A series of geotechnical centrifuge tests to investigate the long-term heave behaviour of basements in over-consolidated clay was performed, where the profiles of slab displacement and underslab pressure were measured simultaneously. The same prototypes were simulated using Plaxis 2D with the clay stratum represented by the small-strain hardening soil model. The results were compared and a good agreement was found in terms of the profiles of slab-soil contact pressures. The data showed that existing semi-analytical methods of long-term heave predictions can be improved by assuming a quadratic distribution of slab-soil contact pressure, and example calculations for the relaxation ratio method and the relative stiffness method are presented.
Deep excavations in over-consolidated clays lead to swelling of the clay, which can exert large swell pressures on the basement slabs. In this paper, four prototype scenarios of basement construction in over-consolidated clay were investigated using both centrifuge modelling and finite element modelling. The main aim was to discern the effects of two aspects of embedment on long-term heave behaviour when relatively flexible and relatively stiff slabs were employed. The extension of diaphragm side walls below the formation level and the presence of a drainage layer between the slab and the clay were investigated. The results confirm that the use of a drainage layer would shorten the time of consolidation as expected. The variations in embedment conditions would also cause some redistribution of heave displacements, though the magnitude of such redistribution is relatively small, both when compared to the overall magnitudes of heave displacement and when compared to the effect of varying base slab stiffness on heave displacement.
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