Abstract: The composite lining is the most frequently used form of lining in new tunnels and existing tunnels. The situation, which is the deterioration or even failure of primary support, will appear inevitably in the long-term operation; and it will reduce the bearing capacity and the durability of the tunnel system. Based on indoor model test, the members of primary support are made by deteriorated gypsum model. The deterioration process is simulated and the state change of secondary lining structure is recorded. The variation of bearing capacity of tunnel is determined by increasing load. The results show that the deterioration of steel frame and shotcrete layer has larger impact on secondary lining structure than the bolt deterioration. Failure of the primary support does not result in destruction of the lining structure; and the secondary lining has adequate safety redundancy. The deterioration of primary support members will reduce the bearing capacity of the tunnel structure system. The effect of anchors is obvious, but the effects of steel frame and shotcrete layer are little.

Key words: composite lining, primary support, model test, deterioration, failure, bearing capacity