This paper is to contribute to the understanding of the behaviour of tunnels in swelling ground. An Italian case study of a tur collapsed due to swelling of a stiff clay, is taken as an example, The stress paths during excavation of elements of ground around opening are computed in order to evidence the significant difference to that reprodured by usual swelling tests in the laboratory. An invative triaxial testing procedure is developed and the stiff-clay tested. A numerical simulation of the swelling phenomenon induced by excavation of the tunnel, based on the experimental results obtained, is then compared to site observations.
Swelling, Tunnelling, Laboratory testing, Numerical simulation
