SOIL DEFORMATIONS DUE TO THE EXCAVATION OF TWO PARALLEL CAVERNS

The new station of Baixa-Chiado in the Lisbon Metro is formed by two parallel 18 m (60 ft) diameter caverns, at 25 m (83 ft) between axes, and a depth of 30 m (98 ft) in stiff Tertiary sands and clays under a densely built area. N.A.T.M was used, with E.P.B. shield for the running tunnels. The measured surface settlements are compared with theoretical and empirical predictions.