Long-term mechanical behavior of wooden pile foundation in Venice

Many historical buildings of the historic city of Venice are founded on short and closely spaced wooden piles used to improve the shallowest layers of very soft silty clay. Some recent evidences have shown that anaerobic bacteria may, in some cases, seriously deteriorate these piles even in anoxic conditions, significantly reducing wood stiffness and strength therefore providing a possible explanation of some observed building settlements. To investigate the effect of such degradation on the overall foundation mechanical response, a series of finite element analyses has been carried out, coupling the wood decay with creeping response of surrounding clayey soil. The model is applied to simulate, along with centuries, the response of the foundations of the ancient Church of Santa Maria Maggiore, that showed important displacements of the external masonry walls.