Experimental study on Inter-ring joint shearing characteristics of gas transmission shield tunnel with bent bolt and tenon

Abstract

When a gas transmission shield tunnel passes through an underwater stratum under high water pressure for a long distance, structural damage due to segment joint dislocation notably affects the tunnel safety during service. Thus, the shearing characteristics of inter-ring joints constitute a critical research topic for the structural mechanical response of a segment. Considering the structure of an inter-ring joint, this study uses positive and negative shearing tests to investigate joint dislocation, shear stiffness, and the mechanism of the shear failure of segment joints. The main findings are as followings. The stress states of a bent bolt and tenon are critical factors affecting the shear performance of the inter-ring joint. Vulnerable areas appear at different positions according to the shear stress mode of the bolt and tenon. The failure process can be classified into the following three stages owing to the stress state. 1) Friction at the contact surface of the joints counteracts the shearing force, 2) the groove and convex tenons contact each other and the bolt begins to bear the force, and 3) visible cracks and collapse appear in the segment structure. Finally, the damage evolution of concrete occurs earlier than that of the bolt. Moreover, until the concrete fails, the bent bolt is close to yielding but is still not damaged. These findings can improve the design and theoretical analysis of oil and gas transmission shield tunnels.