Cyclic and monotonic undrained response of saturated sands

A unified picture of the undrained monotonic and cyclic loading response of saturated sands is presented. A wide range of initial states of sand are covered in order to consider a full spectrum of monotonic loading behaviour from contractive to dilative and its close link with the development of liquefaction or limited liquefaction and cyclic mobility under cyclic loading. A three-dimensional effective stress state diagram for the sand in void ratio, effective normal stress and shear stresses space is proposed. The diagram features a boundary surface separating initial states of sand which are contractive from those that are dilative. Critical stress conditions which mark the onset and arrest of contractive deformation during both monotonic and cyclic loading are identified. The state diagram is shown to provide a link between monotonic and cyclic loading response.