Experimental study on joint behaviour of immersed tunnel subjected to differential settlement

Differential settlement can cause concentrated deformation in the joints of immersed tunnel during its service stage. In this study, a model for simulating immersion joint was proposed, and tests on immersed tunnels under varying differential settlement were conducted. The mechanical behaviours of joints, including vertical displacement, shear displacement, rotation angle, and joint opening, were systematically analysed. Upon the successful simulation of joint against other works, further experiments were performed to underscore the influence of axial constraint and location of differential settlement. Results indicate that axial constraints can enhance the load transfer capacity and improve the uniformity of joint shear forces and rotation angles, accommodating a larger allowable range of differential settlement for immersed tunnel. The parameter of accommodating deformation ratio was defined to characterise the ratio between maximum axial deformation of joint to compression amount of Gina gasket, which could evaluate the effects of axial constraints on joint opening. Setting the accommodating deformation ratio to 1 can increased the allowable differential settlement by 36%. The location of differential settlement affected the load distribution greatly, with respect to shear and bending behaviour of joints. Settlement at the mid-span of a tunnel element rather than a joint was generally safer for immersed tunnel.