Subsidence Induced by the Brescia Metrobus Tunnel Excavation (Italy)

The paper describes the settlements induced by the tunnel construction of the first Metrobus line in Brescia (Italy) and settlement predictions of the historic city hall, the Palazzo della Loggia. The diameter of the shield is 9.15 m, the tunnel is 5.6 km long and excavation was carried out mainly in alluvial gravelly soils. The Palazzo della Loggia (15th-16th centuries) is the venue of the city municipality. Due to the progressive deterioration of the building foundations the soil beneath the piers was improved by low-pressure grouting prior to underground excavation. The forthcoming tunnel construction - located 25m from the building and 20m below ground level required assessment of the building settlements induced by the excavation. A number of numerical simulations were carried out on a calibration-purpose model and preliminary results were compared with measured settlements obtained from tunnel sections previously constructed. Predicted settlements and settlement distribution at the Loggia section were found in good agreement with movements measured during construction.