Experimental and numerical investigation on the shear behavior and damage mechanism of segmental joint under compression-shear load

The segment dislocation at circumferential joints severely impacts on the structural safety of shield tunnels during construction and operation. Especially for the underwater tunnel with a super-large cross-section, the circumferential joint usually consists of oblique bolts and distributed mortises and tenons to control the dislocation. Given this, a series of full-scale loading tests of the circumferential joint is carried out based on Jinan Yellow River Tunnel, and a three-dimensional refined numerical model with concrete damage plastic (CDP) constitutive is also established to reveal the condition of stress and damage. The deformation process of joints, the stress of bolts, and the damage characteristics of mortises and tenons are investigated through the full-scale tests and numerical simulation. Moreover, the mechanical behavior and damage evolution of circumferential joint has been revealed under compression-shear loads. Besides, the influence of mortises and tenons, bolts on the shear resistance of joints is unraveled. The results show that the deformation process of the circumferential joint can be divided into three stages under the ordinal shearing loading scenario (OSLS) and reverse shearing loading scenario (RSLS). The bolt plays an important bearing role under OSLS and the bolt is in an unstressed state under RSLS, which makes the shear stiffness and shear capacity of the joint under OSLS larger than that under RSLS. The tenon and bolt hole damage presents local concrete crushing, while the damage of mortise occurred with concrete spalling. Compared with bolts, the mortises and tenons can significantly improve the shear stiffness and the ultimate bearing capacity of circumferential joints.