Study on bearing characteristics of marine subsoil for semi-rigid immersed tunnel

Abstract

In the project of Hong Kong-Zhuhai-Macau Bridge, the back-silting of natural foundation section is serious, and the tunnel structure is prone to uneven settlement along the longitudinal direction, and the longitudinal depth of the tunnel will be different due to the navigation demand. The traditional flexible joint scheme will cause great deformation of segment joints and reduce the safety reserve of the shear bearing capacity of the joints. Therefore, the Hong Kong-Zhuhai-Macau immersed tunnel has adopted a semi-rigid system design, that is, after the completion of the prestressing construction of segment joints, the prestressing tendons were not be cut off. The pre-stressed reinforcement can not only ensure the opening of segment joints within a certain range, but they are also adapted to the uneven settlement of the seabed. Notably, prestress plays a very important role in the whole immersed tube tunnel. Therefore, this paper is focused on a comprehensive study of the prestress applied in the semi-rigid scheme. A 1:100 small scale model test of the E13 element in the natural foundation of the immersed tube tunnel is taken as an example. Through the study of two factors, the degree of prestress tension and the size of back silting, the settlement characteristics and the distribution of compressive stresses of marine subsoil on the immersed tunnel are analyzed. The results of the model test showed that the increase in the degree of prestress tension is advantageous to management of the stress and uneven settlement of the joints. Through a comparison of the results of different prestress tension values, the rationality behind the selection of semi-rigid tunnel as a practical engineering scheme is demonstrated. This research lays a foundation for further study on the selection and optimal design of immersed tube tunnels, and the results provide a references point for similar immersed tunnel projects.

Keywords:

• Hong Kong Zhuhai Macau Bridge
• immersed tunnel
• prestressed tension
• base compression stress
• settlement characteristics

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The present investigation was the support of the National Natural Science Foundation of China (No. 51908053) and Natural Science Basic Research Plan in Shaanxi Province of China (No. 2018JQ5098).