Prediction of the effects induced by the Metro C construction on an old masonry building

The paper reports the main results obtained through a numerical study aimed to predict the effects induced on an old masonry building by the tunnelling operations for the construction of Metro C line, in Rome. To achieve high quality of prediction, full 3D finite elements numerical analyses are carried out. The most important features simulated are: i) the advancement of tunnel front; ii) the pressure for front support; iii) the TBM geometry (weight and conicity of shield); iv) the tail void grouting; v) the building structure. A simple elastic perfectly plastic model with Mohr-Coulomb strength criterion and tension cut off is used for describing both soil and masonry behaviour. Preliminary analyses using different mesh density and tolerated error are carried out to optimize the complete analyses achieving an acceptable compromise between calculation time and accuracy of the results. In the usual range of pressure distributions for front support, the study underlines the light influence on stresses and strains distribution of the values adopted. The analysis of stress and strain distributions in the building structure before and after tunnel construction, numerically obtained, allows us to assess the category of damage in term of potential cracks induced and also in term of reduction of structural safety level.