Longitudinal structural deformation mechanism of shield tunnel linings considering shearing dislocation of circumferential joints

Abstract

To understand the longitudinal structural deformation mechanism of shield tunnel linings, it is crucial to reasonably consider circumferential joints, especially their shearing deformation. Towards that end, first, the dislocation between lining rings caused by the differential settlement of an actual tunnel project in Shanghai was introduced in detail. Next, the longitudinal deformation model of shield tunnels derived from Timoshenko beam theory was revised to predict the actual deformation more accurately. Then, a homogeneous solid ring-spring numerical model considering a novel treatment for the circumferential joint was proposed and validated with the aid of field data. Furthermore, to enhance the understanding of the longitudinal deformation mechanism caused by differential settlement, the longitudinal deformation of the selected project and additional cases was analysed in detail by using the proposed model. The results show that the longitudinal deformation caused by differential settlement comprises both dislocations (shearing deformation) and openings (bending deformation) between lining rings, although the dislocation deformation is observed to be more significant for the selected case. When the distance is close to the special lining rings (the maximum of the differential settlement), the dislocation increases first and then decreases. There is an abrupt increase between lining rings for the shear stress, which is the main reason for the dislocation of the circumferential joints. The opening of the circumferential joint that occurs at the invert of the shield tunnel next to both sides of the special lining rings is found to be severe and potentially hazardous.