This paper comprises a continuation of the second section of a detailed and riegorous geomechenical analysis of the stability of overpressured, gently‐sloping sediment layers presented in the Journal of Petroleum Geology 2, 3, 1980 and 3,2, 1980. The authors continue to describe the delta model which they use to explain and permit quantitative reproduction of the main features associated with growth faulting; part II(a) considered stress equilibrium, related stress equations, types of overpressure, the representation of the stress state in Mohr space and the plastic/elastic stated of frictional materials in long, fluid‐filled layers. The present article continues with the analysis, with a numerical and analytical examination of slip lines and considerations of plastic, flow and slip.Peak‐strenght phenomena and the effect of purely‐cohesive materials on the theory conclcude the paper in our next issue, together with a discussion of the behaviour of watersaturated soils(as opposed to theoretical solid material with elastic and plastic properties), and the six major conclusions which can be drawn from t