a) Strain curve of vault in case 2. b) Strain curve of invert in case 2.

c) Strain curve of vault in case 3. d) Strain curve of invert in case 3.

Figure.3 Time-histories of strain at different points of right-tunnel( a=0.4g) The structural strain values recorded from various measuring points do not tend to be zero after the vibration is over, which phenomenon is mainly due to the rock and soil producing permanent deformation around the tunnel structure under the condition of the dynamic loading, so that the additional seismic strains occur on tunnel structure

5.2 Patterns of damage of model test comparative analysis

There are various cracks on the surface of the similitude material in both cases, but those cracks of tunnel model appear firstly on both spandrels and then develop diagonally. In Figure. 4a, the cracks arise "X"-shape distribution on the surface of the model soil and the model soil cracks of right tunnel are more than left tunnel at the surface of tunnel. There is a 45 °angle between the direction of cracks and the tunnel longitudinal direction, the numbers of

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