ABSTRACT
This chapter describes the framework for strength and stability design, both in terms of the traditional approach that uses an overall factor of safety, and then via the limit state design approach which is now becoming more dominant. There is an increasing trend for limit state design principles to be adopted in foundation design. Values of the structural and geotechnical reduction factors are often specified in national codes or standards. The ultimate bearing capacity of foundations on non-homogeneous soils has been examined for the important case that arises often in practice where the undrained shear strength of the soil varies approximately linearly with depth below the soil surface. The axial capacity of piles, and in particular, the shaft friction capacity, is influenced by a number of factors in addition to the properties of the supporting ground and the interface conditions. It has long been recognised that piles located within a settling soil profile will be subjected to negative skin friction.
