Effects of sampling on the undrained behaviour of clayey sands

The effects of tube sampling of normally consolidated clayey sands are examined, Triaxial strain path tests, which follow the sequence of strains imposed by a sampling tube on elements on its centre line, are described, Major reductions in effective stress are shown to occur as a result of sampling, Reconsolidation to in situ stresses causes significant reductions in granular void ratio and these, together with fabric changes, modify the behaviour of the sample from that of the in situ soil: undrained brittleness and the effects of ageing in situ may be eliminated, A framework for the behaviour of clayey sands, which relies on the existence of a bounding surface and phase transformation and critical state lines, is used to explain the response to sampling and reconsolidation. Both drainage during tube sampling and sustainable suctions in clayey sand are considered.