1970), and others. Certain aspects of this direction of work can be traced back at least as far as Taylor (1948), who spoke of partial safety factors on the Coulomb strength parameters (c, ϕ) for slope stability, reflecting different levels of uncertainty on the two parameters (p. 414):
It thus appears that there is no such thing as the factor of safety and that when a factor of safety is used its meaning should clearly defined [emphasis in in original]. […] In order to present as general a case as possible it will first be assumed that different margins of safety are desired for the two components of shearing strength, […].
