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Abstract Ground fissure is a special urban geological hazard in Xi¢an；and metro tunnels should be divided by special deformation joints and connected with flexible joints to adapt the large deformation of active ground fissures. Based on the Xi¢an metro tunnel orthogonally passing through active ground fissures，by means of large-scale model tests with a geometric proportion of 1∶5，the adaptability of sectional metro tunnel with flexible joints to active ground fissures is studied. The test results show that the flexible joints prevent tunnel from stress concentration and protect tunnel structures under the influence of active ground fissures；and the sectional tunnel with flexible joints can adapt the large deformation of active ground fissures. To some extent，the special deformation joint with the same dip angle as active ground fissure has certain effect on pressure and displacement of surrounding rock，but affects the safety of tunnel lining structure less. Meanwhile，the oblique special deformation joint can absorb over 20% of the total displacement of active ground fissure. In active ground fissure zones，tunnel can be divided into a few sections and connected in series to eliminate the influence of large deformation of active ground fissure on tunnel lining to the maximum. The watertight belts are undamaged at the top and bottom of lining and mangled on the bilateral wall affected by the vertical displacement of ground fissure，so the bilateral wall of flexible joint should be intensified in waterproof design. The conclusions provide an important reference for structure and waterproof designs of metro tunnel under the influence of active ground fissures.
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Received: 06 January 2010
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