DISTURBANCE OF THE BOTHKENNAR CLAY PRIOR TO LABORATORY TESTING

Interpretation of laboratory tests in the characterization study of the Bothkennar clay required an assessment to be made of the effects of disturbance prior to testing. Disturbance is shown to have occurred as a result of tube sampling, sample transport and specimen preparation. The effects of disturbance in the clay are to reduce the mean effective stress in the sample and shrink the initial bounding surface. The consequences of these changes are illustrated for the case of unconsolidated undrained triaxial tests, undrained triaxial compression and extension tests after reconsolidation to in situ stress, and oedometer tests. Reduction in peak strength, stiffness, yield stress and post-yield compressibility are shown to be a consequence of disturbance. The evaluation of sample quality on the basis of strains during reconsolidation is examined.