Experimental study on reinforcement effects of bonded steel plates of highway tunnels under different damage degrees

The cracking damage of linings is a common damage form of tunnels, which directly affects the bearing capacity of the structure. The reinforcement of bonded steel plates is widely used as the structural reinforcement, but there are few researches on the bearing capacity of the highway tunnels after reinforcement and the reinforcement effects under different damage degrees. The 1∶10 model loading tests are used to study the bearing capacity, mechanical deformation characteristics and failure process of the reinforced highway tunnel structure under different damage degrees, and the reinforcement effects and time are analyzed. The results show that: (1) The deformation process of the original and reinforced structures under loose loads can be divided into four stages, but the failure characteristics and forms are different. (2) When the residual bearing capacity is 50%F and 30%F (F is the ultimate bearing capacity of the original structure), the failure loads are strengthened and increase by 50% and 51% compared with those of the original structure. The steel plates applied before the failure of the structure can effectively improve its ultimate bearing capacity and are less affected by the loads at the reinforcement point. When the residual bearing capacity is 50%F and 30%F, the final deformations increase by 59% and 56% compared with those of the original structure, which can reduce the risk of brittle failure. (3) The failure mode of the reinforced structure is large eccentric compression failure of the vault. (4) When the reinforcement is too late, the steel plates will be difficult to effectively bond or cooperatively deform for a long time due to the surface cracks and deformation speed of the linings, resulting in accelerated failure. It is suggested that the residual bearing capacity of the structure should be between 62%F and 50%F as the reasonable reinforcement time for the highway tunnels.