Abstract:  The secondary lining structures designed by existing loadstructure methods often exist with large covering thickness, low economic efficiency, and poor construction operability problems. Therefore, based on the global and local stability characteristics of a giant cavern with a span of greater than 50 m, the mechanism of a giantspan cavern secondary lining structure undertaking residual deformation and an unstable block load is proposed, and the calculation process of secondary lining structure design is demonstrated. The results indicate the following: (1) The mechanical model of the giantspan cavern secondary lining structure bearing residual deformation and unstable block load conforms to the global and local stability mechanism of the giantspan cavern. (2) The residual deformation of the cavern is the difference between the ultimate and existing settlements; the results obtained using the proposed method are highly consistent with the contact pressure of the secondary lining and shotcrete. (3) The proposed unstable block load is designed for the weak part of the cavern with high safety. (4) The secondary lining structure thicknesses of the arch and sidewall obtained using the designed method are 0.8 and 1.4 m, respectively, which are 27%~53% lower than those of the conventional design method.

Key words:  , giantspan cavern, secondary lining structure design, residual deformation, block, unstable block load