Numerical analysis of the foundation soil behaviour for the Garisenda Tower in Bologna

The fascination of a leaning towers actually descends from to the interaction with the foundation soil, not so clearly deduced at first glimpse. Furthermore, initial defects and non-uniform foundations in a structure and a soil with a low stiffness, can led to long-term critical conditions. The maintenance of existing constructions is one of the fields of activity of Civil Engineering, in particular, Geotechnical Engineering plays a significant role in a number of relevant cases. The conservation of Heritage is one of the most challenging problems facing modern civilization. It involves a number of factors belonging to different fields (cultural, humanistic, technical and economical), joint by inextricable patterns. A convenient way to forecast this long term behavior, is to define a reliable response for the soil-foundation system. Strain-hardening plasticity models, developed in relation to the overall soil-footing system can provide such a relationship, but, in any case, it is rather difficult to validate these models. In this respect, a rather significant contribution comes from an experimental identification analysis, performed before the realization of the numerical model on Plaxis. The behaviour can be modelled in order to predict how large the deformations will be. This thesis investigates the effectiveness of such models, referring to the current state of the tower. The project being examined is located in central Bologna. The analysis focuses on the displacements, stresses and plasticity below the site. An analysis was carried out to investigate the significance of different parameters, of different material models and methods of analysis. Ground investigations, laboratory tests and published data were the main sources used to collect reliable initial input parameters for the material models. A model was created in Plaxis 2D using the Mohr-Coulomb and the Hardening Soil with Small-Strain Stiffness material models.