Experimental and finite element analysis on mechanical performance of prefabricated assembly inverted arch to lining joints of large section highway tunnel under direct shear loding

To investigate the mechanical properties of the prefabricated inverted arch to cast-in-place lining joints, 21 "Z"shaped shear specimens for direct shear testing were designed and manufactured, with the interface planted steel bars ratio, interface size, and interface treatment method as variable parameters. The whole failure process of the joint under a direct shear stress state was observed and recorded during the test, the shear-slip curve of the specimen was obtained, failure mechanism and variation law of the joint's direct shear mechanical characteristics were carefully examined. The results reveal that the specimen's shear performance improves following the interface chiselling treatment. The specimens fail in three ways: simple concrete failure, simple planted steel bars failure, and assimilative failure of the concrete and the planted steel bars. The ultimate shear capacity, ductile failure capacity, resistance to damage evolution, and energy dissipation capacity of the specimens rise as the planted steel bars ratio increases. When the planted steel bars ratio increases from 0.7% to 1.1%, the improvement is the most significant, reaching 66.3%. When the planted steel bars ratio is the same, the shear bearing capacity improves as the interface size grows. The finite element model of the "Z"-shaped shear specimen of the prefabricated inverted arch and the cast-in-place lining joint is established, and the parameter extension analysis is performed. Based on the test results and the Extended Shear-Friction Theory, a high-accuracy calculation model of shear capacity of precast inverted arch and lining joint is presented.