chapter  Chapter 11
21 Pages

Undrained behaviour of clays

ByJ.A.R. Ortigao

This chapter deals with the behaviour of clays in CIU testing. They are used to represent clays in impeded drainage conditions, such as during rapid construction of embankments on clays, at the final stage of a excavation or a foundation on clay, and in the clay core of a dam at the end of construction. Drainage valves are closed and the undrained shear phase starts. If the soil is saturated there is no volume change. Pore pressures are measured throughout this phase. Saturated soils are considered, but some aspects relative to unsaturated clays will be pointed out. The behaviour of NC clays can be understood from typical data on the Rio de Janeiro clay. The chapter also advises that the theoretical framework of critical state is a simple and useful way of interpreting the behaviour of clays. It incorporates the main features of clay behaviour in a simple model.