Ground movements and collapse mechanisms induced by tunneling in clayey soil

Abstract

A series of centrifuge model tests of unlined single and parallel tunnels was carried out in the plane strain condition to investigate the ground movement and the collapse mechanisms induced by tunneling in clayey soil. The measured surface settlement trough due to single tunneling was first fitted by a normal probability curve. Afterwards, a superimposition method with modification factors was suggested for estimating the surface settlement troughs induced by parallel tunneling with various center-to-center distances. The relationships of surface and subsurface settlement troughs versus the ground losses were then proposed as a function of the burial depth of the tunnel. The prediction methodology of settlements based on the ground loss was verified by comparison with 12 sets of monitored field data. The collapse mechanisms of the single and parallel tunnels derived from the upper-bound theory of plasticity were correlated with the observed ground movements in the model tests.