Experimental study on the deformation law of a cracked lining reinforced by a superimposed cover arch

A model plain concrete lining structure with longitudinal cracks in the vault (with a crack depth of one-third of the original lining thickness) was made of gypsum at a similarity ratio of 1:10 and a superimposed concrete cover arch was adopted for reinforcement. After curing, loose earth pressure was applied in a graded manner on the crown by means of indoor peripheral radial loading appliances to study the bearing capability and failure law of the cracked lining reinforced by a superimposed cover arch by considering the effects of stratum resistance. Testing results show that the deforming process of the cracked lining under loading undergoes three stages after reinforcement of the superimposed cover arch: initial loading - cracking of the cover arch vault; cracking at the cover arch vault - cracking at the superimposed interface; and cracking at the superimposed interface of the vault - specimen failure. The sequence of key position failure is: cracking on the vault, ductile failure of the vault, and brittle fracture of the haunch; the failure mode is generally ductile in nature. ©, 2014, Editorial Office of Modern Tunnelling Technology". All right reserved."