ABSTRACT
In the light of recent developments in our understanding of their stress-strain behaviour, this paper reviews requirements for determining the mass stiffness of soils and weak rocks, both from laboratory and field measurements. The effects of bonding, fissuring and jointing, non-homogeneity, anisotropy, nonlinear stress-strain behaviour and creep are noted. Examples are given of their importance when planning an investigation to determine stiffness. Techniques that have recently been used for high-quality stiffness determination during UK site investigations are described. Examples of specialist equipment and the data produced are given, with particular emphasis on the need to test a sufficiently large volume of soil, at relevant stress or strain levels, whilst eliminating the effects of bedding.
