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NON-LINEAR ANALYSIS OF TUNNEL LININGS UNDER LONGITUDINAL BENDING

Tunnel linings are generally analysed transversally as a plane strain problem. Very little attention is given to the flexural behaviour which may occur in the longitudinal direction as a result of settlements along the tunnel. Longitudinal bending is ignored, on the assumption that the settlement will be small and that the linings possess suficient flexibility to cope with the settlements without producing high stresses. This Paper presents an analytical study of the flexure-induced deformations and stresses in tunnel linings subject to settlement. Two tunnels with relevant vertical survey records have been analysed. The results of the analysis revealed that the deformation capacity of the linings under longitudinal bending was provided almost entirely by the lining joints. The joints experienced separation at high flexural stress regions as the stresses in longitudinal bolts in the joints exceeded their pre-tensioning value. Local bending of the transverse flanges appeared to be contributing most to the joint separation