Numerical modelling of tunnelling-induced damage on reinforced concrete buildings

The goal of this study is to gain insight into mechanisms of soil-structure interaction for buildings affected by tunnel excavation and to discuss reliable methods to evaluate the potential damage. Assessing the structural response to excavation-induced deformations involve a combination of both geotechnical and structural aspects, such as soil behaviour, building behavior, soil-structure interaction and modelling techniques. This study focuses on the behavior of reinforced concrete buildings founded on coarse-grained soils. In particular, reference was made to the case study of new Milan (Italy) metro-line 5, excavated in sandy soils by an earth pressure balance (EPB) machine. Observed volume loss was averagely equal to 0.5%, which did not produce any damage on surrounding buildings due to efficient excavation procedure. The goal of this work is to simulate different scenarios of volume losses and structural configurations through numerical FE simulation. Therefore, a maximum volume loss of 3%, index of inappropriate execution of excavation work was considered. Moreover, the influence of structural stiffness is investigated by taking into account different building configurations including the presence of infills and openings due to doors and windows. A 5-storey RC building founded on a strip footing and interacting with tunnel excavation is modelled in detail. The numerical analyses are performed with the commercial software Abaqus. Damage assessment is carried out both by direct analysis of the stress-strain response of the structure in the numerical analyses and by empirical and analytical methods typically used in the engineering design. Recent researches illustrate that infill masonry walls should be taken into consideration as far as they are most sensitive elements to damage when affected by excavation. This thesis illustrates the beneficial effect, in reducing the deflection ratio and damage to building when modeling it with presence of infills.