ABSTRACT
Geotechnical engineers design foundations, retaining structures and slopes with two goals in mind: the structures must function properly in service (this imposes a serviceability requirement on the design) and the structures must be safe (this imposes a safety requirement on the design). States of the structure separating serviceability from loss of functionality are called serviceability limit states. States of the structure separating safe from unsafe states are known as ultimate limit states. Serviceability limit states are often tied to settlements or displacements. Ultimate limit states are often tied to collapse.
