Influence of compaction procedure on the mechanical behaviour of an unsaturated compacted clay. Part 2. shearing and constitutive modelling

The influence of compaction pressure, compaction water content and type of compaction (static or dynamic) on subsequent soil behaviour was investigate d by conducting controlled-suction triaxial tests on samples of unsaturated compacted speswhite kaolin, Compaction pressure influences initial state, by determining the initial position of the yield surface, thus affecting, a mong other things, the shape of stress-strain curves during shearing, Compa ction pressure also influences, to a limited degree, the positions of the n ormal compression lines fur different values of suction, but it has no effe ct on critical state relationships. The effect of compaction pressure can p robably be modelled solely in terms of initial state if an anisotropic elas toplastic model incorporating rotational hardening is employed, whereas the parameters defining. the slopes and intercepts of the normal compression l ines for different values of suction require adjustment with variation of c ompaction pressure if a conventional isotropic hardening elastoplastic mode l is employed. Compaction water content influences the initial suction, but also has a substantial influence on normal compression lines and a noticea ble effect on the volumetric behaviour at critical states. It is likely tha t soil samples compacted at different water contents will have to be modell ed as different materials, irrespective of whether an isotropic or anisotro pic hardening elastoplastic model is employed. A change from static to dyna mic compaction has no significant effect on subsequent behaviour.