ABSTRACT
Experimental results on soil behaviour In this chapter are summarized the main experimental results that characterize the behaviour of granular materials such as sand.
The triaxial test has been introduced into rock mechanics in 1911 by VON KARMAN and into soil mechanics in 1928 by EHRENBERG. A cylindrical soil specimen is loaded by the stress component ai in axial direction and by a-2 = a3 in lateral directions. The corresponding strain components are El and 52 = 63 in axial and radial directions, respectively. We have thus axisymmetric conditions. The lateral stress is exerted by fluid (water or air) pressure acting upon the specimen. A typical load program is to increase a while keeping 0-2 = a3 constant. Another possibility is to increase a l keeping the sum a + a2 + a3 constant. In principle, stress paths of arbitrary directions in a a1-a2 -space can be accomplished, as long as they remain within the so-called limit surface (see Fig. 2.1). The aforementioned loading processes usually start from hydrostatic stress states. The radial strain 62(= 63), or equivalently the volumetric strain E„ = E2 63 is registered by measuring the volume of porewater that is expelled from a water-saturated sample during the deformation.
