Deformation monitoring and analysis for a twin tunnel with super-large-span and small-spacing

The monitoring of deformation including the surface settlement, vault settlement, convergence and surrounding rocks displacement, etc. has been performed for a real twin tunnel with super-large-span, small-spacing and overlying a high voltage tower during the tunnel construction in Shenzhen of China, and the deformation laws of the tunnel are analyzed. Furthermore, the engineering methods to control the deformation during construction are put forward. The result shows that: under protection of the large pipe roof pre-lining, application of double-side-drift method and many stages tunnel division excavation, construction of the inverted arch and close of the lining timely is an effective method to improve the performance of the deformation of the complex tunnel. The results could be adopted in design, construction and research of similar tunnels.